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About aenflex

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  1. I’m not a student, I just have a science question that didn’t seem to fit anywhere else, and the specific sub-forum for those type of questions seems to not have a lot of traffic. Please forgive me if I posted this incorrectly/feel free to move or direct me in the right direction. Small conflict that I’d love to have explained regarding PPD as an accurate measure of UVA1 rays in the spectrum of 340nm - 400nm. UVA1 rays at or above 360nm seem to confer the most damage to skin such as induction of matrix metalloproteinases (i.e., MMPs/collagen degradation enzymes) and secretion of inflammatory cytokines. (1) The Textbook of Cosmetic Dermatology, 2010 Edition, page 201, states that UVA2 is the portion of UVA mostly represented in the PPD testing. (2) Prompting the FDA to propose augmenting the PPD test with additional additional in vitro testing that provides a measure of UVA1 protection, specifically the ratio of UVA1 absorbance to total UV absorbance - which, incidentally, I believe is how it’s measured here in the UK. Another paper in Sunscreens: Development: Evaluation, and Regulatory Aspects: Second Edition, directly states (p. 570) that About 7% of the total PPD response is ascribed to UVA2 and 92% to UVA1.(3) These two items above seem to conflict directly. The last piece of information I found that might be helpful is below. ‘The action spectrum of PPD is maximum at short UVA wavelengths and gradually decreases from 320 to 400 nm.’ (4) Since UVA1 long rays begin at 340nm, and rays at or beyond 360nn seem to confer the most damage to skin, I take that to mean PPD is not an entirely accurate measure of protection against upper-end of spectrum UVA1 rays. Please help me parse this out. I would greatly appreciate it. (1) Vielhaber G, Grether-Beck S, Koch O, et al. Sunscreens with an absorption maximum of≥ 360 nm provide optimal protection against UVA1-induced expression of matrix metalloproteinase-1, interleukin-1, and interleukin-6 in human dermal fibroblasts. Photochemical & Photobiological Sciences. 2006;5(3):275–82.!divAbstract (2) (3) (4)