Insecticides linger in homes, study finds

The insecticides found in roach sprays, flea bombs, ant traps and pet shampoos persist indoors for years after use and collect in the bodies of both adults and children, for whom they may pose health risks, a new UC Davis study has concluded.

Levels of the insecticides – called pyrethroids – were found in a majority of the 173 children and adults tested from 2007-09 in Northern California. Of those families, 22 hailed from the Sacramento region, with 11 from Sacramento County and five from Yolo County.

Pyrethroids, which are synthetic chemicals, have been linked to respiratory ailments, heart palpitations and nausea in farmworkers and have been identified as an endocrine disruptor in lab animals.

“It’s an important pathway for children,” said Kelly Trunnelle, postdoctoral scholar in environmental toxicology at UC Davis and lead researcher of the study.

She said researchers took wipe samples from floor surfaces of homes and also measured urine levels of mothers as well as children born between 2000 and 2005.

The study found levels of multiple pyrethroids in 50 of 83 children tested, and 58 of the 90 adults tested. Exposure differed between mothers and children, and the study found the levels of the pyrethroids found in the floor samples are statistically related to what was found in the urine levels of the children tested. The same correlation was not found with the mothers, said researcher Deborah Bennett, professor of environmental and occupational health at UC Davis.

“That would indicate a child is getting a greater level of pyrethroid exposure from the home environment than the mother,” Bennett said. “The pyrethroid levels in the mothers likely originated from diet or outdoor environmental exposure.”

To date, scant research has been done on pyrethroids, which are commonly used for farming as well as in household products, Bennett said. However, studies on the chemical are increasing, as are concerns about its possible health effects such as endocrine disruption and autism. A 2008 study found that the pyrethroid esfenvalerate delayed the onset of puberty in laboratory rats. A UC Davis study that same year found mothers of autistic children had shampooed their pets with antiflea and antitick shampoos during pregnancy. In that study, the mothers reported they did so twice as much as mothers that gave birth to typically developing children.

Pyrethroids go under other names, including bifenthrin, cypermethrin, and esfenvalerate. The botanical variant is called pyrethrin. Farmers use the chemicals for pest control and they have been linked to respiratory problems in farmworkers, according to the California Department of Public Health.

In 2011, the Environmental Protection Agency found that pyrethroids do not pose any significant health risk concerns for children or adults. However, the EPA also found that in some scenarios – with toddlers’ exposure to the insecticide embedded in carpeting, or from frequent fogger use – exposure levels were above the agency’s level of low concern.

Use of pyrethroids has grown since the insecticide chlorpyrifos was phased out in 2001, Trunnelle said. Chlorpyrifos, phased out because of its neurological health effects, was also found inside the homes tested in the study. Because chlorpyrifos was phased out over a decade ago, its presence, however reduced, suggests that use of the chemicals should be closely monitored given their long-lasting nature in the home.

The state Department of Pesticide Regulation and the U.S. Environmental Protection Agency have been reviewing epidemiological studies on chlorpyrifos and are collaborating on a draft risk assessment that may lead to future regulation of the pesticide at the federal level, said Charlotte Fadipe, spokeswoman for the state agency.

In agricultural use, the chemical binds to soil and quickly degrades in the sun. “In an indoor environment you lack the sunlight to break the pesticide down,” Trunnelle said. “The thing to be wary of is that these products, when used inside the home, last a very long time.”

Trunnelle was lead researcher in a 2012 study of agricultural families in Mendota. That study found pyrethroid in 67 percent of household dust. A 2010 study of farmworker families in the Salinas area and urban homes in Oakland found that all household dust tested showed evidence of pyrethroid levels.

More research will be needed to assess the long-term exposure effects of agricultural workers to pyrethroids and what effect the insecticide may have when it is brought into the home, Trunnelle said.

“It’s well-documented that pyrethroids and chlorpyrifos are more persistent in the indoor environment,” Trunnelle said. “Unfortunately, this information may not be widely understood by the general public.”