3.1 Overview

The process of setting a standard varies among jurisdictions. The procedure used by the U.S. Environmental Protection Agency (EPA) involves the following steps:

1. Preparation of a Criteria Document⁽¹⁾, which summarizes the existing scientific data base and is reasonably complete. A large number of individuals assist in the preparation and approval of this document.
2. Approval of the Criteria Document by Clean Air Scientific Advisory Committee (CASAC), an arm of the Science Advisory Board of U.S. EPA.
3. Preparation of a Staff Paper by U.S. EPA⁽²⁾ which attempts to synthesize the data base and interpret major results. It may extend the data base by calculations of populations at risk etc. and it makes a recommendation of possible limits (upper and lower) for a standard. The economic impact of a possible standard is then reviewed within the government.
4. A proposal for a standard is then made by the Administrator of U.S. EPA, comments are accepted and reviewed, and a final proposal after 60 days of input.
5. In October of 1996, the U.S. EPA confirmed its decision not to alter the existing national ambient air standard for nitrogen dioxide, retaining the primary and secondary standard at an identical level of 0.053 parts per million measured on an annual basis. Concerns were raised about the contribution of nitrogen dioxide (NO₂) to acidification in areas such as the Adirondack Mountains and the eutrophication of Chesapeake Bay. However, the Agency determined that these issues were better addressed through the acid rain control programs and ozone reduction plans.

The next review of the standard is required in the year 2001. This process is quite open, with public and lobbying interests intervening at various stages. Minutes of meetings discussing the criteria document, and of the meetings of CASAC, are available for public review.

In Canada, the standard-setting process is comparatively closed. A basic document is produced, with usually only a small fraction of the available and relevant data referenced. A recommendation is made by a committee of civil servants representing different provinces. Drafts of proposals are not circulated, and the minutes of discussion meetings are not available. Occasionally discussion as to the basis for a standard is available; in the case of the sulphur dioxide review, this revealed that the committee had no epidemiologist on it, nor anyone capable of evaluating the current epidemiological data. This process is perhaps acceptable if the standard is only a "guideline" with no obligatory action should excessive levels occur.

On a multi-lateral basis, the World Health Organization (WHO) convenes meetings of experts from different countries. A brief review of current relevant data is conducted, with a focus on arriving at a consensus around a numerical standard. The final report is incorporated into the WHO Air Quality Guidelines for Europe. There is no coordinated public input into this process.

Other jurisdictions, such as Australia, use a modified WHO process with some public input as discussions of scientific data are held.

3.2 Standards & Guidelines

There are several important points to note about some standards (infringement of which carries a penalty) and guidelines (which may perform an alerting function), currently under discussion.

1. The present epidemiological data on particulate pollution do not indicate a threshold below which no adverse human health impacts occur. A recent mortality analysis of PM_2.5 (particulate matter) in 6 locations in the U.S.⁽³⁾ looked specifically for a threshold, but could not demonstrate one. A particulate standard therefore should acknowledge that some adverse effect may well occur in regions within the attainment of the standard. The new WHO guidelines for Europe recognize this.⁽⁴⁾

2. The ozone standard has been much influenced by controlled exposure studies of normal individuals which have shown:
   • that lung function declines progressively over the duration of a six hour exposure:
     • that decline in lung function is accompanied by evidence that lung inflammation has been induced (the magnitudes of the two phenomena are not closely related).
     • that the loss of lung function and the increase in bronchial responsiveness induced by ozone may be particularly dangerous to asthmatics; and ozone may increase the penetration of allergens.
   • that, with continuous exercise, as in agricultural field work, ozone exerts an adverse effect on lung function at levels below the current Canadian objective⁽⁵⁾ of 80 ppb over one hour. This should be acknowledged if the standard is to be relaxed.
   • Although the relationship of ozone to mortality is not firmly established, because it is not invariably found, the relationship to morbidity indices such as hospital admissions for acute respiratory disease, is well established.
   • Associations between ozone and hospital admissions and emergency visits were emphasized in the proposed U.S. EPA ozone standard.

3. The Canadian guidelines have used the words: "maximum acceptable", "maximum desirable," "maximum tolerable" etc. These words are confusing and might best be avoided altogether. Australian guidelines use the word "Detrimental" which is perhaps clearer than the Canadian "Maximum tolerable." The U.S. EPA does not use such phrases.

4. In some situations, proper protection requires a very short-term standard. Thus, with very large point source emitters of sulphur dioxide (SO₂)(which do still exist) it is sensible to base a standard on a maximum 10 minute ground level concentration. Asthmatics are very sensitive to SO₂, and have been shown to be immediately affected by concentrations much above 0.25 ppm. They would not be adequately protected by an annual SO₂ standard. The WHO guidelines for Europe noted:

   "It appears reasonable to apply a protection factor of 2 for the protection of public health; a guideline value of 500 micrograms/m³ (0.2 ppm) of SO₂ for 10 minutes, not to be exceeded, is recommended."

   The U.S. EPA has not yet recommended a ten minute standard, but it did note the occurrence in the U.S. of a significant number of exceedances of 0.5 ppm for ten minutes, and even a few over 0.75 ppm close to major point sources of sulphur dioxide.

