Exposure to pesticides may significantly increase the risk of developing amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease, according to new research.
ALS destroys motor neurons, which are the nerve cells connecting the brain and spinal cord to muscles. This loss of control over bodily muscles impacts speech, eating, and breathing. The disease is typically fatal, with many patients surviving less than five years after diagnosis.
While the exact causes of ALS remain unknown, scientists have investigated pesticides as a potential risk factor since the 1980s. The latest study, which analyzed data from ALS studies conducted globally over the past 35 years, adds to the growing body of evidence. Researchers found that occupational exposure to pesticides was associated with a 61% to 71% higher risk of developing ALS compared to individuals with no such exposure. The study also indicated that the greater an individual's pesticide exposure, the higher their risk of developing the disease.
The association was particularly pronounced in men, who were twice as likely to develop ALS if they had experienced occupational pesticide exposure.
Pesticides are a broad category of chemicals used to protect crops from pests and weeds. Globally, pesticide use has risen steadily over the past three decades, coinciding with an increase in ALS cases. In the United States, overall pesticide use has seen a decline since the 1980s, but herbicide use has been on the rise.
Herbicides were among the pesticide categories most strongly associated with ALS in the new study. Glyphosate, the most widely used herbicide in the U.S. and sold under brand names like Roundup, has been suggested to disrupt communication between neurons and trigger inflammation in the brain and spinal cord, processes that can lead to neuron death and motor dysfunction—hallmarks of ALS. Atrazine, the second most common herbicide, has also been linked to Parkinson's disease, another neurodegenerative disorder.
The study specifically focused on individuals exposed to pesticides in occupational settings, where high doses can be absorbed over short periods, primarily through skin contact or inhalation. Farmworkers, including harvesters, pesticide mixers, greenhouse employees, and those involved in packing and shipping produce, are regularly exposed to these chemicals through residue on plants, contaminated water, or airborne drift during spraying.
Beyond ALS, higher pesticide exposure has been linked to a range of other health issues, including blood disorders, respiratory illnesses, endocrine dysfunction, nervous system damage, infertility, and certain types of cancer.