A revised version of the Health and Safety Executive Approved Code of Practice outlining the prevention and control of legionellosis has just been released. David Cowles gives a brief explanation of the disease and the risk assessment process used to keep it at bay

Legionnaire's disease is an illness, characterised principally by pneumonia, that is caused by the bacterium Legionella pneumophila. Symptoms can appear quite suddenly and include high fever, chills, headache, muscle pain and a dry cough. Difficulty with breathing is also commonly experienced by patients. The illness can prove fatal. According to the National Surveillance Scheme for Legionnaire's Disease, there were 226 reported cases in England and Wales in 1998, of which 25 resulted in death. Infection can be acquired by the inhalation of airborne water droplets or particles, which contain Legionella and are small enough to pass deep into the lungs.

Many people realise that the name Legionnaire's Disease originates from July 1976, when the disease occurred among people who had attended an American Legion Convention in Philadelphia. Since then, each outbreak has received a lot of publicity and a number of legislative and guidance documents have been published in the UK detailing the required procedures to eliminate or minimise the risk of further outbreaks. There is however, still concern that facilities managers, with their high workload, are not giving this the attention it deserves.

While Legionnaire's disease is an uncommon infection, Legionella organisms are widespread and can be found in both natural and man-made water systems as well as soil. There are numerous different species of Legionella. Where circumstances exist that promote the proliferation and distribution of the bacteria, everyone is at risk, but as with many other diseases the most susceptible are those such as the old and children.

The following conditions affect the growth of Legionella:

• Water temperatures in the range of 20-45oC favour growth. It does not survive at temperatures above about 60oC.
• Sediment, sludge, scale and organic matter can act as a source of nutrients, as can other organisms in water such as other bacteria and algae. The slime, or biofilm, which often forms on the surface of water, provides favourable conditions for growth.
• Biofilms, sludge, corrosion etc can also provide some protection against treatment methods.
  Systems, which eject water as an aerosol, or as droplets, pose the biggest risk, as they can be more easily inhaled.

Systems Particularly at Risk
In view of this from a facility manager's point of view, the following present a particular risk of Legionella:
a) Water systems incorporating cooling towers and condensers.
b) Hot and cold water services.
c) Spray humidifiers which create a spray of water droplets and in which the water temperature is likely to exceed 20oC.
d) Spa baths and pools, in which warm water is deliberately agitated and recirculated.
Other plant and systems containing water which is likely to be in the temperature range 20-45oC and which may release a spray (ie a cloud of droplets and/or droplet nuclei) during operation or when being maintained may also be a risk.

Legislation and guidance
In the UK, the primary regulations relating to employers' responsibilities in respect of Legionnaire's disease are:
-The Health and Safety at Work Act 1974 etc (as amended).
-The Control of Substances Hazardous to Health Regulations 1999.
The Health and Safety Executive (HSE) guidance on the requirements of the above legislation is published in the Approved Code of Practice, document L8 (rev).
This code does not address the technical aspects of controlling the risk, which can be found in various information published by government departments, trade associations and by the Chartered Institute of Building Services Engineers.
However, probably the two most important/useful documents are:
-CIBSE Technical Memoranda 13 (TM13).
-HSE Approved Code of Practice L8 (rev) - The prevention or control of legionellosis (including Legionnaire's disease). The ACOP (L8) is due to be revised (August 2000) and to incorporate the guidance previously available in HSE guidance note HS (G) 70.

Recommendations
The HSE Approved Code of Practice L8 (rev) - The prevention or control of legionellosis (including legionnaire's disease), Section 8 requires that: "A suitable and sufficient assessment should be carried out to identify and assess the risk of legionellosis from work activities and water sources on the premises and any precautionary measures."

In general terms it is recommended that facilities managers should:

1) Undertake a risk assessment to review:
i. the systems in place
ii. the installation, and whether there are items which could be improved in order to reduce risk
iii. the maintenance procedures in place - are they appropriate?

2) Produce systems for operations and maintenance to:
i. identify and record a clear structure of responsibility for implementing and reviewing procedures to manage the risk associated with Legionella within building systems
ii. produce and complete a site logbook to aid risk management and record procedures in place
iii. ensure all staff responsible for maintenance of relevant systems are suitably trained or instructed on how to minimise the risks of Legionella growth and any precautions necessary when maintaining particular systems
iv. set in place a structured programme of maintenance, testing, inspection and disinfecting
v. ensure all appropriate operating and maintenance documentation is easily available and that any necessary information is reproduced for the Legionella site log and

3) Consider installation improvements.
The risk assessment should highlight recommended installation changes, such as the installation of destratification pumps on hot water generators. A pragmatic approach is required. It is not expected that an older system be replaced due to a small risk. Capital outlay needs to be compared to order of risk so that a rational approach can be adopted.

Experience suggests that operational issues are the easiest, less costly and most effective to implement. Once this has been addressed, full consideration can be given to the installation.

David Cowles is a consultant with Buro Happold Facility Management, a multi-disciplinary international practice of consulting engineers established in 1976 offering a range of specialist services.