devising a regulatory and management strategy that recognizes and accommodates this variability, combined with a measurement plan that collects sufficient information to address concerns and direct future efforts. This approach will vary with the substance and with the concern. For example, potential effects on human health will generally be inferred from short-term (e.g., hourly or daily) local concentrations (and compositions in the case of particulate matter), whereas effects on climate change will be inferred from regional or national annual emission inventories.

In an ideal world, the data would be accurate and precise, broad in coverage of both substances and AFO types and operations, based on sound sampling plans, timely, detailed (addressing geography, time intervals, climatic conditions, etc.), well documented, in a readily accessible form, and inexpensive. Meeting all of these desirable features will undoubtedly lead to conflicts, so compromises must be made.

CHALLENGES

Facing the need for defensible information on air emissions from AFOs in a timely manner is a major challenge for EPA and USDA. Neither has yet addressed the need for this information in defining high-priority research programs. Neither has asked for nor secured the level of funding required to provide the necessary information. Each has pursued its regulatory and farm management programs under the assumption that the best currently available information can be used to implement its program goals.

The committee believes that the scope and complexity of the information needed by these agencies, as well as the potential environmental impacts of air emissions from AFOs, require a concentrated, focused, and well-funded research effort. Such an effort is described in this report.

STRUCTURE OF THE FINAL REPORT

Chapter 2 describes in broad terms the economics and operating practices of the animal feeding industry and its major sectors (dairy, beef cattle, swine, and poultry). This chapter, along with Chapter 6 on government regulations and programs, sets the stage for the other chapters, which address more directly air emissions and the scientific bases for estimating their rates, concentration, and distribution.

Chapter 3 describes the kinds of air emissions produced by animal feeding operations and their potential impacts on the environment and human health. Chapter 4 examines the state of the science for measuring air emissions, including measurement principles and techniques suited to various on- and off-farm situations. Chapter 5 describes approaches for estimating air emissions from AFOs, including an evaluation of a process-based (mass balance) approach for



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