### 8202

[6560-01-M]

Title 40-Protection of Environment

CHAPTER I-ENVIRONMENTAL PROTECTION AGENCY

SUBCHAPTER C-AIR PROGRAMS

[FRL1018-2]



### PART 50-NATIONAL PRIMARY AND SECONDARY AMBIENT AIR QUALITY STANDARDS

Revisions to the National Ambient

Air Quality Standards for Photochemical Oxidants

AGENCY: Environmental Protection Agency.
ACTION:Finalrulemaking.
SUMMARY: In accordance with the provisions of Sections 108 and 109 of the Clean Air Act as amended, EPA has reviewed and revised the criteria upon which the existing primary and secondary photochemical oxidant standards are based. These standards

were promulgated in 1971 (36 FR 8186) and were both set at an hourly average level of 0.08 part per million (ppm) not to be exceeded more than 1 hourper year. On June 22, 1978, EPA proposed changes in the standard (43 FR26962) based on.thefindings ofthe revised criteria. The proposedchanges included (1)raising the primary standard to 0.10 ppm, (2) retaining the 0.08 ppmsecondary standard, (3) changing the chemical designation ofthe standard from photochemical oxidants to ozone, and (4) changing to a standard with a statistical -rather than deter-' ministic form. The final rulemaking willmakethree further changes inthe standard: (1) Raising the. primary 

### standard to 0.12 ppm, (2) raising the secondary standard,to 0.12 ppm, and (3) changing the definition of the point at which the standard is attained to "when the expected number of days per calendar year with maximum hourly average concentrations above 0.12 ppmisequal to orless than one."
EFFECTIVE DATE: This revision is effective immediately upon publication.The normal 30-day delay ineffectiveness is not required, when, as in thiscase, arestriction iseased.
FOR FURTHER INFORMATION CONTACT:

Mr. Joseph Padgett, Director (MD12), Strategies and Air Standards Division, Office of Air Quality Planning and Standards, U.S. Environmental Protection Agency, Research Triangle Park,NC 27711, Telephone: 919-541-5204 (FTS629-5204. RULES AND REGULATIONS

AVAILABILITY OF RELATED INFORMATION: A docket (Number OAQPS 78-8) containing information used by EPA in revising the standards is available for public inspection and copying between 8:00 a.m. and 4:30
p.m. 'Monday through Friday, at EPA's Central Docket Section, Room 2903 Waterside Mall, 401 M Street SW,Washington DC 20460. These ma- terials include the "Air Quality Criteria for Ozone and Other Photochemical Oxidants" and "Control Techniques for Volatile Organic Emissions from Stationary Sources," both of which were issued simultaneously when this standard was proposed. The controltechniques document and staff
papers pertaining to the form of the

ozone standard, risk assessment method, secondary standard, and health panel assessment are available upon request from Mr. Joseph Padgett.Statements ofthe environmental, economic, and energy impacts of implementing this standard revision are also available upon request from Mr. Joseph Padgett, at the address shown above. The air quality criteria document can be obtained from: Mr. Michael Berry (MD-52), Environmental Criteria and Assessment Office, Office of Research and Development, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, Telephone: 919-541-2266 (FTS 629-2266).

This preamble describes revisions-to 40 CFR Part 50, Appendix H, "Interpretation ofthe National Ambient Air Quality Standards for Ozone," and Appendix D, "Measurement Principle and Calibration, Procedure for the Measurement of Photochemical Oxidants Corrected forInterferences Due
to Nitrogen Oxides and Sulfur Dioxide," that are related tothe revision of the air quality standard for ozone. In addition,elsewhere in this issue ofthe
FEDERAL REGISTER EPA is promulgating revisions to 40 CFR Part 50, Appendix D, replacing (superseding) the
current calibration procedure with a new, superior calibration procedure based onultraviolet photometry.

Revisions to 40 CFR Part 51, substituting the word "ozone" for "photochemical oxidants" throughout that part, and to Section 51.14, pertaining
to control strategies, are beingpromulgated by EPA elsewhere in this issue oftheFEDERALREGISTER.
SUPPLEMENTARY INFORMATION:

BACKGROUND'

On April 30, 1971, the Environmentdl Protection Agency promulgated in 

### the FEDERAL REGISTER (36 FR 8186) National Ambient Air Quality Standards for photochemical oxidants. The scientific, technical, and medical bases for these standards are contained in the air quality criteria document for photochemical oxidants, published by the'U.S. Department of Health, Education, and Welfare in March 1970. Both the primary and secondary standards were set at an hourly averagelevel of0.08 ppm not to be exceeded more than once per year. The asthma study cited as evidence forthe original standard is based on work by Schoettlin and Landau (1961). As discussed in the June 22, 1978, proposed revision to the original standard, EPA has reassessed Its conclusions regarding this study. This reassessment, plus the evaluation ofmedical evidence accumulated since 1970, led EPA to propose, on June 22, 1978, a revised primary standard of 0.10 ppm (43 FR 26962). EPA did not propose a change in the secondary welfare standard at that time. The proposal was accompanied by publication of revised criteria and control techniques documents, as well as various staff papers relating to the standard Itself and to implementa. tion of the standard. EPA solicited written comments on the proposed standard and, to accept oral testimony, sponsored four public hearings (Washington, D C.-July 18; Altanta, Ga-August 17; Dallas, Tex.-August 22;Los Angeles, Calif.-August 24).

Oxidants are strongly oxidizing com- pounds, which are the primary constituents of photochemical smog. The oxidant found in largest amounts is

ozone (0.), a very reactive form of
oxygen. Oxidants also include the group ofcompounds referred to collectively as peroxyacylnitrates (PANs) and other compounds, all produced in much smaller quantities than ozone.

Most ofthesematerials arenot emitted directly into the atmosphere but result primarily from a series of chemical reactions between oxidant
precursors (nitrogen oxides and organic compounds) in the presence of sunlight. The principal sources of organic compounds are the hydrocarbon emissions from automobile and truck ex- hausts, gasoline vapors, paint solvent evaporation, open burning, dry cleaning fluids, chemical plants and other industrial operations. Nitrogen oxides

are emitted primarily from combustion sources such as electric power generation units, gas and oil-fired
space heaters, and automobile, diesel andjet engines.

The reductions in emissions ofnitrogen oxides and organic compounds are achieved through Federal and State
programs thathave been formalized In regulations promulgated under the Clean Air Act. The Federal programs provide for reduction in emissions na- tionwide through the Federal Motor Vehicle Control Program, the Federal
program for control of aircraft emissions,National Emission Standards for Hazardous Air Pollutants, and the development of New Source Performance Standards. The State prggrams

FEDERAC REGISTER, VOL 44, NO 28-THURSDAY, FEBRUARY 8, 1979RULES AND REGULATIONS

Provide for, additional control meas-
ures through State Implementation Plans in those areas of the country where the Federal programs are not sufficiently stringent to permit attainment ofairquality.standards.

LEGISLATIVE REQu mE s AFCnTG TISPROIUL-GATION

Two sections -ofthe Clean Air Act
govern the develpment-of!a National Ambient Air Quality Standard. Section 108 instructs EPA to document the scientific basis 'criteria) :for the standard, and Section 109 provides guidance on establislhing standards andreviewingthecriteria. I

Air quality criteria are required by Section 108(a)2) to reflect accurately thelatest scientific information useful in indicatingthe kindandextentofall identifiable effects onpublic health or welfare that may be expected from the presence of the pollutant in the ambientair.

The 'Administrator as required to propose simultaneously vith the issuance ofthese criteria, primary andsec- ondary ambient air quality standards basedupon such-criteria.Theprimary standard is defined in Section 109(b)(1) us the,ambient air quality standard the attainment and maite-

nance,ofwhichin the Administrator's judgment, based on such -riteria and allowingan adequate margin ofsafety,

are requisite to protect the public health. 7The-secondary standard 'Section 109(b)(2)) must specify alevel the attainment and maintenance ofwhich in the Administrator's judgmerit, based-on such criteria,are requisite to protect the public welfare from -any known or anticipated adverse effects associated with the presence of the pollutantin theambient air.These ad-

verse welfare effects, which are discussed in Section 302(h)-oftheAct,inelude effects on soils, water, crops, vegetation, man-made materials, animals, weather, -visibility, hazards to transportation, economic 'alues, 'personal -comfort -and well-being, and other factors.

The -CleanAirAct specifies that 'primary National Ambient Air.Quality Standardsareto bebased on scientific criteria relating to -the level that should be attamned to protect public health adequately. Considerations of
cost of achieving those standards or the existence of technology to bring about needed reductions of-emissions

arenot germane to such a determination, as the words of the Act and its legislative history clearly indicate. Section 119d) directs-theAdmitratorto-complete 

### a review of allexisting standards and criteria before the end of1980 and at5-year intervals thereafter and to revise them.in whatever

manner that xeview reveals is necessary. This promulgation Is the result ofsuch a review.

Assuring attainment and mainte-

nance ofambient airquality standards is the responsibility of the States. Under section 110 oftheAct, they are to subrait to EPA for approval State Implementation Plans (SIPs) thatprovide for the necessary legal requirements for sources ofthe relevant pollutant so as to demonstrate attainment and maintenance of the standards by certain deadlines. In many

areas of the country the ambient air quality standards -are not being attained, despite the fact that the ,dead

### line for attainment has 

### -long since passed.As aremnedy, PartD oftheAct requires states withviolations ofambientair quality standards tosubmit re- vised-SIPs toensure attainment ofthe standards and to meet certainnew r- quirements of Part D by January 1, 1979. -Section 129(c), Pub. L. 95-95, 

### noteunder 42 U.S.C. 7502.) The Act does notauthorize the Administrator
to extend that deadline, and conse- quently this revision of the photochemical oxidant standard does not affect the deadline for submittal of SIPrevisions.

Section 110(a)(1) requires that SIP revisions be submitted -within 9 months after a standard is revised. However, thisprovisionrefers to situations where a standard Is tightened. with the resultthat existing SIPs are
no longer adequate to attain and maintain 'the standard in question. Where a standard Is relaxed, no SIP revision is required by the law, since
states may have more stringent con- trolsthan necessary ifthey choose.

Furthermore, the change in the chemical species designation of the standard from photochemical oxidants
to ozorne does not make this standard subject to the provislon of section ll0(a)(1) cited above. The intent of the standard (total-oxidant reduction), the control strategies, and the index ofProgress toward attainment (measuredozone levels) remainunchanged.

SummAny OF GEN- L 

### FnrNGS 

### 'FROM

AI QuAL= CRITRAl voR Ozoxn AND 

### P110T0CHrrQcL OXIANTZS

On April 20, 1977, EPA announced (42 FR 20493) that it wa reviewing and updating the 1970 criteria document for photochemical oxidants In accordance with provisions -ofsection 109(d)(1) of the Clean Air Act as amended. The notice called forInformationand datathatwouldbe helpful inrevising the document In preparing the-criteriadocument.EPA provided a number of opportunities for external review and comment. Two drafts of the document have been made available for external review, and EPA re- cieved more than:Owritten comments

on the first draft and approximately 8203



### 20 on the second draft. TheAmericin Petroleum Institute has submitted extensIve information that EPA consideredInthisstandard review Thecriteria document was the subject of two meetings of the Subcommittee on Scientific Criteriafor Photochemical OxIdants of EPA's Science Advisory Board. Each of these meetings 'was open to the public, and a number of individuals presented both- critical review and newinformation for EPA's consideration. A full discussion of comments received during the review process,aswellasEPA's dlspositionof these comments, can be found in the docket (OAQPS 718-8) assembled for thisrulemaking.

From EPA's review-ofthe scientific information presented in the criteria document, several key areas withpar- ticular relevance to setting the ozone standard haveemerged:

1.27Thshold concept-Although the concept of an adverse health effect threshold has utility in. setting ambient air quality standards, the adverse health effect threshold concentration cannot be Identified with certainty. The lowest concentration which

causes measured health effects in a scientific experiment depends on the particular subjects who have been studied because sensitivity to pollutants varies among different members of,thepopulation.Onlylimitedstudies

canbh perfcrmed ongroupsofunusually sensitive 'persons. Most experi- mental studies ofhuman subjects are performed on small numbers ofrelatively healthy persons who -do not fullyreflect the rangeofhumansensitivity. Also, theair to which thesubjects are exposed does notincludethe full mix ofchemicals other than the pollutant being studied which are in theambient air.Someofthese chemicals may be additive with the given pollutant in causing the adverse health effect, so that lower levels of the pollutant will resultin the effect. Animal exposure studies cannot pro- videprecise models ofsensitivehuman populations. Thus, adverse health effect thresholds for sensitive persons
are difficult or impossible to determine experimentally, while the threshold for healthy persons oranimals Is not likely to be predictive of theresponse ofmore sensitive groups Inthis notice ofrulemakingEPAuses the terminology 'probable effects level" to refer to the level that in its bestjudgment Ismostlikely tobethe adverse health -effect threshold concentration. It is the fact that the adverse health effect threshold concentration Is actually -unknownthat necessitates the margin of safety requiredbytheAct.

2. Ozone health effects-Ozone is a pulmonary irritant that affects the respiratory mucous membranes, other

I

FEDERAL REGISTER, VOL 44, NO. 28-THURSDAY, FEBRUARY 8, 1979

### 8204

lung tissues and respiratory functions. Clinical and epicemiological studies have demonstrated that ozone impairs the normal mechanical function ofthe human lung and causes clinical symptoms such as chest tightness, coughing and wheezing. These effects mayoccur in sensitive individuals, as well as in healthy exercising persons, at shortterm ozone concentrations between 0.15 and 0.25 ppm.The clinical studies data base for these effects is far more extensive than that which was available in 1970, andthese effects have now been demonstrated at lower levels than those cited in.the 1970 criteria document.

3. Effects on Aithmatics-The best available evidence suggests that an elevated proportion of asthmatics ex- perience attacks on days when the peak hourly oxidant concentratiohs reach about 0.25 ppm..This finding is based on areevalution ofthe study-by Schoettlin and Landau (1961).

4. Toxicologic findings-The key finding from toxicologic studies is the increased susceptibility to bacterial infection in laboratory animals exposed
to 0.10 ppm ozone and a bacterial challenge. Infection rates are lower for animals exposed only to the'bacterial challenge. Other effects such as biochemical changes, morphological abnormalities, and genetic changes have been foundin some studies of animals exposed' to ozone concentrations as low as 0.1 to 0.3 ppm. While the data from animal studies cannot be directly extrapolated to man, they can be taken as indicators ofthe fullrange of effects that may occur in humans. The epidemiology study by Durham (1974) that reported increased rates ofillness in college studentsfollowing periods of elevated air pollution levels (withpeak oxidant being the pollution' variable
most strongly associated with illness) further increases our concern regarding the implications for man of the animal study findings.

5. Ozoneeffects onagingprocessesA limited amount of data suggests that ozone may accelerate the aging process in living organisms. Exposure of rabbits to unspecified concentrations ofozone for 1 hour per weekfor

a year has been reported to induce premature aging symptoms such as premature cartilage calcification,

severe depletion of body fat, and the, general signs of aging (Stokinger, 1965).

6. Pollutant interactions-Thefact that ozone exposure is frequently ac- companied by exposure to other pollutants, such as sulfur dioxide, (SO), has prompted several investigators to conduct laboratory evaluations of ex- posure of human subjects to combinations of 0 and other pollutants. Simultaneous exposures to.0.37 ppm 0. and 

### *0.37 ppm SO2 were reported to RULES AND REGULATIONS

produce larger changes in pulmonary function-than exposure to either pollutant alone. No obvious effects were observed in other simultaneous expo-

sure tests using 0.25 ppm 0, and 0.3
ppm nitrogen dioxide (NO.), aswell as "O.;NO2, and' 30 ppm carbon monoxide (CO). Nevertheless, the SO2-03 synergism findings support,the need for an adequate margin of safety in the

ozone standard.

