Variability of urinary concentrations of polycyclic aromatic hydrocarbon metabolite in general population and comparison of spot, first-morning, and 24-h void sampling.

Urinary mono-hydroxy polycyclic aromatic hydrocarbons (OH-PAHs) are commonly used in biomonitoring to assess exposure to polycyclic aromatic hydrocarbons (PAHs). Similar to other biologically non-persistent chemicals, OH-PAHs have relatively short biological half-lives (4.4-35 h). Little information is available on their variability in urinary concentrations over time in non-occupationally exposed subjects. This study was designed to (i) examine the variability of nine urinary OH-PAH metabolite concentrations over time and (ii) calculate sample size requirements for future epidemiological studies on the basis of spot urine, first-morning void, and 24-h void sampling. Individual urine samples (n=427) were collected during 1 week from 8 non-occupationally exposed adults. We recorded the time and volume of each urine excretion, dietary details, and driving activities of the participants. Within subjects, the coefficients of variation (CVs) for the wet-weight concentration of OH-PAHs in all samples ranged from 45% to 297%; creatinine adjustment reduced the CV to 19-288% (P<0.001; paired t-test). The simulated 24-h void concentrations were the least variable measure, with CVs ranging from 13% to 182% for the 9 OH-PAHs. Within-day variability contributed on average 84%, and between-day variability accounted for 16% of the total variance of 1-hydroxypyrene (1-PYR). Intraclass correlation coefficients of 1-PYR levels were 0.55 for spot urine samples, 0.65 [corrected] for first-morning voids, and 0.77 [corrected] for 24-h voids, indicating a high degree of correlation between urine measurements collected from the same subject over time. Sample size calculations were performed to estimate the number of subjects required for detecting differences in the geometric mean at a statistical power of 80% for spot urine, first-morning, and 24-h void sampling. These data will aid in the design of future studies of PAHs and possibly other biologically non-persistent chemicals and in the interpretation of their analytical results.

Measurement of urinary monohydroxy polycyclic aromatic hydrocarbons using automated liquid-liquid extraction and gas chromatography/isotope dilution high-resolution mass spectrometry.

A method for the measurement of 24 hydroxylated polycyclic aromatic hydrocarbon metabolites (OH-PAHs) in urine has been developed. The method is based on enzymatic deconjugation, automated liquid-liquid extraction, and gas chromatography/isotope dilution high-resolution mass spectrometry after derivatization of the OH-PAHs to the trimethylsilylated derivatives. The metabolites included in the current method are formed from eight different parent compounds. The limits of detection were below 7 pg/mL when using a sample size of 2 mL of urine, except for 1- and 2-naphthols (18 and 12 pg/mL, respectively). The enzymatic deconjugation efficiency, verified by deconjugation of urine samples spiked with alpha-naphthyl beta-d-glucuronide sodium salt (1-NAP-GLU) and pyrene-1-sulfate potassium salt (1-PYR-SULF), was determined to be 97% for 1-NAP-GLU conjugate and 84% for 1-PYR-SULF. The overall coefficients of variance for six batches of quality control samples (n = 42), was 2.9-11%. Mean method recoveries of the 13C-labeled internal standards were 66-72%, except for 13C6-1-naphthol (46%). The throughput of this method has been determined to be 40 samples per day per analyst. This method is currently applied to epidemiological studies, such as the National Exposure and Nutrition Examination Survey (NHANES), to measure human exposure to PAHs.