Respiratory Health and Silica Exposure of Stone Carvers in Thailand

Abstract

A cross-sectional study of dust exposures and health outcomes was conducted in a stone-carving company in Thailand. 147 respirable dust samples were collected and 97 subjects participated. Exposure indices were constructed and health outcomes, including respiratory symptoms, pulmonary functions, and chest radiographs, were assessed. Severities of employees' current exposures to quartz were 0.5–8.8 times the ACGIH-TLV,depending on job and site. Durations of exposures ranged from 4 months to 30 years. The prevalence of silicosis (profusion grade ≥ 1/0) was 2%. Pulmonary tuberculosis was also detected in 4%. Linear regression analyses revealed decreased lung function in workers with longer work durations (p < 0.05), regardless of age, sex, height, and smoking status. No clear association was seen between cumulative exposure metrics and indicators of silicosis. Elevated silica exposure levels indicate an ongoing risk of silicosis in this industry. Exposures were increased by the use of grinding tools with no ventilation and by proximity to other workers. However, because the number of workers with dust-exposure histories was limited, exposure measurements were confined to current conditions.

Keywords:

• exposure assessment
• exposure-response relationship
• silicosis
• stone work