Globally, nine out of 10 people inhale unhealthy, polluted air. Air pollution is the impurification of the atmosphere by the dispersion of solids, liquids, and certain gases in the air; it can happen indoors or outdoors.

Air pollution is a growing problem in many cities around the world, and it has far-reaching consequences for human health. The toxic chemicals and particulate matter found in polluted air can cause a range of health problems, from respiratory issues to heart disease. 

Reports¹ indicate that air pollution is the world's largest environmental risk for premature death –, between 1,000 to 4,300 additional premature deaths will occur countrywide each year by 2050 due to the combined health effects from ozone and particulate matter, assuming no change in regulatory measures or population characteristics.

Let’s discuss the various ways in which air pollution affects our health and what we can do to minimize this harmful effect.

Ambient Air Pollution vs. Indoor Air Pollution

What does ambient air pollution mean? The air we breathe, all around us, is what we call ambient air or atmosphere. Naturally, we do not want it to contain any contaminants or pollutants. Ambient air pollution refers to potentially harmful pollutants or toxins that are emitted into the atmosphere by various processes².

Indoor air pollution³ is specifically the dust, filth, or gases in the air inside structures, such as your house or workplace, that are potentially unhealthy to breathe. In developing countries, household air pollution is one of the primary causes of sickness and early mortality.

What Causes Air Pollution?

According to WHO data, 99% of the world's population breathes air that contains high levels of pollutants that exceed WHO guideline limits, with low- and middle-income countries experiencing the highest exposures⁴. 

Both human activities and natural sources contribute to air pollution, but because of the world's accelerating urbanization and industrialization, human activities are having an ever-greater impact. There are two types of air pollutants: 

• Primary pollutants – These are polluting chemicals, particles, or other materials that are released into the atmosphere directly
• Secondary pollutants – These pollutants are created in the ambient environment through physical and chemical processes from precursor gasses that had been directly released 

Depending on the origins of the air pollutants or the sources of their precursors, pollutants may be natural, anthropogenic (from man-made sources), or mixed.

 Forms of primary air pollution include:

• Particulate matter (PM) 
• Black carbon (BC)
• Sulfur oxides (SO₂) 
• Nitrogen oxides (NO_X) (including nitrogen monoxide, NO, and nitrogen dioxide, NO₂)
• Ammonia (NH₃) 
• Carbon monoxide (CO) 
• Methane (CH₄)
• Non-methane volatile organic compounds (NMVOCs), such as benzene
• Certain metals
• Polycyclic aromatic hydrocarbons, including benzo[a]pyrene (BaP)

 Forms of secondary air pollution include:

• Particulate matter (PM) formed from the key precursor gasses of sulfur dioxide (SO₂), NO_X, NH₃ and volatile organic compounds (VOCs)
• Ozone (O₃)
• Smog
• NO₂ 
• Oxidized volatile organic compounds (VOCs)

Sources of Air Pollutants

Both natural and artificial sources might be the source of these pollutants and their precursor gases.

Outdoor Air Pollutants

Outdoor sources include:

• Forest fires/wildfires – Wildfires are a frequent occurrence in wooded areas during prolonged dry spells, which are typically caused by changing seasons and a lack of precipitation. These fires release smoke and carbon monoxide, which are primary pollutants and also contribute to the greenhouse effect (global warming), leading to further wildfires
• Combustion of fossil fuels like coal and petroleum – These are typically used for use as energy in power plants and vehicles. Burning them emits high levels of pollutants like lead, nitric oxide, carbon monoxide, nitric oxide, and particulate matter
• Volcanic eruptions/activity – These are the main cause of natural air pollution. Massive quantities of sulfuric, chlorine, and ash products are produced during an eruption and released into the atmosphere, where they can be carried by the wind and dispersed over a wide area
• Industrial activities – For instance, during mining activities a variety of metal particulate matter are released into the atmosphere due to the crushing and processing of mineralogical deposits
• Agriculture activities – The use of insecticides, pesticides, and fertilizers can cause air pollution, as they can contain toxic volatile organic compounds
• Open burning of waste materials – Similar to wildfires, various toxic gasses, and particulate matter are released into the atmosphere depending on the composition of the material being burned
• Waste in landfills – The degradation of the waste in landfill generates methane, which is a major greenhouse gas, an asphyxiant, highly flammable, and potentially hazardous 
• Cooking and heating the home – Burning dung, wood, or coal in inefficient stoves or open hearths, for cooking or warmth, produces several hazardous gases that are harmful to one's health, including methane, carbon monoxide, nitrogen oxides, polyaromatic hydrocarbons (PAH), and volatile organic compounds
• Acid rain – A buildup of airborne toxins can potentially result in "acid rain," which itself contributes to air pollution by depositing and releasing the collected particles. It occurs when nitric and sulfuric acid particles float into the air and are collected in forming clouds.
• Dust storms – These can cause acute incidents of reduced air quality due to winds whipping up the particulate matter and various harmful gasses into inescapable cyclones

