In 2012, 12.6 million people died as a result of living or working in an unhealthy environment, representing 23% of all deaths. When accounting for both death and disability, the fraction of the global burden of disease due to the environment is 22%. In children under five years, up to 26% of all deaths could be prevented, if environmental risks were removed. 68% of these attributable deaths and 56% of attributable DALYs could be estimated with evidence-based comparative risk assessment methods, the impacts of other environmental exposures were assessed through expert opinion.