Brian Barton
Mexico City has long struggled with air pollution, and in 1992, the United Nations declared it the most polluted city on the planet. The city's high altitude, industrial growth, population boom, and proliferation of vehicles have all contributed to this issue. However, Mexico has implemented various measures to combat pollution, such as ProAire policies, which have reduced pollution by 57% and increased life expectancy. While Mexico City is no longer among the top 500 most polluted cities, air pollution remains a concern, with ozone and suspended matter pollution reaching detrimental levels in 2016. The Mexican government continues to work towards improving air quality through initiatives like vehicular restrictions, expanding green areas, and promoting bicycle accessibility.
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What You'll Learn
Mexico City's air pollution levels have decreased
Mexico City has been notorious for its poor air quality and outdoor air pollution for decades. In 1992, the United Nations named Mexico City the "most polluted city on the planet". The UN's declaration was due to the city's high altitude, which causes its oxygen levels to be 25% lower, and carbon-based fuels not combusting completely. Other factors included the proliferation of vehicles, rapid industrial growth, and the population boom.
However, Mexico City's air pollution levels have decreased. In 2021, Mexico City ranked as the 917th most polluted city in the world, a significant improvement from its previous ranking. This improvement is the result of various factors and measures taken by the Mexican government.
One of the main factors contributing to the decrease in air pollution in Mexico City is the government's requirement that gasoline be reformulated. This has helped to reduce the levels of ozone and other air pollutants. In addition, the government has closed or moved polluting factories and prohibited drivers from using their cars one day a week, which has further reduced emissions.
The Mexican government has also implemented the "Hoy No Circula" policy, which restricts vehicular circulation based on emissions testing results. While the effectiveness of this policy has been questioned, it is one of the many measures the government has implemented to address air pollution.
Another factor contributing to the decrease in air pollution in Mexico City is the expansion of public transportation. The government has invested in the renewal of the bus fleet, introducing more efficient buses and amending routes to minimise unnecessary emissions. Additionally, the expansion of the city's subway network and bike-sharing initiatives aims to decrease public reliance on vehicles.
Despite the improvements, Mexico City's air pollution levels still exceed the World Health Organization's guidelines, and further action is needed to address the issue. However, the significant decrease in air pollution levels in Mexico City offers valuable lessons for other cities facing similar challenges.
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Industrial growth and vehicle proliferation
Mexico City's air pollution reached its peak in the 1980s and 1990s. The air quality was so poor that birds were found dead due to its toxicity. This was mainly due to the rapid industrialisation and urbanisation of the city during the 20th century, which caused a population boom. The number of vehicles in the city also increased significantly during this period. In 1980, there were 124 cars and light-duty trucks per 1000 residents, and by 2010, this number had increased to 267. The topography of Mexico City also contributed to the problem, as it is located in a basin where air pollutants are trapped.
The Mexican government has implemented various policies and programs to combat air pollution in the country's capital. One of the most notable policies was the "Hoy No Circula," which was introduced in 1989. This policy required all vehicles in Mexico City and the state of Mexico to undergo emissions testing every six months. Vehicles were then assigned a verification label, with those labelled "1" and "2" being prohibited from being driven on one weekday per week and two Saturdays per month. However, the effectiveness of this policy has been questioned as air pollution levels did not significantly decrease even after several years of implementation.
To address the issue of industrial growth contributing to air pollution, the government mandated the removal of lead from gasoline, the implementation of catalytic converters in automobiles, and the reduction of sulphur content in diesel fuel. Polluting factories were closed or moved, and the government worked to expand public transportation options and promote non-motorised transport like cycling and walking.
Despite these efforts, air pollution continues to be a problem in Mexico City, and it is recognised that the root causes of the problem need to be tackled. The city's unique topography, with its high altitude and location in a basin, presents a challenge for dispersing air pollutants. Additionally, the regulatory framework for air quality has been criticised as lax and outdated, and there is a lack of timely and valid information on air quality being provided to the public.
