Advertisement Upgrade to remove ads

air pollution

the introduction of chemicals, particulate matter, or microorganisms into the atmosphere at concentrations high enough to harm plants, animals, and materials such as buildings, or to alter ecosystems

particulate matter

solid or liquid particles suspended in air; also known as particles and particulates

photochemical oxidant

a class of air pollutants formed as a result of sunlight acting on compounds such as nitrogen oxides


mixture of oxidants and particulate matter (combination of smoke and fog)

photochemical smog

smog dominated by oxidants such as ozone

sick building syndrome

a buildup of toxic compounds and pollutants in an airtight space; seen in newer buildings with good insulation and tight seals against air leaks

Volatile Organic Compound (VOC)

an organic compound that evaporates at typical atmospheric temperatures

primary pollutants

a polluting compound that comes directly out of the smokestack, exhaust pipe, or natural emission source

Los Angeles-type smog (brown smog)

type of photochemical smog which is dominated by sulfuric oxides (also called sulfurous smog)

sulfurous smog

smog dominated by sulfur dioxide and sulfate compounds (also called Los Angeles-type smog)

London-type smog (grey smog)

type of photochemical smog which is dominated by particulate matter

secondary pollutants

a primary pollutant that has undergone transformation in the presence of sunlight, water, oxygen, or other compounds

thermal inversion

a situation in which a relatively warm layer of air at mid-altitude covers a layer of cold, dense air below

inversion layer

the layer of warm air that traps emissions in a thermal inversion

chlorofluorocarbon (CFC)

a family of organic compounds whose properties make them ideal for use in refrigeration and air-conditioning


a long, thin, fibrous silicate mineral with insulating properties, which can cause cancer when inhaled

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!



Reload the page to try again!


Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom


Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording