Air quality in the world

Air quality index (AQI) and PM2.5 air pollution in the world

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How dangerous is air pollution?

Global ranking of risk factors for death across all ages and both sexes in 2017:1

Risk factordeaths
High blood pressure10.44M
High blood sugar6.53M
Air pollution (Outdoor & Indoor)4.9M
Outdoor air pollution3.41M
Diet high in sodium3.2M
Diet low in whole grains3.07M
Alcohol use2.84M
Diet low in fruits2.42M

Source: Institute for Health Metrics and Evaluation (IHME) - Global health data for air pollution (2020).

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What is Particulate Matter (PM10)?

Particulate matter, or PM, represents a category of pollution describing airborne particles measuring 10 micrograms or smaller. Particulate matter can include, but is not limited to, dust, soot, dirt, smoke, chemicals, bacteria, viruses, and liquid droplets. Since particle pollution has a range of chemical makeups and sources, the level of risk and associated health effects are ascribed to the size of particles rather than their composition...

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What is Particulate Matter (PM2.5)?

PM2.5 refers to particles that are 2.5 micrometers in diameter or smaller. Unlike PM10, PM2.5 particles are not visible to the naked eye – they can only be seen with an electron microscope. PM2.5 particles are considered among the most dangerous airborne pollutants because of their small size. PM2.5 can stay airborne for indefinite amounts of time, and when inhaled, PM2.5 can penetrate lung tissue and enter the bloodstream, causing heart, respiratory, and brain damage...

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What is Ozone?

Ozone is a gaseous pollutant and key component of smog, formed when sunlight or solar ultraviolet radiation causes nitrogen oxides (NOx) and volatile organic compounds (VOCs) to react. While other pollutants are typically emitted directly into the air by various sources, ozone is generally created in the atmosphere...

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What city has the best air quality?

What city has the worst air quality?

How many people die from air pollution?

7 Million Deaths every year as a result of exposure to fine particles in polluted air.

Source: World Health Organization

How many people breathe unhealthy air?

91% Of the world’s population live in places where air quality exceeds WHO guideline limits.

Source: World Health Organization

2023 AQI Country ranking

What country has the worst air quality?

#countryPopulation2023 AVG. US AQI

Which is the cleanest country in the world?

#countryPopulation2023 AVG. US AQI


What causes bad air quality?

Air pollution can be created by both manmade and natural sources. Natural sources include windblown or kicked-up dust, dirt and sand, volcanic smoke, and burning materials. Manmade sources, meaning that pollution is created by the actions of human beings, tend to be the leading contributor to air pollution in cities and are inherently more able to be influenced by regulations. Manmade sources primarily include various forms of combustion, such as from gas-powered transportation (planes, trains, and automobiles) and industrial businesses (power plants, refineries, and factories), biomass burning (the burning of plant matter or coal for heating, cooking, and energy), and agriculture.

The contribution of various air pollution sources to a location’s air quality is highly dependent on the city’s location and regulations. Each location has its own mix of contributors and pollutants. Sources are commonly categorized into the following:


Industry includes pollution from facilities such as manufacturing factories, mines, and oil refineries as well as coal power plants and boilers for heat and power generation.

Industrial activity is a major global source of nitrogen oxides (NOx), hydrogen sulfide, volatile organic compounds (VOCs), and particulate matter, all of which contribute to ozone and smog.


The heavy use of fertilizers on agricultural land is a significant contributor to fine-particulate air pollution. A study in Geophysical Research Letters found that pollution generated from farms outweighed all other manmade sources of PM in much of the United States, Europe, Russia, and China.2

Globally, agricultural land use is on the rise due to an increased demand for animal products and per capita food.


Air pollution from transport refers primarily to fuel combustion in motor vehicles, such as in cars, trucks, trains, planes, and ships. Transport emissions are a major contributor to elevated levels of fine particulate matter (PM2.5), ozone, and nitrogen dioxide (NO2).

The majority of emissions from transportation occur in the world’s top vehicle markets, as there tends to be a strong correlation between per capita transport emissions and incomes. As standards of living and economic activity increases, so too does the demand for transportation.3

Natural sources

Natural air pollution sources include naturally occurring phenomena such as volcanic activity, wildfires, and dust or sandstorms. The impact of natural sources on air quality is highly dependent on the local environment. For example, locations near large deserts like the Sahara are greatly impacted by windblown dust and sand, while forested locations are more likely to experience air pollution from wildfires.


