A new flame retardant in the air
Did a persistent, bioaccumulative, and potentially toxic chemical that has been in use for more than 40 years slip under the U.S. EPA’s radar?
Scientists operating an atmospheric monitoring network in the U.S. Great Lakes have detected significant quantities of a chlorinated organic chemical that has been on the market for more than 40 years, according to research published today on ES&T’s Research ASAP website (10.1021/es051911h). Despite the long commercial history of this compound, which is sold under the name Dechlorane Plus, this is the first report of its presence in the environment. The limited data available for Dechlorane Plus indicates that it is persistent, bioaccumulative, and potentially toxic.
). The scientists confirmed that the compound was bioaccumulating in Great Lakes fish by analyzing archived sediment samples from sites shown with a +. The location where OxyChem manufacturers Dechlorane Plus is shown with a 
.“We always keep our eyes open for new compounds,” says Ronald Hites, who is with Indiana University’s School of Public and Environmental Affairs and is the research’s corresponding author. “This is an example of a relatively old compound that has apparently slipped under the regulatory radar and that is still being used without attracting public attention,” Hites and his colleagues write in their paper.
“The identification of Dechlorane Plus in the environment, so many years after the introduction of the compound, really shows the importance of researchers going [after] new environmental contaminants,” says Åke Bergman of Stockholm University’s environmental chemistry department. “It is indeed disturbing that new organochlorines are still to be detected in our environment, 40 to 50 years after the discovery of DDT in the environment,” he adds.
It is important for scientists to look for previously undetected chemicals in the environment because researchers are currently identifying only a small percentage of the more than 100,000 chemicals currently used in commerce, stresses Derek Muir of Environment Canada’s Ecosystem Protection Research division. “A challenge for environmental chemists and regulators is to figure out which ones are a priority for actual environmental measurements. . . . Lack of consensus on the next priority [persistent organic pollutant] may be holding back environmental analytical chemists,” he says.
Environment Canada’s Existing Substances Division has conducted one of the most comprehensive efforts in the world to screen for new compounds that could be found in the environment. The group evaluated the physical and chemical properties of 23,000 substances that were imported or manufactured in Canada at more than 100 kilograms per year between 1984 and 1986, years chosen to target chemicals that were “grandfathered in” when the country’s Domestic Substances List was created in 1986. Of the 600 compounds that this screening shows are likely to be both persistent and bioaccumulative, Muir says only 3% are currently measured in the environment.
Dechlorane Plus is used for coating electrical wires and cables and in computer connectors and plastic roofing material, and it is actually considered a high-production volume (HPV) chemical because more than 1 million pounds of it are manufactured every year. Hites and his colleagues first found the compound on atmospheric particles they collected through the Integrated Atmospheric Deposition Network (IADN), which is jointly operated by U.S. and Canadian governments and includes seven major sampling stations in the Great Lakes region. They were able to positively identify it as Dechlorane Plus by comparing its gas chromatographic mass spectrometry (GC/MS) signature with that of a sample they obtained from the chemical’s manufacturer, OxyChem, which is part of the Occidental Petroleum Corp.
Most of the flame retardants that have been detected in the environment up until this point are organic compounds based on bromine rather than chlorine. Even so, the levels of Dechlorane Plus in the atmospheric samples from three IADN sampling stations that Hites and his colleagues analyzed—which reached as high as 490 picograms per cubic meter of air—were similar to levels of the “Deca” polybrominated diphenyl ether (PBDE) formulation, which is the world’s most widely used PBDE flame retardant.
Experts familiar with other flame retardants being detected in the environment characterize these atmospheric levels as being relatively high. They also applaud Hites for his painstaking analytical detective work.
By looking at archived samples, Hites and his colleagues discovered that Dechlorane Plus has been in the sediments at the bottom of the Great Lakes since the early 1970s. They also found it in some fish, including walleye—a popular Great Lakes food fish. These data make a convincing case that the compound is persistent and bioaccumulative, says Linda Birnbaum, director of the U.S. EPA’s National Health and Environmental Effects Research Laboratory’s Experimental Toxicology Division.
Although Heather Stapleton, an assistant professor of environmental sciences and policy at Duke University’s Nicholas School of the Environment and Earth Sciences, agrees that the compound is bioaccumulative, she isn’t certain that it is sufficiently bioaccumulative to represent much of an issue. “Based on the structure and properties of Dechlorane Plus, it doesn’t seem likely that the chemical is very bioaccumulative. It’s probably too big to pass biological membranes easily. The levels measured by Hites et al. are very low relative to most contaminants of concern,” she says.
