Terminology Services

Exposure Factors Handbook Glossary

Long Name:

Exposure Factors Handbook: Glossary

Description:

Glossary of relevant terms from ORD Exposure Factors Handbook, a summary of the available statistical data on various factors used in assessing human exposure.

Publishing Organization:

Office of Research and Development /Center for Public Health and Environmental Assessment

Last Update:

September 2011

Program Site:

https://cfpub.epa.gov/ncea/risk/recordisplay.cfm?deid=236252

Terms & Acronyms

Search Terms

Contains Begins Exact Match

	Term
	Absorbed dose	Definition: The amount of an agent that enters a target by crossing an exposure surface that acts as an absorption barrier. See also Absorption barrier, Dose, and Internal dose.
	Absorption barrier	Definition: Any exposure surface that may retard the rate of penetration of an agent into a target. Examples include the skin, respiratory tract lining, and gastrointestinal tract wall.
	Activity pattern data	Definition: Information on human activities used in exposure assessments. These may include a description of the activity, frequency of activity, duration spent performing the activity, and the microenvironment in which the activity occurs.
	Activity pattern (time use) data	Definition: Information on activities in which various individuals engage, length of time spent performing various activities, locations in which individuals spend time and length of time spent by individuals within those various environments.
	Acute exposure	Definition: A single exposure to a toxic substance which may result in severe biological harm or death. Acute exposures are usually characterized as lasting no longer than a day, as compared to longer, continuing exposure over a period of time.
	Adherence factor	Definition: The amount of a material (e.g., soil) that adheres to the skin per unit of surface area.
	Age dependent adjustment factor	Definition: In cases where age-related differences in toxicity occur, differences in both toxicity and exposure need to be integrated across all relevant age intervals, by the use of age dependent potency adjustment factors (ADAFs). This is a departure from the way cancer risks have historically been calculated based upon the premise that risk is proportional to the daily average of the long-term adult dose. Acronym: ADAF
	Agent	Definition: Refers to a chemical, biological, or physical entity that contacts a target.
	Aggregate exposure	Definition: The combined exposure of an individual (or defined population) to a specific agent or stressor via relevant routes, pathways, and sources. Total exposure can include exposure through multiple routes (e.g., dermal, inhalation, and ingestion).
	Agricultural commodity	Definition: Used by U.S. EPA to mean plant (or animal) parts consumed by humans as food. When such items are raw or unprocessed, they are referred to as "raw agricultural commodities."
	Air exchange rate	Definition: Rate of air leakage through windows, doorways, intakes and exhausts, and "adventitious openings" (i.e., cracks and seams) that combine to form the leakage configuration of the building envelope plus natural and mechanical ventilation.
	All water sources	Definition: Includes water from all supply sources such as community water supply (i.e., tap water), bottled water, etc.
	Analytical uncertainty propagation	Definition: Examining how uncertainty in individual parameters affects the overall uncertainty of the exposure assessment.
	Anthropometric	Definition: The study of human body measurements for use in anthropological classification and comparison.
	As-consumed intake	Definition: Intake rate based on the weight of the food in the form that it is consumed (e.g., cooked or prepared).
	Assessment	Definition: A determination or appraisal of possible consequences resulting from an analysis of data.
	Average Daily Dose	Definition: The mean amount of an agent to which a person is exposed on a daily basis, often averaged over a long period of time. U.S. EPA is transitioning from average daily dose methodologies to more refined aggregate and cumulative approaches for estimating exposure across each lifestage. See also Lifetime average daily dose (LADD) and Time-averaged exposure. Acronym: ADD
	Basal Metabolic Rate	Definition: Minimum level of energy required to maintain normal body functions. Acronym: BMR
	Bayesian Analysis	Definition: Bayesian analysis is a method of statistical inference in which the knowledge of prior events is used to predict future events. Bayes' Theorem is a means of quantifying uncertainty.
	Benchmark Dose or Concentration	Definition: An exposure due to a dose or concentration of a substance associated with a specified low incidence of risk, generally in the range of 1% to 10%, of a health effect; or the dose or concentration associated with a specified measure or change of a biological effect.
	Best Tracer Method	Definition: Method for estimating soil ingestion that allows for the selection of the most recoverable tracer for a particular subject or group of subjects. Selection of the best tracer is made on the basis of the food/soil (F/S) ratio. Acronym: BTM
