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| Absorbed Dose |
| | The amount of a substance that actually enters into the body, usually expressed as milligrams of substance per kilogram of body weight (mg/kg). |
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| Absorption |
| | The process by which toxicants cross body membranes and enter the blood stream or lymphatic system. Absorption frequently refers to the movement of a chemical from outside the body across membrane barriers to gain entrance into the body. |
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| Acetylcholine |
| | An important chemical in the body having physiological functions, including the neurotransmission of electrical impulses across synapses of nerve endings. |
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| Acetylcholinesterase |
| | An enzyme present in nervous tissue, muscle, and red blood cells that catalyzes the hydrolysis of acetylcholine to choline and acetic acid. |
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| Acid |
| | A substance with one or more hydrogen atoms that are readily replaceable by electropositive atoms. It is a donator of protons. In aqueous solution, it will undergo dissociation with the formation of hydrogen ions. It has a pH of less than 7.0. |
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| Active Transport |
| | The movement of a substance across a membrane requiring energy. The substance moves against a concentration gradient, from a less concentrated region to a more concentrated region. |
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| Acute Effect |
| | An effect that occurs almost immediately (hours/days) after a single or brief exposure to a toxic agent. Generally, acute effects will be evident within 14 days. |
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| Aerosols |
| | Aerosols are suspensions of very small airborne particles of a liquid or solid in a gas. |
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| Albumin |
| | A simple protein soluble in water and distributed throughout body tissues. It is the most abundant plasma protein. |
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| Allergy |
| | An immune hypersensitivity reaction of body tissues to allergens that can affect the skin (urticaria), respiratory tract (asthma), gastrointestinal tract (vomiting and nausea) or produce a systemic circulatory response (anaphylactic response). |
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| Alveoli |
| | The air sacs at the ends of the tracheo-bronchial tree in which gases are exchanged between inhaled air and the
pulmonary capillary blood. |
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| Anemia |
| | A condition in which there is reduced or impaired red blood cells or hemoglobin resulting in an inadequate capacity of the blood to transport oxygen to body tissues. |
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| Anoxia |
| | An insufficient (below normal) supply of oxygen in body tissues. |
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| Antagonism |
| | An interaction between two chemicals in which one decreases the expected toxic effect of the other. |
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| Antibody |
| | An antibody is a protein molecule (immunoglobulin with a unique amino acid sequence) that only interacts with a specific or closely related foreign substances (antigen). The antibody is induced (a response of the immune system) as a result of prior exposure to the antigen. |
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| Anticholinergic Effects |
| | Neurological effects resulting from the blockage of acetylcholine, which transmits impulses across nerve junctions. |
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| Antidote |
| | A remedy for counteracting a poison. |
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| Aqueous |
| | Of a watery nature. Prepared with water. |
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| Asphyxiant |
| | A substance, that in high concentrations in air, replaces or reduces the oxygen level such that a person inhaling the air mixture suffers hypoxia. |
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