Tires and degrading garbage shed tiny pieces of plastic into the air, creating a form of air pollution that UC San Francisco researchers suspect may be causing respiratory and other illnesses.

A review of some 3,000 studies implicates these particles in a variety of serious health problems. These include male and female infertility, colon cancer and poor lung function. The particles also may contribute to chronic pulmonary inflammation, which can increase the risk of lung cancer.

“These microplastics are basically particulate matter air pollution, and we know this type of air pollution is harmful,” said Tracey J. Woodruff, Ph.D., MPH, a professor of obstetrics, gynecology and reproductive sciences at UCSF.