The government scientists have been using faulty estimates of the amount of fuel used by diesel trains, therefore understating the amount of nitrogen oxide and soot that's emitted by locomotives, The Washington Post reported Monday.
The Environmental Protection Agency is writing new emission standards for trains and ships to reduce nitrogen oxide and particulate pollution by up to 90 percent.
"More than 150 million Americans live in areas that violate public health standards for one or both of these pollutants, and a lot of them live near major rail lines," Frank O'Donnell of the advocacy group Clean Air Watch told The Post. "Millions will probably continue to breathe dirty air in the future unless we reduce public exposure to train pollution."
Although trucks emit more than three times as much soot and more than twice the amount of nitrogen oxide as trains, observers say that will change as stricter motor vehicle standards become effective, the newspaper said. By 2030, trains are expected to emit nearly twice as much soot as trucks unless new rules are issued.
2014: The Year in Fashion [PHOTOS]
MAVEN now orbiting Mars