Student Research: Xiaoqiang Zhu

, , 1998
Faculty Advisor: David A Kalman

Development of a Potential Biomarker of Environmental Wood Smoke Exposures


Abstract

In this study an analytical assay for urinary methoxyphenols was developed as a potential biological marker of environmental wood smoke exposures. The assay was aimed at 11 marker methoxyphenols, which were guaiacol, methylguaiacol, ethyguaiacol, propylguaiacol, vanillin, eugenol, trans-isoeugenol, syringol, methylguaiacol, ethylguaiacol, and syringaldehyde. Methoxyphenol conjugates 10 ml urine samples were hydrolyzed in sulfuric acid solution and then loaded onto XAD-2 SPE cartridges. After separation from the urine matrix, analytes were eluted with ethyl acetate and quantified by GC-MS, using an isotope-dilution assay. The detection limits for methoxyphenols were approximately 8ng/ml in urine for most of the marker phenols. Repetitive testing of a single urine sample gave recoveries ranging from 63% (vanillin) to 89% (guaiacol) at a spiked level of 0.05 ug/ml urine. Intraday coefficients of variation (CV) of recoveries for the methoxyphenols ranged from 5-20% at concentrations typical of background urine, and nine of the eleven methoxyphenols had CV under 10%. A feeding experiment demonstrated that the assay was able to detect elevations of methoxyphenols in urine from three subjects after consumption of food-grade wood smoke flavoring in amounts approximately dose-equivalent to 24-hour inhalation of moderately to badly polluted air. An inhalation experiment showed that urinary methoxyphenols in an exposed subject increased after a campfire was set. A sharp increase in the excretion rate of urinary methoxyphenols was observed following a 2.5-hour exposure to 30ug/m3 methoxyphenols in ambient air.