Science of the Total Environment

Transcription

1 Science of the Total Environment (2018) Contents lists available at ScienceDirect Science of the Total Environment journal homepage: Hexabromocyclododecanes in breast milk from residents in Shenzhen, China: Implications for infant exposure Shaoyou Lu a,zhentan b, Yousheng Jiang a,dongtingwu c, Jianqing Zhang a,,jianzhou a, Xiaoshi Lin a a POPs Lab, Shenzhen Center for Disease Control and Prevention, Shenzhen , China b Shenzhen Academy of Metrology & Quality Inspection, Shenzhen , China c School of Medicine, Shenzhen University, Shenzhen, Guangdong , China HIGHLIGHTS GRAPHICAL ABSTRACT HBCD levels in breast milk were investigated firstly from residents in Shenzhen, China. The duration of residence was significantly positively correlated with the HBCD levels in breast milk. The estimated daily intake (EDI) of HBCDs for infants in Shenzhen via breast milk ingestion was evaluated. Exposure of breast-fed infants via human breast milk was unlikely raises a health concern based on the MOE approach. Hexabromocyclododecanes (HBCDs) exposure for general population and infants. article info abstract Article history: Received 6 July 2017 Received in revised form 23 November 2017 Accepted 24 November 2017 Available online xxxx Editor: Jay Gan Keywords: Hexabromocyclododecanes Breast milk Concentrations Profiles Estimated daily intake Hexabromocyclododecanes (HBCDs) are widely used as flame retardants for various products and have become ubiquitous pollutants in environmental media. However, little is known about HBCD exposure for humans, especially in China. This study aimed to investigate the levels and profiles of hexabromocyclododecanes (HBCDs) in human breast milk and to estimate the daily HBCD intake for infants in Shenzhen, China. Levels of the HBCD diastereoisomers α-, β-, and γ-hbcd in 180 breast milk samples collected from primiparas in Shenzhen were measured. The concentrations of α-, β-, and γ-hbcd (ΣHBCDs) ranged within ng/g lipid and had a median of 1.82 ng/g lipid. ΣHBCDs levels in milk in the present study are comparable to those in milk from other countries and regions but are markedly higher than those for most populations in other regions of China. Among the diastereoisomers, α-hbcd was predominant, accounting for 97.6% of the concentration of ΣHBCDs. The estimated daily intake of ΣHBCDs via breast milk for infants in Shenzhen ranged from to 100 ng/kg bw/day with a median of 8.40 ng/kg bw/day, however, which was unlikely to raises a health concern based on the margin of exposure (MOE) approach. The duration of residence was found to have a significant positive correlation with the HBCD levels in the human breast milk (p b 0.05). To our knowledge, this is the first report on HBCD levels in breast milk from Shenzhen residents Elsevier B.V. All rights reserved. Corresponding author. address: jianqingzh@szcdc.net (J. Zhang) / 2017 Elsevier B.V. All rights reserved.

