320 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS % viability 1201• ...... .. 100 ' . .... 0 ' "" ..................... : ............. :" .......... ' .............. 0 0 0 0 II!-.no. uv treat. 'ment -[::]with UV t• eatm'ent. 48 hours Figure 1. Monolayer phototoxicity assay. STATISTICAL ANALYSIS A statistical analysis of the results from the monolayer and MatTek EPI-100 assays was done using the t-test to measure differences between irradiated and non-irradiated cul- tures. The cutoff for statistical significance was p -- 0.05. The results of the statistical analysis are presented in Table III. Phototoxicity in the yeast assay is not measured sta- tistically (2). % viability iI!n'o UV :treatment E3with UV treatment 48 hours Figure 2. MatTek EPI-100 phototoxicity assay.

NEW PHOTOTOXICITY METHODS 32 ! Zone of inhibition in millimeters 10 8 6 4 2 O •n0:uv treatment r-•with UV treatment 48 hours Fiõur½ 3. Yeast phototoxicity assay. Table III Statistical Analysis of Phototoxicity Results Test material Monolayer fibroblasts MatTek EPI-100 Yeast method • A NST NST Not phototoxic B NST NST Not phototoxic C NST NST Phototoxic D NST NST Not phototoxic E (1%) NST NST Not phototoxic E (3%) NST NST Phototoxic E (5%) NST NST Not phototoxic F (1%) NST NST Not phototoxic G NST a NST Not phototoxic H NST a NST Not phototoxic I NST a NST Not phototoxic 400 •g/ml 8-MOP NST STN Phototoxic NST: No significant (p • 0.05) increase in toxicity due to UVA irradiation. STN: A significant (p • 0.05) increase in toxicity was noted due to UVA irradation. •A significant (p • 0.05) increase in viability was noted after UVA irradiation. b No statistical analysis was done for the yeast assay. MONOLAYER No significant phototoxicity (p • 0.05) was seen in this assay with any of the test ma- terials, including the 8-MOP positive control. The lack of significant phototoxicity with the positive control is attributed to high standard deviations that are inherent in monolayer systems. HTe directional results, however, do indicate phototoxicity of the positive control.