SILICOSIS AMONG FOUNDRY WORKERS - IMPLICATION FOR THE NEED TO REVISE THE OSHA STANDARD

To evaluate the risk of pneumoconiosis among workers in a Midwestern a utomotive foundry, medical records and silica sand exposure data were analyzed for 1,072 current and retired employees with at least 5 years of employment as of June 1991, Approximately half of these employees had worked at the foundry for 20 or more years. Sixty workers were fou nd to have radiographic evidence of pneumocorilosis. Twenty-eight work ers had radiographs consistent with silicosis, of which 25 were consis tent with simple silicosis and three with progressive massive fibrosis . The prevalence of radiographic changes consistent with silicosis inc reased with: number of years worked at the foundry (6% for 20-29 years and 12% for 30 or more years); cigarette smoking (12.2%; among smoker s with high silica exposure vs, 4.4% among never smokers with high sil ica exposure); work area within the foundry (cleaning room, core room, mold area, core knockout); and quantitative silica exposure (0.3-2.7% of workers at the current Occupational Safety and Health Administrati on (OSHA) standard and 4.9-9.9% of workers above the OSHA standard). I n addition, the odds of developing radiographic changes consistent wit h silicosis were increased for African Americans (odds ratio = 2.14, 9 5% confidence interval 0.85-5.60) in comparison with whites. (The risk was similar when silica exposure was equal, but African-American work ers on average had greater exposure to silica, despite having a simila r duration of work as white workers.) Another eight workers had radiog raphic evidence oi asbestosis, and 24 had pleural plaques. These asbes tos-related changes were not: associated with increasing exposure to s ilica but rather were associated with being in the maintenance departm ent and performing repair work. After controlling for cigarette smokin g, race, and exposure to silica at another job besides the foundry, th e authors found a 1.45 increased risk of developing a radiograph consi stent with silicosis after 20 years of work at the current OSHA standa rd, and a 2.10 increased risk after 40 years of work at the current OS HA standard, On the basis of these findings, the authors recommend mai ntaining silica air levels no higher than the exposure level of 0.05 m g/m(3) recommended by the National institute for Occupational Safety a nd Health.