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California Air Resources Board
California Air Resources Board
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California Air Resources Board
Logo
Agency overview
Formed1967
Preceding agencies
  • Bureau of Air Sanitation
  • Motor Vehicle Pollution Control Board
JurisdictionCalifornia
Headquarters1001 I Street, Sacramento, California
Employees1,994 (2024)[1]
Annual budgetUS$1.005 billion (2024-25)[1]
Agency executive
Parent agencyCalifornia Environmental Protection Agency
Websitehttps://ww2.arb.ca.gov/

The California Air Resources Board (CARB or ARB) is an agency of the government of California that aims to reduce air pollution. Established in 1967 when then-governor Ronald Reagan signed the Mulford-Carrell Act, combining the Bureau of Air Sanitation and the Motor Vehicle Pollution Control Board, CARB is a department within the cabinet-level California Environmental Protection Agency.

The stated goals of CARB include attaining and maintaining healthy air quality; protecting the public from exposure to toxic air contaminants; and providing innovative approaches for complying with air pollution rules and regulations. CARB has also been instrumental in driving innovation throughout the global automotive industry through programs such as its ZEV mandate.

One of CARB's responsibilities is to define vehicle emissions standards. California is the only state permitted to issue emissions standards under the federal Clean Air Act, subject to a waiver from the United States Environmental Protection Agency. Other states may choose to follow CARB or the federal vehicle emission standards, but may not set their own.[2]

Governance

[edit]
California Air Resources Board leadership[3]
Name Affiliation Appointed Term ends
Liane M. Randolph Chair December 2020 December 31, 2026
Cliff Rechtschaffen Public Member September 2023 December 31, 2024
John R. Balmes, MD Physician December 2007 December 31, 2027
Hector De La Torre Assembly June 2018 January 1, 2025
John Eisenhut Agriculture August 2013 December 31, 2029
Todd Gloria San Diego APCD January 2025 December 31, 2030
Dean Florez Senate February 2016 December 31, 2024
Corey A. Jackson, DSW Ex Officio (Assembly) February 2025
Lynda Hopkins Bay Area AQMD February 2025 December 31, 2026
Patricia Lock Dawson South Coast AQMD April 2025 December 31, 2026
Henry Stern Ex Officio (Senate) January 2023
Tania Pacheco-Werner, PhD San Joaquin Valley APCD December 2020 December 31, 2026
Eric Guerra Sacramento Region Air Districts Member January 2023 December 31, 2028
Susan Shaheen, PhD Automotive Member January 2023 December 31, 2028
Dawn Ortiz-Legg Air District Member February 2025 December 31, 2028
Diane Tavorkian Public August 31, 2018 December 31, 2029

CARB's governing board is made up of 16 members, with two non-voting members appointed for legislative oversight, one each by the California State Assembly and Senate. Twelve of the 14 voting members are appointed by the governor and are subject to confirmation by the Senate: five from local air districts, four air pollution subject-matter experts, two members of the public, and the Chair. The other two voting members are appointed from environmental justice committees by the Assembly and Senate.[3]

Five of the governor-appointed board members are chosen from regional air pollution control or air quality management districts, including one each from:[3]

Four governor-appointed board members are subject matter experts in specific fields: automotive engineering, currently Susan Shaheen, PhD; science, agriculture, or law, currently John Eisenhut; medicine, currently John R. Balmes, M.D.; and air pollution control. The governor is also responsible for two appointees from members of the public, and the final governor appointee is the Board's Chair. The first Chair of CARB was Dr. Arie Jan Haagen-Smit, who was previously a professor at the California Institute of Technology and started research into air pollution in 1948. Dr. Haagen-Smit is credited with discovering the source of smog in California, which led to the development of air pollution controls and standards.[4] In honor of his legacy, CARB started the Haagen-Smit Clean Air Awards program in 2001 to recognize individuals who have had significant accomplishments in the field of air quality and climate change.[5]

The two legislature-appointed board members work directly with communities affected by air pollution. They are currently Hector De La Torre and Dean Florez, appointed by the Assembly and Senate respectively.

Organizational structure

[edit]

CARB is a part of the California Environmental Protection Agency, an organization which reports directly to the Governor's Office in the Executive Branch of California State Government.[6]

CARB has 15 divisions and offices:[7]

  • Office of the Chair
  • Executive Office
  • Office of Community Air Protection
  • Air Quality Planning and Science Division
  • Emission Certification and Compliance Division
  • Enforcement Division
  • Industrial Strategies Division
  • Mobile Source Control Division
  • Mobile Source Laboratory Division
  • Monitoring and Laboratory Division
  • Research Division
  • Sustainable Transportation and Communities Division
  • Transportation and Toxics Division
  • Office of Information Services
  • Administrative Services Division

Air Quality Planning and Science Division

[edit]
California Air Resources Board Laboratory, Los Angeles, in 1973

The division assesses the extent of California's air quality problems and the progress being made to abate them, coordinates statewide development of clean air plans and maintains databases pertinent to air quality and emissions. The division's technical support work provides a basis for clean air plans and CARB's regulatory programs. This support includes management and interpretation of emission inventories, air quality data, meteorological data and of air quality modeling.[8][9]

The Air Quality Planning and Science Division has five branches:[9]

Researchers at the Statewide Air Pollution Research Center manufacture smog using a photochemical tube reactor (May 1972).

Atmospheric Modeling and Support Section

[edit]

The Atmospheric Modeling & Support Section is one of three sections within the Modeling & Meteorology Branch. The other two sections are the Regional Air Quality Modeling Section and the Meteorology Section.[8]

The air quality and atmospheric pollution dispersion models[10][11] routinely used by this Section include a number of the models recommended by the U.S. Environmental Protection Agency (EPA). The section uses models which were either developed by CARB or whose development was funded by CARB, such as:

  • CALPUFF – Originally developed by the Sigma Research Company (SRC) under contract to CARB. Currently maintained by the TRC Solution Company under contract to the U.S. EPA.
  • CALGRID – Developed by CARB and currently maintained by CARB.[12]
  • SARMAP – Developed by CARB and currently maintained by CARB.[13]

Role in reducing greenhouse gases

[edit]

The California Air Resources Board is charged with implementing California's comprehensive suite of policies to reduce emissions of greenhouse gases. In part due to CARB, California has successfully decoupled greenhouse gas emissions from economic growth, and achieved its goal of reducing emissions to 1990 levels four years earlier than the target date of 2020.[14]

Alternative Fuel Vehicle Incentive Program

[edit]

Alternative Fuel Vehicle Incentive Program (also known as Fueling Alternatives) is funded by the California Air Resources Board (CARB), offered throughout the State of California and administered by the California Center for Sustainable Energy (CCSE).[15]

Low-Emission Vehicle Program

[edit]

The CARB first adopted the Low-Emission Vehicle (LEV) Program standards in 1990 to address smog-forming pollutants,[16][17] which covered automobiles sold in California from 1994 through 2003. An amendment to the LEV Program, known as LEV II, was adopted in 1999, and covered vehicles for the 2004 through 2014 model years.[18] Greenhouse gas (GHG) emission regulations were adopted in 2004 starting for the 2009 model year, and are named the "Pavley" standards after Assemblymember Fran Pavley, who had written Assembly Bill 1493 in 2002 to establish them.[19][20] A second amendment, LEV III, was adopted in 2012, and covers vehicles sold from 2015 onward for both smog (superseding LEV II) and GHG (superseding Pavley) emissions.[21][22] The rules created under the LEV Program have been codified as specific sections in Title 13 of the California Code of Regulations;[23] in general, LEV I is § 1960.1; LEV II is § 1961; Pavley is § 1961.1; LEV III is § 1961.2 (smog-forming pollutants) and 1961.3 (GHG). The ZEV regulations, which were initially part of LEV I, have been broken out separately into § 1962.[24]

For comparison, the average new car sold in 1965 would produce approximately 2,000 lb (910 kg) of hydrocarbons over 100,000 mi (160,000 km) of driving; under the LEV I standards, the average new car sold in 1998 was projected to produce hydrocarbon emissions of 50 lb (23 kg) over the same distance, and under LEV II, the average new car in 2010 would further reduce hydrocarbon emissions to 10 lb (4.5 kg).[25]

Required labeling

[edit]
Global warming and smog scores
Global
warming
score
CO
2

(g/mi)
Smog
score
MY (2009) 2013–2017[a][26] MY 2018+[b][27]
CA
LEV II
EPA
Tier 2
NMOG+NO
x

(g/mi)
CA
LEV III
EPA
Tier 3
NMOG+NO
x

(g/mi)
10 <200 10 ZEV Bin 1 0.000 ZEV Bin 0 0.000
9 200–239 9 AT PZEV, PZEV 0.030
8 240–279 8 SULEV Bin 2 0.030 SULEV20 Bin 20 0.020
7 280–319 7 Bin 3 0.085 SULEV30 Bin 30 0.030
6 320–359 6 Bin 4 0.110 ULEV50 Bin 50 0.050
5 360–399 5 ULEV 0.125 ULEV70 Bin 70 0.070
4 400–439 4 LEV Bin 5 0.160
3 440–479 3 Bin 6 0.190 – 0.200 ULEV125 Bin 125 0.125
2 480–519 2 Bin 7 0.240
1 ≥520 1 [c] Bin 8a 0.325 LEV160 Bin 160 0.160
Notes
  1. ^ Based on the scoring for the "Environmental Performance Label", applied to new vehicles model years 2009–2012 in California. The California label was aligned with Federal standards in 2013.
  2. ^ Scoring realigned with LEV III/Tier 3 scores starting in model year 2018. Note the change in standards; for example, a LEV under LEV II (160 mg/mi) which was rated with a smog score of 4 under the old label would now be rated with as LEV160 under LEV III and would receive a smog score of 1.
  3. ^ ULEV under California LEV I standard.

In 2005, the California State Assembly passed AB 1229, which required all new vehicles manufactured after January 1, 2009, to bear an Environmental Performance Label, which scored the emissions performance of the vehicle on two scales ranging between 1 (worst) and 10 (best): one for global warming (emissions of GHG such as N
2
O
, CH
4
, air conditioning refrigerants, and CO
2
) and one for smog-forming compounds (non-methane organic gases (NMOG), NO
x
, and HC).[26][28] The Federal Government followed suit and required a similar "smog score" on new vehicles sold starting in 2013; the standards were realigned for labels applied to 2018 model year vehicles.

Vehicle categories

[edit]

The LEV program has established several categories of reduced emissions vehicles. LEV I defined LEV and ULEV vehicles, and added TLEV and Tier 1 temporary classifications that would not be sold after 2003. LEV II added SULEV and PZEV vehicles, and LEV III tightened emission standards. The actual emission levels depend on the standards in use.

LEV I defined emission limits for several different classes of vehicle, including passenger cars (PC), light-duty trucks (LDT), and medium-duty vehicles (MDV). Heavy-duty vehicles were specifically excluded from LEV I. LEV I also defined a loaded vehicle weight (LVW) as the vehicle's Curb weight plus an allowance of 300 lb (140 kg). In general, the most stringent standards were applied to passenger cars and light-duty trucks with a LVW up to 3,750 lb (1,700 kg) (these "light" LDTs were later denoted LDT1 under LEV II).[17] LEV II increased the scope of vehicles classed as light-duty trucks to encompass a higher GVWR up to 8,500 lb (3,900 kg), compared to the LEV I standard of 6,000 lb (2,700 kg). In addition, LEV I had defined less stringent limits for heavier LDTs (denoted LDT2 with a LVW 3,751–5,750 lb (1,701–2,608 kg)); LEV II closed that discrepancy and defined a single emissions standard for all PCs and LDTs.[18] Under LEV III, medium-duty passenger vehicles (MDPV) were brought under the most stringent standards alongside PCs and LDTs.[21]

Vehicle classes under the LEV regulations[17][18][21]
Class Abbr. GVWR Notes
Passenger car PC Designed primarily for transportation of persons with a design capacity of ≤12 people.
Light-duty truck LDT ≤6,000 lb
2,700 kg[a]
Designed primarily for transportation of property, derivatives of those, or available with special features for off-street use. LDT1 was defined as those with LVW up to 3,750 lb (1,700 kg), and LDT2 was defined as those with LVW from 3,751 to 5,750 lb (1,701 to 2,608 kg).
≤8,500 lb
3,900 kg[b]
Medium-duty vehicle MDV ≤8,500 lb
3,900 kg[c]
Any non-passenger vehicle with a GVWR >6,000 lb (2,700 kg) and less than the limits shown here.
≤14,000 lb
6,400 kg[d]
Notes
  1. ^ For model years before 2000
  2. ^ For model years 2000 and subsequent
  3. ^ For model years before 1995
  4. ^ For model years 1995 and subsequent, or model years 1992 and subsequent LEV, ULEV, SULEV, or ZEV.

