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In the past few years there has been considerable scientific concern about chemical residues in fish, but almost all investigations have been limited to freshwater lakes and streams. Yet some species of coastal fish have gone into what John R. Clark, curator of the New York Aquarium, describes as "a disastrous decline, a virtual wipeout. The total commercial catch on the Middle Atlantic in 1969 was down to about one-tenth of the 1960 catch. The multimillion-dollar menhaden fishery was nearly eliminated in the late '60s, and weakfish, croaker, spot, porgy and fluke are close to disappearing in the Northeast. Pollution is a major cause. Coastal waters are infested with pesticides, metals and other toxic pollutants, and these poisons can kill fish, their young and the organisms they feed on."
It is also possible that this pollution, unless checked, may kill people. A study sponsored by SPORTS ILLUSTRATED reveals that poisonous chemical compounds in the flesh and eggs of some of the most popular American saltwater sport fishes have reached levels that are alarming to health authorities and fishery biologists. The study, the first ever to involve fishes from the Atlantic, Gulf and Pacific coasts of the U.S., was conducted for this magazine by WARF Institute, Inc. in Madison, Wis., a highly respected laboratory that has done research for the Federal Government, various states and private industry.
Specifically, the study shows that the flesh of spotted seatrout from Louisiana, striped bass from California and Spanish mackerel from South Carolina contains more mercury than allowed by the U.S. Food and Drug Administration in fish sold for human consumption.
Other tests disclose that the reproductive process of at least four different fish populations may be threatened by high residue levels of chlorinated hydrocarbon pesticides in the eggs. High levels of DDT residues (a combination of DDT, DDD and DDE) are in the eggs of striped bass from California, from the Hudson River, New York, from the Rappahannock River, Virginia, and in the eggs of bluefish caught off the coast of South Carolina. Moreover, the eggs of the California and New York bass have high PCB residues, an industrial compound that has escaped into the environment by accident.
The fish studied were all females close to spawning and were collected last spring and summer by fishermen, biologists and two state fish-and-game departments. The sampling of each species from a given location generally included from five to 15 individual fish. All samples were wrapped in aluminum foil, frozen and shipped by air in containers with dry ice to WARF in Madison where Francis Coon, head of the chemical department, supervised the analyses. A complete list of fish species, location taken, residue data and analytical methods employed in the study is shown below.
In recent months there has been public clamor about mercury residues in fish, residues sufficiently high to close or restrict fishing in such famous bodies of freshwater as Lake Champlain between Vermont and New York; the Lake St. Francis section of the St. Lawrence River between Quebec and Ontario; the Niagara and Oswego rivers and lakes Onondaga and Ontario in New York; the Connecticut River in New Hampshire; the Savannah River and Brunswick Estuary in Georgia; Mobile Bay and the lower Mobile River, the Tombigbee River and the Pickwick Lake section of the Tennessee River in Alabama; the Detroit River and Lake St. Clair in Michigan; and the Wisconsin River from its juncture with the Mississippi River to Rhinelander, Wis. In fact, mercury polution is a problem in at least 33 states and eight Canadian provinces.
Mercury pollution offish, shellfish and birds was first discovered in Japan and Sweden in the 1960s. The pollution came from pulp mills, plastic and chlor-alkali plants and mercury-coated seeds. Despite warnings of mercury contamination elsewhere in the world, nothing was done in North America until last year when Norvald Fimreite, a Norwegian graduate student at the University of Western Ontario, tested pheasants from Alberta. The residues were so high that Alberta closed the hunting season. Still Canadian and U.S. authorities did nothing to try to halt the poisoning. Fimreite then found high mercury residues in fish from Lake St. Clair. The major source of the contamination was a Dow Chemical Company plant at Sarnia, Ontario, which was dumping as much as 200 pounds of mercury a day into the St. Clair River. Subsequent investigations elsewhere have uncovered other polluters. One reason that authorities were slow to act was that everyone apparently believed mercury was too valuable to be thrown away. Another reason was that most authorities mistakenly believed that any mercury released to a waterway would sink to the bottom and be inert. However, Swedish scientists discovered that no matter what form of mercury is discharged to the environment, be it inorganic divalent mercury, phenyl mercury or alkoxy-alkyl mercury, it can be eventually converted by either microorganisms or fish into the most toxic form—methyl mercury.
As a trace element, mercury is found naturally in minute amounts in man. According to Dr. Henry A. Schroeder of the Trace Element Laboratory of the Dartmouth Medical School, the human body contains about 0.2 parts per million of mercury. (Chemical residues are measured by scientists on parts per billion and parts per million basis; in layman's language, one part per million, 1.0 ppm, is the equivalent of one ounce of vermouth in 7,812 gallons of gin—the ultimate dry martini.) The danger to man from eating mercury-contaminated fish or birds comes from raising levels in the body. The World Health Organization has recommended that no human food contain any trace whatsoever of mercury, while Japan and Sweden, both countries with strong commercial fishing interests, have set a standard of 1.0 ppm. In Sweden scientists have criticized this maximum as excessive, and one prominent toxicologist has said that the maximum should be lowered to 0.2 ppm. The Swedish government has stuck, by the 1.0-ppm standard but recommended that consumption offish be limited to one meal a week. In the U.S. the Food and Drug Administration maximum in fish is 0.5 ppm.
The human tolerance level of mercury is not precisely known. From 1953 to 1960, 121 persons in Minamata, Japan were killed or severely disabled as the result of eating mercury-contaminated shellfish from Minamata Bay. The mercury levels in the shellfish averaged 20 to 30 ppm. The mercury had been discharged into the bay over a period of years by a plastics plant. In the U.S. three members of the Huckleby family in Alamogordo, N. Mex. suffered severe brain damage after eating a hog that had been fed grain treated with mercury.
Symptoms of mercury poisoning may occur weeks to months after exposure. The symptoms include a numbness and tingling sensation in the hands and feet, disturbed speech, inability to coordinate muscle movement, impaired vision and hearing and emotional disturbances. The 19th century expression "as mad as a hatter" came from cases of insanity suffered by hatters who inhaled vapors of mercury that was used to cure felt. In severe cases the symptoms of mercury poisoning are irreversible. A report submitted by an international committee in Stockholm last year stated: "In infants born to mothers with large amounts of methyl mercury, the symptoms are somewhat different. Most children had mental retardation and also cerebral palsy with convulsions."