The National Green Tribunal today asked all states and Union Territories to identify and inform it about the 'no-pollution' zones in their areas for plying of deregistered diesel cars which have been barred from running in the national capital region. <br/><br/>The states were directed to identify areas where the dispersion of the air is higher and vehicular density is the least. The Tribunal had last year ordered the Delhi government to cancel the registration of all diesel-powered vehicles over 10 years old and barred them from plying.<br/><br/>It had then ordered that only de-registered diesel vehicles which are less than 15-years-old can get No Objection Certificate for plying in select areas outside Delhi-NCR to be decided by states where vehicle density is less. The green panel in July last year had said that all the vehicles which are deregistered would not be permitted to ply in Delhi-NCR.