Air pollution occurs when excessive amounts of noxious gases, particulates, and organic compounds enter the atmosphere.

Anthropological activities and natural phenomenon can introduce these substances into the air.

The major pollutants that cause poor urban air quality are gases like carbon dioxide, sulphur oxides, nitrogen oxides, carbon monoxide, and volatile organic compounds, such as methane.

Chlorofluorocarbons, toxic metals, ammonia, and radioactive pollutants also degrade the air quality and contribute to air pollution.

Respiratory Disorders Caused by Air Pollution

Air pollution is known to have a severe impact on the health and well-being of people as well as animals.

As per the 2014 report of the World Health Organization report, air pollution in 2012 caused the deaths of approximately 7 million people across the globe.

Amongst the anthropogenic sources of emissions, fossil fuel power stations, vehicular sources, and aerosols, such as spray paints add a significant number of pollutants into the air.

Short- and long-term contact with poisonous air pollutants released by vehicular exhausts and the burning of fossil fuels has a toxicological impact on the human body.

Such exposure can lead to severe dysfunctions including respiratory and cardiovascular diseases, irritation of the eyes, neuropsychiatric problems, skin conditions, and even bring about cancer.

This article explores the respiratory disorders brought about by regular exposure to air pollution.

Several investigative studies have established the direct correlation between exposure to the poor air quality and the growing rate of disease morbidity and deaths, particularly caused by respiratory complications.

The most common respiratory disorder caused by breathing in the air suspended with high concentrations of organic and inorganic pollutants is asthma.

Chronic Obstructive Pulmonary Disease (COPD) is usually triggered by the inhalation of sulphur dioxide and nitrogen dioxide.

Chronic bronchitis and lung cancer are long-term disorders that might be caused by sustained exposure.

These diseases can also be exacerbated by poor air quality. Pollutants also provide surface area for pathogenic microbes which can respiratory ailments like pneumonia.

1. Asthma

Asthma is a common respiratory disorder that affects people of all ages, but it most frequently begins in childhood.

In the United States alone, over 25 million people have been diagnosed with asthma and about 7 million of these individuals are below the age of 18.

Asthma denotes a chronic lung disease which affects the airways of the lungs, particularly by constricting (narrowing) them.

This disorder causes frequent periods of difficulties in breathing, wheezing, tightness in the chest, shortness of breath, and moderate to severe coughing. The coughing typically occurs at night or at dawn.

The airways are basically tubing that transport air into and out of the lungs.

People suffering from acute asthma have inflamed and narrowed airways which makes them rather swollen and quite sensitive to irritation.

Therefore, such people react quite strongly to certain inhaled substances.

Sometimes, asthma is restricted to certain families which implies the role of genes in the development of the disorder.

Other risk factors include low weight at birth, hay fever, as well as sex, as it is more commonly observed in younger boys. Children exposed to cigarette smoke might also develop asthma.

Currently, air pollution is a major risk factor for the onset of respiratory problems.

How does air pollution cause asthma?

The notion that outdoor air quality exacerbates pre-existing asthma in children has been supported by scientific evidence for decades but there has been new research which suggests that air pollution is a contributor for new-onset asthma as well.

In a 2013 study of 10 European cities, approximately 14% of the cases of incident asthma in children and around 15% of all exacerbations were attributed to vehicular emissions.

Reports have shown that elevated levels of air pollutants, such as those found in the large cities of India and China, have a major impact on the lungs.

These pollutants act as direct irritants and have an inflammatory effect on the airways of the lungs.

In fact, a 2006 study by the University of California, Irvine showed that certain pollutants such as nitric oxide, ozone, and PM2.5 (particulate matter with a diameter of 2.5 µm) can cause inflammation in the airways of the lungs which leads to asthma.

A 2009 study by Health Canada showed that oxidative stress is another feature of asthma that has been associated with long-term exposure to air pollutants, such as nitrogen dioxide and ozone.

This contact results in the formation of highly reactive free radicals which exacerbate the airway inflammation seen in asthma.

Therefore, air pollutants can cause oxidative injury to the airways of the lungs leading to inflammation and remodeling of the tissues.

If such alterations occur in an individual who is already genetically susceptible, it might lead to clinical asthma. Air pollutants might also enhance the risk of altered response to an inhaled allergen and increase sensitivities.

Read: Detail Article on Air Pollution and Asthma

Summary
Air pollutants cause oxidative damage to the airways of the lungs which leads to inflammation and remodelling of the tissues and, hence, can cause or exacerbate asthma.

