Ultraviolet radiation

Solar UV radiation is the single most significant source of UV radiation and can reach a person on the ground from three sources, directly from the sun, scattered from the open sky and reflected from the environment.

What is ultraviolet radiation?

Ultraviolet radiation (UVR) is defined as the portion of the electromagnetic spectrum between 100 nanometers (nm) and 400nm. UVR is classified by wavelength into three regions:

  • UVA - Ultraviolet radiation in the range 315nm to 400nm is thought to contribute to premature aging and wrinkling of the skin and has recently been implicated as a cause of skin cancer.
  • UVB - Ultraviolet radiation in the range 280nm to 315nm is more dangerous than UVA and has been implicated as the major cause of skin cancers, sunburning and cataracts.
  • UVC - Ultraviolet radiation in the range 100nm to 280nm is extremely dangerous but does not reach the earth’s surface due to absorption in the atmosphere by ozone.
Types of ultraviolet radiation

How are people exposed to UV radiation?

Solar UV radiation is the single most significant source of UV radiation and can reach a person on the ground from three sources, directly from the sun, scattered from the open sky and reflected from the environment. This means that even if a person is shaded from the direct sun they can still receive substantial UV radiation exposure from the open sky. Also some ground and building surfaces reflect UV radiation including white paint, light coloured concrete and metallic surfaces. These surfaces can reflect UV radiation onto the skin and eyes and  reduce the effect of protective measures.

There are also many types of artificial UV radiation sources, some of which emit high levels of UV radiation. Arc welders used in industry produce an intense UV radiation emission and workers exposed to welding radiation may suffer similar health effects to workers with over exposure to solar UV radiation. There are many other forms of artificial UV radiation sources such as fluorescent, mercury vapour, metal halide and quartz halogen lamps used in industry, offices and in the home, however, office and home lighting have been shown to produce very low levels of UVR.

Image showing couple walking on the beach and where exposure to UVR might occur

How is UV radiation measured?

Broadband UV biometers and pyranometers are generally used to measure or monitor solar UVR. These instruments measure solar UVR received on a horizontal surface from the entire hemisphere of the sky. The design of these instruments ensures that both direct and scattered UVR are measured. These measurements can also be used to monitor changes in ozone levels and cloud cover effects by changes in UVR levels.

Further information may be obtained from the following sites:
The Australian Bureau of Meteorology
World Meteorological Organization

What are the effects of exposure to UV radiation?

Due to the very short penetration depth of UVR, the major organs at risk from exposure to UVR are the skin and eyes. 

People who are overexposed to UVR may be unaware of their injury as it cannot be seen or felt and does not produce an immediate reaction. Over-exposure to UVR can cause sunburn, skin damage and skin cancer. The most obvious short-term effect of over-exposure to UVR is sunburn. 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. Sun exposure causes the outer layers of the skin to thicken and long-term exposure can cause skin to wrinkle, sag and become leathery. 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 a dark spot on the skin.

UVR exposure also places the eyes at risk of photokeratitis, photoconjunctivitus and cataracts. 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.

Further information may be obtained from the following sites:
The Cancer Council of Australia
The World Health Organization
Health Protection Agency
Sunsmart

How can I reduce my risk from UV radiation exposure?

Increasing public awareness and interest in UV protection is due in part to the requirements for occupational protection of outdoor workers as well as the provision of UVR protection for the recreational market. Behaviour outdoors can significantly affect a person’s solar UVR exposure, and using personal protection can provide a substantial reduction in the UVR dose received. Many forms of personal protection are available to reduce a person’s exposure to solar UVR. The best protection is to avoid going outdoors in during periods of higher UV levels. When outdoors, wear clothing with good body coverage, a hat, sunglasses, sunscreen and seek shade. Over recent years interest has extended to shade structures and the UVR protection offered by commonly used materials such as shadecloth, plastic roofing materials, glass and window tinting films.

Further information may be obtained from the following sites:
Safe Work Australia
ARPANSA's Radiation Protection Standard - Occupational Exposure to Ultraviolet Radiation
Sunsmart