A core premise of public health is that prevention can be a powerful instrument for improving human health, one that is often cost-effective and minimises harm to individuals from ill health. The core objectives of prevention include the reduction or modification of exposure to risks including metabolic, behavioural, environmental, and occupational factors. Quantifying risks to health and thus the targets of many public health actions is an essential prerequisite for effective public health. The evidence on the relation between risk exposure and health is constantly evolving: new information about the relative risks (RRs) associated with different risks for different outcomes continues to emerge from cohort studies, randomised trials, and case-control studies. These studies can establish evidence for new risks or risk-outcome pairs or reduce the strength of evidence for existing risks. New data are also regularly collected on the levels of exposure……….