Dust, not food, main source of lesser known flame retardants.
Roosens L, MA Abdallah, S Harrad, H Neels and A Covaci. 2009. Exposure to hexabromocyclododecanes via dust ingestion, but not diet, correlates with concentrations in human serum - preliminary results. Environmental Health Perspectives doi:10.1289/ehp.0900869.
Flame retardants are chemicals commonly used in consumer products and construction materials to prevent them from catching on fire.
Use of some polybrominated diphenylethers (PBDEs), a class of flame retardants, has recently been banned in Europe and several US states due to concerns about their persistence in the environment and potential adverse health effects.
Another group of flame retardants, named hexabromocyclododecanes (HBCDs), is believed to increasingly be used as replacements following the PBDE bans. As use increases, so have their levels in the environment.
HBCDs are primarily added to polystyrene insulation foam boards, which are widely used in the construction industry. They are also used in the back coating of textiles, mostly for upholstered furniture.
Health effects are mostly unknown but animal studies show the compounds are linked to liver and thyroid hormone disruption and reproductive disorders.
Similarly to PBDEs, HBCDs are not chemically bound to materials and can thus leach into the environment. HBCDs also share the characteristics of so-called persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs) and the pesticide dichlorodiphenyl trichloroethane (DDT), in that they are persistent in the environment, accumulate in the fat of humans and wildlife, and may be transported over very large distances.
HBCDs, for instance, have been measured in animals living in remote areas such as Greenland and Svalbard, an archipelago located in the Arctic about midway between Norway and the North Pole. These chemicals were also detected in several European and North American countries in bird eggs, marine mammals, fish, lake sediments and air samples. They have also been detected in human serum, body fat and breastmilk.
It is however not entirely clear how humans are exposed to HBCDs.
Belgian researchers measured HCBDs in the blood of 16 adults (7 males and 9 females in their early to mid twenties) who had resided for at least three years in university housing.
Participants were requested to provide an identical duplicate of all the food they ate or to identify what they ordered at the university cafeteria, including meals and snacks, during a one-week period. The concentration of HBCDs was measured in all food samples.
In addition, HBCDs were measured in dust samples collected from participants’ bedrooms. Researchers estimated HBCDs intake through dust based on published dust ingestion rates.
Researchers reported a strong correlation between the estimated dust intake of HBCDs and the blood concentration of the chemical.
No relation was reported between dietary intake and blood HBCD levels, which may be due to the small number of samples with detectable concentrations of HBCDs. Of the 165 duplicate diet samples, only 13 had detectable HBCD concentrations (less than 5 to 20 picograms per gram of food). Only samples containing meat, milk, cheese or fish had detectable concentrations of HBCDs, suggesting that these foods may constitute the main sources of dietary exposure to the flame retardant. These results are consistent with prior studies conducted in Norway and Sweden that reported high HBCD concentrations in fish.
HBCDs were detected in all dust samples and in seven out of 16 blood samples. The median dust (114 nanograms/gram) concentration of HBCDs was lower than most previous studies, but blood levels (1.7 ng/g lipids) were more than 4 times higher than reported in the body fat of 20 New York City residents (Johnson-Restrepo 2007).
These results suggest that house dust is a significant contributor to human exposure to HBCDs. The use of HBCD-treated products, rather than industrial pollution, may thus contribute more importantly to human exposure. In addition, infants and toddlers may be at greatest risk of exposure because they crawl on floors and may increase their exposure due to hand-to-mouth behavior.
While exposure to other persistent organic pollutants appear to occur primarily through food, this result is consistent with studies of other flame retardants, such as PBDEs, which suggest that the main exposure sources are located in homes and other indoor environments.
Although small, this Belgian study is the first to examine the relationship between dust, diet and blood concentrations of HBCDs in humans.
The more recent ban of PBDEs in Europe may be credited for lower exposure to these chemicals in European relative to North American populations. HBCDs annual market demand has been reported to be about three times higher in Europe relative to the Americas.
Replacement of PBDEs with HBCDs in some products may explain why most studies with people report that exposure to this fire retardant is substantially lower in the United States compared to Europe. No study has reported the blood concentrations of HBCDs in US residents, but a recent report found that median concentrations of HBCDs were approximately 100 times lower than PBDE concentrations in breast milk collected from Texan women.
Regulatory agencies in countries around the world are evaluating the potential adverse environmental and human health effects of HBCDs, but very few studies have been published on the subject. Research conducted in animals suggest that this class of fire retardants may disrupt thyroid hormone, which is essential for normal brain development, and that neonatal exposure may cause symptoms suggestive of hyperactivity. Exposure to HBCDs has also been associated with reproductive disorders in animals.
Larger studies with analytical methods capable of detecting HBCDs at lower concentrations are however needed to confirm the main sources of exposure to these chemicals.
Environmental Science and Technology 40(12):3679-88.
Ema, M, S Fujii, M Hirata-Koizumi and M Matsumoto. 2008. Two-generation reproductive toxicity study of the flame retardant hexabromocyclododecane in rats. Reproductive Toxicology (25):335-51.
Johnson-Restrepo B, DH Adams and K Kannan. 2008. Tetrabromobisphenol A (TBBPA) and hexabromocyclododecanes (HBCDs) in tissues of humans, dolphins, and sharks from the United States. Chemosphere, 70(11):1935-44.