Background The high work intensity and possible subsequently increased susceptibility to occupational hazards of calcium carbide plants may lead to hypertension in workers, but there are few studies on the relationship between occupational hazard exposure and hypertension in workers involving the production process of calcium carbide.

Objective To explore the influence of occupational hazards on the incidence of hypertension in calcium carbide plants.

Methods Using historical cohort design, the employees of a calcium carbide factory in the western part of Inner Mongolia Autonomous Region were selected as research subjects. According to the pre-determined inclusion and exclusion criteria, the study population comprised an exposure group of 377 employees (including furnace workers, inspection workers, and maintenance workers) exposed to dust, noise & carbon monoxide, and a control group of 388 employees (including central control workers, electricians, and administrative personnel) without above-mentioned exposure. The total sample size was 765 participants. The follow-up period was from April 2011 to October 2022, and the study endpoint was defined as the conclusion of the follow-up period or diagnosed hypertension in annual occupational health examination. Information on general demographic characteristics, living habits, and work status was collected from all study subjects. Cox proportional hazards regression model was used to analyze the association between occupational hazard exposure and the risk of hypertension among the calcium carbide plant employees.

Results The average age, mean systolic and diastolic blood pressure, proportion of males, smoking rate, and alcohol consumption rate in the exposure group were higher than those in the control group (P<0.05). Compared to baseline, both systolic and diastolic blood pressure levels increased in the exposure group and the control group at the end of the follow-up (P<0.05). At the end of the follow-up, the average differences between systolic/ diastolic blood pressure and baseline values in the exposure group were higher than those in the control group (P<0.05). During the follow-up period, a total of 223 cases of hypertension occurred, with a total follow-up of 2785 person-years, resulting in an incidence density of 8007.18 per 100000 person-years, an average age of onset of (35.90±8.22) years, and an average working age of onset of (2.69±1.97) years. The incidence density in the exposure group was 128.71% higher than that in the control group, and the risk of hypertension in the exposure group was 2.115 times that of the control group. The risk of hypertension was 2.199 times higher for men than for women, 1.344 times higher for those aged 30 and above than for those under 30, 1.546 times higher for smokers than for non-smokers, and 1.750 times higher for drinking workers than for non-drinking ones. The results of Cox proportional hazards regression modeling indicated that the hazard ratio (95%CI) of hypertension among the employees exposed to dust, noise, and carbon monoxide was 2.254 (1.703, 2.982), 1.594 (1.107, 2.295), and 1.567 (1.079, 2.274), respectively, when different covariates (gender, age, smoking, and alcohol consumption) were included. The results of Log-rank test showed that there were statistically significant differences in the distribution of disease-free survival between the exposure group and the control group (P<0.05).

Conclusion Occupational exposures to dust, noise, and carbon monoxide may increase the risk of hypertension among calcium carbide plant workers.