Principles of Air Quality Management - Chapter 3 doc

45 3 Air Quality Standards and Monitoring But, it is manifest, that those who repair to London, no sooner enter into it, but they find a universal alteration in their Bodies, which are either dryed up or enflam‘d, the humours being exasperated and made apt to putrifie, their sensories and perspirations so exceedingly stopp‘d, with the losse of Appetite, and a kind of general stupefaction,… so long as they abide in the place; which yet are immediately restored to their former habit, so soon as they are retired to their Homes and enjoy the fresh Aer again. Fumifugium , 1661 Historically, only qualitative standards were available to estimate the levels of air pollution in a city. These standards usually consisted of generalized descriptions of health effects (as seen in Fumifugium , above) or, in the case of the Great London Smog Disaster of 1952, statistics on the number of excess deaths or hospital admit- tances. These are after-the-fact measures of air pollution. It was only well into the latter half of the 20th century that instruments became available to monitor air pollution levels on a real-time basis. Instruments also made possible the setting of numerical standards for health and welfare as management tools. With the exception of public nuisance, air quality standards are expressed today as a given concentration of the contaminant averaged over a specified period of time. The dose concept for any contaminant is therefore an integral part of evaluating or expressing levels of acceptable air quality. When air quality standards are set, they generally incorporate the dose concept as the basis for the most relevant health effects. The type of health effect and exposure time is also important. Ozone usually has a shorter duration standard; lead, in contrast, is expressed almost exclusively by monthly or annual average concentrations throughout the world. This is a result of chronic health effects being the most prominent for lead. STANDARDS The criteria air pollutants — which are the contaminants of most concern in the United States — are ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, particulate matter, and lead. These are the pollutants for which numerical national ambient air quality standards (NAAQS) have been set, as designated by the federal government, and are in effect for all states, territories, and U.S. possessions. These contaminants have not only a primary standard, which is designed to protect human health, but, in some cases, a secondary standard, which is to protect the environment 7099_book.fm Page 45 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC 46 Principles of Air Quality Management, Second Edition (materials, vegetation, etc.). Individual states may adopt more stringent air quality standards of their own. The noncriteria air pollutants in general have two bases on which standards may be set. These include occupational exposure level (OEL)–based standards and risk- based standards. The OEL-based standards for HAPs use a concentration with a known health effect, such as the threshold limit values (TLVs), as the starting point. For these OEL-based concentrations, regulatory agencies typically apply a safety factor to the acceptable occupational levels. These factors consist of fractions between 1/10 and 1/1000 — “corrections” to allow for the increased sensitivities of the general population and susceptible population groups. Thus, an “acceptable” standard of air quality for a noncriteria air contaminant, using the OEL-based system, could be derived from a TLV divided by a factor between 10 and 1000 that the regulatory body would consider acceptable. Another approach to acceptable air quality for toxic air contaminants includes those that are based on levels of individual or societal risk. These latter approaches form the basis of the health risk assessment methodology considered later. These are risk-based approaches specifically for those airborne contaminants that are car- cinogenic, mutagenic, or teratogenic. Public nuisance, however, is among the oldest of all air quality standards and, indeed, is the only situation for which there is no numerical value. Contaminants that cause a public nuisance , primarily because of odors, do not have an acceptable concentration but are derived from public complaints. This lack of numerical values exists because odor threshold concentrations causing complaints vary significantly among the population at large. Therefore, standards based on odors or public nui- sance commonly require a number of individuals to petition a regulatory body for relief. A CCEPTABLE L EVELS Societal concerns for acceptable air quality range from fears about