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Formaldehyde
Formaldehyde
Formaldehyde
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Formaldehyde
Structural formula of formaldehyde (with hydrogens)
Structural formula of formaldehyde (with hydrogens)
Spacefill model of formaldehyde
Spacefill model of formaldehyde
Ball and stick model of formaldehyde
Ball and stick model of formaldehyde
Names
Preferred IUPAC name
Formaldehyde[1]
Systematic IUPAC name
Methanal[1]
Other names
  • Methyl aldehyde
  • Methylene glycol (diol forms in aqueous solution)
  • Methylene oxide
  • Formalin (aqueous solution)
  • Formol
  • Carbonyl hydride
  • Methanone
  • Oxomethane
  • Formic aldehyde
Identifiers
3D model (JSmol)
1209228
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.000.002 Edit this at Wikidata
EC Number
  • 200-001-8
E number E240 (preservatives)
445
KEGG
MeSH Formaldehyde
RTECS number
  • LP8925000
UNII
UN number 2209
  • InChI=1S/CH2O/c1-2/h1H2 checkY
    Key: WSFSSNUMVMOOMR-UHFFFAOYSA-N checkY
  • InChI=1/CH2O/c1-2/h1H2
    Key: WSFSSNUMVMOOMR-UHFFFAOYAT
  • C=O
Properties[7]
CH2O
Molar mass 30.026 g·mol−1
Appearance Colorless gas
Density 0.8153 g/cm3 (−20 °C)[2] (liquid)
Melting point −92 °C (−134 °F; 181 K)
Boiling point −19 °C (−2 °F; 254 K)[2]
400 g/L
log P 0.350
Vapor pressure > 1 atm[3]
Acidity (pKa) 13.27 (hydrate)[4][5]
−18.6·10−6 cm3/mol
2.330 D[6]
Structure
C2v
Trigonal planar
Thermochemistry[8]
35.387 J·mol−1·K−1
218.760 J·mol−1·K−1
−108.700 kJ·mol−1
−102.667 kJ·mol−1
571 kJ·mol−1
Pharmacology
QP53AX19 (WHO)
Hazards
GHS labelling:
GHS06: ToxicGHS05: CorrosiveGHS08: Health hazard[9]
Danger
H301+H311+H331, H314, H317, H335, H341, H350, H370[9]
P201, P280, P303+P361+P353, P304+P340+P310, P305+P351+P338, P308+P310[9]
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 4: Very short exposure could cause death or major residual injury. E.g. VX gasFlammability 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g. propaneInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazard COR: Corrosive; strong acid or base. E.g. sulfuric acid, potassium hydroxide
4
4
0
COR
Flash point 64 °C (147 °F; 337 K)
430 °C (806 °F; 703 K)
Explosive limits 7–73%
Lethal dose or concentration (LD, LC):
100 mg/kg (oral, rat)[12]
333 ppm (mouse, 2 h)
815 ppm (rat, 30 min)[13]
333 ppm (cat, 2 h)[13]
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 0.75 ppm ST 2 ppm (as formaldehyde and formalin)[10][11]
REL (Recommended)
 Ca TWA 0.016 ppm C 0.1 ppm [15-minute][10]
IDLH (Immediate danger)
 Ca [20 ppm][10]
Safety data sheet (SDS) MSDS(Archived)
Related compounds
Related aldehydes
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Formaldehyde (/fɔːrˈmældɪhaɪd/ ⓘ for-MAL-di-hide, US also /fər-/ ⓘ fər-) (systematic name methanal) is an organic compound with the chemical formula CH2O and structure H2C=O. The compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde. It is stored as aqueous solutions (formalin), which consists mainly of the hydrate CH2(OH)2. It is the simplest of the aldehydes (R−CHO). As a precursor to many other materials and chemical compounds, in 2006 the global production of formaldehyde was estimated at 12 million tons per year.[14] It is mainly used in the production of industrial resins, e.g., for particle board and coatings.

Formaldehyde also occurs naturally. It is derived from the degradation of serine, dimethylglycine, and lipids. Demethylases act by converting N-methyl groups to formaldehyde.[15]

Formaldehyde is classified as a group 1 carcinogen[note 1][17] and can cause respiratory and skin irritation upon exposure.[16]

Forms

[edit]

Formaldehyde is more complicated than many simple carbon compounds in that it adopts several diverse forms. These compounds can often be used interchangeably and can be interconverted.[citation needed]

  • Molecular formaldehyde. A colorless gas with a characteristic pungent, irritating odor. It is stable at about 150 °C, but it polymerizes when condensed to a liquid.
  • 1,3,5-Trioxane, with the formula (CH2O)3. It is a white solid that dissolves without degradation in organic solvents. It is a trimer of molecular formaldehyde.
  • Paraformaldehyde, with the formula HO(CH2O)nH. It is a white solid that is insoluble in most solvents.
  • Methanediol, with the formula CH2(OH)2. This compound also exists in equilibrium with various oligomers (short polymers), depending on the concentration and temperature. A saturated water solution, of about 40% formaldehyde by volume or 37% by mass, is called "100% formalin".

A small amount of stabilizer, such as methanol, is usually added to suppress oxidation and polymerization. A typical commercial-grade formalin may contain 10–12% methanol in addition to various metallic impurities.

"Formaldehyde" was first used as a generic trademark in 1893 following a previous trade name, "formalin".[18]

  • Main forms of formaldehyde
  • Monomeric formaldehyde (subject of this article)
    Monomeric formaldehyde (subject of this article)
  • Trioxane is a stable cyclic trimer of formaldehyde.
    Trioxane is a stable cyclic trimer of formaldehyde.
  • Paraformaldehyde is a common form of formaldehyde for industrial applications.
    Paraformaldehyde is a common form of formaldehyde for industrial applications.
  • Methanediol, the predominant species in dilute aqueous solutions of formaldehyde
    Methanediol, the predominant species in dilute aqueous solutions of formaldehyde

Structure and bonding

[edit]

Molecular formaldehyde contains a central carbon atom with a double bond to the oxygen atom and a single bond to each hydrogen atom. This structure is summarised by the condensed formula H2C=O.[19] The molecule is planar, Y-shaped and its molecular symmetry belongs to the C2v point group.[20] The precise molecular geometry of gaseous formaldehyde has been determined by gas electron diffraction[19][21] and microwave spectroscopy.[22][23] The bond lengths are 1.21 Å for the carbon–oxygen bond[19][21][22][23][24] and around 1.11 Å for the carbon–hydrogen bond,[19][21][22][23] while the H–C–H bond angle is 117°,[22][23] close to the 120° angle found in an ideal trigonal planar molecule.[19] Some excited electronic states of formaldehyde are pyramidal rather than planar as in the ground state.[24]

Occurrence

[edit]

Processes in the upper atmosphere contribute more than 80% of the total formaldehyde in the environment.[25] Formaldehyde is an intermediate in the oxidation (or combustion) of methane, as well as of other carbon compounds, e.g. in forest fires, automobile exhaust, and tobacco smoke. When produced in the atmosphere by the action of sunlight and oxygen on atmospheric methane and other hydrocarbons, it becomes part of smog. Formaldehyde has also been detected in outer space.

Formaldehyde and its adducts are ubiquitous in nature. Food may contain formaldehyde at levels 1–100 mg/kg.[26] Formaldehyde, formed in the metabolism of the amino acids serine and threonine, is found in the bloodstream of humans and other primates at concentrations of approximately 50 micromolar.[27] Experiments in which animals are exposed to an atmosphere containing isotopically labeled formaldehyde have demonstrated that even in deliberately exposed animals, the majority of formaldehyde-DNA adducts found in non-respiratory tissues are derived from endogenously produced formaldehyde.[28]

Formaldehyde does not accumulate in the environment, because it is broken down within a few hours by sunlight or by bacteria present in soil or water. Humans metabolize formaldehyde quickly, converting it to formic acid.[29][30] It nonetheless presents significant health concerns, as a contaminant.

Interstellar formaldehyde

[edit]
Main article: Interstellar formaldehyde

Formaldehyde appears to be a useful probe in astrochemistry due to prominence of the 110←111 and 211←212 K-doublet transitions. It was the first polyatomic organic molecule detected in the interstellar medium.[31] Since its initial detection in 1969, it has been observed in many regions of the galaxy. Because of the widespread interest in interstellar formaldehyde, it has been extensively studied, yielding new extragalactic sources.[32] A proposed mechanism for the formation is the hydrogenation of CO ice:[33]

H + CO → HCO
HCO + H → CH2O

HCN, HNC, H2CO, and dust have also been observed inside the comae of comets C/2012 F6 (Lemmon) and C/2012 S1 (ISON).[34][35]

Synthesis and industrial production

[edit]

Laboratory synthesis

[edit]

Formaldehyde was discovered in 1859 by the Russian chemist Aleksandr Butlerov (1828–1886) when he attempted to synthesize methanediol ("methylene glycol") from iodomethane and silver oxalate.[36] In his paper, Butlerov referred to formaldehyde as "dioxymethylen" (methylene dioxide) because his empirical formula for it was incorrect, as atomic weights were not precisely determined until the Karlsruhe Congress.

The compound was identified as an aldehyde by August Wilhelm von Hofmann, who first announced its production by passing methanol vapor in air over hot platinum wire.[37][38] With modifications, Hofmann's method remains the basis of the present day industrial route.

Solution routes to formaldehyde also entail oxidation of methanol or iodomethane.[39]

Industry

[edit]

Formaldehyde is produced industrially by the catalytic oxidation of methanol. The most common catalysts are silver metal (i.e. the FASIL process), iron(III) oxide,[40] iron molybdenum oxides (e.g. iron(III) molybdate) with a molybdenum-enriched surface,[41] or vanadium oxides. In the commonly used formox process, methanol and oxygen react at c. 250–400 °C in presence of iron oxide in combination with molybdenum and/or vanadium to produce formaldehyde according to the chemical equation:[42]

2 CH3OH + O2 → 2 CH2O + 2 H2O

The silver-based catalyst usually operates at a higher temperature, about 650 °C. Two chemical reactions on it simultaneously produce formaldehyde: that shown above and the dehydrogenation reaction:

CH3OH → CH2O + H2

In principle, formaldehyde could be generated by oxidation of methane, but this route is not industrially viable because the methanol is more easily oxidized than methane.[42]

Biochemistry

[edit]

Formaldehyde is produced via several enzyme-catalyzed routes.[43] Living beings, including humans, produce formaldehyde as part of their metabolism. Formaldehyde is key to several bodily functions (e.g. epigenetics[27]), but its amount must also be tightly controlled to avoid self-poisoning.[44]

Formaldehyde is catabolized by alcohol dehydrogenase ADH5 and aldehyde dehydrogenase ALDH2.[45]

Organic chemistry

[edit]

Formaldehyde is a building block in the synthesis of many other compounds of specialised and industrial significance. It exhibits most of the chemical properties of other aldehydes but is more reactive.[46]

Polymerization and hydration

[edit]

Monomeric CH2O is a gas and is rarely encountered in the laboratory. Aqueous formaldehyde, unlike some other small aldehydes (which need specific conditions to oligomerize through aldol condensation) oligomerizes spontaneously at a common state. The trimer 1,3,5-trioxane, (CH2O)3, is a typical oligomer. Many cyclic oligomers of other sizes have been isolated. Similarly, formaldehyde hydrates to give the geminal diol methanediol, which condenses further to form hydroxy-terminated oligomers HO(CH2O)nH. The polymer is called paraformaldehyde. The higher concentration of formaldehyde—the more equilibrium shifts towards polymerization. Diluting with water or increasing the solution temperature, as well as adding alcohols (such as methanol or ethanol) lowers that tendency.

