by Luisa T. Molina1, Benjamin de Foy2, Oscar Vázquez Martínez3 and Víctor Hugo Páramo Figueroa3
The Mexico City Metropolitan Area (MCMA) is one of the world’s largest megacities with an estimated 20million inhabitants living on the dried bed of the elevated lake Texcoco and its surroundings. The inland basin is at an altitude of 2240msl and is surrounded on three sides by mountains and volcanoes, with an opening to the Mexican Plateau to the north and a mountain gap to the south-east. With a diameter of around 50km and limited room for expansion, MCMA has a high density of population as well as of industrial and commercial activities (Figure 1). It represents around 20 per cent of Mexico’s population and 9 per cent of its greenhouse gas emissions, with emissions of 60 million tonnes of carbon dioxide equivalent per year.
|Figure 1 — Aerial photo of Mexico City (L.T. Molina)|
Air quality management strategies and trends
During the 20th century, Mexico City experienced a huge increase in population and urbanized area as it attracted migrants from other parts of the country and industrialization stimulated economic growth (Figure2). Population growth, increasing motorization and industrial activities, a constrained basin and intense solar radiation combined to cause intense air-quality problems of both primary and secondary pollutants. The automatic air-quality monitoring network, established in the late 1980s, revealed high concentrations of all criteria pollutants: lead, carbon monoxide, nitrogen dioxide, sulphur dioxide, ozone and particulate matter (PM). Ozone exceeded the air quality standards more than 90 per cent of days and peaked above 300 parts per billion (about three times the standard) 40-50 days a year, among the worst in the world (Molina and Molina, 2002).
|Figure 2 — Topographical map of the Mexico City Metropolitan Area showing urban expansion|
Both the Mexican Government and the citizens of Mexico City have recognized air pollution as a major environmental and social concern since the mid-1980s. In the 1990s, comprehensive air quality management programmes were developed and implemented. Specific actions included removal of lead from gasoline and the implementation of catalytic converters in automobiles, reduction of sulphur content in diesel transportation fuel; substitution of fuel oil in industry and power plants with natural gas; reformulation of liquified petroleum gas used for heating and cooking. The government also strengthened the vehicle inspection and maintenance programme; vehicles were required to be inspected in a centralized system and more frequent inspections were required for higher emitting vehicles as incentives to promote fleet turnover and help ensure the proper maintenance of vehicles. In addition, the “no driving day” (Hoy no circula), which stopped private vehicles from circulation one day a week, have been effective in modernizing the vehicle fleet by exempting low-emitting vehicles from the “no driving day” rule.
As a result of these regulatory actions, combined with technology change, concentrations of criteria pollutants have been decreasing over the past decade, despite the continuing increase in population and economic activity (Figure 3). Mexico City’s levels for particulate matter and ozone, however, still exceed standards recommended by the World Health Organization.
|Figure 3 — Trends in population, vehicular fleet, energy consumption and ozone concentration in the Mexico City Metropolitan Area (1990-2006)|
The Metropolitan Environmental Commission (CAM), an interagency body that consists of environmental authorities in federal government, the State of Mexico and the Federal District was created in the mid-1990s to coordinate the policies and programmes that are implemented in the metropolitan area. The current air-quality management programme, PROAIRE 2002-2010, includes a series of new measures to further improve air quality and calls for more extensive observation data to improve the MCMA emissions inventory (Molina and Molina, 2002; CAM 2002). A large field measurement campaign, supported by CAM, was carried out in 2003 (Molina et al., 2007). In 2006, Mexico City was selected as the case study of MILAGRO (Megacity Initiative: Local And Global Research Observation), an international scientific project to investigate the outflow of emissions from a megacity (Molina et al., 2008). These field studies have provided comprehensive datasets for updating and improving the emissions inventory, the chemistry, dispersion and transport processes of the pollutants emitted to the MCMA atmosphere and their regional and global impacts.
