If you live far away from large cities, you may find pictures of air pollution in cities to be shocking. Some pollutants do not discolor the air, while others are very obvious. All pollution contributes to health problems, possible global warming and other environmental concerns.
Researchers continue to look for alternative fuels, alternative methods for producing power and other ways to stop air pollution. Governments have passed laws to help control pollutants found in the larger cities of the world. Tokyo, shown here, battles air pollution from many sources, including automobiles and industries.