See also Abbreviations and Acronyms
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
Abatement - The reduction in degree or intensity
of pollution
Absolute risk – Absolute risk is the risk
of developing a disease or condition over a time-period
Absolute lethal concentration, LC100 - Lowest concentration of
a substance in an environmental medium which kills 100 % of test
organisms or species under defined conditions. This value is dependent
on the number of organisms used in its assessment.
Absolute lethal dose (LD100) - Lowest
amount of a substance that kills 100 % of test animals under defined
conditions.
Absorbed dose (of a substance) -
Amount (of a substance) taken up by an organism or into organs or
tissues of interest. See absorption, systemic.
Absorption (in biology) - Penetration
of a substance into an organism by various processes, some specialized,
some involving expenditure of energy (active transport), some involving
a carrier system, and others involving passive movement
down an electrochemical gradient: in mammals, absorption is
usually through the respiratory tract, gastrointestinal tract, or
skin.
Absorption barrier - 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.
Absorption, systemic - Uptake to the blood
and transport via the blood of a substance to an organ or compartment in
the body distant from the site of absorption.
Absorption coefficient (in biology) -
Ratio of the absorbed quantity (uptake) of a substance to
the administered quantity (intake).
Acceptable Daily Intake - Estimated maximum amount
of an agent, expressed on a body mass basis, to which individuals
in a (sub) population may be exposed daily over their lifetimes without
appreciable health risk.
Acceptable Risk - This is a risk management term.
The acceptability of the risk depends on scientific data, social,
economic, and political factors, and the perceived benefits arising
from exposure to an agent. A risk whose probability of occurrence
is so small, whose consequences are so slight, or whose benefits
(perceived or real) are so great, that persons or groups in society
are willing to take or be subjected to that risk.
Acceptable Risk Level - When it is not possible
to completely eliminate human exposure to a hazardous chemical or
agent, a decision must be made as to how large a risk can be accepted
in order to allow the use of that chemical or agent. >Acceptable=
levels of environmental hazards will vary with the specific application
and substance and, in principle, should be as low as reasonable achievable,
taking into account not only the hazard but also the social and economic
benefits and the available technology. Depending on circumstances,
acceptable levels of risk vary from one extra death per 10 000 (1
x 10-4) people exposed to the contaminant, to one extra cancer death
per million people exposed (1 x 10-6).{McColl, Hicks, et al. 2000
206 /id}
Accepted risk - Probability of suffering disease
or injury that is accepted by an individual.
Accident - That occurrence in
a sequence of events which usually produces unintended injury, death
or property damage.
Accidental exposure - Unintended contact with a
substance or change in the physical environment (including, e.g.,
radiation) resulting from an accident.
Accumulation (in biology) - See bioaccumulation.
Accuracy - The degree of agreement
between a measured value and the true value; usually expressed as
+/- percent of full scale.
Action level
1. Concentration of a substance in air, soil, water, or
other defined medium at which specified emergency counter-measures,
such as the seizure and destruction of contaminated materials, evacuation
of the local population or closing down the sources of pollution,
are to be taken.
2. Concentration of a pollutant in air, soil, water, or other defined
medium at which some kind of preventive action (not necessarily of
an emergency nature) is to be taken.
Active ingredient - Component of a mixture responsible
for the biological effects of the mixture.
Active metabolite - Metabolite causing
biological and (or) toxicological effects.
Activity pattern data - 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.
Acute
1. Of short duration, in relation to exposure or effect.
In experimental toxicology, acute refers to studies where
dosing is either single or limited to one day, although the total
study duration may extend to two weeks.
2. In clinical medicine, sudden and severe, having a rapid onset.
Acute Effects - Effects that occur rapidly following
exposure and are of short duration.
Acute Exposure – A contact between an agent
and a target occurring over a short time, generally less than a day.
Acute Toxicity - The adverse effects occurring
within a short time of administration of a single dose or multiple
doses given within 24 hours.
Adaptive Effect - Effects that enhance an organism's
performance as a whole and/or its ability to withstand a challenge
(i.e., homeostatic mechanism).
Adaptive Response - A physiological response to
environmental chemical exposure that helps to protect the organism
from the harmful effects of toxic substances, or to compensate for
physiological disturbances caused by toxic agents.
Added risk - Difference between the incidence of
an adverse effect in a treated group (of organisms or a
group of exposed humans) and a control group (of the same
organisms or the spontaneous incidence in humans).
Adverse effect - Change in morphology, physiology,
growth, development, reproduction, or lifespan of an organism, system,
or (sub)population that results in an impairment of functional capacity
or impairment of capacity, an impairment of the capacity to compensate
for additional stress or an increase in susceptibility to other influences.
Adverse event - Occurrence that causes an adverse
effect.
Aerosol - System in which the
dispersion medium is a gas and the dispersed phase (composed of solid
particles or liquid droplet) does not settle out under the influence
of gravity.
Aerosol particles - Solid particles <10-6
m in diameter, dispersed in gas.
After-effect of a poison - Ability of a poison to
produce a change in an organism after cessation of contact.
Agent – A chemical, biological, or physical
entity that contacts a target.
Air emissions - The release or
discharge of a pollutant (from a stationary source) into the ambient
air. For anthropogenic sources this may involve release (1) by means
of a stack or (2) as a fugitive dust, mist or vapor as a result inherent
to the manufacturing or formulating process. Pollutants may also
be discharged from mobile sources, from area sources such as roads
and fields, and from non-manufacturing, stationary sources.
Air monitoring - The continuous
sampling for, and measuring of, pollutants present in the atmosphere.
Air pollutant - Dust, fumes, mist,
smoke and other particulate matter, vapor, gas, odorous substances,
or any combination thereof; any air pollution agent or combination
of such agents, including any physical, chemical, biological, radioactive
(including source material, special nuclear material, and by-product
material) substance or matter which is emitted into or otherwise
enters the ambient air.
Air pollution - Presence of substances in the atmosphere
resulting either from human activity or natural processes, in sufficient
concentration, for a sufficient time and under circumstances such
as to interfere with comfort, health, or welfare of persons
or to harm the environment.
Air quality criteria - The levels of pollution
and lengths of exposure above which adverse effects may occur on
health and welfare.
Air quality standards - The level
of pollutants prescribed by law or regulation that cannot be exceeded
during a specified time in a defined area.
Air sampling - The collection
and analysis of air samples for detection or measurement of radioactive
substances, particulate matter, or chemical pollutants.
ALARA - As Low As Reasonably Achievable - A concept
which asserts that environmental exposure to toxic substances should
be kept as low as is reasonably achievable, using pollution control
equipment and industrial processes that can be installed and operated
at reasonable cost.
Allergen - Immunostimulant antigenic substance that may or
may not cause a clinically significant effect but which is capable of producing
immediate hypersensitivity.
Allergy - Symptoms or signs occurring in sensitized
individuals following exposure to a previously encountered
substance (allergen) which would otherwise not cause such symptoms
or signs in non-sensitized individuals. The most common
forms of allergy are rhinitis, urticaria, asthma,
and contact dermatitis.
Ambient - Surrounding (applied to environmental
media such as air, water, sediment, or soil).
Ambient level - The level (of
pollutant) in the general environment as characterized by an average
over a suitably long time and large volume.
Ambient monitoring - Continuous or repeated measurement
of agents in the environment to evaluate ambient exposure and health
risk by comparison with appropriate reference values based on
knowledge of the probable relationship between exposure and resultant adverse health effects.
Analysis - Detailed examination of anything complex,
made in order to understand its nature or to determine through an
appropriate risk assessment.
Anecdotal Data - Data based on descriptions of
individual cases rather than on controlled studies.
Antagonism - Agents are antagonistic when the observed
effect from combined exposure is less than that expected from a simple
summation of single exposures. They produce opposite effects, hence
then lack of simple summation response.
Association - The
non-random occurrence of a disease in relation to an exposure. An
observed association suggests that a cause-effect relationship exists
between an exposure and health effect, but cannot by itself establish
causality.
Anticarcinogen - A substance
or agent that opposes the action of carcinogens.
Anthropogenic
1. Caused by or influenced by human activities.
2. Describing a conversion factor used to calculate a dose or concentration affecting
a human that has been derived from data obtained with another species
(e.g., the rat).
Anthropogenic Hazard - An environmental
hazard attributable to human activity, most commonly ascribed to
synthetic (>man-made=) chemicals and their by-products, but also
encompassing natural agents released by human activities.
Area
source - Widespread origin of emissions.
Artefact
- Observation, effect, or result which
is inaccurate because it is produced by the methodology used in
scientific investigation or by experimental error.
Assay
1. Process of quantitative or qualitative analysis of a component
of a sample.
2. Results of a quantitative or qualitative analysis of a component
of a sample.
3. To carry out quantitative or qualitative analysis of a component
of a sample.
Assessment - Evaluation or appraisal
of an analysis of facts and the inference of possible consequences
concerning a particular object or process.
Assessment end-point -
Quantitative/qualitative expression of a specific factor with which
a risk may be associated as determined through an appropriate risk
assessment.
Assessment factor - Numerical adjustment
used to extrapolate from experimentally determined (dose-response)
relationships to estimate the agent exposure below which an adverse
effect is not likely to occur.
Assimilation - Uptake and incorporation of substances
by a living organism.
Attributable risk - The rate of
a disease in exposed individuals that can be attributed to the exposure.
This measure is derived by subtracting the rate (usually incidence
or mortality) of the disease among non-exposed persons from the corresponding
rate among exposed individuals.
Background level – 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.)
Baseline Risk - The level of risk that exists,
or is predicted to exist, prior to the introduction of remedial or
preventive control actions intended to reduce risk to a lower level.
Benchmark concentration (BMC) -
Statistically calculated lower 95 % confidence limit on the concentration that
produces a defined response (called the benchmark response or
BMR, usually 5 or 10 %) for an adverse effect compared to
background, often defined as 0 or 5 %.
Benchmark response - Response expressed
as an excess of background, at which a benchmark dose or benchmark
concentration is set.
Benefit - Advantage to or improvement in condition
of an individual or a population.
Best Available Control Technology (BACT) - Technical
equipment or industrial processes that are intended to reduce the
emission of chemical contaminants into the environment. The
term >best-available= is often seen as a commitment to employ
state-of-the-art control technology, where the effectiveness of control
measures is deemed more important than its capital and operating
costs or economic efficiency.
