The U.S. Environmental Protection Agency has reversed actions taken by the previous administration concerning the 2012 Mercury and Air Toxics Standards for power plants.
The 1990 Clean Air Act gave the EPA the authority, working in coordination with state, local, and tribal governments, to address three major concerns of that era – acid rain, urban air pollution, and toxic air emissions.
In 2000, the EPA announced that it was “appropriate and necessary” to regulate coal and oil-fired electric utilities under section 112 of the Clean Air Act. This finding, known as the Utility Air Toxics Determination, triggered a requirement for the EPA to propose regulations to control air toxics emissions, including mercury, from these facilities by December 15, 2003.
On January 30, 2004, the EPA proposed a rule with two basic approaches for controlling mercury from power plants.
- Require power plants to meet emissions standards reflecting the application of the “maximum achievable control technology” MACT as set forth in section 112(d) of the Clean Air Act. If implemented, it would reduce nationwide mercury by 14 tons or about 30% by early 2008.
- Create a market-based “cap and trade” program that, if implemented, would reduce nationwide utility emissions of mercury in two phases. If fully implemented, mercury emissions would be reduced by 33 tons (~70%).
The EPA decided to pursue the “cap and trade “approach either under Section 111 or Section 112 of the Clean Air Act. Many other proposals, amendments, and finally a Clean Air Mercury Rule was established in 2005 via the “cap and trade” approach in two phases.
However, in 2008 the D.C. Circuit Court vacated the EPA’s rule removing power plants from the Clean Air Act list of sources of hazardous air pollutants. At the same time, the Court vacated the Clean Air Mercury Rule. Based on this ruling by the court, the EPA announced plans to propose air toxic standards for coal and oil-fired electric generating plants by March 16, 2011, and present a finalized rule by November 16, 2011.
On March 16, 2011, the EPA proposed a rule that would reduce emissions from new and existing coal and oil-fired electric generating and replace the court-vacated Clean Air Act.
In 2012, the Obama administration finalized the MATS rule, which required utilities to meet a 90% reduction in mercury emissions. MATS also required a 50% reduction in other air toxic emissions.
In 2016, the EPA confirmed that it was appropriate and necessary to regulate air toxins, including mercury, from power plants – even after consideration of the costs. Through their investigation, they found that power plants were the nation’s largest industrial source of mercury pollution, and they emit more than half of the range of air toxins, as well as sulfur dioxide, and particulates. Reducing mercury emissions would reduce risks of neurological impacts in children, and reduce emissions of other toxic air pollutants, thereby decreasing risks of cancer and other serious health effects. Reducing particle pollution would also mean fewer premature deaths, asthma attacks, and heart attacks.
In 2017, the EPA estimated that mercury emissions from power plants had been reduced by 86%, acid gas emissions by 96%, and non-mercury metal emissions by 81%.
In 2020, President Trump’s EPA head, Andrew Wheeler, claimed the reduction of power plant toxic emissions was not worth the cost to the electric generating industry. He used a cost-benefit analysis that determined the health benefits of MATS were only $4 million, compared to $6 million in cost to the industry.
In 2021, not long after President Biden was elected, the President issued Executive Order 13990 that directed the EPA to review EPA Wheeler’s finding and consider an action to rescind it. In response to that order, the EPA found that the 2020 action was based on a “fundamentally flawed” interpretation of the Clean Air Act that “improperly ignored or undervalued” the health benefits from reducing hazardous air pollution from power plants. The EPA then reaffirmed that it is “appropriate and necessary” to regulate emissions of hazardous air pollutants from coal and oil-fired power plants.
This final ruling leaves the 2012 MATS rule unchanged and ensures the continuation of public health protections provided by these requirements. When weighing the substantial burden that hazardous air pollutants, including mercury, impose on public health against the reasonable costs of controlling these emissions, the EPA finds that it is appropriate and necessary to regulate emissions of air toxics from power plants under the Clean Air Act. The Agency is also continuing to consider the MATS Risk and Technology Review, as directed by Executive Order 13990, to determine whether more stringent protections for hazardous air pollution from power plants are feasible and warranted and expects to address that review in a separate action.
In January 2022, Senator Caper – Chairman of the Senate Committee on Environment and Public Works praised the EPA’s proposed rule to reinstate the 2012 MATS rule.
The recommended airborne exposure limit is 0.05 mg/m3 (as Mercury vapor) averaged over a 10-hour work shift and 0.1 mg/m3 (as Mercury), not to be exceeded at any time.
Blood mercury levels above 100 ng/mL have been reported to be associated with clear signs of mercury poisoning in some individuals (e.g., poor muscle coordination, tingling and numbness in fingers and toes).
At room temperature, exposed elemental mercury can evaporate and become an invisible, odorless toxic vapor. This vapor has a very long life, up to one year, in the air.
Some health effects with exposure to mercury include irritation to the eyes, skin, and stomach; cough, chest pain, or difficulty breathing, insomnia, irritability, indecision, headache, weakness or exhaustion, and weight loss.
Mercury vapor, being highly volatile and lipid soluble, can cross the blood-brain barrier and the lipid cell membranes and can be accumulated into the cells in its inorganic forms. Also, methylmercury can pass through blood-brain and placental barriers, causing serious damage in the central nervous system.
Mercury toxicity mechanisms have the potential to induce DNA damage and disrupt cellular processes, like mitochondrial function. Proper mitochondrial function is important for cellular bioenergetics and immune signaling and function.