Glossary of Environmental Terms

Glossary Index

A

Abatement: The reducing of the degree or the intensity of pollution. Also, the eliminating of pollution.

Absorbed Dose: Often used In exposure assessment. The amount of a substance penetrating an organism's absorption barriers (e.g.,, skin, mucous membrane, lung tissue, gastrointestinal tract) through physical or biological processes. The term is synonymous with internal dose.

Absorption: The uptake of water, other fluids or dissolved chemicals by a cell or organism (e.g. tree roots absorb nutrients which have been dissolved in a soil media.)

Acclimatization: The physiological and behavioral adjustments an organism makes in response to changes in its environment.

Acid Aerosol: Acidic liquid or solid particles small enough to become airborne. High concentrations often irritate the lungs and have been shown to cause respiratory diseases like asthma.

Acid Deposition: A complex chemical and atmospheric phenomenon that occurs when emissions of sulfur and nitrogen compounds and other substances are transformed by chemical processes in the atmosphere. Often these emissions are carried far from the original sources, and then deposited on earth in either wet or dry form. The wet forms, popularly called "acid rain," can fall to earth as rain, snow, or fog. The dry forms are acidic gases or particulates.

Acid Neutralizing Capacity: Measure of ability of a base (e.g., water or soil) to resist changes in pH.

Acid Rain: (See: acid deposition)

Acidic: The condition of water or soil containing a sufficient amount of acid substances able to lower the pH below 7.0.

Active Ingredient: In any pesticide product, the component that kills, or otherwise controls, target pests. Primarily, pesticides are regulated on the basis of active ingredients.

Acute Exposure: A single exposure to a toxic or otherwise dangerous substance, which as a consequence, may result in severe biological harm or death. Acute exposures are usually characterized as lasting no longer than a day.

Acute Toxicity: The ability of a substance to cause severe biological harm or death soon after a single exposure or dose. Also, any poisonous effect resulting from a single short-term exposure to a toxic substance. (See: chronic toxicity, toxicity.)

Adaptation: Changes in an organism's physiological structure or function or habits that allow it to survive in new surroundings.

Adequately Wet: Material sufficiently mixed or penetrated with liquid to prevent the release of particulates, such as asbestos.

Administered Dose: In exposure assessment, the amount of a substance given to a test subject (human or animal) for the purpose of determining dose-response relationships. However, since exposure to chemicals is usually inadvertent, this quantity is often called potential dose.

Adsorption: Removal of a pollutant from air or water by collecting the pollutant on the surface of a solid material; e.g., an advanced method of treating waste in which activated carbon removes organic matter from wastewater.

Adulterants: Chemical impurities or substances that by law do not belong in a food, or pesticide.

Adulterated: 1. Any pesticide whose strength or purity falls below the quality stated on its label. 2. A food, feed, or product that contains illegal residues of pesticide.

Advanced Treatment: A level of wastewater treatment more stringent than secondary treatment; requires an 85-percent reduction in conventional pollutant concentration or a significant reduction in non-conventional pollutants. Sometimes called tertiary treatment.

Advanced Wastewater Treatment: Any 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. (See primary, secondary treatment.)

Adverse Effects Data: FIFRA requires a pesticide registrant to submit data to EPA on any studies or other information regarding unreasonable adverse effects of a pesticide at any time after its registration.

Advisory: A non-regulatory document that communicates risk information to those involved in risk management decisions.

Aerobic: Life or processes that require, or are not destroyed by, the presence of oxygen. (For an antonym see anaerobic.)

Aerobic Treatment: Process by which microbes decompose complex organic compounds in the presence of oxygen and use the liberated energy for reproduction and growth. (Such processes include extended aeration, trickling filtration, and rotating biological contactors.)

Aerosol: 1. Small droplets or particles suspended in an atmosphere media, typically containing sulfur. They are usually emitted naturally (e.g., in volcanic eruptions) and as the result of anthropogenic (human) activities such as burning fossil fuels. 2. The pressurized gas used to propel substances out of a container. 3. A finely divided material suspended in air or other gaseous environment.

Affected Public: The human population adversely impacted following exposure to a toxic pollutant in food, water, air, or soil.

Agent: Any physical, chemical, or biological entity proved to be harmful to an organism (synonymous with stressor).

Air Changes Per Hour (ACH): The movement of a volume of air in a given period of time. For example, if a house has one air change per hour, it means that the air in the house will be replaced in a one-hour period.

Air Cleaning: Indoor-air quality-control strategy to remove various airborne particulates and/or gases from the air. Most common methods of air cleaning are particulate filtration, electrostatic precipitation, and gas sorption.

Air Plenum: Any space used to convey air in a building, furnace, or structure. The space above a suspended ceiling is often used as an air plenum.

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 of airborne matter capable of being airborne. 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 identifiable sources and (2) those produced in the air by interaction between two or more primary pollutants, or by reaction with normal atmospheric constituents, with or without photo-activation. Exclusive of pollen, fog, and dust, which are of natural origin, about 100 contaminants have been identified. Air pollutants are often grouped in categories for ease in classification; some of the categories of air pollutants are: solids, sulfur compounds, volatile organic chemicals, particulate matter, nitrogen compounds, oxygen compounds, halogen compounds, radioactive compound, and odors. Air Pollution: The presence of contaminants or pollutant substances in the air that interfere with human health or welfare, or produce other harmful environmental effects.

Air Pollution Control Device: Mechanism or equipment that cleans emissions generated by a source by removing pollutants that would otherwise be released to the atmosphere. An example would be an incinerator, industrial smokestack, or an automobile exhaust system.

