[This article has been originally published in Catalan in 'Espai Salut' newsletter of Diputació de Barcelona]
Our Lungs: The Filters
The part of the brain that controls the automatic process of breathing—called the respiratory centre—activates our respiratory muscles about 20,000 times every day, exchanging 500 millilitres of air with each breath. Therefore, the average adult filters approximately 10,000 litres of air every day.
The problem is that the air we breathe is not clean. Ambient (or outdoor) air contains, among other things, visible and invisible particles, chemicals and bacteria. Our bodies are adapted to deal with some of these pollutants: from the nose and mouth down through the various tubes that carry air to our lungs—the organ responsible for removing carbon dioxide and delivering the oxygen our bodies need—the respiratory tract functions as a mechanical air filter. However, despite this filtering system, some of the particles and gases that make up what we call ‘air pollution’ do penetrate our lungs.
What Happens When We Breathe Polluted Air?
As the incoming air travels through the airway from the nose to the lungs, some of the pollutants are trapped by filtering mechanisms, such as the hair-like cilia in the nose and the branching bronchi; however, some manage to evade these obstacles and reach the pulmonary air sacs. These particles cause irritation in the lungs when our immune system recognises them as foreign bodies and responds by generating inflammation in an attempt to expel them, a defence mechanism that can damage the lungs.
These particles cause irritation in the lungs when our immune system recognises them as foreign bodies and responds by generating inflammation in an attempt to expel them, a defence mechanism that can damage the lungs
Scientific advances are helping us to gain a better understanding of how pollution damages our bodies. We now know that some particles eventually pass through tiny orifices in the lungs, enter the bloodstream and travel to other organs. Some of these are trapped by other filters, such as the kidneys, heart, brain and bones, or are neutralised by our immune system, which attacks foreign bodies and stores them in immune cells. However, it has recently been observed that some of these pollutants do reach the placenta and the foetus, and can even penetrate our brains.
The problem is that, once they have penetrated our organs, it appears that these foreign bodies cannot be eliminated. This means that they accumulate, creating a chronic and continuous low level inflammation that has a negative impact on our health.
This illustration is taken from the digital report #CitiesWeWant.
How Does Polluted Air Affect Our Health?
The lungs are the organs most exposed to the air we breathe, so they are inevitably one of the organs that sustain the most damage from pollution. As a result, pollution particularly affects people with respiratory diseases because bronchitis, asthma, chronic respiratory diseases and all the allergic diseases (rhinitis, for example) tend to be exacerbated by any increase in pollution levels. Pollution also disrupts the removal of mucus from the lungs, favouring infections like pneumonia.
The lungs are the organs most exposed to the air we breathe, so they are inevitably one of the organs that sustain the most damage from pollution
The heart is another vital organ affected by pollution. On days when air pollution levels are high, the release of stress hormones and local inflammation make us more susceptible to sudden cardiac death, arrhythmias, myocardial infarction and stroke. Chronic inflammation also accelerates the aging process and causes our arteries to harden, making it easier for cholesterol to stick to the artery walls. This may explain why air pollution is also associated with chronic cardiovascular conditions, such as hypertension, angina pectoris and heart failure.
Air pollution has been shown to be linked to impaired attention, poor school performance and dementia; all those who live in areas affected by high levels of pollution—from young students to individuals of advanced age—are also at higher risk of accelerated loss of cognitive ability.
Finally, pollution also affects the cells in our body that replicate constantly and has been associated with hair loss, eye irritation, poor sperm quality and low fertility rates.
What Should We Do to Combat Air Pollution?
Given that an adult filters about 10,000 litres of air per day, we can say without fear of exaggeration that we are all exposed to the effects of air pollution. And, since we cannot stop breathing, we urgently need to address the sources of this pollution and to reduce ambient levels.
Given that an adult filters about 10,000 litres of air per day, we can say without fear of exaggeration that we are all exposed to the effects of air pollution
From a scientific standpoint, there is no doubt that the air in our cities is harmful to our health, making it urgent to take the logical leap from scientific evidence to political action. Improving the quality of the ambient air in our cities must be a top priority for governments, municipal authorities, and urban planners. The health risks associated with breathing polluted air are too serious for us to just shelve the problem and do nothing.