The Science of Sustainability

Playing Whack-a-Mole with Flame Retardants

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burning house

Emerging research questions whether flame retardants used to meet California's flammability standard increase fire safety. Activists say fire-resistant fabric can protect furniture built to meet industry codes without the use of toxic flame retardants. (Image: Kpahor/Wikipedia)

Countless consumer products sold in California contain a flame retardant flagged as a possible carcinogen nearly 35 years ago. As of this week, finally, they must carry a warning that the chemical causes cancer.

A year ago, the California Office of Environmental Health Hazard Assessment listed chlorinated Tris as a cancer-causing chemical under Proposition 65. Under that 1986 law, businesses using a listed chemical have one year to add a warning label to their products. So now, if you buy foam furniture, car seats, nursing pillows or other baby products treated with chlorinated Tris, you should see the warning: "This product contains a chemical known to the state of California to cause cancer."

Bad Characters
Chlorinated Tris and most other flame retardants are halogenated chemicals. They’re grouped together as halogens on the Periodic Table, which means they share structural and chemical properties and behave similarly. Halogens—which include the elements bromine, chlorine, fluorine, iodine and astatine—are highly reactive and can be extremely toxic at high enough doses. (Chlorine gas was one of the most feared weapons used during World War I.)

Most flame retardants come in brominated and chlorinated forms. Brominated Tris (Tris-BP) was first identified as a possible carcinogen in 1977 by UC Berkeley researchers Arlene Blum and Bruce Ames. Blum and Ames showed that Tris-BP acts as a mutagen—it damages DNA—with a high likelihood of causing cancer. A previous study had shown that adding Tris-BP to a goldfish tank at 1 ppm—that’s one unit of Tris-BP to a million parts of water—could kill the fish in just five days.

arlene blum

Arlene Blum, a biophysical chemist who led the first all-woman ascent of Denali in 1970, leads the call for safer flame retardants. She founded the Green Science Policy Institute after learning that a toxic chemical she helped remove from children’s pajamas in 1977 reappeared in foam furniture and baby products. (Photo courtesy of Steve McCaw/NIEHS)

Thanks to Blum and Ames’ work, the Consumer Product Safety Commission banned Tris-BP from children’s pajamas in 1977. Manufacturers then switched to chlorinated Tris—formally called tris(1,3-dichloro-2-propyl) phosphate, or TDCPP. Again, Blum, Ames and a colleague pegged the chlorinated form as a mutagen. This time, manufacturers voluntarily removed the toxic chemical from kids’ pajamas.

Then six years ago, Blum discovered to her horror that manufacturers were using chlorinated Tris on polyurethane foam in furniture cushions, nursing pillows, car seats and other consumer products to meet California’s flammability standard (called Technical Bulletin 117).

Manufacturers switched to chlorinated Tris after phasing out another brominated chemical, called Penta, which along with its close cousin Octa were banned in California in 2003. Both have now been phased out in the United States, but persist in the environment and are building up in the tissues of wildlife and humans, as well as in women’s breast milk.

Manufacturers next turned to Firemaster 550, a proprietary formula that researchers have been scrambling to characterize. It’s now one of the most common replacements for banned flame retardants and a major component of house dust.

Evidence of Harm
Replacing one halogen with another does nothing to address the safety of these flame retardants, Blum told me. You’re just trading one toxic compound for another, she explained.

“People are so worried about getting rid of bisphenol A," she said. "But the halogenated flame retardants are far more dangerous and far more persistent.”

Research in animals has linked halogenated flame retardants to a wide range of toxic effects, including liver, thyroid, reproductive and developmental damage, disrupted brain development and DNA damage. Human studies, though limited, point to lower IQ in children, reduced fertility, hormonal changes and altered onset of puberty.

Now a preliminary study in rats implicates Firemaster 550 as an endocrine disruptor and “obesogen,” a term coined by UCLA biologist Bruce Blumberg to describe environmental chemicals that alter hormonal and metabolic processes and lead to obesity.

The pilot study, led by Heather Patisaul, an assistant professor of biology at North Carolina State University and expert in endocrine-disruption, exposed pregnant rats to flame retardants at low, high and zero levels (as controls).

In keeping with other flame retardant studies, exposure to Firemaster 500 altered the thyroid levels of pregnant rats. Maternal thyroid hormones play a critical role in the normal growth and development of the fetus. Changes in thyroid levels can wreak havoc on developing organs, particularly the brain. In this study, Firemaster increased thyroid levels in the mothers.

After exposing pregnant rats to Firemaster, the researchers detected a component of the flame retardant, called TBB, in both exposed mothers and their babies, suggesting the babies either ingested the compound while nursing or absorbed it in utero (after it crossed the placenta). Both exposed male and female offspring showed extreme weight gain. But in the female offspring, obesity came with additional costs, including early onset of puberty, high anxiety and insulin resistance.

While taking care to point out that their findings are preliminary, Patisaul and her colleagues also note that endocrine-disrupting effects of prenatal exposure to Firemaster 550 occurred at levels “much lower” than that reported safe by the manufacturer—and that we likely encounter in our homes.

Fire Safety without Toxic Chemicals
Researchers don't understand exactly how diverse halogenated flame retardants cause damage. But they know that their shared chemical properties—which help them persist, accumulate in living tissue, and disrupt molecular processes—means that if one is toxic, the rest may be too. When it comes to this class of flame retardants, there appears to be no safer alternative.

Activists have long argued that regulations favor industry over public health by forcing consumers to prove that chemicals cause harm rather than requiring industry to demonstrate safety. It’s hard to find fault with that complaint when the Environmental Protection Agency has tested just 200 out of some 85,000 chemicals in commerce–and banned five–while the California Department of Toxic Substances Control notes that 45 percent of some 2,500 high production volume compounds lack adequate health and safety toxicity data.

With the flame retardant business growing—from $4.6 billion in 2011 to a projected $6.1 billion in 2014—manufacturers have a clear interest in protecting their investments. They spent more than $23 million to defeat five bills to regulate their products before the California Legislature.

And as a devastating report from the Chicago Tribune showed, the industry deceived the public about the safety and efficacy of their products.

Blum thinks it’s time to end the whack-a-mole approach to regulating flame retardants. And so does Gov. Jerry Brown, judging from his June directive to the Bureau of Electronic Appliance Repair, Home Furnishing and Thermal Insulation, the bureau that controls the state’s flammability standards, to ensure fire safety without toxic flame retardants.

We can have fire safety without toxicity, Blum says. She hopes the research documenting the toxic effects of flame retardants reaches parents just as the pajama studies did. When it does, she believes, they’ll demand safer products.

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Liza Gross

About the Author ()

Liza Gross, a freelance science writer and senior editor at the biomedical journal PLOS Biology, channeled an early love of wildlife into a lifelong exploration of the numerous ways diverse species, including humans, interact in the natural world. She writes mostly about wildlife, conservation, and environmental health. Her stories reflect a deep curiosity about natural and social interactions and often highlight evolutionary relationships that remind humans of their place in, and responsibility to conserve, nature. Her article "Don't Jump!" published in Slate, won an ASJA award in the op-ed category. She's a visiting scholar at NYU, a 2013 recipient of NYU Reporting Award funding and a Dennis Hunt health journalism fellow. Read her previous contributions to QUEST, a project dedicated to exploring the Science of Sustainability.