New DelhiA recent study has found a substantial presence in the ultrafine particulate matter PM1, a dangerous pollutant, in Central Delhi.The PM 1 particle is 70 times finer than the thickness of a human hair, goes directly into the bloodstream and is potentially more dangerous than the more well known PM2.5 and PM10 pollutants. And no one knows how much of it is in the air we breathe.The Lodhi Road monitoring station of the System of Air Quality and Weather Forecasting And Research (SAFAR) under the Ministry of Earth Sciences has recorded the average volume of PM1 during summer, winter and the monsoon at about 46, 49 and 20 micrograms per cubic metres, respectively. The data from the year 2016 is collected in the only station that has the technology, says Gufran Beig, project director of SAFAR.The safe standards of PM1 have not been defined yet, in the absence of which its potentially harmful effects have not been documented. Globally, too, there might not be 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 and can enter deep into the lungs and bloodstream.According to a Central Pollution Control Board 2010 study, small particulate matter can reach the alveolar region, causing heart ailments. These fine particles cover a large surface area, absorb toxic compounds such as heavy metals and organic compounds with high carbon content, the study said.These particles — spewed primarily from vehicles, factories and construction sites — are not dispersed and stay suspended in the air.But why is the air in Central Delhi flooded with these particulates?“PM1 is a major product of vehicular combustion. Roads in and around the Lodhi Road area like other parts of Lutyens’ Delhi see a huge flow of vehicles. This might be the reason behind the prevalence of this finer particulate matter. It also depends on where the station is located, the dispersion capacity, meteorological factors, among others,” Dr Dipankar Saha, additional director and head of the Air Laboratory at the CPCB told Hindustan Times.