IUPAC Glossary of Terms Used in Toxicology – R
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radiant power
Power emitted, transferred or received as radiation.
radiation toxicology
Scientific study involving research, education, prevention and
treatment of diseases caused by ionizing or nonionizing
radiation.
râles
See crepitations
random (probability) sample
antonym biased
sample
Subset of units of a population that is arrived at by selecting
units such that each possible unit has a fixed and known
probability of selection.
rate (in epidemiology)
Measure of the frequency with which an event occurs in a defined
population in a specified period of time.
Note 1: Most such rates are ratios, calculated by dividing a
numerator, e.g. the number of deaths, or newly occurring cases of
a disease in a given period, by a denominator, e.g. the average
population during that period.
Note 2: Some rates are proportions, i.e. the numerator is
contained within the denominator (as when a number of patients
with a given disease is divided by the total population from
which they come).
[2]
rate constant, k
rate coefficient
Numerical constant in a rate-of-reaction (v) equation;
for example, v = k
[A]a[B]b.......where [A],
[B] etc. are reactant concentrations, k is the rate
constant, and a, b, etc. are corresponding
empirical constants.
Note: For further consideration of the relevant mathematics, see
[3]
rate-controlling step
rate-determining step
rate-limiting step
In a reaction occurring by a composite reaction sequence, an
elementary reaction, the rate constant for which exerts a strong
effect, - stronger than that of any other rate constant - on the
overall rate.
Note 1: It is recommended that the expressions rate-controlling, rate-determining and
rate-limiting be regarded as synonymous, but some
special meanings sometimes given to the last two expressions are
considered under a separate heading.
Note 2: For further consideration of this term, see [3].
[3]
rate-determining step
See rate-controlling
step
rate difference (RD)
Absolute difference between two rates.
Note 1: 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.
Note 2: In comparisons of exposed and unexposed groups, the term
‘excess
rate’ may be used as a synonym for rate
difference.
rate-limiting step
See rate controlling
step
rate ratio (in epidemiology) (RR)
Value obtained by dividing the rate
in an exposed population
by the rate in an unexposed population.
ratticide
Substance intended to kill rats.
re-absorption (in biology)
Absorption by a
living organism of a substance which it has previously absorbed
and then released, e.g., the uptake of a substance from the
proximal renal tubule following glomerular filtration.
reactive nitrogen species
(RNS)
Radical nitrogen-based molecules that can act to facilitate
nitrosylation reactions; reactive nitrogen species include
dioxidonitrogen(•) (nitrogen dioxide, nitryl radical)
NO2•, oxidonitrogen(•) (nitrogen monoxide, nitrosyl
radical) NO• oxidonitrogen(1+) (nitrosyl cation)
NO+, hydroxyoxidonitrogen (nitrous acid)
HNO2 and oxidonitrate(1-) NO-.
reactive oxygen species (ROS)
Intermediates in the reduction of molecular dioxygen
O2 to water.
Note: Examples are superoxide anion
O2-•, hydrogen peroxide
H2O2, and hydroxyl radical HO•.
[2]
readily biodegradable
Arbitrary classification of substances that have passed certain
specified screening tests for ultimate biodegradability; these
tests are so stringent that such compounds will be rapidly and
completely biodegraded in a wide variety of aerobic environments.
See also biodegradation
reasonable maximum exposure (RME)
Highest exposure that
is reasonably expected to occur.
Note: Typically the 95% upper confidence limit of the
toxicant distribution is used: if only a few data points
(6-10) are available, the maximum detected concentration is used.
recalcitrance
Ability of a substance to remain in a particular environment in
an unchanged form.
receptor
Molecular structure in or on a cell which specifically recognizes
and binds to a compound and acts as a physiological signal
transducer or mediator of an effect.
[2]
receptor-mediated endocytosis
Endocytosis of a
substance and its receptor following receptor
binding.
[2]
recessive gene
Allele which in the heterozygous state is expected to have no
effect on the phenotype of the organism which carries it.
After [9]
recombinant DNA
DNA made by transplanting or splicing DNA into the DNA of host cells in such a way that the modified DNA can be replicated in the host cells in a normal fashion.
recombinant DNA technology
Methods involving the use of restriction enzymes to cleave DNA
at specific sites, allowing sections of DNA molecules to be
inserted into plasmid or
other vectors and cloned in an appropriate host organism (e.g. a
bacterial or yeast cell).
