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

existence of the species. NMFS also determines whether the action results in the
destruction or adverse modification of designated critical habitat.
Other Considerations
In this Opinion, we evaluated lines of evidence constructed as species-specific risk
hypotheses to ensure relevant endpoints were addressed. Ultimately, our analysis weighs
each line of evidence by evaluating the best commercial and scientific data available that
pertain to a given risk hypothesis. Overall, the analysis is a qualitative approach that uses
some quantitative tools to provide examples of potential risks to listed salmonids and
their habitat. Multiple methods and tools currently exist for addressing contaminantinduced
risk to the environment. Hazard-based assessments, probabilistic risk assessment
techniques, combinations of the two, and deterministic approaches such as screening
level assessments have been applied to questions of risk related to human health and the
environment.
In recent pesticide risk assessments, probabilistic techniques have been used to evaluate
the probability of exceeding a “toxic” threshold for aquatic organisms by combining
pesticide monitoring data with species sensitivity distributions (Geisy, Solomon et al.
1999; Giddings 2009). There is utility in information generated by probabilistic
approaches if supported by robust data. We compared the species sensitivity
distributions presented in Giddings 2009 with the probability distributions of salmonid
prey acute lethality values that we developed to highlight differences in outcomes. The
assessment with carbaryl did not address many of the species-specific risk hypotheses.
We found no other probabilistic assessments that addressed risk to salmonids affected by
short-term sublethal exposures, mixtures, or affects on growth from reduced feeding
ability and reduced abundances of prey.
NMFS considered the use of probabilistic risk assessment techniques for addressing risk
at population and species (ESU and DPS) scales for the stressors of the action. However,
we encountered significant limitations in available data that suggested the information
was not sufficient to define exposure and/or response probabilities necessary to determine
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