life-threatening levels of contaminants to occupational exposures, and to general population stan- dards, sensitive population segments, and exposures corresponding to a level of cancer risk. Figure 3.1 illustrates relative acceptable concentrations for each concern. For workers, both the National Institute for Occupational Safety and Health and the Occupational Safety and Health Administration have derived an “immediately dangerous to life and health” (IDLH) level for emergency situations for a variety of contaminants. This is the maximum concentration one may endure for less than 30 minutes without experiencing an escape-impairing or irreversible health effect. Carcinogens do not have an IDLH. The best known of the allowable exposure levels in the United States for occu- pational standards are the TLVs published by the American Conference of Govern- mental Industrial Hygienists (ACGIH). These are levels of airborne contaminants below which healthy adults, working for 40 hours per week, generally do not suffer adverse health effects for repeated exposures. Unless adopted by a governmental agency, these levels are not government standards but are recommendations made by industrial hygienists. These occupational limit values are updated annually. 7099_book.fm Page 46 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC Air Quality Standards and Monitoring 47 The TLVs are published for two time intervals: the time-weighted average (TWA) and the short-term exposure level (STEL). The time-weighted average is an allowable 8-hour average exposure concentration, and the short-term exposure level is the maximum 15-minute average concentration to which workers may be exposed. The Occupational Safety and Health Administration has adopted certain of these TLVs as permissible exposure levels (PELs). The PEL, therefore, become the legally enforceable level of exposure for industrial workers. Other toxicological levels that may be used include the “no observed adverse effect” level (NOAEL). This level is frequently used as a starting point of allowable exposure for potential human inhalation levels. Other acceptable level approaches use the “no observed effect” level (NOEL), which includes data published in the literature as an equivalent health level. These latter levels are based on animal studies, whereas the TLVs are based on human studies. Table 3.1 compares four common air contaminants and the different levels of “acceptable” air concentration for different situations, exposures, and population groups. In the table, ozone and sulfur dioxide are compared against the hazardous air pollutants vinyl chloride and formaldehyde. The IDLH level is 10 ppm for ozone and 100 ppm for sulfur dioxide. Neither vinyl chloride nor formaldehyde has an IDLH level. In contrast, an 8-hour TLV (for FIGURE 3.1 Relative inhalation levels. IDLH STEL TWA AAQS Odor Risk 0 1000 Various standards Concentration 7099_book.fm Page 47 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC 48 Principles of Air Quality Management, Second Edition industrial workers) does exist for all four contaminants. These levels are 0.10 ppm for ozone, 2 ppm for sulfur dioxide, 5 ppm for vinyl chloride, and 0.3 ppm for formaldehyde. The federal Ambient Air Quality Standards (AAQS) for ozone (0.12 and 0.08 ppm) and sulfur dioxide (0.14 ppm) have different averaging times of 1, 8, and 24 hours, respectively. For comparison, the air quality standards adopted by Cali- fornia are also shown in Table 3.1. For vinyl chloride, a 24-hour standard of 0.01 ppm has been adopted by that state. With respect to the potential for a cancer risk of one chance in a million, there are no standards for ozone or sulfur dioxide. For vinyl chloride and formaldehyde, the cancer risk standards exist at exceedingly low concentrations. Other levels that may present a concern for public nuisance would be the odor thresholds. Table 3.2 lists some of the more common odor-causing compounds and the odor threshold concentrations that are noticed by the general population. It should be noted that all of these levels are subject to change as more health effects infor- mation becomes available. AMBIENT AIR STANDARDS AND EXPOSURES N ATIONAL In excess of 90 million people nationwide are exposed to criteria air pollutants at levels in excess of one or more of the AAQS. Of those individuals, the majority live in areas in which the ozone standard is exceeded. This indicates that there are valid concerns for health and that significant numbers of people are affected by air pollutants. TABLE 3.1 A Comparison of Significant Air Pollutant Concentration Levels — 2005 Level Ozone SO 2 Formaldehyde Vinyl Chloride IDLH 10 100 * * TLV § 0.10 2 0.3 5 Federal AAQS § 0.08 — — — 24 hr. — 0.14 — — California AAQS § 0.07 0.25 —— 24 hr. — 0.04 — 0.01 Odor Threshold 0.015 0.5 <1 — 10 –6 Cancer Risk NA NA 0.000006 µ g/m 3 0.000078 µ g/m 3 Concentrations in ppm, unless otherwise noted. * = carcinogen; IDLH = immediately dangerous to life or health (30 minutes); TLV = threshold limit value, 8-hour time weighted average, ACGIH; NA = not applicable; § = 8-hour average concentration. 