(26)In order to draw up well informed national air pollution control programmes and any significant updates, Member States should make those programmes and updates subject to consultation with the public and competent authorities at all levels and at a time when all options regarding policies and measures remain open. Member States should engage in transboundary consultations where the implementation of their programmes could affect the air quality in another Member State or third country, in accordance with the requirements set out in Union and international law, including the UNECE Convention on Environmental Impact Assessment in a Transboundary Context (the ‘Espoo Convention’) of 1991 and its Protocol on Strategic Environmental Assessment of 2003.