These physical and chemical properties explain why screenings by both Environment Canada and EPA of HPV chemicals concluded that Dechlorane Plus was persistent but not bioaccumulative, Muir says. It also “illustrates the challenges of identifying new persistent, bioaccumulative, and toxic chemicals. If they are similar in structure and properties to chemicals that are already being analyzed . . . then they are more likely to be detected in existing screenings. But then the question becomes more complex. . . . Since the toxicological data is usually very limited (as noted by Hites et al. for Dechlorane Plus), maybe the best we can do is compare levels and trends,” he says.
Hites points out that there is yet another issue to be considered: the possibility that, like the similarly large Deca PBDE molecule, Dechlorane Plus could be broken down metabolically by animals. Birnbaum says that the different compound uptake patterns that Hites and his colleagues are reporting in their fish samples support this hypothesis. The Dechlorane Plus could also be breaking down as it is transported through the atmosphere, and it could be degraded by sunlight, Hites adds. He notes that some of the PAH compounds, as well as the Deca compound, are known to do this.
However, both Birnbaum and Muir disagree with Hites that it is fair to characterize Dechlorane Plus as slipping under their agencies’ radars. Birnbaum points out that the product was in use before EPA’s Toxic Substances Control Act came into force in 1975, and it is also covered by the agency’s High Production Volume program because it is manufactured in such large amounts. At the same time, she acknowledges that “if this was a brand-new chemical, it would probably never get through.”
The limited test data available for Dechlorane Plus indicate that it appears to have ecotoxicological effects in fish, and dermal tests on rabbits show that it could affect reproduction. Birnbaum, Muir and Hites also point out that Dechlorane Plus has chemical properties that are similar to Mirex [212KB PDF], a banned pesticide that was also made by OxyChem. Mirex is “reasonably anticipated to be a human carcinogen,” according to the National Institutes of Health. Mirex was also marketed as a flame retardant under the name Dechlorane and is considered a persistent organic pollutant.
A spokesperson for OxyChem declined to comment for this story. When Dechlorane Plus was first produced, OxyChem was known as Hooker Chemical and the company became infamous for its Love Canal chemical-waste disposal site under that name.
In their paper, Hites and his colleagues note that the market for flame retardants like Dechlorane Plus has been growing rapidly because of the U.S.’s stringent fire safety regulations. They speculate that Dechlorane Plus’s use as a flame retardant could be rising because some of the most heavily used PBDE flame retardants, the formulations known as Penta and Octa, have been banned in Europe and in some places in the U.S. over the past few years. These formulations were pulled off the U.S. market at the end of 2004.
However, Hites also points out that the sediment core samples suggest that that Dechlorane Plus has been floating around in the atmosphere at relatively high levels for years. The main reason that he and his colleagues did not find Dechlorane Plus before was because they had not analyzed the ultrafine particles captured by the network until two years ago, he explains. The particles collected by the IADN network are in the submicrometer range. They are, therefore, considered “ultrafine” particulate matter (PM), and are 10–100 times smaller than the particles regulated as PM2.5 and PM10.
“Most all of the pesticides and all of the PCBs [that are tracked via IADN] end up only in the gas phase,” he explains. The IADN researchers were only inspired to begin looking at the ultrafine particles two years ago to try to get a handle on levels of the PBDE flame retardants because the Deca formulation ends up almost exclusively in the particle phase, he says.
Once they began to look at the particles, Hites and his colleagues found some previously unnoticed GC/MS peaks “that were in some cases quite large,” he adds. Hites says that he has not yet analyzed any of IADN’s archived atmospheric samples for Dechlorane Plus, but he could do so.
“I see this paper as a wake-up call,” Birnbaum says. She says that the paper makes clear that Dechlorane Plus’s potentials for bioaccumulation and toxicity to wildlife and humans need to be assessed more fully. Another important question is whether the compound is subject to long-range atmospheric transport and can travel to sensitive regions such as the Arctic, something that the Deca PBDE compound has been shown to do, says Tom Harner, a research scientist involved with air quality research with Environment Canada’s Science and Technology Branch. “My sense is that this paper will lead to other groups looking for this chemical,” Harner predicts.
