How do we measure UVR?

The ultraviolet index or UV Index is an international standard measurement of the strength of UVR from the sun on the ground at a particular time. The UV Index is an important vehicle to raise public awareness of the risks of excessive exposure to UV radiation, and to alert people about the need to adopt protective measures. Encouraging people to reduce their sun exposure can decrease harmful health effects and significantly reduce health care costs.

As the UV Index increases the hazard increases. There are a number of categories ranging from low exposure to extreme as shown in the table.

UV Index Exposure Category
2 or less Low
3 to 5 Moderate
6 to 7 High
8 to 10 Very High
11+ Extreme

The exposure categories are based on the response to fair-skinned people exposed to UVR. The UV Index may be either a prediction or a measurement.

ARPANSA obtains the measured UV Index from a detector that responds to UV radiation in much the same way as human skin does. The measurements take into account cloud cover and other environmental factors that computations can only approximate. The Bureau of Meteorology (BOM) calculate the predicted value from a radiative transfer model using parameters of date, time, latitude, temperature and ozone concentration. The skin’s response to UV radiation is required for calculating the predicted solar UV Index.

What is your skin type?

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. For other skin types from very fair to dark please refer to the Skin Chart based on the research of Fitzgerald.

How can you reduce your UVR exposure?

Even for very sensitive fair-skinned people, the risk of short-term and long-term UV damage below a UV Index of 2 is limited, and under normal circumstances no protective measures are needed. If sun protection is required, this should include all protective means, i.e. clothing and sunglasses, shade and sunscreen.

For best protection, we recommend a combination of sun protection measures:

  • Slip on some sun-protective clothing that covers as much skin as possible.
  • Slop on broad spectrum, water resistant SPF30+ (or higher) sunscreen. Put it on 20 minutes before you go outdoors and every two hours afterwards
  • Slap on a hat – broad brim or legionnaire style to protect your face, head, neck and ears.
  • Seek shade.
  • Slide on some sunglasses – make sure they meet Australian Standards.

A balance is required between avoiding an increase in the risk of skin cancer by excessive sun exposure and achieving enough exposure to maintain adequate vitamin D levels. Cancer Council Australia provides further advice on vitamin D.

quote from Arpansa