A series of programmes, including poster campaigns, cleanliness, quiz competitions and slogans, marked World Environment Day celebrations in Meghalaya today. Official sources said the state Pollution Control Board (PCB) organised a free vehicular emission testing camp on the occasion. The North East Educational and Development Society, the NSS and NCC units jointly organised functions at a local college here on the theme of "CO2 - Kick the Habit Towards a Low Carbon Economy'. The highlight of the function was a special platform for "innovative inventors' competition which gave the students a chance to come out with innovative ideas of reusing and recycling waster materials to design or rather invent new items.