Is Arctic PFOA contamination a “blast from the past”?
Could much of the perfluorinated chemicals found in the Arctic be the result of a legacy of past contamination?
Against the backdrop of a record EPA fine and a huge class action suit, scientific debate heats up over how and when perfluorocarboxylate (PFCA) contamination entered into the environment. The answers could spur new regulatory controls, put companies at risk for millions of dollars in future legal actions, and threaten product lines that generate billions of dollars in revenues worldwide.
The latest salvo is an ES&T critical review article, published January 1 (pp 32–34), that proposes that PFCA (perfluorocarboxylate) contamination in the Arctic is not just the result of current manufacture and use but also a legacy of past releases. The authors argue that this legacy dwarfs current emissions and resides in the oceans, where currents carry it to remote regions. As a result, they claim that a significant proportion of the PFCAs now found in Arctic wildlife could be decades old.
PFCAs—and related compounds that can generate the perfluorocarboxylates as they break down in the environment—are of increasing scientific and regulatory interest because they are persistent, ubiquitous, and linked to adverse health effects in laboratory animals. In July, a U.S. EPA science advisory board recommended that the agency classify one PFCA, PFOA (perfluorooctanoic acid), as a “likely” human carcinogen. Canada has already temporarily banned some compounds that could break down to PFOA and other PFCAs in the environment.
The presence of PFCAs in Arctic animals and even Arctic snow is an intriguing environmental mystery. An international group of researchers, led by University of Toronto chemist Scott Mabury and Ford Motor Co. atmospheric chemist Tim Wallington, has theorized that the most significant source is fluorotelomer alcohols (FTOHs), volatile compounds currently used in the manufacture of commercial products such as stain-repellant coatings. In more than a dozen papers published in ES&T and other journals over the past two years, Mabury, Wallington, and their colleagues have provided data to support their theory that when these fluorotelomer alcohols are emitted from factories or consumer products, they undergo atmospheric transport and oxidation to form PFCAs.
But all the focus on atmospheric transport means that legacy sources and oceanic transport have been ignored, says Ian Cousins, a Stockholm University chemist and the corresponding author of the ES&T critical review. In their paper, Cousins and his colleagues provide the first global and historical estimate of PFCA production and emissions. The research was underwritten by PERFORCE, an EU-funded consortium.
The paper is significant, says Mabury. “The work highlights the legacy of emissions represented by the manufacture and use of fluoropolymers. It is heartening to see an alternative and testable hypothesis—oceanic transport—for explaining contamination of remote regions,” he adds.
However, many scientists contacted for this story also noted that in addition to good science, hundreds of millions of dollars are at risk over the issue of PFCA sources. Such high stakes can have a chilling effect on scientific discourse, they note. For example, if legacy PFCAs prove to be a major source of Arctic contamination, then any push for regulation of current sources may be weakened.
For DuPont, one of the principal manufacturers of fluorotelomers, large sums are already in play. In February 2005, the company settled a class-action lawsuit brought by neighbors of a DuPont factory who were unwittingly exposed to PFOA for more than $100 million. That was followed in December by a settlement with EPA for a record fine of $16.5 million over accusations that the company violated environmental laws by withholding PFOA data. Other lawsuits wait in the wings.
DuPont disclosed in its November 2005 quarterly report filed with the U.S. Securities and Exchange Commission (SEC) that $1 billion dollars in annual company revenues could be jeopardized by regulatory restraints on PFOA and flourotelomers.
The quarterly report marks the first time that DuPont has put a value on its PFOA and PFCA activities, according to environmental lawyer Stanford Lewis, who represents a coalition of DuPont shareholders interested in corporate environmental responsibility. “The SEC disclosure makes it clearer to investors just how big the stakes are if DuPont’s products are banned by government,” says Lewis. However, DuPont is one of an estimated half-dozen major companies producing these or similar fluorocarbon compounds.
Scientists also note that industries rarely share estimates of production and emission volumes of chemicals, because they are considered trade secrets. They give credit to DuPont for publishing these numbers in ES&T. DuPont chemist and ES&T article coauthor Robert Buck notes that the critical review’s estimates come from publicly available but atypical sources, including EPA’s extensive administrative record for PFOA and from patent applications. Industry scientists who would not comment on the record for this story say that the estimates in the paper are controversial because large, difficult-to-quantify uncertainties exist in the numbers and because some of the estimates point directly to particular companies or manufacturing processes.