5. A recent detailed analysis of asthma costs in Canada⁽⁶⁾ found that there was fairly close agreement with those in the U.S.; higher costs per capita in the U.S. being mainly attributable to more expensive hospital care and drugs.

FINDINGS

1. As the Board has advocated in past, a bilateral objective should be the development of the same or similar standards for public exposure to air pollutants on either side of a political boundary.
2. There are however inherent difficulties in attempting to "harmonize" guidelines with standards. By their very nature "guidelines" are likely to be set at a lower numerical value than standards as the latter carry some penalty if infringed.
3. There is no doubt that the processes which precede the promulgation of a standard, as followed by the U.S. EPA, are very important in achieving consensus on the level of protection which should be afforded, and the possible benefits that might follow enforcement of stricter standards. This process should be in the public domain.

3.3 Health Impacts: Statement on Asthma and Air Pollution

Asthma is a multifactorial disease; in children a genetic predisposition can often be identified through examination of a blood sample. An asthmatic response is presumed to develop after exposure to allergens within the home. Of these, house dust mites are very important in many parts of the world; cats and dogs are universal carriers of protein allergens; and, in tropical climates, cockroaches are probably unavoidable allergens.

The atopic asthmatic child will show sensitivities to some or all of these; in addition, the airway responsiveness to inhaled methacholine (a normal neurotransmitter), or to histamine (an enzyme present in certain cells and stored in the lung) will be increased. Responsiveness also increases to nonspecific stimuli such as cold air.

Adult asthmatics may be atopic, with a response of genetic origin, or may have acquired increased airway responsiveness without being atopic. It is believed that this may occur as a result of airway infections by viruses but the exact mechanism is unclear. What is known is that asthma with increased airway responsiveness can be acquired in adult life by occupational exposure to a wide variety of substances. The lengthy list includes platinum salts, di-isocyanates, plicatic acid (contained in Western Red Cedar), bakers flour, and many others. Prior atopy does not seem to be a factor for the development of this kind of asthma. Removal from the sensitizing environment leads to reduction in airway responsiveness in about half the people so affected. As far as the role of air pollution is concerned, the following points summarizes the Board's present understanding:

• Asthma prevalence is not increased in countries such as those in Eastern Europe, where there has been exposure to high levels of pollution, particularly sulphur dioxide and large particulate, from uncontrolled coal-burning.
• Asthma exacerbations have been shown to be inflammatory in nature
• Ozone induces lung inflammation at very low concentrations, and the degree of inflammatory response is greater in asthmatics
• Ozone increases airway responsiveness in normal subjects and in asthmatics. This may be of more consequence in the asthmatics in whom it is already increased.
• Levels of ozone pollution have been shown to be related to hospital emergency visits for asthma in Atlanta, Montreal and Mexico City and the state of New Jersey.
• Levels of ozone pollution have been shown to be associated with increased hospital admissions for asthma in Toronto and other parts of Southern Ontario and Buffalo and Albany, New York.
• Ozone increases the effect of an allergen administered to the nose in asthmatic subjects.

Ozone exposures may have declined in some urban areas, but the total population exposed to significant levels of ozone may have increased or remained stationary. In the developing world, wherever automobile usage has increased (as in Bangkok for example) downwind ozone has increased.

There are strong reasons for suggesting that asthmatic subjects may be at increased risk from ozone inhalation. Ozone causes both inflammation in the lung, and enhanced airway responsiveness, and both of these are hallmarks of asthma. While initial studies have shown that the percentage decline in lung function was not much different between the normal population and asthmatics, and it has been inferred that asthmatics were no more sensitive to ozone than non-asthmatics, the decline in function occurs in the asthmatic whose function is already lowered, and is therefore of more significance in terms of that individual's airflow limitation and symptomatology. There is also evidence that asthmatics have a greater inflammatory response to ozone than non-asthmatic subjects.

It is clear from these observations that asthmatics are at greater risk from ozone inhalation than are non-asthmatic subjects. It has recently been shown that prior ozone exposure (to levels of 0.12 ppm in one case) may enhance the penetration, and hence the effect of, a subsequently administered allergen. This has been convincingly shown in detailed experiments on the nasal mucosa.

Increased PM₁₀ and PM_2.5 levels may also be important in the aggravation of asthma, since acidic aerosols have been shown to worsen asthmatics (in Denver), and PM₁₀ levels have been shown to be associated with decrements in lung function in children with respiratory symptoms in Utah, and with asthma hospital emergency visits in Seattle. Woodsmoke (typically containing PM_2.5) has been shown to worsen the status of asthmatic children in the Pacific Northwest. The data are at the moment too nonspecific for any definite dose/response conclusion to be drawn in the case of PM₁₀ or PM_2.5.

PARTICULATE MATTER

• The WHO 1995 Revisions, instead of suggesting a guideline standards for particulates, provided tables of effects on which different jurisdictions could base their standards.

