New research has revealed that New York City subway riders who are financially challenged or part of racial minority groups face the greatest levels of exposure to fine particulate matter during their travels.
A recent study, released on August 7, 2024, in the open-access journal PLOS ONE, conducted by Shams Azad from New York University, USA, highlights that shoppers commuting by subway who are either economically disadvantaged or belong to racial minority groups encounter the highest levels of fine particulate matter during their trips.
Fine particulate matter (PM2.5) is a form of air pollution that is small enough to enter the bloodstream when inhaled, leading to various short-term and long-term health issues. Over the last several decades, urban areas have encouraged the use of public transit to minimize traffic and enhance outdoor air quality. While subway systems help cut down on road traffic, the air quality within subways is often very poor.
The study combined data from 3.1 million commuters across the four boroughs of New York City (Manhattan, Brooklyn, Queens, and the Bronx) regarding their home-to-work travel patterns alongside measurements of PM2.5 levels found on subway platforms and trains.
On average, the concentration of PM2.5 on subway platforms was recorded at 139 ± 25 μg/m3, while it was 99 ± 21 μg/m3 on the trains. These figures are considerably above the 15 μg/m3 average 24-hour exposure limit set by the World Health Organization. However, the authors point out that a subway ride is typically shorter than a full day, making these figures a starting point for understanding commuter exposure but only a part of an individual’s overall exposure throughout the day.
The team assessed the differences in exposure levels among racial and income groups by utilizing census data to examine where different demographic groups live and their corresponding commute times, which reflects their exposure. They discovered that individuals from low-income communities generally experienced higher levels of exposure, with Black and Hispanic workers facing 35% and 23% greater PM2.5 exposure, respectively, compared to their Asian and white counterparts. This increased exposure might be due to longer subway commutes for these groups, as they often have fewer job options closer to home. However, it’s important to note that this analysis provides general insights based on population averages at the census block level rather than specific individual exposures.
The authors clarify that their study only considers exposure from subway rides and does not account for other travel types beyond home-to-work commutes. They plan to analyze the exposure levels for all subway users in the future, not just those commuting. Nonetheless, their findings suggest that socioeconomic factors significantly influence individuals’ transportation choices, which in turn likely affects their exposure to PM2.5 from subway travel.
According to the researchers, “The levels of fine particulate matter detected in the NYC subway system are significantly above the guidelines established by the Environmental Protection Agency and the World Health Organization. The main contributors to these fine particles are wear and tear from the metal wheels, brakes, and tracks of the trains. This data was utilized to assess the exposure levels of over 3 million New Yorkers during their commuting trips.”
