Soil contamination by halogenated polycyclic aromatic hydrocarbons from open burning of e-waste in Agbogbloshie (Accra, Ghana)

Detailed composition of chlorinated and brominated polycyclic aromatic hydrocarbons (Cl-PAHs and Br-PAHs) generated during informal recycling of e-waste and their toxic relevance are still poorly understood. This study investigated the occurrence of Cl-PAHs and Br-PAHs in surface soil samples from the Agbogbloshie e-waste recycling site (Accra, Ghana) using quantitative gas chromatography–mass spectrometry (GC–MS) and comprehensive two-dimensional GC–time-of-flight mass spectrometry (GC × GC–ToFMS) profiling. The results of GC–MS analysis showed elevated concentrations in open e-waste burning areas (160–220 and 19–46 ng/g dry weight for Cl- and Br-PAHs, respectively) with substantial contribution from unidentified compounds (respectively, more than 36 and 70%, based on the total areas of potential peaks). Cl- and Br-PAHs from e-waste burning had a distinctive composition dominated by ring–ring compounds. Several homologue groups not monitored with GC–MS were found using GC × GC–ToFMS: PAHs with up to 5Cl or 3Br, mixed halogenated PAHs and chlorinated methylPAHs. The dioxin-like toxic equivalents of the identified Cl-/Br-PAHs in soils, estimated from their in vitro AhR agonist potencies relative to 2,3,7,8-tetrachlorodibenzo- p -dioxin, were much lower than the range reported for chlorinated and brominated dioxins. However, the toxicity of the unidentified halogenated PAHs remained unclear.