Potential Effect of Combined Exposure of Crystalline Silica Dust and Cigarette Smoking on the Incidence of Silicosis among Chinese Male Stone Processing Workers: A Cross-Sectional Study

Background: Silicosis is a progressive and irreversible disease primarily caused by exposure to crystalline silica dust and, to a lesser extent, cigarette smoking. However, further research is needed to validate the potential combined effect of these risk factors on the increased incidence of the disease. Methods: A total of 1688 male workers employed at a Chinese stone processing plant between 1 January 1999 and 31 December 2019, were included in the study. Cumulative exposure to industrial crystalline silica dust and packyears of smoking were collected through health surveillance, and odds ratios (ORs) with 95% confidence intervals (CIs) for silicotic changes due to industrial silica exposure and cigarette smoking were estimated using logistic regression models. Results: Among all participants, a significant exposure-response relationship was observed between long-term exposure to industrial silica dust and radiographic findings resembling silicosis (OR 1.74, 95% CI 1.25 to 2.41). However, among middle-aged workers, a weak and statistically insignificant relationship was found between prolonged cigarette smoking and X-ray evidence of lung silicosis (OR 1.59, 95% CI 1.00 to 2.53). Furthermore, significant combined effects, exceeding the additive models, were identified in each age group and employment sector (relative risk due to interaction 0.51, 95% CI 0.08 to 3.42). Conclusions: It is critically important to implement effective dust removal measures and tobacco control strategies in order to enhance respiratory health among employees across all age groups in the stone processing industry.