Ground-level Ozone (Smog) Information

Ground-level ozone presents a serious air quality problem in New England. In 2008, EPA revised the ozone standard to a level of 0.075 parts per million, 8-hour average. Over the last 5 years (2011 through 2015), there have been an average of 19 days per summer when New England's air exceeded this standard.

On October 1, 2015, EPA strengthened the 8-hour ozone NAAQS to 0.070 ppm based on extensive scientific evidence about the effects of ozone on public health and welfare.

Ground-level ozone is formed by a chemical reaction between VOCs and oxides of nitrogen (NOx) in the presence of sunlight. Ozone concentrations can reach unhealthful levels when the weather is hot and sunny with little or no wind. View ozone concentrations and corresponding weather conditions for a day in 1998 when high ozone concentrations were measured across Southern New England. In New England, high ozone levels usually occur between 1:00 and 7:00 pm from May through September.

Visit EPA-New England's Air Quality Index page to get real-time and forecasted air pollution data in an understandable visual format. This information is provided so the public can take action to protect their health, and reduce pollution.