Glossary

Air Toxics:
Synonym for "hazardous air pollutants." (See below).

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

Benzene:
A colorless, volatile, flammable, toxic liquid aromatic hydrocarbon (C₆H₆) used in organic synthesis, as a solvent, and as a component of motor fuel.

Biomonitoring:
Analysis of blood, urine, tissues, etc., to measure chemical exposure in humans.

Carcinoma:
Cancer that begins in the tissues lining or covering an organ.

Carbon Monoxide (CO):
A colorless, odorless, poisonous gas produced by incomplete fossil fuel combustion.

Chromium:
A heavy metal that is an important hazardous air pollutant. (See "heavy metals.")

Contaminant:
Any physical, chemical, biological, or radiological substance or matter in air, water, or soil that can have adverse health effects.

Criteria Pollutants:
The 1970 amendments to the Clean Air Act required EPA to set National Ambient Air Quality Standards for certain pollutants known to be hazardous to human health. EPA has set standards to protect human health and welfare for six pollutants: ozone, carbon monoxide, total suspended particulates, sulfur dioxide, lead, and nitrogen oxides. The term "criteria pollutants" derives from the requirement that EPA must describe the criteria-characteristics and potential health and welfare effects of these pollutants-for setting or revising standards.

Deciliter:
One-tenth of a liter (0.1 liter).

Exposure:
Human contact with environmental contaminants or concentrations of contaminants in media.

Media:
Specific environments-air, water, soil-that are the subject of regulatory concern and activities because of potential for human exposure.

Environmental Tobacco Smoke:
Mixture of smoke exhaled by a smoker and the smoke from the burning end of the smoker's cigarette, pipe, or cigar.

Germ Cell Tumor:
A type of tumor found in the ovaries or testicles.

Gonadal Tumor:
Tumor specific to the gonads.

Hazardous Air Pollutants:
Air pollutants that are not covered by ambient air quality standards but which, as defined in the Clean Air Act, may reasonably be expected to cause or contribute to irreversible illness or death. Such pollutants include asbestos, beryllium, mercury, benzene, coke oven emissions, radionuclides, and vinyl chloride. A total of 188 hazardous air pollutants are listed in section 112(b) of the Clean Air Act, as amended in 1990.

Heavy Metals:
Metallic elements with high atomic weights, e.g., mercury, chromium, cadmium, arsenic, and lead; can damage living things at low concentrations.

Immunodeficiency:
Inability to produce a normal complement of antibodies or immunologically sensitized T cells, especially in response to specific antigens.

Ionizing Radiation:
Radiation that can strip electrons from atoms, i.e., alpha, beta, and gamma radiation.

Lymphoma:
Lymphomas are tumors in the lymph system, which is responsible for fighting diseases in the body and is part of the immune system. Lymphomas are the third most common form of cancer in children.

Mercury:
A heavy metal that can bioaccumulate in the environment and is highly toxic if breathed or swallowed.

Methemoglobinemia:
The presence of excess methemoglobin in the blood, which replaces hemoglobin and results in loss of the ability to transport oxygen in the blood. A small amount of methemoglobin is present in the blood normally, but injury or toxic agents, such as nitrites, convert a larger proportion of hemoglobin into methemoglobin.

Microgram (µg):
One-millionth of a gram.

Microorganisms:
Tiny living organisms that can be seen only with the aid of a microscope. Some microorganisms can cause acute health problems when consumed in drinking water. Also known as microbes.

Mortality:
Death rate.

National Ambient Air Quality Standards (NAAQS):
Standards established by EPA to protect human health and the environment from criteria pollutants, which apply for outside air throughout the nation.

Nitrogen Dioxide (NO₂):
A chemical that results from nitric oxide combining with oxygen in the atmosphere; a major component of photochemical smog.

Ozone:
A gas that results from complex chemical reactions between nitrogen dioxide and volatile organic compounds; the major component of smog.

Particulate Matter:
Particles in the air, such as dust, dirt, soot, smoke, and liquid droplets; may have significant effects on human health.

Polychlorinated Biphenyls (PCBs):
A group of toxic, persistent chemicals used in electrical transformers and capacitors for insulating purposes, and in gas pipeline systems as a lubricant. The sale and new use of PCBs were banned by law in 1979.

Prenatal:
Occurring, existing, or performed before birth.

Radionuclides:
Radioactive isotopes or unstable forms of elements.

Retinoblastomas:
Tumors of the eye.

Sulfur Dioxide (SO2):
A pungent, colorless, gaseous pollutant formed primarily by the combustion of fossil fuels.

Superfund:
The program operated under the legislative authority of the Comprehensive Environmental Response, Compensation and Liability Act of 1980 (CERCLA) that funds and carries out EPA solid waste emergency and long-term removal and remedial activities. These activities include establishing the National Priorities List, investigating sites for inclusion on the list, determining their priority, and conducting and/or supervising cleanup and other remedial actions.

Trichloroethylene (TCE):
A stable, low boiling-point colorless liquid, toxic if inhaled. Used as a solvent or metal decreasing agent, and in other industrial applications.

Glossary

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