Indoor Air Pollutants

Many people do not understand indoor air pollution as well as they do outdoor pollution. The majority of contaminants that lower indoor air quality come from sources inside buildings, with a small amount of pollutants arriving from the outside.

To that extent, let us look at some of the major sources of air pollutants that infiltrate indoors⁵:

• Outdoor air pollutants drawn in
• Pesticides
• Biological pollutants – For example, bacteria, viruses, animal dander and saliva, mold, house dust, mites, cockroaches, pollen, castor bean dust, and soybean dust
  • Due to high humidity and condensation from hot showers, baths, leaks, hanging damp clothing on indoor garment racks, and poor caulking, bathrooms and laundry rooms can turn into breeding grounds for such indoor pollutants, resulting in airborne mold spores and mildew that are dangerous to human health
• Cleaning products – Chemicals in cleaning products can pollute indoor air, such as gases that readily dissolve into the air at ambient temperature like VOCs
• Heat sources used in the kitchen to cook – Some examples of gasses and other dangerous chemicals released into the air by natural gas and stoves include carbon monoxide and formaldehyde
• Secondhand smoke 
• Consumer products – Such as cosmetics and perfumes
• Various furnishings and building supplies – such as damaged insulation containing asbestos, newly placed carpet, upholstery, or flooring, and certain pressed wood products used to create furniture or cabinets.
• Naturally-occurring radon gas – This is cancer-causing material that can build up in homes as it is released through the surface of the Earth

There are fewer anthropogenic contaminants in arid areas. On a worldwide scale, however, the contribution of man-made pollutants greatly outweighs that of natural sources. Therefore, even if someone resides in a less polluted location, atmospheric circumstances can make it possible for air pollution to travel great distances and damage people distant from the sources of the pollution.

Effects of Air Pollution: How Does Air Pollution Affect Our Health?

The Environmental Protection Agency (EPA) estimates that indoor air pollution levels are often two to five times higher than the same pollutants outdoors⁶ and may be up to 1,000 times higher than outside levels after certain activities⁷, and may potentially have a more detrimental impact on health⁸.

Respiratory problems are one of the most common health effects of air pollution. Pollution has been linked to many respiratory diseases⁹; exposure to polluted air can irritate the airways, leading to conditions such as: 

• Asthma 
• Bronchitis
• Lung cancer

Air pollution can also weaken the immune system, making individuals more susceptible to infections¹⁰. The toxic chemicals in polluted air can disrupt the body's natural defenses, making it harder for the immune system to fight off harmful pathogens. This can lead to various health problems, from colds and flu to more severe infections.

Who Does Air Pollution Affect the Most?