	Bias	Definition: A systematic error inherent in a method or caused by some feature of the measurement system.
	Bioaccumulate	Definition: The increase in concentration in living organisms as they take in contaminated air, water, or food because the substances are very slowly metabolized or excreted.
	Bioavailability	Definition: 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.
	Bioconcentrate	Definition: The accumulation of a chemical in tissues of a fish or other organism to levels greater than in the surrounding medium.
	Biokinetic model comparison	Definition: A methodology that compares direct measurements of a biomarker such as blood or urine levels of a toxicant with predictions from a biokinetic model.
	Biological marker	Definition: An indicator of changes or events in biological systems. Biological markers of exposure are 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. Biomarkers of effect are quantifiable changes, indicating exposure to a compound, while biomarkers of susceptibility are characteristics that make an individual susceptible to the effects of an exposure.
	Biomarker	Definition: An indicator of changes or events in biological systems. Biological markers of exposure are 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. Biomarkers of effect are quantifiable changes, indicating exposure to a compound, while biomarkers of susceptibility are characteristics that make an individual susceptible to the effects of an exposure.
	Biomarker model comparison	Definition: A methodology that compares results from a biokinetic exposure model to biomarker measurements children blood. The method is used to confirm assumptions about ingested soil and dust quantities in this handbook.
	Body Mass Index	Definition: The ratio of weight and height squared. Acronym: BMI
	Bootstrap	Definition: A statistical method of resampling data use to estimate variance and bias of an estimator and provide confidence intervals for parameters.
	Bounding estimate	Definition: An estimate of exposure, dose, or risk that is higher or lower than that incurred by the person with the highest or lowest 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" or "less than" the estimated value, because assumptions are used which define the likely bounding conditions.
	Central tendency exposure	Definition: A measure of the middle or the center of an exposure distribution. The mean is the most commonly used measure of central tendency.
	Chronic exposure	Definition: Repeated exposure by the oral, dermal, or inhalation route for more than approximately 10% of the life span in humans (more than approximately 90 days to 2 years in typically used laboratory animal species).
	Chronic intake	Definition: The long term period over which a substance crosses the outer boundary of an organism without passing an absorption barrier.
	Classical statistical methods	Definition: Estimating the population exposure distribution directly, based on measured values from a representative sample.
	Coating	Definition: Method used to measure skin surface area, in which either the whole body or specific body regions are coated with a substance of known density and thickness.
	Community water	Definition: Includes tap water ingested from community or municipal water supply.
	Comparability	Definition: The ability to describe likenesses and differences in the quality and relevance of two or more data sets.
	Concentration	Definition: Amount of a material or agent dissolved or contained in unit quantity in a given medium or system.
	Confidence intervals	Definition: An estimated range of values with a given probability of including the population parameter of interest. The range of values is usually based on the results of a sample that estimated the mean and the sampling error or standard error.
	Consumer-only intake rate	Definition: The average quantity of food consumed per person in a population composed only of individuals who ate the food item of interest during a specified period.
	Contact boundary	Definition: The 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. It is also referred to as an exposure surface.
	Contaminant concentration	Definition: Contaminant concentration is the concentration of the contaminant in the medium (air, food, soil, etc.) contacting the body and has units of mass/volume or mass/mass.
	Creel study	Definition: A study in which fishermen are interviewed while fishing.
	Cumulative exposure	Definition: Exposure via mixtures of contaminants both indoors and outdoors. Exposure may also occur through more than one pathway. New directions in risk assessments in U.S. EPA put more emphasis on total exposures via multiple pathways.
	Deposition	Definition: The removal of airborne substances to available surfaces that occurs as a result of gravitational settling and diffusion, as well as electrophoresis and thermophoresis.
	Dermal absorption	Definition: A route of exposure by which substances can enter the body through the skin.
	Dermal adherence	Definition: The loading of a substance onto the outer surface of the skin.
