New Delhi: People exposed to pesticides at work may be significantly more likely to develop Amyotrophic Lateral Sclerosis (ALS), a rare and fatal disease that progressively damages the nerve cells controlling muscle movement, according to a new review of global evidence published in the BMJ journal Occupational & Environmental Medicine. ALS remains relatively uncommon, but its incidence has increased in recent years, the researchers also noted.
Pooling data from studies across multiple countries, they found that workers exposed to pesticides had a 60 percent higher risk of developing ALS than those who had never been exposed. “The findings of this review add to the evidence that occupational exposure to pesticides may increase the risk of ALS and should encourage the implementation of interventions aimed at reducing exposure during occupational pesticide use,” the researchers from the University of Montreal in Canada wrote.
The findings could be particularly relevant for India, where agriculture involves the largest chunk of the workforce, with farmers and field labourers exposed to pesticides during spraying and other farm activities.
ALS, also known as Motor Neuron Disease, is a progressive neurological disorder that damages the nerve cells controlling voluntary muscle movement. It is considered a rare disease in India, affecting an estimated 75,000–1 lakh people. While there is no cure, supportive treatment can improve quality of life.
Higher exposure, greater risk
Researchers screened 767 studies published between 1990 and 2025 before including eight case-control studies involving 1,734 ALS patients and three studies on unspecified motor neuron disease. They found that workers with high pesticide exposure had nearly three times the risk of developing ALS compared with those who had never been exposed, while lower exposure nearly doubled the risk.
Workers exposed to herbicides (chemicals used to kill weeds) had a 70 percent higher risk of developing ALS, while those exposed to insecticides or fungicides had about a 60 percent higher risk.
Commenting on the findings, Dr K.K. Jindal, Director of Neurology at CK Birla Hospital in New Delhi, said occupational pesticide exposure may be one of several environmental risk factors for ALS, particularly with long-term exposure, but the overall risk remains low.
“The study does not establish a cause-and-effect relationship. In India, where millions work in agriculture, the focus should be on safer pesticide handling, use of protective equipment and greater awareness. More India-specific research is needed to understand how occupational exposure, genetics and other factors interact to influence the risk of neurological diseases,” he told ThePrint.
Indian studies
The new review adds to existing Indian research examining the neurological effects of pesticide exposure. For instance, a 2012 case-control study from Burdwan Medical College and Hospital in West Bengal found that occupational exposure to insecticides and pesticides was associated with a higher risk of ALS, alongside other possible risk factors such as smoking and previous electric shocks.
A 2025 Indian Council f Medical Research (ICMR) study published in the Indian Journal of Medical Research similarly linked long-term pesticide exposure among agricultural workers to mild cognitive impairment, depression and movement disorders.
Dr Shrey Jain, neurosurgeon at New Delhi’s Sir Ganga Ram Hospital, said the global review broadly supports previous research but should not be interpreted as proof that pesticides alone cause ALS. “Farming is a broad occupation and not everyone working in agriculture is directly exposed to pesticides. Unless studies specifically examine workers who actually use these chemicals, it is difficult to draw firm conclusions. Environmental toxins may be one of several mechanisms involved, but pesticides are unlikely to be the only factor,” he said.
Dr Jain added that researchers are still trying to understand how environmental toxins contribute to neurodegenerative diseases. “When the body is exposed to different toxins, it can trigger immune reactions. Researchers are exploring whether this could be one of the mechanisms linking environmental exposures with diseases such as ALS, but pesticides are unlikely to be the only factor involved,” he added.
Dr Jindal explained that current evidence suggests the disease results from a combination of genetic susceptibility and environmental factors. “Long-term occupational pesticide exposure may be one such risk factor, but a causal relationship has not been established and the overall risk remains low,” he said.
Researchers want better evidence
The authors of this latest research report acknowledged that most studies relied on participants recalling past pesticide exposure and used limited questionnaires to assess exposure. The relatively small number of studies also made it difficult to establish a causal relationship.
“To strengthen the evidence on risk factors for ALS, primary studies particularly need methodological improvements on exposure assessment, on the selection of reference groups, and on adjustment for potential confounders, including analysis for interactions between risk factors,” the researchers wrote.
(Edited by Nardeep Singh Dahiya)
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