While air pollution affects everyone's health, certain groups may be harmed more including:

• Older people¹¹ – Compared to younger people, the elderly are more prone to heart or lung problems. Also, elderly people with existing conditions are the most vulnerable, as their conditions can be exasperated due to poor air quality
• Individuals with lung or heart illness – People are more prone to react badly to poor outdoor air quality if they have heart failure, angina, ischemic heart disease, chronic obstructive pulmonary disease¹², emphysema¹³, or asthma¹⁴.
• Children¹⁵ – Children are especially susceptible to poor indoor air quality since their lungs are still growing, which is why indoor pollution is responsible for many premature deaths. In addition, children tend to be more active outdoors and breathe more air per pound of body weight than adults. They are, therefore, more susceptible to the effects of low air quality. 
• Individuals with diabetes¹⁶ – Increased levels of air pollution are connected with increased indicators of type 2 diabetes  
• Pregnant people¹⁷¹⁸ – While further research is needed, current research indicates exposure to air pollution during pregnancy leads to increased odds of developing complications, particularly during the first trimester
• People with lower incomes¹⁹ – Those with lower salaries and other social and economic disadvantages tend to reside closer to industrial facilities, urban city centers²⁰, or highways, all of which are sources of air pollution. Therefore, compared to people who live in areas with cleaner air, they are more likely to be exposed to contaminated air for an extended time, making a lower socio-economic band a risk factor for air pollution exposure
• People who engage in outdoor activity – It's more likely that you will breathe in hazardous compounds that harm your health if you enjoy exercising or staying active outside in locations with poor air quality

Health Effects From Specific Pollutants

Particulate Matter (PM₁₀, PM_2.5) & Wildfire Smoke (Soot)

Particulate matter is a mix of solid particles and liquid droplets suspended in the air. Typically, it's too small to be seen with the naked eye. It is one of the most harmful air pollutants with many negative health effects. 

Particulate matter is labeled depending on its maximum size in micrometers. One micrometer is 0.001 millimeters. PM₁₀ (particulate matter 10 micrometers or smaller) is linked to nasal and upper respiratory tract health problems, while PM_2.5 poses the most significant health risk because these particles are tiny enough to travel through the lungs and into the bloodstream²¹.

Long-term exposure to PM has been linked to various health problems²²²³, including: 

• Heart/cardiovascular disease
• Stroke 
• Lung cancer
• Asthma
• Bronchitis
• Premature death from heart ailments
• Various other lung diseases
• Impaired infant brain development

PM can also exacerbate symptoms in individuals with pre-existing heart or lung conditions. This is because particulate matter can cause inflammation in the blood vessels, leading to the formation of blood clots.

Recent toxicological research indicates that wildfire particulate matter may be more harmful²⁴ than equivalent amounts of ambient PM_2.5.

Nitrogen Oxides (NO and NO₂)

Nitrogen dioxide is a toxic gas mainly resulting from burning fossil fuels containing sulfur, such as coal, oil, or diesel. It is produced by cars and power plants. Health risks of nitrogen oxides include²⁵. Basic Information about NO2. Retrieved 22 March 2023 from https://www.epa.gov/no2-pollution/basic-information-about-no2#Effects)):

• Irritation of airways (both short- and long-term)
• Short-term exposure – exacerbates respiratory conditions, especially asthma, resulting in respiratory symptoms such as coughing, wheezing, or difficulty breathing, hospital admissions, and ER visits 
• Longer exposures – raise the risk of developing asthma and make people more susceptible to respiratory infections 

Children, the elderly, and those with asthma are typically more vulnerable to the negative health consequences of NO2

Ozone (O₃)

Ozone is a highly reactive gas present in the whole atmosphere. While ozone in the upper atmosphere protects us from harmful UV radiation, ground-level ozone is a toxic air pollutant.

Health risks of ozone²⁶ include:

• Inflammation and irritation of the eyes, nose, throat, and lower airways leading to chest discomfort, soreness, and coughing
• Inability to breathe as deeply as you typically, indicating diminished lung function
• Asthma flare-ups
• Progression of long-term respiratory conditions such as chronic bronchitis/chronic obstructive pulmonary disease (COPD)
• A heightened risk of respiratory infections

Ozone can harm the lungs even after symptoms have subsided.

Sulfur Dioxide (SO₂)

Emissions of SO₂ often also emit other sulfur oxides (e.g., SO₃), which increase the level of PM in the air through forming small particles with other substances in the air.

The EPA's most recent review of sulfur dioxide²⁷ lists the main effect, particularly for asthmatics and children, as difficulty breathing.

