In 1992, Mexico City was singled out as the most polluted megacity in the world. It came just ahead of São Paulo in a World Health Organisation (WHO) and UN Environment Programme (UNEP) study of ‘Air Quality in 20 Megacities’. The upshot was that the Mexican government and the Mexico City administration had to do something about it straight away or suffer the consequences.
To address the city’s disastrous pollution levels, the city’s administration and the Metropolitan Environmental Commission (MEC) have implemented two successive programmes: the Comprehensive Programme Against Air Pollution ( PICCA), which was launched in 1990; and ProAire, which was launched in 1995. The aim of both was to improve the air quality of the metropolitan area of the valle de México (the Metropolitan Area of Mexico City).
ProAire is now into ProAire IV, which addresses eight themes:
- Reduction of energy consumption.
- Cleaner and more efficient energy across all sectors.
- Promoting public transport and regulating fuel consumption.
- Technology shift and controlling emissions.
- Environmental education.
- Creating a sustainability culture and citizen participation.
- Green areas and reforestation.
- Institutional capacity building and scientific research.
The public impact
By 2012, the number of days per year in which dangerous levels of pollution were recorded had fallen to 118 (from 344 in 1994). It also recorded a 7.7 million tons reduction in carbon emissions in just four years (from 2008 to 2012), beating its 7.0 million tons target.
In 2013, Mexico City won the 2013 C40 and Siemens Climate Leadership Awards’ Air Quality category for ProAire IV, the most recent phase of its ProAire programme. The city has proved that a comprehensive, long term strategy can have a major impact on the air quality of a megacity.
Public Confidence Weak
The Mexico City Government set out to find out what the public thought about its air quality initiatives “with support from Canada’s International Development Research Centre … and the Netherlands Trust Fund, through the World Bank and the Pan American Health Organisation.” 
The researchers then took to the streets. “Questionnaires administered by the research team to close to 4,000 residents in all sectors or delegations of the city showed, close to 30% believe the government’s motives in seeking to reduce air pollution to be self-serving.  More than 30% also think that the government’s online air quality reports are false … Close to 40% could not identify any of the government programs to improve air quality. The remainder considered them necessary evils — restrictions rather than preventive measures.”
Stakeholder Engagement Good
The main stakeholder in ProAire is the Mexico City Metropolitan Area, which works together with the MEC. The Metropolitan Environmental Commission is a national interagency body which was created in 1996 to coordinate environmental policy and programmes across the federal and local governments of Mexico. The city’s government, in conjunction with the Metropolitan Environment Commission, has implemented successive phases of ProAire since its launch in 1995.
The other stakeholders are the inhabitants of Mexico City and all those who have been taking positive action to reduce pollution levels. For example, the public transport organisation, Metrobús, works in conjunction with ProAire to improve air quality in the Metropolitan Area of Mexico City by promoting public transport and reducing congestion. Another initiative has been sustainable architecture, such as the eco-friendly façade of the Manuel Gea González Hospital tower.
Political Commitment Good
ProAire is an initiative of the Mexican government, the Ministries of the Environment and of Health, along with the Mexico City area administration. It has been running for over 20 years, with government funding and support, a clear indication of the national and metropolitan governments’ commitment to the programme as a means of improving air quality in the city.
Clear Objectives Strong
The objectives of ProAire have been clear and maintained throughout its successive phases and they have also been measurable, e.g., the content of particulate matter in the air of the city (PM2.5 and PM10). The overriding objective has been to improve the air quality in the Mexico City metropolitan area.
In order to achieve that broad aim, the programme's main focus has been on reducing industrial and automobile emissions and promoting public awareness of the programme so that citizens and businesses are persuaded to adopt the necessary changes.
There was clear and indisputable evidence that Mexico City had intolerably high levels of air pollution. It was also shown, by the Washington-based World Resources Institute, that some 6,400 people died of particulate pollution – from road dust, diesel soot, wood smoke and metallic particles - annually in the Mexico City metropolitan area.
In 1992, the Mexico City Government launched PICCA as a systematic plan to combat air pollution. Following its successful results, Government launched consecutive ProAire programmes, with the current programme, ProAire IV, being launched in 2011.
Legislatively , laws passed in 1988 (LGEEPA) stated that federal authorities must begin reducing emissions. State governments were required to outline details of their own initiatives to the Ministry of Environment and Natural Resources. Initiatives geared towards reducing pollution were therefore politically and legislatively driven. 
The city also recognises that feasibility and success of environmental initiatives is heavily linked to public compliance, therefore Mexico has invested in educating the public and increasing their awareness, to enhance feasibility. 
Solving the pollution problem in Mexico City was a problem of the Metropolitan Environment Commission (MEC), who introduced and managed the ProAire scheme in coordination with Mexico City’s government. The MEC include membership of two federal offices, the Ministry of Health and the Ministry of Environment. It also includes representatives from the National Institute of Ecology, the Government of the Federal District and the Government of the State of Mexico. 
There were several metrics used to measure the impact of ProAire, which together indicated the levels of particulate matter (e.g., PM10), sulphur dioxide (SO2), carbon monoxide (CO), mono-nitrogen oxides (NOx) and volatile organic compounds (VOCs). These parameters were constantly measured by the MEC to track the progress of the initiative. “During ProAire III (2002 to 2010) ... emissions reductions over this period were estimated at 5,078 tons/yr of PM10, 506 tons/yr of SO2, 817,132 tons/yr of CO, 64,779 tons/yr of NOx, and 85,706 tons/yr of VOC." 
The ProAire IV phase of the programme is estimated to have resulted in: a reduction of “490,000 tons in the emission of ‘criteria’ pollutants (hydrocarbons, carbon monoxide, sulphur oxides, PM10 and PM2.5, and ozone); 5,000 tons of toxic pollutants; and 5.5 million tons of greenhouse gases. 
The city administration and the NEC were the main actors. The city recognised the need to get the public on board, and dedicated more resources to education programmes and public awareness campaigns during the later phases of ProAire.
It recommended the adoption of local zoning regulations, control of squatter settlements, natural resource conservation, and environmental education in schools.
It initiated various transport programmes to reduce the use of cars, such as Metrobús (see Stakeholder engagement above) and the Ecobici shared bike programme in order to reduce levels of air pollution.