The UV Index is a tool that is used to help raise public awareness of excessive exposure to UV radiation, and instruct the general popular on how we can best protect ourselves. The UV index was developed by WHO, the United Nations Environment Programme, and the World Meteorological Organization. The ozone absorbs some of the UV radiation that would otherwise reach the Earth’s surface, however, ozone levels vary over the year and even across the day.
Sun protection is important all year round, but with summer here we are at a greater risk of exposure to UV radiation. Paying attention to the UV Index and Ozone are vital to sun protection, here’s why.
Why the UV Index Matters
When rain is in the forecast, people try to pack an umbrella when they leave the house. If the temperature is going to drop, they bring along a sweater. We are always making small adjustments to our daily lives to accommodate the weather, and it’s important we do the same for UV radiation. Reading the UVI (UV Index) can help us make healthy choices when it comes to sun protection as exposure to ultraviolet (UV) radiation is a major risk factor for most skin cancers. On top of an increased risk for skin cancer, UV exposure seems to be responsible for 80% of visible facial aging signs.
According to the EPA, The U.S. National Weather Service calculates the UV Index using a computer model that relates the ground-level strength of solar UV radiation to forecasted stratospheric ozone concentration, forecasted cloud amounts, and elevation of the ground. For example, let’s assume that the elevation is 1 kilometer and there are broken clouds overhead. The total UV effect, adjusted 6% for elevation and 73% for clouds, would be calculated as: 280 (The strength of UV radiation) x 1.06 x 0.73 = 216.7.
The final step of the calculation scales the total UV effect, dividing it by 25 and rounding to the nearest whole number. The result is a number that usually ranges from 0 (darkness or very weak sunlight) to the mid-teens (very strong sunlight). This value is the UV Index. Going back to the example above, the UV Index in that scenario would be: 216.7 / 25 = 8.7, rounded to 9.
Making sense of the UVI is much easier than determining it. The values of the index range from zero and go upward. The higher the UVI, the greater the potential for damage to the skin, and the less time it takes for that damage to occur. It also indicates the protective measures you should take when going outside;
0-2: You can safely stay outside using minimal sun protection.
3-7: Seek shade during late morning through mid-afternoon. When outside, generously apply broad-spectrum SPF-15 or higher sunscreen on exposed skin, and wear protective clothing, a wide-brimmed hat, and sunglasses.
8+: Extra protection needed. Be careful outside, especially during late morning through mid-afternoon. If your shadow is shorter than you, seek shade and wear protective clothing, a wide-brimmed hat, and sunglasses, and generously apply a minimum of SPF-15, broad-spectrum sunscreen on exposed skin.
How the Ozone Affects Your Skin
The stratospheric ozone is a particularly effective UV radiation absorber, and as such, the depletion of the ozone layer can aggravate the existing health effects caused by exposure to UV radiation. As the ozone layer becomes thinner, that protective filter provided by the atmosphere is reduced and ,consequently, we are exposed to higher UV radiation levels. Computational models predict that a 10% decrease in stratospheric ozone could cause an additional 300,000 non-melanoma and 4500 melanoma skin cancers. It’s more important for our health than ever to pay attention to the ozone and UVI and protect ourselves accordingly.
According to the World Health Organization, these environmental factors can also influence the UV level;
- Sun height—the higher the sun in the sky, the higher the UV radiation level. Thus UV radiation varies with time of day and time of year, with maximum levels occurring when the sun is at its maximum elevation, at around midday (solar noon) during the summer months.
- Latitude—the closer the equator, the higher the UV radiation levels.
- Cloud cover— UV radiation levels are highest under cloudless skies. Even with cloud cover, UV radiation levels can be high due to the scattering of UV radiation by water molecules and fine particles in the atmosphere.
- Altitude—at higher altitudes, a thinner atmosphere filters less UV radiation. With every 1000 meters increase in altitude, UV levels increase by 10% to 12%.
- Ground reflection—UV radiation is reflected or scattered to varying extents by different surfaces, e.g. snow can reflect as much as 80% of UV radiation, dry beach sand about 15%, and sea foam about 25%.
How to Keep Your Skin Protected
The best way to stay protected? SUNSCREEN! It is part of my daily routine, and I never leave home without it. Sunscreen can help users avoid serious health issues such as skin cancer, sunburn, heat stroke, heat exhaustion, and much more. This is in addition to the cosmetic benefits of protecting skin from the aging effects of UV rays. I wear two sunscreens every day – I layer Neutrogena Ultra Sheer SPF 100+ under a zinc and titanium oxide blend – and I still get carded often at 34 years old!
You can also add products to your routine that are fortified with Vitamin E and Resveratrol to help prevent and protect your skin from UV and UVB damage. Vitamin E is amongst the most popular antioxidants featured in skin care formulations, and for good reason: it is not only a highly effective antioxidant but also serves as a hydrating agent. According to the journal Skin Pharmacology and Physiology, vitamin E is one of the naturally produced antioxidant substances that protect against skin’s exposure to UV and environmental exposures to ozone. Vitamin E has an environmental protection factor (EPF) of 80, which is relatively high compared to other commonly used antioxidants in skin care formulations. In a 2008 study published in Photochemistry and Photobiology, human skin cells treated with resveratrol prevented UVB-induced damage. The mechanism? Resveratrol inhibited the inflammatory NFkB pathway and decreased the skin cells’ production of hydrogen peroxide. With reduced levels of inflammation, less damage accrued in the cells. Resveratrol has been found to specifically affect the NFkB pathway by inhibition of the MAPK pathway and targets in the regulatory protein cki-cyclin-cdk network (Cell and Molecular Biology review, 2008). Therefore applying a cream containing resveratrol under a broad-spectrum UVA/UVB sunscreen appears to be a great extra means of protection at this time.
You should also limit time in the midday sun, seek shade when UV rays are the most intense, and wear protective clothing like wide brim hats and sunglasses.