“Contra Byrnes on UV & Cancer” by HedonicEscalator

In his recent LessWrong post, Some takes on UV & cancer, Steve Byrnes comes out against the "Public Health Orthodoxy" on UV. Among other topics I won't be addressing, Brynes claims that non-sunburn sun exposure does not increase risk of skin cancer, and suggests that people should aim to "wean off" sunscreen and develop a permanent tan.[1] Brynes is wrong and his advice is dangerous. Non-sunburn UV exposure causes cancer Our mechanistic understanding of UV-induced carcinogenesis is consistent with non-sunburn exposure causing cancer We have a pretty solid understanding of how and why sun exposure causes cancer. UVB exposure causes direct DNA damage, whereas UVA causes damage primarily through oxidative stress.[2] Both of these pathways involve the formation of abnormal structures in DNA called photoproducts, such as cyclobutane pyrimidine dimers (CPDs). CPDs are a primary cause of melanoma.[3] CPDs do not require sunburn to form. For example, look at the second graph of Figure 4 of Miyamura et al. 2010, a small (n=7) study on the tanning process.[4] The black boxes show CPD presence after repeated sub-sunburn threshold UV exposure, designed to induce tanning. The red boxes show CPD presence after another exposure to 2 MED UV.[5] The [...] ---Outline:(00:34) Non-sunburn UV exposure causes cancer(00:39) Our mechanistic understanding of UV-induced carcinogenesis is consistent with non-sunburn exposure causing cancer(02:31) Empirical observations of indoor tanning provide evidence that non-sunburn exposure causes cancer(04:04) Rebuttals to specific arguments from Brynes(04:22) Sunscreen/cancer correlation studies do not control for sun exposure, but randomized trials support sunscreen use(06:23) Skin color variation demonstrates strong evolutionary pressure to mitigate UV damage(07:30) Carcinogens rarely exhibit linear dose-response relationships, and occupational exposure data is hopelessly muddled(10:31) Conclusion(10:34) Subject-level takeaways(11:10) Meta-level takeaways(11:20) Prioritize mechanistic understanding(11:47) Beware the streetlight effect(12:32) The orthodoxy is usually right The original text contained 15 footnotes which were omitted from this narration. --- First published: April 14th, 2026 Source: https://www.lesswrong.com/posts/EFiCGc3YwadZBzvZ3/contra-byrnes-on-uv-and-cancer --- Narrated by TYPE III AUDIO. ---Images from the article:Apple Podcasts and Spotify do not show images in the episode description. Try Pocket Casts, or another podcast app.