After [9]
recommended exposure level (REL) (in toxicology)
Highest allowable regulatory airborne concentration.
Note: This exposure concentration is not expected to injure workers. It may be expressed as a ceiling limit or as a time-weighted average (TWA).
reconstitution
Restoration to original form of a substance previously for
preservation and storage
[2]
recovery
- Process leading to partial or complete restoration of a cell, tissue, organ or organism following its damage from exposure to a harmful substance or agent.
- Term used in analytical and preparative chemistry to denote the fraction of the total quantity of a substance recoverable following a chemical procedure.
recovery factor
Fraction or percentage of the total quantity of a substance
extracted under specified conditions.
recycling (of waste)
Process or method allowing for the recovery of some value from a
waste, either as re-usable
material or as energy.
reference concentration (RfC)
An estimate (with uncertainty spanning perhaps an order of
magnitude) of a continuous inhalation exposure to the human
population (including sensitive subgroups which include children,
asthmatics and the elderly) that is likely to be without an
appreciable risk of deleterious effects during a lifetime.
Note: It can be derived from various types of human or animal
data such as NOAEL, LOAEL, or benchmark concentration, with
uncertainty factors generally applied to reflect limitations of
the data used. It is generally used in EPA's noncancer health
assessments.
reference distribution
Statistical distribution of reference values.
reference dose (RfD)
An estimate (with uncertainty spanning perhaps an order of
magnitude) of a daily oral exposure to the human population
(including sensitive subgroups) that is likely to be without an
appreciable risk of deleterious effects during a lifetime.
Note: It can be derived from a NOAEL, LOAEL, or benchmark dose,
with uncertainty factors generally applied to reflect limitations
of the data used. It is generally used in EPA's noncancer health
assessments.
reference group
See reference sample
group
reference individual
Person selected with the use of defined criteria for comparative
purposes in a clinical study.
reference interval
Area between and including two reference limits, for example the
percentiles 2.5 and 97.5.
reference limit
Boundary value defined so that a stated fraction of the reference
values is less than or exceeds that boundary value with a stated
probability.
reference material (RM)
calibration material
standard material
standard
Material, sufficiently homogeneous and stable regarding one or
more properties, used in calibration, in
assignment of a value to another material, or in quality
assurance.
[7]
reference population
Group of all reference individuals used to establish criteria
against which a population that is being studied can be
compared.
reference sample group
Selected reference individuals, statistically adequate
numerically to represent the reference population.
reference value
Quantity value, generally accepted as having a suitably small
measurement uncertainty, to be used as a basis for comparison
with values of quantities of the same kind.
[14]
regioselectivity, (regioselective)
Terms referring to a reaction in which one direction of bond
making or breaking occurs preferentially over all other possible
directions.
Note: Reactions are termed completely (100%) regioselective if
the discrimination is complete, or partially (x%), if
the product of reaction at one site predominates over the product
of reaction at other sites.
[2]
regression analysis
Statistical methods for modeling a set of dependent variables,
Y, in terms of combinations of predictors,
X.
[2]
regulatory dose
Term used by the USEPA to describe the expected dose resulting
from human exposure to
a substance at the level at which it is regulated in the
environment.
regulatory sequence
DNA sequence to which specific proteins bind to activate or
repress the expression of a gene.
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 R1is the rate in the population,
R2 is the rate in the comparison
population, and R0is the rate in the general population.
Note: Rate is used here as in epidemiology.
[2]
relative odds
See odds ratio
risk ratio
rate ratio
- Ratio of the risk of disease or death among the exposed to the risk among the unexposed.
- Ratio of the cumulative incidence rate in the exposed to the cumulative incidence rate in the unexposed.
relative systemic availability
Quantity of metabolizable substance divided by product of
quantity of absorbed substance and exposure.
[2]
- Giving a remedy.
- Removal of pollution or contaminants from environmental media such as soil, groundwater, sediment, or surface water for the general protection of human health and the environment.
remedy
Anything, such as a medicine or therapy, that relieves pain,
cures disease, or corrects a disorder.
renal
Pertaining to the kidneys.
[2]
renal plasma flow
Volume of plasma passing
through the kidneys in unit time.
[2]
renopathy
See nephropathy
repeatability
measurement repeatability
Measurement precision under repeatability conditions of measurement.
[14]
repeatability condition
repeatability condition of measurement
Condition of measurement in a set of conditions including the
same measurement procedure, same operator, same measuring system,
same operating conditions and same location, and replicated
measurements over a short period of time.
