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8202

[6560-01-M]

Title 40-Protection of Environment

CHAPTER I-ENVIRONMENTAL

PROTECTION AGENCY

SUBCHAPTER C-AIR PROGRAMS

[FRL 1018-2]

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: Final rulemaking.

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

hour per year. On June 22, 1978, EPA

proposed changes in the standard (43 FR 26962) based on.the findings of the

revised criteria. The proposed changes included (1) raising the primary standard to 0.10 ppm, (2) retaining the 0.08

ppm secondary standard, (3) changing the chemical designation of the standard from photochemical oxidants to

ozone, and (4) changing to a standard

with a statistical -rather than deter-'

ministic form. The final rulemaking

will make three further changes in the

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 ppm is equal to or less than

one."

EFFECTIVE DATE: This revision is

effective immediately upon publication. The normal 30-day delay in effectiveness is not required, when, as in

this case, a restriction is eased.

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 (FTS 629-5204.

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

control techniques 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 of the 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 of the National Ambient Air

Quality Standards for Ozone," and Appendix D, "Measurement Principle

and Calibration, Procedure for the

Measurement of Photochemical Oxidants Corrected for Interferences Due

to Nitrogen Oxides and Sulfur Dioxide," that are related to the revision of

the air quality standard for ozone. In

addition, elsewhere in this issue of the

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 on ultraviolet 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 being promulgated by EPA elsewhere in this issue

of the FEDERAL REGISTER.

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 average level of 0.08 ppm not to be exceeded more than once per year. The

asthma study cited as evidence for the

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 of medical 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 of compounds referred to collectively as peroxyacylnitrates (PANs)

and other compounds, all produced in

much smaller quantities than ozone. Most of these materials are not 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

and jet engines.

The reductions in emissions of nitrogen oxides and organic compounds are achieved through Federal and State

programs that have 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, 1979
RULES 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 of air quality.standards.

LEGISLATIVE REQu mE s AFCnTG

TIS PROIUL-GATION

Two sections -of the 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

and reviewing the criteria. I

Air quality criteria are required by

Section 108(a)2) to reflect accurately

the latest scientific information useful

in indicating the kind and extent of all

identifiable effects on public health or welfare that may be expected from

the presence of the pollutant in the

ambient air.

The 'Administrator as required to

propose simultaneously vith the issuance of these criteria, primary and sec- ondary ambient air quality standards

based upon such -criteria. The primary

standard is defined in Section

109(b)(1) us the, ambient air quality

standard the attainment and maite- nance ,of which in the Administrator's

judgment, based on such -riteria and

allowing an adequate margin of safety, are requisite to protect the public

health. 7The- secondary standard 'Section 109(b)(2)) must specify a level the

attainment and maintenance of which

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

pollutant in the ambient air. These ad- verse welfare effects, which are discussed in Section 302(h) -of the Act, 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 -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 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 are not germane to such a determination, as the words of the Act and its

legislative history clearly indicate.

Section 119d) directs- the Admitrator to-complete a review of all existing

standards and criteria before the end

of 1980 and at 5-year intervals thereafter and to revise them.in whatever manner that xeview reveals is necessary. This promulgation Is the result

of such a review.

Assuring attainment and mainte- nance of ambient air quality standards

is the responsibility of the States.

Under section 110 of the Act, they are to subrait to EPA for approval State

Implementation Plans (SIPs) that provide for the necessary legal requirements for sources of the 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 ,deadline for attainment has -long since

passed. As a remnedy, Part D of the Act

requires states with violations of ambient air quality standards to submit re- vised-SIPs to ensure attainment of the

standards and to meet certain new 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 not authorize the Administrator

to extend that deadline, and conse- quently this revision of the photochemical oxidant standard does not

affect the deadline for submittal of

SIP revisions.

Section 110(a)(1) requires that SIP

revisions be submitted -within 9

months after a standard is revised.

However, this provision refers to situations where a standard Is tightened.

with the result that 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- trols than necessary if they 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

of Progress toward attainment (measured ozone levels) remain unchanged.

SummAny OF GEN- L F nrNGS '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 -of section

109(d)(1) of the Clean Air Act as amended. The notice called for Informationand data that would be helpful

in revising the document In preparing

the -criteria document. 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:O written comments on the first draft and approximately

8203

20 on the second draft. The Americin

Petroleum Institute has submitted extensIve information that EPA considered In this standard review The criteria document was the subject of two

meetings of the Subcommittee on Scientific Criteria for 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 new information for EPA's

consideration. A full discussion of

comments received during the review

process, as well as EPA's dlsposition of

these comments, can be found in the

docket (OAQPS 718-8) assembled for

this rulemaking.

From EPA's review -of the scientific

information presented in the criteria

document, several key areas with par- ticular relevance to setting the ozone

standard have emerged: 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. Only limited studies

can bh perfcrmed on groups of unusually sensitive 'persons. Most experi- mental studies of human subjects are

performed on small numbers of relatively healthy persons who -do not

fully reflect the range of human sensitivity. Also, the air to which the subjects are exposed does not include the

full mix of chemicals other than the

pollutant being studied which are in

the ambient air. Some of these chemicals may be additive with the given pollutant in causing the adverse

health effect, so that lower levels of

the pollutant will result in the effect.

Animal exposure studies cannot pro- vide precise models of sensitive human

populations. Thus, adverse health

effect thresholds for sensitive persons

are difficult or impossible to determine experimentally, while the

threshold for healthy persons or animals Is not likely to be predictive of

the response of more sensitive groups In this notice of rulemaking EPA uses

the terminology 'probable effects

level" to refer to the level that in its

best judgment Is most likely to be the

adverse health -effect threshold concentration. It is the fact that the adverse health effect threshold concentration Is actually -unknown that necessitates the margin of safety required by the Act.

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 of the

human lung and causes clinical symptoms such as chest tightness, coughing

and wheezing. These effects may occur

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, and these 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 a reevalution of the 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 found in 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 of the full range of

effects that may occur in humans. The

epidemiology study by Durham (1974)

that reported increased rates of illness

in college students following periods of

elevated air pollution levels (with peak

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. Ozone effects on aging processesA limited amount of data suggests

that ozone may accelerate the aging

process in living organisms. Exposure

of rabbits to unspecified concentrations of ozone for 1 hour per week for 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-The fact

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.), as well 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. Mortality studies-No studies have

conclusively linked exposure to ozone or photochemical oxidants with an in- crease in human mortality. A number

of epidemiologic studies have been designed and conducted to demonstrate

this effect, but in each case the results

have been negative or inconclusive.

8. Welfare effects-Ozone accelerates

the aging of many. materials, resulting

in rubber cracking, dye fading and

paint erosion. These effects are linearly related to the total dose of ozone and can occur at very low levels, given longduration 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. Causes and contr6l of oxidant oollution-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 itself of new research 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

two years.

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 Is given below.

The API petition requested that

EPA revise the air quality criteria document for photochemical "oxidants in

light of new information regarding the

causes, effects, and extent of air 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 other oxidants.

