Spectral comparison of solar simulators and sunlight

Area of Science:

• Photobiology
• Dermatology
• Optical Engineering

Background:

• Sunscreen efficacy testing relies on accurate simulation of solar ultraviolet radiation (UVR).
• Spectral distribution of irradiation sources can significantly influence Sun Protection Factor (SPF) measurements.
• Variability in UV spectral irradiance among testing laboratories can lead to inconsistent SPF estimates.

Purpose of the Study:

• To assess the spectral irradiance uniformity of solar simulators used in SPF testing.
• To compare solar simulator spectra with natural sunlight UVR.
• To establish performance limits for UV sources to minimize SPF variability.

Main Methods:

• Measured spectral irradiance of 26 solar simulators and UV sources.
• Compared measurements to a standard summer noon solar spectrum (Albuquerque, NM).
• Defined critical UVB region (280-320 nm) for erythemogenic effects.

Main Results:

• Xenon-arc solar simulators in the US generally meet proposed spectral standards or can be modified.
• Devices with non-solar spectral characteristics do not meet proposed standards.
• A 6-nm acceptance band centered on the standard spectrum was proposed.

Conclusions:

• Standardized spectral irradiance is crucial for reliable sunscreen SPF testing.
• Xenon-arc simulators are suitable for SPF testing with potential modifications.
• Non-conforming UV sources should not be used for sunscreen SPF evaluation.