Mexico City was once named as the world’s most polluted city in the world, but according to IQAir, a Swiss company which keeps track of the air quality of cities around the globe, Mexico City has now dropped down to the 917th most polluted city in the world in 2021. Though its concentration of airborne particles (PM 2.5) still currently exceeds the guideline of the World Health Organization (WHO), yet the colossal improvement is undoubtable. What has been done to successfully reduce air pollution in Mexico City? And what lessons can other cities learn from it? 

During the 20th century, Mexico City was undergoing industrialisation and urbanisation, and the population of the metropolitan area of the valley of Mexico, also called as Greater Mexico City, grew substantially from 3.1 million in the 1950s to 14 million in the 1980s. The rapid growth in population, the increase in manpower and human activities has resulted in severely poor air quality. Air pollution in Mexico City reached its peak in the 80s and 90s, as ground-level ozone, carbon monoxide, sulphur dioxide, nitrogen dioxide and airborne particles, all five major air pollutants were at their record level respectively. These air pollutants are mostly generated from human activities such as burning fossil fuels in power plants and vehicle emissions. In the 80s, there were about 124 cars per 1,000 residents. Although this number might not seem particularly high, these cars were made in poor quality and ran on very toxic fuel. At the same time, non-regulated and highly polluting factories, power plants, and oil refineries were operating all over the city. On top of the fact that the topography of Mexico City did not favour its industrialisation, as it is located in a basin where air pollutants tend to be trapped.

In 1992, Mexico City was labelled by the United Nations as the world’s most polluted city. Although there is no concrete data on air pollution-related deaths in the 80s and 90s, air quality in Mexico City at that time was described as just as severe as India’s today where birds fell out of sky and were found dead because of air pollution’s toxicity. Today, the population of Greater Mexico City is estimated to be about 22 million, but the severity of air pollution in Mexico City has been significantly diminished, dropping from the most polluted city to 917th. So how did that happen?

Efforts to Improve Air Pollution in Mexico City Throughout The Years

Recognising the severity of air pollution in the 80s and 90s, the city’s government understood the importance of reducing air pollution, both from an idealistic and realistic perspective, as it posed a huge threat to public health and hindered further economic development of the region. As such, the government implemented a range of policies to combat air pollution in the country’s capital.

The most notable among the raft of policies was the “Hoy No Circula”, meaning “today, (these vehicles) don’t circulate”, which was first introduced in 1989. In Mexico City and the state of Mexico, all vehicles are required to go through emissions testing every six months. Then, each vehicle is issued a verification according to their performance in the test. “0” is assigned to vehicles that meet the requirements, while “1” and “2” are assigned to underperforming vehicles. Vehicles with “0” are exempted from the “Hoy No Circula” while those with “1” and “2” labels are prohibited to be driven on one weekday per week and two Saturdays per month. Yet, the effectiveness of such a policy has been questioned because, with the exception of the first few months, air pollution did not decrease even after several years of implementation. Instead of using public transportation, evidence from sales of automobiles indicated that people would simply buy another car to drive on restricted days.

Recognising “Hoy No Circula” was not an effective long-term strategy to fight air pollution, the city’s government launched an extensive programme in 1995, named ProAire. It contains several concrete measures to achieve sustainable development in eight areas: reduction of energy consumption, cleaner and more efficient energy across all sectors, promotion of public transport and regulation of fuel consumption, technology shift and emissions control, environmental education and sustainability, culture and citizen participation, green areas and reforestation, institutional capacity building and scientific research, as well as strengthening of health protection. Today, ProAire is into its fourth iteration, featuring several targeted measures including the renewal of bus fleet, which aims to minimise unnecessary emissions by amending the routes and shifts based on algorithms and introducing buses that can at least meet the standard of EURO V, as well as the expansion of the city’s subway network and bike-sharing initiatives, both of which seeks to decrease public reliance on vehicles. 

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Current Challenges

Yet, despite great improvement, the situation in Mexico City is far from perfect. In many ways, it is still recovering from the environmental impacts from the peak of its air pollution and there is a lack of aggressive policies to combat the root of the problem.

Today, ground-level ozone remains to be the air pollutant of the biggest concern where in the spring of 2016, the concentration of ozone was about 1.9 times the acceptable limit, almost reaching the level in the 80s. A high concentration of ozone typically occurs during the spring season; a phenomenon that is highly related to the climate in Mexico. Ground-level ozone is formed through the interaction of nitrogen oxides (NOx) with volatile organic compounds (VOCs), and ultraviolet (UV) radiation from the sun will accelerate the reaction. In Mexico, the weather during spring is particularly hot and dry, creating the perfect conditions for ozone to form. In 2016, the Mexican Atmospheric Environmental Contingency Plan (AECP) was once again reactivated after being irrelevant for more than a decade. The Plan included a further restriction on the use of vehicles in addition to the “Hoy No Circula”, which forbids driving on two days a week instead of the habitual one day, and the limiting factories’ greenhouse gas emissions (GHG) by up to 40%. These measures are still valid whenever air pollution breaches the acceptable limit.

Another underlying challenge is the attitude of the Mexican federal government. Mexico has yet to set a net zero target, despite ratifying the Paris Agreement. According to the Climate Action Tracker (CAT), the ambition of Mexico to fight climate change is highly insufficient due to its lack of a concrete decarbonisation plan. Although GHG-related policies are not directly linked to air pollution, both derived from the same sources. The ambition of the Mexican government in handling one problem reflects its attitude towards the other. Current environmental policies launched by local governments do not have the financial and political backing from the federal government. 

This is a problem that a federal state like Mexico must eventually tackle. What is considered a national problem and what is considered a local problem? Should environmental issues be left to local governments to handle on their own, like how Mexico does, or shall the federal government trespass into environmental policies that were used to be governed by local governments, like how Canada does?

For now, Mexico City can only rely on policies like the ACEP, the activation of which in the spring season has become a new normal due to seasonal high levels of air pollution from climate change. Ultimately, the eradication of air pollution requires intergovernmental cooperation. Mexico City’s success in reducing air pollution sets an example for other cities to follow. Although its measures cannot simply be replicated and applied to every major city, as each has its own structure and conditions, it shows that even the historically most polluted city can become “clean” with a set of precise policies.

Featured image by: World Bank/Flickr