Pesticides linger in homes, whether we use them or not.
Stout, DM, KD Bradham, PP Egeghy, PA Jones, CW Croghan, PA Ashley, E Pinzer, W Friedman, MC Brinkman, MG Nishioka and DC Cox. 2009. American healthy homes survey: a national study of residential pesticides measured from floor wipes. Environmental Science and Technology 43:4294–4300.
A new study shows that pesticides, some already banned for decades from the US market, continue to persist in homes. Ongoing exposures to these pesticides should be considered in health risk assessments. Children could be at particular risk given their more frequent contact with flooring.
A National Home and Garden Survey conducted in 2000 and 2001 found that about 74 percent of US households use pesticides (Kiely et al. 2004). World pesticide use exceeded 5 billion pounds in 2001, and the US accounts for nearly 25 percent of the world's use.
In the US, herbicides make up the lion’s share of pesticide use, while insecticides account for about 9 percent of the total. Insecticides labeled for residential use are commonly used indoors to fight pests.
Fipronil is a slow acting insecticide used widely in the US for the control of insects such as cockroaches, ants, wasps and fleas. Its slow action allows time for the insect to return to its colony before taking effect. It is also the active ingredient in some topical flea treatments for dogs.
Fipronil is highly toxic to fish and other aquatic life, and has been recently shown to adversely affect thyroid function in rats.
Pyrethrins and pyrethroid compounds are used by both professionals and consumers to control a wide variety of insects. Pyrethrin compounds occur naturally in plants, while pyrethroids are manufactured chemicals. More than 1,000 synthetic pyrethroids have been created, but less than 12 of them are used in the US (ATSDR 2009)
New studies in animals and humans show that pyrethroids can alter the production of hormones and harm sperm production (Meeker et al. 2008).
Many pesticides that are no longer used and have been banned for years – sometimes even decades – continue to persist in the environment.
DDT, once commonly used to control mosquitoes and other disease-carrying insects, was banned for use in the US in 1973. It is still used in some parts of Africa and other tropical areas. DDT is long lived, can accumulate in fat and can act like estrogen hormones. Because it can act like a hormone, it interferes with many aspects of reproduction and development.
The insecticide is associated with many health effects in both humans and wildlife. In humans, DDT has been associated with impaired breast feeding, several cancers and other adverse health effects (reviewed by Longnecker et al. 1997). In wildlife, DDT causes egg shell thinning, genital malformations andreproductive impairment.
Bacteria and sunlight change DDT into another compound called DDE. DDE has similar health concerns as DDT.
Chlordane – a pesticide similar to DDT – was used on agricultural crops and residential lawns. It was banned for all uses in the US in the 1980s due to environmental and human health concerns.
Organophosphate compounds such as chlorpyrifos and diazinon replaced DDT as insecticides. However, these two chemicals were banned for household use in 2000 and 2004.
Chlorpyrifos is still heavily used in agriculture. Nearly 700 food crops are currently exposed to this chemical (US EPA 2006).
Technicians wiped hard surface floors with alcohol wipes to collect dust samples that could be analyzed for insecticide residues. Samples were taken from 500 homes across the US.
Most often, swipes were taken from kitchen floor surfaces away from heavy foot traffic and immediate cooking areas (i.e. in front of the stove).
The swipes were analyzed for 24 current and past use residential insecticides in the organochlorine, organophosphate, pyrethroid and phenylpyrazole classes, and the insecticide synergist piperonyl butoxide.
All 24 insecticides tested for were found in some of the homes.
Fipronil and permethrin, both currently used, were found in 40 percent and 89 percent of homes respectively.
DDT and chlordane – two pesticides that have been banned for decades – were found in 42 percent and 74 percent of homes respectively. DDE, the breakdown product of DDT, was found in 33 percent of homes.
Chlorpyrifos and diazinon, both no longer permitted for residential use for several years, were detected in 78 percent and 35 percent of homes respectively.
The currently used pyrethroid pesticides were found at the highest levels but concentrations varied greatly among houses and among different chemical types. Organochlorines and organophosphates were measured at much lower and fairly consistent levels among the houses tested.
This study shows that many insecticides, some of which have been banned for decades from the US market, continue to persist in homes. .
The persistence of now-banned pesticides, and emerging health concerns for current use pesticides such as permethrins and fipronil, highlight the need to further assess the dangers of the pesticides Americans are currently using. 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."
Adults and children living in these homes are most likely exposed to the chemicals, but at unknown levels and effects. Children could be at particular health risk given their more frequent contact with flooring. Since long-banned pesticides linger in US homes, future generations could also be exposed to them.
These newly-identified exposures should be considered in health risk assessments that guide public safety regulations, the authors recommend.
Despite their decades-long bans, DDT and chlordane (one of the three most frequently detected insecticides) were still present in many homes. DDT was found in a higher percentage of homes than DDE, its breakdown product. This could mean that DDT isn’t degraded well in homes due to a lack of sunlight or microbes. It could also mean that US residents are being exposed to current sources of DDT.
The currently used pyrethroids were the most common insecticides detected and also occurred at the highest levels – the insecticide permethrin had one of the highest concentrations measured. More surprising to the authors were the levels of chlorpyrifos, which seemed "elevated" considering it is no longer available for residential use
Permethrin was also found in nearly 90 percent of homes tested. This is a concern as research shows the chemical can damage human sperm and alter the production of hormones in animals. Beyond that, little is known about human exposure to and effects of permethrin. More research is needed given the high percentage of US homes with measurable amounts of this chemical on the flooring.
This study established a baseline for frequency and amounts of pesticides that can assist regulators in understanding the types and levels of common contaminants people are currently exposed to. Research such as this helps to identify household factors that could contribute to health concerns in the US.
Interim reregistration eligibility decision for chlorpyrifos. 2006. US Environmental Protection Agency.
Kiely, T, D Donaldson and A Grube 2004. Pesticides Industry Sales and Usage: 2000 and 2001 Market Estimates. U.S. Environmental Protection Agency, Office of Prevention, Pesticides, and Toxic Substances: Washington, DC.
Leghati, J, V Gayrard, N Picard-Hagen, M Camp, E Perdu, PL Toutain and C Viguie 2009. Fipronil-induced disruption of thyroid function in rats is mediated by increased total and free thyroxine clearances concomitantly to increased activity of hepatic enzymes. Toxicology, 255: 38-44.
Longnecker, MP, WJ Rogan and G Lucier 1997. The human health effects of DDT (dichlorodiphenyl-trichloroethane) and PCBs (polychlorinated biphenyls) and an overview of organochlorines in public health. Annual Review of Public Health 18: 211-244.
Pyrethrins and pyrethroids. Agency for Toxic Substances and Disease Registry.