Tomorrow, President Obama is expected to announce a major step in U.S. carbon regulation. Using executive authority, the President will issue a new rule to limit carbon dioxide emissions from coal-fired power plants in the United States. This ruling could have many other benefits, including reducing soot, smog, and early-deaths due to repiratory and other illnesses.

According to the President, "[in] just the first year that these standards go into effect, up to 100,000 asthma attacks and 2,100 heart attacks will be avoided – and those numbers will go up from there.”

These illnesses are largely caused by particulate matter (PM), a mix of liquid and solid particles that can contain sulfates, nitrates, ammonium, carbon, metals, and an array of allergens. According to the World Health Organization (WHO) these emissions lead to asthma and other respiratory illnesses, lung cancer and cardiopulmonary diseases. Globally, an estimated 800,000 early deaths occur each year as the result of combustion-related emissions (both particulate matter and ozone) - 200,000 of these are in the United States.

While these particles can come from non-human sources (e.g. volcanoes), anthropogenic sources are the major contributors in cities. Particulate matter that is smaller than 10 micros in diameter (PM10) primarily comes from combustion – in car engines (both diesel and gasoline), power plants (coal, heavy oil and biomass), and other industrial activities (for example mining, the manufacturing of cement, and smelting).

The rule itself will target carbon dioxide emissions. Approximately 37% of electricity in the United States is generated using coal-fired power plants. Last year, 38% of carbon dioxide emissions come from the electricity sector, mostly coal-fired power plants that represent 37& of electricity generation in the nation. Under this new rule, emissions from existing coal-fired power plants would be reduced by 20%. The EPA already has rules in place for emissions limits for new power plants.

The new rule will be issued under the 1970 Clean Air Act section 111(d), which allows the Environmental Protection Agency (EPA) to regulate pollution from existing sources. State regulators can deisgn strategies to either meet or beat the EPA's recommendations. The U.S. Supreme Court upheld the EPA's ability to regulate carbon dioxide and other pollutants that contribute to global climate change in 2007. Since this time, an EPA rule-making has been viewed as an executive-branch backstop if the legislative branch was unable to agree on federal standards for carbon dioxide emissions.

Such an agreement was attempted in 2009 with the American Clean Energy and Security Act (H.R. 2454). However, while the bill narrowly passed a vote in the House of Representatives (219 for and 212 against), the bill did not make it through the Senate. If passed, H.R. 2454 would have established a national emissions trading scheme similar to that seen in Europe.

Instead, the EPA will regulate these emissions under the new rule, which will be announced tomorrow.

Photo Credit: Photo of W.A. Parish Power Plant and a coal-filled train © Copyright roy luck and licensed for reuse under this Creative Commons Licence