Disturbing link discovered between popular weed killers and child brain dysfunction

SAN DIEGO — Researchers from the University of California-San Diego have found a disturbing connection between exposure to certain herbicides and decreased brain function among teenagers. Herbicides are commonly used chemicals meant to kill unwanted plants and are commonly found in farming, households, and industrial settings.

The study analyzed urine samples of 519 adolescents between 11 and 17 years-old from the agricultural county of Pedro Moncayo, Ecuador. These samples were collected in 2016 and were tested for the presence of chemicals from two commonly used herbicides – glyphosate and 2,4-dichlorophenoxyacetic acid (2,4-D), as well as the insect repellent DEET. Along with this, researchers also examined the teens’ performance in various cognitive areas such as attention, memory, language, spatial abilities, and social understanding.

“Many chronic diseases and mental health disorders in adolescents and young adults have increased over the last two decades worldwide, and exposure to neurotoxic contaminants in the environment could explain a part of this increase,” says study senior author Dr. Jose Ricardo Suarez, associate professor in the Herbert Wertheim School of Public Health at UC San Diego, in a media release.

Significant findings from the study include:

  • Glyphosate, used extensively in crops like corn and soy and for managing unwanted plants in residential areas, was found in a whopping 98 percent of the participants.
  • 2,4-D, another herbicide used in various settings such as lawns, water bodies, and farmlands, was detected in 66 percent of the participants.
  • Higher concentrations of 2,4-D were linked with poorer performance in areas of attention, memory, and language.
  • Glyphosate showed a negative impact on the teenagers’ ability to recognize emotions.
  • DEET, the insect repellent, was not found to affect cognitive performance.
spraying pesticide
(Photo by Prakash Aryal from Pexels)

“There is considerable use of herbicides and insecticides in agricultural industries in both developed and developing nations around the world, raising exposure potential for children and adults, especially if they live in agricultural areas, but we don’t know how it impacts each stage of life,” notes study first author Briana Chronister, a doctoral candidate in the UC San Diego – San Diego State University Joint Doctoral Program in Public Health.

Previous research has already shown links between exposure to certain insecticides and altered brain function. Today, about 20 percent of teenagers and 26 percent of young adults are diagnosed with mental health issues ranging from anxiety and depression to learning disorders.

“Hundreds of new chemicals are released into the market each year, and more than 80,000 chemicals are registered for use today,” says Dr. Suarez. “Sadly, very little is known about the safety and long-term effects on humans for most of these chemicals. Additional research is needed to truly understand the impact.”

This particular research is a segment of ESPINA: The Study of Secondary Exposures to Pesticides Among Children and Adolescents, which seeks to understand the effects of pesticide exposure on human development from childhood to adulthood. This extensive research is funded by various organizations, including the National Institute of Environmental Health Sciences and the National Institute of Occupational Safety and Health.

Dr. Suarez and his team are planning to continue their research to see if the observed effects persist as the study participants transition into early adulthood.

The study is published in the journal Environmental Health Perspectives.

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