Dassuncao, C.; Hu, X. C.; Zhang, X.; Bossi, R.; Dam, M.; Mikkelsen, B.; Sunderland, E. M. Temporal shifts in poly- and perfluoroalkyl substances (PFASs) in North Atlantic pilot whales indicate large contributions of atmospheric precursors. Environ. Sci. Technol. 2017. DOI: 10.1021/acs.est.7b00293
The Problem with Persistence
When it comes to persistent pollutants, all roads lead to the ocean. Much like plastic products, your pharmaceuticals, soaps, laundry detergent — even chemicals that leach out of your couch – all end up in the sea eventually. Many of these chemicals accumulate in animals, while others attach to particulate matter and end up sinking to the sea floor.
Perfluorooctanesulfonic acid (PFOS) is a chemical that has recently gained attention due to its toxic effects and widespread presence in drinking water. PFOS, along with other fluorinated chemicals collectively known as PFASs, originates from products like non-stick cookware, rainproofing materials, and foams manufactured to fight fuel fires at places like airports. Where else can PFOS be found? You guessed it – PFOS from human products has become widespread in ocean waters.
Pollutants are Poisoning Marine Mammals
Bioaccumulation (the process where pollutants accumulate in the tissues of living things) is a huge threat to the health of marine animals. You can think of every living animal in the ocean as a sponge that slowly accumulates pollutants from the surrounding water over time. As top predators in the sea, large marine mammals not only accumulate their own pollutants in this sponge-like way, they also eat TONS of fish, squid, and other animals – each with its own toxic burden. With each meal, pollutants are transferred from prey to predator. This process, known as biomagnification, means that seals, orca, pilot whales, dolphins, and other large mammals that must eat a lot of fatty fish and other marine animals to survive are disproportionately affected by marine pollution.
The poisoning of marine mammals has come up repeatedly in the news, including this recent article from BBC states that one of the few remaining UK orca recently washed up on shore, and analysis of its tissues showed some of the highest levels of PCBs, a group of cancer-causing pollutants that were banned in the 1970s, ever seen.
Even though PCBs have been banned and are no longer in use, the oceans are still full of these pollutants, along with newer classes of pollutants, deemed “emerging contaminants”, that are still being used, or have only recently been banned. However, societies are slowly becoming more wary of emitting synthetic compounds willy-nilly, and recently, there have been crackdowns on some groups of emerging contaminants, including PFOS, which was banned and phased out of use in many areas as of 2002 (though PFOS is being replaced with similar chemicals that pose similar problems). Many PFOS “precursor compounds”, which are fluorinated pollutants that degrade in the environment or in organisms to form PFOS, have also been regulated. Is this too little too late? In a recent study, researchers from Harvard University in collaboration with Aarhus University in Denmark set out to answer this question: Since we’ve stopped using PFOS, have levels in marine mammals declined?
The Far-Flung Faroe Islands
To assess trends over time in levels of PFOS in marine mammals, scientists measured levels of PFOS as well as FOSA, a compound which degrades to form PFOS, in samples from juvenile pilot whales caught in the Faroe Islands region of the North Atlantic Ocean from 1986 to 2013. They wanted to see whether time trends responded to changes in human manufacture and usage.
The Faroe Islands are an archipelago between Scotland, Iceland, and Norway. Pilot whales are native to this region and don’t move around much, meaning their pollutant levels weren’t affected greatly by changes in location, and should be representative only of changes over time.
Also, pilot whales are an important part of the traditional diet of humans who live on the Faroe Islands. Human exposure to PFOS and other fluorinated chemicals in the region have been found to have some worrisome health effects. For example, researchers have found that children from Faroe Islands with higher levels of PFOS and other fluorinated chemicals in their bodies have weaker antibody responses to vaccines, meaning that these chemicals are disrupting the children’s immune systems.
Are Pilot Whales Becoming Cleaner?
Unfortunately, almost all fluorinated chemicals measured in the study were increasing through time, even after the phase-out of PFOS. Only FOSA, the precursor which degrades to form PFOS, was declining in pilot whales after 2006. The figure below shows how FOSA began to make up a lower percentage of total fluorinated chemicals over time. FOSA degrades and is not persistent like PFOS, so its levels may respond more rapidly to changes in current emissions.
PFOS levels were increasing more slowly than other fluorinated pollutants, suggesting that the PFOS ban may be slowly having an effect. However, it’s still increasing despite the ban. This is a grave reminder that, while regulation can make a difference eventually, these pollutants can last for a very, very long time in the environment, and we need to think before we emit to prevent long-term environmental damage.
PFOS Closes a Door, but its Replacements Open a Window
While levels FOSA were decreasing in pilot whales, this decline was offset by increases in other types of fluorinated pollutants, meaning that the total fluorinated burden in the pilot whales did not change significantly over time. These other pollutants, known as long-chain fluorinated carboxlyates, have been banned in the United States as of 2015, but are still produced in some other countries.
Pilot whales have a long, arduous struggle ahead of them before they can rid their bodies of fluorinated chemicals, and people who rely on these whales as a source of sustenance could continue to be negatively affected by exposure to these chemicals for decades to come.
I am the founder of oceanbites, and a postdoctoral fellow in the Higgins Lab at Colorado School of Mines, where I study poly- and perfluorinated chemicals. I got my Ph.D. in the Lohmann Lab at the University of Rhode Island Graduate School of Oceanography, where my research focused on how toxic chemicals like flame retardants end up in our lakes and oceans. Before graduate school, I earned a B.Sc. in chemistry from MIT and spent two years in environmental consulting. When I’m not doing chemistry in the lab, I’m doing chemistry at home (brewing beer).