Return to ASDWA's Newsroom

The National Academies Release Report on Legionella

Today, the National Academies of Science, Engineering, and Medicine (NASEM) released a report new report on LegionellaManaging Legionella in Water Systems. The report is a result of the U.S. Centers for Disease Control and Prevention (CDC), the U.S. Image result for national academies of sciences engineering and medicine logoDepartment of Veterans Affairs (DVA), the U.S. Environmental Protection Agency (EPA), and the Alfred P. Sloan Foundation asking NASEM to address the state of the science with regard to Legionella.

The comprehensive report reviews the following:

  • Diagnosis, Ecology, and Exposure Pathways
  • Quantification of Legionnaires’ Disease and Legionella
  • Strategies for Legionella Control and Their Application in Building Water Systems
  • Regulations and Guidelines on Legionella Control in Water Systems

Some of the highlights from the report’s conclusions and recommendations include: 

  • For all types of buildings, hot-water heater temperature should be maintained above 60°C (140°F) and the hot-water temperature to distal points should exceed 55°C (131°F).
  • There is growing evidence that, compared to free chlorine, a monochloramine residual better controls Legionella risk from building water systems, although the reasons for the improved performance are not yet clear.
  • Additional research is needed to evaluate the potential for nutrient limitation (concentration and composition) to control Legionella growth in distribution and building water systems.
  • New NSF/ANSI standards regarding microbial growth potential of materials are needed so that water utilities, plumbers, and building contractors can include Legionella control when making decisions about pipe material usage.
  • There is clear evidence of Legionella amplification in the distal parts of some hot-water systems, likely due to a combination of water stagnation and loss of temperature control and disinfectant residual.
  • Research is needed to better understand the persistence of distribution system disinfectant residuals within building plumbing.
  • Guidance about Legionella is needed for homeowners, especially consumers from at-risk segments of the population.
  • Require Water Management Plans in All Public Buildings Including Hotels, Businesses, Schools, Apartments, and Government Buildings.