GLOSSARY OF TERMS ON CHEMICAL SAFETY
FOR USE IN IPCS PUBLICATIONS
The International Programme on Chemical Safety (IPCS) is a joint venture of the United Nations Environment Programme, the International Labour Organisation, and the World Health Organization. The main objective of the IPCS is to carry out and disseminate evaluations of the effects of chemicals on human health and the quality of the environment. Supporting activities include the development of epidemiological, experimental laboratory, and risk-assessment methods that could produce internationally comparable results, and the development of manpower in the field of toxicology. Other activities carried out by IPCS include the development of know- how for coping with chemical accidents, coordination of laboratory testing and epidemiological studies, and promotion of research on the mechanisms of the biological action of chemicals.
INTRODUCTION
The language of chemical safety is drawn from many sources. These include medicine, toxicology, pharmacology, epidemiology, ecotoxicology and environmental pollution. Its terminology has developed in an unstructured manner with proliferation into multiple terms, some with overlapping, alternative, or even ambiguous meanings. This situation is a source of confusion to both authors and readers of publications on chemical safety and a cause of difficulty in translation into other languages.
To facilitate international communication and comprehension, economy should be exercised in the use of terms and definitions already formulated by various scientific bodies. However, this glossary is not, on the one hand, an exhaustive compilation nor, on the other, a definitive list of approved terms. It is intended to be a guide of terms widely used and adequately defined.
Grateful acknowledgement is made to the experts in the scientific bodies which form the sources for the terms and definitions. In particular the work of the International Epidemiological Association in sponsoring a Dictionary of Epidemiology, ably edited by Dr John M. Last, deserves credit for providing a sound international basis for terminology in this field of science. The glossary has drawn heavily on this publication.
Language and terminology are not static. Comments and suggestions for additions and improvements would be welcomed by the International Programme on Chemical Safety. These should be sent to:
The Manager
International Programme on Chemical Safety
Division of Environmental Health
World Health Organization
1211 Geneva 27
Switzerland
NOTE
Users of the Glossary should note that the terms in the Glossary are defined primarily for use in the Environmental Health Criteria of the International Programme on Chemical Safety (IPCS) and in other IPCS publications, such as those resulting from the activity of the Joint FAO/WHO Expert Meeting on Food Additives (JECFA) and the Joint FAO/WHO Meeting on Pesticide Residues (JMPR). The terms may be used differently by other bodies and in other publications.
abiotic: This is a term used to describe anything which is characterized by the absence of life or incompatible with life. In toxicology and ecotoxicology it refers to physical (e.g. heat, sunlight) or chemical processes (e.g. hydrolysis) that are capable of modifying chemical structures.
abiotic transformation: Any process in which a chemical in the environment is modified by non-biological mechanisms (see also biotransformation) (WHO, 1979).
absorbed dose (in toxicology): The amount of a chemical absorbed into the body or into organs and tissues of interest (WHO, 1978a).
absorbed dose (in radiation): The energy imparted to matter in a suitably small element of volume by ionizing radiation divided by the mass of that element of volume (ISO, 1972). The SI unit for absorbed dose is joule per kilogram (J kgW-1) and its special name is gray (Gy) (ISO, 1972).
absorption (in colloid and surface chemistry): A process whereby, when two phases are brought into contact, a given component is transferred from one phase to the other (after IUPAC, 1972). Experimental differentiation of absorption and adsorption (q.v.) may be difficult, and sometimes the two processes occur simultaneously; in such cases the term ``sorption'' is used (WHO, 1979).
absorption (in radiation): A phenomenon in which radiation transfers to matter which it traverses some or all of its energy (ISO, 1972).
acceptable daily intake: This is an estimate of the amount of substance in the food that can be ingested daily over a lifetime by humans without appreciable health risk. The concept of the ADI has been developed principally by WHO and FAO and is relevant to chemicals such as additives to foodstuffs, residues of pesticides and veterinary drugs in foods. ADIs are derived from laboratory toxicity data, and from human experiences of such chemicals when this is available, and incorporate the safety factor.
acceptable daily intake for man (ADI) (food additives): The acceptable daily intake (ADI) for man, expressed on a body weight basis (mg/kg body weight) is the amount of a food additive that can be taken daily in the diet, even over a lifetime, without risk. It is allocated only to substances for which the available data include either the results of adequate short-term and long-term toxicological investigations, or satisfactory information on the biochemistry and metabolic fate of the compound, or both (Vettorazzi, 1980).
acceptable daily intake (pesticide residues): The acceptable daily intake of a chemical is the daily intake which, during an entire life time, appears to be without appreciable risk to the health of the consumer on the basis of all the known facts at the time when a toxicological assessment is carried out. It is expressed in milligrams of the chemical per kilogram of body weight (Vettorazzi, 1980).
acceptable daily intake not specified: An ADI without an explicit indication of the upper limit of intake may be assigned to substances of very low toxicity, especially those that are food constituents or that may be considered as foods or normal metabolites in man. This expression was adopted as a more suitable expression than ``ADI not limited'', which was previously used. An additive having an ``ADI not specified'' must meet the criteria of good manufacturing practices. For example, it should have proved technological efficacy and be used at the minimum level of technological efficacy, it should not conceal inferior food quality or adulteration, and it should not create a nutritional imbalance. The above expression means that, on the basis of available data (chemical, biochemical, and toxicological), the total daily intake of the substance arising from its use or uses at levels necessary to achieve the desired effect and from its acceptable background in food, does not represent a hazard to health. For this reason, and for reasons stated in the individual evaluations, the establishment of an acceptable daily intake expressed in mg/kg body weight is not deemed necessary (Vettorazzi, 1980).
