Mexico is fighting hard to correct its ozone levels on ground. According to the Metropolitan Commission for the Prevention and control of Mexico City Pollution, lead levels have decreased by almost 90 percent a and CO levels are "with in norms equivalent to those of the US environment protection agency". But ozone emitted by polluting cars is still at "poor air quality levels"

The commission's "Hoy no circula programme, designed to keep some of the city's cars idle everyday by imposing restrictions, was not effective. People hoodwinked the authorities by going for a second, older and more polluting car. Mexican environmentalists argue that the battle can be won by improving public transportation and "cleaning up industries".