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Wipe your shoes
carefully after walking on a lawn or garden treated with herbicides -- otherwise, you could be bringing dangerous chemicals into your home that will linger in carpets and household dust for a year or more, according to a study published in the November issue of
Environmental Science and Technology.
Researchers found that 3 percent of "dislodgeable turf residues" -- the portion of a pesticide that does not adhere to the turf -- were tracked indoors. In homes with carpeting, almost all of the pesticide became deeply-imbedded carpet dust, where it can't degrade through exposure to sunlight, wind, rain or soil microbes. Although the authors reported that only 10 percent of the residue stays on carpet surfaces where it can easily contact human skin, previous research has suggested that transport of pesticides into homes presents significant risks of human exposure, particularly for children who may ingest residues through hand-to-mouth behavior. | |
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In the study,
researchers applied a pesticide formulation
containing 2,4-D, dicamba and mecoprop (X-Gro Broadleaf Weed
Killer) to sections of a lawn that had not been treated with
pesticides for at least 10 years. Participants then walked on
the treated plots, staggering their times and walking in
different areas so that most of the treated ground was
covered. They then either wiped their feet on a mat or walked
directly onto indoor carpeting, both of which had never been
used before. Researchers analyzed residues tracked onto the
carpets as well as levels of
turf dislodgeable residues on the lawn.
Use of entryway mats reduced the level of pesticide residues on carpet surfaces by 25 percent and reduced carpet dust residues by 33 percent. The researchers estimated that 2,4-D residues could remain in household carpet dust for up to one year after turf application at concentrations of approximately 0.3 micrograms/square meter. The authors stated that this level is consistent with levels of 2,4-D that they found in household dust of nine suburban homes. A range of health and environmental impacts have been associated with exposure to 2,4-D, including endocrine disruption, reproductive effects, cancer and toxicity to birds and fish; impacts associated with exposure to dicamba include neurological effects, non Hodgkins' lymphoma (cancer) and mutagenicity.
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The authors
described a recent study of 2,4-D in children's
urine that compared children from a town with a 2,4-D
factory to children from a town without such a
plant. The study found 2,4-D in 18 percent of children from the town
with the 2,4-D plant and 23 percent of children from the town
without the plant, implying that the presence of 2,4-D was
due to some factor or factors other than the manufacturing
plant.
The authors of the track-in study stated that "Given the fact that children's hand-to-mouth activity promotes ingestion of contaminated carpet dust, we might assume that chronic indoor exposure will follow a lawn application and may result in measurable urinary levels." The authors also pointed out that their control lawn, an area to which no herbicide was applied, offered information about spray drift levels. The study found that eight hours after application turf dislodgeable residues on the untreated plot were 2-3 percent of the levels found on treated turf plots at the same time. Detectable levels were also present in the carpet dust after track-in from the unsprayed plot. The authors surmised that their application gun may produce a finer aerosol than some commercial sprayers, which could result in more drift. They pointed out that previous agricultural drift studies have found drift levels up to 8 percent of the application loading rate.
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Albion Monitor February 18, 1997 (http://www.monitor.net/monitor)
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