Gaseous formaldehyde polymerizes at active sites on vessel walls, but the mechanism of the reaction is unknown.[47] Small amounts of hydrogen chloride, boron trifluoride, or stannic chloride present in gaseous formaldehyde provide the catalytic effect and make the polymerization rapid.[48]

Cross-linking reactions

[edit]

Formaldehyde forms cross-links by first combining with a protein to form methylol, which loses a water molecule to form a Schiff base.[49] The Schiff base can then react with DNA or protein to create a cross-linked product.[49] This reaction is the basis for the most common process of chemical fixation.

Oxidation and reduction

[edit]

Formaldehyde is readily oxidized by atmospheric oxygen into formic acid. For this reason, commercial formaldehyde is typically contaminated with formic acid. Formaldehyde can be hydrogenated into methanol.

In the Cannizzaro reaction, formaldehyde and base react to produce formic acid and methanol, a disproportionation reaction.

Hydroxymethylation and chloromethylation

[edit]

Formaldehyde reacts with many compounds, resulting in hydroxymethylation:

X-H + CH2O → X-CH2OH     (X = R2N, RC(O)NR', SH).

The resulting hydroxymethyl derivatives typically react further. Thus, amines give hexahydro-1,3,5-triazines:

3 RNH2 + 3 CH2O → (RNCH2)3 + 3 H2O

Similarly, when combined with hydrogen sulfide, it forms trithiane:[50]

3 CH2O + 3 H2S → (CH2S)3 + 3 H2O

In the presence of acids, it participates in electrophilic aromatic substitution reactions with aromatic compounds resulting in hydroxymethylated derivatives:

ArH + CH2O → ArCH2OH

When conducted in the presence of hydrogen chloride, the product is the chloromethyl compound, as described in the Blanc chloromethylation. If the arene is electron-rich, as in phenols, elaborate condensations ensue. With 4-substituted phenols one obtains calixarenes.[51] Phenol results in polymers.

Other reactions

[edit]

Many amino acids react with formaldehyde.[43] Cysteine converts to thioproline.

Uses

[edit]

Industrial applications

[edit]

Formaldehyde is a common precursor to more complex compounds and materials. In approximate order of decreasing consumption, products generated from formaldehyde include urea formaldehyde resin, melamine resin, phenol formaldehyde resin, polyoxymethylene plastics, 1,4-butanediol, and methylene diphenyl diisocyanate.[42] The textile industry uses formaldehyde-based resins as finishers to make fabrics crease-resistant.[52]

Two steps in formation of urea-formaldehyde resin, which is widely used in the production of particle board

When condensed with phenol, urea, or melamine, formaldehyde produces, respectively, hard thermoset phenol formaldehyde resin, urea formaldehyde resin, and melamine resin. These polymers are permanent adhesives used in plywood and carpeting. They are also foamed to make insulation, or cast into moulded products. Production of formaldehyde resins accounts for more than half of formaldehyde consumption.

Formaldehyde is also a precursor to polyfunctional alcohols such as pentaerythritol, which is used to make paints and explosives. Other formaldehyde derivatives include methylene diphenyl diisocyanate, an important component in polyurethane paints and foams, and hexamine, which is used in phenol-formaldehyde resins as well as the explosive RDX.

Condensation with acetaldehyde affords pentaerythritol, a chemical necessary in synthesizing PETN, a high explosive:[53]

Niche uses

[edit]

Disinfectant and biocide

[edit]

An aqueous solution of formaldehyde can be useful as a disinfectant as it kills most bacteria and fungi (including their spores). It is used as an additive in vaccine manufacturing to inactivate toxins and pathogens.[54] Formaldehyde releasers are used as biocides in personal care products such as cosmetics. Although present at levels not normally considered harmful, they are known to cause allergic contact dermatitis in certain sensitised individuals.[55]

Aquarists use formaldehyde as a treatment for the parasites Ichthyophthirius multifiliis and Cryptocaryon irritans.[56] Formaldehyde is one of the main disinfectants recommended for destroying anthrax.[57]

Formaldehyde is also approved for use in the manufacture of animal feeds in the US. It is an antimicrobial agent used to maintain complete animal feeds or feed ingredients Salmonella negative for up to 21 days.[58]

Tissue fixative and embalming agent

[edit]
Injecting a giant squid specimen with formalin for preservation

Formaldehyde preserves or fixes tissue or cells. The process involves cross-linking of primary amino groups. The European Union has banned the use of formaldehyde as a biocide (including embalming) under the Biocidal Products Directive (98/8/EC) due to its carcinogenic properties.[59][60] Countries with a strong tradition of embalming corpses, such as Ireland and other colder-weather countries, have raised concerns. Despite reports to the contrary,[61] no decision on the inclusion of formaldehyde on Annex I of the Biocidal Products Directive for product-type 22 (embalming and taxidermist fluids) had been made as of September 2009.[62]

Formaldehyde-based crosslinking is exploited in ChIP-on-chip or ChIP-sequencing genomics experiments, where DNA-binding proteins are cross-linked to their cognate binding sites on the chromosome and analyzed to determine what genes are regulated by the proteins. Formaldehyde is also used as a denaturing agent in RNA gel electrophoresis, preventing RNA from forming secondary structures. A solution of 4% formaldehyde fixes pathology tissue specimens at about one mm per hour at room temperature.

Drug testing

[edit]

Formaldehyde and 18 M (concentrated) sulfuric acid makes Marquis reagent—which can identify alkaloids and other compounds.

Photography

[edit]

In photography, formaldehyde is used in low concentrations for the process C-41 (color negative film) stabilizer in the final wash step,[63] as well as in the process E-6 pre-bleach step, to make it unnecessary in the final wash. Due to improvements in dye coupler chemistry, more modern (2006 or later) E-6 and C-41 films do not need formaldehyde, as their dyes are already stable.

Safety

[edit]

In view of its widespread use, toxicity, and volatility, formaldehyde poses a significant danger to human health.[64][65] In 2011, the US National Toxicology Program described formaldehyde as "known to be a human carcinogen".[66][67][68]

Chronic inhalation

[edit]

Concerns are associated with chronic (long-term) exposure by inhalation as may happen from thermal or chemical decomposition of formaldehyde-based resins and the production of formaldehyde resulting from the combustion of a variety of organic compounds (for example, exhaust gases). As formaldehyde resins are used in many construction materials,[69] it is one of the more common indoor air pollutants.[70][71] At concentrations above 0.1 ppm in air, formaldehyde can irritate the eyes and mucous membranes.[72] Formaldehyde inhaled at this concentration may cause headaches, a burning sensation in the throat, and difficulty breathing, and can trigger or aggravate asthma symptoms.[73][74]

The CDC considers formaldehyde as a systemic poison. Formaldehyde poisoning can cause permanent changes in the nervous system's functions.[75]

A 1988 Canadian study of houses with urea-formaldehyde foam insulation found that formaldehyde levels as low as 0.046 ppm were positively correlated with eye and nasal irritation.[76] A 2009 review of studies has shown a strong association between exposure to formaldehyde and the development of childhood asthma.[77]

A theory was proposed for the carcinogenesis of formaldehyde in 1978.[78] In 1987 the United States Environmental Protection Agency (EPA) classified it as a probable human carcinogen, and after more studies the WHO International Agency for Research on Cancer (IARC) in 1995 also classified it as a probable human carcinogen. Further information and evaluation of all known data led the IARC to reclassify formaldehyde as a known human carcinogen[79] associated with nasal sinus cancer and nasopharyngeal cancer.[80] Studies in 2009 and 2010 have also shown a positive correlation between exposure to formaldehyde and the development of leukemia, particularly myeloid leukemia.[81][82] Nasopharyngeal and sinonasal cancers are relatively rare, with a combined annual incidence in the United States of < 4,000 cases.[83][84] About 30,000 cases of myeloid leukemia occur in the United States each year.[85][86] Some evidence suggests that workplace exposure to formaldehyde contributes to sinonasal cancers.[87] Professionals exposed to formaldehyde in their occupation, such as funeral industry workers and embalmers, showed an increased risk of leukemia and brain cancer compared with the general population.[88] Other factors are important in determining individual risk for the development of leukemia or nasopharyngeal cancer.[87][89][90] In yeast, formaldehyde is found to perturb pathways for DNA repair and cell cycle.[91]

In the residential environment, formaldehyde exposure comes from a number of routes; formaldehyde can be emitted by treated wood products, such as plywood or particle board, but it is produced by paints, varnishes, floor finishes, and cigarette smoking as well.[92] In July 2016, the U.S. EPA released a prepublication version of its final rule on Formaldehyde Emission Standards for Composite Wood Products.[93] These new rules impact manufacturers, importers, distributors, and retailers of products containing composite wood, including fiberboard, particleboard, and various laminated products, who must comply with more stringent record-keeping and labeling requirements.[94]

External videos
video icon Where Have All the Trailers Gone?, video by Mariel Carr (Videographer) & Nick Shapiro (Researcher), 2015, Science History Institute

The U.S. EPA allows no more than 0.016 ppm formaldehyde in the air in new buildings constructed for that agency.[95][failed verification] A U.S. EPA study found a new home measured 0.076 ppm when brand new and 0.045 ppm after 30 days.[96] The Federal Emergency Management Agency (FEMA) has also announced limits on the formaldehyde levels in trailers purchased by that agency.[97] The EPA recommends the use of "exterior-grade" pressed-wood products with phenol instead of urea resin to limit formaldehyde exposure, since pressed-wood products containing formaldehyde resins are often a significant source of formaldehyde in homes.[80]

The eyes are most sensitive to formaldehyde exposure: The lowest level at which many people can begin to smell formaldehyde ranges between 0.05 and 1 ppm. The maximum concentration value at the workplace is 0.3 ppm.[98][need quotation to verify] In controlled chamber studies, individuals begin to sense eye irritation at about 0.5 ppm; 5 to 20 percent report eye irritation at 0.5 to 1 ppm; and greater certainty for sensory irritation occurred at 1 ppm and above. While some agencies have used a level as low as 0.1 ppm as a threshold for irritation, the expert panel found that a level of 0.3 ppm would protect against nearly all irritation. In fact, the expert panel found that a level of 1.0 ppm would avoid eye irritation—the most sensitive endpoint—in 75–95% of all people exposed.[99]

Some air purifiers include filtering technology that is supposed to lower indoor formaldehyde concentration.

