LEGIONELLA - World Health Organization

10.4 Designing regulations
Basic principles need to be observed when developing new regulations. There needs to be an
overall aim, which in this case is to reduce the risk and incidence of legionellosis. The aim is
achieved by applying a set of specific requirements, each of which should have a specific and
stated purpose. Compliance with requirements should be measurable and (where appropriate)
enforceable. Monitoring regimes should be defined, and corrective action to remediate noncompliance
should be described.
Specific health-based targets might be established for the incidence of illness or outbreaks. Such
targets can be useful in undertaking cost–benefit analyses as part of a regulatory impact assessment.
If Legionella testing is included in requirements, target concentrations and responses to
detections should be specified.
In some cases, there may need to be a balance between different regulatory requirements. For
example, in the case of water distribution systems, avoiding temperatures between 25 °C and
50 °C will reduce the risk from Legionella; however, regulations designed to reduce the risk
of scalding can require that hot-water temperatures be kept below 50 °C or even below 45 °C.
This can be achieved by lowering water temperatures throughout distribution systems or by
installing thermostatic mixing valves close to the point of water use. In either case, greater levels
of maintenance will be required to compensate for loss of temperature-based control of Legionella.
10.4.1 Managerial responsibilities, registration and notification
Regulations should identify managerial responsibilities associated with systems, and should
include requirements for the training and competence of operators. Requirements could also
be included for registration of devices with regulatory authorities. Consideration should be
given to notification requirements in the event of serious non-compliance.
10.4.2 System assessment and design
System assessment should include inspections of buildings and surrounding areas to identify
potential sources of Legionella and to evaluate the risk associated with devices, taking into account
design, location and operating conditions. A risk assessment could include consideration of:
• the potential for conditions that could favour the survival or growth of Legionella
• the potential for production and dissemination of aerosols
• design features, such as deadlegs, the position of air intakes or cooling tower exhausts, and
the presence of drift eliminators in cooling towers
• control measures to minimize risks (e.g. automated biocide dosing, flushing, cleaning and
general maintenance)
LEGIONELLA AND THE PREVENTION OF LEGIONELLOSIS