National Ambient Air Quality Objectives For Ground-Level Ozone- Summary - Science Assessment Document

Preface

The Canadian Environmental Protection Act (CEPA), passed into law in 1988, replaces and builds upon the Clean Air Act and the Environmental Contaminants Act. The opening statement of the Act declares that "the protection of the environment is essential to the well-being of Canada". CEPA allows the Federal Government to assess substances and control their impact through national environmental quality objectives, guidelines, codes of practice, and/or regulations.

Provincial Governments have the primary responsibility in many areas of air pollution control, with federal actions integrated with those of the provinces. The CEPA Federal/Provincial Working Group on Air Quality Objectives and Guidelines (WGAQOG), consisting of representatives of federal, provincial and territorial departments of environment and health, reviews and recommends national ambient air quality objectives.

Canada's National Ambient Air Quality Objectives(s) (NAAQOs) prescribe targets for air quality, measured at the relevant receptor (persons, plants, animals, materials). National Ambient Air Quality Objectives are national goals¹ for outdoor air quality that protect public health, the environment, or aesthetic properties of the environment. The development of NAAQOs involves first, a scientific review of the physical and chemical properties of a substance, its sources, environmental, animal and human health effects, and an assessment of environmental and human exposure to the substance. Secondly, this information is integrated within a framework of risk assessment. The Science Assessment Document contains this critical scientific evaluation, and lays the scientific groundwork for establishing the air quality objectives. Reference Levels, levels above which there are demonstrated effects on human health and/or the environment, are identified. A document outlining the process followed in reviewing and interpreting the scientific information is published separately.² This document contains the scientific evaluation of Ground Level Ozone.

National Ambient Air Quality Objectives are targets for focussing air quality management strategies and plans. The derivation of these targets may consider some elements of benefit/risk analysis, reflecting a philosophy of environmental health protection and long term risk reduction while recognizing technological and economic limits. The broad range of potential responses by ecosystems, populations, and organisms in the environment are considered. Given the range of sensitivities within and among these environmental components, the resulting objectives may not protect all.

The process of establishing National Ambient Air Quality Objectives is a dynamic and continuous one. Air quality objectives are established to reflect the current state of knowledge about an air pollutant, to provide a national indicator for assessing the quality of air in all parts of Canada, and to provide guidance to governments for making risk management decisions such as planning control strategies and setting local standards.

It is recognized that not all locations in Canada will meet these air quality objectives immediately, or at all times, and that priority given to meeting these values may be based on factors such as available control technology, costs, benefits, and the degree to which the recommended objectives are exceeded. The expectation is that strategies will be implemented to facilitate the reduction of ambient air concentrations to a level at or below the air quality objective(s) as soon as practicable. The principles of continuous improvement and nondegradation of environmental quality are advocated.

NOTE: In January 1998, Canadian Environment Ministers (with the exception of Québec) signed the Canada-Wide Accord on Environmental Harmonization and its sub-agreement on Canada-Wide Standards (CWSs). The CWS process provides new tools for the management of environmental issues of national interest. Recognizing that both NAAQOs and CWSs have a role to play in the management of air quality, federal, provincial, and territorial health and environment departments have integrated the NAAQO and CWS processes. Air pollutants that have been identified by governments as needing to be managed will be targeted for either CWS or NAAQO development, not both.

In January 1998, Environment Ministers identified ozone as a priority for Canada-Wide Standards. As a result, federal, provincial, and territorial health and environment departments agreed that NAAQOs for ozone will no longer be developed. Rather, this Science Assessment Document will form the Risk Assessment report for the development of CWSs for ozone.

NOTE: This Science Assessment Document is, in general, a federal-provincial consensus document. One member of the WGAQOG, Alberta, does not, however, support some of the recommendations, including the form of the LOAEL for vegetation and the recommended Reference Levels for Human Health. This position is based on issues regarding the science and its application with respect to ozone impacts on health and the environment. Alberta nevertheless supports the publication of this document and believes that this document will make a positive contribution to the efforts of reducing ambient ozone levels in Alberta. More information on Alberta's position can be obtained from Alberta Environment, Environmental Sciences Division at (780) 427-5883 or from www.gov.ab.ca/env/protenf.html .

---