no acceptable daily intake allocated: This expression is applicable to substances for which the available information is not sufficient to establish their safety or when the specifications for identity and purity are not adequate. The fact that an ADI for an additive was not established should not be interpreted as casting doubt on its safety nor should it be considered for its withdrawal for use (Vettorazzi, 1980).
acceptable daily intake not specified (pesticide residues): An ADI without an explicit indication of the upper limit of intake may be assigned to substances of very low toxicity, especially those that are food constituents or that may be considered as foods or normal metabolites in man. This expression was adopted as a more suitable expression than ``ADI not limited'' which was previously used. An additive having an ``ADI not specified'' must meet the criteria of good manufacturing practices, for example, it should have proved technological efficacy and be used at the minimum level of technological efficacy, it should not conceal inferior food quality or adulteration, and it should not create a nutritional imbalance. The above expression means that, on the basis of available data (chemical, biochemical, and toxicological), the total daily intake of the substance arising from its use or uses at levels necessary to achieve the desired effect and from its acceptable background in food, does not represent a hazard to health. For this reason, and for reasons stated in the individual evaluations, the establishment of an acceptable daily intake expressed in mg/kg body weight is not deemed necessary (Vettorazzi, 1980).
acceptable level of treatment: Acceptable daily intakes are usually expressed as milligrams of the substance in question per kilogram of body weight. There are, however, certain food additives that are more appropriately limited in terms of levels of treatment applied (Vettorazzi, 1980).
acceptable residue: Acceptable residues in human food that have been established for antibiotics found in foods (Vettorazzi, 1980).
acceptable risk: This concept relates to the probability of suffering disease or injury that will be tolerated by an individual, group or society. Acceptability of risk depends on the scientific data, social, economic and political factors, and on the perceived benefits arising from the a chemical or process.
accumulation: Successive additions of a substance to a target organism, or organ, or to part of the environment, resulting in an increasing quantity or concentration of the substance in the organism, organ, or environment.
accuracy: (i) The closeness of agreement between the ``true'' value and the measured values (ISO, 1981); (ii) the degree to which a measurement, or an estimate based on measurements, represents the true value of the attribute that is being measured (Last, 1988).
acid rain: The deposition of acids (sulphuric and nitric) in rain. An environmental problem resulting from certain industrial activities and the burning of petroleum based fuels (trafic exhaust gases).
action level: (i) The level of a pollutant at which specified emergency countermeasures, 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 (UN, 1972); (ii) the level at which some kind of preventive action (not necessarily of an emergency nature) is to be taken; (iii) a level of exposure of workers to airborne harmful substances in workrooms to be determined by the competent authority; it is distinctly below the exposure limit and consequently such exposures below the action level do not usually necessitate application of all the preventive measures, especially of a medical nature, foreseen for exposures exceeding the action level. This level may lie between a third and a half of the exposure limit (ILO, 1977).
acute effects: Effects that occur rapidly following exposure and are of short duration (WHO, 1979).
acute toxicity: The adverse effects occurring within a short time of administration of a single dose or multiple doses given within 24 hours (Hagan, 1959).
acute toxicity test: An experimental animal study in which the adverse effects occur in a short time (from l-7 days) following the administration of a single or multiple doses of a chemical. The most frequently used acute toxicity test involves determination of the median lethal dose (LD50) of the compound. The LD50 has been defined as ``a statistically derived expression of a single administered dose of a material that can be expected to kill 50% of the animals'' (WHO, 1978a).
additive effect: An additive effect is the overall consequence which is the result of two chemicals acting together and which is the simple sum of the effects of the chemicals acting independently. See also antagonistic effect, synergistic effect.
adsorption: A process whereby one or more components of an interfacial layer between two bulk phases are either enriched or depleted (IUPAC, 1972).
adverse effect: This is abnormal, undesirable or harmful effect to an organism, indicated by some result such as mortality, altered food consumption, altered body and organ weights,altered enzyme levels or visible (pathological) change. An effect may be classed as adverse effect if it causes functional or anatomical damage, causes irreversible changes or increases the susceptibility of the organism to other chemical or biological stress. A non-adverse effect will usually be reversed when exposure to the chemical ceases.
aerodynamic diameter of a particle: The diameter of a spherical particle of unit density that has the same settling velocity in air as the particle in question (IAEA, 1978).
aerosol: This is a very broad term applied to any suspension of solid or liquid particles in a gas. They are fine enough in the particle size (0.001 to 100 micrometers) to remain dispersed for a period of the time.
air pollution: The presence of substances in the atmosphere resulting either from human activity or natural processes, present in sufficient concentration, for a sufficient time and under circumstances such as to interfere with the comfort, health, or welfare of persons or the environment (ISO, 1980).
allergen: This descriptor may be used to any substance which produces an allergic reaction.
allergy: A broad term applied to disease symptoms following exposure to a previously encountered substance (allergen), often one which would otherwise be classified as harmless. Essentially it is a malfunction of the immune system. See sensitization.
analytic study: A hypothesis-testing method of investigating the association between a given disease or health state or other dependent variable and possible causative factors. In an analytic study, individuals in the study population may be classified according to absence or presence (or future development) of specific disease and according to ``attributes'' that may influence disease occurrence. Attributes may include age, race, sex, other disease(s), genetic, biochemical, and physiological characteristics, economic status, occupation, residence, and various aspects of the environment or personal behaviour. Three types of analytic study are cross-sectional (prevalence), cohort (prospective), and case control (retrospective) (Last, 1983).
antagonistic effect: This is the consequence of one chemical (or a group of chemicals) interacting: the situation in which the combined effect of two or more chemicals is less than the simple sum of their independent effects. In bioassay, the term may be used to refer to the situation when a specified response is produced by exposure to either of two factors but not by exposure to both together (Last, 1983).
antibody: A protein produced in body in response, and specific for, a foreign substance or antigen.
antigen: The descriptor applied to any substance that produces a specific immune response and is regognised as foreign by the immune system when it enters the tissue of an animal or human.
asbestosis: The damage to the the lungs caused specifically by exposure to, and inhalation of, asbestos fibres.
assay: The quantitative or quantitative evaluation of a hazardous substance; the results of such an evaluation (Last, 1988).
atrophy: The process which is observed during the wasting of a tissue or an organ.
benign: This adjective is applied to any growth which does not invade surrounding tissue. See malignant, tumour.
