Hexabromocyclododecane in polystyrene based consumer products: An evidence of unregulated use
Introduction
Polystyrene (PS) is one of the most widely used plastics because of its affordability, light weight, resistance to moisture, and high insulation value. With the advancement in technology, the rate of consumption of PS in households, laboratories, and businesses is continually increasing. The estimated global demand for polystyrene and expandable polystyrene was around 14.9 million tons in 2010, and its market would grow at a rate of 5.6% from 2010 to 2020 (GBI Research, 2012). PS is heavily used as a building insulation material, in architectural models, and as packing material for food, laboratory chemicals, and electronic appliances (Wünsch, 2000, Levchik and Weil, 2008). The various forms of PS available in the global market include expanded PS (EPS), extruded PS foam (XPS), and extruded PS. EPS and XPS are injection molded and extruded foams, respectively, while extruded PS is a hard plastic commonly used to make a variety of consumer products, such as disposable cutlery, and mobile phone holders. Currently, PS is an abundant form of litter found in the outdoor environment, mainly along shores and waterways (Zhou et al., 2011). In order to protect it from burning, a brominated flame retardant (BFR) is commonly used, the most important of which is 1,2,5,6,9,10-hexabromocyclododecane (HBCD) (Wünsch, 2000, Levchik and Weil, 2007, Levchik and Weil, 2008). HBCD is intensively used worldwide as an additive to EPS and XPS (0.7–2.5% HBCD w/w) (Alaee et al., 2003) with an annual production of 23 000 tons (POPRC, 2011). The industrial application of HBCD has increased over the past few years subsequently after restrictions on the use of polybrominated diphenyl ethers (PBDEs) (Sellstrom et al., 1998, EU Directive, 2003). Currently, HBCD is the third highest-volume BFR used after tetrabromobisphenol-A (TBBPA) and decabromodiphenyl ether (BDE-209) (Alaee et al., 2003). It can enter the environment through a number of means, such as from emissions during production, by leaching from consumer products, or by disposal into the environment. Acute toxic effects in humans appear to be low; however, some reports indicate that it is highly toxic to rats and induces cancer via a nonmutagenic mechanism (Helleday et al., 1999, Ronisz et al., 2004). HBCD can also affect the normal re-uptake of neurotransmitters in the rat brain (Mariussen and Fonnum, 2003). In May 2013, it was added to the list of global elimination compounds under the Stockholm Convention on Persistence Organic Pollutants and banned for the future production and use (UN, 2013).
Because of the extensive use coupled with its persistence, bioaccumulation potential, and possible adverse effects on biota, a database of HBCD concentrations in PS used in common applications is of paramount importance. Most of previous research has been directed towards the detection of HBCD in the air, water, soil, sediments, and biota (Li et al., 2012, Yang et al., 2012, Du et al., 2013, Zhang et al., 2013). However, determination of BFRs, including HBCD, in PS has received less attention by researchers. Zhang et al. (2012) highlighted the release of HBCD during thermal cutting of PS foams (EPS and XPS). The combustion of fire-retarded XPS was reported to produce various bromophenols (Desmet et al., 2005). Vilaplana et al. (2009) found TBBPA along with minor concentrations of BDE-209 and other PBDE congeners in styrenic plastic fractions obtained from waste electrical and electronic equipment. Thermally-induced transformation of HBCD and isobutoxypentabromocyclododecane (iBPBCD) in flame-retarded PS materials follow first-order kinetics (Heeb et al., 2010). A number of toxic byproducts were identified in thermogravimetry–mass spectrometry (TG–MS) by the degradation of BDE-209 and decabromodiphenylethane (DBDPE) in high-impact PS (Grause et al., 2011). These degradation products, along with the released hazardous brominated compounds, can pose a serious threat to human health.
It is apparent from the above discussion that a number of studies have documented the determination and/or degradation of certain BFRs in PS used in construction and in electric and electronic appliances. However, the relative concentration of HBCD in other PS materials used in various applications may not be the same. Our research group has analyzed HBCD in EPS buoys, and detected a wide range of HBCD in parts per million levels in there (Hong et al., 2013). EPS buoys are extensively used in hanging culture farm for oyster and mussel in Korea and end up in the environment as marine debris. EPS buoy has been recorded as a major item of marine debris in all size classes including micro (1–5 mm), meso (5–25 mm) and macro (>25 mm) (Heo et al., 2013, Lee et al., 2013), implying that EPS debris may be a main source of HBCD in the Korean marine environment (Hong et al., 2013). These observations necessitated to produce a database of the relative HBCD content in various PS products used for common purposes to evaluate its exposure.
The present study is aimed at systematically determining the HBCD content in several PS products (EPS, XPS, and extruded plastic) used in different areas, such as food, laboratory, construction, aquaculture, and electronics. A number of PS products e.g. food packings, chemical packings, food serving containers, cups, trays, styroboards for construction, buoys, etc. were collected. The criterion for selecting these products is based on their worldwide use, intended for single use followed by disposal to the landfill or incineration.
Section snippets
Chemicals and reagents
The isotope-labeled (13C12) HBCD standard (mixture of 3 isomers, 99% purity) and TBBPA (ring-13C12, 99%), were purchased from Cambridge Isotope Laboratories, Inc. (MA, USA). Isotope-labeled 1,2-bis(2,4,6-tribromo[13C6]phenoxy) ethane (13C-BTBPE, ⩾99%), [13C14]-1,2-bis(pentabromophenyl)ethane (13C-DBDPE, ⩾99%) and 2,2′,3,4,4′,6-hexabromo[13C12]diphenyl ether (13C-BDE-139) were obtained from Wellington Laboratories, Inc. (Ontario, Canada). Acetonitrile, dichloromethane, isopropanol and toluene
HBCD in PS products
PS is a highly used polymer material for food packing/serving and in construction. Therefore, it is necessary to consider each type of PS material to present a database on the status of BFRs, especially HBCD. Therefore, a total of 34 samples of PS products (EPS with IDs 1–14, XPS with IDs 15–26, and extruded PS with IDs 27–34) of different categories (food-related, n = 19; construction, n = 6; laboratory, n = 5; aquaculture, n = 2; electronic appliances and others, n = 2) were analyzed (Fig. 1). The
Conclusions
Among the three types of PS investigated, the highest concentration of HBCD was detected in EPS products. Some food-related PS products had a high concentration of HBCD, indicating unregulated addition of HBCD without consideration for the use of a particular product. Therefore, we believe a regulative and controlled method should be used for adding HBCD to PS. In the case of XPS, other BFRs were added along with HBCD. This creates additional contamination of the environment via PS products.
Acknowledgment
The authors would like to acknowledge the Korea Institute of Ocean Sciences and Technology for funding this research (PE99192).
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