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There's No Such Thing as a Safe Tan (theconversation.com)
H. Peter Soyer, Professor of Dermatology, and Katie Lee, Research assistant at The University of Queensland, write: There's a lot to be said for sunshine -- both good and bad. It's our main source of vitamin D, which is essential for bone and muscle health. Populations with higher levels of sun exposure also have better blood pressure and mood levels, and fewer autoimmune diseases such as multiple sclerosis. On the other hand, excess UV exposure is estimated to contribute to 95% of melanomas and 99% of non-melanoma skin cancers. These skin cancers account for a whopping 80% of all new cancers each year in Australia.
Like any medicine, the dose counts. And in Australia, particularly in the summer, our dose of UV is so high that even short incidental exposures -- like while you hang out the washing or walk from your carpark into the shops -- adds up to huge lifetime doses. Fortunately, when it comes to tanning, the advice is clear: don't. A UV dose that's high enough to induce a tan is already much higher than the dose needed for vitamin D production. A four-year-long study of 1,113 people in Nambour, Queensland, found no difference in vitamin D levels between sunscreen users and sunscreen avoiders. Further reading: Is Sunscreen the New Margarine?
Like any medicine, the dose counts. And in Australia, particularly in the summer, our dose of UV is so high that even short incidental exposures -- like while you hang out the washing or walk from your carpark into the shops -- adds up to huge lifetime doses. Fortunately, when it comes to tanning, the advice is clear: don't. A UV dose that's high enough to induce a tan is already much higher than the dose needed for vitamin D production. A four-year-long study of 1,113 people in Nambour, Queensland, found no difference in vitamin D levels between sunscreen users and sunscreen avoiders. Further reading: Is Sunscreen the New Margarine?
From what I can tell, about 15,600 Americans die from skin cancer each year. That puts it at a little less than half your risk of dying in a car accident. So rather than turning vampire and avoiding sunlight as much as you can, just employ safe practices. Just like you buckle your seat belt when riding in a car, use sunscreen when going outdoors. Or put another way, if you're going to freak out about this and avoid going into sunlight, you should be doubly-freaked out about riding in a car.
All tans are caused by damage, but not all tans are equal. There are three types of tan:
* Immediate pigment darkening: Rapid onset. Somewhat grayish appearance. Mostly gone within an hour.
* Persistent pigment darkening: Peaks within a couple hours. Mostly gone a day or so afterwards.
* Delayed tanning: Peaks after 4-7 days. Can take over a month to fully disappear.
Most tanning beds use UVA, which penetrates deeper into the skin. It causes all three forms of tanning, although the delayed tanning is not as strong as with UVB. Relative to the "therapeutic" dose, UVA tends to cause the most damage to the skin (UVB is more damaging per joule, but you use significantly less)
UVB (and UVC, although nobody uses that) also causes tanning. It's not generally used in tanning beds because it also causes sunburn (UVA, particularly UVA2, can also cause sunburn, but it's not as prone to as UVB). A particular target region however is NB-UVB (narrowband), which only has 10-20% of the sunburn risk as BB-UVB (broadband, aka, the whole UVB spectrum). UVB does not penetrate as deeply into the skin as UVA. A "therapeutic" NB-UVB dose may cause mild erythema (reddening), but no immediate darkening. This then transitions to a strong delayed tanning response. UVB tans do more to protect against further sunburn than UVA tans.
An argument can be made for switching from UVA tanning to NB-UVB tanning. But one should be clear, both damage the skin. There are medical applications for UVA or NB-UVB exposure (skin conditions like eczema, vitiligo, etc), but vitamin D is not one of them; the safest way to get it is supplements. Indeed, if you only want vitamin D, you don't want either UVA (which contributes virtually nothing) or NB-UVB exposure; you want a band in the 293-300nm region, where vitamin D synthesis is at a maximum. You can use several orders of magnitude less power than you'd use for a NB-UVB tan (and even less still vs. a UVA tan) - just a couple dozen milliwatts per square meter - and still produce daily doses of vitamin D in minutes.
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When the working class was busy toiling in the fields, a tan was considered quite unkempt among the upper echelons.
Now that the working class are stuck in cubicles, a tan is considered quite robust among the upper echelons.
Similarly, being thicker used to be more attractive, because it meant you could eat well. Walking in ridiculous shoes, and having impractically long nails is still considered attractive, because it means you don't have to do any sort of practical labor—not because working is viewed as a bad thing, but rather because most other people cannot afford to maintain those absurdities and thus it makes you stand out.
It's cool to support mass migration, because it means you get to live in a segregated, gated community that is unaffected by the growing presence of the 3rd world in your neighborhood.
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