Protecting the Public from Air Toxics

Deadline for Public Comments on this Rollback Notice:

September 24, 2019

Read the Proposal @

Comment on the Notice or go to and search for Docket ID: EPA-HQ-OAR-2019-0282

Public Hearing: A public hearing was held at EPA on August 15, 2019, in Washington, DC. 

Save EPA's Comments:  See the comments that Save EPA has submitted to the agency.

What’s at Risk and Talking Points 

The Clean Air Act requires industries and businesses that are large sources of toxic air pollution to meet standards requiring maximum achievable emission reductions.  The Trump Administration has proposed to allow sources to choose at any time to avoid these standards by instead opting to meet small-source requirements that can be much less protective. The proposed rule would broaden and further implement a policy change announced in January 2018.

The Toxic Air Pollution Program

The federal Clean Air Act established a national program to reduce emissions of toxic air pollutants that are known to cause, or may be reasonably anticipated to cause, adverse effects to human health or the environment. The act calls these pollutants “hazardous air pollutants” (HAP); they often are called toxic air pollutants or air toxics.

The law lists almost 190 such substances. Among those are well known toxic substances such as toluene, phosgene, arsenic, cadmium, and mercury. Depending on the pollutant, health effects can include cancer, nervous system damage, damage to internal organs, and other serious health effects.

Under the Act, EPA sets national emission standards for categories of toxic air pollution sources, such as petroleum refineries or dry cleaners. The Clean Air Act calls for any facility that emits or has the potential to emit more than 10 tons a year of any one HAP, or 25 tons per year of a combination of HAP, to be considered “major sources.” (EPA can establish a lesser cutoff when warranted.) Smaller emitters are called “area sources.”

Major sources typically must meet more stringent requirements than area sources. Emission limits for major sources of HAP require the maximum degree of reduction in emissions that is achievable considering cost and other factors. For existing major sources, the limits must be at least as stringent as the emissions level being achieved by the average of the best performing 12 percent of similar sources. For new major sources, the limits must be at least as low as the emissions levels achieved by the single lowest emitting existing source.

The Act also requires that every eight years, EPA review section 112 standards and adjust each regulation if warranted by remaining health risks from the source category, or if technology has advanced so that the maximum achievable emissions reductions warrants a more stringent standard.

For area sources, the program can be much less stringent. For some categories, there are no area source emission standards. Area sources may be subject to pollution limits depending on what kind of HAP they emit and their proximity to populated areas. For source categories that do have area source standards, many require only “generally available” controls rather than the more stringent MACT controls required for major sources.

Since 1990, EPA has issued regulations to cut emissions from all 174 categories of major sources of HAP emissions including petroleum refineries, chemical plants, electric power plants, etc. Another 68 categories of small area sources have been regulated as well. EPA does not have a current assessment of the reductions in HAP emissions since the beginning of the program.1


The Trump Administration Proposed Rollback

Under EPA policy before the Trump Administration, an air toxics source could choose to adopt legal restrictions to qualify as an area source until the first compliance deadline of the major source standard. These legal restrictions must limit the source’s emissions to levels less than the major source cutoff -- 10 tons of a single HAP or 25 tons of a combination of HAPs. Once a facility was regulated as a major source, it remained a major source permanently and had to continue to comply with major source standards requiring maximum achievable reductions.

Trump’s EPA has proposed to allow any major source to switch to area source status at any time – even years after it had complied with the major source standard. The restriction must be legally enforceable. This timing policy change was announced in a guidance memo in January 2018, but would be broadened and further implemented by the proposed rule.

The proposal would reduce protection from toxic air pollution in several ways, as explained in the suggested talking points below.

How to Submit Your Comments

EPA will accept written comments on the proposal until 11:59 p.m. eastern time on September 24, 2019.  To submit comments online, click on the following link:

If you wish to submit comment by mail, email or by fax, see directions in the proposal notice at

Comments should be identified by the following docket number: EPA-HQ-OAR-2019-0282.

What to Say

First, explain why you’re commenting on this notice – why controlling toxic air emissions matter to you. If for example, you fish in local water and you are concerned about mercury or if you live near a source of toxic air emissions, share your experience and concerns.

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 toxic air emissions affects health or the environment, include that information and highlight it. If you are just a concerned citizen, talk about your concerns.

