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Overview of Recent Critical Load Efforts in the U.S.

Richard Haeuber
US EPA, Clean Air Markets Division (6204J)
Ariel Rios Building, 1200 Pennsylvania Ave., N.W., Washington, D.C. 20460


Critical loads may be a promising approach to assess implementation of current air quality programs in the U.S. and inform development of future policies and programs to protect ecosystems from air pollution impacts. Development of critical loads is at an early stage in the U.S., with a relatively small number of critical loads efforts, generally at site-specific scales. While site specific critical loads are useful in assessing ecosystem conditions, a number of technical issues must be addressed before a critical loads approach in the U.S. context can be developed for broader regional scales. These issues include ecological indicators and threshold values, critical loads models, data availability, environmental monitoring, and communicating data and results in a policy and management context. Various national and regional scale critical loads projects and activities are currently underway throughout the U.S. This talk provides an overview of recent critical loads projects and their potential for helping to address technical aspects of critical loads development and implementation in the U.S.