The part of this book covering pathogensis and modes of action begins with a chapter on the physicochemical properties of asbestos fibers and a chapter on the deposition and retention of fibers within the lung and their clearance. Some of the effects of asbestos can be reproduced in animal experiments, and the book includes a full review of the results from animal studies using various routes of administration of fibers. It is also generally accepted that the effects of fibers on pulmonary macrophages is central to all fiber-induced pathology, and the release of macrophage-associated inflammatory and immunological mediatros is dealt with in a further chapter. Examination of pathogenicity by cell culture is described, and areas covered include the role of free radicals and cellular mechanisms in producing genetic damage. The fiber-induced activation of some second messenger pathways is also described, with consideration of whether or not similar cellular mechanisms are responsible for all the clinical conditions associated with fiber exposure. Knowledge of the mechanisms involved should be valuable in the development of safe fibers and the prevention of human exposure to new materials that are dangerous as asbestos. The final chapters expound and resolve the conflicts in evidence, discuss the importance of fibers for human well-being and the possible health impact on nonmineral alternatives, and evaluate risks to the public