Exposure to widely used insecticides decreases sperm concentration, study finds

Exposure to several widely used insecticides probably decreases sperm concentration and may have profound effects on male fertility, new US research finds.

The George Mason University paper analyzed five decades of peer-reviewed studies to determine if organophosphates and carbamate-based pesticides exposure correlated with decreased sperm concentration.

Collectively, the studies researchers included looked at about 1,800 men, and showed what co-author Melissa Perry, dean of the George Mason College of Public Health, characterized as a “strong association”.

“Based on this meta analysis, we believe insecticide exposure … is impacting overall sperm concentration,” she told the Guardian. “The message is we need to reduce insecticide exposure in order to ensure men who are planning a family or want to conceive children are able to do that without interference.”

The findings come amid growing concern over global declines in sperm concentration and quality. Recent research estimated sperm concentration has plummeted by about 50% over the last 50 years, and Perry said the insecticides could represent a piece of that puzzle.

About 15m pounds of organophosphates are spread on US cropland annually, and the chemical formula has been linked to cancer, while exposure during pregnancy is tied to neurodevelopmental disorders like ADHD and autism. The insecticide is also commonly used on lawns or indoors.

The Environmental Protection Agency announced this year it was accelerating new regulations for some types of organophosphates because they are much more toxic than previously thought. Carbamates are similarly utilized, and both are neurotoxins that work by damaging an enzyme that regulates an insect’s nerve signals sent throughout its body.

“These are manufactured to kill things and are biologically active by their very nature,” Perry said, but that can have consequences for larger living organisms.

The chemicals appear to interfere with the human endocrine system’s hormone production, she said, which would “have a direct impact on how much and how normally sperm is produced”. The chemicals may also damage testes cells and alter neurotransmission in the brain related to reproductive purposes.

Agricultural workers face the highest exposure, but about one-third of the studies’ participants were exposed largely through food, or other environmental routes, Perry said. Though the strongest correlation was found among participants who face occupational exposure, that may only be because fewer studies looking at environmental exposure exist, she added.

Public health advocates are increasingly pressuring the EPA to impose stricter regulations of the chemicals, or ban them outright. Perry said the best way individuals can protect themselves is to know which foods typically have high levels of pesticide residues on them.

But, she added, it shouldn’t be “up to each individual person to solve this”.

“The recommendation we’re making is to recognize that these insecticide exposure are a public health issue … and we really need to look toward policy solutions that recognize that a health threat exist,” Perry said.

Photograph: Cappi Thompson/Getty Images