Global ranking of risk factors for death across all ages and both sexes in 2017:1
|High blood pressure
|High blood sugar
|Air pollution (Outdoor & Indoor)
|Outdoor air pollution
|Diet high in sodium
|Diet low in whole grains
|Diet low in fruits
Source: Institute for Health Metrics and Evaluation (IHME) - Global health data for air pollution (2020).
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...Find out More
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...Find out More
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...Find out More
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|2022 AVG. US AQI
|2022 AVG. US AQI
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 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.
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.
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.
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
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.
|Particulate Matter (PM) and Wildfire Smoke
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.
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.
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.
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.
+ Article Resources
 Institute for Health Metrics and Evaluation (IHME) - Global health data for air pollution (2020).
 Baurer S, et al. (2016, May 16). Significant atmospheric aerosol pollution caused by world food cultivation.
 Climate Change 2014: Mitigation of climate change. (2014).
 WHO releases country estimates on air pollution exposure and health impact. (2016).
 More than 90% of the world’s children breathe toxic air every day. (2018).
 Ambient air pollution: Health impacts. (2020).
 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
 Saint Cyr R. (2014) My personal fit testing: Here’s the best and worst pollution mask for me.