Diminished lung function mediating the associations between blood levels of volatile organic compounds and respiratory morbidity and mortality

Exposure to individual volatile organic compound (VOC) is associated with reduced lung function and increased respiratory disease (RD) morbidity and mortality. However, whether a mediating pathway among exposure to VOC mixtures, diminished lung function, and increased RD risk exists statistically remains undisclosed. This study analyzed 6156 adults (aged ≥ 18) from National Health and Nutrition Examination Survey (NHANES) 2007-2012. We applied Bayesian Kernel Machine Regression (BKMR) models to analyze the association between VOCs and lung function, and then used mediation models to assess lung function's role in RD morbidity and mortality. Changes of forced vital capacity (FVC) accounted for 12.22%, 29.76%, and 17.34% of the association of nitromethane with asthma [0.004 (0.002, 0.005), P < 0.001], emphysema [0.001 (0.001, 0.002), P < 0.001], and chronic bronchitis [0.003 (0.002, 0.005), P < 0.001], respectively. We also observed significant indirect effect of nitromethane with all-cause mortality through the mediation of FVC [0.042 (0.018, 0.066), P < 0.001, proportion = 23.13%] and forced expiratory volume at 1 s (FEV₁) [0.054 (0.029, 0.079), P < 0.001, proportion = 27.89%]. Results indicate that VOC exposure reduces lung function, increasing RD morbidity and mortality risks. Nitromethane, in particular, appears to contribute to these risks through lung function impairment.