The average North American now spends approximately 90 percent of the time indoors, 5 percent in cars, and only 5 percent outdoors. In the developed world, four out of five people live in urban settlements, while globally, at the dawn of the twenty-first century more than half of humanity was urbanized.
As a result, the built environment (as distinct from the natural environment) is now the most significant environment for humans, especially in the developed world. The built environment includes both the buildings in which people spend their time (home, school, workplace, recreational facilities, shops and malls, etc.) and the broader built environment of human settlements (villages, towns, suburbs, and cities). It is not only a physical environment, it is also a social environment, where people gather and relate to one another. The design, construction, and operation of built environments has enormous implications for human health.
HOUSING AND HEALTH
Housing is a basic determinant of health, and many organizations, including the World Health Organization (WHO) and the American Public Health Association (APHA), have developed standards for healthy housing. The most important role of housing is to provide shelter from the elements. At its most basic level, housing needs to keep its inhabitants dry, warm (or cool), and safe. Building codes help ensure that housing is safe, while good urban planning ensures that housing is not built in dangerous locations such as floodplains, dangerous hillsides, or next to polluting industries.
In addition to being safe and providing shelter, housing also should be hygienic. This means providing clean water, systems to remove sewage and solid waste, and hygienic food storage and preparation areas. Finally, housing needs to support mental and social well-being—it should be attractive, pleasing, and well maintained, with greenspace, play areas for children, and other elements that help promote health. These same principles also apply to other built environments, such as schools, workplaces, hospitals, government buildings, and shopping areas.
INDOOR AIR QUALITY
Since people spend so much of their time indoors, the quality of indoor air is very important. In some countries, where biomass fuels (e.g., wood, coal, peat, and animal dung) are used indoors for heating and cooking, the indoor air quality can be very poor. The World Bank estimates that 400 million to 700 million women and children are exposed to these conditions, which contribute to 4 million deaths annually from acute respiratory infections. This makes such indoor air pollution one of the four most critical global environmental problems.
In the developed world today, such severe indoor air pollution is seldom a problem. But indoor air quality remains a significant problem because of energy-efficient sealed buildings that have reduced ventilation rates. These sealed environments house a host of pollutants: volatile organic compounds (VOCs) from paints, resins, glues, fabrics, and furnishings; secondhand tobacco smoke; nitrogen oxides and carbon monoxide from fossil fuel combustion; pesticides, cleaning agents, and other toxic materials; house dust mites; animal hair from pets; and molds associated with damp housing (roughly one-third of houses in North America have a problem with dampness and mold). Complaints of "sealed building syndrome" have become commonplace. There is also considerable evidence suggesting that the approximate doubling of asthma among children in North America since the 1980s is due in no small part to this indoor air pollution.
THE URBAN ENVIRONMENT
The quality of the urban built environment is also of great importance to health. Outdoor air pollution, which results in death and disease, comes from industry, from coal-, oil-, and gas-burning electricity generating or heating plants, and from motor vehicles. Particularly in the summer months, nitrogen oxides and volatile organic carbons from these sources combine to form ground level ozone, while particulate pollutants and acid emissions contribute their share to summer smog or winter haze.
Urban settlements also contribute massively to water pollution. Human wastes, industrial wastes, urban runoff from the streets and parking lots, pesticides and herbicides from parks, lawns, and gardens—all end up in the water. Most major cities have some form of waste water treatment, but even so it is not uncommon to find that the lakes and rivers are not safe even for swimming.
Roads and traffic are another major threat to health in the urban environment. In addition to the contribution that traffic makes to air pollution, motor vehicle accidents are a major cause of death and injury, particularly among children and young adults. In addition, traffic noise is a major irritant, while large roads and highways impede access for pedestrians and isolate neighborhoods from each other.
The design of urban environments also has an important influence on crime and violence. Many women's groups now conduct safety audits of their communities to identify streets, parks, and other areas that are dangerous and to identify ways to make them safer. It is not just the violence, but the fear of violence that is debilitating. If people do not feel safe, they will not use their community's streets and facilities, and increasingly will wall themselves off in gated neighborhoods. This only serves to increase the isolation and the disparity between rich and poor, young and old, black and white.
Indeed, the social impacts of the urban environment are at least as important as the physical impacts. Highrise apartments, deserted streets, poor public transportation, gated communities, urban sprawl—these and other aspects of modern cities can contribute to isolation, lack of access for the disadvantaged, and alienation.
THE NEW URBANISM, SUSTAINABLE COMMUNITIES, AND HEALTH
An increasing awareness and concern about the environmental and health impacts of modern cities—especially the sprawling urban and suburban cities of North America—has resulted in a number of new but related movements, all of which are intended to improve the quality of life. One such approach is called "new urbanism." Its focus is on improving the livability of urban communities by making them more dense, by putting home, school, workplace and other facilities closer together, and by designing streets and communities that are more traditional. In such communities, people can more easily walk and bike; there is more active street life, and—it is hoped—a greater sense of community.
The sustainable community movement includes many of these same qualities but focuses on how to reduce the ecological footprint of a community by reducing consumption of energy and other resources and by reducing air and water pollution. The safe communities movement looks at ways of reducing crime and violence (and the fear of crime and violence) and accidental injuries through better design and by involving the community through safety audits and neighborhood watch programs. Finally, the healthy communities movement combines many of these attributes, in an attempt to create healthier, safer, more sustainable and livable communities with a high quality of life. In the twenty-first century, however, health will depend to a considerable extent on how well people are able to create built environments—from individual houses to whole cities—that improve physical, mental, and social well-being.
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