Further research indicates a connection between SO₂ and the following²⁸²⁹ :

• Chronic obstructive pulmonary disease (COPD)
• Cardiovascular disease
• Childhood asthma
• Pre-term birth
• Lung cancer
• Diabetes
• Nervous system damage
• Type 2 diabetes

Carbon Dioxide

Cars and other combustion sources produce carbon monoxide. Carbon monoxide blood levels are typically less than 5%, with symptoms starting to show at around 10%³⁰, and becoming deadly at above 40%³¹. 

The following are possible signs of carbon monoxide poisoning³²:

• Weakness
• Dizziness
• Chest ache
• Nausea
• Vomiting
• Confusion
• Headache
• Migraine
• Disorientation
• Seizures
• Visual disturbances
• Fainting

High-level acute poisonings can also result in³³:

• Jerky movements (cogwheel rigidity)
• Uncontrolled bridging and arching (opisthotonus)
• Floppy, soft limbs (flaccidity)

If someone suspects they may be suffering from carbon monoxide poisoning, they should leave the vicinity and get care right away.

How to Protect Yourself from Air Pollution

Amidst all that comes with air pollution, you will want to protect your health. So how do you do this? Below are a few steps you can take:

• Test your air quality – Although the air may appear clear, that does not mean that there is no pollution. To receive the most recent information, make use of resources like AirNow, the EPA's air quality monitor. You can also find a variety of air quality test kits online or hire a professional to seat it 
• If the air quality is poor – Keep your windows closed and stay indoors
• Proper ventilation –You should allow air to flow freely within your home every day for several reasons:
  • It controls the humidity
  • It purifies the air in your house
  • Fresh air reduces the amount of indoor air pollution
• Clean indoor air with filters –You can purchase a high-quality dehumidifier and air purification system to ensure clean air, which is useful when you are unable to open your windows during the winter for fear of allowing the warm air out and outdoor pollution in
• When in a wildfire-prone area – Try to limit your exposure to toxic smoke and consider storing a few face masks, ideally N95s, to use when the weather is bad.
• Take proper measures to control pollutants and allergens
• Eat and socialize in smoke-free locations – When possible. Toxic compounds can contaminate the air around you when you smoke cigarettes or use vaping or hookah devices, or are near others that are. Second-hand smoke is particularly hazardous for those with a heart or lung condition.
• Consider using indoor plants to purify your air – There are various indoor plants you can buy or plant to improve indoor air quality.

The British Lung Foundation suggests that on days of heavy pollution, it makes sense to take extra precautions if you or your child has a long-term respiratory condition. Such precautions include³⁴:

• Reduce or stop demanding outdoor activity – Exercising makes you breathe more heavily, which should be avoided when surrounded by air pollution. However, exercise is beneficial for those with lung conditions, so if at all possible, continue exercising inside in a well-ventilated room or gym
• Avoid areas with high levels of pollution – These include busy intersections and main roadways
• Try to arrive at work a little earlier – This will help you to avoid traffic and its pollution during rush hour
• Use back streets – This allows you to avoid the majority of the traffic if you commute by running, walking, or cycling
• When walking, stay to the inside of the pavement – The further you are from the road, the lower the pollution levels, 
• Bring your relief inhaler with you at all times

How to Reduce Air Pollution

Since 2013, the WHO has partnered with the Climate and Clean Air Coalition (CCAC), with which is develops various interventions aimed at reducing air pollution³⁵. These currently include:

• The implementation of solid waste management
• The provision of access to clean cookstoves and household fuels
• The growth of the market for renewable energy sources and energy efficiency
• The implementation of industrial emissions reductions 

As far as improved indoor air quality is concerned, the EPA recommends three main steps³⁶:

• Source control – Eliminate or reduce sources of air pollution
• Improving ventilation – Bringing clean, fresh air in can reduce the concentration of air pollution in your building
• Utilizing air cleaners – Find one or more with a decent level of efficiency and air-circulation rate

To this extent, we can help reduce air pollution by:

1. Support Clean Energy Policies

The energy sector is a major source of air pollution. Supporting clean energy policies, such as investing in wind and solar power, can help reduce air pollution from power plants. More people are now using clean energy technologies, and some governments have been giving grants to consumers who are interested in installing solar panels in their homes.

