Legionnaires disease, and the legionella risk assessment process explained

Citation

Cowles, D.J.F. (2001), "Legionnaires disease, and the legionella risk assessment process explained", Facilities, Vol. 19 No. 1/2. https://doi.org/10.1108/f.2001.06919aaf.003

Legionnaires disease, and the legionella risk assessment process explained

Legionnaires disease, and the legionella risk assessment process explained

Keywords: Health and safety, Employees

Legionnaires disease is an illness characterised principally by pneumonia, that is caused by the bacterium Legionella pneumophila. Symptoms of Legionnaires disease 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 Legionnaires 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 "Legionnaires disease" comes from July 1976, when the disease occurred among people who had attended an American Legion Convention in Philadelphia. Since then, each outbreak has received high 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.

Whilst Legionnaires 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, those whom are most susceptible are those such as the old and children.

The following conditions affect the growth of Legionella:

• •

  Water temperatures in the range of 20-45°C favour growth. It does not survive at temperatures above about 60°C.

• •

  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:

• •

  water systems incorporating cooling towers and condensers;

• •

  hot and cold water services;

• •

  spray humidifiers which create a spray of water droplets and in which the water temperature is likely to exceed 20°C; and

• •

  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 20-45°C and which may release a spray or aerosol (i.e. a cloud of droplets and/or droplet nuclei) during operation or when being maintained may also present a risk.

Recommendations

The HSE Approved Code of Practice L8 (rev) – The Prevention or Control of Legionellosis (Including Legionnaires' 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. 1.

   Undertake a risk assessment which should include a review of:

2. 2.
   • •

     the systems in place;

   • •

     the installation, and whether there are items which could be improved in order to reduce risk;

   • •

     the maintenance procedures in place – are they appropriate?

3. 3.

   Produce systems for operations and maintenance:

4. 4.
   • •

     identify and record a clear structure of responsibility for implementing and reviewing procedures to manage the risk associated with Legionella within building systems;

   • •

     produce and complete a site log book to aid risk management and record procedures in place;

   • •

     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;

   • •

     set in place a structured programme of maintenance, testing, inspection and disinfecting; and

   • •

     ensure all appropriate operating and maintenance documentation is easily available and that any necessary information is reproduced for the Legionella site logbook.

5. 5.

   Consider installation improvements: the risk assessment should highlight recommended installation changes, such as the installation of de-stratification 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.

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

Legislation and guidance

In the UK, the primary regulations relating to employer's responsibilities in respect of Legionnaires disease are:

• •

  The Health and Safety at Work etc. Act 1974 (as amended); and

• •

  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 (CIBSE).

However, probably the two most important/useful documents are:

1. 1.

   CIBSE Technical Memoranda 13 (TM13).

2. 2.

   HSE Approved Code of Practice L8 (rev) – The Prevention or Control of Legionellosis (Including Legionnaires' Disease). The ACOP (L8) revised (August 2000) to incorporate the guidance previously available in HSE guidance note HS (G) 70.

Further information is available from Ali Hobbs, Buro Happold, Camden Mill, Lower Bristol Road, Bath BA2 3DQ. Tel: +44 (0)1 225 320 600; Fax: +44 (0)1 225 320 601; E-mail: ali.hobbs@burohappold.com

David J.F. CowlesBuro Happold Facility Management