Erythemal and vitamin D weighted solar UV dose-rates and doses estimated from measurements in mainland France and on Réunion Island.

Solar UV radiation causes beneficial and detrimental changes in human health. International and national Health agencies recommend avoiding sun exposure when the solar rays are strongest (typically 2 h before and after solar noon). In this study we detail and refine such recommendations. We estimated biologically-effective radiation (inductive of erythema and pre-vitamin D) using spectral solar UV radiation measurements on a horizontal plane at three French sites equipped with spectroradiometers: Villeneuve d'Ascq (VDA) (North of France); Observatoire de Haute-Provence (OHP) (French Southern Alps); and Saint-Denis de La Réunion (SDR) on Réunion Island, in the Indian Ocean. These sites are very different: VDA is a semi-urban site in a flat region, OHP a rural mountainous site and SDR a coastal urban site on a small mountainous island. Biologically active radiation was analyzed by studying erythema induction and measuring pre-vitamin D synthesis. Dose-rates, doses and times for sunburn induction and vitamin D production were derived. Regarding the level of vitamin D dose considered here (1000 IU), we found that at mainland sites time required for vitamin D synthesis was relatively long, even around solar noon, in winter months this could be 2-3 h for phototype II individuals exposing their face and hands. In the tropics vitamin D could always be synthesized in a reasonable time (e.g. 20 min in winter). By contrast, in summer, the required duration times (exposing face, hands, arms and legs) are very short, approximately 2-4 min on the mainland and 1 min in the tropics for phototype II individuals. In all skin phototypes the duration of sun exposure required to induce erythema was generally longer than that to produce vitamin D. These quantitative results, obtained using an instrument measuring on a horizontal plane and with an unobstructed view, do not represent realistic values for human exposure. To account for realistic human body exposure, received doses and times of exposure were adjusted. Our study shows that, mostly in summer, the time periods where limited solar exposure is recommended should be extended, especially at low latitude locations.

A cluster randomized trial to evaluate a health education programme "Living with Sun at School".

Over-exposure to sunlight increases the risk of skin cancers, particularly when exposure occurs during childhood. School teachers can play an active role in providing an education programme that can help prevent this. "Living with the Sun," (LWS) is a sun safety education program for school children based on a handy guide for classroom activities designed to improve children's knowledge, but moreover to positively modify their sun safety attitudes and behaviours. The goal of our study was to determine the effectiveness of this programme by examining children's knowledge, attitude and sun exposure behaviours prior to and after the completion of the programme. We carried out a cluster randomised trial in which the classes were randomly assigned to one of two groups; one using the LWS programme and another that didn't, serving as the control. Data was collected before completion of the programme and an additional three times in the year after completion. The 70 participating classes (1,365 schoolchildren) were distributed throughout France. Statistical analysis confirmed that knowledge of sun risk increased significantly in the LWS classes (p < 0.001). Both groups positively changed their attitudes when considering the best sun protection, but the LWS group proved to consistently be more convinced (p = 0.04). After the summer holidays, differences between the two groups decreased throughout the year but stayed globally significant. We also observed some significant behaviour modification during the holidays. For instance, the LWS group applied sunscreen more frequently than the control group, and were more likely to wear a hat (72% versus 59%) and use a sun umbrella on the beach (75% versus 64%).

Dress up for sun protection/creation of public awareness.

A clear or white skin was a sign of distinction for millennia. However, white people, during the last century, sought a tan, which was thought a sign of good health and upper social class. Sun-seekers are now better aware of the risks to their health of UV exposure, but their behaviour has not improved significantly at a global level. The only country deviating from this observation is Australia where aggressive prevention campaigns, such as the "Slip, Slop, Slap" and "Sun Smart" campaigns, have been conducted with success over more than 30 years. However, the financial cost of such campaigns is high, and may be considered too high in countries where skin cancers are fortunately less frequent and/or the culture of public health is unfortunately less developed. The global solar UV index (UVI) program is a response to the increasing skin cancer rate in all white populations. Lead by WHO, the UVI program aims to help people to evaluate the maximum intensity of UV radiation on a given day and at a given location. Since the beginning of the 1990s, UVI forecasts have increasingly been broadcast with weather bulletins. In the matter of protection of the skin, the entire scientific community has agreed that avoiding sun exposure during the 3 to 5 h around noon and to be fully clothed should be recommended. However, for a lot of people to protect the skin means only to apply sunscreen, and these individuals need convincing that it is preferable to use clothes. It may be necessary to involve public health actors in the increasing efforts to educate people and persuade them to adapt their protection strategy to their skin type, to the UV intensity and to their daily activities.