The Task Force on Hemispheric Transport of Air Pollution (TF HTAP) is an international scientific cooperative effort to improve the understanding of the intercontinental transport of air pollution across the Northern Hemisphere. TF HTAP was organized in 2005 under the auspices of the UNECE Convention on Long-range Transboundary Air Pollution (LRTAP Convention) and reports to the Convention’s EMEP Steering Body. However, participation is open to all interested experts, both inside and outside the UNECE region.

TF HTAP organizes scientific cooperation in the areas of emissions inventories and projections, analysis of ambient monitoring and remote sensing, global and regional modeling, and impact assessment to understand the intercontinental flows of ozone and its precursors, fine particles and their components, mercury, and persistent organic pollutants (POPs). The main questions of interest to the TF HTAP relate to the benefits of international cooperation to decrease air pollution emissions:

- How do air pollution concentrations (or deposition) in one region of the world change as emissions change in other regions or the world?

- How do changes in emissions outside a region affect the health, ecosystem, and climate impacts of air pollution within a given region?

- How does the feasibility of further emissions control differ in different regions of the world?