7.Mortalitystudies-Nostudies have conclusively linked exposure to ozone
or photochemical oxidants with an in-

crease in human mortality. A number ofepidemiologic studies have been designed and conducted to demonstrate thiseffect, but in each case the results havebeennegative orinconclusive.

8. Welfare effects-Ozone accelerates the aging of many.materials, resulting in rubber cracking, dye fading and paint erosion. These effects are linearlyrelatedto thetotaldoseofozoneand

can occur atverylow levels, givenlongduration exposures. Damage to vegetation, as expressed by decreased growth and yield, is related to the long-term (growing season) mean of the daily maximum 6- to'-8-hour-average ozone concentrations.

9. Causesandcontr6lofoxidantoollution-All presently available evidence indicates that around urban
centers with severe oxidant problems, the major concern is the formation of photochemical oxidants from man- made organic and nitrogen oxide emissions. Control of these emissions will result in significauit reductions in am- bient ozone, peroxyacetylnitrate (PAN), aldehydes and photchemical aerosol.

As is the case with most standard-' setting activities, the data base on

ozone will continue to expand after the standard is set. EPA will continue
to inform itselfofnewresearch results and also will accelerate the schedule for its own research on the health effects of ozone and other photochemical oxidants at low exposure levels. The Agency plans to make the results of these studies available as they are completed and to issue an interim report on all new research results in
twoyears. 

### RUI.EMAKING PETITIONS

The Agency was petitioned by the American Petroleum Institute (API) and 29 member companies on December 9, 1976, and by the City of Houston on July 11, 1977, to revise the criteria, standards and colitrol strategy guidelines for photochemical oxidants. EPA had already begun such a revision when both petitions were filed, and the Agency responded that It was deferring decision on these petitions until the rulemaking was-completed. EPA considers this final rulemaking and the accompanying one on control strategy guidelines to be the Agency's final action on these petitions. A summary of the two petitions and EPA's
response Isgivenbelow.

The API petition requested that EPA revise the air quality criteria document for photochemical "oxidantsin light ofnew information regarding the

causes, effects, and extent ofair pollution attributed to ozone and other oxidants.EPA has publlshed a revised air quality criteria document for photochemical oxidants; in the Agency's judgment, this document accurately reflects the latest scientific information regarding the causes, effects, and
extent of air pollution attributed to

ozone and otheroxidants.

The second request in the API petition was that EPA establish a national primary ambient air quality standard based on new studies that allegedly demonstrate no significant adverse human health effects at or beloW

ozone levels of 0.25ppm for 2-hour ex- posures. As requested by API and as required under the Clean AirAct, the Agency has considered all new studies published since 1971 that are relevant
to 'setting a revised primary standard the attainment and maintenance of which would, in the Administrator's judgment, protect the public health with an adequate margin of safety, EPA disagrees with API's conclusion that new studies conducted since 1971 demonstrate no significant adverse human-health effects at or below 0.25 ppm.

A more detailed discussion ofEPA's judgments regarding reported or prob. able health consequences at concen- trationsbelow 0.25ppm Ispresented in the rationale for revising the primary standard and In the response to com- ments, which appear elsewhere in this notice.

The third request by API was that the national secondary ambient air quality standard .be based on adverse effects on public welfare as-indicated by studies using ozone-speciflc mea- surement methods. In addition, API concluded that Congress intended that EPA weigh the overall economic and social impact of a lower secondary standard against adverse effects of a pollutant. EPA has reviewed the data presented in the criteria document and concluded that there Is currently

no evidence ofasignificant decrease in yield or growth to commercially im. portant cropsfor short-term exposures to ozone concentrations below 0.12 ppm.: EPA believes a secondary standard more-stringent than the primary standard is unnecessary and that a cost-benefit analysisIsnot required,

In their petitions, both API and Houston requested EPA to state the primary and secondary standards so as topermit reliable assessments ofcom- pliance. EPA agrees that the present

FEDERAL REGISTER, VOL 44, NO. 28.--THURSDAY, FEBRUARY 8, 1979deterministic form of .the oxidant standard has seVeral limitations ,and _ias made reliable assessment of com- pliancedifficult. Therevised ozone air

.-ualityxtandards are stated ina statis- -ical form that Vl more accurately reflect the air quality problems in var- ious regions of the country and allow

more reliable assessment of compli-

ance withthestandards.

The API'and Houston petitions re- quested thatEPA specifythe use ofan afpropriate -measurementmethod for monitoring ambient concentrations of

ozone. API suggested the useof ethyl-

-ene-chemilunminescence calibrated by either gas hasetitration (GPT)orn1- travioletXUV) Photometry. As aresult of EPA's continuing evaluation ofsev

### eral calibration techniques, the Agen&y .as defined the reference methodto be ethylene chemnlumines-

cence calibrated by UV photometry. (See ,the 2mendment toAppendix Dof 40 CYR Part 50 elsewhere inthis edi

### tionofthe YFlEDm-Rsom ) EPAis allowing the use ofa modified version of the -current alibration method (acidified-I) as aninterim measureto avoidproblems that wouldresultfrom immediate conversion to UV photometry.

Boththe APT and -Houston petitions requested revision ofthe State Imple-"' mentation-Plan (SIP)requirements (1)
to delete the assumption of no background -concentration of photochemi- 

### caloxidantsand-2) to specifymorereliable alternative oxidant prediction relationships to replace AppendixJ of 40 CM Tart 51 for determining the degree ofnecessary-precursor emission reductions.

With respect to thefirstpoint,-EPA recognizes thatbackground concentrations and transport of ozone from upwind locations can contribut to high levels of ozone in or near an urban area iduring the aftemoon hours. Therefore, several revisions are beingmadein controlstrategyand implementation guidelines for ozone. Therevised guidelines set forthprocedures for consideration of both

- upwind transport andirreducible natural background by the States in calculating -the-necessary reductions -in hydrocarbon emissions. In response to the second request, EPA has determined that Appendix J of 40 CER Part 51 no longer represents -an ac- Ceptable -analytical relationship between hydrocarbons and ozone. Appendix ff is, therefore, being deleted. EPA will now allow States -to-use-any of four analytical techniquesto determine the amount of hydrocarbon xe- duction necessary to -demonstrate attainment of the national ozone air quality standards: (1) Photochemical dispersion .models, (2) Empirical Kinetics Modeling Approach EKMA), (3) Empirical and statistical-models, 

### RULES AND REGULATIONS

and ,(4) Proportional rollback. These four techniques are discussediurther inthe revision -of Prt 5L which ap

### pears elsewhere in thisedition-ofthe

FEDERALREGISEL



### The Houstonpetitionrequested that EPA consider Information InTheirpetition relative to atmospheric -conditions and other factors that affect photochemical oxidants In the Houston area. The petition claimed that the airpollution problems inHouston warrant special-attentionIn standardsetting -and -tailor-made" control strategies, because the emission and meteorology situations and theoverall pollution picture In that area are "unique °



### In response to the above -claim. it ,shouldbe :noted that the majority of 

### thedatapresented In therevised criteTiadocument arebased onozone exposure. Nearlyall ofthe clinical andtoxicological studies arebased-onthe effects -of ozone. The biomedical -data also suggest that many of the effects observed during periods of elevated 'photochemicaloxidant -concentrations

are reasonably attributable primarily toozone inthe ambient air.Sincethe primary and secondary standards are based on theeffects ofozone, the differences between areasintheiroverall photochemical oxidant mixtures do not bear -uponthe setting ofnational

ozone airqualitystandards.

EPA -agreeswith the Houston peti- tion that components of the photo- chemical oxidant mixture other than

ozonemay have an adverse Impacton health and/or welfare. The data base isnot, however.sufficientatthis time tojustify aseparatestandard forPAN

or other non-ozone oxidants. While EPA does notproposetoestablishsep- -orate standardsforthenon-ozone constituents ofthe mixture at thistime. thoseaneasures taken to reduce ozone precursor emissions will also reduce PAN and othernon-ozone oxidant concentrationlevels.

In response toHouston's requestfor

aunique standard based on theirlocal situation, it must be realized that the Clean Air Act does not contemplate separate standards for different cities. Dealingin termsof -national -ambient air quality standards, the Act charges -EPAtoidentify the air-qualitylevels which must be attained and mantaned to ensure, with an -adequate margin of'safetyo that adverse 3health effects willnot ccur.

The Houston petition alsorequested that 'EPA include realistic requirements for the xeduction of oxides of nitrogen as-conditionsin the-Houston

area may ndicate to be necessary to achieve the revised standards. IEPA's xesponseIsthatIt Istheresponsibility of-theStateofTexas and the City of Houston to'submitState Implementa- tionPlanprovisions tailored tothesit

### 8205

uaton prevailing in Houston. If the
current SIP is not representative of the most efficient means ofreducing

ozone in Houston, then, with Houston's assistance, Texas should submit

-arevision thatIsconsistent -withlocal emission and meteorological condi-- tions.

Suznax orComxa=Ts RECE=vED


### EPA has solicited public comment and critique onproposed revisions to the photochemical oxidantair quality standard during all phases of the standard development process. Prior to proposal (April 20, 1977), EPA an- nounced (42FR 20493) that it wasre- viewing and updating the criteria docUmnentand called forinformation that might behelpfulin revising the document. Public comments were received

ontwo-drafts of.the criteriadocument, and the public was invited to two meetings of the Subcommittee ,onScientific Criteria forPhotochemical Oxidants of EPA's Science Advisory Board.In addition, the Agency helda public meeting onJanuary30, 1978, to 

### receivecomments frominterested parties prior to development of any formal Agency position on the initial proposed revision of -the standad. .In particular, EPA actively solicited the participation,oftheStateand TerritorialAirPollution ProgramAdministrators (STAPPA) and theAssoeiation of Local Air Pollution Control Officials (ATLPCO) in -this meeting; several representatives of these groups offered comments at the meeting. The results ofthismeeting arediscussed in theproposedregulaton X43FR 26970) and a transcript -ofthe meeting is available indocket OAQPS 78-8.

Following proposal, -EPAheld four public meetings to Teceive comments

on the proposed standard revisions. Meetings were held In Washington. D.C.-July 18; Atlanta, 'Ga-August 17; Dallas, Tex.-August 22; and los Angeles, CalIL-August 4;,transcripts

are avallable in ,docket OAQPS I8-. In additIon, 168 -ritten comments

were received during the formal com- mentperiod,-which extendedthrough October 16. 1978.

Theprincipal comments andAgency responses :are summarized in -thefollowing paragraphs (individual re- sponses to comments -are contained in docket OAQPS 78-8). EPA also re- ceived comments on the proposed standard after October 16. .Although EPA does not have a legal obligation to review these comments, all significant issues raisedin thepost-October 16 comments havebeen addressed and responded to aspart ofthe discussion ofcomments inthis preamble. Aswith all other documents considered orex- amined by EPA as partofits decision process, these documents have been placed in the public docket and have

- FEDERAL AEGISTER, VOL44, NO. 28--THUSDAY, FEBRUARY 8, 3979

### RULES AND REGULATIONS

become part of the' administrative record ofthisdecision.

The majority of comments received (132 out of 168) opposed EPA's proposed standard revision, favoring either a more relaxed or a more stringent standard. State airpollution con- trol agencies (and STAPPA) generally supported a standard level of0.12 ppm

on the basis of their assessment of an adequate margin of safety. Municipal grdups generally supported EL standard level of 0.12 ppm or higher, whereas
most industrial groups supported a standard level of 0.15 ppm or higher. Environmental groups generally encouraged EPA to retain the 0.08 ppm standard.

Comments on the proposed revisions

were received from five Federal agen- cies. Three of the agencies endorsed the proposed primary standard, but

one of these agencies requested that EPA consider formulating, the standard on a daily maximum.'hourly aver- age basis. Another agency expressed

concern that EPA had inadequately substantiated the rationale for raising the primary standard level and re- quested 'that the final revisions provide further analysis in this regard.Finally, the Executive Office of the President/Council on Wage and Price Stability suggested, through theRegulatory Analysis Review Group, that the proposed standard was unnecessar- ily stringent, recommending that EPA
set the primary standard using an alternative methodology that focuses on the marginal costs per person-hour of

ozone effects ivoided.

Groups and individuals submitting
comments are identifiedbelow:

CommENTs RECIVED ENDORSING CURRENT

PRIMARY STANDARD LEVELOF0.08PPM

ORGANIZATION AND AGENCIES AmericanLungAssociation ofColorado American Lung Association of Colorado, WestRegion AmericanLungAssociation ofLouisiana AmericanLungAssociation of.New Jersey American Lung Association of New York State,Inc. Bangor-Brewer TB and Health Association, Maine California LungAssociation Connecticut StateDepartment ofHealth Environmental Confederation of Southwest Florida Environmental Defense Fund Ms. Nancy C. Fahden, Supervisor District Two, Contra Costa County (Calif.) Board ofSupervisors FloridaLungAssociation Greenleaf Nurseries,Warsaw, Indiana IssacWaltonLeague,Manasota Chap1ter LeagueofWomenVoters oftheU.S. LeagueofWomenVoters ofDallas,Texas MaineHealth SystemsAgency MaineLungAssociation Medford-Ashland Air Quality Maintenance Advisory Committee, Oregon MichiganLungAssociation Michigan Lung Association, Saginaw Valley Region National Air Conservation Commission, American LungAssociation Natural Resources Advisory Committee, Cedar Grove,N.J. Natural Resources Defense Council

- NewMexicoLungAssociation Oregon Environmental Council Oregon LungAssociation Queensboro Lung Association, Jamaica, 'N.Y. Sierra Club Sierra Club,Houston Chapter South Shore (Ohio) Christmas Seal Association Southwestern Ohio LungAssociation U.S. Department oftheInterior Washington AirQuality Coalition YaleEnvironmental LawAssociation

'Summary.' 35 comments from organizations, agencies or their representatives and 38 comments from concerned citizens supporting the current primary standard level of0.08ppm.

CoMEsTS RECEIVED ENDORSING PROPOSED

PRiMARY STANDARD LEVELOF 0.10 PPM

ORGANIZATIONS AND AGENCIES

Air Pollution Control League of Greater Cincinnati Air Quality Advisory Committee, California Department ofHealth California AirResources Board Coalition of Labor and Business (COLAB), Concord, California Colorado Department ofHealth Connecticut Department of Environmental

,_ Protection Massachusetts bepartment of EnvironmentalQuality Engineering' Public Health Service, U.S. Department of HEW Regional Planning Commission for Jeffer-
.son, Orleans, St. Bernard and St. Tammany'Parishes, Louisiana

- Rhode Island LungAssociation Southern Alameda County Board of Realtors, California U.S. Department dfEnergy U.S. Department ofTransportation Wasatch Front Regional Council, Utah Wayne County Department of Health, Michigan Wisconsin State Department ofNatural Re-

sources Summary. 16 comments from organiza. tions, agencies or their representatives and 1 cqmment from a concerned citizen endorsing the proposed primary standard level of 0.10 ppm.

CoMM= SRECEIVED ENDORSING APRIMARY

STANDARD LEVEL OF 0.12PPM

STATE AND LOCALAOENCIES

Alabama Air Pollution Control Commission Berkeley, Charleston, and Dorchester (S.C.) Council ofGovernments City ofPhiladelphia, Pennsylvania Georgia Department ofNaturalResources Indiana State BoardofHealth Kansas Department ofHealth andEnvironment Kentucky Department for Natural Re-

sources and Environmental Protection Maryland Environmental Health Administration Michigan Department ofNatural Resources Nebraska Department of Environmental Control Nevada Department of Conservation and Natural Resources New York Department of Environmental Conservation North Carolina Department ofNatural Re-

sources and Community Development Pennsylvania Department ofEnvironmental Resources Tennessee.Department ofPublicHealth UtahBureau ofAir Quality Virginia Air Pollution ControlBoard

ORGANIZATIONS AND COMPANIES
Area Cooperation Committee of Tidewater and Virginia Peninsula Chambers of Commerce Evansville, Indiana, Chamber of Commerce SierraPacific Power Company State and Territorial Air Pollution Program

,Administrators Texas OilMarketers Association Vulcan Materials Company, Wichita, Kansas Summary. 17 comments from State and local agencies and 6 comments from organizations and corporations supporting a prmary standard level of0.12ppm.

