Organophosphate esters in indoor and outdoor dust from Iraq: implications for human exposure

Concentrations of 6 organophosphate esters (OPEs) were determined in 60 indoor (ID) and outdoor (OD) dust samples collected from 20 homes from Basrah, Iraq. From each home, two ID samples were collected, one from elevated surfaces (ESD) and one from the floor (FD) of the living room; while the OD samples were collected from the front yard of the same house. Total Σ6OPEs concentrations in dust samples ranged between 681 and 17900 ng/g with median concentrations of 5950, 3590 and 1550 ng/g in ESD, FD and OD samples, respectively. Chlorinated OPEs were the most abundant compounds, contributing mean percentages of 88%, 85% and 78% to Σ6OPEs in ESD, FD and OD, respectively, with tris (1-chloro-2-propyl) phosphate (TCIPP) dominant. Concentrations of our target OPEs in ESD significantly exceeded those in FD (p < 0.05) for tris (2-chloroethyl) phosphate (TCEP) and tris (1,3-dichloro-2-propyl) phosphate (TDCIPP). Ratios of median concentrations of OPEs in ID:OD ranged from 1.5 for tri-n-butyl phosphate (TNBP) to 8.0 for TCEP, indicating the significance of indoor sources. Concentrations of chlorinated OPEs in ID were moderately correlated (R = 0.522–0.591, P < 0.05) with those in OD samples, suggesting interchange of OPEs between the two environments. Concentrations of OPEs in OD from houses with a contiguous front yard car porch exceeded those in OD from houses without a car porch and were significantly higher (P < 0.05) for TCEP, TCIPP and 2-ethylhexyl diphenyl phosphate (EHDPP). Emissions from parked cars and the associated home are likely sources of OPEs in the OD area. Based on the concentrations reported here, the estimated daily intake (EDI) for the Iraqi population through house dust ingestion are all well below the relevant reference dose (RfD) values.