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. Among the ways in which deviation from the truth can occur, are the following: -
-
1. Systematic (one-sided) variation of measurements from the true values (synonym: wsystematic error).
2. Variation of statistical summary measures (means, rates, measures of association, etc.) from their true values as a result of systematic variation of measurements, other flaws in data collection, or flaws in study design or analysis.
3. Deviation of inferences from the truth as a result of flaws in study design, data collection, or the analysis or interpretation of results.
4. A tendency of procedures (in study design, data collection, analysis, interpretation, review or publication) to yield results or conclusions that depart from the truth.
5. Prejudice leading to the conscious or unconscious selection of study procedures that depart from the truth in a particular direction, or to one-sidedness in the interpretation of results.
(from Last, 1988).
bioavailability (synonym:biological availability, physiological availability): The extent to which a chemical substance to which the body is exposed (by ingestion, inhalation, injection, or skin contact) reaches the systemic circulation, and the rate at which this occurs. It is recognized that the bioavailability (for gastrointestinal absorption) of, for example, both essential and non-essential metals, depends on various factors including the composition of the diet and the type of the chemical compound and its state of dispersion. For instance, the absorption of lead and cadmium is increased if the food is deficient in calcium or iron (WHO, 1979).
bioaccumulation: The process by which the amount of a substance in a living organism (or its parts) increases with time (WHO, 1979).
biochemical mechanism: This is the general term for any chemical reaction or series of reactions, usually enzyme catalysed, which produces a given physiological effect in a living organism.
bioconcentration: A process leading to a higher concentration of a chemical in the organism relative to its environment (WHO, 1979).
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 and 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 used for this purpose (e.g., changes in enzyme activity or in the excretion of metabolic intermediates) if they show a relationship to the exposure (WHO, 1979).
biological assessment of exposure: Mainly used for hygienic evaluation of workplaces (deducing from the analytical results the level of exposure, sometimes even correlations with the concentration in the air, the possible absorption by other routes than inhalation, etc.) and for medical prevention or diagnostics (probability of health impairment at certain values of the exposure test). The definition of biological assessment of exposure should include only the chemical and haematological analyses already mentioned and should not be extended to include indicators of general health or sickness, or functional tests (WHO, 1979).
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 (WHO, 1979).
biological half-life (synonym: biological half-time): The time required for the amount of a particular 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 (ISO, 1972). For a one-compartment system describing an exponential biological process, biological half-life = log 2/f where f = elimination or decay constant.
biological monitoring: The periodic examination of biological specimens (in accordance with the definition of monitoring). It is usually applied to exposure monitoring but can also apply to effect monitoring (WHO, 1979).
biomagnification (or ecological magnification): 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 (Dustman & Stickel, 1969).
biomass: The total amount of biotic material, usually expressed per unit surface area or volume of a medium such as water (WHO, 1979).
biota: Living organisms (WHO, 1979).
biotransformation: A process in which a chemical is modified by a living organism (WHO, 1979).
BOD (Biochemical Oxygen Demand): This is defined as the mass of dissolved oxygen required by a specific volume of solution of the substance for process of biochemical oxidation under prescribed conditions. The measurement of BOD indicates the ability of micro-organisms to metabolise an organic substance in the presence of oxygen and thus indicates the potential for depletion of oxygen by the substance. Refers to degradation.
cancer: Cancer is a disease which results from the development of a malignant tumour and its spread into the surrounding tissues. See tumour.
carcinogen: An agent, chemical, physical or biological, that can act on living tissue in such a way as to cause a malignant neoplasm (WHO, 1980).
carcinogenesis: The induction by chemical, physical, or biological agents, of neoplasms that are usually not observed, an earlier induction of neoplasms that are usually observed, and/or the induction of more neoplasms than are usually found although fundamental differences in the mechanisms may be involved (IARC, 1977).
case control study (synonyms: case comparison study, case history study, case referent study, retrospective study): A study that starts with the identification of persons with the disease (or other outcome variable) of interest, and a suitable control (comparison, reference) group of persons without the disease. The relationship of an attribute to the disease is examined by comparing the diseased and nondiseased with regard to how frequently the attribute is present or, if quantitative, the levels of the attribute, in each of the groups.
