Studies on the design of animal tests for the corrosiveness of industrial chemicals.

Using a defined method for the determination of irritant and corrosive effects, the effects of varying the exposure time and the extent of occlusion were investigated and compared in rabbit skin experiments (by occlusive and semi-occlusive methods, each at exposure times of 1 hr and 4 hr). The results for 23 substances demonstrate that exposure for 1 hr normally leads to a realistic assessment of corrosiveness, in agreement with those given in the EEC 'Dangerous Substances Directive' (67/548/EEC; Off. J. Europ. Commun. 1967, 196, 1). With several substances, the 4-hr exposure leads to corrosive effects that do not occur under practical conditions. Moreover, a 4-hr exposure does not lead to a realistic hazard assessment in every case; some substances exhibit a corrosive effect in this test but are not classified as "corrosive" in the EEC Guideline Annex I, no. 1.1. Results using the semi-occlusive method did not usually differ from those obtained with the occlusive method. In general, the semi-occlusive method can be used, and in the case of volatile substances it is strongly advocated.