A new study links a commonly used household pesticide with attention deficit hyperactivity disorder (ADHD) in children and young teens.
The study found an association between pyrethroid pesticide exposure and ADHD, particularly in terms of hyperactivity and impulsivity, rather than inattentiveness. The association was stronger in boys than in girls.
The study, led by researchers at Cincinnati Children’s Hospital Medical Center, is published online in the journal Environmental Health.
“Given the growing use of pyrethroid pesticides and the perception that they may represent a safe alternative, our findings may be of considerable public health importance,” says Tanya Froehlich, MD, a developmental pediatrician at Cincinnati Children’s and the study’s corresponding author.
Due to concerns about adverse health consequences, the United States Environmental Protection Agency banned the two most commonly used organophosphate (organic compounds containing phosphorus) pesticides from residential use in 2000-2001. The ban led to the increased use of pyrethroid pesticides, which are now the most commonly used pesticides for residential pest control and public health purposes. They also are used increasingly in agriculture.
Pyrethroids have often been considered a safer choice because they are not as acutely toxic as the banned organophosphates.
But animal studies have suggested a heightened vulnerability to the effects of pyrethroid exposure on hyperactivity, impulsivity and abnormalities in the dopamine system in male mice. Dopamine is a neurochemical in the brain thought to be involved in many activities, including those that govern ADHD.
In this study, researchers found that boys with detectable urinary 3-PBA, a biomarker of exposure to pyrethroids, were three times as likely to have ADHD compared with those without detectable 3-PBA. Hyperactivity and impulsivity increased by 50 percent for every 10-fold increase in 3-PBA levels in boys. Biomarkers were not associated with increased odds of ADHD diagnosis or symptoms in girls.
“Our study assessed pyrethroid exposure using 3-PBA concentrations in a single urine sample,” says Dr. Froehlich. “Given that pyrethroids are non-persistent and rapidly metabolized, measurements over time would provide a more accurate assessment of typical exposure and are recommended in future studies before we can say definitively whether our results have public health ramifications.”
An earlier study from Rutgers University also provided strong evidence that exposure to pyrethroid pesticides, including deltamethrin, may be a risk factor for ADHD. That study found that even though the pesticide was no longer detected in the systems of the test mice when they reached adulthood, the ADHD-like behaviors persisted.
To recognize pyrethroid pesticides, read the label on the front of the product, and look for the list of active ingredients.
Pyrethroid common names always end in either -thrin or -ate. Examples include allethrin, resmethrin, permethrin, cyfluthrin, and esfenvalerate.
Do not confuse pyrethroid with pyrethrins. Pyrethrins still refers to the original plant-derived mixture from chrysanthemum flowers, which many organic gardeners use. Pyrethrins are organically derived – but there is nothing natural about pyrethroid insecticides. So, if you would like to garden organically, don’t confuse pyrethroids with pyrethins.
The Natural Resources Defense Council provides the following information about pyrethroids:
Pyrethroids are used widely in home insect-control products, including flea bombs, roach sprays, ant bait, flea-and-tick pet shampoos, and lice shampoos. They are toxic to humans and dogs, and are particularly lethal to cats, bees, and fish.
Young children are particularly at risk because they play on surfaces that may have been treated and frequently put their hands in their mouth. People can also absorb the chemicals through the skin while bathing a pet or from lice shampoos.
People also take in pyrethroids from eating conventionally grown fruits and vegetables. Children who regularly ate conventional produce were exposed continuously to pyrethroids in the diet punctuated by high exposures when pesticide products were used in the home, according to a 2009 study in the Journal of Exposure Science and Environmental Epidemiology.
Pyrethroids are also used for insect control in schools and restaurants, in mosquito-abatement programs, and on livestock.
The best way to avoid pyrethroids? Use less toxic and chemical-free options for pest management and pet care. Consume organically-grown produce when possible. Levels of pesticides tend to be highest in the following types of produce: peaches, apples, nectarines, sweet bell peppers, celery, strawberries, cherries, pears, imported grapes, spinach, lettuce, and potatoes.