Unregulated flame retardants can break down into toxic byproducts, study shows

New research shows that two unregulated and widely used flame retardants found in many electronic devices and touted by industry as non-toxic break down into harmful molecules that can pose a health risk to fish and potentially other creatures, including humans.

The chemicals in question, large molecules called polymers, have largely escaped regulation as industry has argued that the materials are unlikely to degrade or make their way into living creatures. Many are even marketed as non-hazardous or environmentally friendly.

But a study published Monday in the journal Nature Sustainability found evidence suggesting that is not true. Researchers reported finding dozens of smaller molecules caused by the breakdown of polymeric flame retardants in soil, dust, and air outside electronic waste recycling facilities in southern China. The scientists exposed zebrafish — commonly used in initial toxicity tests — to the chemicals and found that they caused metabolic dysfunction and showed the potential for development harm.

“Our study suggests polymers can act as a trojan horse for toxic chemicals,” Da Chen, senior author and scientist at Jinan University in China, said in a press release. “They are added to products as inert large molecules, but over time they can degrade, exposing us to their harmful breakdown products.”

In recent years, polymeric flame retardants have been used to replace smaller, toxic molecules, such as chemicals called HBCD and PBDE, which have been partially phased out due to safety concerns.

Most polymers, including all such flame retardants, are considered exempt from major regulations meant to protect humans. But the new research shows regulation is needed, said Arlene Blum, co-author of the study and a research associate at the University of California, Berkeley. Blum also serves as executive director of the Green Science Policy Institute.

“Big molecules made of harmful small molecules need to be regulated. They shouldn’t get a free pass,” she said.

The two chemicals examined in the study are forms of polymers made up of many repeated molecules of tetrabromobisphenol A (TBBPA), which are themselves flame retardants with significant toxicity.

Polymers are very hard to study because they are so complex and large, and have historically been presumed to be less toxic, Blum said. Moreover, little is known about the exact makeup of these flame retardants, how much is manufactured, and what products they’re used in.

Those details are considered proprietary and governments don’t compel companies to release such information, Blum said.

The paper did reference one estimate stating that 450 tons of a TBBPA-based polycarbonate were manufactured annually in the US in recent years. But such data are few and far between.

The study is the first to show that the polymeric flame retardants break down into smaller molecules that can cause adverse effects, said Miriam Diamond, a researcher at the University of Toronto and a co-author of the study.

Widespread use of these flame retardants in electronics may result in exposures when these products are manufactured, when they’re in people’s homes and when they’re discarded or recycled, Diamond said.

“Because the production volume is so high, we think, you’re going to get lots of these small molecules coming out of the environment and into us,” Diamond said.

The potential for harm to wildlife and humans is concerning, she said, and frustrating since “it shouldn’t be up to us as environmental chemists to figure this out after this chemical has gone into high production.”

The researchers said their study has implications for other types of polymers such as per- and polyfluoroalkyl substances (PFAS). PFAS polymers are used in textiles including children’s uniforms, food packaging, and cosmetics.

(Featured photo by Muntaka Chasant via Wikimedia Commons)