The polar bear is the top predator in a lengthy Arctic marine food chain. Pollutants become more concentrated with each link in the chain (a process known as biomagnification), which makes the bears a good place to look for emerging ocean pollutants.
“Recent scientific evidence suggests that there are unknown chemicals in polar bear blood serum that can disrupt natural hormone levels – it was our objective to identify these substances,” says Jonathan Martin, a Professor at Stockholm University. “We were concerned that the mixture of manmade chemicals in their bodies is negatively impacting the health of the bears.”
The researchers removed major protein and phospholipid interferences from the polar bear serum, stirred the serum with small pieces of plastic (polyethersulfone) to concentrate a broad range of analytes, then used HPLC and ultrahigh resolution mass spectrometry to spectrally flag unknown organofluorine and organochlorine compounds. And the news wasn’t good. Martin and his team discovered hundreds of new contaminants in all serum samples, including samples from two locations in the Canadian Arctic dating back to the 1980s. “More specifically, new classes of global pollutants were discovered, including several classes of persistent fluorinated acids. It is worrying that their concentrations appear to be increasing in the bears over time,” says Martin.
The analyses also uncovered many new polychlorinated biphenyl (PCB) metabolites (containing hydroxyl, sulfate and/or methylsulfone moieties) – an unexpected finding: “PCBs are perhaps the most prolific of all environmental pollutants – and I thought we knew everything there was to know about them,” says Martin.
To confirm their findings, the researchers conducted lab-based experiments to see if the same chemicals could be formed following PCB exposure in mice. “They were – and, what’s more, we suspect that other organisms, including humans, are also exposed to most of these fluorinated and chlorinated chemicals,” says Martin.
The emerging nature of these – and other (2) – fluorinated contaminants presents a challenge from an environmental control point of view; after all, as Martin notes, “The new fluorinated chemicals we detected are not banned under the Stockholm Convention on persistent organic pollutants (POPs) […] some have argued that all classes of perfluoroalkyl substances should be banned, because most are highly persistent and can move long-distances in oceans or air (3).”
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References
- Y Liu et al., “Hundreds of unrecognized halogenated contaminants discovered in polar bear serum”, Angew Chem Int Ed, [Epub ahead of print] (2018). DOI: 10.1002/anie.201809906 Y Liu et al., “Nontarget mass spectrometry reveals new perfluoroalkyl substances in fish from the Yangtze River and Tangxun Lake, China”, Environ Sci Technol, 52, 5830–5840 (2018). DOI: 10.1021/acs.est.8b00779 A Blum et al., “The Madrid statement on poly- and perfluoroalkyl substances (PFASs), Environ Health Perspect 123, A107–A111 (2015). DOI: 10.1289/ehp.1509934