Indirect pathway

Information on the species that are harvested and their biology is often available

through surveys and catch statistics from the NMFS, local or state departments of

fisheries, or local universities. Local surveys of recreational fish catches and

consumption information from these sources may also be available. Also, the dietary

and cultural habits of the exposed populations can often allow the risk assessor to

define the list of species likely consumed by recreational fishermen.

Indirect pathway - Recreation/subsistence catch. Many human health risk

assessments assume that recreational or subsistence fishermen obtain all of their

seafood from the disposal site. This is a very conservative assumption which

assessors often make when using the subsistence scenario as a worst-case screening

tool. At dredged material management sites, this guidance recommends modifying

this conservative assumption to incorporate the seasonality of the catch and the

receptor's preferences for different species of seafood. Additionally, the size of the

disposal site relative to the recreational/subsistence fishing area should be

evaluated.

Indirect pathway - Commercially harvested catch. For consumers of

commercially harvested seafood, the risk assessment should assume that:

a. The human receptor's entire seafood diet is derived from seafood landed

locally (i.e., within the state immediately inshore of the disposal site),

unless there are available data to the contrary.

b. The amount of contaminated seafood in this diet is proportional to the

amount of the catch influenced by the disposal site. For example, if one

assumes that the receptor's seafood diet derives from a 20-square-mile bay

inshore of the disposal site, and the site only influences 1 square mile, then

the contaminated portion of the receptor's seafood diet is adjusted by 1/20

(see the example).

The first assumption is conservative (i.e., protective of human health) because it

does not allow the seafood diet to be diluted by catch from distant areas. For the

second assumption, the risk assessor will need to estimate the total landings relative

to the landings influenced by the disposal site. This calculation will require data

from state or Federal statistical reports which tabulate landings by fishing areas

offshore of each coastal state.

In the absence of information for commercial catches, the recreational fishing

exposure scenario should be used.

The product of this section is a narrative or tabular presentation of consumers of

potentially contaminated seafood, that includes where the seafood is landed, what

species of seafood are consumed, and any other information that describes an

individual's or population's behavior relative to seafood consumption. This

information will allow the risk assessor to calculate estimates of contaminant intake

to the identified receptors.

Chapter 4 Human Health Risk Assessment