CommENTs RECEIVED ENDORSING APmRIARy STANDARD LEVEL HIoIIER TILAN 0.12 PPM AND/Oil CONTENDING PROPOSED STANDARD Too STRINGENT

Endorse standard' Proposed standard higher than0.12 toostringent ppm

Organization or hgency: American Petroleum Institute(API)............................ Associationof LocalAr PollutlondControl Officials. Associated BuildingIndustry ofNorthern California

.......... Cook County Dept.ofEnvironmental Control, Illinois. Dow ChemicalCompany...............................

Eastman Kodak Company

............................ GeneralMotorsCorporation

............ ......... GreatPlainsLegal Foundation

............ .... ...... GreaterSanAntonio ChamberofCommerce, Texas

........... Houston Chamberof Commerce, Texas

........ . .. .............. Iowa-Illinois Gas andElectricCompany

.................... LouisianaAirControl Comlssion.............................. ManufacturingChemists Association

. ................ Monsanto Chemical Intermediates Co

............. MotorVehicle Manufacturers Association

............. National FlexiblePackaging Association

.......................... New OrleansPublic Service, Inc

........................................... OklahomaState Dept. ofHealth

.................. X X

.......

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. .°°°...°...........

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FEDERAL REGISTER, VOL 44, NO. 28-THURSDAY, FEBRUARY 8,.1979 

### 8206

### RULES AND REGULATIONS

ComwENis REcErvED ENenOsrNGAPRmARY STARDARD LEVmHIGEMR THAm 0.12PPMAxD/oa CONTENDING PRoPOSED STaNDLUw TooSTRINCET-Continuled

Endorse standard Proposed standard higher than0.12 too stringent

ppm

Owens-Illinois .,_X X RioBlanco Oil Shale Company X St.Louis County, Missouri':-:

_ __ X SanAntonioMetropolitan Health District,Texas._ X Shell Oil Company X Stearns-Roger, Inc, Denver, Colorado

...... X TennesseeEatmen Corp...

. X TexasAir Control Board__............

... 

### z Texas ChemicalCouncil X US. Councilon Wage andPrice Stability

.................... X UtahManufacturers Association_________________ X Virginia AirPollution Control Board X Western Oil and GasAssociation X Wlhite River ShaleProject

..... ...... X

Summary: 15 comments from organizations. agencies, andcompanies and4 comments fromconcerned citizens'supporting a p5rimary standard level higher than 0.12 ppm. 23 comments stating the proposed standard istoo stringent.

The principal issues raised during the comment period relate to the following topics:

LHealth effect criteria andselection oftheprimary standard.

A. Definition of an Adverse Health Effect.

B. EPA's interpretation of cited studies.

C.Marginofsafety. D. Use ofannimal studies. E.Exposure ofsensitive groups.. F. Synergistic effects and chemical species designation ofthe standard.

IL Riskassessment method. MI.Welfare effects and the secondary standard.

IV. Implementation 'and attainabil- .ity. A. Value ofhydrocarbon control and timing ofSIP submissions.

-

B.Consideration ofcontrol costs. C. Natural background concentrations.

V.Procedural issues. The comments xeceived have been reviewed and a document detailing their 'disposition has been placed in the rulemaking docket (OAQPS 78-8) for public inspection. The following sections summarize the significant
comments and present the Agency's
responses.

I. HEALTH EFFECT CRITERIA AND

- SELECTION OF THEPRIMARY STANDARD

A. DEFINITION OF ANADVERSE HEALTIE EFFECT

Comment The proposed standard is unsuitable because EPA has-never defined what constitutes "protection of public health." As-a specific example, EPA has not shown that pulmonary function and ventilatory pattern changes are adverse health effects.

Agency Response As stated in the criteria document, the available evidence regarding' pulmonary function changes observed in clinical exposures of healthy subjects to ozone dbes not suggest that small changes in lung function (unaccompanied by discomfort symptoms or impairment of oxygen uptake) would interfere with normal activity in healthy individuals. However, even small changes in people with underlying respiratory disease such as asthma, chronic bronchitis, and emphysema can interfere with normal activity and, thus, may signal impairment ofpublic health.

Comment EPA should identify where adverse effects begin In the con- tinuum ofresponses topollutants.

Agency Response. In conducting a preliminary risk assessment, EPA interviewed several biomedical experts to obtain their judgments as to the risk of exceeding the threshold of ad-

verse health effects in sensitive per-
sons for alternative standard levels. An essential feature ofthisrisk assess- ment procedure is the utilization of the experts' Judgments as to the point in the continuum of physiological re- sponses to ozone that mustbe exceeded for an adverse 7health effect to

occur. As an example, discussl6ns with several experts indicated that a 1 percent decrease in pulmonary function (e.g., forced expiratory volume 1- second test) would be inconsequential, whereas a 50 percent decrease would be a severe effect in sensitive persons; the experts' Judgments varied as to the point at which adverse effects would begin, but fell within the range ofa 5 to 15.percent decrease.

Comment Quickly reversible Irritation experienced for a short period of time is a welfare effect related to per- sonal comfort and well-being and should therefore be considered incon- nectionwiththe secondary standard.

Agency Response.The criteria document states that physical discomfort,

as manifested by symptoms such as difficulty in breathing, chest tightness, andpain on deep Inspiration, has usually been observed in clinical studies in conjunction with pulmonary function changes. Even when revers- ible, respiratory symptoms may re- 

### strictnormal activity orlimittheper- formance of tasks. In clihbil studies,
exposure of healthysubjects to realistic levels of ozone (0.3 ppm) has produced discomfort sufficient to prevent completion of experimental protocols, particularly when vigorous exercise

was involved. Accordingly the criteria document conluded that increased
rates of respiratory symptoms constitute impairment of public health. On this topic, a physician affiliated with the California Department of Health stated (docket OAQPS 78-8, IV-F-31) that it was his medical opinion that symptoms such as those described above constitute adverse health effects, inasmuchasthey signalp3ulmonary function decrements and an increased pulmonary work load for affected individuals. He expressed his

concern forthe long-term effect ofre- peated exposure tolevels of ozonesufficient to induce such symptoms. EPA

concurs in this view and considers such symptoms, even though transitory, to be of concern in selectingthe level ofthe primarystandard.

B. E'A'SINTERPRETATION OFCITED STUDIES

1.DeLuciaandAdams(1977)

Comments. (a) EPAmisread the DeLucia and Adams study in claiming significant effects have been reported
at0.15ppm foronehour.

(b) Mouthpiece breathing may have invalidated the DeLucia and Adams study.

(c) Since DeLucia and Adams demonstrated effects at 0.15 ppm in healthy individuals, more susceptible, populations would be expected to sus- taineffects atlowerlevels.

Agency Responses. (a) EPA acknowledges that DeLucla and Adams failed
to demonstrate any statistically significant decrements in pulmonary function resulting from exposure to 0.15ppm forone hour.(The investigators did observe statistically significant decrements in pulmonary function resulting from exposure to 0.30 ppm for onehour.) In groups as small

as thosetested byDeLucla and Adams 

### (six subjects),however, tests ofstatistical significance are difficult to interpret. The criteria document concluded that thestudy byDeLucia and Adams, although unreplicated, has raised the question ofwhether 0. concentrations

as low as 0.15 ppm exert effects in a portion of healthy subjects exercising vigorously. Indeed, DeLucia and Adams specifically state that the two most sensitive subjects sustained markedy impaired respiratory function and exercise ventilatory patterns during the two most stressful exercise protocols in the four ozone-exposure

FEDERAL REGISTER, VOL 44, NO. 28-THURSDAY, FEBRUARY 8, 1979 

### 8207

### 8208

experiments (i.e., both 0.15 ppm and 0.30 ppm).

Furthermore, DeLucla and Adams state that most ofthe subjects experl- enced subjective symptoms of discomfoit (e.g., congestion, chest pain, and cough) when exposed to 0.15 ppm for

one hourunder the most,stressful exercise protocol (equivalent torunning about6milesin an hour).These symptomsoccurred atalower excercise rate when the subjects were exposed to 0.30 ppm. DeLticia andAdams did not report the incidence of these symptoms in a quantitative manner, but this fact does notremove EPA's concern about the implications for healthy persons such as those studied by DeLucla and Adams, or for more susceptible persons who may sustain

more severe reactions or who may be affected at lower concentrations'-than thosebbserved.

(b) As noted in the criteria document,persons tendtobreathe through their mouths when exercising. Thus, DeLucia and Adams' utiliiation of mouthpieces to dispense 03 probably represents actual exposuresinpersons who, in the course of their normal daily activities, are undergoing exercise.

(c) EPA agrees with this comment,

as noted above. EPA considered the implications of this study for more susceptible members of thepopulation in its determination of the margin of safety forthe ozone standard.
2. Schoettlinand Landau(1961)
Comments. (a) There are still prob- lems with reliance on this study because (1) ambiguities remain in itsinterpretation and (2).morerecent studies of effects of ozone on asthmatics have failedto corroborate this study's- conclusions.

(b) EPA's interiretation ofthe concentration at which Schoettlin and Landau correlated increased incidence of asthmatic attacks is unnecessarily conservative. There is goodreason to believe that the 0.25-ppm oxidant concentration cited by Schoettlin and Landau was a daily peak (2-minute average) concentration rather than a daily maximum hourly average concentration, as EPA claims. Furthermore, thelevel of ozone occurring on these high oxidant days would have been less than the'level of oxidantreported. " ,

Agency Responses. (a) The criteria document recognizes limitations that' make it difficult to interpret the Schoettlin -and Landau study unequivocally. Nevertheless, Schoettlin and Landau didconclude thatthepro- portion of asthmatics having :attacks

was significantly greater ondays-when the oxidant concentration exceeded 0.25 ppm than on days when -theconcentration was below that level. EPA RULES AND REGULATIONS

* does not believe that this conclusion has beenrefuted by more recent studies. The reported results of the recent epidemiological study by Turata et al (1976) are. qualitatively similar to those ofSchoettlin andLandau. EPA's analysis (docket OAQPS 78-8, IV-A-1) of the data presented in the Kurata study indicates that a statistically significant elevation of the asthma index occurred on days when the maximum 'instantaneous (2-minute average) oxidant, concentrations exceeded 0.28
ppm. While the exact hourly average equivalent of this .value is not known, it must be less than or equal to 0.28
ppm, and'is probably in the range of 0.20 to0.27 ppm.

(b) EPA acknowledges that it is un- certain from Schoettlin :and Landau's
paper what averaging timewas usedin correlating oxidant concentration and incidence of asthma attacks. As stated in the criteria document, however, consultations with the authors have established that daily asthma attack
rates were correlated with daily maxi-

mum hourly average oxidant levels. EPA considers that these consultations (docket OAQPS 78-8, IIA-C-2) have satisfactorily resolved the controversy regarding the averaging times usedby Schoettlin andLandau.

EPA agrees with the comment that

ozone levels mayhave beenlower than the oxidant readings with which Schoettlin and Landau correlated asthma attack incidence. Ozone levels have been shown to range from approximatley 65 percent to nearly 100 percent of the total oxidant levels. This fact provides reason for concern that ozone in the kmbient air at daily maximum hourly average concentrationslessthan 0.25 ppmmay adversely affect asthmatic persons. 3. Hammeretal.(1974)

Comments.(a) This study has methodological problems (such as the fail-

ure to adjust the data for smoking habits and allergy histories) that un- dermine confidence initsconclusions.

(b) It is uncertain that oxidants caused the increase in symptoms observedin thisstudy.

AgencyResponses. (a)Hammer et al. conducted a longitudinal survey of an essentially constant group of subjects

over aperiod oftime. Consequently, in orderforthe authors' failure to adjust the data for smoking habits and allergy historiesto have biased the results, the survey Teponse pattern on 'high pollution days -wouldhad to have differed with respect to the distribution of smokers and allergic persons as compared with the pattern on low pol-

- lution days. Suchan occurrence'seems

unlikely, furthermore,the criteria document noted that the results of this epidemiological study are. generally consistent with the results of clinical exposure studies. This fact, along with the extensive data base evaluated (about 53,000 person-days of observation), enhances the reliability ofHammer's study.

(b) Hammer et al. found that symptom frequencies were more closely correlated to. photochemical oxidants than to several other environmental parameters (e.g., carbon monoxide and nitrogen dioxide). In addition, the criteria document noted that the oxidant levels at which cough and chest discomfort were observed to Increase in the student nurse population were quite similar to ozone concentrations that have been observed 'to produce impairment of pulmonary function and respiratory irritation in experimental exposures of healthy subjects performing intermittent light exercise (0.37 ppm for 2 hours). Consequently, it is reasonable to propose that photochemical oxidants-and specifically

ozone in the ambient air-contributed substantially to observed increases In
rates of cough, chest discomfort, and headache.
4. Hazucha(1973)

Comment.Results reported by Hazucha on impairment ofpulmonary function at ozone levels of 0.25 ppm for 2 hours arenot statistically significant.

Agency Response.The small number of 'subjects (three) examined at that exposure precludes the application of statistical methods to the results. The absolute -valueofthe pulmonary func tion decrements (about 5 percent) in the more relevant factor In evaluating the resultsofthis study. " As described in the criteria document, the small pulmonary function changes*observed by Hazucha in a 2. hour exposure of healthy subjects un- dergolpg intermittent lightexercise lie along a continuum of responses when compared with results at higher con- centrations and similar exposure re- gimes. There is no indication that 0.25 ppin is thethreshold for that exercize level, and indeed the study byDeLucla and Adams (1977) has shown symptomatic effects in healthy individuals that are indicative ofpulmonary function impairment at levels as low as 0.15 ppm under amore strenuous exer- cise protocol.
5. Studiesin which effectswerenotobserved atlevelsabove 0.15ppm

Comments. (a) The 1977 National Academy ofSciences (NAS) document, Ozone and Other Photochemical Oxidants, was cited In several comments

as concluding that effects In human subjects have been observed only from

ozone exposures above'0.25 ppm.

(b) Linn et al. (1978) failed to find any significant pulmonary effects in asthmatics exposed to 0.20-0.25 ppm for 2 hours under conditions of heat' and exercise.

FEDERAL REGISTER, VOL 44, NO. 28-THURSDAY, FEBRUARY 8, 1979

### (c) Hackney et al. (1975) observed human health effects only at exposures above 0.25ppm'for 2hours.

Agency Responses.(a) The NAS document states that "some limited studies show evidence ofhuman health effectsof exposure topureozone atconcentrations as low as 0.25 ppm ***" This document was prepared before publication oftheDeLucia andAdams study, which suggests effects at lower levels: Furthermore, this NAS document innoway concludes that effects resulting from ozone, as it occurs in the ambient photochemical mix, do not occur at concentrations below 0.25 ppm.

(b)AlthoughLlnn etal found statistically significant changes in one of several measures of pulmonary function in their laboratory study, the

manner. in which the investigators' conducted thestudy (e.g.,persons with marked respiratory disability were excluded from the study) and analyzed the data aresuchthatthe observedresults probably underestimate the effects thatwould occur-at similarambientexposure levels. There was a slight increase in symptom scores during

ozone exposure, and statistically significant changes in blood biochemical factors were observed. While the clinical significance ofthese latterchanges is uncertain, they do represent alterations in normal body functions and cannot be discarded in selecting a standard that protects public health withan adequatemargin ofsafety.

