APES UNIT 5

carcinogen

Chemicals, ionizing radiation, and viruses that cause or promote the development of cancer.

dose-response curve

Plot of data showing the effects of various doses of a toxic agent on a group of test organisms.

mutagen

Chemical or form of radiation that causes changes (mutations) in the DNA molecules in genes.

teratogen

Chemical, ionizing agent, or virus that causes birth defects.

LD50

lethal dose that kills 50% of population

nonpoint sources

broad and diffuse areas, rather than points, from which pollutants enter the bodies of surface water or air.

point sources

single identifiable source that discharges pollutants into the environment.

primary sewage treatment

large solids are filtered out by screens and suspended solids settle out as sludge in a sedimentation tank

secondary sewage treatment

aerobic bacteria decompose as much as 90% of degradable, oxygendemanding organic wastes in wastewater.

tertiary sewage treatment

removal of nitrates and phosphates

septic tank

a component of a small-scale underground sewage treatment system used for homes in rural and suburban areas that do not have connections to municipal sewer lines.

integrated waste management

variety of strategies for both waste reduction and waste management designed to deal with the waste we produce.

municipal solid waste (MSW)

solid materials discarded by homes and businesses in or near urban areas.

sanitary landfill

waste-disposal site on land in which waste is spread in thin layers, compacted, and covered with a fresh layer of clay or plastic foam each day.

primary recycling

Process in which materials are recycled into new products of the same type—turning used aluminum cans into new aluminum cans, for example.

secondary recycling

A process in which waste materials are converted into different products; for example, used tires can be shredded and turned into rubberized road surfacing.

acid deposition

the falling of acids and acid-forming compounds from the atmosphere to the earth’s surface.

industrial smog

Type of air pollution consisting mostly of a mixture of sulfur dioxide, suspended droplets of sulfuric acid formed from some of the sulfur dioxide, and suspended solid particles.

photochemical smog

Complex mixture of air pollutants produced in the lower atmosphere by the reaction of hydrocarbons and nitrogen oxides under the influence of sunlight.

primary pollutant

Chemical that has been added directly to the air by natural events or human activities and occurs in a harmful concentration

secondary pollutant

Harmful chemical formed in the atmosphere when a primary air pollutant reacts with normal air components or other air pollutants.

thermal inversion

layer of dense, cool air trapped under a layer of less dense, warm air. It prevents upward-flowing air currents from developing. In a prolonged inversion, air pollution in the trapped layers may build up to harmful levels.