Scientists have expressed concern over high concentrations of sulphur dioxide (SO 2 ) around thermal power plants in India and the danger they pose to agricultural crops in the vicinity. Says C K Varshney, professor, School of Environmental Sciences, Jawaharlal Nehru University, New Delhi, "The present level of research indicates that 20 per cent of the land area under agriculture in India is at risk from high SO 2 levels.'

But lack of data on air quality in rural areas makes actual damage assessment difficult, says Varshney, pointing out that the current standards for SO 2 laid down by the CPCB are "too high and cannot protect crops.'

Varshney has studied around 26 crops, including cereals, pulses, vegetables and fruits, to gauge the impact of SO 2 emissions from thermal power plants on the yield and biomass loss. His study is based on indicators which included reduction in leaf area, weight of grain and shoot length. He has conclusively shown that high level of SO 2 in the air can reduce leaf area by up to 40 per cent, and shoot length by 14 per cent.