Between 1983 and 1998, pathologists from the College of Veterinary Medicine at the University of Montreal carried out postmortems on belugas found dead in the river. The scientists found that 18% had died of various forms of cancer, and that their tissues also contained substances such as heavy metals, organochlorines, polycyclic aromatic hydrocarbons, and tributyltins.
“Different types of tumours have been described in that cetacean population: adenocarcinomas originating from the intestine, the mammary gland, the stomach, the uterus…tumours affecting the reproductive organs, like the ovary or the tubular sensitalia,” said veterinary pathologist, Andre Dallaire of the University of Montreal. “And the interesting thing is that there isn’t a whale population anywhere in the world in which you’ve seen that many tumours.”
The scientists also point out that there is also a high occurrence of cancers in humans in the area.
Reduced from a population of 5,000 in the late 1800’s, to 650 today, the St Lawrence belugas are not migratory, unlike other populations of the species, due to the high level of plankton, small invertebrates, and fish in the river. The meeting of the cold Labrador current and the sediments from the St Lawrence tributary, the Saguenay River, causes an up-welling of nutrients.
However, the St Lawrence drains industrial north-eastern North America, as well as agricultural land, and at the foot of the Saguenay River is an aluminium plant. The area populated by the beluga whales is where the pollutants concentrate.
“The St Lawrence itself is draining one-fourth of North America’s most industrialised area, and the Great Lakes, which are in the centre of this area, are connected to the St Lawrence,” said Dallaire.
There is also concern amongst the scientists that the pollution may be causing immunosuppression, leaving them vulnerable to other opportunistic infections.
One problem that the scientists are encountering is their lack of opportunity to carry out meaningful experiments. “One of the facts of life when you’re dealing with whales and dolphins: they are protected, all of them, and you can’t do experiments on them,” points out Daniel Cowen, a pathologist at the University of Texas. Initial results from laboratory tests on mice have shown the whales to be far more sensitive to mixtures of chemicals.