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IUPAC Glossary of Terms Used in Toxicology - Terms Starting with E

Study of the influence of hereditary factors on the effects of xenobiotics on individual organisms.

Branch of biology which studies the interactions between living organisms and all factors (including other organisms) in their environment: such interactions encompass environmental factors which determine the distributions of living organisms.

Grouping of organisms (micro-organisms, plants, animals) interacting together, with and through their physical and chemical environments, to form a functional entity within a defined environment.

ecotoxicologically (environmentally) relevant concentration (ERC)
Concentration of a pesticide (active ingredient, formulations, and relevant metabolites) that is likely to affect a determinable ecological characteristic of an exposed system.
After [9]

Study of the toxic effects of chemical and physical agents on all living organisms, especially on populations and communities within defined ecosystems; it includes transfer pathways of these agents and their interactions with the environment.

See pheromone

Substance intended to kill parasites living on the exterior of the host.

Acute or chronic skin inflammation with erythema, papules, vesicles, pustules, scales, crusts or scabs, alone or in combination, of varied etiology.

Presence of abnormally large amounts of fluid in intercellular spaces of body tissues.

effect biomarker
See biomarker of effect

effective concentration (EC)
Concentration of a substance that causes a defined magnitude of response in a given system.
Note: EC50 is the median concentration that causes 50 % of maximal response.

effective dose (ED)
Dose of a substance that causes a defined magnitude of response in a given system.
Note: ED50 is the median dose that causes 50 % of maximal response.

Fluid, solid or gas discharged from a given source into the external environment.

element (in molecular biology)
Sequence in the promoter region of a gene that regulates expression of that gene through interaction with a trans-acting factor.

elimination (in toxicology)
Disappearance of a substance from an organism or a part thereof, by processes of metabolism, secretion, or excretion.
See also clearance

elimination half-life or half time
Period taken for the plasma concentration of a substance to decrease by half.
Note: May also be applied to other body compartments such as blood, specific organs, or tissues.

elimination rate
Differential with respect to time of the concentration or amount of a substance in the body, or a part thereof, resulting from elimination.

eliminator (of a poison)
Substance that contributes to the elimination of a poison from an organism.


  1. Stage in the developing mammal at which the characteristic organs and organ systems are being formed: for humans, this involves the stages of development from the second to the eighth week (inclusive post conception).
  2. In birds, the stage of development from the fertilization of the ovum up to hatching.
  3. In plants, the stage of development within the seed.

embryonic period
Period from fertilization to the end of major organogenesis.


  1. Production by a substance of toxic effects in progeny in the first period of pregnancy between conception and the fetal stage.
  2. Any toxic effect on the conceptus as a result of prenatal exposure during the embryonic stages of development: these effects may include malformations and variations, malfunctions, altered growth, prenatal death, and altered postnatal function.

embryotropic effect
Change in the embryo and the regulation of its development.


Release of a substance from a source, including discharges to the wider environment.

emission and exposure control
Technical and administrative procedures and specifications applied for the monitoring, reduction or elimination of emissions from a source or exposure to a target.

emission standard
Quantitative limit on the emission or discharge of a substance from a source, usually expressed in terms of a time-weighted average concentration or a ceiling value.

Present in a community or among a group of people; said of a disease prevailing continually in a region.

Portion of a conjugated metabolite which is derived from a natural product (such as a sugar, amino acid or other organic acid) of the metabolizing organism.
See also exocon, phase II reaction.
After [6]

Pertaining to hormones or to the glands that secrete hormones directly into the bloodstream.

endocrine disrupter
endocrine modifier
Exogenous chemical that alters function(s) of the endocrine system and consequently causes adverse health effects in an intact organism, its progeny or (sub)populations.

endocrine modifier
See endocrine disrupter

Uptake of material into a cell by invagination of the plasma membrane and its internalization in a membrane-bounded vesicle.
See also phagocytosis, pinocytosis

antonym exogenous
Produced within or caused by factors within an organism.

endoplasmic reticulum
Intracellular complex of membranes in which proteins and lipids, as well as molecules for export, are synthesized and in which the biotransformation reactions of the mono-oxygenase enzyme systems occur.
Note: May be isolated as microsomes following cell fractionation procedures.