Table 3. Relationship Between Changes in Concentrations of Air Pollutants and Percentage Change in Human Health Indicator

Health Effect Indicator	% change	Estimated Change in Daily Average Concentration needed for given effect (in micrograms/cubic meter (µg/m3))
		SO4 (particulate sulphate)	PM2.5	PM10
Daily Mortality	5	8	29	50
Hospital Admissions Respiratory Distress	5	8	10	25
Asthmatic B'dilator Use	5			7
Asthma Exacerbation	5			10
PEFR (mean population change)	-5			200

Table 4. Subjects Per Million Population Affected by 3-Day Exposure to Specific Concentrations of PM₁₀

	Number of Subjects per million population affected by 3 day exposure to PM10 at various concentrations
	50µg/m3	100µg/m3	200µg/m3
Mortality	4	8	16
Hospital Admissions Respiratory Distress	6	12	24
B'dilator use Asthmatics	1400	2800	5600
Asthma Exacerbations	1000	2000	4000

OZONE

Table 5. Comparison of Selected National and International Targets ­ Ozone

U.S. EPA Proposed Standard	0.08 ppm measured over 8 hours
UK Proposal	0.05 ppm as 8-hour mean, measured as the 97th percentile to be achieved by the year 2005.
Canadian Objective	82 ppb for one hour
WHO Guideline (1987 edition) (1995 Revision)	0.076 ­ 0.1 ppm for 1-hour 0.05 ­ 0.06 ppm for 8 hours 0.06 ppm for 8 hours

SULPHUR DIOXIDE

Table 6. Comparison of Selected National and International Targets ­ Sulfur Dioxide

Current U.S. EPA	0.03 ppm Annual arithmetic mean 0.14 ppm 24 hour mean
UK Proposal	15 minute mean: 100 ppb measured as the 99.9th percentile, to be achieved by the year 2005
Canadian: (1971)	Maximum Acceptable:	0.02 ppm Annual 0.11 ppm 24 hour 0.34 ppm 1-hour
	Maximum Desirable:	0.01 ppm Annual 0.06 ppm 24 hour 0.17 ppm 1-hour
WHO 1987 Guidelines (unchanged in 1995)	10 minutes 1 hour	0.2 ppm 0.12 ppm

3.4 Ozone

3.4.1 Formation

Ozone is formed in the presence of sunlight when oxides of nitrogen (NO_X) and volatile organic carbons (VOCs) undergo a series of reactions. NO_X and VOCs have numerous anthropogenic and biogenic sources. NO_X are primarily formed by the incomplete combustion of fossil fuels. Electric power generating plants, particularly those fired by coal, and highway vehicles are the largest single emission sources of NO_X. Figure 9 indicates major NO_X sources in the United States.

VOC emissions, on the other hand, have a significant biogenic component, being produced by trees and other vegetation. However, in many population centers, anthropogenic sources of VOCs are primary contributors, due to industrial and transportation processes with highway vehicles accounting for as much as 75% of the emissions from the transportation sector (Figure 10).

The Air Quality Analysis workgroup of Ozone Transport Assessment Group (OTAG) has studied regional emission sources of NO_X and VOCs. Point sources tend to be tall stack NO_X- rich emissions in non-urban industrial regions, such as the Ohio River Valley, being relatively invariant with time. Major urban metropolitan centers are considered as 'area' sources and are composed of emissions rich in VOCs as well as NO_X. Area sources display a diurnal and seasonal cycle. Primary examples of area sources of NO_X are the Washington-New York Corridor, Chicago, Atlanta, Dallas-Fort Worth, Houston, and St. Louis. Reductions are needed in the emission of both NO_X and VOCs in order to effectively control excessive ozone concentrations.

Figure 10.

3.4.2 U.S. EPA Proposed Ozone Standard

Both the primary pollutants (VOCs and NO_X), particularly NO_X, and the secondary pollutant ozone, have been the subjects of on-going monitoring, modeling studies and control under the 1971 Clean Air Act. Under that act, in 1971, EPA set a one hour National Ambient Air Quality Standard for ozone at 0.08 parts per million (ppm). Canada had the same numerical value for its one hour ambient ozone objective (.08 ppm). Thus, the United States and Canada were in harmony on their numerical goal at that time. In 1979, however, the one hour standard for ozone in the United States was relaxed to 0.12 ppm, with one allowable exceedance per year. This remains the current standard.

The EPA is required by the Clean Air Act to review and make any necessary revisions to the National Ambient Air Quality Standards for six air pollutants once every five years. The ozone standard is currently due for review and revision. For this purpose, the EPA compiled an extensive assessment of scientific data pertaining to health and environmental effects associated with ozone. This "criteria document" was then distilled into a "staff paper" containing the most relevant information regarding the primary factors, uncertainties in the scientific data, and alternative standards needing consideration. These documents were then subjected to rigorous review by representatives of the scientific community, industry, public interest groups and the public, as well as the CASAC, which is a Congressionally mandated group of independent scientific and technical experts. The International Air Quality Advisory Board reviewed the CASAC deliberations in its 22nd Progress Report. The resulting recommendations and comments were reviewed by the EPA Administrator Carol Browner who then framed a proposal for changes to the ozone standard. This proposal then was released for an extended public comment period, which concluded on March 12, 1997. A final ruling on the ozone standard is required by July 19, 1997.

The EPA has proposed that the primary ozone standard, which is required to protect the public from adverse health effects, be changed from the current 0.12 ppm 1-hour standard to an 8-hour standard set at 0.08 ppm; an area would be considered in non-attainment when the third highest daily maximum 8-hour concentration, averaged over three years, is above 0.08 ppm. The EPA has also proposed that the secondary standard, which is required to protect the environment, including agricultural crops, national parks, and forests, be changed to agree with the primary standard. Figure 11 shows areas which will likely require significant additional reductions in the ozone precursors, NO_X and VOCs to comply with the new standard.