(c) Although the criteria document
statesthat Hackney et al. observed no lung function changes ofnote at 0.25 ppm for 2 hours even among "reactiv&" subjects (persons givinga history of cough, chest discomfort, or wheezinginresponse to allergy or air pollutionexposure), closer inspection ofthe Hackney pt al. (1975) studies reveals that dose-response 'relationships hold forsensitive subjects forlung function and blood biochemical effects across the range of exposure from 0.20 to 0.50 ppmozone. 6. OtherHumanStudies

Comments. (a) Von Nieding et al. (1976) have demonstrated effects on pulmonary function of healthy individuals at0.10ppm ozone.

(b) EPA cannot justify a conclusion that Japanese epidemiological stidies indicate a risk of symptomatic effects inhuman beingsfromozone exposures below 0.15ppmforonehour.

Agency Responses. (a) EPA is concerned aboutthe findings ofvonNiedng et al. showing decreased oxygen pressure in arterialized blood and increasea.airway resistance after2hours ofexposure to. 0.10 ppm ozone and intermittent light exercise. The criteria document points out, however, that the investigators used non-standard RULES AND REGULATIONSphysiologic measurement methods. Thus, although von Nieding's findings
cannot be ignored in the standard-setting .process, they are unconfirmed, and mustbeinterpreted cautiously.

(b) Makino and Mizoguchi (1975) reported an epidemiological study of Tokyo students that showed Increased
rates ofdiscomfort symptoms on days when the oxidant level (believed to be

a daily maximum hourly average con- centration) exceeded 0.15 ppm as compared with days when Itfell below 0.10
ppm. The criteria document reviewed this and several other Japanese epidemiological studies, and concluded that the studies were appropriately designed but that It is very difficult to interpret their results. In setting a standard with an adequate margin of safety, however, EPA must consider evidence such as these Japanese studies and must evaluate the uncertainties which medical research has not yetresolved.

7. ValidityofClinicalStudiesin General

Comment. At the August 22, 1978 public hearing in Dallas, testimony

was presented alleging that the ozone generators used inclinical health studies produce other toxic materials in addition to ozone. Experimental data obtained using a new total oxidant monitoring method indicated that these additional oxidants were present inlarge quantities (ashigh as300 percent greater than ozone). It was hypothesized that the adverse effects

- noted in clinical studies may be preponderantly caused by the additional oxidants and notozone.

Agency Response EPA has concluded that the experimental evidence offered to support these findings is un- convincing and cannot be substantiated. The results of an experimental
program initiated by EPA after the Dallas hearing.indicate that the new monitoring technique which supposedly measured ozone and any additional oxidants has a variable chemical reaction relationship (stoichiometry) with

ozone depending on whether or not oxygen ispresent. The higher oxidant readings obtained by this technique
appear to result from this variable stoichiometry rather than representing the presence of any additional

non-ozone oxidants. Furthermore, an exhaustive search for such oxidants in theoutput ofozone generators operating under various conditions (using as the inputstream.eitherdry or humidified tank air or oxygen, with very low

or background concentrations of hydrocarbons, mostly methane) failed to produce any evidence ofnon-ozone oxidants. Consequently, EPA judges the hypothesis offered by this comment to be experimentally unsupportable. A report documenting the results of 

### 8209

EPA's experimental program has been placed inthedocket (OAQPS 78-8, IVA-2).

C.MARGIN OFSAFETY

Comment. EPA has proposed a standard with an inappropriate marginofsafety.The margin ofsafety

was criticized as being either inadequate or too great.

Agency-Response. The Clean AirAct requires that EPA set air quality standards that are requiite to protect the public health, allowing an adequate margin of safety. As stated in the legislative history ofthe CleanAir Act, thestandard mustprotect against hazards that research has not yet identified. EPA feels that the decision regarding an adequate margin of safety is ajudgment which must be made by the Administrator after weighing all the medical evidence bearing on ozone. The factors to be taken into account include inconclusive evidence as well as findings from studies that are considered definitive and not subject to challenge. For example, in selecting an adequate margin of safety, the Administrator
must consider- (1) findings from animal studies that show increased susceptibility to infectious respiratory disease and otherserious effects atrelatively low ozone levels, (2) the concern that health studies may not always reflect the health impact in

moresensitive segments ofthe population, and (3) studies suggesting that

ozone mayproduce an enhanced effect when combined with other air pollutants commonly present in the urban atmosphere butnotpresent in clinical study chambers.

D. USE OFANIMAL STUDIES

Comment.EPAhas failedtogive appropriate consideration to the results of animal studies, especially those involving young animals and those examining reduced resistance to infection,

Agency Response EPA is concerned about the studies which have demonstrated effects in young animals and decreased resistance to infection in animals exposed to ozone. The infection effect has been demonstrated at exposures as low as 0.08 ppm for 3 hours. The criteria document concluded that these findings have definite human health implications, although different exposure levels may be asso- ciated with such effects in humans. For this reason, these results cannot be the solefactor used in selectingthe level of the primary standard. However, as is the case with other inconclusive evidence, EPA- must consider these studies in selecting an adequate margin ofsafety.

Comment. There is no evidence of reduced resistance to infection in epiFEDERAL REGISTER, VOL 44, NO. 28--THURSDAY, FEBRUARY 8, 1979

### 8210

demiologic studies in places such as Los Angeles.

Agency Responzse. Epidemiological studies have been inconclusive in demonstrating this effect in man. However, EPA does not agree with this com- ment. The study by Durham (1974) of air pollution effects on college students, indicates that rates of iew ill-

ness increase following short-term ex- posures to elevated pollutant concen- trations. The pollutant variable most strongly associated with illness was peak oxidant.Also, several studies documenting increased levels of mucous membrane irritation during periods of

ozone exposure suggest indirectly that susceptibility to infection may rise during these periods. Furthermore, although animal study findings cannot be directly extrapolated to-man, the criteria document concludes that the reactions observed in inice represent effects on basic biologicalresponses to infectious agents, and there is no
reason to believe thatthepollutant-induced alterations of basic defense mechanisms that occur inmice could
not occur in human beings. Thus, these studies cannot be ignored inthe standard-setting process.

E.

EXPOSURE OF SENSITIVE GROUPS

Comment EPA is being unnecessar- ily stringent in selecting the sensitive population. The standard could be much less stringent without endangering the health of such persons ifEPA accounted for theportion of time that
persons are indoors and, thus, not ex- posed to higher ambient concentrations.'

Agency Response.The.legislative history of the CleanAir Act makes quite. clear Congress' intention to protect sensitive persons (asthmatics and em- physematous patients are cited as ex- amples) who in the normal course of daily activity are exposed to the ambient environment. Air quality standards are to be established with refer-

ence to protecting the health ofa representative sample ofpersons comprising the sensitive group rather than a singl person in such a group. Standards mustbebased on ajudgment ofa safe air qualitylevel and not on an es- timate ofhow many persons will intersect given concentration levels. EPA interprets the Clean AirActas providing citizens the opportunity to'pursue their normal activities in a healthy environmerit.

F. SYNERGISTICEFFECTS AND CHEMIcAL

SPECIES DESIGNATION OFSTANDARD

Comment.There were objections to the proposed change of the chemical designation of the standard from photochemical oxidants to ozone because the health impacts of photochemical air pollution arise not only from

ozone, but also from the spectrum of .RULES AND REGULATIONS

other gaseous and particulate pollutants,that co-exist with ozone. There

was also concern that the change in the chemical designation signalled a change in emphasis in oxidant control efforts that would impede progress in the reduction of non-ozone components of the photochemical oxidant mixture such as peroxyacetylnitrate. (PAN). Specific concern was expressed regarding the eye-irritating components ofthe mixture, since at ambient levels ozone alone is not an eye irritant.

Agency Response. Certain clinical studies (such as Hazucha and Bates, 1975) have demonstrated thepotential for greater health impacts resulting from exposure to ozone in combinationwith otherpollutants whichoccur intheambient air than from exposure to ozone alone. The ozone standard is
notintended merely to protect against the levels of ozone that have been demonstrated to produce effects in clinical studies where subjects have been exposed tohighly purified air to which ozone alone has been added. Rather, setting an ozone standard with an adequate margin of safety involves, among other considerations, evaluating the effects of ozone as it

occurs in the ambient air,in combinationwith other pollutants.

One reason for changing the chemical designation of the standard from photochemical oxidants to ozone is to correct an inconsistency between the title of the standard (photochemical oxidants) and the chemical species (ozone) that has always been meas- ured by thereference method used to estimate ambient oxidant levels and determine compliance with the standard. Consequently, no redirection of control efforts is contemplated; Le.,re- ductions in hydrocarbon and nitrogen oxide emissions will continue to be re- quired In order to reduce the levels of the secondarily generated pollutant (ozone) measured to determine compliance with the standard.

The criteria document examined the issue of whether or not measures taken to reduce ozone will also reduce othermanifestations ofphotochemical pollution such as eye irritation. The evidence from laboratory and theoretical studies indicatesthat,forurban atmospheres, reductions in hydrocarbon and nitrogen oxide emissions should have even greater impacts on ambient PAN than on ambient ozone. Similarly, laboratory data suggest alinear re- lation between hydrocarbon emissions and ambient levels ofphotochemically produced aldehydes. Since PAN and such aldehydes as fomaldehyde and acrolein"are know to be eye irritants, the criteria document concludes that emission control faeasures for ozone reduction will probablyhave a positive effect on reducing eye irritation in those situations where eye irritation is associated with photochemical 'proc-

esses (e.g., Los Angeles).



### II.RISKASSESSMENTMETHOD"

Comment. The risk assessment method should not be used at this time because It has not been reviewed adequately by the Science Advisory Board or the scientific community.

Agency Response. The risk assess- ment method is not being used to set the ozone standard. In determining what ozone standard has an adequate margin of safety, however, the findings of the initial application of the risk assessment method to ozone have been considered. EPA agrees that the method has not received sufficient review. The method will be published in the open literature and the Science Advisory Board Is forming an ad hoc subcommittee to review the method.

Comment EPA's risk assessment method isincomplete.

.

Agency Response. EPA agrees with the comment. As applied to ozone, the risk assessment method assesses the risk (probability) that ozone would contribute to health effects in some sensitive people if alternative standards were just met. A complete risk picture would alsoInclude information



### on:

(a) a best point estimate of the number ofpeople affected;

(a')the "expected number" (in a statistical sense) ofpeople affected:

(a") various risks (probabilities) that the actual number of people affected would be various amounts greater thanthe expected number;

(b) a best point estimate of the
amount ofhealth damage;

(b') the "expected" health damage; and

(b")various risks (probabilities) that the actual health damage would be various am6unts greater than the ex- pectedhealth damage.

Asnoted in the draft EPA document explaining the risk assessment method, there are complex technical problems that must be dealt with in responsibly developing information of this type suitable for use in setting National Ambient Air Quality Standards. EPA is presently developing the 'capability to generate this type of information and will only consider its risk assessment method complete when the method includes this capability.

Comment The main problem with the risk assessment method stems fromits purpose. Instead ofestimating health damage, EPA provides a table ofrisk numbers without providing an estimate of their health significance; thesenumbers serveno function.

Agency Response EPA agrees that the risk estimates provided do not

serve the function of estimating

FEDERAL REGISTER, VOL 44, NO. 28-THURSDAY, FEBRUARY 8, 1979health damage, but the Agency does
not agree that the estimates are withoutvalue. The function of these estimates is to indicate the varying risk (or probability) that some sensitive pjeople would suffer health effects in a given period of time if- alternative

ozone standards were just met. For each health effect category, the re- sponse that is of sufficient concern to be deemed a health effect hasbeendecided upon and its seriousness described. As EPA interprets the Clean Air Act, this determination, which is

an important step in the process of setting National Ambient Air Quality Standards, is a function that is to be served byarisk assessment.

There were many comments onboth the procedural and the technical as- pects of the risk assessment method. EPA will consider these comments in the detailed responses to be placed in the docket. Some of the comments identify improvements that can be made in the risk assessment method, while others reflect misunderstandings that will'be dealt with in the detailed docket responses. Some. of the
comments provide discussion an4 opinions on various complex issues that arise in the conduct of a program involving the difficult subject areas of risk assessment and standard-setting methodology.- EPA will take these
comments into advisement as it develops its risk assessment and standardsetting methodologies.



### I. WELFARE EFFECTS AND THE
SECONDARYSTANDARD

Comment EPA's proposal to retain the existing secondary standard is based entirely on evidence of possible damage to extremely sensitive vegetation. An adequate economic analysis that considers the incremental costs and benefits of alternative secondary standard levels should be conducted. EPA should then weigh the economic
costs of pollution control measures against the benefits of reduced damages from lower ozone concentration levels before

-setting a secondary standard.

Agency Response. The Clean AirAct requires EPAto set anational secondary ambient air quality standard at a level that,in the judgment of the Administrator, is requisite to protect the public welfare from any known or an- ticipated adverse effects. The term "public welfare," which is defined in Section 302(h) of the Clean Air Act, 

### -includesamong otherthings-effectson crops, vegetation, wildlife, visibility, and climate, "as well as effects on eco- nomic values and onpersonal comfort andwell-being."

EPA has carefully examined the data presented in the criteria docu-

- ment concerning ozone-related

damage tovegetation, crops,.materials, 

### RULES AND REGULATIONS

and visibility. A staff paper, "Evaluation of Alternative Secondary Ozone Air Quality ,Standards," has been placed inthe docket (OAQPS 78-8,IVA-3).

Withregard todamage tomaterials, the paper concludes that no effectbased rationale can be offered to decide the level of the secondary standard. Damage to materials Is linearly related to the total dose sustainedby thematerial. Asaresult, the annual average concentration will determine the rate at which material damage occurs. Current evidence Indicates that annual average concentrations for remote rural areas are comparable to urban areas, due to strong night-time scavenging of ozone in urban areas by man-made pollutants. Reducing the peak 1-hour concentration in urban areas will havevirtually

no impact on the annual average concentration. Therefore, there wouldbe

no measurable reduction in materials damage if amore stringent secondary standardlevelwasselected.

The -criteria document states that there is a limited amount ofdata sug- gesting an association between ambient ozone and visibility degradation, particularly in the Los Angeles area. On the basis of EPA's evaluation to date of the information presented in the criteria document, however, EPA Is unable tQconclude atthistime that

a secondary ozone standard more stringentthan theprimary standardIs necessary to prevent visibility deterioration. The relationship between visibility and abmlent ozone will be considered further Inthe development of subsequent PSD programs designed to protect against significant deteriorationofairquality.

Finally, EPA has concluded that there is currentlyno evidence indicating that a significant decrease inyield

or growth or commercially important crops or indigenous vegetation will result from the long-term (growing season)meanofthedailymaximum 7- hour-average ozone concentrations which is expected to occur when the primary standard Is attained. Consequently, EPA does not believe that a secondary standard more stringent than the primary standard Is necessary toprotect vegetation from ozonerelated yieldreduction effects.

On the basis of these conclusions, EPA does not believe that a detailed cost-benefit analysis of alternative standardlevels is required, since a secondary standard more stringent than the primary standard is notnecessary toprotect thepublicwelfareadequately.Comment The current secondary standard of 0.08 ppm should be retained toprotectvegetation andcrops. There Is singificant reduction in 8211

growth and yield to crops exposed to 0.10ppm ofozone.

Agency Respone.. The claims that significant reduction in growth and yield occurs in crops as a result of short-term exposures to ozone at. levels around 0.10 ppm are undocumented. While sensitive plants may incur follar Injury atlow ozonelevels, there iscurrently no evidence thatsignificant yield orgrowth effects in commerically important crops or indig-

enous flora are associated with the long-term (growing season) mean of the daily maximum 7-hour-averaging

ozone concentrations expected to

occurwhen theprimary standard isattained. Consequently, EPA does not believe that a secondary standard

more stringent than the primary standard Is necessary to prevent ozone-related yieldreduction effects in vegetation.