2. Make Use of Public Transportation

One of the major drivers of air pollution is the transportation sector. To reduce pollution caused by transportation, the Department of Transportation suggests a number of actions³⁷:

• Improve and promote public transit alternatives
• Promote biking and walking
• Buy cars with more environmentally friendly features
• Use carpooling where available and implement where not

3, Improve Industrial Processes

Many industrial processes emit harmful pollutants into the air. Improving these processes, such as by developing, using, and providing incentives to use cleaner technologies, can reduce air pollution.

4. Plant Trees

Trees play a crucial role in cleaning the air. By planting more trees, we can absorb pollutants from the air, making it cleaner and healthier for us to breathe.

5. Educate the Public

Raising awareness about the far-reaching effects of air pollution and the ways to reduce it is an important step in controlling air pollution. By educating the public, we can encourage them to take actions that will help reduce air pollution.

6. Local Purchasing and Sourcing

Global supply chains are crucial to continuing our way of life in a linked world. However, buying locally whenever possible can significantly reduce the number of industrial sources of air pollution associated with the transit of those goods.

Why Improving Air Quality Matters

The WHO estimates that air pollution causes nearly seven million deaths annually throughout the world related to pollution. Specifically, ambient air pollution causes 4.2 million fatalities annually³⁸, while indoor air pollution causes 3.2 million preventable deaths³⁹. Alarming, yes?

Worse still, according to WHO data, 99% of people breathe in air that is worse than the levels recommended by the organization⁴⁰. Numerous areas have significant pollution levels, with low- and middle-income nations suffering the most.

Indoor air quality levels in facilities are being held more and more responsible for chronic ailments. Studies suggest that indoor air plays a role in the occurrence of a phenomenon known as "Sick building syndrome⁴¹,” which occurs when people who occupy a building report experiencing similar symptoms after being in the building, with the symptoms subsiding or going away after they leave. 

Ultimately, improving air quality matters because poor air quality can affect your lungs' ability to function adequately indoors or out, which can have major health effects. 

Controlling Air Pollution

The Clean Air Act continues to be an important tool in the fight against air pollution and the protection of public health and the environment⁴². It has been instrumental in reducing air pollution and improving air quality in the United States. Since its passage, levels of criteria pollutants have decreased, resulting in improved health outcomes and a cleaner environment.

The EPA updates and enforces air quality standards to reflect the latest science and technology. The act has also been a model for similar legislation in other countries worldwide. More impressive steps by EPA include the regulations on new vehicles, engines, and cleaner fuels, which have led to a nearly 99% improvement in emissions.

In addition to setting air quality standards, the Clean Air Act also established a national permit program for new and existing industrial sources of air pollution and provided funds for research and development of new pollution control technologies. 

For instance, nanotechnologies can also be used effectively in environmental health. Nanotechnology⁴³ can trap or destroy interior toxins on a molecular level, which may be used to reduce indoor air pollution. Air purifiers are already using this technology, which has the ability to eliminate indoor contaminants at a far finer scale than existing techniques.

Interestingly, numerous businesses have committed to implementing improved environmental practices in their daily operations through both long-term and short-term initiatives, such as California Clean Air Day⁴⁴. Even many major shops have asserted that they will reach net-zero emissions within prodigious time frames.

International efforts outside of the United States to fight pollution include The United Nations Environment Programme's work on “Preventing and reducing air pollution to improve global air quality.”⁴⁵”. In 2019, the 7th of September every year was declared International Day of Clean Air for blue skies⁴⁶.  

Conclusion

Air pollution affects us all. No amount of polluted air is safe to breathe, and everybody is susceptible to its negative effects on health. While visible haze and smog can result from extremely high concentrations, dangerous air pollution can exist even when the sky is clear. 