2 S. Lu et al. / Science of the Total Environment (2018) Introduction Hexabromocyclododecanes (HBCDs) are widely used as flame retardants for expanded polystyrene (EPS) foam, extruded polystyrene (XPS) foam, textile products, and various electronic products. In 2001, the global consumption of HBCDs was 16,700 tons, and reached 28,000 tons in 2011 ( ,000 tons in China, and 13,426 tons in Europe and the United States; POPRC, 2011). Unlike tetrabromobisphenol A, which is chemically bound to products, HBCDs are additives and thus are easily released into environmental compartments from the products. HBCDs are ubiquitous pollutants, they have been frequently detected in air, soils, sediments, and human fluids (Law et al., 2014; Yi et al., 2016). Although animal experiments suggest that HBCDs have low acute toxicity via oral, inhalation, and dermal routes (Wang et al., 2011; Wikoff and Birnbaum, 2011), repeated oral doses lead to chronic toxicity such as hepatotoxicity and thyroid toxicity (Ema et al., 2008; Palace et al., 2008; Ibhazehiebo et al., 2011; Villanger et al., 2011). Previous in vitro studies suggest that HBCDs are cytotoxic (Al-Mousa and Michelangeli, 2012; An et al., 2014; Huang et al., 2016). Moreover, some studies show that HBCDs have adverse effects on the development of juvenile animals (Anselmo et al., 2011; Du et al., 2012b; Usenko et al., 2016). After entering the human body, HBCDs can remain in bodily fluids such as breast milk (Geyer et al., 2004; Kakimoto et al., 2008; Toms et al., 2012) and blood (Bjermo et al., 2017; Drage et al., 2017), or in tissues such as scalp hair (Malarvannan et al., 2013) and adipose tissue (Johnson-Restrepo et al., 2008; Pulkrabova et al., 2009). In contrast to environmental measurements, the biomonitoring of HBCDs in bodily fluids directly reflect the overall exposure via different sources and pathways. Although previous studies have determined environmental pollution of HBCDs in China (Zhang et al., 2009; Hu et al., 2011; Li et al., 2012a), data on the levels of HBCDs in human samples are still very limited. Shenzhen is a coastal city locating east of the Pearl River Delta, which is one of the most economically developed regions in China. In the past three decades, Shenzhen has undergone rapid economic growth and has become a manufacturing center of electronic products in China, and income from the electronic industry reached 1600 billion yuan in 2016 (Xu, 2017). A large amount of brominated flame retardants is required in the production of electronic products. Previous studies have frequently reported polybrominated diphenyl ethers, tetrabromobisphenol A, and HBCDs in soil, air, indoor dust (Li et al., 2012b; Ni and Zeng, 2013), and ecological food chains (Liu et al., 2011) in Shenzhen. A recent study has found that polybrominated diphenyl ethers exist at relatively high levels in human breast milk of Shenzhen residents (Zhang et al., 2012). Breast milk is the most important food for infants, making infants exposed to residual HBCDs. Therefore, more attention should be paid to this issue. Nevertheless, there is still no study on HBCDs in the residents of Shenzhen. The aims of this study were, therefore, to investigate the concentrations and profiles of HBCDs in human breast milk samples in Shenzhen, to estimate the daily intake of HBCDs of infants, and to analyze the probable sources of HBCD exposure for the local residents. This is the first study to report levels of HBCDs in samples from the residents in the city. 2. Materials and methods 2.1. Chemicals and reagents α-, β-, and γ-hbcd and their corresponding internal standards ( 13 C 12 -α-, 13 C 12 -β- and 13 C 12 -γ-hbcd, respectively) with the purity of 98% were purchased from Cambridge Isotope Laboratories (Andover, MA, USA). Methanol, hexane, cyclohexane, toluene, and acetonitrile of high-performance liquid chromatography (HPLC) grade were purchased from Merck (Darmstadt, Germany). HPLC-grade ethyl acetate was purchased from Honeywell Burdick & Jackson (Muskegon, MI, USA). Sulfuric acid (98% purity) and anhydrous sodium sulfate were obtained from Fisher Scientific (Houston, TX, USA). The water used in experiments was deionized by using a Millipore system (Billerica, MA, USA) Study participants and sample collection Total 180 breast milk samples from 18- to 35-year-old primiparas living in Shenzhen were collected from January 2011 to August All participants recruited in the study, 62, 68, and 50 of whom were from three districts of Shenzhen, Longgang, Luohu, and Nanshan Districts, respectively, lived in the city for N3 years. As Longgang is an industrial district in Shenzhen, its local residents typically live around the factories for electronics. Luohu and Nanshan are both central business districts; their local residents therefore live in relatively cleaner environments. Participants were recruited by doctors in the local health centers, and breast milk samples were collected between one month and two months postpartum. Each participant signed a consent form in which the objectives and procedures of this study was informed. Before sampling, each participant was asked to finish a questionnaire under the direction of doctors in the local health centers. General information in the questionnaire included each mother's age, height, occupation, dietary habits, disease history, and occupational exposure, as well as infant information such as number of gestational age, birth weight, and birth length. Demographic details for the participants are summarized in Table S1, and the sampling locations are shown in Fig. S1. From each participant, ml of breast milk was asked to collect into a glass bottle with Teflon seal that had been rinsed with dichloromethane in advance and the collection should be finished in three days. During the sampling period (in three days), the bottle was stored into the participant's refrigerator at 4 C. After finishing the collection, the breast milk sample was taken back to the laboratory and stored at 20 C until chemical analysis Standard preparation and sample preparation Methanolic stock solutions (50.0 mg/l) of the individual HBCD diastereoisomers and internal standards were prepared. The calibration standard solutions, which were prepared by diluting the stock solution with methanol, had the concentrations ranging from to 50.0 μg/l. All standard solutions were stored at 20 C in the laboratory. Liquid breast milk samples were freeze-dried (Millrock Technology, Kingston, NY, USA) and then homogenized. About 3 g of breast milk powder was weighed and transferred into a glass tube. After the sample was spiked with 20 μl of internal standard solution containing 13 C 12 -α-, 13 C 12 -β-, and 13 C 12 -γ-hbcd at 100 μg/l, the resulting mixture was extracted with 80 ml of hexane/acetone (1:1, v/v) solution for 5 hs using a Soxtec 2050 automated Soxhlet extraction system (Foss, Hoganas, Sweden). After the extraction, the crude extract was completely dried and the lipid content of the breast milk was determined by gravimetry. To remove lipids, the extract was subjected to automated gel permeation chromatography (GPC; J2 Scientific Inc., Columbia, MO, USA). Each sample was purified on a column ( mm id) packed with 60 g (dry weight) of 200- to 400-mesh S-X3 Envirobeads (ABC Instruments, Columbia, MO, USA). The dried extract was redissolved in 6 ml of ethyl acetate/cyclohexane (1:1, v/v) solution and then was injected into the GPC system. Ethyl acetate/cyclohexane (1:1, v/v) solution was used as the mobile phase for the GPC column, and elution was done at a flow rate of 4.8 ml/min. The fraction between 8.0 and 15.0 min was collected and concentrated to dryness in a rotary evaporator (Buchi, Flawil, Switzerland). After the extract was redissolved in 7 ml of hexane, it was treated with 2 ml of concentrated sulfuric acid to remove residual lipids. Each sample was vortexed for 10 min, and the supernatant was collected in a 30 ml glass tube. The sulfuric acid fraction was then extracted twice with additional 7 ml portions of hexane. The supernatants

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