Formaldehyde levels in building environments are affected by a number of factors. These include the potency of formaldehyde-emitting products present, the ratio of the surface area of emitting materials to volume of space, environmental factors, product age, interactions with other materials, and ventilation conditions. Formaldehyde emits from a variety of construction materials, furnishings, and consumer products. The three products that emit the highest concentrations are medium density fiberboard, hardwood plywood, and particle board. Environmental factors such as temperature and relative humidity can elevate levels because formaldehyde has a high vapor pressure. Formaldehyde levels from building materials are the highest when a building first opens because materials would have less time to off-gas. Formaldehyde levels decrease over time as the sources suppress.

In operating rooms, formaldehyde is produced as a byproduct of electrosurgery and is present in surgical smoke, exposing surgeons and healthcare workers to potentially unsafe concentrations.[100]

Formaldehyde levels in air can be sampled and tested in several ways, including impinger, treated sorbent, and passive monitors.[101] The National Institute for Occupational Safety and Health (NIOSH) has measurement methods numbered 2016, 2541, 3500, and 3800.[102]

In June 2011, the twelfth edition of the National Toxicology Program (NTP) Report on Carcinogens (RoC) changed the listing status of formaldehyde from "reasonably anticipated to be a human carcinogen" to "known to be a human carcinogen."[66][67][68] Concurrently, a National Academy of Sciences (NAS) committee was convened and issued an independent review of the draft U.S. EPA IRIS assessment of formaldehyde, providing a comprehensive health effects assessment and quantitative estimates of human risks of adverse effects.[103]

Acute irritation and allergic reaction

[edit]
Patch test

For most people, irritation from formaldehyde is temporary and reversible, although formaldehyde can cause allergies and is part of the standard patch test series. In 2005–06, it was the seventh-most-prevalent allergen in patch tests (9.0%).[104] People with formaldehyde allergy are advised to avoid formaldehyde releasers as well (e.g., Quaternium-15, imidazolidinyl urea, and diazolidinyl urea).[105] People who suffer allergic reactions to formaldehyde tend to display lesions on the skin in the areas that have had direct contact with the substance, such as the neck or thighs (often due to formaldehyde released from permanent press finished clothing) or dermatitis on the face (typically from cosmetics).[55] Formaldehyde has been banned in cosmetics in both Sweden[106] and Japan.[107]

Other routes

[edit]

In humans, ingestion of as little as 30 millilitres (1.0 US fl oz) of 37% formaldehyde solution can cause death. Other symptoms associated with ingesting such a solution include gastrointestinal damage (vomiting, abdominal pain), and systematic damage (dizziness).[75] Testing for formaldehyde is by blood and/or urine by gas chromatography–mass spectrometry. Other methods to detect formaldehyde include infrared detection, gas detector tubes, gas detectors using electrochemical sensors, and high-performance liquid chromatography (HPLC). HPLC is the most sensitive.[108]

The fifteenth edition (2021) of the U.S. National Toxicology Program Report on Carcinogens notes that currently in the U.S. "The general population can be exposed to formaldehyde primarily from breathing indoor or outdoor air, from tobacco smoke, from use of cosmetic products containing formaldehyde, and, to a more limited extent, from ingestion of food and water." Affected water includes groundwater, surface water, and bottled water. It also notes that occupational exposure can be significant.[109]

Contaminant in food

[edit]

Formaldehyde in food can be present naturally, added as an inadvertent contaminant, or intentionally added as a preservative, disinfectant, or bacteriostatic agent. Cooking and smoking food can also result in formaldehyde being produced in food. Foods that the U.S. National Toxicology Program has reported to have higher levels compared to other foods are fish, seafood, and smoked ham. It also notes formaldehyde in food generally occurs in a bound form and that formaldehyde is unstable in an aqueous solution. [109]

Scandals have broken in both the 2005 Indonesia food scare and 2007 Vietnam food scare regarding the addition of formaldehyde to foods to extend shelf life. In 2011, after a four-year absence, Indonesian authorities found foods with formaldehyde being sold in markets in a number of regions across the country.[110] In August 2011, at least at two Carrefour supermarkets, the Central Jakarta Livestock and Fishery Sub-Department found cendol containing 10 parts per million of formaldehyde.[111] In 2014, the owner of two noodle factories in Bogor, Indonesia, was arrested for using formaldehyde in noodles.[112] Foods known to be contaminated included noodles, salted fish, and tofu. Chicken and beer were also rumored to be contaminated. In some places, such as China, manufacturers still use formaldehyde illegally as a preservative in foods, which exposes people to formaldehyde ingestion.[113]

In 2011 in Nakhon Ratchasima, Thailand, truckloads of rotten chicken were treated with formaldehyde for sale in which "a large network", including 11 slaughterhouses run by a criminal gang, were implicated.[114] In 2012, 1 billion rupiah (almost US$100,000) of fish imported from Pakistan to Batam, Indonesia, were found laced with formaldehyde.[115]

Formalin contamination of foods has been reported in Bangladesh, with stores and supermarkets selling fruits, fishes, and vegetables that have been treated with formalin to keep them fresh.[116] However, in 2015, a Formalin Control Bill was passed in the Parliament of Bangladesh with a provision of life-term imprisonment as the maximum punishment as well as a maximum fine of 2,000,000 BDT but not less than 500,000 BDT for importing, producing, or hoarding formalin without a license.[117]

In the early 1900s, formaldehyde was frequently added by US milk plants to milk bottles as a method of pasteurization due to the lack of knowledge and concern[118] regarding formaldehyde's toxicity.[119][120]

Formaldehyde was one of the chemicals used in 19th century industrialised food production that was investigated by Dr. Harvey W. Wiley with his famous 'Poison Squad' as part of the US Department of Agriculture. This led to the 1906 Pure Food and Drug Act, a landmark event in the early history of food regulation in the United States.[121]

Regulation

[edit]

Formaldehyde is banned from use in certain applications (preservatives for liquid-cooling and processing systems, slimicides, metalworking-fluid preservatives, and antifouling products) under the Biocidal Products Directive.[122][123] In the EU, the maximum allowed concentration of formaldehyde in finished products is 0.2%, and any product that exceeds 0.05% has to include a warning that the product contains formaldehyde.[55]

In the United States, Congress passed a bill July 7, 2010, regarding the use of formaldehyde in hardwood plywood, particle board, and medium density fiberboard. The bill limited the allowable amount of formaldehyde emissions from these wood products to 0.09 ppm, and required companies to meet this standard by January 2013.[124] The final U.S. EPA rule specified maximum emissions of "0.05 ppm formaldehyde for hardwood plywood, 0.09 ppm formaldehyde for particleboard, 0.11 ppm formaldehyde for medium-density fiberboard, and 0.13 ppm formaldehyde for thin medium-density fiberboard."[125]

Formaldehyde was declared a toxic substance by the 1999 Canadian Environmental Protection Act.[126]

The FDA is proposing a ban on hair relaxers with formaldehyde due to cancer concerns.[127]

See also

[edit]

References

[edit]

Notes

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Formaldehyde

View on Grokipedia
from Grokipedia
Formaldehyde is an with the CH₂O, systematically named methanal, representing the simplest . At , it exists as a colorless, flammable gas with a distinct pungent and molecular weight of 30.03 g/mol. The compound occurs naturally in trace amounts through processes like atmospheric oxidation of hydrocarbons and biological , but it is predominantly produced industrially via oxidation or other synthetic routes, yielding millions of tons annually for commercial applications. Formaldehyde's primary uses include the synthesis of and phenol-formaldehyde resins essential for particleboard, , and other pressed-wood products, as well as intermediates in fertilizers, textiles, and disinfectants. These resins contribute to its widespread presence in building materials, household goods, and consumer products, often leading to indoor air exposure. Despite its industrial significance, formaldehyde is highly reactive and toxic, causing acute irritation to mucous membranes, eyes, , and at low concentrations (0.1–0.5 ppm), with higher exposures inducing severe inflammation, , or systemic effects. Chronic exposure is linked to nasopharyngeal cancer and other upper respiratory malignancies, prompting its classification as carcinogenic to humans () by the International Agency for Research on Cancer based on sufficient evidence from epidemiological studies of exposed workers and animal bioassays. The U.S. Environmental Protection Agency deems it carcinogenic via and identifies unreasonable health risks from certain occupational and uses, particularly acute and chronic respiratory hazards. Regulatory efforts focus on emission controls in products and limits to mitigate these empirically demonstrated effects, underscoring the tension between its utility and inherent hazards.

History

Discovery and Early Characterization

Formaldehyde was first reported in 1859 by Russian chemist during experiments aimed at synthesizing methylene glycol, where he observed a pungent, colorless gas as a byproduct. Butlerov generated the compound through the of methylene or related reactions, noting its irritating odor and reactivity, though he did not fully isolate or characterize it at the time. This initial observation marked the recognition of formaldehyde as a distinct chemical entity, distinct from previously known aldehydes. The compound's identity was conclusively established in 1868 by German chemist August Wilhelm von Hofmann, who synthesized it via the partial oxidation of vapors mixed with air passed over a heated spiral. Hofmann identified formaldehyde as methylaldehyde (CH₂O), the simplest , through detailed analysis of its chemical properties, including its solubility in to form a solution that polymerized upon evaporation and its reactions forming characteristic derivatives like formaldehydemethylene . This work provided the first rigorous structural confirmation, distinguishing it from and other homologs via determination and comparative reactivity tests. Early characterizations highlighted formaldehyde's volatility, with a boiling point around -19°C, high reactivity toward nucleophiles, and tendency to trimerize into trioxane or form paraformaldehyde polymers under certain conditions. These properties were verified through and analyses, confirming its and positioning it as a foundational carbonyl compound in . Subsequent studies in the late built on Hofmann's methods, emphasizing its role in oxidation pathways from alcohols.

