• Carlos Araujo

Bringing Down Particulates: Air Quality Measures

Most people rarely notice the air they breathe on a daily basis. However, in countries with poor air quality, ignoring this everyday pollutant can have serious and even fatal consequences. Air pollution is measured by the concentration of a “mixture of solid and liquid droplets suspended in the air”, better known as particulate matter (PM), and other naturally existing elements including CO, NO2, O2 and SO2. At lower concentrations, the human body can, in most cases, naturally process and expel these elements from its system. However, a high concentration of pollutants can lead to serious health problems, including death.

One such pollutant is PM10, which is particulate matter with 10 micrometers (µm) in diameter (around one fifth the size of a human hair). PM10 can be easily inhaled and reach vital human organs such as the lungs and heart, causing associated illnesses such as lung cancer and heart disease. Other particulates of ultrafine nature such as PM2.5 and PM1 also contribute to the problem as they can easily reach the bloodstream and harm our cardiovascular system. Moreover, these smaller particles are a harder problem to tackle since they are lighter and can be suspended in the air for longer periods of time.

The deterioration of air quality is related to all aspects of our daily lives, including our energy use, transportation, manufacturing and even cooking. With man-made factors at the core of the problem, the solution lies strictly in our hands. However, without coordination at the city, county, country or international level, no viable solution can be reached. As countries see their neighbors ignoring their responsibility, it becomes harder to push for large-scale cooperation.

How to bring down air pollution?

The first measure implemented needs to focus on the assessment of the problem. In the end, we can hardly change a world that we barely understand. As a result, governments at all levels of society need to develop standardized mechanisms to quantify the level of air pollution in their surroundings. There has been significant advancement in this field, as we can now map pollution levels in over half the world. However as per the “Air Quality Database” held by the World Health Organization (WHO), which collects information from several sources, the vast majority of countries in Africa, a considerable part of Latin America and the Middle East do not have a large number of stations in place to conduct measurements. In some cases, the most recent available measurements date back to 2009, which may no longer reflect the reality of the problem today.

The Air Quality Index (AQI) project is working to fix this data gap. Covering over 80 countries and 800 major cities, the Air Quality Index uses a network of more than 10,000 state-promoted and independent measurement stations to provide real time data and allow citizens and governments to assess the gravity of the issue and see which regions require more focus. It also collects data on the particular polluting elements in each region, which is crucial data for any efforts to improve air quality. The scale developed by the AQI also recommends the cautionary measures to be taken under each concentration level. Cities also use these indicators to promote emergency measures such as limiting the number of cars in the city and making public transport temporarily free.

AQI Scale: http://aqicn.org/scale/

With this in mind, several interactive platforms and online apps have developed systems to alert residents of concerned cities in real time about measures to be taken depending on the air pollution level (wear a mask or avoid outdoor activities). Some of these apps include Breezometer and AirVisual. This can be useful as some places in the world may even reach a concentration of PM2.5 of over 999 µm/m3 during the day, and then stabilize during the night.

To put this into perspective, Policy Shift assessed data from the World Health Organization (WHO) on average PM10 and PM2.5 concentration at city level. The following charts show the concerning concentration level in Saudi Arabia’s and Iraq’s capitals. On the other side of the scale, we can also see that several European capitals including Lisbon, Reykjavik and Madrid have, on average, good air quality.

World Health Organization

After assessment, what can be done next?

The world is slowly moving towards energy production that is more abundant, cleaner and decentralized. Coal divestment is going a long way towards making coal power plants less profitable, allowing other cleaner sources of energy to gain spaces that were not economically feasible. Countries moving faster to adopt this new status quo will be able to improve air quality organically.

A comprehensive solution, already in place in most industrialized countries, is the limitation of transit for vehicles with a high polluting coefficient inside cities and the renewal of mass transport vehicles such as buses, metro and tram, as well as shared transportation. In Europe, the pollution coefficient for cars has been reduced decade by decade (see next chart). A similar approach has been adopted in the United States and China.


More drastic measures include Germany’s ruling allowing cities to ban diesel cars and commitments taken by the cities of Madrid, Paris, Mexico City and Athens to ban them by 2025. Among alternative measures figures the setting of maximum speed in highways and cities, which are proven to have positive effects on PM emissions, and the pedestrianization of certain inner city areas.The latter solution may not occur without public resistance, notably neighbors fearing higher levels of noise and car-owners complaining about resulting traffic. One example is the long discussed pedestrianization of Oxford street in London. In other cases, cities have managed to impose the shift: Berges de Seine in Paris and “Superblocks” in Barcelona.

