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Common Toxicology Terms

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Abatement—Reducing the degree or intensity of, or eliminating, pollution. (CEHN)

Absolute lethal concentration (LC100)—Lowest concentration of a substance in an environmental medium which kills 100% of test organisms or species under defined conditions. This value is dependent on the number of organisms used in its assessment. (IUPAC)

Absolute lethal dose (LD100)—Lowest amount of a substance which kills 100% of test animals under defined conditions. This value is dependent on the number of organisms used in its assessment. (IUPAC)

Absorbed dose (of a substance)—Amount of a substance absorbed into an organism or into organs and tissues of interest. (IUPAC)

Absorption—In biology, this is the process of active or passive transport of a substance into an organism—in the case of a mammal or human being, this is usually through the lungs, gastrointestinal tract, or skin. (IUPAC)

Absorption coefficient —Ratio of the absorbed amount of a substance to the administered amount. With respect to exposure by way of the respiratory tract, the coefficient is the ratio of the absorbed amount to the amount of the substance (usually particles) deposited (adsorbed) in the lungs. (IUPAC)

Acceptable daily intake (ADI)—Estimate of the amount of a substance in food or drinking water, expressed on a body mass basis (usually mg/kg body weight), that can be ingested daily over a lifetime by humans without appreciable health risk. A standard body mass of 60 kg is used to calculate the daily intake per person, (WHO)

Acceptable risk—Probability of suffering disease or injury which is considered to be sufficiently small to be “negligible.”

Accidental exposure—Unintended contact with a substance or change in the physical environment.

Accumulation—Successive additions of a substance to a target organism, or organ, or to part of the environment, resulting in an increasing amount or concentration of the substance in the organism, organ, or environment. (IUPAC)

Action level—Concentration of a substance in air, soil, water or other defined medium at which specified emergency counter-measures should be taken. (IUPAC)

Active ingredient—In any pesticide product, the component that kills, or otherwise controls, target pests. Pesticides are regulated primarily on the basis of active ingredients. (CEHN)

Acute—Short-term exposure or effect. In experimental toxicology, “acute” refers to studies of two weeks or less in duration (often less than 24 hours)

Acute effect—Effect of short duration and occurring rapidly (usually in the first 24 hours or up to 14 days) following a single dose or short exposure to a substance. (IUPAC)

Acute exposure—Contact with a substance that occurs once or for only a up to 14 days. (ATSDR)

Acute toxicity—Adverse effects occurring within 14 days after administration of a single dose (or exposure to a given concentration) of a test substance or after multiple doses (exposures), usually within 24 hours.

Acute toxicity test—Experimental animal study to determine what adverse effects occur in a short time, within 14 days after a single dose of a substance or after multiple doses.

Adaptation—Changes in an organism that have no irreversible disruptions in response to changing environmental conditions. (IUPAC)

Added risk—Difference between the incidence of an adverse effect in a treated group (of organisms or a group of exposed humans) and a control group (of the same organisms or the spontaneous incidence in humans).

Addiction—To function normally, the body relies on a substance and there is a physical dependency on the substance as well. If that substance is taken away, it causes withdrawal, that is accompanied by a characteristic set of signs and symptoms.

Additive effect—Consequence which follows exposure to two or more physio-chemical agents which act jointly, but do not interact—commonly, the total effect is the simple sum of the effects of separate exposure to the agents under the same conditions. Substances of simple similar action may show dose or concentration addition (IUPAC) 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.

Adenocarcinoma—A malignant tumor that starts in the glandular epithelium. (IUPAC)

Adenoma—A benign tumor that occurs in the glandular epithelium.

Adjuvant—A substance added to a drug to speed or increase the action of the main component when you are talking about the substance in pharmacology. When you are talking about immunology, adjuvant is a substance or an organism that increases the response to an antigen. (IUPAC)

Adsorption—Enrichment (positive adsorption, or briefly adsorption) of one or more components in an interfacial layer. (IUPAC)

Adverse effect—Change in physiology, development or lifespan of an organism which results in impairment of functional capacity or impairment of capacity to compensate for additional stress or increase in susceptibility to the harmful effects of other environmental influences. (IUPAC)

Adverse event—Occurrence which causes an adverse effect. (IUPAC)

Aerobe—Organism that needs oxygen to live.

