[The contribution of the physico-chemical environment to the genesis of cancer: what extent and how to measure it?].

The growing incidence of cancers for the last 20 years in France and in Europe confronts scientists with the problem of their origin. Apart from standard factors such as addiction to smoking, alcoholism and overweight due to inadequate diets, the hypothesis that other environmental causes have recently appeared, is formulated. The author aims at reinforcing this hypothesis based on epidemiological, biological and toxicological arguments. Addiction to smoking and alcoholism have significantly decreased for the last 20 to 30 years and the incidence rise concerns cancers that are not related to these factors. Endogenous factors of genetic susceptibility can hardly have changed over one generation and actually can favour interaction with exogenous factors involving either our life style or the environment. The role of biological factors associated with ageing to explain the increase in cancer rate according to age is worth discussing. Many factors (radiation and chemical molecules) present in the environment, factors that international organizations have proven to be certainly, probably or possibly cancer-inducing, are considered. Some acting as mutagenic, others as promoters can add their cancer-inducing effects to smoking or other factors associated with our lifestyle. However, with the exception of smoking, most of the factors associated with our lifestyle are not mutagenic, an observation which leads to consider mutagenic factors from the environment, because any cancer implies the occurrence of mutations at its initiation step. The magnitude of the risk related to environmental factors is not yet known, therefore implying the need for new research aiming at assessing them accurately. Although, as far as public health is concerned, fighting addiction to smoking, alcoholism and unhealthy eating habits needs to be pursued, evidence regarding these new environmental factors of physico-chemical nature poses the problem of their prevention.