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

adical) has already dissociated (EPA 2005). No toxicity data for this compound are provided in
either the BE or the Science Chapter. The degradates 3-hydroxycarbofuran and 3ketocarbofuran
are detected in soil photolysis and aerobic soil metabolism studies. These
compounds were each approximately 3-5% of applied (EPA 2004a), and are structurally more
similar to the parent carbofuran. The Science Chapter cites an open literature study using
Microtox (Kross, et. al., as cited in EPA 2005) noting “3-ketocarbofuran appears as toxic or
slightly more toxic than the parent, but 3-hydroxycarbofuran is much less toxic.” A second
study evaluated (Gupta 1994, as cited in EPA 2005) indicates 3-hydroxycarbofuran is “equally as
toxic as the parent.” No specific toxicity values were presented. Other degradates mentioned in
the fate summary are 3-hydroxycarbofuran phenol (3-hydrocy-7-pheonl) and 3-ketocarbofuran
phenol (3-keto-7-phenol), which are less than 5% of applied (EPA 2005).
The methomyl BE notes “a degradate (thiolacetohyroxamic acid 5-methyl ester)… was tested
and found to be practically nontoxic to bluegill” (EPA 2003a). This study is also mentioned in
the Environmental Risk Assessment for the RED (EPA 1998c). The bluegill LC50 for this
degradate is 462,000 μg/L. No other degradate toxicity data were presented. The fate portion of
the BE (EPA 2003a) and the Environmental Risk Assessment (EPA 1998c) both reference Smethyl-N-hydroxythioacetamidate
as a product of hydrolysis in both water and soil. This may
be the same compound expressed under different naming conventions, but no structures were
provided to confirm this identification. No toxicity data were presented for acetonitrile or
acetamide.
Formulations and other (inert) ingredients found in carbaryl’s, carbofuran’s, and methomyl’s
formulations
Assessment endpoint: Fish survival, aquatic invertebrate survival, and primary production
Assessment measure: Aquatic invertebrate survival, growth, and reproduction from acute
and chronic laboratory toxicity tests
The carabaryl BE (EPA 2003c) and the carbaryl Science Chapter (EPA 2003b) provide some
toxicity data on formulations containing 5-81.5% carbaryl for both aquatic invertebrates and fish.
We did not receive information on whether the formulations tested are currently registered. Data
for formulations (referred to in the Science Chapter (EPA 2003b) as technical end-product or
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