Hamden Middle School & Neighborhood
- Glossary of Health Risk Assessments Terms
This glossary contains definitions of terms utilized by
the U.S. EPA in hazard and dose-response assessments. These definitions
are not all-encompassing, but are useful "working definitions".
(Revised October 1999)
[A][B][C][D][E][F][G][H][I][J][K][L][M][N][O][P][Q][R][S][T][U][V][W][X][Y][Z]
A
Acceptable Daily Intake (ADI): The amount of a
chemical a person can be exposed to on a daily basis over an extended
period of time (usually a lifetime) without suffering deleterious effects.
Acute Exposure: One dose or multiple doses of short
duration spanning less than or equal to 24 hours.
Acute Toxicity: Any poisonous effect produced
within a short period of time following an exposure, usually 24 to 96
hours.
Additional Risk (Added, Attributable Risk or Risk
Difference) (AR): The calculated difference in risk of a particular
condition between those who are exposed and those who are not.
Adverse Effect: A biochemical change, functional
impairment, or pathologic lesion that affects the performance of the whole
organism, or reduces an organism's ability to respond to an additional
environmental challenge.
Anecdotal Data: Data based on the description of
individual cases rather than controlled studies.
Average Daily Dose (ADD) : Dose rate averaged over
a pathway-specific period of exposure expressed as a daily dose on a
per-unit-body-weight basis. The ADD is usually expressed in terms of
mg/kg-day or other mass-time units.
B
Background Levels: Two types of background levels
may exist for chemical substances:. (a) Naturally occurring levels:
Ambient concentrations of substances present in the environment, without
human influence; (b) Anthropogenic levels: Concentrations of substances
present in the environment due to human-made, non-site sources (e.g.,
automobiles, industries).
C
Cancer: A disease of heritable, somatic mutations
affecting cell growth and differentiation, characterized by an abnormal,
uncontrolled growth of cells.
Carcinogen: An agent capable of inducing cancer.
Chronic Effect: An effect which occurs as a result
of repeated or long term (chronic) exposures.
Chronic Exposure: Multiple exposures occurring over
an extended period of time, or a significant fraction of the animal's or
the individual's lifetime.
Chronic Toxicity: The capacity of a substance to
cause adverse human health effects as a result of chronic exposure.
D
Developmental Toxicity: Adverse effects on the
developing organism that may result from exposure prior to conception
(either parent), during prenatal development, or postnatally until the
time of sexual maturation.
Dose-Response Relationship: The relationship
between a quantified exposure (dose), and the proportion of subjects
demonstrating specific, biological changes (response).
E
Effective Dose (ED10): The dose corresponding to a
10% increase in an adverse effect, relative to the control response.
Endpoint: An observable or measurable biological
event or chemical concentration (e.g., metabolite concentration in a
target tissue) used as an index of an effect of a chemical exposure.
Epidemiology: The study of disease patterns in
human populations.
Estimated Exposure Dose (EED): The measured or
calculated dose to which humans are likely to be exposed considering all
sources and routes of exposure.
Excess Lifetime Risk: The additional or extra risk
of developing cancer due to exposure to a toxic substance incurred over
the lifetime of an individual.
Exposure: Contact made between a chemical,
physical, or biological agent and the outer boundary of an organism.
Exposure is quantified as the amount of an agent available at the exchange
boundaries of the organism (e.g., skin, lungs, gut).
Exposure Assessment: An identification and
evaluation of the human population exposed to a toxic agent, describing
its composition and size, as well as the type, magnitude, frequency, route
and duration of exposure.
F
Frank Effect Level (FEL): A level of exposure or
dose which produces irreversible, adverse effects at a statistically or
biologically significant increase in frequency or severity between those
exposed and those not exposed.
G
Guidelines (human health risk assessment):
Official, peer-reviewed documentation stating current U.S. EPA methodology
in assessing risk of harm from environmental pollutants to populations.
Examples:
Proposed Guidelines for Carcinogenic Risk Assessment: U.S.EPA
guidelines intended to guide Agency evaluation of suspect carcinogens.
EPA/600/P-92/003C, April 1996.
Guidelines for Exposure Assessment: U.S. EPA guidelines intended to
guide Agency analysis of potential exposure to chemical substances. 51 FR
22888-22938; May 29,1992.
Guidelines for Developmental Toxicity Risk Assessment: U.S. EPA
guidelines intended to guide Agency analysis of developmental toxicity
data. 51 FR 34028-34040, October1996.
Guidelines for the Health Risk Assessment of Chemical Mixtures: U.S.
