By Jason Daley

There's little question that air pollution is toxic for the human body. Studies have shown that particulate matter in the air can lead to lung disease, heart disease, strokes, and lung cancer. But researchers thought the brain might be protected due to the blood brain barrier—a natural system that filters out foreign substances and certain neurotransmitters before they circulate in the brain. A new study from researchers at Cedars-Sinai Medical Center in Los Angeles shows that many heavy metals found in the air may make it into brain tissue, and those pollutants are activating genes that may lead to cancers or neurodegenerative disorders.