Project in-charge Pawan Kumar Bhartia explains the Nasa study report. Picture by Aranya Sen

An ongoing global air pollution study by the US-based National Aeronautics and Space Administration (Nasa) has found that carbon monoxide emitted by cars combine with nitrogen dioxide present in the city atmosphere to cause serious damage to human lungs.

The research, being carried out by the Ultra Violet Remote Sensing Group under the atmospheric chemistry department of Nasa’s Goddard Space Flight Center, has also revealed that the bulk of Calcutta’s dust particles come from West Asia and the neighbouring regions.

The study, in its first phase, is being conducted with the help of Ozone Monitoring Instrument, a satellite recording images of air pollution across the globe.

“The images recorded before monsoon confirm that the dust particles in Calcutta and other parts of the Gangetic valley are blown in from outside,” explained Pawan Kumar Bhartia, in charge of the project. “We are in talks with Indian Space Research Organisation and other Indian research institutes for studies on the ground and sea level. Investigation into India’s air pollution is a complex process, as the direction of air flow changes through the year.”

The satellite images show presence of layers of nitrogen dioxide and aerosols in the city’s atmosphere. Nitrogen dioxide, in the presence of sunlight, forms ozone, which is extremely harmful for crops and lungs. While nitrogen dioxide cannot move from one place to another, ozone flows to other areas. “It is to be seen how much of the thick layer of ozone over Calcutta has flown in from outside,” said the Nasa scientist. The aerosol consists of solid dust particles and sulphuric acid. “The dust particles are blown over the northern part of India to Calcutta before they move south towards Bay of Bengal,” added Bhartia.

According to him, dust particles can travel 700 to 800 km in a day, which means they will take only a couple of days to travel from Delhi to Calcutta.