EPA guidelines intended to guide Agency analysis of information relating
to health effects from exposure to mixtures of chemical substances. 51 FR
34014-34025, September 1986.
Guidelines for Mutagenicity Risk Assessment: U. S. EPA guidelines
intended to guide Agency analysis of mutagenicity data. 51 FR 34006-34016,
September, 1986.
H
Hazard: A potential source of harm.
Hazard Assessment: The process of determining
whether exposure to an agent can cause an increase in the incidence of a
particular adverse health effect (e.g., cancer, birth defect) and whether
the adverse health effect is likely to occur in humans.
I
Incidence: The number of new cases of a disease
that develop within a specified population over a specified period of
time.
Incidence Rate: The ratio of new cases within a
population to the total population at risk given a specified period of
time.
Individual Risk: The probability that an individual
will experience an adverse effect.
J
K
L
Latency Period: The time between first exposure to
an agent and manifestation or detection of a health effect of interest.
Limited Evidence: A term used in evaluating study
data for the classification of a carcinogen by the 1986 U.S. EPA
guidelines for carcinogen risk assessment. This classification indicates
that a causal interpretation is credible but that alternative explanations
such as chance, bias, and confounding variables could not be completely
excluded.
Linear dose response: A pattern of frequency or
severity of biological response that varies proportionately with the
amount of dose of an agent.
Lower limit on Effective Dose 10 (LED10): The 95%
lower confidence limit of the dose of a chemical needed to produce an
adverse effect in 10 percent of those exposed to the chemical, relative to
control.
Lowest-Observed-Adverse-Effect Level (LOAEL): The
lowest exposure level at which there are statistically or biologically
significant increases in frequency or severity of adverse effects between
the exposed population and its appropriate control group. Also referred to
as lowest-effect level (LEL).
Lowest-Observed Effect Level (LOEL or LEL): In a
study, the lowest dose or exposure level at which a statistically or
biologically significant effect is observed in the exposed population
compared with an appropriate unexposed control group.
M
Malignant Tumor: An abnormal growth of tissue which
can invade adjacent or distant tissues.
Margin of Exposure (MOE): The LED10 or other point
of departure divided by the actual or projected environmental exposure of
interest.
Mutagen: A substance that can induce an alteration
in the structure of DNA.
N
No-Observed-Adverse-Effect Level (NOAEL): An
highest exposure level at which there are no statistically or 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, nor
precursors to adverse effects.
No-Observed-Effect Level (NOEL): An exposure level
at which there are no statistically or biologically significant increases
in the frequency or severity of any effect between the exposed population
and its appropriate control.
Non-linear dose response: A pattern of frequency or
severity of biological response that does not vary proportionately with
the amount of dose of an agent. When mode of action information indicates
that responses may not follow a linear pattern below the dose range of the
observed data, non-linear methods for determining risk at low dose may be
justified.
O
Odds Ratio (OR): A relative measure of the
difference in exposure between the diseased (cases) and not diseased
(controls) individuals in a case-control study. The OR is interpreted
similarly to the relative risk.
P
ppb: A unit of measure expressed as parts per
billion. Equivalent to 1 x 10-9.
ppm: A unit of measure expressed as parts per
million. Equivalent to 1 x 10-6.
Prevalence: The proportion of disease cases that exist within a population
at a specific point in time, relative to the number of individuals within
that population at the same point in time.
Proportionate Mortality Ratio (PMR): The proportion
of deaths due to the disease of interest in the exposed population divided
by the proportion of deaths due to the disease of interest in the
unexposed or reference population. It is frequently converted to a percent
by multiplying the ratio by 100.
Q
R
Reference Concentration (RfC): An estimate (with
uncertainty spanning perhaps an order of magnitude) of a continuous
inhalation exposure to the human population (including sensitive
subgroups) 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 EPA's noncancer
health assessments.
Reference Dose (RfD): An estimate (with uncertainty
spanning perhaps an order of magnitude) of a daily oral exposure to the
human population (including sensitive subgroups) 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 dose, with uncertainty
factors generally applied to reflect limitations of the data used.
Generally used in EPA's noncancer health assessments.
Relative Risk (or Risk Ratio (RR)): The relative
measure of the difference in risk between the exposed and unexposed
populations in a study. The relative risk is defined as the rate of
disease among the exposed divided by the rate of the disease among the
unexposed. A relative risk of 2 means that the exposed group has twice the
disease risk as the unexposed group.
