Any exposure surface that may retard the rate of penetration of an agent into a target. Examples of absorption barriers are the skin, respiratory tract lining, and gastrointestinal tract wall (cf. exposure surface).

An aquifer is an underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, silt, or clay) from which groundwater can be usefully extracted using a water well.

The rate and extent to which an agent can be absorbed by an organism and is available for metabolism or interaction with biologically significant receptors. Bioavailability involves both release from a medium (if present) and absorption by an organism.

 

A typical or average level of a chemical in the environment. Background often refers to naturally occurring or uncontaminated levels, i.e., the amount of an agent in a medium (e.g., water, soil) that is not attributed to the source(s) under investigation in an exposure assessment. Background level(s) can be naturally occurring or the result of human activities. (Note: natural background is the concentration of an agent in a medium that occurs naturally or is not the result of human activities).

Indicator of changes or events in biological systems. Biological markers of exposure refer to cellular, biochemical, analytical, or molecular measures that are obtained from biological media such as tissues, cells, or fluids and are indicative of exposure to an agent.

An estimate of exposure, dose, or risk that is higher than that incurred by the person with the highest exposure, dose, or risk in the population being assessed. Bounding estimates are useful in developing statements that exposures, doses, or risks are ‘‘not greater than’’ the estimated value.

Any substance that may produce cancer.

The Comprehensive Environmental Response, Compensation, and Liability Act of 1980, also known as Superfund. This is the legislation that created ATSDR.

A volume containing the mass of agent that contacts the exposure surface.

A continuous or intermittent long-term contact between an agent and a target. (Other terms, such as ‘‘long-term exposure,’’ are also used).

A source of risk that does not necessarily imply potential for occurrence. A hazard produces risk only if an exposure pathway exists, and if exposures create the possibility of adverse consequences.

The total cumulative concentration of hydrocarbons associated with a petroleum product containing 10 or more carbon atoms.

A continuous record of instantaneous values over a time period (e.g., exposure, dose, medium intake rate)

The condition where valid information, usually analytical environmental data, indicates the presence of contaminant(s) of a public health concern in one or more environmental media contacting humans (i.e., air, drinking water, soil, food chain, surface water), and there is evidence that some of those persons have an identified route(s) of exposure (i.e., drinking contaminated water, breathing contaminated air, having contact with contaminated soil, or eating contaminated food).

The way in which a person may contact a chemical substance. For example, drinking (ingestion) and bathing (skin contact) are two different routes of exposure to contaminants that may be found in water.

The integral of instantaneous exposures over the exposure duration. An example is the area under a daily time profile of personal air monitor readings, with units of concentration multiplied by time.

The time-integrated exposure divided by the exposure duration. An example is the daily average exposure of an individual to carbon monoxide. (Also called  timeweighted average exposure).

The process by which an agent crosses an absorption barrier (see dose).

Sites where human exposure to contaminated media is occurring or has occurred in the past, but the exposure is below a level of health hazard.

In risk assessment, the probability that something will cause injury, combined with the potential severity of that injury.

The 1986 legislation that broadened ATSDR's responsibilities in the areas of public health assessments, establishment and maintenance of toxicologic databases, information dissemination, and medical education.

The origin of an agent for the purposes of an exposure assessment.

Any entity, stimulus, or condition that can modulate normal functions of the organism or induce an adverse response (e.g., agent, lack of food, drought).

An area of chemicals in a particular medium, such as air or groundwater, moving away from its source in a long band or column. A plume can be a column of smoke from a chimney or chemicals moving with groundwater.

The Environmental Protection Agency's (EPA) listing of sites that have undergone preliminary assessment and site inspection to determine which locations pose immediate hazard to persons living or working near the release. These sites are most in need of cleanup.

Under the MCP, a RAM is an action that may be taken by the responsible party to limit or localize a chemical release until a more comprehensive remedial action can be taken.

Sites that pose a public health hazard as the result of long-term exposures to hazardous substances.

Another name for the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), which created ATSDR.

The evaluation of data and information on the release of hazardous substances into the environment to assess any current or future effects on public health, develop health advisories or other recommendations, and identify studies or actions needed to evaluate and mitigate or prevent human health effects; also, the document resulting from that evaluation.

