Workplace exposure to pesticides may be associated with a substantially higher risk of amyotrophic lateral sclerosis (ALS), according to a new systematic review and meta-analysis published in Occupational and Environmental Medicine. The analysis found that people exposed to pesticides through their jobs had an approximately 60% greater risk of developing ALS than those without occupational exposure. The findings add to growing concern that repeated contact with agricultural and industrial chemicals could contribute to long-term neurological damage, even when no immediate symptoms are apparent.
ALS is the most common form of motor neuron disease, a group of progressive disorders that destroy the nerve cells responsible for controlling voluntary movement. As motor neurons deteriorate, muscles gradually weaken, affecting walking, hand movement, speech, swallowing and eventually breathing. The disease is usually fatal, and there is currently no cure. Although ALS remains relatively uncommon, researchers note that reported incidence has risen in recent years, increasing the importance of identifying preventable environmental and occupational risk factors.
Pesticides include a wide range of chemical substances designed to kill or control weeds, insects, fungi and other organisms that threaten crops or public health. Their short-term neurotoxic effects, particularly those associated with some insecticides, have been recognised for decades. Acute exposure can interfere with neurotransmission, disrupt nerve signalling or cause tremors, confusion and muscle weakness. The potential consequences of repeated, low-level exposure over many years, however, are far more difficult to measure and remain less clearly understood.
To examine the evidence, researchers searched scientific databases for studies published between 1990 and 2025. They included peer-reviewed research, theses and scientific reports that investigated occupational pesticide exposure in relation to ALS or motor neuron disease. From 767 initially identified articles, the researchers retained eight case-control studies involving 1,734 people with ALS and three additional studies involving 457 people diagnosed with unspecified motor neuron disease. The results were then combined in pooled statistical analyses to estimate the relationship between workplace exposure and disease risk.
Across six studies, any occupational exposure to pesticides was associated with a 60% increase in the likelihood of ALS compared with no reported exposure. The analysis also suggested a possible dose-response pattern, meaning that risk appeared to rise as exposure increased. People exposed to high pesticide levels had almost three times the risk of developing ALS compared with unexposed individuals, while those exposed to lower levels had approximately twice the risk. Such patterns can support the possibility of a biological relationship, although they cannot by themselves prove that pesticides directly cause the disease.
The analysis found differences according to the type of pesticide involved. Occupational exposure to herbicides was associated with a 70% higher risk of ALS, while exposure to insecticides or fungicides was each associated with an approximately 60% higher risk. These categories contain many different active ingredients with distinct chemical properties and biological effects, so the findings do not establish that every herbicide, insecticide or fungicide carries the same danger. Instead, they point to the need for more detailed research examining individual compounds, mixtures and exposure conditions.
Sex-specific results revealed another notable pattern. In the three studies that reported estimates separately for men and women, men exposed to pesticides at work were approximately twice as likely to develop ALS as unexposed men. No statistically apparent increase was observed among exposed women. The researchers caution that this difference should not be interpreted as evidence that women are protected. Women may have been underrepresented in the available studies, may have experienced different types or intensities of exposure, or may have been affected by differences in job history, protective equipment and the accuracy of exposure reporting.
The researchers emphasise that the evidence has important limitations. Most studies assessed exposure using relatively broad questionnaires or participants’ recollections of their work histories, rather than direct measurements of pesticide concentrations or biological markers. Such methods can result in inaccurate estimates and make it difficult to determine which chemicals, exposure routes or durations are most important. The studies also differed in their definitions of exposure, choice of comparison groups and adjustment for factors such as age, smoking, physical workload and other occupational hazards. Because the evidence came largely from observational case-control studies, the findings demonstrate an association rather than definitive proof of causation.
Even with these uncertainties, the researchers say the results support practical efforts to reduce exposure during professional pesticide use. Improved training, safer application procedures, appropriate protective equipment, stronger monitoring and the substitution of less hazardous products could all help limit contact with these chemicals. They also call for future studies with more precise exposure assessment, better-selected control groups and analyses capable of identifying interactions between pesticides and genetic or lifestyle-related risk factors. As ALS likely arises from a combination of biological susceptibility and environmental influences, understanding how occupational exposures fit into that complex picture may be crucial.
Subject of Research: People
Article Title: Occupational exposure to pesticides increases the risk of amyotrophic lateral sclerosis: a systematic review and meta-analysis
News Publication Date: 4-Aug-2026
Web References: https://doi.org/10.1136/oemed-2025-110662
References: Occupational and Environmental Medicine, DOI: 10.1136/oemed-2025-110662
Keywords: Amyotrophic lateral sclerosis, ALS, motor neuron disease, occupational exposure, pesticides, herbicides, insecticides, fungicides, neurotoxicity, workplace health, environmental risk factors, systematic review, meta-analysis