To further reduce air pollution, experts recommend prioritising public transport, particularly electric transport, and enforcing stricter environmental health standards that align with the World Health Organisation's guidelines. Additionally, it is important to regulate sectors that are major contributors to pollution, such as transportation and industry, and to encourage the use of non-polluting means of transport.
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Government policies to reduce emissions
Mexico City was once named the world's most polluted city, but it has since dropped to the 46th most polluted country in the world in terms of PM2.5 levels in 2023. However, its concentration of airborne particles (PM2.5) still exceeds the World Health Organization's (WHO) guidelines. The Mexican government has implemented various policies to combat air pollution, recognizing its severe impact on public health and economic development. Here are some of the government policies and initiatives aimed at reducing emissions:
- "Hoy No Circula" Program: First introduced in 1989, this program involves mandatory emissions testing for all vehicles in Mexico City and the State of Mexico every six months. Vehicles are assigned a verification label based on their performance, with "0" for those meeting requirements and "1" or "2" for underperforming vehicles. Vehicles with "1" and "2" labels are prohibited from being driven on one weekday per week and two Saturdays per month. However, the effectiveness of this policy has been questioned, as air pollution levels did not significantly decrease over the years.
- ProAire Programme: Launched in 1995, this extensive programme aims to achieve sustainable development in eight key areas, including energy consumption reduction, promotion of public transport, environmental education, green areas and reforestation, and strengthening health protection.
- National Air Quality Strategy: In 2017, Mexico presented a cross-sectoral strategic planning document to improve air quality in cities and states.
- Electro Mobility Strategy: Mexico has been working on this strategy since 2018 to reduce transport emissions and promote the use of electric vehicles.
- Climate Change Law: Mexico adopted the "General Climate Change Law" in 2012, providing an institutional framework for climate targets and strategies. The law establishes institutions like the National Institute of Ecology and Climate Change and sets GHG mitigation targets to incentivize renewable energy development.
- Methane Pledge: Mexico signed the Methane Pledge at COP26, recognizing the significant contribution of methane to its GHG emissions, especially from the agriculture and waste sectors.
- Forestry Pledge: Mexico also committed to the forestry pledge at COP26, aiming for zero deforestation by 2030 through its National REDD+ Strategy.
- Mexican Atmospheric Environmental Contingency Plan (AECP): Reactivated in 2016, this plan includes further restrictions on vehicle use, limiting driving to two days a week, and reducing factories' greenhouse gas emissions by up to 40%.
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Topographical factors trapping pollutants
Mexico City has been labelled the world's most polluted city by the United Nations in 1992. The city's high altitude of 7382 feet above sea level causes its oxygen levels to be 25% lower, and carbon-based fuels do not combust completely. The city's topography, located in a basin surrounded by mountains, creates a bowl-like container where air pollutants tend to be trapped. This, combined with the city's substantial population growth, industrialization, and increase in human activities, has resulted in severely poor air quality.
The topographical factors trapping pollutants in Mexico City are primarily due to its location in a basin surrounded by mountains, creating a bowl-like structure. This geographical feature prevents the dispersion of air pollutants, trapping them within the city. The high altitude of the city further exacerbates the issue, as it leads to lower oxygen levels and incomplete combustion of carbon-based fuels.
The combination of the basin-like topography and high altitude has created a perfect storm for trapping pollutants. The basin acts as a container, with the surrounding mountains hindering the escape of pollutants, while the high altitude reduces oxygen levels and impacts combustion processes. This has resulted in a significant accumulation of pollutants in the city's atmosphere.
Additionally, Mexico City's industrialization and population growth have contributed to the problem. The increase in human activities, including the burning of fossil fuels in power plants and vehicle emissions, has released large amounts of pollutants into the air. The proliferation of vehicles, with a doubling of the vehicle fleet from 1992 to 2012, has been a significant source of pollution. The rapid industrialization has also led to the emission of over 11,000 tons of waste material into the atmosphere daily.
