Urinary 2,5-dichlorophenol as biological index for p-dichlorobenzene exposure in the general population

The relationship between exposure to p-dichlorobenzene (p-DCB) and urinary excretion of 2,5-dichlorophenol (2,5-DCP), the major metabolite of p-DCB, was examined to evaluate the usefulness of the metabolite as a biological index for low-level exposure of p-DCB in the general population. Personal exposure concentrations of p-DCB and concentrations of 2,5-DCP excreted in the urine of 119 adults living in Osaka were determined. Airborne p-DCB was collected for 24 h by passive gas sampling tubes packed with charcoal. The tubes were exchanged every 12 h. The sampling was started immediately after the subject woke up in the morning (7 A.M.). The collected p-DCB was desorbed with toluene and measured using a gas chromatograph with an electron capture detector (GC-ECD). On the other hand, the first morning urine samples were collected at the endpoint of airborne p-DCB sampling (7 A.M. the next morning). The urine samples were hydrolyzed with concentrated sulfuric acid. 2,5-DCP in the hydrolysates was extracted with n-hexane and measured by GC-ECD. Both p-DCB and 2,5-DCP were detected in more than 99% of the air and urine samples, respectively, from the participants. The median of p-DCB exposure concentrations for 24 h was 2.5 ppb, with a maximum concentration of 33.3 ppb. The median of urinary 2,5-DCP concentrations was 0.39 mg/g creatinine, with the maximum concentration of 3.32 mg/g creatinine. The regression line between the urinary 2,5-DCP concentration (y) and the p-DCB exposure concentration (x) was y = 0.080 x + 0.181, with the Pearson correlation coefficient of 0.81 (p < 0.001), demonstrating a strong association between these measurements. Consequently, urinary 2,5-DCP should be suitable as an index for monitoring low-level exposure of p-DCB in the general population.