IV. LPurENTAAIox D A:rTAnmAn

A. VALUE OF HYDROCARBON CONTROLAZm
TIB=IG OF SIPSUBMISSIONS
EPA received comments on the effectiveness ofhydrocarbon controls in reducing levels of ozone n the ambient air as well as on the issue of whether ornot the statutory deadline for submission ofrevised State Implementation Plans (SIPs) fornonattainment areas should be postponed because of the changes in

- the photochemical oxidants standard. The Agency responses to these comments

are contained Jn the accompanying FEDERAL Rcismm notice dealing with therevision ofthe 40CFRPart51regulationsp*ertalning totheimplementationofthestandard.

ILCONSIDERATION OFCONTROL COSTS

Comment Costof control should be considered in selecting the level of the primary standard.

Agency Response.The Agency's position with respect to control cost con- sideration was stated in the preamble
to the proposed regulation (43 FR 26963); this position remains un- changed. The Clean Air Act specifies that primary National Ambient Air Quality Standards are to be based on scientific criteria relating to the level that should be attained to protect public health adequately. Considerations ofcost of achievingthese standards or ofthe existence oftechnology to bring about needed reductions of emissions are not germane to such a determination, asthe wordsofthe Act and Its legislative history clearly indicate. EPA has, however, analyzed the
cost and economic impacts of thecon- trol programs required to attain alternative ozone Standard levels in order that thepuble maybebetter informed

FEDERAL REGISTER, VOL 44, NO. 28-THURSDAY, FEBRUARY 8, 1979

### 8212

-of the consequences of the Agency's decision. This analysis and the comments received in response to it are available tothe States fortheir use in developing strategies to implement the standard.

Comment The cost estimates "presented in EPA's cost and economic impact assessment document are understated.

Agency Response.EPA has carefully reviewed and considered these com- ments and is publishing a revised economic impact assessment, which is available from Mr. Padgett atthe previously mentioned address.

C. NATURAL BACKGROUND CONCENTRATIONS
Several comments, were made re- garding the contribution of natural,

sources to ambient ozone concentrations. These comments focus on (1) the extent to which natural background was considered in developing the proposed standards and related control programs and (2) the attainability of these standards, considering the possibility that natural background may at times contravene the proposed levels. Some of the com- ments suggested that EPA ignored, or did not adequately consider, natural background in developing the proposed standards and related control
programs. While this topic was not emphasized in the preamble to the proposed rulemaking, EPA was, and is, cognizant of the background levels that can be attributed to natural

sources. This matter was treated extensiVely in the revised criteria document. Furthermore, EPA procedures for preparation of control plans rec- ommend allowance for natural background in developing control strategies forozone.

For several years, EPA hasbeen conducting an active field and laboratory research program seeking to deterthine the nature and extent of background coricentrations of ozone. The results of these studies have been widely publicized in EPA reports, scientific literature, and public confer-

ences. One comment suggested that EPA had ignored evidence of natural

source, impacts reported in contract work conducted for the Agency and that this information had not been re- leased for public review. Actually, all pertinent information available -to EPA was considered. However, there
may have been some contractually developed information that- had notbeen released o*r could not be specifically cited because the contract studieswere still in progress and the resulting data had not been fully validated or analyzed. Subsequent to the comment, all information in question were released publically or arrangements have been' RULES AND REGULATIONS

made to release them as soon aspossible.

EPA's review of data related to the background contribution leads the Agency to conclude that such levels

are usually well below the proposed levels of the standard, especially during the season of the niost active production of photochemical ozone. It is possible, however, that natural
events could occasionally'cause contravention of the promulgated standard levels. EPA policy (see 40

-.CFR 51.12(d)) permits data for such occurrences to be disregarded forregulatory purposes. Such events are usually distinguishable because they tend not to coincide with conditions conducive to buildup of man-caused, photochemically produced ozone. Field measure- ments at some remote sites, where mkn-caused oiohie is likely to be negligible, have shown low-but not insignificant-rates of exceedances of the 0.08-ppm level originally proposed for the secondary standard. The frequencies decrease markedly for concentrations above 0.12 ppm, so that natural exceedances of the standards 'being promulgated can be considered quite

rare at any particular location.

One comment indicated that stratospheric tracer levels measured at sur- face sites increase by about 40 percent between the front and back side of high pressure systems in the Eastern United States, thus suggesting that stratospheric ozone, through subsidence and horizontal circulation in highs, plays a significant role in the widespread buildup of ozone that tends to occur in the back side, of highs in the Eastern U.S. during the photochemically active season. EPA's estimate is that,.even if commonly occurring natural ozone background

were increased by 40 percent, the re- sulting concentration w~uld be insufficient to exceed the standard levels being promulgated.Also, a corresponding increase between the tracer and

ozone of stratospheric origin would
not be- expected, since the tracer is chemically stable near the surface, while ozone is rapidly depleted by re- actions with surfaces and with aircontaminants.

Some comments referred to a possibly significant contribution to ozone concentrations -from reactions involving organic comppunds emitted by vegetation. Such emissions are abundant, relative to man-made emissions, but are relatively diffuse spatially. Some of the comments cited a recent statistical study that reported a high correlation between vegetative growth in the Bay Area of California, as indicated by winter rainfall, and the frequency of days with concentrations above,0.08 ppm. EPA has not, however,seen sufficient physical evidence of

arelative abundance ofnatural organics orassociated ozone Increases in am- blent air to consider vegetative sources

as significant contributorsto high ambient ozone levels. The principal

source of natural ozone is still considered to be the stratosphere, with grad. ual transfer accounting for the more commonly observed background levels, and sporadic intrusions being the principal cause ofanomalous high values.

Although research will continue to

assess more definitively the contribution of natural sources of ozone, EPA believes that adequate consideration hasbeen given to this Issue in developing control programs and implementa- # tion guideline documents.

V.PROCEDURAL IssuES

Comment.EPA's use ofan "Advisory Panel on Health Effects of Photochemical Oxidants" was proce. durally incorrect in that certain legal requirements on establishment and

use of Advisory Committees were not met.

Agency Response. The ad hoe Advisory Panel consisted of a group of medical experts retained by EPA as consultants for the purpose of obtaining their interpretation of the evidence presented in a preliminary ver- sion ofthe criteria document. As such, EPA did not regard the Panel as an advisory body within the meaning of the Advisory Committee Act of 1972. In any case, the Panel's report has been in the docket and subjectto com- ment since proposal, and bases for Its' recommendations have ,been fully aired.

CommentIn revising Itscriteria document, EPA failed to comply with the recommendations of the statutory scientific review body, the Science Advisory Board (SAB), as evidenced by the SAB's refusal to approve the criteria document.

Agency Response. The function of the Science Advisory Board subcommittee is to advise EPA regarding the scientific and technical accuracy, the

manner of presentation, and the adequacy of the criteria document. Inevitably,no two scientists everagree com- pletely on' the importance, accuracy and manner of presentation of data. In the final analysis the responsibility for the criteria document rests with EPA and, therefore, the decision re- garding the content of the document
must alsorest withEPA.

EPAsolicits the advice ofIts scientific advisors and has attempted to re- spond to the specific comments made by members of the SAB subcommittee established to review the criteria document by incorporating suggested changes in the document. Following the last SAB subcommittee meeting in Febrary 1978, members of the subcommittee who had specific comments

were consulted by EPA personnel, and

FEDERAL REGISTER, VOL 44, NO. 28-THURSDAY, FEBRUARY 8, 1979RULES AND REGULATIONS

their comments and criticisms were discussed with them prior to making the changes in the document. It has always been Agency policy that once the EPA staff had considered the changes suggested by the SAB and, where appropriate, incorporated them into the criteria document,theAgency would proceed with publication.. Consequently, EPA feels that the criteria document adequately reflects the latest scientific knowledge pertaining
to the effects ofozone and other photochemical oxidants.

Comment EPA has failed to submit theproposed standard to the SAB for review as requiredby theEnvironmental Research, Development, and Demonstration Authorization Act of 1978 (Pub. 1, 95-155). EPA -should do so beforepromulgating the standard.

Agency Response. The development of the ozone standard revision, which began in 1976, followed the procedural
process in placebefore the enactment ofPublic Law,95-155. Accordingly,the SAB was asked to review only the criteria document. The independent corn-- mittee established in accordance with the 1978 Act held its first session in October 1978,when there was not adequate time for it to review the standard. The thorough review of the technical and scientific basis for the criteria document, which is in turn thed basis for the standard, substantially complies with the objectives of the Act.

SELECTING THE LEVEL OF THE PRIMARY
STANDARD EPA's objective in setting the standard level is to select an ozone concentration that will reflect an accurate consideration- of the existing medical evidence and an adequate assessment of the uncertainties in this evidence, and, thus, will protect all population
groups with an adequate margin of safety.

The criteria document supports the contention that a clear threshold of adverse health effects cannot be identifled with certainty for ozone. Rather, there is a continuum consisting of ozone levels at which health effects are certain, through levels at which scientists can generally agree that health effects have been clearly demonstrated, and down to levels at which-the indications ofhealth effects

are less certain andharder toIdentify. Given such a body of evidence, in selecting a standard with an adequate margin of safety the decislonmaker is taking into account the uncertainty about whether a possible standard will prevent adverse health effects.

This uncertainty results from several factors. First, human susceptibility
to health effects varies, and wecannot be certain that experimental evidence has accounted for the full range of susceptibility. Second, we cannot be certain.that all effects occurring at low ozone levels have been identified and demonstrated. Third, variations in weather create uncertainty as to the expected annual -maximumozone concentrations.

The Clean Air Act, as the Administrator interprets it. does not permit him to take factors such as cost or attainability into account in setting the standard; it is to be a standard that will adequately protect public health. He recognizes that controlling ozone to very low levels is a task that will have significant impact on economic and social activities. This recognition

causes him to reject as an option the ,setting of a zero-level standard as an expedient way of protecting public health without having to decide
among uncertainties. However, It is public health, and not economic impact, that must be the compelling factor inthe decision. Thus, the decision as to what standard protects publichealth with an adequatemargin of safety is based on the uncertainty that any given level is low enough to preventhealth effects, and on the relative acceptability of various degrees of uncertainty, given the seriousness ofthe effects. In selecting the proper level for the standard, EPAmust make assessments andjudgments ifi five critical areas.

I. Reported effect levels from human studies.

2. Characterizing the sensitive population.

3. Nature and severityofeffects. 4. Probable adverse health effect levelin sensitive persons.

5. Judgment of a standard level below the probable effect level that provides an adequate margin ofsafety.



### REPoRpD EFFECT LEVELS

In the preamble to the proposed standard (43 FR 26965), EPA presented a table of demonstrated effect levels in manranging from 0.15to 0.30
ppm. On the basis of suggestions received during the comment period, that table has been expanded to include a greater number of studies whereeffects havebeenreported. EPA believes that this is a more complete representation ofthemedical evidence since it includes some less conclusive studies at low levels that cannot be discarded in weighing the full body of health data. Nonetheless, the table
mustbe used with caution and in conJunction with qualifying 'statements made in the criteria document regarding the technical merit of each study, particularly the lessconclusive studies
atlowerconcentrations.

While this table does notprovide an undisputed value for adverse health effect levels in sensitive individuals, it does indicate that normal body functions are mostlikely disrupted atrelatively low ozone concentrations. The studies also indicate thatthe intensity and significance of effects increases as the pollutant level increases. The re- ported findings leave open the question ofincreased intensity of effects in

more sensitive persons. and the concern that effects reported in some studies may occur at lower concentrations when ozone is-present in combination with otherurbanpollutants.

FEDERAL REGISTER, VOL 44, NO. 28-THURSDAY, FEBRUARY 8, 1979 

## 8213

### 8214

/ FEDERAL REGISTER;VOL4, NO.28--THURSDAY FEBRUARY 8, 1979 RULES AND REGULATIONS [6560-01-C;] [6560-a 

### 1-Cl 

## ~~~REPORTED EFFECT LEVELS OznorOintxoue 

# ComilationofResultsRpreinHmnSuesEanno, Ooen orOxidantExposure

Concentration. Exposure Duration, Pollutant Reported Reference(s) ppm hours (for clinical measured Effect(s) studies); Averaging (03 'ozone,

- time (for epidemio- 0 x . oxidant) logical studies)

0.01

- hourly 03 Lung function parameters inabout 25% of Japanese Kagawa and Toyamd 0.30 average school children tested were significantly corre- (1975); Kagawa et al. lated with 0 concentrations (over the range of (1976) 0.01

- 0.30 p.) in the 2hours prior totesting.

0.03

- hourly 0 x -Although significant correlation was observed be- Wayne et al. 0.30 average tween decreased athletic verformance and O x con- (1967) centrations inthe ringe of 0.03

- 0.30 ppm, the criteria document states tnat inspection of the data reveals no obvious relationship between' performance and Ox values below 0.10-0.15 nom.

0.10 2 03 Decreased 02 pressure inarterialized blood, von Nieding et al'. increased airway resistance observed using non- (1976) standard measurement techniques.

0.10

- probably daily 0 x Increased rates of respiratory symptoms and head- Makino and Mizoguchi "0.15 maximum hourly ache were reported by Japanese students on days when (1975) average 0 concentrations exceeded 0.15 ppm as compared to days when 0.concentrations were less than 0.10 ppm.

0.15 1 03 Subjective symptoms of discomfort were observed by DoLucia &Adams most subjects, and discernible but not statistical- (1977) ly significant changes inrespiratory patterns oc- curred while performing vigorous exercise.

0.20 3 03 Reduction invisual acuity (nightvision) ob- Lagerwerff 3 served. (1963)

0.20

- 2 03 Asthmatic patients exposed under intermittent Linn et al. 0.25 light exercise conditions showed no statistically (1978) significant changes inrespiratory function. Symptom s.:ores increased slightly ouring 03 ex-, posures. Small buc statistically significant
blood bio.:hemical changes occurred.

0.25 2, 03

- Small changes inlung function were observed in3 Hazucna (1973) subjects performing intermittent llgnt exercise.

0.25 2and 4 03 No lung,function changes of note were observed in Hactney eta1. "rective" subjects (whohad histories of cough, (1975) chest discomfort or wneezing associated with air pollution or allergy) while performing'intermittent, light exercise.

0.25 daily maximm 0 x The average numaer of asthma patients having Schoettlin and hourly average attacks was statistically significantly elevated Landau (1901)

on days when O x levels exceeded 0.25 ppm.

0.25 0.5

- 1 03 Blood samples of exposed subjects had increased Brinkman et al. rates of sphering of red blood cells (1964)

0.28 daily maximum 0 Although the reported results are Inconclusive. Kurata et al., instantaneous EPA's examination of the evidence presented (1976) (Z-minute) suggests exacerbation of asthma when 0 levels average are above 0.28 ppn. x

0.30 1 03 Subjective symptoms of discomfort and statistical- DeLucia and Adams ly significant changes In pulmonary function were (1977) observed insubjects undergoing vigorous exercise,

0.30 daily maximum 0 x Increased rates of cough. chest,discomfort, and Hammer et al. hourly average headache were observed instudent nurses on days (1974) when the 0 x concentrations exceeded 0.30 ppm.

0.37 2 03 Discomfort symptoms and significant changes in Hazucha et al.(1973). lung function-were observed i-n subjects.undergoing Folinsbee et al.(1975); intermittent light exercise. Silverman et al.(1976)

0.37 2 03 Exposure to 0 and SOtogether produced changes Hazucha and Bates (1975) 0.37 2 S03 inlung function substantially greater than the -suof the separate effects of the individual pollutants.

0.37 2 03 The observed 0

- SO interactive effect on lung Bl et al.(1977) 0.37, 2 so- function was c~nside~ably smaller than that seen 

### S0

2 by Hazucha and Bates. The authors concluded that the.earlier study probably more nearl simulated

a smog episode inregions having high oxidant and sulfur oollutlon.

