Determination of UVA protection factors using the persistent pigment darkening (PPD) as the end point. (Part 1). Calibration of the method.
OBJECTIVE
The accuracy and reliability of any method to assess the UVA protection effectiveness of sunscreens needs to be demonstrated. The aim of the present study was to calibrate the effectiveness of a biological end point (Persistent Pigment Darkening, PPD) to assess UVA photoprotection,


METHODS
Persistent Pigment Darkening was selected as the end point because its action spectrum extends across the UVA. A broad UVA source was chosen to challenge all UVA wavelengths. Attenuation of UVA was performed with neutral density filters (equally absorbing at all wavelengths). Human subjects were tested with a series of UVA beams attenuated by the neutral density filters. The UVA protection effectiveness of a standard sunscreen was also tested with four panels of volunteers to assess the reproducibility of the method.


RESULTS
The attenuation factors of the neutral density filters were found to correspond to the UVA protection factors arrived at with PPD as the end point. The repetitive tests showed a good internal consistency of the method.


CONCLUSIONS
The calibration procedure proposed shows threshold PPD, used as an end point in a UVA-PF test method, to be a reliable endogenous dosimeter for UVA radiation that enters the skin.
Moyal
D
D
L'Oréal Research, Clichy, France.
Chardon
A
A
Kollias
N
N
D002138:Calibration; D023381:Endpoint Determination; D006801:Humans; D011837:Radiation-Protective Agents; D015203:Reproducibility of Results; D012867:Skin / Q000528:radiation effects*; D012880:Skin Pigmentation / Q000528:radiation effects*; D013473:Sunscreening Agents; D014466:Ultraviolet Rays / Q000009:adverse effects
D011837:Radiation-Protective Agents; D013473:Sunscreening Agents