Agency for Toxic Substances and Disease Registry (ATSDR)—An agency of the Department of Health and Human Services, the Agency for Toxic Substances and Disease Registry is responsible for chemical safety. The agency’s mission is to use the best science, take responsive action and provide trustworthy health information to prevent and mitigate harmful exposures, toxic substances and related disease.

Air particulates—Total suspended particulate matter found in the atmosphere as solid particles or liquid droplets. Chemical composition of particulates varies widely, depending on location and time of year. Airborne particulates include windblown dust, emissions from industrial processes, smoke from the burning of wood and coal, and motor vehicle or non-road engine exhausts. (CEHN)

Air pollution—Substances that are present in the air that interfere with the health, welfare or comfort of individuals. These substances also cause harm to the environment and result from human activity or natural processes. (ISO)

Air quality standards—The level of pollutants prescribed by regulations that may not be exceeded during a given time in a defined area. (CEHN)

Air toxics—Any air pollutant for which a national ambient air quality standard (NAAQS) does not exist (i.e., excluding ozone, carbon monoxide, PM-10, sulfur dioxide, nitrogen oxide) that may reasonably be anticipated to cause cancer, developmental effects, reproductive dysfunctions, neurological disorders, heritable gene mutations, or other serious or irreversible chronic or acute health effects in humans.(1) (CEHN)

Albuminuria—Presence of albumin, derived from plasma, in the urine. (IUPAC)

Alkalosis—Pathological condition in which the hydrogen ion substance concentration of body fluids is below normal and hence the pH of blood rises above the reference interval. (IUPAC)

Alkylating agent—Substance which introduces an alkyl substituent into a compound (IUPAC)

Allel—One of several alternate forms of a gene which occur at the same relative position (locus) on homologous chromosomes and which become separated during meiosis and can be recombined following fusion of gametes. (IUPAC)

Antagonist—Substance that binds to cell receptors normally responding to naturally occurring substances and produces a response of its own. (IUPAC)

Arsenic—in the periodic table, Arsenic is a semi-metal element that is odorless and tasteless. It can enter drinking water supplies from natural deposits in the earth or from agricultural and industrial practices. This element has been licked to cancer of the skin, kidney, nasal passages, liver, lungs, prostate, and bladder. Common health effects of exposure to arsenic include stomach pain, vomiting, diarrhea, partial paralysis, blindness, thickening and discoloration of the skin. The Environmental Protection Agency set a arsenic standard of .010 parts per million (10 parts per billion) for drinking water.


Bioaccumulate—Absorption of a toxic substances by an organism at a rate that is greater than the rate at which the substance is lost.

Biomarkers—There are three general categories of Biomarkers: Biomarkers of Exposure, Biomarkers of Susceptibility, and Biomarkers of Effect.

  • Biomarkers of Exposure have the ability to identify if exposure to a drug or foreign substance has occurred, and the route or pathway of exposure, Biomarkers of Exposure can be measured in the body of an organism (animal or human) or in the environment. This is also referred to as biomonitoring.
  • Biomarkers of Susceptibility evaluate an individual’s susceptibility to drugs, chemicals, and environmentally mediated disease that may arise from genetic causes or from nongenetic factors such as age, disease state, diet, or dietary supplementation.
  • Biomarkers of Effect may be either early events on the direct pathway to disease or toxic end points or predictors of disease or toxicity outside the direct pathway.

Although biomarkers can indicate events or changes that are not harmful, toxicologists use biomarkers chiefly to determine if exposure has occurred and whether exposure may lead to toxic effects. Also, toxicologists are continually evaluating animals, humans, and the environment to look for more and better biomarkers that represent the earliest signs of exposure. That way, toxicologists and public health professionals can use this information to determine if exposure mitigation efforts are needed.

Biomagnify—the tendency of a substance to increase in concentration as it proceeds up the food chain from prey to the top consumer.

Biomonitoring—is the analysis of human bodily fluids and tissues for purposes of measuring people’s exposure to chemicals. (Mackinac Center 2008)

Biomonitoring—a direct measure of human exposure to substances. Biomonitoring involves measuring actual levels of exposure within the body which can help to make risk assessments far more accurate. (Mackinac Center for Public Policy)

BBP—Butyl benzyl phthalate, used primarily in vinyl flooring.

