Urinary metabolites of volatile organic compounds as biomarkers of indoor exposure: evidence of sex differences in a cross-sectional study using the Korea National Health and Nutrition Examination Survey.
Abstract
Objectives This study examined associations between indoor total volatile organic compound (TVOC) concentrations and urinary volatile organic compound (VOC) metabolites in Korean adults, focusing on potential sex-specific differences. We hypothesized that higher indoor TVOC exposure would be associated with higher urinary VOC metabolite concentrations and that these associations would differ by sex. Methods We conducted a cross-sectional analysis of the 2020-2021 Korea National Health and Nutrition Examination Survey, which included the Republic of Korea's first population-based indoor air quality survey. The analysis included 1,859 adults aged ≥19 years who participated in the indoor air quality survey from July 2020 to August 2021. Indoor TVOC concentrations (µg/m³) were measured using standardized protocols. Nine urinary VOC metabolites were quantified, creatinine-adjusted, and log-transformed. Multivariable linear regression, sex-stratified analyses, and subgroup analyses among unemployed adults were performed to reduce potential confounding from occupational exposure. Results Indoor TVOC concentrations were positively associated with urinary 2-methylhippuric acid (2-MHA; β=0.041; 95% confidence interval [CI], 0.029-0.052) and 3,4-MHA (β=0.040; 95% CI, 0.027-0.052), with no evident sex difference in the overall sample. However, among unemployed adults, sex-by-TVOC interaction terms were statistically significant for both metabolites, and associations were stronger in males for both 2-MHA (β=0.110 vs. 0.024) and 3,4-MHA (β=0.130 vs. 0.031) than in females. Conclusion Indoor TVOC concentrations were associated with urinary VOC metabolites, particularly 2-MHA and 3,4-MHA. These findings support considering sex-specific patterns in VOC-related risk assessment and indoor air quality surveillance, interventions, and management.