Study: Global decline in male fertility linked to common pesticides

11/28/2023 / By Olivia Cook

A new study has found a strong association between the steady decline of sperm concentration in adult men over the last 50 years and insecticide exposure.

Published in the journal Environmental Health Perspectives, the study reviewed findings from 20 studies, 21 study populations, 42 effect sizes and 1,774 adult men. Authors of the study have found sufficient evidence that exposure to two widely used insecticides, namely organophosphates and N-methyl carbamates, lowers sperm concentration in adult men.

Pesticides and reproductive health

Multiple studies by the National Institutes of Health (NIH) have shown that pesticides can cause short-term (within minutes to 24 hours) as well as chronic (from weeks to several years after exposure) adverse health effects, harming different body organs such as the reproductive system. Because of this, pesticide exposure has become a cause for concern, especially with regard to fertility, in recent years. (Related: Sperm counts rapidly declining on all continents, meta-analysis finds.)

In women, reproductive issues that have been associated with pesticide exposure include decreased fertility, spontaneous abortions or miscarriages, developmental abnormalities, disruption of hormone function, low birth weight, premature birth and stillbirth.

Meanwhile, the majority of widely used pesticides, including organophosphates and N-methyl carbonates, have been associated with abnormal semen parameters – affecting the male reproductive system through mechanisms, such as:

Increased DNA damage and abnormal morphology or structure
Inhibition of spermatogenesis
Reduction of sperm count, density or concentration, motility or movement, viability or the percentage of live sperm in a semen sample, and testes weights

Senior study author Melissa Perry said: “This review is the most comprehensive evidence sizing up more than 25 years of research on male fertility and reproductive health. The evidence available has reached a point that we must take regulatory action to reduce insecticide exposure.”

Lauren Ellis, one of the study’s authors, added: “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, who are exposed primarily through the consumption of contaminated food and water.”

Organophosphate and N-methyl carbamate insecticides

Organophosphates are man-made agricultural insecticides, while N-methyl carbamates are a class of insecticides structurally and mechanistically similar to organophosphates.

Organophosphate insecticides, such as chlorpyrifos, diazinon, dichlorvos, ethion, fenthion, malathion and parathion, account for a large share of all insecticides used in the United States.

Organophosphates are used to control mosquitoes and a variety of other insects, as well as mites or ticks that attack fruits, landscaping plants, shrubs and vegetables. They are also used in veterinary practice. However, most home uses of organophosphates have now been phased out in the U.S. (Related: Congress gave EPA 27 years to study how pesticides disrupt human hormones; agency has yet to comply.)

According to the Delaware Health and Social Services, carbamates are often used as baits or sprays to kill insects on crops by affecting their brains and nervous systems. At home, they are used to bait and eliminate ants, aphids, cockroaches, crickets, fleas, lace bugs, mealy bugs, mosquitoes, scales, whiteflies, and so on.

How people are exposed

Organophosphates and carbamates can easily enter the body through inhalation, skin contact with contaminated surfaces or ingestion of foods treated with these chemicals.

People who may have greater exposure to these insecticides compared to the general population include farm workers, florists, gardeners, manufacturers of these insecticides and pesticide applicators.

People who are exposed to smaller amounts over a long time may feel depressed, forgetful, irritable, tired or weak. Sudden exposure to large amounts may cause difficulty in breathing or tightness in the chest, irregular or slow heartbeat, nausea, paralysis, salivation, seizures, vomiting and weakness.

Although fatalities have been rare since the U.S. government introduced tighter rules regarding its use in 2013, organophosphate poisoning still occurs and affects millions annually. Depending on the degree of exposure, individuals could experience mild or severe symptoms. Severe cases of organophosphate poisoning can be life-threatening.

People who work with organophosphates are advised to take the following precautionary measures (as they would when handling or exposed to any toxic chemical):

Know which products contain organophosphates and learn how to recognize them.
Wear protective gear (face masks, face shields, gloves, etc.) during and after applying them.
Wash hands thoroughly before eating and drinking.
Remove any contact lenses and irrigate the eyes with lukewarm water following exposure.
Remove all clothing and take a bath or shower at the end of your work day.
Mark the products clearly and keep them in a secure place when not being used.
Stay indoors with the windows closed if pesticide spraying occurs nearby.
Test your water sources regularly.
Wash all fruits, vegetables and other food crops thoroughly before use.
Seek medical attention if you experience any of the symptoms previously mentioned.
Immediately call 911 in cases of accidental ingestion or attempted suicide with organophosphates.