	Diary study	Definition: Survey in which individuals are asked to record food intake, activities, or other factors in a diary which is later used to evaluate exposure factors associated with specific populations.
	Direct water ingestion	Definition: Consumption of plain water as a beverage. It does not include water used for preparing beverages such as coffee or tea.
	Distribution	Definition: A set of values derived from a specific population or set of measurements that represents the range and array of data for the factor being studied.
	Doers	Definition: Survey respondents who report participating in a specified activity.
	Dose	Definition: The amount of an agent that enters a target after crossing an exposure surface. If the exposure surface is an absorption barrier, the dose is an absorbed dose. If the exposure surface is not an absorption barrier, the dose is an intake dose.
	Dose rate	Definition: Dose per unit time.
	Dose-response assessment	Definition: Analysis of the relationship between the total amount of an agent administered to, taken up by, or absorbed by an organism, system, or target population and the changes developed in that organism, system, or target population in reaction to that agent, and inferences derived from such an analysis with respect to the entire population. Dose-response assessment is the second of four steps in risk assessment.
	Dose-response curve	Definition: Graphical presentation of a dose-response relationship.
	Dose-response relationship	Definition: The resulting biological responses in an organ or organism expressed as a function of a series of doses.
	Dressed weight	Definition: The portion of the harvest brought into kitchens for use, including bones for particular species.
	Drinking water	Definition: All fluids consumed by individuals to satisfy body needs for internal water.
	Dry-weight intake rates	Definition: Intake rates that are based on the weight of the food consumed after the moisture content has been removed.
	Dust Ingestion	Definition: Consumption of dust that results from various behaviors including, but not limited to, mouthing objects or hands, eating dropped food, consuming dust directly, or inhaling dust that passes from the respiratory system into the gastrointestinal tract.
	Effect	Definition: Change in the state or dynamics of an organism, system, or (sub) population caused by exposure to an agent.
	Employer tenure	Definition: The length of time a worker has been with the same employer.
	Energy expenditures	Definition: The amount of energy expended by an individual during activities.
	Exclusively breast fed	Definition: Infants whose sole source of milk comes from human milk with no other milk substitutes.
	Exposed foods	Definition: Foods grown above ground.
	Exposure	Definition: Contact between an agent and a target.
	Exposure assessment	Definition: 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.
	Exposure concentration	Definition: The concentration of a chemical in its transport or carrier medium at the point of contact.
	Exposure duration	Definition: Length of time over which contact with the contaminant lasts.
	Exposure event	Definition: The occurrence of continuous contact between an agent and a target.
	Exposure factor	Definition: Factors related to human behavior and characteristics that help determine an individual's exposure to an agent.
	Exposure frequency	Definition: The number of exposure events in an exposure duration.
	Exposure loading	Definition: 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.
	Exposure pathway	Definition: The physical course a chemical takes from the source to the organism exposed.
	Exposure point
	Exposure route	Definition: The way a chemical pollutant enters an organism after contact, e.g., by ingestion, inhalation, or dermal absorption.
	Exposure scenario	Definition: A set of facts, assumptions, and interferences about how exposure takes place that aids the exposure assessor in evaluating estimating, or quantifying exposures.
	Exposure surface	Definition: See contact boundary.
	Fate	Definition: Pattern of distribution of an agent, its derivatives, or metabolites in an organism, system, compartment, or population of concern as a result of transport, partitioning, transformation, or degradation.
	Forced Ventilation
	Foremilk	Definition: Milk produced at the beginning of breastfeeding.
	General population	Definition: The total of individuals inhabiting an area or making up a whole group.
	Geographic information system	Definition: GIS is a system of hardware and software that captures, stores, analyzes, manages, and presents geographic data. Acronym: GIS
	Geometric mean	Definition: The nth root of the product of n values.
	Geophagy	Definition: A form of soil ingestion involving the intentional ingestion of earths, usually associated with cultural practices.
	Hazard	Definition: Inherent property of an agent or situation having the potential to cause adverse effects when an organism, system, or population is exposed to that agent.
	Hazard assessment	Definition: A process designed to determine the possible adverse effects of an agent or situation to which an organism, system, or target population could be exposed. The process typically includes hazard identification, dose-response evaluation and hazard characterization. The process focuses on the hazard, in contrast to risk assessment, where exposure assessment is a distinct additional step.