Smog-forming compound emissions limits

[edit]

Rather than providing a single standard for vehicles based on age, purpose, and weight, the LEV I standards introduced different tiers of limits for smog-forming compound emissions starting in the 1995 model year. After 2003, LEV was the minimum standard to be met.[17]

California Emissions Standards[a][b][c][29]
Category NMOG[d]+NO
x
[e]
CO PM[f] HCHO
LEV I[g][17] LEV II[h][18] LEV III[i][21] LEV I[g] LEV II[h] LEV III[i] LEV I[g] LEV II[h] LEV III[i] LEV I[g] LEV II[h] LEV III[i]
Tier 1[j] 0.91[k][l][m] 4.2[n] [o]
TLEV[j] 0.756[p] 4.2 0.08 0.018
LEV LEV160 0.390[q] 0.160[r] 0.160 4.2 4.2 4.2 0.08 0.01 0.01 0.018 0.018 0.004
ULEV ULEV125 0.355[s] 0.125[t] 0.125 2.1 2.1 2.1 0.04 0.01 0.01 0.011 0.011 0.004
ULEV70 0.070 1.7
ULEV50 0.050
SULEV[u] SULEV30 0.030[v] 0.030 1.0 1.0 0.01 0.01 0.004 0.004
SULEV20 0.020
Notes
  1. ^ Values are in grams per mile for all passenger cars and those light-duty trucks with a loaded vehicle weight (total of kerb weight plus 300 lb (140 kg) driver) less than 3,750 lb (1,700 kg), tested under the FTP-75 protocol.
  2. ^ Under LEV II and LEV III, the definition of light duty trucks was expanded to encompass all vehicles with a gross vehicle weight rating of 8,500 lb (3,900 kg) or less.
  3. ^ Under LEV III, this category also now includes all medium-duty passenger vehicles with a GVWR of 10,000 lb (4,500 kg) or less.
  4. ^ Non-methane organic gases
  5. ^ NMOG and NO
    x
    were reported separately under LEV I and LEV II
  6. ^ Particulate Matter
  7. ^ a b c d LEV I standards are given for emissions at the 100,000 mi (160,000 km) / 10-year age
  8. ^ a b c d LEV II standards are given for emissions at the 120,000 mi (190,000 km) / 11-year age
  9. ^ a b c d LEV III standards are given for emissions at the 150,000 mi (240,000 km) age
  10. ^ a b Tier 1 and transitional LEV (TLEV) vehicles were not sold after 2003.
  11. ^ LEV I: 0.31 g/mi NMOG + 0.6 g/mi NO
    x
    .
  12. ^ LEV I: 0.31 g/mi NMOG + 1.0 g/mi NO
    x
    for diesel-powered vehicles.
  13. ^ For comparison, the values for 1988–94 model year passenger cars, light-duty trucks, and medium-duty trucks (<3,750 LVW) were 0.39–0.46 g/mi NMOG and 0.4-1.0 g/mi NO
    x
    .
  14. ^ For comparison, the values for 1988–94 model year passenger cars were 7.0-8.3 g/mi CO, and for light-duty trucks and medium-duty trucks (<3,750 LVW), 9.0-10.6 g/mi CO.
  15. ^ Formaldehyde standards provided for 1993 and newer model year vehicles fueled by methanol and ethanol: for passenger cars, light-duty trucks and medium-duty trucks (<3,750 LVW), 0.023 g/mi HCHO for 1993–95 and 0.015 g/mi HCHO for 1996+
  16. ^ LEV I: 0.156 g/mi NMOG + 0.6 g/mi NO
    x
  17. ^ LEV I: 0.090 g/mi NMOG + 0.3 g/mi NO
    x
  18. ^ LEV II: 0.090 g/mi NMOG + 0.07 g/mi NO
    x
  19. ^ LEV I: 0.055 g/mi NMOG + 0.3 g/mi NO
    x
  20. ^ LEV II: 0.055 g/mi NMOG + 0.07 g/mi NO
    x
  21. ^ SULEV for passenger cars and light-duty trucks was not defined until LEV II.
  22. ^ LEV II: 0.010 g/mi NMOG + 0.02 g/mi NO
    x

Greenhouse gas emissions limits

[edit]
Sunlight filtered through smog near Blythe, May 1972

CARB adopted regulations for limits on greenhouse gas emissions in 2004 starting with the 2009 model year to support the direction provided by AB 1493.[19] In June 2005, Governor Arnold Schwarzenegger signed Executive Order S-03-05, which required a reduction in California GHG emissions, targeting an 80% reduction compared to 1990 levels by 2050.[30] Assembly Bill 32, better known as the California Global Warming Solutions Act of 2006, codified these requirements.[31]

CARB filed a waiver request with the United States Environmental Protection Agency (EPA) under Section 209(b) of the Clean Air Act in December 2005 to permit it to establish limits on greenhouse gas emissions; although the waiver request was initially denied in March 2008, it was later approved on June 30, 2009, after President Barack Obama signed a Presidential Memorandum directing the EPA to reconsider the waiver.[19][32] In the initial denial, EPA Administrator Stephen L. Johnson stated the Clean Air Act was not "intended to allow California to promulgate state standards for emissions from new motor vehicles designed to address global climate change problems" and further, that he did not believe "the effects of climate change in California are compelling and extraordinary compared to the effects in the rest of the country."[33] Johnson's successor, Lisa P. Jackson, signed the waiver overturning Johnson's denial, writing that "EPA must grant California a waiver if California determines that its standards are, in the aggregate, at least as protective of the public health and welfare as applicable Federal standards." Jackson also noted that in the history of the waiver process, over 50 waivers had been granted and only one had been fully denied, namely the March 2008 denial of the GHG emissions regulation.[34]

Greenhouse gas fleet average emissions targets[35]
Model
Year
(g/mi CO
2
-equivalent)
PCs & LDT1s LDT2s & MDPVs
2009 323 439
2010 301 420
2011 267 390
2012 233 361
2013 227 355
2014 222 350
2015 213 341
2016+ 205 332

CARB decided to adopt regulation of GHG emissions under Executive Order G-05-061, which provided phase-in targets for fleet average GHG emissions in CO
2
-equivalent grams per mile starting with the 2009 model year.[35] The calculation of CO
2
-equivalent emissions was based on contributions from four different chemicals: CO
2
, N
2
O
, CH
4
, and air conditioning refrigerants.

The emissions in g/mi CO
2
-equivalent are calculated according to the formula , which has two terms for direct and indirect emissions allowances of air conditioning refrigerants, depending on the refrigerant used, such as HFC134a, and the system design. Vehicles powered by alternative fuels use a slightly modified formula, , where is a fuel adjustment factor depending on the alternative fuel used (1.03 for natural gas, 0.89 for LPG, and 0.74 for E85). ZEVs are also required to calculate GHG as the processes to generate the energy (or fuel) used also produce GHG. For ZEVs, , where is the upstream emissions factor (130 g/mi for battery electric vehicles, 210 for hydrogen/fuel cell, and 290 for hydrogen/internal combustion).[35] Direct CO
2
emissions could be calculated in a relatively straightforward fashion based on fuel consumption.[36] Manufacturers that do not wish to measure N
2
O
emissions may assume a value of 0.006 g/mi.[35] An update was issued in 2010 which allowed manufacturers to calculate GHG emissions using CAFE data; for conventionally powered vehicles, the contribution from the nitrous oxide and methane terms could be assumed to be 1.9 g/mi.[37]

CARB voted unanimously in March 2017 to require automakers to average 54.5 miles per US gallon (4.32 L/100 km; 65.5 mpg‑imp) for new cars in 2025.[38]

Section 177 states

[edit]
Section 177 states:
 •   blue=LEV only
 •   green=LEV+ZEV
 •   red=LEV repealed
"California emissions" states[39][40][41]
State LEV ZEV MY
CA Yes Yes 2005
CO Yes Yes 2022
CT Yes Yes 2008
DC Yes No 2012
DE Yes No 2014
MA Yes Yes 2009
MD Yes Yes 2011
ME Yes Yes 2009
MN Yes Yes 2025 (anticipated)
NJ Yes Yes 2009
NM Yes Yes 2026
NV Yes Yes 2025
NY Yes Yes 2009
OR Yes Yes 2009
PA Yes No 2008
RI Yes Yes 2009
VA Yes Yes 2025
VT Yes Yes 2009
WA Yes Yes 2009 (ZEV: 2025)

Because California had emissions regulations prior to the 1977 Clean Air Act, under Section 177 of that bill,[42] other states may adopt the more stringent California emissions regulations as an alternative to federal standards. Thirteen other states and the District of Columbia have chosen to do so, and ten of those have additionally adopted the California Zero-Emission Vehicle regulations.[39][40][43] In December 2020, Minnesota announced its intention to adopt California LEV and ZEV rules;[44] following a hearing before an administrative law judge in February 2021, the Minnesota Pollution Control Agency adopted the California regulations.[45][46] In August 2022, Virginia, citing to a 2021 law, announced it would follow California regulations for ZEV registrations.[47]

Arizona and New Mexico had previously adopted California LEV regulations under Section 177, but later repealed those states' clean car standards in 2012[48] and 2013,[49] respectively.[50]

In Canada, the province of Quebec adopted CARB standards effective in 2010.[51] CARB and the Government of Canada entered into a Memorandum of Understanding in June 2019 to cooperate on greenhouse gas emissions mitigation.[52]

Zero-Emission Vehicle Program

[edit]

The CARB Zero-Emission Vehicle (ZEV) program was enacted by the California government starting in 1990 to promote the use of zero emission vehicles.[53] The program goal is to reduce the pervasive air pollution affecting the main metropolitan areas in the state, particularly in Los Angeles, where prolonged pollution episodes are frequent. The California ZEV rule was first adopted by CARB as part of the 1990 Low-Emission Vehicle (LEV I) Program.[16] The focus of the 1990 rules (ZEV-90) was to meet air quality standards for ozone rather than the reduction of greenhouse gas (GHG) emissions.[54]: 5 

Under LEV II in 1999, the ZEV regulations were moved to a separate section (13 CCR § 1962) and the requirements for ZEVs as a percentage of fleet sales was made more formal. Executive Order S-03-05 (2005) and Assembly Bills 1493 (2002) and 32 (2006) prompted CARB to reevaluate the ZEV program as last amended in 1996, which had been primarily concerned with reducing emissions of smog-forming pollutants.[54] By the time AB 32 passed in 2006, vehicles complying with PZEV and AT PZEV standards had become commercially successful, and the ZEV program could then shift towards reducing both smog-forming compounds and greenhouse gases.[54]

The next set of ZEV regulations were adopted in 2012 with LEV III. CARB put both LEV and ZEV rules together as the Advanced Clean Cars Program (ACC), adopted in 2012, which included regulations for cars sold through the 2025 model year. The regulations include updates to regulations for LEV III (for smog-forming emissions), LEV III GHG (for greenhouse gas emissions), and ZEV.[55][56][57] Since then, in September 2020 Governor Gavin Newsom signed an executive order directing that by 2035, all new cars and passenger trucks sold in California will be zero-emission vehicles.[58] Executive Order N-79-20 directs CARB to develop regulations to require that ZEVs be an increasing share of new vehicles sold in the state, with light-duty cars and trucks and off-road vehicles and equipment meeting the 100% ZEV goal by 2035 and medium and heavy-duty trucks and buses meeting the same 100% ZEV goal by 2045. The order also directs Caltrans to develop near-term actions to encourage "an integrated, statewide rail and transit network" and infrastructure to support bicycles and pedestrians.[59] In response, CARB began development of the Advanced Clean Cars II (ACC II) Program, focusing on emissions of vehicles sold after 2025. ACC II reiterated the aim to have all new passenger cars, trucks and SUVs sold in the state to be zero emissions vehicles by 2035,[60] and was scheduled for consideration before CARB in June 2022.[61] The regulations of ACC II were adopted by California in August 2022.[62]

Vehicle definitions

[edit]

LEV I defined a ZEV as one that produces "zero emissions of any criteria pollutants under any and all possible operational modes and conditions." A vehicle could still qualify as a ZEV with a fuel-fired heater, as long as the heater was unable to be operated at ambient temperatures above 40 °F (4 °C) and did not have any evaporative emissions.[17]: 2–6, 2–7  Under LEV II (ZEV-99), the ZEV definition was updated to include precursor pollutants, but did not consider upstream emissions from power plants.[63]: C-1 

The ZEV regulation has evolved and been modified several times since 1990, and several new partial or low-emission categories were created and defined,[64][65][66][67] including the introduction of PZEV and AT PZEV categories in ZEV-99.[63]: B-1, B-2 

  • PZEV (Partial Zero Emission Vehicle): Meets SULEV tailpipe standards, has a 15-year / 150,000-mile warranty, and zero evaporative emissions. These vehicles are 80% cleaner than the average 2002 model year car.
  • AT PZEV (Advanced Technology PZEV): These are advanced technology vehicles that meet PZEV standards and include ZEV enabling technology, typically hybrid electric vehicles (HEV). They are 80% cleaner than the average 2002 model year car.
  • ZEV (Zero Emission Vehicle): Zero tailpipe emissions, and 98% cleaner than the average new 2003 model year vehicle.

Manufacturer sales volume

[edit]

Under ZEV-90, CARB classified manufacturers according to the average sales per year between 1989 and 1993; small volume manufacturers were those that sold 3,000 or fewer new vehicles per year; intermediate volume manufacturers sold between 3,001 and 35,000; and large volume manufacturers sold more than 35,000 per year.[17]: 2–3  For large volume manufacturers, CARB required that 2% of 1998 to 2000 model year vehicles sold were ZEVs, ramping up to 5% ZEVs by 2001 and 10% ZEVs in 2003 and beyond. Intermediate volume manufacturers were not required to meet the goals until 2003, and small volume manufacturers were exempted. These percentages were calculated based on total production of passenger cars and light-duty trucks with a loaded vehicle weight (LVW) less than 3,750 lb (1,700 kg).[17]: 3-22 to 3-24 [68]

ZEV credit system

[edit]
ZEV-96 credits[69]
Model
Year
2 ZEV Count 3 ZEV Count
Range
(mi)
Specific Energy
(Wh/kg)
Range
(mi)
Specific Energy
(Wh/kg)
1996–97 any any ≥70 ≥40
1998 ≥100 ≥130
1999 ≥50 ≥60
2000 ≥140 ≥175
2001–02 ≥60 ≥90

The LEV I rules also introduced the concept of emission credits. Under LEV I, the vehicle fleet average emissions rate of non-methane organic gases (NMOG) produced by a manufacturer was required to meet increasingly stringent requirements starting in 1994.[17]: 3–18  The calculation of fleet average NMOG emissions was based on a weighted sum of vehicle NMOG emissions, based on the number sold and type of certification (i.e., TLEV, LEV, ULEV, etc.), divided by the total number of vehicles produced, including ZEVs.[17]: 3–20  Manufacturers whose fleet average NMOG emissions met or exceeded the NMOG emissions goal would be subjected to civil penalties; those which fell below the goal would receive credits, which could then be marketed to other manufacturers.[17]: 3–24 

The 1996 amendments to the ZEV regulations in LEV I (ZEV-96) introduced credits where a ZEV could be counted more than once based on vehicle range or battery specific energy to encourage deployment of ZEVs prior to 2003.[69]: 3–4 

