Meridian Star

June 11, 2013

When did sunscreen get so complicated?

By Melinda Wenner Moyer
Slate.com

— Summer is almost here, which means it's time for picnics, pool parties, and every parent's favorite pastime: chasing after your kid with the sunscreen bottle. But what's arguably more arduous than slathering lotion onto a screaming 3-year-old is choosing the right sunscreen.

Not only are we presented with hundreds of choices — cool mist or lotion, sensitive skin or extra sensitive skin, SPF 30 or 50 or 75 — many are apparently unsafe, too. Some critics warn that sunscreens can cause cancer while others claim that certain ingredients increase the risk of infertility. Dr. Oz says your sunscreen might be poisonous. In its 2013 Guide to Sunscreens, the nonprofit Environmental Working Group says that only 25 percent of sunscreens on the market are "free of ingredients with serious safety concerns." So should we keep our kids indoors for the next three months?

There is some scientific evidence to support the safety risks, but it's hardly conclusive. Many media outlets have overinterpreted research results, making broad statements that don't reflect what scientists actually know. Plus, while there is research to support avoiding controversial ingredients like oxybenzone and retinyl palmitate (the Environmental Working Group's guide is an excellent resource for identifying sunscreens without them), some experts warn that other sunscreen compounds could pose similar risks we don't yet know about because only a few have been extensively studied.

It helps to have a short primer on sunscreen and how it works. By far the most popular sunscreens are the "organic" ones, so-called because they contain carbon, not because they were grown without pesticides or on a free-range farm. These include most Coppertone and Banana Boat products. These sunscreens protect us from harmful ultraviolet (UV) radiation by absorbing rays before they penetrate deep into our skin. (Not all organic sunscreens absorb both UVA and UVB rays, which have different wavelengths, so it's important to pick "broad spectrum" versions that protect against both types.)

Inorganic "mineral" sunscreens, on the other hand, typically comprise coated titanium dioxide, zinc oxide or a combination of the two. These formulations, found in Badger and California Baby products, typically reflect or scatter UVA and UVB rays.

Organic sunscreens often contain oxybenzone. One of the most well-publicized claims about oxybenzone, also an ingredient in some cosmetics and in plastic food packaging, is that it disrupts hormones to potentially harmful levels. A 2008 study found traces of oxybenzone in the urine of 96.8 percent of a representative sample of the U.S. population, which suggests the molecule is widely used and is absorbed into the body after being applied onto the skin.

But how confident can we be that its hormone-changing effects are actually harming us? Most studies have been conducted on cells or animals and are difficult to draw conclusions from. One study, for instance, found uterine changes in rats that were fed extremely high doses of oxybenzone and other organic sunscreens, but people don't typically eat sunscreen for lunch.

One 2004 intervention study was, however, conducted in humans. Researchers repeatedly measured blood hormone levels in 32 people before and after they applied lotion that contained two commonly used organic U.S. sunscreen ingredients. The subjects' blood levels of several hormones, including testosterone, changed after using the lotion. But the hormone differences were found only at certain times after lotion application, leading researchers to conclude that the changes "did not seem to be related to the exposure to sunscreen compounds."

Organic sunscreens have another potential downside: When they absorb UV light, they become "excited" and unstable. Research has shown that the common sunscreen ingredients oxybenzone, octocrylene, and octylmethoxycinnamate (OMC) dissipate that extra energy in ways that lead to the production of molecules called reactive oxygen species that could damage the lower layers of skin and our DNA. This finding is ironic, because UV light is thought to increase the risk of cancer and accelerate aging in part because it does the exact same thing. You cannot win.

But remember that UV light also produces these damaging molecules after penetrating unprotected skin. And researchers argue that if you re-apply sunscreen, as you're supposed to, these potentially damaging effects of reactive oxygen species could be mitigated because re-application prevents UV rays from reaching the sunscreen molecules that have penetrated deepest into the skin. Sunscreen manufacturers also try to optimize their formulations so that they stay on the surface of the skin rather than penetrating deep as they did in some of these experiments.