From respiratory problems to heart disease, the effects of air pollution can be far-reaching and devastating. Therefore, by taking simple steps to reduce our exposure and advocating for cleaner air, we can help to protect ourselves and future generations from the harmful effects of air pollution.

1. Centers for Disease Control and Prevention. (2020, December 21). Air Pollution. Centers for Disease Control and Prevention. Retrieved February 6, 2023, from https://www.cdc.gov/climateandhealth/effects/air_pollution.htm[↩]
2. Katsouyanni K. (2003). Ambient air pollution and health. British Medical Bulletin, 68, 143–156. https://doi.org/10.1093/bmb/ldg028[↩]
3. Raju, S., Siddharthan, T., & McCormack, M. C. (2020). Indoor Air Pollution and Respiratory Health. Clinics in Chest Medicine, 41(4), 825–843. https://doi.org/10.1016/j.ccm.2020.08.014[↩]
4. World Health Organization (n.d.) Air Pollution. WHO. Retrieved 12th March 2023 from https://www.who.int/health-topics/air-pollution#tab=tab_1[↩]
5. United States Environmental Protection Agency. (2022). Introduction to Indoor Air Quality. ¦ US EPA. Retrieved 12th March 2023 from https://www.epa.gov/indoor-air-quality-iaq/introduction-indoor-air-quality[↩]
6. Environmental Protection Agency. (2021). Indoor Air Quality. EPA. Retrieved 14th March 2023 from https://www.epa.gov/report-environment/indoor-air-quality[↩]
7. Environmental Protection Agency. (2022). Volatile Organic Compounds’ Impact on Indoor Air Quality ¦ US EPA. Retrieved 14th March 2023 from https://www.epa.gov/indoor-air-quality-iaq/volatile-organic-compounds-impact-indoor-air-quality[↩]
8. Seguel, J. M., Merrill, R., Seguel, D., & Campagna, A. C. (2016). Indoor Air Quality. American Journal of Lifestyle Medicine, 11(4), 284–295. https://doi.org/10.1177/1559827616653343[↩]
9. Manisalidis, I., Stavropoulou, E., Stavropoulos, A., & Bezirtzoglou, E. (2020). Environmental and Health Impacts of Air Pollution: A Review. Frontiers in public health, 8, 14. https://doi.org/10.3389/fpubh.2020.00014[↩]
10. Wang, B., Chen, H., Chan, Y. L., & Oliver, B. G. (2020). Is there an association between the level of ambient air pollution and COVID-19? American Journal of Physiology-Lung Cellular and Molecular Physiology, 319(3), L416–L421. American Physiological Society. https://doi.org/10.1152/ajplung.00244.2020[↩]
11. Simoni, M., Baldacci, S., Maio, S., Cerrai, S., Sarno, G., & Viegi, G. (2015). Adverse effects of outdoor pollution in the elderly. Journal of thoracic disease, 7(1), 34–45. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4311079/[↩]
12. Duan, R. R., Hao, K., & Yang, T. (2020). Air pollution and chronic obstructive pulmonary disease. Chronic diseases and translational medicine, 6(4), 260–269. https://doi.org/10.1016/j.cdtm.2020.05.004[↩]
13. Tung, N. T., Ho, S. C., Lu, Y. H., Chen, T. T., Lee, K. Y., Chen, K. Y., Wu, C. D., Chung, K. F., Kuo, H. P., Thao, H. N. X., Dung, H. B., Thuy, T. P. C., Wu, S. M., Kou, H. Y., Lee, Y. L., & Chuang, H. C. (2021). Association Between Air Pollution and Lung Lobar Emphysema in COPD. Frontiers in Medicine, 8, 705792. https://doi.org/10.3389/fmed.2021.705792[↩]
14. Tiotiu, A. I., Novakova, P., Nedeva, D., Chong-Neto, H. J., Novakova, S., Steiropoulos, P., & Kowal, K. (2020). Impact of Air Pollution on Asthma Outcomes. International journal of environmental research and public health, 17(17), 6212. https://doi.org/10.3390/ijerph17176212[↩]