Under LEV II/ZEV-99, the PZEV and AT PZEV categories were introduced, and the percentage of ZEVs sold by a manufacturer could be partially met by the sales of PZEV and AT PZEVs.[63]: C-2  If a vehicle met PZEV criteria, it qualified for a credit equal to 0.2 of one ZEV for the purposes of calculating that manufacturer's ZEV production.[63]: C-6  AT PZEVs capable of traveling with zero emissions for a limited range were allowed additional credit if the urban all-electric range was at least ten miles.[63]: C-7  ZEVs that were introduced prior to 2003 received a multiplier, with a value ranging up to 10× a single ZEV depending on the all-electric range and fast-charging capability.[63]: C-11, C-12 

MOA demonstration fleet

[edit]
MOA EVs (1997+)[70]
Mfr Model Date Battery Range Qty
(Dec. 97)
Chrysler EPIC ?/97 SLA 60 mi
97 km
17
Ford Ranger EV ?/97 SLA 60 mi
97 km
10
GM EV1 12/96 SLA 75 mi
121 km
265
GM S-10 EV ?/97 SLA 40 mi
64 km
354
NiMH 80 mi
130 km
7
Honda EV Plus 05/97 NiMH 125 mi
201 km
104
Nissan Altra ?/98 Li-ion 120 mi
190 km
Toyota RAV4 EV 10/97 NiMH 125 mi
201 km
69

In March 1996, ZEV-96 eliminated the ZEV ramp-up planned to start in 1998, but the goal of 10% ZEVs by 2003 was retained, with credits granted for sales of partial ZEVs (PZEVs).[69][64] According to comment responses, CARB determined that advanced batteries would not be ready in time to meet the ZEV requirements until at least 2003.[71]: 6–7 

GM EV1

In conjunction with relaxing the requirements in ZEV-96, CARB signed memoranda of agreement (MOAs) with the seven large scale manufacturers to begin rolling out demonstration fleets of ZEVs with limited public availability in the near term. The GM EV1 was the first battery electric vehicle (BEV) offered to the public, in partial fulfillment of the agreement with CARB. The EV1 was available only through a US$399 (equivalent to $800 in 2024)/month lease starting in December 1996; the initial markets were South Coast, San Diego, and Arizona, and expanded to Sacramento and the Bay Area. GM also offered an electric S-10 pickup truck to fleet operators.[70]

In 1997, Honda (EV Plus, May 1997), Toyota (RAV4 EV, October 1997), and Chrysler (EPIC, 1997) followed suit. Ford also introduced the Ranger EV for the 1998 model year, and Nissan stated they planned to offer the Altra in the 1998 model year as well to fulfill the MOA. As an acceptable alternative, Mazda stated they would purchase ZEV credits from Ford.[70]: 7–10 

Advanced Clean Cars

[edit]

The Low-Emission Vehicle Program was revised to define modified ZEV regulations for 2015 models.[64][72][73] CARB estimates that ACC will result in 10% of all sales to be ZEVs by 2025.[74]: 5  The share remained at 3% between 2014 and 2016. Battery vehicles receive 3 or 4 credits, while fuel cell cars receive 9. As of 2016, a credit has a market value of $3-4,000, and some automakers have more credits than required.[75][76]

CARB held a public workshop in September 2020 where several new consumer-friendly regulations for ZEVs were proposed to improve adoption:[77]

  • Standardization of a DC Fast Charge inlet (proposing to use CCS Combo 1, with adapters provided by the vehicle manufacturer if applicable)
  • Standardization of vehicle and battery data (to assist assessment of need for repairs/condition)
  • Implement a standardized battery state-of-health (SOH) indicator (using SAE J1634 dynamometer testing to define battery capacity) and define a value of battery SOH that qualifies for warranty repair
  • Make ZEV powertrain service and repair information available to independent technicians and repair shops (including standardization of communication protocols for vehicle data)

In May 2021, additional draft requirements were added:[78]

  • Durability: BEVs to maintain 80% of certified range for 15 years/150,000 miles
  • Durability: FCEVs to maintain 90% of fuel cell system output power after 4,000 hours of operation
  • Battery Labelling: standardized content to improve the efficiency of recycling batteries to recover materials or potential repurposing

To improve access to ZEVs, CARB added proposed environmental justice (EJ) credits in August 2021 for manufacturers who improve options for clean transportation to underserved communities, such as by providing a discount on a ZEV that would be used in a community-based clean mobility program. The August workshop also included additional regulations for ZEVs:[79]

  • Range: starting in 2026, minimum (2-cycle) range to be 200 mi (320 km)
  • On-board charger: minimum 5.76 kW for AC (Level 2) charging, sufficient for a BEV to charge overnight (8 hours) from a 30A source
Stringency proposal
  Proposed regulatory requirement
  Minimum vehicle stringency (with EJ credits)

The final workshop in October 2021 proposed that ZEVs would be taken out of fleet calculations for vehicle emissions and provided yearly targets for ZEV vehicle sales as a percent of total sales, including potential EJ credits. Additionally, the required warranty period and requirements to take credit for PHEV sales were defined:[80]

  • Battery to retain ≥ 80% SoH for 8 years/100,000 miles
  • PHEVs to meet one of two requirements:
    • Transitional PHEVs (2026–28): minimum 30 mi (48 km) all-electric range with additional credit if vehicle exceeds 10 mi (16 km) on the US06 high speed/acceleration cycle; 8-year/100,000 80%SOH battery warranty, 5.76 kW on-board charger
    • Full credit PHEVs (2026+): minimum 50 mi (80 km) all-electric range, minimum 40 mi (64 km) on the US06 high speed/acceleration cycle; 8-year/100,000 80%SOH battery warranty, 5.76 kW on-board charger
  • "Small volume" manufacturers (defined as those selling fewer than 4,500 cars per year) are required to comply with the ZEV mandate starting with the 2035 model year

OHV Emission Standards

[edit]

The California DMV implements the policy dictates of the California Air Resources Board (CARB) with respect to registration of off-highway motor vehicles (OHVs).[81] Registration consists of ID plates or placards issued by the DMV.[82] Operating a motorized vehicle off-highway in California requires either a Green Sticker or a Red Sticker ID. The Green Sticker indicates that the vehicle has passed emission requirements. The Red Sticker (issued through 2021) restricts OHV use due to not meeting emission standards established by the CARB. The red sticker program began in 1994 when CARB adopted standards for emissions from two-stroke engines used primarily on dirt bikes. Between 1998 and 2003, the red sticker program was refined allowing vehicles that did not meet peak ozone season standards to be operated only at specific times of the year.[83] As of model year 2022, the CARB no longer authorizes issuing of red stickers.[84]

Commercial Harbor Craft Regulation

[edit]

The California Air Resources Board's (CARB) Commercial Harbor Craft regulation is a regulatory framework aimed at reducing emissions from commercial vessels operating in California's harbors and ports. The rule primarily targets diesel-powered vessels such as ferries, tugboats, and other workboats that operate in and around California's ports.[85][86] Since the original adoption of regulation in 2008, and its amendments in 2010 and 2022, vessel owners in the state have been required to either replace their engines or send their boats out of the state.[87][88]

Low-carbon fuel standard

[edit]

The Low-Carbon Fuel Standard (LCFS) requires oil refineries and distributors to ensure that the mix of fuel they sell in the Californian market meets the established declining targets for greenhouse gas emissions measured in CO2-equivalent grams per unit of fuel energy sold for transport purposes. The 2007 Governor's LCFS directive calls for a reduction of at least 10% in the carbon intensity of California's transportation fuels by 2020. These reductions include not only tailpipe emissions but also all other associated emissions from production, distribution and use of transport fuels within the state. Therefore, California LCFS considers the fuel's full life cycle, also known as the "well to wheels" or "seed to wheels" efficiency of transport fuels.[16][89] The standard is aimed to reduce the state's dependence on petroleum, create a market for clean transportation technology, and stimulate the production and use of alternative, low-carbon fuels in California.[90]

On April 23, 2009, CARB approved the specific rules for the LCFS that will go into effect in January 2011.[91][92] The rule proposal prepared by its technical staff was approved by a 9–1 vote, to set the 2020 maximum carbon intensity reference value to 86 grams of carbon dioxide released per megajoule of energy produced.[90][93]

PHEV Research Center

[edit]

The PHEV Research Center was launched with funding from the California Air Resources Board.

Innovative Clean Transit

[edit]

Under the Innovative Clean Transit (formerly known as the Advanced Clean Transit) regulation adopted in December 2018, public transportation agencies in California will gradually transition to a zero-emission bus fleet by 2040.[94] Large transit agencies (defined as those operating more than 65 buses in the San Joaquin Valley Air Basin or South Coast Air Quality Management District, or those operating more than 100 buses elsewhere with populations greater than 200,000) are required to have 25% of new bus purchases as zero-emission buses (ZEBs) starting in 2023, 50% of new purchases as ZEBs starting in 2026, and 100% of new purchases as ZEBs starting in 2029. Small transit agencies are required to make 25% of new purchases as ZEBs in 2026 and 100% of new purchases as ZEBs in 2029+. Per the regulation, ZEBs are defined to include battery electric buses and fuel cell buses, but do not include electric trolleybuses which draw power from overhead lines.[95] The Antelope Valley Transit Authority has set a goal to be the first all-electric fleet by the end of 2018, ahead of the tightened regulations.[96]

Regulation of ozone produced by air cleaners and ionizers

[edit]

The California Air Resources Board has a page listing air cleaners (many with ionizers) meeting their indoor ozone limit of 0.050 parts per million.[97] From that article:

All portable indoor air cleaning devices sold in California must be certified by the California Air Resources Board (CARB). To be certified, air cleaners must be tested for electrical safety and ozone emissions, and meet an ozone emission concentration limit of 0.050 parts per million. For more information about the regulation, visit the air cleaner regulation.

Southern California headquarters, Mary D. Nichols Campus

[edit]
California Air Resources Board's Headquarters in Riverside
California Air Resources Board's Southern California headquarters in Riverside, California

On October 27, 2017, CARB broke ground on its new state-of-the-art Southern California headquarters. CARB chose the site near the University of California, Riverside, in March 2016 and completed environmental studies in June 2017. Construction costs of $419 million, which include $108 million for specialized laboratory and testing equipment, were approved by the Legislature in July. Of those costs, $154 million comes from fines paid by Volkswagen for air quality violations related to the diesel car cheating case. Additional funds will come from the Motor Vehicle Account, the Air Pollution Control Fund and the Vehicle Inspection Repair Fund.[98]

Over a decade of planning has gone into the development of a replacement for CARB's aging Haagen-Smit Laboratory. Opened in 1973 in El Monte, California, the Haagen-Smit Laboratory is the site of many of CARB's groundbreaking efforts to reduce the emissions of cars and trucks, as well as efforts to introduce zero-emission and plug-in vehicles to California. In 2015, engineers and technicians based at the Haagen-Smit Laboratory were instrumental in discovering the infamous VW diesel "defeat device," leading to the largest emissions control violation settlement in national and California history.

The new campus features an extended range of dedicated test cells, including heavy-duty testing. There is also workspace for accommodating new test methods for future generations of vehicles, and space for developing enhanced on-board diagnostics and portable emissions measurement systems. The facility also includes a separate advanced chemistry laboratory. The Southern California Headquarters’ office and administration space accommodates 460 employees and includes visitor reception and public areas, a press room, flexible conference and workshop space, and a 250-person public auditorium.

Sustainability drove the striking architecture and every detail of the campus. Designed by ZGF Architects and built by Hensel Phelps, the new headquarters is built for the future. At 402,000 square feet, it is designed to be the largest Zero Net Energy building in the United States, aided by solar arrays throughout the campus that generate 3.5 Megawatts of electricity, and a chilled beam temperature management system that provides increased energy efficiency and occupant comfort. As a result, the facility achieves Leadership in Energy and Environmental Design (LEED) Platinum certification, and California Green Building Standards Code (CALGreen) Tier 2 standards and is designed to achieve Zero-Net Energy performance .

On November 18, 2021, CARB dedicated the new Southern California headquarters in honor of former Chair Mary D. Nichols whose career at CARB spanned four decades under three different California governors.[99]

See also

[edit]
California Air Resources Board
Other

References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia
from Grokipedia
The California Air Resources Board (CARB or ARB) is an executive branch agency of the California state government tasked with regulating air pollution sources, setting emission standards for vehicles and fuels, and implementing policies to combat climate change while aiming to safeguard public health and ecological resources. Established in 1967 through the consolidation of the Bureau of Air Sanitation and the California Motor Vehicle Pollution Control Board, CARB operates under the California Environmental Protection Agency and wields authority granted by the federal Clean Air Act via waivers that allow California to deviate from national standards, often leading other states to adopt its rules under Section 177. CARB's regulatory framework has driven substantial reductions in criteria pollutants such as smog-forming and particulate matter across the state, crediting its science-based controls for cleaner air since the era of severe photochemical in the mid-20th century. Key achievements include pioneering low-emission vehicle mandates that have curtailed tailpipe emissions from automobiles and heavy-duty trucks, contributing to measurable declines in ambient pollutant concentrations despite population and economic growth. The agency also administers the cap-and-trade program under Assembly Bill 32 (2006), which caps greenhouse gas emissions and has generated revenues redirected toward environmental investments, though empirical assessments indicate mixed outcomes in equitably distributing benefits versus costs. Notable controversies surround CARB's expansive interpretations of its mandate, including federal lawsuits alleging preemption of national commerce powers through stringent truck emission rules enforced despite lacking EPA waiver approval, highlighting tensions between state innovation and interstate economic uniformity. Critics, drawing from economic analyses, contend that regulations like low-carbon fuel standards elevate gasoline and diesel prices—often by tens of cents per gallon—imposing regressive burdens on lower-income households and industries without always yielding proportional health gains, as evidenced by ongoing non-attainment of federal air quality standards in urban basins. CARB's governance by a 16-member board appointed by the governor has also drawn scrutiny for potential political influences overriding rigorous cost-benefit evaluations in rule-making processes.

