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Paracelsus: A 16-century physician (1493-1541) who saw the need for scientific experimentation in toxicology and thus gave toxicology a scientific basis. He recognized that chemicals often have both therapeutic and toxic properties based on dose. His observations laid the foundation for the concept of the dose-response relationship.

parathion: An organophosphate that is used as an insecticide; it is absorbed through the skin, eaten, or inhaled; it is toxic because it acts on the nervous system.

pesticide: Chemicals developed to control a wide variety of pests in primarily agricultural and forest environments.

pollution: The undesirable presence of matter or energy that can cause harmful environmental effects.

population: A group of individuals of the same species living in a particular area.

potency: The measure of a chemical's effectiveness as a medicine or a poison. The more potent the chemical, the less it takes to exert its effect.

response: The variety of reactions to exposure to chemicals that might occur in an organism.

risk assessment: Qualitative and quantitative evaluation of the risk posed to human health and/or the environment by exposure to a chemical.

risk management: The process by which risk is reduced or controlled. Risk assessment information is used, along with other information, such as values, cost, and feasibility, to arrive at a risk management decision.

route of exposure: The way in which a person may contact a chemical substance. For example, a person may ingest a chemical, inhale a chemical, or absorb a chemical through the skin.

solvent: A substance (usually a liquid) capable of dissolving or dispersing one or more other substances. Water is a solvent. Organic solvents include alcohols, aldehydes, benzene, toluene, glycol ethers, trichloroethylene (TCE), formaldehyde, and carbon tetrachloride. Drinking water is an important source of solvent exposure; solvents also pass rapidly through the skin and produce high levels in the bloodstream within minutes after skin exposure. Nearly all solvents (other than water) can cause acute and chronic injury to the central nervous system. Many solvents are associated with development of kidney failure and chronic kidney disease, and others can cause acute toxic damage to the liver.

subacute exposure: Repeated exposure to a chemical for one month or less.

synthetic: Made by forming a compound by combining two or more simpler compounds, elements, or radicals; human-made, not from nature.

threshold: The lowest dose of a chemical at which a certain measurable effect is observed and below which it is not observed.

toxic: Harmful; poisonous.

toxicant: Any chemical or mixture of chemicals that presents a risk of death, disease, injury, or birth defects in organisms that ingest or absorb it.

toxicity: The capacity or property of a substance to cause adverse effects.

toxicologist: A scientist trained to examine the nature of the adverse effects of chemicals on living organisms and assess the probability of their occurrence.

toxicology: The multidisciplinary science that examines the adverse effects of chemicals on organisms.

toxin: A naturally occurring substance or agent that may injure an organism exposed to it.

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