SI Vault
Robert H. Boyle
October 26, 1970
A new study shows that toxic chemical compounds—methyl mercury, DDT and mysterious PCBs—are present in our most popular saltwater fishes. Now rising residue levels endanger human health as well
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October 26, 1970

Poison Roams Our Coastal Seas

A new study shows that toxic chemical compounds—methyl mercury, DDT and mysterious PCBs—are present in our most popular saltwater fishes. Now rising residue levels endanger human health as well

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The highest mercury residues found in the SI study were in the flesh of spotted seatrout from Hackberry, Cameron Parish, La. The initial analysis by WARF Institute revealed 2.2 ppm of mercury, four times more than the FDA maximum of 0.5. In a repeat analysis by WARF, the level was 1.8 ppm. The seatrout were procured from a commercial fish company in Hackberry, and they had been caught in adjacent Lake Calcasieu, a brackish body of water connected to the Gulf of Mexico. On the Gulf coast, seatrout are generally not migratory but localized in one estuary. Last July after SI obtained the fish, the FDA, in an entirely unrelated move, halted interstate shipments of crabs, spotted seatrout, redfish and flounder from Lake Calcasieu because of high mercury levels.

The flesh of striped bass from California also surpassed the FDA limit on mercury. The California Department of Fish and Game took the flesh and eggs from 15 different females caught in the Delta near Antioch, composited flesh and egg samples separately and forwarded them to WARF Institute. The department retained the remainder of the flesh and eggs for testing on its own. At WARF Institute initial flesh analysis was 0.70 ppm; the repeat analysis was 0.68. In order to obtain California striped bass for testing, SI agreed to allow the California Department of Fish and Game to review the results before publication and then to comment upon the significance. After reviewing the data, L. H. Cloyd, deputy director of the department, says that the WARF finding "for the level of mercury was consistent with one of our state laboratory reports." Cloyd also points out "the levels of mercury in stripers, as well as in some catfish, sturgeon—and pheasants—have prompted our governor to assemble a special task force of state agencies and cooperating federal agencies to investigate mercury pollution in California."

Mercury in excess of the FDA limit of 0.5 was also found in the flesh of Spanish mackerel caught four miles off Charleston, S.C. Initial analysis by WARF Institute was 0.57 in the flesh; the repeat analysis was 0.56. The Spanish mackerel is a pelagic fish, one that spends its life near the surface of the ocean and is not known to frequent shallow water. The fish ranges off the coasts of the Carolinas and Florida, and it may migrate into the Gulf of Mexico.

Other species had mercury levels close to the FDA maximum. False albacore from South Carolina, another pelagic fish, had residues of 0.40 in the flesh; spotted seatrout from Shell Point Reef on the panhandle of the Florida Gulf coast had 0.40; striped bass from the Hudson River, 0.34; bluefish from South Carolina, 0.31; and white perch from the James River, Virginia, 0.31. Little is known about the natural or normal mercury level in the flesh of fish, but it is probably not more than 300 parts per billion. The lowest level discovered by WARF Institute was 0.10 parts per million found in the flesh of Atlantic mackerel from Long Island Sound, American shad from the James River and spotted seatrout from South Carolina. SI did not ask WARF Institute to analyze eggs for mercury residues.

The WARF Institute analyzed the egg and flesh samples for DDT residues, dieldrin and BHC, all chlorinated hydrocarbon pesticides. These synthetic compounds have several factors in common. They do not readily break down in nature; indeed, it takes at least a decade for them to lose their toxicity. They are also highly poisonous to a broad spectrum of living organisms. They are used to attack insect pests because they can penetrate the external shell of chitin, a thin layer of hard fatty material that covers an insect body. Once applied, be it on insects, on the ground, on vegetation or in the air, these long-living pesticides are spread by wind and water. Aerial applications of DDT can enter the atmosphere and circle the earth in only two weeks. Last year Drs. Eugene F. Corcoran and Douglas B. Seba of the University of Miami reported surface slicks containing pesticides washing into Biscayne Bay after heavy rains. These areas were several miles long and from five to 300 feet wide, and they contained 10,000 times more chlorinated hydrocarbon pesticides than the water surrounding them.

