Environmental impact of electricity generation electricity sector is unique among industrial sectors in its very large contribution to emissions associated with nearly all air issues. Electricity generation produces a large share of Canadian nitrogen oxides and sulphur dioxide emissions, which contribute to smog and acid rain and the formation of fine particulate matter. It is the largest uncontrolled industrial source of mercury emissions in Canada. Fossil fuel-fired electric power plants also emit carbon dioxide, which may contribute to climate change. In addition, the sector has significant impacts on water and habitat and species. In particular, hydro dams and transmission lines have significant effects on water
21st-century fossil fuel regulations in the United States are subject to New Source Review (NSR) and Prevention of Significant Deterioration (PSD). Emissions from these plants have the largest contributions of sulfur dioxide (SO2) and nitrogen oxides (NOx) into the atmosphere. Facilities in the electric sector are restricted to emission standards defined by the Clean Air Act (United States). While monitoring and controlling environmental releases of plants has been difficult, the EPA has been enforcing their policies regarding air quality over the last decade under President Barack Obama. While the Clean Air Act postulates regulations and rules limiting the emissions of greenhouse gases, other laws are concerned with standards