A national validation project of alternative methods to the Draize rabbit eye test

In June 1988, a 2.5-yr inter-laboratory study involving 13 toxicology laboratories was started in West Germany to validate alternative methods to the Draize rabbit eye test. The aim of this collaborative study is to validate the classification of chemicals with regard to their irritation potential using the neutral red/kenacid blue (NR/KB) cytotoxicity assay and the hen's egg test-chorioallantoic membrane (HET-CAM) assay. The results should make it possible to decide whether and to what extent the NR/KB cytotoxicity test and the HET-CAM assay can replace the Draize test. After two test trials, standard testing procedures and protocols were agreed on. In addition, to facilitate management of the data and to reduce costs, personal computer (PC) software was developed for both tests, which allows storage of all data on floppy discs and statistical analysis on PCs. During the preliminary phase, the applicability of the software was tested and corrected according to the experimental conditions of the validation study. Tests on the following chemicals have so far been completed, and reproducibility and repeatability have been determined: sodium dodecyl sulphate, triethanolamine, zinc pyridinethione, dimethylsulphoxide and butoxyethanol. Only zinc pyridinethione, which is severely irritating in vivo, could not be tested in the HET-CAM test. The preliminary phase has shown that the number of chemicals that can be tested in the HET-CAM test during the validation project will be limited by costs and management problems of manpower and time.