Mexico City's Air Pollution: A Complex Crisis

Mexico City has long been infamous for its poor air quality. In 1992, the United Nations declared it the world's most polluted city, and the air pollution problem has been a concern for the city's population and health officials for decades. While the city's air quality has improved significantly in recent years, dropping to 917th place in the global rankings, it still exceeds the World Health Organization's (WHO) guidelines for airborne particle (PM 2.5) concentration. Various factors have contributed to Mexico City's air pollution crisis, including rapid industrialization, a population boom, a proliferation of vehicles, geographical factors, and the use of polluting fuels. The Mexican government has implemented several measures to combat air pollution, including vehicular restrictions, incentives for cleaner vehicles, investments in public transportation, and the closure or relocation of polluting factories.

Population growth, industrialisation and urbanisation

Mexico City was once the world's most polluted city. While it has since dropped to 917th place, the concentration of airborne particles still exceeds the World Health Organization's guidelines. The air pollution in Mexico City is predominantly caused by human activities, including the burning of fossil fuels in power plants and vehicle emissions.

Population Growth, Industrialisation, and Urbanisation

The population growth, industrialisation, and urbanisation of Mexico City during the 20th century contributed significantly to its poor air quality. The population of the metropolitan area, also known as Greater Mexico City, grew rapidly from 3.1 million in the 1950s to 14 million in the 1980s and now stands at approximately 22 million. This rapid urbanisation and the associated increase in human activities led to a significant decline in air quality.

Industrialisation played a crucial role in the city's air pollution crisis. During the 1980s, the city had a high number of vehicles per resident, and these cars were often of poor quality, running on highly toxic fuel. Additionally, unregulated and highly polluting factories, power plants, and oil refineries were operating throughout the city. The topography of Mexico City further exacerbated the problem, as the city is located in a basin where air pollutants tend to be trapped, making it challenging to disperse them.

The combination of population growth, industrialisation, and urbanisation resulted in a perfect storm of factors contributing to Mexico City's air pollution crisis. The increased population led to a higher demand for energy, transportation, and industrial development, all of which contributed to the emission of air pollutants. The rapid urbanisation and industrialisation also meant that the city's infrastructure struggled to keep up with the growing environmental challenges, leading to a cumulative effect on air quality.

While population growth, industrialisation, and urbanisation are critical factors, it is important to recognise that they are intertwined with other social and economic factors. The development of transportation networks, the expansion of industrial sectors, and the increased energy consumption associated with a growing population all contribute to air pollution. Furthermore, the regulatory and policy responses to air pollution also play a significant role, as evidenced by the successful implementation of policies to improve air quality in Mexico City in recent years.

Poor-quality cars and toxic fuel

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. These pollutants are largely the result of human activities, including vehicle emissions and the burning of fossil fuels.

The proliferation of vehicles, rapid industrial growth, and a population boom contributed to Mexico City's poor air quality. In the 1980s, there were about 124 cars per 1000 residents. While this number may not seem high, the cars were of poor quality and ran on highly toxic fuel. The topography of Mexico City, located in a basin, also meant that air pollutants were trapped, exacerbating the problem.

The Mexican government has implemented various measures to reduce emissions and improve air quality. In 1990, the government introduced air quality management programs that included removing lead from gasoline, implementing catalytic converters in automobiles, and reducing the sulphur content in diesel transportation fuel. The "Hoy No Circula" policy, introduced in 1989, required vehicles to undergo emissions testing every six months and restricted driving on certain days based on their emissions performance.

Despite these efforts, air pollution remains a significant issue in Mexico City. The city's high altitude of 7382 feet above sea level results in oxygen levels that are 25% lower than at sea level, and carbon-based fuels do not combust completely. The basin-like topography of the city, surrounded by mountains, also contributes to the trapping of air pollutants.

The government continues to work towards reducing emission levels through plans that encourage citizen participation, vehicular restrictions, the expansion of green areas, and improved bicycle accessibility. While Mexico City's air quality has shown some improvement, dropping to the 917th most polluted city in the world in 2021, it still exceeds the World Health Organization's guidelines for airborne particle concentrations.

Non-regulated factories, power plants and oil refineries

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 topography of Mexico City does not favour its industrialisation, as it is located in a basin surrounded by mountains, almost like a bowl, where air pollutants are trapped. This, combined with the city's high altitude, which causes oxygen levels to be 25% lower, meant that pollution was at dangerous levels.

Non-regulated factories, power plants, and oil refineries were operating all over the city, adding to the pollution. These industrial activities emitted over 11,000 tons of waste material into the atmosphere every day. The burning of fossil fuels in power plants and the use of fuel oil in industry contributed to the high levels of carbon monoxide and nitrogen dioxide. The Mexican government has since implemented policies to reduce emissions from power plants, such as substituting fuel oil with natural gas.

The proliferation of vehicles also played a significant role in the city's poor air quality. The number of cars and light-duty trucks per 1000 residents doubled from 124 in 1980 to 267 in 2010. These vehicles were of poor quality and ran on very toxic fuel, emitting large amounts of pollutants. The Mexican government has addressed this issue by requiring gasoline reformulation, implementing emissions testing, and restricting vehicular use through the "Hoy No Circula" policy.

To improve air quality further, Mexico City needs to prioritise public transport, particularly electric transport, and active transport such as cycling and walking. The country also has the potential to develop renewable energy projects, with abundant solar radiation, wind capacity, and geothermal sources. By harnessing these renewable energy sources, Mexico can diversify its energy supply, lower electricity costs, and support sustainable development.

Topography of Mexico City

The topography of Mexico City is rugged and steep, surrounded by mountains and hills. The city is located in a basin, surrounded by mountains, which almost forms a bowl-like container. The elevation of the city is 2,321 meters on average, with the city being 7382 feet above sea level. Mexico City is located in the Valley of Mexico, in the Trans-Mexican Volcanic Belt, also known as the Sierra Nevada. The region is characterised by its volcanic landscape, with light volcanic rock, canyons, hills, and volcanoes. The natural geography of the state can be categorised into nine regions, including the Sierra de Zongolica, the Tecolutla Region, and the Central Region. The climate of the state is influenced by its altitude, with temperatures varying from 13°C to 29°C.

Wildfires

Mexico City's topography, surrounded by mountains and located at a significant height, makes it susceptible to trapping air pollutants. The city's high altitude, at 7382 feet above sea level, results in oxygen levels being 25% lower, and carbon-based fuels do not combust completely, contributing to air pollution. The frequent activity of the nearby Popocatepetl volcano has also been linked to increased contamination levels in the city.

The impact of wildfires on air quality in Mexico City is exacerbated by the presence of ground-level ozone, carbon monoxide, sulphur dioxide, nitrogen dioxide, and airborne particles, which are primarily generated by human activities such as burning fossil fuels and vehicle emissions. The basin-like geographical formation of the city, coupled with the high-pressure system, hinders the dispersion of contaminants, leading to their accumulation and further deteriorating air quality.

To address the air pollution crisis, the Mexican government has implemented measures such as requiring gasoline reformulation, closing or relocating polluting factories, and imposing a weekly day without driving. These efforts have shown positive results, with significant decreases in carbon monoxide, ozone, and particulate matter levels between 1992 and 2012.

While wildfires are not the sole cause of Mexico City's air pollution, they significantly contribute to the problem, especially when combined with other geographical and human factors. The city's unique topography and the presence of other pollutants intensify the impact of wildfire smoke, highlighting the importance of proactive measures to mitigate the effects of wildfires and improve overall air quality.

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