A comprehensive review of research indicates that occupational exposure to pesticides may increase the risk of developing amyotrophic lateral sclerosis (ALS), the most common form of motor neurone disease (MND), by up to 70 percent. The study, which analyzed nearly 800 research papers and focused on 11 studies involving data from over 2,000 individuals with ALS or other forms of MND, found that those exposed to pesticides at work were approximately 60 percent more likely to develop ALS.
The risk was particularly pronounced for individuals exposed predominantly to herbicides, who showed a 70 percent increased likelihood of developing the disease. Even lower levels of exposure to any type of pesticide were associated with a doubled risk. The findings suggest a notable gender difference, with the observed link applying primarily to men.
Pesticides are chemicals used to protect crops by controlling or eliminating weeds, insects, and fungi. The review highlighted herbicides, insecticides, and fungicides as common types.
Motor neurone disease affects around 5,000 people in Britain, causing the deterioration of nerve cells that control movement. This leads to symptoms such as muscle weakness, loss of mobility, speech difficulties, and changes in thinking and behavior. The prognosis for ALS is often severe, with only about 20 percent of patients surviving longer than five years, and many having a life expectancy of as little as two years.
Scientists from the Robert Suave Institute For Research in Quebec led the analysis. In their commentary in the journal Occupational and Environmental Medicine, they recommended the implementation of 'interventions aimed at reducing exposure during occupational pesticide use.' The World Health Organization has characterized pesticides as 'intrinsically toxic' and a leading cause of death by self-poisoning.
While some pesticides are banned in the UK, including the insecticide Chlorpyrifos and the herbicide Paraquat, due to health concerns, certain pesticides prohibited by the EU are still permitted for use on British crops. These include Dimethomorph, Benthiavalicarb, and Ipconazole.
Experts not involved in the study have urged caution in interpreting the results. Dr. Johnathan Cooper-Knock from the University of Sheffield's School of Medicine and Population Health noted the strength of the research in its multi-study approach but highlighted that it is a retrospective analysis using indirect measures of exposure, making it difficult to rule out confounding factors. Similarly, Dr. Nick Cole of the MND Association UK emphasized that the study shows a statistical association rather than a direct causal link, advising readers to treat specific percentage increases with caution. The cause of motor neurone disease remains not fully understood.