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

Suggested Talking Points About the Proposal

The proposal would reduce protection from toxic air pollution in several ways:

First, the proposal could in many cases allow a source’s emissions of HAP to rise when complying with major source standards results in lower emissions than simply keeping emissions below the major source cutoff level. Emission increases are of particular concern for HAP that are highly toxic. Although HAP vary in the risks the pose, some HAP are highly toxic in very small quantities – quantities well below the major source threshold.

The agency’s illustrative analysis suggests that the proposed rule may well cause toxic emissions to increase at some unquantified number of individual sources, and is unable to conclude whether toxic emissions from major sources will increase nationally. The agency examined 34 sources that have already switched to area source status under EPA’s January 2018 change in policy. The agency found that none of the 34 will increase emissions because of continueduse of existing controls or because of other requirements that provide a backstop. But based on a look at six source categories, which showed the potential for both emissions increases and emissions decreases, the agency concluded that “due to limited information on how emissions changes could take place across the broad array of HAP emissions sources, we are unable to provide precise estimates of changes in emissions for all source categories that could be impacted by this action.”

EPA asked for comment on the adding a requirement that, should a source adopt area source standards it not be allowed to increase emissions.  If there is authority for such a provision, it would reduce the harm that this proposal would cause.

Second, because of its concern about known and unknown risks of toxic air pollution, Congress required EPA to write major source standards that “require the maximum degree of reduction in emissions of hazardous air pollutants…” With this proposal, EPA would allow major sources an alternative control regime that, for many sources, would be less stringent and less health protective. 

Third, this alternative regime would leave companies free to achieve area source status by reducing high-volume HAP emissions that are less toxic while maintaining, or even increasing, emissions of low-volume, highly toxic emissions that are of greater concern for public health and environmental reasons – even if the major source standards that the company is avoiding would require reductions in those highly toxic emissions.

Take, for example, power plants. EPA has said that mercury is the HAP of greatest concern, and that cadmium, arsenic and a few other toxics pollutants also are of concern.3 Power plants emit these HAP in small amounts, while emitting a large amount of acid gases. Under the proposal, major source power plants complying with the Mercury and Air Toxics Standards could become minor sources by reducing their emissions of acid gases while increasing up to the threshold their emissions of mercury and other HAP. Their compliance costs would fall but the benefits of emission reductions, measured in terms of public health, would fall as well.4

Fourth, restrictions to achieve area source status are not required to be federally enforceable; they can be state-enforceable only. By contrast, major source standards are enforceable by the state, EPA, and citizens filing suit under the federal act. This is another way in which major source standards are more protective than legal restrictions to achieve area source status.

Fifth, under the Clean Air Act, EPA is required every eight years to consider strengthening federal HAP emission standards based on the capability of available control technologies and the residual risk from HAP emissions. Under the Trump Administration proposal, area sources in categories without area source standards could continue to emit up to the major source threshold indefinitely, rather than meet major source standards that must be reviewed, and if warranted, strengthened in the future.

EPA attempts to justify its deregulatory move with a legalistic and debatable argument: That Congress did not explicitly set a cutoff date in the Clean Air Act, and that therefore Congress intended sources to be able to switch to area source status at any time. This argument ignores the fact that the proposed policy would undercut the congressional directive for EPA to set standards for larger sources that require maximum achievable reductions in HAPs.

It is revealing that the only benefit EPA claims for this proposal is a reduction in administrative costs for the regulated industries. The potential costs in harm to human health and the environmental are not taken into consideration.

See also the comments that Save EPA submitted to the agency.

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

Harvard Law School Environmental and Energy Law Program, Regulatory Rollback Tracker, "Once In Always In Guidance for Major Sources under the Clean Air Act,"

US EPA, “Potential to Emit for MACT Standards -- Guidance on Timing Issues” Memorandum from John Seitz, May 16, 1995.

US EPA, “Reclassification of Major Sources as Area Sources under Section 112 of the Clean Air Act”, Memorandum from William Wehrum, January 25, 2018.




  1.  EPA’s most recent assessment of the effect of the air toxics program provides data from 2014, before several very significant regulations became effective. See: National Air Toxics Assessment,

2.   CAA, Section 112(d)(2)

3.   US EPA, Study of Hazardous Air Pollutant Emissions from Electric Utility Steam Generating Units --Final Report to Congress , February, 1998.

4.  EPA has never done a thorough analysis of the benefit of controlling HAP including mercury emissions. We refer here to a well-regarded study that calculated the lifetime benefit of reducing mercury emissions from electric power plants under the 112 program for major sources major source as $3.7 billion annually. 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.

See also: 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.

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.