Category Archives: NAAQS

The D.C. Circuit Vacates Most of EPA’s SSM SIP Call; Generators Breath a Sigh of Relief

Earlier this month, the District of Columbia Court of Appeals vacated most of EPA’s startup, shutdown, and malfunction SIP Call.  The Court’s rationale boils down to EPA’s failure to make a predicate finding that the SIP call was “necessary or appropriate to meet the [CAA’s] applicable requirements.”  Without plumbing the depths of the Clean Air Act’s intricacies, it will give some sense of the nuances of the Act that the Court reached this decision while at the same time rejecting the Petitioners’ argument that EPA:

must make factual findings about adverse effects resulting from the SIP’s deficiencies—for example,… More

EPA Lowers the PM2.5 NAAQS: Goldilocks Can Sleep Soundly

Yesterday, EPA finalized a rule lowering the primary annual National Ambient Air Quality Standard for PM2.5 to 9.00 ug/m3.  This is a significant reduction from the current 12.00 ug/m3 standard and a victory for environmentalists, even though they had advocated for larger reduction.

There is substantial evidence supporting the reduction, both in the legal and the common sense understanding of this term.  The evidence in support of a lower standard has been piling up for some time. … More

Another Study Regarding the Health Impacts of PM Emissions From Power Plants: What Impact Will It Have On Regulation and Litigation?

An article in Science published last week indicates that the mortality risk from exposure to PM2.5 from coal-fired electric generating units is roughly twice as high as the risk posed by PM2.5 from other sources.  According to the article, there were roughly 460,000 excess deaths in the United States from 1999-2020 resulting from exposure to PM2.5 from coal-fired EGUs.  Prior models would have indicated roughly half that number. … More

The EJ Movement Wants to Tighten the NAAQS. Will It Happen?

The White House Environmental Justice Advisory Council recently weighed in on EPA’s decision whether to lower the National Ambient Air Quality Standards for PM2.5 and ozone. 

Specifically, with respect to PM2.5, WHEJAC recommended that the annual primary standard be lowered to 8.0 ug/m3 and the annual daily standard be lowered to 25.0 ug/m3.  Both recommendations are lower than what EPA has proposed.

With respect to the ozone NAAQS,… More

What Happens When the EPA Technical Staff Disagrees with the Clean Air Science Advisory Committee?

Last week, the EPA Clean Air Science Advisory Committee provided EPA its review of EPA’s Policy Assessment for the Reconsideration of the National Ambient Air Quality Standard for ozone.  As expected, CASAC has disagreed with the recommendation of EPA technical staff to retain the current 70 ppb standard.  Instead, CASAC recommends a significantly lower ozone NAAQS of 55-60 ppb. 

This seems to be coming down to a fight between EPA’s reliance on controlled human exposure (CHE) studies and CASAC’s position that EPA is giving too little weight to epidemiological studies,… More

Deja Vu One More Time? What Will Happen If EPA Ignores CASAC Regarding the Ozone NAAQS?

Last week, Inside EPA (subscription required) reported that the Clean Air Science Advisory Committee has pretty much agreed that the National Ambient Air Quality Standards for ozone must be made more stringent.  Apparently, the panel is looking at recommending that the primary standard be reduced from 70 ppb to a range of 55-60 ppb.  CASAC is also recommending a reduction in the secondary standard. 

I’ve blogged numerous times about the role that CASAC recommendations play in judicial review of EPA’s decisions concerning setting the NAAQS. … More

It’s More Important for EPA to Ensure that States Are Good Neighbors Than That They are Perfect Neighbors

Last week, D.C. Circuit Court of Appeals rejected challenges to EPA’s “Revised Cross-State Air Pollution Update Rule”.  The Court found that the Rule was “an appropriate exercise of EPA’s statutory authority”. 

I find the decision noteworthy for two reasons.  First, the decision is a full-throated endorsement of judicial deference to agency decision-making.  Of course, this isn’t a Chevron case;… More

EPA Proposes to Lower the PM2.5 NAAQS — Searching For the Goldilocks Level

EPA has finally proposed revisions to the national ambient air quality standard for PM2.5.  The Administrator is proposing to lower the standard from 12.0 ug/m3 to a range of 9.0 to 10.0 ug/m3. 