Such a study can be called ``retrospective'' because it starts after the onset of disease and looks back to the postulated causal factors. Cases and controls in a case control study may be accumulated ``prospectively;'' that is, as each new case is diagnosed it is entered in the study. Nevertheless, such a study may still be called ``retrospective'' because it looks back from the outcome to its causes. The terms ``cases'' and ``controls'' are sometimes used to describe subjects in a randomized controlled trial but, the term ``case control study'' should not be used to describe such a study (from Last, 1988).
chemobiokinetics: The process of the uptake of chemical 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. Both the amounts and the concentrations of the substances and their metabolites are studied. The term has essentially the same meaning as pharmaco-kinetics, but the latter term should be restricted to the study of pharmaceutical substances (WHO, 1979).
cholinesterase and pseudocholinesterase inhibitors: These are substances which inhibit the cholinesterase-enzyme activity and thus enhance and subsequently prevent transmission of nerve impulses from one nerve cell to another or to a muscle.
chromosomal aberration: Any abnormality of chromosome number or structure may be described as an aberration.
chromosome: This is a structure in the nucleus of the cell composed of deoxyribonucleic acid (DNA) andprotein; the chromosome forms the basis of heredity and carries genetic information in DNA in the form of sequence of nitrogenous bases.
chronic effects: Effects that develop slowly and have a long duration. They are often, but not always, irreversible. Some irreversible effects may appear a long time after the chemical substance was present in the sensitive tissue. For such delayed or late effects, the latent period (or the ``time to occurrence'' of an observable effect) may be very long, particularly if the level of exposure is low (WHO, 1979).
chronic toxicity test: A study in which animals are observed during the whole life span (or the major part of the life span) and in which exposure to the test material takes place over the whole observation time or a substantial part thereof. The term ``long-term toxicity study'' is sometimes used as a synonym for ``chronic toxicity study'' and sometimes to signify a study that falls in between subacute (short- term toxicity studies) and chronic toxicity studies (WHO, 1978a).
ceiling value (CV): The maximum permissible airborne concentration of a potentially toxic substance and is a concentration that should never be exceeded in the breathing zone.
clastogen: A clastogen is any substance which causes chromosomal breaks.
cluster sampling: (i) A method of sampling in which the population is divided into aggregates (or clusters) of items bound together in a certain manner. A sample of these clusters is taken at random and all the items which constitute them are included in the sample (ISO, 1977); (ii) a sampling method in which each unit selected is a group of persons (all persons in a city block, a family, etc.) rather than an individual (Last, 1988).
COD (Chemical Oxygen Demand): The amount of oxygen required to oxidize the substance chemically. Refers to degradation.
cohort study (synonyms: concurrent, follow-up, incidence, longitudinal, prospective study): The method of epidemiologic study in which subsets of a defined population can be identified who are, have been, or in the future may be exposed or not exposed, or exposed in different degrees, to a factor or factors hypothesized to influence the probability of occurrence of a given disease or other outcome. The alternative terms for a cohort study, i.e., follow-up, longitudinal, and prospective study, describe an essential feature of the method, which is observation of the population for a sufficient number of person-years to generate reliable incidence or mortality rates in the population subsets. This generally implies study of a large population, study for a prolonged period (years), or both (Last, 1988).
compartments: The body is composed of a large number of organs, tissues, cells, and fluids, any one of which could be referred to as a compartment. In chemobiokinetics, a compartment often refers collectively to the organs, tissues, cells, and fluids for which the rates of uptake and subsequent distribution and elimination are sufficiently similar to preclude kinetic resolution (WHO, 1979).
concentration: A general term referring to the quantity of a material or substance contained in unit quantity of a given medium. When the term concentration is used without further qualification, it now means amount of substance concentration (WHO, 1979).
conditional acceptable daily intake: A conditional acceptable daily intake is one that is established for a pesticide in order to limit its use to those situations where no satisfactory substitutes are avail- able. This definition will be the subject of further discussion. The allocation of conditional ADIs for intentional food additives has been superseded (Vettorazzi, 1980).
confounding: -
-
1. A situation in which the effects of two processes are not separated. The distortion of the apparent effect of an exposure on risk brought about by the association with other factors that can influence the outcome.
2. A 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 that any single causal factor has made an effect.
3. A 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) that influence the outcome under study.
(Last, 1988).
confounding variable (synonym: confounder): 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 (Last, 1988).
conjunctiva: The term applied to the mucous membrane that covers the eyeball and undersurface of the eyelids.
contaminant: In some contexts (e.g., in relation to gas cleaning equipment), used as a synonym for pollutant (ISO, 1979).
control limit: A regulatory value applied to the airborne concentration in the workplace of a potentially toxic substance which is judged to be "reasonably practicable" for the whole spectrum of work activities and which must not normally be exceeded.
controls matched: Controls (persons) who are selected so that they are similar to the study group, or cases, in specific characteristics. Some commonly used matching variables are age, sex, race and socio-economic status (Last, 1988).
corrosive of tissue: The descriptor applied to any substance which destroys tissues on direct contact.
count mean diameter: The mean of the diameters of all particles in the population (IAEA, 1978).
count median diameter: The diameter in the population above which there are as many particles with larger diameter as there are particles with smaller diameters (IAEA, 1978).
criteria: Validated sets of data used as a basis for judgement (WHO, 1979).
critical concentration for a cell: The concentration at which undesirable (or adverse) functional changes, reversible or irreversible, occur in the cell (Task Group on Metal Toxicity, 1976).
critical effect: The first adverse effect that appears when the critical concentration in the critical organ is reached in an individual (or the adverse effect that occurs as a result of the lowest dose in the critical organ) (WHO, 1979).
critical group: That part of the target population most in need of protection (WHO, 1979).
critical organ (critical tissue)(in toxicology): The particular organ that first attains the critical concentration (of metal) under specified circumstances of exposure and for a given population (Task Group on Metal Toxicology, 1976).
critical organ(in radiation biology): The organ whose damage (by radiation) results in the greatest injury to the individual (or his descendants). The injury may result from inherent radiosensitivity or indispensability of the organ, or from high dose, or from a combination of all three (ICRP, 1965).
