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

chemicals used has decreased (Table 26). However, some AChE a.i.s – such as bensulide
and naled – are increasing in use (CDPR 2007). While the trend indicates decreased
reliance on these products, we note that their current use remains significant.
Table 26. Use figures for AChE inhibiting pesticides in California (CDPR 2007)
1996 2006
lbs a.i. applied 15,473,843 6,857,530
Acres treated (agriculture use only) 11,720,058 5,729,958
Mixtures of organochlorine pesticide compounds were also common in fish-tissue
samples from most streams. About 90% of fish samples collected from urban steams
contained two or more pesticide compounds and 33% contained 10 or more pesticides.
Similarly, 75% of fish samples from streams draining watersheds with agricultural and
mixed land use contained 2 or more pesticide compounds and 10% had 10 or more
compounds (Gilliom, Barbash et al. 2006).
NAWQA analysis of all detections indicates that more than 6,000 unique mixtures of 5
pesticides were detected in agricultural streams (Gilliom, Barbash et al. 2006). The
number of unique mixtures varied with land use. Mixtures of the most often detected
individual pesticides include the herbicides atrazine (and its degradate deethylatrazine),
metolachlor, simazine, and prometon. Each herbicide occurred in more than 30% of all
mixtures found in agricultural and urban uses in streams. Also present in more than 30%
of the mixtures were cyanazine, alachlor, metribuzin, and trifluralin in agricultural
streams. Dacthal and the insecticides diazinon, chlorpyrifos, carbaryl, and malathion
were also present in urban streams. Carbaryl occurred in at least 50% of urban streams.
In 15% of urban streams carbaryl concentration was over 0.1μg/L (Gilliom, Barbash et al.
2006). Insecticides are typical constituents in environmental mixtures and are commonly
found in both agriculatural and urban streams.
The numbers of unique mixtures of organochlorine pesticide compounds found in wholefish
tissue samples were greater in urban streams than in streams from agricultural or
mixed land use watersheds. About 1,400 unique 5-compound mixtures were found in
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