The silhouette of a skyline in front of a bright red and orange sky, obscured by smog.

Ozone Pollution

Smog Pol­lu­tion: Ozone Air Qual­i­ty Standards

Ground-lev­el ozone is pro­duced by the reac­tion of nitro­gen oxides and volatile organ­ic com­pounds in sun­shine. High ozone lev­els cause smog which, in turn, can direct­ly cause asth­ma and oth­er adverse human health effects. In 2015, the Envi­ron­men­tal Pro­tec­tion Agency (EPA) revised down­ward the allow­able lev­el of ozone in Amer­i­ca’s skies from 75 to 70 parts per bil­lion (70 ppb).


  • July 2017

    The EPA has delayed enforc­ing ozone require­ments under the final rule, includ­ing its oblig­a­tion to iden­ti­fy areas of the coun­try that do not meet ozone air qual­i­ty stan­dards (so-called non-attain­ment des­ig­na­tions”). Over the EPA’s oppo­si­tion and in response to weak­ened EPA sup­port for the 2015 smog rule, sev­en attor­neys gen­er­al also suc­cess­ful­ly moved to inter­vene in July 2017 in ongo­ing lit­i­ga­tion brought by indus­try chal­leng­ing the 2015 standard.

  • August 2018

    In August 2018, the EPA waved the white flag in the face of state attor­neys general’s join­der of the 2015 ozone suit. The agency informed the D.C. Cir­cuit Court of Appeals that it does not intend to revis­it the 2015 rule. The D.C. Cir­cuit heard oral argu­ments in the 2015 ozone lit­i­ga­tion in Decem­ber 2018.

  • August 2019

    In August 2019, the D.C. Cir­cuit sided with the attor­neys gen­er­al. The court found that a grand­fa­ther­ing pro­vi­sion in the 2015 rule that exempt­ed sources from com­ply­ing with the 70 ppb stan­dard, if the sources had com­plet­ed appli­ca­tions for pre­con­struc­tion per­mits before the 2015 rule was adopt­ed, was pro­hib­it­ed under the clear lan­guage of the Clean Air Act.

Blunt­ing Leg­isla­tive Efforts to Delay Ozone Standards


In ear­ly 2017, Con­gress intro­duced a bill to delay com­pli­ance with ozone air qual­i­ty stan­dards (the Ozone Stan­dards Imple­men­ta­tion Act). In April 2017, a coali­tion of state attor­neys gen­er­al deliv­ered a joint state­ment to Con­gress express­ing strong oppo­si­tion to the leg­is­la­tion. The pro­posed leg­is­la­tion did not pass.

Forc­ing EPA to Des­ig­nate Ozone Non-Attain­ment Areas

The Clean Air Act requires that the EPA des­ig­nate areas of the coun­ty that are in attain­ment” or non-attain­ment” of air qual­i­ty stan­dards with­in two years of the issuance of new or revised standards.


In the case of the 2015 smog stan­dards dis­cussed above, the EPA was required to issue attain­ment and non-attain­ment des­ig­na­tions by Octo­ber 1, 2017. The EPA has tried to evade its legal duty to iden­ti­fy ozone non-attain­ment areas. State attor­neys gen­er­al have called out the EPA’s fail­ure to iden­ti­fy ozone non-attain­ment areas, and are forc­ing the agency to des­ig­nate such areas, as required by law.

Non-attain­ment Designations


In June 2017, EPA Admin­is­tra­tor Scott Pruitt sought to push back the Octo­ber 2017 dead­line for iden­ti­fy­ing ozone non-attain­ment areas until Octo­ber 2018 on the grounds that the EPA need­ed to col­lect more infor­ma­tion to make final decisions.

Dis­trict of Colum­bia Cir­cuit Court of Appeals Litigation

  • August 2017

    In August 2017, New York Attor­ney Gen­er­al Eric Schnei­der­man and a coali­tion of 16 attor­neys gen­er­al sued the EPA in the Dis­trict of Colum­bia Court of Appeals for ille­gal­ly delay­ing the des­ig­na­tions. The next day, the EPA abrupt­ly reversed course and announced it was with­draw­ing the des­ig­na­tions delay, although it remained equiv­o­cal on whether it would meet the Octo­ber 1, 2017 dead­line. That dead­line passed with­out the EPA mak­ing the required non-attain­ment des­ig­na­tions, in vio­la­tion of the Clean Air Act.

    A few days lat­er, a coali­tion led by state attor­neys gen­er­al noti­fied the EPA of its inten­tion to sue if the agency failed to cor­rect the vio­la­tion with­in 60 days. 