Industrial Development and Key Milestones

Commercial production of began in in the 1880s through the of , enabling the transition from laboratory-scale synthesis to industrial volumes. This development followed the identification of viable methods, with industrial feasibility achieved by 1882 via copper-based . A continuous commercial process was refined in around 1889, improving efficiency and yield from methanol vapor oxidation over silver catalysts. Production subsequently expanded internationally, reaching and shortly thereafter, and the by the early 1900s. In the U.S., Heyden Chemical Works established the first successful commercial facility in , in 1904, followed by an additional plant later that year. The marked a pivotal advancement with the commercialization of high-pressure synthesis, providing a low-cost feedstock that catalyzed widespread scaling of formaldehyde production via . This period aligned with rising demand from applications, such as phenol-formaldehyde polymers introduced commercially around 1910, further driving optimizations including the adoption of iron-molybdate catalysts in later decades for higher selectivity.

Physical and Chemical Properties

Molecular Structure and Bonding

Formaldehyde, with the molecular formula CH₂O, features a central carbon atom bonded to two hydrogen atoms via single bonds and to one oxygen atom via a double bond, resulting in a linear arrangement of the C=O unit flanked by the C-H bonds. The double bond between carbon and oxygen comprises one sigma bond formed by end-to-end overlap of atomic orbitals and one pi bond from sideways overlap of p orbitals. The carbon atom in formaldehyde adopts sp² hybridization, utilizing three sp² hybrid orbitals to form sigma bonds with the two hydrogens and the oxygen, while its unhybridized p orbital participates in the pi bond with oxygen's p orbital. This hybridization configuration dictates the trigonal planar electron and molecular geometry, with the oxygen atom also sp² hybridized, its lone pairs occupying the remaining sp² orbitals and p orbital. Experimental bond lengths measure approximately 1.11 Å for each C-H bond and 1.21 Å for the C=O bond, reflecting the partial double-bond character and electron density distribution. Bond angles deviate slightly from the ideal 120° due to the influence of the double bond and lone pairs on oxygen: the H-C-H angle is about 118°, and each H-C-O angle is roughly 121°. These structural parameters contribute to formaldehyde's polarity, evidenced by a dipole moment of 2.33 debye, arising from the electronegativity difference between carbon and oxygen that polarizes the C=O bond.

Physical Properties and Forms

Formaldehyde exists primarily as a colorless, flammable gas at , characterized by a pungent, irritating detectable at concentrations as low as 1 ppm. Its molecular weight is 30.03 g/mol, with a of 1.04 relative to air and a exceeding 1 atm, reaching approximately 3890 mmHg at 25°C, indicating high volatility. The melting point is -92°C, and the is -19°C, allowing it to liquefy under moderate cooling or compression. In the liquid state at -20°C, its is 0.815 g/cm³. Formaldehyde exhibits high in , with up to 400 g/L dissolving at 25°C, though it readily hydrates to form (CH2(OH)2), the predominant species in dilute s rather than the free . Commercially, it is often handled as an known as formalin, typically 37% by weight formaldehyde stabilized with 10-15% to prevent , appearing as a clear with a around 96°C and near 1.08 g/mL at 25°C. In solid forms, formaldehyde polymerizes to yield stable derivatives such as , a white, crystalline linear polyacetal (n=8-100) used in industrial applications for controlled release of the upon heating or . Another form is trioxane, a cyclic trimer (C3H6O3) that forms as colorless stable under conditions, with a of 61-62°C, serving as a latent source of formaldehyde in . These polymeric forms arise from reversible reactions, contrasting the monomeric gas's instability in concentrated solutions without stabilizers.

Natural Occurrence

Biochemical Production in Organisms

Formaldehyde is produced endogenously in , , animals, and humans as an intermediate in various metabolic processes, including one-carbon metabolism and demethylation reactions. In microorganisms such as methylotrophs and methanotrophs, formaldehyde arises primarily from the oxidation of short-chain hydrocarbons like or , serving as a key intermediate before assimilation or dissimilation. These pathways enable to utilize C1 compounds as carbon and energy sources, with formaldehyde channeled into routes like the ribulose monophosphate or serine pathways for assimilation. In , formaldehyde production occurs at low levels during processes such as the breakdown of certain volatile organic compounds or as a of photosynthetic , though more prominently absorb and metabolize exogenous formaldehyde via enzymatic pathways. Historical studies suggested formaldehyde formation in green via photochemical reactions, but contemporary evidence emphasizes its transient role rather than significant net production. Mammalian cells generate formaldehyde through demethylation of DNA, histones, and other substrates by enzymes like TET proteins; oxidative degradation of folates; serine catabolism; and methanol metabolism. These reactions link to methionine-homocysteine cycles and one-carbon metabolism, where formaldehyde regulates S-adenosylmethionine biosynthesis. Endogenous production rates in humans are estimated at 0.61–0.91 mg/kg body weight per minute, reflecting rapid turnover due to its reactivity, with daily totals around 878–1310 mg/kg body weight assuming a half-life of 1–1.5 minutes. Despite its genotoxic potential, cells divert it into protective metabolic sinks like tetrahydrofolate-dependent pathways.

Environmental and Cosmic Presence

Formaldehyde is present in the Earth's atmosphere from natural sources including biomass combustion during forest fires, volcanic emissions, and photochemical oxidation of naturally emitted hydrocarbons such as and from vegetation. In rural and suburban outdoor air, concentrations typically range from 0.0002 to 0.006 parts per million (ppm), while urban levels are higher at 0.001 to 0.02 ppm, reflecting contributions from both natural and anthropogenic processes, though natural background levels persist even in remote areas. Atmospheric formaldehyde photodegrades rapidly, with a of hours, primarily into and via reaction with hydroxyl radicals. In marine environments, formaldehyde arises from oceanic photochemical processes and , yielding average concentrations of 2.4 ± 0.9 by volume (ppbv) in coastal atmospheres, with peaks up to 6.8 ppbv linked to air masses over bodies. It dissolves readily in but degrades quickly through biological and chemical processes, resulting in low persistence in surface waters and oceans. In soils, formaldehyde is rarely detected due to its rapid microbial degradation and volatilization upon release, maintaining negligible steady-state levels despite occasional natural inputs. In cosmic environments, formaldehyde is ubiquitous in dense interstellar molecular clouds, where it serves as a tracer of nonequilibrium chemistry driven by s, detectable via its ground-state rotational transition at 4830 MHz. It has been observed in cometary comae and nuclei, including emissions from Comet C/2002 T7 (LINEAR) at radio wavelengths, and may form through cosmic ray irradiation of interstellar ices or gas-phase reactions involving precursors like . Formaldehyde's presence in such settings underscores its role as a simple organic building block in prebiotic interstellar chemistry, with detections extending to diffuse clouds and star-forming regions.

Synthesis and Production

Laboratory Synthesis

In laboratories, formaldehyde is commonly synthesized via the dehydrogenation of , where vapor is passed over a heated catalyst, typically maintained at 250–350 °C, producing formaldehyde gas and according to the reaction CH₃OH → H₂C=O + H₂. This requires external heating to sustain the reaction, and the gaseous formaldehyde is often collected by absorption in cold water to form an known as formalin. Yields in this method can exceed 80% under optimized conditions, though side reactions such as further oxidation to or carbon oxides may occur if temperatures fluctuate or catalyst purity is low. An alternative laboratory approach employs of by mixing its vapors with air (approximately 40–50% in air by volume) and passing the mixture over a silver catalyst at higher temperatures of 500–700 °C, facilitating both dehydrogenation and oxygen-mediated oxidation pathways to yield formaldehyde, , and as byproducts. This exothermic variant allows for better heat management in small-scale setups and achieves selectivities up to 90%, but requires precise control of oxygen levels to minimize complete to CO₂. Catalysts like platinized have been used historically for similar oxidative preparations at around 300 °C, though and silver remain preferred for their and availability. Less common methods include chemical oxidation of methanol using strong oxidants such as potassium dichromate in acidic media, which generates formaldehyde alongside reduced chromium species and requires distillation for isolation, but this is inefficient for pure product due to over-oxidation and waste generation. Specialized syntheses, such as those for isotopically labeled formaldehyde (e.g., [¹¹C]formaldehyde from [¹¹C]methanol via oxidation), employ tailored catalysts or reagents like trimethylamine-N-oxide but are confined to radiochemistry applications rather than routine laboratory use. All methods necessitate ventilation and safety precautions given formaldehyde's toxicity and flammability.

Industrial Production Methods

The predominant industrial production of formaldehyde occurs through the catalytic vapor-phase oxidation and dehydrogenation of using air as the oxidant. This process accounts for over 99% of global formaldehyde output, with serving as the primary feedstock due to its availability and cost-effectiveness. Two principal catalytic methods are employed: the silver catalyst process and the metal oxide catalyst process. In the silver catalyst process, vaporized (typically 30-40% concentration in air) is passed over polycrystalline silver catalysts at temperatures of 500-700°C and pressures near atmospheric. The reaction proceeds via (CH₃OH + ½O₂ → CH₂O + H₂O) and dehydrogenation (CH₃OH → CH₂O + H₂), with the latter being endothermic and supported by exothermic oxidation heat; excess (up to 20-25% unconverted) is recycled after . This method yields formaldehyde concentrations up to 40-50% in the reactor effluent, suitable for producing high-purity gas or concentrated solutions, but it consumes more per ton of product (approximately 1.15-1.25 tons per ton formaldehyde) compared to alternatives. The metal oxide catalyst process, often utilizing iron-molybdate (Fe₂(MoO₄)₃-MoO₃) or similar formulations like the Formox system with vanadium and molybdenum promoters, operates at lower temperatures of 250-400°C to enhance selectivity and minimize over-oxidation to CO₂. Methanol vapor (15-20% in air) contacts the catalyst bed, favoring the oxidation pathway with near-complete oxygen utilization and methanol conversions exceeding 95%, yielding 88-92% formaldehyde based on methanol input—requiring about 15% less methanol than the silver process (roughly 1.0-1.1 tons per ton formaldehyde). The effluent is absorbed in water to form 37-50% aqueous solutions (formalin), followed by distillation to remove water, dimethyl ether, and trioxane byproducts. This process dominates modern large-scale production due to higher energy efficiency in feedstock use, though it may incur higher utility costs for compression and cooling in some configurations. Both processes incorporate safety measures for handling flammable mixtures, maintaining methanol-air ratios below the limit (typically 6-15% methanol by volume), and employ multitubular reactors with steam-cooled walls to manage exothermic heat. Global capacity exceeds 50 million tons annually, with metal processes comprising the majority share owing to superior selectivity and scalability for integrated plants. Alternative routes, such as of hydrocarbons (e.g., or ), were used historically but have been largely phased out due to lower yields and higher costs.

