As Delhi Chokes on Smog, Know Your Pollutants—PM 2.5 and PM 10

Particulate matter is the pollutant that, as per the WHO, causes maximum damage to human health. The basic difference between PM 10 and PM 2.5 is size and consequently the sensitivity of instruments required to measure them. PM 10 particles are those with a diameter of 10 microns or less, and PM 2.5 are those with diameter of 2.5 microns or less.

It primarily consists of “sulfate, nitrates, ammonia, sodium chloride, black carbon, mineral dust and water”.

Why are they harmful?

Both can lead to the risk of developing cardiovascular and respiratory disease as well as lung cancer, says the WHO. Both can penetrate the lungs, but the PM 2.5 goes a step further and due its small size can "cross into the blood, causing damage in many organ systems," found the WHO.

Why is air pollution dubbed a 'silent killer'?

Unlike toxic gases, long term exposure to poor air quality can result in eventual death. Depending on the age groups, poor air quality can rapidly deteriorate a person's life by having an adverse impact on how key organs function.

For instance, the entry of pollutants into the blood vessel can lead to the formation of thrombosis—a clot inside a blood vessel that obstructs the flow of blood. Other studies have linked air pollution to a number of diseases, ranging from strokes to nuero-degenerative illnesses.

Who is most at risk?

The most vulnerable groups include newborns, children, pregnant women and those with pre-existing health conditions such as asthma, chronic bronchitis, diabetes and cardiac diseases. Increasingly studies have confirmed that high levels of pollution leads to issues during child birth—ranging from premature birth to miscarriages.

Are those who are otherwise healthy also at risk?

Yes. High levels of pollution impacts those with no history of respiratory diseases as well. The most common symptoms are breathlessness, watering of eyes and nose, burning sensation in eyes, excessive cough, headaches and lethargy.

Increasingly, doctors have diagnosed non-smokers with 'smokers' cough'—the result of perfectly healthy persons suffering from chronic cough due to inflammation of the air tract after foreign particles have lodged themselves in there. Air pollution will also decrease lung function in all age groups, studies have found.​