	High-end exposure	Definition: An estimate of individual exposure or dose for those persons at the upper end of an exposure or dose distribution, conceptually above the 90th percentile, but not higher than the individual in the population who has the highest exposure or dose. See also Bounding estimate.
	Hindmilk	Definition: Milk produced at the end of the breastfeeding.
	Home-produced foods	Definition: Fruits and vegetables produced by home gardeners, meat and dairy products derived from consumer-raised livestock, game meat, and home caught fish.
	Human Equivalent Concentration or Dose	Definition: The human concentration (for inhalation exposure) or dose (for other routes of exposure) of an agent that is believed to induce the same magnitude of toxic effect as the experimental animal species concentration or dose. This adjustment may incorporate toxicokinetic information on the particular agent, if available, or use a default procedure, such as assuming that daily oral doses experienced for a lifetime are proportional to body weight raised to the 0.75 power.
	Indirect water ingestion	Definition: Includes water added during food preparation, but not water intrinsic to purchased foods. Indirect water includes for example, water used to prepare baby formulas, cake mix, and concentrated orange juice.
	Indoor settled dust	Definition: Particles in building interiors that have settled onto objects, surfaces, floors, and carpeting. These particles may include soil particles that have been tracked into the indoor environment from outdoors.
	Infiltration	Definition: Air leakage through random cracks, interstices, and other unintentional openings in the building envelope.
	Inhalation dosimetry	Definition: Process of measuring or estimating inhaled dose.
	Inhalation unit risk	Definition: The upper-bound excess lifetime cancer risk estimated to result from continuous exposure to an agent at a concentration of 1 μg/m3 in air for a lifetime.
	Inhaled dose	Definition: The amount of an inhaled substance that is available for interaction with metabolic processes or biologically significant receptors after crossing the outer boundary of an organism.
	Insensible water loss	Definition: Evaporative water losses that occur during breastfeeding. Corrections are made to account for insensible water loss when estimating breast milk intake using the test weighing method.
	Intake	Definition: The process by which a substance crosses the outer boundary of an organism without passing an absorption barrier (e.g., through ingestion or inhalation).
	Intake dose	Definition: The amount of an agent that enters a target by crossing an exposure surface that does not act as an absorption barrier. See also Absorption barrier and Dose.
	Intake rate	Definition: Rate of inhalation, ingestion, and dermal contact depending on the route of exposure. For ingestion, the intake rate is simply the amount of food containing the contaminant of interest that an individual ingests during some specific time period (units of mass/time). For inhalation, the intake rate is the rate at which contaminated air is inhaled. Factors that affect dermal exposure are the amount of material that comes into contact with the skin, and the rate at which the contaminant is absorbed.
	Inter-individual variability	Definition: Variations between individuals in terms of human characteristics such as age or body weight, or behaviors such as location, activity patterns, and ingestion rates.
	Internal dose	Definition: The amount of an agent that enters a target by crossing an exposure surface that acts as an absorption barrier. Synonymous with absorbed dose. See also Absorption barrier and Dose.
	Interzonal air flows	Definition: Transport of air through doorways, ductwork, and service chaseways that interconnect rooms or zones within a building.
	Intra-individual variability	Definition: Fluctuations in an individual's physiologic (e.g., body weight), or behavioral characteristics (e.g., ingestion rates or activity patterns).
	Key study	Definition: A study that is the most up-to-date and scientifically sound for deriving recommendations for exposure factors. Alternatively, studies may be classified as "relevant" and not "key" for one or more of the following: (1) they provide supporting data (e.g., older studies on food intake that may be useful for trend analysis); (2) they provide information related to the factor of interest (e.g., data on prevalence of breast feeding); or (3) the study design or approach makes the data less applicable for exposure assessment purposes (e.g., studies with small sample size, studies not conducted in the United States). As new data or analyses are published, "key" studies may be moved to the "relevant" category because they are replaced by more up-to-date data or an analysis of improved quality.