Chemical Reactivity

Polymerization and Hydration

In aqueous solutions, formaldehyde undergoes rapid hydration to form methanediol (CH₂(OH)₂), the gem-diol , via of water to the . This equilibrium strongly favors the hydrated form, with the ratio of methanediol to free formaldehyde concentrations reaching approximately 2,200 at 298 K in dilute solutions. The hydration reaction is reversible, and the position of equilibrium shifts toward the diol at lower temperatures and higher , reflecting the solvent's role in stabilizing the hydrate through hydrogen bonding. studies confirm that in low-concentration aqueous formaldehyde, over 99% exists as methanediol, with free detectable only via spectroscopic methods. Polymerization of formaldehyde occurs under conditions of low water content, such as in concentrated solutions or anhydrous media, yielding structures through stepwise or chain-growth mechanisms. Paraformaldehyde, a common linear (CH₂O)ₙ with n typically 8–100, forms by concentrating aqueous formaldehyde solutions and removing water, often accelerated by mild acidification or heating, resulting in a white, solid precipitate used as a convenient formaldehyde source. This depolymerizes back to upon heating or in basic/acidic aqueous media, enabling controlled release. Cyclic polymerization produces 1,3,5-trioxane, a stable trimer, via acid-catalyzed trimerization of formaldehyde in concentrated aqueous solutions, typically employing mineral acids like at elevated temperatures. The reaction proceeds through of the carbonyl, facilitating electrophilic attack and cyclization, with yields optimized by high formaldehyde concentrations (above 50 wt%) to suppress linear formation. High-molecular-weight (POM), a with exceeding 1,000, requires formaldehyde and anionic initiators, such as alkoxides or organometallic compounds, to propagate living chains with minimal termination. This , developed industrially in the mid-20th century, yields crystalline polymers stabilized against by end-capping agents like groups. Unlike paraformaldehyde's thermal instability, stabilized POM resists reversion to below its of approximately 175°C.

Cross-Linking and Condensation Reactions

Formaldehyde cross-links proteins by reacting with nucleophilic side chains, particularly the ε-amino groups of residues and the guanidino groups of , forming methylene bridges (–CH₂–) that covalently link proximal residues within 2 due to the reagent's small size. The initial step involves nucleophilic attack by an on the carbonyl carbon of formaldehyde, yielding a (methylol) intermediate, which dehydrates to an ion () that serves as an for a second nucleophilic attack by another residue's , , or guanidyl group, with optimal efficiency at 1–2% formaldehyde concentration, , and 10–15 minute incubation. Cross-links between amino and primary or guanidyl groups predominate, as evidenced by early studies on model peptides. Mass spectrometry analyses have refined this model, revealing that apparent cross-links often manifest as +24 Da mass shifts between peptides, corresponding to the dimerization of two formaldehyde-modified (each gaining +12 Da via hydroxymethylation or ) rather than a simple direct (+14 Da); this occurs because the reactive intermediates disproportionate or cyclize before bridging distant sites. Such modifications vary by amino acid reactivity— and form stable adducts fastest, while and yield slower, reversible ones—and are reversible under heat or mild base, enabling applications in where 1% formaldehyde fixes protein-DNA interactions . In nucleic acids, formaldehyde cross-links exocyclic amines of bases (e.g., N6, N4) to protein lysines, with reversal rates depending on the specific bridge (e.g., ~0.001–0.01 min⁻¹ at 65°C). In condensation reactions, formaldehyde undergoes or nucleophilic addition-elimination with compounds bearing active methylene or amino groups, eliminating water to form methylene-linked polymers, as in the production of (UF) and phenol-formaldehyde (PF) resins, which account for over 50% of global formaldehyde consumption. UF synthesis begins with and formaldehyde (molar ratio ~1:2) in aqueous alkaline medium at 70–90°C to form mono- and dimethylolureas via addition, followed by acid-catalyzed (pH 4–5) at 90–100°C, yielding branched networks of –NH–CH₂–NH– and –N(CH₂)–N– linkages; curing involves further and , with free formaldehyde content controlled below 0.1% to minimize emissions. PF resins form similarly: phenol reacts with excess formaldehyde under base catalysis to generate ortho- and para-hydroxymethylphenols (resoles), which condense under acid or heat to methylene (–CH₂–) and dibenzyl ether bridges, with resorcinol variants accelerating via quinone methide intermediates in Michael additions. These reactions are stepwise, with self-condensation of methylolphenols dominating in formaldehyde-free stages, influenced by substituent electron density. The exemplifies a related condensation-cross-linking pathway, where formaldehyde, a primary or secondary , and an enolizable carbonyl (e.g., ) or activated arene (e.g., ) react to form β-amino methylene derivatives, enabling network formation in adhesives or ligands; for instance, with formaldehyde and yields aminomethylated products under . In Betti variants, and amines cross-link via methylene bridges, as seen in recent syntheses adding or heteroatoms. These processes underpin durable materials like particleboard binders but require precise to avoid brittleness from over-.

Oxidation, Reduction, and Other Transformations

Formaldehyde is oxidized to (HCOOH) and further to (CO₂) through multiple pathways, depending on conditions and oxidants. In the gas phase, with molecular oxygen occurs via a radical chain mechanism initiated by , involving H-atom abstraction or addition reactions and propagating radicals such as O, H, OH, and HO₂, with peroxides like H₂O₂ forming as intermediates. In , the (OH) oxidizes formaldehyde at 293 K, following detailed kinetics where the rate-determining step involves HCHO• radical formation and subsequent reactions yielding hydrated . A metal-mediated example is the copper(II)-catalyzed oxidation in :
2Cu2++HCHO+H2O→2Cu++HCOOH+2H+2\mathrm{Cu}^{2+} + \mathrm{HCHO} + \mathrm{H_2O} \rightarrow 2\mathrm{Cu}^{+} + \mathrm{HCOOH} + 2\mathrm{H}^{+}
with the reaction rate influenced by and concentration. Reduction of formaldehyde primarily produces (CH₃OH), achievable via with catalysts such as supported metals. In anaerobic microbial processes, formaldehyde serves as both oxidant and reductant in , yielding and or , as observed in experiments where HCHO provided all carbon and reducing equivalents under N₂, confirming balanced oxidation-reduction . Other transformations include the Cannizzaro , prominent for formaldehyde due to its lack of α-hydrogens; in concentrated alkali (e.g., NaOH), two molecules react without external oxidant or reductant:
2HCHO+NaOH→CH3OH+HCOONa2\mathrm{HCHO} + \mathrm{NaOH} \rightarrow \mathrm{CH_3OH} + \mathrm{HCOONa}
a self-redox process where one equivalent is oxidized to and the other reduced to , often quantitative under anhydrous conditions. Metal-promoted variants, such as rhodium-catalyzed , convert formaldehyde to (HOCH₂CHO), involving CO insertion and steps. In electrocatalytic contexts, formaldehyde undergoes multi-electron oxidation to or CO₂ at low potentials on Cu-based electrodes, bypassing . These reactions underscore formaldehyde's role as a versatile C1 , though practical applications prioritize stability over transformation due to its reactivity.

Uses and Applications

Primary Industrial Uses


Formaldehyde is predominantly utilized in the production of thermosetting , which represent the primary industrial application and account for the majority of global consumption. comprised approximately 63% of worldwide formaldehyde use in , with the construction industry alone consuming 60 to 70% of total production for products. These enable efficient bonding of wood fibers, particles, and veneers, facilitating the manufacture of durable, cost-effective materials essential for building and furniture sectors. Urea-formaldehyde (UF) resins, the most common type, serve as adhesives in particleboard, medium-density (MDF), and high-density (HDF), binding wood particles under heat and pressure to form panels used in cabinetry, flooring, and shelving. Phenol-formaldehyde (PF) resins are employed in and (OSB), offering superior moisture resistance suitable for structural applications like exterior sheathing and subflooring. Melamine-formaldehyde (MF) resins provide hard, scratch-resistant surfaces for laminates in countertops and decorative panels. Beyond wood composites, formaldehyde-derived resins support automotive components, such as interior trim and under-hood parts via PF and (POM) plastics, and foundry applications through hexamine in and rubber formulations. It also functions as an intermediate for synthesis, used in resins for paints and varnishes, though these uses constitute smaller shares relative to wood product resins. , a polymeric form, is often preferred in industrial processes for controlled release in formulations.

Specialized and Emerging Applications

In medical applications, formaldehyde functions as a and sterilizing agent for equipment and surfaces in hospitals and laboratories, leveraging its ability to denature proteins and nucleic acids in microorganisms. It is also employed to inactivate viruses and bacteria in production, such as in formulations for , , and , where concentrations around 0.02-0.1% ensure pathogen neutralization while preserving antigenic properties. In tissue fixation for and , aqueous solutions (typically 4-10% formalin) proteins to stabilize cellular structures, enabling long-term preservation of specimens for microscopic analysis or studies. Biotechnological uses include formaldehyde's role in cross-linking DNA-protein complexes for (ChIP) assays, which map protein binding sites on genomes to elucidate mechanisms, with typical exposure times of 10-30 minutes at 1% concentration. It serves as a component in some anti-infective pharmaceuticals and enhances drug absorption in capsules by modifying matrices. Specialized industrial niches encompass leather tanning, where formaldehyde-based agents stabilize collagen fibers against degradation, improving durability in processes handling up to 10-20 kg per ton of hide. In oil and gas extraction, it acts as a and in drilling fluids and well treatments, mitigating microbial-induced souring at dosages of 50-200 ppm. operations utilize it for dust suppression and reagent stabilization in flotation processes. Emerging research explores formaldehyde's integration into , such as resins for components in production, where it contributes to high-strength composites enduring mechanical stresses over 20-year lifespans. In biotechnology, investigations into controlled-release systems for formaldehyde-derived cross-linkers aim to refine protein stabilization in immobilization for industrial biocatalysis, though scalability remains limited as of 2023. These developments prioritize low-emission formulations to address environmental constraints while expanding utility in sustainable technologies.

