Biotransformation and toxicokinetics of 2-phenoxyethanol after oral exposure in humans: a volunteer study

2-Phenoxyethanol (PhE) is an aromatic glycol ether and is used in a variety of functions and applications, e.g., as preservative in pharmaceuticals, cosmetic and personal care products, as biocide in disinfectants (e.g. human hygiene), or as a solvent in formulations (e.g. coatings, functional fluids). Despite its widespread use, little is yet known on its biotransformation and toxicokinetics in humans. Therefore, a pilot study was conducted with oral administration of PhE (5 mg/kg body weight) to five volunteers. Blood and urine samples were collected and analyzed for PhE and three of its presumed metabolites up to 48 h post-exposure. Additionally, one volunteer was dermally exposed to PhE and monitored until 72 h post-exposure. PhE was rapidly resorbed following both oral and dermal application with t_max-levels in blood of about 1 h and 3 h, respectively. Metabolism of PhE was observed to be rather extensive with phenoxyacetic acid (PhAA) and 4-hydroxyphenoxyacetic acid (4-OH-PhAA) as the main metabolites found in blood and urine following oral and dermal exposure. PhE was excreted rapidly and efficiently via urine mostly in metabolized form: following oral exposure, on average 77% and 12% of the applied dose was excreted within 48 h as PhAA and 4-OH-PhAA, respectively. A similar metabolism pattern was observed following the single dermal exposure experiment. The obtained data on biotransformation and toxicokinetics of PhE in humans provide valuable information on this important chemical and will be highly useful for pharmacokinetic modelling and evaluation of human PhE exposure.