Many factors contribute to this increase, including reliance on fossil fuels such as coal fired power plants, dependence on private transport motor vehicles, inefficient use of energy in buildings and the use of biomass for cooking and heating.But some cities are making notable improvements demonstrating that air quality can be improved by implementing policy measures such as banning the use of coal for "space heating" in buildings, using renewable or "clean" fuels for electricity production and improving efficiency of motor vehicle engines.