Urinary excretion of propylene glycol butyl ether (PGBE) and propylene glycol methyl ether (PGME) in healthy human participants and workers

Exposure to organic solvents can affect the central nervous system. Propylene glycol ethers such as propylene glycol methyl ether (PGME) and propylene glycol butyl ether (PGBE) are organic solvents widely used in commercial products including cleaning products. PGME has an established Swiss occupational exposure limit and a biomonitoring limit value while PGBE does not, which is probably due to the absence of toxicokinetic data. Our aim was to (1) Characterize PGBE elimination toxicokinetics in healthy human participants (N = 11) exposed under controlled conditions; (2) Provide urinary elimination kinetics of both conjugated and free PGBE and PGME following exposures to a mixture of PGME (35 ppm) and PGBE (15 ppm) for 6 h, and (3) Assess exposure among six professional cleaners. Urinary PGME and PGBE concentrations were quantified using head-space gas chromatography with flame ionization detection (HS-GC-FID) (LOQ 0.04 mg/L, LOD 0.01 mg/L). PGBE had an apparent elimination of ∼6 h and PGME ∼4 h. PGBE air concentration of 15 ppm corresponded to 1.2 mg/L in urine. Cleaners had low urinary concentrations (<0.5 mg/L). Intriguingly, post-shift concentrations were often lower than the next-day pre-shift values, suggesting skin exposure and possible non-occupational exposures. These findings support biomonitoring as the best approach to assess workers' total PGBE exposures. Future studies should expand human biomonitoring efforts to better characterize exposure to glycol ethers.