World’s Most Used Insecticides Damage Male Fertility in Rodents, Researchers Say

Neonicotinoid pesticides, the world’s most widely used class of insecticides, are linked to male reproductive toxicity in lab animals, especially at higher doses, according to a new scientific review of two decades of evidence.

The findings, published [December 2025] in Environmental Research, add to growing evidence that these insecticides may harm human fertility. Known as “neonics,” neonicotinoid pesticides are banned in the European Union but widely used in the U.S.

The scientists analyzed 21 laboratory studies between 2005 and 2025. Despite differences in design, species, and dosing, more than two-thirds found neonic exposure damaged testicular function and sperm: Sperm counts dropped. Sperm moved more slowly. Shapes became abnormal, and hormone levels changed.

The effects worsened with higher doses or more prolonged exposure to neonics, causing more severe or permanent injury.