Exposure to metal fume and infectious pneumonia.

To test the hypothesis that inhalation of metal fume reversibly increases susceptibility to pneumonia, the authors conducted a case-control study. Men aged 20-64 years, admitted to 11 hospitals in West Midlands, England, with community-acquired pneumonia during 1996-1999 were interviewed about their lifetime occupational history, exposure to metal fume, and potential confounding factors. Similar information was collected from controls admitted to the same hospitals with nonrespiratory illness. For cases, exposures were timed relative to the onset of their illness (on average, 6 months before interview). Exposure histories for controls were censored 6 months before interview. Interviews were completed by 525 cases and 1,122 controls (response rates of 74% and 99%). Pneumonia was associated with reported occupational exposure to metal fume in the previous year (adjusted odds ratio (OR) = 1.6, 95% confidence interval (CI): 1.1, 2.4) but not in earlier periods (OR = 1.1). The risk was highest for lobar pneumonia and recent exposure to ferrous fume (OR = 2.3, 95% CI: 1.2, 4.3). The association was not specific to any one microorganism. These findings support the hypothesis that ferrous and possibly other metal fumes reversibly predispose to infectious pneumonia. Research should now focus on the underlying mechanisms and prevention.