Readers of this space will recall that the Clean Air Science Advisory Committee recommended that EPA lower the PM2.5 NAAQS to between 8.0 and 10.0 ug/m3.  Environmentalists aren’t going to be happy with any standard above 8.0 ug/m3 and it’s likely that conservatives aren’t going to be happy with any decrease from the current standard.… More

The Broken Record Department: PM2.5 Is Bad For Your Health (and EVs can help)

I’ve written before about the developing science regarding the impacts of PM2.5 emissions.  Short version – they’re bad for you.  They’re even worse than we thought, and there’s increasing evidence that they cause a lot of harm at concentrations below the National Ambient Air Quality Standard of 12 ug/m3. 

The most recent report comes from Canada, which is particularly useful in measuring the impact of low concentrations of PM2.5 precisely because PM2.5 concentrations are relatively low there. … More

NEPA Is Still Going to Pose an Obstacle to Leasing Public Lands for Fossil Fuel Extraction

Earlier this month, Chief Judge  Brian Morris made clear that NEPA remains a powerful weapon against the leasing of public lands for fossil fuel extraction.  It’s déjà vu all over again for the projects at issue.  In 2018, Judge Morris ruled that two resource management plans (RMPs) prepared by the Bureau of Land Management concerning potential expansions of coal mines in Wyoming and Montana violated NEPA for a variety of reasons,… More

PM2.5 Emissions From Wildfires — No Longer So Exceptional!

Last week, the Clean Air Scientific Advisory Committee formally transmitted its recommendations to EPA Administrator Regan regarding the PM2.5 NAAQS.  Consistent with trade press reporting over the past few months, the majority of CASAC members recommended that the PM2.5 NAAQS be set between 8-10 ug/m3.  A minority recommended the range be set between 10-11 ug/m3.  I’d be surprised if the revised NAAQS is set above 10 ug/3. 

For me,… More

The Impact of Exposure to Leaded Gasoline Was Horrific: Will We Say the Same in 2050 About the Impact of PM2.5 Exposure?

An article in the Proceedings of the National Academy of Sciences (login required) has documented the devastating impact caused by the use of leaded gasoline.  The study estimates that more than half of Americans alive in 2015 had been subject to unsafe blood lead levels as children.  The study further estimates that the impact of these elevated blood levels was a net loss of 824,097,690 IQ points as of 2015. … More

CASAC Signals that a Lower PM2.5 NAAQS Is On the Way; It Can’t Come Too Soon

The momentum continues to build for a more stringent National Ambient Air Quality Standard for PM2.5.  In June, EPA announced it would revisit the Trump Administration’s decision to keep the PM2.5 NAAQS at 12 ug/m3.  In early October, EPA staff released a supplement to its assessment of the PM2.5 NAAQS.  That supplement also supported a more stringent standard. 

Now, the Clean Air Science Advisory Committee is about to weigh in. … More

EPA Will Reconsider the Ozone NAAQS — What Is An Adequate Margin of Safety, Anyway?

On Friday, EPA announced that it was reconsidering its 2020 decision to leave the National Ambient Air Quality Standards for ozone unchanged.  The reconsideration will be based on the existing record.  The notice does not identify any specific perceived flaws in the 2020 decision.  However, EPA stated that it:

will reconsider the decision to retain the ozone NAAQS in a manner that adheres to rigorous standards of scientific integrity.… More

There’s No Doubt What EPA Staff Thinks Should Be the Result of EPA’s Reconsideration of the PM2.5 NAAQS

Late last week, EPA released an external review draft of the “Supplement to the 2019 Integrated Science Assessment for Particulate Matter.”  For those of you who don’t recall, the original Integrated Science Assessment was the report by EPA scientists that very clearly called for a decrease in the National Ambient Air Quality Standard for PM2.5.  It was criticized by the Chair of the Clean Air Act Science Advisory Committee and ignored by Administrator Wheeler,… More

Does Pollution Make You Dumber? (And Other Questions About Exposure to Particulate Matter.)

Most people other than Andrew Wheeler and the Trump Administration Clean Air Science Advisory Committee know that exposure even to low levels of PM2.5 causes increased morbidity and mortality.  And now comes evidence that exposure to PM2.5 may adversely impact cognitive capacity as well.  If the evidence is correct, then the externalities created by activities that release PM2.5 are likely much more significant than we had realized,… More

EPA Is Reconsidering the PM2.5 NAAQS. The Sooner, the Better.

