Radiation Safety Committee
Sunglasses and protection from solar uv
Some Frequently Asked Questions
- What are the health effects of solar UV radiation?
- How is UV radiation transmitted?
- What part of the UV radiation spectrum causes concern?
- Why do we need to wear sunglasses?
- When do we need to wear sunglasses?
- Is there a Standard for sunglasses?
- What should we look for when purchasing sunglasses?
What are the health effects of solar UV radiation?
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.
How is UV radiation transmitted?
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.
What part of the UV radiation spectrum causes concern?
UV radiation is made up of UVA, UVB and UVC, which has the folowing properties:
- 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 do we need to wear sunglasses?
Sunglasses eliminate solar UVR, in particular the more-damaging UVB radiation. As the eye cannot see UVR, its transmission by sunglasses is not only undesirable, but unnecessary. Reducing the amount of UVR that the eye is exposed to over a person’s lifetime can do no harm and is likely to prove beneficial. Good quality sunglasses (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 do we need 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.
Is there a standard for sunglasses?
Standards Australia have issued the standard AS 1067 Sunglasses and Fashion Spectacles, which sets limits on the allowed transmittances of fashion spectacles, general purpose sunglasses and specific purpose sunglasses. Fashion spectacles provide the least UVR protection and are usually worn for cosmetic purposes only.
General purpose sunglasses are intended to reduce sun glare in ordinary circumstances (including driving in daylight). These offer good protection against solar UVR.
Specific purpose sunglasses are intended for situations where general purpose sunglasses may not provide adequate protection, due to the presence of higher levels of solar UVR, for example, on snowfields. The requirements of the standard are most stringent for specific purpose sunglasses and this type provides the greatest protection against solar UVR.
Sunglasses that comply with the requirements of AS 1067 should be labelled as such. Those labelled "EPF 10" (Eye Protection Factor rating 10) actually exceed the requirements of AS 1067 and thus provide even greater protection. Others may be labelled "absorbs 100% UVR" these should also carry the AS 1067 label.
Sunglasses that are to be worn while driving must also comply with the coloration limits of AS 1067. Colors, in particular traffic signals, will then still be recognisable when viewed through the lens.
What should I look for when purchasing sunglasses?
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.