Field Evaluation of a Potential Exposure Biomarker of Methylated Polycyclic Aromatic Hydrocarbons: Association between Urinary Phenanthrene-2-carboxylic Acid and Personal Exposure to 2-Methylphenanthrene

Previous in vitro studies identified carboxylic acids as the major metabolites of methylated polycyclic aromatic hydrocarbons (PAHs). We have previously detected phenanthrene-2-carboxylic acid (2-PHECA) in human urine, but a direct linkage between this biomarker and external exposure to methylated PAHs remains unestablished. Herein, we analyzed phenanthrene (PHE) and 2-MePHE in 589 personal PM2.5 samples and hydroxy-phenanthrenes (Sigma OH-PHEs) and 2-PHECA in paired urine samples from 120 urban residents. We observed higher personal 2-MePHE and PHE exposure but lower urinary 2-PHECA and Sigma OH-PHEs levels in the heating season, possibly due to changes in gas-particle partitioning, dietary source, and metabolism. After adjusting for seasonal effects, urinary 2-PHECA concentrations were significantly associated with personal exposure to 2-MePHE but not PHE. We also found significant associations between the urinary 2-PHECA/Sigma OH-PHEs ratio and personal 2-MePHE/PHE ratio, an indicator for the petrogenic versus pyrogenic sources. Alcohol consumption was identified as an influencing factor for the 2-PHECA level and 2-PHECA/Sigma OH-PHEs ratio, likely via competing the metabolism of 2-MePHE by alcohol and aldehyde dehydrogenases. These results suggest the potential usefulness of the urinary 2-PHECA level as a biomarker of methylated PAH exposure and the 2-PHECA/Sigma OH-PHEs ratio as a biomarker for the relative importance of petrogenic or pyrogenic sources.