With a view to implementing Directive 96/62/EC in matter of ambient air quality management and assessment, the present Legislative Decree lays down principles to be applied in order to: (a) establish the objectives to be attained to prevent, avoid and reduce harmful effects to human beings and to the environment; (b) assess the ambient air quality; (c) obtain adequate information as regards ambient air quality and make it available to the public; (d) maintain ambient air quality where it is good