Ozone Lowers Sperm Counts April 24, 2002 -- Men who live in air-polluted cities with high levels of ozone may have a harder time becoming a father. A new study shows that high levels of ozone in the lower atmosphere, which is created by the release of pollutants into the air, may be linked to lower sperm counts and decreased sperm motility in otherwise healthy men.

Researchers compared 8,000 sperm samples donated by 50 men in the Los Angeles area with more than 5,500 samples collected from 35 men who lived in Northern California between 1996 and 1998. They found that higher the ozone levels were 10 days prior to the collection of the sperm sample, the worse the quality of the sperm was.

"There was a significant correlation between decreases in sperm count and motility and increased ozone levels in the air, especially in Southern California," says study author Rebecca Z. Sokol, MD, professor at the Keck School of Medicine at the University of Southern California, in a news release.

Sokol presented the study this month at the annual meeting of the Pacific Coast Reproductive Society.

Researchers say they aren't exactly sure how the ozone may affect sperm quality. The body has a built-in system to protect sperm from toxins in the bloodstream.

Sokol suggests that inhaling ozone might trigger another physiological reaction in the body that then somehow affects the sperm.