How dangerous is UVR?

The biological effects of UVR on the human skin depend on the wavelengths of UVR emitted by the sun. To be able to correctly determine the hazard from the sun, or any artificial UVR source, it is necessary to have information about the spectral emissions.

The graph [4] below shows human skin response to UVR and is called the action spectrum for UVR. The biological weighting factor shown in the graph is based on a fair skinned person's response to UVR from the sun. Notice that the line covers the UVB and UVA regions.

The important point to note is that the biological effectiveness of UVR increases by a factor of over 1000 as the wavelength changes from UVA to UVB. This means that UVB exposure causes 1000 times as much skin damage as the same amount of UVA exposure.

What are the risks from UVR exposure?

Over-exposure to UVR can cause sunburn, skin damage and skin cancer. UVR exposure also places our eyes at risk of photokeratitis, photoconjunctivitus and cataracts. The most obvious short-term effect of over-exposure to UVR is sunburn, also known as erythema. The more UVR exposure, the worse the sunburn becomes. A person's cumulative exposure to UVR along with the number of severe sunburns they have received, especially during childhood, increases their risk of developing skin cancer. Skin cancers affect people of all skin types.

Sun exposure causes the outer layers of the skin to thicken. Long-term exposure can cause skin to wrinkle, sag and become leathery. Due to the high levels of UVR and an outdoors lifestyle, Australians also suffer from high rates of skin cancers.

Melanoma, the least common of the skin cancers but the most dangerous, may be related to severe exposure to solar UVR at an early age. Malignant melanomas may appear without warning as a dark mole or other dark spot on the skin. Any concerns regarding moles or skin spots should be referred to a doctor or skin clinic. Further information about skin cancers can be obtained from the Cancer Councils.

Prolonged exposure to solar UVR can have serious consequences for the eyes. Cataract is one of the most common types of eye damage in Australia. Cataract is the clouding of the lens of the eye, which is responsible for focusing light and producing sharp images. Without intervention cataract can lead to blindness. Wearing wrap around sunglasses and a broad brimmed hat can prevent most of the UVR from reaching the eyes.

The sensitivity to sunburn can vary between different parts of the body. The neck, face, ears and trunk tend to be more sensitive than the limbs. These parts of the body are at more risk from UVR exposure.

Our lips have thinner layers of skin than the rest of the body. They have no sweat or oil glands so they can dry and crack easily in the sun. There are lip balms available that contain sunscreens.