Air quality law

Air quality laws govern the emission of air pollutants into the atmosphere. A specialized subset of air quality laws regulate the quality of air inside buildings. Air quality laws are often designed specifically to protect human health by limiting or eliminating airborne pollutant concentrations. Other initiatives are designed to address broader ecological problems, such as limitations on chemicals that affect the ozone layer, and emissions trading programs to address acid rain or climate change. Regulatory efforts include identifying and categorizing air pollutants, setting limits on acceptable emissions levels, and dictating necessary or appropriate mitigation technologies.

Air quality regulation must identify the substances and energies which qualify as "pollution" for purposes of further control. While specific labels vary from jurisdiction to jurisdiction, there is broad consensus among many governments regarding what constitutes air pollution. For example, the United States Clean Air Act identifies ozone, particulate matter, carbon monoxide, nitrogen oxides (NO_x), sulfur dioxide (SO₂), and lead (Pb) as "criteria" pollutants requiring nationwide regulation. EPA has also identified over 180 compounds it has classified as "hazardous" pollutants requiring strict control. Other compounds have been identified as air pollutants due to their adverse impact on the environment (e.g., CFCs as agents of ozone depletion), and on human health (e.g., asbestos in indoor air). A broader conception of air pollution may also incorporate noise, light, and radiation. The United States has recently seen controversy over whether carbon dioxide (CO₂) and other greenhouse gases should be classified as air pollutants.

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