Flame retardants in battery enclosures may do more harm than good

As dangerous lithium-ion battery fires are on the rise, regulators and manufacturers are scrambling for solutions. Unfortunately, one common strategy may cause serious health harm and not work to slow or stop the fires. A new Viewpoint in Environmental Science & Technology explains that adding flame retardants to the plastic cases surrounding these batteries has no proven fire-safety benefit. The scientists further warn that the types of flame retardants widely used in electronics enclosures are linked to cancer and other health harms and can end up in children’s toys, food containers, and other products made from recycled plastic.

“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. “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 power electric cars, e-bikes, and an increasing array of portable electronics like smartphones and earbuds. As their usage expands, standards are being adopted to mitigate their serious fire risks. For example, “flame ratings” for plastic enclosures are common requirements that are met by adding chemical flame retardants. However, there is no publicly available research demonstrating that this use of flame retardants curbs battery fires under real-world conditions. Flame retardants in plastics likely cannot slow or stop the highly energetic fires from a lithium-ion battery 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,” said distinguished fire scientist Dr. Vyto Babrauskas.  

The flame retardants widely used for this purpose are organohalogens and organophosphates linked to cancer as well as neurological, reproductive, and immune harm. Young children and pregnant women are the most vulnerable. The authors illustrate how people may be exposed to these harmful chemicals during battery manufacturing, use of the original product (e.g., earbuds or an e-bike), disposal and recycling, and the use of recycled products (e.g., the infamous black plastic spatula or sushi tray).

This would not be the first time that the use of flame retardants to meet flammability standards has resulted in health harm without proven fire-safety benefits. For example, an unfortunate long-time California furniture flammability standard did not reduce fire deaths. Meanwhile, one of the flame retardants most commonly used to meet that standard was linked to the loss of three to five IQ points among U.S. children and a 300% increase in the risk of dying from cancer. Since that standard was updated a decade ago to be met without flame retardants, furniture fires have remained minimal or 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.”