Researchers at the Herbert Wertheim School of Public Health and Human Longevity Science at the University of California San Diego has shed light on the potential impact of herbicides on adolescents’ brain function. Published in the October 11, 2023, issue of Environmental Health Perspectives, the study investigated the metabolite concentrations of two commonly used herbicides, glyphosate and 2,4-dichlorophenoxyacetic acid (2,4D), as well as the insect repellent DEET in urine samples collected from 519 adolescents aged 11 to 17 in Pedro Moncayo, Ecuador, in 2016. The researchers also assessed neurobehavioral performance in five key areas: attention and inhibitory control, memory and learning, language, visuospatial processing, and social perception.
The key findings were as follows:
- Glyphosate, a widely used nonselective herbicide in crops such as corn and soy, and for residential vegetation control, was detected in 98% of the participants.
- 2,4D, a broadleaf herbicide used on lawns, aquatic sites, and agricultural crops, was detected in 66% of the participants.
- Higher levels of 2,4D in urine were associated with poorer neurobehavioral performance in attention and inhibitory control, memory and learning, and language.
- Glyphosate in urine was associated with lower scores in social perception only, while DEET metabolites showed no significant association with neurobehavioral performance.
The widespread adoption of genetically modified, glyphosate-resistant “Roundup-ready” crops in 1996 and 2,4D resistant crops in 2014 has led to a significant increase in the use of glyphosate and 2,4D, making them the most commonly used herbicides globally.
The study’s lead author, Jose Ricardo Suarez, M.D., Ph.D., M.P.H., highlighted the potential link between exposure to neurotoxic contaminants in the environment and the rising rates of chronic diseases and mental health disorders in adolescents and young adults over the past two decades.
Notably, 2,4D was found to have negative associations with performance in all five neurobehavioral areas, with statistically significant links observed in attention and inhibitory control, memory and learning, and language. Glyphosate had a significant negative association only with social perception.
The authors emphasized the importance of further research to understand the potential long-term effects of exposure to various chemicals, as a vast number of chemicals are introduced to the market each year, with limited knowledge about their safety on human health.
This study is part of the ESPINA project, which investigates secondary pesticide exposures among children and adolescents to understand the impact of such exposures from childhood through adulthood. The researchers plan to evaluate whether the observed associations persist into early adulthood in the follow-up stages of the study. The research was conducted in collaboration with various co-authors from UC San Diego, Fundación Cimas del Ecuador, and Emory University.