EPA announced yesterday that it will “reconsider” the Trump EPA’s decision not to change the PM2.5 National Ambient Air Quality Standard.  I’ve blogged numerous times about the growing body of evidence that exposure to concentrations of PM2.5 below the current NAAQS causes significant additional mortality and morbidity.  The evidence is clear.

I certainly agree that climate change is an existential threat and that’s where our emphasis needs to be. … More

PM2.5 and Environmental Justice — and Electric Vehicles– and Tires

I’ve frequently discussed in recent years the mounting evidence for the need to lower the National Ambient Air Quality Standard for PM2.5.  There is also substantial evidence that PM exposure is an environmental justice issue.  In this context, electrification of our transportation system is seen as having a substantial co-benefit in the reduction of vehicle-related PM emissions, particularly in EJ communities. 

Two recent stories both confirmed the validity of these issues and made manifest the complexity of the problems we are trying to solve. … More

In Case You Were Wondering, EPA’s PM2.5 Decision Really Was Horrible

Last month, I posted that EPA’s decision to retain the current PM2.5 NAAQS of 12 ug/m3 was the single worst decision by Trump’s EPA.  Since then, I have not received any comments suggesting that my ranking was incorrect.  In case anyone was still in doubt, Environmental Research recently released an on-line Pre-proof of A National Difference in Differences Analysis of the Effect of PM2.5 on Annual Death Rates. … More

EPA Finalizes Decision to Retain the Existing PM2.5 NAAQS — Single Worst Environmental Decision of the Trump Administration?

Yesterday, EPA finalized its decision to retain the existing PM2.5 NAAQS of 12 ug/m3, rejecting substantial scientific evidence that PM2.5 causes significant harm at concentrations below 12 ug/m3.  In fact, as noted in one of my prior posts on this subject, an article in the New England Journal of Medicine estimated that exposure to PM2.5 at concentrations below 12 ug/m3 causes more than 10,000 deaths annually. … More

It’s Not Impossible for EPA to Comply with the Good Neighbor Provisions of the Clean Air Act

On Tuesday, Judge John Koeltl ordered EPA to issue a final rule addressing its obligations under the Good Neighbor provisions of the Clean Air Act by no later than March 15, 2021. Two aspects of the decision are worth note.

The big issue in the case, once the Judge disposed of EPA’s jurisdictional arguments, was whether it is impossible for EPA to issue a final rule by the plaintiffs’ suggested date. … More

What is the Burden on States Petitioning EPA Under the Good Neighbor Provisions of the Clean Air Act?

Yesterday, the D.C.. Circuit Court of Appeals granted New York’s petition appealing EPA’s rejection of New York’s request under Section 126 of the Clean Air Act to require emissions reductions from upwind states alleged to be contributing to New York’s noncompliance with the ozone NAAQS.  The Court found that:

The EPA offered insufficient reasoning for the convoluted and seemingly unworkable showing it demanded of New York’s petition.… More

Will Evidence of Causality Be Enough to Change EPA’s Mind About the PM2.5 Standard?

There have been numerous studies that support a decrease in the current PM2.5 annual standard of 12 ug/m3.  EPA has nonetheless proposed to retain the current standard on the basis that there is too much uncertainty regarding whether those studies provide a basis for concluding that PM2.5 concentrations below the standard cause increased mortality.  As I have previously noted, the statutory provision requires that NAAQS be set with an “adequate margin of safety.”  That would seem to require EPA to resolve such uncertainty in favor of a more stringent standard.… More

Particulate Matter Experts Still Think that the PM2.5 NAAQS Should Be Lowered. Will The Courts Defer to Them Or to EPA?

Last week, the New England Journal of Medicine published The Need for a Tighter Particulate-Matter Air-Quality Standard, written by the Independent Particulate Matter Review Panel.  For those who don’t remember, the Review Panel used to be a sub-committee of EPA’s Clean Air Science Advisory Committee, until EPA Administrator Wheeler decided that CASAC did not need the specific advice that the Review Panel had to offer.… More

EPA’s MACT Rule; Some Benefits Are More Equal Than Others

Last week, EPA formally revised the cost-benefit analysis for its rule limiting the emissions of hazardous air pollutants from coal-fired power plants.  The rule jettisons consideration of so-called “co-benefits,” in this case, the benefits from the reduction in emissions of PM2.5 that result from limits on mercury emissions.  The very idea of excluding consideration of co-benefits is just plain incoherent.