The proposed primary standard is expected to have very significant benefits in terms of public health and the economy, including the reduction of significant breathing problems (those which involve a 20% reduction in lung function) by 1.5 million cases; the reduction of needed hospital admissions, missed school and work days; fewer instances of restricted activities and emergency room visits for respiratory problems; the reduction of childhood illnesses ranging from inflamed lungs to irreversible lung damage; and the reduction of asthmatic episodes requiring medication or medical treatment in children. The proposed secondary standard will greatly increase the protection of the environment, including an expected savings of nearly one billion dollars in reduced agricultural crop losses. These improvements, however, will not eliminate the deleterious effects of ozone, as it will continue to occur on occasion in high concentrations throughout North America.

Figure 11.

Attainment of the standard is not required before the year 2004, seven years after promulgation. Furthermore, areas with severe pollution and limited control measures would have the ability to gain a 5 year extension. In these cases, the new standard would not necessarily be attained until 12 years after its promulgation.

3.4.3 Update on the Ozone Transport Assessment Group⁽⁷⁾

The Ozone Transport Assessment Group was formed under a March 2, 1995 agreement between 37 states and the EPA to address the issue of non-attainment due to inter-state transport of ozone and ozone-precursors. Under the agreement, if a State misses the deadline for attainment demonstration but agrees to take some interim measures to reduce ozone precursors and to participate in the multi-state "consultative" process to evaluate ozone transport throughout the eastern United States, the EPA will delay imposition of any sanctions for approximately two years. As part of this process, the state must participate in the Ozone Transport Assessment Group with the EPA and other affected parties to do modeling and analyses to determine potentially effective control measures. The states must then revise their State Implementation Plans to incorporate these resultant control measures. The Ozone Transport Assessment Group planned to have completed regional ozone modeling and determined effective ozone control measures by February 1997. At the time of this report much of the modeling work is complete; however, the development of recommended pollution control initiatives remain to be developed.

While the Board has not had an opportunity to view the OTAG outputs in detail, the major policy-relevant results, conclusions and recommendations include the following topics:

• origins and patterns of ozone in the Ozone Transport Assessment Group domain
• ozone transport in the Ozone Transport Assessment Group domain
• comparison of episodes with climatological data
• air quality management implications of analytical results
• recommendations to foster future analyses

3.4.4 Ozone Transport in the Ozone Transport Assessment Group Domain

The Air Quality Analysis workgroup of the Ozone Transport Assessment Group has completed its background assessment of the current ozone problem and its characteristics. The results are intended to give a broad perspective in which to place the more focused modeling results of individual ozone episodes and control strategy impacts.

The Air Quality Analysis workgroup has modeled the regions of influence of sources of ground level ozone in the OTAG domain. Some of these source regions contribute to excessive ozone concentrations across the Canada-U.S. border. Figures 12, 13, and 14 show the distance ozone could travel in one day based on the data for monitored ozone, meteorological conditions, and photochemical conditions. These transport regions are dependent on numerous factors, such as wind speed and direction, amount of sunlight, and temperature, which are in turn used to calculate transport vectors and normalized residence times, have been calculated for ozone, as shown to the right of the figures showing regions of influence. These figures all refer to ozone transported within one day.

Figure 12.

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Figure 13.

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Figure 14.

3.4.5 Status of Ozone Transport Assessment Group

Currently, OTAG is concluding its modeling efforts and beginning deliberations on control strategies. A discussion of further refined modeling work, and consideration of possible emission trading proposals was held in mid March in Philadelphia, where control scenarios, including one for reductions of 40% in precursors to ozone, with utilities emissions specifically being lowered by as much as 85%, were tabled.

A major meeting in April will seek to develop a consensus interpretation of the modeling outputs and an OTAG position on an emission control program, with trading provisions. The Group recognizes that its response to EPA is tardy and is moving to provide a final report with control recommendations in the near future.

In anticipation of these discussions, the NESCAUM (Northeastern States for Co-ordinated Air Use Management) in March released a report entitled "The Long-Range Transport of Ozone and Its Precursors in the Eastern United States," which, using a weight-of-evidence approach, calls for 'regional NO_X reductions and local hydrocarbon control to reduce elevated ozone levels through the Eastern United States.' The midwestern interests, in turn, have interpreted the OTAG preliminary modeling results as suggesting that there is not significant long-range interstate ozone transport.

Finding

Given the international importance of ozone attainment and the control of its precursors, the Board will continue to track the evolution of control strategies by OTAG and the U.S. EPA and offer the Commission advice as these strategies become available over the next several months.

3.4.6 Canadian Actions on the Revisions of Ozone Objectives

Currently, the Canadian domestic clean air program includes more stringent national ozone objectives than those proposed by the EPA; consideration is being given to further tightening these existing Canadian objectives. The Canadian government is persuaded that, based on a scientific assessment for ozone and particulates, health damage and premature deaths will continue to occur at the levels being proposed by the EPA.

