Proposed Rule to Jeopardize the Mercury and Air Toxics Standards (MATS)

Public Comment Period Closed on April 17, 2019

A public hearing was held on March 18, 2019 in Washington, DC

Read the proposal @

View comments @ , Docket ID:  EPA-HQ-OAR-2018-0794

What’s at Risk and Talking Points 

The Mercury and Air Toxic Standards (MATS)

In December 2011, the Environmental Protection Agency announced the Mercury and Air Toxics Standards (MATS) to reduce emissions of mercury and other toxic air pollution (also called hazardous air pollutants – or HAP) from coal and oil-fired power plants.  The standards were authorized by the 1990 Clean Air Act Amendments.   Mercury is emitted to the air from coal-fired power plants.  When it is deposited to water or runs off into water it can be converted to methylmercury, that can accumulate up the aquatic food chain and lead to high concentrations in predatory fish. When consumed by humans and wildlife, mercury contaminated fish represent a health risk. Methylmercury damages multiple organ systems, including  the cardiovascular, renal and immune systems.  It is best known for the damage it causes to the nervous system. The developing fetus is the most vulnerable population to neurotoxic effects of methylmercury.[i]


Although power plants were among the largest manmade source of mercury emissions, power plants were among the last sources of mercury emissions to be regulated under the Act.  This is because power industry successfully lobbied Congress to require a study and a finding that it was “appropriate and necessary” to regulate emissions from power plants before the regulation could be issued. That plus delays introduced by the George W Bush administration delayed what became MATS for 21 years. 


The appropriate and necessary finding was based largely on the Utility Study Report to Congress[ii], the Mercury Study Report to Congress[iii], a National Academy of Sciences Report entitled the Toxicological Effects of Methylmercury[iv]and data on emissions and coal collected from coal-fired power plants. EPA found that mercury was a significant hazard to public health, that power plants were the largest source of mercury emissions and that there were control strategies available to limit mercury emissions.  Further EPA found that power plants were the largest source of several other HAP as well. EPA found that it must regulate mercury and other HAP emissions because other sections of the CAA did not reduce those emissions. 


In 2015 the Supreme Court said that EPA had erred in its appropriate and necessary find because it did not consider the cost of regulating and the D.C. Circuit Court required EPA to consider cost as a part of it finding. In 2016 EPA issued a supplemental  notice that took cost into consideration and reaffirmed the initial finding that it was appropriate and necessary to regulate mercury and other HAP emissions. 


MATS sets out standards to limit emissions of mercury, acid gases including hydrogen chloride and hydrogen fluoride, and metallic HAP such as arsenic, chromium and nickel.  It also sets out performance standards intended to reduce emissions of dioxins and furans.


MATS provides significant public health benefits.  EPA’s regulatory impact analysis for the 2011 rule estimated that the in the year of full implementation, the rule would prevent up to 11,000 deaths, 4,700 non-fatal heart attacks, 130,000 asthma attacks, 5,700 hospital and emergency room visits.[v]  In spite of these impressive benefits, EPA’s benefit analysis is did not comprehensively account for the benefits to human health resulting from MATS.  That is because, as the analysis notes, EPA lacked the data, time, and resources to more fully quantify and monetize the benefits of MATS.  EPA’s analysis for MATS included a listing of the public health effects that EPA was not able to quantify.


By 2016 power plants across the country had installed pollution controls and monitoring equipment and were in compliance with MATS. 

The Trump Administration Rollback Notice

The Trump Administration is proposing that it is not appropriate and necessary to regulate HAP emissions from coal and oil-fired power plants.  The proposal is based on a new assessment of the benefits of MATS that ignores significant monetized benefits, all of the non-monetized benefits, significant mercury benefits that today with improved science on the behavior and effects of mercury could be monetized.


Based on this faulty assessment, proposal askes for comments as to whether to rescind MATS. It also concludes, based on this assessment that, the residual risk to the public from mercury and other HAP emissions is “acceptable” and no tightening of the MATS requirements is warranted.

Suggestions for What to Say

First, explain why you’re commenting on this notice – why controlling mercury and other toxic air emissions matter to you. If for example, you fish in local water or if you or your family eats a large amount of fish, say that.  If you live near a coal or oil-fired power plant, share your experience. 

If you have relevant expertise, say so. You don’t have to be an expert to make a valid and valuable comment, but if you do have expertise, share your knowledge.

