Pupils are also introduced to the concept of sustainable development. The topics include, among others, the anthropogenic impact on the environment in Belarus: contamination with radionuclides due to the Chernobyl NPP accident, and local problems of air and soil pollution and surface and groundwater contamination as a result of economic activities. In grade XI, pupils are given a scientific understanding of the environment within the context of development. Topics include heat savings in residential houses, the use of alternative sources of energy (wind and hydro), and environmental problems caused by production, transmission and use of electricity.