15. Buka, I., Koranteng, S., & Osornio-Vargas, A. R. (2006). The effects of air pollution on the health of children. Paediatrics & Child Health, 11(8), 513–516. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2528642/[↩]
16. Li, Y., Xu, L., Shan, Z., Teng, W., & Han, C. (2019). Association between air pollution and type 2 diabetes: an updated review of the literature. Therapeutic Advances in Endocrinology and Metabolism, 10, 2042018819897046. https://doi.org/10.1177/2042018819897046[↩]
17. Melody, S. M., Wills, K., Knibbs, L. D., Ford, J., Venn, A., & Johnston, F. (2020). Maternal Exposure to Ambient Air Pollution and Pregnancy Complications in Victoria, Australia. International Journal of Environmental Research and Public Health, 17(7), 2572. https://doi.org/10.3390/ijerph17072572[↩]
18. Bai, W., Li, Y., Niu, Y., Ding, Y., Yu, X., Zhu, B., Duan, R., Duan, H., Kou, C., Li, Y., & Sun, Z. (2020). Association between ambient air pollution and pregnancy complications: A systematic review and meta-analysis of cohort studies. Environmental Research, 185, 109471). https://doi.org/10.1016/j.envres.2020.109471[↩]
19. Hajat, A., Hsia, C., & O'Neill, M. S. (2015). Socioeconomic Disparities and Air Pollution Exposure: a Global Review. Current Environmental Health Reports, 2(4), 440–450. https://doi.org/10.1007/s40572-015-0069-5[↩]
20. Kurt, O. K., Zhang, J., & Pinkerton, K. E. (2016). Pulmonary health effects of air pollution. Current Opinion in Pulmonary Medicine, 22(2), 138–143. https://doi.org/10.1097/MCP.0000000000000248[↩]
21. Environmental Protection Agency. (2022). Particulate Matter (PM) Basics ¦ US EPA. Retrieved 14th March 2023 from https://www.epa.gov/pm-pollution/particulate-matter-pm-basics[↩]
22. Kyung, S. Y., & Jeong, S. H. (2020). Particulate-Matter Related Respiratory Diseases. Tuberculosis and Respiratory Diseases, 83(2). 116). https://doi.org/10.4046/trd.2019.0025[↩]
23. Lee, K. K., Miller, M. R., & Shah, A. S. V. (2018). Air Pollution and Stroke. Journal of Stroke, 20(1), 2–11. https://doi.org/10.5853/jos.2017.02894[↩]
24. Aguilera, R., Corringham, T., Gershunov, A., & Benmarhnia, T. (2021). Wildfire smoke impacts respiratory health more than fine particles from other sources: observational evidence from Southern California. Nature Communications, 12(1), 1493. https://doi.org/10.1038/s41467-021-21708-0[↩]
25. United States Environmental Protection Agencies. (2 August, 2022[↩]
26. Holm, S. M., & Balmes, J. R. (2022). Systematic Review of Ozone Effects on Human Lung Function, 2013 Through 2020. Chest, 161(1), 190–201. https://doi.org/10.1016/j.chest.2021.07.2170[↩]
27. United States Environmental Protection Agency. (16 February 2023). Sulfur Dioxide Basics. Retrieved 22 March 2023 from https://www.epa.gov/so2-pollution/sulfur-dioxide-basics#effects[↩]
28. Chen, Z., Liu, N., Tang, H., Gao, X., Zhang, Y., Kan, H., Deng, F., Zhao, B., Zeng, X., Sun, Y., Qian, H., Liu, W., Mo, J., Zheng, X., Huang, C., Sun, C., & Zhao, Z. (2022). Health effects of exposure to sulfur dioxide, nitrogen dioxide, ozone, and carbon monoxide between 1980 and 2019: A systematic review and meta‐analysis. Indoor Air, 32(11). https://doi.org/10.1111/ina.13170[↩]
29. Khalaf, E. M., Mohammadi, M. J., Sulistiyani, S., Ramírez-Coronel, A. A., Kiani, F., Jalil, A. T., Almulla, A. F., Asban, P., Farhadi, M., & Derikondi, M. (2022). Effects of sulfur dioxide inhalation on human health: a review. Reviews on Environmental Health. https://doi.org/10.1515/reveh-2022-0237[↩]
