Figure 1. Study flow diagram.

^aReasons for study exclusion: no current chest imaging available (n = 2).

^bEight subjects had refused to participate in the follow-up interview. In 20 subjects the provided contact information had become invalid since study inclusion.

^cCauses of death were malignancy (n = 5), cardiovascular diseases (n = 4), silicosis (n = 2), chronic obstructive pulmonary disease (n = 1), and pneumonia (n = 1).