The question of what kind of sun exposure leads to visible skin aging is an empiric one. Saying “We err on the cautious side and assume that an arbitrary value of 0.5 SED could be regarded as an acceptable daily erythemal exposure” does not imply that there’s no visible skin aging under that arbitrary value.
Of course, but there reaches a level of sun exposure at which the marginal increased harm becomes negligible compared to other things that damage your skin (see this meta-analysis—photo-aging is just one component among many), and below that level you’re probably actually getting suboptimal levels of UV exposure for skin health (see this article for benefits of UV—from Norway, aptly).
I’d love to see someone try to measure and compare the specific trade-offs, but I strongly suspect that people at northern latitudes should just trust common sense—only wear sunscreen in summer months, and when you’re actually exposed to the sun for extended periods.
The question of what kind of sun exposure leads to visible skin aging is an empiric one. Saying “We err on the cautious side and assume that an arbitrary value of 0.5 SED could be regarded as an acceptable daily erythemal exposure” does not imply that there’s no visible skin aging under that arbitrary value.
Of course, but there reaches a level of sun exposure at which the marginal increased harm becomes negligible compared to other things that damage your skin (see this meta-analysis—photo-aging is just one component among many), and below that level you’re probably actually getting suboptimal levels of UV exposure for skin health (see this article for benefits of UV—from Norway, aptly).
I’d love to see someone try to measure and compare the specific trade-offs, but I strongly suspect that people at northern latitudes should just trust common sense—only wear sunscreen in summer months, and when you’re actually exposed to the sun for extended periods.