History

Founding in 1967 and Initial Focus on Smog

The California Air Resources Board was created on August 30, 1967, through the Mulford-Carrell Air Resources Act signed by Governor Ronald Reagan, consolidating the fragmented state efforts against air pollution by merging the Bureau of Air Sanitation—responsible for general air quality oversight—and the Motor Vehicle Pollution Control Board into a unified agency under the California Department of Public Health. This legislation empowered the new board to establish emission standards for all pollution sources, enforce compliance, conduct research, and coordinate with local air districts, marking California's commitment to aggressive statewide control amid escalating urban smog crises. California's initial smog focus stemmed from the severe photochemical plaguing regions like the since the 1940s, where vehicle exhaust hydrocarbons and nitrogen oxides reacted under sunlight and inversion layers to form and other irritants, leading to widespread respiratory ailments and visibility reductions documented in early studies. Prior to CARB's formation, the state had pioneered the nation's first tailpipe emissions standards in 1966, targeting and reductions from new vehicles by up to 70-80%, but lacked centralized authority to implement and expand controls effectively. In its founding years, CARB prioritized vehicle emissions as the primary contributor, adopting rules for emissions controls and initiating statewide monitoring networks while researching photochemical reactions to inform standards. By 1969, the board set California's first ambient air quality standards for total suspended particulates, photochemical oxidants (a proxy for ), , and , surpassing federal efforts and laying groundwork for mandatory compliance deadlines. These measures reflected empirical recognition that motor vehicles accounted for over 70% of reactive pollutants in high- areas, driving early enforcement against non-compliant manufacturers and fueling stations.

Expansion Through the 1970s-1990s: Vehicle Emissions and Federal Preemption Battles

In the , the California Air Resources Board intensified its regulatory focus on mobile sources of , recognizing vehicles as a primary contributor to photochemical in urban areas like . Building on pre-1970 tailpipe limits for hydrocarbons and , CARB adopted standards for oxides of nitrogen in 1971, targeting reductions in smog-forming . By 1975, CARB mandated the use of three-way catalytic converters on new gasoline-powered vehicles starting with the 1975 model year, a technology-forcing measure that achieved approximately 70-90% reductions in hydrocarbons, , and nitrogen oxides compared to uncontrolled engines. These standards exceeded emerging federal requirements under the 1970 Clean Air Act, prompting CARB to secure waivers from the U.S. Environmental Protection Agency (EPA) to enforce them statewide, as the Act's Section 209 preempted other states but preserved 's authority if standards were technologically feasible and addressed unique air quality needs. EPA granted initial waivers in the early for 1972-1977 model years, enabling California to pioneer controls like evaporative emission limits and crankcase ventilation systems. ![District of Los Angeles smog obscures the sun near Salton Sea][float-right] Throughout the decade, automotive manufacturers challenged CARB's regulations through petitions to EPA and lawsuits, arguing that the standards imposed undue economic burdens and preempted federal uniformity in safety and emissions testing. For instance, industry groups contested the 1975 catalytic converter mandate, claiming insufficient lead-time for compliance and potential fuel economy penalties, but federal courts upheld CARB's waiver eligibility, affirming California's evidence of severe smog episodes—such as ozone levels exceeding 0.35 ppm in the South Coast Air Basin—as justifying stricter measures. The 1977 Clean Air Act Amendments reinforced this framework by codifying California's waiver process and requiring EPA to approve standards unless they conflicted with federal policy, though delays in waiver decisions occasionally slowed implementation. CARB's expansion continued into diesel vehicles, with 1979 regulations limiting particulate matter from heavy-duty engines, further differentiating state rules from national ones. In the 1980s and 1990s, CARB advanced phased-in standards for light-duty vehicles, including onboard vapor recovery systems in 1982 to curb refueling emissions and enhanced durability requirements for emission controls. The board's authority grew under the 1976 Mulford-Carrell Act, which consolidated enforcement powers and funded expanded monitoring networks to verify compliance. By 1990, amid persistent non-attainment of federal ozone standards in multiple basins, CARB adopted the Low-Emission Vehicle (LEV) program, setting tiered limits that reduced non-methane organic gases by up to 75% and nitrogen oxides by 50-60% from prior levels for 1994-2003 model years. This included a Zero-Emission Vehicle (ZEV) mandate requiring 2% of sales by 1998 and 10% by 2003, driving early investment in battery-electric prototypes despite industry claims of technological infeasibility. Federal preemption battles escalated with the LEV/ZEV adoption, as automakers petitioned EPA to deny waivers, citing conflicts with national fuel economy goals under the Energy Policy and Conservation Act and alleging arbitrary enforcement. EPA approved the 1990 waiver in 1992 after reviewing CARB's health-based justifications, including epidemiological data linking vehicle emissions to respiratory illnesses, but subsequent amendments faced scrutiny; for example, a 1996 ZEV delay was negotiated amid manufacturer lawsuits threatening production halts. The 1990 Clean Air Act Amendments bolstered Section 177, allowing 13 other states to adopt CARB standards without waivers, amplifying California's influence but intensifying lobbying against perceived overreach. These efforts yielded measurable declines, with statewide vehicle emissions of reactive organic gases dropping 40% from 1980 to 1990, though legal and administrative frictions highlighted tensions between state innovation and federal commerce prerogatives.

2000s Onward: Shift to Climate and Broader Pollutants

In the early 2000s, the California Air Resources Board intensified efforts against diesel particulate matter (PM) and other toxic air contaminants, recognizing diesel PM as a primary contributor to cancer risks from air pollution. In September 2000, CARB adopted the Diesel Risk Reduction Plan, aiming for an 85% reduction in diesel PM emissions by 2020 through measures including lower-sulfur diesel fuel (limited to 15 ppm by 2006), engine retrofits, and fleet turnover requirements. This addressed diesel PM's role in approximately 70% of California's estimated cancer risk from toxic air contaminants, based on exposure assessments linking fine PM to respiratory and carcinogenic effects. Subsequent regulations included an Airborne Toxic Control Measure (ATCM) in 2004 limiting idling of diesel-fueled commercial vehicles to five minutes, reducing localized exposures near schools and communities. CARB expanded toxic controls via additional ATCMs targeting stationary and mobile sources, such as facilities and consumer products, contributing to statewide declines in toxic emissions. From 1990 to 2012, emissions of key toxic air contaminants like , 1,3-butadiene, and fell by 50-90%, driven by these measures alongside vehicle standards, though ambient concentrations varied by pollutant and region due to persistent sources like industrial operations. Diesel-focused rules, including the 2008 Truck and Bus regulation mandating PM and reductions from heavy-duty engines, further broadened pollutant coverage beyond traditional precursors to fine PM (PM2.5) and volatile organics, aligning with federal attainment efforts while prioritizing health risks from particulates. Parallel to toxics regulation, CARB pivoted toward (GHG) emissions in response to legislative mandates addressing . Assembly Bill 1493, enacted in 2002, directed CARB to develop standards reducing GHG from passenger vehicles, leading to the 2004 Pavley regulations requiring automakers to cut tailpipe CO2 emissions by up to 30% for 2009-2016 model years through efficiency improvements. These marked the first state-level GHG vehicle standards, emphasizing fuel economy's causal link to CO2 output, though implementation faced challenges resolved by EPA waivers in 2009. The 2006 Global Warming Solutions Act (AB 32) formalized CARB's climate authority, requiring reductions in statewide GHG emissions to 1990 levels by 2020—approximately 431 million metric tons of CO2 equivalent annually—via economy-wide regulations and market mechanisms. CARB's 2008 Scoping Plan outlined pathways including a cap-and-trade program (launched 2013), low-carbon fuel standards, and incentives, projecting a 15% cut below business-as-usual emissions. This shift integrated climate into CARB's mandate, expanding from localized air quality to global-scale pollutants like CO2, , and , while maintaining economic analyses to balance costs against projected benefits like avoided sea-level rise and temperature increases. Subsequent updates, such as the 2017 plan under Senate Bill 32 extending targets to 40% below 1990 levels by 2030, sustained this trajectory amid debates over regulatory stringency's impacts on energy prices and jobs.

Core Statutory Mission and Balancing Health with Economic Considerations

The Air Resources Board (CARB) was established under the Mulford-Carrell Air Resources Act, enacted in 1967 and codified primarily in Division 26 of the California Health and Safety Code (HSC §§ 39000 et seq.), to address as a statewide crisis requiring coordinated control beyond local jurisdictions. The core statutory mission, as articulated in HSC § 39002, directs CARB to achieve and maintain ambient air quality standards sufficient to protect and welfare from any known or anticipated adverse effects, including irritation, illness, or discomfort, while also safeguarding the environment and economic productivity. This mission emphasizes empirical control of criteria pollutants like , particulate matter, and nitrogen oxides, which were primary targets following the Act's passage amid severe episodes in and other basins that impaired visibility, , and by the mid-1960s. In pursuing this mission, CARB is statutorily required to balance imperatives with economic realities through feasibility assessments embedded in its rulemaking authority under HSC §§ 39600–39601, which mandate regulations that achieve the "maximum degree of emission reduction" while considering technological availability, cost-effectiveness, and impacts on employment and industry. For example, HSC § 43018 for standards explicitly directs CARB to adopt controls that are "feasible" based on existing and economic factors, ensuring standards do not impose undue burdens without corresponding gains. This balancing is operationalized via mandatory economic impact analyses, such as those required under the (CEQA) and CARB's own protocols, where proposed rules must quantify compliance costs—e.g., the 2022 Scoping Plan projected Advanced Clean Fleets regulations would slow by less than 1% annually through 2045 against a baseline 3.3% yearly expansion—against monetized benefits like reduced respiratory hospitalizations. Critics, including industry groups, argue that CARB's implementation often prioritizes stringent targets over rigorous economic scrutiny, as evidenced by waivers granted under federal Clean Air Act § 209 despite cost concerns, but statutory prioritizes causal reductions in pollutants linked to verifiable morbidity (e.g., ozone's role in 1,000–2,000 excess deaths annually in pre-regulation) while prohibiting rules deemed economically infeasible. CARB's board resolutions, such as Resolution 25-9 in September 2025, further underscore this by directing staff to identify "all feasible actions" integrating regulatory and non-regulatory measures to minimize economic disruption.

Delegated Powers and Oversight of Local Districts

The California Air Resources Board (CARB) oversees 35 local control districts (APCDs) and air quality management districts (AQMDs), which derive their authority from the California Health and Safety Code (HSC) Division 26 to regulate stationary, indirect, and area sources of criteria pollutants and toxic air contaminants within their jurisdictions. These districts handle permitting, compliance enforcement, and regional monitoring, while CARB coordinates statewide efforts and retains ultimate responsibility for compiling the State Implementation Plan (SIP) under the federal Clean Air Act. Local districts prepare jurisdiction-specific portions of the SIP, including air quality management plans (AQMPs), which CARB reviews for adequacy in achieving state ambient air quality standards before submission to the U.S. Environmental Protection Agency (EPA). CARB's oversight extends to reviewing variances granted by district hearing boards, ensuring they comply with HSC provisions such as not undermining attainment of air quality standards or federal requirements; this process involves thorough evaluation of each variance's technical and legal basis. Additionally, CARB monitors district regulatory adoption, maintaining a database of current rules to promote transparency and alignment with statewide policies, and can require districts to submit data or justify inaction on pollution controls. Under HSC §41500, CARB coordinates enforcement activities, retaining independent investigatory powers even as districts hold primary responsibility for stationary source violations, allowing intervention if local efforts prove insufficient. In cases of district regulatory gaps, CARB possesses authority to adopt supplementary statewide rules applicable -wide, as delegated under HSC provisions empowering the board to address persistent nonattainment areas; for instance, CARB has historically intervened on consumer products and certain where local rules lagged. This balances local tailoring of controls with state-level consistency, though districts retain operational independence in day-to-day permitting and inspections, subject to CARB audits and coordination mandates.

Interstate Influence via Section 177 and Federal Interactions

Section 177 of the Clean Air Act permits other states to adopt emission standards identical to those established by , but only after the Environmental Protection Agency (EPA) has granted California a under Section 209(b) of the Act. This provision enables non-California states to enforce CARB's regulations for criteria pollutants, greenhouse gases, and zero-emission vehicle requirements without violating , provided the adopting state has an EPA-approved State Implementation Plan and the standards do not impose inconsistent requirements on manufacturers. As of 2023, at least 17 states had adopted various CARB vehicle standards under this mechanism, creating a combined market representing approximately 30% of U.S. new vehicle sales and incentivizing manufacturers to produce compliant fleets nationwide to avoid segmented production lines. The adoption process has amplified CARB's influence beyond California, particularly for programs like the Advanced Clean Cars initiative, which integrates low-emission vehicle criteria with zero-emission mandates aiming for 100% zero-emission vehicle sales by 2035. States such as New York, Massachusetts, Oregon, and Washington have incorporated these standards into their air quality plans, often citing California's waiver-granted innovations in electric and hydrogen vehicle promotion as a model for addressing non-attainment areas. However, Section 177 does not extend to standards lacking a federal waiver, limiting adoption to waiver-approved measures and prompting legal challenges when states attempt to exceed or modify them. This interstate alignment has faced opposition from automobile manufacturers, who argue it imposes undue costs and market distortions, though proponents maintain it drives technological advancement without federal overreach. Federal interactions with CARB center on the Section 209(b) waiver process, where the EPA assesses whether California's standards are protective of , address compelling and extraordinary conditions unique to the state (such as severe in the ), and remain consistent with Clean Air Act sections. Since the 1970 Clean Air Act Amendments, the EPA has granted California over 75 waivers, enabling CARB to pioneer stricter tailpipe standards that other states could then adopt. Notable waivers include those for the 2022 Advanced Clean Trucks rule and the 2023 Advanced Clean Fleets regulation, though political shifts have led to revocations—such as the 2019 Trump administration denial of greenhouse gas and zero-emission vehicle waivers, later reversed by the Biden EPA in 2022—and recent 2025 Congressional Review Act resolutions blocking certain heavy-duty vehicle mandates. These interactions underscore tensions between state innovation and federal uniformity, with waiver decisions often litigated in federal courts, as seen in ongoing challenges to the 2023 Advanced Clean Cars II waiver request. CARB's waiver dependency highlights its reliance on EPA cooperation, where denials effectively halt Section 177 adoptions and force reliance on federal baselines.

