Reviewing site-specific information for exposure factors

FI for commercially consumed scenario. In some areas of the country, individuals

purchase seafood from the same vendors who harvest from a particular area

consistently. In these cases, the catch is not diluted and the FI would be 1. Typically,

commercial catches are not taken from one small area, but from many areas. For

commercially harvested seafood, it is best to obtain catch statistics for the area of

interest from state departments of marine fisheries statistical reports, or, if

necessary, from NMFS statistical reports. Often, the state reports may be on a finer

scale, especially for nearshore fishing areas. The species of interest and their

foraging areas represented in the statistical areas should be determined by a fisheries

biologist. If the state fisheries biologists indicate that the disposal site is particularly

attractive to species of concern, then the FI should be adjusted accordingly.

If a site is used repeatedly for dredged material disposal, it may become

disproportionately attractive to certain species such as winter flounder because the

continual disturbance may enhance populations of opportunistic species. Sometimes

these species are the favored prey of winter flounder. State departments of fisheries

or local agencies should be consulted regarding this possibility. If it is occurring, the

FI should be appropriately modified.

This guidance suggests estimating the FI based on the size of the disposal site

relative to the fishery area; the catch from various statistical areas; and the size of

the foraging areas for the species of interest.

Example 17: Calculation of FI by Humans Based on Fishery Statistics for Consumption of Commercially

Caught Flounder

The State Division of Marine Fisheries' winter flounder catch statistics indicate that 30 percent of all of

the flounder landed in the state come from Statistical Area 4. For this example, Area 4 contains the

hypothetical dredged material disposal site and its area of influence. It is known that the foraging area of

a flounder is approximately 2 percent of Area 4.

Therefore:

FI = 0.02 H 0.3

FI = 0.006

In this case, the FI for the local metropolitan consumer of commercially harvested flounder is 0.006.

Six-tenths percent of the flounder consumed by these receptors will be impacted by the

dredge-management site. If there is reason to believe that the disposal site is preferentially attractive to

flounder, this calculation will change accordingly.

Reviewing USEPA Default Exposure Assumptions

In the absence of site-specific information for the exposure factors, the risk

assessor should use the USEPA recommended default exposure assumptions found

in the following four documents.

Chapter 4 Human Health Risk Assessment