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Ultraviolet A radiation: testing and labeling for sunscreen products
J F Nash1, Paul R Tanner, Paul J Matts
1Central Product Safety, The Procter and Gamble Company, Cincinnati, OH 45241, USA. nash.jf@pg.com
Dermatologic Clinics
|November 29, 2005
Summary
Sunscreen efficacy relies on ultraviolet (UV) filters. Standardized testing, including the Sun Protection Factor (SPF) and broad-spectrum UVA assessment, ensures effective photoprotection for consumers.
Area of Science:
- Dermatology and photobiology.
- Cosmetic science and product formulation.
Background:
- Sunscreen products utilize ultraviolet (UV) filters to reduce skin exposure to solar radiation.
- Evaluating sunscreen efficacy and communicating this to consumers involves complex scientific measures.
Purpose of the Study:
- To outline standardized methods for evaluating sunscreen efficacy.
- To recommend clear communication strategies for sunscreen product labeling.
Main Methods:
- The in vivo Sun Protection Factor (SPF) test is the definitive method for measuring sunscreen efficacy.
- Substrate spectrophotometric measurement of absorbance/transmittance and critical wavelength (λc) calculation assess broad-spectrum (UVA) protection.
Main Results:
- The SPF test remains the singular in vivo method for evaluating sunscreen effectiveness.
- Spectrophotometric measures provide objective data for UVA protection assessment.
Conclusions:
- Sunscreen efficacy should be communicated using an SPF value not exceeding 50.
- A single "broad-spectrum" designation should indicate adequate long-wavelength UVA protection.