ARPANSA - Australian Radiation Protection and Nuclear Safety Agency

 

Introduction

Over-exposure to ultraviolet radiation (UVR) from the sun can cause sunburn, skin damage and ultimately, skin cancer. Australians have the highest rate of skin cancer in the world because of factors such as high UVR levels, lightly pigmented skin and an outdoor lifestyle. Our eyes are also at risk from photokerititis, photoconjunctivitis and cataract.

Solar UVR is conventionally divided into UVA, UVB and UVC. UVB and UVC are potentially the most dangerous of the three. However, UVC does not penetrate the earth's atmosphere. In addition, the level of UVB reaching the earth's surface is controlled largely by the amount of ozone in the atmosphere. It is our exposure to UVB radiation, in particular, that is of concern.

What Does The Chart Represent?

The chart shows the variation in solar UVB levels during that day. To allow speedy interpretation, the vertical axis is divided into four parts to indicate the relative degree of risk of exposure - moderate, high, very high and extreme. When "extreme" levels are reached, there is sufficient UVB radiation to cause a sunburn in approximately 15 minutes! The maximum daily 'Effective Ultraviolet Radiation' reading is recorded as the UV-Index in the bottom left hand corner. This figure can be used for comparison between cities both nationally and internationally.

What Affects UVB Levels?

The level of UVB radiation is affected by the sun's position in the sky. The higher the sun (for example, in summer), the larger the UVB level. UVB radiation is also affected by the amount of cloud cover, the concentration of ozone in the atmosphere and altitude. The UVB level increases as the ozone concentration decreases. Very heavy cloud cover can decrease UVB levels by 90% or more. Light, scattered cloud can often have little or no effect. In the example above, cloud during the morning gave way to a clear midday beginning at about 11.00 AM and then intermittent cloud cover during the afternoon. It is important to note that even on days when clouds obscure the sun, UVB levels can still be sufficiently high to be of concern.

As shown above, UVB levels will vary significantly during the year (1 MED is the amount of UVR required to produce a sunburn in sensitive skin). Northern Australia lies in the tropics so, even in winter, UVB Levels are relatively high. In addition, UVB levels will be high on cloud-free days in the snow fields.

Personal UVR Detectors

There are two inexpensive types of detector available. One is worn on the wrist and is a little larger than a watch, while the other is hand-held. These detectors are designed to measure ambient solar UVB levels and give an indication of one's accumulated exposure. Usually these detectors measure UVA as well as or instead of UVB, and therefore may provide little indication of the true hazard level. Their real danger is that they encourage people to MAXIMIZE their solar UVB exposure. However, given the serious short- and long-term consequences of over-exposure to the sun, we must MINIMIZE our solar UVB exposure. This can be achieved by following the advice given below.

How Do We Protect Ourselves

Change Our Behaviour

• Stay out of the sun from 11am to 3pm (daylight saving times) by organizing summer outdoor activities for the early morning or late afternoon hours.
• Utilize natural or artificial shade as much as possible.

Adopt These Personal Protection Strategies:

• Protect our face and neck with a wide-brim hat.
• Cover-up as much as possible with clothing that offers good UVR protection.
• Use an SPF 15+ sunscreen on all exposed skin (white or colored zinc cream provides excellent protection for small areas of the face).
• Protect our eyes with sunglasses that meet the Australian Standards and have a tight wrap around fit.

 

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