7099_book.fm Page 48 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC Air Quality Standards and Monitoring 49 The NAAQS establish a concentration and exposure time criteria for each known health effect threshold. Primary standards are those levels of air quality necessary to protect the public health while allowing for an adequate margin of safety. Sec- ondary standards are those levels necessary to protect the public welfare from known or anticipated adverse effects, including economic values and personal comfort. At this time, secondary AAQS for the United States are the same as the primary standards, with the exception of sulfur dioxide. Table 3.3 lists the federal primary AAQS. Each of these levels indicates what is considered acceptable air quality. These AAQS include provisions for sensitive population groups such as the elderly, asthmatics, young children, and so on. Air contaminants with a chronic adverse health effect have annual based standards, whereas air pollutants with more acute effects tend to have 1–8-hour standards. The only secondary AAQS different from a primary standard is the 3-hour SO 2 concen- tration of 0.5 ppm. The particulate matter standard (PM10) is based on the mass of particles with an aerodynamic diameter less than 10 µ in diameter. There is now a TABLE 3.2 Odor Thresholds Compound Average Odor Threshold, ppm 1,1,1-trichloroethane 390 Ammonia 4 Benzene 10 Butane 5000 Carbon monoxide Odorless Chlorine 0.02 Ether 14 Ethyl alcohol 6.5–84 Ethyl benzene 25 Formaldehyde 0.4 Hydrogen Odorless Hydrogen sulfide 0.1 Isobutyl alcohol 0.03 Isopropyl alcohol 50 m-Cresol 0.005 Methane Odorless Methanol 100 Methyl mercaptan 0.001 Nitric oxide Odorless Nitrogen dioxide 0.5 Octane 150 Ozone 0.015 Styrene 0.1 Sulfur dioxide 0.5 Toluene 3 7099_book.fm Page 49 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC 50 Principles of Air Quality Management, Second Edition transition from the PM10 standards to the PM2.5 standards. PM2.5 particles have greater health effects as a result of the smaller aerodynamic particle sizes. Longer averaging times implemented as societal health effect concerns change from short-term acute effects to longer-term chronic effects. Depending on the severity of the air pollution problem in a given area, those geographical areas of the United States that exhibit air quality in excess of federal standards are considered “nonattainment areas.” Federal and state regulations man- date certain actions to be taken to attain the primary AAQS first, and then the secondary AAQS. For ozone, the 1-hour standard must be attained before the 8-hour standard comes into effect in any given area. The United States is divided geographically into metropolitan statistical areas, which are used for evaluating both exposures to air contaminants and the population in which the AAQS are not attained. Under federal law, the more severe an area is in nonattainment, the more stringent the air quality management requirements become for that area. I NTERNATIONAL A IR P OLLUTION L EVELS Air quality varies dramatically depending on location, meteorology, and emissions. Table 3.4 shows the World Health Organization recommended levels for particulate matter, SO 2 , and NO 2 and for the average levels experienced in 12 cities worldwide. Also shown are the ratios of existing air quality to the World Health Organization standards. These ratios indicate the degree to which air quality is impaired in those locations. Ratios greater than 1.0 exceed the World Health Organization standards; those less than 1.0 are less than the standard. TABLE 3.3 U.S. Ambient Air Quality Standards — 2005 Criteria Pollutants Contaminant Concentration † Duration (hours) Ozone 0.08 8 0.12 1* Carbon monoxide 35 1 98 Nitrogen dioxide 0.05 Annual Sulfur dioxide 0.14 24 0.03 Annual Particulate matter — PM10 150 µ g/m 3 24 50 µ g/m 3 Annual Particulate matter — PM2.5 65 µ g/m 3 24 15 µ g/m 3 Annual Lead 1.5 µ g/m 3 3 months † In parts per million (vol), unless otherwise indicated. * Original standard, in effect until attained, then 8-hour standard comes into effect. 