PM2.5 levels in subways sometimes exceed health guidelines
In a new study, NIEHS-funded researchers found that subway transit workers and commuters may be at increased risk for health problems due to exposure to high levels of air pollutants in subway stations.
The team monitored 71 subway stations across 12 transit lines in Philadelphia, Boston, New York City, New Jersey, and Washington, D.C. during morning and evening rush hours. They measured real-time concentrations of fine particulate matter (PM2.5) at stations — both aboveground and underground — and on trains. X-ray fluorescence spectroscopy was used to evaluate composition of the particulates.
Reported PM2.5 concentrations varied but were very high at some locations. In general, PM2.5 levels were lowest in aboveground stations, followed by inside trains, and were highest in underground stations. Morning rush hour levels tended to be higher than evening rush hour levels across cities. Levels measured in subway stations during rush hours were 2-7 times higher than health standards. Stations serviced by the New York City/New Jersey system had the highest PM2.5 concentrations ever reported for a subway system. Iron and total carbon accounted for approximately 80% of the PM2.5 mass, although composition varied by station and city.
According to the authors, the elevated PM2.5 concentrations measured across Northeastern subway systems during rush hours suggest commuters or transit workers may be at increased risk for death due to cardiovascular health problems.
Citation: Luglio DG, Katsigeorgis M, Hess J, Kim R, Adragna J, Raja A, Gordon C, Fine J, Thurston G, Gordon T, Vilcassim MJR. 2021. PM2.5 concentration and composition in subway systems in the northeastern United States. Environ Health Perspect 129(2):27001.