“Air pollution could be one of the triggering factors for respiratory ailments and associated diseases,” he said in a statement to Parliament, “However, there are no conclusive data available in the country to establish direct correlation between diseases and air pollution.”

In the past months, the minister has stirred a controversy by expressing reservations about the findings of foreign studies that are widely cited in the media to highlight the air pollution problem in India.

“While the levels of Particulate Matter shows fluctuating trend, the value of SO2 (sulphur dioxide) is reported to be generally within the permissible limits,” he said. “Values of NO2 (nitrogen dioxide) are also generally within permissible limits except for few cities.”

He reiterated the ministry’s stand that ozone pollution is within permissible limits in India.

Central Pollution Control Board (CPCB) data showed that the average NO2 levels for 2015 were higher than the national standards in only Delhi and West Bengal.

PM10 (particulate matter-10 micrometres or less in diameter) concentration, however, was higher than prescribed norms for all states and Union Territories except five, Goa, Kerala, Meghalaya, Mizoram and Puducherry.

For Delhi, PM10 annual average concentration was almost four times (220 µg/m3) higher than the permissible limit of 60 µg/m3.

Data for PM2.5 (particulate matter 2.5 micrometres or less in diameter), which is a more pernicious particle that penetrates deeper into the lungs, was not provided.

NO2 irritates the airways and lungs and exacerbates asthma. Children and elderly populations are at higher risk. This oxide is also known to chemically react with other pollutants and produce particulate matter and ozone.

The issue of ozone pollution has become contentious in recent days, with the government claiming that ozone levels were within safe limits for 2016. He countered claims made by the State of Global Air report released earlier this year that India had the highest number of ozone pollution-related premature deaths, with 107,770 deaths in 2015 being directly attributed to ozone pollution.

“The data collected shows that ozone levels have not exceeded the permissible level of 100 µg/m3 at any of the locations during the year 2016,” he noted, “Since the concentration of ozone is less than the permissible limits, the reports published need to be correlated with the data and scrutinised before arriving at any conclusion.”

Closer examination reveals that data on ozone pollution furnished by Central Pollution Control Board gives the annual average of ozone concentration, while the National Ambient Air Quality Standards prescribes a100 µg/m3 norm for 8-hour average concentration.

Expanding on the argument that deaths cannot be directly linked to air pollution, Dave described health impacts as “generally synergistic manifestation of the individual’s food habits, occupational habits, socio-economic status, medical history, immunity, heredity, etc.”

Reacting to similar comments made by the minister last month, Sunita Narain, director general of Centre for Science and Environment, said, “There is more than enough evidence across the world that air pollution kills, “If the Indian minister is in denial it is extremely unfortunate.”

“This suggests that we need to keep the pressure on the government, it is easy for them to stick their neck in the sand. We don't need our governments to be complacent,” she added.