To combat the issue of air pollution, the Mexican government has implemented various measures. These include requiring the reformulation of gasoline, closing or relocating polluting factories, and restricting vehicle usage to one day per week, later increased to two days per week under the Mexican Atmospheric Environmental Contingency Plan (AECP). The government has also focused on expanding public transportation and promoting active transport like cycling and walking to reduce emissions from vehicles, which are the main cause of air pollution in the city centre.
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Health, environmental, and economic impacts
Mexico City was once labelled as the world's most polluted city by the United Nations in 1992. Since then, the city has witnessed a significant improvement in air quality, dropping to the 917th position in the global pollution rankings in 2021. However, the city continues to grapple with the health, environmental, and economic repercussions of pollution.
Health Impacts
The health of Mexico City's residents has been profoundly impacted by air pollution, particularly due to the presence of PM2.5, or fine inhalable particulate matter. Exposure to PM2.5 can lead to coughing, shortness of breath, bronchitis, respiratory infections, and heart problems. The poor and informal workers are more vulnerable to the health effects of air pollution, as evident from increased hospital admissions for respiratory diseases in areas with a high proportion of informal workers. Additionally, air pollution has resulted in school closures and driving restrictions on days with heavy smog, impacting the education and mobility of residents.
Environmental Impacts
Mexico City's environment has been significantly affected by air pollution, with ground-level ozone being the most pressing concern. In 2016, the concentration of ozone was approximately 1.9 times the acceptable limit, nearing the levels recorded in the 1980s. Ground-level ozone is formed by the interaction of nitrogen oxides (NOx) and volatile organic compounds (VOCs), accelerated by ultraviolet (UV) radiation from the sun. The city's topography, nestled in a basin surrounded by mountains and volcanoes, traps air pollutants, exacerbating the issue.
Economic Impacts
Air pollution in Mexico City has had notable economic consequences, particularly in terms of lost labour productivity. On days with extremely high PM contamination, the city's roughly 3.5 million workers lose an average of 7.5% of their working hours. Informal workers, who often work for unregistered companies without fixed salaries, are disproportionately affected, working 20% more on days with hazardous air quality and struggling to compensate for lost hours. This highlights the unequal impact of pollution on income, with the poor bearing the brunt of the economic burden.
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Frequently asked questions
No, it is not. In 2023, Mexico City ranked 46th among countries with the highest PM2.5 concentration, far below Bangladesh, which ranked first. In 2021, Mexico City was the 917th most polluted city in the world, according to IQAir. However, it was named the most polluted city in the world by the United Nations in 1992.
The high levels of pollution in Mexico City during the 1980s and 1990s were caused by a combination of factors, including rapid population growth, industrialisation, urbanisation, and an increase in human activities such as the use of vehicles and the operation of polluting factories, power plants, and oil refineries. The topography of Mexico City, located in a basin, also contributed to trapping air pollutants.
The Mexican government has implemented various policies and regulations to combat air pollution in Mexico City. These include requiring gasoline reformulation, closing or relocating polluting factories, prohibiting driving one day a week, and expanding public transportation. The "Hoy No Circula" policy, implemented in 1989, requires emissions testing for vehicles and prohibits underperforming vehicles from being driven on certain days. The government also has plans to reduce emission levels through citizen participation, vehicular restrictions, increasing green areas, and expanding bicycle accessibility.
Air pollution in Mexico City has been linked to various health issues, including respiratory problems such as asthma and allergies, cardiovascular diseases, reproductive health issues, early death, and increased mortality. It is the eighth-highest cause of death in Mexico, contributing to approximately 33,000 premature deaths annually. Workers in Mexico City lose an average of 7.5% of their working hours on days with high PM2.5 concentrations, resulting in significant economic losses.