Governance and Organizational Structure

Board Composition, Appointments, and Decision-Making

The California Air Resources Board is governed by a 16-member board comprising 14 voting members and 2 ex officio non-voting members selected from the state Legislature—one appointed by the Senate Committee on Rules and the other by the Speaker of the Assembly—to provide legislative oversight without voting rights. The 12 appointed voting members are nominated by the Governor and require confirmation by the California State Senate; these include five representatives from local air pollution control or air quality management districts, one from environmental interests, one from the motor vehicle manufacturing sector, one from the petroleum industry, one from agricultural interests, and three from the general public. This composition, established under state law, aims to balance regional, sectoral, and public perspectives in air quality policymaking. The selects one of the appointed members to serve as —the board's only full-time position—who directs staff, sets agendas, and represents the agency, serving at the 's discretion without a fixed term. Other appointed members serve staggered four-year terms to promote institutional continuity and may be reappointed upon Senate reconfirmation. Board members must disclose potential conflicts of interest, and no member may have a direct financial stake in regulated industries beyond their representational role. Decision-making occurs primarily through monthly public board meetings, with agendas posted at least 10 days in advance to allow stakeholder input via hearings, workshops, and written comments. A requires the presence of a majority of the total appointed voting members (at least eight of 14), and formal actions, such as adopting regulations or approving plans, pass by a simple majority vote of the . The board delegates routine implementation to executive staff but retains authority over major policy, enforcement priorities, and statewide standards, ensuring decisions reflect empirical air quality data and economic impact assessments as mandated by .

Executive Leadership and Key Divisions

The California Air Resources Board (CARB) is led by a 16-member governing board, consisting of 14 appointed voting members, including the , plus two non-voting ex officio members from the . The , appointed by the and confirmed by the , sets policy direction and presides over board meetings. As of October 1, 2025, Lauren Sanchez serves as , having previously advised Gavin on climate policy; she succeeded Liane M. Randolph, who retired after over 20 years in state leadership roles. Operational leadership falls under the Executive Office, headed by the , who manages day-to-day administration, implements board policies, and oversees approximately 1,300 staff across technical, regulatory, and enforcement functions. Steven S. Cliff, Ph.D., has held this position since summer 2022, bringing expertise in and prior roles in air quality research. Supporting Cliff are deputies such as Principal Deputy Executive Officer Courtney Smith and Deputy Executive Officer Edie Chang, who focuses on planning, freight, and related programs. CARB's structure includes several key divisions responsible for core functions in air quality regulation, emissions control, and enforcement:
  • Air Quality Planning and Science Division: Conducts monitoring, modeling, and research to assess pollutant levels and inform standards; operates statewide networks tracking criteria pollutants like and particulate matter.
  • Mobile Source Control Division: Develops and enforces regulations for , , and fuels, including zero-emission mandates and heavy-duty diesel strategies; branches cover incentives, regulatory development, and innovative technologies.
  • Industrial Strategies Division: Oversees stationary sources such as refineries and power plants, managing cap-and-trade programs, , and transportation fuels; includes branches for oil and gas, project assessment, and program supervision.
  • Enforcement Division: Investigates compliance, conducts audits, and imposes penalties for violations of emissions rules; handles field inspections and legal actions against non-compliant entities.
  • Emissions Certification and Compliance Division: Certifies and technologies, verifies emission reductions, and ensures adherence to labeling and requirements.
Additional offices, such as the Office of Community Air Protection and Administrative Services Division, support equity-focused initiatives and internal operations like and budgeting, respectively. This divisional framework enables CARB to address both mobile and stationary emissions sources while coordinating with 35 local air districts.

Headquarters and Operational Resources

The California Air Resources Board (CARB) maintains its primary headquarters at 1001 I Street in , serving as the central administrative hub for policy development, board meetings, and statewide coordination. This location houses key divisions, including the Standards Laboratory within the Monitoring and Laboratory Division, which conducts testing for air monitoring equipment and emissions standards. CARB's operations are centered at the Mary D. Nichols Campus in Riverside, dedicated on November 17, 2021, on a 19-acre site donated by the . This facility, spanning 402,000 square feet, consolidated seven prior locations in the area and accommodates up to 460 employees, with dedicated spaces for advanced emissions testing, heavy-duty vehicle test cells, and an advanced chemistry laboratory supporting research into and portable emissions measurement systems. Designed as the largest zero-net-energy laboratory building in the United States, it features 3.5 megawatts of solar generation, Platinum certification, and systems for efficient climate control. Operational resources include specialized laboratories under the Mobile Source Laboratory Division for vehicle emissions certification and compliance testing, alongside statewide air quality monitoring networks managed by the Monitoring and Laboratory Division. CARB employs approximately 2,000 personnel as of fiscal year 2025-26, distributed across administrative services, air quality planning, emissions compliance, and enforcement divisions to execute its regulatory and research mandates. These resources are funded through state appropriations, fees, and grants, enabling fieldwork, data analysis, and inter-agency oversight of local air districts.

Air Quality Assessment and Standards

Monitoring Networks and Data Collection

The California Ambient Air Monitoring Network, overseen by the California Air Resources Board (CARB), consists of more than 250 stations operated by state, federal, and local air districts to measure ambient concentrations of pollutants across the state. This network, maintained for over 50 years, ranks among the world's most extensive, enabling systematic tracking of air quality trends, attainment of standards, and identification of pollution sources. CARB serves as the primary coordinator and data repository, validating submissions from operators and ensuring compliance with federal requirements under the Clean Air Act. Monitoring targets criteria pollutants—ozone (O₃), fine particulate matter (PM₂.₅), inhalable particulate matter (PM₁₀), (NO₂), (SO₂), and (CO)—as defined by the U.S. Environmental Protection Agency, alongside toxic air contaminants, volatile organic compounds (VOCs), and meteorological parameters like and temperature at select sites. Stations are sited to represent population exposure, background levels, and source influences, with urban areas featuring higher density; for instance, PM₂.₅ monitors emphasize community-oriented locations to assess health risks from sources like and industry. Data from these sites inform State Implementation Plans (SIPs), regulatory adjustments, and advisories, with historical records showing declines in many pollutants since the due to emission controls. Collection methods include continuous analyzers using techniques such as photometry for O₃, for NO₂, and nondispersive for CO, providing near- every hour or less. PM₂.₅ employs federal reference method samplers that collect particles on filters over 24-hour periods, followed by gravimetric laboratory analysis for precise mass measurement, while PM₁₀ and coarse particles use similar filter-based approaches. Supplementary tools, like beta attenuation monitors, offer continuous PM estimates, and specialized sites capture toxics via canister sampling or passive for lab analysis. CARB's interactive mapping tool visualizes station locations and , audited quarterly for accuracy. Quality assurance is enforced through CARB's Primary Quality Assurance Organization, which conducts instrument audits, , and of calibration gases and equipment via its , established to meet federal precision and accuracy thresholds (e.g., ±10-15% for most criteria pollutants). Annual Network Plans, required for districts operating monitors, detail site rationales, pollutant selection, and maintenance protocols, with CARB reviewing for network sufficiency. This framework minimizes errors from instrument drift or siting biases, though challenges persist in capturing episodic events like wildfires, prompting integration of and mobile monitoring supplements. All validated data are archived and accessible via CARB's public portals, supporting research and enforcement without reliance on unverified modeling alone. The Air Resources Board (CARB) sets Ambient Air Quality Standards (CAAQS) for criteria pollutants— (O₃), coarse particulate matter (PM₁₀), fine particulate matter (PM₂.₅), (CO), (NO₂), (SO₂), and lead (Pb)—to protect , with standards often stricter or more comprehensive than federal (NAAQS). These CAAQS include additional averaging periods and pollutants like sulfates, , and visibility-reducing particles not covered federally. CARB's monitoring network collects data to assess compliance, designating areas as attainment (meeting standards), nonattainment, or unclassified based on three years of representative air quality metrics.
PollutantCAAQS (Key Thresholds)NAAQS (Current, as of 2024)Averaging Time
(O₃)0.07 ppm (8-hr); 0.09 ppm (1-hr)0.070 ppm (8-hr)8-hour daily max; 1-hour
PM₂.₅12 µg/m³ (annual arithmetic mean); 35 µg/m³ (24-hr)9.0 µg/m³ (annual); 35 µg/m³ (24-hr)Annual; 98th 24-hr
PM₁₀50 µg/m³ (annual); 50 µg/m³ (24-hr, expected exceedances ≤1/day)No annual; 150 µg/m³ (24-hr)Annual arithmetic mean; 24-hr
CO9.0 ppm (8-hr); 20 ppm (1-hr)9.0 ppm (8-hr); 35 ppm (1-hr)8-hour; 1-hour
NO₂0.18 ppm (1-hr)100 ppb (1-hr); 53 ppb (annual)1-hour; annual
SO₂0.25 ppm (1-hr); 0.04 ppm (24-hr)75 ppb (1-hr); 196 µg/m³ (3-hr, not to exceed more than once/year)1-hour; 24-hr; 3-hr
Pb1.5 µg/m³ (30-day, near sources)0.15 µg/m³ (rolling 3-month)30-day; 3-month
CAAQS and NAAQS levels as documented in CARB's Table of Standards (updated July 2024) and EPA's NAAQS table; California enforces both, with CAAQS predating and supplementing federal requirements. As of 2024 designations (effective following CARB's 2023-2024 updates), California has widespread nonattainment for ozone and PM under both state and federal standards, particularly in the South Coast Air Basin (Extreme nonattainment for 8-hour ozone, with attainment deadline extended to 2037 under federal law) and San Joaquin Valley (Extreme for ozone; Serious for PM₂.₅, with 2024 attainment determination pending data validation for the extended deadline of December 31, 2024). PM₁₀ nonattainment persists in areas like Owens Valley and parts of the San Joaquin Valley, while the new federal PM₂.₅ annual standard of 9 µg/m³ (effective May 2024) is expected to expand nonattainment boundaries, with CARB recommendations due to EPA by February 2025. In contrast, most areas achieve attainment for CO (statewide since 2010s), NO₂, SO₂, and Pb, reflecting effective controls on point sources and fuels. Long-term trends show substantial improvements in criteria pollutant concentrations since the 1970s, driven by CARB regulations on mobile and stationary sources, with statewide emissions of NOx (ozone precursor) declining 60-70% from 1990 to 2022 and CO emissions dropping over 90%. Peak 8-hour ozone levels have fallen 30-50% in urban basins like South Coast since 2000, though exceedance days remain high (e.g., 100+ days/year in nonattainment areas pre-2020, reduced but persistent post-COVID traffic dips). PM₂.₅ annual means improved 20-40% from 2000-2020 in monitoring sites, but recent years (2020-2024) exhibit stagnation or reversals due to wildfires, with 2025 Los Angeles fires causing acute spikes exceeding 100 µg/m³ 24-hour averages. NO₂ and SO₂ trends continue downward (28-53% reductions in urban areas since 2000), supporting attainment, while PM₁₀ trends vary regionally with dust and agriculture influences. Overall, CARB's emissions inventories and monitoring indicate progress toward standards but highlight ongoing challenges from precursors, climate-driven events, and stricter thresholds.

Toxic Air Contaminants Identification and Control

The California Air Resources Board (CARB) operates the Air Toxics Program under (AB 1807), enacted September 23, 1983, granting authority to identify toxic air contaminants (TACs) and adopt control measures without initial regard for cost or technological feasibility. TACs are airborne pollutants that may cause or contribute to increased mortality, serious illness, or substantial present or potential hazards to human health, distinct from criteria pollutants due to their focus on cancer and non-cancer health effects rather than widespread ambient standards. Identification follows a structured scientific process divided into and phases. CARB staff screen candidate substances nominated by the public, districts, or internally, preparing detailed reports on production, uses, emission sources, atmospheric persistence, and exposure pathways. The Office of Hazard Assessment (OEHHA) concurrently evaluates toxicological data, including animal studies, , and dose-response models, to determine potency factors for cancer and non-cancer risks. A draft document integrates these findings, undergoes and 45-day public comment, and culminates in a public hearing before the CARB Board, which votes to list the substance as a TAC if evidence shows significant risk potential. As of 2020, CARB has listed over 200 individual substances and groups, including (identified March 5, 1988), 1,3-butadiene (October 28, 1992), particulate matter (August 26, 1998), and methylene chloride (December 22, 1999). Control measures, known as Airborne Toxic Control Measures (ATCMs), target emission reductions from identified sources post-listing, incorporating feasibility and cost considerations absent in identification. CARB has adopted 26 ATCMs since the program's inception, regulating mobile sources (e.g., diesel engines via the 2008 Truck and Bus Regulation) and stationary sources (e.g., the 1990 Chromium Electroplating ATCM limiting emissions). These measures specify technologies like catalytic converters, vapor recovery systems, or emission caps, with enforcement delegated to local districts and CARB overseeing statewide compliance through inspections and reporting. Emission reductions from ATCMs have contributed to statewide TAC exposure declines, though localized hotspots persist near industrial and traffic corridors. CARB integrates TAC controls with broader emissions reporting via the Criteria and Toxics Reporting (CTR) Regulation, effective January 1, 2020, mandating annual facility submissions of TAC emissions data to inform prioritization and modeling. also involves community notifications under the Air Toxics Hot Spots Program (AB 2588, 1987), where facilities exceeding screening levels trigger health risk assessments, though CARB's role emphasizes statewide identification over site-specific remediation.