critical organ concentration (critical tissue concentration): The mean concentration in the organ (tissue) at the time the most sensitive type of cell reaches the critical concentration (Task Group on Metal Toxicity, 1976).
critical period: A period during the development of a human, animal, or vegetable body, which 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 (WHO, 1972).
cross-sectional study (synonyms:disease frequency survey, prevalence 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 at 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. See also morbidity survey (Last, 1988).
crude death rate: See death rate.
cumulative effect (functional accumulation): Occurs when repeated doses of a toxic substance or harmful radiation summate to give an enhanced effect (WHO, 1979).
cumulative incidence, cumulative incidence rate: The number or proportion of a group of people who experience the onset of a health related event during a specified time interval; this interval is generally the same for all members of the group, but, as in lifetime incidence, it may vary from person to person without reference to age (Last, 1988).
cumulative incidence ratio: The ratio of the cumulative incidence rate in the exposed to the cumulative incidence rate in the unexposed (Last, 1983).
cyanosis: The pathological condition where there is an excessive concentration of reduced haemoglobin in the blood. This results in blue appearance of the skin, especially on the face and extremities, indicating the lack of sufficient oxygen in arterial blood.
cytotoxic: The adjective applied to anything that is harmful to the cell structure and function and ultimately causing cell death.
death rate: An estimate of the proportion of a population that dies during a specified period. The numerator is the number of persons dying during the period; the denominator is the size of the population, usually estimated as the mid-year population. The death rate in a population is generally calculated by the formula
Number of deaths
during a specified period
-------------------------------- x 10n
Number of persons at risk
of dying during the period
This rate is an estimate of the person-time death rate, i.e.,
the death rate per 10n person-years. If the rate is low, it is
also a good estimate of the cumulative death rate. This rate is
also called the crude death rate (Last, 1988).
deoxyribonucleic acid (DNA): is the constituent of the
chromosomes which stores the hereditary information in the form
of a sequence nitrogenous bases. Much of this information is related
to the synthesis of proteins.
deposition: The process by which a certain amount of a
substance arrives at a particular site (e.g., the deposition of
particles on the ciliated epithelium of the bronchial airways)
(WHO, 1979).
dermatitis: Inflammation of the skin.
detoxify: Reduce the toxicity of a substance either (1)
by making it less harmful or (2) by treating patients suffering from poisoning in such away
as to reduce the probability and/or severity of harmful effects.
discharge (or effluent or emission) standard or release limit:
The maximum acceptable release of a pollutant from a given source
to a specified medium under specified circumstances (WHO, 1979).
distribution: This is a general term for the dispersal
of a applied substance and its derivatives throughout an organism
or environmental system.
dose: The amount of a chemical administered to an organism
(WHO, 1978).
dose rate(in radiation protection): The quantity of energy
absorbed per unit of time (WHO, 1979).
dose exposure-response relationship: The relationship between
administered dose or exposure and the biological change in organisms.
It may be expressed as the severity of an effect in one organism
(or part of an organism) or as the proportion of a population
exposed to a chemical that shows a specific reaction (WHO, 1979).
duplicate portion sampling method (duplicate diet study):
This method is frequently used for the same purposes as the total
diet study technique. It implies that test persons consume their
ordinary diet, but that, for each meal, they prepare a duplicate
portion of all food as prepared, served, and consumed (WHO, 1979).
ecotoxicology: The effects of chemical agents on the environment,
including, in addition to effects on man, adverse events that
take place in the general ecosystem. It is not necessarily related
primarily to human health (WHO, 1979).
effect: A biological change in an organism, organ, or tissue
(WHO, 1979).
effective half-life: (i) The time required for the amount
of a radionuclide in a biological system to be reduced to half
its original value. The T½ effect is related to the biological
half-life (T½b) and the physical half-life (T½) by:
T½b x T½
T½ eff. = -------------------------------
T½b + T½
The clearance curve in a biological system may well be complex
and not a simple exponential function. In this case the simple
relationship given above is not valid (Wagner, 1968). (ii) The
time required for the amount of a particular radionuclide in a
system to be reduced to half its value as a consequence of both
radioactive decay and other processes such as biological elimination
and burnup when the rate of removal is approximately exponential
(ISO, 1972).
elimination (in metabolism): The expelling of a
substance or other material from the body (or a defined part thereof),
usually by a process of extrusion or exclusion but sometimes through
metabolic transformation (WHO, 1979).
embryo: This term is applied to the earliest stages of
development of a plant or an animal. The embryo is generally contained
in another structure: the seed, egg or uterus.
embryotoxicity: The potential of a substance to induce
adverse effects in progeny in the first period of pregnancy between
conception and the fetal stage (UNEP/IRPTC, 1982).
emission: The giving off of environmental pollutants from
various sources (WHO, 1979).
emission or exposure control: The technical and administrative
procedures applied for the reduction or elimination of emissions
from the source or of exposure to the target (WHO, 1988).
emission standard: This regulatory value is a quantitative
limit on the emission or discharge of a potentially toxic substance
from a source. See limit values.
enterohepatic circulation: Intestinal reabsorption of material
that has been excreted through the bile and transferred back to
the liver, making it available for biliary excretion again (WHO,
1979).
environment: The aggregate, at a given moment, of all external
conditions and influences to which a system is subjected (ISO,
1975). The term ``system'' covers all living organisms, including
human beings.
environmental health (synonyms: environmental medicine,
environmental hygiene): The health aspects of the human environment,
including technical and administrative measures for improving
the human environment from a health point of view (WHO, 1979).
environmental quality standard (EQS): This regulatory value
defines the maximum concentration of a potentially toxic substance
which can be allowed in an environmental compartment, usually
air or water, over a defined period. Synonym: ambient standard.
