Medical literature as well as public opinion has hitherto focused on the ill effects of air pollution on the respiratory system. Almost everyone staying in the pollution affected areas knows about the risk of aggravation of asthma, respiratory distress and frequent respiratory infection due to air pollution. Respiratory side effects of air pollution were one of the main reasons for the introduction and implementation of the odd-even traffic formula in the Delhi-NCR region.
Relatively lesser known to the general public are the side effects of air pollution on increasing cardiovascular complications. This article focuses on the adverse cardiovascular effects of air pollution.
What is air pollution?
Air pollution refers to the presence of any particulate matter other than the natural gases present in the atmosphere. Pollutants can be of various sizes. Larger particles – above 2.5 PM (micrometers) – can be filtered by human lungs and hence predominantly harm the respiratory system. Particles below the size of 2.5 PM (which is roughly equal to 1/30th the size of a human hair) can bypass the filtering capacity of lungs, into the circulation and thereby affect the cardiovascular system directly. It is important to know the difference in these particle sizes as the sources (and hence exposure) of these pollutants are different.
How does air pollution affect the heart?
Air pollution can have both immediate ill effects as well as long term deleterious cardiac effects.
Broadly speaking, air pollution can negatively impact all three components required for the smooth flow of blood through circulation. It can directly damage the blood vessel wall thereby causing precipitation acute events, thickening of the blood, and also cause an increase in the stiffness of the blood vessels, thereby making blood flow less adaptable to the requirements of the heart. On the demand side, by increasing the stiffness of the heart as well as an increase in blood pressure, air pollution can lead to a higher oxygen demand. Finally, pollutants also increase the irritability of the heart leading to irregular beating of the heart (arrhythmias).
The impact of these changes can be seen with the increase in the incidents of heart attacks, increased heart failure (both systolic and diastolic), increased incidents of strokes as well as higher incidents of arrhythmias during the high air pollution months.
How can one protect himself/herself from the ill effects of air pollution?
The answer to this question lies in two different kinds of modifications:
- Generic or large scale
Generic modifications are those which include efforts at reducing air pollution on a larger scale – such as reducing the impact of industry (including agricultural industry), legislation, restriction in use of vehicles and other similar measures.
On a personal level, modifications include restricting visits to polluted areas, choosing to travel or exercise through less polluted regions and using a face mask (particularly with PM 2.5 grading). Additionally, one must avoid going outdoors during periods when the air tends to be thicker – such as early morning or late evening (particularly during winter months).
There are two additional questions that often crop up during discussions about air pollution:
- Does the positive impact of exercise neutralise the negative impact of air pollution?
This is a tricky question because there is a large inter-person variability in the beneficial impact of exercise versus the negative impact of air pollution. Nevertheless, it’s a good idea to exercise indoors – particularly during high pollution days or chose a less polluted outdoor area, if one is addicted to outdoor exercise.
- Does a face mask protect against air pollution?
A face mask – even with a PM 2.5 grading – only partially protects against air pollution.
To conclude, air pollution is an under-recognised risk factor for heart disease and also a factor whose impact is less understood and less studied. Coupled with the winter season, air pollution can cause serious complications for the cardiovascular system.
The writer, Prof. (Dr.) Hemant Madan, is a Senior Consultant & Director Cardiology at Narayana Superspeciality Hospital, Gurugram