Correlation between Silica Exposure and Risk of Tuberculosis in Lorestan Province of Iran

Tuberculosis is considered a prevalent and hazardous disease in developing countries. Recognition and control of TB risk factors are of special significance. This study sought to determine the frequency of occupational silica exposure in TB patients residing in Lorestan Province.

This cross-sectional study was conducted in 2012. List of registered TB patients was obtained from the Infectious Disease Control Center of Lorestan Province. Data were collected from 871 TB patients through interview and filling out a checklist. Also, 429 subjects presenting to Health Centers of Lorestan Province with respiratory complaints suspicious of TB (which was ruled out) were entered the study as the control group for comparison of frequency of silica occupational exposure. Understudy subjects based on the degree of silica exposure were categorized into 4 groups of no exposure, mild exposure, moderate exposure and severe exposure and compared in terms of frequency of TB incidence.

Frequency of silica exposure was significantly higher in TB patients compared to controls (P < 0.001, OR: 3.39, 95%CI = 2.63-4.36). Additionally, frequency of TB was greater in patients with probable silicosis and silica exposed subjects compared to those with no history of silica exposure (P < 0.05). Logistic regression analysis revealed significant associations between moderate and severe silica exposure and TB frequency. Significant correlations were also detected between age, work experience, level of education, male gender and cigarette smoking with TB frequency (P < 0.05).

The study results revealed that silica exposure was prevalent among TB patients and frequency of TB increased by increased intensity of silica exposure, older age, higher work experience, lower level of education, male gender and cigarette smoking. Provided that our study results are confirmed by prospective studies, TB screening is recommended for workers with occupational silica exposure particularly those with higher work experience.