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

fish, number of eggs per mature female, number of eggs spawned, and hatchability of eggs
(Carlson 1971). Fathead minnows were exposed to five treatments (8, 17, 62, 210, and 680 μg/L
[analytically verified]) of carbaryl in a flow through system for nine months; capturing the life
cycle of the fathead minnow. Fathead minnows showed reduced number of eggs per female and
reduced number of eggs spawned when exposed to 680 μg/L and of the eggs spawned, none
hatched (Carlson 1971).
The carbofuran BE (EPA 2004) stated that no full life cycle fish tests were available, and as it
did not report any early-life stage test results, presumably none of those were available either, as
the only data reported were for a partial life cycle test for rainbow trout (O. mykiss). Reported
NOAECs were based on growth effects, and no reproductive endpoints were discussed. A
definitive reference to the study was not provided in the BE. The carbofuran Science Chapter
(EPA 2005) reports on an early life stage test for rainbow trout, referring to it as Acc.#
GEOCAR08. We were unable to locate a specific citation for this study in the references but the
reported NOAEC (24.8 μg/L) and LOAEC (56.7 μg/L) were the same as the unreferenced study
discussed in the BE. However, the Science Chapter stated that larval survival was the most
sensitive endpoint of those evaluated, and that scoliosis was observed in the larval fish at
carbofuran concentrations ≥56.7 μg/L. The Science Chapter also references a sheepshead
minnow (Cyprinodon varigatus) early life stage study (MRID 432505-01) that resulted in a
NOAEC of 2.6 μg/L and LOAEC of 6.0 μg/L based on reduced embryo hatching. Specific
extent of reduced hatching was not reported. No sublethal effects, such as the scoliosis in the
rainbow trout, were mentioned in this study or two other studies on sheepshead minnow (MRIDs
408184-01 and 426974-01) that were submitted but did not produce definitive NOAECs or
LOAECs.
The Science Chapter for methomyl (EPA 1998) reports a NOAEC (57 μg/L) and LOAEC
(117 μg/L) for fathead minnow (Pimephales promelus) based on larval survival. Specific
reductions in larval survival were not reported. In the Science Chapter for methomyl (EPA
1998), the study is referred to as MRID 00131255 and Driscoll 1982 and appears to reference the
same study as Acc. 251424. The same data are reported in the BE (EPA 2003), but without any
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