Over a quarter of all deaths of adult beluga whales in Canada?s Saint Lawrence Estuary are caused by cancer, researchers have found. Such high rates of cancer are unprecedented in wild animals, except for fish. Industrial pollution is the most likely cause.
Belugas live entirely in the Arctic and sub-Arctic. There are approximately 70,000 worldwide and about 650 of these live in a small region of the St. Lawrence Estuary in Quebec. Between 1983 and 1999, 263 dead whales were reported. Daniel Martineau of the University of Montreal and his team conducted 100 autopsies of the whales and found that cancer, particularly cancer of the digestive tract, was the cause of death of 18 per cent of juvenile belugas and 27 per cent of the adults.
?Cancer in wildlife is not very well studied but such a percentage has never been observed among wild animals anywhere else in the world,? he says. ?In dolphins and terrestrial animals, the figure is closer to two per cent.?
The autopsies revealed evidence for a high level of exposure to carcinogenic polycyclic aromatic hydrocarbons (PAHs). Most PAHs in the St Lawrence Estuary region originate from an aluminium plant upstream. The belugas are exposed because they dig around in contaminated sediments and eat the invertebrates that live there.
Martineau also found high levels of PCBs, another carcinogen, in the adult Lawrence Estuary belugas, as well as heavy metals, which weaken the immune system. People living in the region suffer higher rates of lung, urinary and digestive cancers than those living elsewhere in Quebec and Canada.
The Alcan aluminium plant says it has slashed its PAH output. ?We?ve reduced PAH emissions in the air by 82 per cent, and new technology introduced last year will reduce it by a further 35 per cent. We are concerned and we?ve worked to improve the situation,? a spokesman says.
The St. Lawrence Estuary is open to the Atlantic Ocean so pollutants can enter from other places as well, linking the plant?s emissions and the cancers is difficult. And cleaning up the pollution in the estuary would create its own problems, warns a spokeswoman for the World Wildlife Fund, who says, ?Most of what remains is in sediments, and cleaning that up could be just as harmful. You would end up re-suspending a lot of the matter that is now staying put, impacting on a variety of species.?
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