Air Pollution Episode: A period of abnormally high concentration of air pollutants, often due to low winds and temperature inversion. This situation may cause illness and death. (See: episode, pollution.)

Air Toxics: Any air pollutant for which a national ambient air quality standard (NAAQS) does not exist that may reasonably be anticipated to cause cancer; respiratory, cardiovascular, or developmental effects; reproductive dysfunctions, neurological disorders, heritable gene mutations, or other serious or irreversible chronic or acute health effects in humans.

Airborne 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.

Sources of airborne particulates include: dust, emissions from industrial processes, combustion products from the burning of wood and coal, combustion products associated with motor vehicle or non-road engine exhausts, and reactions to gases in the atmosphere.

Airborne Release: Release of any pollutant into the air.

Algae: Simple rootless plants that grow in sunlit waters in proportion to the amount of available nutrients. They can affect water quality adversely by lowering the dissolved oxygen in the water, this cause eutrophication. They are food for fish and small aquatic animals.

Algal Blooms: Sudden spurts of algal growth, often affecting water quality adversely and may be used to indicate potentially hazardous changes in the local water body's chemistry.

Algicide or Algaecide: Substance or chemical used specifically to kill or control algae.

Alkaline: The condition of water or soil containing a sufficient amount of alkali substance suitable to raise the pH above 7.0.

Alkalinity: The capacity of bases to neutralize acids. An example is lime added to lakes to decrease acidity.

Allergen: A substance causing allergic reactions in those individuals sensitive to the allergen.

Alluvial: Relating to and/or the sand deposited by flowing water.

Alternative Fuels: Substances that may be used as substitutes for traditional liquid, oil-derived motor vehicle fuels like gasoline and diesel. Alternative fuels include mixtures of alcohol-based fuels with gasoline, methanol, ethanol, compressed natural gas, and others.

Ambient Air: Any unconfined portion of the atmosphere: open air, surrounding air.

Ambient Air Quality Standards: (See: Criteria Pollutants and National Ambient Air Quality Standards.)

Ambient Measurement: A measurement of the concentration of a substance or pollutant within the immediate environs of an organism; taken to relate it to the amount of possible exposure.

Ambient Medium: Material surrounding or contacting an organism (e.g., outdoor air, indoor air, water, or soil, through which chemicals or pollutants can reach another organism. (See: biological medium, environmental medium.)

Ambient Temperature: Temperature of the surrounding air or other medium.

Anaerobic: A life or process that occurs in, and/or is not destroyed by the absence of oxygen.

Animal Dander: Tiny scales of animal skin, a common indoor air pollutant.

Antarctic "Ozone Hole": Refers to the seasonal depletion of ozone in the upper atmosphere above a large area of Antarctica. (See: Ozone Hole.)

Anti-Microbial: An agent with the ability to kill microbes.

Applied Dose: In exposure assessment, the amount of a substance coming in contact with the primary absorption boundaries of an organism, such as the skin, lung tissue, gastrointestinal track and thus available for absorption.

Aqueous Solubility: The maximum concentration of a chemical able to dissolve in pure water at a particular reference temperature.

Aqueous: Something made up of or in a solution of water.

Aquifer: An underground geological formation, or group of formations, containing water. Aquifers are sources of groundwater for wells and springs.

Aquifer Test: A test created to determine hydraulic properties of an aquifer.

Area Source: Any source of air pollution released over a relatively small area but which cannot be classified as a point source. Such sources may include vehicles and other small engines, small businesses and household activities, or biogenic sources such as a forest that releases hydrocarbons.

Aromatics: A type of hydrocarbon, such as benzene or toluene, with a specific type of ring structure. Aromatics are sometimes added to gasoline in order to increase octane. Some aromatics are toxic.

Arsenicals: Pesticides containing arsenic.

Artesian (Aquifer or Well): Water held under pressure in porous rock or soil confined by impermeable geological formations.

Asbestos: A mineral fiber that can pollute air or water and cause cancer or asbestosis when inhaled. EPA has banned or severely restricted its use in manufacturing and construction.

Asbestos Abatement: Procedures to control fiber release from asbestos-containing materials in a building or to remove them entirely, including removal, encapsulation, repair, enclosure, encasement, and operations and maintenance programs.

Asbestosis: A disease associated with inhalation of asbestos fibers. The disease makes breathing progressively more difficult and thus may become fatal.

Ash: The mineral content of a product remaining after complete combustion.

Assay: A test for a specific chemical, microbe, or effect.

Assessment Endpoint: In ecological risk assessment, an explicit expression of the environmental value to be protected; includes both an ecological entity and specific attributed thereof. entity (e.g., salmon are a valued ecological entity; reproduction and population maintenance--the attribute--form an assessment endpoint.)

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 deleterious effects and without damage to aquatic life or humans who consume the water.

Attainment Area: An area considered to have air quality as good as or better than the National Ambient Air Quality Standards as defined in the Clean Air Act. An area may be an attainment area for one pollutant and a non-attainment area for others.

Attenuation: The process by which a compound is reduced in concentration over time, through absorption, adsorption, degradation, dilution, and/or transformation. May also be the decrease with distance of sight caused by attenuation of light by particulate pollutants.

Attractant: A chemical or agent that lures insects or other pests by stimulating their sense of smell.

Attrition: Wearing or grinding down of a substance by friction. Dust from such processes often contributes to air pollution.

Available Chlorine: A measure of the amount of chlorine available in chlorinated lime, hypochlorite compounds, and other materials used as a source of chlorine when compared with that of liquid or gaseous chlorines.