Particulate Matter, Ground-Level Ozone,
and the Canada-Wide Standards Regulatory Process

Caitlin Hancey
December 1999




Problem Statement
Health and Environment Link


Problem Statement
Health and Environment Link




Problem Statement

The most recent science assessment document for ground-level ozone (O3) was released in February of 1999 [1], and for particulate matter (PM) in 1998 [2] . Over forty studies have concluded similar results: there is no threshold under which human and environmental effects (arguably intricately interwoven) do not occur, and the health and environment damage relationship to these pollutants is linear.

PM refers to tiny airborne particles which range from approximately 0.005 µm to 100 µm in diameter, in solid or liquid forms, including both primary (emitted directly into the atmosphere) and secondary (formed in the atmosphere) particulates. Particles less that 0.005 µm in diameter are considered negligible. As size is the most appropriate indicator of the behaviour of particulate matter, it is generally divided into two fractions: coarse mode, with particles between 2.5 µm and 10 µm in size (PM10); and fine mode, with particles of 2.5 µm or less (PM2.5).

Natural emissions of both fine and coarse PM include wildfires, windblown dust, sea salt spray, some mineral particles, and natural nitrogen oxide (NOX) and volatile organic compound (VOC) emissions. Anthropogenic emissions, which constitute a substantial influx into the atmosphere, include road and construction dust, mineral dust due to mining and extraction, windblown agricultural soil, VOCs from vehicles, industrial processes and solvents, and sulphates and nitrates from power plants and transportation sources.

PM is directly related to broad issues of environmental concern, such as smog, acid deposition, decreased visibility (up to 70% in some urban areas [3]), and climate change. It penetrates deeply and quickly into the lungs where there are no cilia to act as filters3. In humans, it has been linked to cardiorespiratory diseases, decreased lung function, increased respiratory stress, an increase in chronic bronchitis and asthma, and decreased visibility. PM refracts, reflects or absorbs light, creating a regional haze, reducing visability [4].

Ground-level ozone is a secondary pollutant, a highly reactive and unstable form of oxygen, and the most detrimental of "photochemical" pollutants (photochemical reactions are those that require light). It is being continually created and destroyed in the troposphere by reactions involving oxygen molecules and ultraviolet light. The rate of synthesis of ozone is greatly increased by the presence of high concentrations of NOx and VOCs that react, with oxygen, in sunlight. NOx is primarily emitted by anthropogenic sources, most notably fossil fuel combustion, while natural sources are considered negligible. The transportation sector alone is responsible for 60% of NOx emissions in Canada.

Though VOCs are emitted primarily from natural sources such as forest fires and vegetation, the anthropogenic emissions (from combustion, incineration, industrial processes, evaporation of liquid fuels, paints, solvents, and organic chemicals) are those that dominate during episodes of oxidizing smogs in most affected regions of Canada [5]. As a result of the photochemical reactions required of these pollutants, the synthesis of ground-level ozone is more prolific on hot, sunny days, and is primarily a summer phenomenon.

Ground-level ozone has a variety of adverse effects on humans. There is an 8.5% increase in hospital emergency department visits per 10 ppb increase of ambient ozone levels [6], and a high correlation between high tropospheric ozone levels and worker absenteeism [7]. In the respiratory system, ozone is linked to decreased lung function, chronic and acute bronchitis, asthma and pulmonary emphysema. It also causes headaches, burning eyes and irritated sinuses, while possibly interfering with the immune system. It is the chemical measured for use in smog indexes in urban areas.

Health and Environment Link

In a peer-reviewed document that is the result of twenty-three separate studies, a recent federal-provincial working group under the Canadian Environmental Protection Act (CEPA) identified reference levels to be those above which an effect on a receptor (humans or the environment) has been demonstrated. The reference level for ground-level ozone is considered 15 ppb (as a 1-hour daily maximum), and 25/15 µg/m3 for PM10/2.5 (24-hour average). Numerous studies have shown, however, that there are no levels at which these pollutants do not affect some portion of the population16. Children, the elderly, and those already suffering from cardiorespiratory diseases are especially susceptible. Children breathe in 50% more air per pound of body weight than do adults, making them particularly vulnerable to airborne pollutants [8].

