January 26, 1998
Safety Measures Won't Protect Children from Chlorpyrifos
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.
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