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Carbaryl: One Poison for Another in Urban Creeks
A recent analysis of contamination in urban creeks has found that homeowners in the Pacific Northwest have responded to recent bans on lawncare insecticides by dumping another, equally dangerous pesticide on their lawns. Carbaryl, a likely carcinogen that attacks the nervous system and is highly toxic to aquatic invertebrates, is now a major contaminant in creeks in Seattle and Portland. Sales of the insecticide have also increased, in some areas as much as tenfold, as bans of lawncare uses of diazinon and chlorpyrifos went into effect in 2003 and 2002. Meanwhile, the U.S. Environmental Protection Agency (EPA) is concluding its re-registration of carbaryl and proposes to limit only a fraction of uses, none of which will substantially address the increased stream concentrations that are now a primary concern for endangered salmon in the Northwest.
The study, Toxic Tradeoff: Exit Diazinon, Enter Carbaryl, by the Clean Water for Salmon Campaign, Northwest Coalition for Alternatives to Pesticides (NCAP) and Washington Toxic Coalition (WTC) compared U.S. Geological Survey (USGS) water sampling data for two urban creeks in the Pacific Northwest: Thornton Creek in Seattle and Fanno Creek near Portland. The analysis also looked at sales records for carbaryl (primarily sold under the product name Sevin) and diazinon in retail stores in surrounding watersheds. The study focused on diazinon because chlorpyrifos is not often found in Northwest surface water. Diazinon concentrations in both creeks decreased between the phaseout period, 2000 to 2004, and generally coincided with a sharp decrease in sales of diazinon in 2002.
Meanwhile, carbaryl sales and stream concentrations followed an opposite pattern, with sales climbing in 2002 and sampling data indicating more frequent detections in higher concentrations than ever before. National Academy of Science guidelines recommend that aquatic carbaryl concentrations not exceed 0.02 parts per billion. At Thornton Creek in 2002, four water samples detected carbaryl at levels between 0.054 to 0.48 ppb. Since then, five other samples have shown concentrations greater than the NAS guidelines. The study attributed the higher sales to use of granular formulations to control crane flies on residential lawns.
Carbaryl is a broad spectrum insecticide that inhibits the functioning of the nervous system and is widely used in agriculture and in residential landscaping. First registered for use by the EPA in 1959, the insecticide was targeted for review as early as 1972, when stronger health and environmental protections were incorporated in FIFRA (Federal Insecticide, Fungicide and Rodenticide Act). EPA is finally addressing carbaryl risks, with a draft interim registration decision (IRED) issued in 2003 that proposes no major changes for agricultural uses and will not eliminate the granular applications on lawns that are most problematic for fish and people in the Pacific Northwest. The EPA has recommended phasing out some residential garden and pet applications because they pose unacceptable exposure risks to infants and toddlers.
Multiple studies have reported greater incidence of childhood brain cancer in homes where carbaryl or products that may contain carbaryl are used and elevated risks of non-Hodgkins lymphoma among farmers using carbaryl. Laboratory studies have also found carbaryl an especially potent inhibitor of immune system responses, and found it mimics the hormones estrogen and progesterone.
The report faults the EPA environmental review of impacts on endangered salmon, noting the agency issued a “not likely to affect” determination for carbaryl on Puget Sound Chinook, despite the USGS data on rising concentrations in salmon streams. The agency has recently announced it will re-do its effects determination, but it is not clear if the new evaluation will incorporate important evidence of sub-lethal impacts that the agency has previously ignored, such as reducing the ability of salmon to metabolize food and resist parasites or the impacts of carbaryl on the aquatic invertebrates that are a major source of food for salmon.
Once the EPA phaseout of residential uses of diazinon and chlorpyrifos began to take effect, manufacturers aggressively marketed carbaryl as a replacement. Toxic Tradeoff reports that mailers for Sevin were sent to Master Gardeners around the country in 2004, offering a free ten-pound bag of the granular formulation to “test on your lawn or use in field trials.” Manufacturers also continue to promote insecticides containing pyrethroids, which are also harmful to aquatic life.
Not willing to stand by while pesticide manufacturers dangle substitute pesticides in front of consumers, local governments concerned about water quality impacts in the Pacific Northwest have developed consumer advisories for non-toxic lawn care. The report suggests that EPA should take a page from these local efforts and encourage use of these established, non-chemical alternatives for lawn care.
EPA closed a public comment period for modifying all tolerances for food residues of carbaryl as recently as May 31, 2005. Research on alternatives to carbaryl and full evaluation of the ecological and human health risks of carbaryl products are commonsense steps EPA could take to stop the toxic tradeoff of one toxic pesticide for another.
Sources: Toxic Tradeoff, Exit Diazinon, Enter Carbaryl,Phaseout Leads to Risk Replacement, Erika Schreder and Philip Dickey, A Clean Water for Salmon Campaign report, May 2005, Washington Toxics Coalition, http://www.watoxics.org; US EPA IRED, Carbaryl, REDs and Pesticide Re-registration Status, http://www.epa.gov/pesticides.
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