Killer sunscreen? What your mama never told you about sun protection.
Ultraviolet (UV) light is divided into 3 wavelength ranges that are referred to as UVA, UVB, and UVC rays. UVC is the most energetic and shortest of the UV rays. It burns quickly and in small doses. It is also absorbed entirely by the ozone layer. Thus when talking sunscreen, we are primarily dealing with UVA and UVB rays.
UVB is the UV ray that is primarily responsible for sunburn. It also stimulates the body’s production of Vitamin D; melanin, which protects human skin from sun damage; and Melanocyte Stimulating Hormone (MSH), an important hormone in weight loss and energy production. Only 5% of the UVB light range goes through glass and it does not penetrate clouds, smog, or fog. Most sunscreens only protect against UVB rays and the SPF (sun protection factor) rating refers to efficacy in protecting against UVB light.
UVA is primarily responsible for aging and darkening the pigment in our skin. UVA is less energetic than UVB, but has a longer wavelength. This means UVA rays penetrate deeper. UVA rays are less likely to cause sunburn, however UVA rays are now considered to be a major contributor to non-melanoma skin cancers. Until recently, UVA was not blocked by sunscreens (and still isn’t blocked by most sunscreens sold in America) and 78% of UVA can even penetrate through glass windows. UVA sunscreen ratings are measured by PPD (persistent pigment darkening), theoretically a rating of 10 would allow you to stay out 10 times longer.
Vitamin D and sunlight
Vitamin D might be referred to as the miracle Vitamin. It does it all: contributes to strong bones, healthy immune and endocrine systems, and can help prevent a plethora of today’s diseases from diabetes and obesity to depression and infertility.
As you read above, Vitamin D can be absorbed from sunlight: UVB rays to be exact. However, getting enough Vitamin D from the sun is hard. Unlike the UVA rays which are steady throughout the day and penetrate through just about anything, UVB rays are fickle—you have to get them at just the right angle and without clouds, clothes, or other barriers. For a person who lives in the “northern latitudes” (think Chicago, New York, all of Canada) to get a healthy daily dose of Vitamin D from sunlight, a light-skinned person would have to spend 10 to 20 minutes in full sunlight between the hours of 10 a.m. and 2 p.m. A dark-skinned person 90 to 120 minutes. That’s right—the exact hours our mothers told us to stay indoors. Any earlier or later and the angle of the UVB rays would mean spending more time and more time means more exposure to those deep penetrating UVA rays. Oh, and it has to be the WHOLE body exposed—85%—not just hands and feet.
Ingredients to watch for in sunscreen and the problem with label reading.
In the U.S. and Canada sunscreens are regulated as drugs. This means it has taken longer for both of the countries to approve some of the newer chemicals thought to be safer and provide more UVA protection. This also means that they are not required to list all of the ingredients on their labels in either country.
Fragrance or Parfums are considered trade secrets so even in Canada where ingredients are supposed to be listed, dozens of chemicals—including suspected neurotoxins and endocrine disruptors—can be hidden behind these seemingly innocuous terms.
High SPF factors. High SPF ratings were found by the FDA to be “inherently misleading.” These high-SPF products often contain more of the above offending ingredients and can encourage people to stay in the sun longer without providing any additional protection.
Nanoparticles. Micronized or nanoscale particles of minerals are often found in titanium or zinc based sunscreens. These tiny particles are easily absorbed into the body and blood.