Mobile Source Emission Regulations

Light-Duty Vehicle Programs: LEV, ZEV, and Labeling Requirements

The Low-Emission Vehicle (LEV) program, adopted by the California Air Resources Board (CARB) in 1990, establishes fleet-average emission standards for light-duty passenger cars and light-duty trucks up to 6,000 pounds gross vehicle weight, targeting reductions in smog-forming non-methane organic gases (NMOG), , particulate matter, , and other criteria . Initial LEV I standards phased in for model years (MY) 1994 through 2003, followed by LEV II standards effective MY 2004, which tightened NMOG limits to 0.075 grams per mile for LEV-certified vehicles and introduced partial zero-emission vehicle (PZEV) categories with superior performance. LEV III standards, part of the 2012 Advanced Clean Cars (ACC) package, applied from MY 2015 to 2025, requiring near-zero evaporative emissions and NMOG fleet averages as low as 0.030 grams per mile by MY 2025 for partial credits toward zero-emission mandates. LEV IV standards, integrated into the 2022 Advanced Clean Cars II (ACC II) regulation, phase in from MY 2026 to 2030 with further NMOG reductions to 0.010 grams per mile or less, alongside supplemental federal controls, aiming for 50% cuts in criteria pollutant emissions from light-duty vehicles by 2040 relative to 2026 baselines. The Zero-Emission Vehicle (ZEV) program, also originating in CARB's 1990 LEV regulations, mandates that automakers produce and deliver an increasing percentage of zero-emission light-duty vehicles as a share of their California sales, enforced through a credit-trading system where deficits incur penalties and surpluses can be banked or sold. Qualifying ZEVs include (BEVs), electric vehicles (FCEVs), and hydrogen internal combustion engines, while electric vehicles (PHEVs) earn partial credits based on (e.g., up to 100% credit for vehicles with over 75 miles of range). Early mandates required 2% ZEV sales by MY 1998 (later relaxed), escalating to 10% by 2003 before revisions; the program was revitalized under ACC II in August 2022, requiring 35% of new light-duty vehicle sales to be ZEVs or PHEVs in MY 2026, rising to 68% by MY 2030 and 100% by MY 2035, with strict ZEV (non-PHEV) shares starting at approximately 13% in 2026 and reaching full compliance without hybrids by 2035. As of 2025, the regulation remains in effect despite federal challenges under , with CARB tracking compliance via quarterly credit dashboards showing over 1.5 million ZEVs delivered cumulatively by mid-2024. Automakers like Tesla generate excess credits, subsidizing compliance for others, though the program's reliance on utility-scale and mineral supply chains has drawn scrutiny for potential indirect emissions not fully accounted in tailpipe-focused metrics. Labeling requirements under these programs mandate that manufacturers affix durable emission control labels to certified light-duty vehicles, typically under the hood on the support or valve cover, detailing the engine family, emission standards met (e.g., "LEV III," "ULEV," or ""), calibration codes, and required maintenance intervals to ensure compliance verification during inspections. California-specific labels distinguish from federal ones by specifying CARB-executable standards, with vehicles failing to bear proper labels ineligible for registration; for compliance, additional window stickers or digital disclosures must indicate zero-emission capability and . These labels facilitate enforcement through CARB's Smog Check program and support consumer awareness, though critics note they do not convey full lifecycle emissions, focusing solely on tailpipe outputs. Non-compliance with labeling can result in denial or fines up to $10,000 per vehicle.

Heavy-Duty, Commercial, and Off-Highway Vehicle Rules

The Air Resources Board (CARB) imposes stringent emission controls on heavy-duty on-road vehicles, including trucks, buses, and commercial fleets, primarily through the Truck and Bus Regulation adopted in December 2008. This regulation targets in-use diesel-powered vehicles with a gross rating (GVWR) exceeding 14,000 pounds, mandating reductions in diesel particulate matter (PM), (NOx), and other criteria pollutants via engine upgrades, retrofits, or vehicle replacements. Compliance phases began in 2012 for PM filter installations and escalated through 2023, by which date all applicable vehicles operating in must be equipped with or newer model-year engines featuring advanced emission control systems, with limited exemptions for agricultural and small fleets. The rule has achieved substantial emission cuts, including an estimated 10 tons per day reduction in PM by 2020 and ongoing NOx decreases, enforced via annual reporting through the Transport Refrigeration Unit Compliance and Reporting System (TRUCRS) and fleet audits. Complementing these measures, the Clean Truck Check program, fully implemented by January 2024, establishes a statewide heavy-duty inspection and maintenance regime for diesel, alternative-fuel, and hybrid vehicles over 14,000 pounds GVWR operating on public roads. It requires biennial opacity or electronic testing at credentialed stations, roadside inspections, and to verify exhaust system integrity, with non-compliant vehicles barred from operation until repairs. This addresses post-manufacture tampering and deterioration, building on federal standards by incorporating California-specific limits and aiming to sustain emission reductions amid high-mileage use in commercial applications like and vocational trucking. For commercial and heavy-duty fleets, CARB's Advanced Clean Fleets regulation, adopted in 2022 and phased in from 2024, mandates progressive procurement of zero-emission vehicles (ZEVs) such as battery-electric or hydrogen fuel-cell trucks, with fleets required to achieve 100% ZEV sales by 2035 and other large fleets following suit by 2042. Manufacturers face sales quotas under the parallel Advanced Clean Trucks rule, starting at 5-9% ZEV penetration in 2024 and rising to 75% by 2035 for Class 2b-8 vehicles. These rules prioritize sectors with concentrated emissions, like and logistics operations, while offering reporting flexibilities and incentives, though compliance hinges on availability and feasibility. Off-highway vehicles and equipment, encompassing construction, agricultural, and industrial machinery with compression-ignition engines over 25 horsepower, fall under the In-Use Off-Road Diesel-Fueled Fleets Regulation adopted in 2007. Fleets with five or more applicable vehicles must inventory assets via the Diesel Off-Road Online Reporting System (DOORS), phase out pre-1976 engines entirely by 2028, and meet best available control technology (BACT) retrofits for NOx and PM in non-attainment areas. Since January 2023, all subject fleets are required to fuel exclusively with renewable diesel to curb PM and NOx, with exemptions for small engines or infeasible operations; the regulation projects a 75% NOx reduction from off-road sources by 2031 through attrition, repowers, and electrification mandates where feasible by 2035. Enforcement includes zone-specific restrictions in high-pollution areas and penalties for unreported fleets, reflecting CARB's focus on localized impacts from idling and intermittent operations. Additional standards for heavy-duty engines and vehicles, harmonized with U.S. EPA rules since 2008 and updated through 2027 model years, impose efficiency requirements like aerodynamic kits and low-rolling-resistance tires on tractor-trailers, achieving phased CO2 reductions of up to 25% from 2010 baselines. These on-road and off-highway frameworks collectively address the disproportionate contribution of heavy-duty sources—estimated at 30-40% of statewide despite comprising few vehicles—via technology forcing and fleet turnover, though implementation faces challenges from cost, grid capacity, and variable duty cycles.

Fuel Standards and Enforcement Mechanisms

The California Air Resources Board (CARB) promulgates fuel standards under authority granted by the California Clean Air Act to achieve emission reductions from combustion sources, focusing on properties that influence evaporative, toxic, and particulate emissions. For , the California Reformulated Phase 3 (CaRFG3) standards, adopted in March 2002 and effective March 1, 2003, eliminated oxygenates like methyl tertiary-butyl ether (MTBE) due to groundwater contamination risks while capping at 10 parts per million (ppm), at an annual average of 0.8 volume percent, and total aromatics alongside limits to curb formation and photochemical precursors. These specifications exceed federal reformulated requirements by emphasizing downstream averaging caps and predictive modeling for emission . Diesel fuel regulations, codified in Title 13, California Code of Regulations, section 2281 et seq., mandate ultra-low content at 15 ppm by weight for on-highway, most off-highway, and marine applications, phased in starting , 1993, with full compliance by 2006 in alignment with U.S. Environmental Protection Agency rules to enable particulate filters and aftertreatment in engines. Additional constraints include limits on polycyclic aromatic hydrocarbons (8% volume maximum) and (minimum 40) to reduce and improve combustion efficiency, with exemptions for certain backup generators or legacy equipment until retrofits. These standards apply to fuel produced, imported, or sold within , verified through documented transfer records tracing from refineries to end-users. Enforcement relies on CARB's Fuels Program, which deploys a statewide network for quarterly sampling at over 1,000 points including refineries, bulk terminals, pipelines, and retail stations, analyzed via and other ASTM-approved methods for compliance with , , and additive specifications. Non-conforming triggers immediate quarantines, mandatory reprocessing, or disposal orders, with enforced through producer-supplier agreements and electronic reporting to prevent adulteration or mislabeling. For diesel, targeted inspections at high-volume fleet depots and ports supplement general , integrating with emission testing to link quality to on-road performance. Penalties for violations are structured under Health and Safety Code sections 42400-42407, imposing fines up to $5,000 per vehicle or engine for -related non-compliance, escalating to $10,000 per day for ongoing breaches, with multipliers (up to fivefold) for negligent or intentional acts and minimum penalties of $1,000 for minor infractions; criminal sanctions apply for knowing distribution of adulterated . In 2022, CARB resolved 8,293 cases agency-wide, collecting $21.5 million in penalties, including fuels program actions for exceedances and formulation deviations, often via settlements requiring plans over outright litigation. Judicial remedies include temporary restraining orders and permanent injunctions against repeat offenders, coordinated with district attorneys and the California Attorney General, while self-reporting incentives under audit policies can reduce assessments for voluntary disclosures. This regime prioritizes deterrence through economic disincentives, with annual policy adjustments for inflation per statute.

Stationary and Area Source Regulations

Oversight of Industrial Emissions and Permits

The California Air Resources Board (CARB) exercises oversight over industrial emissions primarily through coordination with California's 35 local air districts, which hold primary authority for issuing permits to stationary sources such as factories and manufacturing facilities. These districts enforce rules limiting emissions of criteria pollutants and toxic air contaminants from industrial operations, requiring facilities to obtain Authorities to Construct (ATCs) and Permits to Operate (PTOs) that incorporate best available control technology (BACT) or best available retrofit control technology (BARCT) where applicable. CARB does not directly issue these permits but reviews district programs to ensure they align with statewide ambient air quality standards and support attainment plans, as mandated under the California Health and Safety Code. CARB's review authority extends to evaluating proposed and existing rules for stationary sources, particularly those impacting regional air basins or conflicting with mobile source regulations. For instance, state law empowers CARB to assess permitting thresholds and new source review (NSR) processes for sufficiency in non-attainment areas, as demonstrated in its 2025 review of the San Joaquin Valley Air Pollution Control 's stationary source programs, which analyzed emissions inventories and control strategies for facilities like refineries and power plants. CARB can disapprove rules that fail to meet state standards or hinder federal State Implementation Plan (SIP) compliance, ensuring uniform application of emission limits across . This oversight includes auditing data, with CARB providing and support to maintain consistent application of rules for pollutants like particulate matter and volatile organic compounds from industrial processes. For toxic air contaminants (TACs), CARB identifies substances via scientific review and adopts Airborne Toxic Control Measures (ATCMs) that districts must incorporate into permitting and operations for affected industries, such as semiconductor manufacturing or petroleum refining. Examples include the 1990s ATCM for chrome electroplating, which mandated emission capture efficiencies exceeding 99% and was enforced through district permits, reducing emissions by over 90% statewide by 2010. Districts report facility-specific TAC inventories to CARB under programs like AB 2588 (Air Toxics Hot Spots), enabling CARB to track cumulative risks and direct additional controls if district measures prove inadequate. This layered approach balances local flexibility with statewide accountability, though critics argue it can lead to permitting delays, with average ATC processing times exceeding 180 days in major districts as of 2023.

Low Carbon Fuel Standard: Mechanics and Updates

The Low Carbon Fuel Standard (LCFS), implemented by the California Air Resources Board effective January 1, 2011, establishes declining annual carbon intensity (CI) benchmarks for transportation fuels, requiring an average 20% CI reduction by 2030 from a 2010 baseline of 95.86 gCO₂e/MJ for gasoline and diesel equivalents. Carbon intensity measures lifecycle greenhouse gas emissions—including production, transportation, refining, and combustion—in grams of CO₂ equivalent per megajoule (gCO₂e/MJ), calculated via CARB-approved models such as CA-GREET3.0, which incorporate direct emissions, indirect land-use changes, and upstream energy inputs. Regulated entities, primarily fuel producers and importers, must ensure the statewide fuel pool meets benchmarks; fuels with CI below the benchmark generate tradeable credits (calculated as [benchmark CI - actual CI] × energy density × volume), while those above create equivalent deficits to be offset by credit purchases. Compliance operates through a market-based system where , verified quarterly and certified annually by independent third parties, can be banked (up to two years) or traded without restriction, though a Clearance Market enforces deficits if aggregate compliance fails, capped at three times the previous year's average price. also arise from approved pathways like biofuels (e.g., via OPGEE for oil production emissions), for zero-emission vehicles, , and fuels certified under simplified CI values, as well as non-fuel projects such as methane capture or supply equipment deployment. Entities submit quarterly reports by March 31, June 30, September 30, and December 31 via CARB's LCFS Reporting Tool, detailing fuel volumes, CIs, and transactions, with full annual verification due by April 30; non-compliance incurs penalties up to $20 per excess gCO₂e/MJ plus purchase costs. In November 2024, CARB approved amendments to the LCFS regulation, resubmitted to the Office of Administrative Law after an initial February 2025 disapproval, with final approval on June 27, 2025, and implementation effective July 1, 2025, applying revised benchmarks to fuels supplied in the third quarter of 2025 onward. These updates accelerate CI reduction targets through 2045, lowering benchmarks beyond the prior 2030 goal (e.g., targeting deeper cuts via enhanced stringency for fossil fuels while expanding credits for low-CI alternatives like sustainable aviation fuels and direct air capture integration), and introduce provisions for updated lifecycle analysis models to reflect technological advancements in low-carbon pathways. The amendments also refine credit generation mechanics, such as adjustments for electricity pathways tied to renewable sources and biofuels from waste feedstocks, aiming to incentivize zero-emission infrastructure while maintaining the program's market-driven enforcement. As of October 2025, CARB continues monitoring implementation, with FAQs updated September 15, 2025, addressing transitional reporting for the new benchmarks.

