Most coal-fired power plants within a 300-km radius of Delhi-NCR lack flue gas desulphurisation (FGD) systems, contributing to around 90% of sulphur dioxide (SO2) emissions, according to a CREA report. The analysis said 81% of SO2 emissions came from plants exempted from installing the pollution-control equipment. The findings raise fresh concerns over air pollution in and around Delhi-NCR.