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

exposure values for a few labeled uses using the GENEEC model, which is intended to
provide screening estimates over large geographic regions (Table 50) 1 . The input
parameters used were consistent with recent EPA model inputs (EPA 2006; EPA 2007;
EPA 2007).
Table 50. GENEEC estimated concentrations of carbaryl, carbofuran, and methomyl in
surface water adjacent to sweet corn, potatoes, sweet corn, potatoes, and citrus.
Chemical use Rate No.* Interval Buffer EEC (μg/L)
Foliar/ ground
application
lbs/
acre
days ft
Sweet Corn
Carbaryl 2 8 3 0 397 390 348 272 229
Carbofuran 0.5 2 7 0 56 56 55 54 53
Methomyl
0.45
0.225
14
28
1
1
25
25
Potatoes
307
288
276
259
163
153
72
68
49
46
Carbaryl 2 3 7 0 175 172 153 120 101
Carbofuran 1 2 5 0 112 112 111 108 106
Methomyl 0.9 5 5 25
Citrus
212 191 113 50 34
Carbaryl 12 1 - 0 485 476 424 332 280
Carbofuran - - - - - - - - -
Methomyl 0.9 3 5 25 133 120 71 31 21
*Number of applications
-Not applicable
The EECs for EPA’s effect determinations were derived primarily using the PRZM-
EXAMS model. This model predicts runoff to a “farm pond” based on application
specifications (rate and method), properties of the a.i. (solubility, soil adsorption
coefficient, soil metabolisms rate, etc.,), assumed meteorological conditions (amount of
rainfall), and other site-specific assumptions [soil type, slope, etc. (EPA 2004)]. The
farm pond scenario is likely a poor surrogate of certain habitats used by salmonids.
In particular, listed salmonids rely extensively upon a variety of off-channel habitats that
would be expected to yield higher pesticide concentrations than would be predicted with
the “farm pond” based PRZM/EXAMS model. Examples of off-channel habitats include
1 EPA characterizes GENEEC as a tier-1 screening model (EPA 2004c). GENEEC is a meta-model of the
PRZM-EXAMS model that incorporates assumptions that are intended to model exposure estimates on a
site vulnerable to runoff. The size of the treated area and aquatic habitat (farm pond) are the same as
described for PRZM-EXAMS.
284
24-h
avg
4-d
avg
21-d
avg
60-d
avg
90-d
avg