Best Practicable Control Technology (BPCT) - Technical
equipment or industrial processes that are intended to reduce the
emission of chemical contaminants into the environment, using technology
where cost of control and economic efficiency are considered in conjunction
with overall effectiveness of the control measures.
Best Practical Technology - That technology (machinery,
software etc.) that is easily available and affordable which will
fulfil the needs of the proposed health strategies.
Bias - Deviation of results or inferences from
the truth, or processes leading to such deviation. Any trend
in the collection, analysis, interpretation, publication, or review
of data that can lead to conclusions that are systematically different
from the truth.
Biased sample - Any sample that is not a random sample.
Bioaccessible - Able to come in contact with a
living organism and interact with it.
Bioaccessibility - Potential for a substance to
come in contact with a living organism and then interact with it.
This may lead to absorption.
Bioaccumulation - The process by which the amount
of a substance in a living organism (or its parts) increases with
time.
Bioaccumulation potential - Ability of living organisms
to concentrate a substance obtained either directly from the environment
or indirectly through its food.
Bioassay - Procedure for estimating the concentration or
biological activity of a substance by measuring its effect on a living
system compared to a standard system.
Bioavailability – 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 the release from a medium (if present)
and absorption by an organism.
Bioconcentration - A process leading to a higher
concentration of a chemical in the organism relative to its environment.
Biological Assessment of Exposure - Exposure to
chemicals may be assessed by the analysis of specimens taken in the
environment (air, water, food, etc.) or of specimens of biological
material. Most often, urine an blood are analyzed, but other
materials such as expired air, faeces, saliva, bile, hair, and biopsy
or autopsy material are sometimes analyzed. In these samples,
the content of the xenobiotic(s) or its metabolite(s) is determined
and, on this basis, the exposure level (concentration in the air,
absorbed amount of the substance) or the probability of health impairment
due to exposure is derived. Biochemical changes in the components
of an organism can also be sued for this purpose (e.g., changes in
enzyme activity or in the excretion of metabolic intermediates) if
they show a relationship to the exposure.
Biological Cycle - The process through which a
chemical substance passes in the biosphere. It may involve
transport through the various media (air, water, soil), followed
by environmental transformation, and carriage through various ecosystems. Chemical
compounds that occur naturally have a natural biological cycle.
Biological effect monitoring (BEM) - Continuous
or repeated measurement of early biological effects of exposure to
a substance to evaluate ambient exposure and health
risk by comparison with appropriate reference values based on
knowledge of the probable relationship between ambient exposure and
biological effects.
Biological exposure indices (BEI) - Guidance
values recommended by ACGIH for assessing biological monitoring results.
Biological half life - For a substance, the time
required for the amount of that substance in a biological system
to be reduced to one half of its value by biological processes, when
the rate of removal is approximately exponential.
Biological magnification - The
concentration of certain substances up a food chain. A very important
mechanism in concentrating pesticides and heavy metals in organisms
such as fish.
Biological monitoring (biomonitoring) - Continuous
or repeated measurement of any naturally occurring or synthetic chemical,
including potentially toxic substances or their metabolites or
biochemical effects in tissues, secreta, excreta, expired air, or
any combination of these in order to evaluate occupational or environmental exposure and health
risk by comparison with appropriate reference values based on
knowledge of the probable relationship between ambient exposure and
resultant adverse health effects.
Biomagnification - A sequence of processes in an
ecosystem by which higher concentrations are attained in organisms
of higher trophic level i.e., of higher levels in the food chain.
Biomarker/biological marker - 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.
Biomarker of effect - Biomarkerthat, depending
on its magnitude, can be recognized as associated with an established
or possible health impairment or disease.
Biomarker of exposure - Biomarkerthat relates exposure to
a xenobioticto the levels of the substance or its metabolite,
or of the product of an interaction between the substance and some target molecule
or cell that can be measured in a compartment within an
organism.
Biomarker of susceptibility - Biomarkerof an inherent
or acquired ability of an organism to respond to exposure to
a specific substance.
Biotransformation - Chemical conversionof a substance
that is mediated by living organisms or enzyme preparations derived
there from.
Blood–brain barrier - Barrier formed by the
blood vessels and supporting tissues of the brain that prevents some
substances from entering the brain from the blood.
Blood–placenta barrier - Physiological interface
between maternal and fetal blood circulations that filters out some
substances which could harm the fetus while favoring the passage
of others such as nutrients: Many fat-soluble substances such as
alcohol are not filtered out, and several types of virus can also
cross this barrier. The effectiveness of the interface as a barrier
varies with species and different forms of placentation.
Body burden - The total amount
of a specific substance (for example, lead) in an organism, including
the amount stored, the amount that is mobile, and the amount absorbed.
Bounding estimate - 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.
Bystander exposure - Liability of members of the
general public to come in contact with substances arising from operations
or processes carried out by other individuals in their vicinity.
Calibration - Operation that, under specified conditions,
in a first step establishes a relation between the quantity values
with measurement uncertainties provided by measurement standards and
corresponding indications with associated measurement uncertainties
and, in a second step, uses this information to establish a relation
for obtaining a measurement result from an indication.
Cancer - Disease resulting from the development
of a malignant tumor.
Carcinogen - An agent, chemical, physical or biological,
that can act on living tissue in such a way as to cause a malignant
neoplasm, thus causing cancer.
Carcinogenesis - Development of carcinoma; or,
in more recent usage, producing any kind of malignancy.
Carcinogenic - Cancer causing.
Carcinogenic potency - The gradient of the dose-response
curve for a carcinogen.
Carcinogenicity - Process of induction of malignant
neoplasms, and thus cancer, by chemical, physical,
or biological agents.
Carcinogenicity test - Long-term (chronic)
test designed to detect any possible carcinogenic effect of a test
substance.
Carcinoma - Malignant new growth
made up of epithelial cells tending to infiltrate the surrounding
tissues and give rise to metastases.
Case-Control Study - An analytical design in epidemiology
involving the selection of diseased cases and non-diseased controls,
followed by assessment of prior exposures in the case group and control
group.
Case-fatality rate - A ratio of
the number of deaths due to a disease to the number of cases of that
disease in a specified period of time. It expresses the frequency
with which affected individuals die of the disease.
Categorical Data - Specify the form or severity
of adverse effects as a function of dose rate without reference to
the number of animals- affected-or to a continuous measure of one
parameter. Graded data often are presented as categories (liver
necrosis, lung lesions) or as judgments of severity. Fatty infiltration
of the liver, single-cell liver necrosis, and liver necrosis are
examples of sequence of severity judgments. Graded data can
be used to construct a dose severity curve.
Causality, Causal Relationship - The relationship
between an environmental exposure and a health effect where the exposure
is found to cause the observed effect. Where possible, causality
can be best established directly by experimental studies, but in
environmental health causality is often determined from observational
studies (e.g. epidemiology) using a combination of causality criteria
that constitute a weight-of-evidence.
Ceiling value, CV - Airborne concentration of
a potentially toxic substance which should never be exceeded
in a worker’s breathing zone.
Chemical safety - Practical certainty that there
will be no exposure of organisms to toxic amounts of any
substance or group of substances: This implies attaining an acceptably
low risk of exposure to potentially toxic substances.
Chemical species (of an element) - Specific
form of an element defined as to isotopic composition, electronic
or oxidation state, and/or complex or molecular structure.
Chronic - Having a persistent,
recurring or long-term nature. As distinguished from acute.
Chronic effect - Consequence that develops slowly
and/or has a long lasting course: may be applied to an effect that
develops rapidly and is long lasting.
Chronic Exposure – A continuous or intermittent
long-term contact between an agent and a target.
Chronic Toxicity - Another term used to describe
delayed toxicity. However, the term "chronic toxicity" also
refers to effects that persist over a long period of time whether
or not they occur immediately or are delays. The term "chronic
toxicity" is often confused with that of chronic exposure.
Chronic Toxicity Study - A toxicity study designed
to measure the (toxic) effects of chronic exposure to a chemical
Chronic toxicity test - Study in which organisms
are observed during the greater part of the life span and in which exposure to
the test agent takes place over the whole observation time or a substantial
part thereof.
Clearance (in toxicology) - Volume
of blood or plasma or mass of an organ effectively cleared
of a substance by elimination (metabolism and excretion)
divided by time of elimination.
Clinical toxicology - Scientific study involving
research, education, prevention, and treatment of diseases caused
by substances such as drugs and toxins.
Co-Carcinogenic Agent - A chemical, physical or
biological factor which acts synergistically with another carcinogen
to induce a cancerous state.
Cohort - Component of the population born during
a particular period and identified by period of birth so that its
characteristics (such as causes of death and numbers still living)
can be ascertained as it enters successive time and age periods.
The term “cohort” has broadened to describe any designated
group of persons followed or traced over a period of time, as in
the term cohort study (prospective study).
Cohort analysis - Tabulation and analysis of morbidity or mortality rates
in relationship to the ages of a specific group of people (cohort),
identified by their birth period, and followed as they pass through
different ages during part or all of their life span. In certain
circumstances such as studies of migrant populations, cohort analysis
may be performed according to duration of residence in a country
rather than year of birth, in order to relate health or
mortality experience to duration of exposure.
Cohort Study - An epidemiologic study that observes
subjects in differently exposed groups and compares the incidence
of symptoms. Although ordinarily prospective in nature, such
a study is sometimes carried out retrospectively, using historical
data.
Comparable Hazard - A hazard that bears sufficient
similarity in its harmful effects and societal consequences to be
readily compared by decision-makers when considering the nature and
degree of health risks for different environmental hazards.
Comparative risk - An expression
of the risks associated with two (or more) actions leading to the
same goal; may be expressed quantitatively (a ratio of 1.5) or qualitatively
(one risk greater than another risk).
Compartment - Conceptualized part of the body (organs,
tissues, cells, or fluids) considered as an independent system for
purposes of modeling and assessment of distribution and clearance of
a substance.
Complete Carcinogen - An agent that, by itself,
can cause cancer. This agent does not require separate promoters
and initiators; it is all these things in itself.
Compounded Conservatism - The use of a series of
conservative (pessimistic) assumptions is a risk analysis, where
each conservative assumption taken alone is not unreasonable, but
where the overall effect of many conservative assumptions taken together
results in an extremely pessimistic prediction of possible risk.
