The Effects of Occupational Noise Pollution and Shift Work on Oxidative Stress Markers in Cement Workers, Iran

Both noise and shift work generate oxidative stress, independently; however, in some work places workers are exposed to both at the same time, where their combined effect might increase the oxidative damage. This research is based on the question whether noise and shift work have a synergistic effect on oxidative stress or not. It tries to investigate the effects of these two factors simultaneously, at the biggest cement factory of Iran. For so doing, it enrols 88 male workers, equally in four groups, with one group serving as the control (i.e., Group 1 with 8 hours of fixed shift, exposed to less than 85 dB sound level) and three groups as the cases (Group 2 with 12 hours of rotational shifts, exposed to less than 85 dB sound level; Group 3 with 8 hours of fixed shift, exposed to more than 85 dB sound level; and Group 4 with 12 hours of rotational shifts, exposed to more than 85 dB sound level). Stress oxidative is evaluated by Malondialdehyde (MDA) and Superoxide dismutase (SOD).  Finally, the results show that SOD levels (p<0.001) are significantly decreased in Group 4 and Group 3, compared to the control. Also, MDA levels are significantly increased in Group 4 (in which, the workers are exposed to noise and shift work simultaneously) compared to the control (p < 0.001). The current study shows that co-exposure to noise and shift work has a combined effect (a synergistic role) in MDA. Thereore, more attention should be paid to shift workers, who are exposure to noise simultaneously.