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, read State of New Hampshire Air Quality – 2017: Air Pollution Trends, Effects and Regulation. Report highlights and main points are provided in State of New Hampshire Air Quality – 2017: Executive Edition. Additional background can be found in the 2004 report: Air Pollution Transport and How It Affects New Hampshire.