This study was conducted to determine the combined effects of noise and shift work on physiological parameters including body temperature, heart rate and blood pressure. This study was performed in a chemical industry in Tehran in 1993.

          The workers’ physiological parameters was recorded at the beginning and at the end of all work shifts. Groups under study included : day workers (n=115) , day workers with continuous noise exposure (n=44) , two-shift workers without noise exposure (n=180) , three-shift workers without noise exposure and three-shift workers with continous noise exposure (n=216). In
   workers with continuous noise exposure, noise dosimetry was performed using B & K noise dose meter type 4428.

          The results showed that noise and shift work hove more effects on systolic and diastolic blood pressure than body temperature. The statistical analysis showed that in 3-shift workers, combined effects of noise and shift work on systolic and diastolic blood pressure caused considerable differences between exposed and control group.  In general, regarding research design of this study to determine probable combined effects of noise and shiftwork on physiological parameters, our findings confirmed the
   additive effects of noise and shiftwork on systolic and diastolic blood pressure in which the effect of noise was more significant.

          Our findings showed that combined exposure to shiftwork and noise may be regarded as a risk factor for cardiovascular diseases because it is responsible for increasing blood pressure in exposed workers.