	Lead isotope ratio methodology	Definition: A method that measures different lead isotopes in children's blood and/or urine, food, water, and house dust and compares the ratio of these isotopes to infer sources of lead exposure that may include dust or other environmental exposures.
	Life expectancy	Definition: The length of an individual's life.
	Lifestage	Definition: A distinguishable time frame in an individual's life characterized by unique and relatively stable behavioral and/or physiological characteristics that are associated with development and growth.
	Lifetime Average Daily Dose	Definition: Dose rate averaged over a lifetime. The LADD is used for compounds with carcinogenic or chronic effects. The LADD is usually expressed in terms of mg/kg-day or other mass/mass-time units. Often used in carcinogen risk assessments that employ linear low-dose extrapolation methods. See also Average daily dose and Time-averaged exposure. Acronym: LADD
	Limiting Tracer Method	Definition: Method for evaluating soil ingestion that assumes that the maximum amount of soil ingested corresponds with the lowest estimate from various tracer elements. Acronym: LTM
	Local circulation	Definition: Convective and adjective air circulation and mixing within a room or within a zone.
	Long-term exposure	Definition: Repeated exposure for more than 30 days, up to approximately 10% of the life span in humans (more than 30 days).
	Lowest-Observed-Adverse-Effect Level	Definition: The lowest exposure level at which there are biologically significant increases in frequency or severity of adverse effects between the exposed population and its appropriate control group. Acronym: LOAEL
	Margin of safety	Definition: For some experts, margin of safety has the same meaning as margin of exposure, while for others, margin of safety means the margin between the reference dose and the actual exposure.
	Mass-balance/tracer techniques	Definition: Method for evaluating soil intake that accounts for both inputs and outputs of tracer elements. Tracers in soil, food, medicine and other ingested items as well as in feces and urine are accounted for.
	Mean value	Definition: Simple or arithmetic average of a range of values, computed by dividing the total of all values by the number of values.
	Measurement end-point	Definition: Measurable (ecological) characteristic that is related to the valued characteristic chosen as an assessment point.
	Measurement error	Definition: A systematic error arising from inaccurate measurement (or classification) of subjects on the study variables.
	Mechanical ventilation	Definition: Controlled air movement driven by fans. Also referred to as forced ventilation.
	Median value	Definition: The value in a measurement data set such that half the measured values are greater and half are less.
	Metabolic Equivalent of Work	Definition: A dimensionless energy expenditure metric used to represent an activity level. Acronym: MET
	Microenvironment	Definition: Surroundings that can be treated as homogeneous or well characterized in the concentrations of an agent (e.g., home, office, automobile, kitchen, store).
	Mode of action	Definition: Defined as a sequence of key events and processes, starting with interaction of an agent with a cell, proceeding through operational and anatomical changes, and resulting in cancer formation.
	Model uncertainty	Definition: Uncertainty regarding gaps in scientific theory required to make predictions on the basis of causal inferences.
	Moisture content	Definition: The portion of foods made up by water. The percent water is needed for converting food intake rates and residue concentrations between whole-weight and dry-weight values.
	Monte Carlo technique	Definition: A repeated random sampling from the distribution of values for each of the parameters in a generic (exposure or dose) equation to derive an estimate of the distribution of (exposures or doses in) the population.
	Mouthing behavior	Definition: Activities in which objects, including fingers, are touched by the mouth or put into the mouth except for eating and drinking, and includes licking, sucking, chewing, and biting.
	Natural ventilation	Definition: Airflow through open windows, doors, and other designed openings in the building envelope.
	No-Observed-Adverse-Effect-Level	Definition: The highest exposure level at which there are no biologically significant increases in the frequency or severity of adverse effect between the exposed population and its appropriate control; some effects may be produced at this level, but they are not considered adverse or precursors of adverse effects. Acronym: NOAEL
	Non-dietary ingestion	Definition: Ingestion of non-food substances, typically resulting from the mouthing of hands and objects.
	Occupational mobility	Definition: An indicator of the frequency at which workers change from one occupation to another.
	Occupational tenure	Definition: The cumulative number of years a person worked in his or her current occupation, regardless of number of employers, interruptions in employment, or time spent in other occupations.
	Outdoor settled dust	Definition: Particles that have settled onto outdoor objects and surfaces due to either wet or dry deposition.
