This position statement is endorsed by the Australasian College of Dermatologists
Key messages and recommendations
Both episodic and cumulative exposure to UV radiation are associated with an increased risk of skin cancer. Clear or tinted films and window covers on the side windows of vehicles can provide protection by substantially reducing the amount of solar ultraviolet (UV) radiation that is transmitted through glass.
Cancer Council Australia recommends that people who spend long periods of time in a vehicle when the UV index levels are at 3 or above use a combination of sun protection measures, such as long sleeved clothing, sunglasses and sunscreen that is SPF 30 or higher. This will ensure occupants are protected both in the vehicle and when they leave it.
The need for window tinting on car and building glass should be considered with regard to the risks to the occupants. In general, UV radiation through the windows of buildings and cars poses little health risk to people unless they are spending extended periods of time close to windows that receive direct sun.
Definition of solar UV radiation
Solar UV radiation is divided in to three types, based on wavelength: UVA (320–400 nm); UVB (290–320 nm); and UVC (200–290 nm). Solar UVC does not reach the earth's surface as it is absorbed or scattered in the atmosphere. UVA and UVB are of concern because of their potential to cause skin and eye damage. Both UVA and UVB are associated with the development of skin cancer.
Transmission of UV radiation through glass
All types of commercial and automobile glass block the majority of UVB, but the degree of UVA transmission depends on the type of glass. While the thickness of glass does affect UV radiation transmission, the effect is limited compared with other factors.
Vehicle windscreens and side windows
UV radiation levels inside a car vary depending on factors such as whether the side windows are open or closed and the position of the vehicle in relation to the sun. UV radiation levels are generally much lower inside the vehicle than outside in full sunlight.
Laminated glass, used for windscreens, and tempered glass, usually used for side and rear windows, both block UVB radiation. However, UVA transmission depends on the type of glass. Laminated windscreens, made from a tough plastic layer bonded between two panes of glass, provide better protection against UV radiation compared with tempered glass, blocking about 98% of UVA radiation.
In comparison, tempered glass, used for side and rear windows, allows the transmission of substantially more UVA radiation. However the amount transmitted can vary widely depending on the thickness and colour of the glass. Estimates of UVA transmission through tempered glass range as high as 79%.
Clear or tinted films can reduce the amount of UV radiation penetrating through the side glass by over 99%. Alternatively, fabric side window covers can provide shade and UV protection. The amount of protection varies with different products. Tints and covers are only effective in providing protection against UV radiation when windows are closed.
Film and tint applied to car windows must meet state and territory regulations. All states and territories in Australia stipulate a maximum darkness, known as the visible light transmission level (VLT) for the windscreen, and side and rear windows. Windscreens are not to be tinted as the minimum requirement for VLT is 75% and even clear film reduces VLT below 75%. The Window Film Association of Australia and New Zealand website has information on regulations.
UVA transmission through building glass is highly dependent on the type of glass. Laminated building glass reduces transmission of UVA completely, while tempered building glass and smooth annealed building glass allow 71.6% and 74.3% of UVA transmission respectively. Where windows under deep eaves, verandas or awnings the transmission of UV radiation is reduced.
While tinting of windows in buildings can further reduce UV radiation transmission, the need for this should be weighed against the actual health risks to occupants. Generally, UV radiation through windows of buildings poses little risk to people unless they are spending extended periods of time close to a window that receives the direct sun or have a severe photosensitive skin disorder.
Position statement details
This position statement was developed by Cancer Council Australia's National Skin Cancer Committee. It was endorsed by Cancer Council Australia's principal Public Health Committee and published in June 2013.
- Polefka TG, Meyer TA, Agin PP, Bianchini RJ. Effects of solar radiation on the skin. J Cosmet Dermatol 2012 Jun;11(2):134-43 [Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/22672278].
- Rigel DS. Cutaneous ultraviolet exposure and its relationship to the development of skin cancer. J Am Acad Dermatol 2008 May;58(5 Suppl 2):S129-32 [Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/18410798].
- Heng MC. Curcumin targeted signaling pathways: basis for anti-photoaging and anti-carcinogenic therapy. Int J Dermatol 2010 Jun;49(6):608-22 [Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/20618464].
- Almutawa F, Vandal R, Wang SQ, Lim HW. Current status of photoprotection by window glass, automobile glass, window films, and sunglasses. Photodermatol Photoimmunol Photomed 2013 Apr;29(2):65-72 [Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/23458389].
- Duarte I, Rotter A, Malvestiti A, Silva M. The role of glass as a barrier against the transmission of ultraviolet radiation: an experimental study. Photodermatol Photoimmunol Photomed 2009 Aug;25(4):181-4 [Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/19614895].
- Bernstein EF, Schwartz M, Viehmeyer R, Arocena MS, Sambuco CP, Ksenzenko SM. Measurement of protection afforded by ultraviolet-absorbing window film using an in vitro model of photodamage. Lasers Surg Med 2006 Apr;38(4):337-42 [Abstract available at http://www.ncbi.nlm.nih.gov/pubmed/16596658].