Determining in vitro effectiveness of protection of product against exposure to sun's rays involves considering behavior of product while exposed to sunlight

摘要

A photobiological cutaneous phenomenon is caused by exposure to the sun's rays over an operating spectrum S(lambda). The method includes determining a dynamic absorption spectrum DO(lambda,t) showing the product's absorption spectrum as a function of the duration of exposure to an ultraviolet light source, and calculating the effectiveness of the product's protection The effectiveness of protection is determined by the ratio (tintegral lambdaintegralS(lambda).I(lambda).dlambda.dt)/ (tintegral lambdaintegralS(lambda).I(lambda).10(-c.DO(lambda,t))dlambda.dt) where I(lambda) is the spectral radiance received from the source by the support and c is a constant, calculated so that SPFr = (integralt=0 tmax integrallambda=290nm 400nm e(lambda). I(lambda). dlambda.dt)/ (integralt=0 tmax integrallambda=290nm 400nm e(lambda). I(lambda). 10(-c.DO(lambda,t)).dlambda.dt) is equal to SPF in vivo, tmax being the time required for the transmitted erythemal dose to be equal to the minimum erythemal dose DEM and E(lambda) being the erythemal action spectrum. To determine the dynamic absorption spectrum DO(lambda,t), the absorption spectrum DO(lambda,t) is measured after different exposure times t to the light source and the absorption spectra are adjusted relative to each other to make the optical densities DO(lambda',t) equal for a particular value lambda' of the wavelength where lambda' is 290nm, most preferably 260-270nm. The action spectrum S(lambda) is that of immediate persistent pigmentation P(lambda) and a protection factor APF against UVA is calculated using the formula APFr = (integralt=0 t=k.tmax integrallambda=320nm 400nm e(lambda). I(lambda). dlambda.dt)/ (integralt=0 t=k.tmax integrallambda=320nm 400nm e(lambda). I(lambda). 10(-c.DO(lambdat)).dlambda.dt) where k is a non-zero constant, preferably between 0.5 and 3 and in particular k=2. An Independent claim is included for a method of determining the dynamic absorption spectrum DO(lambda,t) of a photosensitive product where one seeks to know the effectiveness of protection relative to a photobiological phenomenon with an active spectrum S(lambda), measuring the absorption spectrum SO(lambda,t) after different exposure times t to a constant ultraviolet source and adjusting the spectra relative to each other to make the optical densities DO(lambda',t) equal for a particular value of the wavelength lambda' where lambda' is 290nm, most preferably 260-270nm.