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After a decade of improvements in air pollution, the U.S. is backsliding. And that means more people are dying prematurely, according to new research. The paper authors don’t point to a specific reason why the increase happened, but the numbers are clear that it occurred under the presidency of Donald Trump.


A team of economists at Carnegie Mellon University published their working paper Monday with the National Bureau of Economic Research. The paper is not peer-reviewed, but the authors wanted to get it out quickly because the results were so striking. Between 2009 and 2016, the annual average of air pollution from fine particulate matter decreased by more than 24 percent. From 2016 to 2018, however, the rate increased by more than 5 percent and the rise resulted in Americans dying.


While regions throughout the country saw rises in air pollution, the biggest uptick was in California. There, this air pollution increased by 12.5 percent. The authors speculate it could be due to the giant wildfires the state’s seen in recent years.

“We had expected that things would be getting worse—and that they would perhaps be getting worse in lots of places,” co-author Karen Clay, an economics professor at Carnegie Mellon, told Earther. “I think the fact that California accounts for such a large chunk was a little bit of a surprise for us.”

Regardless of whether it’s from wildfires or other sources, increasing air pollution poses a direct threat to public health. Studies have linked air pollution to degenerative eye disease, heart attacks, and premature death. Research has also found that it can reach the placenta and the brain. What this paper took a look at, though, was premature death—and it found that the recent increase in particulate matter could be responsible for an additional 9,700 premature deaths with nearly 43 percent taking place in California. Eighty percent of these deaths hit the elderly. Some might lose days or weeks of life, but the research shows that many others are losing years due to polluted air.

To reach these conclusions, the researchers analyzed more than 1.8 million daily readings from the Air Quality System the Environmental Protection Agency manages. They broke down the data so that they were able to see the specific types of particulate matter the monitors captured, which includes ammonium nitrate, sulfate, and elemental carbon. These different particles largely originate from specific sources of combustion, which allowed the authors to hypothesize what might be driving this recent increase in air pollution.


It’s hard to know for sure without a specific analysis, but an increase in wildfires, vehicle miles traveled, and natural gas use, coupled with decreases in Clean Air Act enforcement could all be playing a role. The authors are hoping that this study could help set up future research to take a closer look at the cause of the increase. The authors weren’t able to attribute any percentage of deaths to specific sources of pollution, but they were able to pinpoint what type of particulate matter increased during this period, which led them to believe these factors are driving the increase.

The uptick has taken place under the Trump administration, and that may not be a coincidence. The president has voiced support for polluting industries and appointed industry-friendly regulators at various agencies. That includes the Environmental Protection Agency (EPA), which enforces many air quality regulations and regulates polluting industries. While the EPA has been reducing its enforcement actions since 2013, the trend has continued since 2016. But under Trump, even the limited enforcement that is happening has been much more lax with polluters paying smaller fines.


The administration has also pursued deregulatory actions that would likely increase air pollution and impact public health. And while many have yet to be implemented, they’re another signal to polluters that they can get away with behavior that’s dangerous to public health.

“Since 2017, the agency, through a variety of actions, has signaled it is going to take a more relaxed approach,” Joe Goffman, former associate administrator for Climate and Senior Counsel at the EPA’s Office of Air and Radiation who now helps run Harvard Law School’s Environmental Law Program, told Earther. “This administration has sent enough signals to sources that they are operating under a more lenient regime that could corroborate the data that is the focus of this report.”


Environmental regulations have driven improvements to the U.S. air quality and reduced the number of deaths as a result. It wasn’t that long ago that Los Angeles suffered from smog-filled skies that made headlines. Report author Clay worries this increase might signal a new pattern if we don’t act quickly: Could air pollution continue to increase?

“It’s not just that people are dying,” she said. “People are probably having more asthma attacks and other kinds of events that are cardiovascular or pulmonary in origin, so we’re concerned about that. But I think our primary concern is that if we just don’t pay any attention to this [increase in air pollution], it could continue to rise.”