The Clean Air Act identifies six common air pollutants that are found all over the United States and can injure health, harm the environment or cause property damage. These pollutants include:
The United States Environmental Protection Agency (EPA) has established National Ambient Air Quality Standards (NAAQS) for each of these pollutants. If the air quality in a geographic area meets the NAAQS, it is called an attainment area; areas that do not meet the NAAQS are called nonattainment areas and must develop comprehensive state plans to reduce pollutant concentrations to a safe level.
Knox County Air Quality Status
Air monitoring stations collect representative data that indicates how much of a pollutant is in the air. Currently, 7 air-monitoring stations are strategically located across Knox County collecting data on four criteria pollutants.
Surface ozone vs. the ozone layer
Although the ozone found at the Earth's surface is the same chemical species as that found in the ozone layer, they have very different sources, atmospheric chemistry, and affect human health differently as well. The ozone layer protects people from the sun's most damaging ultraviolet rays. Because the ozone layer is located high in the atmosphere, people are not directly exposed to it.
Ground-level ozone, however, is a health hazard because people breathe it. It is formed through a complex set of chemical reactions involving hydrocarbons, nitrogen oxides and sunlight on calm summer days where the weather may also be warm and humid. High levels of ground ozone affects the breathing process and aggravates asthma in chronic sufferers. The young, elderly, and those with lung diseases are especially susceptible.
Ozone is most likely to exceed safety limits from May through October when seasonal heat and sunlight are at their highest.