Tuberculosis Immunity And Silicosis In Thailand

Objective: The first and foremost purpose of this study was to investigate the morbidity of silicosis and pulmonary tuberculosis among stone grinding workers and to discover the related risk factors that could proliferate the morbidity of silicosis and pulmonary tuberculosis.Secondly, this research aimed to investigate the relationship between TB immunity and silicosis incidence through comparison between the case and control groups who had TB immunity and non-TB immunity, and to study the reaction time among silicosis cases who had TB immunity and non-TB immunity, after exposure to the silica dust (SiO2). Methodology: Radiograph pattern indicated the silicosis cases or the control group and sex, age and working area matched controls. The sputum analysis by acid-fast staining, polymerase chain reaction and culture confirmed pulmonary tuberculosis (TB). The reaction of tuberculin skin testing without TB disease was immunity criteria. In addition, the dust samples were analyzed to determine the dust concentration and the content of SiO2%. Results: The results showed that during 1995-2001 the silicosis incidence was 16.9, 17.0, 7.1, 20.7, 13.2 and 17.1 per 1000, respectively. According to monitoring record, the highest respirable dust concentration was 9.35 mg/m3 (SD=10.08) and the content of SiO2 was 6.47% (SD=9.32) that was 50 per cent exceeding threshold limit value (TLV). The highest silicosis incidence was 56.3 per 1000 in the south region and the incidence of increment was significantly associated with the higher dust concentration. The incidence of pulmonary tuberculosis was 3.7 per 1000 and the highest was 15.1 per 1000 in the northeast region. For the silicotuberculosis in the central and east regions, the incidence was 0.44 per 1000. Finally, the related risk factors were studied. The study found that the prevalence of silicosis was significantly associated with the age, exposure time, year of smoking and lack of PPE usage. Afterward, it was proved that the risk related factors between case and control groups were not significantly different . In addition, the samples' exposure year (was calculated by multiplying exposure time and dust exposed concentration) and the exposure time, were significantly different between reactive and non-reactive among silicosis and silicotuberculosis groups. Conclusion: The incidence of silicosis in Thailand was constantly at a high level in the last 5 years ranging from 7.1 to 20.7 per 1000 and was obviously due to the high level of silica dust exposure in the working environment. In addition, the study found that the incidence of pulmonary tuberculosis (PTB) among the risk workers of Thailand was 5.69 per cent that near caused by both Mycobacterium tuberculosis and non Mycobacterium tuberculosis. Finally, the finding of the study that significantly associated mean of person exposure year and exposure times with tuberculin skin testing result. However, the skin test usually use for screening case. So the high accuracy investigation method still need more for taking together and leading to the strongly summary service program later. The results suggested that there is a need for developing a national database for silicosis and pulmonary tuberculosis among stone grinding workers and executing a medical surveillance and a national occupational medical.