How air pollution affects the lungs

This blogpost discusses the adverse effects of air pollution on the respiratory system, particularly the lungs. Furthermore, we elaborate upon the various pollutant species responsible for affecting the lungs, and how they do so.

Does air pollution affect the lungs?

Yes, several studies have shown the adverse effects of air pollution on the respiratory system, more particularly on the lungs. 

Air pollution refers to the presence of undesirable substances that exist in the form of solid, liquid, or gas, in the ambient air. Air pollution is still a serious public health hazard, impacting nine out of ten people living in cities throughout the world.

Recent research has linked air pollution to acute and chronic cardiopulmonary mortality, as well as all causes of death.

Air pollution has been shown to have an impact on asthma, chronic obstructive pulmonary disease (COPD), lung cancer and respiratory infection.

What pollutants affect the lungs?

Amongst the various pollutants that are present in the ambient air, there are mainly four major pollutants which include:

  • Ozone (O3)
  • Nitrous oxides (NOx)
  • Sulphur dioxide (SO2)
  • Particulate matter (PM)
  • Radon, Rn

We shall discuss their effects on the lungs in detail.

Ozone (O3)

Ozone is a gaseous molecule which is naturally present in the higher layers of the atmosphere, where it absorbs the harmful UV rays of the sun.

However, when present in the lower atmosphere layers, it acts as a pollutant, and can cause various pulmonary diseases.

Ozone formation in the lower atmosphere is due to interaction of sunlight with fumes emitted from vehicles, which contain hydrocarbons and nitrogen oxides (NOx). 

It is a major component of “Los Angeles Smog”, or summertime smog, which occurs during summer in metropolitan cities.

Ozone has been shown to cause oxidative stress, inflammatory responses and immunologic disease in laboratory animals.

Ozone has a characteristic pungent odor, which can irritate the inner linings of the airways, as well as the lungs. It can hamper one’s ability to breathe deeply, and reduce lung function.

Poor air quality caused by high ozone levels has been demonstrated to not only contribute to asthma aggravation, but also to be a cause towards onset of asthma.

Exposure to ozone for a short period of time has been linked to an increase in hospitalizations in children.

Nitrous oxides (NOx)

Nitrous oxides, or simply NOx species, refers to the family of compounds that are composed of nitrogen and oxygen in varying numbers. Amongst these, nitrogen dioxide (NO2), is the main concern.

Nitrogen dioxide is a gaseous substance which originates primarily from anthropogenic activities such as vehicular exhausts, emission from industrial chimneys, and combustion of firewood.

Higher concentrations of NO2 are usually associated  with  more  frequent  asthma  symptoms  and  asthma-related problems.

Long-term NO2 exposure lowered lung function measures, according to a longitudinal cohort research published in 2015.

Previous studies have shown a link between exposure to local traffic-related pollution to onset of asthma in children. A study estimated that an increase in NO2 concentration by 20.4 ppb (parts per billion) was associated with a 67% increase in the risk of asthma-related school absence.

NO2 exposures are also positively associated with lung cancer risk in other studies, and also have the highest correlations with all-cause mortality and lung cancer.

Sulphur dioxide (SO2)

Sulphur dioxide is a major air pollutant. It is released from natural sources such as volcanic activities, and from human activities such as combustion of fossil fuels and industrial emissions. 

Various studies have shown that children, old people, and people with preexisting respiratory illnesses are more prone to skin and lung diseases.

SO2 acts as a sensory irritant, and can cause asthma or asthma-like symptoms such as elevated mucus secretion and bronchitis. It can also aggravate pre-existing cardiovascular diseases.

A study by Li et al. showed that SO2 impacts asthmatic rats’ airway inflammatory and immunological responses, increasing their vulnerability by exacerbating inflammatory reactions in the lungs.

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. It’s 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 on PM2.5 have linked it to several pulmonary diseases, with positive associations found between long term exposure to PM2.5 and lung cancer, and premature deaths in people suffering from preexisting cardiovascular and pulmonary illnesses.

According to a meta-analysis, each 10 g/m3 increase 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.

Certain studies have also shown that PM2.5 generated from traffic related air pollution (TRAP) have shown to cause asthma in nonsmokers, children, and adult women.

Radon, Rn

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 is unique to indoor pollution because of proximity to the soil, where this harmful element might directly penetrate 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.

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 issues such as asthma, COPD, emphysema, and 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 so on.

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. It can cause oxidative stress, poor lung function, asthma, COPD, and emphysema.

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

Does air quality affect running?

Does Air Quality change during the Day?

Does air quality cause headaches?


A positive association between exposure to air pollution and diseases related to the pulmonary system has been shown by numerous studies. The various sources, such as traffic, industrial emissions, combustion, and smoking, have been shown to produce major air pollutants such as ozone, nitrous oxides, sulphur dioxide, particulate matter. Lastly, it is also important to note the role of radon gas in development of serious issues such as lung cancer.


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.

Can air pollution cause lung infections?

Yes, air pollution can cause infections such as bronchitis, hay fever, asthma, COPD, and so on. For people suffering from asthma or have a family history of asthma, the risk of lung infections can be even higher than the rest of people.


Leave a Comment