Computational toxicology - Application of mathematical
and computer models to predict adverse effects and to better
understand the mechanism(s) through which a given chemical causes
harm.
Concentration – Amount of a material or
agent dissolved or contained in unit quantity in a given medium
or system.
Concentration-effect relationship – Relationship
between the exposure, expressed in concentration, of a given organism,
system, or (sub)population to an agent in a specific pattern during
a given time and the magnitude of a continuously graded effect to
that organism, system, or (sub)population.
Confidence interval - A range
of values (a1 < a < a2) determined from a sample of definite
rules so chosen that, in repeated random samples from the hypothesized
population, an arbitrarily fixed proportion of that range will include
the true value, x, of an estimated parameter. The limits, a1 and
a2, are called confidence limits; the relative frequency with which
these limits include a is called the confidence coefficient; and
the complementary probability is called the confidence level. As
with significance levels, confidence levels are commonly chosen as
0.05 or 0.01, the corresponding confidence coefficients being 0.95
or 0.99. Confidence intervals should not be interpreted as implying
that the parameter itself has a range of values; it has only one
value, a. On the other hand, the confidence limits (a1, a2) being
derived from a sample, are random variables, the values of which
on a particular sample either do or do not include the true value
a of the parameter. However, in repeated samples, a certain proportion
of these intervals will include a provided that the actual population
satisfied the initial hypothesis.
Confounder - A condition or variable that may be
a factor in producing the same response as the agent under study. The
effects of such factors may be discerned through careful design and
analysis.
Confounding (in data analysis)
1. Situation in which the effects of two processes are not distinguishable
from one another: The distortion of the apparent effect of an exposure on risk brought
about by the association of other factors which can influence the
outcome.
2. Relationship between the effects of two or more causal factors
as observed in a set of data, such that it is not logically possible
to separate the contribution which any single causal factor has made
to an effect.
3. Situation in which a measure of the effect of an exposure on risk
is distorted because of the association of exposure with other factor(s)
which influence the outcome under study.
Confounding Variable - A variable that can cause
or prevent the outcome of interest, is not an intermediate variable,
and is not associated with the factor under investigation. Such
a variable must be controlled in order to obtain an undistorted estimate
of the effect of the study factor on risk.
Conservatism - 1. In empirical science: A
tendency to avoid making premature judgments about a scientific issue
until the uncertainties are reduced by further study. 2. In
public health: One or more reasonable worst-case assumptions in environmental
health risk assessment, which are intended to ensure that potential
risks are seldom underestimated, but at the cost of over-estimating
some risks. Often applied to risk identification and risk estimation
procedures to ensure adherence with a Precautionary Principle in
public health.
Conservative assessment of risk - Assessment of risk that
assumes the worst possible case scenario and therefore gives the
highest possible value for risk: Risk management decisions based
on this value will maximize safety.
Construct validity - Extent to which a measurement
corresponds to theoretical concepts (constructs) concerning the phenomenon
under study; for example, if on theoretical grounds, the phenomenon
should change with age, a measurement with construct validity would
reflect such a change.
Contact volume - A volume containing the mass of
agent that contacts the exposure surface.
Containment - Process by which possible release,
discharge, or spill of a toxic substance during normal use
or after an accident is prevented by appropriate action.
Contaminant - A substance foreign to a natural
system of present at unnatural concentrations. A contaminant
is an unwanted agent in the environment which has the potential under
certain circumstances to cause harmful health effects or ecological
damage, depending on the degree of exposure and the susceptibility
of exposed individuals. An environmental contaminant may originate
both from natural processes and from anthropogenic (>man-made=)
activities, although for the purposes of risk management the principal
focus is usually on anthropogenic contaminants.
Content validity - Extent to which the measurement
incorporates the domain of the phenomenon under study; for example,
a measurement of functional health status should embrace
activities of daily living, occupational, family, and social functioning,
etc.
Contingent valuation - Willingness to pay for something
that is non-marketed (e.g. improved health status), as derived from
people=s responses to questions about preferences for various combinations
of situations and/or controlled discussion groups.
Continuous Data - represent the change in some
measured value of a biological indicator (e.g., organ weights, triglyceride
levels in the liver, and serum enzyme measurements) as a function
of dose rate. Continuous data can be used to construct a dose-effect
curve.
Control Group - A group of subjects observed in
the absence of agent exposure or, in the instance of a case/control
study, in the absence of an adverse response.
Control, matched - Control (individual or group
or case) selected to be similar to a study individual or group, or
case, in specific characteristics: some commonly used matching variables
are age, sex, race, and socioeconomic status.
Corrosive
1. Causing a surface-destructive effect on contact; in toxicology,
this normally means causing visible destruction of the skin, eyes,
or the lining of the respiratory tract or the gastrointestinal tract.
Cost-Benefit Analysis (CBA) - It is measured by
difference between the sum of all costs and the sum of all benefits
to give a net benefit figure. A positive CBA implies that the program
of health improvement is predicted to be worthwhile. This term can
be modified by looking only at certain costs and certain benefits
to fit the needs of the particular decision-maker. Clearly, the effectiveness
of such an analysis depends on how the benefits are quantified.
Cost-Effectiveness - The relationship describing
the cost of control for reducing the level of a risk by a specified
amount. For example, cost-effectiveness is often measured as
the number of dollars expended per life saved for a series of alternative
control options.
Cost-Effectiveness Analysis (CEA) - A CEA assumes
that money will be spent on improving health and examines the best
or most effective way to effect improvements. A standard way
of measuring this is by a cost-effectiveness ratio (CE = cost/gains)
where the lowest CE will represent the most effective program; the
CE measurement is a useful way of comparing the costs of different
strategies for effecting health improvements.
Cost-Utility Analysis (CUA) - QALYs are a standardized
measure of mortality and morbidity rates used to describe the quality
of health. Use of identical units in differing CUAs allows for simultaneous
comparison among varying programs.
Criterion - Validated set of data used as a basis
for judgment.
Criterion validity - Extent to which the measurement
correlates with an external criterion of the phenomenon under study.
Critical concentration (for a cell or
an organ) - Concentration of a substance at
and above which adverse functional changes, reversible or irreversible,
occur in a cell or an organ.
Critical dose - Dose of a substance at
and above which adverse functional changes, reversible or irreversible,
occur in a cell or an organ.
Critical effect - For deterministic effects,
the first adverse effect which appears when the threshold
(critical) concentration or dose is reached in the critical
organ: adverse effects with no defined threshold concentration
are regarded as critical.
Critical organ (in toxicology) - Organ
that attains the critical concentration of a substance and
exhibits the critical effect under specified circumstances
of exposure and for a given population.
Critical period (of development) - Stage
of development of an organism that is of particular importance in
the life cycle if the normal full development of some anatomical,
physiological, metabolic, or psychological structure or function
is to be attained.
Critical toxic effect - The most
sensitive and specific biological change which is outside of acceptable
physiological variation.
Cross-Sectional Study - A study that examines the
relationship between diseases (or other health-related characteristics)
and other variables of interest as they exist in a defined population
oat one particular time. The presence or absence of disease
and the presence or absence of the other variables (or, if they are
quantitative, their level) are determined in each member of the study
population or in a representative sample at one particular time. The
relationship between a variable and the disease can be examined 1. In
terms of the prevalence of disease in different population subgroups
defined according to the presence or absence (or level) of the variables
2. In terms of the presence or absence (or level) of the variables
in the diseased versus the nondiseased. Note that disease prevalence
rather than incidence is normally recorded in a cross-sectional study. The
temporal sequence of cause and effect cannot necessarily be determined
in a cross-sectional study.
Cumulative effect - Overall change that occurs
after repeated doses of a substance or radiation.
Cumulative risk
1. Probability of a common harmful effect associated with concurrent exposure by
all relevant pathways and routes of exposure to a group of substances
that share a common chemical mechanism of toxicity.
2. Total probability of a harmful effect over time.
Damage - Damage is the severity
of injury or the physical, functional, or monetary loss that could
result if control of a hazard is lost.
Danger - Expresses a relative
exposure to a hazard. A hazard may be present, but there may be little
danger because of the precautions taken.
Decision Criteria - Critical factors of a subjective
non-scientific nature that help to identify and select an optimal
control strategy from a variety of possible control options.
Decision Maker - A person or group with the power
or authority to make decisions.
>de manifestis= risk
- A predicted health risk that is sufficiently large and
serious to be considered for immediate risk control, usually set
by convention at a lifetime risk level of 10-4.{McColl, Hicks,
et al. 2000 206 /id}
>de minimus= risk
- A predicted risk that is so small or its expected health
consequences so slight that society is deemed willing to accept
or be subjected to that risk, as an >insignificant risk= or >trivial
risk=. Based on a traditional legal principle that trivial
risks are not subject to legal proceedings. Often held by
convention to be a default risk value of 1 in a million (10-6)
or one in a hundred thousand (10-5) risk of severe illness or death
over an individual lifetime.{McColl, Hicks, et al. 2000 206 /id}
Deterministic effect, deterministic process - Phenomenon
committed to a particular outcome determined by fundamental physical
principles.
Deterministic Process - A biological disease process
that occurs through the gradual accumulation of cell damage or harmful
physiological changes, so that greater exposure to a toxic substance
typically leads to greater expression of the disease along a continuous
measure of severity.
Detoxification
1. Process, or processes, of chemical modification which make a toxic molecule
less toxic.
2. Treatment of patients suffering from poisoning in such a way as
to promote physiological processes which reduce the probability or
severity of harmful effects.
Developmental Toxicity - The study of adverse effects
on the developing organism (including death, structural abnormality,
altered growth, or functional deficiency) resulting from exposure
prior to conception (in either parent), during prenatal development,
or postnatally up to the time of sexual maturation.
Diffusion - Spontaneous differential movement of
components in a system.
Disability Adjusted Life Year (DALY) – Disability
Adjusted Life Year (DALY) is the sum of Years of Life Lost due to
premature mortality (YLL) and the Years Lost due Disability (YLD).
DALY= YLL+YLD
Disabling injury - An injury causing
death, permanent disability, or any degree of temporary total disability
beyond the day of the accident.