	Oxygen consumption	Definition: The rate at which oxygen is used by tissues. Acronym: VO2
	Parameter uncertainty	Definition: Uncertainty regarding some parameter.
	Partially breast fed	Definition: Infants whose source of milk comes from both human milk and other milk substitutes.
	Pathway	Definition: The physical course a chemical or pollutant takes from the source to the organism exposed.
	Per capita intake rate	Definition: The average quantity of food consumed per person in a population composed of both individuals who ate the food during a specified time period and those that did not.
	Physiologically-based pharmacokinetic modeling	Definition: PBPK modeling is an approach for predicting the absorption, distribution, metabolism and excretion of a compound in humans. Acronym: PBPK modeling
	Pica	Definition: Pica behavior is the repeated eating of non-nutritive substances, whereas soil-pica is a form of soil ingestion that is characterized by the recurrent ingestion of unusually high amounts of soil (i.e., on the order of 1,000-5,000 milligrams per day or more).
	Plain tap water	Definition: Excludes tap water consumed in the form of juices and other beverages containing tap water.
	Population mobility	Definition: An indicator of the frequency at which individuals move from one residential location to another.
	Population risk descriptor	Definition: An assessment of the extent of harm to the population being addressed. It can be either an estimate of the number of cases of a particular effect that might occur in a population (or population segment), or a description of what fraction of the population receives exposures, doses, or risks greater than a specified value.
	Potential dose	Definition: The amount of a chemical contained in material ingested, air breathed, or bulk material applied to the skin.
	Poverty/income ratio	Definition: Ratio of reported family income to federal poverty level.
	Precision	Definition: A measure of the reproducibility of a measured value under a given set of circumstances.
	Preparation losses	Definition: Net cooking losses, which include dripping and volatile losses, post cooking losses, which involve losses from cutting, bones, excess fat, scraps and juices, and other preparation losses which include losses from paring or coring.
	Primary data/analysis	Definition: Information gathered from observations or measurements of a phenomena or the surveying of respondents.
	Probabilistic uncertainty analysis	Definition: Technique that assigns a probability density function to each input parameter, then randomly selects values from each of the distributions and inserts them into the exposure equation. Repeated calculations produce a distribution of predicted values, reflecting the combined impact of variability in each input to the calculation. Monte Carlo is a common type of probabilistic Uncertainty analysis.
	Protected products	Definition: Foods that have an outer protective coating that is typically removed before consumption.
	Questionnaire/survey response	Definition: A "question and answer" data collection methodology conducted via in-person interview, mailed questionnaire, or questions administered in a test format in a school setting.
	Random samples	Definition: Samples selected from a statistical population such that each sample has an equal probability of being selected.
	Range	Definition: The difference between the largest and smallest values in a measurement data set.
	Ready-to-feed	Definition: Infant and baby products (formula, juices, beverages, baby food), and table foods that do not need to have water added to them prior to feeding.
	Real-time hand recording	Definition: Method by which trained observers manually record information on children's behavior.
	Reasonable maximum exposure	Definition: A semiquantitative term referring to the lower portion of the high end of the exposure, dose, or risk distribution. As a semiquantitative term, it should refer to a range that can conceptually be described as above the 90th percentile in the distribution, but below the 98th percentile.
	Recreational/sport fishermen	Definition: Individuals who catch fish as part of a sporting or recreational activity and not for the purpose of providing a primary source of food for themselves or for their families.
	Reference Concentration	Definition: An estimate (with uncertainty spanning perhaps an order of magnitude) of a continuous inhalation exposure to the human population (including sensitive target groups) that is likely to be without an appreciable risk of deleterious effects during a lifetime. It can be derived from a NOAEL, LOAEL, or benchmark concentration, with uncertainty factors generally applied to reflect limitations of the data used. Generally used in U.S. EPA's noncancer health assessments. Durations include acute, short-term, subchronic, and chronic. Acronym: RfC
	Reference Dose	Definition: An estimate (with uncertainty spanning perhaps an order of magnitude) of a daily oral exposure to the human population (including sensitive target groups) that is likely to be without an appreciable risk of deleterious noncancer effects during a lifetime. It can be derived from a NOAEL, LOAEL, or benchmark dose, with uncertainty factors generally applied to reflect limitations of the data used. Generally used in U.S. EPA's noncancer health assessments. Durations include acute, short-term, subchronic, and chronic. Acronym: RfD
