Co-exposure to polycyclic aromatic hydrocarbons, benzene and toluene may impair lung function by increasing oxidative damage and airway inflammation in asthmatic children

As previous studies found that the direct associations between urinary polycyclic aromatic hydrocarbon (PAH), benzene and toluene (BT) metabolites and the decreased lung function were not conclusive, we further investigated relationship of oxidative damage and airway inflammation induced by PAHs and BTs exposure with lung function. A total of 262 children diagnosed with asthma and 72 heathy children were recruited. Results showed that asthmatic children had higher levels of PAHs and BTs exposure, as well as Malonaldehyde (MDA) and 8-hydroxy-2′-deoxyguanosine (8-OHdG) compared with healthy children. Furthermore, binary logistic regression showed that each unit increases in level of urinary 2-&3-hydroxyfluorene (2-&3-OHF), 2-hydroxyphenanthrene (2-OHPhe), 1-hydroxyphenanthrene (1-OHP) and S-phenylmercapturic acid (S-PMA) were significantly associated with an elevated risk of asthma in children with odds ratios of 1.5, 2.3, 1.7 and 1.4, respectively, suggesting that PAHs and BTs exposure could increase the risk of asthma for children. Neither PAH nor BT metabolite could comprehensively indicate the decreased lung function as only 2-&3-OHF and 1-OHP were significantly and negatively correlated with forced vital capacity (FVC). Moreover, levels of most individual PAH and BT metabolite were significantly correlated to MDA and 8-OHdG. Further hierarchical regression analysis indicated that MDA and 8-OHdG levels did not show significant effects on the decreased lung function, suggesting that they are not the suitable biomarkers to indirectly indicate the altered lung function induced by PAHs and BTs. Urinary 2-OHPhe and 1-&9-hydroxyphenanthrene (1-&9-OHPhe) were significantly correlated with fractional exhaled nitric oxide (FeNO). Moreover, FeNO significantly contributed to decreased lung function and explained 7.7% of variance in ratio of forced expiratory volume in 1 s (FEV₁) and FVC (FEV₁/FVC%). Hence, FeNO, rather than oxidative damage indicators or any urinary PAH and BT metabolite, is more sensitive to indirectly reflect the decreased lung function induced by PAHs and BTs exposure for asthmatic children.