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As if you needed another reason to care about air pollution, new research finds that the tiny particles in city smog don’t just damage your heart and lungs, they also may increase risk of kidney disease and even contribute to kidney failure.

Breathing in dirty air may leave you with more than just a bad cough. The study, published Thursday in the Journal of the American Society of Nephrology, found a linear relationship between air pollution levels and risk of decreased kidney function. This, in turn, increased risk of kidney disease or kidney failure. All in all, the findings paint a grim image of how living in polluted areas can affect all aspects of human health.

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For their research, scientists from both the Washington University School of Medicine and the Veterans Affairs’ Clinical Epidemiology Center in St. Louis looked at the Department of Veterans Affairs database to compare rates of kidney disease among individuals living in different U.S. regions with various air pollution qualities based on readings from the Environmental Protection Agency (EPA).

The data included information on about 5 million people over the course of eight years. The team also looked at air pollution information from NASA satellites in order to more accurately identify pollution levels.  

Results showed 44,793 new cases of kidney disease during that time and 2,438 new cases of kidney failure in areas with the highest levels of air pollution—which were still considered safe for the public based on EPA regulations.

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“What was really striking was that NASA data gave us identical results, which was a very intense and important signal that there is a relationship between exposure to CKD [air pollution] and kidney health,” lead researcher Dr. Ziyad Al-Aly, director of clinical epidemiology at the VA Saint Louis Health Care System, tells Newsweek.

While it’s no surprise that breathing dirty air can harm the lungs, its effects on the kidneys are a bit less clear. Al-Aly explained that tiny particles in air pollution can pass through our lungs and enter our bloodstream. Here, they travel until they finally reach our kidneys. Our body's main filters, kidneys sift these particles out of the blood, but too much exposure to these harmful pollutants can take its toll. Al-Aly suggests his findings show there really is no “safe” level for air pollution, as even the lowest levels can do harm.

Dr. Edward Avol, a professor in the department of Clinical Preventative Medicine who specializes in air pollution exposure at the University of Southern California, who was not involved in this study, tells Newsweek he agrees that it’s difficult to set a safe level of air pollution exposure.

“...If we do additional research we are finding indications that this line is not low enough,” says Avol.” We need to set standards for safety, but health data is increasingly showing that there is no line to safely be behind.”

What’s also notable about this research is that is has finally revealed a possible explanation for chronic kidney disease of unknown origin. Doctors are aware that certain factors such as diabetes and hypertension can contribute to kidney disease, but they are increasingly seeing this health problem in individuals without any pre-existing risk factors. Al-Aly believes his new research may have finally identified at least one possible cause for inexplicable kidney problems.

“If you map the world and map what are the kidney disease hotspots, they significantly overlap with areas of high pollution,” said Al-Aly.

The research adds to the conversation on the tangible effects of pollution, and how simply ignoring the problem can have deadly consequen