Exposure and Health Effects

Routes of Exposure

The primary route of human exposure to formaldehyde is inhalation of its gas or vapor, which is readily absorbed through the due to its high and reactivity. This pathway predominates in both occupational settings, such as manufacturing of resins or textiles, and environmental contexts like indoor air from off-gassing building materials or combustion sources including tobacco smoke. Inhaled formaldehyde is primarily deposited in the upper airways, where concentrations above 0.1 ppm can cause sensory irritation. Dermal exposure occurs through direct contact with formaldehyde-containing liquids or solutions, leading to absorption across intact , though systemic effects are limited by rapid local metabolism to . Skin absorption is more significant in occupational scenarios involving handling of formalin (aqueous formaldehyde solutions) for or sterilization, often resulting in localized irritation or rather than widespread distribution. , frequently concurrent with dermal exposure, causes immediate lacrimation and conjunctival irritation at concentrations as low as 0.5 ppm. Ingestion represents a minor route of exposure, typically accidental or suicidal, though low natural levels occur in many foods such as fruits, vegetables, and meats, where they are rapidly metabolized without harm. High exposure from illegal addition to food can cause acute effects including irritation and nausea, with potential long-term risks. Formaldehyde is absorbed efficiently from the after dilution in aqueous forms like formalin, and bound formaldehyde in cookware handles (e.g., phenolic resins) does not significantly leach into food during normal use. Oral uptake leads to rapid corrosive damage to mucosal surfaces in high doses, but chronic low-level dietary ingestion poses no widespread concerns in regulated markets. Overall, while all routes contribute to total body burden, accounts for the majority of population-level exposures, with dermal and oral pathways more relevant in specific high-risk activities.

Acute and Irritant Effects


Formaldehyde gas causes acute to the eyes, , and at airborne concentrations as low as 0.3 parts per million (ppm), manifesting as burning sensations, tearing, and nasal discharge. At levels above 0.1 ppm, occurs, with symptom severity increasing with higher concentrations, including , wheezing, and . Eye thresholds range from 0.3 to 0.9 ppm in occupational settings, while severe ocular effects develop between 4 and 20 ppm. Higher acute exposures, exceeding 5 ppm, can lead to intense , , and potentially fatal respiratory distress due to direct corrosive action on tissues. Sensory irritation thresholds in controlled studies indicate eye effects as the most sensitive, with general sensory evident around 1 ppm. Nasal is reported at 0.5 ppm with peaks to 1.0 ppm or lower levels (0.3–0.5 ppm) in combination with other irritants. Skin contact with liquid formaldehyde solutions, such as formalin, produces immediate irritant characterized by , , and vesiculation, particularly in sensitized individuals. Acute results in corrosive gastrointestinal , vascular , and systemic , often without prompt intervention. These effects stem from formaldehyde's reactivity as an , forming adducts with proteins and nucleic acids in biological tissues, triggering inflammatory cascades. Symptoms typically resolve upon cessation of exposure, though severe cases may require medical management including bronchodilators and supportive care.

Chronic Effects and Carcinogenicity Data

Chronic exposure to formaldehyde at low to moderate levels has been associated with persistent irritation, including symptoms such as coughing, wheezing, and decreased pulmonary function in occupational cohorts. Studies of workers in industries like particleboard and embalmers report chronic effects including nasal dryness, epithelial , and olfactory impairment, with some evidence of over time reducing symptom intensity after initial exposure periods of 4-6 weeks. Sensitization leading to allergic responses, such as , occurs in a subset of exposed individuals, characterized by chest tightness, , and reversible airway obstruction upon re-exposure. These effects are primarily localized to the upper respiratory mucosa due to formaldehyde's high reactivity, with dose-dependent risks observed below 1 ppm in long-term studies. Formaldehyde is classified as carcinogenic to humans by the International Agency for Research on Cancer (IARC) in Group 1, based primarily on sufficient evidence from inhalation exposures linking high occupational levels to nasopharyngeal cancer and sinonasal cancer, with carcinogenicity mainly associated with inhalation rather than typical dietary intake. Cohort studies of formaldehyde-exposed workers, such as those in chemical manufacturing and , show relative risks for nasopharyngeal cancer elevated by 1.3- to 3-fold at cumulative exposures exceeding 10 ppm-years, with risks concentrated in the highest exposure quartiles and supported by consistent findings across multiple international datasets. The National Toxicology Program (NTP) lists formaldehyde as a known , citing mechanistic evidence of DNA-protein crosslinks and in nasal tissues as precursors to tumorigenesis in rodent models mirroring site-specific effects. The U.S. Environmental Protection Agency's Integrated Risk Information System (IRIS) assessment affirms inhalation-related carcinogenicity for nasopharyngeal and sinonasal sites, deriving unit risk estimates from pooled occupational data indicating no safe threshold for these portal-of-entry cancers. Associations with and other lymphohematopoietic cancers have been reported in some cohort analyses, particularly with peak or cumulative exposure metrics, but causal evidence remains limited and contested. IARC and NTP include in their classifications based on positive findings in select studies, such as elevated standardized mortality ratios in embalmers and industrial workers; however, systematic reviews highlight inconsistencies, including lack of exposure-response trends, absence of in humans, and formaldehyde's rapid local preventing systemic circulation to hematopoietic tissues. Recent meta-analyses and re-evaluations, integrating negative findings from large updated cohorts, conclude no convincing causal link, attributing apparent associations to factors like concurrent exposures or diagnostic biases rather than direct leukemogenesis. Overall, while nasopharyngeal risks are empirically robust from high-exposure data, claims rely on weaker, non-localized evidence, underscoring the need for site-specific causality in assessments.

Safety, Regulation, and Controversies

Occupational and Consumer Safety Measures

Occupational safety measures for formaldehyde emphasize exposure monitoring, , and (PPE) to mitigate risks from inhalation, skin contact, and eye exposure. The (OSHA) mandates a (PEL) of 0.75 parts per million (ppm) as an 8-hour time-weighted average (TWA), with a (STEL) of 2 ppm over 15 minutes and an action level of 0.5 ppm triggering monitoring and medical surveillance. The National Institute for Occupational Safety and Health (NIOSH) recommends a more stringent REL of 0.016 ppm TWA or 0.1 ppm 15-minute ceiling, reflecting concerns over carcinogenicity even at low levels. Employers must implement feasible such as local exhaust ventilation and enclosed systems before relying on PPE, alongside initial and periodic air monitoring to assess exposures.
AgencyExposure LimitDescriptionSource
OSHA PEL0.75 ppm8-hour
OSHA STEL2 ppm15-minute maximum
NIOSH REL0.016 ppm (carcinogen policy)
NIOSH Ceiling0.1 ppm15-minute limit
PPE requirements include chemical-resistant gloves (e.g., , , or PVC for concentrated solutions), safety or face shields, and full-body protective clothing for splashes or high concentrations exceeding 1% formaldehyde. Respirators, such as half-face with organic vapor cartridges or supplied-air types, are required when are infeasible, with NIOSH recommending the most protective options above 0.016 ppm due to formaldehyde's status as a potential occupational . Workers handling formaldehyde must receive training on hazards, emergency procedures, and decontamination, including immediate skin washing and eyewash use. Medical surveillance, including annual exams and for those exposed above the action level, is required under OSHA to detect or respiratory effects early. Consumer safety measures focus on minimizing indoor emissions from products like composite wood, textiles, and containing formaldehyde or releasers such as quaternium-15. Ventilation through open windows, exhaust fans, or HVAC systems reduces airborne concentrations, while maintaining low (below 50%) and moderate temperatures via dehumidifiers or inhibits off-gassing from resins in furniture and flooring. Selecting low-emission products certified under standards like the EPA's TSCA Title VI for composite wood or those labeled formaldehyde-free helps limit exposure, as pressed-wood items can emit up to several ppm initially. In , avoiding those with formaldehyde releasers—required to be labeled if exceeding 0.05% in the —prevents skin sensitization, though trace releases below this threshold are deemed by some assessments. Banning indoor further curbs secondary exposures, as tobacco smoke contains formaldehyde. The EPA's 2025 risk identifies unreasonable from consumer dermal and routes in certain uses, prompting ongoing proposals, but emphasizes practical over outright bans.

Regulatory Frameworks and Recent Assessments

In the United States, the Occupational Safety and Health Administration (OSHA) regulates occupational exposure to formaldehyde under 29 CFR 1910.1048, establishing a permissible exposure limit (PEL) of 0.75 parts per million (ppm) as an 8-hour time-weighted average and a short-term exposure limit (STEL) of 2 ppm over 15 minutes, with requirements for medical surveillance, hazard communication, and engineering controls for exposures at or above the action level of 0.5 ppm. The Environmental Protection Agency (EPA) designates formaldehyde as a hazardous air pollutant under the Clean Air Act, subjecting it to National Emission Standards for Hazardous Air Pollutants (NESHAP), particularly for industries like plywood and particleboard manufacturing, and regulates it under the Toxic Substances Control Act (TSCA) for chemical risk management. Internationally, the International Agency for Research on Cancer (IARC), part of the (WHO), classifies formaldehyde as a , confirming sufficient evidence of nasopharyngeal cancer in humans from occupational exposure, though it notes endogenous production and lack of data for some endpoints. WHO provides guidelines recommending a 30-minute average concentration below 0.1 mg/m³ to minimize sensory irritation, based on chamber studies showing no significant effects at or below this level in sensitive populations. In the , formaldehyde is classified as a Category 1B under the Classification, Labelling and Packaging () Regulation and listed as a (SVHC) under REACH since 2011, requiring authorization for certain uses and restrictions on emissions from wood-based products under the Construction Products Regulation, with emission limits such as E1 class (≤0.124 mg/m³ for panels). Recent assessments include the EPA's final TSCA risk evaluation released on December 1, 2024, which determined that 16 of 23 conditions of use present unreasonable risks to human health, primarily through and dermal exposures causing , , and cancer, particularly for workers in and , prompting forthcoming rules despite industry critiques of overestimation in exposure modeling. This evaluation incorporated updated hazard data, including myeloperoxidase-mediated genotoxicity mechanisms, but faced scrutiny for relying on conservative assumptions in occupational non-user exposures. In December 2025, under the Trump administration, the U.S. EPA released an updated draft risk calculation memorandum for formaldehyde under TSCA, proposing a safe threshold for exposure, reversing prior no-threshold cancer risk assumptions, and potentially doubling acceptable inhalation levels to inform revisions to the 2024 final risk evaluation. No major revisions to IARC or WHO classifications occurred between 2020 and 2025, though ongoing REACH reviews continue to evaluate biocidal uses and consumer products for alignment with emerging exposure data.

