Workplace exposure to pesticides boosts risk of ALS, study finds
For those exposed to herbicides, risk may be as much as 71% higher
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- A study found occupational exposure to pesticides significantly increases the risk of developing ALS, particularly among workers with higher exposure intensity.
- Exposure to herbicides was associated with up to a 71% higher risk of ALS.
- Researchers emphasized the need for workplace safety measures to reduce pesticide exposure.
People whose jobs expose them to pesticides may be more likely to develop amyotrophic lateral sclerosis (ALS) than workers who aren’t exposed, according to a systematic review and meta-analysis.
Researchers found that occupational pesticide exposure was associated with a 61% higher risk of developing ALS. Among different pesticide classes, exposure to herbicides was associated with the highest estimated increase in ALS risk, at 71%.
In studies that assessed exposure intensity, workers with lower levels of occupational pesticide exposure were about twice as likely to develop ALS as unexposed workers, while those with the highest levels of exposure were nearly three times as likely to develop the disease.
“Despite the small number of studies and some heterogeneity, our results add to the evidence suggesting that occupational exposure to pesticides may increase the risk of ALS,” the researchers wrote. The findings support efforts to reduce pesticide exposure in the workplace, they said.
The study, “Occupational exposure to pesticides increases the risk of amyotrophic lateral sclerosis: a systematic review and meta-analysis,” was published in Occupational & Environmental Medicine.
Risk identified decades ago
Pesticide use has increased steadily over the past 30 years amid growing demands for food production and uncertainties related to climate change. While the acute neurotoxic effects of pesticides — particularly insecticides — have long been recognized, whether long-term exposure contributes to neurodegenerative diseases such as ALS remains under debate.
ALS damages the nerve cells responsible for controlling movement. Although several genetic mutations have been linked to the disease, the exact causes of ALS remain poorly understood. Increasing evidence suggests that, in addition to genetic factors, environmental and occupational exposures — including electromagnetic fields, heavy metals, and pesticides — may contribute to ALS risk.
Pesticides were first proposed as a possible ALS risk factor more than 40 years ago, and numerous studies and systematic reviews have since examined the association. However, most did not account for differences in how exposure was assessed or distinguish between occupational and nonoccupational pesticide exposure.
The researchers said this distinction is important because people who work with pesticides are often exposed to higher doses and have more frequent contact with these chemicals than the general population, making workplace exposure a distinct risk that should be evaluated separately.
They conducted a systematic review of studies published between 1990 and 2025 examining the association between occupational exposure to pesticides and ALS. After screening more than 700 published papers, eight case-control studies — studies that compare past exposure to a certain factor in people with and without a certain trait — involving 1,734 people with ALS met the criteria for the main analysis.
Pooling data from six studies, the researchers found that workers with any occupational exposure to pesticides had a 58% higher risk of developing ALS than those without workplace exposure.
Among the pesticide classes evaluated, herbicide exposure was associated with a 71% higher risk of ALS, while insecticide and fungicide exposure were associated with 57% and 61% higher risk, respectively. However, the researchers cautioned that these findings should be interpreted carefully because relatively few studies examined each pesticide class.
Three studies also evaluated exposure intensity. Compared with workers who had never been exposed, those with lower levels of occupational pesticide exposure had about twice the risk of developing ALS, while those with the highest exposure levels had nearly three times the risk.
When the researchers analyzed studies that reported results separately for men and women, the association between occupational pesticide exposure and ALS onset was statistically significant among men but not among women. The researchers cautioned that larger studies are needed to determine whether the association truly differs between men and women.
The scientists noted that the limited number of available studies and differences in how pesticide exposure was assessed prevented more detailed analyses. While additional studies are needed to strengthen the evidence, they said, their findings “add to the evidence that occupational exposure to pesticides may increase the risk of ALS” and should encourage efforts to reduce pesticide exposure during occupational use.
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