“ The current CIE previtamin D3 action spectrum is valid for 25(OH)D3 induced by two diverse solar-simulated sources but not for sources containing nonsolar UVB, which are widely used in laboratory studies. Thus, published risk/benefit solar UVR calculations using the CIE ac- tion spectra for erythema and previtamin D3 are likely to be valid, though this remains to be tested. Nonetheless, an improved action spectrum based on serum 25(OH)D3, rather than cutaneous previtamin D3, will result in more refined assessments of risks and benefits of solar exposure that should result in better public health advice. In contrast, the CIE previtamin D3 action spectrum is not valid when using broad-spectrum sources with nonsolar UVB wavelengths” from the full paper at
https://www.pnas.org/content/pnas/118/40/e2015867118.full.pd...