  • Novem­ber 2017

    In Novem­ber 2017, EPA issued des­ig­na­tions for some areas of the coun­try, but failed to make any non-attain­ment” area des­ig­na­tions, which are the des­ig­na­tions that trig­ger smog reduc­tion mea­sures to improve air qual­i­ty and to com­ply with the ozone standards.

  • Decem­ber 2017

    In Decem­ber 2017, the D.C. Cir­cuit Court, in lit­i­ga­tion con­sol­i­dat­ed (“con­sol­i­dat­ed lit­i­ga­tion”) with the states’ August 2017 law­suit, ordered the EPA to spell out the timetable for remain­ing com­pli­ance deci­sions relat­ed to its 2015 ground-lev­el ozone stan­dard. The order instruct­ed agency offi­cials to report with pre­ci­sion and speci­fici­ty” when the EPA would issue a final rule to set remain­ing des­ig­na­tions for the 70 parts per bil­lion standard.

  • Jan­u­ary 2018

    In Jan­u­ary 2018, the EPA announced its inten­tion to make its non-attain­ment des­ig­na­tions by April 30, 2018. It sub­se­quent­ly amend­ed its announce­ment, not­ing that it would not com­plete non-attain­ment des­ig­na­tions for cer­tain areas in Texas until after April 2018. On April 30, 2018, the EPA released its non-attain­ment des­ig­na­tions, except for eight coun­ties in Texas; EPA des­ig­nat­ed the remain­ing Texas coun­ties in July 2018.

  • May 2018

    In May 2018, New York Attor­ney Gen­er­al Bar­bara Under­wood and 14 oth­er attor­neys gen­er­al filed a response in the con­sol­i­dat­ed lit­i­ga­tion chal­leng­ing EPA’s fail­ure to issue ozone des­ig­na­tions. The response to the EPA’s sta­tus report to the court in the lit­i­ga­tion not­ed that the EPA, con­trary to its claims, had not com­plet­ed all steps regard­ing nonat­tain­ment area des­ig­na­tions because the des­ig­na­tions were not yet effec­tive as they had not been pub­lished in the Fed­er­al Reg­is­ter. Con­se­quent­ly, the attor­neys gen­er­al asked the D.C. Cir­cuit to vacate the EPA’s June 2017 one-year exten­sion of the ozone des­ig­na­tion process and to deny the EPA’s request to moot the August 2017 litigation.

  • June 2018

    In June 2018, the D.C. Cir­cuit sided with the attor­neys gen­er­al and ordered the EPA to file a sta­tus update on the ozone des­ig­na­tions by July 312018.

  • Jan­u­ary 2019

    In Jan­u­ary 2019, the D.C. Cir­cuit, stat­ing that the notice extend­ing the dead­line for EPA to pro­mul­gate ozone des­ig­na­tions had been with­drawn and that EPA had issued final des­ig­na­tions, dis­missed the states’ chal­lenge in the con­sol­i­dat­ed lit­i­ga­tion to EPA’s fail­ure to time­ly issue ozone sta­tus des­ig­na­tions. The court found that it could no longer pro­vide an effec­tive rem­e­dy” because the states had already obtained all the relief” sought and that their claims were moot.

Cal­i­for­nia Fed­er­al Dis­trict Court Litigation

  • Decem­ber 2017

    In Decem­ber 2017, for­mer New York Attor­ney Gen­er­al Schnei­der­man, lead­ing a coali­tion of 15 state attor­neys gen­er­al, filed a law­suit against the EPA in fed­er­al dis­trict court in Cal­i­for­nia for fail­ing to meet the Clean Air Act’s statu­to­ry dead­line for des­ig­nat­ing areas of the coun­try impact­ed by unhealthy lev­els of ground-lev­el ozone. 

  • March 2018

    In March 2018, the court ruled that the EPA had failed to meet the statu­to­ry dead­line and ordered the EPA to des­ig­nate areas of the coun­try impact­ed by unhealthy lev­els of smog by April 302018.

Attain­ment Designations


  • April 2018

    With­in a week of the release of the April 2018 non-attain­ment des­ig­na­tions, Illi­nois Attor­ney Gen­er­al Lisa Madi­gan announced her inten­tion to file a law­suit chal­leng­ing the EPA’s deci­sion that Wisconsin’s Racine Coun­ty is an ozone attain­ment area, despite data indi­cat­ing that it should be clas­si­fied as in a non-attain­ment area because the area exceeds the 70 parts per bil­lion ozone stan­dard. If it stood, the EPA’s des­ig­na­tion would have allowed Fox­conn, which had stat­ed its inten­tion to build a large man­u­fac­tur­ing plant in the Coun­ty, to avoid installing emis­sions controls.

