FRESH air is the environmental issue uppermost in most school children's minds, as a vote by primary pupils attending an environmental camp has shown. Nearly 1,500 Primary 4 and 5 pupils from 14 schools voted air pollution (441 votes) as their main concern, followed by chemical and waste management (200), greening the city (176), environmental education (166), water conservation (126) and noise pollution (118). The students were taking part in a series of environmental camps, organised by TREATS, a registered charitable trust founded in 1979. TREATS aims to give Hong Kong's disabled children and able-bodied youngsters brought up in overcrowded estates, temporary housing areas, squatters huts and institutions, a ''treat they would otherwise not have''. Since 1990 it has been running camping programmes to develop children's self-esteem and confidence by using non-competitive activities and imaginative workshops. ''We recognise the importance of recreation and play to the physical, intellectual, emotional and social growth of young people. The camps aim to give them a chance to learn and expand their horizons in a new way,'' said a spokesman. The environmental camps, held between December 1992 and July this year in the Sai Kung Outdoor Recreation Centre, served students from old government public estates in densely populated areas. Camp leaders, trained by Friends of the Earth, opened the workshop with a sketch illustrating ways the earth is being destroyed and showing ways it can be improved, particularly in Hong Kong. Each group of students picked an environmental topic to discuss. A secret ballot was then held with every student voting for the topic they felt to be the most important. The children signed a declaration that air pollution was their biggest concern and that they would try their best to protect the environment. Friends of the Earth Director, Mrs Mei Ng, who helped devise the workshop, said she was not surprised by the results. ''Most of the students live in very densely populated areas, so naturally they are worried about the air they breathe.'' The results have been sent to the Education Department, the Environmental Protection Department and the Centre of Urban Planning and Environmental Management at the University of Hong Kong. ''This workshop has allowed the students to express their own opinions on the importance of a clean environment,'' said a TREATS spokesman. ''Through the voting system they have learnt to exercise their rights in prioritising the most critical environmental problem facing Hong Kong and hence fostering awareness and commitment to combat it themselves.'' TREATS also run other activities for deserving children ranging from a day at sea on the Adventure Ship, Ocean Park, to simple beach picnics and visits to a variety of cultural performances. ''Some outings are pure enjoyment. But many introduce the children to new skills and experiences,'' the organisation said.