Pertaining to the layer of flat cells lining the inner surface of blood and lymphatic vessels, and the surface lining of serous and synovial membranes.

Layer of flattened epithelial cells lining the heart, blood vessels and lymphatic vessels.

Toxin that forms an integral part of the cell wall of certain bacteria and is released only upon breakdown of the bacterial cell.; endotoxins do not form toxoids.

Intestinal inflammation.

enterohepatic circulation
Cyclical process involving intestinal re-absorption of a substance that has been excreted through the bile, followed by transfer back to the liver, making it available for biliary excretion again.

Aggregate, at a given moment, of all external conditions and influences to which a system under study is subjected.

environmental damage
Adverse effects to the natural environment.

environmental exposure level (EEL)
Level (concentration or amount or a time integral of either) of a substance to which an organism or other component of the environment is exposed in its natural surroundings.

environmental fate
Destiny of a chemical or biological pollutant after release into the natural environment.

environmental health
Human welfare and its influence by the environment, including technical and administrative measures for improving the human environment from a health point of view.

environmental health impact assessment
Estimate of the adverse effects to health or risks likely to follow from a proposed or expected environmental change or development.

environmental health criteria documents
Critical publications of IPCS containing reviews of methodologies and existing knowledge - expressed, if possible, in quantitative terms - of selected substances (or groups of substances) on identifiable, immediate, and long-term effects on human health and welfare.

environmental hygiene
environmental sanitation
Practical control measures used to improve the basic environmental conditions affecting human health, for example clean 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.

environmental impact assessment (EIA)
Appraisal of the possible environmental consequences of a past, ongoing, or planned action, resulting in the production of an environmental impact statement or ‘finding of no significant impact (FONSI)’.

environmental impact statement (EIS)
Report resulting from an environmental impact assessment.

environmental medicine
Specialty devoted to the prevention and management of environmentally-induced injury, illness and disability, and the promotion of the health of individuals, families, and communities by ensuring a healthy environment.

environmental monitoring
Continuous or repeated measurement of agents in the environment to evaluate environmental exposure and possible damage by comparison with appropriate reference values based on knowledge of the probable relationship between ambient exposure and resultant adverse effects.

environmental protection

  1. Actions taken to prevent or minimize adverse effects to the natural environment.
  2. Complex of measures including monitoring of environmental pollution, development and practice of environmental protection principles (legal, technical, and hygienic), including risk assessment, risk management and risk communication.

environmental quality objective (EQO)
Overall state to be aimed for in a particular aspect of the natural environment, for example, “water in an estuary such that shellfish populations survive in good health”.
Note: Unlike an environmental quality standard, the EQO is usually expressed in qualitative and not quantitative terms.

environmental quality standard (EQS)
ambient standard
Amount concentration or mass concentration of a substance that should not be exceeded in an environmental system, often expressed as a time-weighted average measurement over a defined period.

environmental risk assessment
Estimate of the probability that harm will result from a defined exposure to a substance in an environmental medium. The estimate is valid only for a given species and set of conditions.

environmental sanitation
See environmental hygiene

environmental tobacco smoke (ETS)
See sidestream smoke

environmental transformation
Chemical transformation of substances resulting from interactions in the environment.

environmentally relevant concentration
See ecotoxicologically relevant concentration

Present in a community or among a group of animals; said of a disease prevailing continually in a region.

Biological catalyst: a protein, nucleic acid or a conjugate of a protein with another compound (coenzyme).

enzyme induction
Process whereby an enzyme is synthesized in response to a specific substance or to other agents such as heat or a metal species.

Study of the distribution and determinants of health-related states or events in specified populations and the application of this study to control of health problems.

Pertaining to the upper-middle region of the abdomen.

epigen/esis n., -etic adj.
Changes in an organism brought about by alterations in the expression of genetic information without any change in the genome itself (e.g. base hypermethylation or histone modification).
Note: The genotype is unaffected by such a change but the phenotype is altered.

Occurring in severe or sudden spasms, as in convulsion or epilepsy.

Any tumor derived from epithelium.

Sheet of one or more layers of cells covering the internal and external surfaces of the body and hollow organs.

Any part of a molecule that acts as an antigenic determinant: a macromolecule can contain many different epitopes each capable of stimulating production of a different specific antibody.

