264 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS • 15 • lO z• o v/-/• 4 Min • õ Min 0.5 1 1.5 2 3 4 5 6 24 TIME in Hours Figure 3. Mean a* chromaticity coordinate values at each observation time for 4- and 8-minute mustard vapor exposures on hairless guinea pigs. N = 33 error bars = _+ 95% confidence intervals. Draize scores and the measured Chroma Meter values. The Spearman correlation coeffi- cient was calculated to be 1.00, and it is statistically significant. The time course of developing erythema as measured by the mean Chroma Meter a* values for the 4- and 8-minute HD vapor exposures is illustrated in Figure 3. The 95% confidence intervals and the corresponding Draize scores are also included on the bar graph. These data indicate that erythema was first observed at about 2 hours and reached a maximum between 4 and 6 hours. By 24 hours there was a slight decrease. At the 6-hour observation time the mean a* Chroma Meter values of the 4- and 8-minute HD exposures were 15.0 and 16.7, while the median Draize scores were 3 and 4, respectively. This represented a significant difference at the 95% level. Other analytical methods of lesion evaluation, including high-resolution ultrasound, laser Doppler flow measurements, and transepidermal water loss, would be useful but are not yet available in our laboratory. We plan to acquire and evaluate these methods in the future. CONCLUSIONS We have demonstrated that the Minolta CR-200 Chroma Meter is capable of providing a reproducible and quantitative assessment of the degree of erythema produced on the skin of euthymic hairless guinea pigs exposed to HD vapor. Furthermore, the a* chro- maticity coordinate very closely parallels the visual Draize scores. We have demon- strated for the first time that an objective analytical method can be used for the assess- ment of skin damage caused by HD exposure. We plan to develop this technique into a validated in vivo model for the assessment of antivesicant prophylactic and therapeutic drugs.

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