A series of questions and answers about ultraviolet radiation, including from the sun, and how you can protect yourself from their harmful effects.
What is solar ultraviolet radiation (UVR)?
Solar radiation is electromagnetic radiation emitted by the sun. At the earth's surface it consists mainly of visible light and infrared radiation (IR). Our eyes respond to visible light and IR can be felt on the skin as heat. Ultraviolet radiation (UVR) is also present and is invisible, high-energy radiation, which is capable of causing damage to living organisms. Further information about ultraviolet radiation can be obtained from Understanding radiation.
Can you feel solar UVR?
When people state that the sun has 'sting in it' they are confusing infrared radiation with UVR. The skin detects infrared radiation as a sensation of heat but it does not detect UVR. If enough UVR exposure has occurred to cause sunburn, the damaged skin may become more sensitive to IR.
Is temperature related to solar UVR?
Solar UVR levels are generally not related to temperature. There can be high UVR levels even on cool days unless there is considerable cloud cover. UVR and temperature peak at different times of the day. UVR is usually highest around midday but the temperature is often highest later in the afternoon. In general there is a misconception that high temperatures and UVR intensity are related, as most people tend to get sunburnt when temperatures are higher. Therefore, people tend to assume they require less protection from the sun when temperatures are lower. The intensity of UVR can be high on cool clear days as well as hot days during certain times of the year. Without knowing the level of UVR people may incorrectly use temperature as a guide to the level of sun protection required.
Why is there so much solar UVR in Australia?
Due to its geographical location and close proximity to the equator, Australia experiences some of the highest levels of solar UVR in the world. The earth's elliptical orbit brings the earth closer to the sun in January, during summer in the southern hemisphere, resulting in higher levels of UVR. Also, relatively clear atmospheric conditions and the influence of ozone depletion over Antarctica contribute to higher levels of solar UVR in the southern hemisphere than at similar latitudes in the northern hemisphere.
What factors affect solar UVR levels?
The most important factor affecting the level of solar UVR at the earth's surface is the height of the sun in the sky. The higher the sun is in the sky, the shorter the path the UVR has to travel through the atmosphere, so less is absorbed resulting in higher levels of UVR at the surface. Conversely, when the sun is low in the sky the longer path to travel results in more UVR absorption and scattering by the atmosphere results in lower levels at the surface. Other key factors include proximity to the equator, seasonal effects, cloud cover, ozone, scattering in the open sky, reflections from the environment and altitude.
What is the UV Index?
The World Health Organization (WHO) led the development of the UV Index, 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. For more information, see World Health Organization UV Index.
What are the risks from UVR exposure?
Overexposure to UVR can cause sunburn, skin damage and skin cancer. Two in three Australians will be diagnosed with skin cancer by the time they reach 70 years of age. UVR exposure also places our eyes at risk of photokeratitis, photoconjunctivitus and cataracts. The most obvious short-term effect of overexposure to UVR is sunburn, also known as erythema. The more UVR exposure, the worse the sunburn becomes. A person's cumulative exposure to UVR along with the number of severe sunburns they have received, especially during childhood, increases their risk of developing skin cancer. Skin cancers affect people of all skin types. Further information about skin cancers can be obtained from the Cancer Councils.
Why is skin colour important?
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 according to the Fitzpatrick Skin Phototype system. People with skin type 1 have the highest risk of premature skin aging and greatest risk of developing some form of skin cancer. 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 (olive 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 that reduces the risk of health effects, so they rarely burn and easily tan. However, even though darker skin offers some natural protection against UVR those people are still not immune to developing skin cancers. Sun protection is recommended regardless of skin type.
How can you reduce your UVR exposure?
Many forms of protection are available to reduce your exposure to solar UVR. The best protection is to avoid going outdoors during periods of high UV levels. When outdoors, wear clothing with good body coverage, apply sunscreen, wear a hat, seek shade and slide on sunglasses. Young children can be unaware of the dangers of solar UVR and may require supervision for best protection. SunSmart programs operate in each state and territory of Australia by respective Cancer Councils, all using common principals but tailored to jurisdictional needs. The sun protection message is Slip! Slop! Slap! Seek! Slide! See Sun Protection for more information.
