At a meeting today chaired by Union Environment Minister Prakash Javedkar which included his counterparts from the states of Haryana, Uttar Pradesh and Rajasthan, Delhi Environment Minister Asim Ahmed Khan said that air pollution does not recognise geographical boundaries.

At any point, air pollution is caused by several sources, even from long distances, he said.

"Since NCR is a contiguous area with high-population density and multiple pollutant sources, it is difficult to pinpoint and isolate the source of pollution in Delhi alone.

So, the same rule and standards pertaining to pollution should be followed by the adjoining states," Khan said.

Khan had recently written to the Union Environment Ministry saying that combating pollution should be a priority for all concerned.

His letter had come in the wake of Javadekar exhorting Delhi government to act against air pollution.

There is a ban on vehicles more than 15 years old in the national capital and, in view of this, the ban should also be implemented in Haryana, Rajasthan and Uttar Pradesh so that together they could minimise pollution levels in Delhi-NCR, Khan said.

"We have asked the Union Minister to convene the same meeting in the next three or four days so that we can make a strong plan to check the increasing pollution in Delhi," Khan added.

"Several towns of Haryana and Uttar Pradesh fall within NCR... May I request you to ask them to set-up joint check posts well within their territories to ensure that overloaded vehicles can be checked and turned back before they enter Delhi," Khan had said in his letter to the ministry.