7099_book.fm Page 50 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC Air Quality Standards and Monitoring 51 Weather, population density, fuels used, automobile traffic, industrialization, and degree of control systems are all components of the air quality experienced in various cities. THE POLLUTION STANDARD INDEX Because of the wide range of contaminants, concentrations, and averaging times for the NAAQS, the federal Environmental Protection Agency has determined that a normalized reporting system would be appropriate for public use. The pollutant standards index (PSI) has found widespread use in the air pollution field to report daily air quality to the general public. The PSI integrates information for the different criteria pollutants across an entire monitoring network into one normalized figure. This index, ranging in numerical values from 0 to 500, is intended to represent the daily air quality experience in an area. The PSI is computed daily for particulate matter (PM10), ozone, carbon monoxide, sulfur dioxide, and NO 2 , based on short-term NAAQS, federal episode criteria, and federal significant harm levels. Lead is not included, as it does not have a short-term air quality standard, episode criteria, or significant harm level. The PSI converts daily monitoring information into a single measure of air quality by first computing a separate subindex for each pollutant and averaging time for that day. The PSI itself is a single, dimensionless number. Table 3.5 lists the PSI TABLE 3.4 International Air Quality and 2002 WHO Standards Area PM10: µµ µµ g/m 3 PM10 Ratio to WHO Level Sulfur Dioxide: µµ µµ g/m 3 SO 2 Ratio to WHO Level Nitrogen Dioxide: µµ µµ g/m 3 NO 2 Ratio to WHO Level World Health Organization Recommended Levels 90 50 50 Amsterdam 40 0.4 10 0.2 58 1.16 Athens 178 2.0 34 0.68 64 1.28 Beijing 377 4.2 90 1.8 122 2.44 Bombay 240 2.7 33 0.66 39 0.78 Copenhagen 61 0.7 7 0.14 54 1.08 Kuala Lumpur 85 0.9 24 0.48 — — London — — 25 0.5 77 1.54 Moscow 100 1.1 109 2.18 — — Mexico City 279 3.1 74 1.48 130 2.6 Milan 77 0.9 31 0.62 248 4.96 Montreal 34 0.4 10 0.2 42 0.84 Tokyo490.5 18 0.36 68 1.36 7099_book.fm Page 51 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC 52 Principles of Air Quality Management, Second Edition ranges and their air quality designations for each range. The PSI is used primarily to report daily air quality in a large urban area as a single number or descriptive word. Frequently, the index is reported as a regular feature on the news media or in the newspapers. It should be noted that in general, ozone and carbon monoxide receive the majority of the emphasis in the designation of PSI levels, as those are the contam- inants that cause most of the ambient air quality standard violations in urban areas. A PSI of zero is assigned to the limit of detection for the contaminant, and 100 is designated as the ambient air quality standard for whichever contaminant is expected to show the worst air quality on a given day. E PISODIC S TANDARDS There are concentrations of the gaseous criteria contaminants that will result in acute health effects. These episodic standards range from the AAQS to significant harm levels. Table 3.6 shows the acute health effect designations for the two contaminants, TABLE 3.5 Pollutant Standard Index (PSI) Levels PSI Range Air Quality 0–50 Good for all persons 51–100 Moderate 101–200 Unhealthful* 201–300 Very Unhealthful* >300 Hazardous* *EPA designation. TABLE 3.6 Acute Health Effect Designations PSI Designation Criteria Pollutant Time, hours ppm 100 Federal AAQS Ozone 1 0.12 CO 1 35 200 Federal Alert California Stage 1 Episode Ozone Ozone 1 1 0.20 0.20 CO 1 40 CO 12 20 300 Federal Warning Ozone 1 0.40 400 Federal Emergency Ozone 1 0.50 500 Significant Harm Level Ozone 1 0.60 Source: 40 CFR 51. Appendix L and Title 26, California Code of Regulations. 7099_book.fm Page 52 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC Air Quality Standards and Monitoring 53 ozone and carbon monoxide, that are the most likely to cause acute health effects. The pollutants are listed by their respective PSI numbers. The lowest designation is the federal primary AAQS with a PSI of 100. Levels in excess of 200 are a federal alert level and are designated as Stage 1 episode levels in California. This is the first level of warning for the general population, at which susceptible persons, especially those with heart or lung diseases, should stay indoors. In general, healthy adults and children are advised to avoid vigorous outdoor exercise when these levels are exceeded. When PSI levels of 300 (warning levels) are attained, the outdoor air quality environment has become hazardous. Therefore, all susceptible persons are directed to stay indoors, and the general population is recommended to avoid all outdoor activities. When PSI levels exceed 400, a federal emergency results. At PSI 500, significant harm results, and all individuals