Mexico City's Air Pollution: The Physical Culprit Unveiled

Mexico 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 city's high altitude of 7382 ft above sea level, its topography, and its rapid population growth have all contributed to its poor air quality. The proliferation of vehicles, rapid industrial growth, and the use of carbon-based fuels have also played a significant role in making Mexico City one of the most polluted cities in the world.

High altitude

Mexico City is located 7,300 feet or 7,382 feet above sea level, in a valley surrounded by mountains and volcanoes. This high altitude causes oxygen levels to be 25% lower than at sea level. The topography of the city means that air pollutants tend to be trapped.

The combination of high altitude and topography means that Mexico City has long suffered from thick layers of smog, produced by cars, factories, and wildfires. The poor air quality that prevails in the country kills 17,000 people every year, including 1,680 children under the age of five.

The main cause of air pollution in Mexico City is emissions from vehicles, which account for 75% of emissions. The number of vehicles in the city has doubled since 1992, and many of these vehicles are old and run on very toxic fuel. In addition, the use of fuel ethers has contributed to a decrease in carbon monoxide levels but has also been linked to an increase in ground-level ozone, a major air pollutant.

To combat air pollution, the Mexican government has implemented several measures, including requiring the reformulation of gasoline, closing or moving polluting factories, and prohibiting drivers from using their cars one day a week. The government has also invested in public transport, created incentives for the purchase of cleaner vehicles, and built bike lanes. Despite these efforts, air pollution remains a major issue in Mexico City, and the government has been criticized for its lack of aggressive policies to address the root causes of the problem.

Incomplete combustion of carbon-based fuels

Mexico City has long struggled with air pollution, which has been a concern for the city's population and health officials for decades. One of the physical factors contributing to this issue is the incomplete combustion of carbon-based fuels. This problem is exacerbated by the city's high altitude, which causes lower oxygen levels.

Particulate matter, especially the smaller PM2.5 particles, can have detrimental health effects. These particles are so small that they can be inhaled deep into the lungs, potentially reaching the alveoli, the tiny air sacs responsible for gas exchange. This can lead to respiratory issues and other health problems. Additionally, the incomplete combustion of carbon-based fuels also releases other harmful pollutants such as carbon monoxide, nitrogen dioxide, and sulfur dioxide.

Carbon monoxide is a toxic gas that is emitted primarily by vehicles. Inhaling carbon monoxide can cause dizziness, brain dysfunction, and even death. Nitrogen dioxide, another pollutant formed from vehicle emissions and industrial activities, can also have adverse effects on human health. Sulfur dioxide, produced by the combustion of fossil fuels, is associated with increased respiratory symptoms, difficulty in breathing, and premature death.

To combat the air pollution caused by incomplete combustion, the Mexican government has implemented various measures. These include requiring the reformulation of gasoline, closing or relocating polluting factories, and prohibiting drivers from using their cars one day a week. There has also been an expansion of public transportation and a push for increased bicycle accessibility. While these efforts have led to improvements, air pollution remains a significant problem in Mexico City, and further efforts are needed to ensure the health and well-being of its residents.

Population boom

Mexico City's population witnessed a rapid increase in the 20th century as industrialization attracted thousands of migrants from across the globe. This population boom, coupled with other factors, contributed significantly to the city's air pollution issues.

From 1950 to 2015, the population of Mexico City skyrocketed from three million to twenty million, primarily driven by migrants seeking improved opportunities. This massive influx of people triggered an era of industrialization, releasing over 11,000 tons of waste into the atmosphere daily. The economy flourished, but so did the proliferation of vehicles, with the number of cars and light-duty trucks per 1000 residents more than doubling from 124 in 1980 to 267 by 2010.

The combination of population growth, increased motorization, and industrial activities had a detrimental impact on air quality. The basin-like topography of Mexico City, surrounded by mountains, traps air pollutants, further exacerbating the problem. The city's high altitude of 7382 feet above sea level also contributes to lower oxygen levels, with a 25% reduction compared to sea level.

The strain on the city's infrastructure and environment due to the population boom is evident. The lengthening of automobile trips and the yearly increase in the number of vehicles in the city add to the pollution burden. While the Mexican government has implemented measures to improve air quality, such as reformulating gasoline and restricting vehicle use on certain days, the challenges posed by the growing population continue to be a critical factor in Mexico City's air pollution crisis.

Industrial growth

Mexico City's air pollution reached its peak in the 1980s and 1990s, with the city earning the title of the "'most polluted city in the world'" by the United Nations in 1992. Since then, the air quality has improved significantly, dropping to the 917th position in the list of polluted cities in 2021. However, the concentration of airborne particles (PM 2.5) still exceeds the World Health Organization's guidelines.

The topography of Mexico City also played a role in trapping air pollutants. The city is located in a basin, which makes it difficult for pollutants to disperse. Additionally, the city's high altitude of 7382 feet above sea level results in oxygen levels that are 25% lower, and carbon-based fuels do not combust completely, further contributing to the air quality issues.

To combat the air pollution crisis, the Mexican government has implemented various measures over the years. In 1992, the government mandated the reformulation of gasoline, the closure or relocation of polluting factories, and the introduction of the "Hoy No Circula" program, which prohibited drivers from using their cars one day a week. The government has also expanded public transportation, increased green areas, and promoted bicycle accessibility. These efforts have yielded positive results, with significant reductions in CO, ozone, and particulate matter levels over the past two decades.

While the Mexican government's efforts have led to improvements, more needs to be done to address the root causes of air pollution. This includes modifying mobility systems to prioritize public and active transport, such as electric transportation, cycling, and walking, to reduce emissions from vehicles, which remain a significant contributor to air pollution in the city center. Additionally, updating and expanding environmental health standards to align with the World Health Organization's health protection limits and strengthening programs to improve air quality are crucial steps toward ensuring clean air for Mexico City's residents.

Proliferation of vehicles

Mexico City's air pollution has been a concern for its population and health officials for decades. One of the main physical factors contributing to this issue is the proliferation of vehicles.

The number of vehicles in Mexico City has seen a significant increase over the years, with a doubling of the vehicle fleet from 1992 to 2012. This increase in vehicles has had a direct impact on the city's air quality, as vehicle emissions are a major source of air pollutants. In the 1980s, there were about 124 cars per 1000 residents, and while this may not seem high, the cars were of poor quality and used highly toxic fuel. The use of fuel ethers during this period contributed to a 86% decrease in carbon monoxide, a 53% decrease in ozone, and a 32% decrease in particulate matter over a 20-year span.

The high number of vehicles in Mexico City is due in part to the lack of effective, clean, and safe alternatives to mobility within the city. This has resulted in a heavy reliance on private vehicles, exacerbating the problem of air pollution. The topography of Mexico City, located in a basin, also does not help, as air pollutants tend to be trapped in the valley.

To address the problem of vehicle emissions, the Mexican government has implemented several measures. These include restricting the use of vehicles, with the ""Hoy No Circula" program forbidding driving on one or two days a week, and promoting the purchase of cleaner vehicles. The government has also invested in public transportation and expanded bicycle accessibility by creating bike lanes.

Despite these efforts, the proliferation of vehicles remains a significant contributor to air pollution in Mexico City. With more than 3.5 million vehicles registered in the country, of which 30% are over 20 years old, the problem persists. Modifying mobility systems to prioritize public and active transport, such as electric transportation, cycling, and walking, is essential to reducing transport emissions, which are the main cause of air pollution in the city centre.

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