“We’ve put together a starting point—a hypothesis—so that when people make measurements or decide what to measure, there’s a road map that lays out the bigger picture,” says Buck. The paper’s authors estimate that from 1951, when production started, to 2004, the global industry-wide emissions of PFCAs were 3200–7300 metric tons (t)—most of which was emitted before 2000.
Scientists agree that publication of these estimates marks the beginning a lively debate on the numbers and their significance. Such a debate should be as broad as possible and held in full public view, says science policy expert David Michaels at George Washington University. “Data interpretation and synthesis is as much an art as a science. It is, therefore, an area in which conflict of interest is an even greater concern than it is in studies that generate new data,” says the former U.S. Department of Energy Assistant Secretary for the Environment, Safety, and Health. A good example of this, he says, is the data interpretation, which was conducted by scientists working for the pharmaceutical’s manufacturer, Merck, that the arthritis drug Vioxx did not cause heart problems. “It is not in the public interest to limit the interpretation of data to those with a financial interest in the outcome,” he says.
Still many unknowns
Perfluorinated chemicals came to the attention of most environmental scientists in 2000 when 3M Corp., at that time the principal manufacturer of PFOA, announced that it would no longer manufacture that compound or PFOS (perfluorooctane sulfonate). Scientists learned an enormous amount about these chemicals since then, says Trent University fate and transport pioneer Don Mackay. But questions still abound, even over fundamental physicochemical properties, he notes. The oceans do seem a likely reservoir for PFOA and PFCAs, he says, but he notes that data on oceanic concentrations of PFOA are rare and in some instances problematic.
To estimate how much PFOA might end up in the Arctic, Cousins and his colleagues combined the lowest value of the compound measured in surface ocean water (0.015–0.062 nanograms per liter) in the Central Pacific Ocean with the estimated total flow of water entering the Arctic surface ocean ([4.86 ± 1.3] × 106 cubic meters per second). The result is that 2–12 t of PFOA enter the Arctic from the ocean each year.
“It’s a reasonable first estimate,” says oceanographer Rob MacDonald with Fisheries and Oceans Canada. It is also comparable in size with Mabury and colleagues’ estimate of the flux of PFCAs blown into the region by atmospheric transport and degradation processes. Nevertheless, environmental sources and sinks for PFOA remain a major unknown, says Mackay, who notes that soil could prove to be an important reservoir. As part of EPA’s effort to monitor contaminated sites, agency scientists John Washington and Tim Colette have found that PFOA readily attaches to soil particles. Background data collected for an analytical comparison show that soil in rural Georgia, which is far from any obvious source, contains 2 nanograms per gram of PFOA notes Washington. Using this value as a maximum background soil concentration, he estimates that the reservoir of PFOA in soil worldwide could be comparable with or perhaps greater than that in the oceans.
Time trends and fingerprints
Determining how PFOA is currently reaching the Arctic is not simple, warns fate and transport modeler Frank Wania at the University of Toronto. In general, ocean transport should be much slower than atmospheric transport. Thus, time-trend data and chemical fingerprinting may provide additional clues, he stresses.
The few available time-trend data suggest the dominance of an atmospheric source, says Environment Canada chemist Derek Muir. “Atmospheric transport and deposition better explains the temporal trends we see in polar bears, which suggest doubling times of 4–13 years,” he points out. However, Cousins and colleagues question the statistical validity of these data in their article.
PFCAs are a large family of chemicals with different carbon–fluorine chain lengths and chemical structures that reflect how they were manufactured. Thus, it may be possible to use the ratios of different PFCAs as chemical fingerprints for pinpointing their sources. The production and emissions estimates in the critical review could be used this way if the data are good enough, several experts say.
One chemical that may provide such fingerprint information is PFDA (perfluorodecanoic acid) and its salts, which have no significant commercial uses, according to a fluorochemicals consultant. PFDA has not been detected in the open oceans, but it is found in Arctic snow at levels comparable with those of PFOA. If direct emissions of PFDA are tiny, then the acid deposited into Arctic snow must come from atmospheric degradation of current-use volatile precursors as envisaged by the atmospheric-transport-and-degradation theory, says the consultant. This suggests that atmospheric transport, at least for this compound, is the main mechanism.
“I suspect that the presence of perfluorinated acids in the Arctic is a result of both the atmospheric transport and the oceanic transport mechanisms,” Wania says. More data, including better information on time trends and chemical fingerprinting, should help to tease out the relative importance of the sources, he adds.