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 0.25 ppm for 2-hour ex- posures. As requested by API and as required under the Clean Air Act, 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 of EPA's

judgments regarding reported or prob.

able health consequences at concen- trations below 0.25 ppm Is presented 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 of a significant decrease in

yield or growth to commercially im.

portant crops for 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 analysis Is not required,

In their petitions, both API and

Houston requested EPA to state the

primary and secondary standards so as to permit reliable assessments of com- pliance. EPA agrees that the present

FEDERAL REGISTER, VOL 44, NO. 28.--THURSDAY, FEBRUARY 8, 1979
deterministic form of .the oxidant

standard has seVeral limitations ,and

_ias made reliable assessment of com- pliance difficult. The revised ozone air .- ualityxtandards are stated in a 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 with the standards.

The API'and Houston petitions re- quested that EPA specify the use of an

afpropriate -measurement method for

monitoring ambient concentrations of

ozone. API suggested the use of ethyl- -ene -chemilunminescence calibrated by

either gas hase titration (GPT) or n1- traviolet XUV) Photometry. As a result

of EPA's continuing evaluation of several calibration techniques, the

Agen&y .as defined the reference

method to be ethylene chemnlumines- cence calibrated by UV photometry.

(See ,the 2mendment to Appendix D of

40 CYR Part 50 elsewhere in this edition of the YFlED m -Rsom ) EPA is

allowing the use of a modified version

of the -current alibration method

(acidified -I) as an interim measure to

avoid problems that would result from

immediate conversion to UV photometry.

Both the APT and -Houston petitions

requested revision of the State Imple-"'

mentation-Plan (SIP) requirements (1)

to delete the assumption of no background -concentration of photochemi- cal oxidants and -2) to specify more reliable alternative oxidant prediction

relationships to replace Appendix J of

40 CM Tart 51 for determining the

degree of necessary-precursor emission

reductions.

With respect to the first point, -EPA

recognizes that background 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 being made in controlstrategy and implementation guidelines for ozone. The revised guidelines set forth procedures for consideration of both - upwind transport and irreducible 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 techniques to 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 discussed iurther

in the revision -of Prt 5L which appears elsewhere in this edition -of the

FEDERAL REGI SEL

The Houstonpetition requested that

EPA consider Information In Their petition relative to atmospheric -conditions and other factors that affect

photochemical oxidants In the Houston area. The petition claimed that

the air pollution problems in Houston

warrant special -attention In standardsetting -and -tailor-made" control

strategies, because the emission and

meteorology situations and the overall

pollution picture In that area are

"unique °

In response to the above -claim. it

,should be :noted that the majority of

the data presented In the revised criteTia document are based on ozone exposure. Nearly all of the clinical and toxicological studies are based -on the effects -of ozone. The biomedical -data

also suggest that many of the effects

observed during periods of elevated

'photochemical oxidant -concentrations

are reasonably attributable primarily

to ozone in the ambient air. Since the

primary and secondary standards are

based on the effects of ozone, the differences between areas in their overall

photochemical oxidant mixtures do

not bear -upon the setting of national

ozone air quality standards.

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

ozone may have an adverse Impact on

health and/or welfare. The data base

is not, however. sufficient at this time

to justify a separate standard for PAN

or other non-ozone oxidants. While

EPA does not propose to establish sep-

-orate standards for the non-ozone constituents of the mixture at this time.

those aneasures taken to reduce ozone

precursor emissions will also reduce

PAN and other non-ozone oxidant concentration levels.

In response to Houston's request for

a unique standard based on their local

situation, it must be realized that the

Clean Air Act does not contemplate

separate standards for different cities.

Dealing in terms of -national -ambient

air quality standards, the Act charges -EPA to identify the air -quality levels

which must be attained and mantaned to ensure, with an -adequate margin of 'safetyo that adverse 3health

effects will not ccur.

The Houston petition also requested that 'EPA include realistic requirements for the xeduction of oxides of

nitrogen as -conditions in the -Houston

area may ndicate to be necessary to

achieve the revised standards. IEPA's

xesponse Is that It Is the responsibility of -the State of Texas and the City of

Houston to 'submit State Implementa- tion Plan provisions tailored to the sit8205

uaton prevailing in Houston. If the

current SIP is not representative of

the most efficient means of reducing

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

-a revision that Is consistent -with local

emission and meteorological condi--

tions.

Suznax or Comxa=Ts RECE=vED

EPA has solicited public comment

and critique on proposed revisions to

the photochemical oxidant air quality

standard during all phases of the

standard development process. Prior

to proposal (April 20, 1977), EPA an- nounced (42 FR 20493) that it was re- viewing and updating the criteria docUmnent and called for information that

might be helpful in revising the document. Public comments were received on two-drafts of.the criteria document,

and the public was invited to two

meetings of the Subcommittee ,on Scientific Criteria for Photochemical Oxidants of EPA's Science Advisory

Board. In addition, the Agency held a

public meeting onJanuary30, 1978, to

receive comments from interested parties prior to development of any

formal Agency position on the initial

proposed revision of -the standad. .In

particular, EPA actively solicited the

participation ,of the State and Territorial Air Pollution Program Administrators (STAPPA) and the Assoeiation of

Local Air Pollution Control Officials

(ATLPCO) in -this meeting; several

representatives of these groups offered comments at the meeting. The

results of this meeting are discussed in

the proposed regulaton X43 FR 26970)

and a transcript -of the meeting is

available in docket OAQPS 78-8.

Following proposal, -EPA held 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- ment period, -which extended through

October 16. 1978.

The principal comments and Agency

responses :are summarized in -the following 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 raised in the post-October

16 comments have been addressed and

responded to as part of the discussion

of comments in this preamble. As with

all other documents considered or ex- amined by EPA as part of its decision

process, these documents have been

placed in the public docket and have

- FEDERAL AEGISTER, VOL 44, NO. 28--THUSDAY, FEBRUARY 8, 3979
RULES AND REGULATIONS

become part of the' administrative

record of this decision.

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 air pollution con- trol agencies (and STAPPA) generally

supported a standard level of 0.12 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 the Regulatory 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 identified below:

CommENTs RECIVED ENDORSING CURRENT

PRIMARY STANDARD LEVEL OF 0.08 PPM

ORGANIZATION AND AGENCIES

American Lung Association of Colorado

American Lung Association of Colorado,

West Region American Lung Association of Louisiana

American Lung Association of.New Jersey American Lung Association of New York

State, Inc.

Bangor-Brewer TB and Health Association, Maine

California Lung Association

Connecticut State Department of Health

Environmental Confederation of Southwest

Florida

Environmental Defense Fund

Ms. Nancy C. Fahden, Supervisor District

Two, Contra Costa County (Calif.) Board of Supervisors Florida LungAssociation Greenleaf Nurseries, Warsaw, Indiana

Issac Walton League, Manasota Chap1ter League of Women Voters of the U.S.

League of Women Voters of Dallas, Texas

Maine Health Systems Agency Maine Lung Association

Medford-Ashland Air Quality Maintenance

Advisory Committee, Oregon Michigan Lung Association

Michigan Lung Association, Saginaw Valley

Region

National Air Conservation Commission,

American Lung Association

Natural Resources Advisory Committee, Cedar Grove, N.J.

Natural Resources Defense Council -

New Mexico Lung Association

Oregon Environmental Council

Oregon Lung Association

Queensboro Lung Association, Jamaica,

'N.Y.

