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Even if you don’t use insecticides on your lawn, you’re being exposed to them all the time — mostly through contaminated food and water, which is extremely difficult to avoid. And a new review study finds that exposure to insecticides is linked to a crucial aspect of men’s fertility: sperm concentration.

“Understanding how insecticides affect sperm concentration in humans is critical given their ubiquity in the environment and documented reproductive hazards. Insecticides are a concern for public health and all men,” Lauren Ellis, a researcher on the study and a doctoral student at Northeastern University, said in a statement.

For the new meta-analysis study, published in the journal Environmental Health Perspectives, the researchers analyzed global data on two widely used insecticide classes, organophosphates and N-methyl carbamates, and their link to male fertility and reproductive health. They included data from 25 human studies and more than 1,700 men, conducted over nearly 50 years.

They found that these studies consistently demonstrated a link between higher exposure to these insecticides, such as in farmers, and lower sperm concentration.

The researchers write that this is especially concerning given that previous studies have demonstrated a major downward trend in sperm count and quality over the past half century. To prevent further blows to male reproductive health, they call for health policy and engineering solutions to reduce men’s insecticide exposure.

“This review is the most comprehensive review to date,” Melissa J. Perry, Sc.D., dean of the George Mason University College of Public Health and senior author on the paper, said in the statement. “The evidence available has reached a point that we must take regulatory action to reduce insecticide exposure.”

Previous studies have suggested that there are several ways insecticides could reduce sperm concentration, a common measure of male fertility. They probably mess with hormone receptors that impact sperm production and damage cells in the testicles, and they could also interfere with neurotransmitters that affect sperm production.

Although studies haven’t been able to determine that insecticide exposure causes lower sperm concentration (correlation versus causation is always an import distinction), animal studies and experiments that test the mechanisms of how it could hurt sperm production suggest that this is likely the case.

One of the two classes of insecticides studied, organophosphates, are found in nerve gas, herbicides, pesticides, insecticides, and are used to make plastics, according to CNN. The other class, N-methyl carbamates, are found in insecticides used by farmers.

It’s unclear so far whether the drop in sperm concentration linked to these insecticides actually decreases men’s fertility. However, “there’s enough evidence to really start to say yes, these types of compounds can negatively affect fertility in men,” Alexander Pastuszak, M.D., Ph.D., an assistant professor of surgery and urology at the University of Utah School of Medicine in Salt Lake City, who was not involved in the study, told CNN. “Ultimately, you don’t know the impact on actual fertility until and unless you start trying to get pregnant.”

“As we sort of start to close the net around factors that could negatively impact fertility, these pesticides start to rise to the top,” he added.

Beyond potential impacts on fertility, low sperm concentration is also linked to health issues such as testicular cancer, Axios reports.

“Sperm is an incredibly sensitive endpoint when it comes to overall health for men,” Perry told CNN. “My best advice is to be aware of insecticides in one’s environment and to recognize that avoiding unnecessary insecticide exposure is a good thing, especially if you’re planning on a family and wanting to conceive children.”

Because contaminated water is one of the biggest sources of exposure, it could help to use a water filter — but be aware that not all types can filters reduce pesticide levels. It could also help to clean your fruits and veggies before you eat or cook with them. Scrub them under running water, but don’t use soaps or detergents, which can get trapped in the food — and haven’t been proven to be any more effective than scrubbing water alone. However, if the insecticides were applied when the produce was still a seed, it makes its way into the whole fruit, so scrubbing isn’t a foolproof methods.

And that’s why regulation of these pesticides is so important.