ARPANSA - Australian Radiation Protection and Nuclear Safety Agency

 

Health Effects of Solar UVR

Both the skin and eyes are at risk from solar ultraviolet radiation (UVR). It is well known that overexposure to UVR from the sun can cause sunburn, skin damage and, ultimately, skin cancer. This UVR can also cause cataracts, a clouding in the lens of the eye which obscures vision. As well as such damage, UVR can also cause eye damage, if the UVR intensity is sufficiently high.

Direct and Scattered Solar UVR

Part of the solar radiation spectrum is shown in the figure below. In general, there is almost as much UVR scattered from the sky as there is direct from the sun. Hence staying out of the direct sun does not eliminate the hazard and still means that both the skin and the eyes can suffer long term damage from scattered UVR.

The Sun's Radiation Spectrum

• UVC and part of UVB are absorbed high in the atmosphere.
• UVB is very damaging to the skin and eyes, causes sunburn and is implicated in skin cancer induction.
• UVA is less damaging than UVB but lately there has been concern over long term hazards of exposure.

Why Wear Sunglasses?

As there is an association between UVR and eye damage, the eye should be protected from exposure to UVR. Sunglasses should decrease visible light to a comfortable level while blocking the invisible and potentially harmful UVR. The tint of the lens does not indicate the UVR absorbing characteristics of the lens. Good quality sunglasses that pass the transmittance requirements of the AS/NZS 1067(particularly, the "wraparound" type) provide the eyes with substantial protection against solar UVR. These sunglasses should be worn by both children and adults. The important points to look for when purchasing sunglasses are detailed below.

When to Wear Sunglasses?

Outdoors, particularly in the following circumstances:

• During Summer. The level of UVR at noon in summer is about three times as high as that for winter. More importantly, the levels of UVB can be as much as ten times higher (which is why sunburn takes such a short time in summer).
• Around noon (1 pm during daylight saving). 70% of the harmful UVB radiation that is received each day occurs within three hours either side of this time.
• On the beach or boating. There are usually few buildings or objects to block out part of the sky, so people are exposed to direct and scattered radiation from the whole sky.
• Skiing at high altitude. Solar UVR increases with altitude and, at 2000 metres (typical of Australian ski fields), can be as much as 30% higher than that at sea level. The high reflection of snow worsens the problem, so that the UVR dose to the eye can be quite large. Consequently, good eye protection while skiing is very important.
• When using medication which may act as a photosensitiser. Some medical treatments involve drugs which make people more sensitive to UVR, so that UVR exposures that would not normally be a problem are sufficient to cause damage.

Psoriasis patients undergoing PUVA therapy are extremely sensitive to UVA radiation for some time afterwards. They therefore require good eye protection and should wear sunglasses which absorb 100% of the UVR.

Note: Sunglasses should not be worn at night, especially while driving, as they reduce visibility in an environment which already has low light levels.

A Standard for Sunglasses

In 1971 Australia was the first country to introduce a national standard for sunglasses (AS 1067.1: 1990 'Sunglasses and fashion spectacles'). Australia is now one of the few countries along with UK, Germany, France and USA to have a standard for sunglasses. AS/NZS 1067 is the only mandatory sunglass standard in the world and the requirements for complying with the Safety Requirements and Performance Requirements sections are quite demanding. All sunglasses sold in Australia must comply with the standard.

In 2003 a revised sunglass standard AS/NZS 1067:2003: 'Sunglasses and Fashion Spectacles' was released. The new standard defines five categories of lenses:

Description of lens

• Fashion spectacles that are not sunglasses and provide very low reduction in sunglare with some UV protection
• Fashion spectacles that are not sunglasses and provide a limited reduction in sunglare with some UV protection
• Sunglasses that provide a medium level protection against sunglare with good UV protection
• Sunglasses that provide a high level of protection against sunglare with good UV protection
• Sunglasses for special purposes that provide a very high level of protection against sunglare with good UV protection

All sunglasses sold in Australia must be labelled to indicate which AS/NZS 1067:2003 category they comply with to provide consumers with the necessary information to select the correct sunglasses or fashion spectacles depending on their intended use.

For best protection choose wrap around sunglasses to reduce the amount of UVR entering from the sides. Non-wraparound designs allow UVR to enter from the sides reducing protection to the eyes even though the lenses themselves may provide 100% UVR protection. ARPANSA developed an eye protection factor (EPF) where sunglasses that comply with AS/NZS 1067:2003 can be assigned an EPF rating from 1 to 10. Sunglasses with EPF values of 9 and 10 transmit almost no UVR.

Sunglasses that provide excellent protection need not be expensive; the price of the sunglasses should not be used to gauge the quality of the lenses in respect to protection from UVR. Low cost sunglasses, which comply with the sunglass standard, may also provide excellent protection against UVR.

Prescription glasses, either clear or tinted, are excluded from the AS/NZS 1067 but may still provide protection against UVR. Optometrists have a professional duty to ensure that prescription sunglasses comply with the standard. The standard also covers children's sunglasses. It does not cover toy sunglasses that are clearly identified as such, ski goggles, spectacles for special purposes such as protection in solariums and protection against artificial UVR sources.

Summary

Look for the following points when purchasing good quality sunglasses.

• The sunglasses are actually general or specific purpose sunglasses and not fashion spectacles.
• The sunglasses carry a label that indicates they comply with or exceed the requirements of AS 1067 or are rated EPF 10.
• The sunglasses absorb more than 95% UVR (or transmit less than 5% UVR). Some sunglasses may even provide 99% or greater UVR absorption.
• If the sunglasses are to be used while driving, then colours should still be easily recognized when viewed through the lens.

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