Debates on Risk-Benefit and Overregulation

Critics of stringent formaldehyde regulations argue that the compound's risks, particularly at low environmental and exposure levels, are overstated relative to its indispensable industrial benefits. Formaldehyde is a key precursor in and phenol-formaldehyde resins used in products like particleboard and , which constitute essential, cost-effective materials for furniture, , and housing construction, enabling affordable building practices worldwide. The has emphasized that decades of scientific data affirm safe exposure thresholds below current occupational limits, such as OSHA's 0.75 parts per million (ppm) , and that further restrictions could elevate production costs, disrupt supply chains, and indirectly increase housing prices without commensurate reductions in cancer incidence. Empirical evidence supports a threshold for formaldehyde's carcinogenicity, with robust links to nasopharyngeal cancer and myeloid leukemia observed only in high-occupational-exposure cohorts exceeding 1-2 ppm over years, but minimal genotoxic effects at ambient indoor levels below 0.1 ppm. A 2019 University of North Carolina study found no detectable DNA adducts—the precursors to mutations—in human respiratory tissues at doses mimicking typical environmental exposures (around 0.015 ppm), suggesting that low-dose risks do not extrapolate linearly from high-dose animal and worker studies. Similarly, a 2021 meta-review concluded that the association between formaldehyde and leukemia remains controversial, with inconsistent epidemiological data failing to establish causality at non-occupational levels due to confounding factors like co-exposures in industrial settings. Regulatory bodies like the EPA, in its January 2025 TSCA risk evaluation, have asserted "unreasonable risk" across most uses without PPE, potentially overlooking this dose-response nuance in favor of precautionary linear no-threshold models criticized for lacking mechanistic support at trace concentrations. Proponents of tighter controls, including the EPA, prioritize averting even probabilistic harms from ubiquitous sources like building emissions and consumer goods, estimating thousands of annual cancer cases attributable to aggregate low-level exposures, though such projections rely on models contested for inflating risks by ignoring metabolic detoxification and population variability. In contrast, industry analyses highlight formaldehyde's net societal value, including its role in vaccine preservatives (at microgram-per-dose levels far below thresholds for irritation) and automotive adhesives enhancing fuel efficiency through lighter composite materials, where bans or emission caps below 0.05 ppm—as in California's Airborne Toxic Control Measure—have driven reformulations yielding marginal air quality gains at the expense of product durability and economic output estimated in billions annually. The American Chemistry Council has warned that the EPA's accelerated 2024-2025 assessments prioritize timelines over peer-reviewed science, potentially leading to overregulation that undermines applications in agriculture, transportation, and healthcare without evidence of proportional benefits. This tension reflects broader causal realism in : while acute irritancy and high-dose oncogenicity warrant targeted safeguards, blanket restrictions risk causal by equating all exposures equally, disregarding first-principles where formaldehyde's rapid oxidation to limits systemic at low doses. Ongoing disputes, including stakeholder comments on the EPA's draft evaluations, underscore calls for risk-benefit frameworks incorporating verifiable exposure data over modeled extrapolations, as existing multilayered regulations—spanning OSHA, EPA, and state rules—already mitigate identified hazards without necessitating further economic burdens.

Environmental Considerations

Sources of Emissions

Formaldehyde emissions to the environment occur through direct releases and secondary atmospheric formation from both and anthropogenic precursors. In the ambient atmosphere, secondary production via photo-oxidation of hydrocarbons predominates, with sources contributing through oxidation of biogenic volatile organic compounds (VOCs) emitted by and direct emissions from events like forest fires and volcanic activity. Anthropogenic direct emissions arise mainly from incomplete processes, including stationary sources such as coal-fired boilers (emission factor 0.027–0.53 ng/J), (0.038–0.43 ng/J), and mobile sources like vehicles (0.05–0.83 g/). Industrial activities contribute via formaldehyde production (e.g., 0.38 kg/Mg from silver catalyst processes uncontrolled) and downstream uses like manufacturing (0.15–1.5 kg/Mg). Oil refining operations, such as catalytic cracking, release 1.0–2.2 kg per 1000 barrels processed. In the United States, residential wood burning accounts for 2.33 × 10³ to 2.56 × 10⁵ metric tons annually, while nationwide atmospheric photo-oxidation from all VOC sources ranges from 5 × 10¹⁰ to 2 × 10¹¹ kg per year. Secondary anthropogenic formation, driven by oxidation of emitted VOCs from , solvents, and industry, often exceeds primary emissions in urban and polluted regions. and soil emissions are minor, typically from industrial effluents or leaching, but atmospheric deposition represents the primary environmental pathway.

Fate, Transport, and Mitigation

Formaldehyde exhibits limited persistence in environmental compartments due to rapid degradation processes. In the atmosphere, it undergoes photolysis and oxidation primarily by hydroxyl radicals, resulting in an atmospheric lifetime of approximately 1 to 4 hours under typical conditions, though estimates range up to 19 hours in cleaner air scenarios. This degradation yields products such as and , limiting long-term accumulation. In aqueous environments, formaldehyde is subject to microbial breakdown by , with a of 2 to 20 days, and it exists predominantly as (the hydrated form) in dilute solutions. In , it shows low persistence due to volatility and , with minimal potential for leaching to owing to its high reactivity and low adsorption. Transport of formaldehyde is dominated by its gaseous phase in air, where it is emitted from anthropogenic sources like and , as well as natural ones such as burning. Approximately 99% of released formaldehyde partitions to the atmosphere, facilitating short-range dispersion via but restricting long-distance transport due to its brief lifetime. In water and soil, mobility is constrained by rapid transformation, preventing significant contamination or in sediments. Overall, its environmental distribution favors air, with negligible deposition to other media under ambient conditions. Mitigation strategies emphasize source reduction to curb emissions, as formaldehyde's short environmental residence time reduces the efficacy of post-release remediation. For combustion-related releases, such as from and industrial stacks, catalytic converters and maintenance can substantially lower output. Regulatory measures, including U.S. EPA designation of formaldehyde as a hazardous air under Section 112 of the Clean Air Act, enforce national emission standards for major sources, targeting industrial facilities and products like composite wood. Additional approaches involve substituting high-emission materials in manufacturing and enhancing combustion efficiency to minimize incomplete oxidation, which generates formaldehyde as a . These interventions, grounded in empirical emission inventories, prioritize prevention over abatement given the compound's reactivity.

