Concentrations of organophosphate esters in drinking water from the United Kingdom: Implications for human exposure

Data on the presence of organophosphate esters (OPEs) in drinking water and its significance as a pathway of exposure are limited. In this study, we measure for the first time, concentrations of eight OPEs in 50 UK drinking water samples. Arithmetic mean concentrations of ∑₈OPEs were: 6.4 and 11 ng/L in bottled (n = 25) and tap water samples (n = 25), respectively. Concentrations of ∑₈OPEs in tap water (mean: 11 ng/L) exceed significantly those in bottled water (mean: 6.4 ng/L) (p ˂ 0.01). Moreover, UK tap water is more contaminated with chlorinated, aryl-, and alkyl-OPEs than bottled water. The predominant OPEs detected were: tris (butoxyethyl) phosphate (TBOEP), tris (2-chloroethyl) phosphate (TCEP), and tris(2-chloroisopropyl) phosphate (TCIPP) with arithmetic mean concentrations in the two water sample types ranging between (3.5–3.8 ng/L), (0.60–3.0 ng/L), and (1.02–2.9 ng/L), respectively. Estimated daily intakes (EDIs) (mean and high-end exposure) via drinking water for different sectors of the UK population were: infants (0.93 and 6.4 ng/kg bw/day) ˃ toddlers (0.46 and 3.1 ng/kg bw/day) ˃ children (0.35 and 2.3 ng/kg bw/day) ˃ adults (0.28 and 2.1 ng/kg bw/day). Based on these data, exposure to Σ₈OPEs via drinking water is much lower than via: food, indoor dust ingestion, inhalation, and dermal uptake for adults and toddlers. Reassuringly, our EDIs were lower than relevant reference dose (RfD) values. However, combining our drinking water ingestion data with exposure via other pathways revealed overall exposure to 2-ethylhexyl diphenyl phosphate (EHDPP) and TCIPP to approach health-based limit values for UK toddlers under a high-end exposure scenario.