As incidents of dangerous lithium-ion battery fires increase, regulators and manufacturers are scrambling for solutions. However, a common strategy — adding flame retardants to plastic battery casings — may fail to prevent fires and introduce serious health risks. A new Viewpoint published in Environmental Science & Technology argues that flame retardants in battery enclosures offer no proven fire-safety benefits and are linked to cancer and other health issues. These chemicals can also migrate into recycled plastics, contaminating products like children’s toys and food containers.
“The use of flame retardants in plastic battery enclosures has no demonstrated benefit and poses threats that can last generations,” said lead author Lydia Jahl, a scientist at the Green Science Policy Institute, quoted in EurekaAlert! “For example, toxic flame retardants migrate out of plastics into the air and drop into house dust, which we inadvertently breathe and ingest. When those flame-retarded plastics are recycled years later, additional people will be exposed from products made with the recycled plastic.”
Lithium-ion batteries are widely used in electric vehicles, e-bikes, and portable electronics like smartphones and earbuds. To address fire risks, many standards now require plastic enclosures to meet specific “flame ratings,” often achieved by adding chemical flame retardants. However, no publicly available evidence exists that these additives effectively prevent or mitigate battery fires in real-world scenarios. According to the authors, flame retardants in plastics are unlikely to slow or stop the intense fires caused by lithium-ion batteries in thermal runaway.
Trying to stop thermal runaway fires by adding flame retardants to plastic is like adding a screen door to a submarine. It’s a futile effort against an overwhelming force.
Flame retardants commonly used in battery enclosures, such as organohalogens and organophosphates, are associated with cancer, neurological damage, reproductive harm, and immune system disruption. Children and pregnant women are particularly vulnerable. The authors highlight how exposure can occur at multiple stages: during battery manufacturing, product use, disposal, and recycling, and through recycled products like black plastic utensils or food containers.
This is not the first time that flame retardants have been linked to health risks without clear fire-safety benefits. For instance, a long-standing California furniture flammability standard, which required flame retardants, did not reduce fire deaths. One of the chemicals used to meet this standard was linked to a 300% increase in cancer mortality risk and a loss of three to five IQ points among U.S. children. After the standard was updated a decade ago to eliminate the need for flame retardants, furniture fires did not increase and may have even decreased.
“The best solution for both public health and fire safety is to prevent battery fires from occurring in the first place,” said co-author Arlene Blum, executive director of the Green Science Policy Institute. “Strategies like improving battery management systems and stopping the use of faulty batteries can prevent dangerous thermal runaway fires. This would save lives both from fires as well as from cancer and the many other health harms linked to flame retardants.”
Policy updates and research implications
Recent policy discussions have focused on balancing fire safety with public health concerns. In the European Union, regulations under the REACH (Registration, Evaluation, Authorization, and Restriction of Chemicals) framework have restricted the use of certain flame retardants in consumer products. Similarly, in the U.S., states like California and Washington have introduced legislation to limit the use of harmful flame retardants in furniture and children’s products.
Research continues to highlight the need for alternative approaches to fire safety. Studies have shown that improving battery design, enhancing thermal management systems, and implementing stricter quality control measures can reduce the risk of thermal runaway without relying on hazardous chemicals. Policymakers and industry leaders are increasingly recognizing the importance of these strategies, which prioritize both safety and sustainability.
As the use of lithium-ion batteries grows, the findings from this Viewpoint underscore the urgent need for evidence-based policies that protect public health while addressing fire risks. By shifting focus from chemical additives to preventive measures, regulators and manufacturers can mitigate the dual threats of battery fires and toxic exposure.