Bisphenol A (BPA)—A chemical that is an important building block that is used primarily to make polycarbonate plastic and epoxy resins, which are used to make a variety of products such as eyeglass lenses, CDs, DVDs, personal computers, applications, helmets, goggles, food and water containers etc. Commercial use began in the 1950s.


DBP—Dibutyl phthalate, used in the manufacture of cellulose polymers, adhesives, inks and caulking. Also used in small amounts in cosmetics and nail polish.

DEP—Diethyl phthalate used in cosmetics and nail polish and as a solvent.

DEHP—Di(2-ethyl hexyl) phthalate, a common, general purpose plasticizer used for producing flexible vinyl, which is used to make certain medical devices including bags and intravenous tubing.

DINP—Diisononyl phthalate, a vinyl plasticizer used in vinyl toys, although it finds many other applications such as garden hoses, shower curtains, vinyl flooring and wall covering.

DIDP—Diisodecyl phthalate, a general use vinyl plasticizer found in numerous applications such as garden hoses, shower curtains, vinyl flooring and wall covering, and sheathing for wiring and cables.

DNA—DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms. Nearly every cell in a person’s body has the same DNA. Most DNA is located in the cell nucleus (where it is called nuclear DNA), but a small amount of DNA can also be found in the mitochondria.


Endocrine Disruptor—generally, a substance that interacts with one or more components of the endocrine system to cause adverse effects.

Endocrine Modulator—An endocrine modulator is a compound or chemical that changes the function of the endocrine system, which makes and controls the hormones in the body. Thus, endocrine modulators can change how these hormones are formed and how they behave. The endocrine system has many components, located virtually all over the body, and these components include the hypothalamus, pituitary, pineal, thyroid, and parathyroid glands, the kidney, heart, stomach, and intestines, along with fat cells, testes, and ovaries. The endocrine system is contrasted to the exocrine system, which is comprised of salivary glands, sweat glands, and some gastrointestinal glands. Thus, compounds which act as endocrine modulators can have far-reaching consequences if they obstruct crucial bodily functions such as child-bearing, body temperature regulation, bone density, and organ function.

Estrogen—any female sex hormone.

Etiology—Science dealing with the cause or origin of disease.

Exposure—in health matters, a measurement of the level at which one encounters any substance.


Genomics—the study of genes of a cell or tissue, according to the DNA messenger.


Hazard—the biological effects produced by substances (i.e., toxicity). Hazards pose risks only if the exposure is sufficiently high.

Hazardous air pollutants—Air pollutants that may reasonably be expected to cause or contribute to irreversible illness or death as defined under the Clean Air Act. These pollutants include asbestos, beryllium, mercury, benzene, coke-oven emissions or radionuclides, and vinyl chloride. (CEHN)


Hormones—chemical messengers that are formed in the endocrine glands, such as the adrenal or thyroid gland, and which affect the function of organs or tissues designed to receive them.


Margin of Safety

Metabolism—literally, change. Any process in an organism that produces, changes, or breaks down a compound. Digestion is a process of metabolizing the foods taken into the body.

Mercury—a naturally occurring element that is found in air, water and soil which exists in the following forms—elemental or metallic mercury, inorganic mercury compounds, and organic mercury compounds. Mercury is an element in the earth's crust and is found in many rocks as well as coal. When coal is burned, mercury is released into the environment. The largest source of mercury emissions is Coal-burning power plants, which account for 40 percent of all domestic human-caused mercury emissions. Mercury in the air eventually settles into water or onto land where it can be washed into water. Once deposited, certain microorganisms can change it into methylmercury, a highly toxic form that builds up in fish, shellfish and animals that eat fish. Fish and shellfish are the main sources of methylmercury exposure to humans. Methylmercury builds up more in some types of fish and shellfish than others.The levels of methylmercury in fish and shellfish depend on what they eat, how long they live and how high they are in the food chain.


