A research endeavor conducted by the Herbert Wertheim School of Public Health at the University of California San Diego (UCSD) suggests that commonly employed herbicides, particularly glyphosate and 2,4-D, could have detrimental effects on the cognitive functions of adolescents.
Recent scientific evidence indicates that exposure to prevalent herbicides may adversely influence cognitive capabilities in adolescents. Herbicides, universally recognized as weed killers, stand as the most commonly applied category of pesticides on a global scale. Their applications span agriculture, residential environments, and industrial sectors. A study spearheaded by investigators at the Herbert Wertheim School of Public Health and Human Longevity Science at UCSD associates exposure to two of the most frequently used herbicides with impaired cognitive performance among adolescents.
Published on October 11, 2023, in the online issue of the scholarly journal Environmental Health Perspectives, the researchers quantified the concentrations of metabolites from the herbicides glyphosate and 2,4-dichlorophenoxyacetic acid (2,4-D), along with the insect repellent DEET, in urine samples. These samples were gathered in 2016 from 519 adolescents, aged between 11 and 17, residing in the agriculturally active county of Pedro Moncayo, Ecuador. The study also evaluated neurobehavioral capacities in five domains: attention and inhibitory control, memory and learning, language skills, visuospatial processing, and social perception.
Credit: The concentrations of widely-used herbicides and DEET were measured in adolescent urine samples from Pedro Moncayo, Ecuador, to ascertain their influence on adolescent cognitive functions. Credit goes to Briana Chronister and the team at UC San Diego.
Noteworthy Observations and Historical Background
“Rates of chronic illnesses and mental health disorders in young people have surged globally over the past two decades, and environmental neurotoxicants could partially account for this uptick,” remarked senior author Jose Ricardo Suarez, M.D., Ph.D., M.P.H., an associate professor in the Herbert Wertheim School of Public Health.
Among the critical observations:
- Glyphosate, a non-discriminatory herbicide commonly applied in various crops such as corn and soy and for vegetation management in domestic settings, was found in 98% of the participants.
- 2,4-D, a broadleaf herbicide used in aquatic sites, agricultural fields, and lawns, was identified in 66% of the subjects.
- Elevated levels of 2,4-D in urine correlated with diminished performance in areas including attention and inhibitory control, memory and learning, and linguistic abilities.
- Concentrations of glyphosate in urine were linked only to reduced scores in social perception, while DEET metabolites exhibited no connection to neurobehavioral performance.
The authors noted that following the 1996 introduction of genetically engineered, glyphosate-resistant crops and 2,4-D resistant crops in 2014, there has been a marked surge in the utilization of these herbicides, making them the most commonly used worldwide.
Pending Questions and Future Investigations
“Herbicides and insecticides see extensive application in agricultural sectors globally, thus amplifying exposure risks for both children and adults, particularly those residing in agricultural regions. However, the effects on different life stages remain largely unknown,” stated first author Briana Chronister, a doctoral candidate in the UC San Diego–San Diego State University Joint Doctoral Program in Public Health.
Earlier research has associated exposure to frequently used insecticides with altered neurocognitive performance. Additionally, modern statistics reveal that 20% of adolescents and 26% of young adults suffer from diagnosable mental health conditions such as anxiety, depression, impulsivity, aggression, or learning disorders.
Statistically significant relationships were found between 2,4-D and lower performance in three neurobehavioral domains—attention and inhibitory control, memory and learning, and language. Glyphosate demonstrated a significant negative relationship solely with social perception, a test evaluating the recognition of emotions. In contrast, DEET metabolites showed no correlation with neurobehavioral changes.
“An alarming number of new chemicals enter the market annually, and regrettably, scant information exists about the long-term safety and effects of the vast majority of these substances on human health. More research is crucial to genuinely comprehend the implications,” cautioned Suarez.
This study is a segment of ESPINA: The Study of Secondary Exposures to Pesticides Among Children and Adolescents, a prospective cohort research initiative supported by the National Institute of Environmental Health Sciences, part of the National Institutes of Health, the National Institute of Occupational Safety and Health, and various private funding organizations. ESPINA aims to explore the repercussions of pesticide exposure on human development from childhood through adulthood.
In 2022, Suarez and his research team completed the 14th year of follow-up studies with the participating subjects, with intentions to investigate whether these observed relationships persist into early adulthood.
References and additional acknowledgments for this research are available in the original publication.
Frequently Asked Questions (FAQs) about Adolescent Cognitive Effects of Herbicides
What is the primary focus of the research conducted by the Herbert Wertheim School of Public Health at UCSD?
The primary focus of the study is to examine the potential negative effects of commonly used herbicides, specifically glyphosate and 2,4-D, on adolescent cognitive functions. The research aims to understand how exposure to these herbicides could impact neurobehavioral performance in adolescents.
Who are the subjects of this study?
The subjects are 519 adolescents aged between 11 and 17. They reside in the agriculturally active county of Pedro Moncayo, Ecuador.
The study found that glyphosate was detected in 98% of the participants, while 2,4-D was found in 66%. Elevated levels of 2,4-D were associated with decreased performance in attention and inhibitory control, memory and learning, and language skills. Glyphosate was notably linked to lower scores in the domain of social perception.
What methods were used to assess the impact of herbicides on adolescents?
The researchers collected urine samples to measure the concentrations of metabolites from glyphosate and 2,4-D, along with the insect repellent DEET. They also evaluated neurobehavioral capacities in five domains: attention and inhibitory control, memory and learning, language skills, visuospatial processing, and social perception.
What is the significance of the findings in a broader context?
The findings are significant as they add to the growing body of evidence suggesting that exposure to environmental toxins like herbicides may contribute to the rise in chronic diseases and mental health disorders among adolescents and young adults. The study identifies potential risks associated with widely-used herbicides, opening avenues for further research.
Are there any future plans for this research?
Yes, the researchers plan to continue monitoring the study participants to evaluate whether the observed associations persist into early adulthood. This is part of a larger ongoing cohort study called ESPINA, which aims to understand the effects of pesticide exposure on human development from childhood through adulthood.
Who funded this research?
The research was funded, in part, by the National Institutes of Health, the National Institute of Environmental Health Sciences, and the National Institute of Occupational Safety and Health, along with other private funding sources.
What are the implications for public health and policy?
The results point to the urgent need for a deeper understanding of the safety and long-term effects of herbicides and other environmental chemicals. This could lead to revisions in regulations and guidelines concerning the use of these substances, especially in settings where children and adolescents could be exposed.
More about Adolescent Cognitive Effects of Herbicides
- Herbert Wertheim School of Public Health at UCSD
- Environmental Health Perspectives Journal
- National Institute of Environmental Health Sciences
- National Institute of Occupational Safety and Health
- ESPINA: The Study of Secondary Exposures to Pesticides Among Children and Adolescents
- National Institutes of Health Funding Information