Workers' pesticide exposure linked to 60–70% heightened motor neuron disease risk

A synthesis of research on workplace exposure to pesticides has revealed a 60-70% increased risk of the most common form of motor neuron disease—amyotrophic lateral sclerosis (ALS), or motor neuron disease—for those who have been exposed. Men are twice as likely to develop the condition compared to those who have not been exposed.

Despite ALS being rare, its incidence has been on the rise recently. While short-term neurotoxic effects are known, long-term neurotoxicity from pesticides, especially insecticides, is not well-established. The researchers analyzed eight case-control studies involving 1,734 ALS cases and three studies with 457 cases of unspecified motor neuron disease.

The analysis found that any workplace exposure to pesticides raised the risk of ALS by 60%, with high exposure linked to nearly tripling the risk compared to no exposure. Lower-level exposure doubled the risk. Herbicide exposure was associated with a 70% heightened risk, while insecticide and fungicide exposure showed a 60% increased risk.

In studies reporting sex-stratified risks, men exposed to pesticides were twice as likely to develop ALS compared to unexposed men, but no increased risk was found in women. The findings highlight the need for improved exposure assessment methods, better selection of reference groups, and adjustment for potential confounders in future primary studies.

The review concludes that occupational pesticide exposure likely increases the risk of ALS and calls for interventions to reduce exposure during occupational pesticide use.