3.4.7 Current Canadian Ground-Level Ozone Objectives

The current air quality objective for ozone of 82 ppb over 1-hour was established in 1976 under Canada's Clean Air Act of 1973 and confirmed in 1989 under the 1988 Canadian Environmental Protection Act (CEPA). This objective is 50% more stringent than the existing U.S. standard of 120 ppb over 1-hour and estimated to be approximately 25% more stringent than an 80 ppb

8-hour standard, which is roughly equivalent to 100 ppb 1-hour. The lower level of a 70 ppb 8-hour value is close to the existing Canadian objective for ozone.

3.4.8 Current Canadian Air Quality with Respect to Ground-Level Ozone

Three regions in Canada regularly experience ground-level ozone levels in excess of Canada's 1-hour ambient air quality objective of 82 ppb; the Lower Fraser Valley in British Columbia, the Windsor-Quebec City Corridor in Ontario and Quebec, and the Southern Atlantic Region (New Brunswick and Nova Scotia). U.S. sources are important contributors to Canadian ozone formation in the Windsor-Quebec City Corridor and the Southern Atlantic Region. Figure 15 illustrates the average number of days (between 1987 and 1992) when air quality objectives for ozone were exceeded in selected Canadian cities.

Figure 15.

To control the number of days of excessive ozone concentrations, the Canadian Council of Ministers of the Environment agreed to a three phase NO_X/VOC Management Plan in 1991. The second phase of the Plan is being developed by federal and provincial governments for presentation to Canadian Governments in Fall, 1997. The associated science assessment is comprised of seven scientific reports and a summary for policy makers. Included are a review of the current ozone objectives based on health and vegetation effects, analysis of ambient ground-level ozone and its precursors, monitoring guidelines and implementation, emissions inventories, and modeling of ground-level ozone in the Windsor-Quebec City Corridor, the Southern Atlantic Region and the Lower Fraser Valley of the British Columbia. The NO_X/VOC Science Assessment reports are to be published in the late spring of this year.

The NO_X/VOC Science Assessment Health Objectives reports review the current ozone objectives in Canada based on health and vegetation effects. The conclusions regarding the health impact of ozone are :

• There is clear evidence of associations between daily variations in ozone at ambient concentrations commonly encountered in Canada and acute adverse health effects. These effects range from small lung function changes, increases in symptoms of respiratory discomfort, increases in medication use, increased doctor's and hospital Emergency Department visits, through to increased hospitalizations. The evidence is less clear that there is an association between ozone and increases in mortality.
• In terms of human health, a "safe" level cannot be distinguished. The concentration-response relationship observed in the epidemiological studies provided no evidence of a threshold, monotonically increasing from an ozone concentration as low as 20 ppb up to 95 ppb.
• The vast majority (>95%) of the Canadian population was exposed at least once during 1988 (the year studied) to 1-hour daily maximum ozone levels above 50 ppb, a range associated with adverse health effects in the epidemiological studies. It is clear that these ozone-associated increases in adverse effects are occurring below the current 1-hour Canadian National Ambient Air Quality Objective of 82 ppb. The mean and 95th percentile of the 1-hour daily maximum, averaged over an 11 year period from April to September in the 16-city Canadian study, were 39 and 70 ppb, respectively. Summertime 1-hour maximum ozone levels have been recorded in Canada up to 213 ppb.
• In considering the question of "who is at risk," the clinical studies provide evidence that normal individuals very actively exercising outdoors in summer constitute a susceptible group, due to increased ventilation rates and corresponding increased doses of ozone to the respiratory tract. Children are expected to be more susceptible due to their high activity levels during play and greater exposure at peak outdoor ozone concentrations.
• There is some evidence that asthmatics and "hyper-responders," when under stress of exercise, constitute another group more susceptible than the normal population, though this has been difficult to establish.
• The clinical results for asthmatics, combined with the epidemiological evidence of hospitalizations, emergency room visits and reduced activity days, suggest the likelihood that the subpopulation defined by pre-existing respiratory and lower baseline respiratory function is most susceptible to exacerbation of effects by ozone.
• A principal question for consideration is whether the associations observed between adverse respiratory effects and environmental ozone is causal. The coherence of effects seen in all the studies including the epidemiological studies on hospitalizations, field study results, the controlled chamber/clinical studies, and even mortality lend support to an assumption of causality.
• Strong evidence for the biological plausibility of the hypothesis of a causal relationship between ozone and adverse respiratory health effects is obtained in the findings from animal toxicology studies, supported by clinical studies, of a strong inflammatory response mechanism resulting from ozone exposure. This response is known to occur in asthmatic individuals, who are at increased risk of hospitalizations and other adverse health effects due to exposure to ozone.

In light of these considerations, the Canadian government has urged the U.S. EPA to adopt an 8-hour standard for ozone at the 0.07 ppm level.

3.4.9 North American Research Strategy for Tropospheric Ozone (NARSTO)

The North American Research Strategy for Tropospheric (Ground level) Ozone (NARSTO) program is a public/private partnership, whose membership spans government, the utilities, industry, and academia throughout Mexico, the United States, and Canada. Its primary mission is to coordinate and enhance policy-relevant scientific research and assessment of tropospheric ozone behaviour, with the central goal of determining workable, efficient, and effective strategies for local and regional ozone management.

