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

habitats is then assessed. This portion of the analysis is conducted in the Integration and
Synthesis section.
Below we discuss an example of one risk hypothesis to show the relationship between
assessment endpoints and measures with species responses. In risk hypothesis 1 (d),
aquatic exposure to carbaryl, carbofuran, and methomyl can impair a salmonid’s nervous
system and consequently affect swimming ability of fish. Behavioral modifications, such
as changes in swimming performance, are regularly considered in NMFS’ Opinions.
Swimming performance therefore is an assessment endpoint. Measurable changes in
swimming speed are the assessment measure used to evaluate this endpoint. Reductions
in swimming performance could also affect other assessment endpoints such as migration
and predator avoidance. We may or may not have empirical data that address these
endpoints, resulting in a recognized data gap. This uncertainty would be identified
during the problem formulation phase, and discussed in the risk characterization phase.
In the problem formulation phase, we also identify the toxic mode and mechanism of
action of chemical stressors, particularly for the pesticide a.i.s. This information helps us
understand what an organism’s physiological consequences may be following exposure.
It also helps us evaluate whether mixture toxicity occurs because we identify other
pesticides that share similar modes of action and the likelihood for co-occurrence in listed
species habitats. A similar mode of action with other pesticides is a key determinant of
the likelihood of mixture toxicity. With vertebrates (fish and mammals) and
invertebrates, the three a.i.s share a common mode and mechanism of action,
acetylcholinesterase inhibition. Given this information, a range of potential adverse
responses are possible (Figure 4). We then search, compile, and review the available
toxicity information to ascertain which physiological systems are known to be affected
and to what degree.
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