Can air pollution cause lung cancer?

This blog post discusses whether air pollution can contribute towards the increased risk of lung cancer. Furthermore, we discuss how various pollutants play a role in causing lung cancer.

Can air pollution cause lung cancer?

Several studies over the previous years have shown that exposure to air pollution is positively correlated with the increased risk of developing lung cancer.

Air pollution refers to the presence of undesirable substances, that exist as solid, liquid, or gas, in the ambient air, that can have adverse effects on human health.

Over the previous decades, air pollution has been a prevalent problem, and has been worsening with time, particularly in the urban areas. 

This is mainly due to anthropogenic (i.e., human based) activities, which heavily contribute to release of pollutants in the ambient air.

Studies have shown that over time, with the rise in air pollution, the risk of developing lung cancer in individuals living in polluted conditions has also increased.

We shall discuss how various pollutant species contribute to the risk of development of lung cancer, and their respective sources.

Pollutants that are linked with lung cancer

There are various pollutants that are generated by a human being in their daily activities. However, not all pollutants affect the lungs, and not all pollutants cause cancer.

The biggest factors that determine the risk of lung cancer in an individual from air pollution are – 1. Concentration of the pollutant, and; 2. Duration of exposure to the pollutant.

Studies have found out that amongst the various pollutants present in the atmosphere, the following have shown to be linked with development of lung cancer.

  • Nitrogen dioxide, NO2
  • Sulphur dioxide, SO2
  • Particulate matter, PM
  • Asbestos
  • Polycyclic Aromatic Hydrocarbons, PAHs
  • Radon

We shall discuss the following in more detail.

Nitrogen dioxide (NO2)


Nitrogen dioxide is a component of the nitrous oxide (NOx) family of chemicals, which includes a variety of molecules containing nitrogen and oxygen atoms in variable amounts. 

These are a significant contaminant because they raise the risk of illnesses pertaining to the respiratory as well as the cardiovascular system.

Because nitrogen dioxide is released via vehicle exhaust, it is largely a traffic-related contaminant. They are also released by coal-fired thermal power plants (CTPPs), steel and iron mills, and can occur naturally following lightning strikes.

There are studies that show the link between exposure to NO2 from traffic related air pollution and increased chances of lung cancer. 

Sulphur dioxide (SO2)

Sulphur dioxide is a significant contaminant in the atmosphere. Natural causes, such as volcanic eruptions, as well as human activities, such as fossil fuel burning and industrial emissions, produce it.

In studies which aimed to find a link between traffic related air pollution and lung cancer, it was found out that exposure to SO2 can significantly increase risk of lung cancer.

In another study on workers in a paper and pulp industry who were subjected to SO2 exposure, it was found out that there was a significant link between lung cancer and SO2 exposure, other than links with non-Hodgkin lymphoma and leukemia.

Particulate matter (PM)

Amongst the above mentioned pollutants, the worst is particulate matter, or simply PM. PM refers to particles in the sub-micron range that are suspended in the air. 

There are two forms of particulate matter: coarse particulate matter (PM10) and tiny particulate matter (PM2.5). PM2.5 is a prevalent problem among them.

There are many sources of PM in the ambient air. Some of the main sources include factories, power plants, refuse incinerators, fumes from automobiles, construction activities, fires and natural windblown dust.

Indoor sources include burning of  fuels, smoking, and other hobbies, such as woodworking, painting, etc.

Given the variety of PM present, they have various sources. These particles can originate from a variety of sources, which can be indoors, or outdoor pollution that enters through doors, windows, seeps, cracks, and so on.

PM2.5 is of major concern. Its small size allows it to reach the deep recesses of the lung alveoli, where oxygen is exchanged with carbon dioxide in the bloodstream.

Several studies have shown the link between PM2.5 and increased risk of lung cancer. A study found out that for every rise in 10 g/m3 in PM2.5 increased the meta-relative risk of lung cancer by 1.09. 

