Clothing and textiles

Clothing provides a physical barrier to the UVR and the extent of this barrier is determined by the fabric’s natural ability to block UVR, or its UPF.  Some fabrics are chemically treated to increase their UPF.  A material with a UPF rating of 20 would allow 1/20^th of the UVR falling on its surface to pass through.  In other words, a fabric with UPF 20 would reduce UVR exposure on the areas of skin it covered by a factor of 20.

There are many factors that determine how effective a fabric is at blocking UVR:

• fabric composition. Different materials such as cotton, hemp, polyester have different UPFs.  100 percent polyester has the highest UPF of all fabrics, but natural fibres are better for our bodies and overall health.
• density of weave. A tightly woven or knitted material will let less UVR pass through.  Nylon spandex knits have a very high UPF regardless of colour.
• colour. Dark colours absorb more UVR than lighter, pastel colours, and consequently have a higher UPF.  Black clothing provides 5 times more protection than white clothing – a white T-shirt has only a UPF 5.
• tension. If a fabric is stretched it will in effect look like it has a looser weave and so have a lower UPF.  Sun protection clothing should be the right size, or large, for the wearer.
• weight. Heavier weight materials tend to have a higher UPF.  A double layer of fabric almost doubles the UPF of clothing regardless of fabric type.
• moisture content. As a material gains water, it often becomes less resistant to penetration of UVR and so have a lower UPF.  Wet fabrics can increase the penetration of UVR by as much as one-third
• design. Sun protection clothing needs to cover as much of the body, arms, legs and neck as possible.  It is important not to forget hands and feet – these are becoming a common site for skin cancers.
• condition. As clothing gets older it will decline in its ability to give UVR protection due to washing, shrinking, fading, and general wear.
• UVR absorbers. Some fabrics are treated with chemicals to increase their UPF.  This is usually done when the fabric is manufactured, but can be added to laundry to help block the UVR.