Air Quality Glossary

Definitions for terms used within Environmental Perspectives focused on air quality
airshed - a geographical area within which air is confined or channeled and where all parts of the area may be subjected to similar conditions of air pollution
air toxics - hazardous air pollutants which are known to cause cancer and other serious health impacts, such as reproductive effects or birth defects, or adverse environmental and ecological effects
black carbon - the most strongly light-absorbing component of particulate matter; formed by the incomplete combustion of fossil fuels, biofuels, biomass
carbon dioxide - (CO2) gas which is naturally present in the atmosphere as part of Earth's carbon cycle; primary greenhouse gas emitted through human activities, such as fossil fuel combustion
carbon monoxide - (CO) a colorless, odorless gas that can be harmful when inhaled in large amounts; may be created by vehicles or machinery that burn fossil fuels
carbon sink - a natural or artificial system that captures and hold carbon dioxide from the atmosphere
criteria pollutant - the six common air pollutants that the Clean Air Act requires the EPA to set National Ambient Air Quality Standards (NAAQS) for: ground level ozone, particulate matter, carbon monoxide, lead, sulfur dioxide, nitrogen dioxide
design value - a statistic that describes the air quality status of a given location relative to the level of the National Ambient Air Quality Standards (NAAQS)
emissions permit - permit that outlines air pollution control requirements and documents how pollution sources demonstrate compliance with emission limits and work practices; determines how sources will monitor for compliance
fossil fuel - combustible geologic deposits of organic materials; include oil, coal, natural gas, petroleum
ground level ozone - (O3) main ingredient in "smog" created by chemical reactions between nitrogen oxides and volatile organic compounds in the presence of sunlight; may come from reactions of pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants, etc.
lead - (Pb) a naturally-occurring element found in the earth's crust; can be toxic to humans and animals; most exposure to lead is from human activities including the use of fossil fuels, industrial facilities, and past use of lead paint in homes
nitrogen dioxide - (NO2) a group of highly reactive gases caused primarily by the burning of fuel from vehicles, power plants, and off-road equipment; component of acid rain; contributes to haze; contributes to nutrient pollution in water
nutrient pollution - too much nitrogen and phosphorus in the water causes significant increases in algal growth, which harms the water quality and food resources and habitats and decreases the oxygen that fish and other aquatic life need to survive
particulate matter - a mixture of solid particles and liquid droplets found in the air; measured as PM10: particles with diameters of 10 micrometers and smaller, or PM2.5: fine particles with diameters of 2.5 micrometers and smaller; may contribute to health effects when inhaled
point source - a single identifiable source of pollution, i.e. pipe, ditch, smokestack
sulfur dioxide - (SO2) a group of gases caused largely by fossil fuel combustion at power plants and other industrial facilities; may be caused naturally by volcanic eruptions
volatile organic compound - gases emitted from certain solids or liquids; include a variety of chemicals made up of organic compounds from paints, wood preservatives, aerosols, cleaners, fuels, pesticides, etc.

Page reviewed 4/3/19