Household air pollution refers to personal activities, such as residential cooking and heating with coal or wood burning as well as the building and construction of homes and furnishings.

Wildfires and open burning

The burning of plant matter emits large amounts of pollutants, as does burning other solid fuels like coal. Burning organic material emits particulate matter (PM), nitrogen oxides (NOx), carbon monoxide (CO), sulfur dioxide (SO2), lead, mercury, and other hazardous air pollutants (HAPs). These fires may occur organically, accidentally, or intentionally. Due to the frequently massive size of these fires, both wildfires and open burning have the potential to cause far-reaching air pollution.


Can air pollution cause health problems?

Air pollution refers to substances in the air that are detrimental to either human health and/or the planet as a whole. At significant levels, all types of air pollution pose a risk for adverse health effects. The amount of risk for health complications depends on one’s overall health, the pollutant type, the concentration, and the length of exposure to polluted air.

Impact of breathing unhealthy air - overview:

The World Health Organization (WHO) has deemed air pollution as the greatest environmental health risk today, estimated to contribute to 7 million premature deaths annually.4 Among children under the age of 15, it is the leading cause of death, killing 600,000 every year.5

Air pollution is described as a ‘silent killer’ because it is rarely the direct cause of death. Rather, air pollution is the world’s 4th leading contributing cause of early death, accounting for:6

  • 29% of all deaths and disease from lung cancer
  • 17% of all deaths and disease from acute lower respiratory infection
  • 24% of all deaths from stroke
  • 25% of all deaths and disease from coronary heart disease
  • 43% of all deaths and disease from chronic obstructive pulmonary disease

It is estimated that 92% of the global population breathes unhealthy air. While this figure varies region to region, nowhere is without risk. The 2019 World Air Quality Report found that 72.7% of people living in Europe breathe air exceeding the WHO’s PM2.5 guideline for annual exposure (< 10 µg), while 98.8% of people breathe unhealthy air in South Asia, the most polluted region globally.

High air pollution levels can cause health problems including:

  • Short-term effects: difficulty breathing, chest pain, wheezing, coughing, general respiratory discomfort, and irritation of the eye, nose, and throat.
  • Long-term effects: lung tissue damage, cancer, early death, and the development of respiratory illnesses such as asthma, bronchitis, and emphysema.

Groups most susceptible to severe adverse health effects from air pollution include those with:

  • Heart disease, such as coronary artery disease (CAD) or congestive heart failure
  • Lung disease, such as asthma, emphysema, or chronic obstructive pulmonary disease (COPD)
  • Older adults and the elderly
  • Children under the age of 14
  • Pregnant women
  • Outdoor workers
  • Athletes who exercise outdoors vigorously

Health effects from specific air pollutants

Ground-level OzoneParticulate Matter (PM) and Wildfire Smoke
  • Reduced lung function
  • Aggravated asthma
  • Throat irritation and cough
  • Chest pain and shortness of breath
  • Inflammation of lung tissue
  • Higher susceptibility to respiratory infection
  • Irregular heartbeats
  • Chest pain
  • Coughing
  • Irritation of the eye, nose, and throat
  • Aggravated asthma
  • Decreased lung function
  • Lung tissue damage
  • Cancer
  • Development of respiratory illnesses such as asthma, bronchitis, and emphysema
  • Early death

Protect from air pollution

Which mask is best for air pollution?

Masks are very effective in reducing exposure to air pollution. While the broad category of air pollution masks includes gas masks for dealing with highly toxic chemicals, the majority of ambient air pollution masks on the market only filter particle pollution. For daily use, these masks are generally sufficient because outdoor environments rarely experience gases at the same dangerous levels as particles. Ambient air pollution masks can help protect an individual from PM2.5, viruses, bacteria, and allergens.

In evaluating the effectiveness of pollution masks, three components should be evaluated: pollution filter, mask seal, and ventilation.