[14]
repellent
Substance used mainly to repel blood sucking insects in order to
protect man and animals.
Note: This term may also be used for substances used to repel
mammals, birds, rodents, mites, plant pests, etc.
replicate sampling
Act of taking multiple samples concurrently under comparable
conditions.
Note: Replicate sampling may be accomplished by taking samples
adjacent in time or space.
replication
- Duplicated or repeated performance of an experiment under similar (controlled) conditions to reduce to a minimum the error, and to estimate the variations and thus obtain a more precise result: each determination, including the first is called a replicate.
- Process whereby the genetic material is duplicated.
reproducibility
measurement reproducibility
Measurement precision under reproducibility conditions of
measurement.
[14]
reproducibility condition
reproducibility condition of measurement
Condition of measurement in a set of conditions including
different locations, operators, and measuring systems.
Note 1: The different measuring systems may use different
measurement procedures.
Note 2: A specification should give the conditions changed and
unchanged, to the extent practical.
[14]
reproductive toxicant
Substance or preparation that produces non-heritable adverse effects on male and
female reproductive function or capacity and on resultant
progeny.
reproductive toxicology
Study of the nonheritable adverse effects of substances
on male and female reproductive function or capacity and on
resultant progeny.
reserve capacity
Physiological or biochemical capacity that may be available to
maintain homeostasis when the body or an organism is exposed to an environmental
change.
reservoir (in biology)
Storage compartment
from which a substance may be released with subsequent biological
effects.
[2]
residence time
See mean residence time
residual risk
Health risk remaining after risk reduction actions are
implemented.
[2]
residual time
See mean residence time
residue
Contaminant remaining in an organism or in other material such as
food or packaging, following exposure.
resistance (in toxicology)
Ability to withstand the effect of various factors including
potentially toxic substances.
resorption (in biology)
Process in which the components of some differentiated structure
that has been produced by the body undergo lysis and
assimilation.
Note: Specifically in developmental toxicology, term applied to
the lysis and assimilation of the fetus caused by chemical or
biological stress of the pregnant mother.
resorptive effect
Action of a substance after its re-absorption from the gut into
the blood.
respirable dust
respirable particles
Mass fraction of dust (particles) that penetrates to the
unciliated airways of the lung (the alveolar region).
Note: This fraction is represented by a cumulative log-normal
curve having a median aerodynamic diameter of 4 μm, standard
deviation 2 μm (values for humans).
[2]
response
Proportion of an exposed
population with a defined effect or the proportion of a group of
individuals that demonstrates a defined effect in a given time at
a given dose rate.
restriction enzymes
Endonucleases which recognize specific base sequences within a
DNA helix, creating a double-strand break of DNA.
Note: Type I restriction enzymes bind to these recognition sites
but subsequently cut the DNA at different sites. Type II
restriction enzymes both bind and cut within their recognition or
target sites.
[3]
retention
- Amount of a substance that is left from the total absorbed after a certain time following exposure.
- Holding back within the body or within an organ, tissue or cell of matter that is normally eliminated.
retrospective study
Research design used to test etiological hypotheses in which
inferences about exposure to the putative causal
factor(s) are derived from data relating to characteristics of
the persons or organisms under study or to events or experiences
in their past.
Note: The essential feature is that some of the persons under
study have the disease or other outcome condition of interest,
and their characteristics and past experiences are compared with
those of other, unaffected persons. Persons who differ in the
severity of the disease may also be compared.
returned effect of poisons
Enhancement of the dose-effect relationship for a
poison following repeated exposure to decreasing doses.
reverse mutation (back mutation)
Mutation in a mutant allele which makes it capable of producing
the nonmutant phenotype; this may result from restoration of the
original DNA sequence of the gene or from production of a new DNA
sequence which has the same effect.
reverse transcription
Process by which an RNA
molecule is used as a template to make a single-stranded
DNA copy.
reversible alteration
Change from normal structure or function, induced by a substance
or other agent(s), that returns to normal status or within normal
limits after cessation of exposure.
rhabdomyolysis
Acute, fulminating, potentially lethal disease of skeletal muscle
that causes disintegration of striated muscle fibers as evidenced
by myoglobin in the blood and urine.
rhinitis
Inflammation of the
nasal mucosa.
rhonch/us sing., /i pl.)
Harsh crepitation in the throat, often resembling snoring.
ribonucleic acid (RNA)
Linear, usually single stranded, polymer of ribonucleotides, each
containing the sugar ribose in association with a phosphate group
and one of 4 nitrogenous bases: adenine, guanine, cytosine, or
uracil.
