Air pollution is one of the many problems that the authorities of the Mexican capital face.
In 1986, a system was put in place for atmospheric monitoring (Simat), which each day gives the weather Indice Metropolitan Air Quality.
In 2008, 1.
5% of greenhouse gases in the world were produced by the agglomeration of Mexico.
4000 deaths per year are attributed to pollution caused by this area of the world.
However, these figures are only estimates.
This pollution is the result of intense traffic - there are 4 million cars, 27 000 microbuses, 92 000 taxis which consumes about 14 million gallons of gasoline every day - and an industry which has seen extremely rapid growth (60 000 industrial companies working in the town of Mexico).
Urban sprawl and the construction of new highways over the past thirty years reinforce the use of cars in Mexico.
According to a report of the Committee on Human Rights of the Federal District (CDHDF) published in December 2008, 80% of GHG emissions are produced by transport .
The bowl situation worsens the effect of pollution by promoting the thermal inversion.
The long dry season favors the stagnation of air over the city for half of the year.
Because of the altitude, some districts cover more than 2 800 m, it freezes ten nights between December and February.
The cooling of the soil causes a thermal inversion: a layer of cold stagnant air of a few hundred meters thick filled with an accumulation of gases, fumes, dust is dispersed as part of warming during the middle of the day (not all day).
This combination of elements conducive to the concentration of air pollution is reduced during the rainy season.