Summertime motorists should consider wearing gloves to reduce their risk of developing skin cancer, the Cancer Society warns - even when their car windows are closed.

The society yesterday spoke out against the myth that glass protects against the sun's ultraviolet (UV) radiation, which can cause malignant melanoma and other skin cancers.

Plain, clear vehicle glass blocks only 37 per cent of UV-A radiation. The main risk comes from long or frequent trips exposed to sun through side windows.

The issue was highlighted by sunscreen maker Oasis Beauty, which urged drivers to apply sunscreen before driving.

But the society says covering up with protective clothing is preferable.

"The International Agency for Research on Cancer says sunscreen should never be the first line of defence unless it's exposed skin that can't otherwise be covered," said its adviser on skin cancer control, Judith Galtry.

People who spent long periods in a vehicle during summer, especially those who drove as part of their work, should wear long sleeves and sunglasses and apply sunscreen to any exposed skin.

And as an alternative to putting sunscreen on their hands, "they may wish to use driving gloves".

The Transport Agency said laminated windscreens were a legal requirement for all cars built from mid-1986 and for all buses and trucks built from mid-1997.

Side and rear windows did not have to be laminated, and most were not, although the side and rear windows of many modern vehicles were tinted to varying degrees.

Mid-January is the peak time for UV radiation levels within the high-risk season that lasts from September to April for most of New Zealand.

In these months, the Cancer Society recommends personal protection - seeking shade, wearing cover-up clothing, sunglasses and sunhats, and applying sunscreen - for much of the day and especially from 11am to 4pm.

Each year malignant melanoma kills more than 200 people and about 2000 new cases are diagnosed.

Sunscreen:

* Clear auto-glass (side windows) blocks 97 per cent of ultraviolet B radiation and 37 per cent of UV-A

* Laminated windscreens block all UV-B and 80 per cent UV-A

* Clear windscreen films block up to 97 per cent of UV-A

* Clear or tinted films on side windows reduce UV-A and B by varying amounts, depending on product.

Source: Cancer Council Australia