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06:24
Minimal Erythema Dose (MED) Testing
Published on: May 28, 2013
At what time should one go out in the sun?
Johan Moan1, Arne Dahlback, Alina Carmen Porojnicu
1Department of Radiation Biology, Institute for Cancer Research, Montebello, Oslo, Norway. johan.moan@labmed.uio.no
Advances in Experimental Medicine and Biology
|March 20, 2008
Summary
Optimal sun exposure for vitamin D synthesis and minimal cutaneous malignant melanoma (CMM) risk occurs around noon. Current advice to avoid midday sun may inadvertently increase CMM risk by promoting longer afternoon exposures.
Area of Science:
- Dermatology
- Photobiology
- Public Health
Background:
- Current public health guidelines often recommend avoiding midday sun exposure.
- This advice is based on the assumption of uniform ultraviolet radiation (UVR) effects and risks.
- The differing action spectra and atmospheric scattering properties of UVA and UVB are often overlooked.
Purpose of the Study:
- To reassess optimal sun exposure timing for vitamin D synthesis while minimizing cutaneous malignant melanoma (CMM) risk.
- To challenge conventional recommendations regarding midday sun avoidance.
- To investigate the differential effects of UVA and UVB radiation based on wavelength and body geometry.
Main Methods:
- Analysis of the action spectrum for CMM versus vitamin D production (UVB).
- Consideration of Rayleigh scattering effects on UVA and UVB transmission.
- Application of a vertical cylinder model for human body UVR exposure, contrasting with traditional planar models.
Main Results:
- Cutaneous malignant melanoma (CMM) risk is primarily associated with longer UVA wavelengths, while vitamin D synthesis relies on shorter UVB wavelengths.
- UVA radiation penetrates the atmosphere more directly than UVB due to less scattering.
- The vertical cylinder model indicates that high UVA exposure persists longer post-noon compared to UVB.
Conclusions:
- Short, non-erythematogenic sun exposures around noon maximize vitamin D production with minimal CMM risk.
- Conventional recommendations to avoid midday sun and favor afternoon exposure may be counterproductive, potentially increasing CMM risk.
- Revised public health guidance should emphasize brief midday sunning for optimal vitamin D benefits and reduced melanoma risk.
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