Know the Law: The Effects of Wildfire on Air Quality in New Hampshire

Photo of Viggo C. Fish
Viggo C. Fish
Counsel, Administrative Law Department
Published: Union Leader
September 14, 2021

Q: Smoke and haze from more widespread wildfires is affecting parts of the northeast.  Should I be worried about the effects of air quality on my health?

A: Wood smoke in general, and the enormous plumes of wildfire smoke in particular, contain numerous hazardous pollutants. Especially concerning are what are referred to as Particulate Matter (PM), one of six criteria air pollutants regulated by the Clean Air Act (CAA).  These small particles, that are described by their size, PM10 and PM2.5 (microns), can cause serious lung damage, among other harmful effects.  To put this in perspective, a particle size of 2.5 microns is roughly 30 times smaller than the width of the average human hair.

The United States Environmental Protection Agency (EPA) sets National Ambient Air Quality Standards (NAAQS) for PM (and the five other criteria pollutants to protect human health and the environment).  42 U.S.C. §7409(b).  The federal standards for PM2.5 are 35 microns per cubic meter (35 ug/m3) for a 24-hour period and an annual average concentration of 12 ug/m3.  New Hampshire is classified as “in attainment” for PM2.5, although bad days do occur.  When PM2.5 exceeds 35 ug/m3 the Department of Environmental Services (DES) will normally issue an advisory for affected regions.  DES issued one such advisory in July 2021 related to wildfire smoke.

Due to its extremely small particle size, PM2.5 can remain airborne for long periods of time and be transported over very long distances.  When present in the air and inhaled into the lungs PM2.5 can penetrate deep into the body.  Its small size also facilitates its penetration into lung tissue and the blood stream reaching other organs, potentially including the brain.  As a consequence, human exposure to PM2.5 can cause damage to the respiratory and cardiovascular systems and, possibly, cognitive functions.

Environmental regulation has resulted, generally, in a decline in PM concentrations; however, PM produced by large, regional, climate change-fueled wildfires, is transported in enormous plumes, reaching heights as high as 6 miles, over thousands of miles.  The result is visible in haze that has, at times, overspread the northeast.

The DES monitors and reports current and forecasted State air quality data on its website available at:  When levels of PM2.5 exceed, in varying degrees, the federal standard, State and federal environmental agencies recommend that people take steps to protect themselves.  During periods of higher PM2.5, those with underlying health conditions such as heart disease or asthma are well-advised to stay indoors, ideally in a space with filtered air.  If you must go outside, you should limit your exposure and curtail vigorous activity accordingly.

Know the Law is a bi-weekly column sponsored by McLane Middleton.  Questions and ideas for future columns should be emailed to  Know the Law provides general legal information, not legal advice.  We recommend that you consult a lawyer for guidance specific to your particular situation