When last we talked, we had discussed the most common type of skin cancer, basal cell carcinoma (BCC) and in order to understand what basal cells are, we talked a little about the structure of the epidermis.  It’s like the bark of a tree, where the new cells form on the inside and then slowly migrate out, dying along the way but toughening into the structure that protects us.

BCC is cancer of the basal cells before they differentiate into true keratinocytes.  Squamous cell carcinoma (SCC) is the cancer of squamous (latin for scaly) cells, which is just another word for the keratinocytes once they differentiate and start to become hard and scaly.  SCC is also caused mainly by UVB rays.  It is less common than BCC, but more likely to spread (metastasize) and therefore more likely to be fatal.

What I didn’t mention yet is that while the epidermis is composed mainly of keratinocytes, it also has other types of cells embedded in it.  The basal layer where the basal cells propagate is also inhabited by cells that produce the pigment of the skin, called melanin.  Hence these cells are called melanocytes.  And, you guess it, the cancer that afflicts these cells is called melanoma.

The name melanoma probably sounds the scariest of these three even if you, like me, didn’t know much about skin cancer before today.  The reason is, melanoma is the biggest killer.  The rarest of the three types of cancer, it is also the worst if you are unlucky enough to get it, responsible for three quarters of all skin cancer deaths.

Because melanoma is the cells that produce pigment run wild, it has a dark appearance.  And like the other two types of skin cancer, it is easier to get for people whose ancestors evolved in higher latitudes where resistance to sunlight is less important.

Unlike the other two main types of skin cancer, melanoma is caused mainly by type A ultraviolet light (UVA).  And with that, our little excursion into biology has told us just about everything we need to know to understand the basic need for sunscreen.

Sunscreen was first developed to block UVB because that was just easier.  Lately sunscreen formulae have been developed that also block UVA, but these are not universal. Part of the problem is that for some time it was thought that UVA rays weren’t harmful and that they only caused tanning, so many products were formulated to allow them through.  And for the same reason, tanning beds were developed that radiated UVA.  It was later discovered that these tanning beds were major causes of melanoma.

Not all sunscreens were clearly labelled as to whether they blocked UVA and how much.  But recently, regulators have caught up to this issue.  Europe has for years required sunscreens to have a “UVA” label if they sufficiently block UVA, and no such label if they don’t.  In the USA, we haven’t been quite so quick about this.  From what I can gather, we’ve been debating new labeling for sunscreen since 1978.  Final rules are finally be implemented this year to require a “Broad Spectrum” designation on the container only if the product sufficiently blocks UVA.

This same rulemaking contains regulations for other labeling as well.  Manufacturers will no longer be able to claim simply “water resistant”, but must either prove such, or put a limited label such as “water resistant for 40 minutes”.  They also can’t claim cancer prevention benefits if the SPF is under 15, and can’t use the word sunblock at all, as it implies more protection than any product can actually give.  And no product can claim to be effective for more than two hours without reapplication unless there is data to back it up.

All of which means that before these rules take effect, you can’t really trust anything you read on a bottle of sunscreen.

With the hole in the ozone layer as one possible cause, the rate of skin cancer has been increasing on a steady basis, despite the fact that many other forms of cancer have become less common.  What can be done to reduce the risk of skin cancer?

One idea I have is to make it more convenient to wear sunscreen.  In their 2008 book Nudge, Richard Thaler and Cass Sunstein make the case that small incentives or even just facilitations have the capability to effect changes in mass behavior.  If there’s a sunscreen dispenser in every restroom, somewhere near the soap, then it will be much easier to put on a dab when needed.

You might go out at 8 am and not think about the sun, but when you’re in the washroom at work at 11:30 about to go have lunch al fresco, you might think to put on some sunscreen if it’s right there.  Sunscreen bought in bulk can’t be much more expensive than soap.  And if people don’t use it, it won’t cost much.  Manufacturers shouldn’t complain that companies are giving away free sunscreen since it still has to be made somewhere.  Only retailers might lose out a bit.

But in the name of public health, this seems like a no-brainer.  Sure, there are many things that would help public health that could be given away for free: vegetables, vitamins, running shoes, pedometers, and cars with collision avoidance systems.  But beyond expense, I don’t think there’s any reason not to do all of these.  And expense for some things is quite small.  So let’s start with those.

I’m not suggesting a big government program.  It could start with employers restrooms as a benefit to employees (and a saving for private insurance provided by those companies).  There could be tax benefits for employers and others that do this in order to nudge the nudgers.  But it could just start with enlightened self-interest.