Air pollution is sending 200,000 Americans to an early grave every year, according to new research from the Massachusetts Institute of Technology.

“In the past five to 10 years, the evidence linking air-pollution exposure to risk of early death has really solidified and gained scientific and political traction,” co-author Steven Barrett, an assistant professor of aeronautics and astronautics at MIT, said in a statement. “There’s a realization that air pollution is a major problem in any city, and there’s a desire to do something about it.”

Barrett and his colleagues looked at ground-level emissions from a variety of sources, including car and truck tailpipes, factory smokestacks, and commercial and residential heating systems. They gathered data on air emissions in 2005 from the U.S. Environmental Protection Agency’s National Emissions Inventory, and plugged it into an air-quality simulation. Then, they laid this simulated air quality for each kind of air pollution over population density maps of the U.S.

In their paper, published in the journal Atmospheric Environment, the team says they found that California has the deadliest air pollution – 21,000 early deaths a year – while Baltimore, Md., has the worst air pollution mortality rate of any U.S. city. Due to air pollution, 130 out of every 100,000 Baltimoreans will expire about a decade earlier than they might have in a place with cleaner air, the researchers say.

Most emissions-related premature deaths stemmed from car and truck exhaust, the researchers say. Those tailpipes on the road belch enough pollution to account for 53,000 early deaths every year, they claim.

“It was surprising to me just how significant road transportation was,” Barrett said, “especially when you imagine [that] coal-fired power stations are burning relatively dirty fuel.”

The emissions generated by electrical power plants ran in at a close second, the MIT team said, causing 52,000 premature deaths every year. These sorts of early deaths occur more on the central East Coast and U.S., where power plants use coal with higher sulfur content, the researchers said.

Though the underlying data is from 2005, the researchers say the trends they found likely hold true for recent years.

“The results are indicative of the extent to which policy measures could be undertaken in order to mitigate the impact of specific emissions from different sectors — in particular black carbon emissions from road transportation and sulfur dioxide emissions from power generation,” the authors wrote.

SOURCE: Caiazzo et al. “Air pollution and early deaths in the United States. Part I: Quantifying the impact of major sectors in 2005.” Atmospheric Environment 79: 198-208, November 2013.