Redefining idiopathic interstitial lung disease into occupational lung diseases by analysis of chemical composition of inhaled dust particles in induced sputum and/or lung biopsy specimens

There has been increased public awareness of the potential danger from exposure to hazardous dust in various occupations. This study aims to validate the qualitative analysis of scanning electron microscopy (SEM) of lung samples by 1) correlation of induced sputum (IS) findings to clinical findings, 2) comparing hazardous particles in IS to those in biopsied lung specimens, and 3) assessing whether the particles present in the lungs of transplanted patients correlate with occupational history of dust exposure. Forty patients with occupational history were included; of whom 35 filled in questionnaires. Twenty-four of them had SEM analysis of their IS, and 11 of these 24 also had SEM analysis of their lung tissue. Another 11 lung biopsies from patients with occupational history were scanned by SEM and compared with 10 lung biopsies from patients with no occupational history. SEM analysis of IS was as efficient for detecting hazardous particles as was SEM analysis of lung tissue; silica was detected better in sputum. Exposure to silica was the main chemical element associated with a high likelihood to show abnormalities in IS (Odds ratio 19.41 CI = 0.270–1398.33). The average number of detected hazardous chemical elements in patients with an occupational history of exposure was 4 ± 1.61 in IS and 3.55 ± 2.02 in lung tissue (P = 0.57); it was 1.5 ± 0.85 from transplanted occupationally exposed patients compared with 0.36 ± 0.67 in transplanted non-exposed patients (P = 0.003). SEM analysis of particles in IS and lung tissue can elucidate the causative agent(s) of otherwise idiopathic interstitial lung disease among occupationally exposed workers.