Disease - A general term describing
a morbid condition which can be defined by objective, physical signs
(e.g. hypertension), subjective symptoms or mental phobias, disorder
of function (e.g. biochemical abnormality), or disorders of structure
(anatomic or pathological change). Existence of disease may be questioned
in disorder of structure without associated disorder of function.
Dispersion (in environmental chemistry)
- Dilution of a pollutant by spreading in the atmosphere
or water due to diffusion or turbulent action.
Disposition
1. Natural tendency shown by an individual or group of individuals,
including any tendency to acquisition of specific diseases, often
due to hereditary factors.
2. Total of the processes of absorption of a chemical into
the circulatory systems, distribution throughout the body, biotransformation,
and excretion.
Distribution
1. Apportionment of a solute between two phases. The terms “partition” or “extraction” may
also be used in this sense where appropriate.
2. Dispersal of a substance and its derivatives throughout the natural
environment or throughout an organism.
3. Final location(s) of a substance within an organism after dispersal.
Distribution volume - Theoretical volume of a body compartment throughout
which a substance is calculated to be distributed.
Dominant half life - Half life of a fraction
of a substance in a specific organ or compartment if it
defines approximately the overall clearance rate for that
substance at a specific time point.
Dosage - Dose divided by product of mass
of organism and duration of dose. Often expressed mg (kg body weight)–1
day–1 and may be used as a synonym for dose.
Dose - Total amount of an agent administered to,
taken up by, or absorbed by an organism, system, or (sub)population.
Dose–effect - Relation between dose and
the magnitude of a measured biological change
Dose–effect curve - Graph of the relation
between dose and the magnitude of the biological change
produced measured in appropriate units.
Dose–effect relationship – Relationship
between the total amount of an agent administered to, taken up by,
or absorbed by an organism, system, or (sub)population and the magnitude
of a continuously graded effect to that organism, system, or (sub)population.
Dose-Rate - dose per unit time.
Dose-related effect – Any effect to an organism,
system, or (sub)population as a result of the quantity of an agent
administered to, taken up by, or absorbed by that organism, system,
or (sub)population.
Dose-response – Relationship
between the amount of an agent administered to, taken up by, or absorbed
by an organism, system, or (sub)population and the change developed
in that organism, system or (sub)population in reaction to the agent.
Dose-Response Assessment – Analysis of the
relationship between the total amount of an agent administered to,
taken up by, or absorbed by an organism, system, or (sub)population
in reaction to that agent, and inferences derived from such an analysis
with respect to the entire population.
Dose–response curve – Graphical presentation
of a dose-response relationship.
Dose-Response Relationship – Relationship
between the amount of an agent administered to, taken up by, or absorbed
by an organism, system, or (sub)population and the change developed
in that organism, system, or (sub)population in reaction to the agent.
Ecological impact - The total
effect of an environmental change, natural or man-made, on the community
of living things.
Ecology - The science dealing
with the relationship of all living things with each other and with
their environment.
Ecosystem - The interacting system of a biological
community and its nonliving surroundings.
Effect – Change in the state
or dynamics of an organism, system, or (sub)population caused by
the exposure to an agent.
Effect assessment – Combination of analysis
and inference of possible consequences of the exposure to a particular
agent based on knowledge of the dose-effect relationship associated
with that agent in a specific target organism, system, or (sub)population.
Efficacy - A measure of the probability
and intensity of beneficial effects.
Elimination (in toxicology) - Disappearance
of a substance from an organism or a part thereof, by processes of metabolism,
secretion, or excretion.
Elimination rate - Differential with respect to
time of the concentration or amount of a substance in the
body, or a part thereof, resulting from elimination.
Endpoint - A response measure in a toxicity study.
Emission - Like effluent but
used in regard to air pollution.
Emission rate - The amount of
pollutant emitted per unit of time.
Environment - Water, air, land,
and all plants and man and other animals living therein, and the
interrelationships which exist among them.
Environmental monitoring - Continuous or repeated
measurement of agents in the environment to evaluate environmental exposure and
possible damage by comparison with appropriate reference values
based on knowledge of the probable relationship between ambient
exposure and resultant adverse effects.
Environmental pathway - All routes of transport
by which a toxicant can travel from its release site to human populations
including air, food chain, and water.
Epidemiology - The study of the distribution
and determinants of health-related states or events in populations,
and the application of this study to control of health problems.
Equilibrium - State of a system in which the
defining variables (temperature, pressure, chemical potential)
have constant values.
Estimated Exposure Dose (LEO) - The measured
or calculated dose to which humans are likely to be exposed considering
exposure by all sources and routes.
Event - Occurrence of a particular set of circumstances
1. The event may be certain or uncertain 2. The event
can be singular or multiple 3. The probability associated
with the event can be estimated for a given period of time.
Excess deaths - The excess over
statistically expected deaths in a population within a given time
interval. Attempts are made to relate excess deaths to specific
causes. Note that since every person can (and must) die only once;
there can be no excess deaths over all time.
Expected deaths - The number
of deaths statistically expected in a population in a given time
interval obtained by summing the product of age-, sex-, and race-specific
mortality rates from a standard population and person-years in
each age, sex, and race category in the study population.
Expected loss - The quantity
obtained by multiplying the magnitude of health or environmental
effect loss by the probability (or risk) of that loss and adding
the products. The expected loss is the average loss over a large
number of trials; one must reflect on the appropriateness of its
use in cases for which there will be only one, or a few, trials.
Extrapolation - In risk assessment,
this process entails postulating a biologic reality based on observable
responses and developing a mathematical model to describe this
reality. The model may then be used to extrapolate to response
levels which cannot be directly observed.
Excretion- Discharge or elimination of
an absorbed or endogenous substance, or of a waste product,
and/or its metabolites, through some tissue of the body
and its appearance in urine, feces, or other products normally
leaving the body.
Excretion rate - Amount of substance and/or its metabolites
that is excreted divided by time of excretion.
Exposure - Concentration or amount of a particular
agent that reaches a target organism, system, or (sub)population
in a specific frequency for a defined duration.
Exposure Assessment - Evaluation of the exposure
of an organism, system, or (sub)population to an agent (and its
derivatives). Exposure assessment is the third step in the process
of risk assessment.
Exposure Estimation - Estimation of the amount
and duration of contact between a receptor and an agent. May
consider such factors as concentration, route, receptor, population,
and timescale.
Exposure Identification - Identification of the
conditions of contact between a receptor and an agent. May involve
identification of concentration, route, receptor population, and
timescale.
Exposure scenario - A set of conditions or assumptions
about sources, exposure pathways, amounts or concentrations of
agent(s) involved, and exposed organism, system, or (sub)population
(i.e., numbers, characteristics, habits) used to aid in the evaluation
and quantification of exposure(s) in a given situation.
Extrapolation - The calculation, based on quantitative
observations in exposed test species, of predicted dose-effect
and dose-response relationships for a chemical in humans and other
environmental biota.
False negative results - Results
which show no effect when one is there.
False positive results - Results
which show an effect when one is not there.
Fate - Pattern of distribution of an agent, its
derivatives, or metabolites in an organism, system, compartment,
or (sub)population of concern as a result of transport, partitioning,
transformation, or degredation.
First-order process
1. Chemical reaction where the rate is directly proportional
to the concentration of reactant.
2. Any reaction changing at a constant fractional rate.
First-pass effect - Biotransformation and,
in some cases, elimination of a substance in the liver
after absorption from the intestine and before it reaches
the systemic circulation.
Food chain - Dependence of a
series of organisms, one upon the other, for food. The chain begins
with plants and ends with the largest carnivores.
Frank-Effect Level (FEL) - The exposure level
which produces unmistakable adverse effects, such as irreversible
functional impairment or mortality, at a statistically or biologically
significant increase in frequency or severity between an exposed
population and its appropriate control.
Genetic effects - Effects that
are inheritable and appear in the descendants of those exposed.
Genotoxic - Capable of causing a heritable change
to the structure of DNA thereby producing a mutation.
Guideline - A guideline is a recommended exposure
limit for a substance or an agent intended to protect human health
or the environment, that is not legally enforceable.
Guidance value - Value, such as concentration
in air or water, that is derived after allocation of the reference
dose among the different possible media (routes) of exposure. The
aim of the guidance value is to provide quantitative information
from risk assessment to the risk managers to enable them to make
decisions.
Half-life - The time in which
half the molecules of a chemical substance disappear as a result
of chemical or biochemical transformation.
Half-life, biological - The
time required for a living organism to eliminate, by natural processes,
half the amount of a substance that has entered it.
Half-life, effective - The time
required for a radionuclide contained in a biological system to
reduce its activity by half due to the combined result of radioactive
decay and biological.
Harmonization - Harmonization represents the
attempts by regulatory bodies at the provincial/state, federal,
and international level to adopt identical or similar regulatory
limits, including definitions of allowable limits, monitoring and
measurement methods, and legal penalties.
Hazard – Inherent property of an agent
or situation having the potential to cause adverse effects when
an organism, system, or (sub)population is exposed to that agent.
Hazard assessment – A
process designed to determine the possible adverse effects of an
agent or situation to which an organism, system, or (sub)population
could be exposed. The process focuses on the hazard identification
and hazard characterization. The process focuses on the hazard,
in contrast to risk assessment, where exposure assessment is a
distinct additional step.
Hazard characterization – The qualitative
and, wherever possible, quantitative description of the inherent
property of an agent or situation having the potential to cause
adverse effects. This should, where possible, include a dose-response
assessment and its attendant uncertainties. Hazard characterization
is the second stage in the process of hazard assessment and the
second of four steps in risk assessment.
Hazard Identification - The identification of
the type and nature of adverse effects that an agent has an inherent
capacity to cause in an organism, system, or (sub)population. Hazard
identification is the first stage in hazard assessment and the
first of four steps in risk assessment.
Hazardous waste - Any waste
or combination of wastes which pose a substantial present or potential
hazard to human health or living organisms because such wastes
are nondegradable or persistent in nature or because they can be
biologically magnified, or because they can be lethal, or because
they may otherwise cause or tend to cause detrimental cumulative
effects; also, a waste or combination of wastes of a solid, liquid,
contained gaseous, or semisolid form which may cause, or contribute
to, an increase in mortality or an increase in serious irreversible,
or incapacitating reversible illness, taking into account the toxicity
of such waste, its persistence and degradability in nature, its
potential for accumulation or concentration in tissue, and other
factors that may otherwise cause or contribute to adverse acute
or chronic effects on the health of persons or other organisms.