If you have information relevant to the rule (for example, news articles or anecdotal information about how mercury or other air toxic emissions affects health or the environment, include that information and highlight it.

Be constructive and civil.  Don’t write a lot if less will do. 

Suggested Talking Points

Mercury is highly toxic.  It damages multiple organ systems.  The most studied impact is to the nervous system and especially the nervous system of the developing fetus. Although these effects were laid out in the cost benefit analysis EPA produced when it issued MATS, EPA now is using the old cost-benefit analysis to justify its proposal.  There is plenty wrong with that.

In the first place, and as Save EPA and the Environmental Protection Network said in comments to EPA several months ago, EPA’s authorizing statutes including section 112 of the Clean Air Act on which MATS depends, lay out the factors that may be considered in setting standards and rules.  The act is clear that standards under section 112 must be at least as stringent as the performance already achieved by  the better performing plants.  Standards can be more stringent than that in which case cost must be considered.  But there is no basis for using cost-benefit analysis as the sole determinant of whether and to what level to control emissions under section 112.[vi]

If EPA were to honestly assess the cost-benefit analysis of MATS compliance, with the science and engineering information that is now available, the costs would be much lower and the benefits much higher. Let’s look at that.


EPA is misleading the public on the cost of MATS

First, the capital and operating cost of complying with MATS turned out to be much lower than EPA had estimated for MATS.[vii]  There were a number of reasons for this including:

  • mercury and acid gas controls became less expensive as the industry developed activated carbon and sorbents that were tailored to power plant control;
  • power plant operators learned by using continuous emission monitors to measure emissions, the monitors act as a process control.  The monitors allow plant operators to fine-tune their use of activated carbon and other additives and avoid using more than is  necessary;
  • EPA had assumed that the use of activated carbon and sorbents would increase the cost of waste disposal at coal plants but in fact, with the improved activated carbon and sorbents, this did not happen;
  • EPA had overestimated the amount of generating capacity that would need to retrofit with fabric filters, dry flue gas desulfurization (FGD), and that would need to upgrade their existing wet FGD.
  • natural gas prices did not rise as EPA had assumed based on Energy Information Administration projection, and as a result generators switched to less costly natural gas generation which requires no mercury or toxic pollutant control.[viii]

One industry analyst estimated that the actual cost of complying with MATS was less than one-quarter of EPA’s original estimate of $9.6 billion.[ix]  It is not unusual for EPA’s cost estimates to be overstated as they tend to be conservative in estimating costs, and rightly so.  But now there is real data on the cost of MATS compliance, yet EPA continues to pretend that original cost estimates for MATS is what MATS actually cost.  This is  misleading at best.


EPA is hiding benefits from the public

There is plenty wrong with EPA’s claims about the benefits of MATS too.  First, and most obviously, EPA wants to ignore the large benefits to public health because MATS reduces particle pollution (or PM).  EPA’s justification is that PM is not the “target pollutant”. That is incorrect.  Many of the hazardous air pollutants, including almost all the metals, are attached to particles and MATS has a PM standard that allows operators to avoid having to monitor for individual metals.  But most of MATS’s PM benefits come from PM that is formed in the atmosphere as result of chemical reactions of pollutants such as sulfur dioxide and nitrogen oxides, that are emitted bypower plants and other facilities.


The controls that are put on power plants to reduce mercury and other toxic pollution, also reduce pollutants that form PM. PM is among the pollutants for which EPA has robust data allowing  it to calculate public health benefits.  It appears that EPA now wants to hide these benefits from the public. To  present them would make it clear that the rule’s benefits are much higher than the cost.  It has come up with a sham justification for omitting consideration of those benefits (that PM isn’t a “target pollutant”) thus hiding MATS benefits from the public.


EPA is pretending that unquantified benefits don’t exist

In 2011, EPA quantified a limited subset of the direct benefits associated with reducing mercury and the other toxic air pollutants. At the time they said that lack of data, time and resources prevented full accounting of the benefits of reducing these pollutants.  EPA did present a discussion and listing of the unquantified benefits in the MATS Regulatory Impact Analysis.[x]  But in this proposal they are treated as if they did not exist.


In the MATS analysis EPA did present a valuation of the effect of IQ point loss in children of recreational anglers eating self-caught fresh water fish.  But IQ point loss is not the most sensitive neurotoxic effect of mercury exposure, most people don’t catch their own fish and every U.S. citizen has detectable mercury in his or her blood.  Most people are exposed to mercury by eating commercial marine fish.  Clearly the population considered was much too small.


