Scientists in the US say drivers who roll down the side windows are at an even greater risk.
A story in the Daily Mail this week suggests that glass blocks the UVB rays that cause sunburn but not the deeper-penetrating UVA rays linked to cancer.
The scientists from the St Louis University School of Medicine in Missouri studied almost 900 patients – 559 men and 339 women – with skin cancer on either side of their bodies.
It found that the rate of cancers directly correlated to the areas of the body most often exposed to ultraviolet radiation when driving. In the US this was obviously on the left-hand side of the body.
Report author Dr Scott Fosko said: ‘Drivers who spend more hours in the car are more likely to develop skin cancer on the left side of the body, particularly skin cancers that develop gradually over time.’