Cap-and-Trade System for GHGs and Criteria Pollutants

The California Air Resources Board's Cap-and-Trade Program, authorized under the Global Warming Solutions Act (AB 32) of 2006, imposes a statewide declining cap on (GHG) emissions from covered entities to achieve reductions aligned with statutory targets, including returning to 1990 levels by 2020 and further cuts of at least 40% below 1990 levels by 2030. The program, which began compliance reporting in 2012 and full enforcement on January 1, 2013, covers six GHGs— (CO₂), (CH₄), (N₂O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and (SF₆)—expressed in carbon dioxide equivalent (CO₂e) units. It targets emissions from electric power generation (including imports), large industrial facilities emitting over 25,000 metric tons of CO₂e annually, and upstream fuel distributors covering transportation, commercial, and residential combustion, encompassing approximately 85% of the state's GHG emissions. The system does not establish caps or trading mechanisms for criteria pollutants such as nitrogen oxides (NOx), sulfur oxides (SOx), particulate matter, or precursors, which are regulated separately through facility-specific permits, best available control technology requirements, and local air district rules. Covered entities must comply with existing criteria pollutant limits alongside GHG obligations, with no evidence of systematic increases in local criteria emissions attributable to the program. The program's mechanics center on allowances, each authorizing one metric ton of CO₂e emissions, with the annual —initially set at about 478 million allowances in 2013—declining progressively through 2030 and beyond to enforce reductions. Allowances are distributed via free allocations to emissions-intensive, trade-exposed industries (phasing down over time), quarterly public auctions (generating revenue for clean energy and transit investments), and limited offsets from verified protocols such as improved or capture, capped at 4% of compliance obligations for most entities (8% for ). Entities report verified emissions annually through the Compliance Instrument Tracking System Service (CITSS) and retire allowances or offsets equal to their emissions by specified deadlines, with provisions for banking unused allowances indefinitely but three-year use limits on certain early allocations. Trading occurs over-the-counter or via exchanges, with price containment reserves releasing additional allowances at escalating floors (starting at $22.50 per allowance in , adjusted for inflation) to prevent excessive volatility. In September 2025, the California Legislature extended the program through 2045—renaming it the "Cap-and-Invest Program"—to align covered emissions with net-zero GHG goals by 2045, while tightening offset eligibility, increasing minimum prices to $25 per allowance, and directing more proceeds (over $20 billion since inception) toward communities, zero-emission vehicles, and prevention. The system links with Quebec's cap-and-trade market under the Western Climate Initiative, enabling cross-border allowance use since 2014, which has facilitated about 10-15% of compliance instruments from external sources at times. While designed solely for GHGs, the program's coverage indirectly incentivizes shifts away from high-carbon sources that also emit criteria pollutants, though empirical analyses indicate co-benefits for local air quality are incidental and not assured without targeted controls.

Greenhouse Gas and Climate Initiatives

Scoping Plans and Long-Term Targets

The California Global Warming Solutions Act (AB 32), enacted in 2006, mandates the California Air Resources Board (CARB) to develop and update a Scoping Plan at least every five years to identify strategies for achieving greenhouse gas (GHG) emission reduction targets, including returning emissions to 1990 levels by 2020. The initial 2008 Scoping Plan outlined measures across sectors such as transportation, electricity, industry, and agriculture to meet the 2020 goal, emphasizing cap-and-trade, low-carbon fuels, and efficiency standards, with projected reductions of approximately 28.5 million metric tons of CO2 equivalent annually by 2020. California achieved the 1990 levels target ahead of schedule in 2016, though per capita emissions remained higher than the national average due to population growth. Subsequent updates incorporated stricter interim goals under Senate Bill 32 (2016), which codified a 40% reduction below 1990 levels by 2030. The 2017 Scoping Plan refined pathways, relying on expanded , zero-emission vehicles, and capture, estimating compliance costs of $76 billion but potential health benefits exceeding $100 billion. The most recent 2022 Scoping Plan, adopted in December 2022, accelerates reductions to 48% below 1990 levels by 2030 and charts a sector-specific roadmap—projecting 85% cuts in anthropogenic GHGs by 2045 through , biofuels, and carbon capture—while addressing equity via community investments. Long-term targets evolved from Executive Order S-3-05 (2005), aiming for an 80% reduction below 1990 levels by 2050, to B-55-18 (2018), which sets carbon neutrality no later than 2045, defined as balancing residual emissions with removals like offsets. The 2022 Scoping Plan aligns with this by modeling net-zero scenarios, including 100% clean electricity by 2045 and near-elimination of combustion, though implementation depends on technological feasibility and federal alignment. These plans integrate with broader policies but face scrutiny over assumptions of unproven scales in and , with CARB-required updates every five years to track progress against inventory data showing 2022 emissions at 336 million metric tons CO2 equivalent.

Incentives, Credits, and Alternative Fuel Programs

The California Air Resources Board (CARB) administers various programs to promote the adoption of zero-emission and low-carbon vehicles and fuels, primarily funded through cap-and-trade auction proceeds under the California Climate Investments initiative. These programs include rebates, vouchers, and credit trading mechanisms designed to offset the higher upfront costs of technologies and encourage shifts away from conventional fuels. For instance, the Clean Vehicle Rebate Project (CVRP), launched in 2010 and closed to new applications on November 8, 2023, provided point-of-sale rebates ranging from $1,000 to $7,500 for eligible battery-electric, , and vehicles, disbursing over $1.4 billion and supporting more than 500,000 vehicle purchases or leases by incentivizing consumer adoption in the light-duty sector. A core incentive mechanism is the credit trading system under the Low Carbon Fuel Standard (LCFS), which generates tradable credits for fuels with carbon intensities below mandated benchmarks, equivalent to one metric ton of CO2-equivalent reduction per credit. Fuel producers and importers exceeding the average carbon intensity standard incur deficits and must purchase credits from those generating surpluses through low-carbon alternatives like electricity for vehicles, hydrogen, biofuels, or renewable diesel; since inception in 2011, the program has generated credits valued at over $22 billion, with prices fluctuating based on supply and demand, recently capped to limit pass-through costs to consumers under 2024 amendments. These credits incentivize infrastructure for alternative fuels, including enhanced rewards for zero-emission vehicle charging and hydrogen refueling stations, as updated in November 2024 to accelerate deployment. For heavy-duty applications, the Hybrid and Zero-Emission Truck and Bus Voucher Incentive Project (HVIP) offers vouchers up to $120,000 per vehicle to offset incremental costs for battery-electric, fuel cell, and hybrid trucks, prioritizing small fleets with 20 or fewer vehicles and operations near ports. Complementary programs target underserved communities, such as Clean Cars 4 All, which provides grants up to $9,500 plus financing assistance for low-income residents in disadvantaged areas to scrap older polluting vehicles for cleaner alternatives, including electric models. CARB also enforces standards for alternative fuels like (LPG) and supports development to meet zero-emission mandates, integrating these with LCFS pathways for biogas-derived and crop-based biofuels while imposing safeguards on credit generation to prevent over-reliance on high-land-use feedstocks. Overall, these initiatives aim to reduce transportation sector by fostering market demand for alternative fuels, though program efficacy depends on credit values, funding availability, and infrastructure scalability.

Integration with Broader State Energy Policies

The California Air Resources Board (CARB) integrates its air quality and greenhouse gas (GHG) regulations with broader state energy policies primarily through coordination with the California Energy Commission (CEC) and the (CPUC), focusing on aligning transportation electrification, deployment, and electricity sector decarbonization. Under the Clean Energy and Pollution Reduction Act of 2015 (Senate Bill 350), CARB establishes annual GHG emission reduction targets for the electricity sector in collaboration with the CEC and CPUC, ensuring that power generation aligns with statewide climate goals such as reducing emissions to 40% below 1990 levels by 2030. This coordination extends to infrastructure development, including joint workgroups with the CEC to support zero-emission vehicle charging and hydrogen fueling networks, which address the increased electricity demand from CARB's Zero-Emission Vehicle (ZEV) mandates. CARB's cap-and-trade program, implemented under Assembly Bill 32 (2006), directly interfaces with energy policies by allocating free compliance instruments to electricity providers and natural gas distributors, incentivizing a shift toward low-carbon generation while linking to Senate Bill 100's requirement for 100% clean electricity by 2045. The program's coverage of combustion emissions from imported electricity further ties it to interstate energy imports, promoting alignment with CEC-led integrated resource planning that incorporates renewables and storage to meet CARB's sectoral targets. Additionally, CARB's Low Carbon Fuel Standard (LCFS) encourages low-carbon alternatives like biofuels and electricity for transportation, which complements CEC programs for renewable energy in agriculture and heavy-duty applications, such as the $225 million funding pool for off-road equipment electrification. The 2022 Scoping Plan for Achieving Carbon Neutrality exemplifies this integration by modeling pathways that synchronize CARB's measures with energy sector transformations, including a phasedown of in-state oil refining by 2045 and expanded clean power procurement to offset transportation loads projected to double demand by mid-century. Joint initiatives, such as the Hybrid and Zero-Emission and Bus Project (HVIP) set-asides for school buses, demonstrate practical coordination where CARB provides air quality expertise and CEC contributes energy planning and funding to accelerate fleet transitions without overburdening . However, this alignment has faced scrutiny for potential reliability risks, as rapid ZEV adoption under CARB rules strains CEC-overseen transmission infrastructure, prompting integrated assessments in SB 350 updates to balance emissions reductions with .

Controversies and Criticisms

Economic Costs: Fuel Prices, Job Losses, and Industry Burdens

The (LCFS), implemented by the California Air Resources Board (CARB) in 2011 and amended in 2024 with targets for 30% carbon intensity reduction by 2030 and 90% by 2045, has contributed to higher transportation fuel prices through mandatory credits for low-carbon alternatives, with compliance costs typically passed to consumers. Recent LCFS amendments, effective July 1, 2025, are projected to add 5 to 8 cents per gallon to gasoline and diesel prices in the near term, amid declining credit prices around $70 per metric ton of CO2 equivalent in early 2025 that have moderated but not eliminated passthrough effects. Broader regulatory pressures, including refinery maintenance restrictions and biofuel mandates, exacerbate this, with analyses forecasting gasoline prices exceeding $8 per gallon by 2026 due to supply constraints from closures. Job losses in California's sector have accelerated under CARB's emissions rules, which critics attribute to squeezed margins and operational constraints like mandated inventory stockpiles during maintenance. The 2020 closure of the Marathon refinery displaced workers who, per surveys, secured reemployment but at reduced wages averaging 20-30% lower, highlighting mismatches in transitioning to alternative sectors. Subsequent announcements include Valero's Benicia shutdown by April 2026, eliminating operations at a 145,000-barrel-per-day facility and affecting hundreds of high-wage positions (often over $100,000 annually for non-degree holders). These displacements, numbering in the thousands across recent closures, stem from policies favoring and renewables, with limited retraining efficacy despite state pilots funded at $20 million in 2022-2023. Industry burdens extend to compliance with cap-and-trade, extended through 2045, requiring emitters to acquire allowances or offsets covering up to 6% of obligations, with administrative complexities adding overhead for sectors like and utilities. Refineries face heightened reporting and shutdown controls, contributing to exit decisions amid low-carbon mandates. Agriculture incurs elevated diesel costs from LCFS-driven shifts, potentially raising operational expenses by tens of cents per and threatening viability if prices hit $8-10, as warned by farm leaders. These policies impose regressive effects, disproportionately burdening low-income households and fuel-dependent industries without commensurate short-term emissions offsets from leakage to unregulated fuels.

Effectiveness Debates: Empirical Outcomes vs. Projected Benefits

Critics of the California Air Resources Board (CARB) contend that its regulatory projections often inflate anticipated environmental gains while empirical data reveal more modest outcomes, particularly when accounting for factors like technological advancements and economic leakage. For instance, CARB's models for programs like the Cap-and-Trade system and (LCFS) forecast substantial (GHG) reductions based on assumed compliance pathways and high social costs of carbon, yet actual statewide GHG emissions in 2022 remained approximately 13% below 2004 levels—far short of the 40% reduction below 1990 levels targeted for 2030. Independent analyses, including those by economists like Severin Borenstein, argue that such projections overlook global leakage, where emissions shift to less-regulated jurisdictions, diminishing California's net climate impact. Air quality improvements provide a clearer empirical success story, with fine particulate matter (PM2.5) exposure declining 65% statewide since 2000 and toxic air contaminants reduced by 78% from 1998 to 2022, correlating with lower attributable mortality rates. However, CARB's attribution of these gains primarily to its standards—such as emissions controls and goods movement regulations—faces scrutiny, as national technological shifts, including catalytic converters and , drove similar reductions elsewhere without equivalent mandates. California's South Coast Air Basin continues to violate federal ozone standards, with exceedance days persisting despite decades of rules, suggesting geographic factors (e.g., inversion layers) and limit further progress beyond what cleaner technologies alone achieve. Projections from CARB's early plans anticipated attainment of all standards by the , yet non-attainment persists in eight areas as of 2023, highlighting overoptimism in modeling assumptions. For GHG initiatives, empirical reductions lag projections amid implementation challenges. The Cap-and-Trade program, launched in 2013, coincided with a 5.3% statewide drop in emissions through 2017, largely in power generation via renewable shifts, but isolating its causal role proves elusive amid concurrent federal incentives and falling solar costs. By 2022, total emissions exceeded the 2030 trajectory by 111 million metric tons CO2e annually, with transportation—the LCFS's focus—showing stalled declines until recent uptake, partly offset by increased credits whose lifecycle GHG savings are debated due to indirect land-use changes. The LCFS aimed for a 10 grams CO2e per megajoule carbon intensity cut by , achieving partial compliance through credits, but studies indicate actual savings fall short of modeled benefits when factoring demand inelasticity and higher fuel costs (adding $0.10–$0.65 per ), which may induce cross-border leakage without global caps.
ProgramProjected Benefit (e.g., by CARB Models)Empirical Outcome (as of 2022–2023)
Cap-and-Trade~25% of 2030 GHG cuts; full sectoral coverage reducing emissions to cap levels5.3% statewide drop (2013–2017); power sector gains but uncertain attribution amid renewables boom; total emissions off 2030 pace
LCFS20% transport fuel CI reduction by 2030; billions in avoided emissionsPartial CI declines via credits; net savings questioned by lifecycle analyses; fuel price hikes without proportional demand reduction
Proponents cite co-benefits like localized health gains from reduced criteria pollutants, yet detractors, drawing on peer-reviewed economic modeling, emphasize that CARB's layered regulations yield —high compliance burdens for marginal global GHG impacts—compared to revenue-neutral carbon pricing, which projections suggest could achieve similar cuts at lower cost. This tension underscores a broader : while empirical air toxics data validate some rules' efficacy, GHG outcomes reveal projections' vulnerability to behavioral responses and external drivers, prompting calls for rigorous, independent counterfactual analyses over agency self-assessments. The California Air Resources Board (CARB) has faced accusations of regulatory overreach, particularly in imposing stringent emissions standards on heavy-duty vehicles and that critics argue exceed state and intrude on federal or interstate . In August 2025, the U.S. Department of Justice filed lawsuits against CARB, alleging the agency continued enforcing truck emissions standards invalidated by federal actions, including the revocation of California's Clean Air Act waivers under the Trump administration. These suits contend that CARB's persistence in applying rules like the Advanced Clean Trucks regulation represents an unlawful extension of state power, potentially disrupting national supply chains and raising compliance costs without commensurate federal approval. Similarly, CARB's 2024 locomotive emissions rule has been criticized as an overreach due to the immaturity of zero-emission technologies, forcing railroads to adopt unproven systems that could halt freight operations across state lines. Critics, including trucking industry groups and federal lawmakers, have highlighted CARB's influence extending beyond California borders via Section 177 states adopting its standards, prompting legislative responses like the proposed Stop CARB Act in 2025 to curtail the agency's ability to set de facto national rules. The expressed antitrust concerns in August 2025 over CARB's Clean Truck Partnership, which involved manufacturers agreeing to phase out diesel engines, viewing it as coercive collaboration that threatens competition and innovation in the sector. Proponents of these criticisms argue that CARB's approach prioritizes aggressive decarbonization targets over empirical feasibility, leading to mandates like zero-emission truck requirements by 2035 that impose billions in retrofitting costs on small operators without adequate technological alternatives. Transparency issues have compounded these concerns, with CARB accused of opacity in rulemaking processes, particularly ahead of decisions impacting fuel prices and economic sectors. In October 2024, state Senator Rosilicie Ochoa Bogh publicly demanded greater disclosure from CARB regarding the Low Carbon Fuel Standard amendments, citing the board's rejection of requests for detailed economic impact analyses that could justify projected gasoline price hikes of up to 85 cents per gallon. CARB's resistance to providing full data on compliance costs and alternatives prior to its November 2024 vote drew bipartisan criticism for undermining public trust and legislative oversight. A CARB board member, John Dickerson, opposed the amendments in November 2024, arguing that the lack of transparent, peer-reviewed modeling failed to demonstrate protections for vulnerable communities or accurate emissions reductions. Legal challenges to CARB's authority have proliferated, encompassing suits over fuel standards, disclosures, and equipment mandates. Environmental groups filed a in July 2025 against CARB's updated , claiming the agency violated state law by expanding credits for unproven biofuels without sufficient safeguards against or food price inflation. Challenges to CARB's disclosure laws under SB 253 and SB 261 persisted into 2025, with suing in October 2025 on First Amendment grounds, arguing the mandates compel speech on speculative risks without clear evidentiary thresholds. A federal court denied a preliminary against these laws in August 2025 but allowed the case to proceed, highlighting ongoing disputes over CARB's interpretive authority. Additional litigation targets CARB's zero-emission , alleging it arbitrarily burdens intrastate by mandating battery-electric models incompatible with certain industrial applications as of January 2025. These cases underscore tensions between CARB's expansive regulatory scope and requirements for statutory fidelity, with outcomes potentially reshaping state-federal environmental dynamics.

