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.

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.

* Cadmium levels in all waters ranged from less than 0.1 ppm in the muscle of most fish to well above 1.0 ppm for oysters and northern lobster.

* The average US intake of cadmium is some 250 micrograms a week. Smokers average some 400 micrograms a week. That is also the World Health Organization's recommended limit of exposure.

''Right now,'' Mr. Lombardo says, ''the public is getting about as much (exposure to cadmium) as it should be getting.'' Yet when a New York University graduate student reported finding high cadmium concentrations in Hudson River blue claw crabs, the FDA was powerless to act.

The metal was concentrated in that part of the crab known to seafood gourmets as the ''mustard'' or in lobsters as the tomalley. The organ acts as the liver does in vertebrates, as a filter for contaminants. The problem, however, is that in the crab the organ is often eaten. A half-dozen of the whole crabs with the highest levels of cadmium could, said Dr. Joseph O'Connor of the New York University Medical Center, bring on acute intoxication.

Along the Hudson, Dr. O'Connor added, ''ethnic tendencies'' in the preparation of the crabs made the concern all the greater. The crabs are most often boiled in tomato sauce. ''The acid in the tomatoes,'' Dr. O'Connor said, ''leeches out the cadmium into the sauce, thereby making use of every last microgram of the contaminant.

''What we were most concerned about is the possibility that less-affluent populations may be making use of the crab as a main part of their diet.'' The FDA, however, had no regulations - and even if they had, there was no evidence of any interstate commerce in the crabs. The New York conservation agency consulted with the World Health Organization and took the precaution of issuing its own advisory.

It was the second seafood advisory for the Hudson. The first was issued in 1976, when Hudson River striped bass were found severely contaminated by PCBs, which had been dumped into the river as industrial waste discharge.

Many researchers are also concerned about petroleum compounds. Dr. Malcolm Meaburn of the National Marine Fisheries Service is working on a comprehensive survey of such organic contaminants, especially the petroleum byproducts, in US seafood resources. As opposed to the poisonous metals, the petroleum compounds, which include some several thousand compounds that make up crude oil, are suspected carcinogens.

''We need baseline data,'' Dr. Meaburn says, ''to establish good benchmarks to measure against.'' Especially where oil spills are concerned, ''we quite often are without the capability to know what was there before the spill.''

Dr. John Pearce, chief of environmental studies for the Commerce Department's Northeast Fisheries Center, sees an even larger danger than poisoned seafood. He is head of Ocean Pulse, a program designed to monitor the spread of marine pollution. The concern, he says, is not only for man, but for the integrity of the sea's ecosystem. Contamination accumulates up the food chain from bottom sediments, through microscopic plankton, to fish and shellfish.

Since 1978, using data gathered from collection ships and even U-2 aircraft, Dr. Pearce has been tracing the rate of the geographic spread of pollution. ''We've found that specimens of fish collected far from immediate sources of pollutants did show . . . significant levels of substances such as PCBs and petroleum hydrocarbons,'' he says.

''The game everyone is fighting,'' Dr. Lombardo says, ''is to minimize the problems. But in the last 10 or 15 years we've recognized that it would be naive to think about eliminating contaminants (completely). Some are worse than others , and we're trying to reduce the degree of hazard as much as we can.''

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