In accomplishing this goal, NARSTO is charged with establishing and maintaining effective communication channels between its scientific effort and its client community of planners, decision-makers, stakeholders, and strategic analysts. It is also charged with providing a cross-organization planning process, which determines the most effective strategies for scientific investigation. NARSTO coordinates the allocation of financial resources to implement these strategies, and monitors progress of its effort toward fulfillment of its programmatic goal.

3.4.10 Historical Summary

The origins of the NARSTO program stem from a 1991 report, entitled Rethinking the Ozone Problem in Urban and Regional Air Pollution (National Research Council (NRC), 1991). In addition to providing a technical description of the chemistry and meteorology associated with tropospheric ozone formation, this report presents a historical overview of North American tropospheric ozone trends and control measures since the 1963 enactment of the original United States Clean Air Act. It notes that, despite major regulatory programs over the past 20 years, efforts to attain North American ozone standards have been only marginally successful throughout major portions of the continent.

Multiple factors contribute to this slow progress in resolving the ozone issue. Such factors include uncertainties in characterizing local meteorological influences, reaction chemistry, deposition, and the contribution of stratospheric ozone, as well as the present inability to quantify anthropogenic emissions in a satisfactory manner. These are combined with the uncertain but often important role of naturally emitted pollutants and the propensity of ozone and its nitrogen-oxide and organic-compound precursors to travel several hundreds of kilometers in the atmosphere prior to their removal by chemical reaction or deposition. It is noteworthy within this context that only one of these factors ­ anthropogenic emissions ­ is subject to control under any practical management ­ strategy; but the effective and wise design of such control depends heavily on the joint behaviour of the others.

All of these effects vary markedly with geographical location, and all complicate regulatory considerations appreciably. The above-noted long-range transport feature limits the efficacy of local emission-control strategies in many regions of the continent, because large quantities of ozone and its precursors are likely to be introduced from remote upwind sources that lie beyond the local control domain in question. This situation is particularly troublesome in the United States owing to interstate transport, which is essentially ignored by the basic state-level regulatory strategy under the U.S. Clean Air Act. Natural emissions are problematic both because they are extremely difficult to quantify and because several elements of their atmospheric chemistry are not well understood at the present time.

Reflecting on these features and on the number of ozone studies conducted on a somewhat mutually uncoordinated basis, the NRC report concluded that "Progress toward reducing [tropospheric urban and regional] ozone concentrations has been severely hampered by the lack of a coordinated national program directed at elucidating the chemical, physical, and meteorological processes that control ozone formation and concentrations over North America." The NARSTO program is a direct response to this NRC conclusion.

The NARSTO concept was initiated through a series of technical workshops conducted with joint efforts of the U.S. National Oceanic and Atmospheric Administration (NOAA), the Electric Power Research Institute (EPRI), the California Air Resources Board (ARB), and the U.S. Environmental Protection Agency (EPA). These workshops are aimed at producing a general NARSTO strategy document, and culminated in a 1994 Boulder, Colorado meeting, which set the basis for the NARSTO Research Strategy and Charter (NARSTO 1994), a formal report published in November of 1994. In addition to setting forth the functional structure of the NARSTO organization, this report documents the program's basic rationale, itemizes key science and policy questions to be addressed by the program, and summarizes the scientific activities required for fulfillment of the NARSTO goals.

3.4.11 Current Developments

During the summer of 1996 a joint U.S./Canada field experiment took place in the eastern half of the continent (NARSTO-NE in the U.S.A. and NARSTO-CE in Canada). The project was undertaken to gather data to improve and verify models for the prediction of tropospheric ozone. Presently data collected during these experiments are being analyzed. The next major event is the completion of the 1998 NARSTO assessment. The 1998 Assessment will compile and evaluate the state of knowledge of tropospheric ozone and related chemical and physical processes and will be the first major synthesis report produced by NARSTO. Prior to publication of the assessment, a symposium is planned for November 1997 where the peer reviewed reports making up the assessment will be presented for comment.

3.5 Particulate Matter

3.5.1 Formation

Total suspended particles (TSP) have been divided into two categories, fine and course, as defined by size, sources, formation mechanisms, and chemical composition. Table 7 shows these different characteristics for both fine and coarse particles.

Coarse particles are referred to as PM₁₀, and have a diameter ranging between 2.5 and 10 micrometers (microns). Sources include windblown dust from deserts, agricultural fields, and unpaved roads with vehicle traffic.

Fine particles are referred to as PM_2.5, having a diameter less than 2.5 micrometers. Fine particles may be emitted by industrial and residential combustion of fossil fuels, as well as vehicle exhaust. They may also be formed in the atmosphere by chemical transformations of gases such as sulphur dioxide, nitrogen oxides, and volatile organic compounds, which are largely associated with combustion activities.

3.5.2 EPA Proposed Particulate Standard

The EPA is proposing to revise the current primary and secondary national ambient air quality standards (NAAQS) for particulate matter.

The primary standard is required under the Clean Air Act to protect against adverse health effects among sensitive populations, with an adequate margin of safety. The secondary standard, also required under the Clean Air Act, is to protect against welfare effects, including impacts on vegetation, crops, ecosystems, visibility, climate and man-made materials.

