Oxygen is vital to the human body for survival, and we depend on air (atmospheric oxygen) for breathing. But the air we inhale now consists of a combination of dust, pollen, mould, dirt, soil, and numerous other compounds that can lead to various diseases. The consequent ailments usually start with mild presentations that accumulate over time. These may result in intense manifestations, including an elevated risk of cardiovascular diseases.
Proportion of oxygen in ideal air best for health is approximately 21% (ref. link). The remaining part of the air comprises nitrogen, argon, and carbon dioxide. Nitrogen and argon are inert and hence redundant. Other constituents include volatile organic compounds from vegetation and natural events, such as volcanic eruptions or wildfires. The fusion of these components constitute the ideal composition of air for humans to stay healthy and devoid of diseases.
Currently, the air we breathe is not ideal for optimal health, with significant evidence of air pollution and global warming. Vehicles, manufacturing industries, and other human activities are the main sources of the emission of poisonous substances. Air pollution is one of the most pertinent global concerns right now. In 2019, about 12% (ref. link) of global deaths were attributed to household air pollution.
A study demonstrated an increase in cardiovascular diseases from 0.5 to 1.5 % (ref. link) for every boost in particulate matter as low as 5 micrograms per cubic metre. This particulate matter is invisible to the naked eye and results from chemical reactions between pollutants. For example, sulphur dioxide and carbon dioxide reactions are ejected from automobiles, the combustion of materials, and industrial processes.
In 2021, the WHO released air quality guidelines (ref. link) recommending permissible concentration of pollutants.
The absorption of harmful chemicals that enter our bodies through food or water depends on the barriers that it encounters while passing through the gastrointestinal tract. On the other hand, the air that we inhale directly meets internal structures within the lungs; along the inner surface of windpipes and finally alveoli where exchange of oxygen and carbon dioxide occurs. Minimal obstacles enable the constituents, including pollutants, to enter the bloodstream.
Eventually, the blood passing through the lungs reaches every part of the body, affecting the organs. However, the heart can be the most affected (ref. link) as blood from the lungs reaches the heart before being pumped to other parts. This means to pollutants are at the highest concentration they will be at in the body, while in the heart. Mentioned below are a few ways in which the air quality can affect the heart:
Prolonged exposure to air polluted with carbon dioxide, ozone, carbon monoxide, and particulate matter increase systolic and diastolic blood pressure (ref. link). Many studies conclude positive correlation between pollution and high blood pressure.
Oxidative stress is one of the predominant pathways underlying cardiovascular diseases due to air pollutants. Several epidemiological and controlled exposure studies have produced strong evidence that supports the finding. Let us know more about cardiovascular events resulting from poor air quality.
The tone of blood vessels plays a crucial role in homeostasis, which refers to altering body functions in response to an undesirably dynamic environment or changes within the body itself. Some homeostatic responses need changes in blood vessel tone, especially arterioles. Pollutants in circulation disturb the endothelium, an interface between blood and blood vessels. This leads to the loss of endothelial response to dilators which increases the blood flow rate and reduces blood pressure. As a result, chronic cardiovascular diseases set in.
Another mechanism involves nitrogen monoxide (NO) scavenging activities of superoxide pollutants. Depleting NO and inhibiting NO-releasing vasodilators reduce vasodilation activity leading to elevated blood pressure. Many studies (ref. link) have demonstrated that individuals exposed to different types of air pollution have higher levels of biomarkers of oxidative stress in their blood and in urine samples.
Endothelial dysfunction caused by the pollutants forms the basis for another condition called atherosclerosis. Loss of endothelial function and expression of adherent molecules attract circulating inflammatory cells to the vascular walls. Inhibition of NO promotes the oxidation of lipids in the blood, and the inflammatory cells retain the resulting product.
The accumulation of the cells and oxidised lipids form plaques that grow into the lumen. It narrows the blood vessels and increases pressure. The plaques grow and may erode or rupture. The erosion leads to a blood clot and may occlude arteries, which can lead to cardiovascular events such as a stroke or heart attack.
When you’re bleeding, the process of blood clotting is actually life saving. However, the body regulates it to prevent cardiovascular conditions caused by thrombotic obstruction of arteries. Many studies have shown pollutants to elevate activities of blood clotting factors that pose high risks for thrombosis.
The heart supplies blood to its muscles via coronary arteries. The prolonged oxidative stress due to substandard air quality alters coronary circulation and weakens cardiac muscles. It ultimately renders the heart unable to deliver blood to meet the body’s needs. The substantial loss of cardiac function is called heart failure. The organ tries to compensate for the loss of function, But it reduces contractility and pressure on the coronary artery. A meta-analysis found an association between air pollution and the incidence of heart failure.
Conditions in coronary arteries, such as atherosclerosis and thrombosis, limit blood supply to cardiac muscles. It deprives a part of the heart muscles of oxygen, and the fibres die, which is called Myocardial Infarction (MI). Unlike cardiac remodelling, MI does not lead to heart failure shortly. Many studies have linked NO2 and PM25 exposure with risks of myocardial infarction.
Air quality has a significant influence on the heart. Respiration is an indispensable process, but is difficult to manipulate. Hence, improving the quality of ambient air and having low exposure to pollutants are the only options to safeguard your heart. Devices like air purifiers are plausible options, but only for small places like homes.
Dirty or polluted air can cause various health related problems, especially in the cardiovascular and respiratory systems. Due to the added stress, the heart is required to work harder to pump enough blood and circulate oxygen throughout the body. The issues can be severe for people already suffering from underlying heart (ref. link) conditions
The presence of air pollutants can be damaging to the heart (ref. link) in more ways than one. The harmful pollutants can lead to heart diseases such as artery blockages which eventually lead to heart attacks. Further, due to oxygen deprivation there can be severe damage to the heart in the long run.
Air pollution and a bad air quality index directly impacts (ref. link) heart health. Study shows even a slight drop in the air quality can lead to increased cases of heart arrhythmias and palpitations.
Fresh and clean air cleans the lungs and de-stresses the cardio and respiratory systems. It even helps in decreasing (ref. link) the heart rate.
A study has shown that poor air quality or air pollution leads (ref. link) to elevated blood pressure levels. People with other underlying medical conditions are more prone to be affected by high blood pressure owing to poor air quality.