In this article, we discuss the link between air pollution and cancer. We shall elaborate on the certain pollutants that are known carcinogens i.e., cancer-causing chemicals, along with the source of emission of each of these pollutants.
Can air pollution cause cancer?
Yes, air pollution can cause cancer. Air pollution refers to the presence of undesirable substances in the ambient air that are detrimental to the health and well-being of living organisms.
Most of the global population resides in places where air pollution levels, because of emissions from industry, power generation, transportation, and domestic burning, have been rising steadily, thereby deprecating the quality of health.
Cancer is a disease in which cells start showing uncontrolled growth, and destroy body tissue. It can be caused due to genetic or environmental factors, or both.
Carcinogens are chemicals that are known for causing cancer. The effectiveness of a carcinogen depends upon two main factors – concentration of the carcinogen in the ambient air, and duration of exposure to it.
Many common substances and human activities give rise to potential carcinogens. Hence, it is important to regulate emissions from various sources and switch to practical alternatives which can eliminate the risk of cancer.
What does research suggest?
Numerous studies have been carried out that well-establish a link between air pollution and lung cancer. However, the major culprit that stands out is particulate matter.
Particulate matter refers to particles in the sub-micron range that are suspended in the ambient air. They are either directly emitted into the atmosphere, or are formed due to reaction between certain gaseous species.
On the basis of size, these particles are classified as:
- PM10 (PM ≤10 µm in aerodynamic diameter) includes the largest inhalable particles. These particles are usually not inhaled past the trachea, get trapped in the nose and throat regions, hence do not get deposited in the lungs. PM10 also includes:
- PM2.5-10, which is also known as coarse particulate matter (PM with an aerodynamic diameter >2.5 µm but ≤10 µm).
- PM2.5, which is also known as fine particulate matter (PM with an aerodynamic diameter ≤2.5 µm). These particles can be inhaled into the deepest recesses of the lung, including to the alveoli sacs, where oxygen exchange occurs.
Nowadays, PM2.5 has increasingly become a major research focus of adverse human health impacts of outdoor air pollution exposure over recent decades.
Studies suggest that PM2.5 is the biggest culprit for the increase in the risk of cancer, particularly lung cancer. Given its small size, large number, and large surface area-to-volume ratio.
PM2.5 can remain suspended in the air for a long time, and can easily transmit to a distance of hundreds to thousands of kilometers.
Certain studies have shown that for every 10 microgram per cubic meter (µg/m3) of increased exposure to PM2.5, the risk of dying from any cancer rose by 22 percent.
Who is at risk?
Although everyone is at risk of getting cancer if subjected to continuous exposure to air pollution, studies suggest that certain groups are at a higher risk with respect to others. These include:
- People in developing countries
- People with pre-existing respiratory or cardiac diseases
- Older people
- People subjected to respiratory occupational hazards
We shall elaborate on each group below.
People in developing countries
Developing countries refers to countries with a lesser developed industrial base and a lower human development index.
These also include major countries such as India, China, Brazil, Argentina, and so on. These happen to be the regions where the majority of the world’s population resides
Over the previous decades, the rate of industrialisation and urbanisation observed in these countries has been rapid and uncontrolled. As a result, there has been a degradation in the air quality as well.
Developed nations have a higher amount of PM2.5 concentration in the ambient air.
For example, Among the 10 largest countries by population, population-weighted ambient PM2.5 in 2017 varied by more than 12-fold, from 7 µg/m3 in the United States to 91 µg/m3 in India.
Based upon this statistic, it is evident that people from developing nations face a higher risk of getting cancer than those from developed nations.
Women have a higher risk of getting cancer from exposure to air pollution than men.
A study involving 66,280 people in Hong Kong found out that other than the fact that exposure to PM2.5 is linked to an increased risk of getting cancer, the risk of mortality from breast cancer was up to 80%.
Furthermore, another study showed that the risk of lung cancer from smoking or exposure to secondhand smoke had a higher incidence rate among women in North America, Northern and Western Europe, and Australia/New Zealand.
In several European countries, lung cancer incidence rates are beginning to converge in men and women as increasing rates in women are approaching declining rates in men.
People with pre-existing respiratory or cardiac diseases
People with pre-existing respiratory or cardiac diseases are at a higher risk, since their systems are inefficient in elimination of toxins. These toxins, if allowed to stay, interfere with the natural cell function, and can cause uncontrolled proliferation of cells.
A number of studies showed that exposure to PM2.5 levels had caused premature deaths of people suffering from respiratory diseases such as asthma, COPD, etc., or from cardiovascular diseases such as hypertension, arrhythmia, etc.
With age, the body’s mechanism of restricting cell growth becomes less effective. As a result, the chances of getting cancer even in the absence of air pollution is still more for older people than their younger counterparts.
However, if subjected to elevated levels of air pollution, the risk of getting cancer for old people is even higher.