### RULES AND REGULATIONS

SENSITIVEPOPULATION

The legislative history of the Clean Air Act indicates that, in setting primary ambient air quality standards, EPA isto directits efforts atgroups of "particularly sensitive citizens such as bronchial asthmatics and emphysematics who in the normal course of daily activity are exposed tothe ambient en- vironment." (U.S. Senate Serial No. 93-18, 93dCong. 2d Sess.p.410).

Clinical and epidemiological studies have shown thatpersons with chronic obstructive airway disease,,particularly asthmatics, appearmost sensitiveto changes in ozone concentrations. This sensitivity results from the fact that their airways are hyper-reactive to Irritants such as ozone. These people

are, thus, judged to be the principal sensitive group of concern in setting the standard.

Studies have also established that exercise effectively increases the

ozone dose delivered to the target tis-

sues in the respiratory tract. Thus, persons engaging in exercise are particularlyvulnerable to the acutely irritating effects of ozone. The response of these groups to such changes in concentrations has not, however, been systematically studied.

NATURE AND SEVERITY OFErF s ImpairedPulmonaryFunction and ClinicalSymptoms-Ozone Is a pulmonary irritant that affects the

mucous lining, other lung tissue, and respiratory function. Changes in lung function appear as increased airway. resistance and as reductions in vital capacity, expiratory flow rates, and diffusion capacity. These effects are greater in exercising individuals and individuals with hyper-reactive airways (Le., individuals with ahistory of developing symptoms during light ac- tivity in smog or history of asthma). Changes in lung function are accom- panied by clinical symptoms such as coughing, chest tightness, and lower chest soreness.

Because the human respiratory system is endowed with a large re- serve, even airway-resistance increases of50 to 100 percent will not ordifiarily be perceived in normal individuals. As stated in the criteria document, however, two considerations suggest that oxidant-associated changes in, lung function may signal impairment of public health, first, inpeople with un- derlying respiratory illness such as asthma, chronic bronchitis, and em- physema, even small decrements in lung function often interfere with normal activity. Second, at experimental ozone concentrations as low as 0.30 ppm, decrements in lung function have usually been accompanied by physical discomfort, as manifested in symptoms such as sore throat, chest pain, cough, and headache. At times this discomfort has been great enough
to prevent the completion of experi-. mental protocols, particularly when subjects have been exercising vigorously. It appears quite likely that the pulmonary Irritantproperties of ozone (and perhaps other oxidants) underlie both the discomfort and the decrements infunction. Thus,atleast when associated with ozone exposure, changes in lung function often represent a level ofdiscomfort which, even among healthy people, may restrict normal activity or impair theperformance oftasks.

DecreasedResistance to InfectionThis effect Is represented by an in. creased rate ofmortality in laboratory animals subjected to both a bacterial ,challenge and exposures to ozone. According to some studies, the effect may be enhanced by the addition of such stresses as exercise or the addition of other pollutants In combination with the ozone dose.Desplte the uncertainties involved in predicting human-effects from animal studies, medical experts agree that decreased resistance to infection probably does

occur in man. The Durham study (1974) reporting increased illness in college students following periods of elevated pollution levels (with peak oxidant being the pollution variable
most strongly associated with illness) reinforces this hypothesis and adds to EPA's concern about the relationship of ozone to the occurrence of such an effectin man.

AggravationofChronicRespiratory Disease-Although the relationship between ambient oxidant or ozone levels and chronic pulmonary disease has not been fully assessed, available evidence suggests that the incidence and severity of asthma attacks in-

crease when short-term total oxidant concentrations exceed 0.25 to 0.28
ppm. Also, several investigators have reported a relationship between shortterm oxidant exposure and aggravation of other chronic obstructive lung diseases. However, theirreports are Inconclusive since short-term fluctuations in cigarette smoking habits

were not considered in their data 

### analyses.

Air pollution Is one of the many stresses that can, precipitate an asthma attack or worsen the disease state in persons with chronic cardiopulmonary disease. Other factors that

can precipitate attacks includerespiratory infections, passage of cold fronts. seasonal pollens, extreme heat orcold, and emotional disturbances.

EyeIrritation-Eye irritation isasso- ciated with selected chemical species (such as PAN) in the photochemical oxidant mix and with other organic
vapors. While there is no evidence that eye irritation is produced by
ozone, an ozone standard will serve to limit this effect because controlmeasures thatreduce ozone will alsoreduce the eye-irritating components in the 

### totaloxidantmix.

Biochemical Effects-Experimentalexposures of human subjects to ozone have produced.changes in blood biochemistry, such as increased fragility of red blood cells and altered enzyme activities in the serum. The signifi.- cance ofthese ozone-mediated changes isnot yetknown, butthe criteria document states that changes of the magnitude observed in human experimental exposureshave notyet'been linked
to any clinical diseases.

Carcinogenic, MutagenicandRelatedEffects-Studies havebeenconducted in an attempt to relate ozone to carcinogenic, mutagenic, and related effects. Available evidence in these

areas isnotparticularly helpful in setting ambient ozone standards because
most ofthe studies have not yet been replicated (in spite of some attempts to do so), andbecause some effects observed In lower life forms are ofquestionable significance forman. The criteria document states that the signifi-

cance of effects such'as chromosomal aberatlons has not been established and that some studies have produced conflicting results. In addition, EPA's Science Advisory Board recommended that certain studies on the mutagenic effects of ozone, which have not been replicated, not be emphasized in the criteria document.

PRDMARY STANDARD

As Illustrated in the table ofreported effect levels, there is no clear threshold air concentration of ozone indicated by the data as the onset of adverse health effects.It isEPA's best Judgment thatphysiological responses probably occur In extremely sensitive persons at very low levels. At what point these responses become an ad-

verse health effect and at what level they most likely occurin sensitive per-

sons must necessarily be an informed judgment. As stated In the proposal, this judgment is based on (1) the Agency's understanding ofthe medical evidence presented inthe criteria document and in the table of reported effectlevels, (2) thefindings ofthe advisory panel on health effects, a-ad (3) the Judgment ofmedical experts as to the adverse effect level in sensitive
persons. The health experts who were consulted were asked tofocusnotonly

on the most sensitive population group,but also on a very sensitive portion of that group (specifically, those persons who are more sensitive than 99 percent of the sensitive group, but less sensitive than 1 percent of that group). The lowest adverse health effect level estimate cited by thr health panel and the median valuedeveloped through the expert inter

FEDERAL REGISTER, VOL 44, NO. 28-THURSDAY, FEBRUARY 8, 1979 

## 8215

### 8216

view process are reasonably consistent, ranging from 0.15 to 0.18 ppm. (See table below.) On thebasis ofthe effect levels citedin the criteria document,it isEPA'sjudgmentthat the most probable level for adverse health effects in' sensitive persons, as well as in health

### RULES AND REGULATIONS

ier (less sensitive)persons who are exercising vigorously, falls In the range of0.15-0.25 ppm.While theevidenceis

more convincing and theeffects more pronounced at the higher .end of this range, the data shows effects of concern atthelowerconcentration.

PnOBABLE EFFECtLE ELESTn.ATES
[Estimates forSensitive PopulationSegments]

Aggravation of Reduced .Chestdiscomfort
asthmna, resistance to ReductionIn andirritationof •emphysema, and ,bacterial

- pulmonary the respiratory' chronic Ifection (animal ' function tract. bronchitis

, studies)

Health panel judgment of effect 0.15-0.25 ppm Notavailable 0.15-0.25 ppm 0.15-0.25 ppm

level. Probable or median effect level as 0.17ppm" 0.18 ppm 0.15 ppm 0.15 ppm

estimated from nterviews with (0.14-0.25 ppm) (0.07-0.38 ppma) (0.07-0.18 ppm) (0.11-0.18 ppm) health experts (Range of estimatesgiven Inparentheses).

In order to set an ambient air qimality standard that protects the public health with an adequate margin of safety, EPA must deal with the uncer- tainty inherent in the judgment that the probable level for adverse effects in sensitive persons is in the range of 0.15-0.25 ppm. ,

Because the nature 'and intensity of' effects vary from pollutant to pollutant andbecause medical research produces new and different findings'as science progresses, EPA does not believe that afixed acceptable margin of safety can be established for allpollutants or"for a' single. pollutant over time.Each decision on a standard level
must be made on the best, evidence available at, the time and should include consideration ofsuch factors as:

1. Concernfor more.sensitiveindividuals-Sensitive persons may respond to ozone differently from the less sensitive persons who generally

are tested in clinical studies. Individuals with underlying respiratory ill-

ness such as asthma, chronic bronchi-- tis, and 'emphysema are particularly sensitive to even modest impairments of pulmonary function resulting from

ozone exposure. For ethical reasons, clinical investigators normally do not expose persons with these illnesses and thus caution- that such studies may not represent the full range of sensitivity to ozone. Also of concern

are individuals engaged in vigorous outdoor activity (construction work, tennis, Jogging, etc.) where the effects ofozone areenhanced ormay occur at lower ambient concentrations.

2. Pollutantinteractions-Thereis real concern that effects .reported in

some ozone studies mayoccur atlower concentratioiis and may be enhanced' when ozone Is present in bombination with other urban pollutants. Laboratorystudies of a single pollutant (e.g.,

ozone in clean, filtered air)rwhile important in elucidating physiological effects peculiar tothatpollutant, cannot be viewed as providing definitive evidence of the minimum level at which these effects occur when that pollutant is present as only a pait of the total insult delivered to an individual in the urban environment. Also ofcon-
cern are other toxic oxidant species, such as'PAN, that are often present with ozone in the ambient photochemical pollution mixture and cause other adverse effects such as eye irritation.Thus,the effects ofozone must be considered in the context of the total environment ofthe exposed individual; this environment includes con- centrations ofotherpollutants consistent with their maximum allowable levels, high relative humidity, high ambient temperature, and high levels ofphysical stress.

3. Long-term deleterious effects of ozone-Unfortunately, there are few studies that have attempted to document the long-term adverse effect of human exposure to repeated peaks of

ozone. Some animal studies do indicate that long-term ozone exposures act as

an inducer of biochemical*or morphological changes. Some of these changes are transient and, on a shortterm basis, maj have a physiological significance in thatthey confer aresistance againstfurther lunginjury in an oxidant environment (a similar re- spons6 has been-observed n human clinical studies). Some animal studies have indicated, however, that effects from continued exposure can result in

an emphysema-like condition (e.g., P'an etal., 1972).

4. Animal infectivity studies-Although evidence of reduced resistance
to bacterial infection has not reached the point where Itcan be meaningfully used to extrapolate concentrations that w'ould similarly affect man, these studies cannot be dismissed In selecting a standard level that provides an adequate margin ofsafety.Despite the present inability to extrapolate to an effect level in humanS, most experts agree that ozone exposures may well result in decreased resistance to Infection in humans. Further, Itis the kind of effect that is serious enough in its implications to raise a need for cau- tion. Thus, it is prudent public health practice to set a standard more stringent than the probable effect level es- timated from human studies, In order *toaccount in some measure for these uniquantified, but possibly serious, effects.

5. Inconclusivestudies-reportingeffects atlow levels-A similar caution is suggested by both the Makino and MIzoguch epidemiological study and the

von Nieding clinical study reporting effects atlevels around 0.10ppm.

6. Uncertainties arisingfrom air quality variations due to meteorology--Since EPA's revised standard Is statistically based and permits an ex- pected number of allowable violations
per year, there is concern about the magnitude of these excursions and how they might impact an exposed sensitive individual.

7. Effects of calibrationprocedure change-Another factor that has been, considered in establishing a margin of i safety is the variability that exists ino the measurement and calibration techniques used in health studies and how these measurements may differ from those made with the ultraviolet (UV) reference calibration procedure being ,promulgated elsewhere In this Issue of the FnmERAL REGISTER. Most ofthe relevant clinical studies utilized monitoring instruments calibrated with the
current (NBKI colorimetric) reference calibration procedure ormodifications thereof. EPA's best judgment Is that the reference NBKI procedure shows

a positive bias of about 10 percent -with respect to the UV procedure when these techniques are compared under carefully controlled expeimental conditions. However, due to the variability that can reasonably be ex. pected In any clinical exposure monitoring measurements, as well as tho uncertainty Introduced by the modified calibrations procedures, EPA cannot determine a precise quantitative factor to adjust the findings of these health studies. In the case ofthe study done by DeLucla and Adams (1977), the authors have indicated to EPAi that the reported ozone values

FEDERAL REGISTER, VOL 44, NO. 28--THURSDAY, FEBRUARY 8, 1979ROLES AND REGULATIONS

might be high with respect to the UV calibration procedure. While the exact magnitude ofany required adjustment in the reported ozone values is uncertain, adjusted values could range from 0.12 to 0.15 ppm for the 0.15 ppm value reported by the authors, and from 0.23 to 0.30 ppm forthe 0.30 ppm concentration. EPA will continue its evaluation of this issue through its program ofclinical exposure studies.

8; Findingsfrom the preliminary risk assessment-The preamble to the proposed standard described apreliminary risk assessment methof per-

.formed toaid EPA in accurately treating the uncertainties associated with a standard decision. While this method
cannot be used atthis time as the sole tool -for making that decision, the Agency does believe that the findings resulted from this initial application of the method do not permit any relaxation of the standard above 0.12
ppm.

After reviewing the comments received from all segments ofthe public, including those fromthe public health .community, EPA remains convinced that- at levels in the range of 0.15-0.25 ppm, adverse health effects will almost certainly be experienced bysignificant numbers of sensitive persons. Unless the standard is set somewhat below thatlevel,theAgency wouldnot be exercising that degree of prudence called for by the "adequate margin of safety" requirement of the Clean Air Act. The Administrator must exercise the informed scientific judgment that Congress has authorized him to bring tobear onthese difficult problems.

There is no collection of facts or medical evidence that permits selecting an undisputed value forthe standard level EPA proposed a standard of 0.10 p'pm, taking several)factors into
account in providing a margin of safety, as discussed above. Among those were epidemiological studies indicating effects below 0.15 ppm which the criteria document didnot fully en- dorse, but which EPA thought it unwise to disregard. (See 43 FR 26966.) Also considered were animal studies indicating reduced resistance
to bacterial infection, although ex- trapolation to.human effects levels is
notpossible. (Id.)During the comment periods, EPA received informed scientific opinion disputing the interpretation and application of such studies. Based on its current understanding of these studies, EPAhas concluded that they do not dictate as wide a margin ofsafety aswas established inthe proposaL EPA does believe, however,that thesestudies do suggestthe realpossibility of significant human adverse health effects below 0.15 ppm. Consequently, the Administrator has determined that a standard of 0.12 ppm is
necessary and is sufficiently prudent unless and until further studies demonstrate reason to doubt that It adequately protects public health.

WELFAREEFFL 

### s A"P TESEcONDARY STANDARD

The Clean AirActmandates the setting of a national secondary ambient air quality standard to protect the public welfare from any known or anticipated adverse effects associated with an air pollutant In the ambient air. Ozone and other photochemical oxidants constitute a form ofairpollution that has been shown to affect vegetation and materials and thatmay have an impact on visibility. The economic loss resulting from rurrent oxidant levels has been estimated to bein the range of several hundred million dollars peryear nationwide. Non-quantifiable losses to the natural environment occur aswell. A staff paper, "Assessment of Welfare Effects and the Secondary Air Quality Standard for Ozone," was placed in the docket at the time of proposal. The following paragraphs summarize this report and informationreceived afterIts release.

Exposure of vegetation to harmful levels of ozone may result in leaf injury, decreased growth and yield, or reproductive effects. Visible leaf injury is the most readily detectable and frequently reported symptom of

ozone damage; however,it isnot an accurate indicator of yield or growth re- duction.

