High cancer rate stalks St. Lawrence belugas
Scientists and industry disagree over cause of whale deaths
An alarming rate of cancer in an isolated and once-populous pod of St. Lawrence River belugas is threatening the whales' survival, marine mammal researchers in Quebec say.
Rare beluga commune
The fact that belugas live as far south as the St. Lawrence estuary at all is considered a minor scientific miracle. Most of the world's beluga population lives in Arctic and sub-Arctic waters.
But unique conditions that bring cold ocean salt water — along with the krill and other food staples belugas normally eat — up the St. Lawrence have brought the whales, as well as thousands of tourists who flock to towns such as Tadoussac, Que., to enjoy some whale-watching.
Croisières AML, one of the region's most popular outfitters taking visitors on whale-watching excursions, says typically 200,000 people come from all over the world each year, hoping to spot belugas and other types of whales that populate the area.
Stéphane Lair, an associate professor at the college of veterinary medicine at the University of Montreal, says he fears the whales — which once numbered close to 10,000 — may one day disappear.
"Will there be beluga whales in this area 50 years from now? I don't know," Lair told CBC News.
Current estimates place the population of belugas in the St. Lawrence at about 1,000. Hunting of the belugas, which went on until the mid-1970s, is blamed for most of the population drop. But another killer has haunted the creatures.
Lair is in charge of an ongoing study that began in the early 1980s to track the population and health of the whales. In a research paper published in 2002, Lair's department warned that the whales were dying of cancer at an unusually high rate. Seven years later, cancer is still a major problem plaguing the St. Lawrence belugas.
Toxins to blame?
Researchers blame the elevated cancer rates on the presence of chemicals known as polycyclic aromatic hydrocarbons in the estuary where the belugas live and feed during the summer months. PAHs are considered a carcinogen for humans and animals.
The study pointed to the aluminum smelters that have operated nearby for decades and that used to dump PAHs directly into the Saguenay River, where they were carried downstream into the St. Lawrence estuary.
Researchers say they have no conclusive scientific evidence that places the blame on the aluminum smelters. However, Lair says chemicals discharged into the river in the past may help explain why a quarter of the beluga whales in the area now seem to be dying of cancer.
"We have a very unusual cluster of cases of cancer. The number of cases appears to be unusually high compared with other clusters of marine mammals," Lair said.
Polycyclic aromatic hydrocarbons (PAHs)
PAHs are a group of more than 100 different chemicals formed during the incomplete burning of coal, oil and gas, garbage, tobacco and charbroiled food.
Some PAHs are manufactured — existing as colourless, white or pale yellow-green solids — and are found in coal tar, crude oil, creosote and roofing tar. A few are used in medicines or to make dyes, plastics and pesticides.
The U.S. Department of Health and Human Services has determined that some PAHs may reasonably be expected to be carcinogenic. In studies, mice fed high levels of one PAH during pregnancy had difficulty reproducing, as did their offspring.
The reason to suspect PAHs, Lair says, is simple: Unlike other species that live in the same water, belugas feed from the river's bed, dredging through sediment to scoop out the krill and mudworms that form a large part of their diet. The sediment is where the PAHs settled years ago, and the toxins still have not dissipated completely.
"If you look in their stomachs, you find rocks and sand. That indicates they [belugas] do ingest sediment," Lair said.
The company that has been making aluminum in the area for decades says there is no proof that places the blame for cancer among whales on its industrial activities.
"The Saguenay River is a river that is 100 kilometres long, and there is no scientific evidence that allows us to make that connection directly," says Guy Bouchard, director of environment with Rio Tinto Alcan, which operates four smelters in the area.
"Belugas are exposed to many things."
Bouchard says rather than blaming the aluminum industry for the whales' woes, scientists should turn their sights on the shipping and tourism industries, which spew pollutants into the marine mammals' habitat.
"They are also exposed to the marine industry, with releases of oil, PCBs and PAHs. The tourism industry is also contributing to that," he said.
Cleaner industry
Though the company refutes responsibility for causing cancer in whales, significant steps have been taken to clean up the way aluminum is made, Bouchard says.
"If we look at discharges to the air, we are 90-per-cent-plus cleaner than before. In terms of direct discharges to water, we're 99 per cent cleaner, since the early 1980s," Bouchard said.
The industry was cleaned up in an effort to achieve better efficiency, he says, and to safeguard the health of its workers.
Lair says those efforts are paying off for the whales and their habitat. He says while toxins are still present in the river's sediment, the level of contamination has dropped.
'They [belugas] can live up to 60 years, so the ones that are dying were around when the contamination was very high.' —Dr. Stéphane Lair
New data suggest toxic sediment appears to be dissipating gradually, possibly because much of it has been consumed by whales over the years. The falling levels of toxins in the sediment are an encouraging sign, Lair says, offering some hope for the long-term survival of the beluga whale population in the St. Lawrence.
But he says for much of the current population, and the older whales in particular, the outlook is bleak. The latest observations indicate the cancer rate is as high as ever, about 25 per cent, Lair says.
"They can live up to 60 years old, so the ones that are dying were around when the contamination was very high," he said.
Researchers can do little except monitor the belugas and wait to see whether the cancer rates drop and the whale population's health improves as the toxins in the river sediment gradually dissipate.
"The level of PAH in the sediment doesn't appear to be that high now. It will be interesting to see if, in 30 years, belugas born now will have developed as much cancer as their parents did," Lair said.
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