The Centre has described the smog that recently engulfed the Capital as "an extreme pollution episode" and blamed "both man and metrological conditions" for its effects.
The government has admitted such conditions lead to "increased frequency of respiratory-related asthmatic troubles" in the elderly and children and advised them to ensure reduced exposure to minimise adverse effects during smog periods.
The union ministry of earth sciences has done a scientific analysis of the thick smog cover that covered the Capital for 12 days (October 26 to November 8, this year).
"It was due to short-range transport of smoke from Punjab and Haryana. The smoke caused by burning of crop stubble in the harvesting season of 'kharif' moved towards Delhi due to favourable northerly winds as determined from back trajectory analysis and air quality forecasting," the study says.
At a meeting with the Supreme Court-appointed Environment Pollution Control Authority, officials from Delhi, Uttar Pradesh, Punjab and Haryana have decided to enforce a ban on the burning of farm waste.
The study says low wind speed in and around Delhi prevented the dispersion of smoke particles. These particles remained trapped in the layer above the ground.
"Incrementally, diesel-operated urban transport adds to the air pollution levels that reduces the visibility further," it says. But after the wind speed got back to normal, the pollution levels dipped.
The ministry has said the government is already taking possible steps to discourage diesel-run public transport, encourage CNG-run vehicles and enforce stricter emission norms.
The Delhi government has already decided to install electronic display boards for air quality index, issue smog alerts and health advisory across the Capital.