Overview
Air pollutants are any gas or particle found in concentrations in excess of natural levels. While some are relatively benign, others may be found in concentrations high enough to cause significant health or environmental impacts.

The air pollutants of greatest concern are typically broken into three categories: criteria pollutants, toxic air pollutants, and greenhouse gases. For information about each type of pollutant, please click on the buttons at the top of the page.

For help identifying pollutants by their source, please read What’s in that Smoke?

For a comprehensive look at air pollution in New Hampshire, also read Air Pollution Transport and How It Affects New Hampshire.