A Class Act? Regulating Organohalogen Flame Retardants in Groups versus Singly

Short abstract

Regulating chemicals by class based on chemical similarities may help reduce risk of regrettable substitutions while enhancing health protection. A new Commentary summarizes OFR toxicity and exposure research to inform this effort.

Flame retardants made with organohalogen compounds are added to furniture, electronics, and textiles, including many intended for use by infants and young children, to delay ignition or slow the spread of fire.^1,2 Three widely used organohalogen (containing one or more halogen atoms such as bromine or chlorine) flame retardants (OFRs) were phased out in 2004 and 2013 owing to concerns about health effects,³ but many others are still in use—despite evidence that adding flame retardants to, for example, upholstered furniture is not as protective as intended.⁴ In fact, the use of flame-retardant chemicals—particularly OFRs—in flammable consumer goods may in some cases amount to trading one risk for another, suggest the authors of a new Commentary in Environmental Health Perspectives (EHP).¹

OFRs are used in manufacturing a wide range of consumer products for infants, children, and adults. The present Commentary discusses opportunities and challenges of treating OFRs as 14 chemical subclasses for purposes of risk assessment, rather than approaching each substance individually. Image: © iStock.com/Rich Hobson.

Balancing the risks and rewards of flame retardant use in consumer products calls for understanding both potential household fire hazards and potential health hazards associated with exposure to these chemicals, write the authors of the Commentary. Given the sheer number and variety of OFRs in use today, health data can be hard to come by. Lack of data can result in a “regrettable substitution,”⁵ in which a known hazard is replaced with another chemical that later proves to have similar (or even more severe) health effects, such as happened with the bisphenol A replacements bisphenol S and bisphenol F.⁶

“The ability to conduct extensive and timely testing for hundreds of “OFRs” in animals or humans is limited,” the authors wrote.¹ As an alternative, they explored the possibilities and challenges of using inferences based on variations in chemical structure to formulate class-based risk assessments. Such an approach is not unprecedented: Regulatory bodies in the United States and Europe use class-based frameworks to manage polychlorinated biphenyls,⁷ dioxins,⁸ particulate matter,⁹ phthalates,¹⁰ and per- and polyfluoroalkyl substances.¹¹

The Commentary was coauthored by researchers with federal research and regulatory agencies, the American Chemistry Council (a trade association for US chemical companies), and academia, building upon a 2019 report¹² from the National Academies of Sciences, Engineering, and Medicine (NASEM). The NASEM report was requested by the US Consumer Product Safety Commission (CPSC) after it was petitioned¹³ by organizations representing consumers, doctors, firefighters, and others to regulate all OFRs as a single “inherently toxic” chemical class. The NASEM report instead proposed dividing 161 unique OFRs into 14 subclasses based on similarities in chemical structure.

For most OFRs, little is known about human exposure and toxicity. Yet for a handful, existing data show the potential for harmful effects on the brain, thyroid, liver, and kidneys.¹ Infants and young children are considered among the most vulnerable, as well as the most exposed.¹ “Much of the exposure for children comes from mouthing things,” says Linda Birnbaum, former director of the National Institute of Environmental Health Sciences (NIEHS) and a coauthor of the Commentary. She adds that OFRs are not chemically bonded to the material to which they are added, so they may leach out. “Dust tends to be a really major exposure source—for kids as well as for all of us,” she says.

Deborah Bennett, a professor at the University of California, Davis, who was not associated with the Commentary, says that manufacturers are increasingly using flame-retardant compounds that have little or no health data. “We’re exposing the US population to many of these compounds without having a good idea of their potential toxicity,” she says. “That’s problematic, and I definitely support the idea of regulating these [OFR] compounds by class.” Bennet was the senior author of another recent paper¹⁴ in EHP investigating the impact of exposure to a new class of flame retardants on birth outcomes.¹⁵ These compounds, called nonhalogenated organophosphate esters, are proposed by some as a safer alternative to OFRs. Bennett and her colleagues concluded that gestational exposures to several of the chemicals were associated with earlier timing of birth, especially among female neonates, and with greater fetal growth.

As practical and efficient as a class-based approach may sound, it is not without pitfalls, notes Alexandra Maertens, an assistant scientist with the Johns Hopkins Bloomberg School of Public Health who also was not involved in the Commentary. “The thrust of our research¹⁶ is that it is pretty hard to make distinctions between a lot of these chemicals because the chemical backbone is very similar,” she says. “The million-dollar question is which differences in chemical structure make a difference biologically. That problem just remains difficult right now, with the data that we have.” Maertens suggests prioritizing chemicals and subclasses by determining which have the highest exposure rates, bioavailability, and absorption rates in humans.

For Birnbaum, meanwhile, the question of OFR regulation raises larger questions of risk assessment. In this case, for example, she recommends reconsidering the need for flame retardants in the first place. Birnbaum has followed the issue for more than a decade and testified as director of the NIEHS at a 2015 CPSC public hearing¹⁷ on the original petition to regulate OFRs as a class. She believes that some of the CPSC’s flammability standards may be outdated owing to not only what researchers have learned about potential health risks of flame retardants, but also the sizable reduction in household fire risk posed by smoldering cigarettes.^18,19 “When some of the first flame retardant standards really got going, it was at a time in our history when the majority of the population were smoking,” Birnbaum says. “Only 11% of the [adult] population smokes today,²⁰ and most cigarettes are self-extinguishing.²¹ I think that we have to say, ‘Do we really need this stuff? Do we really need a baby stroller to have flame retardants in it?’”

Biography

Nate Seltenrich covers science and the environment from the San Francisco Bay Area. His work on subjects including energy, ecology, and environmental health has appeared in a wide variety of regional, national, and international publications.