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HEALTH AND SANITATION
Q&A on legionella control
in premise plumbing
As we conclude our legionella series, we address some common topics.
By Environmental Protection Agency, document EPA 810-R-16-001
Although these are some common points that arise,
it is important to always seek the advice of qualified
professionals who can give the correct guidance
required for such instances where legionella occurs
or is discovered. It must also be noted that advances
in the control of legionella and such pathogens are
continuous, and updated methods of control may be
applicable. Please see the EPA document EPA 810-
R-16-001 for any supporting information.
What are the threats from legionella
in a premise plumbing system?
Legionella spp. are naturally occurring bacterial
pathogens that can be present in municipal and other
water supplies. Premise plumbing systems may provide
conditions (for example long water residence times,
water temperatures favourable {warm} for legionella
growth, and low disinfectant residual levels) that favour
growth of legionella, to levels that may result in increased
risk to public health.
Do all species of legionella cause disease?
Although most of the diagnosed cases of legionellosis
(legionnaires’ disease and Pontiac fever) are associated
with legionella pneumophila (serogroup 1), approximately
half of all the species of legionella have been associated
with clinical cases of legionellosis. However, it is probable
that most legionellae can cause human disease under
the appropriate conditions (for example in individuals in
higher-risk groups).
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Do you need to eliminate all legionellae
in order to have a safe building environment?
Not necessarily. Due to the highly variable and
inconclusive information that is available, it is not feasible
to establish a definitive action level below which the risk
from disease is eliminated.
Facility owners or operators may choose to assess
the population they serve for individual factors that
may increase the risk of disease (for example age,
immunosuppression) to reduce the risks from legionellae.
The facility owner/operator may want to evaluate
the premise plumbing system processes that could
contribute to legionella growth (for example long water
residence times and low disinfectant residual levels).
This assessment should allow the facility manager
to determine the necessary stringency of the risk
management plan and measures.
What measures can a facility owner or operator
take to control the colonisation and amplification
of legionella in a premise plumbing system?
Buildings can vary in their characteristics (for example
dimensions, location with respect to the servicing PWS)
as well as their purposes. The appropriate measures
depend on those characteristics and purposes. A risk
management approach, including good design and
engineering, can ensure a comprehensive preventative
method is followed to address potential health risks
related to the premise plumbing system.
Continued on page 39 >>
June 2018 Volume 24 I Number 4