Urinary methoxyacetic acid as an indicator of occupational exposure to ethylene glycol dimethyl ether

Abstract

Objective: To investigate whether methoxyacetic acid (MAA) is the metabolite of ethylene glycol dimethyl ether (EGdiME) in humans and whether its metabolite in urine can be used as a biomarker for exposure to EGdiME. Methods: Workers occupationally exposed to EGdiME, as well as nonexposed controls, were studied. Urine samples were collected from 20 control subjects and, on Friday postshift, from 14 workers. The identification and quantification of the metabolite were performed by gas chromatography/mass spectrometry (GC/MS) and GC/FID, respectively. Air samples were collected on activated charcoal tubes by area sampling with battery-operated pumps. The glycol ether was analyzed by GC/FID. Results: GC/MS clearly showed the metabolite of EGdiME to be MAA. Urinary MAA levels in the control subjects (background levels) were 0.0–0.3 mg/g crea. The levels of urinary MAA in the solvent-exposed workers were significantly (P<0.0001) higher than those in the control subjects. In the eight workers exposed to an average of 0.3 ppm of EGdiME and the six workers exposed to an average of 2.9 ppm, the mean urinary MAA level was 1.08 (range 0.6–1.5) mg/g crea and 9.33 (range 5.7–18.1) mg/g crea, respectively. These results can be explained by differences in the exposure intensity. Conclusions: Our results suggest that MAA is the metabolite of EGdiME, and that MAA in urine may be used for biological monitoring of EGdiME exposures.