Do PAHs (toxic contaminants) cause cancer in St. Lawrence beluga whales?

The St. Lawrence beluga whale population is heavily contaminated by various toxic products including heavy metals, polycyclic aromatic hydrocarbons (PAHs), PCBs and DDT. This population also has the highest rate of cancer detected in wild animals. Is there a link between beluga whale cancer and the contamination of their environment?

To go through the looking glass:

Between 1983 and 1999, 129 of the 263 beluga whales found dead along the shores of the St. Lawrence were examined in the Université de Montréal’s Faculty of Veterinary Medicine necropsy room at Saint-Hyacinthe to determine cause of death.

In short

With a 27 percent incidence, cancer is the main cause of death of adult St. Lawrence beluga whales. This cancer rate is much higher than what has been discovered in Arctic beluga whales. It is also higher than the rate of any other wild mammal species. It is, in fact, quite comparable to the human cancer rate. Six of the 18 cases of cancer detected affected the small intestine. This type of cancer is very rare in both animals and in humans. Mammary gland cancer—a first for marine mammals—, ovary cancer, cancer of the uterus, skin cancer, stomach cancer, salivary gland cancer, cancer of the thymus, neuroendocrine and bladder cancers were also detected.

Stomach, digestive system and breast cancer in the human population living near the beluga whale home range are also particularly high when compared to other regions of Quebec and Canada. Several studies have established a link between cancer in humans and exposure to polycyclic aromatic hydrocarbons (PAHs), powerful carcinogenic agents discharged into the atmosphere by aluminum smelters. Considering the presence of high levels of PAHs in the beluga whale environment and their contamination by these products, it is possible that the high rates of cancer found in St. Lawrence beluga whales are caused by these toxic emissions.

Project leader:

Daniel Martineau, Karin Lemberger, André Dallaire and Philippe Labelle of the Département de pathologie et microbiologie de médecine vétérinaire of the Université de Montréal, Thomas P. Lipscomb of the Department of Veterinary Pathology of the Armed Forces Institute of Pathology in Washington, Pascal Michel and Igor Mikaelian of the Faculté de médecine vétérinaire of the Université de Montréal.

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