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Green Building News

Researchers Raise Questions About Rigid Foam Flame Retardant

A flame retardant used in polystyrene insulation can break down into other components whose environmental risks are unknown, researchers say

Rigid polystyrene foam is frequently used in residential construction, but a group of German researchers says more study is needed to understand the potential environmental risks of a flame retardant it's treated with. (Image credit: studio-tm.com/construction blog)

A flame retardant introduced in 2011 as an environmentally safer alternative for polystyrene insulation can break down in the presence of sunlight and heat into chemicals that are potentially harmful to the environment, a group of German researchers said in a published report.

In an article in the journal Environmental Science & Technology, the researchers said they had tested a flame retardant called Polymeric FR. The compound was designed to replace hexabromocyclodecane (HBCD) in extruded and expanded polystyrene (XPS and EPS) foam insulation. Both are commonly used in residential construction.

Polymeric FR, developed by Dow Chemical, has a higher molecular weight than HBCD, making it less likely to travel in the environment and was therefore considered safer. But a team led by Christoph Koch of the University of Duisburg-Essen said Dow hadn’t considered that the new compound might degrade into other chemicals whose long-term behavior in the environment wasn’t clear.

Koch and his colleagues subjected the chemical to UV radiation and temperatures of 140°F, conditions which they said could be replicated over the course of the insulation’s lifetime.

“To the best of our knowledge, all government risk evaluations until now focused on the polymer itself without considering possible degradation products,” the report notes. Exposure to heat and sunlight, it adds, “could result in smaller molecules with a different mobility and toxic potential.”

Results of the study were first reported in Environmental Health News.

The study is attacked as unfair and inaccurate

Dow came out swinging. In a letter to Koch and in a statement posted at a Dow Dupont website, the company called results of the study technically flawed and accused Koch of being less than forthright about his employment with a competing insulation maker. Dow also criticized Environmental Health News for the way it reported the story, claiming the website failed to recognize the “serious flaws” in Koch’s work.

“EHN further compounded the study authors’ glaring omission by reporting uncritically on their conclusions without doing even the most basic due diligence,” Dow’s statement said. “The result, whether by error or intention, is highly slanted reporting that is indistinguishable from outright advocacy.”

Dow’s letter to Koch cited “serious ethical concerns” about the study. The title page of the study notes Koch’s connection with Dow competitor Deutsche Rockwool GmbH & Co., the German subsidiary of Rockwool International. But, Dow says, Koch said in a footnote to the article that he had no competing financial interest that would affect his work.

Rockwool is a competing product to the EPS and XPS insulation used in construction.

Dow also wrote to Environmental Science & Technology, denouncing Koch’s “ulterior motives” and citing what it said were technical inaccuracies. Dow said it wanted an “expression of regret” for Koch’s lack of disclosure and space in the magazine to “set the record straight.”

Asked about his ties with Rockwool, Koch said in an email that he started the research before taking a part-time job with the company as he pursued his PhD.

“During the whole project, there was no funding received from this company or any other source,” Koch wrote. “All the work that I have contributed for this publication has been done outside of my paid labour time for Deutsche Rockwool GmbH & Co. KG — thus in my private time. No facilities of this company have been used and no information regarding this publication has been exchanged.”

Koch also said he had shared the results of his work with Dow prior to publication. “Yes, we had contact with Dow,” his email said. “We informed them about our work before submitting the manuscript to the journal Environmental Science and Technology. There were no major disagreements about our findings.”

Brian Bienkowski, senior editor at Environmental Health News and the author of the January 9 story, said in an email that EHN contacted Dow as soon as the Koch study was published.

“Rather than make a scientist or representative available to speak, they immediately made these posts disparaging the study and the story,” Bienkowski wrote. “While we updated the story with their statements and concerns about the study, they still have not made a scientist — or anyone — available for us to talk to. I offered to talk on the phone or even meet in person.

“We stand by the accuracy of our reporting on the study and find it regretful that Dow will not engage with journalists but, rather, chooses to attack them,” he said.

A “next generation” flame retardant

Polymeric FR was developed because of the environmental and health risks of HBCD. Dow Global Technologies announced in 2011 that its Dow Chemical Company subsidiary had invented Polymeric FR and said that it expected the compound to become the “next generation industry standard” flame retardant for both XPS and EPS. It was commercialized as Bluedge Polymeric Flame Retardant Technology.

The U.S. Environmental Protection Agency said in a 2014 assessment that Polymeric FR was the best of the few available options to replace HBCD in polystyrene building insulation.

North American producers of XPS and EPS have since switched to Polymeric FR, their respective trade associations said. Roughly 52 million pounds of Polymeric FR are produced each year.

In an email, Koch said conditions causing the flame retardant to break down occur in hot attics or after the foam has been landfilled. But the research is far from conclusive.

“We have not studied the toxicity of these smaller molecules,” Koch added, “and there is almost no scientific information available about them. Previous studies suggest that flame retardants — which are used in building insulation (this is different for flame retardants which are for instance used in textiles) generally do not immediately affect building occupants, but can end up in the environment and enter the food chain.”

Koch also said their research focused on the flame retardant itself, without the “surrounding polystyrene matrix” of the insulation — a point Dow also makes. In other words, researchers tested the chemical, not polystyrene treated with the chemical. That, he said, might affect its degradation process.

The only known use for Polymeric FR is in EPS and XPS, Koch said. It’s not used as a fire retardant in textiles, electronics, or furniture upholstery.

Asked whether Polymeric FR is a better option than HBCD, Koch said it wasn’t possible to say based on the limited knowledge that’s currently available.

“As the U.S. EPA and others stated, the long-term behaviour of ‘Polymeric FR’ is largely unknown,” Koch said. “It seems however indeed possible, that the development of ‘Polymeric FR’ is a step in the right direction. But certainly more research is know to give a solid reply to this question.

“To underline this: Hundreds of peer-reviewed studies have been published for HBCD (and we still have open questions),” he added, “but there are not even ten studies for ‘Polymeric FR.’ ”

Publication responds

Environmental Science & Technology is a publication of the American Chemical Society, a Washington, D.C.-based organization with more than 150,000 members worldwide. GBA asked the publication for comment on Dow’s demands and received a written statement from Glenn S. Ruskin, ACS vice president for external affairs and communications.

“Be assured that ACS takes all expressions of concern very seriously,” the statement reads. “When such concerns are raised, ACS editorial staff will look into them, but will not comment while the review is ongoing. Regarding the scientific content of the manuscript in this particular case, ACS editorial staff contacted the authors, who have confirmed that the paper accurately discloses potential conflict of interests.”

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