Sierra Club

Sierra Club, Houston Chapter

South Shore (Ohio) Christmas Seal Association

Southwestern Ohio Lung Association

U.S. Department of the Interior

Washington Air Quality Coalition

Yale Environmental Law Association

'Summary.' 35 comments from organizations, agencies or their representatives and

38 comments from concerned citizens supporting the current primary standard level

of 0.08 ppm.

CoMEsTS RECEIVED ENDORSING PROPOSED

PRiMARY STANDARD LEVEL OF 0.10 PPM

ORGANIZATIONS AND AGENCIES

Air Pollution Control League of Greater

Cincinnati

Air Quality Advisory Committee, California

Department of Health

California Air Resources Board

Coalition of Labor and Business (COLAB),

Concord, California

Colorado Department of Health

Connecticut Department of Environmental ,_ Protection

Massachusetts bepartment of Environmental Quality 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 Lung Association

Southern Alameda County Board of Realtors, California

U.S. Department df Energy

U.S. Department of Transportation

Wasatch Front Regional Council, Utah

Wayne County Department of Health,

Michigan

Wisconsin State Department of Natural 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= S RECEIVED ENDORSING A PRIMARY

STANDARD LEVEL OF 0.12 PPM

STATE AND LOCAL AOENCIES

Alabama Air Pollution Control Commission

Berkeley, Charleston, and Dorchester (S.C.)

Council of Governments

City of Philadelphia, Pennsylvania

Georgia Department of Natural Resources

Indiana State Board of Health

Kansas Department of Health and Environment

Kentucky Department for Natural Re- sources and Environmental Protection

Maryland Environmental Health Administration

Michigan Department of Natural Resources

Nebraska Department of Environmental

Control

Nevada Department of Conservation and

Natural Resources

New York Department of Environmental

Conservation

North Carolina Department of Natural Re- sources and Community Development

Pennsylvania Department of Environmental

Resources

Tennessee.Department of Public Health

Utah Bureau of Air Quality

Virginia Air Pollution Control Board

ORGANIZATIONS AND COMPANIES

Area Cooperation Committee of Tidewater

and Virginia Peninsula Chambers of

Commerce

Evansville, Indiana, Chamber of Commerce

Sierra Pacific Power Company

State and Territorial Air Pollution Program , Administrators

Texas Oil Marketers 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 of 0.12 ppm.

CommENTs RECEIVED ENDORSING A PmRIARy STANDARD LEVEL HIoIIER TILAN 0.12 PPM AND/Oil

CONTENDING PROPOSED STANDARD Too STRINGENT

Endorse standard' Proposed standard

higher than 0.12 too stringent

ppm

Organization or hgency:

American Petroleum Institute (API)............................

Association of Local Ar PollutlondControl Officials.

Associated Building Industry of Northern California .......... Cook County Dept. of Environmental Control, Illinois.

Dow Chemical Company............................... Eastman Kodak Company ............................

General Motors Corporation ............ .........

Great Plains Legal Foundation ............ .... ......

Greater San Antonio Chamber of Commerce, Texas ........... Houston Chamber of Commerce, Texas ........ . .. ..............

Iowa-Illinois Gas and Electric Company .................... Louisiana Air Control Comlssion..............................

Manufacturing Chemists Association . ................

Monsanto Chemical Intermediates Co ............. Motor Vehicle Manufacturers Association .............

National Flexible Packaging Association .......................... New Orleans Public Service, Inc ........................................... Oklahoma State Dept. of Health ..................

X X ....... °...° .°°°...°........... .

°.. .. ... °.......I .°......... X

. . ..............................

X ..........°..... . .

x x

.. o...............°. . . °... ... X

°°.°. ........... I°...........° X

.............. °,°°° ° .. °...°...

.... ...... °.............°... °° X

X X

X X x

X .....

.................... . x, .

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

8206
RULES AND REGULATIONS

ComwENis REcErvED ENenOsrNG A PRmARY STARDARD LEVm HIGEMR THAm 0.12 PPM AxD/oa

CONTENDING PRoPOSED STaNDLUw Too STRINCET-Continuled

Endorse standard Proposed standard

higher than 0.12 too stringent

ppm

Owens-Illinois .,_X X Rio Blanco Oil Shale Company X St. Louis County, Missouri':-: _ __ X

San Antonio Metropolitan Health District, Texas._ X Shell Oil Company X

Stearns-Roger, Inc, Denver, Colorado ...... X Tennessee Eatmen Corp... . X

Texas Air Control Board__............ ... z Texas Chemical Council X

US. Council on Wage and Price Stability .................... X Utah Manufacturers Association_________________ X

Virginia Air Pollution Control Board X

Western Oil and Gas Association X Wlhite River Shale Project ..... ...... X

Summary: 15 comments from organizations. agencies, and companies and 4 comments from concerned

citizens'supporting a p5rimary standard level higher than 0.12 ppm. 23 comments stating the proposed

standard is too stringent.

The principal issues raised during

the comment period relate to the following topics:

L Health effect criteria and selection

of the primary standard.

A. Definition of an Adverse Health

Effect.

B. EPA's interpretation of cited

studies.

C. Margin of safety.

D. Use of annimal studies.

E. Exposure of sensitive groups..

F. Synergistic effects and chemical

species designation of the standard.

IL Risk assessment method.

MI. Welfare effects and the secondary standard.

IV. Implementation 'and attainabil-

.ity.

A. Value of hydrocarbon control and

timing of SIP submissions. -

B. Consideration of control 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 THE PRIMARY STANDARD

A. DEFINITION OF AN ADVERSE 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 of public health.

Comment EPA should identify

where adverse effects begin In the con- tinuum of responses to pollutants.

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 of this risk assess- ment procedure is the utilization of

the experts' Judgments as to the point

in the continuum of physiological re- sponses to ozone that must be 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

of a 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 in con- nection with the secondary standard.

Agency Response. The criteria document states that physical discomfort, as manifested by symptoms such as difficulty in breathing, chest tightness, and pain on deep Inspiration, has

usually been observed in clinical studies in conjunction with pulmonary

function changes. Even when revers- ible, respiratory symptoms may re- strict normal activity or limit the per- formance of tasks. In clihbil studies,

exposure of healthy subjects 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, inasmuch as they signal p3ulmonary function decrements and an increased pulmonary work load for affected individuals. He expressed his concern for the long-term effect of re- peated exposure to levels of ozone sufficient to induce such symptoms. EPA concurs in this view and considers

such symptoms, even though transitory, to be of concern in selecting the

level of the primary standard.

B. E'A'S INTERPRETATION OF CITED

STUDIES

1. DeLucia and Adams (1977)

Comments. (a) EPA misread the DeLucia and Adams study in claiming

significant effects have been reported

at 0.15 ppm for one hour.

(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- tain effects at lower levels.

Agency Responses. (a) EPA acknowledges that DeLucla and Adams failed

to demonstrate any statistically significant decrements in pulmonary

function resulting from exposure to

0.15 ppm for one hour. (The investigators did observe statistically significant decrements in pulmonary function resulting from exposure to 0.30

ppm for one hour.) In groups as small as those tested by DeLucla and Adams

(six subjects), however, tests of statistical significance are difficult to interpret. The criteria document concluded

that the study by DeLucia and Adams,

although unreplicated, has raised the

question of whether 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 of the subjects experl- enced subjective symptoms of discomfoit (e.g., congestion, chest pain, and

cough) when exposed to 0.15 ppm for

one hour under the most, stressful exercise protocol (equivalent to running about 6 miles in an hour). These symptoms occurred at a lower excercise rate

when the subjects were exposed to

0.30 ppm. DeLticia and Adams did not

report the incidence of these symptoms in a quantitative manner, but

this fact does not remove 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

those bbserved.