In a case–control research from Canada, a combination of PM2.5 and NO2 exposure was linked to a higher incidence of adenocarcinomas than other cancer subtypes.

Another study on cigarette smokers found out that the PM generated by cigarettes not only raises the risk of lung cancer in active smokers, but also increases the risk of lung cancer in people that were subjected to secondhand smoke.

Multiple studies have found that employees exposed to particulate matter present in diesel pollution, such as railroad, bus garage, and dock workers, as well as truck drivers, are at an elevated risk of lung cancer.

Asbestos

Asbestos is a mineral fiber that was used earlier in a variety of construction materials since it acts as an insulator and a flame retardant. 

Although it is now banned in 55 countries, it is still used in major countries such as China, India, Russia, Canada, and the United States, although the EPA and CPSC have banned several asbestos products. 

Asbestos is purely an indoor air pollutant, as it concentrates in the indoor air due to activities such as remodelling, cutting, and sanding of asbestos-bearing products.

Elevated concentrations of respirable asbestos particles can cause lung cancer, mesothelioma (a cancer of abdominal and respiratory linings), and asbestosis (irreversible scarring of lung tissues). 

Polycyclic Aromatic Hydrocarbons (PAHs)

Polycyclic Aromatic Hydrocarbons (PAHs) are compounds that contain a benzene ring (C6H6) in their structure. They are generated as a byproduct of combustion of fuel, especially from vehicles with a diesel engine.

Many studies have shown the association of PAHs with cancer, based on studies carried out on people who were subjected to long-term PAH exposure.

PAHs cause mutations of the oncogenes, genes which are responsible for maintaining cell growth, division, and cell death.

Radon

Like asbestos, radon is an indoor air pollutant. It is a colourless, odourless, radioactive gas that originates from the radioactive disintegration of uranium present in the nearby soil or the rocks. 

Being a relatively heavy and radioactive gas, it is unique to ground level pollution because of proximity to the soil, where this harmful element might directly penetrate indoors through the building environment, through dirt floors, cracks in concrete walls and floors, floor drains and sumps. 

It does not have any short-term effects on health, but long-term exposure to elevated levels of radon can cause lung cancer. 

For smokers that live in such conditions, the risk is even higher. There are various kits for detecting and measuring indoor radon levels that are available easily and are inexpensive.

Sources of pollutants that affect the lungs


There are numerous sources of air pollution which can adversely affect the human lungs. However, the major sources that contribute to this are:

  • Traffic related air pollution (TRAP)
  • Industrial emissions
  • Cigarette smoking

Let us discuss these in more detail.

Over the past years, the number of automobiles used for transport has risen significantly. Traffic is one of the biggest polluters in metropolitan cities.

The exhaust gases released from vehicles contain pollutants such as ozone, NOx species such as NO2, SO2, soot, heavy metals, carbon monoxide, and so on. 

These species have been shown to affect the lungs, and on the basis of duration of exposure, can cause serious issues, even lung cancer.

Industrial emissions

In industrial areas, the air quality is much worse than compared to other places. The main contributors are steel and iron manufacturing plants, coal-based thermal power plants (CTPPs), brick kilns, chemical manufacturing plants, and so on.

The majority of emissions from industries comprise PM, SO2, NOx species, and these pollutants can react to give rise to O3. Workers in such industries often present respiratory issues such as asthma, poor lung function, emphysema, and lung cancer.

Cigarette smoking

Cigarette smoke is the worst enemy of healthy lungs. It is now well established by numerous studies that active smoking, as well as exposure to secondhand smoke are positively correlated with increased risk of lung cancer.

Cigarette smoke contains a lot of toxic substances and particulate matter that can affect the lungs in various manners. Other than lung cancer, cigarettes can also cause oxidative stress, poor lung function, asthma, COPD, and emphysema.

Other FAQs about Air Quality that you may be interested in.