One of the important PROAIRE 2002-2010 measures is in the transportation sector, the most important source of pollutants emitted to the MCMA atmosphere. Mexico City has recently adopted the bus rapid transit system, designed initially in the city of Curitiba, Brazil, and successfully adopted in Bogotá, Colombia, where prime road space was allocated to low-emission, high-capacity buses. A recent study conducted by researchers at INE/SEMARNAT showed that commuters’ exposure to carbon monoxide, hydrocarbons and particulate matter was reduced by about 50 per cent when the popular 22-seater gasoline minibuses were replaced by modern diesel buses (Metrobus) running in a confined or dedicated lane (Wöhrnschimmel et al., 2008). This study corroborated Bogotá’s findings that the bus rapid transit system can simultaneously reduce criteria pollutant and greenhouse-gas emissions, commuters’ exposure levels and travel time.
The Government has also increased its efforts to encourage public participation and stakeholder input. Information on air-quality levels and new initiatives are available on line and published in news media.
Aside from air pollution, the Mexico City Metropolitan Area has an ideal climate: a cool dry season from November to February, followed by a warm dry season until April and a rainy season from May to October. Temperatures are moderate and humidity is low. With mountain shielding on most sides, winds are weak inside the basin. In terms of air pollutants, the cool season has strong surface inversions and higher peaks of primary pollutants in the morning. The warm season has more ultraviolet radiation and hence more smog. Drier conditions cause increased aerosol loadings due to dust and biomass burning. The rainy season has lower PM10 and carbon monoxide but continues to have high ozone due to intense photochemistry before the afternoon showers. Air quality is therefore a year-round concern.
Part of the problem lies with meteorology. Weak winds and strong temperature inversions at night lead to high primary pollutant concentrations during rush hour and into the morning. Being at low latitudes (20°N), synoptic forcing is weak and the weather is strongly influenced by the mountain-valley winds in the basin. A typical warm-season circulation starts with weak drainage winds into the basin. This is followed by very rapid boundary layer growth to maximum heights of 2-4km in the early afternoon. A gap flow enters the basin from the south-east and creates a convergence line across MCMA (see Figure 4). The timing of the gap flow determines the location and magnitude of maximum ozone concentrations (de Foy et al., 2008).
|Figure 4 — Conceptual circulation model for a warm-season day. Surface winds from the north meet the gap flow from the south (red) and form a convergence line (pink). Vertical mixing leads to basin venting due to westerlies aloft (blue). MODIS true colour image projected on terrain elevation model (vertical scale exaggerated).|
With such weak winds and intense smog, it is tempting to compare MCMA with Los Angeles. In Los Angeles, stable high-pressure systems with subsidence aloft lead to multi-day accumulation of pollutants and peak smog episodes. In MCMA, simulations of particle trajectories show that the rapid growth of the boundary layer leads to efficient vertical mixing. When the convergence line moves north-east, the air mass is vented from the basin by the winds aloft. There is therefore limited recirculation and day-to-day carry-over in the basin. In fact, MCMA is more similar to Houston, where a polluted airmass is vented out to sea in the morning and transported back over the city by the afternoon sea breeze (Banta et al., 2005).
From the climate point of view, a 100-year time series of temperature from the meteorological observatory shows a slight decrease in the first half of the century followed by a marked increase up to the present of 2 to 4 °C. There has also been an increase in the number and duration of heat waves in MCMA. Modelling studies of land use change suggest that up to three quarters of this may be attributed to the urban heat island and the remainder to climate change. Studies of the urban heat island show that it may interact with the mountain-valley winds and influence night-time drainage flows and afternoon ventilation.
