Sunscreen use and intentional exposure to ultraviolet A and B radiation: adouble blind randomized trial using personal dosimeters

A previous randomized trial found that sunscreen use could extend intention al sun exposure, thereby possibly increasing the risk of cutaneous melanoma . In a similarly designed trial, we examined the effect of the use of sunsc reens having different sun protection factor (SPF) on actual exposure to ul traviolet B (UVB) and ultraviolet A (UVA) radiation. In June 1998, 58 Europ ean participants 18-24 years old were randomized to receive a SPF 10 or 30 sunscreens and were asked to complete daily records of their sun exposure d uring their summer holidays of whom 44 utilized a personal UVA and UVB dosi meter in a standard way during their sunbathing sessions. The median daily sunbathing duration was 2.4 hours in the SPF 10 group and 3.0 hours in the SPF 30 group (P = 0.054). The increase in daily sunbathing duration was par alleled by an increase in daily UVB exposure, but not by changes in UVA or UVB accumulated over all sunbathing sessions, or in daily UVA exposure. Of all participants, those who used the SPF 30 sunscreen and had no sunburn sp ent the highest number of hours in sunbathing activities. Differences betwe en the two SPF groups in total number of sunbathing hours, daily sunbathing duration, and daily UVB exposure were largest among participants without s unburn during holidays. Among those with sunburn, the differences between t he two groups tended to reduce. in conclusion, sunscreens used during sunba thing tended to increase the duration of exposures to doses of ultraviolet radiation below the sunburn threshold. (C) 2000 Cancer Research Campaign.