Rheumatoid arthritis in workers exposed to silica in the pottery industry.

OBJECTIVE To investigate the relation between rheumatoid arthritis and occupational exposure to silica in pottery and related industries. METHODS Medical records of 8325 men and women born 1916-45 and employed in pottery, refractory material (aluminosilicate or silica), and sandstone industries were examined to identify cases of rheumatoid arthritis. Medical and employment histories were extracted for cases and matched referents. Indices of duration, cumulative exposure, and mean silica concentration were compiled. Conditional logistic regression was used to investigate the relation between rheumatoid arthritis and indices of exposure, having allowed for potential confounders of smoking, employment in the coal mining industry, and number of pregnancies. RESULTS 58 Cases of rheumatoid arthritis (43 men, 15 women) were identified. Cases had significantly shorter duration of exposure than referents. There was no significant difference between cases and referents in mean silica concentration. Men who had worked in the coal mining industry were particularly at risk (odds ratio 5.36, 95% confidence interval 1.92 to 15.03). CONCLUSION There was no evidence of increased risk of developing rheumatoid arthritis after occupational exposure to silica at mean exposures within the current United Kingdom exposure limits.