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Jonathan Campbell

Helping people take charge of their health

January 26, 1998

A new study shows that household use of chlorpyrifos products can lead to exposures well above the level considered safe by the U.S. Environmental Protection Agency (EPA), even when used according to the manufacturer's instructions. The study suggests that children have a particularly high risk of being exposed to dangerous levels of chlorpyrifos.

Chlorpyrifos, a broad-spectrum organophosphate insecticide, is one of the most widely used pesticides in the United States. Sold under the brand names Dursban and Lorsban (both manufactured by DowElanco of Indianapolis, Indiana), it is the sixth most commonly used pesticide in U.S. home and garden applications. Approximately two to four million lbs. were applied in homes and gardens in 1995.

Potentially hazardous exposures may occur as a result of household applications, according to scientists from the Environmental and Occupational Health Sciences Institute of Rutgers University in Piscataway, New Jersey, who authored the new study. The study, published in Environmental Health Perspectives, investigates levels of chlorpyrifos adhering to surfaces and objects in a room after it has been treated with the pesticide and then ventilated according to the manufacturer's instructions. The authors propose that the semi-volatility of the pesticide allows it to be deposited on surfaces in treated rooms weeks after application; it may adhere to objects such as children's toys that are brought into the room hours or days after the pesticide is applied.

To test this proposal, the authors treated rooms in two apartments with Dursban and then opened windows and used fans to ventilate the rooms for the recommended four hours. After a fifth hour, they placed groups of plastic and plush toys in the rooms, and periodically thereafter removed one plastic toy and one plush toy to measure surface chlorpyrifos contamination. They found that significant amounts of chlorpyrifos were volatilizing from other surfaces and adhering to the toys long after the pesticide was applied. Peak deposits on surfaces in the room took place 36 hours after the original application.

The authors conclude that applications of chlorpyrifos could result in significant doses of the pesticide to children who play in recently treated rooms. For a child between the ages of three and six, the total nondietary dose of chlorpyrifos after normal home treatment was calculated by the authors to be about 208 micrograms per kilogram of body weight per day (micrograms/kg/day) -- well above the EPA's reference dose for chlorpyrifos of 3 micrograms/kg/day (the daily dose that the agency believes is unlikely to cause any harm over a lifetime). For children who exhibit high levels of hand-to- mouth activity, the authors conclude that this dose could be as high as 634 micrograms/kg/day. The study also demonstrates that dermal and oral exposure to the pesticide via toys and other surfaces may present a greater risk to children than inhalation of chlorpyrifos.

According to an Environmental Health Perspectives assessment, this study is likely to shed doubt on whether a June 1997 agreement between EPA and industry to reduce consumer exposure to the pesticide will be sufficient to protect children. That agreement calls for elimination of chlorpyrifos in pet products such as flea dips and shampoos and in broadcast pesticide products such as foggers. The agreement also commits chlorpyrifos manufacturers to take steps to ensure that the pesticide is not applied on inappropriate surfaces such as toys, drapes, and furniture. New warning labels, based on the agreement, should begin appearing on chlorpyrifos products sometime this year.

Though the treatment used in the study apartments was a broadcast application of chlorpyrifos, which industry and the EPA have already agreed to phase out, the research indicates that more care must be taken than previously thought to avoid exposures to this pesticide. It also signals that regulators can no longer simply measure air concentration to determine if dangerous levels of certain pesticides are present.

Source: Environmental Health Perspectives, Volume 106, Number 1, January 1998.

Contact: PANNA

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Pesticide Action Network North America (PANNA) 116 New Montgomery, #810, San Francisco, CA 94105 Phone:(415) 541-9140 Fax:(415) 541-9253  http://www.panna.org/panna/

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