High Ozone Levels Hurt Sperm Count, Study Finds
Fri Apr 19, 5:57 PM ETBy Kathleen Doheny
RANCHO MIRAGE, California (Reuters Health) - Ozone can adversely affect a man's sperm, reducing their numbers as well as their crucial ability to move or "swim," according to new research that evaluated more than 14,000 sperm samples.
"Our most significant finding was that as the ozone level went up, the sperm concentration went down," said Dr. Rebecca Z. Sokol, a professor of medicine and obstetrics and gynecology at the University of Southern California's Keck School of Medicine. Sokol presented her findings here Friday at a meeting of the Pacific Coast Reproductive Society.
Sokol's team evaluated 8,513 samples from 50 sperm donors in the Los Angeles area over a 3-year period from 1996 to 1999 and compared them with 5,574 samples donated by 35 men from Northern California during the same time period. The donors' average age was about 25, and most were college students. The researchers also analyzed data on air quality in both regions.
The greater the increase in ground level ozone--popularly known as smog--the greater the drop in sperm counts, the investigators found.
Ozone occurs in two layers in the atmosphere--at ground level, where it is an air pollutant that can damage human health, and far up in the stratosphere, where it helps shield the Earth from harmful ultraviolet radiation.
In these very fertile young men, the drop didn't make much of a difference. Their average counts were 90 million sperm per cubic centimeter, Sokol noted. But in less fertile men, it could matter more. A sperm count of less than 20 million is considered low and less than 10 million is considered worrisome by fertility experts if a man is trying to impregnate a partner.
Sokol believes her team's study is the first US investigation to examine the relationship between air quality and sperm quality. "I don't think this study suggests in any way, shape or form that being exposed to ozone makes you infertile," Sokol told Reuters Health. "It just suggests that exposure to air pollution is not good for sperm."
It's not the ozone, per se, that is causing the damage, Sokol added. Ozone, once inhaled, is rapidly metabolized. Ozone may trigger an inflammatory reaction, she speculates, which in turn adversely affects the sperm.
"The data is far too preliminary to make any far-reaching conclusions," according to Dr. Larry Lipshultz, a professor of urology and chief of the division of male reproductive medicine and surgery at Baylor College of Medicine in Houston. More study is needed, he said. "It's important to look at an environment with low ozone to see if there's no effect (on sperm)," he added.
Next, Sokol plans next to conduct a multicenter study evaluating sperm specimens from donors in other polluted metropolitan areas as well as areas with less pollution.
