Have you ever wondered why your throat feels clogged, your nose feels stuffy, and your cough gets worse after entering polluted areas? Could the air we always breathe be linked to a higher chance of viral respiratory infections? You may be onto something, the science included in this article will answer this question.

Air pollution is a prevalent issue particularly in urban areas, significantly increasing the risk of another major public health issue labelled as acute viral respiratory infections. Environmental factors can play a huge role in impairing our natural defence systems, including our respiratory airways. Constant exposure to these harmful pollutants could manifest in a multitude of health issues, especially for vulnerable people like children.

The link between a poor environment and obtaining acute viral respiratory infections has a deeper connection than you may think. Find out what factors are influencing these conditions and the best ways to avoid the consumption of harmful pollutants when living in an urban environment. 

Air pollution and its impact on health

The environment we live in has a significant impact on our overall health, with respiratory infections affecting many qualities of our lives. Air pollution is a staggeringly increasing public health concern affecting millions across the world.¹ Subjecting these harmful pollutants into our system through inhalation has been associated with various respiratory diseases like asthma, especially for children living in urban areas.¹ Amongst the myriad origins of pollution, road traffic pollution remains a ubiquitous feature in urban areas, posing a substantial threat to public health due to elevated exposure levels of particulate matter and harmful pollutants.² According to the World Health Organization (WHO), 99% of the population lives in areas exceeding air quality guidelines, with overpopulated and developing countries bearing the impacts of this burden, resulting in 4.2 million premature deaths attributable to ambient air pollution.³ As the population continues to grow, the overuse of cars and transportation systems increases the concentration of harmful pollutants in the air, degrading the air quality that we breathe.⁴

Respiratory diseases emerge as a formidable challenge too, where asthma reigns as the most dominant affliction, impacting approximately 14% globally.⁵ Acute viral infections are a prominent disease worldwide, affecting mostly children.¹

Traffic-related air pollution (TRAP): what are the harmful emissions?

Air pollution is a combination of emissions from both natural sources and man-made resources.⁶ A common form of air pollution is caused by vehicle emissions, where road pollution is known to contribute to over 50% of NO2 emissions.^6,7

Common pollutants include sulphur dioxide, nitrogen dioxide, carbon dioxide, carbon monoxide and volatile organic compounds (VOCs).⁷ Another common exhaust particularly from diesel fuel is Black Smoke, which was observed to have relevant associations with detrimental respiratory effects.⁸

Ozone, a secondary pollutant that forms through nitrogen dioxide in the atmosphere that reacts with sunlight, can severely irritate the airways leading to potential breathing difficulties and worsened conditions for asthmatics.⁹ Acute ozone exposures have been correlated to the manifestation of the influenza A virus.¹ It is evident that these harmful pollutants can lead to a cascade of negative consequences, which are even more pronounced in overcrowded urban areas.⁸

The limited number of green spaces available in urban areas makes it difficult to counteract the astronomical number of pollutants that fill the air and keep it clean, exacerbating the situation of eliciting various health conditions.¹⁰

Air pollution and its link to viral respiratory diseases

COVID-19

The world faced unimaginable fates with COVID-19, alongside wildfire spread across the western United States.¹¹ Those exposed to increased particulate matter through air pollution from wildfires were shown to have a greater susceptibility to COVID-19 and a higher risk of death.¹¹ Furthermore, exposures to carbon monoxide and nitrogen dioxide were shown to have associations towards experiencing COVID-19.¹ This may support the strong correlation between air pollution and acute viral infections. 

Chronic bronchitis

It was found that women exposed to high concentrations of nitrogen dioxide and other particulates had increased cases of chronic bronchitis; a persistent cough that could last for months.^6,12 This shows that gender differences may exist, which will be discussed later in this article. 

Influenza 

Subjection to PM_2.5 has been shown to increase the chances of exposure to influenza, particularly in winter months when temperatures are low.¹³

Vulnerability in children

Studies have shown that children and infants are particularly vulnerable to the adverse effects of road traffic, due to their developing respiratory systems, alongside higher respiratory rates, inhalation rates and baseline metabolic rates in comparison to adults.^14,15

However, respiratory illnesses often present with overlapping symptoms, such as wheezing which has been commonly associated with viral illnesses in children, affecting approximately 30%.¹⁶ Exposure to secondary smoking, such as parental smoking, could introduce over 7000 harmful chemicals that can trigger asthmatic symptoms.² Underlying genetic predispositions in conjunction with exposures to road traffic pollution could further influence the development of respiratory illnesses in children too.²

How does this happen?

The particles in these harmful pollutants may consist of reactive oxygen species (ROS), known to stimulate inflammation in the airways that we breathe in.¹ The conjunction of air pollutants with viruses can elicit the development of various respiratory illnesses and hyperreactive responses.¹ Toxicological reports and controlled experiments strongly displayed correlations between harmful diesel particulate matter and IgE-mediated allergic reactions, conveying a clear health response to road traffic pollution.¹⁷ A toxic environment has the power to alter our immune responses, allowing easy penetration and infection of our respiratory systems.¹

Gender risk variations

Studies have shown consistent patterns of gender-specific variations in the association between road traffic and respiratory illnesses, with stronger links observed in girls.¹⁸ Physiological differences, including larger respiratory airways relative to lung size in girls, may indicate a potential reason for this.¹⁸

Socioeconomic backgrounds

Environmental risks persist worldwide, however, with a disproportionate influence on middle, and low-income countries.¹⁵ Studies consistently demonstrate that children from low socioeconomic backgrounds have a heightened vulnerability to road traffic pollution compared to their affluent counterparts, presenting the significance of socioeconomic aspects in respiratory diseases.¹⁹

How can I prevent this?

There are a couple of ways you limit your exposure to harmful pollutants. Advising the public to select low-traffic routes, keeping windows closed whilst driving through high-emission areas and utilising filtration systems are promising ways to handle this issue.² Opting for low-emission vehicles or electric cars is a sustainable way to help yourself and your environment.²⁰

Addressing alternative factors that also exacerbate respiratory illnesses, such as indoor pollution and secondary smoking, through the promotion of air purifiers and educating families about the effects of secondary smoking, can collectively make a difference in improving respiratory health outcomes in children and our lives.²

Summary

Air pollution, a major environmental risk factor, is known to play a distinct role in exacerbating respiratory illnesses and various other conditions including asthma, lung cancer and other cardiovascular problems.²¹ Alongside acute effects, long-term damages to our DNA and lungs are noticed, highlighting the severity of this issue.¹

FAQs

What are the environmental conditions that lead to the infection of the respiratory tract?

The main one that we spoke about in this article today is air pollution, where traffic-related air pollution (TRAP) makes up a huge majority. Exposure to harmful pollutants can induce various respiratory illnesses due to inflamed airways and a weakened immune system, allowing viral pathogens to harvest.

Does indoor pollution affect the respiratory system?

Yes, various other environmental factors can induce respiratory illnesses, including lung cancer and asthma. Cooking with solid fuels, open fires, smoking, or secondary smoking are some examples.²² People who already have lung disease are at greater risk of respiratory illnesses.²³

What are the main pollutants that I should be aware of?

Carbon dioxide, carbon monoxide, nitrogen dioxide, and volatile organic compounds (VOC) are some pollutants with evident effects on respiratory health.²⁴ More coarse but harmful pollutants are PM_10-2.5, which can penetrate deeper into the lungs.²⁴ However, there are many other pollutants from vehicle emissions that need further studies on the effects.