It would perhaps be wise to junk the perception that Delhi’s Lutyens’ zone with its wide tree-lined boulevards is less polluted than the city’s peripheral areas which are visibly dusty. A study has found a substantial presence of PM1 ultrafine particulates in the Lodhi Road area. These particulates are finer and potentially more harmful than the PM2.5 and PM10 particles, which have a larger presence in the capital’s air in terms of volume.
The monitoring station of the System of Air Quality and Weather Forecasting And Research (SAFAR) has recorded that the average volume of PM1 during summer, winter and the monsoon remain around 46, 49 and 20 micrograms per cubic metre respectively. However, it has not attracted much attention till now as the safe standards of PM1 have not been defined yet, in the absence of which its potentially harmful effects have not been documented, scientist Gufran Beig, the project director of SAFAR, told PTI. Presently, only SAFAR, which comes under the Ministry of Earth Sciences, monitors PM1 in the national capital.
“Globally you may not have a standard but PM1 is considered the most dangerous among all particulate matter, particularly because of its size. It measures around 1 micron or less in diameter. So it can enter deep into lungs and bloodstream,” chief of CSE’s air lab, Anumita Roychowdhury, said.
World over, scientists are yet to define standards using which one will be able to say in clear terms that PM1 above a certain limit can cause harm to the respiratory system as in the case of PM2.5 and the more coarser PM10. The prescribed 24-hour-average of PM2.5 is 60 micrograms per cubic metre while the same is 100 in case of PM10 in India and anything beyond that sets the alarm bells ringing.
But in the absence of any major source of pollution, why is the air in the Central Delhi area, with its lush greenery and manicured landscape, teeming with these particulates? The answer may lie in the fact that PM1 is a major product of vehicular combustion. And the roads in and around the Lodhi Road area like other parts of Lutyens’ see a huge flow of vehicles.
“The tinier the particle, the greater its share would be from combustion sources. If you profile the particulate matter emitted by diesel vehicles, more than 90 per cent would measure less than 1 micron,” Roychowdhury said. She said globally, governments are focusing on control measures at the source level of these particulates to eliminate them as far as possible, which will get a boost in India following the introduction of BS VI compliant vehicles in 2020.
“Under the BS IV emission standards, level of particulates are measured as gram per kilometre per vehicle. In case of BS VI, apart from the current mechanism, particulate matter coming out from a vehicle will also be measured. That is needed to ensure that diesel vehicles are equipped with particulate traps,” she said.