EPA's Vessel General Permit and Small Vessel General

And:
“As a general rule, the use of alternative endpoints is discouraged unless a compelling
argument can be made that inclusion would reduce the overall level of uncertainty in the
analysis towards achieving the assessment goal.”
“EPA relies on the 1985 Guidelines data requirements and data selection process as the
process by which information is fully-vetted for its utility and applicability in the BE
analysis. “
Services Assessment of Uncertainty in the Repose Analysis
EPAs decisions to select the most sensitive surrogate species, assess risk of metals and PAH
mixtures, and perform risk threshold analyses using water quality criteria adjusted by a factor of
two to account for potential increased sensitivity of threatened and endangered species are, at
this time, appropriate adjustments for the uncertainties introduced by interspecies extrapolation.
However, EPA did not acknowledge that an adjustment of water quality criteria by a factor of
two may also be necessary to account for the greater significance of effects on individuals to the
survival of a population when protecting threatened and endangered species.
When selecting its response thresholds, EPA stated that it relies on the 1985 Guidelines data
requirements and data selection process. However, these guidelines also state:
"For any threshold material, continuous exposure to any combination of concentrations
below the threshold will not cause an unacceptable effect … However, it is important to
note that this is a threshold of unacceptable effect, not a threshold of adverse effect.
Some adverse effect, possibly even a small reduction in the survival, growth, or
reproduction of a commercially or recreationally important species, will probably occur
at, and possibly even below, the threshold. The Criterion Continuous
Concentration (CCC) is intended to be a good estimate of this threshold of unacceptable
effect."
What constitutes an unacceptable effect for threatened and endangered species was not addressed
in EPA’s guidelines. For some sublethal effects, such as olfaction, effects may occur at
concentrations below which traditional endpoints (survival growth and reproduction) are affected
(reference Copper section of the BO). If such responses are not considered when selecting
chronic toxicity values, the resulting effects analyses may underestimate risk to susceptible
species.
The services also have further comment on the ecological relevance of NOECs/LOECs and
MATCs. Due to the hypothesis driven selection of response thresholds, the underlying “level of
effect” associated with NOECs, LOECs, and MATCs may be high. For example, Suter et al.
(1987) reported that MATCs for fish fecundity, on average, corresponded to a 42% level of
adverse effect. These shortcomings can be addressed by using a regression approach to derive
point estimates of chronic toxicity, such as the EC10.
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