Pesticide exposure linked to 70% higher ALS risk in workers, study finds

Two Australians wake up each day to a diagnosis of ALS—amyotrophic lateral sclerosis, a fatal disease that attacks the nervous system. A new study suggests that for workers who have spent years around pesticides, the risk of joining that daily count may be significantly higher than for the general population.

Researchers reviewing data on occupational exposure found that men who have worked with pesticides face roughly double the risk of developing ALS compared to men with no such exposure. The increase amounts to approximately 70 per cent above baseline risk. Women showed no apparent elevation in risk according to the paper, published in the BMJ. The finding arrives as global rates of ALS have climbed in tandem with expanding pesticide use across agriculture—a pattern researchers say warrants attention, particularly as food production pressures intensify worldwide.

The chemicals in question are familiar to farming. Paraquat and glyphosate are synthetic pesticides deployed across grain and horticultural operations to manage weeds, insects, fungi, and rodents. Both have drawn legal and regulatory fire in recent years. Tens of thousands of lawsuits in the United States have alleged links between glyphosate exposure and cancer, while Australia's Federal Court examined a class action against Bayer over its glyphosate product Roundup. Though courts have generally stopped short of establishing proven scientific causation, dozens of countries have moved to ban or restrict glyphosate use. In June, Australia's chemical regulator announced new restrictions on paraquat after some neurologists connected it to Parkinson's disease. The regulator stated the evidence did not conclusively show paraquat caused Parkinson's through approved uses, but imposed significant constraints anyway—lower application rates, tighter environmental safeguards. In response, major manufacturer Syngenta withdrew paraquat from the Australian market, citing regulatory burden and supply chain costs.

The study's authors acknowledge that ALS causes remain poorly understood. Their conclusion is measured: the evidence "adds to" the case that occupational pesticide exposure may increase ALS risk. They do not claim to have solved the puzzle. Associate professor Rachel Tan, a motor neurone disease specialist uninvolved in the research, echoed that caution. She said the findings support the pesticide-ALS link but that crucial questions remain unanswered—which specific chemicals drive the risk, whether longer exposure compounds danger, why the effect appears concentrated in men. "The overall evidence base is not entirely consistent," she noted. Some studies find no clear association; others suggest the connection is stronger in men than women.

Oliver Jones, an RMIT professor of analytical chemistry, urged perspective. The study, he pointed out, synthesized existing research rather than presenting new experimental data. "There is unlikely to be a single cause of motor neurone diseases," he said, and cautioned against treating the findings as a breakthrough. "While reducing exposure to pesticides is a sensible general precaution, the paper is not a eureka moment about the risks of pesticide exposure." He advised against panic.

Australia's farming sector acknowledges the stakes. Hamish McIntyre, president of the National Farmers' Federation, said agricultural workers are aware of chemical risks and support further research into pesticide safety and environmental impact. He has worked with pesticides since the early 1980s and emphasized that appropriate training and evolving safety protocols are standard. But he also stressed that farm chemicals remain essential to food and fibre production. The tension is real: the industry cannot easily abandon tools it depends on, yet the health questions will not disappear. What remains to be determined is which components of pesticides pose the greatest threat, and whether the risk scales with years of exposure—questions that will shape both regulation and farming practice in the years ahead.