The Federal Trade Commission has said that garments with UPF above 50 can be labeled UPF 50+, but they may not offer much more protection than UPF 50. The Skin Cancer Foundation recommends clothing with a UPF of 30+ (Skin Cancer Foundation 2014). No garment can be labeled "sun protective" if its UPF is less than 15. Both use a common rating scale, on which 15-24 means "good," 25-39 means "very good" and 40 and higher means "excellent" (Fan and Hunter 2009). Two major international UPF standards are those of ASTM International and Standards Australia/New Zealand. Studies have shown that UPF ratings for clothing are often underestimated because clothing is tested assuming direct sunlight, but in the real world, the angle of the sun is altered by the clothing and shifts over the course of the day. Underuse may explain why a survey conducted by the Centers for Disease Control and Prevention found that people who relied on sunscreens were more likely to get sunburns than those who wore protective clothing and sought shade (Linos 2011). An SPF 30 product applied thinly may act like SPF 5 or 10. Numerous research studies show that users typically apply just a third to half of the quantity of sunscreen used to establish the SPF (Autier 2003, Azurdia 2001, Reich 2009). Research has shown that few users apply an adequate coating of sunscreen with uniform thickness to sun exposed skin for the duration of sun exposure (Diffey 2009). There's no way to apply clothing wrong: the shirt is either on or it's off.īut for a sunscreen to live up to its advertised SPF value, users must apply and reapply it correctly and often. In the real world, clothing tends to offer greater protection than the UPF label might imply, and sunscreen generally offers less protection than the SPF number. Sunscreen SPF and clothing UPF ratings are comparable in laboratory settings, but reality is more complicated. In contrast, a high SPF sunscreen may filter UVB rays well, but that's no guarantee of good UVA protection. A shirt that blocks most UVB rays will also block most UVA rays (Diffey 2012). This is usually not a problem because protection offered by clothing is naturally well balanced between UVA and UVB. The UPF number does not convey the effectiveness of UVA protection. UPF 50 allows 2 percent of UVB rays to pass. A fabric rated UPF 15 allows 7 percent of UVB rays that burn to pass through. Like SPF, the higher the number, the less UV radiation that passes through. It is a measure of how much ultraviolet light passes through fabric in a laboratory. The UPF number is based on reduction of UVB rays that cause sunburns (Fisher 2006). The Food and Drug Administration approved the first sun protective clothing in 1992 as a medical device, but today, the Federal Trade Commission regulates these wares by policing marketing claims. Some chemical additives like titanium dioxide, zinc oxide and Tinosorb FD are infused into fabric to improve UV filtering, but we don't advise buying clothes with chemicals. If the fabric is wet, stretched out or too tight, it will block fewer UV rays. The reason: tighter weaves, dark or bright colors and thicker fabrics block more UV rays. Denim jeans can have a UPF value of 1700 (Geis 2012). A white cotton shirt's UPF may hover around 10. For everyday use, most clothing without a UPF label can provide adequate sun protection. UPF clothing is distinguished from regular clothes by lab tests that show it shields the body from UV rays by a factor of 15 or greater. A recent search of the Amazon website for sun protective clothing returned nearly 25,000 products. Over the past two decades, clothing claiming an ultraviolet protection factor - UPF for short - has enjoyed a soaring growth curve.
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