Rainfall had an even more pronounced trend over the last century than temperature (see Figure 5). Annual rainfall at the observatory has increased by 50 per cent. Whereas there used to be 0-3 days per year with extreme events (> 30 mm/day) at the beginning of the century, there are routinely 5 to 10 days per year in more recent decades. It is still unclear how much of the change can be attributed to the urban heat island and how much to climate change.
|Figure 5— Historical trends in rainfall at one meteorological observatory in MCMA|
Climate Change Action Plan
The MCMA’s Climate Change Action Plan (Acción Climática), designed for 2008-2012, consists of 26 emission-reduction measures, 12 adaptation measures and six communication and education measures with a total budget of nearly US$5.955billion. It was initiated with World Bank support, developed with analysis of costs, benefits, barriers and impacts and concluded with public consultation and consensus-building between 32governmental organizations. The aim is to reduce greenhouse-gas emissions by 7 million tonnes of carbon dioxide equivalent for the period from 2008 to 2012 and to have an adaptation plan ready for 2012.
The largest emission-reduction measures are for biogas capture projects and waste-management projects. Next come the transportation sector with public transport for school children, a new Metro (subway) line, up to 10 new Metrobus lines and special transport corridors. These are complemented by fleet renewal projects for taxis and medium-capacity buses, inspection and maintenance measures and modernization of fleet transfer and renovation stations. In the residential sector, efficient lighting for homes is particularly cost-effective. Additional measures will address residential energy and water use and sustainable housing development. Energy efficiency will be promoted through targeted projects in government agencies and public utility sectors. Further measures include renewable energy generation projects and recycling centres.
Adaptation to increased rain and extreme events will consist of improved flood management by developing flood gates and alert systems. Rural development projects will promote soil and water conservation, reforestation and crop protection projects. These will further include monitoring of genetically modified crops, promotion of organic agriculture, planting of climate-change-resistant tree species and the promotion of green roofs. Adaptation to increased temperature will focus on remote-sensing and monitoring of forest fires and an epidemiological monitoring system for vulnerable populations.
Education and communication projects include a permanent education program for climate change, education for resource-efficient housing, water conservation, public understanding campaigns and integrated waste management campaigns. The focus is on raising awareness, understanding risks and promoting adaptation and mitigation measures.
Results to date include a “solar standard” being promoted for solar collectors for hot water provision. This has already been adopted by 30per cent of swimming pools (6957m2 installed) where it has a 1.5 year pay back period. Installation will continue with 6500 new housing projects by 2012, as well as adoption by hotels and other commercial partners.
The Metrobus system is a resounding success with one of the most highly used lines in the world carrying 265000 passengers per day. This is the first project in the world to sell emission reductions as part of its financing. For the period from 2005 to 2007, there was reduction of about 67400 tonnes carbon dioxide equivalent, which sold for 281600 euros. New lines are being developed and 10 new transport corridors will be installed by 2012 leading to a reduction of 369500 tonnes of carbon dioxide equivalent along with an improved urban environment.
Urban meteorology research
WMO Members reacted to the needs to develop meteorological and environmental capabilities in urban areas by establishing the Global Atmosphere (GAW) Urban Research Meteorology and Environment (GURME) project in 1999. The interest arose from the difficulties countries were facing from growing urbanization and related air pollution problems.
Several projects have been undertaken under GURME to assist and facilitate related research activities and consequently in establishing urban applications. These projects include such activities as:
- Studies to understand the formation of local atmospheric pollution;
- Heat island studies;
- Designing, establishing and enhancing both meteorological and air pollution measurement networks;
- Building air-quality modelling and forecasting systems and services;
- Training and capacity-building for air-quality modelling and forecasting;
- Studies on the impact the urban area has on regional air quality;
- Building Web-based communication systems for informing authorities and the public on special weather conditions (such as ice, snow, smoke and haze) and on air pollution.
GURME has concentrated its efforts on air-quality modelling and forecasting—activities needed to support effective environmental management on the urban scale. Expert meetings are conducted to gather up-to-date information on new methods for chemical weather forecasting and to help identify future research needs to improve the forecasts. Training has been offered to Latin American and South Asia regions. Both research and operational sectors have come together in these events.
