Sunscreen Safety

Photo by Sujin Jetkasettakorn

Summer is here and we all love to spend time outdoors. Some sunshine is good for us, we all need Vitamin D. But how much is too much? And how do we protect ourselves with safely and effectively? To select the best sunscreens, first we should understand the sun's radiation. There are two types of ultraviolet radiation we need to protect our skin from, UVA and UVB.


What's the difference between UVA and UVB?
UVA is ultraviolet radiation between 400-320nm wavelength and UVB is between 320-290nm wavelength. The shorter the wavelength, the higher the energy of radiation. UVA rays account for 90 to 95% of UV radiation that reaches the earth. While UVB makes up only 5-10% of solar radiation, its high energy damages surface epidermal layers and causes sunburn. UVB is strongest between 10AM and 4PM, from April to October and do not significantly penetrate glass. UVA is present equally throughout the daylight hours and throughout the seasons, and can penetrate cloud and glass. UVA penetrates deeper layers of skin and causes tanning. However, both types of UV rays can cause skin cancer because they damage skin cells and alter their DNA. Both types of rays also contribute to premature aging of skin.


What is SPF?
SPF stands for Sun Protection Factor. It is a measurement of the number of times it takes for skin to redden under UVB radiation with the sunscreen compared to no sunscreen. For example, SPF 15 means that it takes 15 times for skin with the sunscreen to redden compared to no sunscreen. As a rule of thumb, a SPF15 sunscreen screens 93% of the sun’s UVB rays; SPF 30 protects against 97%; and SPF 50, 98%. Health professionals agree that at least SPF15 is needed for adequate sun protection. However, a high SPF number doesn't necessarily mean that the sunscreen also protects against UVA rays. And just because the sunscreen has a high SPF number, it doesn't mean it's safe to stay out in the sun longer.


Types of sunscreen ingredients: Physical and Chemical
Physical sunscreens are particles that reflect sun's rays away from skin. Two are approved by the FDA: Titanium Dioxide and Zinc Oxide. Both of them offer protection against UVA and UVB rays.

Chemical sunscreens form a thin layer on top of skin and absorb UV rays before they reach the skin. The downside of chemical sunscreens is that some of them form free radicals and can contribute to skin aging, cause  irritation, allergic reactions, and possible long term health effects. The FDA approves 17 active ingredients for sunscreens, 15 of which are chemical sunscreens. Some are powerful free radical generators, estrogenic, mutagenic, and may even cause skin cancer.

FDA-Approved Sunscreens
Active Ingredient/UV Filter Name	Range Covered
	UVA1: 340-400 nm
	UVA2: 320-340 nm
	UVB: 290-320 nm
Chemical Absorbers:
Aminobenzoic acid (PABA)	UVB
Avobenzone	UVA1
Cinoxate	UVB
Dioxybenzone	UVB, UVA2
Ecamsule (Mexoryl SX)	UVA2
Ensulizole (Phenylbenzimiazole Sulfonic Acid)	UVB
Homosalate	UVB
Meradimate (Menthyl Anthranilate)	UVA2
Octocrylene	UVB
Octinoxate (Octyl Methoxycinnamate)	UVB
Octisalate ( Octyl Salicylate)	UVB
Oxybenzone	UVB, UVA2
Padimate O	UVB
Sulisobenzone	UVB, UVA2
Trolamine Salicylate	UVB
Physical Filters:
Titanium Dioxide	UVB, UVA2
Zinc Oxide	UVB,UVA2, UVA1

The only downside to physical sunscreen formulations is that they tend to leave white streaks on skin and are thicker so may take longer to apply. However, since physical sunscreens are particles, they do not get absorbed into skin like chemical sunscreens do. They also don't react or release any potentially harmful by-products, and can be easily washed off. Physical sunscreens are really be best choice because they are low risk and offer wide-spectrum UV protection.

Sun Protection Tips
Staying out of the sun by using shade and tightly meshed clothing is your best protection against damaging UV rays. However, when sunscreens are needed, opt for one that contain both zinc oxide and titanium oxide as active ingredients, together they protect against both UVA and UVB rays. Look for SPF15 or higher for everyday activities such as a stroll in the park; opt for SPF30 or higher for physical activities such as swimming or running. Also remember to re-apply every 2 hours to ensure adequate protection. For babies under 6 months, it's best keep them out of sun altogether.

Organiworks offers physical sunscreens by Goddess Garden. This is the only brand we found of physical sunscreens that go on sheer, no white streaks! We offer varieties for kids, adults, babies, and even safe non-aerosol spray-on sunscreen! For more choices, check out the EWG's list of best sunscreens for more great natural products.

References:
The Skin Cancer Foundation
Environmental Working Group Sunscreen Guide 2011
Knowland et. al. FEBS Letters "Sunlight-induced mutagenicity of a common sunscreen ingredient" (1993)