Why Legionella Isn’t Just a Hot Water Problem: Risks in Cold Water
Legionella is a waterborne pathogen that contaminates nearly half of all building water systems. It typically enters through the municipal cold water supply and thrives in areas of the water system with sediment accumulation, stagnant water, warm temperatures, or where other microbes are present. While hot water is often seen as the biggest risk for Legionella growth, cold water systems can also harbor the bacteria, making it a hidden threat in many buildings. Legionella in hot water systems Potable hot water systems, particularly untreated ones, can act as major reservoirs for Legionella growth. The most suitable temperature for Legionella growth is between 90°F and 120°F, making hot water systems a high-risk environment for Legionella. Legionella in cold water systems Legionella can survive in water temperatures below 77°F, making cold water systems susceptible to colonization. In fact, a research article published by the CDC found as many as 47% of surveyed cold water taps were positive for Legionella. Although cold water systems typically present less favorable conditions for Legionella growth compared to hot water systems, certain factors—such as elevated cold water temperatures and high sediment levels—can create an environment conducive to its survival. In warmer regions where cold water temperatures tend to be higher, the risk of Legionella colonization increases significantly. Legionella species in cold water Several types of Legionella can survive and grow in low temperatures, including Legionella pneumophila, the species responsible for most cases of Legionnaires’ disease in the United States. This strain prefers higher cold water temperatures, while other species like Legionella anisa and Legionella longbeachae tend to survive in colder environments. Although these non-pneumophila species are less likely to cause illness, they’ve been linked to outbreaks of Pontiac Fever. Controlling Legionella in cold water Effectively controlling Legionella in cold water systems requires a strategic approach that combines proven methods. The right solution will depend on factors like the level of contamination, the building’s location, and the vulnerability of its occupants, but a combination of the below water treatment technologies is typically recommended. By combining these solutions, you can significantly reduce the risk of Legionella in cold water systems. Copper-silver ionization, UV disinfection, and sediment filtration together offer a complete and proactive approach to creating safer and healthier environments in buildings. References Garner E, Brown CL, Schwake D, Rhoads WJ, Arango-Argoty G, Zhang L, et al. Comparison of Whole-Genome Sequences of Legionella pneumophila in Tap Water and in Clinical Strains, Flint, Michigan, USA, 2016. Emerg Infect Dis. 2019;25(11):2013-2020. https://doi.org/10.3201/eid2511.181032 Wadowsky, R. M., R. Wolford, A. M. McNamara, and R. B. Yee. 1986. Effect of temperature, pH, and oxygen level on the multiplication of naturally occurring Legionella pneumophila in potable water. Appl. Environ. Microbiol. 49:1197-1205. Rogers, J., A. B. Dowsett, P. J. Dennis, J. V. Lee, and C. W. Keevil. 1994. Influence of temperature and plumbing material selection on biofilm formation and growth of Legionella pneumophila in a model potable water system containing complex microbial flora. Appl. Environ. Microbiol. 60:1585–1592. Mauchline WS, James BW, Fitzgeorge RB, Dennis PJ, Keevil CW. Growth temperature reversibly modulates the virulence of Legionella pneumophila. Infect Immun. 1994 Jul;62(7):2995-7. Soderberg, M.A., Dao, J., Starkenburg, S.R., Cianciotto, N.P. 2008. Importance of type II secretion for the survival of Legionella pneumophila in tap water and in amoebae at low temperatures. Appl. Environ. Microbiol. 74(17):5583-5588. De Giglio, O., D’Ambrosio, M., Spagnuolo, V., Diella, G., Fasano, F., Leone, C. M., Lopuzzo, M., Trallo, V., Calia, C., Oliva, M., Pazzani, C., Iacumin, L., Barigelli, S., Petricciuolo, M., Federici, E., Lisena, F. P., Minicucci, A. M., & Montagna, M. T. 2023. Legionella anisa or Legionella bozemanii? Traditional and molecular techniques as support in the environmental surveillance of a hospital water network. Environmental monitoring and assessment, 195(4), 496.
