Source identification and human exposure assessment of organophosphate flame retardants and plasticisers in soil and outdoor dust from Nigerian e-waste dismantling and dumpsites.

Abstract

Electronic waste (e-waste) dismantling and dumpsite processes are major sources of organophosphate flame retardant and plasticiser emissions and may pose potentially adverse effects on environment and human health. In 20 outdoor dust and 49 soil samples collected from four e-waste dismantling and three e-waste dumpsites in two States of Nigeria (Lagos and Ogun), we identified 13 alternative plasticisers (APs), 7 legacy phthalate plasticisers (LPs), and 17 organophosphorus flame retardants (OPFRs) for the first time in African e-waste streams. In the samples from dismantling sites, the range (median) concentrations of ∑₁₃APs, ∑₇LPs, and ∑₁₇OPFRs were 11-2747 μg/g (144 μg/g), 11-396 μg/g (125 μg/g), and 0.2-68 μg/g (5.5 μg), in dust respectively and 1.8-297 μg/g (55 μg/g), 1.3-274 μg/g (48.5 μg/g), and 1.6-62 μg/g (1.6 μg/g), in soil respectively. Results for soil samples from e-waste dumpsites were (6.6-195 μg/g (23.7 μg/g), 6.0-295 μg/g (54.8), and 0.4-42.3 μg/g (9.0 μg/g) for ∑₁₃APs, ∑₇LPs, and ∑₁₇OPFRs respectively. Overall, concentrations of APs were significantly higher at the dismantling sites (p = 0.005) compared to dumpsites, levels of LPs were higher at dismantling sites but not significant, while OPFR concentrations were significantly higher in dumpsite samples (p = 0.005). Plasticisers were found to be major contributors to pollution at e-waste dismantling sites, while OPFRs were associated with both automobile dismantling and e-waste dumpsite processes. Following particle size fractionation of selected soil samples, higher concentrations of targeted compounds were observed in the smaller mesh (180 μm) soil sieve fraction. For dust, the total median estimated daily intake via ingestion and dermal adsorption (EDI_ing and EDI_derm) ranged from 43 to 74 ng/kg bw/day and 0.4-0.7 ng/kg bw/day, respectively. Correspondingly, 4.6-45 ng/kg bw/day and 0.015-0.57 ng/kg bw/day were the values found for soil, respectively. According to these results, the targeted chemicals do not appear to pose a non-carcinogenic risk to e-waste workers through ingestion or dermal contact of bio-accessible fractions of the chemicals. Human biomonitoring campaigns are recommended in the Nigerian e-waste environment considering the elevated concentration levels found for the majority of targeted compounds and that risk parameters required for exposure assessment were only available for a limited number of compounds.