While EPA quantified and monetized IQ loss, The NRC in a 2000 report, identified neurodevelopmental effects such as deficits in attention, fine-motor function, confrontational naming, visual-spatial abilities, and verbal memory as important health effects.[xi]  While a tremendous amount of data would be necessary to quantify and monetize, these health end points, that is not a reason to pretend that they do not exist as EPA is now doing.


EPA is Ignoring more recent science that would allow it to quantify more benefits. 

Recent research would allow EPA to present estimates of benefits that are much greater than what was presented in when MATS was developed. [vii]  But rather than do the hard work of examining the state of the science and reevaluating the cost and benefits, EPA is relied on the old analysis.  Here are a few of the newer findings that would substantially change the results of a cost benefit analysis of MATS.


  1. Locally deposited mercury appears to have been underestimated by EPA. EPA’s air modelling assumed that to a large extent the mercury emitted in the US spread around the globe and so the benefit to the US of reducing emissions was small. This assumptions appears to be wrong.  Researches have, for the last few decades, noticed a steady decline in atmospheric concentrations in North America even though global mercury emissions had been increasing.  When global models have been corrected to account for these observations the modelled results reproduce the observations.[viii]  There is no justification for EPA to continue to rely on it outdated and incorrect modelling except that it serves to conceal much of the benefit of MATS.
  2. EPA’s benefits analysis is very limited. It is based on a small subset of the population: those who catch fish from fresh water only, for recreation, and consume it during pregnancy.  Also, for this population EPA considered only the value of lost IQ points for children of this group, ignoring the full range of known health effects.  EPA concluded that the benefit of reducing mercury from power plants was between $4 and $6 million dollars annually.   There are far more comprehensive  studies that have concluded benefits that are orders of magnitude larger than this.[ix]  Yet, EPA sticks with its old, extremely limited analysis.
  3. Recent studies could allow EPA to estimate the reduction in fish mercury concentrations in near coastal waters, including the Atlantic and Gulf coasts where a significant amount of the fish that American eat are found.[x]
  4. Some significant benefits that are unquantified in the MATS analyses could and should be quantified. Of particular significance is the effect of methylmercury on cardiovascular health.   Several studies have documented these effects and an independent panel concluded that there was sufficient evidence to include analyses of these effects in regulatory analyses.[xi]  If EPA were to include the effects of methylmercury on cardiovascular health, as it should,  the quantified benefits would increase by orders of magnitude.[xii]
  5. EPA’s analysis assumes that there is a threshold for neurological effects of methylmercury and that exposures below the reference dose have no adverse effects. More recent science does not support that approach. [xiii]   Second, EPA also undercounts  benefits because it does not take into account the background mercury exposure in all people: This means it takes less additional exposure to reach the reference dose level than the EPA analysis assumes. If EPA had factored in the background exposure, it would have found many more people in this limited group to be exposed above the reference dose and the calculated benefits would be greater.

Given how outdated EPA’s 2011 regulatory impact analysis is, EPA should make no regulatory decision based on it.  MATS has been complied with.  At this point EPA should revise its benefits analysis to be consisted with current science to better inform the public and to determine whether MATS should be strengthened to address residual risk to public health, as called for by the Clean Air Act.

There Is More That You Can Do

It would be great if well-reasoned, fact-based comments were enough to win the day, but in today's deregulatory environment, raising the political stakes of regulatory rollbacks is crucial to stopping or slowing them down.  Submitting comments is a good first step. For rules that are particularly important to you, please consider taking one or more of the following steps, too. These methods can help to mobilize public opinion and spur elected leaders to fight the destructive changes that the Trump Administration is promoting.

Write to your members of Congress and other elected officials.  Let them know your concerns and ask them to weigh in on this rollback and speak out publicly in favor EPA’s existing statements on this issue.  These links make it easy to write your members of Congress (your representative in the House of Representatives and your two senators).  If you're willing to register with Countable, this link -- -- allows you to identify your members of Congress and send a message to all three at once.  Or, you can write them separately -- you can use or to find your members' email contact forms or snail mail addresses.

Let your state officials know that you are concerned about this issue.  Write to your elected leaders, get involved with local activists who are encouraging local or state action.

Voice your concern and encouragement in the media, social media, at local meetings, and at every opportunity.  In the absence of federal leadership, it is vitally important that states and local governments fill the void.

