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Exposure assessment
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Exposure assessment
Exposure assessment is a branch of environmental science, toxicology, epidemiology, environmental engineering, and occupational hygiene that focuses on the processes that take place at the interface between the environment containing the contaminant of interest and the organism being considered. These are the final steps in the path to release an environmental contaminant, through transport to its effect in a biological system. The assessment includes measurements of the amount of a contaminant absorbed by an exposed target organism, in what form, at what rate, and how much of the absorbed amount is actually available to produce a biological effect. Although the same general concepts apply to other organisms, the overwhelming majority of applications of exposure assessment are concerned with human health, making it an important tool in public health.
Risk is a function of exposure to an agent and the agent's inherent hazard. An environmental risk assessment consists of steps to identify and to characterize a hazard, to determine the dose-response relationship between an agent and an adverse outcome, to estimate potential exposures and, ultimately, to characterize the risk posed by an exposure to a biological, chemical or physical agent. Exposure assessments can be conducted for human populations at various scales, such as entire populations of a city or a sensitive subpopulation or community within the city. They may also be conducted for ecosystems or habitats within an ecosystem. They may even be conducted for nonliving, i.e., "abiotic", systems, such as exposure of structures and materials to an air pollutant. Exposure assessments are key tools for risk management, such as when a hazardous waste site is found to have contaminated a community's water supply. In this case, the data and information from the exposure assessment will be part of the calculations of the difference between present exposures to a contaminant and desired exposures during cleanup, e.g., zero exposure if an alternate source of clean water, e.g., bottled water, temporarily replaces the public water supply, and expected exposures when target pollutant concentrations will have been reached following the remediation of the waste site.
Exposure assessment is the process of estimating or measuring the magnitude, frequency and duration of exposure to an agent, along with the number and characteristics of the population exposed. Ideally, it describes the sources, pathways, routes, and the uncertainties in the assessment. It is a necessary part of risk analysis and hence risk assessment.[citation needed]
Exposure analysis is the science that describes how an individual or population comes in contact with a contaminant, including quantification of the amount of contact across space and time. 'Exposure assessment' and 'exposure analysis' are often used as synonyms in many practical contexts. Risk is a function of exposure and hazard. For example, even for an extremely toxic (high hazard) substance, the risk of an adverse outcome is unlikely if exposures are near zero. Conversely, a moderately toxic substance may present substantial risk if an individual or a population is highly exposed.
Quantitative measures of exposure are used: in risk assessment, together with inputs from toxicology, to determine risk from substances released to the environment, to establish protective standards, in epidemiology, to distinguish between exposed and control groups, and to protect workers from occupational hazards.[citation needed]
The receptor-based approach is used in exposure science. It starts by looking at different contaminants and concentrations that reach people. An exposure analyst can use direct or indirect measurements to determine if a person has been in contact with a specific contaminant or has been exposed to a specific risk (e.g. accident). Once a contaminant has been proved to reach people, exposure analysts work backwards to determine its source. After the identification of the source, it is important to find out the most efficient way to reduce adverse health effects. If the contaminant reaches a person, it is very hard to reduce the associated adverse effects. Therefore, it is very important to reduce exposure in order to diminish the risk of adverse health effects. It is highly important to use both regulatory and non-regulatory approaches in order to decrease people's exposure to contaminants. In many cases, it is better to change people's activities in order to reduce their exposures rather than regulating a source of contaminants. The receptor-based approach can be opposed to the source-based approach. This approach begins by looking at different sources of contaminants such as industries and power plants. Then, it is important to find out if the contaminant of interest has reached a receptor (usually humans). With this approach, it is very hard to prove that a pollutant from a source has reached a target.[citation needed]
In this context exposure is defined as the contact between an agent and a target. Contact takes place at an exposure surface over an exposure period.
Mathematically, exposure is defined as
where E is exposure, C(t) is a concentration that varies with time between the beginning and end of exposure. It has dimensions of mass times time divided by volume. This quantity is related to the potential dose of contaminant by multiplying it by the relevant contact rate, such as breathing rate, food intake rate etc. The contact rate itself may be a function of time.
