Air quality laws are often designed specifically to protect human health by limiting or eliminating airborne pollutant concentrations.
Regulatory efforts include identifying and categorising air pollutants, setting limits on acceptable emissions levels, and dictating necessary or appropriate mitigation technologies.
For example, the United States Clean Air Act identifies ozone, particulate matter, carbon monoxide, nitrogen oxides (NOx), sulfur dioxide (SO2), and lead (Pb) as "criteria" pollutants requiring nationwide regulation.
[5] Determining appropriate air quality standards generally requires up-to-date scientific data on the health effects of the pollutant under review, with specific information on exposure times and sensitive populations.
As an example, the United States Environmental Protection Agency has developed the National Ambient Air Quality Standards (NAAQS)[6] NAAQS set attainment thresholds for sulfur dioxide, particulate matter (PM10 and PM2.5), carbon monoxide, ozone, nitrogen oxides NOx, and lead (Pb) in outdoor air throughout the United States.
Numerous methods exist for determining appropriate emissions standards, and different regulatory approaches may be taken depending on the source, industry, and air pollutant under review.
[10] Flexibility alternatives are implemented in U.S. programs to eliminate acid rain, protect the ozone layer, achieve permitting standards, and reduce greenhouse gas emissions.
The selection of emissions control technology may be the subject of complex regulation that may balance multiple conflicting considerations and interests, including economic cost, availability, feasibility, and effectiveness.
[13] Residential and commercial burning of wood materials may be restricted during times of poor air quality, eliminating the immediate emission of particulate matter and requiring use of non-polluting heating methods.
Its manufacture was prohibited as part of a suite of restrictions adopted internationally in the Montreal Protocol to the Vienna Convention for the Protection of the Ozone Layer.
[14] Air quality laws may impose substantial requirements for collecting, storing, submitting, and providing access to technical data for various purposes, including regulatory enforcement, public health programs, and policy development.
Fossil power plants may required to monitor emissions at a flue-gas stack to determine quantities of relevant pollutants emitted.
Automobile manufacturers may be required to collect data regarding car sales, which, when combined with technical specifications regarding fuel consumption and efficiency, may be used to estimate total vehicle emissions.
Such requirements may be developed at a national level and reflect consensus or compromise between government agencies, regulated industry, and public interest groups.
For example, the United States Environmental Protection Agency, National Oceanic and Atmospheric Administration, National Park Service, and tribal, state, and local agencies coordinate to produce an online mapping and data access tool called AirNow, which provides real-time public access to U.S. air quality index information, searchable by location.
For example, atmospheric dispersion modeling may be employed to examine the potential impact of new regulatory requirements on existing populations or geographic areas.
For example, the "estimates that the benefits of reducing fine particle and ground level ozone pollution under the 1990 Clean Air Act amendments will reach approximately $2 trillion in 2020 while saving 230,000 people from early death in that year alone."
[26] Additionally, the government introduced the National Clean Air Programme (NCAP) in 2019, aiming to reduce particulate matter (PM) pollution by 20-30% in at least 102 cities by 2024.
[31] The biggest domestic impact comes from Part III, Smoke Control Areas, which are designated by local authorities and can vary by street in large towns.