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RAY HOZALSKI CONT...6 CEGE | CSE.UMN.EDU/CEGE study was looking at various disinfectants, the byproducts produced, and what concentrations led to the best results in terms of minimizing exposures to both opportunistic pathogens and disinfection byproducts. The research team working on the large USEPA project consisted of Hozalski, his CEGE colleague Timothy LaPara, and their students and post-doc at the University of Minnesota, along with professors Srijan Aggarwal from the University of Alaska Fairbanks, Carsten Prasse of Johns Hopkins University (Baltimore, Maryland), and John Sivey of Towson University (Towson, Maryland) and their staffs. That project was carefully planned: the researchers planned to gather data over six seasons, including twice in consecutive summer and fall seasons, where the warmer water favors the growth of Legionella pneumophila. The researchers gathered samples from 21 water treatment plants operated by 18 water utilities across the continental U.S. and Alaska. Samples from each site were gathered by utility personnel and half of the samples shipped to Maryland for analysis of disinfection byproducts at Towson University. The Minnesota team would analyze the other half for Legionella pneumophilaand other opportunistic pathogens. When he got the call from MDH, Hozalski was able to add the Grand Rapids system into his larger, ongoing research project. This proved to be helpful from a research perspective because of the unique aspects of the Grand Rapids situation, but also from a public health perspective because it enabled rapid high quality data to be collected to help the team of experts recommend potential solutions. Results from Grand RapidsBecause of the number of buildings around the city that tested positive for Legionella pneumophila in testing done by MDH, the City, and Hozalski%u2019s team, it was determined that the source of the organism had to be the city water supply. Interestingly, despite the ongoing outbreak, Legionella pneumophila was not detected in the so-called %u201cfinished water%u201d leaving the treatment facility nor was it detected in water samples collected from the city%u2019s water mains. The next step was to analyze water from several buildings within the city. There the team often found high levels of Legionella pneumophila. It seemed the bacteria was growing in the plumbing within the buildings. Finding high concentrations of these bacteria at showers and sinks, while failing to detect Legionella pneumophila in the water entering the buildings suggested that the organism was either present intermittently in the city supply or at concentrations too low to be detected by the team%u2019s methods.It appeared that without disinfection the combination of sufficient nutrients in the water supply and plumbing in the homes and commercial buildings of Grand Rapids was creating an environment conducive to the growth of Legionella pneumophila. Water from premise plumbing, showers in particular, seemed to be making some people sick.The Chosen Solution One option was to %u201cspot treat%u201d the problem, to flush and disinfect specific buildings found to have high levels of Legionella pneumophila. A few buildings did just that as a quick fix. However, disinfection at the individual buildinglevel would be difficult to implement and monitor, and the results would likely be inconsistent, perhaps resulting in continually chasing after contamination events. After lengthy deliberation among the team of experts, a centralized action involving disinfection at the water treatment plant was recommended, that would allow the disinfectant to spread and protect the entire city. Hozalski concurred. The City and the researchers determined that the source of the problem, the City water system, could also be the key to the solution. Because of his extensive research background and outstanding team of colleagues and students, Hozalski was able to offer insight into the occurrence of Legionella pneumophila in the system and remedial alternative. More careful consideration and testing by a consulting firm led the City to select the specific disinfectant to be used. In June of 2024, the City of Grand Rapids began dosing the disinfectant chloramine into the city%u2019s drinking water distribution system. Hozalski%u2019s USEPA Team was standing by to do the analysis.The ResultsIt has been a year since disinfection with chloramines was implemented in Grand Rapids, and no new cases of Legionnaires%u2019 disease have been reported. The intervention proved to be speedy and successful. This was very good news for the residents of Grand Rapids and an exciting scientific study for the Hozalski research team. Hozalski previously served on the U.S. EPA Science Advisory Board Drinking Water Committee. He was appointed to the U.S. EPA Science Advisory Board Microbial and Disinfection Byproduct (MDBP) Revision Review Panel for 2025. The MDBP Revision Review Panel planned to review the draft analysis to support the EPA%u2019s revisions of the MDBP National Primary Drinking Water rules.