Air Pollution's Impact On Mexico City's Health

Mexico City has long been notorious for its poor air quality. In 1992, the United Nations declared it the most polluted city in the world. The city's air pollution is caused by a combination of factors, including industrialization, urbanisation, a population boom, vehicle emissions, and the topography of the city, which is located in a basin where air pollutants are trapped. While Mexico City has since dropped to the 917th most polluted city in the world, air pollution remains a significant issue, with the city registering poor air quality 77% of the time from January to August 2023. To combat this, the Mexican government has implemented various measures, such as requiring gasoline reformulation, closing polluting factories, and expanding public transportation. Mexico City has also joined the Breathe Cities initiative to improve air quality, reduce carbon emissions, and enhance public health.

Population growth and industrialisation

Mexico City's population grew from 3 million in 1950 to 20 million in 2015, with 22 million estimated in 2022. This population boom was largely driven by migration, as people from all over the world were drawn to the city in search of better opportunities. This rapid and unexpected growth, coupled with industrialisation, led to a significant increase in human activities, severely degrading the air quality.

The industrialisation era, which began due to the population boom, emitted over 11,000 tons of waste material into the atmosphere daily. The economy boomed, and the proliferation of vehicles added to the air pollution problem. The number of cars and light-duty trucks per 1000 residents increased from 124 in 1980 to 267 in 2010. These vehicles were not only numerous but also of poor quality, running on highly toxic fuel. The topography of Mexico City, located in a basin surrounded by mountains, further exacerbated the issue as air pollutants were trapped, unable to disperse.

The combination of population growth and industrialisation resulted in a perfect storm of factors contributing to air pollution. The increase in human activities, including the use of carbon-based fuels that do not combust completely, led to high levels of primary pollutants like carbon monoxide and sulfur dioxide. The proliferation of vehicles, many of which were older and less efficient, added significantly to the problem.

To combat the air pollution crisis, the Mexican government has implemented various measures over the years. Successive local governments have imposed driving restrictions, such as allowing vehicles to be driven on certain days based on license plate numbers, incentivised the purchase of cleaner vehicles, and invested in public transport and bicycle infrastructure. While these efforts have led to improvements, other factors like the doubling of vehicles in two decades have caused air pollution levels to remain a concern.

Poor dispersion of pollutants

Mexico City's air pollution has been a concern for its population and health officials for decades. The city was once named the world's most polluted city, and while it has since dropped to 917th, its concentration of airborne particles still exceeds WHO guidelines. The poor dispersion of pollutants is a key factor in this issue.

The geographical location of Mexico City in a high-altitude basin, surrounded by mountains, limits air circulation and traps pollutants. This unique setting, coupled with frequent temperature inversions, prevents pollution from rising and dispersing, leading to smog formation and increased pollution levels. The temperature inversion phenomenon occurs when a layer of warmer air traps cooler air and the pollutants within it close to the ground. This condition is more common during the winter months and significantly impacts the city's air quality.

The city's high elevation of over 7,000 feet above sea level also contributes to the poor dispersion of pollutants. The cold air in the atmosphere prevents pollution from rising, causing a buildup of smog. This issue is exacerbated by the frequent use of solid fuels for cooking and heating, which emit large amounts of toxic pollutants, especially in households with limited ventilation.

In addition to geographical factors, varying weather patterns can also worsen pollution levels. Lack of rain, low rainfall, drought, and high-pressure systems can prevent the dispersal of air pollutants, allowing them to concentrate in the city's air. Wildfires, which are sometimes caused by the frequent activity of the nearby Popocatépetl volcano, contribute to the poor dispersion of pollutants by adding smoke and particles to the atmosphere.

The combination of geographical location, elevation, weather conditions, and wildfires creates a challenging environment for the dispersal of pollutants in Mexico City. These factors have led to the city's historical struggle with trapped pollution and the associated health risks for its inhabitants.

Slow response from authorities

Mexico City's air pollution problem has been a concern for decades, and while there have been improvements, the slow response from authorities has hindered progress. In 1992, the United Nations declared Mexico City the "most polluted city in the world", and it retained this title for over two decades.

The Mexican government has implemented various plans and policies to reduce emission levels, but these often require citizen participation, which is not always forthcoming. For example, the government has tried to encourage the use of cleaner transportation options, such as expanding bicycle accessibility and pedestrianised areas, but these initiatives rely on people choosing to change their behaviour. Similarly, the "Hoy No Circula" policy, introduced in 1989, restricts driving on certain days based on license plate numbers, but it is not always followed. While these policies have helped, other factors, like the increasing number of vehicles, have caused air pollution levels to rise again.