are to remain indoors and minimize physical activity. As we will see in Chapter 10, PSI levels above 150–200 are now exceedingly rare. Other regulatory actions take effect at these various stages in attempts to abate the acute health effects either predicted or attained by these contaminants. Local agencies, of course, may designate their own warning or advisory levels for the population at large and for sensitive population groups, such as school children. For instance, within Southern California, a PSI of 138, which corresponds to an ozone concentration of 0.15 ppm, becomes a school health advisory level, at which pro- longed vigorous outdoor exercise is not recommended. This is not an enforceable regulatory standard but is an advisory to the public to take protective measures for school children. NONCRITERIA AIR CONTAMINANT STANDARDS There are two major approaches to determining acceptable air quality levels for noncriteria contaminants. The first of these approaches is based on human health effects and extrapolations from epidemiologic data. This approach includes occupa- tional exposure levels corrected by some factor less than 1.00. The other approach is a health risk assessment, whereby individual and societal risks to exposed populations are factored into the determination of acceptable air quality concentrations. These calculations are based on risk probability and assume that carcinogens, mutagens, and teratogens pose a risk in any amount. O CCUPATIONAL D ERIVED S TANDARDS In this approach, regulatory agencies adopt what they consider to be acceptable concentrations in the ambient atmosphere for noncriteria pollutants. These concen- trations are based on either health effects data generated through toxicological studies or published data from the ACGIH in the TLVs or recommendations from the National Institute for Occupational Safety and Health. As noted earlier, these approaches modify occupationally based levels acceptable in work situations to become acceptable air concentrations for the general public. 7099_book.fm Page 53 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC 54 Principles of Air Quality Management, Second Edition These approaches typically use the 8-hour TLVs and divide them by an appro- priate factor, such as 42, 100, 300, or 1000, to arrive at an acceptable ambient concentration for the noncriteria air contaminants. Again, as with air quality for criteria pollutants, the averaging times are different, as well as the numerical values. RISK ASSESSMENT For other hazardous air pollutants, a different approach is taken. This approach focuses on the probability of an individual or a number of persons potentially contracting a fatal condition or being severely affected by an air contaminant. When a risk assessment is performed, it is an attempt to derive a quantitative value of either a societal or an individual risk. A societal risk is the number of adverse consequences that might occur as a result of exposure to a hazardous air pollutant. An individual risk is the probability of an adverse consequence occurring to an individual during a year. For health risk assessments, one is typically concerned with the potential for a particular activity to cause chronic health problems. These assessments usually deal with cancer rather than acute incidents such as injury or death. Unfortunately, for a number of chemical contaminants, one is faced with a relatively small body of health data. Therefore, many assumptions and uncertainties are present. The criteria air pollutants are not subject to a risk assessment; when these standards were set, appropriate safety factors were included in setting such standards. T HE R ISK A SSESSMENT P ROCESS The Environmental Protection Agency (EPA) has published formal guidelines to be followed for risk assessment. These include guidelines for carcinogens, mutagens, chemical mixtures, and suspected developmental toxicants. One guideline exists for the estimation of exposure. As policy, the EPA holds that there is no safe threshold concentration for a chemical carcinogen. The four major elements in a health risk assessment process, per the EPA guidelines, are 1. Hazard identification 2. Dose–response assessment 3. Exposure assessment 4. Risk characterization Hazard Identification The hazard identification part of health risk assessment is a qualitative assessment based on a review of relevant biological and chemical information. The elements involved in making a hazard identification of a given chemical are •Physical and chemical properties of the agent • Routes of exposure • Structural or activity relationships that may support or argue against prediction of carcinogenicity 7099_book.fm Page 54 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC [...]