Some sunscreen companies add antioxidants like vitamin E and vitamin C to their formulations to absorb some of these reactive compounds. One 2011 study found that the addition of antioxidants to SPF 15 or 50 sunscreen formulations reduced the numbers of reactive oxygen species in skin more than two-fold. (To find sunscreens with added antioxidants, look for inactive ingredients such as sodium ascorbyl phosphate, tocopherol, tocopheryl acetate or diethylhexyl syringylidenemalonate.)

But antioxidants don't always behave as expected, bringing us to another sunscreen controversy. Retinyl palmitate, a form of vitamin A, is an antioxidant added to many sunscreens and cosmetics (it's also used to fortify some dairy products and cereals). Although the FDA considers retinyl palmitate to be safe, research suggests that upon interaction with UVA light, the compound produces reactive oxygen species. Yes, that's correct: An antioxidant added to organic sunscreens to help quench these potentially damaging reactive molecules is actually producing them instead. When's winter?

Retinyl palmitate has gotten an especially bad reputation lately because of a series of studies (yet to be published, but available online) conducted by the National Institute of Health's national toxicology program. Researchers there slathered mice with a retinyl palmitate lotion and then exposed them to different amounts of UV light. Some of the treated mice developed a greater number of malignant tumors than mice that weren't given the cream, but it's hard to know how to interpret the results in part because the mice had all been genetically engineered to be predisposed to cancer. Mice also have extremely thin skin, so compared to humans, UV light probably penetrates more easily into their lower skin layers.

At this point you might be thinking that the best solution is to just buy only non-organic, mineral-based sunscreens. Maybe, but these aren't perfect, either. Although most mineral sunscreens don't absorb UV light — the molecules sit on top of the skin and reflect or scatter the rays _they leave a white, greasy film on the skin that many people find annoying. Yes, annoying sounds preferable to damaging, but the only way sunscreen works is if your kids apply it. The less thick and greasy, the better. Newer "nano" formulations of these mineral sunscreens are much more pleasant, but they don't reflect UV light as effectively — and they also absorb UV light in addition to reflecting it, which means they too can produce reactive oxygen species.

As for SPF, most dermatologists and the Environmental Working Group now recommend avoiding anything above 50 because they give us a false sense of security, so we stay out longer while forgoing necessary reapplication. The numbers are deceiving anyway: SPF 50 protects against 98 percent of the UVB rays, but SPF 30 protects against 97 percent of them — not exactly a critical difference.

And what about application method-sprays, gels, wipes, or old-fashioned lotions? The Environmental Working Group warns against sprays because of the risk that the chemicals could be inhaled or get into the eyes. But if your child won't let you near her with anything but a cool mist, by all means use it-just ask him to hold his breath and close his eyes as you apply it. The EWG also warns against combination sunscreen/bug sprays, which may increase absorption of the repellant chemicals, and sunscreen wipes, which might not deliver adequate protection.

As for all the other sunscreen chemicals you might see listed on the back of your bottle: They have been FDA-approved, so they have been tested for safety to a certain degree, but few academic scientists have independently assessed their potential health effects because it's difficult to get funded for such studies.

"The funding agencies that we've submitted to have said that this is something that industry should fund, but industry has cut [budgets for] research and development," explains Kerry Hanson, a chemist and sunscreen researcher at the University of California at Riverside. As a result, so-called "safe" sunscreen ingredients may simply be the ones that haven't been as thoroughly researched.

The one thing that is clear is that any sunscreen is far better than no sunscreen_ sunburns, especially in children, are much more dangerous than a little oxybenzone or retinyl palmitate. That said, don't rely on sunscreen to do all the work. If your family spends lots of time outside, invest in sun hats and sun-protective clothes, which pose no known risks except maybe to your bank account.