In response to a Parliament question, the Union environment minister Prakash Javadekar in his written response in Lok Sabha said a comprehensive set of actions following an integrated approach was required to make substantial improvement in air quality.

Noting that the decision on implementation of odd-even scheme is within the purview of state\UT governments, Javadekar said the Central Pollution Control Board (CPCB) had assessed the impact of the scheme, launched by Delhi government from January 1-15 this year.

"The assessment of CPCB has revealed no clear trend and wide fluctuations were observed in the concentrations. It is evident that the meteorology and emissions from other polluting sources have been major factors impacting air quality of Delhi during the period", the minister said.

"Overall it can be stated that while some reduction in air pollution is likely to happen due to odd-even scheme, a single factor or action cannot substantially reduce air pollution in Delhi. Therefore, a comprehensive set of actions following an integrated approach is required to make substantial improvement of air quality," Javadekar said.

Asserting that an overwhelming majority of respondents were in favour of the vehicle-rationing scheme, Delhi chief minister Arvind Kejriwal had, however, earlier announced that the second phase of the odd-even scheme will be implemented in the city from April 15 to 30.

He had said government was "seriously deliberating" on the idea of enforcing the scheme every month for a fortnight, while admitting the city's public transport was not capable of handling the resultant passenger rush. Responding to another Parliament question, Javadekar also downplayed Greenpeace India's recent report which said India overtook China's air pollution levels in 2015 and said the study was based on "extrapolated and constructed" data "without" field validation.

"The Greenpeace India published a report titled 'Clean Air Action Plan: The Way Forward' in February 2016. The report is on the basis of NASA satellite data which is based on extrapolated and constructed data without field validation," the minister said in a written reply.

The Greenpeace's analysis said India had overtaken China's air pollution levels in 2015 and its average particulate matter (PM) exposure was higher for the first time in the 21st century.

"China's strong measures to curb pollution have contributed to the biggest year-on-year air quality improvement on record while in contrast, India's pollution levels continued a decade-long increase to reach the highest level on record," it had said.