United States
                Environmental Protection
                Agency
                Office of Air Quality
                Planning and Standards
                Research Triangle Park, NC 27711
               August 1980
v>EPA
Carbon Monoxide

               Proposed
               NAAQS  Revisions
    SSI*5*


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-Text and graphic arts	
 prepared by Northrop Services, Inc.
 Research Triangle Park, NC

 Bottom photo, cover,
 courtesy of the
 Daily Tar Heel
 UNC-Chapel Hill
 North Carolina

 All other photos
 from  EPA Collection

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National Ambient
Air Quality Standards
                                       (~  I £,

The U.S. Environmental Protection Agency (EPA),
under the provisions of the Clean Air Act, is author-
ized to develop a comprehensive national  program
for curtailing air pollution and improving air  quality.
With these clean air goals in mind, EPA has estab-
lished ambient air quality standards for the  seven
major or "criteria" pollutants:  carbon monoxide,
ozone, particulate matter, sulfur oxide, hydro-
carbons,  nitrogen oxides,  and lead.  A National
Ambient Air Quality Standard (NAAQS) is the
maximum amount of pollutant that is permitted  in
the ambient (surrounding) air in order to protect the
public health and welfare.

These NAAQS consist of  primary and secondary
standards. A primary standard is intended to protect
the health of the general public, as well as sensitive
population groups, with an adequate  margin of
safety. A secondary standard is one set to  protect
public welfare, which includes such things as soil,
crops, water,  vegetation,  and other similar  con-
siderations.
                          Primary standards are established to protect public
                          health;  secondary standards protect  wildlife, crops,
                          and other similar considerations.
                         Carbon monoxide (CO) is one major air pollutant for
                         which EPA has set primary and secondary ambient
                         air quality standards. In accordance with Clean Air
                         Act Provisions,  EPA recently reviewed the current
                         NAAQS for CO and, on the basis of data made
                         available since the standards were initially published
                         in 1971, has proposed revisions for these NAAQS.

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Revising NAAQS
to Meet Clean Air Act
Requirements
The existing primary and secondary standards for
CO were established by EPA in April 1971, and re-
flect the human  health and welfare effects data
available at that time.  The primary and secondary
standards are currently set at 9  parts per million
(ppm), averaged  over an 8-hour period, and at 35
ppm, averaged over a 1-hour period, not to be ex-
ceeded more than once per year.
                         The proposed revisions would tighten the 1-hour
                         primary standard, so that the average hourly CO
                         concentration could not exceed 25 ppm on more
                         than one day per year on average.   The 8-hour
                         primary standard would remain at 9 ppm.  EPA's
                         proposed revisions would rescind  the secondary
                         standards, since no adverse impacts on vegetation,
                         materials, or soils have been associated with existing
                         ambient CO concentrations.

                         Compliance with NAAQS is primarily the respon-
                         sibility of the States, who must incorporate CO
                         pollution controls into  their State Implementation
                         Plans (SIPs).  The 1977 Amendments to  the Clean
                         Air Act require that States demonstrate attainment
                         of the standards by the end of 1982.

                         EPA must review the scientific basis for each NAAQS
                         by the end of 1980, and at  least once every five
                         years thereafter.  Results of numerous studies for

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                        determining CO's harmful effects on public health
                        and welfare are summarized in the Air Quality Cri-
                        teria Document for Carbon Monoxide.*

                        Public participation is a key factor in the develop-
                        ment of air pollution laws that establish NAAQS
                        and other standards.  This material, which presents
                        pertinent  facts and issues associated with the pro-
                        posed NAAQS revisions, is intended to inform mem-
                        bers of public and private sectors who may wish to
                        contribute to EPA's rule making by participating in
                        public hearings, and in the public comment process.
Carbon Monoxide        A colorless, odorless, and generally unreactive gas,
                        CO is usually formed when carbon-containing fuels
                        are incompletely burned, and is emitted from some
                        natural processes as well. Forest fires, methane ox-
                        idation, and certain biological activities contribute
                        to a nearly constant CO background concentration
                        of about 0.044 ppm. When this amount is combined
                        with emissions from urban and industrial sources,
                        global background concentration of CO increases to
                        0.18 ppm in the northern hemisphere, and to 0.05
                        ppm in the southern hemisphere.

