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absorbed dose -
The amount of a substance (e.g., a chemical) that enters the body tissue of an exposed organism.
The movement of a chemical from the point of initial contact across a biologic barrier (such as skin) into the bloodstream.
acceptable daily intake (ADI) -
The maximal dose of a hazardous substance that can be consumed daily without causing adverse health effects over a lifetime.
acute effect -
An effect that results from a brief exposure or shortly after an acute exposure.
acute exposure -
A short-term exposure that lasts from hours to several days.
additive effects -
The combined biologic effects of 2 or more risk agents are additive when equal to the sum of the effects of the agents acting alone.
Army Environmental Hygiene Agency
Liquid or solid particles suspended in air.
air model -
Mathematical description of the transport of contaminants from their source through the air to their receptor populations.
ambient air -
Any unconfined portion or the atmosphere; open air; surrounding air.
ambient concentration -
The average amount of a substance in a particular environmental medium: air, water, soil, or vegetation.
Ames test -
A relatively rapid and inexpensive screening procedure using bacteria to determine whether a substance causes mutations.
Agency for Toxic Substances and Disease Registry.
background levels -
The levels of chemicals normally present in environmental media.
benign tumor -
A tumor that is confined to the vicinity in which it arises and does not invade surrounding tissue or metastasize to distant organs.
In experimental design, inaccuracy that leads to results or conclusions not representative of the population under study.
A metabolic process wherein an inactive chemical is converted to an active one in the body.
The use of organisms to measure the biological effect of an agent or condition.
The extent to which a drug or a toxic substance reaches its site of action.
A process wherein matter is decomposed by microorganisms.
biologic modeling -
Models of the fate and effects of chemicals in a biologic system.
biologic simulant -
A living microorganism that is not normally capable of causing infection, that represents the physical and biologic characteristics of potential microbiologic agents, and that is considered medically safe to operating personnel and surrounding communities.
biologic-warfare agent -
An organism (such as a bacterium or virus) used to kill or inflict disease.
A series of chemical alterations within the body whereby a foreign substance is transformed to a more or less toxic substance.
cancer potency factor -
A value used by regulatory agencies to describe the cancer risk as a function of dose of carcinogens.
cancer risk -
Expressed as a probability or proportion of individuals in a population and determined for a particular chemical by multiplying its lifetime exposure level times by cancer potency factor.
Any chemical or physical agent that can induce cancer.
case-control study -
An epidemiologic study in which persons are selected because they have a specific disease or other outcome (cases) and are compared to a control (referent comparison) group without the disease to evaluate whether there is a difference in their reported frequency of exposure to possible diseaserisk factors. Also termed a retrospective study or case referent study.
Centers for Disease Control and Prevention.
One of the bodies (normally 46 in man) in the cell nucleus that is the bearer of genes or thread-like structures in animal or plant nuclei that carry genetic material.
Having a persistent, recurring, or long-term nature; distinguished from acute.
chronic effect -
An effect of gradual onset and duration of months and years.
chronic exposure -
An exposure (usually at low concentration) of long duration, such as months or years.
cohort study -
An epidemiologic study in which a defined group of persons known to be exposed to a potential disease risk factor is followed over time and compared to a group of persons who were not known to be exposed to the potential risk factor to evaluate the differences in rates of the outcome. Also termed a prospective study, follow-up study, incidence study, retospective cohort, or historical cohort study.
A substance formed by the union of two or more elements.
The quantity of a substance per unit volume or weight.
confidence interval (95%) -
A range of values for the effect estimate within which the true value is thought to lie with a 95 % level of confidence.
confounder (confounding factor) -
A factor that is associated with both the exposure and outcome of interest and can distort the apparent magnitude of the effect of the study factor.
Any physical, chemical, biologic, or radioactive substance or matter that has been introduced into air, water, soil, food, drugs, cosmetics, industrial or consumer products.
Individuals who are similar to cases usually with respect to age, sex, and race and who are free of the disease of interest.
cumulative exposure -
The summation of exposures of an organism to a substance (e.g., a chemical) over a period of time.
default assumption -
An assumption about a receptor-population characteristic that is made when actual information about that characteristic is absent.
dermal exposure -
Contact between a substance (e.g., a chemical) and the skin.
developmental effects -
Effects on the physical or behavioral development of offspring.
The movement of suspended or dissolved particles from a more concentrated to a less
concentrated region as a result of the random movement of individual particles. The process tends to distribute the particles uniformly throughout the available volume.
To dissipate; to scatter; to dilute.
The act of dispersing or being dispersed.
The molecule that encodes genetic information (genes) contained in chromosomes. It may be altered by mutagens.
The amount of a risk agent that enters or interacts with organisms. An administered dose is the amount of substance administered to an animal or human, usually measured in milligrams per kilogram of body weight; milligrams per square meter of body surface area; or parts per million of the diet, drinking water, or ambient air. An effective dose is the amount of the substance reaching the target organ.
