ECNIS is a Network of Excellence within the European Union’s Sixth Framework Programme, Priority 5: Food Quality and Safety. It brings together some of the best European research groups in a concerted effort to achieve improved understanding of the environmental causes of cancer, of the potential of diet to prevent cancer, and of the ways by which heredity can affect individual susceptibility to carcinogens, with the ultimate aim of reducing the cancer burden in Europe. ECNIS is coordinated by Prof. Konrad Rydzyński, The Nofer Institute of Occupational Medicine, św. Teresy 8, 91‑348 Łódź, Poland This review has been prepared as part of ECNIS Work Package 7: Development and Validation of Biomarkers of Individual Susceptibility.