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Exposure assessment
Exposure assessment is a branch of environmental science, toxicology, epidemiology, environmental engineering, and occupational hygiene that focuses on the processes that take place at the interface between the environment containing the contaminant of interest and the organism being considered. These are the final steps in the path to release an environmental contaminant, through transport to its effect in a biological system. The assessment includes measurements of the amount of a contaminant absorbed by an exposed target organism, in what form, at what rate, and how much of the absorbed amount is actually available to produce a biological effect. Although the same general concepts apply to other organisms, the overwhelming majority of applications of exposure assessment are concerned with human health, making it an important tool in public health.
Risk is a function of exposure to an agent and the agent's inherent hazard. An environmental risk assessment consists of steps to identify and to characterize a hazard, to determine the dose-response relationship between an agent and an adverse outcome, to estimate potential exposures and, ultimately, to characterize the risk posed by an exposure to a biological, chemical or physical agent. Exposure assessments can be conducted for human populations at various scales, such as entire populations of a city or a sensitive subpopulation or community within the city. They may also be conducted for ecosystems or habitats within an ecosystem. They may even be conducted for nonliving, i.e., "abiotic", systems, such as exposure of structures and materials to an air pollutant. Exposure assessments are key tools for risk management, such as when a hazardous waste site is found to have contaminated a community's water supply. In this case, the data and information from the exposure assessment will be part of the calculations of the difference between present exposures to a contaminant and desired exposures during cleanup, e.g., zero exposure if an alternate source of clean water, e.g., bottled water, temporarily replaces the public water supply, and expected exposures when target pollutant concentrations will have been reached following the remediation of the waste site.
Exposure assessment is the process of estimating or measuring the magnitude, frequency and duration of exposure to an agent, along with the number and characteristics of the population exposed. Ideally, it describes the sources, pathways, routes, and the uncertainties in the assessment. It is a necessary part of risk analysis and hence risk assessment.[citation needed]
Exposure analysis is the science that describes how an individual or population comes in contact with a contaminant, including quantification of the amount of contact across space and time. 'Exposure assessment' and 'exposure analysis' are often used as synonyms in many practical contexts. Risk is a function of exposure and hazard. For example, even for an extremely toxic (high hazard) substance, the risk of an adverse outcome is unlikely if exposures are near zero. Conversely, a moderately toxic substance may present substantial risk if an individual or a population is highly exposed.
Quantitative measures of exposure are used: in risk assessment, together with inputs from toxicology, to determine risk from substances released to the environment, to establish protective standards, in epidemiology, to distinguish between exposed and control groups, and to protect workers from occupational hazards.[citation needed]
The receptor-based approach is used in exposure science. It starts by looking at different contaminants and concentrations that reach people. An exposure analyst can use direct or indirect measurements to determine if a person has been in contact with a specific contaminant or has been exposed to a specific risk (e.g. accident). Once a contaminant has been proved to reach people, exposure analysts work backwards to determine its source. After the identification of the source, it is important to find out the most efficient way to reduce adverse health effects. If the contaminant reaches a person, it is very hard to reduce the associated adverse effects. Therefore, it is very important to reduce exposure in order to diminish the risk of adverse health effects. It is highly important to use both regulatory and non-regulatory approaches in order to decrease people's exposure to contaminants. In many cases, it is better to change people's activities in order to reduce their exposures rather than regulating a source of contaminants. The receptor-based approach can be opposed to the source-based approach. This approach begins by looking at different sources of contaminants such as industries and power plants. Then, it is important to find out if the contaminant of interest has reached a receptor (usually humans). With this approach, it is very hard to prove that a pollutant from a source has reached a target.[citation needed]
In this context exposure is defined as the contact between an agent and a target. Contact takes place at an exposure surface over an exposure period.
Mathematically, exposure is defined as
where E is exposure, C(t) is a concentration that varies with time between the beginning and end of exposure. It has dimensions of mass times time divided by volume. This quantity is related to the potential dose of contaminant by multiplying it by the relevant contact rate, such as breathing rate, food intake rate etc. The contact rate itself may be a function of time.