GURME involves cooperation between organizations and agencies acting in different fields. Working in concert with different authorities is important for the successful carrying-out of the studies, implementation of activities and fostering of improved prevention strategies.
GURME also engages collaboration that extends to regional and global scales. There is growing appreciation that accurately forecasting chemical weather requires consideration of the influence of pollution sources from larger-scale phenomena (such as duststorms and forest fires). The multiscale nature of the issues addressed in GURME necessitate and facilitates collaboration across scales.
Mexico City has been working on improving air quality for a number of years. Much progress has been made in tackling air-pollution problems through comprehensive air-quality management programmes based on scientific, technical, social and political considerations. Yet continuing pressure from increasing urban population and the desire of people to have a better quality of life causes an ongoing need to improve air quality.
The Government has also taken actions to mitigate greenhouse-gas emissions. The aim of the plan is to promote “no-regrets” policies that are beneficial even in the absence of climate change. The plan also seeks to focus on “win-win” strategies that promote social development at the same time as environmental benefits.
There are substantial air-quality co-benefits to mitigating climate change. Integrated assessments evaluating co-benefits of coordinated air pollution and climate mitigation efforts have been conducted for Mexico City. An examination of four megacities (Mexico City, New York City, Santiago de Chile, and São Paulo) by Cifuentes et al. (2001) indicated that greenhouse-gas mitigation would lead to large reductions in ozone and particulate matter concentrations with substantial resulting improvements in public health. McKinley et al. (2005) found that five proposed control measures in Mexico City, estimated to reduce annual particle exposure by 1 per cent and maximum daily ozone by 3 per cent, would also reduce greenhouse gas emissions by 2 per cent for both periods 2003-2010 and 2003-2020. Another study showed that if the current air-quality management programme (PROAIRE 2002-2010) for Mexico City were implemented as planned, they would result in a reduction of 3.1 per cent of projected carbon dioxide emissions in 2010, in addition to substantial local air-pollutant reductions (West et al., 2004). It is therefore important to integrate air-quality and climate-stabilization goals in the design of environmental policy to realize potential synergistic benefits.
Banta, R.M., C.J. Seniff, J. Nielsen-Gammon, L.S. Darby, T.B. Ryerson, R.J.Alvarez, S.R. Sandberg, E.J.Williams and M. Trainer, 2005: A bad air day in Houston, Bul. Amer. Meteoro. Soc., 86: 657-669.
Cifuentes, L., V.H. Borja-Aburto, N.Gouveia, G. Thurston and D.L.Davis, 2001: Climate change: hidden health benefits of greenhouse gas mitigation, Science, 293, 1257-1259.
De Foy, B., J.D. Fast, S.J. Paech, D.Phillips, J.T. Walters, R.L.Coulter, T.J. Martin, M.S. Pekour, W.J. Shaw, P.P.Kastendeuch, N.A. Marley, A.Retama and L.T.Molina, 2008: Basin-scale wind transport during the MILAGRO field campaign and comparison to climatology using cluster analysis. Atmos. Chem. Phys., 8:1209-1224.
CAM, 2002: Programa para Mejorar la Calidad del Aire en el Valle de México 2002-2010, Comisión Ambiental Metropolitana, Mexico.
McKinley, G., M. Zuk, M. Hojer, M.Ávalos, I. González, R. Iniestra, I.Laguna, M.A.Martínez, P. Osnaya, L.M.Reynales, R. Valdés and J.Martínez, 2005. Quantification of local and global benefits from air pollution control in Mexico City. Environ. Sci. Technol., 39, 1954-1961.
Molina, L.T. and M.J. Molina (Eds), 2002: Air Quality in the Mexico Megacity: An Integrated Assessment, Kluwer Academic Publishers.
