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BACKGROUND: Silicosis commonly occurs among workers in the Manufacturing, Construction, and Mining industries. Two states, Michigan and New Jersey, with funding from the National Institute for Occupational Safety and Health, conduct case-based surveillance for silicosis using a standard case definition and questionnaire.
METHODS: We used provisional data from Michigan and New Jersey to characterize the confirmed cases of silicosis for 1993‒2009. The case definition includes a history of occupational exposure to airborne silica dust and a chest radiograph (or computed tomography) or pathologic findings consistent with silicosis. Information on industry and occupation was coded using the 2002 North American Industry Classification System and the 2000 U.S. Bureau of the Census Occupation Codes, respectively. Opacity profusion was categorized in accordance with International Labour Organization guidelines for interpreting films for pneumoconiosis.
RESULTS: Between 1993 and 2009, 854 confirmed cases of silicosis (74.2% from Michigan and 25.8% from New Jersey) were reported. The mean age of silicosis cases was 72 years (range: 36–98 years), 65.5% were white, and 95.2% were male. By industry, 647 (75.8%) confirmed cases were associated with silica exposure in Manufacturing (e.g., Primary Metals Manufacturing), 111 (13.0%) in Construction (e.g., Specialty Trade Contractors), and 62 (7.3%) in Mining. Overall, 554 (64.9%) cases were associated with Production occupations (e.g., Molders and Molding Machine Setters, Operators, and Tenders, Metal and Plastic) and 170 (19.9%) cases were associated with Construction and Extraction occupations (e.g., Construction Laborers). Sixty-four (7.5%) of the confirmed cases had < 10 years, 140 (16.4%) had 10‒19 years, and 650 (76.1%) had ≥ 20 years of employment in jobs with potential exposure to dust containing silica. Among confirmed cases, 204 (23.9%) had filed a workers’ compensation claim and 227 (26.6%) had a history of sandblasting. Among individuals with information on pneumoconiotic opacities on chest radiograph (96.8%), 1.2% had small opacity profusion category 0, 46.3% had category 1, 36.9% had category 2, and 14.4% had category 3. Progressive massive fibrosis was seen in 141 (17.0%) of these individuals, of which 31 (22.0%) had filed a workers’ compensation claim and 42 (29.8%) had a history of sandblasting.
CONCLUSIONS: Cases of silicosis are sentinel events that indicate the need for surveillance to identify workplaces for intervention. The proportion of cases who submitted a workers’ compensation claim is low; the reasons for this are unclear and need to be explored, particularly among those with severe disease.