Environmental Determinants of the Social Gradient in Cancer Incidence

Environmental determinants encompass the features of both physical and socioeconomic environments where people live, work and recreate. Growing evidence suggests that the socioeconomic gradient in cancer incidence might be in part attributed to environmental factors, particularly air pollution, radon, water contamination and, to a lesser degree, neighbourhood socioeconomic deprivation, access to green space and noise exposure. Two interrelated mechanisms that might explain the relationship between environmental determinants and the social gradient in cancer risk are: environmental factors linked to cancer are unevenly distributed across socioeconomic groups (differential exposure) and/or the effect of environmental factors causing cancer differs across socioeconomic groups (differential susceptibility). Investigations on the connections between cancer risk and environmental dominants might be affected by a particular set of bias and errors related to the definition of residential neighbourhoods and the mismatch between direct and indirect measures of exposure. While the evidence is becoming increasingly robust, this is a relatively new research field with substantial room for conceptual and methodological improvement. Such research will serve not only to disentangle epidemiological models of causation but may also point to unique environmental and territorial planning interventions towards the reduction of cancer risk at a population level.