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The beluga whale's enigmatic "smile" and snow-coloured tint have always made it a standout: In the 1860s, showman P.T. Barnum captured several and put them on display in New York.

More than a century later, the mammals have gained attention again, for a more grim distinction. A new study says the beluga is afflicted with the highest rate of cancer of any wild animal on Earth.

The likely cause is industrial pollution, researchers say.

"Belugas are the cancer champions of the wildlife world," Daniel Martineau, a veterinary pathologist at the University of Montreal, said yesterday.

The study by Dr. Martineau, to be published in the journal Environmental Health Perspective, says 27 per cent of adult belugas in the St. Lawrence River suffer from cancer. "Percentages like that haven't been seen in a population of wild animals anywhere in the world," he said.

The researchers link the whales' alarming cancer rates to polycyclical aromatic hydrocarbons, carcinogens produced by aluminum smelters at the source of the Saguenay River.

Dr. Martineau said the same contaminants help explain the higher-than-average rates of cancer among people living near the belugas' habitat.

Residents of the Saguenay-Lac St. Jean region suffer from high rates of cancer of the digestive system.

Their drinking water is drawn from surface waters exposed to airborne PAH contamination.

"This suggests that the same things are causing cancer among humans and belugas in that region," Dr. Martineau said.

Humans and belugas "are inhabitants of the same ecosystem."

Studies have also shown that aluminum workers from the Lac St. Jean region are afflicted by high rates of bladder and lung cancers. The studies link those rates to PAHs produced at the smelters.

Smelters have operated in the region since 1929, drawn there by inexpensive hydroelectric power and access to the sea.

Their presence puts them at "ecological war" with the belugas, Dr. Martineau said.

Belugas used to be plentiful in the St. Lawrence River in the 19th century, leading to their slaughter and capture. Abundant, eye-catching and easy to snare, belugas were put on exhibit in New York and in London.

About 5,000 belugas travelled the St. Lawrence's frigid waters a century ago.

After seeing their numbers collapse, Canada placed them on the endangered list in 1980.

The whales' failure to recover was something of a mystery. So Dr. Martineau began to examine beluga carcasses that had washed up on the shores of the St. Lawrence, a total of 129 carcasses between 1983 and 1999.

He estimates about 650 belugas now live in the St. Lawrence, which receives the effluent of one of the most industrialized regions of the world. Cancer in Beluga whales A study shows the adjusted annual rate (cases per 100,000) of cancer in Beluga whales of the St. Lawrence estuary is high because of the water contamination from local aluminum smelters. How it compares:

Total cancer          570      476      75      507    412     0.03

Epithelial cancer,

small intestine       222      0.8     0.1      0.5    1.8       -

Epithelial cancer,

stomach                63       15       0      0.8      0       -

Epithelial cancer,

G.I. tract            285       56     0.2      2.6    2.2       -

Mammary gland

cancer                 95       99     0.1      134     37       -