Health and safety study - Any study of any effect
of a chemical substance or mixture on health or the environment
or on both, including underlying data and epidemiological studies,
studies of occupational exposure to a chemical substance or mixture,
toxicological, clinical, and ecological studies of a chemical substance
or mixture, and any test performed pursuant to this [TSCA] Act.
Health effect - A deviation
in the normal function of the human body.
Health risk - Risk in which
an adverse event affects human health.
Healthy worker effect - The
difference in mortality risk due to selection forces between a
population of active workers healthy enough to have been (and remain)
employed and the general population which includes sick and disabled
persons. If working in a safe environment, such a population of
active workers has been variously estimated to have a mortality
risk 60-90% that of the general population.
Human Equivalent Dose - The human dose of an
agent that is believed to induce the same magnitude of toxic effect
as that which the known animal dose has induced.
Hypersensitivity - A hyper susceptible individual
is one who will experience an adverse health effect significantly
before the general population, because of one or more factors which
predispose the individual to the harmful effects of pollutant exposure.
Idiosyncratic Reaction - A genetically-determined
abnormal reactivity to a chemical.
Idiosyncrasy - The increased individual sensitivity
of an organism to the effect of certain substances.
Immediate versus Delayed Toxicity - Immediate
effects occur or develop rapidly after a single administration
of a substance, while delayed effects are those that occur after
the lapse of some time. These effects have also been referred to
as acute and chronic, respectively.
Impact - The force of impression
of one thing on another.
Incidence - The number of instances of illness
commencing, or of persons falling ill, during a given period in
a specific population. Incidence is usually expressed as
a rate, the denominator being the average number of persons in
the specified population during a defined period or the estimated
number of persons at the mid-point of that period. The basic
distinction between incidence and prevalence is that whereas incidence
refers only to new cases, prevalence refers to all cases, irrespective
of whether they are new or old. When the terms incidence
and prevalence are used, it should be stated clearly whether the
data represent the numbers of instances of the disease recorded
or the numbers of persons ill.
Incidence Rate - The rate at which new events
occur in a population. The numerator is the number of new
events that occur in a defined period; the denominator is the population
at risk of experiencing the event during this period, sometimes
expressed as person-time. The incidence rate most often used
in public health practice is calculated by the formula
Number of new events in a specified period X 10n
Number of persons exposed to risk during the period
In a dynamic population, the denominator is the average size of
the population, often the estimated population at the mid-period. If
the period is a year, this is the annual incidence rate. This
rate is an estimate of the person-time incidence rate, i.e., the
rate per 10n person-years. If the rate is low, as
with many chronic diseases, it is also a good estimate of the cumulative
incidence rate. In follow-up studies with no censoring, the
incidence rate is calculate by dividing the number of new cases
in a specified period by the initials size of the cohort of person
being followed; this is equivalent to the cumulative incidence
rate during the period. If the number of new cases during
a specified period is divided by the sum of the person-time units
at risk for all persons during the period, the result is the person-time
incidence rate.
Individual Risk - The probability that an individual
person will experience an adverse effect. This is identical
to population risk unless specific population subgroups can be
identified that have different (higher or lower) risks.
Individual susceptibility - The
marked variability in the manner in which individuals will respond
to a given exposure to a toxic agent.
Initiator - An agent that causes a cell to become
immortalized. This is the first step in the multi-step process
of carcinogenesis in which a cell continues to divide and fails
to terminally differentiate. This step may be referred to as anti-differentiation.
Intake – 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.
Interspecies Dose Conversion - The process of
extrapolating from animal doses to equivalent human doses.
In vitro - Outside the living
organism.
In vivo - Within the living
organism.
Involuntary Risks - Exposures which are not under
individual control, for example, exposure to air or water pollutants. In
general, voluntary risks (such as smoking) are more seen as more
acceptable than involuntary risks.
Iterative Process - A process that is repeated
periodically in a systematic fashion. Some or all of the
steps in the risk management process can be revisited as new information
becomes available, allowing for more informed decisions to be considered
as uncertainty is reduced by further study and analysis.
Kinetics (in chemistry) - Branch
of chemistry concerned with measuring and studying rates of chemical
reactions.
Latent Period - Delay between exposure to a disease-causing
agent and the appearance of manifestation of the disease. After
exposure to ionizing radiation, for instance, there is a latent
period of five years, on average, before development of leukemia,
and more than 20 years before development of certain other malignant
conditions. The term Alatent period@ is often used synonymously
with Ainduction period@, that is, the period between exposure to
a disease-causing agent and the appearance of manifestations of
the disease. It has also been defined as the period from
disease initiation to disease detection.
Lethal concentration, LC - Concentration of
a substance in an environmental medium that causes death following
a certain period of exposure.
Lethal concentration fifty (LC50)
- A calculated concentration [in air] which when administered
by the respiratory route is expected to kill 50% of a population
of experimental animals during an exposure of four hours. Ambient
concentration is expressed in milligrams per liter.
Lethal dose, LD - Amount of
a substance or physical agent (e.g., radiation) that causes death
when taken into the body.
Lethal dose fifty (LD50) - A
calculated dose of a chemical substance which is expected to kill
50% of a population of experimental animals exposed through a route
other than respiration. Dose is expressed in milligrams per kilogram
of body weight.
Lethal synthesis - Metabolic formation of a highly toxic compound
often leading to death of affected cells.
Lifetime Risk – Lifetime Risk is the risk
of developing a disease during an individual’s lifetime.
Linearized multistage model - Sequence of steps
in which (a) a multistage model is fitted to tumor
incidence data; (b) the maximum linear term consistent with
the data is calculated; (c) the low-dose slope of the dose–response function
is equated to the coefficient of the maximum linear term; and (d)
the resulting slope is then equated to the upper bound of potency.
Linear No-Threshold Model (LNT) - The simplest
of toxicological dose-response relationships in which a doubling
of the original dose would be expected to result in a doubling
of the response frequency, and a halving of the original dose would
produce a halving of the response frequency and so on down the
dose ladder all the way to zero dose. Used primarily for
carcinogenic or mutagenic environmental contaminants.
Local effect - Change occurring at the site of
contact between an organism and a toxicant.
Local versus Systemic Toxicity - Local effects
refer to those that occur at the site of first contact between
the biological system and the toxicant: systemic effects are those
that are elicited after absorption and distribution of the toxicant
from its entry point to a distant site.
Lowest effective dose, LED - Lowest dose of
a chemical inducing a specified effect in a specified fraction
of exposed individuals.
Lowest-observed-adverse-effect level, LOAEL -
Lowest concentration or amount of a substance (dose),
found by experiment or observation, which causes an adverse
effect on morphology, functional capacity, growth, development,
or life span of a target organism distinguishable from
normal (control) organisms of the same species and strain under
defined conditions of exposure.
Lowest-observed-effect level, LOEL - Lowest concentration or
amount of a substance (dose), found by experiment or observation,
that causes any alteration in morphology, functional capacity,
growth, development, or life span of target organisms
distinguishable from normal (control) organisms of the same species
and strain under the same defined conditions of exposure.
Margin of exposure, MOE - Ratio
of the no-observed-adverse-effect level (NOAEL) for the critical
effect to the theoretical, predicted, or estimated exposure dose
or concentration.
Margin of Safety – 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.
Maximum tolerable concentration, MTC
- Highest concentration of a substance in an
environmental medium that does not cause death of test organisms
or species (denoted by LC0).
Maximum tolerable dose, MTD - Highest
amount of a substance that, when introduced into the body, does
not kill test animals (denoted by LD0).
Maximum tolerable exposure level, MTEL
- Maximum amount (dose) or concentration of
a substance to which an organism can be exposed without leading
to an adverse effect after prolonged exposure time.
Measurement end-point - Measurable (ecological)
characteristic that is related to the valued characteristic chosen
as an assessment point.
Median effective concentration, EC50
- Statistically derived concentration of a
substance in an environmental medium expected to produce a certain
effect in test organisms in a given population under a defined
set of conditions.
Note: ECn refers to the median concentration
that is effective in n % of the test population.
Median effective dose, ED50 - Statistically
derived dose of a chemical or physical agent (radiation)
expected to produce a certain effect in test organisms in a given
population or to produce a half-maximal effect in a biological
system under a defined set of conditions.
Note: EDn refers to the median dose that is
effective in n % of the test population.
Median lethal concentration, LC50 - Statistically
derived concentration of a substance in an environmental
medium expected to kill 50 % of organisms in a given population
under a defined set of conditions.
Median lethal dose, LD50 - Statistically
derived dose of a chemical or physical agent (radiation)
expected to kill 50 % of organisms in a given population under
a defined set of conditions.
Median lethal time, TL50 - Statistically
derived average time interval during which 50 % of a given population
may be expected to die following acute administration
of a chemical or physical agent (radiation) at a given concentration under
a defined set of conditions.
Medium - Material (e.g., air, water, soil, food,
consumer products) surrounding or containing an agent.
Medium intake rate - The rate at which the medium
crosses the outer exposure surface of a target during ingestion
or inhalation.
Metabolic activation - Biotransformation of
a substance to a more biologically active derivative.
Synonym: bioactivation
Metabolic Model - An analysis and theoretical
reconstruction of the way in which the body deals with a specific
substance, showing the proportion of the intake that is absorbed,
the proportion that is stored and in what tissues, the proportion
and rate of breakdown in the body and the subsequent fate of the
metabolic products, and the proportion of the substance and the
rate at which it is eliminated by different organs.
Metabolic transformation - Biotransformation of
a substance that takes place within a living organism.
Metabolism - Sum total of all physical and chemical
processes that take place within an organism; in a narrower sense,
the physical and chemical changes that take place in a substance
within an organism.
Metabolite - Intermediate or product resulting
from metabolism.
Metabonomics - Evaluation of tissues and biological
fluids for changes in metabolite levels that follow exposure to
a given substance, in order to determine the metabolic processes
involved and to evaluate the disruption in intermediary metabolic
processes that results from exposure to that substance.
Microenvironment - 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.
Mitigation - Limitation of any negative consequence
of a particular event.
Model - A formalized expression of a theory or
the causal situation which is regarded as having generated observed
data. In statistical analyses the model is generally expressed
in symbols, that is to say in a mathematical from, but diagrammatic
models are also found.