Note: RNA encodes the information for the sequence of amino-acids
in proteins synthesized using it as a template.
- Probability of adverse effects caused under specified circumstances by an agent in an organism, a population or an ecological system.
- Probability of a hazard causing an adverse effect.
- Expected frequency of occurrence of a harmful event arising
from such an exposure.
After [2]
risk assessment
Identification and quantification of the risk resulting from a specific use or occurrence
of a chemical or physical agent, taking into account possible
harmful effects on individuals or populations exposed to the agent in the amount
and manner proposed and all the possible routes of exposure.
Note: Quantification ideally requires the establishment of
dose-effect and
dose-response
relationships in likely target individuals and
populations.
risk assessment management process
Global term for the whole process from hazard identification to risk management.
risk associated with a life time exposure
Probability of the occurrence of a specified undesirable event
following exposure of
an individual person from a given population to a specified
substance at a defined level for the expected lifetime of the
average member of that population.
risk aversion
Tendency of an individual person to avoid risk.
risk characterization
Outcome of hazard
identification and risk estimation
applied to a specific use of a substance or occurrence of an
environmental health
hazard.
Note: Risk characterization requires quantitative data on the
exposure of organisms
or people at risk in the specific
situation. The end product is a quantitative statement about the
proportion of organisms or people affected in a target
population.
risk communication
Interpretation and communication of risk assessments in terms that are
comprehensible to the general public or to others without
specialist knowledge.
risk de minimis
negligible risk
risk that is negligible and too
small to be of societal concern (usually assumed to be a
probability below 10-5 or 10-6).
Note 1: This term can also mean ‘virtually safe’.
Note 2: In the USA, this is a legal term used to mean
‘negligible risk to the
individual’.
risk estimation
Assessment, with or without mathematical modeling, of the
probability and nature of effects of exposure to a substance based on
quantification of dose-effect and dose-response relationships for
that substance and the population(s) and environmental components
likely to be exposed and
on assessment of the levels of potential exposure of people,
organisms and environment at risk.
risk evaluation
Establishment of a qualitative or quantitative relationship
between risks and benefits,
involving the complex process of determining the significance of
the identified hazards
and estimated risks to those organisms or people concerned with
or affected by them.
risk identification
Recognition of a potential hazard and definition of the factors
required to assess the probability of exposure of organisms or people to
that hazard and of harm resulting from such exposure.
risk indicator
See risk marker
risk management
Decision-making process involving considerations of political,
social, economic, and engineering factors with relevant
risk assessments relating to a
potential hazard so as to
develop, analyse, and compare regulatory options and to select
the optimal regulatory response for safety from that hazard.
Note: Essentially risk management is the combination of three
steps: risk evaluation;
emission and
exposure control;
risk monitoring.
risk marker
risk indicator
Attribute that is associated with an increased probability of
occurrence of a disease or other specified outcome and that can
be used as an indicator of this increased risk.
Note: A risk marker is not necessarily a causal factor.
risk monitoring
Process of following up the decisions and actions within
risk management in order
to check whether the aims of reduced exposure and risk are achieved.
risk perception
Subjective perception of the gravity or importance of the
risk based on a person's knowledge
of different risks and the moral, economic, and political
judgment of their implications.
risk phrases
Word groups identifying potential health or environmental hazards required under CPL
Directives (European Community); may be incorporated into
Safety Data Sheets.
risk quotient
Ratio of predicted exposure
concentration to predicted no effect
concentration.
predicted environmental
concentration (PEC) predicted no effect
concentration (PNEC)
Note: The higher this value above one, the greater the risk. If
the value is below one, there should be no risk as a result of
the predicted exposure.
risk ratio
Value obtained by dividing the probability of occurrence of a
specific effect in one group by the probability of occurrence of
the same effect in another group, or the value obtained by
dividing the probability of occurrence of one potentially
hazardous event by the probability of occurrence of another.
Note: Calculation of such ratios is used in choosing between
options in risk
management.
risk-specific dose
Amount of exposure
corresponding to a specified level of risk.
rodenticide
Substance intended to kill rodents.
route of exposure
Means by which a toxic
agent gains access to an organism by administration through the
gastrointestinal tract (ingestion), lungs (inhalation), skin
(topical), or by other routes such as intravenous, subcutaneous,
intramuscular or intraperitoneal routes.