Table 9.
Tuberculosis among Silica-exposed Workers
| First Author, Year, Location (Reference) | Study Type | TB Definition/Diagnosis | Exposure/Job Information | Population Cases (n)/Control or Total Population (N) | Risk Estimates (95% CI when available) | Occupational Burden (%) |
|---|---|---|---|---|---|---|
| Rosenman, 1996, USA (209) | Case–control | Bacteriological or reporting of treatment | SIC and SOC codes used as proxy for exposures | HIV-positive and foreign-born individuals excluded; 149 cases from New Jersey TB Register, 209 control subjects from previous cancer studies | Adjusted OR for silica industries: 1.6 (0.7–3.8) | 4.9 |
| Chen, 1997, USA (210) | Case–control | Death certificate data from NOMS database | Silica-exposed workers | 8,740 cases: 2% intermediate, 14% high; 83,338 control subjects | ORintermed: 1.1 (0.8–1.5) | Intermediate: 0.2 |
| ORhigh: 1.3 (1.1–1.5) | High: 3.2 | |||||
| Calvert, 2003, USA (211) | Case–control | Death certificate data from NOMS database | Subjects assigned to a qualitative silica exposure category | 6,570 cases: medium (11.7%), high (9.5%), super high (0.6%), 32,843 TB control subjects | ORmed: 1.3 (1.2–1.5) | Medium: 3.04 |
| ORhigh: 1.6 (1.5–1.8) | High: 3.4 | |||||
| ORsuper high: 2.5 (1.7–3.7) | Super high: 3.6 | |||||
| Kleinschmidt, 1997, South Africa (212) | Cohort | Bacteriological and clinical diagnosis | Gold miners from a single mine, followed from 1975 to 1996 | 449 cases (total cohort = 4,976 gold miners) | IRR, 2.5 | 2.3 |
| Murray, 1999, South Africa (213) | Cohort | Culture-positive sputum | Gold miners from four mines | 376 cases (total cohort = 28,522 gold miners) | IRR, 4.2 | 4.8 |
| Churchyard, 2000, South Africa (214) | Cohort | Bacteriological and clinical diagnosis | Gold miners at a single mine followed from 1993 to 1997 | 2,893 cases | IRR, 7.5 | 7.9 |
| Sonnenberg, 2005, South Africa (215) | Cohort | Culture-positive “probable TB” = score of radiography, sputum, tuberculin, histology, and trial | Gold miners from four mines followed from 1991 to 1997 | 747 cases (total cohort = 23,874) | IRR, 3.9 | 3.8 |
| Glynn, 2008, South Africa (216) | Cohort | Culture and clinical findings | Gold miners from four mines followed from 1991 to 2004 | 620 new cases among 7,583 participants | IRR, 4.3 | 2.0 |
| van Halsema, 2012, South Africa (217) | Cohort | Culture | Gold miners from two mines followed from 2002 to 2008 | 4,268 TB/19,476 (mine A) | IRR, 3.1 (mine A) | Mine A: 1.1 |
| 1,472 TB/8,414 (mine B) | IRR, 2.5 (mine B) | Mine B: 0.8 |
Definition of abbreviations: CI = confidence interval; IRR = incidence rate ratio; NOMS = National Occupational Mortality Surveillance; OR = odds ratio; SIC = Standard Industrial Classification; SOC = Standard Occupational Classification; TB = tuberculosis; USA = United States.
Except for publications providing an OR, the occupational burden is estimated from an IRR derived from World Bank and World Health Organization data for the silica-exposed labor force and national TB rates. The median silica-associated burden of TB was 2.3% (range, 0.8–7.9%).