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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: Post Author Corrections: April 17, 2012
doi: 10.1097/JOM.0b013e31824e6784
Original Article: PDF Only


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


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.


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).


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.

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 © 2017 by the American College of Occupational and Environmental Medicine