Impact/Purpose:

To provide an interpretive tool to evaluate the potential human health effects associated with the disposal of contaminated dredged material at open water and ocean sites. The model utilizes data from the standard laboratory 28 day bioaccumulation test as required by the Marine Protection, Research and Sanctuaries Act and the Clean Water Act regulatory programs administered by the U.S. Army Corps of Engineer

Description:

The laboratory bioaccumulation test has been a standard testing requirement to evaluate the open water disposal dredged materials since the late 1970's. Heretofore, the interpretation of these test results, using the clam, Macoma nasuta, and worm, Nereis virens, has been an assessment of exposure as an indicator of impact as required by the Clean Water and the Marine Protection Research and Sanctuaries Acts that regulate disposal activities. Since the advent of risk assessment tools, dredged material managers are beginning to employ such techniques to assess more directly and quantitatively the potential impact of any observed bioaccumulation. A risk screening model for non-polar organic compounds was developed to support EPA=s assessment and approval of the open water disposal of dredging projects. The model provides a conservative screening estimate of carcinogenic and non- carcinogenic risk to a human consumer of seafood at a disposal site for a variety of non-polar organic compounds. The human food species, lobster and winter flounder, are common benthic- feeders at nearly all New England dredged material disposal sites and are assumed to prey on contaminated clam and worm species at the site. The risk of consuming a molluscan shellfish is also directly assessed based on the clam and worm test data. In addition to the 28 day bioaccumulation test results, input parameters to the model include cancer slope factors, reference doses, species lipid levels, consumption rates and other toxicological and exposure variables, some of which may vary with each project and/or disposal site. Because the test data is from only a 28 day exposure, the model provides for an adjustment for steady state accumulation using known octanol/water partitioning coefficients. Trophic transfer of the clam and worm contaminants to edible lobster and fish tissues is estimated using of the Gobas (1993) model which uses octanol/water partitioning coefficients and known lipid values. Although the risk model was first developed with spreadsheets, it has now been incorporated into a report-writing program that performs the calculations automatically.

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