mumbai

Updated: May 07, 2018 09:58 IST

The city’s air is full of deadly, tiny pollutant particles that are less than a micrometre in diameter — a human hair is 100 micrometres — a new study of air pollution levels in three Indian cities found. Just days earlier, the World Health Organization (WHO) declared Mumbai the fourth most polluted mega city in the world.

So just how harmful are these particles, called particulate matter 1 (PM1), and why should it worry you?

“PM1 particles are like micro needles that can travel to different organs of the body through our blood,” said Gufran Beig, project director, System of Air Quality Weather Forecasting and Research (SAFAR), which conducted the study.

The study found that Mumbai recorded the highest concentration of PM1 in the larger PM 2.5 pollutants that float around in the air, across seasons in 2017. PM 2.5 are slightly larger particulate matter — 2.5 microns in diameter — and are also harmful as they easily enter the lungs. Unlike PM2.5, and the even larger, coarser PM10, there are no international or Indian standards determining a safe limit for PM1.

This means, calculating its levels as a part of PM2.5 is one of the few ways to assess how much damage it can do to the human body. The study found the average concentration of PM1 in PM2.5 was the highest in Mumbai (50%) in summer, winter and monsoon 2017.

In Delhi, it was 48% and in Ahmedabad, 38%. “The high concentration of PM1 in Mumbai’s air is a health concern because 50% of the PM2.5 pollutant in Mumbai’s air is made up of PM1,” Beig said. “This is dangerous for all citizens, but especially children and senior citizens.” Beig said that while the overall concentration of PM1 levels in Mumbai was lower than Delhi’s, its high concentration in PM2.5 showed that more citizens were breathing polluted air.

Further, the probability of inhaling PM1 particles is high as they stay suspended in the air and closer to the surface much longer when compared to coarser particles that get dispersed faster, Beig said.

According to the SAFAR study, the share of PM1 in PM2.5 for Mumbai during the monsoon and summer was 67% and 46%, the highest among all three cities. Delhi recorded 61% during the monsoon and 44% during summer, while Ahmedabad saw 40% and 35% during both seasons. During the winter, Delhi saw the highest concentration of PM1 in PM2.5 at 47%, followed by Mumbai and Ahmedabad at 46% and 41%. Meanwhile, the average individual concentration of PM1 in 2017 was the highest in Delhi at 48 microgrammes per cubic metre (µg/m3), followed by Mumbai at 30µg/m3 and Ahmedabad at 27µg/m3. “The individual concentration of PM1 is not indicative of a pollution problem as there is no safe limit for the pollutant. However, when the concentration is high within PM2.5, it shows how citizens are exposed to these tiny, deadly small pollutant particles,” said Beig.

READ: PM2.5 in Mumbai in 2017 was six times the safe limit: SAFAR study

Where is PM1 coming from? SAFAR found the major source as the transport sector.

“Vehicular emissions at busy traffic junctions are the main source of PM1 in PM2.5. This can be tallied as the number of vehicles in Mumbai and Delhi is much higher as compared to Ahmedabad,” said Beig, adding the three-city study highlighted the sources of PM1 that need to be controlled in order to reduce this ‘invisible killer pollutant’. “During the summer and monsoon months, owing to high humidity and low wind speed in Mumbai, pollutants remain suspended close to the surface longer. The other source of this pollutant, mainly observed in Delhi and some parts of Mumbai was bio-fuel emissions, most likely be black carbon from domestic cooking. Higher the fossil fuel emissions, worse is the PM1 problem.” Doctors said health ailments such as chronic obstructive pulmonary disease (COPD), bronchitis, hypersensitivity pneumonitis (inflammation of lung tissue) and asthma are all triggered as a result of these ultrafine particles.

“PM1 particles can damages our respiratory system the most, as compared to any other pollutant. Our cerebral system can also be affected as these particles are minuscule and can travel through our bloodstream,” said Dr Sanjeev Mehta, pulmonologist and senior specialist, Lilavati Hospital, Bandra.