Toxic chemicals, originating from oil emissions and wildfire smoke, have been discovered in muscle and liver samples from Southern Resident killer whales and Bigg’s killer whales off the coast of British Columbia. This groundbreaking study, published in Scientific Reports, is the first to identify polycyclic aromatic hydrocarbons (PAHs) in orcas in this region, shedding light on the transfer of these chemicals from mother to fetus.
Dr. Juan José Alava, senior author and principal investigator of the UBC Ocean Pollution Research Unit, highlights the significance of killer whales as indicators of ocean health, emphasizing that their ability to metabolically process PAHs suggests recent exposures. PAHs, found in coal, oil, and gasoline, are known to be carcinogenic and mutagenic, posing toxic risks to mammals. Sources of these chemicals in the ocean include oil spills, coal combustion, and particles from forest fire smoke.
The study analyzed samples from six Bigg’s killer whales and six Southern Resident killer whales stranded between 2006 and 2018. Testing for 76 PAHs revealed their presence in all samples, with some compounds appearing in at least 50% of the samples. A particular PAH derivative, C3-phenanthrenes/anthracenes, accounted for 33% of total contamination, demonstrating the persistence and toxicity of alkylated PAHs in the orcas.
This research is unprecedented in B.C., and though the contamination levels were lower than in some other regions, they highlight the threats killer whales face. The study found variations in contaminant types between Bigg’s and Southern Resident killer whales, linked to their distinct habitats and feeding behaviors. The findings underscore the impact of human activities, such as oil pipeline developments, industrial effluents, and forest fires, on marine ecosystems.
Dr. Stephen Raverty, co-author and veterinary pathologist, warns that pollution could contribute to the decline of killer whale populations. The study includes Luna, an orca with extensive human contact, showing a mixture of hydrocarbon contaminants, underlining the complex interplay of factors affecting individual whales.
Paul Cottrell of Fisheries and Oceans Canada acknowledges the importance of baseline data on PAH levels in killer whales for monitoring trends and impacts. Dr. Alava concludes that reducing fossil fuel consumption is crucial for combating climate change, preserving marine biodiversity, and safeguarding the health of marine ecosystems and communities.
