Pyrethroids are a class of common pesticide found in a variety of household plant and bug sprays that many people believe to be harmless to humans ̶ or at least less harmful ̶ because their key ingredient is derived from chrysanthemum flowers. But that may not, in fact, be the case, suggests recent research from UCLA Health.
A study published late last year of older adults who live in California’s Central Valley and are exposed to pyrethroids from agricultural pesticides found them to be at greater risk for depression and anxiety disorders.
Beate Ritz, MD, PhD, professor of neurology in the David Geffen School of Medicine at UCLA, describes the environment in which the study participants live as a toxic “soup of pesticides.” Her research lays the groundwork for a more in-depth examination of the relationship between these pesticides and mental illness.
To reach their conclusion, Dr. Ritz and her colleagues examined records of agricultural pesticide use over the past 40 years from the California Department of Pesticide Regulation and cross-referenced that with responses from study participants who reported what medications they were taking and if a physician had ever diagnosed them with anxiety or depression. By combining this information with crop and land-use data, they were able to calculate the level of pyrethroid pesticides in use within 500 meters of the home of each participant who reported a diagnosis of anxiety or depression.
When those who had been diagnosed with depression or anxiety were compared with a healthy control group, the correlation between pyrethroid exposure five years prior to the diagnosis and behavioral health issues appeared to be clear.
For those with greater exposure, “We saw consistent associations with MD-diagnosed depression, MD-diagnosed anxiety and depression medications,” said co-researcher Melissa Furlong, assistant professor of environmental health sciences at the University of Arizona.
The study has potentially significant implications for consumers who live well outside of agricultural areas. The use of pyrethroid pesticides, which are less toxic in the short term than other pesticides but have been shown to cause damage over the long term to the nervous system of susceptible individuals, has increased in both agricultural and household products over the past 20 years. They now are the active ingredient in most home and garden pesticides, including roach foggers and fruit and vegetable and flea and tick sprays.
Based on these findings, Dr. Ritz cautions consumers to be wary. “I would not use pyrethroids to kill insects inside my home,” she said.
Caroline Seydel is the author of this article.