Write letters to the editor and even op-eds in your local papers.  Letters to the editor should be fairly brief.

Organize or participate in campaigns to make phone calls or write letters to members of Congress and make phone calls to radio stations during call-in days, or take other actions to spread the word.

Inform your local officials about these issues and ask them to make a public statement or submit comments on a proposed rollback if your jurisdiction has a stake in these issues.  Bring up these issues at town hall meetings.

Spread the word via social media.  Tag your elected officials so they know how you feel.

Join or organize demonstrations.

Talk to your friends, colleagues and neighbors and encourage them to comment and otherwise join in this effort.


For More Information

National Research Council. 2000. Toxicological Effects of Methylmercury. Washington, DC: The National Academies Press.

US EPA, Mercury Study Report to Congress, 1997.

US EPA, Utility Study Report to Congress, 1998.

EPN & Save EPA comments on Changes in How EPA Weighs Costs and Benefits in Decision-making, August 2018.

Driscoll, Jr., C.T.; Sunderland, E.M.; Hammitt, J.K.; Grandjean, P.; Evans, J.S.; Blum, J.D.; Chen, C.Y.; Evers, D.C.; Jaffe, D.A.; Mason, R.P.; Goho, S.; Jacobs, W., Mercury Matters 2018: A Science Brief for Journalists and Policymakers, December 2018.



[i]National Research Council, The Toxicological Effects of Methylmercury, 2000, p145 – 249.

[ii]US EPA, Utility Study Report to Congress, February 1998.

[iii]US EPA, Mercury Study Report to Congress, December 1997.

[iv]National Research Council, The Toxicological Effects of Methylmercury, 2000.

[v]US EPA, Regulatory Impact Analysis for Mercury and Air Toxics Standards, December 2011.

[vi] Save EPA and the Environmental Protection Network, EPA Alums Express Concerns About Possible Changs in how EPA Weighs Costs and Benefits in Decision-making.

[vii]Declaration of James E. Staudt, PH.D. CFA, September 24, 2015, White Stallion Energy Center, et. al., v. United States Environmental Protection Agency, Case No. 12-1100 and consolidated cases, U.S. Court of Appeals for the District of Columbia.

For an interesting discussion on the development of mercury controls, see: International Energy Agency, Sloss, Leslie, “The Emerging Market for Mercury Control” February 2015.

[viii]EIA had estimated that by 2015 the delivered price of natural gas to the power industry would be $5.23 per thousand cubic feet in nominal dollars.  Annual Energy Outlook, 2011, p142.  The actual delivered cost of natural gas to the power industry in 2015 was $3.38 per thousand cubic feet in nominal dollars, less than it had been when MATS was promulgated.

[ix]Declaration, Op. cit. , see exhibit 2.

[x]US EPA, Regulatory Impact Analysis for the Final Mercury and Air Toxics Standards, December 2011, p.5-61.

[xi]National Research Council .op cit.p.310

[xii]Sunderland, E.M.; Driscoll, C.T.;  Hammitt, J.K.; Grandjean, P.; Evan, J.S.; Blum, J.D.; Chen, C.Y.; Evers, D.C.; Jaffe, D.A.; Mason, R.P.; Goho, S.; Jacobs, W.; Benefits of Regulating Hazardous Air Pollutants from Coal ad oil-fired Utilities in the United States. Environmental Science and Technology, 2016, 20 pp2117-2120.

[xiii]A sample of published literature on this topic is as follows:

Zhang, Y.; Jacob, D.J.; Horowitz, H.M.; Chen, L.; Amos, H.M.; Krabbenhoft, D.P.; Slemr, F.; St. Louis, V.; Sunderland, E.M. Observed decrease in atmospheric mercury explained by global decline in anthropogenic emissions, Proc, National Academy of Sciences, U.S.A. 2016.

Evers, D.C.; Han, Y.J.; Driscoll, C.T.;  Kamman, N.C.; Goodale, W.; Fallon Lambert, K.; Chen, C.Y.; Clair, T.A.; Butler, T. Biological mercury hotspots in the northeastern United States and southeastern Canada. BioScience 2007, 57 (1) pp. 29-43.

