‘Nanoparticles from vehicle fumes can cause acute illness’: Study looks at 2021 Delhi data over two periods

In urban road environments, nanoparticles come mainly from the combustion process in automobiles, the study noted, adding that the concentration of these particles in urban roadside environments varies with human activity, particularly vehicular emissions.

The study, by Rajeev Kumar Mishra and Kanagaraj Rajagopal at the Department of Enviro-nmental Engineering, Delhi Technological University (DTU), and S Ramachandran at the Space and Atmospheric Sciences Division, Physical Research Laboratory, Ahmedabad, was recently published in the journal ‘Urban Climate.’

Noting that nanoparticles in the road environment can penetrate deeper into the respiratory system than other pollutants, the study stated that in urban environments, ultrafine particles of 1 to 100 nanometers can contribute up to 90% to the total particle number concentration.

For the study, researchers drew data from a monitoring station located adjacent to the DTU campus on Bawana Road in Northwest Delhi. The April to June 2021 period, which saw Covid-related restrictions, experienced around 31% less concentration of particles, the study found. The recorded vehicle fleet was found to be 49% less than the normal period during this time.

In the second period, which included Diwali, particle concentration increased by 35% compared to normal conditions due to “sudden rise in firework emissions,” according to the study.

Researchers also found that the size of these particles varies depending on sources. In the second period, when emission sources were more complex, the size of the particles ranged from 20 nm (nanometers) to 200 nm, while it was 15 to 80 nm in the first period, when emission sources were restricted on account of Covid restrictions.

Meteorology and other factors can also influence concentration of these particles: With rise in relative humidity, coagulation of these particles results in their concentration becoming high; high concentrations of these pollutants are found during peak morning and evening hours due to vehicular emissions; and higher wind speed can result in dispersion of these particles.

The study stated: “The PNC (particle number concentration) estimates will be useful to determine deposition of particles in the human respiratory system based on various inhalation rates and associated physical activities. The particles in the nano-size range, after deposition, can potentially be transported to other parts of the body, creating more chronic and acute illnesses. The quantitative outcomes of the present study can be used to estimate human health impacts, develop policies/standards, and initiate mitigation measures for pollution events with implications to climate change, and help move towards sustainability measures.