Once introduced into the food web, chlorinated hydrocarbons are able to move up from phytoplankton to zoo-plankton to fish to bird or mammal, and they become more and more concentrated as they are retained by a higher level of animals. The chlorinated hydrocarbons tend to center in the body fats, such as those in the reproductive organs, and it is generally agreed that these chemicals are to blame for the current decline in North America of the brown pelican, the peregrine falcon and the bald eagle, our national symbol. All have fish in their food web.

In the past two years the FDA has seized shipments of coho salmon from Lake Michigan and jack mackerel from the Pacific near Los Angeles for exceeding 5.0 ppm of DDT residues, and the U.S. Bureau of Sport Fisheries and Wildlife has noted DDT levels of from 31 to 45 ppm in the flesh of white perch taken from the Delaware River at Camden, N.J. Last month John MacGregor of the U.S. Bureau of Commercial Fisheries announced that a federal study of fish from Santa Monica Bay contained new research information. The study showed DDT residues in those fish to be astronomically high, ranging from 63 ppm in the liver of Dover sole to 1,026 ppm in the liver of starry rockfish. A major source of the residues was two sewage plants emptying into the bay. The City of Los Angeles plant at Hyperion was releasing one to seven pounds of DDT components per day, while the Los Angeles County White Point plant was daily discharging from 200 to 400 pounds of DDT residues. However, none of the flesh samples tested for SI by WARF Institute approached the federal maximum. DDT residues were detected in the flesh of every species submitted, but the closest to the FDA maximum were the Hudson River striped bass that had DDT residues totaling 2.42 ppm.

The WARF Institute also tested all eggs for chlorinated hydrocarbon residues. Inasmuch as these pesticides have an affinity for fat, it came as no surprise that there were higher residues in the eggs than in the flesh. DDT residues in the eggs can affect reproduction or the survival of young fish. In Jasper National Park, Canada there was a 70% mortality of brook-trout fry hatched from eggs with 0.46 ppm of DDT residues. In Michigan 700,000 coho salmon fry died in hatcheries in 1968. They had been hatched from eggs with DDT residues of 1.5 to 3 ppm. When the larval salmon were three weeks old and absorbed their yolk sac during the so-called "button up" stage they died. DDT residues were in the yolk, and quickly made contact with the central nervous system. Dr. Philip A. Butler of the Bureau of Commercial Fisheries Laboratory in Gulf Breeze, Fla. reports that in a joint study with the Texas Department of Parks and Wildlife virtually no young spotted seatrout were observed in the Laguna Madre in 1968 and 1969. The gonads of females had DDT residues up to 8.0 ppm.

Different species of fish seem to have different levels of tolerance to DDT residues in the eggs. Precise levels are simply not known for most marine fish, but based on the above 0.5 ppm seems to be cause for concern and 1.5 ppm serious cause for concern about survival of the young. According to WARF Institute results, the highest DDT residues in eggs were in the California striped bass, 9.05 ppm. Commenting upon DDT residues in California stripers, L. H. Cloyd of the Department of Fish and Game notes: "Numerous studies conducted by our department of the levels of recruitment of striped bass demonstrate no adverse effects from the levels of DDT and its metabolites in striper eggs and larvae. We are, however, continuing to investigate this aspect."

Striped bass from the Hudson, which migrate to New Jersey, New York and Connecticut coastal waters, had 7.40 ppm of DDT residues in the eggs. They also had 0.33 ppm of dieldrin. By FDA standards, the eggs of these striped bass should not be eaten. Dieldrin is more toxic than DDT, and the FDA has imposed a maximum of 0.30 ppm of dieldrin on fish products.

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