Soil contamination by brominated flame retardants in open waste dumping sites in Asian developing countries

Abstract

In Asian developing countries, large amounts of municipal wastes are dumped into open dumping sites each day without adequate management. This practice may cause several adverse environmental consequences and increase health risks to local communities. These dumping sites are contaminated with many chemicals including brominated flame retardants (BFRs) such as polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs).

BFRs may be released into the environment through production processes and through the disposal of plastics and electronic wastes that contain them.

The purpose of this study was to elucidate the status of BFR pollution in municipal waste dumping sites in Asian developing countries. Soil samples were collected from six open waste dumping sites and five reference sites in Cambodia, India, Indonesia, Malaysia, and Vietnam from 1999 to 2007. The results suggest that PBDEs are the dominant contaminants in the dumping sites in Asian developing countries, whereas HBCD contamination remains low. Concentrations of PBDEs and HBCDs ranged from ND to 180 μg/kg dry wt and ND to 1.4 μg/kg dry wt, respectively, in the reference sites and from 0.20 to 430 μg/kg dry wt and ND to 2.5 μg/kg dry wt, respectively, in the dumping sites. Contamination levels of PBDEs in Asian municipal dumping sites were comparable with those reported from electronic waste dismantling areas in Pearl River delta, China.

Introduction

Environmental contamination by brominated flame retardants (BFRs), such as polybrominated diethyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs), has received increasing public attention because of the persistence, bioaccumulation potential, and possible adverse effects of these chemicals on humans and wildlife (Hites, 2004, Covaci et al., 2006).

PBDEs can have adverse in vitro and in vivo physiological effects, including endocrine disruption and interference with neurobehavioral development (Darnerud, 2003, Birnbaum and Staskal, 2004, Herbstman et al., 2010). Several studies have shown that effects of PBDEs are similar to those of organohalogen compounds, such as reduction in serum thyroid hormone levels (Hallgren et al., 2001). Reported toxicities of HBCDs include developmental neurotoxic effects such as aberrations in spontaneous behavior, learning, and memory functions (Eriksson et al., 2002, Eriksson et al., 2004). HBCDs also alter the normal transport of neurotransmitters in rat brain (Mariussen and Fonnum, 2003, Ibhazehiebo et al., 2011).

PBDEs and HBCDs are used as flame-retardant additives in a wide variety of commercial and household products such as plastics, textiles, and electronic appliances including computers and televisions (Kemmlein et al., 2009). In 2001, global consumption of the technical PBDE mixtures penta-, octa-, and deca-BDE and HBCDs was 7500, 3800, 56 000, and 15 900 tons, respectively. In Asia, the total consumption volumes of penta-, octa-, deca-BDEs and HBCDs were 150, 2000, 23 000, and 3900 tons, respectively, during 2001 (BSEF, 2003, Watanabe and Sakai, 2003). This widespread usage and bioaccumulation potential of BFRs resulted in both classes of these chemicals being present in air, water, fish, birds, marine mammals, and humans throughout the world (Law et al., 2008).

In Asian developing countries, the majority of the municipal solid waste, which consists of a wide variety of materials such as food waste, paper, plastics, building material, metal wastes, and ash (Gullett et al., 2010, Fiedler and Solorzano Ochoa, 2010), were disposed directly into open waste dumping sites without appropriate processes (Minh et al., 2003). Apart from the enormous amounts of waste dumped in such areas, not much information on their quality and quantity is available from Asian developing countries. As a result, these open dumping sites could be a major source of contaminant emission on the environment and human exposure route. This practice has led to public concerns over potential impacts on the environment and local communities. These concerns were justified by more recent intensive studies that demonstrated an increased human health risk caused by exposure to toxic chemicals such as persistent organic pollutants (POPs) from dumping sites (Minh et al., 2006). However, previous studies on BFRs in soil samples from Asian developing countries were confined to Chinese e-waste recycling sites and Indonesian municipal waste dumping sites (Leung et al., 2007, Zou et al., 2007, Ilyas et al., 2011). A comprehensive survey monitoring BFRs in background soils in Asian developing countries has not yet been conducted. Thus, the present study investigated BFR contamination of soils from municipal waste dumping sites and background areas in five Asian developing countries to elucidate the role of municipal waste dumping sites as potential sources of BFR pollution in these countries.