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Does air quality cause headaches?

Conclusion

Air pollution is known for adversely affecting pulmonary health, and has also been established to cause lung cancer in people. Various pollutants, such as nitrogen dioxide, sulphur dioxide, particulate matter, asbestos, PAHs, and Radon are positively correlated with increased chances of lung cancer. These pollutants mainly arise from traffic, industrial emissions, and cigarette smoke.

FAQs

How can I keep myself safe from air pollution?

Avoid places with traffic congestion

As it is evident, traffic-related pollution is a major contributor to many health issues. So, it is best practice to avoid areas which have high traffic congestion or are prone to it. If it is convenient, one should travel in off-peak hours when there’s no traffic.

On the other hand, one can choose an alternate way of transit via a route which doesn’t have much traffic and is economical as well.

Check pollution levels before leaving

If you live in an urban area, it would be a good idea to check the pollution levels before leaving, so that you can plan your trip accordingly. 

There are many government and non-government organisations that are responsible for tracking the concentration of major air pollutants in the city and provide real-time data for the public.

Clean your indoor air

An average American spends 93% of their total life indoors. 87% of their life is inside buildings, then another 6% of their life is in automobiles.

Over the last several years, a significant amount of scientific reports provide evidence of air pollution inside buildings and homes, referred to as indoor air pollution (IAP), which is more serious than outdoor air pollution, even in industrialised cities and metropolitan areas. 

Thus, a person has a higher health risk from indoor air pollution than from outdoor air pollution. The best way to deal with IAP is by the following methods:

  • Improving ventilation of the house.
  • Using an air dehumidifier to reduce the relative humidity of the home.
  • Avoid smoking or combustion of fuels inside the house, as these processes adversely affect the indoor air quality.
  • You can invest in a HEPA air purifier.
    Air purifiers with HEPA (High-Efficiency Particulate Air) filters are best suited for indoor purposes. The presence of an activated charcoal filter and a UV light further increases the efficiency of the filters.

Who is at a higher risk of lung cancer?

Certain groups of individuals face a higher risk of developing lung cancer due to long term exposure to air pollution. These include:

  • Older people
  • Cigarette smokers as well as people exposed to secondhand smoke
  • A person with a family history of lung cancer.

References

  • Nyberg, Fredrik; Gustavsson, Per; Järup, Lars; Bellander, Tom; Berglind, Niklas; Jakobsson, Robert; Pershagen, Göran. Urban Air Pollution and Lung Cancer in Stockholm, Epidemiology: September 2000 – Volume 11 – Issue 5 – p 487-495
  • Lee WJ, Teschke K, Kauppinen T, Andersen A, Jäppinen P, Szadkowska-Stanczyk I, Pearce N, Persson B, Bergeret A, Facchini LA, Kishi R, Kielkowski D, Rix BA, Henneberger P, Sunyer J, Colin D, Kogevinas M, Boffetta P. Mortality from lung cancer in workers exposed to sulfur dioxide in the pulp and paper industry. Environ Health Perspect. 2002 Oct;110(10):991-5. doi: 10.1289/ehp.02110991. PMID: 12361923; PMCID: PMC1241024.
  • Cohen AJ, Pope CA 3rd. Lung cancer and air pollution. Environ Health Perspect. 1995;103 Suppl 8(Suppl 8):219-224. doi:10.1289/ehp.95103s8219
  • Pope III CA, Burnett RT, Thun MJ, et al. Lung Cancer, Cardiopulmonary Mortality, and Long-term Exposure to Fine Particulate Air Pollution. JAMA. 2002;287(9):1132–1141. doi:10.1001/jama.287.9.1132
  • Cancer Research UK. How can air pollution cause cancer?
    https://www.cancerresearchuk.org/about-cancer/causes-of-cancer/air-pollution-radon-gas-and-cancer/how-can-air-pollution-cause-cancer

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