See limit values.
environmental sanitation: Traditionally used to indicate
activities concerned with the improvement of the basic environmental
conditions affecting health, i.e., water supply, human and animal
waste disposal, protection of food from biological contamination,
and housing conditions, all of which are concerned with the quality
of the human environment (WHO, 1979).
environmental transformation: Once emitted into the environment,
a chemical substance may be transported in the biosphere and undergo
various types of chemical changes (WHO, 1979).
enzymes: Proteins which act as highly selective catalyst.
This permits reactions in living cells to take place rapidly under
physiological conditions. Enzymes are also used in the industry,
for example as additives in the detergents.
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 (from Last, 1988).
equivalent diameter (of a particle): The diameter of a
spherical particle of the same density that, relative to a given
phenomenon or property, would behave as the particle under investigation
(ISO, 1979).
erythema: In medicine, this term is applied to redness
of the skin due to blood vessel distension.
excretion: The discharge or elimination of an absorbed
or endogenous substance, or of a waste product, via some tissue
of the body and its appearance in urine, faeces, or other products
normally leaving the body. Excretion of chemical compounds from
the body occurs mainly through the kidney and the gut. For volatile
compounds, however, elimination by exhalation may be important.
Excretion via perspiration and through hair and nails may also
be of importance under special circumstances. Excretion via the
gastrointestinal tract may take place by various routes such as
the bile, the shedding of intestinal cells, and transport through
the intestinal mucosa (WHO, 1979).
excretion rate: The amount or proportion of a substance
that is excreted per unit time. It should be noted that according
to this definition excretion does not include the passing of a
substance through the intestine without absorption. When discussing
the total amount of a substance in faeces (including the unabsorbed
part), it is preferable to speak about faecal content of substance
(Task Group on Metal Accumulation, 1973).
exposed group (in epidemiology): A group whose members
have been exposed to a supposed cause of a disease or health state
of interest, or possess a characteristic that is a determinant
of the health outcome of interest. The abbreviated term ``the
exposed'' is sometimes used.
exposed or non-exposed: Qualitative terms defining the
existence of or lack of a hazard in the environment of individuals
(WHO, 1988).
exposure: The amount of an environmental agent that has
reached the individual (external dose) or has been absorbed into
the individual (internal dose, absorbed dose) (WHO, 1979).
exposure assessment: The quantification of the amount of
exposure to a hazard for an individual or group (WHO, 1979).
exposure control: see emission or exposure control.
exposure limit: A general term implying the level of exposure
that should not be exceeded (WHO, 1979).
extraneous residue limit: An extraneous residue limit is,
for a particular commodity, the maximum toxicologically acceptable
concentration of a residue unavoidably arising from sources other
than the use of a pesticide directly or indirectly for the production
of that commodity (WHO, 1976).
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 (WHO, 1979).
fetus (foetus): In medicine, this term is applied to the
young of mammals when fully developed in the womb. In humans,
this stage is reached after about 3 months of pregnancy. Prior
to this, the developing mammal is in embryo stage.
follow-up study (synonym: cohort study): A study
in which individuals or populations, selected on the basis of
whether they have been exposed to risk, received a specified preventive
or therapeutic procedure, or possess a certain characteristic,
are followed to assess the outcome of exposure, the procedure,
or effect of the characteristic, e.g., occurrence of disease (from
Last, 1988).
food additive: Any non-nutritive substances added intentionally
to food, generally in small quantities, to improve its appearance,
flavour, texture or storage properties, with the exception of
sub- stances which are added to food exclusively for their nutritive
properties, but including animal feed adjuncts which may result
in residues in human food and components of packaging materials
which may find their way into human food, and other contaminants
(Vettorazzi, 1980).
food chain: The sequence of transfer of matter and energy
in the form of food from organism to organism in ascending or
descending trophic levels (WHO, 1979).
food web: A network of food chains (WHO, 1979).
fungicide: A chemical used to kill fungi. See pesticide.
gavage: Dose given by intragastric intubation (WHO, 1979).
gene: This is the part of the DNA molecule in chromosomes
which carries the information defining the sequence of amino-acids
in a specific polypeptide chain.
good agricultural practice in the use of pesticides: Good
agricultural practice in the use of pesticide is the officially
recommended or authorized usage of pesticides under practical
conditions at any stage of production, storage, transport, distribution,
and processing of food and other agricultural commodities, bearing
in mind the variations in requirements within and between regions
and taking into account the minimum quantities necessary to achieve
adequate control, the pesticide being applied in such a manner
as to leave residues that are the smallest amounts practicable
and that are toxicologically acceptable (WHO, 1976).
graded effect: An effect that can usually be measured on
a graded scale of intensity or severity and its magnitude related
directly to the dose (WHO, 1978a).
guideline level: A guideline level is the maximum concentration
of a pesticide residue that might occur after the officially recommended
or authorized use of a pesticide for which no acceptable daily
intake or temporary acceptable daily intake is established and
that need not to be exceeded if good practices are followed. It
is expressed in milligrams for the residue per kilogram of food
(WHO, 1976).
guides to air quality: Sets of concentrations and exposure
times that are associated with specific effects of varying degrees
of air pollution on man, animals, vegetation, and on the environment
in general (WHO, 1979).
guides to environmental quality: Sets of levels and exposure
times that are associated with the specific effects of varying
levels of environmental factors on man, animals, vegetation, and
the environment in general (WHO, 1979).
guinea pig maximization test: This is a skin test for screening
possible contact allergens. It is concidered to be a useful model
for predicting moderate and strong sensitizers in humans.
