Solar Flares

Shameless self-promotion: I have been very fortunate recently, having been given the opportunity to join the cool cats at Whole9 as a member of their consulting team.  I’ve long admired the work Melissa and Dallas do, the professionalism with which they do it, and the smart people they surround themselves withI’m looking forward to working closely with Melissa, Dallas, Amy, and  Ann and the rest of the Whole9 family.

_______

Before I climb into a few interesting papers I have had laying about for a while, I just want to finish off (read as: close some tabs down), on the sun and tanning topic…

In my last post I referred to the Medical Hypothesis paper suggesting that melanoma risk was highest amongst indoor workers, putting the evidence out of step with the public health message.  Further to the sentiment that it isn’t sensible sun exposure adding to melanoma risk, was a Medscape article from March suggesting that indoor tanning is more a risk factor than sun exposure…

Indoor More Risky Than Outdoor Tanning for Melanoma?

Indoor tanning might be a more reliable predictor of invasive cutaneous melanoma than outdoor sunburns, according to a study presented here at the American Academy of Dermatology 70th Annual Meeting…

…”Outdoor sun exposure means different things to different people,” DeAnn Lazovich, PhD, from the University of Minnesota, Minneapolis, and senior investigator on the study, told Medscape Medical News. “In this study, it is measured by lifetime sunburns, which represents intense intermittent exposure…even if the person had very little regular outdoor exposure.”…

…The study found that 4 UV risk factors were significantly associated with melanoma: outdoor lifetime sunburns, indoor tanning, frequency of indoor tanning, and burns from indoor tanning…

Interestingly, when they further filtered those risk factors for personal risk factors such as age, sex, family history, and phenotypic factors (such as skin type), outdoor lifetime sunburns became much less significant than indoor tanning frequency.

The authors were a bit perplexed by this finding…

“We have never come up with a good explanation for why sun exposure is not more strongly associated with melanoma risk in our study.”

“Whether the UV comes from sun or artificial devices, I think that it likely increases the risk of melanoma in the same range of magnitude — it’s just that we did not find that in our report.”

Perhaps we can help them out a bit…

Another senior investigator on the study, David Polsky, MD, PhD, also from New York University, added that “one difference between outdoor and indoor UV exposure is the wavelengths to which the person is exposed. Indoor tanning uses primarily UVA, and outdoor exposure has both UVA and UVB.

Bingo.  The wavelengths of and balance between UVA and UVB are completely different for indoor tanning beds versus the sun.  Yes, both are ultraviolet radiation emitters, but that is where the similarity should begin and end.  However, we have taken the attitude that because skin cancers can carry a UV signature, then the source of that UV matters not.  But I think that is the wrong approach to take.

A second, more recent Medscape article on the topic of tanning highlights the differences between indoor bed wavelengths and the sun…

Ultraviolet (UV) radiation levels from indoor tanning devices “far exceed those from sunlight,”… “The UVA (long wavelengths, 320–400 nm) output of tanning devices has been shown to be four times higher than the noon sunlight in Washington, DC, during the summer, and the UVB (midrange wavelengths, 290–320 nm) output was twice as high.”

Whilst sunbeds tend to be either UVA or UVB dominant, most would seem to emit their radiation doses at higher intensities than what we might expect to get from natural sun exposure.  Both my previous post, and this post, discuss the balances between UVA and UVB radiation.  Being out in the sun, particularly during the early part of the day and up to about solar noon, seems to see a good balance between these two radiation sources and probably offers a net health benefit.  Regularly baking yourself on sunbeds, or spending large chunks of time indoors before heading out into the afternoon sun to microwave yourself on the beach for a few hours, probably offers a net health risk. Context matters…

3 thoughts on “Solar Flares

  1. Jay Jay

    Hi Jamie,

    I just wanted to add that this topic is way more complex (IMO) than just UVA/UVB ratios. The Sun cranks out radiation from x-rays to RF, and everything in between. The vast majority of that energy occurs in the visible spectrum, with a fairly rapid taper towards both the UV and the IR ranges (which is often touted as evidence that we as a species did indeed evolve under this Sun, but that’s another topic…).

    This is a decent little article that discusses some of this.

    http://www.windows2universe.org/sun/spectrum/multispectral_sun_overview.html

    This article doesn’t touch on the fact that various portions of the atmosphere filter out different frequencies of energy, and this effect varies depending on the angle of the Sun relative to Earth. This effect causes differences in frequency balance across the time of day, year, and at various latitudes.

    Now my point after all of this is, when we are out in natural light, we are bombarded with many types of radiation beyond just UV, and in fact, the UV is swamped by visible, and possibly infrared. So there could be all sorts of protective effects of which we are currently unaware which are associated with the other frequencies of solar radiation.

    So for instance, indoor light is of course heavily skewed toward visible, with minimal UV or IR. Some of the RF and x rays would still hit us though. And tanning bed light is skewed heavily toward UV, with little visible and even less IR. So from an evolutionary perspective, neither exposure would be “normal”.

  2. Claudia Gilbert

    I’m looking forward to getting my copy of the Whole9 book! Very exciting! Great post Jamie!

  3. Dan

    So many variables. I wonder how much more physical activity the outside workers received and whether that gave a measure of protection.

    Either way, I’m worrying less about the sunshine so a big thank you is due!

Comments are closed.