Hexabromocyclododecanes in breast milk from residents in Shenzhen, China: Implications for infant exposure

Highlights

• 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.

Abstract

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 0.103–15.1 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 0.481 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 < 0.05). To our knowledge, this is the first report on HBCD levels in breast milk from Shenzhen residents.

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 (9000–15,000 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.