hazard: A source of danger: a qualitative term expressing
the potential that an environmental agent can harm health (WHO,
1988).
hazard identification: The identification of the substance
of concern, its adverse effects, target populations, and conditions
of exposure (WHO, 1988).
health: A state of complete physical, mental and social
well-being, and not merely the absence of disease or infirmity
(WHO, 1978b).
healthy worker effect: A phenomenon observed initially
in studies of occupational diseases: workers usually exhibit
lower overall death rates than the general population, due to
the fact that the severely ill and disabled are ordinarily excluded
from employment. Death rates in the general population may be
inappropriate for comparison if this effect is not taken into
account (Last, 1983).
hepatotoxic: The adjective applied to anything which is
harmful to the liver.
herbicide: The descriptor applied to a chemical used to
kill plants. See pesticide.
hypersensitivity: See allergy.
human ecology: The interrelations between man and his physical,
biological, socio-economic, and cultural environment, including
the interrelations between himself and other individuals or groups
of other species, and the interrelationship between himself and
his entire environment. Because of the broad approach, human ecology
studies are almost always multidisciplinary (WHO, 1988).
idiosyncrasy: The increased individual sensitivity of an
organism to the effect of certain substances (UNEP/IRPTC, 1982).
immune response: The immune response is a general reaction
of the body to substances that are foreign or treated as foreign.
It may take various forms: antibody production,cell-mediated immunity,
immunological tolerance, or allergy.
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 betweenincidenceandprevalenceis
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 (WHO, 1966).
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
--------------------------------------------x10n
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 calculated by dividing the number of new cases in a specified
period by the initial size of the cohort of persons 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
(Last, 1988).
insecticide: A chemical used to kill insects. See pesticides.
intake: The amount of a substance or material that is taken
into the body, regardless of whether or not it is absorbed. The
daily intake may be expressed as the amount taken in by a particular
exposure route, e.g., ingestion or inhalation. The daily intake
from food is the total amount of a given substance taken in during
one day through the consumption of food. The daily intake by inhalation
is calculated by multiplying the concentration of the substance
(or agent) in air by the total amount of air inhaled during one
day (24 hours). The total daily intake is the sum of the daily
intake by an individual from food, drinking-water, and inhaled
air (WHO, 1979).
interpretation of data: The evaluation of all the facts
available from a given investigation or study with a view to their
significance for health (IRPTC, 1982).
intervention study: An epidemiologic investigation designed
to test a hypothesized cause-effect relationship by modifying
a supposed causal factor in a population (Last, 1988).
intestinal reabsorption: Absorption further down the intestinal
tract of material that has been absorbed before and subsequently
excreted into the intestinal tract, usually through the bile (WHO,
1979).
intravenous: Into or inside the vein
in vitro: A term applied to any study carried out in isolation
from the living organism in an experimental system (`in a test
tube').
in vivo: The term used in contrast with `in vitro' describing
any study carried out within the living organism.
irritant: Applied to any substance causing inflammation
following immediate, prolonged or repeated contact with skin or
mucous membranes.
latent period (synonym: latency): Delay between
exposure to a disease-causing agent and the appearance of manifestations
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 ``latent period'' is often
used as synonym with ``induction 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 (Last,
1988).
LC50: This abbreviation is used for the exposure concentration
of a toxic substance lethal to 50% of a test population. See median
lethal concentration.
LD50: This abbreviation is used for the dose of a toxic
substance lethal to 50% of a test population. See median lethal
dose.
limit of detection: (i) The smallest amount, or lowest
concentration, of a given substance that a given procedure will
detect (WHO, 1980); (ii) for a pesticide residue it is the lowest
concentration that can be qualitatively detected in a specified
commodity (WHO, 1976).
limit of determination (pesticide residue): The limit of
determination of a method of analysis is the lowest concentration
of a pesticide residue that can be quantitatively measured in
the specified commodity with an acceptable degree of certainty
(WHO, 1976).
lower explosive limit (LEL): The lower limit of flammability
of a gas or vapour at normal ambient temperatures expressed as
percentage of the gas or vapour in air by volume. This limit is
assumed constant for temperatures up to 130oC.
mainstream smoke (tobacco smoking): The smoke that is inhaled.
malignant: Adjective describing cells in a cancerous growth.
See tumour.
mass mean diameter: The diameter of a particle with a mass
equal to the mean mass of all the particles in the population
(IAEA, 1978).
mass median diameter: The diameter of a particle with the
median mass (IAEA, 1978).
maximum allowable concentration (MAC): Exposure concentration
not to be exceeded under any circumstances.
maximum residue limit: The maximum concentration of a pesticide
residue resulting from the use of a pesticide according to good
agricultural practice directly or indirectly for the production
and/or protection of the commodity for which the limit is recommended.
The maximum residue limit should be legally recognized. It is
expressed in milligrams of the residue per kilogram of the commodity
(WHO, 1976).
mean life (synonym: mean time, turnover time): The
average lifetime of an atomic or nuclear system in a specified
state. For an exponentially decaying system, it is the average
time for the number of atoms or nuclei in a specified state to
decrease by a factor of e (ISO, 1972).
median lethal concentration: Statistically derived concentration
of a chemical in water solution that can be expected to cause
death in 50% of given population of organism under defined set
of experimental conditions.
median lethal dose: Statistically derived single dose of
a chemical that can be expected to cause death in 50% of given
population of organism under defined set of experimental conditions
(for example oral administration, rat).
mesothelioma: Malignant spreading tumour in mesothelium
of pleura, pericardium or peritoneum arising as a result of the
presence of asbestos fibres, after exposure to asbestos.
metabolic activation: Biotransformation of relatively inert
chemicals to biologically reactive metabolites (compounds). See
biotransformation.
metabolic half-life (synonym:metabolic half-time):
The time required for one half of the quantity of the compound
in the body to be metabolically transformed into a modified chemical
compound (WHO, 1979).
