Sunday, May 30, 2010

Do sunscreens cause cancer?

Being a parent is a harrowing task. In addition to worrying about the practical things - is my child eating enough, or learning to walk or speak fast enough - there are a whole host of less tangible concerns we modern parents are presented with:

Do my baby's bottles contain bisphenol A? Do his pacifiers contain phthalates? Are his veggies laced with pesticides? If all of the above is true, does it actually make the blindest bit of difference?

The latest worry I developed this evening, when a well-informed and extremely credible family member raised concerns about sunscreen. Like any concerned parent, I lather the stuff on Mini Militant - not least of which because his pale and interesting Anglo-Scots genes probably cancel out his leathery Italian-Jewish ones.

But recently, the media has jumped on concerns that some of the ingredients in sunscreen have been linked to increased risks of malignant melanoma in mice.

A scientific study has shown that if you lather mice in sunscreen and shove them under a sunlamp, an increased percentage of them develop a rarer, but more deadly form of skin cancer than the 'control' group.

Cue gasps of horrors and concern - and not without good reason. Malignant melanoma might be a much rarer form of skin cancer, but it's also much more deadly - responsible for 75% of skin cancer deaths.

But this is where the issue gets tricky - because the mice in that 'control' group I mentioned - the ones who were shoved under a sunlamp without lathering them in sunscreen first - continued to show a literally blistering higher percentage of squamous cell carcinoma and basal cell carcinoma than the mice who were wearing the SPF 15.

Which presents the most significant flaw in the 'sunscreens may cause cancer' argument - that not wearing sunscreen definitely causes cancer.

And here's were it gets really tricky - because the only solution to the sunscreen dilemma appears to be to stay out of the sunlight altogether - and that has been linked to the skyrocketing rates of Vitamin D deficiency in western society (which - no joke - has also been linked to increased rates of cancer.)

So just to recap:
  1. Wearing sunscreen presents an increased risk of cancer.
  2. Not wearing sunscreen presents an increased risk of cancer.
  3. Not going out into the sunlight at all presents an increased risk of cancer.
As Shakespeare probably paraphrased: "Thou art screwest if thou dost, yet thou art screwest if thou dost not."

Ultimately, there's a lot more to the 'does sunscreen cause cancer issue' than the terrifying headlines would have you believe - and ultimately the solution is not to send your tender-fleshed children out into the broiling sun without some SPF 15 on.

Let's Get Cooking

Exposure to the sun's ultraviolet sunlight causes cancer - of that there is no doubt whatsoever.

But when it comes to the recent concerns about sunscreen, there's quite a lot of doubt indeed.

The issue basically boils down into three areas:
  1. That some of the ingredients in sunscreen cause cancer.
  2. That sunscreen is less of a protection against skin cancer than advertised.
  3. That it increases your risk for cancer by increasing the risk of Vitamin D deficiency.
Let's actually examine those issues one-by-one.

Some of the ingredients in sunscreen cause cancer.

Oxybenzone, benzophenone, octocrylene, or octyl methoxycinnamate are all popular ingredients in sunscreen - and concerns have been raised that the way they're absorbed by the body - and then illuminated with the sun's UV radiation - increase the risk of malignant melanoma.

This theory partly came about from a Journal of National Cancer Research study called Effect of Sunscreens on UV Radiation-Induced Enhancement of Melanoma Growth in Mice by Doctors P. Wolf, C.K. Donawho and M.L. Kripke.

The only problem with this study is that it contradicts every other animal study - each of which showed the use of sunscreen reducing the risk for animals developing malignant melanomas after exposure to ultraviolet radiation.

Basically, one study doesn't cancel out a number of other ones (unless that one happens to be correct, but unless you're a oncologist or a dermatologist, I argue you're not qualified to make that call.)

Sunscreen is less of a protection against skin cancer than advertised.

While Wolf et. al. didn't reach a consensus with the majority of medical research on malignant melanomas, their study did match other reports that sunscreen-slathered test subjects did indeed experience some negative effects from long-term sun exposure.

"Mice to which sunscreens were applied never obtained a sunburn after UV exposure," wrote Dr. H.C. Wulf in his 1982 study Sunscreens for delay of ultraviolet induction of skin tumors. However, he also admitted: "Toxic reactions, such as eczematous-like skin reactions, dark coloring, and amyloidosis, were observed predominantly in the group treated with the sunscreen of highest SPF value."

This, he and his colleagues eventually concluded, was because many sunscreens protect against some of the effects of the sun's ultraviolet rays - but not all of them.

UV radiation is split into two types - A and B.

B is the stuff that causes squamous cell carcinoma and basal cell carcinoma - the two most common forms of skin cancer. It's also the stuff sunscreen protects you from.

UV-A radiation also has negative effects - like skin aging, discoloration and the increased risk of malignant melanoma - the more serious type of cancer everybody is worried about. The problem with many sunscreens is that they don't protect against UV-A radiation.

This becomes a problem because nature's way of telling you you've been out in the sun too long - sunburn and blistering - doesn't happen when you're wearing sunscreen. This results in sunscreen wearers exposing themselves to hours more UV-A radiation than they would if they weren't wearing any sunblock at all.