(b) As noted in the criteria document, persons tend to breathe through their mouths when exercising. Thus,

DeLucia and Adams' utiliiation of

mouthpieces to dispense 03 probably

represents actual exposures in persons 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 the population in its determination of the margin of

safety for the ozone standard.

2. Schoettlin and Landau (1961)

Comments. (a) There are still prob- lems with reliance on this study because (1) ambiguities remain in its interpretation and (2).more recent studies of effects of ozone on asthmatics

have failed to corroborate this study's- conclusions.

(b) EPA's interiretation of the concentration at which Schoettlin and

Landau correlated increased incidence

of asthmatic attacks is unnecessarily conservative. There is good reason 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, the level of ozone occurring on

these high oxidant days would have

been less than the'level of oxidant reported. " , Agency Responses. (a) The criteria

document recognizes limitations that'

make it difficult to interpret the

Schoettlin -and Landau study unequivocally. Nevertheless, Schoettlin

and Landau did conclude that the pro- portion of asthmatics having :attacks

was significantly greater on days -when

the oxidant concentration exceeded

0.25 ppm than on days when -the concentration was below that level. EPA

RULES AND REGULATIONS

* does not believe that this conclusion

has been refuted by more recent studies. The reported results of the recent

epidemiological study by Turata et al

(1976) are. qualitatively similar to

those of Schoettlin and Landau. 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 to 0.27 ppm.

(b) EPA acknowledges that it is un- certain from Schoettlin :and Landau's

paper what averaging time was used in

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

used by Schoettlin and Landau.

EPA agrees with the comment that ozone levels may have been lower 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 concentrations less than 0.25 ppm may adversely

affect asthmatic persons.

3. Hammer et al. (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 in its conclusions.

(b) It is uncertain that oxidants

caused the increase in symptoms observed in this study.

Agency Responses. (a) Hammer et al.

conducted a longitudinal survey of an essentially constant group of subjects over a period of time. Consequently, in

order for the authors' failure to adjust

the data for smoking habits and allergy histories to have biased the results,

the survey Teponse pattern on 'high

pollution days -would had to have differed with respect to the distribution

of smokers and allergic persons as compared with the pattern on low pol- - lution days. Such an 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 of Hammer'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 of pulmonary function at ozone levels of 0.25 ppm for 2

hours are not 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 -value of the pulmonary func

tion decrements (about 5 percent) in

the more relevant factor In evaluating

the results of this 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 light exercise 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 the threshold for that exercize

level, and indeed the study by DeLucla

and Adams (1977) has shown symptomatic effects in healthy individuals

that are indicative of pulmonary function impairment at levels as low as 0.15 ppm under a more strenuous exer- cise protocol.

5. Studies in which effects were not observed at levels above 0.15 ppm

Comments. (a) The 1977 National

Academy of Sciences (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 0.25 ppm'for 2 hours.

Agency Responses. (a) The NAS document states that "some limited studies show evidence of human health effects of exposure to pure ozone at concentrations as low as 0.25 ppm * * *" This document was prepared before

publication of the DeLucia and Adams

study, which suggests effects at lower

levels: Furthermore, this NAS document in no way concludes that effects

resulting from ozone, as it occurs in

the ambient photochemical mix, do

not occur at concentrations below 0.25

ppm.

(b) Although Llnn et al found statistically significant changes in one of

several measures of pulmonary function in their laboratory study, the

manner. in which the investigators'

conducted the study (e.g., persons with

marked respiratory disability were excluded from the study) and analyzed

the data are such that the observed results probably underestimate the effects that would occur-at similar ambient exposure 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 of these latter changes

is uncertain, they do represent alterations in normal body functions and

cannot be discarded in selecting a

standard that protects public health

with an adequate margin of safety.

(c) Although the criteria document

states that Hackney et al. observed no

lung function changes of note at 0.25

ppm for 2 hours even among "reactiv&" subjects (persons giving a history

of cough, chest discomfort, or wheezing in response to allergy or air pollution exposure), closer inspection of the

Hackney pt al. (1975) studies reveals

that dose-response 'relationships hold

for sensitive subjects for lung function

and blood biochemical effects across

the range of exposure from 0.20 to

0.50 ppm ozone.

6. Other Human Studies

Comments. (a) Von Nieding et al.

(1976) have demonstrated effects on

pulmonary function of healthy individuals at 0.10 ppm ozone.

(b) EPA cannot justify a conclusion

that Japanese epidemiological stidies

indicate a risk of symptomatic effects

in human beings from ozone exposures

below 0.15 ppm for one hour.

Agency Responses. (a) EPA is concerned about the findings of von Niedng et al. showing decreased oxygen

pressure in arterialized blood and increasea.airway resistance after 2 hours

of exposure 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 must be interpreted cautiously.

(b) Makino and Mizoguchi (1975) reported an epidemiological study of

Tokyo students that showed Increased

rates of discomfort 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 It fell 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

yet resolved.

7. Validity of Clinical Studies in General

Comment. At the August 22, 1978

public hearing in Dallas, testimony was presented alleging that the ozone

generators used in clinical 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

in large quantities (as high as 300 percent greater than ozone). It was hypothesized that the adverse effects

- noted in clinical studies may be preponderantly caused by the additional

oxidants and not ozone.

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 is present. 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

the output of ozone generators operating under various conditions (using as

the input stream. either dry or humidified tank air or oxygen, with very low

or background concentrations of hydrocarbons, mostly methane) failed to

produce any evidence of non-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 in the docket (OAQPS 78-8, IVA-2).

C. MARGIN OF SAFETY

Comment. EPA has proposed a

standard with an inappropriate

margin of safety. The margin of safety was criticized as being either inadequate or too great.

Agency-Response. The Clean Air Act

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 of the Clean Air

Act, the standard must protect against

hazards that research has not yet

identified. EPA feels that the decision

regarding an adequate margin of

safety is a judgment 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 other serious effects at relatively low ozone levels, (2) the concern that health studies may not

always reflect the health impact in

more sensitive segments of the population, and (3) studies suggesting that ozone may produce an enhanced effect

when combined with other air pollutants commonly present in the urban

atmosphere but not present in clinical

study chambers.

D. USE OF ANIMAL STUDIES

Comment. EPA has failed to give 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 sole factor used in selecting the

level of the primary standard. However, as is the case with other inconclusive evidence, EPA- must consider

these studies in selecting an adequate

margin of safety.

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 biological responses to

infectious agents, and there is no reason to believe that the pollutant-induced alterations of basic defense

mechanisms that occur in mice could

not occur in human beings. Thus,

these studies cannot be ignored in the

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 if EPA

accounted for the portion of time that

persons are indoors and, thus, not ex- posed to higher ambient concentrations.'