I’ve spent my career defending cost-benefit analysis to many of my environmentalist friends. … More

EPA Remains the “Anti-Environmental Protection Agency”; Wheeler Refuses to Tighten the PM 2.5 NAAQS

After more than three years of ignoring science whenever it does not support this Administration’s preferred outcomes, the issue of the future of science in environmental regulation has now been well and truly joined.  Yesterday, Administrator Wheeler, disagreeing with the recommendation of EPA’s own staff, announced that EPA is proposing to retain the current National Ambient Air Quality Standard for PM2.5 of 12 ug/m3, notwithstanding substantial evidence that PM2.5 poses significant risks even below 10 ug/m3. … More

If You Thought That COVID-19 Was Bad, Try It Mixed With Some PM2.5!

Last week, I discussed the Administration’s guidance concerning the exercise of its enforcement discretion during the COVID-19 pandemic. Now comes evidence that the guidance may actually be self-defeating.  While the administration is – understandably – trying to cut regulated industries some slack while they are trying to deal with COVID-19, it turns out that exposure to PM2.5 has a significant impact on the COVID-19 death rate.… More

Evidence That Low Exposures to Particulate Matter Pose Health Risks Continues to Accumulate — Will Administrator Wheeler Listen?

EPA’s Office of Air Quality Planning and Standards has issued its final “Policy Assessment for the Review of the National Ambient Air Quality Standards for Particulate Matter.”  The Policy Assessment comes with the standard disclaimer that its “findings and conclusions are those of the authors and do not necessarily reflect the views of EPA.”  Sadly, truer words were never spoken.

Those following this issue know that,… More

Particulate Matter Has Not Clouded My Crystal Ball

Last month, I noted that EPA’s Office of Air Quality Planning and Standards had released a draft reassessment of the particulate matter NAAQS.  In a bold moment of speculation, I indicated that it would be difficult for EPA to avoid lowering the PM2.5 NAAQS to between 8.0 and 10.0 micrograms/cubic meter.  Following issuance of the draft, and in order to ensure that EPA does not ignore the emerging scientific consensus,… More

Injunctive Relief Is Available Outside the Fenceline

On Monday, District Judge Rodney Sippel ordered sweeping injunctive relief against Ameren Missouri, intended to remedy violations of PSD requirements he had previously identified resulting from upgrades to the Ameren Missouri Rush Island generating plant. 

Notwithstanding the lengthy opinion, most of the Court’s findings are fairly plain vanilla.  Basically, Judge Sippel ordered Ameren Missouri to submit a PSD permit application and he ruled that BACT for control of SO2 emissions at Rush Island required installation of wet flue gas desulfurization equipment.… More

Good Neighbors Delayed Are Good Neighbors Denied

Last Friday, the D.C. Circuit Court of Appeals ruled that EPA violated the Clean Air Act in failing to impose deadlines on upwind states violating the CAA’s Good Neighbor provisions.  The Court concluded that, where downwind states face significant consequences in not meeting statutory deadlines to attain National Ambient Air Quality Standards, but don’t control their own fate because upwind states are contributing significantly to the downwind states’ nonattainment,… More

Particulate Matter Is More Dangerous Than We Thought: What Will EPA Do With the NAAQS?

EPA’s Office of Air Quality Planning and Standards has released a draft of its reassessment of the adequacy of the current national ambient air quality standard for particulate matter.  Here’s the primary takeaway concerning PM2.5:

The risk assessment estimates that the current primary PM2.5 standards could allow a substantial number of PM2.5-associated deaths in the U.S.

When taken together, we reach the preliminary conclusion that the available scientific evidence,… More

EPA’s Latest Particulate Review Shows Impacts Below the Current NAAQS. How Will Trump Avoid Doing Something About It?

Last week, EPA posted its draft Integrated Science Assessment for Particulate MatterIt’s the foundational document for EPA’s periodic review of its National Ambient Air Quality Standard for PM.  The current standard for PM2.5, promulgated in 2012, is 12 ug/m3.

Section 109 of the Clean Air Act requires the Administrator to set the NAAQS “requisite to protect the public health” with “an adequate margin of safety.”

