Q&A: how Mexico City is tackling air pollution and protecting public health
Throughout the 1990s, Mexico City was notorious for being one of the world’s most polluted cities. However, through a series of impactful and sustained policies, the city has made significant strides in combating air pollution, even as the challenge persists. These efforts serve as a testament to the power of committed policy and are a central focus for Mexico, a key partner of the United Nations Environment Programme (UNEP).
A Look Back: From Smog to Progress
Mexico City’s journey toward cleaner air began with major policy changes. A key refinery was relocated out of the valley, and limits were placed on the sulfur content in industrial fuels. The city also launched the “Hoy No Circula” program, which restricts vehicle usage one day a week based on license plate numbers. Additionally, stringent emissions inspections were introduced to ensure compliance and curb corruption, while the public transit system was expanded. Currently, the city is in the process of phasing out diesel vehicles entirely.
These sustained efforts have borne fruit. Mexico City has fallen from its spot among the world’s most polluted capitals, reflecting the tangible progress made.
The Ongoing Battle: Ground-Level Ozone
Despite significant reductions in particulate matter and gases like nitrogen and sulfur oxides, the city’s biggest challenge remains ground-level ozone. According to Sergio Zirath, Director General of Industry, Clean Energy and Air Quality Management in Mexico’s Undersecretariat of Environmental Regulation, the Valley of Mexico’s unique geography a high altitude bowl home to 22 million people and 5.5 million vehicles creates the perfect conditions for ozone to form and accumulate, especially during warm, dry seasons.
The difficulty in controlling ozone stems from its unpredictable atmospheric chemistry. As Zirath notes, even during the pandemic when traffic and industrial activity dropped, ozone levels in many parts of the world, including Mexico City, actually increased. This complexity highlights the need for a comprehensive approach that goes beyond simply reducing traffic.
Revolutionizing Air Quality Monitoring
Mexico City has been a pioneer in air quality monitoring, having established the nation’s first air quality index in the 1980s. To improve public health protection, the government standardized how the index is calculated and published, making the information more accessible.
Today, Mexico uses the NowCast model, which prioritizes recent data. Unlike a 24-hour average, which can mask brief but severe pollution spikes, NowCast gives more weight to recent hours. This allows authorities to issue timely warnings for residents to take precautions, such as avoiding outdoor exercise.
To further enhance public health communication, Mexico City is developing an app that will use a person’s location to provide personalized, real-time pollution alerts. This system will also consider individual factors like age and existing health conditions, making the warnings even more relevant.
Connecting Clean Air to Climate Action
Mexico’s efforts to improve air quality are deeply intertwined with its climate goals. As Zirath explains, the sources of air pollutants and greenhouse gases are often the same, so policies that target one can generate co-benefits for the other. For example, reducing vehicle emissions lowers both air pollutants and carbon dioxide.
Furthermore, climate change itself can worsen air quality. Higher temperatures lead to increased emissions of volatile organic compounds and accelerate the chemical reactions that form ground-level ozone. By tackling ozone precursors, Mexico City is also addressing short-lived climate pollutants and other greenhouse gases, demonstrating how local action can have a global impact.
Mexico’s support for the UNEP is critical in this fight. The country’s voluntary funding enables the global exchange of best practices and lessons learned, helping nations avoid “repeating the mistakes of others” and accelerate progress in the fight against pollution.
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