Ozone causes injury to foliage, increases susceptibility to diseases and other stresses in plants and tree species, reduces yields in sensitive crops at levels of 60 ppb [9], and increases mortality rates of individual trees, eventually leading to a decline of species. According to the most recent Science Assessment Document, ozone is also linked to detrimental effects in the respiratory systems of animals, such as lung haemorrhages in birds [10].

PM causes unnatural biochemical interactions, soil effects, increased susceptibility of disease in vegetation, the smothering of leaves by blocking stomata, and reduction of visibility in wilderness as well as urban environments. It is associated with animal toxification (demonstrated by a reduction in lung clearance), changes in immunological responses, and possible onset of chronic alveolitis, fibrosis and lung cancer. PM can also cause degradation of inorganic materials (buildings, playground equipment, etc.), resulting corrosion, erosion, soiling and discoloration.

There are two primary difficulties in clearly establishing the environmental links to PM and ground-level ozone. These are the debates regarding natural background levels and transboundary air pollutants, and how they interact with and relate to regional anthropogenic emissions. Background levels are said to be the "natural" levels at which the pollutants occur in the atmosphere. Recorded background levels range from 25-40 ppb over a 1-hour averaging period for ground-level ozone, and from 4-11 µg/m3 for PM10 and 1-5 µg/m3 for PM2.5 over a 24-hour averaging period.

The debate revolves around the accuracy of studies that indicate that there are no lower thresholds at which adverse effects to do occur, while there are measured "natural" levels well in exceedence of zero. In other words, why should a fuss be made over the amount of pollutants we emit when nature is substantially emitting her own? It is established that there are natural sources for both PM and ground-level ozone, yet as previously mentioned, the anthropogenic emissions are found to be those most conducive to smog conditions because of their location and abundance. (Location and abundance operate as both individual and cooperative factors.) Further explanation of this is intricately related to the following area of debate.

Transboundary air pollutants include air pollutants that are located in a region, but were produced elsewhere and travelled through the atmosphere without regard for political borders. NOx, VOCs and ozone can travel substantial distances in the atmosphere, causing problems through their introduction to regions that may not have marked emissions, or by further aggravating areas that are already suffering from excess emissions (such as in the Windsor-Quebec Corridor) [11].

Travelling PM results in a reduction of visibility in wilderness areas that hold no local sources of emissions. There is also interaction and cooperation between the two types of pollutants. For instance, VOCs can be absorbed in particles and transported to rural areas where they can act as part of a "haze," then be released in response to temperature rise during the day and further facilitate the formation of ozone. The concept of Long-Range Transport of Atmospheric Pollutants (LRTAP) has been well established through case studies [12].

The background levels for PM were taken relatively recently from remote sites in North America [13]. In light of the well accepted notions of LRTAP, it is arguable that there is no site in North America that is not suffering to a significant degree from anthropogenic emissions of these pollutants. Five studies cited in a ground-level ozone SAD examined youth while at summer camp. The studies observed "exposure of normal non-asthmatic children and adolescents to ozone under ambient conditions," which demonstrated "measurable declines in lung function and increases in symptoms." [14]

In fact, it is common knowledge among those familiar with the pollutant that ground-level ozone concentrations tend to be highest at rural sites. What is uncommon, unfortunately, is the explanation. LRTAP explains ozone's presence in rural areas, but not necessarily its particular abundance. Even without a clear explanation of ozone's abundance in rural areas, it should remain evident that North America, with our excessively high industrial and domestic emissions levels, is not the first place to look for samples of natural backround emissions. Considering LRTAP, there may in fact be difficulties finding a purely natural, uncontaminated site anywhere on this planet.


With such evidence, it is becoming increasingly obvious that if Earth's vegetation is damaged even as much as we can currently prove with hard science, the inevitable results will be not only increased difficulty with food-growing and food supply and a reduction of the ecological services provided by the planet (only one of which is the increasingly relied-upon use of forest and ocean vegetation as "carbon sinks"). We will suffer a dramatic and sustained attack on human lifestyle, health and well-being.

There is broad enough consensus in the scientific community regarding the seriously detrimental effects of ground-level ozone, especially as it relates to vegetation. There is enough research to make most scientists and policy makers comfortable in this assertion. More research, however, is widely believed to be required with regard to particulate matter (both PM10 and PM2.5). PM has long been associated with chronic bronchitis and asthma, but has never been established as a causal agent, only an aggravate.

