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

Acute EC50s are also reported for several species of estuarine/marine shrimp in both the BE
(EPA 2003) and the RED Science Chapter (EPA 1998). Again, there are inconsistencies
between the documents, with the same EC50s from formulation tests reported in the BE as 30%
a.i. and in the Science Chapter as 24% a.i. Some EC50s were also reported for the a.i. Only one
species, grass shrimp (Palmonetes vulgaris) appears to have been tested with both the a.i. and the
formulation (EPA 2003). In this case, the formulation (EC50 130 μg/L, reported as a 30% a.i.),
appears less toxic than the technical (EC50 49 μg/L). Other EC50s listed in the BE were for
pink shrimp (P. duorarum, 19 μg/L) and mysid shrimp (M. bahia, 230 μg/L), both of which
appear to be technical a.i. (90-98.4%).
The methomyl BE (EPA 2003) reports NOAECs and LOAECs for reproductive endpoints for
two studies conducted on D. magna, both with the technical a.i. In one study, with a NOAEC of
0.4 μg/L and a LOAEC of 0.8 μg/L, the number of young per female was reduced. A second
resulted in a NOAEC of 1.6 μg/L and a LOAEC of 3.1 μg/L, based on an unspecified
reproductive endpoint. The BE also reports a NOAEC of 29 μg/L and a LOAEC of 59 μg/L for
the estuarine mysid shrimp, based on “reproduction and/or growth.”
The BE and Science Chapter both report on an outdoor microcosom study conducted with
methomyl (MRID 437444-02). The Science Chapter, Appendix C (EPA 1998), describes the
study design as: “Methomyl was applied to seven treatment groups, at two application rates, at
three different application intervals, over a period of 22 days (pg 51).” Specific application rates
and intervals were not provided, nor was use of a control specifically mentioned. Zooplankton
(Cladocera, Copepodia and Rotifera) abundance and community composition were altered in at
least some treatments, and Ephemeroptera abundance decreased in the two highest treatments.
Toxicity of Carbaryl, Carbofuran, and Methomyl Degradates
The BEs briefly addressed the issues of degradates. The carbaryl BE (EPA 2003c) provides
acute fish and invertebrate toxicity data the degradate, 1-napthol. The LC50s for three species of
fish tested (freshwater (O. mykiss, Lepomis macrochirus)) and marine/estuarine (Cyprinodon
varigatus) range from 750 – 1,800 μg/L. LC50s presented for aquatic invertebrates include 700-
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