Toxic chemicals found in beached pilot whales in Scotland

            An article published in the Guardian in February of this year covered a study done on the level of toxic metals found in whales that were stranded on the Scottish coast. These whales were found to have abnormally high levels of Mercury, Cadmium and other toxic heavy metals in their bodies, with accumulation in the brain, liver, kidneys, and other bodily reservoirs (1). The presence of toxic heavy metals in the environment has become increasingly problematic, from the industrialization of many countries, as well as the historical dumping of metallic byproducts from mining and ore refinery into the oceans, from centuries. Toxic metals have been seen to have widespread distribution, historical heavy use, and many environmental hazards, including uptake into animals, humans, and natural water supplies.

            The study presented in this article, led by a group of environmental analytical chemists from the University of Aberdeen, was conducted after a stranding of 21 Pilot whales in September of 2012. These whales were analyzed for toxic metals known to be present in whales, due to their presence in the greater oceanic environment, and found that Cadmium, a known issue in younger whales, as it is able to cross the blood-brain barrier, was found in high concentrations in the brains of adult whales. That these heavy metals are found in the brain has led to the suggestion, though no concrete evidence, that accumulation leads to a loss of brain function, and thus increased strandings from a lack of ability to navigate properly (2).

            The article published in Science of the Total Environment (2), from which the Guardian took their information, is from Dr. Eva Krupp’s group out of the University of Aberdeen, and focuses on the levels of Mercury and Cadmium that are detectable in the bodies of Pilot Whales at different stages in their lives. As stated above, the study used for this article was focused on the bodies of 21 stranded whales, with various ages from juvenile to adult. In whales, it is generally the role of selenium to act as a detoxifying agent for these metals, processing the absorbed toxins, and expelling them from the bodies. However, with infant, juvenile and in-utero calves, there is not enough selenium present in their systems to act in this purifying manner, and accumulation can lead to premature deaths. The main point, here, the article states, is that while heavy metal toxins will accumulate in the body from environmental and dietary intake, the amount and availability of selenium in the body will not (3).

            The study concludes with a hopeful outlook on understanding the mechanism of Cadmium accumulation within the bodies of adult whales, as there is limited information on the subject, and Krupp’s group was able to study the accumulation within a single pod, all with various ages, allowing for a more select testing group, than would be provided by random stranded whales that may have no connection. Krupp also states that as this study also found the highest levels of Mercury (by concentration) in mammals living within the Arctic circle, that there is an increasing level of toxic metals within seawater (2).

Although the Guardian article presents good coverage of the scientific article, they rely heavily on quotes from the Journal itself, rather than attempting to draw conclusions based on the scientific data. However, I thought that the quotations that they did choose presented information in a relatable way, even to a public that may not be science savvy. There is also a point of contention in the title of the two articles; the Guardian with the headline of “Scientists have found clear evidence that whales are absorbing high levels of toxic heavy metals…” and the Krupp article with “Possible link between Hg and Cd accumulation in the brain of long-finned pilot whales (Globicephala melas)”

 That the journal article seems to rely more on the idea that the accumulation of these metals in the brain is a factor in strandings, and the Guardian article states (by quote) that it is not a proven connection was odd to me, as the Guardian quotation was attributed to Dr. Krupp, herself. Overall, I think that with the heavy reliance on quotations from the Science of the Total Environment article, and the lack of general background information of metal toxicity, I would rate the Guardian at 5/10, as it does present interesting results, though not within the best context for its readers.

References:

      1.       Carrell, Severin. (11 February, 2016). “Toxic chemicals found in beached Pilot Whales in Scotland” The Guardian: https://www.theguardian.com/environment/2016/feb/11/toxic-chemicals-found-in-beached-pilot-whales-in-soctland
2.       Gajdosechova, Z. et al. Possible link between Hg and Cd accumulation in the brain of long-finned pilot whales (Globicephala melas). Science of The Total Environment 545–546, 407–413, doi: 10.1016/j.scitotenv.2015.12.082 (2016)
3.     N. Sakulsak et. al, Metallothionein: an overview on its metal homeostatic regulation in mammals Int. J. Morphol., 30 (2012), pp. 1007–1012