2. Chronic Obstructive Pulmonary Disorder (COPD)

The chronic obstructive pulmonary disease is a mounting healthcare complication that has been projected to worsen as the average population ages and the global consumption of tobacco products increases.

As the disorder is characterized by a long asymptomatic phase, patients only seek medical attention when they reach an advanced stage of pulmonary dysfunction.

COPD is actually an almost irreversible disease of the lungs and is, therefore, one of the major causes of respiratory disease morbidity and mortality across the globe.

In fact, by the year 2020, it is estimated to become the 3rd leading cause of death worldwide.

The disorder is constituted by several clinical syndromes which all share the common characteristic of restricted expiratory airflow i.e., limitation in breathing out air.

This limitation is usually related to an unusual inflammatory response of the lung tissue to toxic particulates and gases .

Cigarette smoking, both active and passive, is the chief risk factor for COPD.

Barring indoor pollution, exposure to poor outside air laced with noxious chemical fumes, gaseous particles, dust, and other lung irritants are responsible for almost 20% of the cases.

People with a childhood history of pulmonary infections also stand at increased risks of developing COPD.

How does air pollution affect COPD?

Acute exposure to the main air pollutants like carbon dioxide, oxides of nitrogen and sulphur, ozone, carbon monoxide, and PM has been connected with increased respiratory risk.

A 2016 study by the University of Hong Kong investigated the role of several pollutants in exacerbating COPD by assessing single-pollutant models.

The risks of COPD were calculated for every 10µg/m3 increase in the concentration of the pollutants, such as ozone, nitric oxide, and many more.

The results showed that there was indeed a noteworthy relationship between the levels of ambient air pollutants and increased COPD risk.

It was inferred that during the course of ventilation and gaseous exchange in the lungs, these inhaled pollutants induce oxidative and inflammatory damage on the airways resulting in their dysfunction.

Studies have proved that pollutants such as PM generated by fossil fuel combustion can cause pulmonary inflammation and further impair the proper functioning of the lungs in COPD patients.

When exposed to high levels of atmospheric PM2.5, COPD patients were more likely to be admitted to hospitals due to breathing difficulties. A 2016 review by the Anhui Medical University showed that one of the main factors that exacerbate COPD  infection.

As PM can attach microbes on their surfaces, inhalation of such infected particles might contribute to worsening of the condition of COPD patients.

Pollutants also impair the resistance ability of the immune system to provide protection from such pathogens.

Read the Detailed article on Air Pollution and COPD

Summary
COPD is exacerbated by air pollutants as they bring about pulmonary inflammation and reduce lung functioning.

3. Chronic Bronchitis

Chronic bronchitis (CB) is a common phenomenon often observed in patients suffering from COPD.

It has several clinical outcomes which include an increased deterioration in pulmonary function, heightened risk of the development of obstructed airways in active smokers, a tendency to develop lower respiratory tract infections, higher chances of COPD exacerbation, and worsened overall mortality.

CB is caused by hyperproliferation and over-secretion of mucus (a slimy substance) by the goblet cells, which are column-shaped cells found in the respiratory lining.

This leads to worsening of the airflow obstruction, particularly of the small airways.

CB also remodels lung tissue and alters the surface tension of the airways increases the risk of collapse.

The principal risk factor of CB is smoking.

However, the recent scientific literature suggests that occupational exposures to noxious gases, biomass fuels, dust, fine particulates, and chemical fumes increase the likelihood of developing CB.

How does air pollution affect people with CB?

In the 1960’s, environmental researchers showed that outdoor air pollution was not the only reason for the sudden deterioration in patients suffering from COPD.

It was found that chronic bronchitis was more prevalent in highly polluted areas, which promoted the exacerbation of chronic respiratory diseases.

Several cross-sectional studies in adult populations were performed to compare the prevalence of respiratory symptoms in different areas.

The results showed that areas polluted with the oxides of nitrogen and sulphur recorded higher incidences of chronic bronchitis because these pollutants increase the secretion of mucus and induce an inflammatory response.

However, recent research has shown that CB is also caused by indoor air pollution.

A 2010 study at the University of Birmingham assessed the roles of different fuels in the development of respiratory problems.

The researchers found that exposure to solid fuel smoke, such as wood smoke, increased the risk of CB as compared to other fuels.

Hence, women performing domestic work were more susceptible to developing this disorder.

In line with this finding, another 2010 study by the Guangzhou Medical University found that the risk of CB was increased with exposure to solid/biomass smoke.

Several researchers also reported that chronic bronchitis was enhanced by vehicular emissions, which had high concentrations of gaseous particles.

