Americans have begun to focus on the downside of certain patterns of growth and development-increasing dependence on automobiles; worsening traffic congestion; and contributing to the loss of farmland, forests, and open space. Increasingly, some are also concerned that this prevailing pattern of land use, commonly called "urban sprawl," can increase air and water pollution, threatening their health and, in some cases, their livelihood. Vehicle emissions in congested areas can trigger respiratory and other illnesses, and runoff from impervious surfaces can carry lawn chemicals and other pollutants into lakes, streams, and rivers, thus threatening aquatic environments. Some states and localities-spurred in part by citizens' lawsuits and ballot initiatives-recognize that growth provides housing and economic development opportunities and is inevitable, but would like to better manage their future land use. The Congress has also expressed an interest in better understanding how federal policies and programs affect growth and land use.