A behaviour characterized by deliberate ingestion of non-nutritive substances such as soil.

A contact between an agent and a target of intermediate duration between acute and chronic

Any biological entity that receives an exposure or a dose (e.g., a human, human population, or a human organ).

Surroundings that can be treated as homogeneous or well characterized in the concentrations of an agent (e.g., home, office, automobile, kitchen, store). This term is generally used for estimating inhalation exposures.

The rate at which the medium crosses the outer exposure surface of a target, during ingestion or inhalation.

Material (e.g., air, water, soil, food, consumer products) surrounding or containing an agent, i.e.,  soil, water, air, plants, animals, or any other parts of the environment that can contain contaminants.

The MCP is the Massachusetts Department of Environmental Protection regulation for reporting, assessing, and cleaning up releases of oil and hazardous material.

Under the MCP, an IRA can be any of a number of assessments or actions performed quickly to address a sudden chemical release.

The process by which an agent crosses an outer exposure surface of a target without passing an absorption barrier, i.e. through ingestion or inhalation (see dose).

Breathing. Exposure may occur from inhaling contaminants because they can be deposited in the lungs, taken into the blood, or both.

Swallowing (such as eating or drinking). Chemicals can get in or on food, drink, utensils, cigarettes, or hands where they can be ingested. After ingestion, chemicals can be absorbed into the blood and distributed throughout the body.

A surface on a target where an agent is present. Examples of outer exposure surfaces include the exterior of an eyeball, the skin surface, and a conceptual surface over the nose and open mouth. Examples of inner exposure surfaces include the gastrointestinal tract, the respiratory tract, and the urinary tract lining. As an exposure surface gets smaller, the limit is an exposure point.

A combination of facts, assumptions, and inferences that define a discrete situation where potential exposures may occur. These may include the source, the exposed population, the time frame of exposure, microenvironment(s), and  activities. Scenarios are often created to aid exposure assessors in estimating exposure.

The way an agent enters a target after contact (e.g., by ingestion, inhalation, or dermal absorption).

Estimated contaminant concentrations in specific media that are not likely to cause adverse health effects, given a standard daily ingestion rate and standard body weight. The comparison values are calculated from the scientific literature available on exposure and health effects.

The time of continuous contact between an agent and a target

The amount of one substance dissolved or contained in a given amount of another. For example, sea water contains a higher concentration of salt than fresh water.

The course an agent takes from the source to the target.

A conceptual or mathematical representation of the exposure process.

The amount of agent present in the contact volume. For example, the total mass of residue collected with a skin wipe sample over the entire exposure surface is an exposure mass.

The exposure mass divided by the exposure surface area. For example, a dermal exposure measurement based on a skin wipe sample, expressed as a mass of residue per skin surface area, is an exposure loading.

The number of exposure events in an exposure duration.

The occurrence of continuous contact between an agent and a target.

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The length of time over which continuous or intermittent contacts occur between an agent and a target. For example, if an individual is in contact with an agent for 10min a day, for 300 days over a 1-year time period, the exposure duration is 1-year.

Under the MCP, when cleanup of a chemical release is complete the responsible party submits an RAO to the MADEP. The RAO classifies the disposal site as posing no significant risk.

The exposure mass divided by the contact volume or the exposure mass divided by the mass of contact volume depending on the medium.

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.

Contact with a chemical by swallowing, by breathing, or by direct contact (such as through the skin or eyes [exposure surfaces]). Exposure may be short term (acute) or long term (chronic), and the duration of exposure may be relevant.

The presence of hazardous substances in the environment. From the public health perspective, environmental contamination is addressed when it potentially affects the health and quality of life of people living and working near the contamination.

Dose per unit time

The amount of substance to which a person is exposed, i.e. the amount of agent tat enters a target after crossing an exposure surface. Dose often takes body weight into account.

Referring to the skin. Dermal absorption means absorption through the skin.

Any substance or material that enters a system (the environment, human body, food, etc.) where it is not normally found.

Substances containing carbon and different proportions of other elements such as hydrogen, oxygen, fluorine, chlorine, bromine, sulfur, or nitrogen; these substances easily become vapors or gases. A significant number of the VOCs are commonly used as solvents (paint thinners, lacquer thinner, degreasers, and dry cleaning fluids).