The government has also attempted to address industrial emissions, a major source of pollution in Mexico City. They have moved factories out of the capital and tightened regulations on fuel, but this has not been enough to prevent the city from exceeding World Health Organization guidelines for air quality. The government has also tried to increase public awareness and education about air quality and monitoring tools, but it is unclear how effective these efforts have been.

The slow response from authorities can be attributed to several factors, including the complexity of the problem, limited resources, and competing priorities. However, the consequences of this slow response are serious. Air pollution in Mexico City continues to pose a significant threat to public health, with respiratory diseases, heart problems, and even premature death being linked to poor air quality. It also impacts the economy, with workers losing a significant portion of their working hours on days with high levels of air pollution.

Vehicle emissions

The proliferation of vehicles has been a significant factor in the city's air pollution problems. In 1980, there were 124 cars and light-duty trucks per 1,000 residents, and by 2010, this number had increased to 267. While the number of vehicles has continued to grow, the quality of these vehicles has also improved. Older vehicles, which are typically less efficient and more polluting, contribute significantly to the city's air quality issues. The poor quality of fuel used in these older vehicles further exacerbates the problem.

To combat vehicle emissions, the Mexican government has implemented various measures. These include traffic regulations that restrict vehicles from being driven on certain days based on odd or even license plate numbers, as well as bans on older vehicles that do not meet emissions standards. The "Hoy No Circula" policy, introduced in 1989, requires all vehicles in Mexico City and the state of Mexico to undergo emissions testing every six months. This policy has helped to reduce the number of vehicles on the road and lower overall emissions.

In addition to these regulations, the government has also incentivized the purchase of cleaner vehicles and invested in public transport and infrastructure for active transport, such as bicycle lanes and pedestrianized areas. These measures aim to reduce the number of vehicles on the road and encourage the use of more environmentally friendly modes of transportation.

While these efforts have led to a significant improvement in air quality, with Mexico City dropping to the 917th most polluted city in the world in 2021, there is still work to be done. The continued increase in the number of vehicles and the impact of vehicle emissions on public health remain concerns. It is crucial to address these issues through further regulatory measures, incentives for low-emission vehicles, and the promotion of sustainable modes of transportation to ensure a healthier environment for the residents of Mexico City.

High levels of ground-level ozone

Mexico City has long struggled with air pollution due to various factors, including its geographical location, industrial emissions, and vehicle emissions. One of the critical issues contributing to the city's poor air quality is the high levels of ground-level ozone.

Ozone (O3) is a secondary pollutant formed primarily from photochemical reactions between organic compounds and nitrogen oxides. It is a significant component of smog, which is a prominent issue in Mexico City. The high levels of ground-level ozone in the city are a result of several factors. Firstly, the city's geographical location in a mountain basin, surrounded by mountains, creates a unique setting that limits air circulation. This topography, coupled with frequent temperature inversions, traps ozone and other pollutants close to the ground, preventing their dispersal.

The temperature inversion phenomenon occurs when a layer of warmer air traps cooler air, along with the pollutants, close to the ground. This condition is more common during the winter months and significantly increases pollution levels. The trapped ozone contributes to the formation of smog, creating a thick layer that restricts the view of the horizon and signifies unhealthy air quality.

Ground-level ozone has severe health implications for the inhabitants of Mexico City. Ozone has been shown to affect the respiratory, cardiovascular, and central nervous systems. Exposure to ozone is associated with early death, problems in reproductive health and development, and various respiratory issues. The high levels of ground-level ozone, combined with other pollutants, pose a severe risk to the health and well-being of the city's residents.

To combat the issue of high ozone levels, the Mexican government has implemented various measures. These include vehicular restrictions, such as driving bans based on license plate numbers and the prohibition of older vehicles that do not meet emission standards. Additionally, the government has promoted cleaner transportation options, such as expanding bicycle accessibility and prioritizing the development of public transport, mainly electric.

While the efforts to reduce ozone levels have shown some improvements, Mexico City still faces challenges in maintaining healthy air quality. The combination of geographical factors and human activities, such as industrial emissions and vehicle usage, continues to contribute to high levels of ground-level ozone, impacting the health and quality of life of the city's residents.

Frequently asked questions