The asbestos dilemma: I. Assessment of risk.

This paper gives a critical review of current problems related to quantitative health risk assessment of exposure to asbestos, and particularly to chrysotile, the only type of asbestos still available on the market. The paper reviews types, sources, uses and the main recognised health effects of asbestos, paying particular attention to the health-related properties of fibres and the role of their biopersistence. The main focus is on yet unresolved issues which introduce a large margin of uncertainty into the published quantitative risk assessments: 1) Are all asbestos types equally dangerous or is chrysotile asbestos less dangerous than amphiboles? 2) Are health effects of asbestos fibres threshold or non-threshold effects? 3) Are errors in mathematical modelling of risks so great as to make the risk evaluations worthless? Attention is also given to errors in estimates of past exposures, uncertainties and unspecificities of models and to the unfeasibility of practical application of some well recognized risk assessment models.