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

macroinvertebrate community did not recover rapidly. Several species similar to salmonid prey
items were significantly affected.
Zooplankton and insect taxa appeared the most sensitive in studies with diazinon. In particular,
the salmonid prey taxa Trichoptera, Diptera, and Cladocera were highly sensitive (Giddings, Hall
et al. 2000). Field studies in salmonid habitat also show reductions in salmonid prey
abundances. For example, in listed steelhead habitat in the Salinas River, California, abundances
of the salmonid prey items including mayfly taxa, daphnids, and an amphipod (Hyalella azteca)
were significantly reduced downstream of an irrigation return drain compared to upstream
(Anderson, Hunt et al. 2003; Anderson, Hunt et al. 2003; Anderson, Phillips et al. 2006).
Diazinon and chlorpyrifos were detected above acute toxicity thresholds in surface waters and
sediments. Combined toxicity of the two OPs using a toxic unit approach correlated strongly
with mortality of daphnids. For H. azteca, acute toxicity was attributed to sediment pore-water
concentrations of chlorpyrifos (Anderson, Hunt et al. 2003). Other pesticides, including
carbaryl, were likely present and responsible for some of the toxicity in the Salinas River,. In a
subsequent study on the Salinas River, TIE demonstrated that chlorpyrifos and diazinon were
responsible for the observed death of the daphnid C. dubia (Hunt, Anderson et al. 2003). These
data support the line of evidence that field concentrations of OPs can and do adversely affect
aquatic invertebrates in salmonid habitats. It is reasonable to assume that the same situation
occurs with carbamates, given the toxicity of the compounds and the similar mode of action.
Adjuvant toxicity
Assessment endpoints: Survival of fish and aquatic prey items, endocrine disruption in fish
Assessment measures: 24, 48, 96 h LC50s, and vitellogenin levels in fish plasma
Although no data were provided in the BEs related to adjuvant toxicity, an abundance of toxicity
information is available on the effects of the alkylphenol polyethoxylates, a family of non-ionic
surfactants used extensively in combination with pesticides as dispersing agents, detergents,
emulsifiers, adjuvants, and solubilizers (Xie, Thrippleton et al. 2005). Two types of alkylphenol
polyethoxylates, NP ethoxylates and octylphenol ethoxylates, degrade in aquatic environments to
the more persistent, toxic, and bioaccumulative degradates, NP and octylphenol, respectively.
We note that the technical registrant of methomyl stated that no nonylphenol ethoxylates are
used within methomyl formulations. We did not receive information on the presence or absence
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