  • Pollution filter:  Pollution filters are typically given a rating of either N90, N95, N99, or N100. The rating states the percentage of particulate matter (> 0.3 µg) the mask is capable of blocking. An N95 mask, for example, blocks against 95% of particulate matter larger than 0.3 micrograms. This includes the vast majority of PM2.5 and PM10. The higher the rating, the more effective the mask filter, assuming the mask seal and ventilation components work properly.
  • Mask seal:  Regardless of a mask’s pollution filter rating, masks that do not seal around one’s face are not effective because air will primarily flow in unfiltered through the sides of the mask. A good mask seal should cause the mask to suction to one's face during inhalation. For flexible, disposable masks, this suction should be visible, causing the filter to bend inwards creating a concave surface. For masks with a more solid construction, it should be possible to feel a slight increase in pressure when breathing in. If a mask is not sealed well to one’s face, air will primarily flow in through the open sides of the mask.
  • Ventilation (CO2 valve):  Ventilation makes masks more breathable while also reducing moisture and CO2 accumulation. While not a feature of all masks, many use a coin-sized CO2 valve to provide directed outflow. Breathing in poorly ventilated air high in CO2 can contribute to short-term effects such as headaches, lethargy, dizziness, and nausea.,Masks with a ventilation valve are not effective for reducing the spread of viruses, as breathing output is not filtered.

Are surgical masks effective at filtering air pollution?

Disposable surgical masks are affordable and accessible. They are also surprisingly effective against particle pollution. An Edinburgh study conducted by the Particle and Fiber Toxicology tested surgical masks down to .007 µg and found that the material of surgical masks were capable of blocking 80% of particles.7

In another study, a fit test was applied to surgical masks in order to more accurately test their effectiveness, noting the generally loose fit.8 In this test, the rate of filtration fell to 63% as a result of the leakage around the mask.

While both tests reveal that surgical masks are significantly less efficient than respirator masks (rated N90-N100), they do help reduce exposure to fine particulate pollution at a very low cost.

Difference between N95 and FFP2

The most prevalent and commonly discussed type of pollution mask is the N95. These masks are the American standard as rated and maintained by the National Institute for Occupational Safety and Health (NIOSH), a department of the Center for Disease Control (CDC).

Europe uses a similar standard called the “filtering face piece” score, or FFP. This standard uses P1, P2 and P3 ratings maintained by CEN (European Committee for Standardization). The FFP2 closely compares to the US N95 in that the FFP2 is tested to filter at least 94% of particles that are 0.3 microns in diameter or larger, while the N95 filter at least 95% of particles measuring the same size.

While an N95 mask has a slightly higher standard than the FFP2, a mask rated FFP2 is not necessarily worse than a N95 mask. This is because the rating only states the required minimum filtration and not the precise filtration rate. For example, a FFP2 rated mask may truly filter 96% of particulate matter, rather than the 94% minimum for obtaining the rating. A precise filtration rate can typically be found on the mask manufacturer’s website or product specifications.

Respirator Mask

How can I improve the air quality in my home?

Indoor air quality is not safe from outdoor air pollution. Moreover, there are numerous emission sources specific to indoor environments that can lead to heightened indoor air pollution levels. In order to improve air quality at home, both indoor ventilation and indoor sources should be managed.

Indoor air pollution mitigation methods include

  • Check current and forecast air quality levels in your area. Follow the health recommendations for current conditions.
  • Keep windows and doors closed. Seal door and window gaps to minimize leakage.
  • When outdoor air is heavily polluted, set air conditioning (HVAC) systems with fresh air intake to their recirculate mode.
  • Use air purifiers or high-efficiency HVAC filters (such as HEPA or HyperHEPA filters) to remove fine particles from the air.

In the event indoor air pollution levels are already exceedingly high

  • Avoid strenuous activity, such as working out, to reduce the amount of polluted air you inhale.
  • Wear an N95 pollution mask, if available.
  • Run air purifiers frequently on their highest output setting.
  • Evacuate if indoor air quality levels become “hazardous,” which can happen in the event of nearby wildfires.

+ Article Resources

[1] Institute for Health Metrics and Evaluation (IHME) - Global health data for air pollution (2020).

[2] Baurer S, et al. (2016, May 16). Significant atmospheric aerosol pollution caused by world food cultivation.

[3] Climate Change 2014: Mitigation of climate change. (2014).

[4] WHO releases country estimates on air pollution exposure and health impact. (2016).

[5] More than 90% of the world’s children breathe toxic air every day. (2018).

[6] Ambient air pollution: Health impacts. (2020).

[7] Langrish J, et al. (2009) Beneficial cardiovascular effects of reducing exposure to particulate air pollution with a simple facemask. DOI: 10.1186/1743-8977-6-8

[8] Saint Cyr R. (2014) My personal fit testing: Here’s the best and worst pollution mask for me.

What is the most polluted country/region in the world?

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