Agency Response. The.legislative history of the Clean Air 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 of a representative sample of persons comprising the sensitive group rather than a singl person in such a group. Standards must be based on a judgment of a safe air quality level and not on an es- timate of how many persons will intersect given concentration levels. EPA

interprets the Clean Air Act as providing citizens the opportunity to 'pursue

their normal activities in a healthy environmerit.

F. SYNERGISTIC EFFECTS AND CHEMIcAL

SPECIES DESIGNATION OF STANDARD

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 of the 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 the potential

for greater health impacts resulting

from exposure to ozone in combination with other pollutants which occur in the ambient air than from exposure

to ozone alone. The ozone standard is

not intended merely to protect against

the levels of ozone that have been

demonstrated to produce effects in

clinical studies where subjects have

been exposed to highly 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 combination with 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 the reference 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

other manifestations of photochemical

pollution such as eye irritation. The

evidence from laboratory and theoretical studies indicates that, for urban atmospheres, reductions in hydrocarbon

and nitrogen oxide emissions should

have even greater impacts on ambient

PAN than on ambient ozone. Similarly, laboratory data suggest a linear re- lation between hydrocarbon emissions

and ambient levels of photochemically

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 probably have a positive

effect on reducing eye irritation in

those situations where eye irritation is

associated with photochemical 'proc- esses (e.g., Los Angeles).

II. RISK ASSESSMENT METHOD"

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 is incomplete. . 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 also Include information

on:

(a) a best point estimate of the

number of people affected;

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

(a") various risks (probabilities) that

the actual number of people affected

would be various amounts greater

than the expected number;

(b) a best point estimate of the

amount of health damage;

(b') the "expected" health damage;

and

(b") various risks (probabilities) that

the actual health damage would be

various am6unts greater than the ex- pected health damage.

As noted 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

from its purpose. Instead of estimating

health damage, EPA provides a table

of risk numbers without providing an estimate of their health significance;

these numbers serve no 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, 1979
health damage, but the Agency does

not agree that the estimates are without value. 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 has been decided 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 by a risk assessment.

There were many comments on both

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

SECONDARY STANDARD

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 Air Act

requires EPA to set a national 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,

-includes among other things-effects on

crops, vegetation, wildlife, visibility,

and climate, "as well as effects on eco- nomic values and on personal comfort

and well-being."

EPA has carefully examined the

data presented in the criteria docu- - ment concerning ozone-related

damage to vegetation, crops,.materials,

RULES AND REGULATIONS

and visibility. A staff paper, "Evaluation of Alternative Secondary Ozone

Air Quality ,Standards," has been

placed in the docket (OAQPS 78-8, IVA-3).

With regard to damage to materials,

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 sustained by the material. As a result, 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 have virtually

no impact on the annual average concentration. Therefore, there would be

no measurable reduction in materials

damage if a more stringent secondary

standard level was selected.

The -criteria document states that

there is a limited amount of data 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 tQ conclude at this time that

a secondary ozone standard more

stringent than the primary standard Is

necessary to prevent visibility deterioration. The relationship between visibility and abmlent ozone will be considered further In the development of

subsequent PSD programs designed to

protect against significant deterioration of air quality. Finally, EPA has concluded that

there is currently no evidence indicating that a significant decrease in yield

or growth or commercially important

crops or indigenous vegetation will

result from the long-term (growing

season) mean of the daily maximum 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 to protect vegetation from ozonerelated yield reduction effects.

On the basis of these conclusions,

EPA does not believe that a detailed

cost-benefit analysis of alternative

standard levels is required, since a secondary standard more stringent than

the primary standard is not necessary

to protect the public welfare adequately.

Comment The current secondary standard of 0.08 ppm should be retained to protect vegetation and crops. There Is singificant reduction in

8211

growth and yield to crops exposed to

0.10 ppm of ozone.

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 at low ozone levels,

there is currently no evidence that significant yield or growth 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

occur when the primary standard is attained. Consequently, EPA does not

believe that a secondary standard

more stringent than the primary

standard Is necessary to prevent

ozone-related yield reduction effects in

vegetation.

IV. LPurENTAAIox D

A:rTAnmAn

A. VALUE OF HYDROCARBON CONTROL AZm

TIB=IG OF SIP SUBMISSIONS

EPA received comments on the effectiveness of hydrocarbon controls in

reducing levels of ozone n the ambient air as well as on the issue of

whether or not the statutory deadline

for submission of revised State Implementation Plans (SIPs) for nonattainment 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

the revision of the 40 CFR Part 51 regulationsp*ertalning to the implementation of the standard.

IL CONSIDERATION OF CONTROL COSTS

Comment

Cost of 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 of cost of achieving these standards or of the existence of technology

to bring about needed reductions of

emissions are not germane to such a determination, as the words of the Act

and Its legislative history clearly indicate. EPA has, however, analyzed the

cost and economic impacts of the con- trol programs required to attain alternative ozone Standard levels in order

that the puble may be better 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 to the States for their 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 at the 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 for ozone. For several years, EPA has been 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 not been

released o*r could not be specifically

cited because the contract studies were 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 as possible.

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 for regulatory

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 air contaminants.

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 a relative abundance of natural organics or associated 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 of anomalous high values.

Although research will continue to assess more definitively the contribution of natural sources of ozone, EPA

believes that adequate consideration

has been given to this Issue in developing control programs and implementa- #

tion guideline documents.

V. PROCEDURAL IssuES

Comment. EPA's use of an "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 of the 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 subject to com- ment since proposal, and bases for Its'

recommendations have , been fully

aired.

Comment In revising Its criteria 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 ever agree 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 also rest with EPA.

EPA solicits the advice of Its 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, 1979
RULES 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, the Agency

would proceed with publication.. Consequently, EPA feels that the criteria

document adequately reflects the

latest scientific knowledge pertaining

to the effects of ozone and other photochemical oxidants.

Comment EPA has failed to submit

the proposed standard to the SAB for

review as required by the Environmental Research, Development, and Demonstration Authorization Act of 1978

(Pub. 1, 95-155). EPA -should do so

before promulgating the standard.

Agency Response. The development

of the ozone standard revision, which

began in 1976, followed the procedural

process in place before the enactment

of Public 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 of health effects

are less certain and harder to Identify.

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 we cannot

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 -maximum ozone 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

public health with an adequate margin

of safety is based on the uncertainty

that any given level is low enough to

prevent health effects, and on the relative acceptability of various degrees

of uncertainty, given the seriousness

of the effects.

In selecting the proper level for the

standard, EPA must make assessments

and judgments ifi five critical areas.

I. Reported effect levels from

human studies.

2. Characterizing the sensitive population.

3. Nature and severity of effects.

4. Probable adverse health effect

level in sensitive persons.

5. Judgment of a standard level

below the probable effect level that

provides an adequate margin of safety.

REPoRpD EFFECT LEVELS

In the preamble to the proposed

standard (43 FR 26965), EPA presented a table of demonstrated effect

levels in man ranging from 0.15 to 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

where effects have been reported. EPA

believes that this is a more complete

representation of the medical 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

must be used with caution and in conJunction with qualifying 'statements

made in the criteria document regarding the technical merit of each study,

particularly the less conclusive studies

at lower concentrations.

While this table does not provide an

undisputed value for adverse health

effect levels in sensitive individuals, it

does indicate that normal body functions are most likely disrupted at relatively low ozone concentrations. The

studies also indicate that the intensity

and significance of effects increases as

the pollutant level increases. The re- ported findings leave open the question of increased 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 other urban pollutants.

