In this article, we will discuss the effects of air pollution on people with asthma. We will discuss the link between certain air pollutants with asthma, and which groups of individuals face a higher susceptibility to asthma attacks from air pollution. Lastly, we will discuss ways one can prevent asthma from air pollution.
Does air quality affect asthma?
Yes, air quality can affect asthma. Air quality is the measure of how clean the ambient air of a given region is. Higher the concentration of pollutants, the poorer the air quality gets.
In this case, poor air quality can cause asthma, a condition in which a person’s airways become inflamed, narrow and swell and produce extra mucus, which makes it difficult to breathe.
What species of air pollution are linked to asthma?
There are various species of air pollution that can affect people with asthma. Some of the pollutants that are linked to asthma are listed below.
- Ozone (O3)
- Particulate matter (PM)
- Nitrogen dioxide (NO2)
- Sulphur dioxide (SO2)
- Carbon monoxide (CO)
We shall discuss the above mentioned pollutants in more detail.
Ozone is a highly reactive gaseous molecule which is naturally present in the upper layers of the atmosphere, where it absorbs the sun’s damaging ultraviolet radiation. When present in the lower levels of the atmosphere, however, it behaves as a pollutant and can aggravate asthma.
The combination of sunlight with fumes generated from cars, which contain hydrocarbons and nitrogen oxides (NOx), causes ozone generation in the lower atmosphere.
It is a key contributor to “Los Angeles Smog,” or summer smog, which occurs in large cities during the summer. According to studies, cities where LA smog occurs have a greater incidence of asthma sufferers recorded.
Ozone has a distinctive strong odour that irritates the inner linings of the airways and the lungs. It can make it difficult to breathe deeply and decrease lung function.
Particulate Matter (PM)
Particulate matter is defined as sub-micron-sized solid or liquid particles 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.
PM stems from two origins: natural sources like pollens, moulds, and dust particles, and anthropogenic (human-based) activities like combustion, automotive exhausts, industrial emissions, and so on.
PM is found in greater amounts in contaminated air. According to studies, greater PM concentrations can induce a decline in lung function.
Furthermore, PM may comprise chemicals that act as an irritant to the inner linings of the airway. For example, ‘hay fever’, which is related to pollen allergy, serves as a trigger for people suffering from asthma.
Nitrogen dioxide (NO2)
Nitrogen dioxide is a gaseous chemical that is a part of the nitrous oxide (NOx) species, which refers to various compounds that contain nitrogen and oxygen atoms in varying numbers.
It is predominantly produced by anthropogenic activities such as vehicle exhaust, industrial chimney emissions, and firewood burning. More frequent asthma symptoms and asthma-related issues are frequently associated with higher NO2 concentrations.
According to a recent study, children who were exposed to high levels of NO2 in their early lives had 1.25 times the chance of developing asthma later in life than children who were exposed to low levels of NO2.
Sulphur dioxide (SO2)
Sulphur dioxide is a major air pollutant, Naturally, it is produced from volcanoes, but it is mainly an anthropogenic pollutant, produced by emissions from vehicles, particularly diesel vehicles and ships, and industrial emissions.
Those with allergic asthma might be exceedingly sensitive to inhaled SO2. Bronchitis, mucus production, and bronchospasm are the most common health concerns linked to SO2.
It’s an irritant that gets deep into the lungs, where it’s converted to bisulfite and interacts with sensory receptors to cause bronchoconstriction. This in turn makes it difficult to breathe and trigger an asthma attack.
Carbon monoxide (CO)
Carbon monoxide is a serious air pollutant, and in higher concentrations, it can prove to be lethal. Carbon monoxide is a colourless, odorless gas, therefore cannot be detected by human senses.
Carbon monoxide is formed from incomplete combustion of fossil fuels and wood. It is also formed from smoking cigarettes.
Carbon monoxide forms a strong bond with haemoglobin, the compound present in red blood cells (RBCs), which is responsible for transportation of oxygen from the lungs to the tissues, and carbon dioxide from the tissues back to the lungs.
In adults, evidence supports a relationship between CO exposure and moderate or severe asthma exacerbations, although the link has not been verified in children. Decreased CO levels were shown to have a significant relationship with lower asthma mortality rates.
Which individuals are at a higher risk of developing asthma from air pollution
Vulnerability to asthma from air pollution depends upon several factors, such as physiological factors (eg.: age, comorbidities, etc.), geographic factors (i.e., whether an individual lives in a city or a rural area, climate), and other factors such as occupation, lifestyle, etc.
On this basis, the following groups face a higher risk of developing asthma from pollution
- Old people
- People living in polluted environments
- Occupational asthma
We shall discuss these in detail.
Over the previous years, the annual reported case of children being diagnosed with asthma has steadily risen. At a young age, the lungs are still developing, and their breathing rate is relatively faster with respect to adults.
A study found out that exposure to PM10 and maternal smoking during pregnancy increased the risk factor of wheezing and asthma in children .
Some studies have found a link between indoor air pollution, which is mostly caused by cooking with polluting fuels, and the development of asthma in children.
A favourable link between gas cooking, NO2 exposure, and childhood asthma or wheeze was discovered in an analysis of 41 studies.
