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

Some toxicity data were available in the BEs for formulations not containing additional a.i.s.
Based on that data, no specific conclusions can be drawn as to whether formulations are, in
general, more or less toxic than the technical grade a.i. However, it should be noted that
adjuvants which increase either uptake (such as penetrants or surfactants that make physiological
membranes more permeable) or length of exposure (attractants, or emulsions that increase time
in the water column) are likely to increase toxicity of the a.i.
Only a limited amount of data were available to evaluate toxicity of the degradates of carbaryl,
carbofuran, and methomyl. Monitoring data indicate that 1-napthol, a degradate of carbaryl, and
3-hydoxycarbofuran, a degradate of carbofuran, occur in measurable quantities in the
environment. Based on the monitoring data, 1-napthol co-occurs with carbaryl in both water
column and sediment. Toxicity information presented in the BE indicates that 1-napthol is
approximately an order of magnitude less toxic than parent carbaryl for aquatic invertebrates.
No data were given in the BE regarding the toxicity of 1-napthol to fish. We did locate one open
literature study evaluating the effects of 1-napthol on fish, which indicated it was 2-5 times more
toxic than the parent carbaryl (Shea and Berry 1983). No toxicity data were located for 3hydroxycarbofuran
or 3-ketocarbofuran, but based on structural similarities, the toxicity is likely
similar to the parent carbofuran. Based on fate data presented in the BEs, 3-hydroxycarbofuran
and 3-ketocarbofuran appear to occur in soil rather than in the water column. Both are shown as
being non-detectable to representing 2-5% of applied parent material. Together, they could
represent 6-7% of applied, assuming they were measured in the same test. Neither the BE nor
the Science Chapter specify if that is the case.
Overall, while NMFS cannot quantify the increased toxicity of exposure to other stressors of the
action such as additional a.i.s, degradates, and adjuvants, the existing body of information
indicates these compounds are likely to cause and/or exacerbate adverse effects on salmonids
and their habitat caused by carbaryl, carbofuran, and methomyl.
We did not receive a complete list of the currently registered formulations containing carbaryl,
carbofuran, and methomyl from EPA. Thus, we cannot make any definitive conclusions for
every stressor of the action. However, we did evaluate the exposure and response to a commonly
396