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

8213
8214

/ FEDERAL REGISTER; VOL 4, NO. 28--THURSDAY FEBRUARY 8, 1979

RULES AND REGULATIONS

[6560-01-C;][6560-a 1-Cl Comilation of Results RpreinHmnSuesEanno, ~~~REPORTED EFFECT LEVELS OznorOintxoue Ooen or Oxidant Exposure

Concentration. Exposure Duration, Pollutant Reported Reference(s)

ppm hours (for clinical measured Effect(s)

studies); Averaging (03 ' ozone, -

time (for epidemio- 0x . oxidant)

logical studies)

0.01 - hourly 03 Lung function parameters in about 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 2 hours prior to testing.

0.03 - hourly 0x -Although significant correlation was observed be- Wayne et al.

0.30 average tween decreased athletic verformance and Ox con- (1967)

centrations in the 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 in arterialized blood, von Nieding et al'.

increased airway resistance observed using non- (1976)

standard measurement techniques.

0.10 - probably daily 0x 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 in respiratory patterns oc- curred while performing vigorous exercise.

0.20 3 03 Reduction in visual acuity (night vision) 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 in respiratory 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 in lung function were observed in 3 Hazucna (1973)

subjects performing intermittent llgnt exercise.

0.25 2 and 4 03 No lung,function changes of note were observed in Hactney et a1.

"rective" subjects (who had histories of cough, (1975) chest discomfort or wneezing associated with air

pollution or allergy) while performing'intermittent, light exercise.

0.25 daily maximm 0x The average numaer of asthma patients having Schoettlin and

hourly average attacks was statistically significantly elevated Landau (1901) on days when Ox 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 in subjects undergoing vigorous exercise,

0.30 daily maximum 0x Increased rates of cough. chest, discomfort, and Hammer et al.

hourly average headache were observed in student nurses on days (1974)

when the 0x 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 SO together produced changes Hazucha and Bates (1975) 0.37 2 S03 in lung function substantially greater than the -su of 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- S0 function was c~nside~ably smaller than that seen 2 by Hazucha and Bates. The authors concluded that

the.earlier study probably more nearl simulated

a smog episode in regions having high oxidant and

sulfur oollutlon.
RULES AND REGULATIONS

SENSITIVE POPULATION

The legislative history of the Clean

Air Act indicates that, in setting primary ambient air quality standards,

EPA is to direct its efforts at groups of

"particularly sensitive citizens such as bronchial asthmatics and emphysematics who in the normal course of daily

activity are exposed to the ambient en- vironment." (U.S. Senate Serial No.

93-18, 93d Cong. 2d Sess. p. 410).

Clinical and epidemiological studies

have shown that persons with chronic

obstructive airway disease,, particularly asthmatics, appear most sensitive to

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 particularly vulnerable 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 OF ErF s

Impaired Pulmonary Function and

Clinical Symptoms-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 a history 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

of 50 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, in people 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 Irritant properties of ozone (and perhaps other oxidants) underlie

both the discomfort and the decrements in function. Thus, at least when

associated with ozone exposure,

changes in lung function often represent a level of discomfort which, even among healthy people, may restrict

normal activity or impair the performance of tasks.

Decreased Resistance to InfectionThis effect Is represented by an in.

creased rate of mortality 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

effect in man. Aggravation of Chronic Respiratory

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, their reports 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 include respiratory infections, passage of cold fronts.

seasonal pollens, extreme heat or cold,

and emotional disturbances.

Eye Irritation-Eye irritation is asso- 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 control measures that reduce ozone will also reduce

the eye-irritating components in the

total oxidant mix.

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 of these ozone-mediated changes

is not yet known, but the criteria document states that changes of the magnitude observed in human experimental exposures have not yet'been linked

to any clinical diseases.

Carcinogenic, Mutagenic and Related Effects-Studies have been conducted in an attempt to relate ozone to

carcinogenic, mutagenic, and related

effects. Available evidence in these areas is not particularly helpful in setting ambient ozone standards because

most of the studies have not yet been

replicated (in spite of some attempts

to do so), and because some effects observed In lower life forms are of questionable significance for man. 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 of reported effect levels, there is no clear

threshold air concentration of ozone indicated by the data as the onset of

adverse health effects. It is EPA's best

Judgment that physiological 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 occur in sensitive per- sons must necessarily be an informed

judgment. As stated In the proposal,

this judgment is based on (1) the

Agency's understanding of the medical

evidence presented in the criteria document and in the table of reported

effect levels, (2) the findings of the advisory panel on health effects, a-ad (3)

the Judgment of medical experts as to

the adverse effect level in sensitive

persons. The health experts who were consulted were asked to focus not only 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 the basis of the effect

levels cited in the criteria document, it

is EPA's judgment that the most probable level for adverse health effects in'

sensitive persons, as well as in healthRULES AND REGULATIONS

ier (less sensitive) persons who are exercising vigorously, falls In the range of 0.15-0.25 ppm. While the evidence is

more convincing and the effects more

pronounced at the higher .end of this

range, the data shows effects of concern at the lower concentration.

PnOBABLE EFFECt LE EL ESTn.ATES

[Estimates for Sensitive Population Segments]

A ggravation of Reduced .Chest discomfort

asthmna, resistance to Reduction In and irritation of

•emphysema, and ,bacterial - pulmonary the respiratory'

chronic Ifection (animal ' function tract.

bronchitis , studies)

Health panel judgment of effect 0.15-0.25 ppm Not available 0.15-0.25 ppm 0.15-0.25 ppm level.

Probable or median effect level as 0.17 ppm" 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 estimates given In parentheses).

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 and because medical research produces new and different findings'as

science progresses, EPA does not believe that a fixed acceptable margin of

safety can be established for all pollutants 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 of such factors as:

1. Concern for more.sensitive individuals-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

of ozone are enhanced or may occur at

lower ambient concentrations.

2. Pollutant interactions-There is

real concern that effects .reported in some ozone studies may occur at lower

concentratioiis and may be enhanced' when ozone Is present in bombination

with other urban pollutants. Laboratory studies of a single pollutant (e.g.,

ozone in clean, filtered air)r while important in elucidating physiological effects peculiar to that pollutant, 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 of con- 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 of ozone must

be considered in the context of the

total environment of the exposed individual; this environment includes con- centrations of other pollutants consistent with their maximum allowable

levels, high relative humidity, high

ambient temperature, and high levels

of physical 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 that they confer a resistance against further lung injury 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 et al., 1972).

4. Animal infectivity studies-Although evidence of reduced resistance

to bacterial infection has not reached

the point where It can 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 of safety. 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, It is 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

*to account in some measure for these

uniquantified, but possibly serious, effects.

5. Inconclusive studies- reporting effects at low levels-A similar caution is

suggested by both the Makino and MIzoguch epidemiological study and the von Nieding clinical study reporting

effects at levels around 0.10 ppm. 6. Uncertainties arising from 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 calibration procedure

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 of the relevant clinical studies utilized monitoring instruments calibrated with the

current (NBKI colorimetric) reference

calibration procedure or modifications

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 of the

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, 1979
ROLES AND REGULATIONS

might be high with respect to the UV

calibration procedure. While the exact

magnitude of any 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 for the 0.30 ppm

concentration. EPA will continue its

evaluation of this issue through its

program of clinical exposure studies.