                        Through its conversion by natural processes to harm-
                        less carbon dioxide,  any significant CO buildup is
                        usually prevented. But  in congested  urban areas
                        where the ambient standard is being  violated, and
                        where industrial sources and heavy vehicular traffic
                        exist in close proximity, CO  pollution may reach
                        unsafe levels of 50-200 ppm.

                        Nationwide, more than 103 million metric tons of
                        CO enter the atmosphere each year. According to
                        figures realeased in the  most recent EPA Emissions
                        *EPA-600/8-79-022 (October 1979)
                        An earlier edition was published in  1971 when the
                        original NAAQS were adopted.

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                         Trends Report,** transportation - including high-
                         way and  non-highway vehicles — contributes over
                         83 percent of total CO  emissions.   Industrial pro-
                         cesses such as primary metal, carbon  black, and
                         maleic anhydride production contribute about  8
                         percent of the  total.   Miscellaneous  combustion
                         such as agricultural burning and forest fires account
                         for 4.8 percent; solid  waste incineration, 2.5 per-
                         cent; and electric power and heat  generation,  1.2
                         percent.
                                       Industrial
                                       Processes
                                                   Forest Fires and
                                                 Agricultural Burning
                                                         Solid Waste
                                                       _jj. Incineration
                                      Sources of CO Pollution
Environmental Effects
Most forms of plant life metabolize and produce CO
through photosynthesis.  This may explain why only
very high CO concentrations have detrimental effects
on plant life.  One study has reported that the thres-
hold exposure for significant effects on vegetation
occurs at 100 ppm CO for 3 to 34 days, resulting in
reduced nitrogen fixation in  plants.  Such  studies,
however, give little indication of the effects occur-
ring at ambient levels, since the test exposures are
much greater than those recorded in urban areas.
                         **National Air Quality, Monitoring, and Emission
                         Trends Report, 1977, EPA-450/2-78-052.

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                        Because observed CO pollution levels have not been
                        shown to adversely affect crops, wildlife, or other
                        aspects of public welfare, EPA is proposing that the
                        existing secondary standard for CO be eliminated.
                        CO  levels required by the primary standards are
                        expected to provide adequate protection for public
                        welfare.
Health Effects            Exposure to carbon monoxide concentrations that
                        exceed levels set by the primary standards results in
                        pronounced adverse effects on the human body. CO
                        has a strong affinity for  hemoglobin, the blood's
                        oxygen-carrying protein.  Blood hemoglobin is 200
                        times more likely to bond with CO than with oxygen.
                        When CO and hemoglobin combine, carboxyhemo-
                        globin (COHb) is produced in the blood.

                        Some  COHb is formed through natural processes,
                        (i.e; the body's own metabolic breakdown of hemo-
                        globin and other heme-containing materials) resulting
                        in a normal background (or endogenous) COHb level
                        of between 0.3 and 0.7 percent. Significant amounts
                        of inhaled CO can raise COHb levels dramatically,
                        triggering hypoxemia, a deficient oxygenation of the
                        blood.  Hypoxemia occurs when hemoglobin bonded
                        with CO is no longer available to transport adequate
                        amounts of oxygen throughout the body. In addi-
                        tion, high COHb levels inhibit oxygen release from
                        "free"  hemoglobin.  This oxygen starvation  asso-
                        ciated with hypoxemia can have detrimental con-
                        sequences for the cardiovascular, pulmonary, central
                        nervous, and other body systems.

                        CO exposure producing elevated  COHb  levels of 2.5
                        to 3.0 percent can aggravate angina pectoris, a car-
                        diovascular disease where low level  oxygen depri-
                        vation results in chest pressure and pain.

                        Aggravation of angina may cause cardiovascular
                        damage that current medical technology is incapable
                        of measuring.  In addition, symptoms triggered by
                        increased COHb levels  may be the first in a series of
                        progressively more serious symptoms that accompany

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coronary insufficiency, myocardial infarction (heart
attack) and other cardiovascular diseases.  For in-
dividuals with more serious forms of heart disease,
the consequences of relatively  low-level CO  ex-
posure may have more immediate, serious health
implications.

Studies have indicated that short-term,  high level
exposure to CO can produce a "bolus effect", where
a portion of  the blood supply becomes essentially
devoid of oxygen.  Life-threatening consequences
may result when this portion of blood reaches the
heart. The 1-hour and 8-hour standards are intended
to provide reasonable protection against this con-
dition.
Finally, some studies have suggested that carbon
monoxide exposures resulting in blood COHb levels
of 3.0  6.5 percent can produce  "decrements in-
vigilance," or the ability to detect small changes in
one's environment that take place at unpredictable
times.  Blood COHb levels of 4.0 to 5.0 percent can
result in decrements invisual function and sensitivity-
important functions that are components of more

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Protecting
Sensitive Groups
complex tasks like driving.  Thus, reduced alertness
or visual sensitivity may lead to increased accidents.


