Mexico City's Pollution: A Health Crisis?

Mexico City has long been notorious for its poor air quality, with the UN declaring it the most polluted city in the world in 1992. The city's high altitude means its oxygen levels are 25% lower, leading to incomplete fuel combustion and higher pollution levels. Industrialisation, rapid population growth, and the proliferation of vehicles have also contributed to the problem. While the Mexican government has implemented various measures to improve air quality, including regulating fuel blends and restricting vehicle use, pollution remains a significant issue. In 2023, Mexico City's average particulate matter pollution was 22.3 micrograms per cubic meter, exceeding the World Health Organization's guidelines.

Mexico City's air pollution history

Mexico City's air pollution problem has been a concern for decades. The city's air pollution reached its peak in the 1980s and 1990s, with ground-level ozone, carbon monoxide, sulphur dioxide, nitrogen dioxide, and airborne particles all at record levels. The air quality was described as so severe that birds were found dead from its toxicity.

Several factors contributed to this crisis. Firstly, the city underwent rapid industrialization and urbanization during the 20th century, with its population growing from 3.1 million in the 1950s to 14 million in the 1980s. This population boom was fueled by migrants seeking better opportunities, leading to an increase in human activities that severely impacted air quality. The proliferation of vehicles, including poorly made cars running on toxic fuel, also played a significant role. Additionally, the city's topography, located in a basin, trapped air pollutants from unregulated factories, power plants, and oil refineries.

Recognizing the severity of the problem, the Mexican government implemented various measures to combat air pollution. The "Hoy No Circula" policy, introduced in 1989, required vehicles to undergo emissions testing and prohibited underperforming vehicles from being driven on certain days. The government also mandated the reformulation of gasoline, the closure or relocation of polluting factories, and the expansion of public transportation. These efforts led to significant improvements in air quality, with ozone and other pollutants dropping to levels comparable to Los Angeles by 2012.

Despite these improvements, Mexico City still faces air quality issues. In 2023, the city's average particulate matter pollution stood at 22.3 micrograms per cubic meter, exceeding the World Health Organization's guidelines. However, the city has shown a strong commitment to tackling air pollution, joining the Breathe Cities initiative in 2024 to reduce air pollution by promoting sustainable mobility options such as cycling and electric buses, and expanding public-private collaboration to adopt less polluting technologies. As a result, Mexico City has dropped to the 917th most polluted city in the world in 2021, according to IQAir, a Swiss company that tracks global air quality.

Current air quality

Mexico City's air quality has improved significantly since the 1980s and 1990s, when it was deemed the "most polluted city in the world" by the United Nations. This improvement is evident as, in 2021, Mexico City ranked as the 917th most polluted city globally, a colossal improvement. However, the city's air pollution levels remain above global averages and World Health Organization (WHO) guidelines, with the annual mean PM2.5 levels exceeding the recommended limit of 10 micrograms per square meter, reaching 22.3 to 23 micrograms per square meter.

The poor air quality in Mexico City is attributed to various factors, including industrial growth, a sharp increase in population, and the proliferation of vehicles. The city's topography, located in a basin surrounded by mountains, creates a bowl-like structure that traps air pollutants. The high altitude of the city also results in oxygen levels being 25% lower, leading to incomplete combustion of carbon-based fuels and higher pollution levels.

To combat air pollution, the Mexican government has implemented several measures over the years. They mandated the reformulation of petrol with cleaner blends, closed or relocated polluting factories, and introduced the ""Hoy No Circula" policy, which restricts vehicles from circulating based on their emissions performance. These initiatives have contributed to significant reductions in CO, ozone, and particulate matter levels.

Despite these efforts, air pollution remains a pressing issue in Mexico City, with levels exceeding WHO guidelines. The problem is further exacerbated by wildfires, drought conditions, and the activity of the nearby Popocatepetl volcano, which contribute to the concentration of airborne particles. The government continues to face the challenge of balancing economic development with the urgent need to address air pollution and its associated health risks.

While Mexico City's air quality has shown remarkable improvement since its peak pollution levels in the 1980s and 1990s, continued efforts and stricter regulations are necessary to ensure the health and well-being of its residents.

Causes of air pollution

Air pollution in Mexico City is caused by a combination of geographical factors and human activities. The city's location in a basin surrounded by mountains creates a "bowl" effect that hinders the natural dispersion of pollutants, leading to them lingering for longer periods. This, coupled with the city's high altitude, which causes oxygen levels to be 25% lower, exacerbates the problem.

The industrial areas surrounding and within Mexico City significantly contribute to the air quality issues. The unchecked release of pollutants from manufacturing plants, power stations, and oil refineries has severe environmental consequences. While regulations have been put in place, compliance and modernisation remain challenging.

