Beluga whales are a kind of toothed whale, whales with teeth rather than baleen, that may be endangered in part because of chemical pollution. Although they are protected from hunting, toxins such as DDT and PCBs contaminate the food they eat accumulate in their fatty tissues and cause a high rate of cancer in adult belugas. The level of toxins is even greater in the rich milk that mothers produce to nurse their babies. The babies feed on this milk for a year or longer, and in this way each succeeding generation becomes more contaminated. The Atlantic population of belugas was reduced to about 500 whales in the 1970s, and chemical pollution may help explain why their numbers have not increased at all since then.
Oil is another kind of chemical pollution that can harm whales.
Whales may ingest contaminated prey and sediments, or contact with oil may impair the filtering efficiency of their baleen. Another important concern is that air pollution has depleted the ozone layer above the Antarctic. Exposure to UVR also may be responsible for skin lesions observed on whales in the area. Shipping Shipping poses a threat to some whale species. The North Atlantic right whale is highly endangered, and collisions with ships in the southeastern United States are killing one or two whales per year.