Abstract Microbial source tracking (MST) is a powerful emerging technology that identifies sources of fecal pollution in impaired waters. Four different approaches to MST methods are currently being developed. The first uses a database or “library” of known sources of fecal bacteria (i.e., humans, livestock, companion animals, wildlife, etc.) that are “fingerprinted” by a variety of biochemical or molecular protocols. Fecal bacteria of unknown source (isolated from polluted waters) are compared against the library to look for fingerprint. To date this has been the most widely used approach. The second uses DNA sequences in fecal organisms that are unique to specific sources. At this time, only a few useful source-specific sequences have been found, but this approach probably represents the future of MST as libraries, and in some cases cultivation of the fecal organisms, are not needed. The third involves detection of chemicals that are unique to human-origin pollution, such as optical brighteners in detergents and caffeine from beverages. This approach has been successfully deployed, especially in urban settings. The fourth approach uses DNA sequences or serum immunoglobins from specific sources rather than from fecal organisms within those sources. This is a new approach that has not been thoroughly tested. Currently a great deal of attention is focused on the problem of guarding the safety of the nation’s waters food supply from both accidental and deliberate threats. But the very recognition of a threat can only be made by comparison of that potential threat with a baseline of “normal” conditions. MST is a technology that can be utilized both for creation of that baseline and for analysis of changes from the baseline. This poster analyzes how the lessons learned in the development of MST can be applied to problems faced identifying sources and/or remediation of threats to food and water safety. Application of Microbial Source Tracking Methods to Food Safety and Protection of Water Resources Charles Hagedorn 1 and Susan Allender-Hagedorn 2 1 Department of Crop and Soil Environmental Sciences, 2 Department of English and founding editor, Environmental Detection News and The Journal of Environmental Detection Source DNA Sequencing* (non-microbial) Source-specific DNA Source-specific immunoglobulins *humans, dogs, cattle, deer, waterfowl, etc. Library Fingerprinting of Target Organisms* Antibiotic/biochemical patterns Ribotyping and/or repetitive PCR Denaturing gradient gel electrophoresis Pulse field gel electrophoresis Amplified fragment length polymorphism *bacteria, viruses, protozoa Fecal DNA Sequencing (non-library methodology) Toxin biomarkers Reverse transcriptase PCR Length heterogeneity PCR Terminal restriction fragment length polymorphism Chemical Detection (non-microbial) Optical brighteners- detergents Fecal sterols and stanols Caffeine Cosmetic and drug residues Problems of Detection In Food Safety and Water Resource Protection  Source tracking is an emerging field and all methods are still under development and need improvement. It is not yet clear which methods and approaches will best serve the needs of other scientific disciplines.  Selected methods and target organisms will need to be evaluated for accuracy, specificity, and geographical and temporal stability when deployed by different communities for purposes other than water quality.  Criteria for determining reliability, management relevance, and cost and logistics will have to be developed as source technology is transferred to new environments and is expected to measure different things.  Once the issues with technology transfer have been accommodated, baselines, similar to those used in water quality, will have to be determined for new environments so that unusual occurrences (e.g., introduction of an introduced bioterrorism agent) would be recognized.  Many approaches to source tracking meet the requirements for new technologies desired by the food safety and water resource protection communities.