Low-dose blood BTEX are associated with pulmonary function through changes in inflammatory markers among US adults: NHANES 2007-2012

The effects of blood benzene, toluene, ethylbenzene, and xylenes (BTEX) on lung function among general adults remain unknown. We enrolled 5519 adults with measured blood BTEX concentrations and lung function from the US National Health and Nutrition Examination Survey 2007-2012. Weighted linear models were fitted to assess the associations of BTEX with lung function and inflammation parameters (white blood cell five-part differential count and C-reactive protein). The mediating effect of inflammation between BTEX and lung function was also examined. Blood BTEX concentrations decreased yearly from 1999 and were extremely low from 2007 to 2012. Benzene and toluene exerted the greatest influence on lung function in terms of forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), calculated FEV1:FVC ratio, peak expiratory flow rate (PEFR), and forced mid expiratory flow (FEF25-75%). Both ethylbenzene and all xylene isomers had no effects on FVC but reduced FEV1, FEV1:FVC ratio, PEFR, and FEF25-75%. Weighted quantile analyses demonstrated that BTEX mixture was associated with decreases in FVC, FEV1, FEV1:FVC ratio, PEFR, and FEF25-75%, with benzene weighted most heavily for all lung function parameters. BTEX also increased the levels of inflammation indicated by white blood cell five-part differential count and C-reactive protein, and increased levels of inflammation also reduced lung function. From multiple mediation analysis, inflammation mediated the effects of benzene on FEV1 and PEFR, the effects of toluene on FEV1, and the effects of ethylbenzene on FEV1 and PEFR. Low-dose exposure to BTEX was associated with reduced pulmonary function both in large and small airways. Inflammation could be involved in this pathogenesis.