Occurrence and risk assessment of organophosphorus esters in drinking water collected from water dispenser systems in Japan

The presence of organophosphorus esters (OPEs) in drinking water has raised concerns about health risks. Despite the growing popularity of water dispensers as a source of drinking water, there have been few studies of OPE contamination in these systems. We investigated the occurrence and potential sources of OPEs in drinking water collected from 31 water dispensers in Japan. The median concentrations of OPEs ranged from below the limit of detection to 170 ng L−1 (triphenyl phosphine oxide: TPhPO). The most frequently detected compounds were tris(butoxyethyl) phosphate (TBOEP), tributyl phosphate (TBP), tris(2-chloroethyl) phosphate, tris(2-chloroisopropyl) phosphate, tricresyl phosphate, and triphenyl phosphate. The highest concentrations were 1300 ng L−1 for TBP and 810 ng L−1 for TPhPO. The tendency of relatively high concentrations to be associated with newer dispensers and more hydrophilic OPEs suggested that migration from dispenser materials might be a major source of contamination. The estimated daily intake of OPEs ranged from 0.0073 ng kg-bw−1 day−1 for tripropyl phosphate (TPP) to 5.5 ng kg-bw−1 day−1 for TPhPO. The hazard quotients for all the OPEs were well below 1. The indication was that health risks associated with OPE exposure from water dispensers under current conditions were negligible. However, exposure to OPEs through drinking water was found to be comparable to, or even higher than, previously recognized major exposure pathways such as inhalation via indoor air and oral ingestion through diet and indoor dust. Drinking water may therefore be a significant and potentially major pathway of human exposure to OPEs. © 2025 Elsevier B.V.