Drevnick, P.E.; Engstrom, D.R.; Driscoll, C.T.;  Swain, E.B.; Balogh, S.J.; Kamman, N.C.; Long, D.T.; Muir, D.G.C.; Parsons, M.J.;Rolfhus, K.R.; Rossmann, R. Spatial and temporal patterns of mercury accumulation in lacustrine sediments cross the Great Lakes region. Environmental Pollution 2012 ,161 pp.252-260.

[xiv]See: Giang, A.; Selin, N.E.  Benefits of mercury controls for the United States. Proc. National Academy of Sciences, U.S.A., 2016, 113, p. 286.

Rice, G.; Hammitt, J.A.; Evans, J.A. A Probabilistic characterization of the health benefits of reducing methyl mercury intake in the United States. Environmental Science and Technology 2010, 44, pp. 5216-5224.

[xv]Evers, D. C.; et. Al. op. cit.

Cross, F.A.; Evans, D.W.; Barber, R.T. Decadal declines of mercury in adult bluefish (1972-2011) from the mid-Atlantic coast of the U.S.A., Environmental Science and Technology, 2015, 49, pp. 9064-9072.

Evans, D. W., M. Cohen, C. Hammerschmidt, W. Landing, D. Rumbold, J. Simons, and S. Wolfe. 2015. White Paper on Gulf of Mexico Mercury Fate and Transport: Applying Scientific Research to Reduce the Risk from Mercury in Gulf of Mexico Seafood. NOAA Technical Memorandum NOS NCCOS 192. 54 p.

Harris, R.; Pollman, C.; Landing, W.;  Evans, D.; Axelrad, D.; Hutchinson, D.; Morey, S.; Rumbold, Dm; Dukhovskoy, D.;  Adams, D.;  Vijayaraghavan, K.;  Holmes, C.; Atkinson, R.D.;  Myers, T.; Sunderland, E.Mercury in the Gulf of Mexico: Sources to Receptors, Environmental Research 119 (2012) pp.42–52.

[xvi]Roman HA, Walsh TL, Coull BA, Dewailly É, Guallar E, Hattis D, Mariën K, Schwartz J, Stern AH, Virtanen JK, Rice G.  Evaluation of the cardiovascular effects of methylmercury exposures: current evidence supports development of a dose-response function for regulatory benefits analysis.Environmental Health Perspectives 2011 May;119(5):607-14. doi: 10.1289/ehp.1003012. Epub 2011 Jan 10. Review.

[xvii]A 2011 study that found no adverse cardiovascular effect for methylmercury exposure. See Mozaffarian, D.; Shi, P.; Morris, S.J.’ Spiegelman, D.; Grandjean, P.; Siscovick, D.S.; Willett, W.C.; Rimm, E.B. Mercury exposure and risk of cardiovascular disease in two U.S. cohorts. New England Journal of Medicine, 2011, 364, pp. 1116-1125. This study included only low to moderate fish consumers and thus lacked statistical power to detect effects. Sunderland, E.M. op. cit.

[xviii]Karagas, M.R.; Choi, A.L.; Oken, E.; Horvat, M.;Schoeny, R.; Kamai, E.; Cowell, W.; Grandjean, P.; Korrick, S. Evidence on the human health effects of low-level methylmercury exposure. Environmental Health Perspectives, 2012, 120 (6), pp.700-806.

Grandjean, P.; Pichery, C.; Bellanger, M.; Budtz-Jorgensen, E.  Calculation of mercury’s effect on neurodevelopment. Environmental Health Perspectives 2012, 120 (12) p A452.



Save EPA has been an all-volunteer group of former EPA officials who became alarmed about the Trump agenda for EPA and joined together to fight it.

With newly-elected President-Elect Biden and VP-Elect Harris coming in January, the need to "save EPA" is much less urgent. This is not to imply all clear skies ahead - there is much re-building to do, there will be negative pressures on the new administration, and we will likely have policy differences in the future. However, we are hopeful that these differences will be discussed rationally, using science as a basis for moving forward, and keeping EPA's mission of protecting human health and the environment in the forefront.

And so, we are going back to retirement!  We're keeping our website up at , as a resource for those who want to follow and influence the restoration work. Our report on the Trump record at EPA describes the actions that need to be reversed [], and our guide to participating in the rulemaking process [] can help you be part of the solution.

Thank you for your support and commitment during the past 3.5 years.  While the Trump assaults were unending, they were also frequently unsuccessful, and that was due in large part to public outrage.  Keep it up!  Although EPA will be in much better hands with a Biden administration, there is always a need for an informed and engaged public.