Marjorie F. Shepherd is Senior Science Advisor at the Atmospheric and Climate Science Directorate, Meteorological Service of Canada. Her work involves investigating sampling and analysis methodologies for ambient volatile organic compounds. She has coordinated several projects within the Canadian multi-stakeholder science assessment for ground-level ozone. As science advisor for the Meteorological Service of Canada, she co-lead, with Health Canada, the development of science assessments for HF, CO, ozone and particulate matter - all in support of developing Canadian air quality objectives and standards.

James S. Vickery is one of the founding members of NARSTO and a member of the Executive Steering Committee. He is a Co-Leader of the US Committee on Environment and Natural Resources - Particulate Matter Research Work Group, which coordinates all U.S. Federally sponsored research concerning particulate matter. He is Special Assistant to the Director of EPA's National Exposure Research Laboratory, where he has also held the positions of Division Director and Assistant Laboratory Director. He has also managed several different program and policy offices in EPA's Washington, DC headquarters.