Recent Developments

2024-2025 LCFS Amendments and Implementation Hurdles

In November 2024, the California Air Resources Board (CARB) approved amendments to the (LCFS), accelerating carbon intensity (CI) reduction targets for transportation fuels to align with California's climate goals. The revisions mandate a 30% CI reduction by 2030 from the 2010 baseline, up from the prior 20% target, and a 90% reduction by 2045, compared to 85% previously. To address the accumulated credit bank—standing at nearly 29.19 million credits by Q2 2024—a one-time 9% step-down in the 2025 annual CI benchmarks was introduced, resulting in a 13.75% reduction target for the first half of 2025 under legacy rules, escalating to 22.75% from July 1 onward. These changes, filed with the (OAL) on January 3, 2025, faced initial rejection on February 18, 2025, due to regulatory clarity deficiencies, including ambiguous language, undefined terms, and formatting issues, necessitating resubmission and delaying full implementation until OAL approval on June 27, 2025, with an effective date of July 1, 2025, applying to fuels supplied in Q3 2025 and later. Implementation hurdles emerged prominently during the regulatory review and market transition phases. The OAL's disapproval prompted CARB to revise provisions for precision, highlighting ongoing challenges in drafting enforceable rules amid complex CI pathways and generation mechanisms, which delayed market certainty and contributed to LCFS volatility—rising from lows near $40 per metric to around $75 in of tighter standards. Fuel producers reported potential increases of approximately 10 cents per attributable to the amendments, exacerbating debates over cost pass-through to consumers, as deficits from higher-CI fuels like outpace generation from alternatives. Although 2024 compliance obligations were met without a credit clearance market—yielding a net bank of 37.97 million metric s through Q4—no deficits materialized that year, but the amendments' -supply constraints risk future shortfalls absent scaled low-CI production. Judicial and operational challenges further complicate rollout. Ongoing lawsuits question the amendments' economic impacts and procedural validity, with critics arguing that accelerated targets impose undue burdens on refiners and importers without commensurate low-carbon fuel supply growth, potentially diverting resources from broader emissions reductions. CARB has issued FAQs and anticipates additional guidance for compliance, but fluctuating prices—dependent on market dynamics—undermine incentives for biofuels and , as noted in analyses of similar programs. Cumulatively, through Q4 2024, the LCFS generated 193.48 million against 155.51 million deficits, but post-amendment stringency could strain this balance if production lags, prompting calls for enhanced transparency in CI modeling and offset crediting to mitigate unintended price spikes.

Mobile Source Strategy Updates and Clean Fleet Mandates

The California Air Resources Board (CARB) released a discussion draft of the 2025 Mobile Source Strategy (MSS) on October 11, 2024, outlining an integrated framework to accelerate deployment of zero-emission and cleaner mobile sources across sectors including light-duty vehicles, medium- and heavy-duty trucks, off-road equipment, and locomotives to meet state air quality standards and reduction targets under the 2022 Scoping Plan. The strategy builds on the MSS by emphasizing pathways for emissions reductions through technology deployment, infrastructure expansion, and regulatory alignment, with public webinars held in October 2024 to gather input amid ongoing development paused for further evaluation as of late 2025. It projects the need for rapid scaling of zero-emission vehicles (ZEVs), such as achieving significant market penetration in heavy-duty sectors by 2030-2045, though specific enforceable targets remain under refinement to address feasibility gaps in supply chains and grid capacity. A core component of mobile source efforts is the Advanced Clean Fleets (ACF) regulation, adopted by CARB in 2023 and effective from that date, which mandates state and local government fleets to transition to ZEVs for medium- and heavy-duty vehicles on a phased schedule starting January 1, 2024, by replacing retiring vehicles with ZEVs based on , mileage, or engine hours thresholds. The rule initially required public fleets to reach 100% ZEV sales for new purchases by 2027, complementing manufacturer sales mandates under the Advanced Clean Trucks regulation, with reporting obligations for fleets exceeding 15 vehicles to track compliance via annual submissions. Provisions also targeted high-priority fleets like trucks and private operators in nonattainment areas, aiming for zero-emission operations by 2035-2042 depending on vehicle class. In September 2025, CARB approved amendments to the ACF regulation to introduce compliance flexibility, such as extended timelines and alternative reporting for public fleets, while repealing enforcement mechanisms for private, federal, and certain fleets due to the January 13, 2025, withdrawal of the state's EPA waiver request under Section 209 of the Clean Air Act, which had been necessary to preempt . The amendments delay the full mandate for state and fleets from 2027 to 2030, allowing continued of zero-emission technologies where feasible while addressing supply shortages and limitations, with the board citing the need to maintain progress amid federal regulatory uncertainty. These changes effectively limit ACF's scope to intrastate public operations not requiring waivers, reducing projected adoption rates for affected private sectors until potential future authorizations.

Climate Disclosure Regulations and Ongoing Federal Tensions

In 2023, enacted Senate Bill 253, the Climate Corporate Data Accountability Act, mandating that entities with annual global revenues exceeding $1 billion and doing business in the state annually disclose their Scope 1, Scope 2, and Scope 3 beginning with data from fiscal year 2025. The (CARB) is authorized to develop implementing regulations, including verification requirements such as limited assurance for Scope 1 and 2 emissions in initial reporting years, and to establish a digital reporting platform for submissions. CARB must also assess annual fees from covered entities to fund program administration, with reporting deadlines proposed for June 30, 2026, for the first disclosures. CARB's rulemaking process has faced delays; originally required to adopt regulations by January 1, 2025, the deadline was extended to July 1, 2025, via subsequent legislation, but as of October 2025, draft regulations for Scope 1 and 2 emissions verification remain pending until the first quarter of 2026. workshops, including one on August 21, 2025, addressed guidance on covered entities, exemptions, and minimum disclosure standards, while a preliminary list of approximately 5,500 potentially affected companies was published in September 2025 based on revenue thresholds. Scope 3 emissions reporting, which encompasses indirect value chain emissions and poses methodological challenges due to data aggregation from third parties, is required without initial assurance but subject to future regulatory refinement by CARB. Federal tensions stem from lawsuits alleging that SB 253 unlawfully intrudes on exclusive federal authority over air pollution regulation under the Clean Air Act's Supremacy Clause, as states lack independent authority to mandate GHG emissions disclosures that effectively regulate emissions sources nationwide. In January 2024, the U.S. Chamber of Commerce and other business groups filed suit in the U.S. District Court for the Northern District of California, arguing preemption because the law compels disclosures akin to federal GHG permitting and reporting under the EPA, while also claiming extraterritorial overreach on out-of-state activities. The court dismissed preemption and extraterritoriality claims in early 2025 but denied a preliminary injunction against implementation in August 2025, prompting an appeal to the Ninth Circuit; plaintiffs contend the laws conflict with the SEC's scaled-back federal climate disclosure rule, vacated in part by the Eighth Circuit in 2024 and further limited under the incoming Trump administration. ExxonMobil joined challenges in October 2025, asserting that CARB's rules under SB 253 impose unconstitutional burdens on interstate commerce by requiring detailed Scope 3 data that influences national supply chains without federal consent. Proponents, including CARB, maintain the disclosures are purely informational and do not directly regulate emissions, thus avoiding preemption, though critics highlight empirical difficulties in verifying Scope 3 figures, which often rely on estimates prone to inconsistency across jurisdictions. These disputes underscore broader conflicts between California's expansive state-level mandates and federal primacy in environmental reporting, with potential for Supreme Court review if appeals escalate.

Overall Impacts and Evaluations

Environmental and Health Results: Verifiable Data and Causal Analysis

California's ambient concentrations of key criteria pollutants have declined substantially since CARB's formation, with statewide levels decreasing by approximately 25% from 1990 to 2020 and fine particulate matter (PM2.5) dropping by over 40% in the same period, based on monitoring data from state and federal networks. These reductions align with CARB's implementation of stricter vehicle emissions standards under Clean Air Act waivers, which have accelerated turnover to cleaner technologies beyond federal baselines. However, national trends show similar proportional declines in pollutants like (NO2) and PM2.5 across the U.S., suggesting shared drivers such as catalytic converters and fuel reforms mandated federally since the 1970s, which complicates isolating CARB's unique causal contributions. Peer-reviewed analyses attribute specific portions of improvements to CARB policies; for example, aggressive controls from to correlated with a 65% modeled reduction in statewide average PM2.5 exposure, though socioeconomic disparities in exposure persisted in overburdened communities. In , goods movement emission controls under CARB's 2007 led to 28-53% NO2 declines and PM2.5 reductions between 1994 and 2011, outperforming non-targeted areas in quasi-experimental designs. Causal inference relies on difference-in-differences methods comparing regulated versus unregulated zones or states adopting California's standards, indicating additive effects from waiver-enabled rules, yet confounders like economic slowdowns and variability limit full attribution. Health outcomes show correlations with these air quality gains, including reduced visits for respiratory issues following targeted interventions; a study of CARB-influenced policies in disadvantaged areas found decreased ambient NO2, PM2.5, and CO levels alongside lower asthma-related healthcare utilization. Diesel particulate matter (DPM) cancer risks fell significantly from 2012 to 2017, linked to fleet modernization mandates, with population-weighted exposures dropping amid stricter standards. from port-area regulations demonstrates averted premature deaths and morbidity, estimated via concentration-response functions from epidemiological data, though many such analyses originate from regulatory proponents and may overestimate benefits by assuming linear dose-responses without thresholds. Despite progress, retains multiple non-attainment basins for and PM2.5 under federal standards as of 2023, underscoring that CARB measures have not fully resolved chronic exceedances driven by geography and persistent sources.

Societal Trade-Offs: Equity, Innovation, and Unintended Consequences

CARB's regulatory framework, including cap-and-trade programs and zero-emission vehicle mandates, has raised equity concerns by imposing regressive costs that disproportionately affect low-income households and communities of color. The cap-and-trade system functions as a , with limited revenue recycling to offset impacts on vulnerable populations, resulting in higher and transportation expenses that exacerbate economic disparities. Similarly, electric vehicle rebates and incentives have primarily benefited affluent buyers, with new car purchasers—including EV adopters—skewing toward higher-income demographics, while low-income and minority groups face barriers like upfront costs and limited charging access. Racial and ethnic minorities own fewer zero-emission vehicles, even in areas, leading to uneven air quality benefits despite targeted programs. On innovation, CARB's zero-emission vehicle regulations have accelerated advancements in battery and electric powertrain technologies by mandating increasing sales shares, contributing to California's leadership in EV production and deployment. These policies created market demand that spurred companies like Tesla to scale operations, fostering iterative improvements in vehicle range and affordability. However, compliance costs have strained traditional automakers, potentially diverting resources from diverse low-carbon alternatives like or advanced biofuels, and reliance on state waivers has introduced regulatory uncertainty that hampers long-term R&D investment. Unintended consequences include operational disruptions in freight and trucking sectors, where zero-emission mandates overlook infrastructure gaps and economic realities for small operators, leading to potential inefficiencies and higher costs passed to consumers. Carbon offset mechanisms in low-carbon fuel standards risk over-crediting indirect emissions reductions, such as from biofuels, without verifiable lifecycle benefits, potentially undermining actual cuts. Additionally, accelerated EV adoption has strained the state's grid and increased dependence on imported components, amplifying vulnerabilities to supply disruptions without proportional gains in domestic resilience.

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