The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated the general aspects of the toxicity of inorganic fibrous dusts. As a first step, a documentation on the effects caused by inhalation of inorganic fibrous dusts and the mode of action for their toxicity was set up. For the elucidation of the mechanism of the toxicity and carcinogenicity of fibres, data derived from studies with asbestos fibres were also considered, in order to obtain some knowledge with regard to the biological effects of the other inorganic fibrous dusts. The formation of tumours in the lungs and on serous membranes is mainly the result of inflammatory processes. Chronic inflammation and cell proliferation are caused by the impairment of fibre clearance, whereby inflammation‐promoting cytokines, growth factors, reactive oxygen (ROS) and nitrogen species (RNS) and chlorine radicals are released from the macrophages, inflammatory cells, alveolar cells and mesothelial cells. The generation of these radicals leads to genotoxic effects. In addition, intracellular formation of ROS and RNS can be caused by the fibres themselves, as a result of their own surface reactivity. Fibres can stimulate cell receptors and inflammasomes.
Each fibre dust group will be evaluated individually and, depending on the data available, may be classified in one of the categories for carcinogens. The Commission has already begun this procedure.