Summary
Inhalation of solid/biomass smoke increases the risk of chronic bronchitis as the smoke contains irritants that stimulate over-secretion of mucus.

4. Lung Cancer

Lung cancer forms in the tissues of the lung, particularly in the cells lining airways.

The two major forms of lung cancer include small cell lung cancer (small and oval-shaped) and non-small cell lung cancer.

The three types of non-small cell lung cancer are squamous cell carcinoma, large cell carcinoma, and adenocarcinoma.

The typical symptoms of this type of cancer include severe coughing to the extent of coughing up blood, rapid weight loss, shortness of breath, and chest pains.

Lung cancer is one of the leading causes of cancer deaths across the globe and millions of new cases are diagnosed each year. Approximately 85% of the cases are due to long-term smoking.

Other risk factors include ingestion of toxic gases such as radon and sulphur dioxide, exposure to asbestos particulates, as well as a family history of cancer.

How does air pollution cause lung cancer?

Recently, outdoor air pollution has met with attention, particularly because research has established a connection between the exposure, even at low levels, to a wide array of adverse health impacts including rising mortality and morbidity from non-malignant respiratory diseases as well as lung cancers.

Over the past four decades, studies have shown that gradual exposure to outdoor air pollution has been linked to small but relative increases in lung cancer.

In a detailed study by the American Cancer Society (ACS) which investigated lung cancer deaths, it was reported that for every 10 μg/m3 increase in PM2.5, there was almost 8–14% increase in lung cancer.

Polluted urban air contains some known as well as certain suspected human carcinogens such as benzo[α]pyrene, 1,3-butadiene, and benzene and carbon-based fine particles on whose surfaces the carcinogens may be adsorbed, oxidizing agents like ozone and nitrogen dioxide, as well as oxides of both sulphur and nitrogen as fine, inhalable particles.

Increased incidence of lung cancer has also been recorded amongst workers occupationally exposed to air pollutants, such as polycyclic aromatic hydrocarbons (PAHs) and diesel exhaust.

Summary
Inhalable air pollutants often act as carcinogens which can induce the development of malignant cancers in the lung tissue.

5. Air Pollution Spreads Pneumonia

Pneumonia refers to a pathogenic (microbial source) infection of either one or both sides of the lungs. It causes the alveoli (air sacs) of the lungs to get filled up with a pus-like fluid.

Symptoms can range from mild to severe coughing along with chills, fever, a cough with phlegm (a slimy substance), and breathing difficulties.

Pneumonia tends to be particularly severe for vulnerable individuals, such as young children, elderly patients, people with medical conditions like heart failure, diabetes, or COPD (chronic obstructive pulmonary disease).

It can be fatal for people with weakened immune systems due to HIV/AIDS.

Recently, several lines of evidence have shown that air pollution plays a role in the propagation of this disease.

How does air pollution spread pneumonia?

In order to better understand the relationship between the high concentration of atmospheric particulates and the incidence of pneumonia, the Intermountain Medical Center and the LDS Hospital undertook a collaborative study involving patients from seven emergency departments.

The results showed that among the elderly patients, there was a positive correlation between the increase in PM 2.5 and instances of pneumonia.

Furthermore, ozone exposure and nitrogen dioxide were also found to be linked with a higher incidence of the disease.

It was inferred that atmospheric pollutants help to carry pathogens that cause the disease.

In a more recent study by the Hanoi University of Public Health, it was established that even short-term exposure to air pollutants like PM2.5 and noxious gases increased the incidence of pneumonia in young children which were marked by increased hospitalization.

Summary
Air pollutants can increase the risk of contracting pneumonia by providing surfaces to carry the pathogenic microbes and help in infection.

In the end..

To summarize, it can be said that air pollution affects the respiratory system in several ways.

The most common disorder caused by air pollution is asthma which occurs due to oxidative damage and inflammation of the airways. For the same reason, pollutants exacerbate chronic obstructive pulmonary disorders.

Particulate matter pollution also promotes over-secretion of mucus which worsens the condition of people with chronic bronchitis.

Air pollution also increases the risk of lung cancer as several of the pollutants act as carcinogens. Finally, it increases the risk of pneumonia by propagating the pathogens.

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Team AirHealth.in
Author

This article is written by AirHealth's team which consists of writers with degrees in medicine, biotechnology, pharmacy, nutrition, engineering, etc. The work is peer-reviewed by the core team or by our Advisors before it is published. Check out more about us in "Our Team" section.

2 Comments

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    My younger kid has been facing this since 2 years. Delhi pollution is severe , we now put air purifiers in our rooms but in winters even they don’t help much.

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