But could it affect your ability to have children in the first place?

Maybe, according to preliminary research by a Utah infertility doctor.

Ahmad Hammoud, a fellow at the University of Utah's division of reproductive endocrinology and infertility, recently analyzed Salt Lake City air quality data and linked it to sperm quality data collected at the U.'s infertility clinic.

His preliminary results showed that as fine-particle pollution increased - the peaks are in December, January and February - the ability of sperm to wriggle and swim slightly dropped a month or two later. The delay is because it takes sperm between two to three months to mature.

Hammoud said the decline in motility is so low that it wouldn't be expected to affect fertility. And the correlation between air pollution and poor sperm quality was "not very strong." But the results were intriguing enough to warrant further study, he said.

"Air pollution is one factor among others. We need to figure out this relationship," he said Wednesday.

The findings intrigue Cherise Udell, founder of Utah Moms for Clean Air, which has been focused on how air quality affects children.

"That's a new take on the air pollution story that I had not heard before. It's more fuel for the fire," she said. "The more we learn about air pollution, the more we find it has ramifications throughout all stages of life."

Other recent studies have linked fine-particle pollution exposures during pregnancy to premature births in California and low birth weight in Connecticut and Massachusetts. Evidence linking air pollution to reduced sperm quality has been mixed.

But Hammoud said there is some evidence chemicals that mimic estrogen are found in air pollution and affect sperm.

"It's a new issue for me," said Bryce Bird, who works in the state Division of Air Quality. He was cautious in drawing a connection, noting other factors could be causing the change in sperm.

"When we have high [particulate matter pollution], that's also when we have the lowest temperatures in the valley," he said.

Hammoud looked at the monthly averages of fine-particle pollution called PM2.5 from 2002 to 2007. PM2.5 is microscopic dust and soot particles released by fuel combustion from automobiles, power plants, wood burning, industrial processes and diesel-powered vehicles.

Eventually, Hammoud would like to determine what in the particulate matter could be causing the drop in sperm motility. And he'd like to analyze the effects of carbon monoxide and ozone levels on sperm, too.

He was quick to point out potential flaws in the analysis: Men with low sperm count may have been overrepresented in his analysis. Sperm production may be seasonal, which could be the reason for the drop instead of pollution.

Still, his data was reviewed by the American Society for Reproductive Medicine and will be highlighted at its November meeting in California.

hmay@sltrib.com