Context

Exposure to ultraviolet radiation can be either beneficial or harmful, depending on the dose received. For example, a brief daily exposure (10 to 15 minutes) is essential in order to encourage synthesis of vitamin D, a hormone that plays a role in regulating calcium metabolism. Also, certain skin diseases are treated by controlled exposure to UVA and UVB radiation. Overexposure to UV radiation, on the other hand, can cause numerous health problems involving the eyes (cataracts, keratitis and macular degeneration) and skin (sunburn, premature aging, photocarcinogenesis and immunosuppression). Photocarcinogenesis of the skin leads to two types of cancer:
• Melanoma: caused by intermittent exposure to ultraviolet radiation; the advanced stages of this cancer are very difficult to treat. The rate of incidence among fair-skinned populations world-wide is doubling every 10 years.
• Skin carcinoma: caused by chronic exposure to UV radiation; this group of cancers are rarely fatal but leave disfiguring scars when surgically removed. The incidence of carcinomas is also rising.

There are several potential causes for the increase in these cancers:

• Changes in human behaviour, resulting in longer and/or more intensive exposure (e.g. more frequent holidays in sunny locations and a fashion culture that values a tanned appearance);
• Longer life expectancy;
• Changes in the intensity of the ultraviolet radiation reaching the earth's surface as a result of disruption to environmental parameters (e.g. stratospheric ozone, cloud cover, aerosols and reflectivity) due to climate change or human activity.
Relatively few epidemiological studies into these possible causes have been conducted. 

Objectives

Based on these observations, the RISC-UV project aims to determine whether there is a link between the observed increase in skin cancer incidence rates and the variation in UV radiation caused by chemical changes in the atmosphere, and to assess the relative weights of behavioural and environmental factors in this rise in skin cancer. The project relies on scientific collaboration between a medical community concerned by health problems associated with exposure to ultraviolet radiation (i.e. dermatologists, oncologists and epidemiologists) and atmospheric physicists studying variations in solar radiation at the earth's surface prompted by environmental changes. 

Mélanome de la peau Evolution de l'incidence et de la mortalité en France (1980-2005)

Methodology

Part 1: Organization of a conference with the aim of describing the state of the art in each community concerned by this issue and defining additional joint projects

During the conference, which is scheduled for November 2008, experts will speak on the state of the art in the following areas:
• UV radiation measurement techniques and artefacts;
• Epidemiological models relating to UV exposure;
• Research into social behaviour with regard to UV exposure;
• Modelling variations in ultraviolet radiation caused by climate change and related skin cancer risks.

Discussions arising out of this conference may lead to the setting-up of further joint projects at national or European level.

Part 2: Measurement of ultraviolet radiation and related studies

1) Measurement campaign for UV radiation and associated parameters

An experimental campaign will be conducted at SIRTA from 8^th September to 8^th October 2008. The purpose of this campaign is to obtain, analyze and quantitatively link the UV radiation data obtained at various spatial scales (satellite, ground-based and spot measurements) by a variety of measuring systems:

The aim of the campaign is to evaluate the consistency of the measurements obtained simultaneously by satellite instruments, ground-based measuring instruments and individual dosimeters. The following studies will be carried out to this end:
• Analysis of erythematous doses and UV-A radiation measured by the UV-E and UV-A pyranometer in a variety of situations (solar zenith angle, ozone and aerosol concentrations and cloud cover), and comparison with the measurements obtained by the UV spectroradiometer and satellite observations (with scale conversion).
• Analysis of individual dosimeter measurements and comparison with the estimated erythematous doses obtained by UV pyranometry and satellite observations. 

Pyranomètre UV

Dosimètre individuel

2) Analysis of the long-term consistency of data series relating to UV radiation and related parameters

• Literature study for the purpose of producing an assessment of the numerous confirmations of satellite measurements by ground-based instruments;
• Study based on measurements made by LOA and the Observatoire de Haute Provence, with the aim of producing a long-term assessment of the influence of aerosols, cloud cover and the total ozone column on the surface ultraviolet radiation values measured by satellite and ground-based instruments.

Part 3: Analysis of the medical, behavioural and environmental parameters involved in skin carcinogenesis

Although most of the factors involved in the skin cancer development have now been identified, the relative weights of the medical, behavioural and environmental parameters are still poorly understood. This issue will be addressed in a two-stage approach:
• A literature study using a meta-analysis technique to identify and determine the relative weights of human parameters (i.e. medical, demographic and behavioural characteristics) on the risk of developing skin cancer. In addition to the general population, this study will consider populations at higher risk of developing skin cancers, such as recipients of organ transplants and patients infected with HIV.
• In the second stage of the programme, UV exposure and temperature variations between regions and over time will be incorporated into the human risk factors identified by the literature-based analysis. This research will be carried out on retrospective patient cohorts (melanoma cohort, cohorts of transplant recipients with and without carcinomas, etc.).
It will then be possible to obtain a fairly precise estimate of the relative weights of the human, behavioural and environmental factors in skin carcinogenesis. This information should in turn allow the development of prognostic epidemiological models to represent changes in skin cancer rates according to future changes to the various parameters.