Mexico City's Air Pollution: Four Key Causes

Mexico City has long struggled with air pollution, which has been a concern for the city's population and health officials for decades. In 1992, the United Nations declared it the most polluted city in the world. While the city's air quality has improved significantly since then, it still faces several challenges. Here, we will explore four key causes of air pollution in Mexico City and the efforts to address them.

Population boom and industrial growth

Mexico City's population rapidly increased during the 20th century as industrialization brought thousands of migrants from all over the world. The population in Mexico City increased from three million in 1950 to twenty million in 2015. This population boom occurred mainly because of migrants seeking better opportunities, and as a consequence, the industrialization era began.

The rapid and unexpected population growth and industrialization led to the UN declaring Mexico City as the most polluted city in the world in 1992. This was partly due to Mexico City's high altitude (7382 ft above sea level), which causes its oxygen levels to be 25% lower. Carbon-based fuels also do not combust completely, which further contributes to air pollution.

The industrialization era resulted in the emission of over 11,000 tons of waste material into the atmosphere every day. The burning of fossil fuels, stubble burning, power plants, road dust, wet cooling towers, and various industrial processes generate significant amounts of particulate matter that contribute to air pollution.

The proliferation of vehicles has also played a significant role in the city's air pollution. The number of vehicles in the city has increased annually, with a total of more than 3.5 million vehicles registered in the country, 30% of which are over 20 years old. In the 1980s, there were about 124 cars per 1000 residents, and by 2010, this number had increased to 267. The poor quality of these vehicles and the use of toxic fuel further exacerbated the problem.

The combination of population growth, industrialization, and the proliferation of vehicles has resulted in severely poor air quality in Mexico City. The city's unique topography, located in a basin surrounded by mountains, also contributes to the trapping of air pollutants.

Vehicle emissions

In the 1980s, the number of cars in Mexico City was approximately 124 per 1,000 residents. While this may not seem high, the vehicles were of poor quality and used highly toxic fuel. The proliferation of vehicles, coupled with the city's topography, has led to a concentration of airborne particles and smog. Mexico City is located in a basin surrounded by mountains, creating a bowl-like effect that traps air pollutants. The city's high altitude, at 7382 feet above sea level, further exacerbates the problem by causing oxygen levels to be 25% lower.

The impact of vehicle emissions on air quality in Mexico City has been addressed through various initiatives. The "Cars Don't Circulate" programme, introduced in 1989, restricts the use of a fifth of all vehicles on weekdays, depending on the registration plate number. This initiative aims to reduce emissions by limiting the number of vehicles on the road. Additionally, the ProAire programme has overseen the renovation of the city's fleet of taxis and minibuses, improving fuel efficiency and reducing emissions.

Despite these efforts, transport emissions remain a significant contributor to air pollution in Mexico City. The growing population and urban sprawl have led to longer automobile trips and an increasing number of vehicles in the city each year. To address this, there is a focus on modifying mobility systems to prioritise public transport, active transport such as cycling and walking, and electric vehicles to reduce transport emissions.

The Mexican government has also implemented plans to reduce emission levels, including vehicular restrictions, the expansion of green areas, and improved bicycle accessibility. These measures aim to decrease the public's reliance on vehicles and encourage the use of more environmentally friendly modes of transportation.

Wildfires

Mexico City's topography also plays a role in trapping air pollutants. The city is located in a basin surrounded by mountains, forming a bowl-like container. Additionally, the high altitude of the city, at 7382 feet above sea level, results in oxygen levels being 25% lower than at sea level. This contributes to the difficulty in dispersing pollutants and improving air quality.

To address the air pollution crisis, 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 on certain days. There has also been a focus on expanding public transportation, with efforts to renew the bus fleet, optimize routes, and introduce more efficient buses. The government has also implemented vehicular restrictions, increased green areas, and promoted bicycle accessibility to reduce emissions and improve air quality.

Topography

Mexico City is situated in a valley, surrounded by mountains, which almost forms a bowl-like shape. The city is also at a high altitude of 7382 feet above sea level. This unique topography has contributed to the air pollution problem in the city.

The basin-like shape of the valley tends to trap air pollutants, preventing their dispersion. This natural geographical feature, coupled with the city's high altitude, has made Mexico City particularly susceptible to poor air quality. The high altitude means that the city already has lower oxygen levels, which are about 25% lower than at sea level.

The trapped air pollutants, including ground-level ozone, carbon monoxide, sulphur dioxide, nitrogen dioxide, and airborne particles, have severe health implications. These pollutants are largely the result of human activities, such as burning fossil fuels in power plants and vehicle emissions. The topography of the city, therefore, exacerbates the effects of these human-caused pollutants by creating a natural barrier that hinders their dispersal.

The combination of geographical features and human activities has led to Mexico City being labelled as the world's most polluted city by the United Nations in 1992. However, it is important to note that through various measures, the city has since improved its air quality significantly, dropping to the 917th most polluted city in the world in 2021.

Poor fuel quality

Mexico City's air pollution has been a concern for its population and health officials for decades. In 1992, the United Nations declared it the most polluted city in the world. While the air quality has improved since, the city still faces challenges due to poor fuel quality.

One factor that contributes to poor fuel quality in Mexico City is the presence of impurities in the gasoline. While the state-run petroleum company, PEMEX, has implemented measures to monitor and control fuel quality, some consumers still perceive Mexican gasoline as inferior to that of the United States. However, it is important to note that Mexican fuel standards are similar to those in the United States, and efforts are made to ensure the fuel meets the required specifications.

The type of fuel used in vehicles and power plants also plays a role in air pollution. In the past, power plants and vehicles in Mexico City burned fossil fuels, which release harmful pollutants into the atmosphere. Additionally, the topography of the city, located in a basin surrounded by mountains, traps air pollutants, further contributing to poor air quality.

To address the issue of poor fuel quality and reduce emissions, the Mexican government has implemented various measures. These include the reformulation of gasoline, the closure or relocation of polluting factories, and the promotion of public transportation. The government has also focused on reducing energy consumption, improving energy efficiency, and regulating fuel consumption.

While efforts to improve air quality in Mexico City have shown progress, it is crucial to continue implementing strategies to address the issue of poor fuel quality and reduce emissions. By prioritizing public transportation, electric mobility, and active transport like cycling and walking, Mexico City can further reduce the emissions generated by transportation, which is currently the main source of air pollution in the city centre.

Frequently asked questions