The exposome: from concept to utility

the broad sense of ‘non-genetic’. The exposome, therefore, complements the genome by providing a comprehensive description of lifelong exposure history. Remaining focused on the element of application (to epidemiology) is a key to ensuring that the exposome is translated from concept to utility for better delineating the causes and prevention of human disease. At the time of the original proposal, it was recognized that whereas exquisite tools had been developed to sequence the human genome and to interrogate individual susceptibility through genome-wide association studies (GWAS), there was a relative paucity of comparable tools, or indeed investment, in relation to exposure assessment. Given that cancer and other chronic diseases develop predominantly from a combination of environmental exposures played out on a particular genetic background, the inability to measure one part of the gene:environment combination with anything approaching the precision of the other will stymie progress. This becomes particularly acute as epidemiology aims to tease out relatively modest effect sizes associated with specific environmental exposures. This commentary seeks to further define the exposome and to describe how its realisation may be achieved in epidemiological studies. The commentary focuses on cancer but many of the concepts are applicable to other chronic diseases.