Orcas in the waters of British Columbia (Canada) were found to have some of the highest levels of man-made pollutants (PCBs and PBDEs) of any marine mammals in the world. These pollutants are linked to issues with reproductive health, the immune system and development. As orcas are at the top of the food chain, these pollutants accumulate in their system, giving us an insight into ocean health and pollution throughout the entire ecosystem.
I've briefly summarised the article "Fireproof killer whales (Orcinus orca): flameretardant chemicals and the conservation imperative in the charismatic icon of British Columbia, Canada" (published in 2006 by Peter S. Ross in The Canadian Journal of Fisheries and Aquatic Sciences) partially because it has such a kick-ass title, and partially because I think it is increasingly relevant now that we know more about how these pollutants are moving through a food chain in which we are also a top predator.
This issue is not just relevant to orcas (and Canadians) but to all of us, as these same pollutants are increasingly found in humans.
Some Handy Definitions
A breakdown of some of the science lingo.
PCBs: Polychlorinated Biphenyls; a man-made chemical used in a range of products including cars, household appliances, paint & electric equipment (usually as an insulator). They are very soluble in fat, which means they attach to fatty tissues in animals and can build up over time. Banned in most countries since the 1970s, but still present in existing products, as well as in sea water & ocean sediment (and, of course, in oceanic microplastics).
PBDEs: Polybrominated Diphenyl Ethers; a man-made chemical used as a flame retardant (added to plastic and other products to prevent them from catching fire) often used in electronics, furniture, building materials, cars, planes and consumer products. Industrial production of some PBDEs is limited under the Stockholm Convention (an environmental treaty aiming to phase out POPs). Humans are exposed to these primarily through food and they bioaccumulate in blood, breast milk and fat tissues.
POPs: Persistent Organic Pollutants; chemicals which stick around for a long time in the environment (persistently) and accumulate in animal fats. This includes pesticides, industrial chemicals and by-products. For example, PCBs which can enter the environment through spills or dumping and then stay in the sea water or accumulate in sediment, on microplastics, or in animal tissue.
Bioaccumulate: building up of substances inside a living organism. Illustrated nicely in this diagram:
The Abstract "Long-lived and high trophic level marine mammals are vulnerable to accumulating often very high concentrations of persistent chemicals, including pesticides, industrial by-products, and flame retardants. In the case of killer whales (Orcinus orca), some of the older individuals currently frequenting the coastal waters of British Columbia (BC) were born during the First World War, well before the advent of widespread chemical manufacture and use. BC’s killer whales are now among the most polychlorinated biphenyl (PCB) contaminated marine mammals in the world. While the “legacy” PCBs have largely been banned, polybrominated diphenyl ethers (PBDEs) have recently emerged as a major concern. The endocrine-disrupting nature of these two persistent fire retardants in biota spells trouble at the top of the food chain, with increasing evidence of effects on reproductive health, the immune system, and development in exposed mammals. The heavy contamination of BC’s killer whales, coupled with their long life span and high trophic level, highlights the need for a “weight of evidence” approach in research, conservation planning, and regulatory decisions. Given the global nature of contaminant dispersion, such approaches can only be effective when carried out on both national and international scales."
Essentially these potentially dangerous (and in some cases already banned) chemicals have been found at extremely high levels in a top ocean predator. This is not just an issue because orcas are adorable and extremely cool, but also because of what this means for our oceans, and ourselves. At the very least, in the water off Vancouver our man-made toxins are accumulating inside large marine mammals. In a broader sense, we have filled our oceans with so much waste that it's now accumulating in the higher trophic animals (like us). The environment cannot process these man-made chemicals and, while invisible to the naked eye, they don't just go away.
Unfortunately this article is not unique, with POPs found in bottlenose dolphins in Mexico and Florida; in Indian Ocean orcas; in pilot, fin and sperm whales in the Mediterranean; in North Atlantic humpback whales; in polar bears and ringed seals in the Arctic; just to name a few...
This issue is challenging as the pollutants themselves are not visible. The range of potential health impacts (like cancer, or birth deformations) may or may not ever be linked back to PCBs and PBDEs in individuals.
However the high levels of these toxins in orcas is a worrying sign.
I personally don't eat seafood or sea creatures. This is for a whole range of reasons, one of which is that I have read A Lot of scientific journal articles about the pollutants and toxins hidden inside. So, while even some fish markets are telling you that eating smaller fish is a better option, avoiding seafood altogether is probably a better one. There's a reason that limiting fish consumption is recommended to pregnant women and young children. Take a look here for more ways to be part of the solution to plastic & ocean pollution.
The full journal article is available here: http://www.orcanetwork.org/Main/PDF/RossPBDE.pdf