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Selenosis in animals is reported to produce infertility and congenital malformations (Harr, 1978). Selenosis in man appears to be a relatively rare occurrence, most often due to acute occupational exposure or chronic exposure to contaminated water or food sources. There appears to be very little information regarding the effect on man of chronically high levels of selenium in the diet and its potential risk (Wilber, 1983). Recently, however, levels have been reached in fish that have prompted health alerts in California (Fan et al., 1988).
In this section, some of the potential contaminants of seafood that have come to the committee's attention, and about which there are at least some minimal data, are surveyed. These include the chlorinated hydrocarbon pesticides that came into widespread use in the United States and elsewhere immediately after World War II (Hansen et al., 1985). Among the chlorinated hydrocarbon pesticides detected in seafood were benzene hexachloride (BHC) or hexachlorobenzene (HCB), chlordane, dieldrin, dichlorodiphenyltrichloroethane (DDT), endrin, heptachlor, lindane, nonachlor, octachlor, and pentachlorophenol. In addition, industrial chemicals and by-products such as PCBs and dioxins are routinely detected in seafood. Less frequently detected pesticides included chlorpyrifos, dacthal (DCPA), diazinon, ethylene dibromide (EDB), malathion, mirex, omethoate, pentachloroaniline, tecnazene, and trifluralin (FDA, 1988; Gunderson, 1988). In quite specific circumstances, such as in farm ponds in heavily agricultural areas, other chemicals — even those that are not known to bioconcentrate, such as atrazine — can be found in fish (Kansas DHE, 1988). Some pesticides detected are specific to various regions. The carboxylic acid herbicide 2,4-(dichlorophenoxy)acetic acid (2,4-D) has been found in oysters from the northern Chesapeake Bay and Alaskan bivalves (NOAA, 1988). Fish from the Arroyo Colorado and adjacent lower Laguna Madre in Texas contained measurable concentrations of pesticides such as ethion, carbophenothion, ethyl parathion, and methyl parathion (NOAA, 1988). The organic compounds classified here have been reviewed by Murphy (1980).
Polychlorinated biphenyls (PCBs)
Polychlorinated biphenyls include more than 200 different compounds ("congeners") that were used in various formulations as liquid insulators in electrical equipment, as encapsulating agents, in carbonless carbon paper, and in hydraulic fluids. The use of PCBs in "open" applications such as carbonless carbon paper was phased out in the early 1970s, and any new use for the remaining applications was stopped in the late 1970s with the passage of the Toxic Substances Control Act. The U.S. usage of approximately 500,000 tons of PCBs in 1930-1970 accounted for about half of the total world production. However, the unusually slow rate of environmental degradation of the more highly chlorinated PCBs in the environment and in higher organisms, and slow continued discharge of PCBs from old equipment and dump sites, have led to a