Poisoned shellfish: how hazardous is it to consumers?
When mercury, PCBs, cadmium, and other toxic wastes polluted Japanese waters, the names of stricken cities such as Minimata and Niigata became synonymous with chemical pollution. Now research has found the same substances in US coastal waters, too.Skip to next paragraph
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This has raised questions as to whether, or to what extent, poisoned shellfish are a hazard to US consumers.
A recent report of the National Oceanic and Atmospheric Administration on chemical pollutants in New York-New Jersey coastal waters identified some 25 types of contaminants. Of these, seven were considered ''major perceived threats.'' They include lead, mercury, cadmium, PCBs (polychlorinated biphenyls) , and the pesticides.
Ten more compounds were designated ''potentially significant threats,'' among them arsenic and the petroleum pollutants. In seafood, the levels of only three of them - mercury, the PCBs, and DDT - are now regulated by the US Food and Drug Administration.
The challenge is to find out what threat the other contaminants may represent and how to regulate them, if necessary.
Faced with the contamination of Hudson River blue claw crabs last year, the New York State Department of Environmental Conservation was forced to turn to the UN World Health Organization for help in setting acceptable standards of human cadmium intake.
Pat Lombardo, deputy director of the Division of Chemical Technology for the US Bureau of Foods, says regulation lags behind research partly because advances in contaminant research have so outstripped advances in toxicology. Contaminants once measured in parts per million, then in parts per billion, now can be assayed by the single molecule.
''The toxicologists can't keep up,'' Mr. Lombardo says. ''We are finding less and less of a whole lot more.''
When the first reports of mercury poisoning came out of Minimata, Japan, in the 1950s, there was little scientific literature on the effects of industrial pollutants. However, the images of human misery emanating from Minimata - and in 1965, from Niigata - were compelling. Severe poisonings were traced directly to contaminated fish and shellfish.
In 1969, based on the work of Swedish scientists, the US Food and Drug Administration established an action level of 0.5 parts per million (ppm) mercury in seafood. All seafood which exceeded that level might be confiscated.
The industry moved the matter into the courts. In 1976 a Florida judge ruled the FDA level capricious. Based upon the research of the National Marine Fisheries Service, the judge set the mercury limit at 1.0 ppm.
''What that decision meant,'' says Mr. Lombardo, ''is that now you could get twice as much legal mercury as you could before.'' He adds: ''The FDA doesn't want to say one level is safe. If it exceeds a certain level, we are saying it's unsafe. We remove anything from the market that exceeds 1.0 ppm. Because we do not remove from the market anything below 1.0 ppm does not mean it's not a concern to us.''
The New York report concluded that, for its study area, ''ingestion of a high seafood diet would significantly increase human daily intake of the metal. Because a proportion of the mercury will be the more toxic (form called) methyl mercury, there is significant cause for concern.'' The report presented similar conclusions concerning both lead and cadmium.
New York's bays are not the only waters whose resources are contaminated. Here are some other examples:
* Tilefish from the Gulf of Mexico averaged between a 1.0 and 2.0 ppm mercury level. Similar levels were found in king mackerel. Sharks, now being promoted for their food value, averaged a 1.24 ppm mercury level.