Under the Sun

Under the Sun The article by Stacie Zoe Berg1 raises the interesting possibility that exposure to solar UV-B radiation could induce autoimmune diseases. This certainly sounds plausible. We know that prolonged exposure to UV-B causes basal-cell and squamous-cell cancers in susceptible individuals, particularly fair-skinned people. [Melanoma appears to be caused by both UV-B and the much stronger UV-A radiation.] But the report states that autoimmune incidence decreases towards lower latitu

Fred Singer
Jun 15, 2003

Under the Sun


The article by Stacie Zoe Berg1 raises the interesting possibility that exposure to solar UV-B radiation could induce autoimmune diseases. This certainly sounds plausible. We know that prolonged exposure to UV-B causes basal-cell and squamous-cell cancers in susceptible individuals, particularly fair-skinned people. [Melanoma appears to be caused by both UV-B and the much stronger UV-A radiation.]

But the report states that autoimmune incidence decreases towards lower latitudes, whereas UV-B exposure increases strongly towards lower latitudes. Direct measurements indicate an increase of 200-300% in going from northern to southern states. The increase is about 10% in going from Washington, DC, to Richmond, Va. The increase stems from the lower average zenith angle of the sun as one approaches the equator. Combined with a horizontal layer of stratospheric ozone, this leads to reduced absorption of the incident solar UV-B. [UV-A is not absorbed by ozone.]

Skin cancer occurrence...

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