Flame retardant (FR) chemicals are found everywhere scientists look: in the blood of newborns and adults, in breast milk, in Arctic air, in polar bears, in the waters of the Great Lakes. Many FR chemicals are highly persistent—they don’t break down easily.

Chemical FRs also pose a hazard to our health. Some of the most widely used flame retardants since the 1970s are carcinogens, causing cancer in multiple organs in laboratory animals. Some disrupt hormones and reproduction and may contribute to obesity. Effects on fetal and child development and on the immune system have also been reported.  

Halogen-free FRs such as phosphate-based flame retardants (PFRs) have increased in popularity as alternatives to the halogenated products such as brominated and chlorinated flame retardants. However, some PFRs have been found to be toxic and bioaccumulative; many have not yet been adequately assessed.

Flame retardants can become acutely hazardous when they burn. When foam containing pentaBDE (a brominated FR) burned in one study, for example, it produced twice as much smoke, seven times as much carbon monoxide, and 70 times as much soot as foam without flame retardants. It was also found that a typical foam containing pentaBDE provided only a three-second delay in ignition compared to the untreated foam.

In addition to smoke, soot, and carbon monoxide, increased levels of furans and dioxins are emitted when FR-containing materials burn. Furans and dioxins are known to cause cancer. Firefighters have higher rates of cancer than the general population, and exposure to FRs and their toxic combustion products may be a contributing factor.

Below are descriptions of the chemicals found in at least one seat in the 2016 study, "Traveling with Toxics: Flame Retardants and Other Chemicals in Children’s Car Seats." We did not find chlorinated flame retardants. For references, please see Table 9 in the report. The three main categories of FRs found are:

Brominated Flame Retardants (BFRs)

Brominated Polystyrene (BrPS)

  • Use: An additive in nylon and polyester fabric and used as a reactive FR in polystyrene.
  • Toxicity: Unknown, Expected to be less hazardous than nonpolymeric BFRs
  • Environment: Likely to persist in the environment. Low solubility in water.

Hexabromocyclododecane (HBCD)

  • Use: Common in expanded polystyrene foam. Also carpet backing, computer housings, building insulation.
  • Toxicity: Persistent, Bioaccumulative, Toxic. Accumulates in fatty tissues. Hormone disruptor: Interferes with estrogen receptors, interferes with thyroid hormone in rats.
  • Environment: Transported long distances through air and water. Found in wildlife and sediments in San Francisco Bay, Detroit River and Lake Erie. In Arctic air and polar bears.
  • Regulations: Slated for global phase-out under Stockholm Convention. Phased out of commercial use in Europe 2015.

Tris(2,3-dibromopropyl) isocyanurate (TBC)

  • Use: An alternative to PBDEs to treat polyester textiles and many other products.
  • Toxicity: Toxic to organs in zebrafish and mice.
  • Environment: Widely distributed in the environment. Has been detected in mollusks off nine coastal Chinese cities in 2009 and in all soil samples collected around Beijing in 2011. Impairs photosynthesis and growth in algae.

Tetrabromobisphenol A (TBBPA)

  • Use: A reactive FR in printed circuit boards and an additive FR in other plastics.
  • Toxicity: Inconsistent data for human health endpoints; may bioaccumulate. Binds to estrogen hormone receptors. Possible obesogen (a hormone-disrupting chemical that causes obesity).
  • Environment: Toxic to aquatic organisms.
  • Regulations: None: Approved for unrestricted use in the EU, Canada, and the U.S.

Unidentified brominated chemicals

  • We report XRF measurement of elemental bromine in the concentration range (>500 ppm) typical of BFRs in products like car seat foams and fabrics even when a specific chemical identity could not be determined. We have previously demonstrated the reliability of XRF bromine detection as a proxy for BFRs. For fabrics, however, another possibility exists for the source of bromine: brominated azo dyes.

Phosphorus Flame Retardants (PFRs)

Triethyl Phosphate (TEP)

  • Toxicity: TEP does not pose a known significant health risk for humans
  • Comments: In the present study, very low concentration measured along with TBEP.

Triphenyl Phosphate (TPP)

  • Use: A flame retardant in plastic products, including car seat foams. Found in other children’s products.
  • Toxicity: Not a carcinogen. May impact metabolism and contribute to obesity. Interferes with estrogen receptors and other sex hormones. Altered hormone levels, decreased reproductive function and developmental outcomes. Not highly bioaccumulative, but detection rate is high in humans due to widespread use.
  • Environment: Highly toxic to aquatic organisms. Found in household dust, soil, sediment, air, and water.

Tris(butoxyethyl)phosphate (TBEP) 

  • Use: In addition to FR use, used in floor polishes and waxes as an antifoam agent, and as a plasticizer in plastics and rubbers.
  • Toxicity: No studies on long-term toxicity or carcinogenicity. Anti-estrogenic and other hormone effects in vitro. TBEP was in 100% of indoor dust samples from houses in North America. Found in urine in adults and children and in breast milk.
  • Environment: World Health Organization says general health risk is low. Detected in air around the Great Lakes and in the Arctic.

Cyclic Phosphonate Ester

  • Use: Applied to polyester and nylon fabrics in a thermosol process.
  • Toxicity: Not studied directly, but a representative compound for this chemical class is a possible carcinogen and may be dermally absorbed (absorbed through the skin).
  • Environment: Soluble in water

Ammonium polyphosphate

  • Used in furniture upholstery, automotive interior fabrics, draperies.
  • Toxicity: Unlikely to be carcinogenic. Low toxicity to rats.
  • Environment: Low to moderate toxicity to aquatic species. Low bioaccumulation potential. Very high persistence.

Unidentified phosphorus-containing chemicals

  • We report XRF measurement of elemental phosphorus in the concentration range (>5,000 ppm) typical of PFRs in products like car seat foams and fabrics even when a specific chemical identity could not be determined. We have previously demonstrated the reliability of XRF phosphorus detection as a proxy for PFRs in this type of product.

Inorganic Flame Retardants

Antimony Trioxide (a likely source of elemental antimony measured in several car seats)

  • Use: Synergist used in many polymers.
  • Toxicity: Does not bioaccumulate.
  • Environment: Highly toxic to aquatic organisms.
  • Regulations: Listed as a possible carcinogen (by inhalation) by the Internationals Agency for Research on Cancer.
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