Modifying Factor (MF) - An uncertainty factor
that is greater than zero and less than or equal to 10; the magnitude
of the MF depends upon the professional assessment of scientific
uncertainties of the study and data base not explicitly treated
with the standard uncertainty factors (e.g., the number of
animals tested); the default value for the MF is 1.
Monitoring - Continuous or repeated observation,
measurement, and evaluation of health and/or environmental
or technical data for defined purposes, according to prearranged
schedules in space and time, using comparable methods for sensing
and data collection.
Morbidity - A departure from a state of physical or mental well-being,
resulting from disease or injury. Frequently used only if the affected
individual is aware of the condition. Awareness itself connotes
a degree of measurable impact. Frequently, but not always, there
is a further restriction that some action has been taken such as
restriction of activity, loss of work, seeking of medical advice,
etc.
Mortality - Death; the death
rate; ratio of number of deaths to a given population.
Mortality rate - The number
of deaths that occur in a given population during a given time
interval; usually deaths per l03 or l05 people per year. Can be
age, sex, race, and cause specific.
Mutagen - Agent that can induce heritable changes
(mutations) of the genotype in a cell as a consequence
of alterations or loss of genetic material.
Mutation - Any heritable change in genetic material. This
may be a chemical transformation of an individual gene (a gene
or point mutation), which alters its function. On the other
hand, this change may involve a rearrangement, or a gain or loss
of part of a chromosome, which may be microscopically visible. This
is designated a chromosomal mutation.
Negligible risk
1. Probability of adverse effects occurring that can reasonably
be described as trivial.
2. Probability of adverse effects occurring that is so low that
it cannot be reduced appreciably by increased regulation or investment
of resources.
No-effect level, NEL - Maximum dose (of
a substance) that produces no detectable changes under defined
conditions of exposure.
Note: This term tends to be substituted by no-observed-adverse-effect
level (NOAEL) or no-observed- effect level (NOEL).
No-Observed-Adverse-Effect Level (NOAEL) - The
greatest concentration or amount of a chemical, found by experiment
or observation, that causes no detectable adverse alteration of
morphology, functional capacity, growth, development, or life span
of the target.
No Observed Effect Level (NOEL) - The highest
dose level, in a toxicological dose-response study, where no detectable
biological effect is found (usually in test animals). Used
as an experimental estimate of the threshold dose at which toxic
effects begin to appear in the dose-response relationship.
Non-Threshold Toxicity - A class of toxicity
mechanisms where the damaging biological processes are thought
to occur at any exposure level above zero dose, often in a linear
dose-response relationship. Usually applied to environmental
substances (ionizing radiation, genotoxic chemicals) that are thought
to act by a carcinogenic or mutagenic mechanism involving genetic
damage to body (somatic) cells or reproductive (germ) cells.
Odds Ratio - The statistical odds or probability
of disease occurrence in the exposed group of individuals compared
with the unexposed group of individuals in case-control studies.
Oncogenic - A substance that
causes tumors, whether benign or malignant.
One-compartment model - Kinetic model, where
the whole body is thought of as a single compartment in
which the substance distributes rapidly, achieving an equilibrium between
blood and tissue immediately.
Option Evaluation - The process of developing
and analysing options for risk management. Development
of options may involve consideration of program objectives and
current institutional policies, and the regulatory environment. Option
analysis may involve consideration of risks and benefits; uncertainties
in risk estimations; public awareness and perception; technical
feasibility; and economic, social, political, and cultural impacts.
Organoleptic - Affecting or involving a sense
organ as of taste, smell, or sight.
Other Supportive Data - In the weight-of-evidence
determination of the Agency's hazard identification process this
phrase refers to information on structure activity relationships
(SARs), results of short-term in vitro studies, mechanistic
studies and pharmacokinetics.
Ozone (O3) - A pungent, colorless,
toxic gas that contributes to photochemical smog.
Particulates - Fine liquid or
solid particles such as dust, smoke, mist, fumes, or smog, found
in the air or emissions.
Particulate matter (in atmospheric chemistry)
1. General term used to describe airborne solid or liquid particles
of all sizes.
Note: The term aerosol is recommended
to describe airborne particulate matter.
2. Particles in air, usually of a defined size and specified as
PMn
Persistence, Persistent Pollutant - A persistent
pollutant is one that remains for a long time in the environment. For
example, under the Canada/U.S. Great Lakes Water Quality Agreement,
a persistent pollutant is one with a half-life of eight weeks or
longer.
Person-year - The sum
of the number of years each person in the study population is at
risk; a metric used to aggregate the total population at risk assuming
that 10 people at risk for one year is equivalent to 1 person at
risk for 10 years.
Pharmacodynamics - The study of the actions of
drugs on the living organism. It involves the biochemical and physiological
effects of drugs and the mechanisms of their actions, including
the correlation of actions and effects of drugs with their chemical
structure. The pharmacodynamics of a toxic substance is called
toxicodynamics.
Pharmacogenetics - Study of the influence of
genetic factors on the effects of drugs on individual organisms.
Pharmacokinetics - The study of the movement
of drugs within biological systems. The absorption, distribution,
biotransformation and excretion of substances in the organism are
examined. The pharmacokinetics of a toxic substance is called
toxicokinetics.
Phenotype - Observable structural and functional
characteristics of an organism determined by its genotype and
modulated by its environment.
Physiologically based pharmacokinetic modeling, PBPK
- Mathematical modeling of kinetic behavior of a substance,
based on measured physiological parameters.
Synonym: toxicologically based pharmacokinetic modeling
PMR - Proportionate mortality
ratio.
Poison (in toxicology) - Substance
that, taken into or formed within the organism, impairs the health
of the organism and may kill it.
Point source - A single isolated
stationary source of pollution.
Pollutant - Any undesirable solid, liquid, or
gaseous matter in a gaseous, liquid, or solid medium.
Pollution - The presence of
matter or energy whose nature, location or quantity produces undesired
environmental effects
Population at Risk - The number of people who
can develop the adverse health effect under study and who are potentially
exposed to the risk factor of interest. For example, all
people in a population who have not developed immunity to an infectious
disease are at risk of developing the disease, if they are exposed. Similarly,
people already having chronic disease are excluded from the population
at risk in studies of the incidence of the disease.
Potency (in toxicology) - Expression
of relative toxicity of an agent as compared to a given
or implied standard or reference
Potential Years of Life Lost (PYLL) – Potential
Years of Life Lost (PYLL) is an indicator that measures the number
of years of life lost when a person dies prematurely.
ppm (Parts per million) - A measurement
of concentration such as 1 µg per gram.
Precautionary Principle - A decision criterion
that impels decision-makers towards action in situations where a
health or ecological hazard is believed to exist as a possibility,
although the exact probability of the suspected hazard is imperfectly
understood.
Precision - A measure of how consistently
the result is determined by repeated determinations without reference
to any "true" value.
Premature death - A death that
occurs before statistical expectation, usually attributable to a
specific cause, and usually referring to deaths statistically estimated
in a population rather than to individuals.
Prevalence - The proportion of a population that
has a specified disease at a particular time. Both previous
and newly occurring cases of the disease are counted, so prevalence
for a chronic disease usually exceeds its annual incidence.
Prevalence, annual (an occasionally used index) - the
total number of persons with the disease or attribute at any time
during a year. It includes cases of the disease arising before
but extending into or through the year as well as those having their
inception during the year.
Prevalence, lifetime - The total number of persons
known to have had the disease or attribute for at least part of their
life.
Prevalence, period - The total number of persons
known to have had the disease or attribute at any time during a specified
period.
Prevalence, point - The number of persons with
a disease or an attribute at a specified point in time.
Prevalence Rate - The total number of individuals
who have an attribute or disease at a particular time (or during
a particular period) divided by the population at risk of having
the attribute or disease at this point in time or midway through
the period. A problem may arise with calculating period prevalence
rates because of the difficulty of defining the most appropriate
denominator.
Principal Study - The study that contributes most
significantly to the qualitative and quantitative risk assessment.
Probability - The likelihood or frequency of occurrence
of an event.
Probable error - The magnitude
of error which is estimated to have been made in determination of
results.
Procarcinogen - Substance that has to be metabolized
before it becomes a carcinogen.
Progressor/Completer - A factor that acts synergistically
with carcinogens, initiators, promotors to induce the neoplastic
state.
Promoter - An agent, usually chemical, that causes
an initiated cell to become malignant. This is one of the final steps
in carcinogenesis and leads to the formation of a tumour and may
ultimately result in metastasis.
Proportionate mortality ratio (PMR) - The
fraction of all deaths from a given cause in the study population
divided by the same fraction from a standard population. A tool for
investigating cause-specific risks when only data on deaths are available.
If data on the population at risk are also available, SMRs are preferred.
Prospective Study - A way in which subjects are
followed forward in time from initiation of the study. This
is often called a longitudinal or cohort study.
Public accident - Any accident
other than motor vehicle that occurs in the public use of any premises.
Includes deaths in recreation (swimming, hunting, etc.), transportation
except motor vehicle, public buildings, etc., and deaths from widespread
natural disasters even though some may have happened on home premises.
Excludes accidents to persons in the course of gainful employment.
Pulmonary - Pertaining to the lung(s).
Quality Adjusted Life Year (QALY) – A quality-adjusted
life year (QALY) measures both the quantity and the quality of life
achieved by an intervention.
Quantal Data - specify the number of animals affected
as a function of dose rate (e.g., mg/kg bw/day) for a single type
of effect. The numbers of animals with tumors or that die from
a chemical exposure are examples. Quantal data are often reported
as an incidence (percent response) and, thus, can be used to construct
a dose-response curve.
Quantal Effect - An effect that can be expressed
only as Aoccurring@ or Anot occurring”. Typical examples of
quantal effects are death or occurrence of a tumour.
Rate - A measure of the frequency of a phenomenon. An
expression of the frequency with which an event occurs in a defined
population.
Rate Difference (RD) - The absolute difference
between two rates, for example, the difference in incidence rate
between a population group exposed to a causal factor and a population
group not exposed to the factor: RD = Ie - Iu where
Ie = incidence rate among exposed, and Iu = incidence
rate among unexposed. In comparisons of exposed and unexposed
groups, the term excess rate may be used as a synonym for rate difference.
