ARPANSA - Australian Radiation Protection and Nuclear Safety Agency

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Why measure solar UVR?

Every year in Australia there are 270,000 new cases of skin cancer diagnosed. Over 1200 Australians die of skin cancer each year. The occurrence of skin cancers is related to UVR exposure. Australia has the highest incidence of skin cancers in the world so accurate information about the levels of solar UVR is very important.

In the mid 1980s ARPANSA, then known as the Australian Radiation Laboratory (ARL) set up a network of detectors to measure UVR levels around Australia and in Antarctica. Evidence of depletion of stratospheric ozone, which has a direct effect on UVR levels, over the Antarctic region has encouraged the monitoring of solar UVR in the region.

How does ARPANSA measure solar UVR?

ARPANSA has measured solar UVR levels using a network of detectors in Australian capital cities and at other sites since 1986. These UVR monitoring devices cover a wide range of latitudes and different climates and record data for the study and reporting of variations and magnitude of UVR changes. However, care must be taken in assuming that a specific site in one city represents all locations within a region, as there can be significant localized differences due to cloud cover and air pollution.

There are currently 12 sites in Australia and Antarctica that have broadband UVR detectors installed. Broadband detectors measure the total energy received over a range of wavelengths in the UVR region. The detectors measure both direct and diffuse radiation. The information is analysed by computer then distributed daily to news services and other interested organisations.

How are UVR levels reported?

ARPANSA has been reporting solar UVR levels for Australian capital cities since 1990. UVR levels are reported as a solar UV-Index, which is a measure of the highest level of UVR each day. The World Health Organization (WHO) developed this standardised method for reporting solar UV-Indexes. The UV-Index is designed to provide the public with a numerical indication of the maximum potential solar UVR level during the day - the higher the number the higher the solar UVR hazard. The UV-Index allows for cloud cover and other environmental factors and is used worldwide for reporting UVR levels. UV-Index values are grouped into exposure categories of low, moderate, high, very high and extreme with corresponding colour codes. UV-Index values are related to UVR exposure as shown in the table below. By following some simple precautions shown in the table below you can reduce your risk of sun related damage.

UV-Index level	Exposure category	Recommended sun protection precautions	UV-Index colour code
2 or less	Low	You can safely stay outdoors with minimal protection.	Green
3 to 5	Moderate	hat, sunscreen, sunglasses, shady area.	Yellow
6 to 7	High	hat, sunscreen, sunglasses, shady area, stay indoors between 10-2pm (11-3pm daylight savings).	Orange
8 to 10	Very High	Stay indoors as much as possible otherwise use all precautions above.	Red
11+	Extreme	Same as for the previous category.	Purple

The UV-Index exposure categories are based on the response of fair-skinned people to UVR. People who have skin types that are less likely to burn should note that although they may not sunburn easily, they can still receive high UVR exposures which can increase their long-term risk of skin cancer.

UV-Index reports for Australian capital cities, updated daily, can be found on ARPANSA's UV-Index page.

What are skin types?

Skin is classified by sensitivity to UV radiation. If you are very fair skinned (white skin) and tend to burn easily in the summer sun and find it difficult to achieve a tan you have skin type 1. People with skin type 1 have the highest risk of premature skin aging and greatest risk of developing some form of skin cancer. If you are of this type then you should limit your exposure to the sun and always dress to minimise sun exposure, wear a hat and use sunscreen.

People with skin type 2 (white skin) usually burn and only rarely tan so they need to take the same precautions as skin type 1.

People with skin types 3 and 4 (white and light brown skin respectively) usually tan and occasionally burn so they still require protection from the higher levels of UVR in summer.

People with skin types 5 and 6 (moderate brown and dark brown-black respectively) have sufficient levels of melanin pigment in their skin to provide protection from solar UVR so they rarely burn and easily tan. However, even though darker skin offers natural protection against UVR those people are still not immune to developing skin cancers.

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