30. Olson, K., & Smollin, C. (2008). Carbon monoxide poisoning (acute). BMJ Clinical Evidence, 2008(, 2103). https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2907971/[↩]
31. Blumenthal, I. (2001). Carbon Monoxide Poisoning. Journal of the Royal Society of Medicine, 94(6), pp. 270–272. https://doi.org/10.1177/014107680109400604[↩]
32. Blumenthal, I. (2001). Carbon Monoxide Poisoning. Journal of the Royal Society of Medicine, 94(6), pp. 270–272. https://doi.org/10.1177/014107680109400604[↩]
33. Blumenthal, I. (2001). Carbon Monoxide Poisoning. Journal of the Royal Society of Medicine, 94(6), pp. 270–272. https://doi.org/10.1177/014107680109400604[↩]
34. Asthma + Lung UK. (2023). Lowering your risk from air pollution. British Lung Foundation. Retrieved 29th March 2023 from https://www.asthmaandlung.org.uk/living-with/air-pollution/lower-risk#top-tips-for-high-pollution-days[↩]
35. Climate & Clean Air Coalition. (n.d.) World Health Organization (WHO). Retrieved 29th March 2023 from https://www.ccacoalition.org/en/partners/world-health-organization-who[↩]
36. Environmental Protection Agency. (2022). Improving Indoor Air Quality. Retrieved 29th March 2023 from https://www.epa.gov/indoor-air-quality-iaq/improving-indoor-air-quality[↩]
37. U.S. Department of Transportation. (2015). Cleaner Air. Retrieved 29th March 2023 from https://www.epa.gov/indoor-air-quality-iaq/improving-indoor-air-quality[↩]
38. WHO. (2022). Ambient (outdoor) air pollution. Retrieved 29th March 2023 from https://www.who.int/news-room/fact-sheets/detail/ambient-(outdoor)-air-quality-and-health[↩]
39. WHO. (2022). Household air pollution. Retrieved 29th March 2023 from https://www.who.int/news-room/fact-sheets/detail/household-air-pollution-and-health[↩]
40. WHO. (n.d.). Air pollution. Retrieved 29th March 2023 from https://www.who.int/health-topics/air-pollution#tab=tab_1[↩]
41. Gawande, S., Tiwari, R. R., Narayanan, P., & Bhadri, A. (2020). Indoor Air Quality and Sick Building Syndrome: Are Green Buildings Better than Conventional Buildings?. Indian Journal of Occupational and Environmental Medicine, 24(1), 30–32. https://doi.org/10.4103/ijoem.IJOEM_148_19[↩]
42. Environmental Protection Agency. (2020). Overview of the Clean Air Act. EPA. Retrieved 29th March 2023 from https://www.epa.gov/clean-air-act-overview[↩]
43. Larkin, A., & Hystad, P. (2017). Towards Personal Exposures: How Technology Is Changing Air Pollution and Health Research. Current Environmental Health Reports, 4(4), 463–471. https://doi.org/10.1007/s40572-017-0163-y[↩]
44. Coalition for Clean Air. (2023). About Californian Clear Air Day. Retrieved 29th March 2023 from https://www.cleanairday.org/about/[↩]
45. United Nations Environment Assembly of the United Nations Environment Programme. (2018). 3/8. Preventing and reducing air pollution to improve air quality globally. United Nations. UNEP/EA.3/Res.8 Available from https://www.un.org/en/observances/clean-air-day[↩]
46. United Nations General Assembly. (2019). Resolution adopted by the General Assembly on 19 December 2019. United Nations. A/RES/74/212. Available from https://www.un.org/en/observances/clean-air-day[↩]

Marion Sereti

Marion is a freelance health and wellness writer with a passion for all things digital health. She loves diving deep into the latest research and trends in the industry and distilling them down into fun, relatable pieces that people can relate to. Whether you're a health nut or a tech geek, she is always looking for new and interesting ways to help readers access quality and evidence-based information.