Currently the standards for particulate matter are measured in terms of the concentration of PM₁₀ over a 3-year averaging period. The primary standard is attained if there is one day or less per year (averaged over 3 years) when the PM₁₀ concentration is greater than 150 micrograms per cubic meter (µg/m³). The secondary standard is attained if the annual average (averaged over 3 years) of the daily average PM₁₀ concentration is less than or equal to 50 µg/m³.

Source: Adapted from Wilson and Suh (1996) U.S. EPA

The proposed standard for particulate matter includes PM_2.5 as well as PM₁₀.

The proposed PM₁₀ primary standard retains the current annual standard; the standard is met if the 3-year average of the annual arithmetic mean PM₁₀ concentration, spatially averaged across designated air quality monitors in an area, is less than or equal to 50 micrograms per cubic meter. The 24-hour primary PM₁₀ standard would be revised such that the standard is attained if the 98th percentile of 24-hour PM₁₀ concentrations in a year (averaged over 3 years), based on the single population-oriented monitoring site with the highest measured values in an area, is less than or equal to 150 (µg/m³).

It is proposed that the secondary PM₁₀ standard match the primary standard PM₁₀, as described above. Again, there would also be both an annual standard and a 24-hour standard for PM₁₀. Figure 16 reflects the areas expected to be impacted by the proposed PM₁₀ standard.

The proposed standard for particulate matter is also to include PM_2.5. According to the proposed primary standard, attainment requires that the annual PM_2.5 level be less than or equal to 15 micrograms per cubic meter, and that the 24-hour PM_2.5 level be less than or equal to 50 micrograms per cubic meter, based on the 98th percentile form, as proposed for the revised PM₁₀ standard.

It is proposed that the secondary PM_2.5 standard also be set equal to the primary PM_2.5 standard. The public would thereby be protected from welfare effects of PM_2.5 and PM₁₀ to the same degree as the primary standard protects the public from health effects.

The proposed primary particulate matter standard is expected to reduce premature deaths by 50%, or approximately 20,000 individuals; reduce aggravated asthma episodes by more than a quarter million cases each year; reduce incidents of acute childhood respiratory problems by more than a quarter million occurrences each year; reduce chronic bronchitis by an estimated 60,000 cases each year; and reduce hospital admissions due to respiratory problems by 9,000 each year.

The proposed secondary standard for particulate matter would cut haze and visibility problems by as much as 77% in some areas, such as national parks. The possible benefits in the mitigation of acid rain and ground-level ozone pollution are unquantified.

The time line for the implementation allows as much as 13 years following promulgation, including possible extensions in particularly severe regions.

3.5.3 Monitoring Requirements

Changes in the ambient air quality monitoring network are needed in order to determine the compliance of states with the proposed standard for particulate matter. While PM₁₀ has been monitored since the 1980s, PM_2.5 has not been extensively and consistently monitored. A PM_2.5 monitoring network will need to be established. On the other hand, PM₁₀ monitoring may be required at a reduced frequency and at fewer sites. PM₁₀ and PM_2.5 monitoring locations are to be collocated at key population-oriented stations in order to allow better understanding of the relationships between them and thereby promote effective emission monitoring and control strategies. The most extensive changes of current monitoring procedures will be required in order to create a PM_2.5 monitoring network.

Currently, site data for long-term collocated PM₁₀ and PM_2.5 measurements in the United States are limited. EPA's Aerometric Information Retrieval System (AIRS) contains data collected between 1989 and 1994 at rural, suburban, and urban locations across the United States. The AIRS database also contains PM₁₀ and PM_2.5 measurements taken between 1989 and 1995 at a number of sites in California. The Harvard Six-City Study provided data between 1980 and 1986 for Steubenville, St. Louis, Harrison, Topeka, Watertown, and Portage. Fine and coarse particulate matter has also been measured in Philadelphia between 1980 and 1990. A more extensive network is needed for measuring PM₁₀ and PM_2.5.

Included with the proposed standard for particulate matter is a proposal on network design and sampling methodology to further monitor particulate matter. The monitoring system would be phased-in over a 3-year period, and focused in heavily populated areas. Special purpose monitors would also be utilized as needed for special studies and for days having high concentrations of PM_2.5. The methodology specifications include sampling devices, data collection and reporting, quality assurance, and comparison of the collected data with the standards. The methodology for achieving the proposed PM₁₀ and PM_2.5 standard has been designed on the national level with a high degree of detail.

RECOMMENDATION

The Board recommends that the Commission encourage the U.S. Government to adapt standards that emphasize the protection of human health and welfare and move toward similar numerical values on both sides of the boundary.

3.5.4 Current Canadian Particulate Matter in Air Objectives

The existing Canadian government ambient air quality objectives for particulate matter in air are in transition. National ambient air quality objectives still exist for TSP. However, some provinces have already put provincial standards for PM₁₀ and PM_2.5 in place which reflect levels more appropriate to observed human health effects.

3.5.5 Current Canadian Air Quality with Respect to Particulate Matter in Air

In 1993, there were 36 monitoring sites across Canada measuring particulate concentrations. As in the United States, Canadian cities tend to be well above the background estimates. Concentrations of particulates in the ambient air of major cities across the country are illustrated in Figures 17 and 18. The levels for the proposed annual and 24-hour U.S. NAAQS are indicated by solid lines at 50 µg/m³ and 150 µg/m³ for PM₁₀ and 50 µg/m³ and 15 µg/m³ for PM_2.5, respectively.

