And yet I never use sunscreen. In part, this is because I don't have to worry about sunburns as much as do the fair-haired, and because I have a mild aversion to skin creams and lotions. But it's also because I've never understood how sunscreens work; and because I've long heard rumors of dire side effects: for example, my ex-physiotherapist once told me that sunscreen causes skin cancer.
However, I certainly appreciate the power of ultraviolet (UV) sunlight, which can sunburn, bleach pigments, and sterilize drinking water. So I can't help but wonder: are my coworkers and I really better off without sunscreen?
Like Sunbathing through a Window
Before planting this year I tried to develop a gradual tan, and maybe synthesize a little vitamin D, by doing my studying in short sleeves next to a window. So imagine my surprise when I discovered that most windows are actually opaque to the very portion of the UV spectrum, called UVB, that is primarily responsible for inducing vitamin D synthesis, and for causing tans and sunburns. Catching rays through a window, apparently, is a complete waste of time unless you're cold.But I was even surpriseder when I discovered that most windows are transparent to another portion of the UV spectrum, called UVA, which penetrates more deeply into the skin. Because it does not cause sunburns - or any other acute symptoms - UVA is sometimes referred to as "silent" radiation; however it is now known that both UVA and UVB can cause "photoaging" and cancer. Thus, those who spend much time behind sunny windows, including car door windows, probably absorb more solar radiation than they are aware - in fact, this may help explain why skin cancers in the United States are more common on the left side of the body.
What does that have to do with sunscreen?
Indeed, some observational studies have actually seen a correlation between sunscreen use and an increased risk of melanoma (the deadliest form of skin cancer) and the idea that sunscreen is carcinogenic doubtless owes a favor to these alarming results. But a recent review criticized these studies for their "failure to control for confounding factors" - such as incomplete UVA protection (and the fact that previously high-risk people are more likely to use sunscreen). In other words: these studies do not imply that the chemicals in sunscreens cause cancer; but they may suggest that sunscreen results in riskier behavior. Among others, this may be of interest to those who use so-called "natural" sunscreens in the belief that they are safer.
(Side note: by blocking UVB sunscreens also interfere with vitamin D synthesis, but it's highly doubtful that this is significant for those - like tree planters - who get enough sun to warrant the use of sunscreen.)
Why aren't sunscreens effective against UVA?In defense of the industry, sunscreen manufacturers have traditionally focused on UVB because UVB causes sunburns, and sunburns have long provided the best way to test their products on human skin. Moreover, the dangers posed by UVA haven't always been appreciated; and commercial formulations are always improving.
But it seems fair to say that change has been painfully slow: the Food and Drug Administration (FDA) just recently updated their sunscreen regulations for the first time in over three decades. And although the new regulations include improved UVA standards, these have already seen bitter criticism. Most notably, the Environmental Working Group (EWG) risked making the FDA very sad when it responded that under the new rules even so-called "broad spectrum" sunscreens may not provide sufficient UVA protection, and that
"After 33 years it is evident people just can't trust the FDA on this issue."
Instead, the EWG advises consumers to look past advertised claims like "High SPF" and "broad spectrum" to the ingredients list when attempting to gauge a sunscreen's UVA effectiveness and overall safety.
The Ingredients of Controversy
"No ingredient is without hazard" warns the EWG's online sunscreen guide, and I agree on the grounds that even the most innocuous substance can be hazardous in the wrong circumstances. They also point out that higher SPF ratings often indicate a higher concentration of active ingredients and thus a potentially greater risk of side effects. |
| Half non-nano, half nano zinc sunscreen |
More controversy surrounds UV-absorbing ingredients, although this doesn't appear to be because they're inherently riskier, as is often implied. In particular, despite it's UVA effectiveness, the EWG has singled out oxybenzone as an ingredient to avoid. In part this is due to the fact that it can permeate the skin and mimic the effects of estrogen in the body, and because some people are allergic to it - but only after it's been exposed to sunlight (ie., it's a "photoallergen"). Most alarmingly, the EWG suspects that sunlight could also cause oxybenzone to degrade into cancer-causing free radicals (which, if true, would make it a "photocarcinogen").
But, among others, The Skin Cancer Foundation have begged to differ, saying
"there has never been any evidence that oxybenzone, which has been available for 20 years, has any adverse health effect in humans."Indeed, it appears to be a very weak estrogen mimic, and as such it is arguably insignificant when topically applied (it turns out that many things can mimic estrogen). And although oxybenzone can penetrate the skin, it's expelled in the urine and doesn't accumulate in the body. Most importantly for my purposes here, evidence of its photocarcinogenic potential appears slight (no evidence links it directly to cancer in humans); and in any case oxybenzone-free sunscreens are widely available.
A very similar controversy surrounds a vitamin A derivative called retinyl palmitate, which is often added to sunscreens as a inactive ingredient. It too is widely used to make both cosmetics and foods; and although it too is considered safe by most other authorities, the EWG suspects it of being a photocarcinogen. The basis for this concern appears to be a sinlge unpublished study on hairless mice, and the EWG's interpretation of it's results has been hotly contested. The bottom line: there is no credible link between cancer in humans and retinyl palminate; and sunscreens free of it are available to the wary.
* * *
In the end, my investigation probably won't change my habit of relying on clothing to protect me at work, as I feel I can responsibly manage my sun exposure without sunscreen (besides, oily lotions are scientifically proven to be totally gross, and effective sunscreens have yet to be marketed in the form of a pill).But this is not to give credence to the idea that sunscreens cause cancer, which, despite the sheer number of sunscreen controversies, appears to lack a solid foundation. In fact, it now seems obvious to me that those who actively propagate the notion that sunscreens cause cancer are simply being irresponsible: there is nothing intrinsically wrong with sunscreens as far as I can tell. In part because of this rumor, I have long avoided sunscreens, and I worry it might also discourage those who are in even greater danger from the sun than I. So from now on, when I encounter this rumor I will make a point of asking for justification - I encourage readers do the same.
On the other hand, I am also going to start voicing concern to those of my coworkers who seem to depend too heavily on sunscreen, for I am convinced that clothing should be a prudent tree planter's first line of defense. They're cheap. They're relatively free of controversy and potential side-effects. They're UVA-effective and won't instill a false sense of security. They're unquestionably sweat-proof. And - even among tree planters - there's a smaller danger of their being imperfectly applied.
A special thanks to PM ;)
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