Pesticide exposure at work linked to 60-70% higher ALS risk

A synthesis of decades of occupational health research has found something troubling in the data: workers exposed to pesticides on the job face a substantially elevated risk of developing ALS, the progressive neurological disease that gradually robs people of their ability to move, speak, and breathe. The heightened risk ranges from 60 to 70 percent compared to workers with no such exposure, according to the analysis published in Occupational & Environmental Medicine. For men specifically, the picture darkens further—those who have encountered these chemicals in their work are roughly twice as likely to develop the condition as their unexposed counterparts.

ALS, or amyotrophic lateral sclerosis, is the most common form of motor neuron disease. It is progressive, it is rapidly fatal, and there is no cure. In recent years, its incidence has been climbing, a trend that has prompted researchers to look more carefully at what might be driving the increase. While the short-term neurotoxic effects of pesticides—particularly insecticides—have been documented for decades, the long-term consequences of exposure have remained poorly understood. This gap in knowledge motivated a team of researchers to conduct a comprehensive review of the scientific literature.

They searched research databases for studies published between 1990 and 2025 that examined the relationship between workplace pesticide exposure and ALS. From 767 articles initially screened, they retained eight case-control studies that together documented 1,734 cases of ALS, along with three additional studies covering 457 cases of unspecified motor neuron disease. The pooled analysis of this data revealed a consistent pattern: any workplace exposure to pesticides was associated with a 60 percent increase in ALS risk compared to no exposure.

The dose matters. Workers exposed to high levels of pesticides faced a risk that nearly tripled compared to those with no exposure, while those with lower-level exposure saw their risk roughly double. When the researchers broke down the findings by chemical type, herbicides emerged as particularly concerning, associated with a 70 percent heightened risk. Insecticides and fungicides each carried a 60 percent increased risk. The sex difference in the data was striking: among the studies that reported results stratified by gender, men who had been exposed showed twice the risk of developing ALS compared to unexposed men. Women exposed to pesticides, by contrast, showed no statistically significant increase in risk compared to unexposed women—a finding that raises questions about biological mechanisms and warrants further investigation.

The researchers are careful to acknowledge the limitations of their work. The number of primary studies available for analysis remains small. The exposure assessments in those studies were often crude, typically based on answers to a handful of limited questions rather than detailed occupational histories or biological measurements. The selection of comparison groups varied across studies, and not all analyses adequately controlled for potential confounding factors. These methodological gaps mean the true relationship between pesticide exposure and ALS risk may be stronger, weaker, or more complex than the current numbers suggest.

Yet despite these caveats, the researchers conclude that the evidence is substantial enough to warrant action. They call for improvements in how future studies measure exposure, select their reference populations, and account for confounding variables and interactions between risk factors. More fundamentally, they argue that the findings should prompt the implementation of interventions designed to reduce occupational pesticide exposure. For workers in agriculture, pest control, and related fields, the message is clear: the chemicals they handle carry a documented risk to their neurological health, and that risk deserves serious attention from employers, regulators, and public health authorities.