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Toxicology Glossary - R

râles: See SN crepitations

random sample: Subset of a population that is arrived at by selecting units such that each possible unit has a fixed and determinate probability of selection
After Last, 1988
AN biased sample
BT sample

rate: Measure of the frequency of a phenomenon: an expression of the frequency with which an event occurs in a defined population during a specified time interval
Last, 1988

rate difference (RD): 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: in comparisons of exposed and unexposed groups, the term "excess rate" may be used as a synonym for rate difference
Last, 1988

rate ratio (RR): In epidemiology, the value obtained by dividing the rate in an exposed population by the rate in an unexposed population
After Last, 1988

ratticide: Substance intended to kill rats
RT rodenticide

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

reasonable maximum exposure (RME): Highest exposure that is reasonably expected to occur: 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.
USEPA, 1989

recalcitrance: Ability of a substance to remain in a particular environment in an unchanged form.
Nagel et al. (eds), 1991
RT persistence

receptor: High affinity binding site for a particular toxicant
BT target, target organ

recovery:

1. 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
2. Term used in analytical and preparative chemistry to denote the fraction of the total quantity of a substance recoverable following a chemical procedure
   RT recovery factor

recovery factor: Fraction or percentage of the total quantity of a substance extracted under specified conditions
Gold, Loening, McNaught and Sehmi, 1987

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: Term used for an estimate of air exposure concentration to the human population (including sensitive subgroups) that is likely to be without appreciable risk of deleterious effects during a lifetime
USEPA, 1989
RT acceptable daily intake
BT dose

reference distribution: Statistical distribution of reference values
Solberg, 1987

reference dose: Term used for an estimate (with uncertainty spanning perhaps an order of magnitude) of a daily exposure to the human population (including sensitive subgroups) that is likely to be without appreciable risk of deleterious effects during a lifetime
Barnes and Dourson, 1988
RT acceptable daily intake
BT dose

reference group: See SN reference sample group

reference individual: Person selected with the use of defined criteria for comparative purposes in a clinical study
Solberg, 1987

reference interval: Area between and including two reference limits, for example the percentiles 2.5 and 97.5
Solberg, 1987

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
Solberg, 1987

reference material: Substance for which one or more properties are sufficiently well established to be used for the calibration of an apparatus, the assessment of a measurement method, or for assigning values to other substances
SN calibration material, standard material
Solberg, 1987

reference population: Group of all reference individuals used to establish criteria against which a population that is being studied can be compared
Solberg, 1987

reference sample group: Selected reference individuals, statistically adequate numerically to represent the reference population
Solberg, 1987

reference value: According to IFCC, measured value of a property in a reference individual or sample from a reference individual
Solberg, 1987

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
Barnes and Dourson, 1988

relative odds: See SN odds ratio

relative risk:

1. Ratio of the risk of disease or death among the exposed to that among the unexposed
   SN risk ratio
2. Ratio of the cumulative incidence rate in the exposed to the cumulative incidence rate in the unexposed; the cumulative incidence ratio
   Last, 1988

renal: Pertaining to the kidneys

repellent: Substance used mainly to repel blood sucking insects in order to protect man and animals: also used to repel mammals, birds, rodents, mites, plant pests, etc.

replicate sampling: Act of taking multiple samples concurrently under comparable conditions; may be accomplished by taking samples adjacent in time or space
PAC, 1990

replication:

1. 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
2. Process whereby the genetic material is duplicated.

reproducibility: Closeness of agreement between test results obtained under reproducibility conditions (see below)
ISO 5725, 1986
RT reproducibility conditions

reproducibility conditions: Situation where test results are obtained with the same method on identical test material in different laboratories with different operators using different equipment
ISO 5725, 1986

reproductive toxicant: Substance or preparation that produces non-heritable harmful effects on the progeny and/or an impairment of male and female reproductive function or capacity
USEPA, 1986
RT teratogen

reproductive toxicology: Study of the adverse effects of substances on the embryo, fetus, neonate and prepubertal mammal and the adult reproductive and neuro-endocrine systems
RT embryo, fetus, neonate

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

resistance (in toxicology): Ability to withstand the effect of various factors including potentially toxic substances

resorptive effect: Action of a substance after its resorption from the gut into the blood
IRPTC, 1982

response:

1. Proportion of an exposed population with a defined effect or the proportion of a group of individuals that demonstrate a defined effect in a given time at a given dose rate
   RT dose-response relationship
2. Reaction of an organism or part of an organism (such as a muscle) to a stimulus

retention:

1. Holding back within the body or within an organ, tissue or cell of matter that is normally eliminated
   AN elimination
2. Holding in memory of what has been learned for later use as recall, recognition or relearning
3. Amount of a substance that is left from the total absorbed after a certain time following exposure: if the retention follows a course in relation to time that is a first order process, it may be described in terms of biological half-life (half-time)
   RT half-life

retrospective study: Research design used to test aetiological 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: 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
RT case control study
Last, 1988

returned effect of poisons: Enhancement of the dose-effect relationship for a poison following repeated exposure to decreasing doses

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 fibres as evidenced by myoglobin in the blood and urine

rhinitis: Inflammation of the nasal mucosa

rhonch/us (pl -i): Harsh crepitation in the throat, often resembling snoring
BT crepitations

ribonucleic acid: 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: it encodes the information for the sequence of amino-acids in proteins synthesized using it as a template
RT deoxyribonucleic acid

risk:

1. Possibility that a harmful event (death, injury or loss) arising from exposure to a chemical or physical agent may occur under specific conditions
2. Expected frequency of occurrence of a harmful event (death, injury or loss) arising from exposure to a chemical or physical agent under specific conditions
   NT excess lifetime risk, extra risk
   RT hazard

risk acceptance: Decision that the risk associated with a given chemical exposure or an event leading to such exposure is low enough to be tolerated in order to gain associated benefits
RT acceptable risk

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 individual people or society of using the chemical or physical agent in the amount and manner proposed and all the possible routes of exposure. Quantification ideally requires the establishment of dose-effect and dose-response relationships in likely target individuals and populations
RT exposure assessment, hazard identification, risk characterization, risk estimation, risk evaluation, risk identification, risk management, risk perception.

risk assessment management process: Global term for the whole process from hazard identification to risk management
WHO, 1988
RT hazard identification, 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: Term used to describe the 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: the assessment 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
After WHO, 1979
RT hazard identification, risk estimation

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: Risk that is negligible and too small to be of societal concern (usually assumed to be a probability below 10-5 or 10-6); can also mean 'virtually safe'. In the USA, this is a legal term used to mean "negligible risk to the individual"
SN negligible risk

risk estimation: Assessment, with or without mathematical modelling, 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
RT risk evaluation
RT exposure assessment, hazard identification

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
RT exposure evaluation, hazard identification, risk assessment, risk characterization, risk estimation, risk identification, risk perception

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 SN 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. Essentially risk management is the combination of three steps: risk evaluation; emission and exposure control; risk monitoring
RT emission and exposure control, risk evaluation, risk monitoring

risk marker: 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: not necessarily a causal or pathogenic factor
SN risk indicator
Last, 1988

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
BT monitoring
RT risk management
WHO, 1988

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 judgement of their implications
RT risk evaluation
WHO, 1988

risk phrases: Word groups identifying potential health or environmental hazards required under CPL Directives (European Community); may be incorporated into Safety Data Sheets
RT material safety data sheet, safety data sheet

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. Calculation of such ratios is used in choosing between options in risk management
RT risk management

risk-specific dose: Amount of exposure corresponding to a specified level of risk
USEPA, 1989

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