State of a system in which the defining variables (temperature, pressure, chemical potential) have constant values in time.

equivalent diameter (of a particle)
Diameter of a spherical particle of the same density as a particle under investigation that, relative to a given phenomenon or property, would behave in the same way as the particle under investigation.

Redness of the skin produced by congestion of the capillaries.

Slough or dry scab on an area of skin that has been burnt.

estimated daily intake (EDI)
Prediction of the daily intake of a residue of a potentially harmful agent based on the most realistic estimation of the residue levels in food and the best available food consumption data for a specific population: residue levels are estimated taking into account known uses of the agent, the range of contaminated commodities, the proportion of a commodity treated, and the quantity of home-grown or imported commodities.
Note: The EDI is expressed in mg residue per person.

estimated environmental concentration (EEC)
Predicted concentration of a substance, typically a pesticide, within an environmental compartment based on estimates of quantities released, discharge patterns and inherent disposition of the substance (fate and distribution) as well as the nature of the specific receiving ecosystems.
See also expected environmental concentration
After [9]

estimated exposure concentration (EEC)
Measured or calculated amount or mass concentration of a substance to which an organism is likely to be exposed, considering exposure by all sources and routes.

estimated exposure dose (EED)
Measured or calculated dose of a substance to which an organism is likely to be exposed, considering exposure by all sources and routes.

estimated maximum daily intake (EMDI)
Prediction of the maximum daily intake of a residue of a potentially harmful agent based on assumptions of average food consumption per person and maximum residues in the edible portion of a commodity, corrected for the reduction or increase in residues resulting from preparation, cooking, or commercial processing.
Note: The EMDI is expressed in mg residue per person.


  1. Science dealing with the cause or origin of disease.
  2. In individuals, the cause or origin of disease.

antonym prokaryote
Cell or organism with the genetic material packed in a membrane-surrounded structurally discrete nucleus and with well-developed cell organelles.
Note: The term includes all organisms except archaebacteria, eubacteria and cyanobacteria (until recently classified as cyanophyta or blue-green algae).

European Inventory of Existing Chemical Substances (EINECS)
List of all substances supplied either singly or as components in preparations to persons in a Member State of the European Community on any occasion between 1 January 1971 and 18 September 1981.

Describes a body of water with a high concentration of nutrient salts and a high or excessive rate of biological production.

Adverse change in the chemical and biological status of a body of water following depletion of the oxygen content caused by decay of organic matter resulting from high primary production as a result of enhanced input of nutrients.

excess lifetime risk
Additional or excess risk incurred over the lifetime of an individual by exposure to a toxic substance.

excess rate
See rate difference

exchange transfusion
Method of active artificial elimination of toxicity consisting in complete replacement of blood of the patient by donor blood.

Any largely inert substance added to a drug to give suitable consistency or form to the drug.

Pathological process by which neurons are damaged and killed by the overactivation of receptors for the excitatory neurotransmitter glutamate, such as the NMDA receptor and AMPA receptor.
Note: Excitotoxins like NMDA and kainic acid bind to glutamate t receptors, and can cause excitotoxicity by allowing high levels of calcium ions to enter cells, activating enzymes such as phospholipases, endonucleases, and proteases such as calpain which damage cell structures including the cytoskeleton, membranes, and DNA.

Discharge or elimination of an absorbed or endogenous substance, or of a waste product, and (or) its metabolites, through some tissue of the body and its appearance in urine, feces, or other products normally leaving the body.
Note: Excretion does not include the passing of a substance through the intestines without absorption.
See also clearance, elimination

excretion rate
Amount of substance and (or) its metabolites that is excreted divided by time of excretion.

Portion of a conjugated metabolite that is derived from the parent molecule.

antonym endogenous
Resulting from causes or derived from materials external to an organism.

exogenous substance
See xenobiotic

Coding section of a gene that is separated from other coding sequences of the same gene by intervening noncoding sequences.
See intron

Layer of flattened epithelial cells external to an organ or tissue.

expected environmental concentration (EEC)
Calculated concentrations of a substance, typically a pesticide, in various environmental compartments based on calculations using maximum-exposure scenarios.
Note: EEC models assume a maximum number of applications per growing season at the maximum rate of application according to the application methods stated on the product label.
After [10]

experimental model ecosystem
See microcosm

Living tissue removed from its normal environment and transferred to an artificial medium for growth.

exponential decay
Variation of a quantity according to the law
A = Ae λt
where A and A0are the values of the quantity being considered at time t and zero respectively, and λ is an appropriate constant.

antonyms non-exposed, unexposed
Subject to a factor that is under study in the environment, for instance an environmental hazard.

exposed group (sometimes abbreviated to exposed) (in epidemiology)
People (or other organisms) who 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.


