Never before have Canadians been as concerned about clean air. The federal government estimates that air pollution causes 5,000 premature deaths in Canada each year. Environmental and public health advocates believe the number closer to 16,000. If they are right, air pollution is responsible for approximately forty premature deaths across Canada every day. The magnitude and complexity of the threats to our clean air are staggering. Some of these threats - including smog, acid rain, and hazardous air pollutants - tend to be local or regional in scope. Others - such as ozone layer depletion and climate change - are truly global in nature. The need for action at all levels and in all sectors of society, within and beyond our borders, is undeniable. If solutions are to be found, citizens everywhere must become more effective advocates for clean air. This guide has been written in the belief that citizens can make a difference. Making a difference, however, depends heavily on being informed and strategic in advocating for change. A legal and scientific primer on clean air issues, this guide is intended to provide an accessible way for citizens across Canada to become informed about air issues and to serve as a practical reference source for those working to protect our air resources.