Science is essential as the U.S. Environmental Protection Agency carries out its mission to protect human health and the ...

This measure, based on data from the Environmental Protection Agency, evaluates states on the number of days the Air Quality Index in counties was not rated “good.” U.S. News calculated a ...

The EPA measures regional air quality index (AQI) by how hazardous it is to the general public. Discover the AQI in your city by searching below.

Advertisement Article continues below this ad In fact, laws passed by Congress require the EPA to use the “best available ... standards and health-based air quality standards.