外文翻译(Urban_Health_Isues).docx

Urban Health IssuesDemographic trends suggest that there is an urgent need to consider the health of urbanpopulations. Cities are becoming the predominant mode of living for the worlds population. According to the United Nations, approximately 29% of the worlds population lived in urban areas in 1950. By 2000, 47% lived in urban areas, and the United Nations projects that approximately 61% of the worlds population will live in cities by 2030. Overall, the worlds urban population is expected to grow from 2.86 billion in 2000 to 4.94 billion in 2030. As the worlds urban population grows, so does the number of urban centers. The number of cities with populations of 500,000 or more grew from 447 in 1975 to 804 in 2000. In 1975, there were four megacities with populations of 10 million or more worldwide; by 2000, there were 18, and 22 are projected by 2015. Most cities are in middle to low-income countries; in 2000, middle to low income countries contained 72% of the worlds cities. Epidemiology can play a central role in studying both health and disease in the urban context and how urban characteristics may influence the health of populations. Characteristics of the urban environment that may shape population health include features of the social and physical environment and features of the urban resource infrastructure. Features of the social and physical environment and the urban resource infrastructure in turn are shaped by municipal, national, and global forces and trends. Defining Urban Areas One of the key challenges that faces epidemiologic inquiry about health in cities and how city characteristics influence health is that there is little consensus about the definition of urban and what constitutes a city. The U.S. Bureau of the Census defines an urbanized area by specifying a minimum population (50,000 people) and a particular minimum population density (1,000 people per square mile). The Census Bureau thus provides a dichotomy whereby territory, population, and