Anthony S. Wexler, Professor of mechanical engineering at the University of Delaware, states that there is "an apparent correlation between concentrations of particulate matter and data on people getting sick and dying. Butthe physiological connection between particulate matter and health has never been fully explained."3 He and partner Ramesh Sarangapani are currently conducting research which they claim is "a first step toward better understanding of how theseparticles affect us."3 Their work hopes to describe two unresearched ways that the particles effect humans: dispersion and expansion of the particulates in the respiratory system, resulting from contact with moisture. Initiatives of this nature will hopefully lead to stronger links between exposure to PM and health and environmental effects.

More research is also required with regard to the natural background levels of both PM and Ozone. Scientists have been able to collect data on the ambient concentrations of carbon dioxide in the atmosphere through the study of ancient ice cores. The rise and fall of the concentration through many centuries has been traced - particularly the marked rise which has occurred since the Industrial Revolution in the mid-nineteenth century.

Evidence of this nature would surely be of more use than samples taken in our current, widely-polluted atmosphere. Perhaps such data collection is not possible for the constituents and precursors of PM and ozone respectively. In that case, there should be concerted effort to seek out more appropriate sample areas; areas that are outside of the industrial world, have lowest-possible regional anthropological emissions, are out of range of intense, misrepresentative natural emission sources such as volcanoes, and have lowest-possible evidence of LRTAP. That is, if we wish to compare ourselves with the natural, regular, biochemical activities of the planet.


Continued research in all areas which pertain to PM, ozone and their effects on humans, animals, and their biotic and abiotic environments, with stronger emphasis on the gapped areas such as PM, are of particular importance. Epidemiological studies, despite their numerous difficulties, are especially useful for the assessment of human response to these pollutants, because they test the "real world" soup of pollutants that populations are exposed to in the ambient environment, and can also isolate the detrimental effects of particular pollutants, such as ozone.

There are available scientific statistics and findings describing the detrimental effects of particulate matter and ground-level ozone on humans, the environment, and the other organisms within it. This information should be shared with the general public by publishing it in a manner that is accessible and that translates the effects as clearly as possible. Such sharing should communicate to the public the possibility (and the need) for action on the parts of individuals, industry and government, against further development of health and environmental complications that are the results of exposure to these pollutants. The scientific evidence alone, if shared and published adequately, is enough to incite devoted response from the majority of individuals in this country (and on this planet) who, one would assume, are at least concerned about the air that they and future generations will breathe. After all, it is still individuals, for the most part, who make up our industries and government and influence the decisions made therein.


Problem Statement

The Canada-Wide Standards process, underway in cooperation with the Canadian Council of Ministers of the Environment (CCME), is a result of the Canada-Wide Accord on Environmental Harmonization. The Accord was designed to reduce overlap and duplication in environmental regulation (despite word that a government-hired consultant found little overlap and duplication on environmental matters.) The process includes multi-stakeholder consultations, conducted with the purpose of gathering the input of members of the public from a variety of sectors (industry, health, aboriginal, and environmental non-governmental organizations - ENGOs). The CWS development committee (DC) is established to propose targets, time frames, and reporting protocols that are "achievablebased on sound science and the evaluation of risk to human health and the environment, recognizing environmental and socio-economic considerations." [15]

The responsibility for environmental regulation is being delegated to the CCME rather than the federal government (which is of concern at least with regard to the protection of aboriginal lands, which come only under federal jurisdiction). The consensual decision making process, while an attractive alternative to top-down federalism, gives each province vetoing power. Any party may withdraw from the CWS agreement with three months notice. This results in a sort of dysfunctional federalism with lowest-common-denominator results, as the provinces enter a race to the bottom in the effort to come up with a Canada-Wide Standard.

Two stakeholder consultations, in October of 1998 and May of 1999 were held for the development of CWS for PM and ozone. As a result, "in part," [16] of stakeholder input, the following standards were accepted by the CCME on November 29, 1999 for endorsement in May of 2000:

  • · PM2.5: 30 µg/m3, 24-hour averaging time, by 2010; achievement to be based on the 98th percentile ambient measurement annually, averaged over 3 consecutive years
  • · Ozone: 65 ppb, 8-hour averaging time, by 2015; achievement to be based on the 4th highest measurement annually, averaged over 3 consecutive years.