The new ISA states that:

Evidence from U.S.… More

BLM Loses Another One: Resource Management Plans for Coal Leasing Areas Are Sent Back to the Drawing Board

Late last month, Judge Brian Morris granted summary judgment to plaintiffs on three claims alleging that the environmental impact analysis supported BLM’s Resource Management Plans for managing coal leases in the Powder River Basis were flawed.  It’s a very thoughtful decision.  Judge Morris rejected three of plaintiffs’ claims and did not provide the injunctive relief that they sought.  Nonetheless, it’s an important setback for BLM and further evidence that courts are going to require more of BLM in assessing climate impacts associated with energy resource development.… More

The Clean Air Act is Really Complicated; Can’t We Call the Whole Thing Off?

Last week, the Court of Appeals for the District of Columbia struck down EPA’s rule implementing the 2008 ozone standards.  My primary take-away?  The structure of the Clean Air Act is so dense and so complicated that it gives me a headache, and I do like to think I’m something of an expert.  Those of us who believe in government regulation need to be honest and admit that there’s a reason why some people become Libertarians.  … More

EPA Will NOT Second-Guess Generators’ Projections of Future Emissions Under the NSR Program

I’ve noted numerous times that the NSR program is incomprehensible gibberish.  These are scientific and objective comments.  The most recent example of this is the DTE litigation, in which a one-judge minority somehow ended up writing the opinion of the 6th Circuit Court of Appeals, allowing EPA enforcement claims against DTE Energy to continue.

The question in DTE Energy is whether EPA can second-guess a generator’s pre-construction prediction of future actual emissions and bring a claim for an NSR violation – even where post-project actual emissions did not show a significant net increase in emissions. … More

Sometimes Guidance Actually Provides Guidance

As regular readers know, the tension between guidance and regulation is one of my favorite topics.  My view is that, in general, guidance is too often used simply to avoid notice and comment rulemaking and that, once issued, it is treated by those implementing it in the agency street-level bureaucracy as though it were a rule.  Nonetheless, guidance is sometimes appropriate.  The recent decision in Sierra Club v.… More

What’s a Court to Do When EPA Misses a Statutory Deadline?

Earlier this week, a divided 9th Circuit Court of Appeals affirmed entry of a consent decree between the Sierra Club and EPA, resolving litigation over EPA’s failure to promulgate attainment designations for the sulfur dioxide NAAQS under the Clean Air Act.

I would have thought that entry of the settlement would be fairly straightforward.  EPA misses deadlines with some regularity.  Persons sue over such failures with some regularity. … More

EPA Eliminates “But For” Causation From the Exceptional Events Rule: Tort Professors Everywhere Get Excited

On Monday, EPA promulgated amendments to its “Exceptional Events” Rule.  The rule is important, particularly in the Western states, and most particularly in connection with EPA’s latest iteration of the ozone NAAQS.  EPA’s most significant revision was to eliminate the requirement that state air agencies demonstrate that, “but for” the exceptional event, the state or relevant area would have complied with the applicable NAAQS.  The change is important for two reasons. … More

The D.C. Circuit Sends EPA Back to the Drawing Board to Fix Its Transport Rule Emissions Budgets

The Clean Air Act’s good neighbor national_good_neighbor_day_zps2a06b34b (1)provision prohibits upwind states from emitting air pollutants in amounts that will “contribute significantly to nonattainment” of a national ambient air quality standard in a downwind state.  On Wednesday, the D.C. Circuit Court of Appeals held that, while upwind states have to be good neighbors, EPA cannot force them to be extraordinarily super-special neighbors.  Just good enough will have to do.… More

Kansas Thumbed Its Nose at EPA’s SIP Requirements — How’d That Work Out?

The D.C. Circuit Court of Appeals today rejected Kansas’s challenge to EPA’s disapproval of Kansas’s SIP revisions intended to comply with the Interstate Transport Rule.  The Court found that EPA was not arbitrary or capricious in rejecting Kansas’s SIP, noting that:

The discussion of interstate transport in Kansas’s SIP was only one page long and failed to provide any analysis at all of the downwind effect of its in-state emissions.… More

Half a Loaf May Not Be Too Bad: The 9th Circuit Affirms Most of EPA’s Approval of the San Joaquin Valley SIP

Earlier this week, the 9th Circuit Court of Appeals granted part of a petition challenging EPA’s approval of California’s SIP for ozone and PM 2.5 in the San Joaquin Valley.  ca_san_joaquin (1)While the trade press has been focusing on the partial reversal, I think that EPA won much more than it lost.

