It is unrealistic to place on building owners and operators the burden and risk for providing pathogen-free water throughout buildings when the water delivered to their buildings contains Legionella bacteria.

Legionella is commonly found in source waters and in the soil, and thus, if untreated at the municipal water treatment plant and in the distribution systems, the Legionella bacteria will necessarily find its way into buildings.

More needs to be done by the municipal water suppliers to minimize Legionella bacteria in the drinking water supply before it can enter building water systems. Legionnaires’ disease is the number one waterborne disease associated with potable water in the United States, and it is lethal; approximately 10% of those who contract the disease will lose their lives.

Preventive measures

Minimizing water pathogen risks is a shared responsibility between municipal water suppliers and building owners. At present, however, regulatory efforts seek to put responsibility for all preventive measures on building owners and operators. Consider the following:

Water management plans based on standards like ANSI/ASHRAE Standard 188, Legionellosis: Risk Management for Building Water Systems, or the Centers for Disease Control and Prevention’s (CDC) toolkit, “Developing a Water Management Program to Reduce Legionella Growth and Spread in Buildings: A Practical Guide to Implementing Industry Standards,” typically require testing for Legionella in building water systems.

Current U.S. Environmental Protection Agency (EPA) regulations do not require municipal water suppliers to test directly for Legionella bacteria in their water systems.

Providing pathogen-free water

Water management plans are recommended and encouraged for building water systems

Water management plans are recommended and encouraged for building water systems, especially in high-risk buildings like hospitals and senior citizen housing. But water suppliers must also assume responsibility for providing pathogen-free water in the first place.

Typically, after Legionnaires’ disease outbreaks, water suppliers state that the water “meets all EPA regulations.” This may be true, but that does not mean that the water is Legionella-free. As discussed below, EPA regulations are inadequate when it comes to requiring municipal water utilities to take actions to eliminate bacteria in the water supply.

A Paradigm Shift is Due

Water utilities/municipal providers are not required to monitor for Legionella

Because Legionella bacteria exist in nature and are common in source waters, measures can and must be used to minimize Legionella levels in the municipal water supply. This, in turn, would minimize the presence of such bacteria in our homes and buildings.

There is, however, a fundamental flaw in the EPA rules used to control or regulate Legionella bacteria. The EPA does set a maximum contaminant level goal (MCLG) of zero for Legionella. The problem is that it is simply a goal. Therefore, it is not enforceable, so water utilities/municipal providers are not required to monitor for Legionella, nor are they required to take action to minimize its presence.

Presence of Legionella

This column explores three recent studies that investigated the presence of Legionella in downstream water systems, including sediments in municipal drinking water storage tanks (MDWST) with 1 to 5 million gallon (3.8 to 19 million L) capacity, point-of-use cold water taps, and cooling towers. These studies show that the EPA’s policies for controlling Legionella are not working.

The flaw is in the EPA National Primary Drinking Water Regulations (NPDWR) and how this is putting additional stress on public and private systems downstream of treatment plants. These studies sampled sites across the nation and evaluated for Legionella using quantitative polymerase chain reaction (qPCR).

The qPCR technique screens and quantifies selected microorganisms like Legionella and has the distinct advantage of being able to detect even low levels of the bacteria. It works by amplifying the specific sections of DNA being investigated and measures them in real time, giving researchers information on the type and concentration of DNA.

Inadequate methods of control

The results demonstrate that the current methods to control the spread of Legionella are inadequate

The samples tested positive for Legionella pneumophila and Legionella pneumophila serogroup 1 (the most virulent strain) in all studies. The results demonstrate that the current methods to control the spread of Legionella are inadequate to minimize the risk of infection in municipal water distribution systems, allowing contaminated and potentially lethal water to enter facilities 24/7/365.

These three broad, independent studies were carried out by the EPA and the CDC to measure pathogen levels across the country in diverse drinking water systems: water storage tanks, tap water, and cooling towers.

Looking at all three studies combined, approximately one-third of the drinking water samples tested positive for Legionella pneumophila at all three points along the drinking water distribution route after leaving water treatment plants. Notably, 20% to 28% of samples in each of the three studies were infected with Legionella pneumophila serogroup 1, the most lethal strain responsible for 90% of Legionnaires’ cases.

Water Storage Tanks Study

The remarkable similarity of the results provides evidence that Legionella is present when it leaves the municipal source and can and does enter building systems where people are exposed.

In 2015, the EPA published the results of a study carried out to determine the level of potential pathogens including Legionella pneumophila bacteria present in municipal water storage tanks.

Eighty-seven sediment samples were taken from municipal drinking water storage tanks (MDWSTs) in 18 locations in 10 states that spanned five regions: Northeast, East Coast, Midwest, South and West Coast, providing a diverse sample set.

Samples tested

Statistical analyses were done to establish correlations between Legionella, Acanthamoeba and temperature

These municipalities sourced their water from a mixture of 61% groundwater and 39% surface water. At all locations, the water in the tanks contained chlorine concentrations that met EPA regulations.

The water was completely drained from each tank before sediment collection was carried out using a sterile plastic spatula and bottle. A quantitative polymerase chain reaction (qPCR) analysis was performed on each sample.

Statistical analyses were done to establish correlations between Legionella, Acanthamoeba and temperature as well as other independent variables like total organic carbon (TOC), total organic matter (TOM), particle size and pH. These variables were recorded at the time of sampling for use in the analysis.

Detection of Acanthamoeba

The results of the study indicated that Legionella bacteria were present in 66.7% of the samples; Legionella pneumophila was present in 33% of samples; and Legionella pneumophila serogroup 1 was present in 28% of the samples. In contrast, Escherichia coli (commonly known as E. coli) and Giardia were undetected.

This shows that while efforts to control E. coli and Giardia work, the efforts to control Legionella do not. Another important finding: there was a significant correlation between Legionella and Acanthamoeba.

Survival in drinking water storage tanks

Legionella bacteria will amplify and increase its virulence inside amoeba. This further supports a relationship between the two, so the detection of Acanthamoeba may be used as a potential indicator of Legionella contamination.

The results of this nationwide study, demonstrate that Legionella that is present in the municipal water system will continue to survive in drinking water storage tanks in addition to surviving in large buildings’ plumbing systems.

This reinforces the need for anti-Legionella measures at the water treatment plant and distribution system - before the water gets to water storage tanks where it will then be passed on to buildings and homes.

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