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 (WHO, 1979).
metabolic transformation (synonym: biotransformation):
The chemical transformation of substances that takes place within
an organism (WHO, 1979).
metabolism: In general, the 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
given chemical sub- stance within an organism. It includes the
uptake and distribution within the body of chemical compounds,
the changes (biotransformations) undergone by such substances,
and the elimination of the compounds and of their metabolites
(WHO, 1979).
metabolite: A substance resulting from chemical transformation
in an organism (WHO, 1979).
methaemoglobin/methaemoglobinaemia: In some poisonings,
haemoglobin (the substance in the red blood cells to which the
oxygen is fixed) may be transformed to methaemoglobin. Methaemoglobin
lacks the ability of binding the oxygen, concequently lack of
oxygen occures in the organism. When a certain amount of haemoglobi
has been transformed to methaemoglobin, mucous memranes and skin
become bluish and discolored.
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 form, but diagrammatic models
are also found (Kendall & Buckland, 1982).
molluscicide: A chemical used to kill molluscs.
monitoring (for health, environmental, and associated technical
purposes): The repetitive and continued observation, measurement,
and evaluation of health and/or environmental or technical data
for defined purposes, according to prearranged schedules in space
and time, and using comparable methods for sensing and data collection
(WHO, 1980).
morbidity: Any departure, subjective or objective, from
a state of physiological or psychological well-being. In this
sense, sickness, illness, and morbid condition are similarly defined
and synonymous (Last, 1988).
The WHO Expert Committee on Health Statistics noted in its Sixth
report (1959) that morbidity could be measured in terms of three
units: (i) persons who were ill; (ii) the illnesses (periods or
spells of illnesses) that these persons experienced; and (iii)
the duration (days, weeks, etc.) of these illnesses (Last, 1988).
morbidity survey: A method for the estimation of the prevalence
and/or incidence of disease or diseases in a population. A morbidity
survey is usually designed simply to ascertain the facts as to
disease distribution, and not to test a hypothesis (Last, 1988).
mortality rate: See death rate.
multigeneration study: Toxicity test in which at least
3 generations of the test organism are exposed to the substance
being assessed. Exposure is usually continuous.
multiple (or multiphasic) screening: This procedure has
evolved by combining single screening tests, and is the logical
corollary of mass screening. Where much time and effort has been
spent by a population in attending for a single test (e.g., mass
radiography), it is natural to consider the economy of offering
other tests at the same time. Multiple (or multiphasic) screening
implies the administration of a number of tests, in combination,
to large groups of people (Wilson & Jungner, 1968).
multistage cluster sampling: Cluster sampling with more
than two stages, each sampling being made on aggregates (or clusters)
in which the clusters already obtained by the preceding sampling
have been divided (ISO, 1977).
multistage sampling: A type of sampling in which the sample
is selected by stages, the sampling units at each stage being
subsampled from the larger units chosen at the previous state
(ISO, 1977).
mutagenicity: The property of a physical, chemical, or
biological agent to induce mutations in living tissue (WHO, 1979).
mutagen: An agent that induces mutation (WHO, 1979).
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 (WHO, 1979).
natural occurrence: The occurrence in nature of a compound,
when there are no man-made sources of the compound. The contamination
of nature by some compounds may be so widespread that it is virtually
impossible at the present time to get access to biota with a natural
level and only ``normal'' levels can be measured, i.e., the levels
that are usually prevalent at places where there is no obvious
local contamination (WHO, 1979).
necrosis: Mass death of areas of tissues surrounded by
otherwise healthy tissue.
nematicide: A chemical used to kill nematodes.
neoplasm: Any formation of tissue assiciated with disease
such as tumour. See malignant, tumour.
no-observed-adverse-effect-level (NOEL): 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 (WHO,
1979).
nutritional table method: A method of evaluating the dietary
intake of a large number of people. The accuracy of the method
largely depends on the accuracy with which records of the food
consumption can be established and the accuracy of the nutritional
tables specifying the concentration of various nutrients, vitamins,
and essential and non-essential substances including pesticide
residues. For each record of quantity of food consumed during
a certain time period, the daily intake of the substance in question
is calculated by multiplying the substance concentration in the
food item (as obtained from the nutritional table) by the quantity
of food consumed and dividing by the time of observation (WHO,
1979).
objective environment: The actual physical, chemical, and
social environment as described by objective measurements, such
as noise levels in decibels and concentrations of air pollutants
(WHO, 1979).
occupational environment: The environment at a work place
(WHO, 1979).
occupational hygiene: The applied science concerned with
recognition, evaluation and control of chemical, physical or biological
factors arising from the workplace and which may affect the well-being
of those at work or in the community.
occurrence (synonym:frequency): In epidemiology,
a general term describing the frequency of a disease or other
attribute or event in a population without distinguishing between
incidence and prevalence (Last, 1988).
ocular: The adjective applying to anything pertaining to
the eye.
odds: The ratio of the probability of occurrence of an
event to that of non-occurrence, or the ratio of the probability
that something is so, to the probability that it is not so (from
Last, 1983).
odds ratio (synonym:cross-product ratio, relative odds):
The ratio of two odds. The term ``odds'' is defined differently
according to the situation under discussion. Consider the following
notation for the distribution of a binary exposure and a disease
in a population or a sample.
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