The ratio of direct inhalation exposure of ZnCdS and indirect exposures (ingestion and through skin contact).
dose-response assessment -
Evaluation of the relationship between exposure levels and the incidence of adverse effects.
dose-response model -
A mathematical description of the relationship between exposure levels and the biological effect or incidence of an effect.
end points of toxicity -
Adverse effects elicited as a result of exposure to a substance.
environmental effect -
Effect on the living and nonliving components of the environment.
environmental fate -
The disposition of a substance in various environmental media such as air, water, and soil.
environmental media -
The components of the environment that can become contaminated and to which human exposure could occur.
A large protein that speeds up the rate of a biochemical reaction.
Environmental Protection Agency.
The study of the distribution and determinants of health-related states or events in specified populations.
1. Proximity to/or contact with a source of a disease agent in such a maimer that effective transmission of the agent or harmful effects of the agent can occur.
2. The amount of a factor to which a group or individual was exposed; sometimes contrasted with dose, the amount that enters or interacts with the organism.
exposure assessment -
Determination of the conditions under which people could be exposed to contaminants and of the frequency and levels of exposure that could occur.
exposure dose -
The level (amount) of contaminant in the air, water, or soil to which people are exposed.
exposure duration -
The length of time that a receptor population is exposed to a contaminant.
exposure pathway -
How receptor populations are exposed to contaminated media.
exposure route -
Route by which a contaminant enters the body, dermal, inhalation, or oral.
The formation of fibrous tissue, usually as a reparative or reactive process.
Forced feeding of a test animal, usually through a tube passed into the stomach.
Capable of causing heritable changes or damage leading to heritable changes in genetic material.
A potential source of risk that does not necessarily produce risk. A hazard produces risk only if an exposure pathway exists and if exposures create the possibility of adverse consequences.
hazard identification -
Determination of the identities and quantities of environmental contaminants
present that can pose a hazard to human health.
hazardous substance -
Any substance that poses a threat to human health or the environment.
Pertaining to the liver.
High- and Low-Dose Extrapolation -
The process of making inferences about a chemical's effects on humans who are exposed to low doses of it in the environment, for example, on the basis of experiments in which laboratory animals were exposed to very high doses of the chemical.
human health risk assessment -
A process used to estimate the likelihood of adverse health outcomes of environmental exposures to chemicals.
An increase in number of cells in a tissue or an organ.
immunologic effects -
Effects on the immune system that increase susceptibility to infections or other diseases.
International Agency for Research on Cancer.
The number of instances of illness during a given period of time in a specified population.
Amount of material inhaled, absored through the skin, or ingested during a specified period of time.
A dose resulting from the movement of a substance from the breathing zone through the air passages of the lung and into the blood.
interspecies extrapolation -
The process of making inferences regarding the human toxicity of a chemical on the basis of experiments with laboratory animals exposed to that chemical.
in vitro -
Outside living organisms (e.g., for instance, in a test tube).
in vivo -
Within living organisms.
The line connecting points on a graph or map that have equal or corresponding values with regard to specific variables.
kilogram (kg) -
One thousand grams. A kilogram is about 2.2 pounds.
Time from the first exposure to a substance (e.g., a chemical) until the appearance of a toxic effect. For cancer, this period may be 10 to 20 years in humans.
The dose that when administered to all animals in a test (over a specified period) is lethal to 50% of the animals.
lifetime exposure -
Total amount of exposure to a substance that a human would receive in a lifetime (usually assumed to be 75 years).
linearized multistage model -
A dose-response model that is used most often by regulatory agencies to perform high- to low-dose extrapolation for carcinogens using animal data.
Breakdown of lipoproteins--complexes or compounds containing lipid and protein.
Liter (I) -
A liter is a little larger than a liquid quart.
lowest-observed-adverse-effect level (LOAEL) -
The lowest dose of a chemical that produced an adverse effect when it was administered to animals in a toxicity study.
malignant tumor -
A tumor that has invaded neighboring tissue and/or undergone metastasis to distant body sites.
margin of safety -
The ratio of a dose that causes an effect in animals to the expected human dose level.
maximal contaminant level (MCL) -
A level of chemical that may not be exceeded in drinking water.
maximally exposed individual (MEI) -
A hypothetical person whose exposure to contaminated media is assumed to occur at the highest levels possible throughout his or her entire lifetime.
maximal tolerated dose -
The highest dose that can be administered to animals for 2 yr without causing death from causes other than cancer or other excessive toxicity, often indicated by significant body weight loss.
mechanism of action -
The way in which a substance (e.g., a chemical) exerts its toxic effect(s).
A statistical procedure that combines the results of several studies to produce a result that is hoped to be more reliable than that of a single study.
