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Biology

Disconcerting trends of pollutants in the Scandinavian Otter Population

 

Article: Roos, A.; Berger, U.; Järnberg, U.; van Dijk, J.; Bignert, A. Increasing concentrations of perfluoroalkyl acids in Scandinavian otters between 1972 and 2011: A new threat to the otter population? 2013. Environ. Sci. Technol. DOI: 10.1021/es401485t

 

European Otter (Lutra lutra) and trends of some perfluorinated compounds (PFCs).

European Otter (Lutra lutra) and trends of some perfluorinated compounds (PFCs).

Background – What are PFCs?

Teflon® and Scotchgard™ are brand names that most people recognize and use regularly.  What many people might not have thought of is the behind the scenes production of these products.  What makes them so effective?  The answer lies largely in the chemistry of a particular group of compounds, known as perfluroalkyl compounds, or PFCs.  While production methods of these popular name brands have begun to change, that doesn’t mean they are automatically gone from existence.  In fact, they may linger for many years to come.  PFCs are synthetically derived substances that have been in wide-scale production and use for over 50 years in both industrial and consumer applications.  Chemically speaking, the majority of these compounds have a chain that consists of 4 or more carbons where the hydrogen atoms have all been replaced with fluorine atoms.  At the end of the chain is usually a functional group of carboxylic or sulfonic acids, which separates these PFCs into either perfluoroalkyl carboxylic acids (PFCAs) or perfluoro alkane sulfonic acids (PFSAs).  

Their chemical structure imparts unique properties on these compounds, making them extremely useful for numerous things, including stain repellents for carpets, furniture and textiles, water repellents on clothing and food packaging, and fire-fighting foams to name a few, but also making them extremely resistant to degradation, allowing them to persist in the environment and potentially bioaccumulate up the food chain.

Previous Research and Current Status

Due to their extreme usefulness, production of PFCs occurred on a wide scale and generally unregulated basis until relatively recently.  Within the last two decades, measurements of certain PFCs in both environmental and biological matrices, such as water, air, sediment, liver, and blood serum have been made.  The findings show that many PFCs have near global distribution and potentially adverse health effects, which is a cause for great concern.

The two compounds typically found in the environment at the highest concentrations are the PFSA perfluorooctane sulfonic acid (PFOS) and the PFCA perfluorooctanoic acid (PFOA).  Laboratory studies, primarily on rodents, found that as concentrations of both compounds increase, combined negative effects may be observed on the liver, lungs, reproductive, developmental, and endocrine systems.  This research led to the recent listing of PFOS under Annex B of the Stockholm Convention in 2009, which largely restricted its production and use.  Even prior to this listing, one of the world’s largest producers of PFOS, the 3M Company participated in a voluntary phase-out of their PFOS production.  The combination of this phase-out and production restriction lead people to believe that concentrations of, at least PFOS, would decline in recent years.  Indeed studies performed on human serum, Baltic gray seals, and guillemots from Sweden, observed decreasing trends of some PFCs.  However, in a recent analysis of data from otters (Lutra lutra) from Scandinavia, trends observed were not the same and did not appear to be decreasing over time.

This Study

A recent study analyzed livers of otters from Sweden and Norway for a variety of PFCs to see if there are any existing trends over time or differences between the regions.  While PFCs are not known to be produced in Scandinavia, products that contain them are imported and previous research states that concentrations of PFCs near urban centers are almost always higher than concentrations from undeveloped and rural areas.  The otters in question from Norway were from a primarily marine environment, and from Sweden, a primarily limnic, or freshwater, environment.  Liver samples from otters collected between 1972 and 2011 were analyzed for fifteen different PFCs, and of those, PFCs with 8 or more carbons were detected in >80% of all samples, with PFOS being the most prevalent compound found, followed by perfluorononanoic acid (PFNA).

In comparison to other research, the concentrations of some PFCs found in otters from this study were similar to the concentration levels found in polar bears, which are top predators and are generally associated with some of the highest concentrations of pollutants; and higher than other mammals, such as the arctic fox, ringed seal, and mink.  The authors suggest that otters may accumulate PFCs up to a certain concentration, where a “steady-state” is reached and the concentration levels remain more or less the same for the rest of their lives.  This is different than what has been observed in other species, such as seals and bottlenose dolphins, where loss of pollutants has been observed via lactation and urine.

From 1972 – 2011, a clear and significant increase in concentrations of 9 out of 11 compounds investigated was observed.  When breaking it down into the subgroups of PFCAs and PFSAs, and looking only from the ten year period from 2002 – 2011, the rates of increase of PFCA concentrations are even faster than over the 40-year time scale, yet there is no significant trend observed for PFSAs.  This is attributed to the fact that the PFOS falls under the category of PFSA and while its production has largely decreased due to regulations, it is still very persistent and very prevalent in the environment.

Implications

One of the main issues addressed by the article are the differences between otters and other biota. Where other research has shown PFC concentrations beginning to decline in many mammals and fish, the concentrations in these otters have remained both relatively constant, and relatively high.  Historically speaking, the otter population in Sweden was greatly affected by more traditional persistent organic pollutants, such as DDT and PCBs in the 1970s and 80s, but rebounded in the 1990s after the banning and phasing out of those pollutants.  Now there are new chemicals of concern, such as these PFCs, and more research needs to be done in order for threats to the otter population, as well as other populations (including humans), to be better understood.  As more information is gathered and the data becomes more available, hopefully it will be easier for agencies to implement regulations on the production and use of these chemicals that are now found ubiquitously in the environment.

Erin Markham

Erin Markham

Erin received her B.S. in Environmental Science from the University of Rhode Island in 2010 and is currently working towards her Masters at the University of Rhode Island's Graduate School of Oceanography.Her current research involves persistent organic pollutants in the Atlantic Ocean.
Erin Markham

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