Catherine Day , stressed the importance of practical applications of policy instruments and of translating theory into political , economic , social and environmental reality . The workshop agreed to : ( a ) give evidence with regard to a change of approach in decreasing the emissions of sulphur dioxide and nitrogen oxides in Europe , whether taxes or charges would be politically acceptable alternatives ; ( b ) and to give advice on whether national regional or European Union ( EU ) -wide emissions trading would be a better alternative for land and sea areas .