National Children’s Study—The National Children’s Study will examine the effects of environmental influences on the health and development of 100,000 children across the United States, following them from before birth until age 21. The goal of the study, mandated by the Children’s Health Act of 2000, is to improve the health and well-being of children. The National Children’s Study is led by various government agencies including—the US Department of Health and Human Services (including the Eunice Kennedy Shriver National Institute of Child Health and Human Development and the National Institute of Environmental Health Sciences, of the National Institutes of Health and the Centers for Disease Control and Prevention), and the US Environmental Protection Agency.


PBT—a material that is considered to be persistent in the environment, Bioaccumulative, and toxic to fish and wildlife. Phthalates are often improperly referred to as PBTs although they do not have the same characteristics that genuine PBT materials possess.

Pharmacokinetic Models—A pharmacokinetic model is a mathematical description of the movement of a drug or compound through the body. This includes Absorption (from the moment of entry at ingestion or initial exposure), Distribution (and transport throughout the body), Metabolism (biochemical modification or degradation, usually through specialized enzymatic systems) and Excretion of the drug or compound from the body. Toxicologists use models like these, but refer to them as toxicokinetic models when the goal is to determine the relationship between the systemic exposure of a compound in experimental animals and its toxicity. Toxicologists use pharmacokinetic models to predict how chemicals will behave in the body.

Pharmacokinetics—The study of how the human body absorbs and eliminates chemicals. (Mackinac Center for Public Policy)

Phthalates—Phthalates are a family of compounds made from alcohols and phthalic anhydride. Phthalates, or plasticizers as they are commonly called, are colorless, oily and odorless liquids that do not evaporate quickly. They are commonly used to make vinyl soft and pliable. For the past several years, phthalates have been used as a key ingredient in fragrances and nail polish. The phthalate used in perfume makes the scent last longer and the phthalate used in nail polish helps keep the polish from chipping. Some of the most commonly known phthalates that are used include plastic bags, garden hoses, inflatable toys, children’s toys, vinyl flooring, adhesives, detergents, lubricating oils, food packaging, raincoats, automotive plastics and such personal products as soap, hair spray, and shampoo.

Phthalates have been referred to as endocrine disruptors by some groups, but most phthalates do not interfere with either the estrogen or androgen receptors when tested in laboratory animals.

PVC—polyvinyl chloride is a polymer of vinyl chloride monomer. Vinyl chloride monomer is a volatile liquid. PVC is an essentially inert, rigid plastic material.


Reference dose (RfD)—An exposure level defined by the Environmental Protection Agency as “a numerical estimate of a daily oral exposure to the human population, including sensitive subgroups such as children, that is not likely to cause harmful effects during a lifetime.”

Risk—Probability a substance will cause harm under specific conditions of use, i.e., a function of the hazard potential of an exposure to the substance


SNPS—Single nucleotide polymorphisms, or SNPs (pronounced “snips”), are DNA sequence variations that occur when a single nucleotide (A,T,C,or G) in the genome sequence is altered. Scientists believe SNP maps will help them identify the multiple genes associated with complex ailments such as cancer, diabetes, vascular disease, and some forms of mental illness.

Systems Biology—A relatively young science that attempts to study the biological processes in terms of gender networks and pathways.


Toxicity—the biological effect of a substance. In this context, toxicity and hazard are used interchangeably.

The Three Rs—Reduce, refine and replace.



Sources Consulted

“ATSDR Glossary of Terms.” Agency for Toxic Subtances and Disease Registry. Department of Health and Human Services. 18 Jan. 2008 <>.

“CEHN: Glossary of Children’s Environmental Health Terms.” Resource Guide. 2004. Children’s Environmental Health Network. 18 Jan. 2008. <>.

“Glossary of Environmental Health Terms.” Department of Health. 2006. New York State. 18 Jan. 2008.

“International Union of Pure and Applied Chemistry: Clinical Chemistry Division: Commission on Toxicology: Glossary for Chemists of Terms Used in Toxicology: IUPAC Recommendations 1993.” Pure and Appl. Chem., Vol. 65 No 9. 1993: 2003-2122. Environmental Health and Toxicology SIS Specialized Information Services. United States National Library of Medicine. 18 Jan. 2008. <>.

*Information for these definitions and topics attributed in part to

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