(Beyond Pesticides, November 3, 2008) A new study, Pyrethroid pesticides and their metabolites in vacuum cleaner dust collected from homes and day-care centers (doi:10.1016/j.envres.2008.07.022), by the U.S. Environmental Protection Agency’s (EPA) National Exposure Research Laboratory finds concentrations of 13 synthetic pyrethroids and their degradates in indoor dust collected from homes and childcare centers in North Carolina and Ohio. The study results show the extent to which hazardous pesticides are present in indoor environments and threaten the public’s health, especially the health of children. With 85 vacuum cleaner bags analyzed, permethrin was present in all 85 dust samples, at least one pyrethroid pesticide was found in 69 samples and phenothrin was found in 36 samples.
According to the study findings published in the November issue of the journal Environmental Research, the median concentration of permethrin in the samples is 1454ng/g of dust. Excluding permethrin, pyrethroid conectrations are less than or equal to 100ng/g of dust. The majority of the metabolites are present in more than half of the dust samples.
This is not the first time researchers have found pesticides in dust in homes. A study published in the International Journal of Hygiene and Environmental Health (208: 193-199) also found that synthetic pyrethroids persist in house dust and air in significant concentrations for months after they are applied, disproving the popular myth that they are not long lasting. The researchers collected dust and airborne particles in 19 houses and buildings one day before treatments by pest control operators. They compared these baseline levels of synthetic pyrethroids to levels one day after the treatment, 4-6 months after, and 10-12 months after. One day after application, all of the pyrethroids were detected in significantly increased concentrations in the houses. Over the course of the following months, the concentrations all decreased. However, after 4-6 months, all four chemicals (cyfluthrin, cypermethrin, deltamethrin, and permethrin) could still be detected. As long as one year after treatment, both permethrin and cyfluthrin levels remained elevated in house dust, in what the authors called “general background level[s],” indicating that these two pyrethroids especially have very slow degradation times.
A 2003 study published in Environmental Science & Technology also found pesticides in the homes tested. The study authors measured concentrations of 89 different chemicals identified as endocrine disrupting compounds (EDCs) in indoor air and house dust samples from 120 homes on Cape Cod, Massachusetts. EDCs are chemicals that can mimic or interfere with human hormones. The study, “Phthalates, Alkylphenol, Pesticides, Polybrominated Diphenyl Ethers, and Other Endocrine Disrupting Compounds in Indoor Air and Dust,” detected 52 different compounds in air and 66 in dust. The number of chemicals detected in a home ranged from 13-28 for indoor air and from 6-42 for dust. Pesticides detected included DDT, carbaryl, chlordane, methoxychlor, propoxur, pentachlorophenol, diazinon, permethrin, and chlorpyrifos.
A 1998 study found that chlorpyrifos accumulated on furniture, toys and other sorbant surfaces up to two weeks after application. A separate study involving chlorpyrifos found substantially higher concentrations in the infant breathing zone. Airborne concentrations of seven insecticides were tested 3 days following their application in separate rooms. Six of the seven pesticides left residues behind through the third day. A 1996 study found that 2,4-D can be tracked from lawns into homes, leaving residues of the herbicide in carpets. EPA’s Non-Occupational Pesticide Exposure Study (NOPES) found that tested households had at least five pesticides in indoor air, at levels often ten times greater than levels measured in outdoor air. Another EPA study found 23 pesticides in indoor household dust and air that was recently applied or used in the home. The study also found residues of pesticides in and around the home even when there had been no known use of them on the premises.
Synthetic pyrethroids are chemically formulated versions of the natural-based pesticide pyrethrum, made from extracts from plants in the chrysanthemum family. A widely used class of insecticides, synthetic pyrethroids, are designed to be more toxic and longer lasting than pyrethrum, and therefore are more potent to insects and pose more risks to humans.
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. EPA lists permethrin as suspected endocrine disruptors. Synthetic pyrethroids have also been linked to respiratory problems such as hypersensitization, and may be triggers for asthma attacks. Material Safety Data Sheets, issued by the Occupational Safety and Health Administration (OSHA), for pyrethroid products often warn, “Persons with history of asthma, emphysema, and other respiratory tract disorders may experience symptoms at low exposures.” In view of the fact that asthma is the most common long-term childhood illness today, persistent residues of pyrethroids in house dust and air need to be taken very seriously.
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. Additionally, studies on newborn mice have shown that permethrin may inhibit neonatal brain development.
Although synthetic pyrethroids are often seen as safe alternatives to organophosphate insecticides, this study clearly demonstrates that when these chemicals are applied in houses, they do not disappear. Moreover, they are making their way into human bodies at alarming rates. At the same time, there are clear established methods for managing homes and schools that prevent infestation of unwanted insects without the use of synthetic chemicals, including exclusion techniques, sanitation and maintenance practices, as well as mechanical and least toxic
controls (which include boric acid and diatomaceous earth). Based on the host of health effects linked to this chemical class, synthetic pyrethroid use in the home is hazardous and unnecessary.