Molina, L.T., C.E. Kolb, B. de Foy, B.K.Lamb, W.H. Brune, J.L.Jimenez, R. Ramos-Villegas, J.Sarmiento, V.H.Paramo-Figueroa, B.Cardenas, V. Gutierrez-Avedoy and M.J.Molina, 2007: Air quality in North America’s most populous city—overview of the MCMA-2003 campaign, Atmos. Chem. Phys., 7, 2447– 2473.
Molina, L.T., S. Madronich, J.S.Gaffney and H.B. Singh, 2008: Overview of MILAGRO/INTEX-B Campaign, IGAC Newsletter, 38, 2-15.
West, J., P. Osnaya, I. Laguna, J.Martínez and A. Fernández-Bremauntz, 2004: Co-control of urban air pollutants and greenhouse gases in Mexico City. Environmental Science and Technology, 38:3474-3481.
Wöhrnschimmel, H., M. Zuk, G.Martínez-Villa, J. Cerón, B.Cárdenas, L. Rojas-Bracho and A.Fernández-Bremauntz, 2008: The impact of a rapid bus transit system on commuters’ exposure to benzene, CO, PM2.5 and PM10 in Mexico City. Atmospheric Environment (in press).
1 Molina Center for Energy and the Environment, California and Massachusetts Institute of Technology, Massachusetts, USA
2 Saint Louis University, Saint Louis, Missouri, USA
3 Environment Secretariat, Government of the Federal District, Mexico
What is the air quality like in Mexico City? ›
Meteorology. Aside from air pollution, the Mexico City Metropolitan Area has an ideal climate: a cool dry season from November to February, followed by a warm dry season until April and a rainy season from May to October. Temperatures are moderate and humidity is low.Does Mexico City have good air quality? ›
It earned the accolade of the world's most polluted city. A management programme was introduced which introduced reforms that would clean up the air. Levels of ozone were reported to be around 500 parts per billion (ppb), they are now at a more respectable level of between 120 and 150 ppb.What type of air pollution does Mexico City face? ›
In Mexico City's atmosphere, the pollutants are found as primary and secondary pollutants. Primary Pollutants are known as those that are emitted directly to the environment, such as Carbon Monoxide and Sulfur Dioxide.Why is air quality bad in Mexico City? ›
Located in the crater of an extinct volcano, Mexico City is about 2,240 metres above sea level. The lower atmospheric oxygen levels at this altitude cause incomplete fuel combustion in engines and higher emissions of carbon monoxide and other compounds. Intense sunlight turns these into higher than normal smog levels.Is Mexico City still very polluted? ›
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.Does Mexico City have a good climate? ›
Although Mexico City is located within the tropics, its elevation of 7,350 feet makes for fairly pleasant weather year-round. 1 However, summers are rainy and during the winter, it can get quite chilly, especially at night. 2 The annual average temperature is 64 degrees F (18 degrees C).What type of climate is in Mexico? ›
Mexico's climate varies from arid to tropical, with a defined split. The Tropic of Cancer divides the country into two so one part is temperate and the other, tropical. Therefore, land to the north has cooler temperatures during the winter months while more southerly regions see temperatures remain constant year-round.What is Mexico's main climate? ›
The northern and central parts of the country are very arid, and semi-arid and occupy 56% of the territory. 37% of the area is sub-humid and is found in mountains and coastal plains of the Pacific, the Gulf of Mexico and the northeastern part of the Yucatan. Humid areas are located in the remaining 7% of the territory.Which city has the highest air quality? ›
|San Jose-San Francisco-Oakland, CA||san-jose-san-francisco-oakland-ca.html||4|
|Redding-Red Bluff, CA||redding-red-bluff-ca.html||5|
What city has the healthiest air quality? ›
|Urban Honolulu, HI||urban-honolulu-hi.html||3|
At 2,240 meters, Mexico City is well above the limit, although lots of people visit with no symptoms of sickness at all. As you go up in altitude, available oxygen for sustaining mental and physical alertness decreases. Air pressure is lower even though the percentage of oxygen in the air is essentially the same.What is the biggest environmental problem in Mexico City? ›
With more than 18 million people and 6 million cars in Mexico City alone, most of the air pollution is from industrial and automobile emissions (Luck, "The World's Dirtiest Cities").When was Mexico City the most polluted city? ›