All the biologic reactions that take in a cell or an organism.
A chemical product of metabolism.
microgram (µg) -
One millionth of a gram.
milligram (rag) -
One thousandth of a gram.
Any substance that can cause a change in genetic material.
mutagenic effects -
Irreversible alterations in the structure of DNA.
National Research Council.
Death of cells, tissues, or organ of the body.
Aberrant new abnormal cells or tissue whose growth is uncontrollable and progressive.
neurologic effects -
Effects on the nervous system.
A chemical that produces adverse effects on the nervous system.
nonbiologic simulant -
A nonliving inert (usually inorganic) material chosen to resemble the size of biological warfare (BW) agents for penetration in the respiratory tract; it is not itself a BW agent.
no-observed-adverse-effect-level (NOAEL) -
The highest dose of a chemical that could be administered to animals in a toxicity study without producing an adverse effect.
odds ratio -
Measure of association in case-control studies which estimates the ratio of odds of exposure among cases compared to the odds of exposure among controls. The measure approximates the relative risk.
The formation of bone.
Occupational Safety and Health Administration.
Microorganisms potentially harmful to humans or animals, such as bacteria, viruses, and parasites.
Capable of causing disease.
pharmacokinetic model -
A mathematical representation of pharmacokinetics.
The sum of the absorption, distribution, metabolism, and excretion of a chemical between the time it enters the body and when it leaves.
A visible or measurable discharge of a contaminant into air or water from a given point of origin.
Any material entering the environment whose nature, location, or quantity produces undesired effects.
The degree of ability to cause strong physiologic or toxic effects.
Ability of a study to detect a true relation between an exposure and a health outcome.
A numerical value between 0 and 1 that represents the likelihood of something.
proportionate mortality ratio (PMR) -
The number of the observed deaths from a particular cause in the study of population per 100 total deaths in the same period.
quantitative risk assessment -
The probability of disease or proportion of individuals in a population that would develop a disease as a result of exposure to a toxic substance.
receptor population -
The groups of people that may be exposed to contaminated media.
reference concentration (RfC) -
A value used by the Environmental Protection Agency to limit human exposure to potentially hazardous levels of chemicals in air. Derived in the same manner as the reference dose.
reference dose (RfD) -
An estimate of the highest daily dose of a risk agent that is unlikely to produce an appreciable deleterious effect in humans. Used by Environmental Protection Agency to express
a conservative threshold value for a dose-response relationship for noncarcinogenic effects. Similar to the acceptable daily intake (ADI).
relative risk -
Ratio of the risk of a disease or outcome in persons exposed to a particular risk factor to the risk in unexposed persons.
The degree of stability exhibited when a measurement is repeated. The degree to which the results obtained by a measurement procedure can be replicated. Lack of reliability can arise from divergence between observers or instruments of measurement or from instability of the attribute being measured.
Related to the kidney.
reproductive effects -
Effects on fertility or offspring survival.
Capable of being inhaled.
The probability of a specific outcome given a particular set of conditions.
risk assessment -
A systematic process for quantifying and describing the risk associated with some substance.
risk characterization -
Estimate of the likelihood of an adverse health outcome in an exposed population.
risk management -
The process of deciding what should be done about the results of risk assessments.
A location where pollutants are collected by such means or processes as absorption. The opposite of source.
Able to dissolve in a liquid.
subchronic exposure -
Exposures that last about 10 % of an organism's life span.
Refers to chemicals and other external, nonliving sources of potential hazard, such as ionizing radiation and microwaves.
Substitute; one put into the place of another.
Production of an effect by two or more agents acting together that is greater than the sum of the effects that would be produced by each agent individually.
synergistic effects -
The combined biologic effects of two or more risk agents that are synergistic.
systemic effects -
Toxic effects of a substance at sites remote from the point of initial contact; presence of systemic effects implies that absorption and distribution have occurred.
target organ -
The specific organ affected by a dose of a toxic substance; not necessarily the organ receiving the highest concentration.
Substance that causes birth defects (malformation or serious deviation from normal development of embryos and fetuses).
The lowest dose of a substance (e.g., a chemical) at which a specified measurable effect is observed and below which it is not observed.
Harmful to living organisms.
The adverse effects of chemicals on living organisms.
The study of adverse effects of chemicals on living organisms.
toxic substance -
A substance that, when introduced into or absorbed by a living organism, destroys life or injures health.
Abnormal growth of tissue that is uncontrolled and progressive. A neoplasm.
ultraviolet (UV) light -
A form of high-energy, invisible light capable of causing tissue damage.
uncertainty factors -
Factors used to divide a no-observed-adverse-effect level (NOAEL) or low-observed-adverse-effects level (LOAEL) to obtain a reference dose (RfD) that is intended to be health-protective by accounting for the uncertainty inherent in interspecies extrapolation. The