  1. Concentration, amount or intensity of a particular physical or chemical agent or environmental agent that reaches the target population, organism, organ, tissue or cell, usually expressed in numerical terms of concentration, duration, and frequency (for chemical agents and micro-organisms) or intensity (for physical agents).
  2. Process by which a substance becomes available for absorption by the target population, organism, organ, tissue or cell, by any route.
  3. For X- or gamma radiation in air, the sum of the electrical charges of all the ions of one sign produced when all electrons liberated by photons in a suitably small element of volume of air completely stopped, divided by the mass of the air in the volume element.

exposure assessment
Process of measuring or estimating concentration (or intensity), duration and frequency of exposures to an agent present in the environment or, if estimating hypothetical exposures, that might arise from the release of a substance, or radionuclide, into the environment.

exposure biomarker
See biomarker of exposure

exposure control
See emission and exposure control

exposure-effect curve
See concentration-effect curve

exposure limit
General term defining an administrative substance concentration or intensity of exposure that should not be exceeded.

exposure ratio
In a case control study, value obtained by dividing the rate at which persons in the case group are exposed to a risk factor (or to a protective factor) by the rate at which persons in the control group are exposed to the risk factor (or to the protective factor) of interest.

exposure-response relationship
See concentration-response relationship, dose-response relationship

exposure surface
Surface on a target where a substance, e.g., a pesticide is present. With mammals, examples of outer exposure surfaces include the exterior of an eyeball, the skin surface and a conceptual surface over the nose and open mouth. Examples of inner exposure surfaces include the gastrointestinal tract, the respiratory tract and the urinary tract lining.

exposure test
Determination of the level, concentration or uptake of a potentially toxic compound and (or) its metabolite(s) in biological samples from an organism (blood, urine, hair etc.) and the interpretation of the results to estimate the absorbed dose or degree of environmental pollution; or the measuring of biochemical effects, usually not direct adverse effects of the substance, and relating them to the quantity of substance absorbed, or to its concentration in the environment.

expressed sequence tag (EST)
Partial or full complementary DNA sequence which can serve as a marker for a region of the genome which encodes an expressed product.

expression (in genetics)
Conversion of the genetic information encoded in DNA into a final gene product (either a protein or any of the different types of RNA).
Note: Because changes in RNA synthesis are often estimated by measuring mRNA levels, the term “gene expression” is often misleadingly used as synonymous with transcription. The term “gene expression” includes transcription, processing, and splicing of mRNA, as well as translation, and post-translational modification of the protein product.

external validity
Generalizability of the results of a particular study, beyond the limits of the population actually studied.

extracellular space
Volume within a tissue, outside cells and excluding vascular and lymphatic space.

extracellular volume
Volume of fluid outside the cells but within the outer surface of an organism.

extraction ratio
Amount of substance extracted from a source divided by the total contained within the source.

extra risk
Probability that an agent produces an observed response, as distinguished from the probability that the response is caused by a spontaneous event unrelated to the agent.

extraneous residue limit (ERL)
Refers to a pesticide residue or contaminant arising from environmental sources (including former agricultural uses) other than the use of a pesticide or contaminant substance directly or indirectly on the commodity. It is the maximum concentration of a pesticide residue or contaminant that is recommended by the Codex Alimentarius Commission to be legally permitted or recognized as acceptable in or on food, agricultural commodity or animal feed.
Note: The mass content is expressed in milligrams of pesticide residue or contaminant per kilogram of commodity.

Calculation, based on quantitative observations in exposed test species or in vitro test systems, of predicted dose-effect and dose-response relationships for a substance in humans and other biota including interspecies extrapolations and extrapolation to susceptible groups of individuals.
Note: The term may also be used for qualitative information applied to species or conditions that are different from the ones in which the original investigations were carried out.

extrapyramidal movement disorders
Involuntary movements, e.g., those that occur as a side effect of psychiatric medications.