A STUDY ON UV FILTER CHEMICALS FROM ANNEX-VII OF EUROPEAN-UNION DIRECTIVE 76 768/EEC, IN THE IN-VITRO 3T3 NRU PHOTOTOXICITY TEST/

In 1996, the Scientific Committee on Cosmetology of DGXXIV of the Euro pean Commission asked the European Centre for the Validation of Altern ative Methods to test eight UV filter chemicals from the 1995 edition of Annex VII of Directive 76/768/EEC in a blind trial in the in vitro 3T3 cell neutral red uptake phototoxicity (3T3 NRU PT) test, which had been scientifically validated between 1992 and 1996. Since all the UV filter chemicals on the positive list of EU Directive 76/768/EEC have been shown Rot to be phototoxic in vivo in humans under use condition s, only negative effects would be expected in the 3T3 NRU PT test. To balance the number of positive and negative chemicals, ten phototoxic and ten non-phototoxic chemicals were tested under blind conditions in four laboratories. Moreover, to assess the optimum concentration rang e for testing, information was provided on appropriate solvents and on the solubility of the coded chemicals. In this study, the phototoxic potential of test chemicals was evaluated in a prediction model in whi ch either the Photoirritation Factor (PIF) or the Mean Photo Effect (M PE) were determined. The results obtained with both PIF and MPE were h ighly reproducible in the four laboratories, and the correlation betwe en in vitro and in vivo data was almost perfect. All the phototoxic te st chemicals provided a positive result at concentrations of 1 mu g/ml , while nine of the ten non-phototoxic chemicals gave clear negative r esults, even, at the highest test concentrations. One of the UV filter chemicals gave positive results in three of the four laboratories onl y at concentrations greater than 100 mu g/ml; the other laboratory cor rectly identified all 20 of the lest chemicals. An analysis of the imp act that exposure concentrations had on the performance of the test re vealed that the optimum concentration range in the 3T3 NRU PT test for determining the phototoxic potential of chemicals is between 0.1 mu g /ml and 10 mu g/ml, and that false positive results can be obtained at concentrations greater than 100 mu g/ml. Therefore, the positive resu lts obtained with some of the UV filter chemicals only at concentratio ns greater than 100 mu g/ml do not indicate a phototoxic potential in vivo. When this information was taken into account during calculation of the overall predictivity of the 3T3 NRU PT test in the present stud y, an almost perfect correlation of in vitro versus in vivo results wa s obtained (between 95% and 100%), when either PIF or MPE were used to predict the phototoxic potential. The management team and participant s therefore conclude that the 3T3 NRU PT test is a valid test for corr ectly assessing the phototoxic potential of UV filter chemicals, if th e defined concentration limits are taken into account.