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METHOD DETECTION LIMITS AND NON-DETECTS IN THE WORLD OF MICROBIOLOGY
Citation:
WASSON, S. J. METHOD DETECTION LIMITS AND NON-DETECTS IN THE WORLD OF MICROBIOLOGY. In Proceedings, 25th Annual EPA Conference on Managing Environmental Quality Systems, Austin, TX, April 24 - 27, 2006. U.S. Environmental Protection Agency, Washington, DC, 2006.
Description:
Examining indoor air for microorganisms is generally performed by sampling for viable microbes, growing them on sterile media, and counting the colony forming units. A negative result does not indicate that the source of the sample was free of fungi or bacteria, only that if present, the number of viable fungi or bacteria was below the limits of detection.
This is a problem where government officials declare a building inhabitable on the basis of no growth in a sample. The Government Accountability Office (GAO) and the public want the answer to a more pragmatic question: Is this building contaminated? Likewise lack of confidence in negative results is at issue where professional remediators of water damaged buildings are trying to gauge efficacy of their efforts to eradicate fungi and their spores, or where in-duct ultraviolet light technologies are being tested for kill of vegetative bacteria.
Decision makers want to know with certainty whether potentially dangerous microbiological organisms still exist in the structure while even the most sophisticated sampling and analysis methods available cannot provide conclusions with 100% certainty.
This paper explores sampling indoor air and surfaces for microorganisms, their analysis, the interpretation of the results, and the state of governmental regulation of acceptable levels of such organisms.