References

  1. https://pubchem.ncbi.nlm.nih.gov/compound/Formaldehyde
  2. https://www.epa.gov/sites/default/files/2016-09/documents/formaldehyde.pdf
  3. https://www.epa.gov/formaldehyde/facts-about-formaldehyde
  4. https://wwwn.cdc.gov/TSP/PHS/PHS.aspx?phsid=218&toxid=39
  5. https://www.epa.gov/indoor-air-quality-iaq/what-should-i-know-about-formaldehyde-and-indoor-air-quality
  6. https://wwwn.cdc.gov/TSP/MMG/MMGDetails.aspx?mmgid=216&toxid=39
  7. https://wwwn.cdc.gov/Tsp/ToxFAQs/ToxFAQsDetails.aspx?faqid=219&toxid=39
  8. https://publications.iarc.who.int/_publications/media/download/3805/c24b0ad4f82efe0d57ddf335f2c12e9badb9507b.pdf
  9. https://www.cancer.gov/about-cancer/causes-prevention/risk/substances/formaldehyde/formaldehyde-fact-sheet
  10. https://www.epa.gov/assessing-and-managing-chemicals-under-tsca/risk-evaluation-formaldehyde
  11. https://www.formacare.eu/about-formaldehyde/history-of-formaldehyde/
  12. https://capitalresin.com/the-long-preserved-history-of-formaldehyde/
  13. https://www.chemicals.co.uk/blog/what-is-formaldehyde
  14. https://pubs.acs.org/doi/10.1021/cen-v032n014.p1398
  15. https://library.sciencemadness.org/library/books/formaldehyde.pdf
  16. https://www.americanchemistry.com/chemistry-in-america/chemistries/formaldehyde
  17. https://www.wired.com/2012/10/the-formaldehyde-conspiracy/
  18. https://www.slchemtech.com/news/formaldehyde-manufacturing-process.html
  19. https://www.icis.com/explore/resources/news/2008/05/12/9122818/a-timeline-of-chemical-manufacturing/
  20. https://topblogtenz.com/formaldehyde-ch2o-lewis-structure-molecular-geometry-hybridization-bond-angle/
  21. https://www-backup.salemstate.edu/molecular-geometry-of-formaldehyde
  22. https://www.ck12.org/flexi/chemistry/hybrid-orbitals-sp-and-sp2/what-is-the-molecular-shape-hybridization-and-polarity-of-h2co/
  23. https://www.chegg.com/homework-help/questions-and-answers/calculate-dipole-moment-formaldehyde-debye-partial-charge-oxygen-calculated-037-partial-ch-q27974451
  24. https://chem.libretexts.org/Courses/Williams_School/Chemistry_II/01%253A_Introduction_to_Organic_Chemistry/1.09%253A_Polar_Covalent_Bonds_-_Dipole_Moments
  25. https://www.dcceew.gov.au/environment/protection/npi/substances/fact-sheets/formaldehyde-methyl-aldehyde
  26. https://cameochemicals.noaa.gov/chemical/22034
  27. https://www.inchem.org/documents/icsc/icsc/eics0275.htm
  28. https://www.atsdr.cdc.gov/toxprofiles/tp111-c3.pdf
  29. https://www.ncbi.nlm.nih.gov/books/NBK590839/table/formaldehyde_t01/
  30. https://pmc.ncbi.nlm.nih.gov/articles/PMC3519217/
  31. https://hsrm.umn.edu/sites/hsrm.umn.edu/files/2021-10/fs_formaldehyde_oct_2018_jo_final.pdf
  32. https://www.statlab.com/pdfs/sds/Formaldehyde_37_Safety_Data_Sheet.pdf
  33. https://www.epa.gov/sites/default/files/2020-11/documents/formaldehyde.pdf
  34. https://publish.uwo.ca/~jkiernan/formglut.htm
  35. https://pubs.acs.org/doi/10.1021/acs.biochem.7b01304
  36. https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.00257/full
  37. https://pmc.ncbi.nlm.nih.gov/articles/PMC8879981/
  38. https://www.sciencedirect.com/science/article/pii/S0304389422010949
  39. https://royalsocietypublishing.org/doi/10.1098/rspb.1910.0013
  40. https://www.nature.com/articles/s42004-020-0324-z
  41. https://pubmed.ncbi.nlm.nih.gov/12570834/
  42. https://www.science.org/doi/10.1126/science.abp9201
  43. https://www.efsa.europa.eu/en/efsajournal/pub/3550
  44. https://pubmed.ncbi.nlm.nih.gov/28813411/
  45. https://www.ncbi.nlm.nih.gov/books/NBK138711/
  46. https://ww2.arb.ca.gov/resources/fact-sheets/formaldehyde
  47. https://www.dcceew.gov.au/environment/protection/npi/resource/student/formaldehyde
  48. https://www.sciencedirect.com/science/article/abs/pii/S2095927324006753
  49. https://iopscience.iop.org/article/10.1086/507118/pdf
  50. https://www.pnas.org/doi/10.1073/pnas.1604426113
  51. https://unacademy.com/content/cbse-class-12/study-material/chemistry/formaldehyde/
  52. https://www.phxequip.com/resource-detail/40/comparing-the-different-formaldehyde-production-processes
  53. https://patents.google.com/patent/US6362305B1/en
  54. http://www.sciencemadness.org/talk/viewthread.php?tid=525
  55. https://www.sciencedirect.com/science/article/abs/pii/S0926860X0200340X
  56. https://www.youtube.com/watch?v=g_B5t-y2Lcg
  57. https://pmc.ncbi.nlm.nih.gov/articles/PMC2522306/
  58. https://www.ncbi.nlm.nih.gov/books/NBK597639/
  59. https://pubs.acs.org/doi/10.1021/acs.iecr.7b02388
  60. http://www.alder.it/formaldehyde-production-process/
  61. https://www.mdpi.com/2073-4344/11/8/893
  62. https://www.mdpi.com/2227-9717/8/5/571
  63. https://www.slchemtech.com/news/comparing-different-formaldehyde-production-processes.html
  64. https://pmc.ncbi.nlm.nih.gov/articles/PMC10691333/
  65. https://www.sciencedirect.com/science/article/pii/S0167732206003138
  66. https://pubmed.ncbi.nlm.nih.gov/25742498/
  67. https://microscopy.duke.edu/guides/paraformaldehyde-formaldehyde-formalin
  68. https://link.springer.com/article/10.1007/s11144-021-02016-6
  69. https://www.sciencedirect.com/science/article/abs/pii/S0255270121003949
  70. https://patents.google.com/patent/US3979480A/en
  71. https://www.sciencedirect.com/topics/engineering/polyformaldehyde
  72. https://www.zero-engineeringplastics.com/news/introduction-to-pom-64226383.html
  73. https://pmc.ncbi.nlm.nih.gov/articles/PMC2896913/
  74. https://pmc.ncbi.nlm.nih.gov/articles/PMC4646298/
  75. https://pubs.acs.org/doi/10.1021/ja01188a018
  76. https://www.nature.com/articles/s41467-020-16935-w
  77. https://www.nature.com/articles/s42004-019-0224-2
  78. https://www.sciencedirect.com/science/article/pii/S1568786420301737
  79. https://pubs.acs.org/doi/10.1021/ac501354y
  80. https://www.sciencedirect.com/topics/engineering/formaldehyde-resin
  81. https://bioresources.cnr.ncsu.edu/resources/condensation-reaction-and-crystallization-of-urea-formaldehyde-resin-during-the-curing-process/
  82. https://as-proceeding.com/index.php/ijanser/article/view/1818
  83. https://pmc.ncbi.nlm.nih.gov/articles/PMC6418521/
  84. https://www.sciencedirect.com/science/article/pii/0032386196872776
  85. https://pubs.acs.org/doi/10.1021/jo01055a011
  86. https://www.chinesechemsoc.org/doi/10.31635/ccschem.024.202404848
  87. https://research.fs.usda.gov/treesearch/download/8581.pdf
  88. https://pubs.acs.org/doi/10.1021/acsomega.1c06375
  89. https://pubs.rsc.org/en/content/articlelanding/1991/ft/ft9918701513
  90. https://cdnsciencepub.com/doi/pdf/10.1139/v69-556
  91. https://pubmed.ncbi.nlm.nih.gov/6427185/
  92. https://link.springer.com/article/10.1007/BF00696960
  93. https://www.sciopen.com/article/10.26599/NR.2025.94907110
  94. https://pubs.acs.org/doi/10.1021/om00143a005
  95. https://www.turi.org/wp-content/uploads/2024/03/FactSheetFormaldehyde2013.pdf
  96. https://durablebuildingsolutions.org/building-future/materials-science/formaldehyde/
  97. https://www.americanchemistry.com/industry-groups/formaldehyde/benefits-applications
  98. https://www.formacare.eu/about-formaldehyde/applications/
  99. https://www.niehs.nih.gov/health/topics/agents/formaldehyde
  100. https://www.chemicalsafetyfacts.org/chemicals/formaldehyde/
  101. https://www.ncbi.nlm.nih.gov/books/NBK493462/
  102. https://www.americanchemistry.com/industry-groups/formaldehyde/resources/formaldehyde-medicine-medical-applications
  103. https://cloudsds.com/chemical-hazard-and-safety/use-of-formaldehyde-in-the-medical-field-a-detail-guide/
  104. https://www.americanchemistry.com/content/download/15235/file/Formaldehyde-Applications-in-Science-and-Preservation.pdf
  105. http://www.geosc.com/Assets/Files/Products-Docs/P-C-Product-Docs/Trimet-Products/Formaldehyde-TDS-EU
  106. https://gaotek.com/applications-of-formaldehyde-in-mining-quarrying-and-oil-and-gas-extraction-industry/
  107. https://www.cancer.org/cancer/risk-prevention/chemicals/formaldehyde.html
  108. https://www.osha.gov/sites/default/files/publications/formaldehyde-factsheet.pdf
  109. https://www.gov.uk/government/publications/formaldehyde-properties-incident-management-and-toxicology/formaldehyde-toxicological-overview
  110. https://www.osha.gov/formaldehyde/exposure-evaluation
  111. https://www.ncbi.nlm.nih.gov/books/NBK217652/
  112. https://www.osha.gov/formaldehyde/hazards
  113. https://pubmed.ncbi.nlm.nih.gov/18786592/
  114. https://www.sciencedirect.com/science/article/abs/pii/S0273230007001134
  115. https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1048AppC
  116. https://www.ncbi.nlm.nih.gov/books/NBK597627/
  117. https://publications.iarc.who.int/Book-And-Report-Series/Iarc-Monographs-On-The-Identification-Of-Carcinogenic-Hazards-To-Humans/Formaldehyde-2-Butoxyethanol-And-1--Em-Tert-Em--Butoxypropan-2-ol-2006
  118. https://ntp.niehs.nih.gov/sites/default/files/ntp/roc/content/profiles/formaldehyde.pdf
  119. https://iris.epa.gov/document/&deid=223614
  120. https://academic.oup.com/toxsci/article/199/2/172/7636988
  121. https://www.tandfonline.com/doi/full/10.1080/10408444.2020.1854678
  122. https://pubmed.ncbi.nlm.nih.gov/15450712/
  123. https://blogs.the-hospitalist.org/content/formaldehyde-probably-doesnt-cause-leukemia-team-says
  124. https://www.americanchemistry.com/chemistry-in-america/news-trends/press-release/2021/studies-confirm-no-causal-association-between-formaldehyde-and-leukemia
  125. http://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1048
  126. https://www.cdc.gov/niosh/npg/npgd0293.html
  127. https://www.concordia.ca/content/dam/concordia/services/safety/docs/EHS-DOC-141_FormaldehydeSafetyGuidelines.pdf
  128. https://www.cdc.gov/niosh/idlh/50000.html
  129. https://www.cdc.gov/niosh/reproductive-health/prevention/formaldehyde.html
  130. https://www.epa.gov/formaldehyde/protect-against-exposures-formaldehyde
  131. https://www.health.state.mn.us/communities/environment/air/toxins/formaldehyde.htm
  132. https://pmc.ncbi.nlm.nih.gov/articles/PMC5152996/
  133. https://www.federalregister.gov/documents/2025/01/03/2024-31571/formaldehyde-risk-evaluation-under-the-toxic-substances-control-act-tsc-notice-of-availability
  134. https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.1048
  135. https://www.epa.gov/formaldehyde/laws-and-regulations-concerning-formaldehyde
  136. https://publications.iarc.who.int/_publications/media/download/2766/22ab0b88b2d96379f2497baea6a2ae168a9a12c8.pdf
  137. https://chimarhellas.com/wp-content/uploads/2021/06/formaldehyde_2008.pdf
  138. https://www.epa.gov/system/files/documents/2025-01/14.-formaldehyde-.-occupational-exposure-assessment-.-public-release-.-hero-.-dec-2024.pdf
  139. https://www.epa.gov/chemicals-under-tsca/epa-releases-updated-draft-risk-calculation-memorandum-formaldehyde-under-tsca
  140. https://cen.acs.org/policy/chemical-regulation/EPA-reverses-course-safe-formaldehyde/103/web/2025/12
  141. https://www.americanchemistry.com/chemistry-in-america/news-trends/blog-post/2024/propublica-s-misleading-report-on-formaldehyde-what-you-need-to-know
  142. https://cen.acs.org/policy/chemical-regulation/Fight-over-formaldehyde-safety-continues/103/web/2025/01
  143. https://www.americanchemistry.com/chemistry-in-america/news-trends/press-release/2023/epa-scientific-advisory-body-raises-fundamental-issues-about-agency-s-draft-formaldehyde-assessment
  144. https://www.rgj.com/story/opinion/2023/12/04/epas-crackdown-on-formaldehyde-ignores-its-use-in-fuel-efficiency-green-construction/71758371007/
  145. https://sph.unc.edu/sph-news/low-doses-of-formaldehyde-not-likely-to-produce-cancer-causing-dna-adducts/
  146. https://pmc.ncbi.nlm.nih.gov/articles/PMC8042688/
  147. https://www.epa.gov/chemicals-under-tsca/epa-finalizes-tsca-risk-evaluation-formaldehyde
  148. https://www.propublica.org/article/formaldehyde-epa-report-public-health
  149. https://www.americanchemistry.com/chemistry-in-america/news-trends/press-release/2024/potential-epa-midnight-actions-on-formaldehyde-risk-prioritizing-political-timelines-over-requirement-to-use-best-available-science
  150. https://www.epa.gov/system/files/documents/2025-01/59.-formaldehyde-.-response-to-comments-.-public-release-.-hero-.-dec-2024.pdf
  151. https://acp.copernicus.org/articles/19/6717/2019/
  152. https://pubs.acs.org/doi/full/10.1021/acsestair.4c00317
  153. https://www.atsdr.cdc.gov/toxprofiles/tp111-c5.pdf
  154. https://acp.copernicus.org/articles/23/2997/2023/
  155. https://sitem.herts.ac.uk/aeru/ppdb/en/Reports/359.htm
  156. https://www.epa.gov/system/files/documents/2024-03/formaldehyde-draft-re-environmental-risk-assessment-public-release-hero-march-2024.pdf
  157. https://montrose-env.com/blog/understanding-formaldehyde-emissions-and-their-impacts-on-the-environment/
  158. https://www.epa.gov/system/files/documents/2024-03/2.-formaldehyde-draft-re-chemistry-fate-and-transport-assessment-public-release-hero-march-2024.pdf
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