The air in Delhi is "foul" and unfit to breath even in the morning when walkers stroll out to seek fresh air, environment experts said Thursday demanding an immediate pollution control action.

Researchers at Centre for Science and Environment (CSE) monitored people's level of exposure to pollution in the city and found the results to be posing a "serious risk to public health".

Delhiites are "not safe" from polluted air even at home and workplaces, they said.

A 24-hour real time monitoring for a select group of people and patients suffering from asthma was carried out using a portable air quality monitoring equipment on assigned days during Nov 5, 2014 to Dec 9, 2014.

Their average exposure was found three times higher in certain cases when compared with ambient exposure levels measured by the Delhi Pollution Control Committee.

CSE director general Sunita Narain said: "This is a unique initiative to assess how much pollution people breathe on a daily basis in Delhi when the overall winter pollution levels are already high."

The level of exposure recorded in the case of lawyer Harish Salve confirmed that individuals are exposed to highest pollution levels during night and early morning, said a CSE statement.

Those suffering from respiratory problems and asthma were found to be particularly vulnerable, so were the walkers and cyclists who were also highly exposed to air pollution in the capital.

Anumita Roychowdhury, who heads the CSE air pollution control team, said: "The key lesson from this exercise is that exposure monitoring has to complement ambient monitoring to refine pollution control measures and reduce health risk."

As air pollution has been consistently rising over the years, a stringent road map suggested by the CSE called for implementation of the Air Quality Index and a nation-wide adherence to Euro IV emissions standards by 2015.

Controlled dieselisation with tax measures, marking Pollution Under Control certificate a prerequisite for annual vehicular insurance, testing private vehicles for their road worthiness, and diverting non-destined trucks away from the city were a few other measures offered by the CSE to control air pollution.