Revisions proposed forthecarbon monoxide NAAQS
are intended to provide an adequate margin  of safety
for the nearly 8 million Americans who have cardio-
vascular or peripheral vascular disease. Available
health effects data indicate that, for members of this
"sensitive population," the accumulation of relatively
low COHb levels may trigger the onset of symptoms
associated with  angina  or  other cardiovascular
diseases.
                         In determining what margin of safety the revised
                         standards should provide, EPA also considered CO's
                         effects on other sensitive groups, including persons
                         with central nervous system defects, pregnant wo-
                         men (fetuses),  older persons,  children, persons
                         living  at high altitudes, persons under medication,
                         and anemics (who have higher  endogenous COHb
                         levels).
Attaining Levels
Set by NAAQS
The Clean Air Act allows maximum participation
by state and local agencies in achieving NAAQS.
States must submit to EPA State Implementation
Plans (SIPs) that outline in detail their approaches
towards attainment and maintenance of the CO
standards.  In non-attainment areas where the CO
standards are exceeded, SIPs must be revised to

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Public Participation
                        include control strategies that will insure attainment
                        of the standards by December 31, 1982. In areas
                        where the CO pollution problem  is so severe that
                        attainment cannot be achieved through implementing
                        reasonably available control measures, the deadline
                        can be extended to 1987.

                        Federal programs  like the Federal Motor Vehicle
                        Emissions Program (FMVCP) have been implemented
                        to lower CO pollution levels. The FMVCP focuses
                        on controls for automobiles, trucks, and other mobile
                        sources. States can achieve compliance with the CO
                        standard by  establishing automobile inspection and
                        maintenance (I/M) programs, and by establishing
                        other reasonable strategies for reducing air pollution.
                        Other control strategies might include transportation
                        control measures (TCMs) for reducing vehicle miles
                        travelled  and  alleviating traffic  flow problems.
The cost of implementing I/M and TCM programs to
meet the proposed standards is expected to be ap-
proximately $450 million per year. Total costs of
CO emission control are estimated at about $2.9
billion annually; nearly $2.4 billion of that amount
is linked to the FMVCP.


The criteria document developed by EPA reflects
consideration given to public comments solicited by
the Agency; EPA will continue to solicit public com-
ments prior to final decision making for revisions to
this air quality standard, which was proposed  in the

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Federal Register on August 18, 1980 (45FR55066).
Public meetings on the NAAQS revisions are sched-
uled for October 2, 1980, at the U.S. Environmental
Protection Agency Headquarters, Room 3906-3908,
401 M Street, SW, Washington,  DC.  A public
meeting is also scheduled for October 10, 1980 at
the U.S. Post Office Building Auditorium, Denver,
Colorado.

Written comments on the proposed regulation must
be received in duplicate no later than November 10,
1980, and must be addressed to:  Central Docket
Section (A-130), Environmental Protection Agency,
Attn:  Docket No. OAQPS 79-7, 401 M Street SW,
Washington, DC 20460.

Docket No. OAQPS 79-7, containing material rele-
vant to the proposed rulemaking, is available for
public inspection during the Agency's normal work-
ing hours.

Documents generated as part of the NAAQS review
and revision, such as the Control Techniques Docu-
ment, Regulatory and Community Impact Analysis,
Exposure Analysis,  and  Environmental Impact
Statement can be obtained from the EPA Library
(MD-35), Research Triangle Park, NC 27711, tele-
phone (919)  541-2777.

The Air Quality Criteria Document for carbon mon-
oxide is available from: Environmental Criteria and
Assessment Office (MD-52), U.S. Environmental
Protection Agency,  Research Triangle Park, NC
27711, Attn:  Dr. David McKee.  The criteria docu-
ment also may be received by calling (919)  541-
3746 (FTS 629-3749).

For further information on the proposed rulemaking
contact:  Michael Jones, Strategies and Air  Stan-
dards  Divisions (MD-12),  Office of Air Quality
Planning  and  Standards,  U.S.  Environmental
Protection Agency,  Research Triangle Park, NC
27711, telephone (919) 541-5231 (FTS 629-5231).

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