8; Findings from the preliminary

risk assessment-The preamble to the

proposed standard described a preliminary risk assessment methof per- . formed to aid EPA in accurately treating the uncertainties associated with a standard decision. While this method

cannot be used at this 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 of the public,

including those from the 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 by significant numbers of sensitive persons.

Unless the standard is set somewhat

below that level, the Agency would not

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

to bear on these difficult problems.

There is no collection of facts or

medical evidence that permits selecting an undisputed value for the 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 did not 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

not possible. (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, EPA has concluded that

they do not dictate as wide a margin

of safety as was established in the proposaL EPA does believe, however, that

these studies do suggest the real possibility 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.

WELFARE EFFL s A"P TE SEcONDARY

STANDARD

The Clean Air Act mandates 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 of air pollution that has been shown to affect

vegetation and materials and that may

have an impact on visibility. The economic loss resulting from rurrent oxidant levels has been estimated to be in

the range of several hundred million

dollars per year nationwide. Non-quantifiable losses to the natural environment occur as well. 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

information received after Its 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 is not an accurate indicator of yield or growth re- duction.

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

was stated that several investigators

suggested that follar injury rates in

thb range of 5 to 10 percent could produce detectable reductions in growth or yield, depending on the timing of

the injury and other environmental

factors. Since proposal of the standard

in June, EPA has discussed the matter

further with several experts in the

field of air pollution damage to vegetation, particularly regarding what level

of leaf injury should be of concern in

protecting against significant reductions in yield or growth 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

of yield 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 if it were applied over a longer period. EPA used a

mathematical model to summarize, for

several crops, the experimental results

which depict the variation in foliar response with short-term (0.5-hour to 8-

hour) ozone exposures. The notice of

proposed rulemaking predicted (on the

basis of the mathematical model) that

a secondary ozone air quality standard

set at an 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 of this prediction

and the aforementioned assumptions

regarding the relationship of foliar

injury and yield reduction, EPA proposed to set the secondary standard

level at 0.08 ppm.

As a result of its further consultations with researchers, EPA decided to

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 used and in which moisture

and temperature are optimal for producing injury. In addition, a given

short-term dose of ozone, which can produce 5, 10, or even 20 percent follar

injury in a given plant, is unlikely to

have an Impact on yield unless the

plant is exposed during a critical stage

in the plant's life cycle.

Consequently, EPA has decided to

base Its decision on the secondary ozone air quality standard on the information currently available on growth and yield reduction in commer- cially Important crops and indigenous

vegetation exposed to ozone under

field conditions. As discussed in a staff

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 of the daily maximum 6-

to 8-hour-average ozone concentrations. Based on an examination 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 from the long-term mean of the

daily maximum 7-hour-average ozone

concentrations expected to. occur when

the primary standard is attained. Consequently, EPA believes that a 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 of ozone-related yield -reduction effects in vegetation.

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 than in

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 as much

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 also be reduced resulting in

little If any change in the annual aver- age. Consequently, no effect-based ra- tionale can be offered to decide the

leveL of the secondary standard needed

to protect materials. Accordingly, EPA

believes that a secondary standard

more stringent than the primary

standard is not necessary -on the basis

of ozone damage to materials.

The criteria document states that

there is a limited 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 at this time that a secondary. ozone standard more -stringent than 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 of air quality.

On the basis of tjiese conclusions

with respect to ozone damage to vegetation and materials and the association of ozone with visibility reduction

in some areas, EPA is revising the sec- ondary ozone air quality standard

level to 0.12 ppm.

OTHER AsPEcTs or THE 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 of hourly averages from

which the number of exceedances of

the standard level is counted, and (2)

the exclusion criteria for missing data.

DAILY MAXIMUM HOURLY AVERAGE

.INTERPRETATION OF THE STANDARD

The maximum ozone concentrations

which will occur in any given time

period will vary from one period 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 of the 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 is changing the standard

to a statistical form that allows one expected exceedance per year.

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 a daily

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 that a -day with two hourly values over the standard level counts as one exceedance of the standard* level

rather than two; similarly for days

with more than two hourly values over the standard level. As was indicated in

the proposal notice, the daily interpre-'

tation has some advantages and it is

evident from the comments received

that there is considerable support for

the use of this interpretation.

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 is not concluding that 3 hours of

exposure 'above a given level; for ex- ample, are no worse than 1 hour of ex- posure above the same 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 a daily 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

easy to.incorporate into data-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 but for which

known seasonal patterns of ozone and

related meteorological factors make it

unlikely that the level of the standard

would have been exceeded.

This second criterion would be 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 also possiole 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, 1979
34892) that would grant waivers of the ozone monitoring requirements for

certain times of the year at the discretion of the appropriate Regional Administrator. Therefore, the second exclusion criterion has been eliminated,

and the computation formulas for estiinating the -expected number of

exceedances have been modified to re- flect the number of required monitoring days for the year.

Definition of When the Standard is,

Attained-EPA is adding Appendix H

to 40 CFR Part 50 to explain when the --standard is or is not being attained.

Certain modifications to the proposal were necessary to accommodate the

daily interpretation and the previously

mentioned changes in the treatment

of missing data. In order to implement

the change from an hourly to a daily

interpretation, it is necessary 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 day have been monitored and that

the hourly values in question reflect

the time of day when high. ozone values are likely 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 proposed 40

CFR Part 58 and, therefore, the total

number of required monitoring days is

less than a full year. The use of the

exclusion criterion may result in an underestimate of the'probability of an 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 is necessary to show attainment. Accounting for missing data can -"never, however, decrease the number

of exceedances, and thus it is possible

to establish non-attainment without

tile use-of this 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 a minimum percent completeness requirement, rather than estimating the

number of exceedances. The problem

with that approach, however, Is that It

.remains unclear as to what should be

done with data sets that fail to meet

such a completeness requiremenL Some comments discussed the use of

3 years of data. As Indicated In the

proposal, the choice of a 3-year period

represents a compromise- between

added stability and reasonably 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 on more than 1 year. Furthermore, although 3 years are

used in estimating the expected number of exceedances 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 year still applies under the new

form.

Ecoxoiuc, Exraor, AxD

ENMIONIMN L IMACTS

As has been noted, the Clean Air Act

specifically requires that National Ambient Air Quality Standards be based

on scientific criteria relating to the

level that should be attained to protect public health and -welfare adequately. EPA Interprets the Act as excluding any consideration of the cost

of achieving such a standard In determining the level of the primary standard. However, In compliance with the

requirements of Executive Orders

11821 and 11949 and OMB Circular A107 and with the provisions of the recently Issued Executive Order 12044

for rulemaking proceedings that are

currently pending, EPA has prepared

an analysis of economic impacts associated with efforts to attain this 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. Control of the organic precursor materials that generate photo- chemical oxidants Is a major effort In

this country and a multibilllon-dollar

program. The existing control pro8219

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 not expected to change the level of control re- quirements in the near term. The

move to a 0.12 ppm standard will, however, eliminate the theoretical need

for major control programs in many

rural and wilderness areas that cur- rently exceed the present standard.

