Four occupational lung diseases are given, each caused by breathing in a different kind of mineral dust. The radiograph pattern each one produces depends mainly on the shape of the dust particle, so let's look at each option through that lens.
- Silicosis: Caused by silica dust, whose particles are fairly rounded. The lung reacts by forming small, well rounded, sharply outlined opacities, mostly in the upper zones. This is a nodular pattern, not a web like one.
- Asbestosis: Caused by asbestos, a mineral that occurs as very long, thin fibres. These fibres settle deep in the small airways and spread along the connective tissue of the lung, laying down thin, branching, irregular fibrous strands. On a radiograph this shows up as a fine, net like or cobweb pattern, mainly in the lower lung zones, and can blur the heart's outline.
- Talcosis: Talc dust often carries traces of other minerals such as silica or asbestos, so its radiograph can show a mixed picture of nodules and irregular shadows along with pleural plaques. It does not have a single, well known cobweb sign as its defining feature.
- Coal workers' pneumoconiosis: Caused by coal dust, whose particles are again rounded rather than fibrous. Early disease shows small rounded opacities, and advanced disease can show large fused masses called progressive massive fibrosis. Neither stage looks like a cobweb.
Because only asbestos dust is fibrous, only asbestosis produces the fine, irregular, web like scarring described as a cobweb pattern on a chest radiograph.
Let's summarize:
- Rounded dust particles (silica, coal) give rounded nodular opacities.
- Fibrous dust particles (asbestos) give fine linear, cobweb-like opacities in the lower lung zones.
- Talcosis shows a mixed, less specific pattern.
So the cobweb-like radiograph appearance in a miner's lung is diagnosed as asbestosis.