Risk (in the context of human health): The
probability of injury, disease, or death from exposure to a chemical agent
or a mixture of chemicals. In quantitative terms, risk is expressed in
values ranging from zero (representing the certainty that harm will not
occur) to one (representing the certainty that harm will occur). The
following are examples of how risk is expressed: E-4 or 10-4 = a risk of
1/10,000; E-5 or 10-5 = 1/100,000; E-6 or 10-6 = 1/1,000,000
Risk Assessment (in the context of human health): The
determination of potential adverse health effects from exposure to
chemicals, including both quantitative and qualitative expressions of
risk. The process of risk assessment involves four major steps: hazard
identification, dose-response assessment, exposure assessment, and risk
characterization.
Risk Management (in the context of human health): A
decision making process that accounts for political, social, economic and
engineering implications together with risk-related information in order
to develop, analyze and compare management options and select the
appropriate managerial response to a potential chronic health hazard.
S
Short-Term Exposure: Multiple or continuous
exposure to an agent for a short period of time, usually one week.
Slope Factor: 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.
Standardized Mortality Ratio (SMR): This is the
relative measure of the difference in risk between the exposed and
unexposed populations in a cohort study. The SMR is similar to the
relative risk in both definition and interpretation. This measure is
usually standardized to control for any differences in age, sex, and/or
race between the exposed and reference populations. It is frequently
converted to a percent by multiplying the ratio by 100.
Statistical Significance: The probability that a
result likely to be due to chance alone. By convention, a difference
between two groups is usually considered statistically significant if
chance could explain it only 5% of the time or less. Study design
considerations may influence the a priori choice of a different
statistical significance level.
Sufficient Evidence: A term used in evaluating
study data for the classification of a carcinogen under the 1986 U.S. EPA
guidelines for carcinogen risk assessment. This classification indicates
that there is a causal relationship between the agent or agents and human
cancer.
Superfund: Federal authority, established by the
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA)
in 1980, to respond directly to releases or threatened releases of
hazardous substances that may endanger health or welfare.
Supporting Studies: Studies that contain
information useful for providing insight and support for conclusions.
Systemic Effects or Systemic Toxicity: Toxic
effects as a result of absorption and distribution of a toxicant to a site
distant from its entry point, at which point effects are produced. Not all
chemicals that produce systemic effects cause the same degree of toxicity
in all organs.
T
Target Organ: The biological organ(s) most
adversely effected by exposure to a chemical substance.
Teratogenic: Structural developmental defects due
to exposure to a chemical agent during formation of individual organs.
Threshold: The dose or exposure below which no
deleterious effect is expected to occur.
Tidal Volume (VT): The volume of air
inhaled/exhaled during normal breathing.
Toxicity: The degree to which a chemical substance
elicits a deleterious or adverse effect upon the biological system of an
organism exposed to the substance over a designated time period.
Toxicology: The study of harmful interactions
between chemicals and biological systems.
Toxic Substance: A chemical substance or agent
which may cause an adverse effect or effects to biological systems.
Tumor: An abnormal, uncontrolled growth of cells.
Synonym: neoplasm
Threshold Limit Value (TLV): Recommended guidelines
for occupational exposure to airborne contaminants published by the
American Conference of Governmental Industrial Hygienists (ACGIH). TLVs
represent the average concentration in mg/m3 for an 8-hour workday and a
40-hour work week to which nearly all workers may be repeatedly exposed,
day after day, without adverse effect.
U
Uncertainty Factor (UF): One of several, generally
10-fold factors, used in operationally deriving the RfD and RfC from
experimental data. UFs are intended to account for (1) the variation in
sensitivity among the members of the human population, i.e., interhuman or
intraspecies variability; (2) the uncertainty in extrapolating animal data
to humans, i.e., interspecies variability; (3) the uncertainty in
extrapolating from data obtained in a study with less-than-lifetime
exposure to lifetime exposure, i.e., extrapolating from subchronic to
chronic exposure; (4) the uncertainty in extrapolating from a LOAEL rather
than from a NOAEL; and (5) the uncertainty associated with extrapolation
from animal data when the data base is incomplete.
V
W
Weight-of-Evidence (WOE) for Carcinogenicity: A
system used by the U.S. EPA for characterizing the extent to which the
available data support the hypothesis that an agent causes cancer in
humans. Under EPA's 1986 risk assessment guidelines, the WOE was described
by categories "A through E", Group A for known human carcinogens
through Group E for agents with evidence of noncarcinogenicity. The
approach outlined in EPA's proposed guidelines for carcinogen risk
assessment (1996) considers all scientific information in determining
whether and under what conditions an agent may cause cancer in humans, and
provides a narrative approach to characterize carcinogenicity rather than
categories.
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