On March 13, 2014 the peer-reviewed journal Chemosphere published the article “Hexabromocyclododecane in polystyrene based consumer products: An evidence of unregulated use” investigated the amounts of 1,2,5,6,9,10-hexabromocyclododecane (HBCD) and three further brominated flame retardants (BFR) contained in polystyrene (PS) plastics for use as building materials, laboratory equipment and food contact materials (FCM). HBCD and further BFRs are ubiquitous, persistent in the environment and are suspected of having a high potential for bioaccumulation. The authors of the study, Manviri Rani from the Korea Institute of Ocean Science and Technology at Geoje-shi and colleagues from the University of Science and Technology at Daejeon, both in the Republic of Korea, analyzed four types of BFRs contained in 34 products based on three types of PS: expanded PS (EPS; n=14), extruded PS foam (XPS; n=12), and extruded PS (n=8). While EPS and XPS are foams used mainly for products as construction materials and laboratory equipment, extruded PS is a common rigid plastic used for consumer goods like cutlery, bottles, trays, cups, freezer bags, prepackaged fresh produce, food storage containers and other FCMs. 19 out of 34 samples analyzed were FCMs. BFRs like HBCD are added to plastics at various degrees due to their combustion inhibiting properties. BFRs also migrate from the materials during production, use and disposal, and might thereby contaminate the environment and food stuff. HBCD is currently the third most used BFR worldwide. Even though acute toxicity in humans appears to be low, animal experiments in rats have proven that it is a potent carcinogen acting via non-mutagenic pathways and interfering with neurotransmitter uptake in the brain, among other effects. Moreover, hazardous brominated by-products of BFRs were found in PS, which are thought to be a serious threat to human health. Furthermore, PS debris affects the environment, whereby mainly aquatic organisms are contaminated and chemicals like HBCD find their way into the food chain. HBCD is also abundantly found in air, water, soil, sediments, and biota, whereby it also poses a direct and indirect health risk for humans due to its persistence and bioaccumulating potential. In May 2013, HBCD was added to the list of the Stockholm Convention on Persistent Organic Pollutants and will be banned starting from August 2015 from production and use (UN, 2013; EU 143/2011). The industry has partly reacted to the ban by introducing bromine-free alternatives, such as polymeric flame retardants (PolyFRs), which for the moment are still more expensive and are bulkier in the plastic matrix (Plastic Europe, 2014). However, such polymeric flame retardants can be made from bisphenol A (BPA), another chemical of concern.
Apart from HBCD, Rani and colleagues also investigated the presence of 3 further BFRs: tetrabromobisphenol-A (TBBPA), 1,2-Bis(2,4,6-tribromophenoxy)ethane (BTBPE), and decabromodiphenylethane (DBDPE) (Table 1).
Food related PS materials showed low levels of HBCD (24.3 ng g-1). Exception hereof are the remarkably elevated levels found for an ice box made out of EPS (960,000 ng g-1) and a disposable tray (8,430 ng g-1). Far lower levels were found for the other BFRs TBBPA, BTBPE and DBDPE, which ranged from 3.83 – 545 ng g-1, 44 – 216 ng g-1 and 215 – 4,200 ng g-1, respectively.
In an additional step the researchers analyzed the composition of the three diastereoisomers of HBCD in the analyzed PS materials. The diastereomisomeric composition is of particular interest because of the striking differences in water solubility among the HBCD diastereoisomers. αHBCD is with 48.8 mg L-1 considerably more water soluble than β and γ with water solubilities of 14.7 mg L-1and 2.1 mg L-1, respectively. Hence, the study’s authors conclude that αHBCD is more likely to migrate into aqueous foods and be of concern for human health due to its elevated biomagnifications characteristics. The diastereoisomer composition of HBCD ranged from 4.9 % – 70.5 % (α), 5.7 % – 46.7 % (β) and 44 – 84 % (γ). In 30 out of 34 samples γHBCD was the most abundant diastereoisomer. α diastereoisomers were found at higher ratios in food related materials based on XPS and extruded PS. The authors argue that the heat in the production of these final products leads to the higher fraction of α diastereoisomers in XPS and extruded PS. While the bioaccumulating properties of BFRs arise from their lipophilicity rather than from their still rather low water solubility, information on solubility might contribute to the assessment of risks coupled with exposure to HBCD.
Summarizing, Rani and colleagues show that EPS products contain the highest concentrations of HBCD, and that some FCMs contain considerable amounts of BFRs. The presence of BFRs in FCMs is associated with a potential health risk for consumers. It is questionable why and how BFRs find their way into FCMs; the use of BFRs in FCMs is not authorized. Finally, due to varying water solubility between HBCD diastereoisomers the evaluation of its isomeric composition is crucial for assessing its risk.
Rani M. et al. (March 13, 2014). “Hexabromocyclododecane in polystyrene based consumer products: An evidence of unregulated use”. Chemosphere
Plastic Europe (March 11, 2014) “EPS Insulation”
ECHA (2013). “Registered Substance”. European Chemicals Agency, Helsinki.
EU 143/2011 (February 17, 2011). “No 143/2011 of amending Annex XIV to Regulation (EC) No 1907/2006 of the European Parliament and of the Council on the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH)”, EU Commission Regulation
2011/65/EU (June 8, 2011). “Directive 2011/65/EU of the European Parliament and of the Council of 8 June 2011 on the restriction of the use of certain hazardous substances in electrical and electronic equipment”. European Parliament and Council.