BTEX chrono-metabolism and leukemogenic effects of night shift work in workers of gasoline stations: the EXPOSOWORK prospective panel study in Bulgaria.

BACKGROUND

Exposures to benzene, toluene, ethylbenzene and xylenes (BTEX) have been associated with impairment of the hematopoietic system, often leading to leukemogenesis. A prospective panel study: i) characterized the effect of night shift work (NSW) (12-hr night shift vs. 12-hr day shift) on urinary BTEX and metabolites in gasoline station workers in Plovdiv, Bulgaria, ii) evaluated the NSW effect on chrono-based BTEX genotoxic effects (as measured by 8-OHdG, a nonspecific biomarker of genotoxicity) including the influence of the downstream urinary metabolome.

METHODS

During a week's working period, workers (n=71) followed both day shift and night shift work schedules (12-h long each shift) collecting four urine samples per worker (pre and end of shift). Airborne BTEX exposures were evaluated over 12-h shift periods using wearable passive samplers. Urinary BTEX and the metabolome were measured using mass spectrometry. 8-OHdG was measured using an ELISA immunoassay. Associations were examined using mixed-effect regression models and corrected for false-discovery rates of 0.05.

RESULTS

Median personal airborne benzene levels were 3.05 (IQR: 2.89), and 2.92 (IQR: 1.86) μg/m3 for day and night work shifts, respectively, suggestive of a low-level BTEX study. Results supported a consistent trend of lower urinary BTEX levels in NSW than those observed in day shift, after adjusting for airborne BTEX and confounders. Metabolomic signatures revealed a few significant metabolites associated with NSW or 8-OHdG with 4-hydroxybenzeneacetic acid (level I) being associated with both NSW and 8-OHdG. The biological pathway with high metabolic pathway impact were glycine, serine and threonine metabolism.

CONCLUSION

Larger NSW studies with longer and more frequent follow-up times are warranted to better delineate the possible influence of NSW chrono-modulated working activities in leukemogenic processes.