Toxic Chemicals: Page 1 Endangered Species Handbook

Aquatic Ecosystems

Toxic Chemicals: Page 1

Beluga whales (Delphinapterus leucas) in the St. Lawrence River have also been affected. Isolated from members of their species living further north for thousands of years, they have declined dramatically in recent years. Many of these beautiful whales, known for the lyrical songs they sing to one another, have been found dead with tumors, malformations and impairment of female reproductive organs. This river, which links Lake Erie to the Atlantic Ocean, has become severely polluted with chemical contaminants, resulting in declines in wildlife. American eels (Anguilla rostrata) accumulate high levels of toxins on their spring migration from the Great Lakes down the St. Lawrence River to the sea and contaminate the Belugas when they feed on them. A major source of PCBs in the river is a sunken barge in the Gulf of St. Lawrence, which has been oozing these toxins for more than 25 years; its cleanup is difficult because there is fear it will break apart either on its own or if moved (Nickerson 1996).

The St. Lawrence belugas numbered about 5,000 in the 1600s, but whaling, which went on until the 1940s, reduced their population to about 2,500 (Katona et al. 1993). Before they could fully recover, contaminants from industries surrounding the Great Lakes and St. Lawrence seaway took a tragic toll on them. Today, only 400 to 500 belugas remain in this river. A study by Dr. Pierre Beland of the St. Lawrence National Institute of Toxicology in Quebec found that 40 percent of all belugas necropsied had malignant tumors in their digestive systems, mouths, esophagi, intestines and respiratory systems. Two percent of the belugas found at the mouth of the Saguanay River were visibly deformed. PCBs, which cause malformations in mammals and birds, were found at levels up to 3,400 parts per million (ppm) in the milk of a lactating female beluga and up to 576 ppm in blubber (Katona et al. 1993). Fish is unfit for human consumption if it contains 2 ppm of PCBs.

In 1976, the United States banned the manufacture of PCBs, and other industrialized countries followed. But in the nearly 50 years that they were manufactured, an estimated 3.4 billion pounds had been produced, and they have become pervasive in the environment, spreading on air currents and through aquatic food chains. PCBs are now found in animals thousands of miles away from locations where these chemicals were used, in the blubber of whales and the milk of nursing polar bears (Colborn et al. 1996). Once PCBs are deposited in the fat of animals and humans, they remain indefinitely and do not biodegrade. These and related chemicals continue to cause birth defects and reproductive failure in wildlife (Colborn et al. 1996). Virtually all humans carry PCBs and other persistent chemicals in their body fat, and a nursing mother passes these chemicals on to her baby (Colborn et al. 1996). The higher the animal on the food chain, such as birds of prey, whales, seals and land predators, the higher the concentrations of PCBs and chlorinated hydrocarbons like DDT, multiplying up to 3 billion times as they move up the food chain from microorganisms to polar bears (Colborn et al. 1996).

PCBs have also contaminated killer whales (Orcinus orca) in the Pacific Northwest. The Institute of Ocean Sciences tested 47 of these giant dolphins living off the British Columbia coast, finding levels two to five times as high as belugas in the St. Lawrence River (NG 2000). Just to the south, the killer whales off the San Juan Islands of Washington State are in decline, with the highest PCB levels ever found in wildlife (White 2000b). Deformed polar bear cubs have been found in Norway's Svalbard Islands. Researchers in 1996 found seven cubs with both male and female sex organs (NG 1999). These islands receive three times the PCB exposure of northern Canada, where only one such case has been seen (NG 1999). Pesticides and PCBs are carried here by air and water from Europe, North America and Asia.

During the 1990s, bald eagles (Haliaeetus leucocephalus) feeding on seagulls near Lake Superior accumulated contaminants 20 times higher than fish-eating birds of the same area (Colborn et al. 1996). Bald eagle chicks hatched in the Great Lakes were found with severe birth defects, from crossed bills to missing eyes, clubbed feet and a wasting disease that causes chicks to weaken and die (Colborn et al. 1996). Scientists have detected high residues of contaminants such as dioxin, PCBs and furans in the eagles. PCBs are the most likely cause of these abnormalities, but several chemicals might interact with toxic effects (Colborn et al. 1996).

Almost the entire length of the Hudson River has been contaminated by PCB dumping and outflow from a General Electric plant. Seepage of PCBs continues from the plant foundations, even though the chemical is no longer produced here, rendering fish from the river commercially unmarketable. After decades of conservation, striped bass recovered from heavy fishing in the Hudson River, but they contain such high amounts of PCBs that if caught by sport fishermen, they cannot be sold, and pregnant women are warned not to eat them. The removal of these residues from the Hudson and other river bottoms has not been carried out because of the difficulty of containing them in such a way as to prevent their dispersal into the atmosphere. General Electric was ordered to dredge the PCB residues in 2000, but local communities along the Hudson River have expressed opposition, fearing that they would disperse throughout the river. These chemicals may be impossible to eliminate from the Earth.

Like PCBs, persistent types of pesticides and herbicides, even in minute quantities, can be stored in the tissues of aquatic organisms and accumulate in greater and greater amounts in the ascending food chain. These chemicals can accumulate to toxic levels, killing the animals or interfering with their production of eggs, a known effect of chlorinated hydrocarbon pesticides, primarily DDT, that nearly caused the extinction of the Peregrine falcon (Falco peregrinus) in North America and great declines in bald eagles and other birds. The most injurious of these, DDT, dieldrin and chlordane, have been banned in the United States for most uses, but are used in foreign countries and remain in many areas where they were manufactured.