Legionellosis

INTRODUCTION

Legionnaires Disease is one of a group of diseases collectively known as Legionellosis. Thirty-seven different species of bacteria are associated with Legionellosis, the most dangerous being Legionella pneumophilia. Infection by L. pneumophilia can result in pneumonia and other potentially life-threatening effects. Legionellosis is associated with a fatality rate of approximately 12%.

SOURCE

Legionella organisms are widespread in natural water sources and have been found in rivers, lakes, mud and soil. However, Legionella can also colonise man-made re-circulating hot and water systems such as storage tanks, calorifiers and air conditioning systems.

ROUTE OF INFECTION

Legionellosis is caused by the inhalation of airborne droplet's which contain Legionella bacteria. However, infection can only occur under certain conditions which permit the growth and multiplication of the organism and involve the creation of droplets which can be inhaled.

LEGAL REQUIREMENTS

1. Duties under the Health and Safety at Work etc. Act 1974 extend to risks from Legionella arising from work activities.
2. The Control of Substances Hazardous to Health Regulations 1999 relate to risks from biological hazards such as Legionella.
3. Legionnaires disease. The control of legionella bacteria in water systems. Approved Code of Practice and guidance L8 (second edition). The most significant change of this document, is the removal of the 300 litre limit for hot and cold water services. This was an artificially chosen limit and its removal means that ALLpremises with a water system are now within the scope of the revised ACOP. Also recent research shows that legionella does occur in smaller domestic systems.

4. The Notification of Cooling Towers and Evaporative Condensers Regulations 1992 require notification to the local authority of installations of wet cooling towers and evaporative condensers.

ACTIONS REQUIRED

The principles of a Legionella control system are :

• The identification and assessment, by a competent person, of sources of risk.
• The preparation of a scheme for the prevention or control of such risks.
• The implementation and management of precautions.
• Keeping records of precautions implemented.
• The appointment of a person who is managerially responsible for the system.

THE PREVENTION OF LEGIONELLOSIS

Legionellosis can be prevented and controlled as follows :

• Eliminating conditions which permit the proliferation of Legionella bacteria
• Minimising the creation and release of water sprays and aerosols.

Precautions which limit the proliferation of Legionella species include :

• Avoiding water temperatures between 20ºC and 45ºC.
• Avoiding water stagnation.
• Avoiding the use of materials in the system which can harbour or provide nutrients for bacteria.
• Keeping the system clean to avoid the build up of sediments which may provide nutrients or harbourage.
• The use of a suitable water treatment programme which involves the disinfection and maintenance of the system.
• Ensuring that the system operates safely and is well maintained.

CHECKLIST - LEGIONELLOSIS

REFERENCES/FURTHER DETAILS

1. Approved Code of Practice L8 (Rev) - The Prevention or Control of Legionellosis (HSE)
2. HSE Books:
3. Leaflet Legionaires' disease A guide for employers (HSE) IAC27(rev2)
4. Leaflet Controlling risks in spa baths

5. HSE website:

6. Essential information for providers of residential accomodation

7. HPA website information about legionella:-

8. HSE information about Legionella

Alternatively e-mail ehs@gosport.gov.uk any time