In 1992, the United Nations declared Mexico City the most polluted city on Earth. By that point, the government had begun to implement policies to confront it, beginning with the Comprehensive Program Against Air Pollution (PICCA) in 1990.Why is Mexico City so clean? ›
Alongside a doubling of the vehicle fleet in Mexico City from 1992 to 2012, and the slow implementation of low-sulphur standards, the use of fuel ethers contributed greatly to an 86% decrease in CO, a 53% decrease in ozone, and a 32% decrease in particulate matter in that 20-year span.Is air pollution a problem in Mexico? ›
Perched 7,300 feet above sea level in a valley wrapped round by mountains and volcanoes, Mexico City has long suffered from thick layers of smog produced by cars, factories, and wildfires. Among the worst hazards of that air pollution for its 21 million inhabitants is PM 2.5, inhalable fine particulate matter.What problems do Mexico City have? ›
In addition to its own peculiar problems, Mexico City faces all the troubles shared by other large cities in the western world: interruptions of electric power, low water pressure, inadequate police and fire protection, garbage in the streets, and crime—although violent crime is less of a problem in Mexico City than in ...What is Mexico City problem? ›
Due to the quickly depleting aquifer, Mexico City is sinking downwards an estimated 1 meter every year. Within the center of the Mexico City, the water scarcity issue has led to frequent water shut-offs. However, it is in the mountainous outskirts, that people are most vulnerable.What is wrong with Mexico's air quality? ›
Air pollution is a real problem in Mexico, causing about one in 17 (5.9%) of all deaths in the country. It is the eighth largest cause of death, after factors such as diet, overweight, high blood pressure, alcohol and drugs, smoking and lack of exercise. The most dangerous of the airborne particles are known as PM2.
What are 3 types of climate in Mexico? ›
Mexico has a wide range of climate zones including deserts, steppes, and tropical rain forests.Is Mexico City safe to live? ›
Unlike other Mexican regions, such as Veracruz and Tamaulipas, Mexico City has for a long time had the reputation of being relatively safe from the long drug war affecting the country. Recently, however, Mexico City itself has experienced some violent episodes which seem to be linked to drug cartels.Does Mexico City have 4 seasons? ›
In Mexico, there are two main seasons. Although there is some variation in temperature over the year, the most obvious difference is between rainy and dry seasons. The rainy season through most of Mexico falls roughly from May through September or October. During the rest of the year, there is little or no rain.What part of Mexico has the best climate? ›
Mazatlán has one of the best coastal climates in all of Mexico, especially for snow birds who visit for half the year. The winters are sunny and dry with lower humidity, almost a 0% change of rain, and cooler refreshing night temperatures.What are the 4 climate zones in Mexico? ›
Mexico is divided into four climatic zones according to altitude. These are referred to as “Tierra caliente” (hot zone), “Tierra templada” (temperate zone), “Tierra fría” (cold zone) und “Tierra helada” (ice zone).What are the seasons in Mexico City? ›
Although the vibrant country is a year-round destination, there are two seasons in central and southern Mexico. The rainy season lasts from May to October, and the dry season is between the middle of November and April.Does it rain a lot in Mexico City? ›
The rainy season in Mexico City runs from June through September. September is the wettest month of the rainy season, averaging 3.54 inches of rain annually. June and August are the drier months of the rainy season in Mexico City, both with an average of 1.57 inches of rain annually.What is the number 1 most polluted city in the world? ›
The capital of New Zealand, Wellington is considered one of the cities with the cleanest air in the world. Also one of the windiest cities in the world, this clean air city is perfect for anything from sunbathing on the beach to spotting some wildlife at the ZEALANDIA Ecosanctuary.Who has the cleanest air in the world? ›
Finland has the cleanest air in the world
Air quality in Finland is the best in the world according to data released by the World Health Organisation, WHO. The level of airborne particles in Finland is on average 6 micrograms per cubic metre – the lowest level for any individual country.
