Locals and children play on the surf at high tide on Redcar Beach in the shadow of Corus Steelworks in Middlesborough, England, Jul. 21, 2008. Getty

Air pollution, a severe problem worldwide, has long been known to cause health problems, be it heart disease, lung cancer or other respiratory ailments. But new evidence has shown that the effects of pollution might extend to the brain: namely, in the form of Alzheimer’s disease. A study published Tuesday in the journal Translational Psychiatry found that exposure to certain pollutants could increase risk for dementia, including Alzheimer’s disease.

Researchers at the University of Southern California analyzed the health of 3,647 women aged 65 to 79 across the country and found that those who lived in areas where fine particle air pollution exceeded governmental health standards were almost twice as likely to develop dementia, including Alzheimer’s disease. Women who were genetically predisposed to getting the disease had a 263 percent increased risk. Should the same findings apply to the overall population, it could mean an estimated 21 percent of Alzheimer's cases were caused by air pollution.

“Although the link between air pollution and Alzheimer’s disease is a new scientific frontier, we now have evidence that air pollution, like tobacco, is dangerous to the aging brain,” said Caleb Finch, a professor at the USC Leonard Davis School of Gerontology and co-senior author of the study.

As of 2014, an estimated 92 percent of the world’s population lived in places where the air did not meet the World Health Organization’s guidelines for quality. Ultrafine and fine particles in the air are caused by wood-burning and industrial combustion as well as emissions from cars and planes. The smallest parties are the most deadly, as they are not filtered out by the body’s natural defenses and become lodged in the bloodstream and lungs.

“Microscopic particles generated by fossil fuels get into our body directly through the nose into the brain,” said Finch. “Cells in the brain treat these particles as invaders and react with inflammatory responses, which over the course of time, appear to exacerbate and promote Alzheimer’s disease.”

Even without including data from the proposed link between pollutants and Alzheimer’s, air pollution around the world was estimated to cause three million premature deaths in 2012.

Pollution covers Beijing, China, Feb. 25, 2014. Getty