Distribution characteristics and risk assessment of hexabromocyclododecanes in soil from e-waste dismantling areas

Electronic waste releases brominated fire retardants such as hexabromocyclododecane (HBCD) into the environment during the recycling and dismantling process. This study presents the first integrated assessment of the ecological and human health risks associated with HBCD in soils from e-waste dismantling areas. It offers a comprehensive investigation into the concentration, distribution, and diastereomer profiles of HBCD across different land-use types. This study investigated the contamination levels of HBCD in 51 soil samples collected from an e-waste dismantling area in Qingyuan, Guangdong Province, China. The concentrations of ΣHBCD (the sum of α-, β-, and γ-HBCD) ranged from 0.05 to 27.47 ng/g dry weight (dw), with a mean value of 2.10 ng/g dw. Significant differences were observed in the levels and profiles of HBCD diastereomers across various land-use areas. The levels of HBCD were significantly influenced by e-waste dismantling and industrial activities. The estimated mean mass stock of HBCD in soil is 63 ng/cm², with a total environmental burden of 199 kg in Qingyuan City. The risk quotient values of HBCD ranged from 0.01 to 1; however, two sampling points in the industrial area exceeded a value of 1, indicating a potential risk. The total daily intake of HBCD from soil ranged from 5.16 × 10^-4 to 1.7 ng/kg-bw/day, which is lower than the dietary intake levels of HBCD reported in China. Nevertheless, non-dietary intake as an important pathway for humans to exposure to HBCD in e-waste dismantling areas cannot be ignored. Infants, as a high-exposure group, exhibit significantly higher non-dietary intake levels of HBCD compared to other age groups. These findings not only advance our understanding of HBCD contamination in e-waste areas but also provide crucial scientific evidence for developing targeted environmental management and pollution control strategies.