With the relaxation of the standard,

EPA's economic impact analysis indicates that most urban areas are expected to achieve the standard by

1987. Even with aggressive control programs, however, It will be very difficult for some urban areas to achieve

the standard within the next 10 years.

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

result in those areas that utilize transportation 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 energy requirements.

Fnally, environmental impacts assoclated with control of oxidant precur- 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 at the address given earlier.

Rvnsxoxs To PART 50 REauLAaxoxs

In addition to the revised standard,

this action necessitates two other revisions to 40 CFR Part 50 as follows:

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 of the 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 TO PART 51 REGULATIONS

Elsewhere in this issue of the FEDERAL REGISTER, three revisions to 40 CFR

Part 51 are promulgated concurrently

with the revision to the photochemical

oxidant standard. They are as follows:

1. The term "photochemical oxidants" is changed to "ozone" throughout Part 51.

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 in the 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 and ozone trafisport. 3. Appendix J is deleted from Part

51.

FEDERAL REFERENCE METHOD

The measurement principle and calibration 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 set forth in Appendix D of 40

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 with 40 CFR Part

53 (40 FR 7044). A list of all methods

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." Lancet 1 (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 and student

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. Health 28: 255-

260, 1974. -__

Hazucha, M. "Effects of ozone and sulfur

dioxide on pulmonary function jn man." Ph.

D. Thesis. McGill University, Montreal,

Canada. 1973. 233 p.

Hazucha, M., and D. V. Bates. "Combined

effect of ozone and sulfur dioxide on human

pulmonary function." Nature 257 (5521): 50-

51, 1975.

Hazucha, M., F. Silverman, C. Parent, S.

Field, and D. V. Bates. "Pulmonary function

in man 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 air pollution." in" Clinical Inmplications of Air Pollution Research. A. J. Finkel

and W. C. Duel "(eds.). Acton, MA. Publishing Sciences Group, Inc. 1976. pp. 305-320.

Kurata, J. H., M. M. Glovsky, R. L. Newcomb, and J. G. Easton. "A multi-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 of concentraflon 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,

and Welfare. Air Quality Criteria for Photochemical Oxidants. National Air Pollution

Control Administration, Public Health 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 der Luft Col.

loquim on Ozone and Related Substances it

Photochemical Smog, Duesseldorf, W. Ger.

many, September 22-24, 1976.

Wayne, W. S., P. P. Wehrle, and R. 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 of Federal Regulations as 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 of the 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 as follows:

APPENDIX H-INTERPRETATION OF TuE NATIONAL AMBzENT Ain QUALITY STANDARDS

FOR OZONE

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)

is equal to or less 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 of days with maximum hourly aver- age ozone concentrations above the level of

the standard" may be simply stated as the

"expected number of exceedances."

The basic principle in making this determination is relatively straightforward. Most.

of the complications that arise In determining the expected number of annual exceed- ances relate to accounting for incomplete

sampling. In genera], the average number of

exceedances per calendar year musthe less

than or equal to 1. In Its simplest form,, the

number of exceedances at a 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

than or equal to 1.

2. Interpretation of Expected Exceedances

The ozone- standard states that the ex- pected number of exceedances per year

must be less than or equal to 1. 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 of standard.

Suppose a monitoring station records a valid

daily maximum hourly average ozone value

for every day of the year during the past 3

years. At the end of each year, the number

of daysr with- maximum hourly concentrations above 0.12 ppm is determined and this

number is averaged with the results of previous years. As long as this average remains

"less than or equal to 1" the area is In com- pliance.

3. Estimating the Number of Exceedances

fora Year

In general, a valid daily maximum hourly

average value may not be available for each

day of the year, and it will be necessary 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 of exceedancesper year is

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 the procedures of this section to account for incomplete 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 been missed but in other cases no measurement may have been scheduled

for that day. A daily maximum ozone value

is defined to -be the highest hourly ozone value recorded for the day. This daily maxi- mum value is considered to be valid If 75

percent of the hours from 9:01 am. to 9:00

p.m. (MST) were measured or if the highest

-hour is greater than thp level of the standard.

In some areas, the seasonal pattern of ozone is so pronounced that entire months

need not be sampled because it is extremely

unlikely that the standard would be exceeded. Any such waiver of the ozone monitoring requirement would be handled under

provisions of 40 CFR Part 58. Some allow- ance should also be made for days for which

valid daily maximum hourly values were not

obtained but which would quite likely have

been below the standard. Such an allowance

introduces a complication in that it becomes

necessary to define under what conditions a missingvalue may be assumed to have been

less than the level of the standard. The following criterion may be used for ozone:

A missing daily maximum ozone value

may be assumed to be less than the level of

the standard f the valid daily maxima on both the preceding day and the following

day do not exceed 75 percent of the level of

the standard.

Let z denote the number of missing daily maximum values thatmay be assumed to be

less than the standard. Then the following

formula shall be used to estimate the ex- pected number of exceedances for the year

e=v+£E(v/n)'(N-n-z)] (1)

(Indicates multiplication.)

Where:

e=the estimated number of exceedances

for the year,

N=the number of required monitoring.

days in the year.

n=the number of valid daily maxima,

v=the number of daily values above the

level-of the standard; and

z=the number of days assumed to be less

than the standa-d level.

*Indicates multiplication.

This estimated number of exceedances

shall be rounded to one decimal place (fractional parts equal to 0.05 round up).

It should be noted that N will be the total

number of days in the year unless the appropriate Regional Administrator has granted a waiver under the provisions of 40 CFR

Part 58.

The above equation may be interpreted intuitively in the following manner. The estimated 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 year but a certain number of

these, namely z. were assumed to be less

than the standard. Therefore, (N-n-z) iming values are considered toinclude possible

exceedances. The fraction of measured

values that are above the level of the standard is v/n. It is assumed that this same fraction applies to the (N-n-z) missing values

and that (v/n)'(N-n-z) of these values would

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).

(FR Doc. 79-4056 Filed 2-7-79; 8:45 am]

[6560-01-M]

FRL 1018-31

PART 50-NATIONAL PRIMARY AND

SECONDARY AMBIENT AIR QUALITY STANDARDS

Calibration of Ozone Reference

Methods

AGENCY: U.S. Environmental Protection Agency.

ACTION: Final rule.

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

be used for calibrating those ozone reference methods. EPA has evidence

that another calibration procedure for ozone reference methods is significantly more accurate and less variable

than the procedure 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 ultraviolet photometry.

EFFECTIVE DATE: This action is effective immediately upon publication

because the revised standard to which

It applies Is immediately effective.

FOR FURTHMR INFORMATION

CONTAM.

Mr. Larry J. 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 of Title 40, Chapter I of the

Code of Federal Regulations specifies

the National Ambient Air Quality

Standards for several air pollutants including ozone. Appendixes to Part 50

provide information concerning the

reference methods which are used to measure those pollutants. In particular, Appendix D to Part 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 of ozone 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, and accordingly EPA

proposed an amendment to Appendix

D to replace the NBKI procedure with

the new procedure, based on ultraviolet (UV) photometry (43 FR 26971-

26984). The rationale for the proposed

amendment was discussed In -the preamble to that proposal. Interested per- sons and organizations were afforded

En opportunity to comment on all as- pects of the proposed changes. The

amendment, revised slightly after con- 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 formerly used in Part 50.

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