These standards can be compared to the published reference levels for both pollutants, keeping in mind the evidence, as ratified by the CCME in its CWS document, that there are in fact no lower thresholds at which adverse human and environmental effects do not occur. Also notable is the absence of a standard for PM10. The explanation given is that there is higher correlation for health effects with PM2.5, PM10 affects a smaller proportion of the general population, and reduction to ambient levels of PM2.5 will result in some reduction of PM10 levels. Annexes to the Standards document describe "Keeping Clean Areas Clean" and "Continuous Improvement" clauses, as well as details for exemptions of communities unable to reach achievement due to transboundary pollutants and high "natural" background levels.

The Keeping Clean Areas Clean clause discourages communities with achievement below CWS from "polluting to the limit." Continuous Improvement is related in that it calls to communities which have levels below CWS, but still well above those at which adverse human health effects occur (ie. zero), to encourage them to achieve continuously lower levels. Communities that after "best efforts" still cannot achieve CWS levels due to transboundary pollutants and notably higher "natural" levels, will be exempt from achievement. Action will be taken on the part of federal and provincial governments to reduce external and internal transboundary flow so that achievement of CWS can eventually be reached.

There are various other components to the CWS for PM and ozone. Included is that CWS achievement is only applicable to communities with populations larger than 100,000, excluding rural communities and non-urban industrial sites. Monitoring equipment, as well, will only be stationed where the people "live, work and play," not at "rural (or background) and source specific sites."

Health and Environment Link

In perusing the CWS document pending endorsement by the CCME, the environmental link to human health, as well as to the pollutants in general, is significantly lacking. Despite the initial quote in the Problem Statement of this section that was issued in June of 1998, the most current document states that "since the current CWS are related primarily to protection of human health, their adequacy for the protection of vegetation, visibility impairment, material damage or other adverse effects may need to be assessed."16

As mentioned in the Science section of this paper, scientific links are established between PM and ozone and effects on vegetation, visibility impairment, material damage and animal health. That those generally-accepted links exist in the scientific community is not a controversial notion. The controversy exists over the details of particular links.

Within the regulatory process, as with the science, controversy remains over how to deal with transboundary pollutants and "natural" background levels of pollutants. This is because the CWS follow the science without a clearly established position. Many industries in the stakeholder process argued that background levels in some areas were higher than, or too close to, proposed targets (these were targets of 20 µg/m3 and 25 µg/m3 for PM2.5 and 40 ppb or 60 ppb for ozone proposed by the ENGO and Health sectors respectively). They argued that background levels made such targets fundamentally unachievable, and that such standards blew out of proportion the adverse effects of these pollutants at background levels (ie. if mother nature is doing it too, it can't be so bad for us.) As mentioned in the Science section, LRTAP is likely to significantly effect "natural" background levels, rendering the levels as they are recorded and established now misleading.


The existence of the division between human health and environmental effects is arguable in itself, and is exemplified through the integral notion of primary importance that is given to human health above destruction of the environment. As mentioned, if vegetation and other wildlife are affected by these pollutants, is it not prudent to assume direct potential risk to humans, if not to assume that we will in fact be affected through the complicated interdependency of food chains and webs in the biosphere? The protection of the environment and all organisms it hosts for their intrinsic value, not only for their utilitarian and service values, is also arguable.

The CWS approach, in terms of the calculations used to arrive at the standards, is ineffective in dealing with background levels of pollutants and LRTAP. Clauses exist for the exemption of communities unsuccessful of achievement due to high background levels, but exemption of accountability due to these and transboundary pollutants (that arguably affect background levels in the first place) is already worked in to the calculation for achievement. For PM2.5, achievement is based on the 98th percentile measurement annually, averaged over three consecutive years. This already allows for a so-called smoothing out of extreme data from "high days" due to background, transboundary, or internal levels.

The makeup and thus the application of scientific health studies (whether epidemiological or lab oriented) is also of concern. Aside from the specified studies using children, most are conducted on healthy, younger-middle-aged men. As long as these tests are conducted and thus applied in this manner, they will not sufficiently represent the needs and concerns of women and the elderly, who outnumber the population represented by the data. This concerns the represented population directly as well, not only in regard to their friends and family. A woman's body is, after all, the first environment for all humans, past and present.