	Relevant study	Definition: Studies that are applicable or pertinent, but not necessarily the most important to derive exposure factors. See also Key study.
	Representativeness	Definition: The degree to which a sample is, or samples are, characteristic of the whole medium, exposure, or dose for which the samples are being used to make inferences.
	Residential occupancy period	Definition: The time between a person moving into a residence and the time the person moves out or dies.
	Residential volume	Definition: The volume (m3) of the structure in which an individual resides and may be exposed to airborne contaminants.
	Risk	Definition: The probability of an adverse effect in an organism, system, or population caused under specified circumstances by exposure to an agent.
	Risk assessment	Definition: A process intended to calculate or estimate the risk to a given target organism, system, or population, including the identification of attendant uncertainties, following exposure to a particular agent, taking into account the inherent characteristics of the agent of concern as well as the characteristics of the specific target system. The risk assessment process includes four steps: hazard identification, hazard characterization (related term: Dose-response assessment), exposure assessment, and risk characterization. It is the first component in a risk analysis process.
	Risk characterization	Definition: The qualitative and, wherever possible, quantitative determination, including attendant uncertainties, of the probability of occurrence of known and potential adverse effects of an agent in a given organism, system, or population, under defined exposure conditions. Risk characterization is the fourth step in the risk assessment process.
	Risk communication	Definition: Interactive exchange of information about (health or environmental) risks among risk assessors, managers, news media, interested groups, and the general public.
	Route	Definition: The way a chemical or pollutant enters an organism after contact, e.g., by ingestion, inhalation, or dermal absorption.
	Sample	Definition: A small part of something designed to show the nature or quality of the whole. Exposure-related measurements are usually samples of environmental or ambient media, exposures of a small portion of a population for a short time, or biological samples, all for the purpose of inferring the nature and quality of parameters important to evaluating exposure.
	Scenario uncertainty	Definition: Uncertainty regarding missing or incomplete information needed to fully define exposure and dose.
	Screening-level assessment	Definition: An exposure assessment that examines exposures that would fall on or beyond the high end of the expected exposure distribution.
	Secondary data/analysis	Definition: The reanalysis of data collected by other individuals or group; an analysis of data for purposes other than those for which the data were originally collected.
	Sensitivity analysis	Definition: Process of changing one variable while leaving the others constant to determine its effect on the output. This procedure fixes each uncertain quantity at its credible lower and upper bounds (holding all others at their nominal values, such as medians) and computes the results of each combination of values. The results help to identify the variables that have the greatest effect on exposure estimates and help focus further information-gathering efforts.
	Serving sizes	Definition: The quantities of individual foods consumed per eating occasion. These estimates may be useful for assessing acute exposures.
	Short-term exposure	Definition: Repeated exposure for more than 24 hours, up to 30 days.
	Slope Factor	Definition: An upper bound, approximating a 95% confidence limit, on the increased cancer risk from a lifetime exposure to an agent. This estimate, usually expressed in units of proportion (of a population) affected per mg/kg-day, is generally reserved for use in the low-dose region of the dose-response relationship, that is, for exposures corresponding to risks less than 1 in 100.
	Soil	Definition: Particles of unconsolidated mineral and/or organic matter from the earth's surface that are located outdoors, or are used indoors to support plant growth.
	Soil adherence	Definition: The quantity of soil that adheres to the skin and from which chemical contaminants are available for uptake at the skin surface.
	Soil ingestion	Definition: The intentional or unintentional consumption of soil, resulting from various behaviors including, but not limited to, mouthing, contacting dirty hands, eating dropped food, or consuming soil directly. Soil-pica is a form of soil ingestion that is characterized by the recurrent ingestion of unusually high amounts of soil (i.e., on the order of 1,000-5,000 milligrams per day or more). Geophagy is also a form of soil ingestion defined as the intentional ingestion of earths and is usually associated with cultural practices.
