Industrial noise exposure and salivary cortisol in blue collar industrial workers.

Measuring non-auditory effects of noise such as stress-inducing ones have become of interest recently. Salivary cortisol has become a popular measure in stress research. So, assessing noise-induced stress via saliva cortisol evaluation can present a bright future in non-invasive exposure assessment methods. This study had 3 goals: (1) Assess and compare saliva cortisol concentrations in the morning and evening in normal work day and leisure day in industrial workers, (2) assess the relationship between industrial noise exposure and salivary cortisol concentrations, and (3) assess the possibility of using salivary cortisol as a possible marker of noise-induced stress. This study included 80 male participants working in 4 different parts (painting, assembling lines, casting, and packaging) of a household manufacturing company. Morning and evening saliva samples were collected at 7.00 am and 4.00 pm, respectively. Noise exposure levels were assessed by sound level meter and noise dosimeter. All measurements occurred in two days: One in leisure day and other in working day. Descriptive statistics, paired sample t-test, and regression analysis were used as statistical tools of this study with P < 0.05. On the leisure day, morning salivary cortisol (geometric mean [GM], 15.0; 95% CI, 12.0 to 19.0 nmol/L) was significantly higher than evening cortisol (GM, 5.2; 95% CI, 4.2 to 6.3 nmol/L) (P < 0.05). Also, on the working day, morning salivary cortisol (GM, 14.0; 95% CI, 11.25 to 18.0 nmol/L) was significantly higher than evening cortisol (GM, 8.0; 95% CI, 6.5 to 10.0 nmol/L) (P < 0.05). No significant difference was obtained for morning cortisol levels between leisure day and working day samples (P = 0.117). But, for evening cortisol concentrations, a strong significant difference was noted leisure day and working day (P < 0.001). The evening cortisol in the working day correlated significantly with noise exposure > 80 dBA. Our study revealed that industrial noise, with levels > 80 dBA, has a significant effect on salivary cortisol elevation.