Appendix D Food Codes for NHANES - OEHHA

SRP Review Draft Version 2 June, 2012
muscle of trophic level 3-4 freshwater sport fish even though much of the Hg analyzed
in the water was in inorganic Hg (Bloom, 1992; Kuwabara et al., 2007). In whole fish,
the proportion of inorganic Hg is greater (5% or more of total Hg) because whole body
samples include visceral tissue, such as kidney and liver, which is the principal site of
inorganic Hg accumulation in fish (Hill et al., 1996; Watras et al., 1998).
As summarized by Southworth et al. (2004), MeHg is produced in aquatic environments
by the action of microorganisms on inorganic Hg. It can also be removed from the
aquatic systems by microorganisms that demethylate MeHg. Once formed, MeHg is
taken up by microorganisms, primary producers, aquatic invertebrates, and fish. MeHg
in the organisms shows the classical biomagnification process, with MeHg concentration
increasing with trophic level. The concentrations of MeHg that are accumulated in fish
are greatly affected by the nature of the aquatic food chain, and are sensitive to factors
such as aquatic community composition and productivity. In many waters, minute
concentrations (