Evidence from nearly 20 years of research in acidic deposition indicates that the U.S. is a significant contributor to Canadian particulate concentrations in regions experiencing transboundary air pollution. Most Canadian cities have daily concentrations that are below the proposed 24-hour U.S. NAAQS for both PM₁₀ and PM_2.5. However, some sites have a significant portion, sometimes greater than 50% for PM_2.5, of daily events above the proposed annual U.S. NAAQS levels.

An extensive review of data collected by TSP, PM₁₀, and PM_2.5 monitors co-located at 19 Canadian sites covering a variety of urban and rural locations noted that, for all the 24 hour measurements, the 10th and the 90th percentile TSP concentrations were 22 and 98 µg/m³ respectively and a majority of the PM₁₀ concentrations were below 47 µg/m³; most of the PM_2.5 concentrations were below 26 µg/m³.

On average, PM_2.5 accounts for 49% of the PM₁₀ and PM₁₀ accounts for 44% of the TSP. Excluding one site strongly influenced by local sources, particle levels were highest in Southwestern Ontario. Particulate concentrations also tended to increase from winter to summer in that region, in contrast to the balance of the sites. Fine particle sulphate dispersed over long distances and originating from sources on both sides of the boundary were a significant contributing factor to these phenomena.

3.5.6 Particulate Matter in Air: The Science

Scientific evidence on the effects of ambient particulate matter on human health is comprehensive. On the basis of this evidence, Canadian national ambient air quality objectives are being developed by the Working Group on Air Quality Objectives and Guidelines (WGAQOG), which reports to the Federal/Provincial Advisory Committee (FPAC) under the Canadian Environmental Protection Act (CEPA).

The scientific assessment process underway within the WGAQOG is nearing completion. Peer-reviewed documentation and a recommendation regarding new "levels" for particulate matter with less than a diameter of 10 micrometers and 2.5 micrometers are expected within the next several weeks.

The Canadian science assessment has been based on the same health evidence available and used by the EPA to define NAAQS proposals, as well as some recent Canadian work. Although not yet public, evidence in the Canadian assessment clearly supports the concern that U.S. EPA NAAQS proposals for particulate matter remain, if implemented, at levels that are in the adverse effects range. Among the conclusions are :

• All the evidence for all of the end points that have been considered - mortality, hospitalizations, chronic bronchitis - would indicate that in the observable range of ambient levels, effects are being seen without any apparent "threshold."
• The EPA has recognized this lack of a threshold by considering a range of NAAQS for PM_2.5 from a daily average of 20 micrograms per cubic metre up to 65 micrograms per cubic metre and from 12 micrograms per cubic metre up to 20 micrograms per cubic metre for an annual average.
• Certain endpoints, especially those in the upper respiratory tract such as chronic bronchitis, indicate a continuing concern over the coarse fraction of PM₁₀.
• The logical consequence of the health data is that the lower the ambient standard, the greater the health benefit.
• Although Canadian particulate concentrations are, on average, lower than American levels, recent Canadian studies show that health effects are consistently related both in type and magnitude to particulate concentrations even at the lower ambient levels observed in Canada.

As has been clearly noted in the U.S. assessment, the Canadian science assessment of particulate matter finds adverse health effects at the ambient levels of PM currently being experienced by the Canadian population. The debate on recommendations for particulate objectives currently underway in Canada is focusing on levels for Canada which span those in the full range considered by the U.S. EPA, with emphasis on values towards the lower end of that range. Canada has urged the U.S. EPA to adopt a more stringent standard for PM_2.5 at the lower end of the ranges under consideration by the Agency, along with a more stringent standard for PM₁₀.

Adapted from Submission by the Canadian Government under U.S. EPA Docket No. A-95-58 (Ozone), March 11, 1997

1. Air Quality Criteria for Ozone and Related Photochemical Oxidants. 3 Volumes: Office of Research & Development, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, USA. EPA/600/P-93/004cF. July 1996.

2. Review of the National Ambient Air Quality Standards for Particulate Matter; Policy Assessment of Scientific and Technical Information: OAQPS Staff Paper. Office of Air Quality Planning & Standards, U.S. EPA. April 1996.

3. Schwartz, J., D.W. Dockery, & L. Neas. Is Daily Mortality Associated Specifically with Fine Particles? J Air & Waste Manage. Assoc. 46, 927-939, 1996

4. Update and Revision of the Air Quality Guidelines for Europe. Meeting of the Working Group "Classical" Air Pollutants, Bilthoven, The Netherlands, 11-14 October 1994. Regional WHO Office for Europe, Copenhagen. 1995.

5. Brauer, M., J. Blair, & S. Vedal. Effect of Ambient Ozone Exposure on Lung Function in Farm Workers. Am J Respir Crit Care Med 154, 981-987, 1996

6. Krahn, M.D., C. Berka, P. Langlois & A.S. Detsky. Direct and Indirect Costs of Asthma in Canada, 1990. Can Med Assoc J 154, 821-831, 1996

7. More detailed information may be obtained on the World Wide Web at "http://capita.wustl.edu/OTAG".

URL: http://www.ijc.org/rel/boards/iaqab/r23-ch3.html