Ans: b (Crocidolite) Ref: Davidson, 20th ed, p. 72; 19th ed, p. 573Crocidolite is the most potent cause of mesotheliomaTypes of Asbestos:Serpentine (curly and flexible fibres) e.g., chrysoliteAmphibole (straight stiff and brittle) e.g., crocidolite.Amphiboles are more pathogenic than chrysoliteThe greater pathogenicity of amphibole is apparently related to their aerodymanic properties and solubility. The straight stiff amphiboles may align themselves in the airstream and are delivered to the deeper long tissues, where they can penetrate epithelial cells and reach interstitium.AsbestosisCaused by chrysolite, amosite, anthophyllite and crocidolite. Crocidolite or blue asbestos exposure is the most dangerous. Length of amphibole also plays a role in pathogenicity, those longer than 8 micrometer and thinner than 0.5 micrometer being more injurious than shorter thicker ones.Occupational exposure in - mining, milling, pipe fitters and boiler makersPathologyDiffuse interstitial fibrosis is mainly seen in the lower lobe.Asbestos bodies - Golden brown, fusiform or beaded rods (ferruginous) with translucent centre with asbestos fibres coated with an iron containing proteinacious material.Asbestos exposure causes pulmonary fibrosis (asbestosis) and carcinoma of lung, pleura (mesothelioma) and peritoneum.Atleast 10 years of exposure is needed for Asbestosis to manifest.But the disease may manifest many years after leaving the exposure site (similar to silica and coal)Lung cancer in asbestos exposure is associated with a minimum lapse of 15-19 years between first exposure and development of the disease.Mesothelioma is not associated with smoking (i.e., smoking does not increase the risk of mesothelioma in asbestos exposure)Radiological featuresCalcification of parietal pleura along the lower lung field, the diaphragm and the cardiac border.Ground glass appearance of the lung fields may be seen.