... Page 61 Friday, July 14, 2006 3: 13 PM Air Quality Standards and Monitoring 61 ACCEPTABLE AIR QUALITY For the criteria pollutants, there are a number of ways of expressing whether ambient air quality is within the acceptable range These include the number of “exposure hours,” the number of “station days,” or the percentage of time above a standard For purposes of the Clean Air Act, the most important... seasonal Such a © 2007 by Taylor & Francis Group, LLC FIGURE 3. 2 8-hour ozone nonattainments areas Principles of Air Quality Management, Second Edition 7099_book.fm Page 62 Friday, July 14, 2006 3: 13 PM 62 © 2007 by Taylor & Francis Group, LLC USEPA, 2004 7099_book.fm Page 63 Friday, July 14, 2006 3: 13 PM Air Quality Standards and Monitoring 63 case would be for ozone during the summer in an urban area... — 20 03 Substance Inhalation (µg/m3)* Ammonia Arsenic Benzene Cadmium Carbon tetrachloride Chlorinated dibenzo-p-dioxins (as 2 ,3, 7,8-equivalents) Chromium (hexavalent) Ethylene oxide Formaldehyde Hydrogen cyanide Mercury and compounds (inorganic) Methanol Methylene chloride Perchloroethylene Toluene 2.0E+2 3. 0E+2 6.0E+1 2.0E+2 4.0E+1 4.0E+5 2.0E+1 3. 0E+1 3. 0E+0 9.0E+0 9.0E+2 4.0E +3 4.0E+2 3. 5E+1 3. 0E+2... cubic meter of air sampled The determination of PM10 concentrations requires the installation of a sizeselective inlet head on top of the filter chamber The size-selective inlet takes Sampling vessel Sampling tube Vacuum trap Limiting orifice Absorbing solution Vacuum pump FIGURE 3. 3 A gas sampling train © 2007 by Taylor & Francis Group, LLC 7099_book.fm Page 65 Friday, July 14, 2006 3: 13 PM Air Quality. .. 56 Friday, July 14, 2006 3: 13 PM 56 Principles of Air Quality Management, Second Edition when much uncertainty exists regarding the mechanism of carcinogenic activity, models or procedures that incorporate low-dose linearity are preferred when they are compatible with limited information The true value of the risk is unknown and may even be as low as zero Therefore, the range of risk defined by the upper... a speciation of different contaminants, as well as their concentrations Some hot spot analyses or survey instruments used in determining noncriteria air pollutants involve taking samples over a very short duration of time in a container, © 2007 by Taylor & Francis Group, LLC 7099_book.fm Page 66 Friday, July 14, 2006 3: 13 PM 66 Principles of Air Quality Management, Second Edition FIGURE 3. 5 A particulate... TABLE 3. 9 Typical Noncancer Reference Exposure Levels (Acute) — 20 03 Substance Ammonia Benzene Carbon tetrachloride Formaldehyde Hydrogen cyanide Hydrogen sulfide Mercury (inorganic) Methyl chloroform Nickel compounds Perchloroethylene (tetrachloroethylene) Xylenes * E denotes scientific notation, base 10 © 2007 by Taylor & Francis Group, LLC Exposure Level (µg/m3)* 3. 2E +3 1.3E +3 1.9E +3 9.4E+1 3. 4E+2... quantitative © 2007 by Taylor & Francis Group, LLC 7099_book.fm Page 64 Friday, July 14, 2006 3: 13 PM 64 Principles of Air Quality Management, Second Edition CUMULATIVE SAMPLERS The earliest numerical methods were simple, weight-based measurements of particles as “dustfall.” This technique measured the weight of heavy particles falling into a glass jar on a monthly basis Sulfur dioxide was indirectly... 14, 2006 3: 13 PM Air Quality Standards and Monitoring • • • 55 Metabolic properties of the agent Toxicological effects of the agent Information on both short- and long-term animal studies that have been performed to date Because animal studies are frequently used in determining carcinogenicity in humans, these studies receive a great deal of weight in the hazard identification process The weight of evidence... Denver area, the Virginia-to-Maine eastern corridor, the Appalachian mountain areas, and portions of the Midwest These are the areas in which the greatest efforts are being made to manage air quality MONITORING AMBIENT AIR QUALITY Monitoring air quality is important for three major reasons The major concern is to determine compliance with federal law regarding the attainment of the NAAQS The second . 4.96 Montreal 34 0.4 10 0.2 42 0.84 Tokyo490.5 18 0 .36 68 1 .36 7099_book.fm Page 51 Friday, July 14, 2006 3: 13 PM © 2007 by Taylor & Francis Group, LLC 52 Principles of Air Quality Management, . acceptable air concentrations for the general public. 7099_book.fm Page 53 Friday, July 14, 2006 3: 13 PM © 2007 by Taylor & Francis Group, LLC 54 Principles of Air Quality Management, . a 7099_book.fm Page 61 Friday, July 14, 2006 3: 13 PM © 2007 by Taylor & Francis Group, LLC 62 Principles of Air Quality Management, Second Edition FIGURE 3. 2 8-hour ozone nonattainments areas. USEPA,