Where is the purest air on Earth? ›
The cleanest air was found in the South Pacific island nation of New Caledonia (3.8), while Finland had the lowest PM2. 5 concentrations among developed nations (5.5).What country has the dirtiest air quality? ›
- Bangladesh - 77.10.
- Pakistan - 59.00.
- India - 51.90.
- Mongolia - 46.60.
- Afghanistan - 46.50.
- Oman - 44.40.
- Qatar - 44.30.
- Kyrgyzstan - 43.50.
|1||General Escobedo, Nuevo Leon||147|
|2||Tepotzotlan, Mexico City||146|
|3||Coacalco, State of Mexico||144|
|4||Juarez, Nuevo Leon||140|
Mexico City is the largest city in North America followed by New York City and Los Angeles. Mexico City is capital of Mexico and seat of the federal powers of Mexico.What should I be careful of in Mexico City? ›
The areas you should avoid in Mexico City are Iztapalapa, Tepito, Ciudad Neza and Doctores. These neighborhoods tend to have the most crime, especially at night.How can I avoid getting sick in Mexico City? ›
- Eat your meals cooked well done and served hot.
- Avoid street vendors that prepared their food at home.
- Look for the crowds. Let's face it, we're not going to completely avoid hole-in-the-wall taco stands. ...
- Avoid eating in the markets. ...
- Be judicious with fruits and vegetables.
According to WebMD, “Any time you go above 8,000-feet, you can be at risk for altitude sickness.” While the Mexico City altitude in feet is just shy of that height at 7,350-feet, a lot of travelers still experience altitude sickness in Mexico City.What city in Mexico has the cleanest air? ›
Due to Mexico City's high altitude, its oxygen levels are 25% lower, meaning that fuels do not combust completely – leading to higher levels of pollution.
What is the oxygen level in Mexico City? ›
Young adults in Mexico City have an SaO2 between 92% and 94% versus 97% at sea level, frequently decreasing below 90% during sleep and intense exercise.What rank is Mexico City in pollution? ›
|39||Mexico City, Mexico||81.88|
|42||Phnom Penh, Cambodia||80.50|
Finland has the cleanest air in the world
Air quality in Finland is the best in the world according to data released by the World Health Organisation, WHO. The level of airborne particles in Finland is on average 6 micrograms per cubic metre – the lowest level for any individual country.
- New Zealand.
- The Bahamas.
What is Mexico City Altitude Sickness? Mexico City altitude sickness happens because the amount of pressure in the atmosphere (called barometric pressure) drops at high altitudes. As the barometric pressure drops, there's less oxygen available to breathe, and you may experience dehydration and difficulty breathing.Is it difficult to breathe in Mexico City? ›
Mexico City is located 2,250 meters (7,500 feet) above sea level, an elevation considered as “high altitude.” At this level, blood oxygen levels are low enough that many people will suffer to some degree from the effects of “altitude sickness.” Symptoms of altitude sickness include a feeling of 'air-hunger' that can ...Will I get altitude sickness in Mexico City? ›
Mexico City is located at 2,250m (7,400-feet) above sea level. If you're not used to this, you can get altitude sickness — which has flu-like symptoms including nausea, dizziness, dehydration, headaches and body aches.Where is the best oxygen in the world? ›
Puerto Rico, an unincorporated territory of the United States, has the cleanest air in the world, followed by the French territory of New Caledonia in the Pacific Ocean with the territory of the US Virgin Islands in third.Which is the No 1 polluted city in world? ›