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

We attempted to compare expected concentrations of these pesticides to U.S. Water Quality
Criteria designated pursuant the Clean Water Act, however none are published. We then
evaluated whether any of the state waters within designated critical habitat are listed as impaired
by carbaryl, carbofuran, and/or methomyl by searching state 303(d) lists (discussed in the
Environmental Baseline section). Currently, state water quality standards have been developed
for carbaryl and carbofuran, but not for methomyl. Unfortunately, surface water sampling is not
conducted on all freshwater habitats (including designated critical habitats) within the action area
and as a result we do not discount areas not sampled. For these reasons, it is also not possible to
determine from 303(d) lists the magnitude of water quality degradation to designated critical
habitat. We also do not rely on 303(d) lists as the sole source of information for degradation of
water quality. In California, Oregon, and Washington some streams have been placed on the
303(d) list for carbaryl and carbofuran (see Environmental Baseline section) which indicates that
water quality can be degraded by the stressors of the action in salmonid habitats. We located no
listings for methomyl, and we located no listings for the three pesticides in the state of Idaho.
Areas of Uncertainty
In this section we list the predominant uncertainties and data gaps uncovered by our analysis of
the effects of the proposed action. We do not discuss the entire suite of uncertainties, but
highlight those likely have the most influence on the present analysis.
• Description of the action. We lacked a complete description of EPA-authorized uses of
pesticides containing carbaryl, carbofuran, and methomyl as described in labeling of all
pesticide products containing these a.i.s.
• Exposure resulting from non-agricultural uses. We lacked exposure estimates of stressors
of the action associated with non-agricultural uses of these pesticides.
• Exposure to and toxicity of pesticide formulations and adjuvants. Minimal information
was found on formulations, adjuvants, and on other/inert ingredients within registered
formulations.
• Exposure to mixtures. We lacked information on permitted tank mixtures. Additionally,
given that relatively few tank mix combinations are prohibited, it was not feasible to
evaluate all potential combinations of tank mixtures. Pesticide mixtures are found in
427