The International Air Quality Advisory Board (IAQAB) was established by the International Joint Commission (IJC) in 1966 in response to a request to the IJC from the Canadian and United States governments to observe air quality along the boundary between these two countries. Since that time, the Board has provided advice on transboundary air issues by various means, including the preparation of progress reports.

In this, its 25 ^th progress report, the Board continues to inform and advise the International Joint Commission on transboundary air quality issues pertaining to the Criteria or common air pollutants - particulate matter, ozone, sulphur dioxide, and nitrogen oxides. Given the Commission's focus on climate change in its report "The IJC in the 21 ^st Century," the Board also considers the most recent evidence of warming of the earth's surface and possible associated effects of this phenomenon.

The Board also continues its reporting on the control, transport and deposition of persistent toxic substances with regard to the Great Lakes basin. Its most recent summary on this subject can be found on the Board's website at http://www.ijc.org/rel/boards/iaqab . A written summary of transport and deposition aspects of this work is part of the 1997/99 Report on Great Lakes Priorities which is available on the Commission website ( www.ijc.org ) as well as in printed form through the IJC Great Lakes Regional Office. The Board's Special Report, issued in November of 1998 and also available on the IAQAB website, brought these two themes together as part of its survey of issues of particular interest in specific regions along the boundary.

In this report, the Board reviews and advises on current developments, including consideration of an Ozone Annex by the Canada-United States Air Quality Committee, the evolution of Canada-wide standards (CWS) for particulate matter, ozone, mercury and benzene, the Ontario Strategic Attack on Air Pollution, principally sulphur dioxide and nitrogen oxide control and associated emissions trading provisions, United States Environmental Protection Agency (USEPA) actions on NO _X emissions, particularly from coal-fired utilities and the status of the NO _X State Implementation Plan (SIP) call affecting several states, further restrictions on vehicle emissions, including fuel content regulation, consideration of particulate emissions from diesel engines, and discussion of sources of mercury (coal-fired utilities) and dioxin (open residential burning of refuse). As mentioned, climate change indicators and possible effects are also reviewed.