Workers whose jobs ever exposed them to pesticides had about a 60% higher risk of developing amyotrophic lateral sclerosis than workers with no such exposure, according to a systematic review and meta-analysis published online August 4, 2026 in Occupational and Environmental Medicine.
The analysis was led by France Labrèche and colleagues at the Institut de recherche Robert-Sauvé en santé et en sécurité du travail in Montreal, who pooled eight case-control studies covering 1,734 people with ALS. Herbicides carried a slightly larger signal than insecticides, and the risk climbed with the level of exposure.
Key takeaways
- Ever being exposed to pesticides at work was tied to about a 60% higher relative risk of ALS (pooled odds ratio 1.6).
- The risk was higher at high exposure levels, close to a tripling, than at low levels.
- These are relative comparisons between exposed and unexposed workers, not head counts of how many people in each group developed ALS.
What the study found
The researchers searched eight bibliographic databases for studies published between 1990 and 2025 and screened 767 articles. Eight case-control studies, covering 1,734 ALS cases, were kept for the pooled analysis.
Across six of those studies, “ever” occupational exposure to pesticides was linked to about a 60% higher risk of ALS (pooled odds ratio 1.6). The true increase is very likely somewhere between about 10% and 120% (95% CI 1.1, 2.2).
Exposure type mattered a little. Herbicides were tied to about a 70% higher risk (pooled OR 1.7), while insecticides or fungicides were tied to about a 60% higher risk (pooled OR 1.6).
Dose mattered more. Based on three studies, high-level exposure was tied to about a 170% higher risk, close to a tripling (pooled OR 2.7; very likely between 40% and 400% higher, 95% CI 1.4, 5.0). Low-level exposure was tied to about a 90% higher risk, though that range runs from no increase at all up to nearly four times the risk (pooled OR 1.9; 95% CI 1.0, 3.7).
In the three studies that split results by sex, exposed men were twice as likely to develop ALS as unexposed men, according to the BMJ Group summary of the paper. No increased risk was apparent in exposed women.
Dr. Kumar’s take
ALS is a devastating diagnosis, so it matters how a number like this one lands.
A 60% higher relative risk is a comparison, not a count. The paper reports how much more likely exposed workers were to develop ALS than unexposed workers, as a pooled odds ratio, not as a number of cases in each group.
The design is the bigger caveat. Every study in this pool was a case-control study, which means people who already have ALS were asked to recall jobs and chemical exposures from decades earlier. Someone living with a devastating diagnosis searches their past harder than a healthy comparison subject does. That is recall bias, and it inflates associations.
The authors found evidence of exactly this problem in their own data. Self-reported exposure assessment methods and older publication dates before 2015 were statistically significant predictors of the effect size. In plain terms, the studies that leaned on what workers remembered produced bigger numbers than the studies that measured exposure more rigorously.
The male-specific finding deserves the same skepticism. It rests on three studies, and the jobs that involve mixing and spraying pesticides have historically been held by men. A result that shows up in men and not women more likely reflects who held those jobs, and at what intensity, than a biological difference between male and female motor neurons.
There is also real disagreement between the pooled studies (I² of 57% for the main result), another reason to treat 60% as a rough signal rather than a precise figure.
None of that makes the finding meaningless. It fits a wider pattern, including work linking heavy pesticide exposure to 2 to 8 times higher cancer risk. And the dose gradient, where higher exposure tracked with higher risk, is not something recall bias alone explains easily.
What it means for you
If your work involves mixing, loading or applying pesticides, this is the paper to bring to your safety officer. The authors conclude that the findings “should encourage the implementation of interventions aimed at reducing exposure during occupational pesticide use.” Respirators, gloves, closed mixing systems and washing before you eat or drive home are not overkill.
If you do not work with these chemicals, this study says nothing about your grocery cart. The exposures measured here are occupational: hours of direct handling, over years. That is a different world from residue on an apple.
The same care applies to any pooled relative risk in a headline, whether it is this one or a finding like PPIs and a 43% higher risk of low magnesium. Ask what the starting risk was before you decide how much the increase should change what you do.