In a study funded by the US Environmental Protection Agency (EPA), evidence suggests that air pollutants can suppress genes that regulate the immune system’s ability to differentiate an allergen from a dangerous foreign substance, such as a virus or bacteria.
Old people have a weaker immune system, due to aging. Poor respiratory muscle strength, decrease in elastic recoil, and greater rigidity of the chest wall are often all part of the natural aging process that increase the susceptibility to asthma.
All these factors combined makes elderly people prone to develop asthma if exposed to air pollution. In the US, asthma affects 4%-13% of individuals aged 65 years or older.
They are at a 5 times higher risk from dying from asthma or asthma-related issues than the younger population.
People living in metropolitan areas
Large cities which have a high vehicular traffic and industrial areas have a higher level of pollution, particularly of substances such as NO2, SO2, PM2.5, O3, and CO.
These substances are harmful in nature and their contribution to triggering asthma is well-documented in previous studies.
In such conditions, even healthy people who had no pre-existing health conditions can end up developing asthma or asthma-related issues if subjected to higher levels of pollution.
For people with a family history of asthma, or allergic asthma, their condition can worsen even more if they are continuously subjected to a polluted environment.
Occupational asthma refers to development of asthma due to exposure to certain factors in the workplace environment. It is caused due to inhalation of irritants during work.
Occupational asthma can be triggered by many factors, which also include:
1. Chemical dyes and solvents
2. Dust from processes involving wood, flour, grain, etc.
3. Working in a quarry or a mining facility.
4. Working with animals or insects
Occupational asthma is avoidable, and if caught early, can be treated as well.
How to prevent asthma attacks from air pollution
Avoid places with traffic congestion
As it is evident, traffic-related pollution is a major contributor to triggering asthma. 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, which would help to dilute the indoor air pollution level by introducing outdoor air, and carry the pollutants out of the house. Furthermore, you can install exhaust fans at your windows or in the central air ducts to improve the efficiency of ventilation.
- Using an air dehumidifier to reduce the relative humidity of the home. A high humidity level can promote the growth of mold and mildews, which give rise to spores, which can cause asthma .
- Avoid smoking or combustion of fuels inside the house, as these processes adversely affect the indoor air quality.
Cigarette smoke contains several toxins, which can act as irritants to the airway and affect the respiration system, thereby causing asthma .
- You can invest in an air purifier. A major component of IAP is particulate matter (PM). These particles can originate indoors from various sources, or enter the house from the outdoor air.
PM has serious implications on health, depending upon its composition and abundance, and can also cause premature death in people ailing from respiratory and cardiovascular diseases.
The best method for reducing PM concentrations is by using an air purifier. Depending upon the size of the basement, an adequate air purifier should be used.
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.
Other FAQs about Air Quality that you may be interested in.
Exposure to air pollution can affect asthma, with intensity varying upon concentration and exposure time.
Certain pollutants such as NO2, O3, SO2, CO, and PM2.5 have more implications to asthma, especially on certain groups of people such as the young and old, people living in metropolitan cities, and people with occupations that can trigger asthma.
Certain ways to prevent asthma attacks from air pollution is by avoiding places with high traffic activity, by checking pollution levels beforehand and planning the activity accordingly, and by keeping the indoor air clean.
How can I, as someone who is affected by asthma, keep myself safe while visiting or travelling through polluted areas?
You can keep yourself safe when travelling through polluted areas by following prevention methods, such as wearing a face mask which can block sub-micron particles from entering your airway.
Furthermore, you must carry a reliever inhaler with you in order to quickly deal with the symptoms. You can ask your doctor or GP to direct you on the type of inhaler you should buy and how to use it.
Does weather play a role in asthma?
Yes, weather plays a significant role in triggering asthma. In winter seasons, when the near surface air is cold, a condition of “inversion” exists, due to which the air doesn’t move vertically.
Under such conditions, the pollutants get trapped near the ground surface, and subsequent emissions from various sources increase the pollution levels, thereby making one more susceptible to asthma.
On windy days, the pollutants get unsettled and cannot accumulate, making the air cleaner.
Lastly, certain biological activities that can cause asthma also are dependent on the weather. For example, on warm days, in the absence of wind, people could face a chance of experiencing asthma due to the presence of pollen.
- Pablo Orellano, Nancy Quaranta, Julieta Reynoso, Brenda Balbi, Julia Vasquez; “Effect of outdoor air pollution on asthma exacerbations in children and adults: Systematic review and multilevel meta-analysis”. PLoS One. 2017; 12(3): e0174050. Published online 2017 Mar 20. doi: 10.1371/journal.pone.0174050
- Holst G J, Pedersen C B, Thygesen M, Brandt J, Geels C, Bønløkke J H et al. “Air pollution and family related determinants of asthma onset and persistent wheezing in children: nationwide case-control study” BMJ 2020; 370:m2791 doi:10.1136/bmj.m2791
The Links Between Air Pollution and Childhood Asthma: https://www.epa.gov/sciencematters/links-between-air-pollution-and-childhood-asthma
Asthma and Allergy Foundation of America (AAFA):
Asthma in the Elderly: Important Considerations for Diagnosis and Treatment:
Is Your Job Giving You Asthma?: