Hexabromocyclododecanes (HBCDs) in fish: Evidence of recent HBCD input into the coastal environment

Highlights

• HBCDs were measured in three fish species from the PRD region.

• Plecostomus had significantly higher HBCD levels than mud carp and tilapia.

• Highest HBCD levels were founded in fish from the e-waste site and a harbor.

• HBCD concentrations were not correlated with population and GDP data.

Abstract

Hexabromocyclododecanes (HBCDs) are flame retardants and emerging persistent organic pollutants. In the present study, α-, β-, and γ-HBCDs were measured in several fish species from rivers and an electronic waste (e-waste) recycling site in Pearl River Delta, South China. The concentrations of HBCDs were 12.8 to 640, 5.90 to 115, and 34.3 to 518 ng/g lipid weight (lw) in mud carp (Cirrhinus molitorella), tilapia (Tilapia nilotica), and plecostomus (Hypostomus plecostomus), respectively. Plecostomus showed the highest HBCD concentrations among three fish species. The contributions of α-HBCD to total HBCDs were 78% to 97%, 93% to 99%, and 87% to 98% in carp, tilapia, and plecostomus, respectively. Fish samples from a harbor and the e-waste site exhibited the highest HBCD concentrations among all samples. The HBCD concentrations were not significantly correlated with the gross domestic product or population data. e-Waste recycling activities, harbor construction, and shipment might be recent HBCD sources.

Introduction

Hexabromocyclododecanes (HBCDs) are additives widely used as flame retardants in textiles, electronics, and especially thermal insulation in building materials. In the last few decades, the occurrence of HBCDs in environmental matrices and biota samples has been reported in the literature (Covaci et al., 2006, Law et al., 2014, Marvin et al., 2011). HBCDs are bioaccumulative in aquatic and terrestrial food webs (Tomy et al., 2004, Sun et al., 2012), and exert toxic effects on creatures (Hong et al., 2015, Marvin et al., 2011, Koch et al., 2015). Effects of HBCD on the thyroid axis were first described by Chengelis (1997). van der Ven et al. (2006) described an increased pituitary weight, an increased immunostaining of thyrotropin (TSH, thyroid stimulating hormone), and an increased thyroid weight in female rats. Johnson et al. (2013) found an association between increased concentrations of HBCDs in indoor dust and an increase of the free androgen index in men. Fernie et al. (2011) observed reproductive changes in American kestrels, in relation to exposure to HBCDs, in environmentally relevant concentrations. In 2013, HBCDs were listed under Annex A (POPRC8.3, 2013) of the Stockholm Convention on persistent organic pollutants (POPs), but have not been banned yet (Koch et al., 2015). The environmental occurrence and bioaccumulation potential of HBCDs still warrants attention.

The occurrence and fate of HBCDs in the coastal environment is of major concern and a priority issue due to their deleterious effects on aquatic creatures in estuarine ecosystems, and the consequent pollution in marine environments. Fish have been widely used to monitor legacy and emerging environmental contaminants in aquatic ecosystems (Iqbal et al., 2017). In addition, fish are among the most important foods of coastal population, and the consumption of contaminated fish is a major human exposure pathway to harmful chemicals (Malarvannan et al., 2015, Meng et al., 2012). HBCDs are bioaccumulative in aquatic ecosystem (Law, 2014, Tomy et al., 2004). In general, the concentrations of HBCDs in fish have increased with the continuous usage of HBCDs in the last few decades. Law et al. (2014) have recently summarized temporal trends of environmental HBCD concentrations. They found mixed temporal trends for HBCD, with both increasing and decreasing levels in different matrices (Law et al., 2014).

The Pearl River Delta (PRD) region covers several most developed cities and biggest harbors in south China. The PRD region has been known among the most significant manufactures and export bases for electronic and electrical products, textiles, and plastic products in the world. The developed industry and the large populations would bring a large amount of flame retardants and plasticizers into the local environment. Furthermore, the PRD region also contains several e-waste recycling sites. The improper transport, storage, and dismantling of e-wastes are great threat to the environment and human health. The occurrence of legacy and emerging flame retardants has been ubiquitously found in water, sediment, fish, and bird species in the PRD (Feng et al., 2012, He et al., 2012, Meng et al., 2012, Sun et al., 2015a, Sun et al., 2015b, Sun et al., 2015c). HBCDs have been important pollutants in the PRD region. He et al. (2010) detected HBCDs in water, soil, fish, and various bird species from the e-waste recycling region, which was attributed to the HBCD emission during the improper dismantling of e-wastes. HBCDs were also detected in the sediments from the main rivers in PRD (Feng et al., 2012), which emphasized the HBCD contamination brought by the domestic products and local industry.

In the present study, HBCDs were determined in three fish species collected from the major rivers, including the Pearl River, Xijiang (West River), Beijiang (North River), and Dongjiang (East River) in PRD region. HBCDs were also measured in fish and sediment samples from an e-waste recycling site in the PRD. The objectives of the study were to get a general understanding about the recent pollution of HBCDs in the coastal environment of the PRD, and to identify the potential sources of these contaminants in the studied region. The accumulation of HBCDs in different fish species and the temporal trends of HBCD pollution were also discussed.