I wanted to educate myself on UPF and SPF ratings and what they mean, and I wanted to pass along the information I found, and how it applies to those of us that venture outside. Some/many of you may already be aware of this information, but it was new to me.
SPF is a multiplier for how long you can be exposed to UVB rays before getting sunburned. So if you normally would get burned in 10 minutes, a sunscreen rated SPF 15 prolongs that time to 150 minutes. SPF ratings are measured using human subjects.
UPF is a measurement that indicates how much of the sun's UV rays is absorbed by a fabric. This is verified using spectrophotometer equipment in a lab setting. If a fabric is rated UPF 15, it means it absorbs or blocks all but 1/15th of UV rays. If it is rated UPF 50, it absorbs or blocks all but 1/50th of UV rays. In simple percentages, UPF 15 protects your skin from about 93% of all UV rays. UPF 50 fabric protects you from 98% of all UV rays.
The average white cotton t-shirt has a UPF rating around 5. A blue t-shirt has a UPF of 20 or higher. Denim blue jeans have a UPF rating of 1,700.
Darker colors absorb more UV rays, shinier fabrics reflect more UV rays, and tighter weave fabrics block more UV rays. Loose weave cotton or linen clothing allows the most UV rays to pass through. Thicker and/or more reflective fabrics like wool, polyester, or denim allow the least UV rays to pass through.
It is important to note that UV rays increase in intensity as you go up in altitude. For every 1,000 meters in increased elevation, UV levels increase by roughly 10%. The intensity of UVB rays in Vail, Colorado at 8,500 feet on a sunny day are 60% higher than at sea level in New York City, and equivalent to the intensity of UVB rays in Orlando, Florida, which is 775 miles closer to the equator. An individual that may develop a sunburn in 25 minutes in New York, would develop the same sun burn in only 14 minutes in Vail or Orlando, and thus individuals living at higher elevations are at a considerably higher risk for developing skin cancer.
Skin cancer is by far the most common type of cancer in the US. 1 in 5 Americans will develop skin cancer during their lifetime. Men are 2 to 3 times more likely to develop skin cancer than women. While the risk of developing skin cancer is 20 times higher for fair skinned individuals, those with darker skin tones are much more likely to be diagnosed at a later stage, and subsequently have a much higher mortality rate. Skin cancer is most likely to occur on the nose, lips, face, ears, neck, hands, or forearms. Men are much more likely to have melanoma form on their backs than women. Women tend to form melanoma more often on their arms or legs. It’s very important to be vigilant and take care of your skin throughout your lifetime!