Safe Sunscreens 101
Overall Sunscreen Guidelines:
1. For safety, avoid nanoparticles and chemicals
2. For effectiveness, choose a broad spectrum and photostable product containing non-nano zinc oxide
3. For lasting protection, follow the two hour reapplication rule
What You Need to Know:
Potential Health Risks: Avoid Chemicals and Nanoparticles
Common UVB sunscreen ingredients include octyl methoxycinnamate (OMC), octocrylene, octyl salicylate (OCS), and/or octyl dimethyl paba (PABA). The most common short-wave UVA ingredient is oxybenzone (benzophenone-3). All have been linked to either endocrine disruption or free radical generation. Emerging studies suggest that sunscreens containing nano-sized particles of organic and/or inorganic compounds may not be safe. We do know that nanoparticles of zinc oxide and titanium dioxide, while probably safer than their organic (chemical) counterparts, generate free radicals upon exposure to UV and water.
According to investigators quoted by the EWG
, “the primary toxicity concern of nanoparticles is free radical generation. This can provoke intense oxidative stress, inflammation and damage proteins, lipids and DNA.” A little warning: many manufacturers are calling products with zinc oxide particles greater than or equal to 100 nanometers “non nano”. We feel very strongly that until such small particles are proven safe (particles the size of 250 nm have been shown to penetrate the placental barrier), it is important for you know what size particles are in your products.
Eliminating chemicals and nanos from the list narrows the search to two inorganic ingredients; zinc oxide and titanium dioxide.
Unlike many chemical sunscreen agents, non-nano zinc oxide is safe and never irritating. It is even recognized by the Food and Drug Administration as a Category I skin protectant, meaning it is safe for compromised or environmentally challenged skin. Zinc oxide has over a 300-year history of safety, with no known adverse reactions (which is why it is often used to treat babies).
2) Effectiveness: Broad spectrum protection and photostability
Broad spectrum protection
SPF ratings tell you what level of protection you will get from UVB, or burning rays, but there’s more to the story than just avoiding a sunburn.
According to MD Anderson Cancer Center: “a sunscreen with an SPF (Sun Protection Factor) of at least 15 is a good choice for most people. It’s important to remember that the protection an SPF offers does not increase proportionately with the designated SPF number. SPF 15 absorbs 93% of the sun’s burning rays, while SPF 30 absorbs 97%.”
You tend to get better protection with an SPF 15-25 than an SPF 30+ because you are more likely to use the two hour rule (apply every two hours and/or after swimming, sweating). A bonus to following the every two hour rule is that spots you may have missed the first time around will get another chance at coverage.
The most important thing to be aware of is that an SPF rating does not take into account UVA protection. A sunscreen with a very high SPF rating that offers little or no UVA protection could expose you to UVA damage before you burn.
One study involving the irradiation of human skin shows that it takes only eight modest doses (defined as 1 hour of summer midday sun) of UVA exposure to cause photoaging, and that these changes occur before any sunburn or tanning is evident. While titanium dioxide effectively attenuates UVB and short-wave UVA it is much less effective than zinc oxide in protecting against long-wave UVA.
Zinc oxide is the closest thing to a total sunblock on the market today. It uniformly covers from 290 to 400 nm, thus protecting against the UVB and UVA spectrum. No other sunscreen ingredient provides broader protection. *
Photostability refers to the ability of a molecule to remain intact with irradiation. While all sunscreens degrade over time upon exposure to UV, most chemical sunscreens in particular lose UVA protection very quickly (avobenzone degrades after one hour), and, as chemicals and nanoparticles degrade they begin to generate free radicals, thus increasing the risk of photoaging.
Photostability tests show that zinc oxide, compared to titanium dioxide as well as chemical sunscreen ingredients, is very stable.
The potential for sunscreen agents to degrade reminds us to use the two hour rule to make sure protection remains adequate throughout the day.
1) *Sheldon R. Pinnell, MD and Doren L. Madey, PhD, Aesthetic Surgery Journal May/June 1999
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