The average sperm count in healthy men worldwide has dropped by half in the last 50 years, according to a Danish review of 61 studies including 14,947 men.

Experts say the study, directed by Dr. Niels E. Skakkebaek of the University of Copenhagen, lends credence to speculation that environmental pollutants may damage production of sperm cells.

Conflicting results have emerged from previous studies. Skakkebaek, whose findings are published in the Sept. 12 issue of the British Medical Journal, said his review was the first to collect worldwide statistics and limit the analysis to healthy men.

“I think there is cause for concern,” said Dr. Richard Sharpe, a respected reproductive biologist at the University of Edinburgh. “If there is something in our environment having an effect that is drastic enough to decrease sperm count by 50%, we should know what this factor is.”


Dr. Sherman Silber, an infertility specialist at St. Luke’s Hospital in St. Louis, cautioned against jumping to conclusions. He said he has not found a decline in average sperm count among patients at his clinic in the last 20 years.