A German researcher who earlier this year warned that not enough is known about the potential environmental hazards of a fire retardant widely used in rigid foam insulation has authored another article, this one suggesting that actual risks are probably limited.

Christoph Koch, a researcher and faculty member at University Duisburg-Essen, warned in a January paper that a flame retardant called Polymeric FR could degrade when exposed to heat and UV radiation into smaller molecules whose environmental effects aren’t known. The article, published in Environmental Science & Technology, said studies covering these compounds are limited.

“As the U.S. EPA and others stated, the long-term behavior of Polymeric FR is largely unknown,” Koch said at the time. Although the flame retardant might indeed be a step in the right direction environmentally, he added, it would take more research to confirm it.

In the new article, the authors said, “Detected degradation products cause almost no acute toxicity, whereas chronic toxicity might be relevant. Nevertheless, as long as polymeric flame retardants are only used in building insulation, the actual risk seems to be rather limited.” Based on the few studies that are available, it adds, Polymeric FR is “an important step towards environmentally safer [flame retardants].”

Polymeric FR was developed by Dow in 2011 as a replacement for HBCD (hexabromocyclodecane), a brominated flame retardant considered too persistent and too toxic for continued use. U.S. manufacturers of expanded and extruded polystyrene insulation (EPS and XPS) have since switched to Polymeric FR, and millions of pounds of it are produced every year.

Dow reacted angrily to the initial report from Koch and his colleagues. The company criticized both Koch and Environmental Health News, which originally reported his findings, for what it claimed were technical lapses. Dow also castigated Koch for failing to reveal that he had a part-time job with Rockwool, a manufacturer of mineral wool insulation and a Dow competitor.

One key point of contention was how Polymeric FR was tested. Koch subjected the compound to heat and UV radiation but did not run the same tests on samples of insulation that had been treated with it. That, Dow claimed, skewed the results.

Original findings have not changed, author says

In a new paper, published by Chemosphere earlier this month, Koch and co-author Bernd Sures said they were summing up what had already been published and reiterated their finding that Polymeric FR could degrade into other molecules under specific circumstances.

Koch said in an email that nothing in this new article (the body of which is behind a paywall) changes his original conclusions.

“This review does not alter the conclusions of the scientific article which was published earlier this year in Environmental Science and Technology,” he wrote. “This scientific article dealt with the potential degradation of ‘Polymeric FR’ and concludes that degradation of ‘Polymeric FR’ can indeed take place under certain circumstances. The review does not change this conclusion — ‘Polymeric FR’ can still degrade under certain circumstances.”

DuPont, however, seized on wording of the second article to claim Koch’s new analysis looked at Polymeric FR more favorably. (Dow and Dupont merged in 2017 before dividing into three separate companies.)

“As a result, Koch’s new analysis of his prior research walks back many of his original conclusions,” Greg Bergtold, business advocacy director at DuPont de Nemours, Inc., said in a letter emailed to GBA. He also pointed out that Polymeric FR is currently licensed only for use in plastic building materials — not in textiles, electronics or other consumer products — where it might be exposed to heat and sunlight.

Manufacturer submits rebuttal paper

DuPont also has submitted a rebuttal to Environmental Sciences & Technology that hat yet to be published, Bergtold said in an email. It repeats arguments that Koch’s original work “contains multiple flaws.”

“The speculation by Koch et al. that Polymeric FR technology may lead to degradation products that ‘might have potentially adverse environmental effects’ is both unsupported by the results presented and contradicted by their own work in a separate publication,” the paper says. “On the contrary, studies of Polymeric FR to date show good stability for environmentally-relevant degradation pathways, and show little toxicity concern for degradation that could be expected to occur over the life cycle of PS foam insulation.”

In a footnote to that original research paper in Environmental Science & Technology, the authors said said none of the money for the research came from Rockwool, “nor has there been any other influence regarding this research project.”

An addendum to that article said Koch’s affiliation with Deutsche Rockwool DmbH & Co. came after he had started work on his Ph.D. project. “The study was solely supported by university funds,” it says. “The conflict of interest statement and other funding sources are correct as published in this article.”