Even the most diligent, well-intentioned daily sunscreen wearers are likely doing it wrong.
The most popular WSJ.com post this past week was about sunscreen, in which it observed: “Even the most diligent, well-intentioned daily sunscreen wearers are likely doing it wrong.” It’s disturbingly easy to get it wrong, and the problem lies more with a deluge of information, sometimes conflicting, on the subject rather than a lack of it. This post sheds some light on the important factors to take into account when choosing and using a sunscreen.
Not all UV rays reach the earth and therefore your skin. Some UVB rays are absorbed by the earth’s ozone layer while 97% of the radiation that reaches the earth’s surface is UVA. This is important to note because up until recently, most sunscreens only addressed UVB radiation.
UVB rays are shorter-wave length, higher energy waves. They penetrate to the epidermis, cause burning and are carcinogenic because they damage DNA. UVB exposure is related to how many short waves penetrate the earth’s atmosphere at any given time. Most burning occurs during summer between the hours of 10 and 4. High altitudes, proximity to the equator and reflected rays (from snow or water) also heighten the risk of burning.
UVA rays are long wave-length, low energy waves. They penetrate to the dermis and are present from sunup to sundown. They are responsible for skin aging effects like hyperpigmentation and wrinkles. Studies suggest that UVA rays are not only more carcinogenic than UVB rays (see DNA damage induced in cells by gamma and UVA radiation), but they are more dangerous due to their association with the deadliest form of skin cancer, melanoma. See:http://www.pnas.org/content/90/14/6666.full.pdf
Zinc oxide reflects UV rays throughout the entire spectrum and is the best protection against longer wave-length exposure. It is the only mineral UV filter that protects up to 400 nm without generating free radicals. Titanium dioxide, the other mineral often used, protects across a shorter range and, unlike non-nano zinc oxide, must be coated to limit its propensity to generate free radicals upon exposure to UV. As for the chemical sunscreens, people are often advised to look for avobenzone, since it provides broad spectrum protection. While it is true that avobenzone protects up to 400 nm, it must be stabilized (generally with octocrylene) because it degrades so quickly upon exposure to UV. Unfortunately octocrylene is itself on the list of chemical UV filters which generate free radicals. In addition, more studies associating hormone disruption with chemical sunscreens are emerging.
Most people associate sunscreen with a day at the beach or on the slopes, but protecting against the more serious damage done by ubiquitous UVA rays means wearing sunscreen every day, rain or shine. This is where the wearability factor comes in. A sunscreen is only as good as one’s willingness to wear it, and this has long been the dilemma with zinc oxide. Even though it is the safest and most effective UV filter we know of it is also probably the least popular with the public, which tends to associate ZnO with a white greasy film that looks dreadful. The good news is not all zinc oxide sunscreens are created equal.
Sunscreens tinted with iron oxides (which increase sun protection) that do not contain wax and do contain non-nano zinc oxide would seem to be the best answer, and yes, they do exist. For every day wear an ideal sunscreen should do double duty as foundation and sunscreen, thus encouraging people to use it.
A big part of adequate protection is choosing an appropriate sunscreen. Here are some things to think about as you shop around.
Orginal WSJ.com article: Is Your Sunscreen Protecting You?
Image via Mother Earth News
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