Severe air pollution in China is primarily caused by heavy demands for energy, especially from fossil fuels. Having the majority of China's energy resources, northwestern China played an increasingly significant role in China's energy supply over the past two decades, but the associated environmental consequences and energy justice are almost unknown or ignored. Here we conduct extensive model simulations using a multi-regional input-output (MRIO) model to measure sulphur dioxide (SO2) emissions resulting from the interprovincial trade associated with the west-east energy transmission in China. We examine the environmental consequences using a coupled weather forecast-atmospheric chemistry model. We show that SO2 emissions from the virtual west-east energy transmission accounted for over 40% of total SO2 emissions in northwestern China in the 2000s. Accordingly, 35-52% of SO2 atmospheric concentrations in this region could be attributed to the virtual west east energy transmission for the same period. At some of the large-scale national energy and chemical industry bases in northwestern China, SO2 concentrations induced by the energy supply due to the demand from eastern China exceeded 60%. A tagging technique was employed to identify the source-receptor relationship of SO2 emissions embodied in west-east energy transmission by estimating the sensitivity and efficiency of the energy demanding regions to energy and heavy industry products. The results discerned eastern China to be a major sensitive energy demand region causing SO2 emission from the energy and high energy consuming industries in northwestern China. We propose that the Chinese authorities should subsidize the environmental losses in northwestern China subject to the virtual west-east energy transmission to promote energy justice.