How many micromorts do you get per UV-index-hour?

post by David Scott Krueger (formerly: capybaralet) (capybaralet) · 2021-03-30T17:23:26.566Z · LW · GW · 4 comments

This is a question post.

Contents

  Answers
    3 Davidmanheim
    1 Underdog
    -4 Gerald Monroe
None
4 comments

I'm trying to get a good estimate of the risks associated with sun exposure.

I'm assuming things scale linearly (the UV index units, which need a name ("UVees"?) are linear).

This may not be a good assumption, but it seems somewhat likely that it would be within the range I most care about (significant exposure, but not enough to get burnt -- if I'd get burnt, I'll certainly cover up or wear sunscreen).

I know sun exposure is a major source of skin cancer risk, but I'm not sure how much of that is coming from people who have tons of exposure, and how much risk a moderate level of exposure actually brings.

 

Answers

answer by Davidmanheim · 2021-03-31T17:04:21.658Z · LW(p) · GW(p)

About 20% of Americans develop skin cancer during their lifetime, and the 5-year overall survival rate for melanoma is over 90 percent. Taking this as the mortality risk, i.e. ignoring timing and varied risk levels, it's a 2% risk of (eventual) death.

But risk of skin cancer depends on far more than sun exposure - and the more important determinant is frequency of sunbathing below age 30. Other factors that seem to matter are skin color, skin response (how much you burn,) weight, and family history of cancers.
 

answer by Underdog · 2021-05-14T19:48:44.084Z · LW(p) · GW(p)

Long story short, good estimates of overall mortality caused by sun exposure and sunburn do not exist. Some studies have even suggested that higher sun exposure reduces overall mortality. Unfortunately there is no answer to your question, but the following article outlines some of the risks and benefits to sun exposure: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5129901/

answer by [deleted] · 2021-03-30T23:43:55.303Z · LW(p) · GW(p)

You're talking about exposure to ionizing radiation.  This means there is a chance each UV photon that hits exactly in the right spot will cause permanent DNA changes that eventually lead to cancer.  So the right answer when asking how many invisible bullets you want to be shot with until one is fatal is "as few as practical".  

You can get vitamin D from a tablet.

Now, yes, a lack of sun may cause depression and you die from that, or other malfunctions, and most humans don't die from skin cancer.  

So I don't see it in terms of 'micromorts', I see it in terms of 'the outdoor activity had better be really fun' and "i'm going to protect myself as much as practical".  

Hanging out on a beach with potential mates?  Worth the risk.  Mowing or weeding your lawn?  I'm gonna wait til dusk or use a lot of protective gear.

↑ comment by Bernhard · 2021-04-10T20:49:29.968Z · LW(p) · GW(p)

each UV photon that hits exactly in the right spot will cause permanent DNA changes that eventually lead to cancer

Pretty sure this is incorrect. It's not the damage that causes cancer, but the failure of the body to heal/repair it. Such failures can be caused for example by you being very old, and therefore healing slower, or by getting a sunburn (= too much exposure in a short time, overwhelming repair capability).

I think the most important thing here is that things scale very much not linearly.

See also this, which argues/claims that more sun exposure (without getting sunburnt) actually leads to less cancer than getting less UV total, but with sunburns:

↑ comment by Josh Jacobson (joshjacobson) · 2021-07-30T19:35:26.169Z · LW(p) · GW(p)

It's not just about Vitamin D. An example:

Liu et al. 201487 found that hypertension is reduced by UVR-induced nitric oxide independent of vitamin D. They showed that stores of nitrogen oxides in the human skin are mobilized to the systemic circulation by exposure of the body to UVA radiation, causing arterial vasodilation and a resultant decrease in blood pressure independent of vitamin D, confirming the hypothesis of Feelisch et al. 2010.88 These results correlate with the findings of Afzal et al. 201477 that genetically low 25(OH)D levels were associated with increased all-cause mortality but not with cardiovascular mortality, indicating that a mediator other than vitamin D may be involved in cardiovascular mortality, and with the results of Tunstall-Pedoe et al. 201589 challenging vitamin D's alleged role in cardiovascular disease.

https://www.tandfonline.com/doi/full/10.1080/19381980.2016.1248325

4 comments

Comments sorted by top scores.

comment by gjm · 2021-03-30T21:28:19.478Z · LW(p) · GW(p)

Note that exposure to UV from sunlight has benefits as well as costs (e.g., vitamin D production). I personally wouldn't want to bet heavily that in the "interesting" range the effect is close to linear, nor that the linear term has the sign you think it has.

Replies from: capybaralet
↑ comment by David Scott Krueger (formerly: capybaralet) (capybaralet) · 2021-03-31T17:30:31.732Z · LW(p) · GW(p)

Oh yeah, sorry I was not clear about this...

I am actually trying to just consider the effects via cancer risk in isolation, and ignoring the potential benefits (which I think do go beyond just Vitamin D... probably a lot of stuff happening that we don't understand... certainly seems to have effect on mood, e.g.)

comment by capisce · 2021-03-31T14:25:10.680Z · LW(p) · GW(p)

Might depend on your polyunsaturated fat intake: https://pubmed.ncbi.nlm.nih.gov/29636341/

Replies from: capybaralet
↑ comment by David Scott Krueger (formerly: capybaralet) (capybaralet) · 2021-03-31T17:29:58.849Z · LW(p) · GW(p)

Thanks!
Looks like just correlations, tho(?)
I basically wouldn't update on a single study that only looks at correlation.