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

maximum concentrations. Maximum concentrations reported for the various land categories
were: agricultural land (7 μg/L), mixed land use (0.678 μg/L), urban land use (0.034 μg/L), and
undeveloped land use (0.034 μg/L). An additional table summarizing NAWQA data (1984-
2004) by state (California, Idaho, Oregon, and Washington) reported a maximum concentration
of 32.2 μg/L. This concentration occurred in surface water sampled from Zollner Creek, near
Mt. Angel, Oregon on April 17, 2002, and was also the maximum residue found in the database
on a national scale. CDPR data (1990-2003) were presented by county. Zollner Creek is a
tributary to the Willamette River and within the distribution of threatened Upper Willamette
River Chinook salmon and Upper Willamette River steelhead. The maximum concentration
measured in California was 5.5 μg/L, in Imperial County. Date and specific location were not
provided.
The BEs for carbaryl (EPA 2003) and methomyl (EPA 2003) provided less detailed information
about monitoring data on a national basis. The BE for carbaryl provided a national maximum
reported concentration of 5.5 μg/L, and noted that carbaryl was the second most commonly
detected insecticide in the NAWQA database. It also noted there were more frequent detections
and higher concentrations in urban streams than in streams draining agricultural or mixed land
use areas. The BE for methomyl reported that few national level monitoring data were available,
and reported data located in EPA’s STORET database. The highest reported concentration
nationally was 1 μg/L (in Texas).
Table 53. National Maximum Concentrations of Carbaryl, Carbofuran, and Methomyl as Reported
in EPA BEs (EPA 2003a, EPA 2003b, and EPA 2004)
Pesticide
Maximum
Concentration (μg/L)
Data Source Years Reported
Carbaryl 5.5 USGS NAWQA 1991-1998
Carbofuran 32.2 USGS NAWQA 1984-2004
Methomyl 1.0 EPA STORET Not Reported
1-Napthol Not Reported
USGS NAWQA Data for California, Idaho, Oregon, and Washington
We obtained updated data from the USGS NAWQA database to evaluate the occurrence of
carbofuran, carbaryl, methomyl, and 1-napthol (a degradate of carbaryl) in surface waters
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