Presence, source attribution, and human exposure to organophosphate esters in indoor dust from various microenvironments in Nigeria

Very few studies have reported the presence of the organophosphate esters (OPEs) in African indoor microenvironments. We therefore document here, the concentrations, profiles, and human exposure to eight organophosphate esters (OPEs) for the first time in indoor dust from various microenvironments in Nigeria, specifically: cars/buses (n = 10), homes (n = 20), offices (n = 20), and medical centres (n = 14). The concentrations of OPEs in these indoor dust samples were among the lowest reported internationally. Concentrations of ∑₈OPEs varied substantially between individual samples and the predominant OPEs were: tris(2-butoxyethyl) phosphate (TBOEP) (detection frequency (DF) = 90–100%), tris(1-chloro-2-propyl) phosphate (TCIPP) (DF = 100%), and 2-ethylhexyl-diphenyl phosphate (EHDPP) (DF = 100%). There were no significant differences (P˃0.05) between ∑₈OPEs concentrations in dust samples from cars/buses (average = 295 ng/g), offices (231 ng/g), homes (277 ng/g), and medical centres (127 ng/g). Concentrations of chlorinated OPEs: tris(2-chloroethyl) phosphate (TCEP), TCIPP, and tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) were significantly correlated with those of triphenyl phosphate (TPhP), EHDPP, and TBOEP. Estimated daily intakes (EDI) of target OPEs via indoor dust ingestion and dermal absorption were lower than the corresponding reference dose (RfD) values, indicating that exposure to the studied OPEs in the indoor environment does not pose a significant health risk for the general population in Nigeria, even under a high-end exposure scenario.