Absorbed Dose: The amount of a chemical that enters the body of an exposed organism.
Absorption : The uptake of water or dissolved chemicals by a cell or an organism (as tree roots absorb dissolved nutrients in the soil).
Absorption Factor: The fraction of a chemical making contact with an organism that is absorbed by the organism.
Acceptable Daily Intake (ADI): The largest amount of chemical to which a person can be exposed on a daily basis that should not result in adverse effects; usually expressed in mg/kg/day). Same as RfD.
Acclimation : Physiological and behavioral adjustments of any organism to changes in the environment.
Acid : A corrosive solution with a pH less than 7. An inorganic or organic compound that (1) reacts with metals to yield hydrogen; (2) reacts with a base to form a salt; (3) dissociates in water to yield hydrogen or hydronium ions; (4) has a pH of less than 7.0; and (5) neutralizes bases or alkaline. All acids contain hydrogen and turn litmus paper red. They are corrosive to human tissue.
Acid Rain: The precipitation of dilute solutions of strong mineral acids, formed of various industrial pollutants that mix in the earth's atmosphere. Sulfur dioxide and nitrogen oxides mix with naturally occurring oxygen and water vapor.
Activated Sludge Process : A sewage treatment process by which bacteria that feed on organic wastes are circulated and put in contact with organic waste and oxygen to increase the rate of decomposition.
Active Ingredient : The component that kills, or otherwise controls, target pests. Pesticides are regulated primarily on the basis of active ingredients.
Acute Effect : An adverse effect on any living organism in which severe symptoms develop rapidly and often subside after the exposure stops.
Acute Toxicity : Adverse effects that result from a single dose or exposure to a chemical; any poisonous effect produced within a short time, usually less than 96 hours. This term normally is used to describe effects in experimental animals.
Adsorption : A process by which chemicals are on the surface of a mineral or soil particle (compare with Absorption).
Advanced Wastewater Treatment : Treatment of sewage that goes beyond the secondary or biological water treatment stage and includes the removal of nutrients such as phosphorus and nitrogen and a high percentage of suspended solids.
Aerobic Digestion (Sludge Processing): Biochemical decomposition of organic matter by organisms which results in the formation of mineral and organic compounds.
Aerosol : A suspension of liquid or solid particles in a gas, the particles. Fog and smoke are common examples of natural aerosols; fine sprays (perfumes, insecticides, inhalants, antiperspirants, paints, etc.) are man-made aerosols. Various kinds may be formed by placing the components, together with a compressed gas, in a container (bomb). The pressure of the gas causes the mixture to be released as a fine spray (aerosol) or foam (aerogel) when a valve is opened.
Agricultural Waste: Poultry and livestock manure, and materials in liquid or solid form generated from the production and marketing of poultry, livestock and their products. Also includes grain, vegetable, and fruit harvest residue.
Air Pollutant: Any substance in air that could, in high enough concentration, harm man, other animals, vegetation, or material. Pollutants may include almost any natural or artificial composition. They may be in the form of solid particles, liquid droplets, gases, or in combination thereof. Generally, they fall into two main groups: (1) those emitted directly from sources and (2) those produced in the air by interaction between two or more primary pollutants, or by reaction with normal atmospheric constituents. Roughly 100 contaminants have been identified; some of the categories are: solids, sulfur compounds, volatile organic chemicals, particulate matter, nitrogen compounds, oxygen compounds, halogen compounds, radioactive compound, and odors.
Air Pollution: Toxic gases introduced into the atmosphere, usually as a result of human activity.
Air Quality Standards : The level of selected pollutants set by law that may not be exceeded. Used to determine the amount of pollutants that may be emitted by industry.
Algae : Rootless plants that grow in waters in proportion to the amount of available nutrients. They can affect water quality adversely by lowering the dissolved oxygen in the water. They are food for fish and small aquatic animals.
Alkali : Alkalis (or bases) are materials that have pH values from 8 to 14. Alkalis with pHs between 12 to 14 are corrosive and will cause severe damage to skin and eyes. Any compound having highly basic properties Alkalies are caustic and dissolve human tissue. Common commercial alkalis are sodium carbonate (soda ash), NaOH, lime, lye, potash, caustic soda, KOH, water glass, regular mortar, portland cement, and bicarbonate of soda (see Acid; pH).
Allergen: A substance that causes an allergic reaction in sensitive individuals.
Alternative Energy: Environmentally sound energy that is not extensively used in the United States, such as solar or wind energy (as opposed to fossil fuels).
Alternative Fuels: Transportation fuels other than gasoline or diesel. Including natural gas, methanol, and electricity.
Alternative Technology: An approach that uses resources efficiently or substitutes resources in order to do minimum damage to the environment.
Ambient : Any portion of the atmosphere; open air; outside surrounding air.
Asbestos : A fiber that can pollute air or water and cause cancer or asbestosis when inhaled. The Environmental Protection Agency has banned or severely restricted the use of asbestos in manufacturing and construction.
Asphyxiation : A condition that causes asphyxia or suffocation. Asphyxiation is one of the potential hazardous of working in confined spaces.
Assimilation : The ability of a body of water to purify itself of pollutants.
Assimilative Capacity: The capacity of a natural body of water to receive wastewaters or toxic materials without adverse effects and without damage to aquatic life or humans who consume the water.
Atomic Energy: Energy released in nuclear reactions. Fission occurs when a neutron splits an atom's nucleus into smaller pieces. Fusion occurs when two nuclei are joined together under millions of degrees of heat.
Autotrophic : An organism that produces food from inorganic substances.
Avoided Cost : The cost that the utility would have incurred for producing the same amount of power.
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