  • August 2018

    Attor­ney Gen­er­al Madi­gan fol­lowed through and filed suit chal­leng­ing the EPA’s ozone attain­ment deci­sion in August 2018.

  • May 2019

    In May 2019, the EPA request­ed that the D.C. Cir­cuit, which is hear­ing Illinois’s chal­lenge of the EPA’s Racine Coun­ty des­ig­na­tion deci­sion, remand the mat­ter back to the agency in order to review the des­ig­na­tion and pos­si­bly revise it.

  • July 2020

    In July 2020, the D.C. Cir­cuit released a deci­sion on the mer­its of the EPA’s attain­men­t/non-attain­ment des­ig­na­tions in a slew of states. In a com­pli­cat­ed deci­sion, the court sided with the Illi­nois attor­ney gen­er­al in con­clud­ing that EPA’s des­ig­na­tion for Wisconsin’s Racine Coun­ty as an attain­ment area was arbi­trary and capri­cious in vio­la­tion of the Admin­is­tra­tive Pro­ce­dure Act (APA). The Racine Coun­ty des­ig­na­tion was remand­ed to the EPA, which was direct­ed to com­plete the des­ig­na­tion as expe­di­tious­ly as practicable.”


The Clean Air Act requires the EPA to review the pub­lic health impacts of ozone and oth­er pol­lu­tants every five years and set an ambi­ent thresh­old to pro­tect pub­lic health and welfare. 


  • August 2020

    In August 2020, the EPA released a pro­posed deci­sion to retain the exist­ing Nation­al Ambi­ent Air Qual­i­ty Stan­dards (NAAQS) for ozone. Since the last review of the ozone NAAQS was com­plet­ed in 2015, new data and sci­en­tif­ic research has emerged on the neg­a­tive impacts of ozone. Numer­ous epi­demi­o­log­i­cal stud­ies and sev­er­al reviews from health and envi­ron­men­tal agen­cies have found that short-term expo­sure to ozone pol­lu­tion is asso­ci­at­ed with increased mor­tal­i­ty and numer­ous oth­er med­ical conditions.

  • Sep­tem­ber 2020

    In Sep­tem­ber 2020, a coali­tion of 14 attor­neys gen­er­al led by New York Attor­ney Gen­er­al Leti­tia James sub­mit­ted com­ments in oppo­si­tion to the pro­pos­al. The coali­tion high­light­ed that leav­ing the stan­dards unchanged will be par­tic­u­lar­ly harm­ful to envi­ron­men­tal jus­tice com­mu­ni­ties, who bear a dis­pro­por­tion­ate bur­den of the pub­lic health impacts of ozone pol­lu­tion. The attor­neys gen­er­al empha­sized that their states have an inter­est in pro­tect­ing minor­i­ty, low-income, and indige­nous com­mu­ni­ties from the dis­parate impacts of air pol­lu­tion, but are unable to do so with­out reli­able stan­dards in place.

    The coali­tion also high­light­ed changes to the NAAQS review process the EPA made in 2018 that under­mine the sci­en­tif­ic cred­i­bil­i­ty of the agency’s analy­sis by arbi­trar­i­ly exclud­ing sci­en­tif­ic experts, trun­cat­ing and elim­i­nat­ing impor­tant steps, reduc­ing trans­paren­cy and cur­tail­ing oppor­tu­ni­ties for pub­lic input. The attor­neys gen­er­al empha­sized that the EPA failed to pro­vide any expla­na­tion for the changes to the review process, which col­lec­tive­ly ren­der the agency’s pro­pos­al to retain the exist­ing stan­dards arbi­trary and capricious.

  • Decem­ber 2020

    In Decem­ber 2020, the EPA final­ized its deci­sion to retain cur­rent stan­dards for ozone pol­lu­tion, fail­ing to pro­tect the health of peo­ple suf­fer­ing from expo­sure to the dan­ger­ous pollutant.

  • Jan­u­ary 2021

    In Jan­u­ary 2021, a coali­tion of 16 attor­neys gen­er­al led by New York Attor­ney Gen­er­al James filed a peti­tion for review chal­leng­ing the deci­sion as unlaw­ful, arbi­trary, and capri­cious. As of June 2021, the lit­i­ga­tion was in abeyance.