What is a Protection Factor?
The concept of a protection factor (PF) is useful when quantifying the UVR protection that products such as fabrics, sunscreen and eyewear can provide. The PF indicates how much UVR is blocked by a material. For example, a material with a UPF rating of 20 would only allow 1/20th of the hazardous UVR falling on its surface to pass through it. This means that this material would reduce the UVR exposure by a factor of 20. In other words, this material would block 95% of the UVR and transmit only 5%. To provide adequate sun protection, materials must usually have a PF of 15 or higher.
How effective are windows and window tints at solar UVR protection?
Although most cars provide substantial shading for the occupants, glassed areas create the potential for UVR exposure. Laminated windscreens, which consist of a tough plastic layer bonded between two panes of glass, typically have Protection Factor (PF) ratings of 70 or higher. However the PF of plain window glass as used in car side windows is usually about 15 or less. The amount of UVB radiation transmitted through plain window glass varies widely between glass types, however most types transmit about 60% of the UVA. This means that a person sitting in a car where the sun can reach them may still be exposed to UVR.
Most automotive window tints absorb a significant amount of UVR and provide excellent protection. Some tints appear clear to the human eye but strongly absorb UVR. Wearing sunscreen whilst driving is an effective way of preventing sunburn.
Are solariums safe?
No. Sunbeds used in solariums, and sun tanning lamps are artificial tanning procedures said to offer an effective, quick and harmless alternative to natural sunlight. There is no evidence to support that tanning in a solarium is safer than tanning in the sun. Both have been shown to increase adverse health risks. There is strong evidence that the UVR emitted by the lamps used in solariums damage the skin and increase the risk of developing skin cancer. Individuals with skin that does not tan and burns easily are most at risk of developing skin cancer later in life.
People must also consider exposure of their eyes to UVR emitted from the lamps, which are in close proximity when lying on a sunbed. Permanent eye damage may result from long-term exposure to the UVR.
It is illegal to operate commercial solarium units in all states and territories of Australia.
Do artificial light sources used in the home emit UVR?
Fluorescent and halogen lamps may emit small amounts UVR. However, research has shown that most do not pose a risk, especially if they are fitted with a diffuser or filter that absorbs the UVR.
Tungsten halogen lamps with incorporated reflectors are used extensively in area, display and home lighting. These lamps emit some UVR, which may be a hazard to the skin and eyes of people who remain in close proximity for long periods. In lighting applications where the lamps are close to people they should be fitted with a glass cover to block the UVR emissions.
What sun protection precautions should outdoor workers take?
For most outdoor workers the sun is the primary source of UVR exposure. Construction workers, landscape gardeners, lifeguards and farmers, for example, have potentially high-risk workplaces due to the long hours they spend outdoors in the sun. This results in greater solar UVR exposures than indoor workers and places them at greater risk of developing skin cancers. Further information regarding sun protection guidance for workers can be obtained from Safe Work Australia.
Are manufactured UVR sources dangerous?
UVR sources are used in a range of industrial and medical applications including phototherapy, lithography, materials testing, sterilisation and welding. High levels of UV radiation may be emitted by some sources and adequate protective measures must be taken to prevent exposure of the equipment operators. This may include shielding the sources and providing protective clothing for the operators. Further information regarding guidance for workers can be obtained from Safe Work Australia and the ARPANSA Radiation Protection Standard for Occupational Exposure to Ultraviolet Radiation.
How do I get enough Vitamin D from the sun without having too much exposure to UVR?
The sun's UVR is both the major cause of skin cancer and the best source of vitamin D. In Australia, we need to balance the risk of skin cancer from too much sun exposure with maintaining adequate vitamin D levels. Sensible sun protection does not put people at risk of vitamin D deficiency.
Vitamin D generation in the skin from sunlight depends on many factors including location, time of year, day-to-day activities and individual circumstances.
For most people, adequate vitamin D levels are reached through regular daily activity and incidental exposure to the sun. In winter in the southern parts of Australia, where UVR levels are less intense, people may need to increase their hours of sunlight exposure to maintain adequate vitamin D levels.
More information is available from Cancer Council Australia.
