Mexico City is one of the most air polluted capitals in the world, if not the most polluted in city in North America. Much of its pollution is caused by the tens of thousands of cars that flood the streets each day. The volume of exhaust, whether CO2, carbon monoxide, or just plain soot, fouls the air. $20 Off AeroGardens
According to Reuters, as found on greenroofs.org
"The smog-choked metropolis plans to replace gas tanks, clothes lines and heat-reflecting asphalt on 100,000 square feet (9,300 square metres) of publicly owned roof space each year with grass and bushes that will absorb carbon dioxide."
The other benefits, as found in the Chicago experiments with green roofs are by planting green roofs, the urban heat island effect is reduced, as well as fine particulate pollution. Additionally, storm water runoff is reduced, as the green roof absorbs and retains much of the rain. Water Barrels and Storage
Green roofs offer Mexico City an economic way of improving their air quality, water quality, and quality of life for its citizens and visitors. Green roofs may be more expensive than traditional roofs, but are definitely cheaper than the most modern pollution-reducing devices used in modern, Western factories.