The past decade has been noteworthy for an increase in frequency, severity, and variety of recreational water illness (RWIs) associated with treated pool and spa water. During this same period, the standard practice has been to rely strictly upon rapid tests of the free chlorine concentration as a surrogate of microbial water quality. This practice was developed at least forty years ago and has not been reassessed in North America since. Thus, we have failed to develop an appreciation of the microbial flora on treated pool and spa water during normal operations – and we know that the water is far from sterile. Further, the reliance on free chlorine alone developed long before we recognized threats from moderately to highly resistant parasites (Giardia and Cryptosporidium, respectively), biofilm associated bacteria (Pseudomonas and Legionella), or those from inhalation of microbial fractions (hypersensitivity pneumonitis induced by Mycobacterium avium complex). While the CDC’s biennial waterborne disease outbreak summaries report the types o RWI outbreaks that have occurred, those same summaries are seldom able to document the concentration of pathogens during the outbreak and do not deal with the planktonic flora during normal operations. Not only is data on the diversity of normal flora rather spotty, the data on the survival rates of pathogenic bacteria, parasites and viruses in actual pool or spa water is almost entirely lacking. Most recently, this paucity of data has resulted in academic debates on the hazard potential of Naegleria and community acquired methicillin-resistant Staphylococcus aureus (ca-MRSA) in pools and spas, respectively. This paper will summarize the historical findings and contrast them with the results of a flora study currently underway in our laboratory. Roy D. Vore, Ph.D. is currently the Senior Research Microbiologist for DuPont Chemical Solutions Enterprise in Wilmington, DE. Dr. Vore has 29 years experience in manufacturing and applied product development. He has 15 years of industry experience in the management of microbiological issues, including recreational water. He has participated in numerous product launches from concept to technical support in the market. He has worked extensively with regulatory agencies including the US EPA, California Department of Pesticide Regulations and the Canadian Pesticide Management Agency. He has written 40+ technical articles and presentations on microbiology, microbial physiology, the preservation of aqueous systems, and the protection of human health in recreational water. Dr. Vore has been the co-inventor on four patents on the use of antimicrobials in recreational water. He received his M.B.A. from Pittsburg State University and his Ph.D. from the University of Arkansas.
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