Amphibole

Asbestos exists in two structural classes: serpentine (chrysotile — curly, more common, ~95% of commercial asbestos) and amphibole (crocidolite, amosite, tremolite — straight, rigid). Amphibole fibers, particularly crocidolite ('blue asbestos'), penetrate deeply into distal airways and pleura because of their aerodynamic shape and are less efficiently cleared, giving them disproportionately higher carcinogenic potential — especially for malignant mesothelioma. Asbestosis presents 15-20+ years after exposure (shipyards, insulation, brake linings) with lower-lobe interstitial fibrosis, ferruginous bodies (iron-coated fibers) on biopsy, pleural plaques (calcified, on diaphragm/parietal pleura — pathognomonic), and increased risk of bronchogenic carcinoma (highest absolute risk, synergistic with smoking) and mesothelioma (highest relative risk; smoking does not multiply this).