Rate Ratio (RR) - The ratio of two rates. The
term is used in epidemiologic research with a precise meaning, i.e.,
the ratio of the rate in the exposed population to the rate in the
unexposed population: RR= Ie / Iu where
Ie is the incidence rate among exposed and Iu is
the incidence rate among unexposed.
Reasonably Consistent - In the weight-of-evidence
determination of the Agency's hazard identification process this
phrase refers to evidence of an effect in most species adequately
tested.
Reference Dose (RfD) - An estimate of the daily
exposure dose that is likely to be without deleterious effect even
if continued exposure occurs over a lifetime.
Regression analysis - Statistical methods for modeling
a set of dependent variables, Y, in terms of combinations
of predictors, X.
Relative Risk - i) the ratio of the risk of disease
or death among the exposed to the risk among the unexposed; this
usage is synonymous with risk ratio; ii) alternatively, the ratio
of the cumulative incidence rate in the exposed to the cumulative
incidence rate in the unexposed, i.e., the cumulative incidence ratio,
and iii) the term Arelative risk@ has also been used synonymously
with Aodds ratio@ and, in some biostatistical articles, has been
used for the ratio of forces of morbidity. The use of the term
Arelative risk@ for several different quantities arises from the
fact that for Arare@ diseases (e.g., most cancers) all the quantities
approximate one another. For common occurrences (e.g., neonatal
mortality in infants under 1500 g birth weight), the approximations
do not hold.
Relative excess risk, RER - Measure
that can be used in comparison of adverse reactions to drugs, or
other exposures, based solely on the component of risk due
to the exposure or drug under investigation, removing the risk due
to background exposure experienced by all in the population. The relative
excess risk, R, is given by
R = (R1 – R0)/(R2 – R0)
where R1 is the rate in the population, R2
is the rate in the comparison population, and R0 is the
rate in the general population.
Note: Rate is used here as in epidemiology
Reliability - The probability
a system performs a specified function or mission under given conditions
for a prescribed time.
Reproducibility - The degree of
variation obtained when the same measurement is made with similar
instruments and many operators.
Reservoir (in biology) - Storage compartment from
which a substance may be released with subsequent biological effects.
Residence time - The period of
time during which a substance resides in a designated area.
Residual risk - Health risk remaining
after risk reduction actions are implemented.
Respirable particle - Particle of the size (<5.0 µm)
most likely to be deposited in the pulmonary portion of the respiratory
tract.
Response - Change developed in the state or dynamics
of an organism, system, or (sub)population in reaction to exposure
to an agent.
Retention
1. Amount of a substance that is left from the total absorbed after
a certain time following exposure.
2. Holding back within the body or within an organ, tissue or cell
of matter that is normally eliminated.
Reversible versus Irreversible Toxicity - Reversible
toxic effects are those that can be repaired, usually by a specific
tissue's ability to regenerate or mend itself after chemical exposure,
while irreversible toxic effects are those that cannot be repaired.
Risk - The probability of an adverse effect in
an organism, system, or (sub)population caused under specified circumstances
by exposure to an agent.
Risk Acceptance - a decision to accept a risk 1.The
verb Ato accept@ is chosen to convey the idea that acceptance has
its basic dictionary meaning 2. Risk acceptance depends on risk criteria.
Risk analysis - A process for
controlling situations where an organism, system, or (sub)population
could be exposed to a hazard. The risk analysis process consists
of three components: risk assessment, risk management, and risk communication.
Risk Assessment - A process intended to calculate
or estimate the risk to a given target organism, system, or (sub)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 Avoidance - Decision not to become involved
in, or action to withdraw from a risk situation 1. The decision
may be taken based on the result of risk evaluation.
Risk-Benefit Analysis (RBA) - Economic gains less
the costs of a particular program. Essentially, the RBA is a CBA
minus the qualitative gains in health status. It ignores
aspects, such as human suffering which are difficult to quantify.
Risk Characterization - 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 (sub)population, under
defined exposure conditions. Risk characterization is the fourth
step in the risk assessment process
Risk Communication - Interactive exchange of
information about (health or environmental) risks among risk assessors,
managers, news media, interested groups, and the general public.
Risk Control - the step in the Risk Management
Framework which focuses on choosing a particular course of preventive
or remedial action from an array of possible control options, all
of which are intended to reduce health risks through various strategies
identified by the stakeholders and the risk management team.
Risk Criteria - Terms of reference by which the
significance of risk is assessed 1. Risk criteria may include
associated cost and benefits, legal and statutory requirements,
socio-economic and environmental aspects, concerns of stakeholders,
priorities and other inputs to the assessment.
Risk Estimation - Quantification of the probability,
including attendant uncertainties, that specific adverse effects
will occur in an organism, system, or (sub)population due to actual
or predicted exposure.
Risk Evaluation - Establishment of a qualitative
or quantitative relationship between risks and benefits of exposure
to an agent, involving the complex process of determining the significance
of the identified hazards and estimated risks to the system concerned
or affected by the exposure, as well as the significance of the
benefits brought about the agent. Risk evaluation is an element
of risk management. Risk evaluation is synonymous with risk-benefit
evaluation.
Risk Financing - Provision of funds to meet the
cost of implementing risk treatment and related costs 1. In
some industries risk financing only relates to funding the financial
consequences of risk.
Risk identification - Recognizing
that a hazard exists and trying to define its characteristics.
Often risks exist and are even measured for some time before their
adverse consequences are recognized. In other cases, risk identification
is a deliberate procedure to review, and it is hoped, anticipate
possible hazards
Risk Management - Decision-making process involving
considerations of political, social, economic, and technical factors
with relevant risk assessment information relating to a hazard
so as to develop, analyse, and compare regulatory and non-regulatory
options and to select and implement appropriate regulatory response
to that hazard. Risk management comprises three elements: risk
evaluation; emission and exposure control; and risk monitoring.
Risk Management Framework - A systematic decision-making
process for assessing and managing health risks.
Risk Management System - Set of elements of an
organisation=s management system concerned with managing risk 1. Management
system elements may include: strategic planning; decision making;
and other processes for dealing with risk 2. Risk management
systems reflect the culture of the organisation.
Risk Monitoring - Process of following up the
decisions and actions within risk management in order to ascertain
that risk containment or reduction with respect to a particular
hazard is assured. Risk monitoring is an element of risk management.
Risk Optimization - Process, related to a risk,
to minimize the negative and to maximize the positive consequences
and their respective probabilities 1. In a safety context risk
optimization is focused on reducing the risk 2. Risk optimization
follows risk criteria, including costs and legal requirements 3. Risks
associated with risk control may be considered.
Risk Perception - The significance assigned to
risks by stakeholders. This perception is derived form the
stakeholders= expressed needs, issues, and concerns.
Risk Reduction - Actions taken to lessen the
probability, negative consequences, or both, associated with a
particular risk.
Risk Retention - Acceptance of the burden of
loss or benefit of gain from a particular risk. 1. Risk
retention includes the acceptance of risks that have not been identified
2. Risk retention does not include treatments involving
insurance, or transfer by other means 3. There may be variability
in the degree of acceptance and dependence on risk criteria.
Risk Transfer - Share with another party the
benefit of gain or burden of loss for a particular risk 1. Risk
transfer may be effected through insurance or other agreements
2. Risk transfer may create new risks or modify existing
risk 3. Relocation of the source is not risk transfer 4. Legal
or statutory requirements may limit, prohibit, or mandate the transfer
of certain risk.
Risk Treatment - Process of selection and implementation
of measures to modify risk 1. The term risk treatment is
sometimes used for measures themselves 2. Risk treatment
measures may include avoiding, optimizing, transferring or retaining
risk.
Safety - Practical certainty
that adverse effects will not result from exposure to an agent
under defined circumstances. It is reciprocal of risk.
Safety Factor - Composite (reductive) factor
by which an observed or estimated no-observed-adverse-effect level
(NOAEL) is divided to arrive at a criterion or standard that is
considered safe or without appreciable risk.
Safety Factors (in food additives and contaminants) - A
factor applied to the no-observed-effect level to derive acceptable
daily intake (ADI) (the no-observed-effect level is divided by
the safety factor to calculate the ADI). The value of the
safety factor depends on the nature of the toxic effect, the size
and type of population to be protected, and the quality of the
toxicological information available.
Sample (in statistics)
1. Group of individuals often taken at random from a population
for research purposes.
2. One or more items taken from a population or a process and intended
to provide information on the population or process.
3. Portion of material selected from a larger quantity so as to
be representative of the whole.
Severity - Connotes the toxicological significance
attached to the continuum of effects, including adaptive, compensatory
and adverse effects, potentially associated with exposure to xenobiotics.
Short-Term Exposure - Multiple or continuous
exposures occurring over a week or so.
Short-term exposure limit, STEL - Fifteen-minute
time-weighted average (TWA) exposure recommended by ACGIH
which should not be exceeded at any time during a workday, even
if the 8-h TWA is within the threshold limit value–timeweighted
average, TLV–TWA.
SMR - Standardized mortality
ratio.
Socioeconomic Impact Analysis (SEIA) - An assessment
of both allocative (market efficiency as measured by production
and consumption) and non-allocative effects (income distribution,
market structure, international trade, inflation etc.) on proposed
regulations.
Socioeconomic Analysis - An analysis in monetary
values of the costs and benefits of various actions to protect
health or the environment.
Stakeholder - Any individual, group, or organization
able to affect, be affected by, or believe it might be affected
by, a decision or activity. The decision-maker(s) is often,
but not always, considered as a stakeholder.
Standard - A standard is a legally enforceable
limit for a substance or an agent intended to protect human health
or the environment. Exceeding the standard could result in
unacceptable harm.
Statistical significance - The
statistical significance determined by using appropriate standard
techniques of statistical analysis with results interpreted at
the stated confidence level and based on data relating species
which are present in sufficient numbers at control areas to permit
a valid statistical comparison with the areas being tested.
Steady state (in toxicology) - State
of a system in which the conditions do not change in time.
Stochastic - Pertaining to or arising from chance
and hence obeying the laws of probability.
Stochastic Effect - Effect for which the probability
of occurrence depends on the absorbed dose. Hereditary effects
and cancer induced by radiation are considered to be stochastic
effects {ICRP 1977 434 /id}. The term Astochastic@ indicates
that the occurrence of effects so named would be random. This
means that, even for an individual, there is no threshold of dose
below which the effect will not appear, but the chance of experiencing
the effect increases with increasing dose.