	Spatial variability	Definition: Variability across location, whether long- or short-term.
	Subchronic exposure	Definition: Repeated exposure by the oral, dermal, or inhalation route for more than 30 days, up to approximately 10% of the life span in humans (more than 30 days up to approximately 90 days in typically used laboratory animal species).
	Subsistence fishermen	Definition: Individuals who consume fresh caught fish as a major source of food.
	Surface area	Definition: Coating, triangulation, and surface integration are direct measurement techniques that have been used to measure total body surface area and the surface area of specific body parts. Consideration has been given for differences due to age, gender, and race. Surface integration is performed by using a planimeter and adding the areas.
	Surface integration	Definition: Method used to measure skin surface area in which a planimeter is used to measure areas of the skin, and the areas of various surfaces are summed.
	Survey response methodology	Definition: Responses to survey questions are analyzed. This methodology includes questions asked of children directly, or their care givers, about behaviors affecting exposures.
	Tap water from food manufacturing	Definition: Water used in industrial production of foods.
	Target	Definition: refers to any physical, biological, or ecological object exposed to an agent.
	Temporal variability	Definition: Variability over time, whether long- or short-term.
	Threshold	Definition: Dose or exposure concentration of an agent below which a stated effect is not observed or expected to occur.
	Time-averaged exposure	Definition: 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.)
	Timeweighted average exposure
	Total dietary intake	Definition: The sum of all foods in the following food categories: dairy, meats, fish, eggs, grains, vegetables, fruits, and fats. It does not include beverages, sugar, candy, sweets, nuts and nut products.
	Total fluid intake	Definition: Consumption of all types of fluids including tap water, milk, soft drinks, alcoholic beverages, and water intrinsic to purchased foods.
	Total tap water	Definition: Water consumed directly from the tap as a beverage or used in the preparation of foods and beverages (i.e., coffee, tea, frozen juices, soups, etc.).
	Total water	Definition: Water from tap water and non tap water sources including water contained in food.
	Toxicodynamics	Definition: The physiological mechanisms by which toxins are absorbed, distributed, metabolized and excreted.
	Toxicokinetics	Definition: The passage through the body of a toxic agent or its metabolites, usually in an action similar to that of pharmacokinetics.
	Tracer-element studies	Definition: Soil ingestion studies that use trace elements found in soil and poorly metabolized in the human gut as indicators of soil intake.
	Triangulation	Definition: Method used to measure skin surface area in which areas of the body are marked into geometric figures, then their linear dimensions are calculated.
	Uncertainty	Definition: Uncertainty represents a lack of knowledge about factors affecting exposure or risk and can lead to inaccurate or biased estimates of exposure. The types of uncertainty include: scenario, parameter, and model.
	Unit risk	Definition: The quantitative estimate in terms of either risk per μg/L drinking water (water unit risk) or risk per μg/m3 air breathed (air unit risk).
	Upper percentile	Definition: Values in the upper tail (i.e., between 90th and 99.9th percentile) of the distribution of values for a particular exposure factor. Values at the upper end of the distribution of values for a particular set of data.
	Uptake	Definition: The process by which a substance crosses an absorption barrier and is absorbed into the body.
	Usual dietary intakes	Definition: Refers to the long-term average daily intake by an individual.
	Vapor intrusion	Definition: The migration of volatile chemicals from contaminated groundwater or soil into an overlying building.
	Variability	Definition: Variability arises from true heterogeneity across people, places or time and can affect the precision of exposure estimates and the degree to which they can be generalized. The types of variability include: spatial, temporal, and inter-individual.
	Ventilation Rate	Definition: Alternative term for inhalation rate or breathing rate. Usually measured as minute volume, i.e., volume (liters) of air exhaled per minute. Acronym: VR
	Video transcription	Definition: Method by which trained videographers tape a child's activities and subsequently extract data manually with computer software.
	Wet-weight intake rates	Definition: Intake rates that are based on the wet (or whole) weight of the food consumed. This in contrast to dry-weight intake rates.
	Worst case scenario	Definition: The maximum possible exposure, when everything that can plausibly happen to maximize exposure happens. The worst case represents a hypothetical individual and an extreme set of conditions that usually will not be observed in an actual population.

Export options: Excel | XML | PDF | RTF