Exposure to pesticides used in agriculture may significantly increase the risk of developing amyotrophic lateral sclerosis (ALS), the most common form of motor neurone disease, a comprehensive study has found. The review of research, spanning 35 years, indicated that individuals exposed to these chemicals at work could face up to a 70 percent higher risk of developing the devastating neurodegenerative condition.
ALS affects nerve cells responsible for controlling voluntary muscle movement, leading to progressive muscle weakness, mobility loss, speech difficulties, and changes in cognitive function. The prognosis for ALS patients is often grim, with only about 20 percent living longer than five years after diagnosis, and many facing a survival period of as little as two years.
The study, which analyzed data from over 2,000 individuals with ALS or other forms of motor neurone disease by reviewing nearly 800 studies, found that workers with occupational pesticide exposure were approximately 60 percent more likely to develop ALS. The risk increased to 70 percent for those primarily exposed to herbicides, commonly known as weedkiller.
Even lower levels of exposure to any type of pesticide were associated with a doubling of the risk. Interestingly, the association appeared to be significant only in men when researchers analyzed data separately for males and females.
Scientists from the Robert Suave Institute For Research in Quebec, who conducted the review, urged authorities to implement measures aimed at reducing occupational exposure during pesticide use. The World Health Organization has previously characterized pesticides as 'intrinsically toxic' and identified them as a leading cause of death through self-poisoning.
While some pesticides are banned in the UK due to identified health risks, including the insecticide Chlorpyrifos and the weedkiller Paraquat, others that are banned by the EU remain in use in Britain. These include Dimethomorph, Benthiavalicarb, and Ipconazole, used on various crops and seeds.
Experts not involved in the study have advised caution in interpreting the findings. Dr. Johnathan Cooper-Knock from the University of Sheffield noted that while the research's strength lies in its extensive data, it is a retrospective analysis using indirect measurements of exposure, making it difficult to definitively attribute the effect solely to pesticides without considering other correlated factors.
Dr. Nick Cole of the MND Association UK highlighted that the study establishes a statistical association rather than a direct causal link, emphasizing that the specific percentage increases should be treated with caution due to limitations in the available data. Motor neurone disease itself is a rare condition primarily affecting individuals in their 60s and 70s, though it can occur at any adult age. The exact cause remains unknown, although genetic factors and family history can sometimes play a role. Early symptoms may include weakness in limbs, slurred speech, and swallowing difficulties.