Association of Lung Function With Benzene, Toluene and Xylenes (Btx) in End-exhaled Air in Gas Station Attendants

Background: - Gas station attendants are exposed to benzene, toluene and xylenes (BTX) from fuels. The aim was to study the association between this exposure and spirometry parameters in gas station attendants and office workers as controls.Method – In 44 male gas station attendants and 38 office workers in the Gampaha district of Sri Lanka spirometry was performed according to the guidelines of the American Thoracic Society (ATS). Pre- and post-shift end-exhaled air samples were collected from a subset of both study groups and analysed for BTX by gas chromatography-mass spectrometry.Results – Among gas station attendants ( n =  20) median pre-/post-shift exhaled air concentrations (ng/L) were: benzene 11.23/21.05; toluene 10.39/22.19; m/p-xylene 1.62/2.45; o-xylene 1.01/1.45. For controls ( n =  11) these values were (ng/L): 9.47/12.04, 3.13/4.00, 1.52/1.25 and 0.50/0.48, respectively. The peak expiratory flow rate (PEFR) and %-predicted PEFR were significantly lower among gas station attendants compared to controls ( p  < 0.012). The % predicted FVC and FEV 1 /FVC ratio were not different but in gas station attendants benzene in post-shift samples was associated with %-predicted FVC (Spearman’s correlation coefficient of -0.469, p  = 0.037). In addition, the %-predicted FVC was lower in gas station attendants working ≥ 5 years compared to those who worked < 5 years. In controls a distinct pattern was observed, indicating a moderate to strong association of post-shift toluene and m/p-xylenes with all lung function parameter but not benzene. These results were adjusted for smoking. Air pollutants other than BTX may have contributed to explaining our findings.Conclusion – Overall, we did not observe changes to the lung function of clinical relevance that can be explained by occupational exposure to BTX. In gas station attendants we observed obstructive responses in spirometry that were most pronounced for the level of work-related benzene exposure and also associated with duration of employment. In office workers (as controls) a distinct pattern of associations with BTX exposure was observed, indicating a moderate to strong association of the exposure level of toluene and m/p-xylenes with all lung function parameters.