Parks over buildings

Countries can reduce air pollution by creating green areas in zones with a high concentration of particles. One groundbreaking solution can be found in Singapore with the construction of structures known as “Supertrees”, which were opened to the public in June 2012 as part of the Gardens by the Bay, in the center of its capital. The 101 hectares complex is comprised of 50-meters tall structures with more than 162,900 plants of 200 species serving as Cooled Conservatories with energy-generating systems. The complex also serves as a mechanism for the conservation of plants, house of wild species and rainwater harvesting. Moreover, projects to include solar panels are underway. In addition, it provides visitors and residents a healthier place to profit from amidst a highly industrialized city. In terms of benefits to air quality, a study has shown that this park decreased the area’s air quality index from 50 µm/m3 to 40 µm/m3 on average between 2004 and 2015.

This type of solution can be replicated in industrialized and developing countries, and notably near construction areas, where the concentration of particulates is common. In some countries, construction companies engage in sustainable construction, which includes practices such as the installation of vegetation on and near construction sites. Vegetation can absorb particles emanating from highly polluting activities, hence, avoiding a major concentration. Vegetation can also be installed in inner cities to populate unused walls, residential buildings or bridges to reduce vehicle-generated particles.

Urban planning solutions

Population growth and density have often been signalled as the main cause behind air pollution. However, a sound organization at city level can facilitate that our lifestyles do not have an even greater impact on the air we breath. In this sense, urban planning, as well as urban transformations, can play a crucial role in preventing a major deterioration. For instance, zoning laws can define how far a residential area needs to be from the closest industrial complex, or the density of parks per kilometer squared, as well as reserving areas for agriculture or forestry, or creating buffer zones near rivers and tourist activities. Cities such as London, New York or Munich, which benefit from large public parks in the heart of the city, would face different pollution levels if these parks had been defined as residential areas.

These laws are related to height restriction laws, which set the maximum height of buildings within a certain city. For instance, after 1977, all new buildings in Paris had to respect the maximum height of 36 meters, and several cities in the United States (San Jose, Portland, Washington D.C.) have imposed limits to their buildings. Similarly, Indonesia has determined that no building can be higher than a coconut tree (15 meters height). These type of laws help reduce population density within cities, which has an impact on traffic and pollution.

International cooperation (and oversight)

International challenges such as particles flying from one country, and causing air pollution elsewhere, can only be solved through international cooperation. Creating shared reduction targets and sanction mechanism between countries could not only curb air pollution, but also open the door for countries to buy out polluting rights. In May 2018, the European Commission referred France, Germany and the UK to the European Court of Justice over exceeding levels of Nitrogen Oxide (NO2). Moreover, other countries have been previously referred to the Court over persistent high levels of PM10, namely Italy, Romania and Hungary.

This multinational solutions must be implemented under the scope of integrated cooperation with well-established and clear rules for the parties involved. It can also be implemented at the country level, where national governments could set targets at the local scale (municipalities or cities). This could have the impact of making cities compete to reduce pollution and make citizens aware of the air quality they breathe. In the case of low-income countries, a sanction mechanism could be counterproductive as it would reduce state funding that could be earmarked towards alternative air pollution.

Any other well-thought solution

The WHO has thoroughly assessed this problem and created guidelines to include a comprehensive pool of relevant solutions. These guidelines include different stakeholders and approaches, and propose solutions such as favouring low emissions cookstoves, improving waste management and related energy recovery, reducing the burning of agricultural fields, and promoting healthy diets away from red and processed meat.

In the end, none of these solutions are sufficient on their own. Air pollution remains a complex problem floating around a large number of causes, as such, it requires a combination of well-targeted solutions larger than this non-exhaustive list. As stated before, we need to acknowledge and assess the core of the problem in each case to transit towards action. Innovative solutions in the form of cleaner technology for energy production and transportation can help tackle part of the issue, but, it is only through coordination at local, national and international level that we can limit the intensity of this man-made problem. The positive side of this problem is that we already have the solutions in our minds.


- “Clean cooking clean living: a case study for rural India” – GPP Network – 01/2018

- “Air quality: Commission takes action to protect citizens from air pollution” – European Commission – 05/2018

- “Ambient air pollution: Interventions & tools” – World Health Organization – Accessed June 2018

- “Policy update: China´s stage 6 emission standard for new light-duty vehicles” – International Council on Clean Transportation – 03/2017

- “Emission factors of SO2, NOx and particles from ships in Neva Bay from ground-based and helicopter-borne measurements and AIS-based modeling” – Atmospheric Chemistry and Physics – 10/2014

- “What is Particle Pollution? – Environmental Protection Agency – Accessed June 2018

- “What is PM2.5 and Why You Should Care” – Bliss Air – Accessed June 2018

- “Worldwide Air Quality” – AQICN – Accessed June 2018

- “Urban Design Analysis: Singapore Super Trees“ – Sabrina Samin – 07/2015

- “Emissions in the automotive sector” - European Commission - Accessed June 2018

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Policy Shift is proud to partner with OPALC, the Latin American Observatory at Sciences Po