According to National Geographic, researchers have found that a species of bottom-feeding fish, Atlantic tomcod, who live in the Hudson River has come to develop genes which make them immune to the effects of polychlorinated biphenyls (PCBs) present in the water from toxic dumping years ago.
PCBs first entered the market in 1929 and were used in various industrial and commercial applications, especially electrical insulators. Though they were banned in 1979, they do not degrade easily. Due in part to PCB contamination, 200 miles of the Hudson River are considered by the Environmental Protection Agency
the largest cleanup site in the nation under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA). Scientists have only recently begun to understand why Atlantic tomcod are surviving PCB exposure that kills most other fish.
Lab experiments have shown that fish embryos exposed to PBCs have been found to have smaller hearts which don't beat properly. But Atlantic tomcod in the Hudson River, likely the most highly exposed fish in nature, have shown the ability to modify a gene which encodes a protein regulating the toxic effects of PCBs. The adaptive mechanism is nearly universal in Atlantic tomcod appearing in the Hudson River, and occurs infrequently in tomcod populations in other locations. Researchers believe that the tomcod populations in the Hudson already had a genetic mutation prior to their heavy exposure to PBCs beginning in 1929, and that they may have been wiped out completely had they not had such a mutation.
Researchers say that the development represents a very rapid evolutionary change that occurred over 20 to 50 generations, making the tomcod one of the world's fastest evolving fish populations.
General Electric, the company bearing the most responsibility for PBC cleanup in the Hudson River, dumped roughly 1.3 million pounds into Hudson from 1947 to 1976. Experimental dredging conducted by GE in 2009 led the EPA to conclude that cleanup up the Hudson is the best response to the toxic dumping. While the dumping, theoretically, may not be the best for tomcods who now might be dependent on PBCs, it is believed that fish populations across the spectrum will benefit.
PCB is one of various chemical compounds that may adversely affect not only animals, but humans. Other toxic chemicals to which people are commonly exposed are asbestos, benzene, lead and dioxins or DDT.
Source: National Geographic, "Hudson River Fish Evolve Toxic PCB Immunity," Anne Minard, 17 Feb 2011.
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