Background  Exposure to tobacco dust or noise is associated with the risk of cardiovascular disease in workers, but there are few studies on their effects on workers' serum bilirubin levels.

Objective  To analyze the effects of combined exposure to tobacco dust and noise on workers' serum bilirubin levels.

Methods  We selected 824 employees from a large cigarette factory in Wuhan. According to the status of occupational hazards on site, we divided the participants into a control group (n=149), a tobacco dust exposure group (n=198), a noise exposure group (n=299), and a tobacco dust and noise combined exposure group (n=178). We collected general information of the participants. We collected blood samples and measured serum bilirubin. We used chi-square test to compare between-group categorical indicators. We used analysis of variance to compare measurement data. Taking the control group as the reference category, we used generalized linear regression model to analyze serum bilirubin concentration across the three exposure groups and the control group.

Results  The abnormal rates of serum indirect bilirubin concentrations in the control group, the tobacco dust exposure group, the noise exposure group, and the tobacco dust and noise combined exposure group were 6.04% (9/149), 12.63% (25/198), 13.38% (40/299), and 17.42% (31/178), respectively, showing a clear increasing trend (P<0.05). The mean concentrations of indirect bilirubin in the tobacco dust and noise combined exposure group were significantly higher than that in the tobacco dust and the noise groups (P<0.05). The serum indirect bilirubin concentrations in the tobacco dust exposure group, the noise exposure group, and the tobacco dust and noise combined exposure group were 1.833, 1.774, and 1.634 times higher than those of the control group (P<0.05).

Conclusion  Occupational exposure to tobacco dust or noise may associate with elevated serum total bilirubin concentration in cigarette factory workers, mainly indirect bilirubin concentration. Serum indirect bilirubin anomaly is higher among workers simultaneously exposed to tobacco dust and noise.