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

1. Introduction

The Canadian Environmental Protection Act (CEPA) allows the Federal Government to assess substances and control their impact through national environmental quality guidelines, codes of practice, and/or regulation. Provincial Governments have primary responsibility in many other areas of air pollution control, with Federal actions integrated with those of the Provinces. Under CEPA, the 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 (NAAQOs) are national goals¹ for outdoor air quality that protect public health, the environment, or aesthetic properties of the environment. NAAQOs are developed in two stages, the first of which is the science assessment stage, embodied within the Science Assessment Document. Reference Levels for the pollutant of concern are identified as part of the science assessment process. A Reference Level is a level above which an effect on a receptor (human or environment) has been demonstrated. Reference Levels may be proposed for one or more time periods (e.g. 24 hour, annual) and for one or more receptors (e.g. humans, vegetation). The Science Assessment Document concludes with a characterization of the risk to various receptors from exposure to ambient levels of the pollutant in the Canadian environment.

This document contains the scientific assessment of Ground Level Ozone effects on human health, vegetation, materials and animals. The document was prepared primarily as a compilation of the Canadian 1996 NO_x/VOC Science Assessment Reports². Consequently, background sections of the document, included to provide contextual information for understanding the material on effects, have not been updated since publication of the NO_xVOC reports. The information on health and environmental effects was augmented by a review of the most recent peer-reviewed and publicly available literature, current to mid-1997. The issue of the human health effects of ozone is, in particular, a field of inquiry that is evolving rapidly. The document itself has been externally peer-reviewed. Although prepared in support of revisions to the current NAAQOs for ground level ozone, this document will be used as scientific support for the development of Canada Wide Standards for ground-level ozone.

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