The scientific community has long believed that polymers—very large molecules—are too big to migrate out of products into people and therefore pose no health risks. As a result, polymers have largely evaded regulation. For example, polymers are exempt from the major toxics acts: Toxic Substances Control Act in the U.S. and REACH in the E.U. However, a breakthrough peer-reviewed study published today in Nature Sustainability demonstrates that polymers used as flame retardants can break down into smaller harmful chemicals.
"Our study suggests polymers can act as a trojan horse for toxic chemicals," said Da Chen, senior author and scientist at Jinan University in China. "They are added to products as inert large molecules, but over time they can degrade, exposing us to their harmful breakdown products."
The researchers tested two polymeric brominated flame retardants (polyBFRs) that were developed as "non-toxic" alternatives to banned flame retardants. They found that both polyBFRs broke down into dozens of types of smaller molecules. Toxicity testing of these smaller molecules in zebrafish showed significant potential for causing mitochondrial dysfunction and developmental and cardiovascular harm.
The scientists went on to search for these polymer break-down products in the environment and, further raising alarm, detected them in soil, air, and dust. The levels were highest near electronic waste recycling facilities and lessened moving away from the facilities. These results confirm that the use of polyBFRs in electronics leads to the release of toxic breakdown products into the environment with potential for human and wildlife exposure and harm.
"Widespread use of these polyBFRs in electronics may result in exposures when these products are manufactured, when they're in our homes, and when they're discarded or recycled," said Miriam Diamond, co-author and professor at the University of Toronto. "Since it is suspected that production volumes are very high (the chemical industry does not disclose the volumes), the potential for pollution—and resulting serious harm to people and wildlife— greatly concerns me."
The chemical producers and their trade groups promote polyBFRs as environmentally friendly and non-hazardous substitutes for banned monomeric flame retardants (e.g., hexabromocyclododecane and decabromodiphenyl ether) to meet flammability standards for electronics, building materials, and vehicles. However, real-world fire-safety benefits for many of these standards have not been demonstrated.
The study also has implications for other types of polymers used in consumer products such as per- and polyfluoroalkyl substances (PFAS). PFAS polymers have been put into textiles including children's uniforms, food packaging, and cosmetics to name a few uses. Similar to this study, previous research has shown that fluorinated polymers contain numerous impurities and release smaller toxic molecules. Although the producers of PFAS argue that fluorinated polymers should be exempt from regulation, scientists maintain that fluorinated polymers are members of the class of PFAS and that the use of the whole class of PFAS should be avoided.
"To escape regulation, flame retardant and PFAS producers are increasingly pivoting to polymers for use in everyday products," said Arlene Blum, co-author and Executive Director of the Green Science Policy Institute. "As a result, problematic polymers emit toxic small molecules from products we touch, sit on, wear, and keep in our homes. Regulators need to close this loophole to protect consumers—especially children—from the possibility of serious chemical harm."
