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Situated in a valley, and relying heavily on automobiles, Mexico City often suffers from poor air quality. Author \Creator:Fidel Gonzalez.

Photochemical smog over Mexico City, December 2010. Author \Creator:Fidel Gonzalez.


The Mexico City Photogenic Smog has persistently hung over the city since the 1950s.

Originally much of the valley laid beneath the waters of Lake Texcoco, a system of interconnected salt and freshwater lakes. The Aztecs built dikes to separate the fresh water used to raise crops in chinampas and to prevent recurrent floods. These dikes were destroyed during the siege of Tenochtitlan, and during colonial times the Spanish regularly drained the lake to prevent floods. Only a small section of the original lake remains, located outside the Federal District, in the municipality of Atenco, State of Mexico.

Due to its location in a highland "bowl", cold air sinks down onto the urban area of Mexico City, trapping industrial and vehicle pollution underneath, and turning it into the most infamously smog-plagued city of Latin America. Within one generation, the city has changed from being known for some of the cleanest air of the world into one with some of the worst pollution, with pollutants like nitrogen dioxide being double or even triple international standards.

The event[]

The Mexico City Photogenic Smog has persistently hung over the city since the 1950s.

By the 1990s Mexico City had become infamous as one of the world's most polluted cities; however, the city has become a model for dramatically lowering pollution levels. By 2014 carbon monoxide pollution had dropped dramatically, while levels of sulfur dioxide and nitrogen dioxide were nearly three times lower than in 1992. The levels of signature pollutants in Mexico City are similar to those of Los Angeles. Despite the cleanup, the metropolitan area is still the most ozone-polluted part of the country, with ozone levels 2.5 times beyond WHO-defined safe limits.

Given the size and political importance of Greater Mexico City, a major flood or a major water supply interruption would be a national political crisis potentially threatening the stability of the federal government. The security of water supply and the functioning of the storm water drainage of the metropolitan area thus are major concerns for the local, state, district and federal governments. In response to the challenges outlined above, the Federal Government, the State of Mexico and the Federal District initiated a US$2.8 billion Water Sustainability Program in 2007.

In parallel, the government of the Federal District launched a Green Plan which includes water conservation as an important element. Investments envisaged under both plans include an increase in wastewater treatment, the import of groundwater from irrigated areas North of the city where the groundwater table increased due to irrigation with wastewater, the construction of a major new storm water drainage tunnel, increased water imports from an expansion of the energy-intensive Cutzamala system that pumps water up over more than 1000 meters, and the reduction of non-revenue water from 36% to 25%.


To clean up pollution, the federal and local governments implemented numerous plans including the constant monitoring and reporting of environmental conditions, such as ozone and nitrogen oxides. When the levels of these two pollutants reached critical levels, contingency actions were implemented which included closing factories, changing school hours, and extending the A day without a car program to two days of the week. The government also instituted industrial technology improvements, a strict biannual vehicle emission inspection and the reformulation of gasoline and diesel fuels. The introduction of Metrobús bus rapid transit and the Ecobici bike-sharing were among efforts to encourage alternate, greener forms of transportation.

Architects Teodoro González de León and Alberto Kalach along with a group of Mexican urbanists, engineers and biologists have developed the project plan for Recovering the City of Lakes. If approved by the government the project will contribute to the supply of water from natural sources to the Valley of Mexico, the creation of new natural spaces, a great improvement in air quality, and greater population establishment planning.

Also see[]

  1. Photogenic smog
  2. The New York Photogenic Smogs and river polution


  1. https://www.wikiwand.com/en/Smog
  2. https://www.wikiwand.com/en/Mexico_City
  3. https://en.wikipedia.org/wiki/Mexico_City?oldformat=true#Environment
  4. https://www.wikiwand.com/en/Air_pollution_in_Mexico_City
  5. https://www.wikiwand.com/en/Water_management_in_Greater_Mexico_City
  6. http://www.laweekly.com/news/los-angeles-and-mexico-city-a-tale-of-two-cities-2152222
  7. https://news.harvard.edu/gazette/story/2014/10/coming-up-for-air/
  8. http://www.nbcnews.com/id/28391130/wid/18298287/page/2/#.WjivQlVl-M8
  9. http://biophysics.sbg.ac.at/mexico/air.htm