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Increased Micronodule Counts Are More Common in Occupationally Silica Dust–Exposed Smokers Than in Control Smokers

Mets, Onno M. MD; Rooyackers, Jos MD, PhD; van Amelsvoort-van de Vorst, Saskia MSc; Mali, Willem PThM MD, PhD; de Jong, Pim A. MD, PhD; Prokop, Mathias MD, PhD

Journal of Occupational and Environmental Medicine: April 17, 2012 - Volume Publish Ahead of Print - Issue - p
doi: 10.1097/JOM.0b013e31824e6784
Original Article: PDF Only

Objective: To determine the prevalence of increased micronodule counts in silica dust–exposed smokers.

Methods: We evaluated 54 male smokers with severe silica dust exposure and 54 male control smokers. Both groups underwent low-dose chest computed tomography and lung function testing. Computed tomographic scans were visually evaluated for solid micronodules (<3 mm). The 95th percentile of micronodule count was calculated for the control smokers. Prevalence of an increased micronodule count was assessed for the dust-exposed subjects.

Results: Solid micronodules were present in most participants of both groups. The 95th percentile of micronodule count in the control group was 13. Increased micronodule counts were significantly more common in the exposed group than in the control group (P = 0.01).

Conclusions: A substantial number of silica-exposed heavy smokers evaluated for silicosis have increased micronodule counts on chest computed tomographic scan. This finding might represent an early stage of silicosis.

From the Department of Radiology (Drs Mets, Mali, de Jong, and Prokop and Ms van Amelsvoort-van de Vorst), and Netherlands Expertise Centre for Occupational Respiratory Disorders (Dr Rooyackers), Division of Heart and Lungs, University Medical Centre Utrecht; Institute for Risk Assessment Sciences (Dr Rooyackers), Division Environmental Epidemiology, Utrecht University, Utrecht; and Department of Radiology (Dr Prokop), Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands.

Address correspondence to: Onno M. Mets, MD, Department of Radiology, University Medical Centre Utrecht, Huispostnummer E01.132, Postbus 85500, 3508 GA Utrecht, the Netherlands (

The authors declare no conflicts of interest.

Copyright © 2018 by the American College of Occupational and Environmental Medicine