The respiratory system is less efficient in filtering out the inhaled particulate matter, which increases the particulate load on the lower respiratory tract.
Therefore, it is important to ensure that old people are provided with cleaner surroundings.
People subjected to respiratory occupational hazards
Occupational hazards refer to substances that can have detrimental effects on the worker’s health, which, in this case, is the risk of acquiring cancer.
Certain occupations, such as working with chemicals, solvents, dyes, or other compounds that emit VOCs, or for people working in mines, quarries, and so on.
Under such conditions, there is extra load put onto the respiratory system, which if not treated in time could cause lung cancer. Several studies have shown the effects on the respiratory system of miners, with some reporting lung cancers.
Smoking is one of the worst forms of air pollution. Not only does it put the smoker at risk, it also puts secondhand smokers i.e., non-smokers exposed to cigarette smoke, at an equal risk.
The active ingredient of cigarettes, nicotine, contains several chemicals that are potential carcinogens. It is well-established that smoking can cause cancer of the mouth, throat, or the lungs.
Lung cancer is a dangerous cancer, as it has a low survival rate.
What pollutant species increase the risk of cancer
Other than particulate matter, there are other chemical species that can increase the risk of cancer if a person is subjected to exposure of elevated concentrations to these substances. These include:
- Polycyclic Aromatic Hydrocarbons (PAHs)
- Certain Volatile Organic Compounds (VOCs)
We shall discuss about these chemicals in detail
Radon 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.
Reducing radon requires technical knowledge, and can be addressed by contractors trained to fix radon problems.
For residential complexes that rely upon well water and have detected elevated levels of radon in their basement, you should get the water tested from a certified lab or trained individual.
Ozone is a gas that is formed by interaction of light with oxygen molecules. It is a vital gas in the upper atmosphere, where it blocks the harmful UV rays from entering the atmosphere. However, when present at the ground level, it has negative implications on human health.
The characteristic pungent odor of ozone can irritate the inner linings of the airways and can trigger an asthma attack. However, ozone is an unstable molecule, and it can attack the DNA, causing impairment of cellular function.
This can cause loss of the cell’s ability to regulate its growth and division, which can cause development of tumours. Certain studies have shown an association between PM2.5 and ozone with the increased risk of cancer.
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.
Certain Volatile Organic Compounds (VOCs)
VOCs refer to a variety of organic compounds that are emitted from certain materials in the form of a gas. These compounds are generated as a byproduct of fuel combustion, and are also present in common household items, such as paints, solvents, cleaning products, cosmetics, and fuels.
Certain VOC species, such as benzo[a]pyrene, have been shown to cause cancer, in a mechanism similar to that of PAHs. So, careless usage of household items that contain VOCs is very risky for health.
Other FAQs about Air quality that you may be interested in.
We discussed how air pollution can cause cancer, especially when subjected to elevated levels of exposure to PM2.5.
Furthermore, we discussed what groups of people are at risk of getting cancer, which includes women, older people, smokers, people with pre-existing medical conditions, people in developing countries, and people subjected to respiratory-related occupational hazards.
Lastly, we talked about chemical species that are also responsible for causing cancer.
Can asbestos cause lung cancer?
Yes, asbestos can cause lung cancer. As of today, asbestos is banned in 55 countries. It was used as an insulator and a flame retardant in construction equipment.
The asbestos-bearing minerals from older materials can flake off, which if inhaled can cause issues such as fibrosis, and even lung cancer.
How can I keep my indoor environment safe?
You can keep your indoor environment safe by using an air purifier. These are devices that help to filter out particulate matter and certain gaseous species from the indoor environment.
Am I, a non-smoker at risk, if I’m not exposed to secondhand smoke?
Even if you aren’t exposed to secondhand smoke, but live or work in a polluted environment, you might still be at risk.
New studies show that there is a link between exposure to pollution and other forms of cancer such as bladder cancer, kidney cancer, and so on.
- Michelle C. Turner, Daniel Krewski, W. Ryan Diver, C. Arden Pope III, Richard T. Burnett,Michael Jerrett,Julian D. Marshall, and Susan M. Gapstur 2017 Ambient Air Pollution and Cancer Mortality in the Cancer Prevention Study II Environmental Health Perspectives 125:8 CID: 087013 https://doi.org/10.1289/EHP1249
- Turner, M. C., Andersen, Z. J., Baccarelli, A., Diver, W. R., Gapstur, S. M., Pope, C. A., Prada, D., Samet, J., Thurston, G., & Cohen, A. (2020). Outdoor air pollution and cancer: An overview of the current evidence and public health recommendations. CA Cancer Journal for Clinicians, 70(6), 460-479. https://doi.org/10.3322/caac.21632
- Wong CM, Tsang H, Lai HK, Thomas GN, Lam KB, Chan KP, et al. Cancer mortality risks from long-term exposure to ambient fine particle. Cancer Epidemiol Biomarkers Prev 2016;25:839–45.
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