Ultimately, this is a very serious issue - and an important one to be aware of - but it's not so much that the chemical ingredients of sunblock cause cancer; but that sunscreen manufacturers lead us to believe we can spend much longer in the sun than we actually can, even if we think we have protected ourselves from burning with their products.

(Incidentally, a bunch of class action lawsuits claiming exactly that have recently been launched.)

Sunscreen increases your risk for cancer by increasing the risk of Vitamin D deficiency.

The human body has a few neat tricks up its sleeve - and one of them is converting nutrients into Vitamin D through a chemical reaction brought about by exposure to the sun's UV radiation. Basically, just like a flower, you need the sun for your body to grow properly.

The toils of modern life have presented us with all sorts of new medical problems to solve, but one of the most ridiculous is the explosion of cases of hypovitaminosis D - or Vitamin D deficiency. More and more people are going to their doctors complaining about symptoms like depression, weight-gain, blood sugar irregularities, poor liver function and even bone density loss - all eventually attributed to unusually low levels of Vitamin D in their body.

This is because they simply didn't get enough sun!

Long working hours, cramped offices and gloomy living spaces are one reason humans don't get the same exposure to the sun's light as they used to - but the emerging popularity of sunscreen is another factor. In the past few decades, the message to 'never go out without suncreen' has been so drummed into us that people slather themselves up to a ridiculous degree - and the problem with wearing all that sunscreen to 'protect' yourself from the sun is that it cancels out the entirely natural, entirely healthy and actually essential chemical reactions that UV radiation causes upon exposure to your skin.

The message is - go outside and get some damn sun!


You can take away what you will from the evidence I've presented. There's nothing stupid about being concerned with the safety or efficiency of sunscreen - especially as a parent - but ultimately the news reports shouldn't be what guides your decision to use suncream or not; merely the catalyst that gets you to do some research into the issue yourself.

And for me, this research confirmed that the 'sunscreen controversy' was just the latest health-scare du jour. Sadly, it won't be the last. That's not to say it didn't raise issues we should be aware of. My analysis is this:
  • Firstly, if the ingredients of sunscreen do increase your risk of melanoma (and that's a big 'if') then you have to weigh that against the scientific certainty that not wearing sunscreen dramatically increases your risk of squamous cell carcinoma and basal cell carcinoma. One is more dangerous, sure - but the others are far more common.
  • Secondly, while this hysteria about sunscreen shouldn't make you stop using the stuff, it definitely should make you a little more conscious of just how much protection sunscreen really gives you. All sunscreens protect against UV-B, but many don't protect against UV-A - so just because you're slathered in SPF 15, it doesn't mean you're truly safe. It's not the fault of the sunscreen, more the wearer. It would be like a cop wearing a bullet-proof jacket and then complaining when he gets stabbed. Sunscreen does the job it's designed to do wonderfully - but doesn't protect you against everything.
  • And finally, blaming sunscreen for possibly causing cancer is a dubious proposition because it's been definitely proven to prevent cancer. This recent scare about sunscreen is part of an increasing trend to label every single aspect of modern existence as 'carcinogenic' (although arguably, it is.)
That last issue is the most important one. These days, you're told that everything causes cancer. You shouldn't microwave food, or use non-stick frying pans, or eat soy - all because a single study claimed that it might cause cancer.

And in all honesty, breathing might cause cancer. We suck in engine fumes, and pesticides, and the exhaust gases of our air conditioners and space heaters for days on end and our lungs are a like a sponge for all sorts of carcinogens we simply can't avoid (or don't want to avoid.)

We don't complain about these cancer-causing conveniences because we don't want to live without them - and perhaps that's the attitude we ought to take with sunscreen (amongst other things.)

After all - I've just argued that breathing is the leading cause of cancer - and you're not going to stop doing that any time soon, are you?


ashley said...

excellent post, Rols.

Eve said...

I try not to worry too much about it one way or another.

I do have to be careful. The Swedish/Russian/Polish/English/Irish/Scottish/Welsh/possibly German portion of my genetic makeup equals PALE! Though I do seem to get a little melanin assistance from the little bit of Jewish/Spanish/slight hint of Native American genes I have. I don't bother with sunscreen if I'm just going to be in the sun for short or intermittent periods of time. Depending on the day, I can handle 30 minutes to an hour of direct sun before burning noticeably. I use sunscreen if I'm going to be out in direct sun for longer than that, like when I'm running around on the beach in a swimsuit.

Occasionally I will actually let myself burn very slightly before I put sunscreen on (usually in the beginning of May). As soon as I see pink, it goes on. The mini-tan it turns into helps a lot with not burning badly throughout the rest of the summer. Otherwise I WILL burn even with sunscreen on.

I don't worry about cancer. I try not to do anything too stupid, like trying to suntan, or letting myself turn lobster-red (everything in moderation!). The rest is up to chance. Either I'll get cancer, or I won't, but being paranoid about it won't do me any good.

Julia said...

The Environmental Working Group has a great sunscreen section on its website that takes all the hard work out of finding an effective, non-toxic sunscreen: