City Receives Air Quality Monitoring Study Report from NH Department of Environmental Services

May 28, 2024

The City of Portsmouth has received a final report from the NH Department of Environmental Services (NHDES) on the air quality monitoring results from the devices placed in locations surrounding the Foundry Place Garage and at New Franklin School. The air quality study was authorized by NHDES in consultation with U.S. Environmental Protection Agency (EPA) Region 1, and the Office of U.S. Representative Chris Pappas. The study was conducted in response to City concerns arising from complaints by residents about air quality from the locomotive emissions at the railyard and highway emissions from I-95 and Route 1 at the school. 

Four monitors collected several months of data for analysis by NHDES and measured particulate matter concentrations in the air, commonly referred to as PM2.5. NHDES reported that while the “overall concentrations of PM2.5 measured throughout the study were in the Good range…short variations did occur.” This range is based on the National Ambient Air Quality Standards (NAAQS) set by the EPA under the Clean Air Act.

“The study found potential train exhaust signals in the PM2.5 concentration data when comparing the two monitors located on opposite sides of the railyard…While locomotives were seen idling at different locations in the railyard during the duration of the study, records were not available to allow NHDES to draw a conclusive determination that train exhaust was the primary emission source for each signal discovered. Measurements taken at the New Franklin School did not show the same types of concentration spike events…PM2.5 concentration increases at the school approximated traffic increases on I-95.”

NHDES concluded that “even though the measured PM2.5 concentrations did not exceed the federal health standards (NAAQS), odors can be present at significantly lower concentrations. Diesel exhaust has a strong distinct metallic odor that can be especially irritating, particularly in areas such as residential neighborhoods and playgrounds.” 

Both an Executive Summary and the Final Report are available on the City’s website:

Air quality monitoring devices supplied the data for the NHDES report.