This sixty-eighth volume of IARC Monographs considers certain forms of crystalIine and amorphous silica, some silicates (palygorskite, also called attapulgite; sepiolite; wollastonite; and some natura1 and synthetic zeolites, exc1uding erionite), coa1 dust and para-aramid fibrils. Some of these agents are fibrous in nature (palygorskite, sepiolite, wollastonite and sorne natural zeolites, as we...