Measurement of Urinary Methoxyphenols and Their Use for Biological Monitoring of Wood Smoke Exposure

A urinary assay for methoxyphenols was developed for the biological monitoring of wood smoke exposure. Methoxyphenols in 10-ml samples of urine were extracted after acid hydrolysis using XAD in a solid-phase extraction cartridge. The methoxyphenols were eluted with ethyl acetate and then analyzed by gas chromatography/mass spectrometry. Specific chemicals quantified were guaiacol, 4-methylguaiacol, 4-ethylguaiacol, 4-propylguaiacol, syringol, 4-methylsyringol, 4-ethylsyringol, vanillin, eugenol, and syringaldehyde. Recoveries ranged from 60 to 90%, with coefficients of variation of ≤20%. Background levels of the compounds were measured in 21 nonsmoking adults. Guaiacol, 4-methylguaiacol, eugenol, and vanillin were detected in all subjects. An experimental feeding of a commercial wood smoke flavoring demonstrated that methoxyphenols were rapidly and efficiently eliminated in urine. Preliminary field studies demonstrated that urinary excretion rates of some methoxyphenols increased after inhalation exposure to wood smoke.