The Clean Air Act (CAA) requires the US EPA to set primary and secondary National Ambient Air Quality Standards (NAAQS) for six “criteria” pollutants considered harmful to public health and the environment: carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter (PM), and sulfur dioxide. The EPA is required to review air quality standards every five years to ensure the standards are “requisite to protect public health with an adequate margin of safety” and “requisite to protect the public welfare.”

When areas are found to be out of compliance with NAAQS, they are designated as nonattainment. Nonattainment states are required to submit state implementation plans (SIPs) outlining the steps that will be taken to bring nonattainment areas into compliance.

As changes are made to NAAQS limits, EPA must also revisit the limits imposed by CSAPR to ensure that up-wind states do not impede the ability of down-wind states to comply.

AECOM Process Technologies offers several services and products that help ensure compliance with the ever-more-stringent National Ambient Air Quality Standards.