Environmental pollutants and skin cancer.

We are increasingly exposed to environmental pollution. Pollutants can be inhaled, ingested or come into contact with the skin depending on the form in which they occur. On metabolization, activation, or accumulation, pollutants can become extremely toxic for the vital organs and this is often related to a strong genotoxic effect. Since the skin acts as a barrier between the organism and the environment, it is frequently directly exposed to pollution. It is very often degraded by polluting agents and acts as an inlet toward other tissues. Numerous studies in man recognize and demonstrate the carcinogenic power of certain pollutants in the digestive and respiratory tracts. The "pollutants" that react most specifically with the skin are: ultraviolet radiation, polycyclic aromatic hydrocarbons (e.g., benzo[a]pyrene), volatile organic compounds (e.g., benzene), heavy metals, and ozone. Ultraviolet radiation, a "physical" pollutant, has been described as being the factor responsible for most skin cancers in man. The genotoxicity of UV light is well documented (type of lesion or mutation, etc.) and its carcinogenic effect is clearly demonstrated in vivo in man. A few epidemiological studies describe the carcinogenicity of certain pollutants such as arsenic or lead on the skin. However, most of the evidence for the role of pollutants in skin cancers comes from in vivo animal studies or from in vitro studies (e.g., PAHs). In this report, different studies are presented to illustrate the research strategies developed to investigate the mechanism of action of "chemical" pollutants and their potential role in human skin pathology. All the study models and the associated techniques of investigation are tools for a better understanding and thus more efficient prevention of the deleterious effects caused by the environment.