Carbon nanotube flame retardants - two wrongs don't make a right

Carbon nanotubes are wee little microscopic-sized tubes made of  sheets of carbon atoms, rolled up into a tube like a paper towel roll. One roll is a single walled carbon nanotube, and a few rolls will make a multiwalled carbon nanotube (MWCNT).

These tubes resemble asbestos fibers – rigid, long, and once inside the body they are persistent over weeks or months, similar to asbestos.

They also share asbestos’ fire-retardant properties, and asbestos’ ability to make materials stronger and more durable. In fact, carbon nanotubes are touted as being 100-times stronger and 6-times lighter than steel, making them very useful to strengthen and lighten car parts, high-end racing bicycles, military protective wear, and even airplane parts. That's the good news.

But, like asbestos, they can damage lungs, and may lead to asbestos-like diseases and cancer in animal tests. That's bad news!

And, there is more bad news. MWCNTs are being marketed by a company called Nanocyl  for use as a flame retardant in textiles such as couch coverings and curtains. Their website says the company will, “Nano-Engineer Your Future”.

EPA reviewed the health and safety hazards associated with using MWCNTs as a fire retardant in textiles, in a hefty 600+ page report issued September 2013. Here are some of the concerns that EPA identified, based on dozens of available laboratory and animal studies.

EPA identified exposure concerns for multiwalled carbon nanotubes in textiles:

  • Workplace inhalation risks are greatest concern
  • The MWCNTs are in a particulate form when inhaled
  • Consumer exposures are likely during use of the treated textiles
  • MWCNTs may be released from finished products in particulate form, into dust in the home
  • Biopersistent –  MWCNTs could remain in lungs for months after inhalation
  • Increased concern for workers and children, based on their activity patterns

EPA also identified human health concerns for multiwalled carbon nanotubes:

Over a dozen laboratory and animal studies have shown that carbon nanotubes are likely to pose some very severe, and possibly deadly, health risks to humans. Existing toxicity studies are mainly of dermal and inhalation exposures, with only a few from oral exposure routes. There are no data from humans.

EPA identified the following human health concerns for MWCNTs in textiles:

  • Skin and eye irritation
  • Respiratory sensitization
  • Respiratory/lung inflammation
  • Immune function altered
  • Genotoxicity studies showed conflicting results
  • tracheal installation studies (exposure to the test animal through a tube going down the throat and into the lungs) report that carbon nanotubes behave like asbestos, causing pre-mesothelioma, lung fibrosis, and lung inflammation; carbon nanotubes may be more toxic than asbestos.

From the pan to the fire

Ironically, we may be jumping from the pan into the fire. The carbon nanotubes are intended to replace the highly toxic flame retardant chemicals called  polybrominated diphenyl ethers (PBDEs) – and, especially one type, called decaBDE -  after several states banned them due to their very high toxicity.

The PBDEs can be found in the blood and breast milk of most Americans, and in wildlife at the North Pole, which are traditional food sources. Women with higher levels of flame retardants in their blood take longer to get pregnant and have smaller babies. Children exposed in the womb have altered brain development resulting in delayed physical development, lower IQs and attention problems. Other studies have linked flame retardants to male infertility, male birth defects, and early puberty in girls. A study in animals has linked flame retardants to autism.

(See NRDC’s Toxic Couch video and fact sheet about PBDE flame retardant chemicals for more information. See Dr. Sarah Janssen's blog on toxic flame retardants in couches)

California’s Technical Bulletin 117: The Source of the Problem

In 1978, the California Department of Consumer Affairs created a flammability standard that was both harsh and ineffective. The standard – TB117 - required furniture to be fire resistant to an open flame (such as a cigarette lighter or match) and applied not only to the upholstery covering (for example of a couch cushion), but also separately to the foam interior.

The standard was crafted and fiercely defended by chemical manufacturers, despite overwhelming evidence that the chemicals didn’t save lives, and in fact made fires much more toxic. An excellent in-depth investigative journalism series in the Chicago Tribune called “Playing With Fire” provided overwhelming documentation that the chemical industry was not only manufacturing chemicals, but also phony science to defend its toxic products, mislead consumers, and fool lawmakers.

Fortunately, California recently passed a new furniture flammability standard called TB 117-2013. This new standard is smolder test of the furniture fabric and doesn’t require toxic chemicals, and - unlike the old rule - is effective at improving fire safety.

Regrettable Substitutions

In December 2009, once the writing was on the wall, the largest U.S producers and importers of decaBDE announced a phase-out of the chemical by 2013. That created a market space for alternative replacement chemicals. Unfortunately, this is where we sometimes end up playing whack-a-mole with substitute chemicals that are as bad or worse as the ones they are replacing. For example:

  • Firemaster 550 A toxic flame retardant that doesn’t break down in the environment (persistent), collects in peoples bodies (bioaccumulative), and was promoted by its manufacturer as a “safe substitute” for certain PBDE flame retardants that were being phased out. Now, Firemaster 550 is being ubiquitously found in house dust and wildlife. Some of the chemical components of Firemaster 550 had been on the EPA Toxic Substances inventory for decades before showing up in the mix of this particular flame retardant. A recent study linked the chemical to obesity in laboratory animals.
  • TDCPP or “chlorinated Tris” - was removed from kid’s pajamas in the 1970s due to its high toxicity, but it was not banned for any other use and is now showing up as one of the most common chemicals found in a recent survey of couch foam. From furniture foam it can travel into house dust where people are exposed.
  • Emerald 3000 - copolymer of polystyrene and brominated polybutadiene marketed as a flame retardant for furniture foam and textiles. It contains several toxic chemicals, including benzene and 1,3-butadiene which are both known to cause cancer in people. It is also brominated, like the PBDEs it is meant to replace, which will make it last a long time in the environment.

Toxic Free Fire Prevention

The truth is that toxic chemicals – even fire retardant ones – do not significantly slow fires, but they do make the fire much more toxic. House fires have decreased nationwide, probably because of reduced smoking rates, and the introduction of fire-safe cigarettes. Other effective strategies for fires are upgraded wiring in homes, naturally fire-resistant materials in furniture and construction, and the use of functioning smoke alarms. These non-chemical fire prevention strategies make sense and save lives.


An inventory of nanotechnology- based consumer products currently on the market can be found at The Project on Emerging Nanotechnologies website. Nanomaterials are in many consumer products including cosmetics, sports gear, clothing, and children’s products.

About the Authors

Jennifer Sass

Senior Scientist, Federal Toxics, Health and Food, Healthy People & Thriving Communities Program

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