We are increasingly aware of the importance of proper skin photoprotection to prevent skin cancer, especially when outdoors (on the beach or in the mountains). However, we fail to attach the same importance to other daily activities. What happens when we are driving? Can car windows protect us from ultraviolet radiation?
Last year, a photograph of a 69-year-old man, a truck driver for 28 years, was posted around the world. This photograph, also featured in our blog, clearly shows how ongoing sun exposure was much more evident on the left side of the face. The fact is we rarely consider using sunscreen in the car. A recent study made among skin cancer patiens shows that, even being aware people, few applied sunscreen when in their car, even though they usually did so when outdoors. The reason is they didn’t think it was necessary, especially if driving with the windows closed.
The same study also revealed a higher incidence of non-melanoma skin cancers in the left half of the face of these patients, except in those whose cars had tinted glass.
Be grateful for glass
The main factors influencing the transmission of ultraviolet (UV) light through the windows of a car are the type of glass (laminated or not), the degree of tint and whether the glass has a UV radiation absorber film.
Ultraviolet light type B (UVB) – the cause of sunburn and of certain types of skin cancer – is filtered fully by any type of glass. But not so for ultraviolet light type A (UVA), which is partly responsible for photoageing and certain types of skin cancer.
It is important to remember that car windshields and rear windows are made with laminated glass, which absorbs 98% of UV radiation. However, the side windows are often made from unlaminated glass and so allow through a higher level of UVA radiation.
This explains why, in countries where people drive on the right, the left arm and shoulder and the left side of the face receive more UV radiation.
Enhance protection inside the car
In the USA, driving is the main activity performed away from home, more so even than gardening or outdoor exercising. A person from the USA is estimated to spend between 80 and 100 minutes a day driving; in Europe the figure is probably lower, but still significant.
Naturally, there is always the option of applying suitable sunscreen half an hour before driving, but the reality shows that almost no one does this. It is therefore advisable to enhance the protection provided by car windows, especially if our work involves driving.
Some cars are equipped ex-factory with tinted side windows that ensure very little radiation. Another option is approved anti-UV adhesive tinted film applied to the windows. And if the laws of your country do not allow this kind of film for safety reasons, adhesives are available in the market that transmit a mere 0.4% of UV radiation and so reduce sun damage; but since they have hardly any tint, they have the additional advantage that visibility is not reduced.
Virtually any type of glass can effectively block UVB rays, but not necessarily UVA rays, which have a longer wavelength. This is clinically significant for patients affected by photosensitivity, which can be caused by various diseases (among them, porphyria and lupus erythematosus).
A low dose (5 joules/cm2) of UVA – equivalent to only about 30 minutes of exposure behind non-laminated glass – may be sufficient to induce a potentially severe skin eruption in such patients. With protection from laminated glass, at least 50 hours of exposure would be needed to cause skin lesions.
Don’t forget ...
To sum up, when travelling by car, whether or not as a driver, we need to remain aware of the harmful effects of the sun on our skin. Remember also that these effects are cumulative over a lifetime and that we spent many hours in the car each year.
Here are some practical suggestions:
- Always apply sunscreen to the face and hands.
- Wear sunglasses and long-sleeved clothing.
- Keep the windows closed.
- Apply an anti-UV treatment to the glass.