The Link Appeared Stronger in Men Than Women, Though the Evidence Was Too Limited to Confirm a Biological Difference

A new study pooling data from eight prior studies found that occupational pesticide exposure raises the risk of developing amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, by 61% to 71%. The analysis, published today, combined 1,734 ALS cases from studies conducted in the United States, Canada, France, Italy, and Australia. Overall, people who had ever been exposed to pesticides at work were 61% more likely to develop ALS, while exposure to herbicides specifically was linked to a 71% heightened risk.

The link appeared stronger in men than women, though the evidence was too limited to confirm a biological difference. ALS, the most common form of motor neurone disease, affects speech, eating, breathing, and swallowing, with most patients surviving just 2–3 years after diagnosis. The disease occurs sporadically in over 90% of cases, with no known genetic cause, and men are about 20% more likely to develop it than women.

While the study supports a connection, experts caution that most included research relied on self-reported exposure, which may introduce recall bias, and the analysis could not fully separate pesticide exposure from other risk factors like head trauma or other toxins. The findings underscore the need for more rigorous research to identify which chemicals or doses may be responsible.