What did it lose?  California’s plans for complying with the ozone and PM 2.5 NAAQS relied in part on emissions reductions to be attained as a result of California’s authority under the CAA to impose more stringent mobile source emissions standards than are applicable nationally. … More

You Can’t Estop the Government — Even When It Wants to Be Estopped

Last week, the 9th Circuit Court of Appeals issued a decision that arguably explains everything from why the Tea Party exists to why otherwise calm and sane executives suddenly lose all their hair. Perhaps most astounding, the decision is clearly correct. Perhaps the law is an ass.

In 2008, Avenal Power submitted an application to EPA for a PSD permit to construct a new 600 MW natural gas-fired power plant in Avenal,… More

The SJC Gives “Great Deference” to the Energy Facilities Siting Board. That’s An Understatement

In two related decisions last week, the Supreme Judicial Court issued three important rulings, and handed the Brockton Power Company one major problem in its long-running effort to build a combined-cycle gas plant in Brockton.

First, in City of Brockton v. EFSB, the SJC rejected all of the challenges by the City of Brockton and certain citizens to the Energy Facilities Siting Board approval of the Brockton Power project.… More

83% of a Loaf Is Better Than None: The Supreme Court Affirms EPA’s Authority to Regulate “Anyway Sources”, But Rejects Regulation of Otherwise Exempt Sources

The Supreme Court today affirmed EPA’s authority to subject 83% of greenhouse gas emissions to its PSD and Title V Operating Permit programs. However, EPA’s rationale for the rule did not fare so well, and EPA does not have authority to regulate GHG emissions from facilities not otherwise subject to PSD review or the Title V program.

To EPA and the court below, the main issue – EPA’s authority – was not difficult.… More

The Wind Bloweth Where It Listeth — And the Supreme Court Says EPA Therefore Has Discretion in Regulating Wind-Borne Pollution

The Supreme Court today reversed the D.C. Circuit and affirmed EPA’s Transport Rule (known more formally as the Cross-State Air Pollution Rule). Whatever the hopes and dreams of the upwind states and the industry opponents, the decision does not surprise me. EPA pretty much did what it was told when the Bush era CAIR rule was struck down. Moreover, EPA crafted a rule that seems to me fully within its discretion under the Clean Air Act and which,… More

What Do Midwestern States Have In Common With Groucho Marx? Ask Them Whether They Want to Be Part of the Ozone Transport Region

As the Supreme Court gets ready to consider the validity of EPA’s Cross-State Air Pollution Rule, some of the Northeastern and Mid-Atlantic states are taking another tack to address at least part of the air pollution transport issue.  They have petitioned EPA under § 176A of the Clean Air Act to add Illinois, Indiana, Kentucky, Michigan, North Carolina, Ohio, Tennessee, Virginia, and West Virginia to the Ozone Transport Region established under § 184 of the CAA.… More

Mississippi v. EPA: Support of the Clean Air Science Advisory Committee is Not Necessary to Affirm EPA’s NAAQS

On Tuesday, in Mississippi v. EPA, the Court of Appeals for the D.C. Circuit affirmed EPA’s 2008 NAAQS for ozone of 0.075 ppm.  However, it remanded EPA’s decision to set the secondary NAAQS, for public welfare, at the same 0.075 ppm level.  With respect to the primary standard, the Court gave short shrift to industry and red-state challenges that the standard was too stringent.  This is not surprising,… More

Section 126 of the Clean Air Act and Cooperative Federalism: EPA May Cooperate with the Downwind State Rather than the Upwind State

On Friday, in GenOn REMA v. EPA, the 3rd Circuit Court of Appeals ruled that, in response to a petition from a downwind state under § 126 of the Clean Air Act, EPA may issue a rule imposing emission limits on a source in the upwind state without waiting for the upwind state to complete its own SIP process, which would presumably result in appropriate controls to protect the downwind state. … More

EPA Loses Another PSD Case: The Clean Air Act is “Extraordinarily Rigid”

In Sierra Club v. EPA, issued today, The Court of Appeals for the District of Columbia rejected EPA’s rules governing “significant impact levels” and “significant monitoring concentrations” for determining PSD permitting requirements for new sources of PM2.5.  Both the SIL and SMC provisions provided important exemptions from the PSD permitting regime. The Court ruled that neither provision was justified given the inflexible language of the Clean Air Act.… More