2.9 SHELLFISH INGESTION
Shellfish raised and caught in contaminated surface
waters provide a potential for human health impacts to those individuals
who eat the fish. This aquatic food pathway is treated similarly to the
fin fish pathway described in the previous section. This pathway is one
of two aquatic food pathways considered in MEPAS: fin fish and shellfish
ingestion.
The transport medium, special processes, and exposure
considerations are the same as those for the fin fish ingestion pathway
as defined in Subsection 2.9, except that the exposure medium is contaminated
shellfish.
The loss of pollutants during transport in the surface
water body is evaluated using Equation (3). The concentration in edible
shellfish parts is estimated using bioaccumulation factors for the pollutant
of interest. At the time of consumption by humans, the concentration in
shellfish is given as follows:
(67)
where
Csfi = concentration of pollutant i in shellfish at time of consumption by humans (mg/kg or pCi/kg)
Cswi = concentration of pollutant i in surface water in which shellfish are grown, corrected for losses in transit through the surface water system (mg/L or pCi/L)
Bsi = bioaccumulation factor for pollutant i in shellfish (mg/kg edible shellfish per mg/L water, or pCi/kg edible shellfish per pCi/L water)
lgi = rate constant for loss and decay within confined water systems used here to represent losses inside shellfish meat (d-1)
THsf = holdup time between catching and consumption of shellfish(d).
The average daily dose from ingestion of shellfish is estimated as follows, for chemical pollutants:
(68)
where
Dsfi = average daily dose from ingestion of shellfish for chemical pollutant i (mg/kg/d)
Usf = ingestion rate of shellfish by the exposed individual (kg/d)
Fsf = fraction of days per year that shellfish is eaten (dimensionless)
EDsf = exposure duration for the shellfish ingestion pathway (yr)
ATsfi = averaging time for the shellfish ingestion pathway for exposure to pollutant i (yr)
BWsf = body weight of individuals exposed by the shellfish ingestion pathway (kg).
For radionuclides, the total lifetime dose for shellfish ingestion is estimated as follows:
(69)
where
Dsfi = total lifetime dose from ingestion of shellfish for radionuclide i (rem)
DFgi = dose conversion factor for ingestion of radionuclide i (rem/pCi ingested)
and other terms are as previously defined.