In the June 22, 1978, FEEALREcxsTER proposal (43 FR 26968-26969). it

was stated that several investigators suggested that follar injury rates in thb range of 5to 10percent could produce detectable reductions in growth

or yield, depending on the timing of the injury and other environmental factors. Since proposal ofthe standard in June,EPAhas discussed the matter further with several experts in the field ofairpollution damage to vegetation, particularly regarding what level of leaf injury should be of concern in protecting against significant reductions in yield orgrowth in commercially important crops and indigenous flora. These experts emphasized the uncertainty associated with correlating yield reduction with foliar injury. Some stated that detectable yield reductions would not occur until leaf injury reached values as high as 10 to 20 percent, and others felt that folIar injury was an inappropriate indicator ofyield reduction.

The foliar responses of plants to

ozone exposures are not linearly dependent on the dose (product of con- centration and exposure duration) sus- tained by the plant. A given dose applied over a short period of time is

more damaging than ifit were applied

over a longer period. EPA used a mathematical model to summarize,for severalcrops, theexperimental results which depict the variation in foliarresponse with short-term (0.5-hour to 8- hour) ozone exposures. The notice of proposedrulemaking predicted (onthe basis ofthe mathematical model) that

a secondary ozone airquality standard
setatan hourly average concentration of 0.08 ppm, expected to be exceeded only once per year,would prevent any important commercial crop from re- ceiving more than 3 percent leaf Injury. On the basis ofthis prediction and the aforementioned assumptions regarding the relationship of foliar injury and yield reduction, EPA proposed to set the secondary standard level at0.08 ppm.

As a result of its further consultations withresearchers, EPAdecidedto

reassess the uncertainties associated with the Judgments that led to the proposed 0.08 ppm 1-hour average sec- ondary standard. These experts pointed out that there are large unce.-tainties In the assumptions relating yield reduction to foliar injury. The mathematical model used to predict follar injury was based on chamber studies,
not on studies conducted under field conditions.The experts cautioned that these chamber studies generally represent experimental conditions.in which the most sensitive varieties of a given species are usedandin whichmoisture and temperature are optimal for producing injury. In addition, a given short-term dose of ozone, which can produce 5, 10, oreven 20percent follar injury in a given plant, is unlikely to have an Impact on yield unless the plant isexposed during a critical stage in theplant'slife cycle.

Consequently, EPA has decided to base Its decision on the secondary

ozone air quality standard on the information currently available on growth and yieldreduction in commer- cially Important crops and indigenous vegetation exposed to ozone under fieldconditions. Asdiscussed in astaff paper that has been placed in the docket (OAQPS 78-8, IV-A-3), "Evaluation of Alternative Secondary Ozone' Air Quality Standards," these data in-. dicate that growth and yield responses

are related to the long-term (growing season) mean ofthe daily maximum 6-
to 8-hour-average ozone concentrations.Based on anexamination of this Information, and the available air quality data, EPA concludes that there is currentlyno evidence indicating that a significant decrease in growth or yield of commercially important crops or indigenous flora will result fromthe long-term mean ofthe daily maximum 7-hour-average ozone concentrations expected to.occurwhen theprimary standard is attained. Consequently, EPAbelieves thata secondary standard more stringent than the primary standard is not necessary on

FEDERAL REGISTER, VOL 44, NO. 28--THURSDAY, FEBRUARY 8, 1979 

### 8217

### 8218

the basis ofozone-related yield -reduction effects invegetation.

Materials damage resulting from

ozone can be described as an acceleration of aging processes; for example, rubber cracking, dye fading, and paint weathering. In contrast to the effects of ozone on vegetation, these effects

are linearly dependent on the total

ozone dose sustained by the material. As a result, the annual-average concentration will determine the rate at which material is damaged. Any non-

zero ozone concentration (including natural background levels), will con- tribute to the deterioration of sensitive materials over a sufficient expo-

sure duration. While peak 1-hour

ozone concentrations in urban areas -tend to be considerably higher thanin

rural areas remote from man-made emission sources, the annual average concentrations observed in these areas

are essentially the same. This finding is believed to be due to the impact of very low urban-area nighttime ozone concentrations on the annual average values; nighttime ozone levels in
remote areas are not reduced asmuch from the daytime levels dale to the ab-

sence of scavenging by man-made urban pollutants. As peak ozone levels in urban areas are reduced through control of man-made pollutants, scav- enging will alsobereduced resultingin little Ifany change in the annual aver- age. Consequently, no effect-based ra- tionale can be offered to decide the leveL ofthe secondary standardneeded
to protect materials. Accordingly, EPA believes that a secondary standard

more stringent than the primary standard is not necessary -onthe basis ofozone damage tomaterials.

The criteria document states that there is alimited amount of data suggesting an association, between am-- blent ozone and visibility degradation, particularly in the Los,Angeles area. On the basis of EPA's evaluation to date of the information presented in the criteria document, however, EPA is unable to conclude atthis time that

a secondary. ozone standard more -stringentthan the primary standard is
necessary to prevent visibility deterioration. The relationship between visibility 'and ambient ozone will be con- sidered further in the development of subsequent PSD programs designed to protect against significant deterioration ofairquality.

On the basis of tjiese conclusions with respect to ozone damage to vegetation and materials and the association of ozone with visibilityreduction in some areas, EPA isrevising the sec- ondary ozone air quality standard level to 0.12 ppm.
OTHERAsPEcTs orTHE STANDARD

On the basis of EPA's evaluation of evidence submitted and comments,reRULES AND REGULATIONS

ceived during the public review process, no major changes will be made in the following aspects of the proposed standard: (1) Averaging time: 1 hour; (2) chemical species: ozone; (3) form: statistical; and (4) a separate standard for PAN is not being promulgated. As discussed below, changes will be made in (1) the set ofhourly averages from which the number of exceedances of the standard level is counted, and (2) the exclusion criteria formissing data.

DAILY MAXIMUM HOURLY AVERAGE .INTERPRETATION OF THE STANDARD

The maximum ozone concentrations which will occur in any given time period willvaryfrom oneperiod to the next, even if precursor emissions re- main constant. These variations are mainly due to the random nature of meteorological factors which affect' the formatioi and dispersion of ozone in the atmosphere. The present deterministic form of the standard, which permits only a single hourly exceedance ofthe standard level in any year, inadequately deals with this situation. The risk to public health contributed
to by ozone can be managed better if the ozone standard reflects the fact that maximum ozone concentrations

are probabilistic in nature. Consequently,EPA ischanging the standard
to a statistical form that allows one expected exceedance peryear.

The proposed standard Wbuld have alloved one expected hourly exceed-

ance per year. EPA is further modifying the standard so tha. the one ex- pected exceedance will be given adaily interpretation; that is,.a calendar day will exceed the standard level if the maximum hourly average concentration for the day exceeds the level of the standard. This modification means thata-daywith twohourly values over the standard level counts as one exceedance of the standard* level rather than two; similarly for days withmore thantwo hourlyvalues over the standard level. Aswas indicated in theproposal notice,the daily interpre-' tation has some advantages and it is evident from the comments received that there is considerable support for theuse ofthisinterpretation.

It should be understood that the change to a daily interpretation is not predicated on a reinterpretation -of health data. In making this change, EPA isnot concluding that 3 hours of
exposure 'above a given level; for ex- ample, are no worse than 1 hour of ex- posure above thesame level as long as the 3 hours of exposure occur during the same day. The impact of ozone is related to-the total dose delivered to the respiratory tract, and obviously for a given concentration a 3-hour ex- posure gives a greater dose than a 1- hour exposure. In the case of ozone, the pattern of hourly levels is mainly determined by meteorological fluctuations, and EPA's decision to promulgate a daily standard does not affect meteorological fluctuations. Ozone
precursor emissions are not easily ma- nipulated on a short-term basis, so there is little likelihood that emission

sources could readily alter emission patterns to*take advantage of the daily interpretation.

The change to adaily interpretation does make the standard slightly less stringent, and hence there is a small increase in the risk to health. In general, the reduction in emissions of or- ganic compounds needed to meet the standard under the daily interpretation will be smaller. As discussed in a report placed in the docket (OAQPS 78-8, IV-A-4), the long-term Increase in health risk at an average geographical location is estimated to be equivalent to the increase that would result from raising the level of the standard
to 0.123 ppm and keeping the hourly interpretation of the number of exceedances.

EXCLUSION CRITERIA 

### r MISSION DATA

EPA is, additionally modifying the standard with respect to the treatment of missing data. The proposed standard permitted certain missing values to be excluded from the estimated exceedances calculation If either of two exclusion criteria Were satisfied. The first criterion recognized the impact-of short-term meteorological influences by allowing a missing value to be excluded if the adjacent values were below an arbitrary limit (75 percent of the standard level), This criterion should be relatively
easyto.incorporate intodata-handling schenes and has been retained, although it now applies to daily maximum hourly average values. The second criterion dealt with compari-

sons with data from the previous 3
years. The purpose of this second criterion Ivas to accommodate situations for which ozone data for a particular

season are not available butfor which known seasonal patterns of ozone and related meteorological factors make it unlikely that the level of the standard wouldhave been exceeded.

This second criterion wouldbe more difficult to Implement because it 'necessitates the cross-referencing of earlier historical data. For newly established monitors, the historical data needed to invoke this exclusion would
not be available..Thus, this second criterion in the proposal is difficult to implement and could be potentially burdensome in geographic areas where the climate makes high ozone valueS during certain seasons very unlikely. It is alsopossiole to accomplish the Intended purpose of this exclusion through provisions of the recently proposed 40 CFR Part 58 (see 43 FR

FEDERAL REGISTER, VOL 44, NO. 28-THURSDAY, FEBRUARY 8, 197934892) that would grant waivers ofthe

ozone monitoring requirements for certain times ofthe year atthe discretion of the appropriate Regional Administrator. Therefore,the second exclusion criterion has been eliminated, and the computationformulasfor estiinating the -expected number of exceedances have beenmodified tore- flectthe number ofrequired monitoring daysfortheyear.

DefinitionofWhen the Standardis, Attained-EPAis adding Appendix H
to 40 CFR Part50 to explain when the

-- standard is or is not being attained. Certain modifications to the proposal

were necessary to accommodate the daily interpretation andthe previously mentioned changes in the treatment ofmissing data. In orderto implement the change from an hourly to a daily interpretation, it isnecessary to define what is meant by a valid day of ozone data. Such a definition must ensure that.a sufficient number of hours of the dayhave beenmonitored andthat the hourly values in question reflect the time of day when high. ozone values arelikely to occur. At the same time, this criterion should be relatively easy to implement, it should allow time for routine maintenance, and yet it should protect against high values being ignored merely because not enough hours of the day were meas- ured. According'ily, A daily maximum hourly average concentration will be considered valid if 75 percent of the 'hourly values from 9:01 a.m. to 9:00
p.m. MST) were recorded or if an hourly

-alue above the level of the standard was measured. This validity criterion is intended as a minimum re- quirement and not as a recommended schedule.

The computation formula for-calculating the estimated number of exceedances per year has been modified to correspond to the daily interpretation of the standard. Allowance has also been made for any situation in which the Regional Administrator has granted a waiver of the ozone monitoring requirements under the provisions of the recently proposed40 CFR Part 58 and,therefore, the total number ofrequired monitoring days is less than a full year. The use of the exclusion criterion may result in an underestimate of the'probability ofan exceedance in some situations but is relatively easy to implement and should suffice to account for the effect of missing data. It should be noted that the formula given in Appendix H isnecessary to show attainment.Accounting formissing data can -"never, however, decrease the number

of exceedances, and thus it ispossible
to establish non-attainment without tileuse-ofthis equation.

These modifications to Appendix H

are intended to simplify somewhat the 

### RULES AND REGULATIONS

calculations and to allow for more flexible monitoring schedules. The comments received on Appendix H

were varied. A few commenters thought it was too complicated while others suggested .even more complex techniques. Most cmments were, however, supportive of (or, at least, neutral toward) the proposed approach. One suggestion was to employ aminimum percent completeness requirement, rather than estimating the number of exceedances. The problem with that approach,however,IsthatIt .remains unclear as towhat should be done with data sets that fail to meet such a completenessrequiremenL

Some comments discussed theuse of 3 years of data. As Indicated In the proposal,the choice of a 3-yearperiod represents a compromise- between addedstability andreasonably current status assessments. Even under the present deterministic form of the standard, ,attainment designations (e.g., 40 CFR Part 81, Section 107) have been based onmore than 1 year. Furthermore, although 3 years are used in estimating the expected number ofexceedances under the statistical form of the standard being promulgated, It Is still possible to establish non-attainment after one year if, for example, four or more exceedances were reported. Therefore, an upper bound to exceedances during a single yearstillapplies underthe new form.
Ecoxoiuc,Exraor, AxD ENMIONIMN LIMACTS
Ashasbeennoted,the CleanAirAct specifically requiresthatNationalAmbient Air QualityStandards be based

on scientific criteria relating to the level that should be attained to protect public health and -welfare adequately.EPAInterprets theAct as excluding any consideration of the cost of achieving such a standard In determining the leveloftheprimary standard. However, In compliance with the requirements of Executive Orders 11821 and 11949 and OMB Circular A107 andwith the provisions of the recently Issued Executive Order 12044 for rulemaking proceedings that are currently pending, EPA has prepared

an analysis of economic impacts associatedwith effortsto attainthis standard.

Ozone air pollution Is a pervasive problem throughout the country. Most urban and many rural areas exceed the existing standard. Even with the less stringent'standard, most of the major urban areas are not expected to attain the standard In the

near term. Controlofthe organic precursor materials that generate photo- chemical oxidants Is a major effortIn this country and a multibilllon-dollar program. The existing control pro

### 8219

gram Includes measures to reduce or- ganic emissions from automobile and truck exhausts, productioft of chemical and petroleum products, the drycleaning Industry, most painting operations (including the automotive industry), and other industrial operations.

Because the attainment problem in
most urban areas is so severe, the relaxation of the standard is notexpected to change the level of control re- quirements in the near term. The

move toa 0.12ppm standard will, however, eliminate the theoretical need for major control programs in many rural and wilderness areas that cur- rently exceed thepresentstandard.

With therelaxation ofthe standard, EPA's economic impact analysis indicates that most urban areas are expected to achieve the standard by 1987. Evenwith aggressive controlprograms, however, It will be very difficult for some urban areas to achieve the standard within thenext 10years.

In addition, a document has been prepared assessing the impacts that efforts to attain the standard may have on the nation's energy requirements. This document examines the
extent to which ozone precursors will be controlled by recovery of organic materials that would otherwise be emitted to the atmosphere, with resultant energy savings. Furthermore, an additional energy conservation should resultin those areas thatutilizetransportation control measures to reduce
precursor emissions by reducing the total number of vehicle-miles travelled.Because of such energy savings, EPA believes that ozone precursor control measures may well lessen the nation's energyrequirements.

Fnally, environmental impacts assoclated with control of oxidantprecur-

sors have been examined in a document available in docket number OAQPS 78-8. This study indicates that modifying the current standard should have mnimal environmental Impacts.

Copies of these analyses of the eco- nomic, energy, and environmental impacts involved in the revised ozone standard are available from Joseph Padgett atthe address given earlier.

Rvnsxoxs ToPART 50REauLAaxoxs

In addition to the revised standard, this action necessitates two otherrevi

### sionsto 40CFR Part50 asfollows:

1. In Appendix D, as well as in the table of sections for Part 50, the title Is revised to read as follows: "Appendix D-Measurement Principle and Calibration Procedure for the Measurement of Ozone in the Atmosphere." The substitution of "ozone" for "photochemical oxidants corrected for interferences due to nitrogen oxides and sulfur dioxide" is a result

FEDERAL REGISTER, VOL 44, NO. 28-THURSDAY, FEBRUARY 8, 1979

### 8220

of the change in the chemical species' designation ofthe standard.

