Advantages and limits of in vivo screening tests.

Several methods have been proposed to ascertain the potential toxicity of man-made vitreous fibres (MMVF) in animals. The most frequently used in vivo methods include inhalation (IH) (whole body and nose-only), intratracheal (IT) instillation, intrapleural injection-implantation and intraperitoneal (IP) injection. This report compares reports of studies using these methods in terms of their: (1) relevance to humans; (2) standardization of technique; (3) validation of method; (4) need for fibre preparation; (5) estimation of maximum tolerated dose; (6) determination of 'overload'; (7) exposure regimen; (8) pathology requirements; (9) quality control procedures; (10) extent and type of peer review; and (11) value of data for risk assessment. The results of this investigation showed that the inhalation method was clearly superior to the other exposure methods in all respects, although it is the most expensive. The intratracheal instillation method was considered a second choice, while injection-implantation methods were fraught with scientific and practical problems and the data derived from studies using these techniques were considered of value only for the study of specific mechanistic issues.