Carbaryl, Carbofuran, and Methomyl - National Marine Fisheries ...

After states develop their lists of impaired waters, they are required to prioritize and
submit their lists to EPA for review and approval. States are expected to identify high
priority waters targeted for Total Maximum Daily Load (TMDL) development within
two years of the 303(d) listing process. A TMDL includes a plan for reducing
contaminant loading and is required for all impaired waterways. Each state also
establishes a priority ranking for the development of TMDLs for such waters, considering
the severity of the pollution and the uses to be made of such waters.
Federal non-priority water quality standards have been established for carbaryl and
carbofuran, but not for methomyl. The California 303(d) list includes a 49 mile section
of the Colusa Basin Drain that exceeds carbofuran standards (Category 5). Several areas
in Washington and Oregon have been listed under Category 2 for carbaryl and
carbofuran. They include: Willapa Bay, WA (carbaryl, 18 separate listings); Grays
Harbor County Drainage Ditch #1, WA (carbaryl); Pacific County Drainage Ditch #1,
WA (carbaryl); North River, WA (carbaryl); Palix River, WA (carbaryl); Johnson
Creek, OR (carbaryl & carbofuran, 23.7 river miles); Beaverton Creek, OR (carbaryl, 9.8
river miles); Tualatin River, OR (carbaryl, 44.7 river miles); and Mill Creek, OR
(carbofuran, 25.7 river miles). In addition to specific compounds, water bodies are listed
as impaired due to “pesticides” as a general category. We did not consider these
waterways as there was no way to tell what compounds were present.
Temperature is significant for the health of aquatic life. Water temperatures affect the
distribution, health, and survival of native cold-blooded salmonids in the Pacific
Northwest. These fish will experience adverse health effects when exposed to
temperatures outside their optimal range. For listed Pacific salmonids, water temperature
tolerance varies between species and life stages. Optimal temperatures for rearing
salmonids range from 10ºC and 16ºC. In general, the increased exposure to stressful
water temperatures and the reduction of suitable habitat caused by drought conditions
reduce the abundance of salmon. Warm temperatures can reduce fecundity, increase egg
survival, retard growth of fry and smolts, reduce rearing densities, increase susceptibility
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