2. Appendix H, "Interpretation of the National Ambient Air Quality Standards for Ozone," is added because additional guidance is necessary to un- derstand the statistical nature of the revised standard.

REVISIONS TOPART 51REGULATIONS


### Elsewhere in this issue ofthe FEDERAL REGISTER, three revisions to40 CFR Part 51 are promulgated concurrently with therevisiontothe photochemical oxidant standard. They are asfollows:

1. The term "photochemical oxidants" ischanged to "ozone" throughout Part51.

2. Section 51.14, "Control strategy: Carbon monoxide, hydrocarbons, photochemical oxidants, and- nitrogen dioxide," is revised to (a) allow the states to use any of four analytical techniques inthe place of Appendix J to calculate the percent hydrocarbon reduction peeded to attain the ozone standard, and (b) require that the states consider background ozone concentrations andozone trafisport.

3. Appendix J is deleted from Part 51.

FEDERAL REFERENCEMETHOD



### The measurement principle andcalibration procedure applicable to reference methods for measuring ambient

ozone concentrations to determine compliance with the standard are-not affected by this rulemaking. Elsewhere 

### in this issue of the FEDERAL REGISTER, however, EPA is replacing 

### (superseding) the current calibration procedure with a new, superior calibration procedure based on ultraviolet

- 

### photometry. The measurement princi- ple and the current calibration procedure are setforth inAppendix D of40 CFR Part 50 (as amended in the February 18, 1975: issue of the FEDERAL REGISTER, 40 

### FR 7042). Reference 

### methods-as well as equivalent methods-for monitoring ozone are desig- 

### nated in accordance with40 CFR Part 53 (40 FR 7044). A list of allmethods designated' by EPA as reference or equivalent methods for measuring

ozone is available from iny EPA regional office, or from EPA, Department E (MD-76), Research ,Triangle Park,NC 27711.

Dated:January 26, 1979. DOUGLAS M.COSTLE, Administrator.

REFERENCEs Bell,K.A., W. S.Linn, M. Hazucha, J. D. 

### Hackney, and D.V."Bates. "Respiratory effects of exposure to ozone plus sulfur dioxide in Southern Californians and Eastern Canadians." Am. Ind.Hyg.Assoc. J. 38: 696- 706,1977. 1 RULES AND REGULATIONS

,Brinkman, R., H. Ba.Lamberts, and T. S. Veninga. "Radiomimetic toxicity of ozon- Ized air." Lancet1(7325): 133-136, 1964.

DeLucia, A. J., and W. C.Adams. '!Effects of 03 inhalation during exercise of pulmonary function and blood biochemistry." J. Appl. Physiol.: Respirat. Environ. Exercise Physiol.43 (1): 75-81, 1977.

Durham, W.H. "Air pollution andstudent health." Arch.Environ. Health. 28:241-254, 1974.

Folinsbee, L..J., F. Silverman, and R. J. Shephard. "Exercise responses, following

ozone exposure." J. Appl. Physol. 38: 996- 1001, 1975.

Hackney, J. D., W. S. Linn. and others. "Experimental studies on human health effects of air. pollutants." Arch. Environ. Health 30:373-390, 1975.

Hammer, D. I., V.Hasselblad, B.Portnoy, and P. F. Wehrle. "The Los Angeles student

nurse study." Arch.Environ. Health28: 255- 260, 1974. -__

Hazucha, M. "Effects of ozone and sulfur dioxide onpulmonary functionjnman." Ph. D. Thesis. McGill University, Montreal, Canada. 1973. 233 p.

Hazucha, M., and D. V. Bates. "Combined effect ofozone and sulfurdioxide on human pulmonary function." Nature 257(5521): 50- 51, 1975.

Hazucha, M., F. Silverman, C. Parent, S. Field,andD. V.Bates. "Pulmonary function inman after short-term exposure to ozone." Arch.Environ.Health 27:183-188, 1973.

Kagawa, J., and T.Toyama. "Photochemical air pollution: Its effects on respiratory function of elementary school children." Arch.Environ.Health 30:117-122,1975.

Kagawa, J., T. Toyama, and M. Nakaza. "Pulmonary function tests in children ex- posed to airpollution." in"Clinical InmplicationsofAirPollution Research. A.J. Finkel and W. C. Duel"(eds.).Acton, MA. PublishingSciences Group, Inc. 1976. pp.305-320.

Kurata, J. H., M.M. Glovsky, R. L.Newcomb, and J. G. Easton. "Amulti-factorial study of patients with asthma. Part 2: Air pollution, animal dander and asthma symptoms." Annals of Allergy. 37: 398-409, 1976.

Lagerwerff, J.M. "Prolonged ozone inhalation and its effects on visual parameters." Aerospace Med. 34:479-489, 1973.

"A Legislative History of the Clean Air 'Amendments of 1970."U.S. Senate Committee on Public Works. Serial No. 93-18, Vol. 1. 93d Congress, 2d. Session.January 1974.

Linn, W. S., R. D. Buckley, C. E. Spier, R. L.Blessey, M. P. Jones,D. A. Fischer, and J. D. Hackney. "Health effects of ozone expo-

sure in asthmatics." Amer. Rev. Resp. Dis. 117.835-843, 1978.

Makino, K., and I. Mizoguchi. "Symptoms caused by photochemical smog." Japanese Journal of Public Health 22 (8): 421-430, 1975.

National Academy of Sciences. Ozone and, Other Photochemical Oxidants. Prepared by the Committee on Medical and Biologic Effects of Environmental Pollutants, National Academy of Sciences. Washington, D.C. 1977.

P'an, A., J. Beland, and Z. Jegier. "Ozoneinduced arterial lesions." Arch. Environ. Health. 24:229-232, 1972.

Schoettlip, C. E., and E.Landau. "Air pollution and asthmatic attacks in the Los Angeles area." Public Health Repts. 76: 545- 548, 1961.

Silverman, P., L. J. Folnsbee,J. Barnard, and R. J. Shephard. "Pulmonary function changes in ozone--interaction ofconcentraflon and ventilation." J. Appl. Physiol. 41 (6): 859-864, 1976.

Stokinger, H. E. "Ozone toxicology: A review of research and industrial experli

ence, 1954-1964." Arch. Environ. Health 10: 719-731, 1965.

U.S. Department of Health, Education, andWelfare. Air Quality Criteria for Photochemical Oxidants. National Air Pollution Control Administration, PublicHealth Service, U.S. DHEW. NAPCA Publ. AP-63. Washington, DC. U.S. Government Printing Office. 1970.

U.S. Environmental Protection Adency. Air Quality Criteria for Ozone and Other Photochemical Oxidants. Preprint. U.S. EPA Publ. EPA-600/8-78-004, Washington, DC.Aphil 1978.

von Nieding, A., H. M. Wagner, H, L. Loellgen, and H. Krekeler. Presented at the VDI Kommission Reinhaltung derLuft Col. loquim onOzone andRelated Substances it Photochemical Smog, Duesseldorf, W. Ger. many,September 22-24, 1976.

Wayne,W. S., P. P.Wehrle, andR. E. Car' roll. "Pollution and athletic performance," J.Amer. Med, Assoc. 199 (12): 901-904. 1967.

EPA amends Part 50 of Chapter I, Title 40, of the Code ofFederalRegulationsas follows:

1. Section 50.9 Is revised to read as follows: §50.9 National primary and secondary ambient air quality standards for

ozone. (a) The level ofthe national primary and secondary ambient air quality standards for ozone measured by a referdnde method based on Appendix D
to this part and designated in accordance with Part 53 of this chapter, is 0.12 part per million (235 pg/ 3). The standard is attained when the expected number of days per calendar year with maximum hourly average concentrations above 0.12 part per million (235 pg/m 3 ) is equal to or less than 1,

as determined by Appendix H.

2. In Appendix D, as well as In the table of sections for Part 50,the title is revised to read as follows:

APPENDIX D-MEASUREMENT PRINCIPLE

AND CALIBRATION PROCEDURE FOR THE MEASUREMENT OF OZONE IN TIlE ATMOSPHERE

3. Appendix H is added asfollows:

APPENDIX H-INTERPRETATION OF TuE NATIONAL AMBzENT 

### Ain QUALITY STANDARDS
FOROZONE 1.General

This appendix explains how to determine when the expected number of days per calendar year with maximum hourly average concentrations above 0.12 ppm (235 pg/ml) isequal to orless than 1.An expanded discussion of these procedures and associated examples are contained in the "Guideline for Interpretation of Ozone Air Quality Standards." For purposes of clarity in the following discussion, it is convenient to use 'the term "exceedance" to describe a daily maximum hourly average ozone measure- ment that is greater than the level of the standard. Therefore, the phrase "expected

FEDERAL REGISTER,'VOL. 44, NO. 28-THURSDAY, FEBRUARY 8, 1979

### RULES AND REGULATIONS

number ofdayswithmaximumhourly aver- age ozone concentrations above the level of the standard" may be simply stated as the "expected numberofexceedances."

The basic principle in making this determination isrelatively straightforward. Most. ofthe complications that arise In determining the expected number of annual exceed-

ances relate to accounting for incomplete sampling. Ingenera], theaverage number of exceedances per calendar yearmusthe less thanor equal to 1. In Itssimplestform,,the number of exceedances ata monitoring site would be recorded for each calendar year and then averaged over the past 3 calendar
years to determine if this ayerage is less thanor equalto 1.

2.Interpretation of

ExpectedExceedances

The ozone-standard states that the ex- pected number of exceedances per year must beless than or equal to1. The statistlk cal term "expected number" is basically an arithmetic average. The following example explains what it would mean for an area to be in compliance with this type ofstandard. Supposea monitoringstationrecords avalid daily maximum hourly average ozone value for every dayof theyear during the past 3 years.At the end ofeach year, the number of daysr with-maximum hourly concentrations above 0.12ppm is determined and this number is averaged with theresults ofprevious years. Aslong asthis averageremains "lessthan or equal to 1" the area isIncom- pliance.

3. Estimating the Number ofExceedances

foraYear

Ingeneral, a valid daily maximum hourly average valuemay notbe available for each day ofthe year, and it will benecessary to account for these missing values -when estimating the number-of exceedances for a

. particular calendar year. The purpose of

these computations is to determine if the expected number ofexceedancesper yearis less than or equal to 1. Thus, if a site has
two or more observed exceedances each year, the standard is not met and it is not necessary to use theprocedures ofthis sectionto accountforincomplete sampling.

The term "'missing- value" is used here in the general sense to describe all days that do not have an associated ozone measure- ment. In some cases, a measurement might actually-have beenmissedbutin other cases

no measurement mayhave been scheduled forthat day.A daily maximum ozone value is defined to-be the highest hourly ozone value recordedfortheday.This dailymaxi-

mum value is considered to be valid If 75 percent ofthe hours from 9:01 am. to 9:00 p.m. (MST)weremeasured or ifthe highest -hour is greaterthan thp level ofthe standard.

In some areas, the seasonal pattern of

ozone is so pronounced that entire months need notbe sampled because it is extremely unlikely thatthe standard wouldbe exceeded. Any such waiver of the ozone monitoring requirement would be handled under provisions of 40 CFR Part 58. Some allow-

ance should alsobemade for daysfor which valid daily maximumhourly values werenot obtained but which would quite likely have been belowthestandard. Suchan allowance introduces a complication inthat itbecomes necessary todefine underwhat conditions a missingvalue maybe assumed to havebeen less than the level ofthestandard. The followingcriterion maybeusedfor ozone: A missing daily maximum ozone value may be assumed to beless than the level of the standard f the valid daily maxima on both the preceding day and the following day do notexceed 75 percent ofthe levelof thestandard.

Letz denote the number ofmissing daily maximumvalues thatmaybe assumed tobe less than the standard. Then the following formula shall be used to estimate the ex- pected number ofexceedances for the year e=v+£E(v/n)'(N-n-z)] (1)

(Indicates multiplication.)

Where:

e=the estimated number of exceedances

fortheyear, N=the number of required monitoring.

daysin theyear. n=the numberofvaliddailymaxima, v=the number of daily values above the

level-of thestandard; and z=the number ofdays assumed to beless

thanthe standa-d level.

*Indicatesmultiplication.
This estimated number of exceedances shall be rounded to one decimal place (fractional parts equal to0.05 roundup).

It should benoted thatN will be thetotal number of days in the year unless the appropriate Regional Administrator has granted awaiver undertheprovisions of40 CFR Part58.

The above equationmay beinterpreted intuitively in the following manner. Theestimated number of exceedances Is equal to the observed number of exceedances (v) plus an increment that accounts for Incomplete sampling. There were (N-n) mlsing values for the yearbut a certain number of these, namely z. were assumed to be less than the standard. Therefore, (N-n-z) imingvalues are considered toinclude possible exceedances. The fraction of measured values thatare above the levelofthe standard isv/n. It is assumed that this same fraction applies to the (N-n-z) missing values and that (v/n)'(N-n-z) ofthese valueswould also have exceeded the level of the standard.

AoHonmrr. Sections 109 and 301 of the Clean Air Act, as amended (42 U.S.C. 7409. 7601).

(FRDoc. 79-4056Filed2-7-79; 8:45 am]



### [6560-01-M]

FRL1018-31



### PART 50-NATIONAL PRIMARY AND SECONDARY AMBIENT AIR QUALITY STANDARDS

Calibration of Ozone Reference Methods
AGENCY: U.S. EnvironmentalProtectionAgency. ACTION: Finalrule.
SUMMARY: Appendix D to 40 

### CFR Part 50 prescribes a measurement 

### principle upon which reference methods for the measurement of ozoneO In

*The term "ozone" Is used herein to be consistent with another EPA action in this 

### 8221

the atmosphere must be based. This appendix also specifies a procedure to beusedforcalibrating those ozonereference methods. EPA has evidence that another calibration procedure for

ozone reference methods is significantly more accurate and less variable than theprocedure currently specified in Appendix D. Accordingly, EPA is amending 40 CFR Part 50, Appendix D, to replace (supersede) the current calibration procedure with a superior calibration procedure based on ultravioletphotometry.
EFFECTIVEDATE: This action is effective immediately upon publication because the revised standard to which It appliesIsimmediately effective.

FOR FURTHMR INFORMATION CONTAM.

Mr.LarryJ. Purdue,Telephone 919- 541-2665 (FTS: 629-2665). 

### ADDRESS: Department E (MD-77), Environmental Monitoring 'and Support Laboratory, U.S. Environmental Protection Agency, Research Triangle Park,NC 27711.
SUPPLEMENTARY INFORMATION:

BACKGROUND

Part 50 ofTitle 40, Chapter I of the Code of Federal Regulations specifies the National Ambient Air Quality Standards forseveral airpollutants including ozone. Appendixes to Part 50 provide information concerning the reference methods which are used to

measure those pollutants. In particular,Appendix D toPart 50 describes a measurement principle upon which

ozone reference methods must be/ based, and specifies a calibration procedure to be used for calibrating such methods. Previously, the calibration procedure specified by Appendix D

was based on assay ofozone with 1% neutral buffered potassium iodide (NBKI) and was known as the "NBKI procedure."

On June 22, 1978, EPA indicated its conclusion that another calibration procedure was clearly superior to the NBKI procedure, andaccordingly EPA proposed an amendment to Appendix D toreplace the NBKIprocedure with the new procedure, based on ultraviolet (UV) photometry (43 FR 26971- 26984). Therationale forthe proposed amendment was discussed In-thepreambletothatproposal. Interested per-
sons and organizations were afforded En opportunity to comment on all as- pects of the proposed changes. The amendment,revised slightly aftercon- sideration of the public comments, is being promulgated today in conjuncIssue of the FERAI REGis substituting "ozone" for "photochemical oxidants cor- rected for Interferences due to nitrogen oxides and sulfur dioxide," which was formerlyused inPart50.

FEDERAL REGISTER, VOL 44, NO. 28--THURSDAY, FEBRUARY 8, 1979