(Beyond Pesticides, June 17, 2009)
A new study finds that toxic pesticides, including those already banned, persist in homes. The study’s results indicate that most floors in occupied homes in the U.S. have measurable levels of insecticides that serve as sources of exposure to home dwellers. These persistent residues continue to expose people, especially vulnerable children, to the health risks associated with these chemicals.
Published in Environmental Science and Technology, the study, entitled “American Healthy Homes Survey: A National Study of Residential Pesticides Measured from Floor Wipes,” was conducted as a collaboration between the U.S. Environmental Protection Agency (EPA) and the U.S. Department of Housing and Urban Development. Five hundred randomly selected homes were sampled using alcohol wipes to collect dust from hard surface floors, mostly kitchen floor surfaces. The swipes were analyzed for 24 currently and previously use residential insecticides in the organochlorine, organophosphate, pyrethroid and phenylpyrazole classes, and the insecticide synergist piperonyl butoxide.
Researchers found that currently used pyrethroid pesticides were, not surprisingly, at the highest levels with varied concentrations. Fipronil and permethrin, both currently used, were found in 40 percent and 89 percent of homes respectively. However, the researchers found that long discontinued pesticides like DDT and chlordane were found in 42 percent and 74 percent of homes respectively, with DDE, the breakdown product of DDT, also found in 33 percent of homes. Even chemicals no longer permitted for residential use, such as chlorpyrifos and diazinon, were detected in 78 percent and 35 percent of homes. The results, according to most commonly detected, are arranged as follows: permethrin (89%), chlorpyrifos (78%), chlordane (64%), piperonyl butoxide (52%), cypermethrin (46%), and fipronil (40%).
The authors point out that the “high detection frequencies observed for chlordane, chlorpyrifos, and permethrin suggest these compounds are essentially ubiquitous in our living areas and that popular use, both past and present, has a major influence on their occurrence in homes.” Children are at particular health risk given their more frequent contact with flooring, as well as hand to mouth activity. Concerning is the fact that DDT was found in a higher percentage of homes than its breakdown product, DDE. This could mean that DDT is not degraded well in homes, due to a lack of sunlight or microbes, and that residents are being exposed to current sources of DDT.
This is not the first study to document the prevalence of pesticide residues in households. In 2008, a study found significant amounts of pyrethroid pesticides in indoor dust of homes and childcare centers. Other studies throughout the years have also documented the occurrence of pesticide residues in indoor dusts and air samples, including a sampling of homes of pregnant women which found that 75% of their homes were contaminated with pesticides. A 1998 study (Gurunathan, S. et al) found that chlorpyrifos accumulated on furniture, toys and other sorbant surfaces up to two weeks after application, while another 1996 study (Nishioka, M., et al) found that the herbicide 2,4-D can be tracked from lawns into homes, leaving residues of the herbicide in carpets.
Exposure to synthetic pyrethroids has been reported to lead to headaches, dizziness, nausea, irritation, and skin sensations. There are also serious chronic health concerns related to synthetic pyrethroids. EPA classifies permethrin as a possible human carcinogen, based on evidence of lung tumors in lab animals exposed to these chemicals. Many synthetic pyrethroids have been linked to disruption of the endocrine system, which can adversely affect reproduction and sexual development, interfere with the immune system, and increase chances of breast cancer. Children are especially sensitive to the effects of permethrin and other synthetic pyrethroids. A study found that permethrin is almost five times more toxic to eight-day-old rats than to adult rats due to incomplete development of the enzymes that break down pyrethroids in the liver.