In the US, national emission standards for hazardous air pollutants (NESHAP) have been established for industries emitting toxic air emissions that require the use of Maximum Achievable Control Technology (MACT) for compliance.
Mercury NESHAP/MACT standards have been published for hazardous and municipal waste incineration, commercial/industrial boilers, chlor-alkali plants, and Portland cement kilns. Strategies for controlling mercury and other toxic air pollutants include pollution prevention measures, including product substitution, process modification, work-practice standards and materials separation; coal cleaning (relevant to mercury control); flue gas treatment technologies; and others.
More than 20 years after Congress passed the 1990 Clean Air Act Amendments, the US Environmental Protection Agency (EPA) on December 21, 2011, issued the first national standards for mercury pollution from power plants ̶ the Mercury and Air Toxics Standards (MATS).
The 1990 Clean Air Act Amendments required the stricter standards on power plants in an effort to reduce toxic emissions across the country. These new rules finalize standards to reduce air pollution from coal and oil-fired power plants under sections 111 (new source performance standards) and 112 (toxics program) of the 1990 Clean Air Act Amendments.
Power plants are the largest source of air pollution from mercury, arsenic and cyanide, and are responsible for half the mercury and over 75 percent of the acid gas emissions in the United States.
Mercury has been shown to harm the nervous system of children exposed in the womb, thereby causing impaired thinking, learning and early development. According to the EPA, the standards will prevent 130,000 cases of childhood asthma symptoms and about 6,300 fewer cases of acute bronchitis among children each year.
Today, more than half of all coal-fired power plants already use pollution control technologies that will help them meet these standards. Once finalized, these standards will ensure the remaining plants – about 40 percent of all coal-fired power plants – take similar steps to decrease these hazardous pollutants.
In addition to reducing emissions of mercury and other toxic air pollutants, the controls needed to meet the standards will result in reduced emissions of sulfur dioxide and fine particles, which will lower airborne soot levels throughout the United States.
Under these standards, the EPA is providing the standard three years for compliance, but is also encouraging permitting authorities to make a fourth year available for technology installations. If still more time is needed, they will provide a pathway to address any localized electric reliability problems, should they arise.
Among the improvements that will result, it is estimated there will be approximately 540,000 missed work or “sick” days avoided each year, enhancing productivity and lowering health care costs, and 3,200,000 fewer Restricted Activity days.
People exposed to toxic air pollutants at sufficient concentrations and durations may have an increased chance of getting cancer or experiencing other serious adverse health effects. These health effects can include disruption to the immune system, as well as neurological, reproductive, developmental, respiratory and other health problems. In addition to exposure from breathing air toxics, some toxic air pollutants such as mercury can deposit onto soils or surface waters. They are then taken up by plants and ingested by animals and are eventually magnified up through the food chain.
The Mercury and Air Toxics Standards, combined with the final Cross State Air Pollution Rule issued in 2011, are estimated to prevent up to 46,000 premature deaths, 540,000 asthma attacks among children, and 24,500 emergency room visits and hospital admissions. The two programs are estimated to provide a total of up to $380 billion in return to American families in the form of longer, healthier lives and reduced health care costs.
