Organophosphate esters in indoor and outdoor air in Birmingham, UK: implications for human exposure

We report concentrations of organophosphate esters (OPEs) in air from living rooms, bedrooms, and offices in Birmingham, UK. To place concentrations in these commonly frequented indoor microenvironments in context, we also measured the same OPEs in air samples collected from an outdoor location on the University of Birmingham campus. Concentrations of tris(2-chloroethyl) phosphate (TCEP), tris(2-chloroisopropyl) phosphate (TCIPP), and tri-n-butyl phosphate (TnBP) in indoor air significantly exceeded (P > 0.05) those in outdoor air. In contrast, concentrations of tris(1,3-dichloroisopropyl) phosphate (TDCIPP), triphenyl phosphate (TPhP), and 2-ethylhexyl diphenyl phosphate (EHDPP) in indoor and outdoor air were statistically indistinguishable (P < 0.05). Comparison of estimates of human exposure via inhalation derived from our data with previous estimates of exposure via dust ingestion, diet, drinking water, and dermal contact with furniture reveals that inhalation is the most important contributor to aggregate UK adult exposure to TCIPP (85% exposure) and TCEP (67% exposure). While average aggregate exposures of UK adults were well below health-based reference dose values, continued evaluation of human exposure is recommended as high-end exposures of some individuals (e.g., those inhabiting microenvironments containing concentrations of TCIPP at the high end of the range reported here) likely exceed substantially average exposures.