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Page Title: Benthic bioaccumulation (Cont.)
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The bioaccumulation potential must be demonstrated to be in compliance with
the regulations before a dredged material can be considered to be acceptable for
placement in an unrestricted open-water disposal site.
Concentrations of contaminants in organisms should reach steady state by the
end of the standard test (e.g., 28-day tests for organic contaminants). Where it is
desirable to estimate the steady-state concentration of neutral organic
contaminants, a correction can be made to estimate the concentration at steady
state. Steady-state concentrations of contaminants are compared in Tier III to
applicable Food and Drug Administration (FDA) Action or Tolerance Levels for
Poisonous or Deleterious Substances in Fish and Shellfish for Human Food.
Tissue contaminant concentrations measured in the bioassay that are
statistically lower than FDA Action levels, or for which there are no levels, are
compared to tissue concentrations for organisms similarly exposed to reference
sediment. If tissue concentrations of COCs in organisms exposed to dredged
material do not statistically exceed those of organisms exposed to the reference
sediment, the dredged material is predicted not to result in unacceptable
bioaccumulation of contaminants in benthic invertebrates (although benthic
toxicity must be considered). If tissue concentrations of COCs in organisms
exposed to the dredged material do statistically exceed those of organisms
exposed to reference sediments, the final determination of compliance is assessed
by consideration of the following factors:
a. Number of species in which bioaccumulation from the dredged material
is statistically greater than bioaccumulation from the reference material.
b. Number of contaminants for which bioaccumulation from the dredged
material is statistically greater than bioaccumulation from the reference
material.
c. Magnitude by which bioaccumulation from the dredged material exceeds
bioaccumulation from the reference material.
d. Toxicological importance of the contaminants whose bioaccumulation
from the dredged material statistically exceeds that from the reference
material.
e. Phylogenetic diversity of the species in which bioaccumulation from the
dredged material statistically exceeds bioaccumulation from the
reference material.
f. Propensity for the contaminants with statistically significant
bioaccumulation to biomagnify within aquatic food webs.
g. Magnitude by which contaminants whose bioaccumulation from the
dredged material exceeds that from the reference material also exceed the
concentrations found in comparable species living near the proposed site.
Uncertainties associated with benthic bioaccumulation bioassays include the
following:
25
Chapter 4 Uncertainty in Tiered Evaluation of Dredged Material

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