Factors affecting TRI release estimate change from year to year for American Electric Power facilities:

Overview: TRI release estimates are influenced by numerous factors. These factors include: fuel use and characteristics, data source changes, facility operational changes and updated estimation methodologies.

1. Fuel Use and Characteristics: Fuel for a facility is purchased from different sources depending on market conditions. The chemical characteristics of different coal mixes can vary depending on the amount of fuel from each source, which contributes to fluctuations in TRI estimates from calendar year to calendar year.

2. Data Source Changes: New or additional sampling data was collected to meet existing regulation requirements.This new data, coupled with inherent analytical variability is used in release estimates.

3. Facility Operational Changes: Changes in customer demand and economic conditions cause fluctuations in generation. These operational changes impact fuel usage, which in turn impacts TRI release estimates. Coal combustion products, which correlate directly to fuel usage, also may change, which contributes to a change in total releases to land.

4. Estimation Methodologies: TRI data are developed using Electric Power Research Institute (EPRI), U.S. EPA, and other research and government organization estimation methods. Continuing research revises and updates these methods to provide more accurate estimates and this affects data from year to year.

5. New Technologies: Installation of equipment for process improvements or pollution prevention may impact releases. Process or equipment modifications may change the release totals, shift the release amounts from one media to another, or require use of chemicals not previously reported.