Stochastic Process - A biological disease process
that produces as an all-or-nothing outcome (e.g. cancer) through
a series of stepwise cellular changes (e.g. gene mutations). The
likelihood of the disease is determined by the statistical probability
of the occurrence of each of the underlying steps in the disease
process.
Strength-of-Evidence - A common variant of the
weight-of-evidence approach for Risk Identification, in which positive
findings of harmful health effects are given greater weight than
negative findings. This may lead to the classification of
many environmental agents as harmful, when the evidence from animal
and human pollution studies is actually contradictory or inconclusive.
Stressor - 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).
Subacute Toxicity Test - An animal experiment
serving to study the effects produced by the test material when
administered in repeated doses (or continuously in food, drinking-water)
over a period of up to about 90 days.
Subchronic - Repeated over a short period, usually
about 10 % of the life span; an imprecise term used to describe exposures of
intermediate duration.
Subchronic effect - Biological change resulting
from an environmental alteration lasting about 10 % of the lifetime
of the test organism.
Note: In practice with experimental animals, such an
effect is usually identified as resulting from
multiple or continuous exposures occurring over 3 months (90 days).
Subchronic exposure - A contact between an agent
and a target of intermediate duration between acute and chronic.
(Other terms, such as “less-than-lifetime exposure,” are
also used.)
Subchronic Study - A toxicity study designed
to measure effects from subchronic exposure to a chemical.
Subchronic toxicity test - Animal experiment
serving to study the effects produced by a test substance when
administered in repeated doses (or continually in food,
drinking-water, air) over a period of up to about 90 days.
Surrogate - Something that serves
as a substitute. In risk analysis, surrogates are often used when
data on the item of interest (a chemical, an industry, an exposure,
etc.) is lacking. As an example, underground mining of coal and
hardrock minerals can be used as a surrogate for underground oil
shale mining.
Susceptible - Describing a group of organisms
more vulnerable to a given exposure than the majority
of the population to which they belong.
Note: Susceptibility may reflect gender, age, physiological
status, or genetic constitution of the
organisms at risk.
Synergetic - Working together;
an agent that works synergistically with one or more other agents.
Synergism - Co-ordinated or concerted action
of two or more agents. The effect observed from combined
exposure is greater than the sum of effects of single exposure. Also
referred to as potentiation.
Synergism (in toxicology) - Pharmacological
or toxicological interaction in which the combined biological effect
of two or more substances is greater than expected on the basis
of the simple summation of the toxicity of each of the
individual substances
Systematic error - A reproducible
inaccuracy introduced by faulty equipment, calibration, or technique.
Systemic - Relating to the body as a whole.
Systemic effect - Consequence that is either
of a generalized nature or that occurs at a site distant from the
point of entry of a substance.
Note: A systemic effect requires absorption and
distribution of the substance in the body.
Target – Any biological entity that receives
an exposure or a dose (e.g. a human, a human population, or a human
organ).
Teratogen - An agent or factor that causes production
of developmental anomalies and/or abnormalities in the developing
embryo ie. in utero.
Teratogenic - Substances that
are suspected of causing malformations or serious deviations from
the normal type, which can not be inherited in or on animal embryos
or fetuses.
Teratology - Science that deals
with abnormal development of the fetus and congenital malformation.
Threshold - Dose or exposure concentration of
an agent below which a stated effect is not observed or expected
to occur.
Threshold Dose - The minimum exposure level which
induces a statistically significant response in the organism.
Threshold Level - A theoretical concept for the
exposure level of a substance that represents the change from the
maximum exposure producing no (adverse) effects to the minimum
exposure producing an (adverse) effect under defined conditions.
Threshold Limit Value (TLV) - The concentration
of a material to which most workers can be exposed daily without
adverse effect - - - These values are time weighted concentrations
for a 7-or 8-hour workday and a 40-hour workweek. For most materials,
the value may be exceeded to a certain extent, provided there are
compensatory periods of exposure below the value during the workday
(or in some case the week). For a few materials, (mainly those
that produce a rapid response) the limit is given as ceiling concentration
(ie. a maximum permissible concentration) that should never
be exceeded.
Threshold limit value-ceiling, TLV-C
- Concentration of a potentially toxic
substance that should not be exceeded during any part of
the working exposure.
Threshold limit value–time-weighted average, TLV–TWA
- Time-weighted average concentration for a
conventional 8-h workday and a 40-h workweek, to which it is
believed nearly all workers may be repeatedly exposed, day after
day, without adverse effect.
Threshold limit value–short-term exposure
limit, TLV–STEL - Concentration to
which it is believed that workers can be exposed continuously
for a short period of time without suffering from (1) irritation,
(2) chronic or irreversible tissue damage, or (3) narcosis
of sufficient degree to increase the likelihood of accidental
injury, impair self rescue or materially reduce work efficiency,
and provided that the daily TLV–TWA is not exceeded.
Note: It is not a separate independent exposure guideline;
rather, it supplements the TLV–TWA
limit where there are recognized acute effects from a substance
whose toxic effects are primarily
of a chronic nature. TLV–STELs are recommended only
where toxic effects have been reported
from high short-term exposures in either humans or animals.
Time Weighted Average - An expression of permissible
levels for occupational exposure. Time weighted average permits
exposure above the level, provided they are compensated by equivalent
excursions below the level during the work-day shift. In some cases,
the magnitude, duration and frequency of permissible excursions
above these averages are specified.
Tolerable daily intake, TDI - Estimate
of the amount of a potentially harmful substance (e.g., contaminant)
in food or drinking water that can be ingested daily over a lifetime
without appreciable health risk.
Note: Acceptable daily intake (ADI) is normally
used for substances not known to be harmful, such as food additives.
Tolerable weekly intake, TWI - Estimate
of the amount of a potentially harmful substance (e.g., contaminant)
in food or drinking water that can be ingested weekly over a lifetime
without appreciable health risk.
Tolerance - An adaptive state characterized by
diminished responses to the same dose of a chemical.
Toxic - Able to cause injury to living organisms
as a result of physicochemical interaction.
Toxicity – Inherent property of an agent
to cause an adverse biological effect.
Toxicity test - Experimental study of the adverse
effects of exposure of a living organism to a substance
for a defined duration under defined conditions.
Toxicodynamics - Process of interaction of potentially toxic
substances with target sites, and the biochemical
and physiological consequences leading to adverse effects.
Toxicogenetics - Study of the influence of hereditary
factors on the effects of potentially toxic substances on
individual organisms.
Toxicokinetics - Process of the uptake of
potentially toxic substances by the body, the biotransformation they
undergo, the distribution of the substances and their metabolites
in the tissues, and the elimination of the substances
and their metabolites from the body.
Toxicology - Scientific discipline involving
the study of the actual or potential danger presented by the harmful
effects of substances on living organisms and ecosystems, of the
relationship of such harmful effects to exposure, and
of the mechanisms of action, diagnosis, prevention, and treatment
of intoxications.
Toxin - Poisonous substance produced by a biological
organism such as a microbe, animal, or plant.
Trace - A very small amount
of a material. Usually used in reference to concentrations which
are on the order of or less than 1-10 parts per million.
Tumor - Any abnormal mass of
cells resulting from excessive cellular multiplication.
Two-compartment model - Product of compartmental
analysis requiring two compartments.
Uncertainty - Imperfect knowledge concerning
the present or future state of an organism, system, or (sub)population
under consideration.
Uncertainty analysis - A detailed
examination of the systematic and random errors of a measurement
or estimate; an analytical process to provide information regarding
the uncertainty
Uncertainty Factor - Reductive factor by which
an observed or estimated no-observed-adverse-effect level (NOAEL)
is divided to arrive at a criterion or standard that is considered
safe or without appreciable risk.
Uptake (absorption) - The process by which an agent
crosses an absorption barrier.
Validation - Process by which the reliability and relevance
of a particular approach, method, process, or assessment is established for
a defined purpose.
Virtually Safe Dose (VSD) - The VSD is an expression
of the daily dose (exposure) over a lifespan that is predicted to
produce no more than a pre-defined low level of risk, usually set
according to an >acceptable risk level= (e.g. 10-6 cancer risk
over a 70 year lifetime).
Volume of distribution - Apparent (hypothetical)
volume of fluid required to contain the total amount of a substance
in the body at the same concentration as that present in
the plasma, assuming equilibrium has been attained.
Weight-of-Evidence - Considerations involved in
assessing the reliability of available information about hazard;
and the quality of testing methods, the size and power of the study
design, the consistency of results across studies, and the biological
plausibility of exposure-response relationships and statistical associations.
Willingness-to-Pay - An economic approach used
to estimate the monetary value of avoiding an adverse health effect
based on an individual=s willingness-to-pay (WTP) for risk reduction. By
summing many individuals= WTP to avoid small increases in risk over
a large sample, the value of a statistical premature death avoided
can be inferred. This valuation is expressed as Adollars per
mortality avoided@ or Avalue of a statistical life@ (VSL) even though
the actual valuation represents small changes on mortality risk experience
by a large number of people. The VSL method estimates the dollar
value of a given reduction in risk, in reference to an indivdual=s
WTP to reduce that risk. WTP is often based on wage-risk studies,
which derive WTP values from estimates of the additional compensation
demanded in the labour market for riskier jobs, or from contingent
valuation (CV) studies which directly solicit WTP information from
personal interviews.
Xenobiotic - Compound with a chemical structure
foreign to a given organism.
Note: The term is frequently restricted to manmade compounds.
Years Lost due to Disability (YLD) – Years
Lost due to Disability (YLD) gives the number of healthy years lost
to a disability.
Years of Life Lost (YLL) – Years of Life
Lost is simply the number of years lost due to premature mortality.
Zero order analysis - The
simplest approach to quantification of a risk with a limited treatment
of each risk component (e.g. source terms, transport, health effects,
etc.).
131I (Iodine – 131) - is a radioactive isotope
of the chemical element Iodine with mass number 131. It is a beta-emitter
with a half-life of 8 days.
137Cs (Cesium-137) - is a radioactive isotope
of the chemical element Cesium with mass number 137, which has a
half life of 30.2 years and decays by beta-decay.
|