UVA, UVB & Sunscreen
The ultraviolet light spectrum we are exposed to is divided into two components: UVA and UVB. UVB is the major cause of sunburn while UVA can cause deep skin damage, both are risk factors for skin cancers. UV alerts are issued by the Bureau of Meteorology for times when the UV index is 3 or above and protection from the sun is required to avoid skin damage.
Sun protection factor (SPF) is a measure of how many times longer protection from sunburn (UVB exposure) is provided to skin with a particular sunscreen thickly applied compared to the same skin unprotected. To gain protection from UVA it is important that the sunscreen is also labelled broad spectrum as SPF alone is not a measure of protection from UVA.
Generally people do not apply enough sunscreen to achieve the label SPF, the Cancer Council Australia recommends at least a teaspoon for each limb, front and back of the body, and half a teaspoon for the face, neck and ears. Sunscreen should be reapplied every two hours.
Ultraviolet Protection Factor (UPF) is a measure of how much ultraviolet light (both UVA and UVB) is transmitted through clothing. For example clothing rated UPF 50 allows only one fiftieth of the UV light through, so 98% (49/50) of the UV is blocked.
Ultimately the best protection from sun is to shade yourself by wearing high UPF clothing, as this will last all day and does not need to be reapplied.
