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I think this might be a good place to add this reminder:

"Vitamin D is made when UV (more precisely, UVB rays) react with a compound (7-dehydrocholesterol) in the skin. The best rays for UV synthesis have wavelengths between 270–300 nm." [1]

[1] https://www.sciencelearn.org.nz/resources/1313-vitamin-d-and...

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270nm is UVC territory. Did you mean 280nm instead?

That is a fair question. This is what I find. [1]

Ultraviolet B UV‑B 280–315

Ultraviolet C UV‑C 100–280

[1] https://en.wikipedia.org/wiki/Ultraviolet

My read is "UVB" is the popular medicine way of saying UV is needed for the body to synthesize vitamin D. It was not considered necessary to point out part of the useful spectrum is in "UVC" territory.

Also kills microbes on surfaces.

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