Another major cause of air pollution in Mexico City is vehicle emissions. The proliferation of vehicles, especially older models with outdated emissions systems, has resulted in a significant release of harmful pollutants. The number of cars on the roads, coupled with inefficient public transportation systems, further compounds the issue. In the 1980s, there were about 124 cars per 1,000 residents, and these cars were of poor quality and used highly toxic fuel.

Wildfires, especially during dry spells, also contribute to the air pollution problem in Mexico City. Fanned by climate change and human activities, these fires release massive amounts of smoke and ash, deteriorating air quality and exacerbating respiratory conditions.

Crop burning in Mexico's agricultural regions is another contributor to air pollution. This annual practice adds large quantities of PM2.5 and other contaminants into the air, which can get trapped in valleys like Mexico City.

While the Mexican government has implemented various policies and regulations to combat air pollution, such as requiring emissions testing for vehicles and prohibiting driving on certain days, the effectiveness of these measures has been questioned.

Health risks

Air pollution in Mexico City has been a concern for the city's population and health officials for decades. In 1992, the United Nations declared Mexico City the most polluted city in the world. The city's high altitude of 7,300 feet above sea level contributes to its poor air quality, as oxygen levels are 25% lower. The proliferation of vehicles, rapid industrial growth, and a population boom have also played a significant role in the city's air pollution.

The health effects of air pollution in Mexico City are wide-ranging and serious. Air pollution is linked to various health issues, including asthma, bronchitis, and cancer, with lung cancer being the most prevalent type in the city. Other health effects include brain infarction, heart disease, respiratory distress, headache, dizziness, irritation, and eye inflammation. Even young, healthy people can suffer from the effects of air pollution, and longer periods of exposure can lead to permanent health issues such as accelerated ageing of the lungs, reduced lung capacity, and shortened life expectancy. Those with pre-existing heart conditions, pregnant women, children, and senior citizens are especially vulnerable to the adverse effects of air pollution.

The impact of air pollution goes beyond the physical health of individuals. It is a major concern for the labour force and quality of life in the city. Studies have shown that high levels of air pollution lead to a significant loss of working hours, particularly for informal workers who work for small, unregistered companies without fixed salaries. These workers are more vulnerable to the health effects of air pollution and are less able to make up for lost hours, resulting in serious economic implications.

Mexico's government has implemented various plans and policies to reduce emission levels and improve air quality. These plans include vehicular restrictions, the promotion of public and sustainable transportation, the expansion of green areas, and increased bicycle and pedestrian accessibility. While these measures have shown some success, with Mexico City dropping to the 917th most polluted city in the world in 2021, more action is needed to address the persistent air quality crisis and guarantee the population's right to a healthy environment.

Action against pollution

Mexico City has made significant progress in reducing its air pollution, dropping from the most polluted city in 1992 to the 917th most polluted city in 2021. However, there is still work to be done, as the city's concentration of airborne particles (PM 2.5) exceeds the World Health Organization's guidelines.

To further combat air pollution in Mexico City, the following actions can be taken:

Education and Public Awareness:

As suggested by the Science Center of the Atmosphere researcher Ricardo Torres, enhancing public awareness and education about air quality and monitoring tools can help reduce the health effects associated with poor air quality. Educating the public about the sources and impacts of air pollution can empower individuals to take action and make informed decisions to improve air quality.

Government Policies and Regulations:

The Mexican government has implemented several successful policies in the past, such as requiring the reformulation of gasoline, closing or relocating polluting factories, and implementing the ""Hoy No Circula" program, which restricts vehicle usage based on emissions testing. Continuing to enforce and expand upon these policies can further reduce air pollution.

Encouraging Alternative Transportation:

As car-related pollution is a significant contributor to air pollution, encouraging the use of public transportation, carpooling, biking, and walking can help reduce vehicle emissions. Expanding and improving public transportation systems and infrastructure for cyclists and pedestrians can make these alternatives more accessible and attractive to residents.

Industrial Emission Reductions:

Mexico City's industrialization contributed significantly to its air pollution. While some polluting factories have been closed or moved, further action can be taken to reduce emissions from remaining industrial sources. This includes implementing and enforcing stricter regulations on fuel and power plants, as well as providing incentives for industries to adopt cleaner technologies and practices.

Individual Actions:

Individuals can also take small steps to reduce their contribution to air pollution. In addition to reducing car usage, people can avoid using gas-powered equipment for lawn care and refrain from burning leaves, trash, or other materials. Using perfumes and refrigerators sparingly can also help, as these products can contain polluting gases.

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