The active ingredients in commonly used bug sprays such as RAID leave significant residues that persist for over a year in the home, according to a study published by Brazilian researchers in the journal Environmental Toxicology and Chemistry. The pesticides tested, synthetic pyrethroids, have been linked to a range of health effects, most notably in children. The results of this study add to calls for homeowners to rethink a chemical-based approach to home pest control, in favor of simple, non-toxic practices.

In the recent study, researchers compared the breakdown time of two synthetic pyrethroids, cypermethrin and beta-cyfluthrin, between laboratory conditions and those in an average home. Under lab conditions, with temperature controlled and without sunlight or ventilation, both active ingredients broke down little within the 112 day test period observed. However, the test house, where insecticides were applied according to indoor label conditions, displayed breakdown times similar to the lab results during the first 112 days. Researchers continued their observation of pyrethroids in the home for up to a year, finding after that period 44% of beta-cyfluthrin and 70% cypermethrin remained in household dust samples from the singular, original application.

A 2014 study published by scientists at the University of California, Davis, found that homes with detectable levels of pyrethoids in floor wipe tests were associated with higher levels of pyrethoids in their urine. In their study of both adults and children in California communities, 63% of participants had detectable levels of pyrethroids in their urine. Exposure and presense of these chemicals in the human body has been linked to concerning health effects. A 2013 study published by Canadian researchers found high scores on emotional difficulties tests and conduct problems in children was significantly associated with the use of pesticides in or around the home. Another study published by French scientists earlier this year reinforced the Canadian study’s results, finding strong associations between childhood behavioral problems and pyrethroid pesticide exposure. A 2017 study found that urinary metabolite levels of cypermethrin were associated with an increase in early onset of puberty in boys. In addition to developmental and behavioral problems, past research has connected pyrethroid use to cancer. A 2013 study found that termite applications in the home within a year of pregnancy increased the risk of a child developing a brain tumor by twofold.