The idea of healthy public policy arose in the health promotion movement and calls for governments to use policy in all sectors to promote health. Examples of policy areas that affect health include income support (pensions, child benefits, minimum wage, unemployment insurance), environmental protection (legislation and regulations intended to preserve air and food quality), subsidized child care, housing (public housing, rent controls, urban planning) and transportation (whether to encourage public transportation or private cars). Of course, nearly all policy can influence health in some way, and we must be wary of practising health imperialism (in which we would argue that public policy should be guided only by health impact), but that is a philosophical question... Policy exists at the municipal, state (provincial), national and (in a limited way) international levels.