A prolonged decreased male fertility in the form of sperm concentrations appears to be related to pesticide use, according to a study published Wednesday.
Researchers compiled, scored and reviewed the results of 25 studies on certain pesticides and male fertility and found that 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 the results, we saw a persistent association between increasing levels of insecticide and decreasing sperm concentration,” said study author Melissa Perry, an environmental epidemiologist and dean of the School of Public Health at George Mason University. “I hope this study draws the attention of regulators looking to make decisions to keep the public safe from the unintended and unplanned impacts of insecticides.”
For decades, scientists have been trying to unravel perplexing questions about male fertility. Sperm concentrations are one of several factors that are a useful indicator. A report last year found that sperm counts were declining in all regions of the world. and the pace of that decline was accelerating.
“There has been some nice, I would say, compelling and somewhat scary data on measures of male fertility over the last 50 to 70 years, whatever they are, from different places around the world, suggesting that sperm concentration is declining. 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 any of the recent studies. “It’s concerning.”
Scientists have long suspected that changes in the environment could be contributing, and have been investigating the role of pesticides for decades in animal studies and human epidemiology research.
The new analysis focuses on two groups of chemicals (organophosphates and some carbamates) that are commonly used in insecticides. The researchers looked at data collected from groups of people exposed to pesticides and others who were not. Most, but not all, of the research focused on workplace exposure. The researchers controlled for external factors that could contribute to lower sperm counts, such as smoking and age.
“It was very well done, very carefully done and very complete,” Meeker said.
Perry said researchers are not sure how pesticides affect sperm concentrations and that more research will be needed.
Pesticides are likely one of many environmental factors that could be contributing to a decrease in sperm concentrations.
“The more you study something, the more complicated it seems to become, especially when it comes to biology and the human body,” Meeker said. “We’re slowly pointing out various chemicals or classes of chemicals that we think could be harmful to something like reproductive health, but as far as a single smoking gun, I haven’t seen anything to that extent.”
The trend of decreasing sperm concentration has been widely observed in studies around the world, but it is a complicated topic and some scientists still have reservations. Sperm are very difficult to count and the technology for doing so has changed over the years. There are many confounding factors that can affect male fertility, including age, obesity, and opioid use, to name a few.
Sperm concentrations are an important data point to consider, but other factors (such as the shape of the sperm and how they swim) are also critical to male fertility.
Perry said she hopes agencies like the Environmental Protection Agency will begin to factor in their assessments the impact of chemicals and pesticides on reproductive health.
“Given the body of evidence and these consistent findings, it is time to proactively reduce insecticide exposure for men who want to have families,” Perry said.