The dermal acute toxic class method: test procedures and biometric evaluations

A dermal acute toxic class (ATC) method is presented with the use of signif icantly fewer animals in comparison with the classical dermal 50% lethal do se (LD50) test. The principle of the dermal ATC method is based on the oral and the inhalation ATC method. The method was developed for three fixed st arting doses. Depending on the dermal LD50 the slope, the classification sy stem and the starting dose on average 40 to 90% fewer animals will be used in comparison to at least 30 animals with the dermal LD50 test. The method was biometrically evaluated by using the Probit model for dose-response rel ationships. At present, there are eight different international classificat ion systems based on dermal LD50 values. The test procedures and the calcul ations of the classification probabilities demonstrate that the dermal ATC method is a reliable alternative to the dermal LD50 test with the use of si gnificantly fewer animals. Classification probabilities are presented for a ll classification systems currently in use, and expected numbers of experim ental and of moribund/dead animals are demonstrated for the system of chemi cals in the European Union for all three starting doses. The conclusion is justified that, similarly to the inhalation ATC method, there is no need to validate the dermal ATC method with the use of experimental animals.