Men who had been exposed to certain classes of pesticides had significantly lower sperm concentrations. The study, published Wednesday in Environmental Health Perspectives, included data from more than 1,700 men and spanned several decades.

“No matter how we looked at the analysis and results, we saw a persistent association between increasing levels of insecticide and decreases in sperm concentration,” said study author Melissa Perry, who is an environmental epidemiologist and the dean of the College of Public Health at George Mason University. “I would hope this study would get the attention of regulators seeking to make decisions to keep the public safe from inadvertent, unplanned impacts of insecticides.”

For decades, scientists have been trying to untangle puzzling questions over male fertility. Sperm concentrations are one of several factors that are a useful indicator. A report last year found that sperm counts were falling in every region of the globe and the pace of that decline was accelerating.

“There’s been some pretty, I’d say, convincing and sort of scary data on measures of male fertility over the previous 50-70 years, whatever it might be, from different places around the world suggesting sperm concentration is on decline and not just a little bit,” said John Meeker, a professor of environmental health sciences at the University of Michigan School of Public Health who was not involved in either of the recent studies. “It’s concerning.”

https://www.nbcnews.com/science/science-news/global-decline-sperm-concentrations-linked-common-pesticides-rcna125164