Polymer flame retardants, originally developed as a “non-toxic” alternative to banned chemicals, may be harboring a dangerous risk of their own, a new study suggests.
New analysis of two polymeric brominated flame retardant compounds has shown that, as they degrade in the environment, these long polymer molecules can break down into dozens of smaller, potentially more dangerous compounds. The study also found traces of these breakdown products in environmental samples taken from near electronic waste recycling facilities and demonstrated the toxicity of these compounds in a zebrafish embryo model.
The researchers say their study, published inNature Sustainability, highlights the need for increased scrutiny and regulation on the environmental effects of polymer compounds.
Watch: Dr. Arlene Blum explains the context and impact of this research
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Investigating polymer breakdown products
Non-polymeric brominated flame retardants (BFRs) are a class of relatively small molecules that were used for years as a popular additive to electronics or furniture items to reduce their flammability. At the turn of the century, these BFRs began to be phased out of production and use after studies linked the compounds toendocrine and thyroid dysfunction.
In subsequent years, polymeric flame retardants (polyBFRs) have become an increasingly popular replacement for BFRs, as their long polymer chain molecules were generally thought to be too large to migrate out of products and into the environment. As a result, these polymer compounds have largely evaded scrutiny from regulating bodies.
“The producers of flame retardants have increasingly stopped making the monomers, which are regulated, and stuck together a lot of monomers to make a big polymer and say, ‘it’s fine,’” study co-authorDr. Arlene Blum, founder and executive director of the Green Science Policy Institute, told Technology Networks. “We think it’s really important that the polymers also have to have scrutiny and regulation before they are used.”
In a bit to provide this extra scrutiny, the study authors conducted experiments on two typical polyBFRs that are known to be in use – a tetrabromobisphenol A (TBBPA) epoxy and a TBBPA-based polycarbonate.
These TBBPA-based polymers were subjected to various photolytic, microbial and ball milling degradation experiments to simulate the sorts of environmental conditions that they might be exposed to during e-waste recycling. The identification of any breakdown products was done using a novel non-targeted screening algorithm named BrMiner, which was developed by the study authors from Jinan University and the East China University of Science and Technology.
“BrMiner is developed to screen for and identify bromine-containing compounds based on high resolution mass spectrometer (HRMS) analysis. It is employed to identify specific compounds related to tetrabromobisphenol A-based polymers in this study, but can also be used to identify other types of Br-containing compounds,” lead study authorDa Chen, a professor in the Jinan University College of Environment and Climate, told Technology Networks.
“BrMiner can automatically generate a list of candidates with characteristic fragment ions, predicted number of bromine atoms and simulated molecular formulas from raw HRMS data, based on the algorithms of isotopologue distribution simulation and similarity scores between measured and simulated isotopologue distributions,” he explained.
The team’s analysis successfully identified a total of 76 breakdown products generated by the exposure of polyTBBPAs to environment-like conditions.
Toxic breakdown products found near e-waste recycling facilities
After having identified that polyBFRs can produce dozens of unique breakdown products during e-waste handling-like conditions, the team set out to confirm whether these products might already be present in the environment around recycling facilities.
Soil, dust and particulate matter samples were taken from various locations across China, including from the immediate vicinity of e-waste recycling facilities, their general surroundings (up to 50 kilometers away) and unconnected urban regions more than 100 kilometers away from a recycling facility.
“The samples with the highest abundances and most complex composition of breakdown products were taken from electronic waste recycling sites, indicating the use of polymeric BFRs in electronic products,” Chen said. “The environmental abundances declined along with the distance from the e-waste sites.”
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Having found real-world examples of these breakdown products, the team then moved on to conducting toxicity tests to evaluate their potential risks.
“The zebrafish model is commonly employed to study the toxic effects of environmental chemicals,“ Chen explained. “Zebrafish embryos can be used to systematically investigate adverse effects and key events from one cell to organogenesis stages, while meeting the replacement, reduction and refinement principles of animal research.”
Ultimately, 9 out of 15 developmental toxicity end points were significantly affected by at least one of the tested breakdown products. This included abnormalities in the brain, heartbeat and locomotor activity, as well as a curved spine and decreased body length. The researchers believe that these effects could be a result of mitochondrial dysfunction – an effect thatTBBPA monomers are known to have.
The push for polymer regulation
The researchers believe that these results highlight an important association between polymeric flame retardants and potential environmental health risks. In light of these findings, they conclude that the use of these compounds should be subject to more assessment and regulation.
“The real problem is that small molecules are subject to a lot of testing and regulation and have to go through a lot of hoops to get used. But polymers do not have [similar] regulation, either in the EU or US,” Blum said. “You need a body of science, but I think this paper is unique in that it went beyond just showing the breakdown [of polyTBBPAs], to showing it in the environment and then showing the toxicity of the breakdown products. So it’s a big step.”
Reference: Liu X, Xiong Y, Gou X, et al. Environmental impacts of polymeric flame retardant breakdown. Nat Sustain. 2025. doi:10.1038/s41893-025-01513-z
About the interviewees:
Arlene Blum, PhD, is a biophysical chemist, author and mountaineer. She is a research associate in chemistry at UC Berkeley and executive director of the Green Science Policy Institute.
Da Chen, PhD, is a professor in the College of Environment and Climate at Jinan University.