Pesticide exposure appears to be linked to lower sperm concentrations in men around the world, a new large-scale evidence review has concluded.

A review of 25 studies spanning nearly 50 years found consistent links between lower sperm concentrations and two widely used classes of insecticides, organophosphates and N-methyl carbamates, researchers said.

"This review is the most comprehensive review to date," said senior researcher Melissa Perry, dean of the George Mason University College of Public Health in Fairfax, Va. "The evidence available has reached a point that we must take regulatory action to reduce insecticide exposure."

Perry's team systematically reviewed 25 human studies of occupational and environmental insecticide exposure, conducted over the past half-century.

The findings, published Wednesday in the journal Environmental Health Perspectives, revealed evidence of robust associations between insecticide exposure and lower sperm concentration.

"Understanding how insecticides affect sperm concentration in humans is critical given their ubiquity in the environment and documented reproductive hazards," said co-researcher Lauren Ellis, a doctoral student at Northeastern University. "Insecticides are a concern for public health and all men, who are exposed primarily through the consumption of contaminated food and water."