Most importantly, in direct relation to the regulatory process, there is more than enough research detailing the risks of exposure to PM and ozone to warrant the implementation of the Precautionary Principle. This is described in the Canada-Wide Environmental Standards Sub-Agreement as: "where there are threats of serious or irreversible environmental damage, lack of full scientific certainty shall not be used as a reason for postponing the development and implementation of standards." An unrecognized, uncertain or denied risk is still a risk. Despite attractive attributes such as the Keeping Clean Areas Clean and Continuous Improvement clauses, the standards as proposed to the CCME do not reflect implementation, serious or otherwise, of the precautionary principle.

Instead of the Precautionary Principle, cost/benefit analyses such as the Air Quality Valuation Model (AQVM) are given increased weight in the determination of standards. This raises many questions regarding the efficacy of these analyses that address how they are conducted as well as how they are used in the standard-setting process: Can non-monetary costs and benefits be accurately given dollar values? Should they be given dollar values? Can and/or should we risk financial debt or economic shift in order to eliminate these pollutants? Should we let finances influence our decision at all?

There are a few examples that illustrate potential destinies for us, depending on the decisions all of us make today (and some of us make in May of 2000). The issues of banning Bovine Growth Hormone in Canada, and the labelling of cigarette packages by the attorney general of the US were both carried out in adherence to the precautionary principle, without infallible scientific proof. They avoided potential or continued risks to human health in varying degrees, all of which is proven to us as research continues. And as research continues, there is always possibility for ammendment - which may result in more stringent or less stringent standards, depending on the research. In either case, the possibility of further human and environmental health risks are avoided.

The question is whether we would rather risk futher debilitated human and environmental health, or risk moderate decreases of monetary profits. The issues of lead in gasoline and DDT are examples of the opposite. Both substances took many years to be banned, and waited for the infallible evidence that was eventually provided by not only the scientists, but the numerous living and dead subjects of what turned out to be a vast human experiment.

Note: This paper was undertaken as part of a student term project at Dalhousie University


[1]. Ground-Level Ozone - Science Assessment Document (SAD), Federal-Provincial Working Group on Air Quality Objectives and Guidelines for the Canada-Wide Standards (CWS) process (Feb. 1999).

[2]. Health Canada, Environment Canada. Particulate Matter - SAD, CEPA Working Group on Air Quality Objectives (1998).

[3].University of Delaware. "Smog Impacts: Hurtling through airways, tiny particles may do more damage than previously assumed." August 1999. Available: Dec. 1999.

[4].Health Canada, Environment Canada. National Ambient Air Quality Objectives for Particulate Matter, Executive Summary "Part 1: Science Assessment Document" Report by the CEPA Working Group on Air Quality Objectives. October 1998. 8-10.

[5].Government of Canada. "Phase 2 Federal Smog Management Plan." November 1997. 14-15.

[6].Ground-Level Ozone - Science Assessment Document (SAD), Federal-Provincial Working Group on Air Quality Objectives and Guidelines for the Canada-Wide Standards (CWS) process (Feb. 1999).

[7].Dockery DW. et al., "An Association between Air Pollution and Mortality in Six US Cities," The New England Journal of Medicine 329 (24) (1993). 1753-1759.

[8].University of Delaware. "Smog Impacts: Hurtling through airways, tiny particles may do more damage than previously assumed." August 1999. Available: Dec. 1999.

[9].CWS Development Committee (DC) for PM and Ozone. "Discussion Paper on Particulate Matter (PM) and Ozone: CWS Scenarios for Consultation." May, 1999.

[10].Ground-Level Ozone - Science Assessment Document (SAD), Federal-Provincial Working Group on Air Quality Objectives and Guidelines for the Canada-Wide Standards (CWS) process (Feb. 1999).

[11].Tilman, Anna. "The Quality of Air Why We Need To Care: A Critique of Current Air Quality Issues in Ontario." York University, Toronto. November, 1998.

[12].Freedman, Bill. "Environmental Science: A Canadian Perspective." Scarborough, ON: Prentice-Hall Canada. 1998. 331-332.

[13].University of Delaware. "Smog Impacts: Hurtling through airways, tiny particles may do more damage than previously assumed." August 1999. Available: Dec. 1999.

[14].Federal-Provincial Working Group on Air Quality Objectives and Guidelines for the Canada-Wide Standards (CWS) process. Ground-Level Ozone - Science Assessment Document (SAD). Executive Summary. (Feb. 1999).

[15].CWS-DC for PM and Ozone Information Package for Consultations. June 1998.

[16].CCME, CWS for PM and Ozone. November 29, 1999.