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* ------- -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 ------- 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. ------- 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 ------- 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. ------- 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. ------- 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 ------- 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 ------- 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 ------- 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 ------- 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). ------- |