HSE's Approved Code of Practice (ACoP) L8. S.1-11

In the UK the Health and Safety Executive’s Approved Code of Practice (ACoP) and Guidance document titled "Legionnaires' disease: The control of legionella bacteria in water systems" (L8) gives practical advice on how to comply with UK health and safety law with respect to the control of Legionella bacteria.

This Code is important in that it has a special legal status. If you are prosecuted for a breach of health and safety law, and it is proved that you did not follow the relevant provisions of the Code, you would need to demonstrate that you have complied with the law in some other way or a Court would find you at fault.

The document also contains guidance issued by the Health and Safety Executive. Following the guidance is not compulsory and organisations are free to take other action. However, if you do follow the guidance you would normally be doing enough to comply with the law.

Accepta have negotiated special permission from the copyright owners of the Approved Code of Practice, L8 document, the Controller of HMSO and the Queen’s Printer for Scotland, to reproduce the Code in full. Consequently, we are proud to be serialising the Code in our Accepta newsletter.

Approved Code of Practice (ACoP) and Guidance

Introduction

1 - This Approved Code of Practice gives practical advice on the requirements of the Health and Safety at Work etc Act 1974 (HSWA) and the Control of Substances Hazardous to Health Regulations 1999 (COSHH) concerning the risk from exposure to legionella bacteria. In particular it gives guidance on sections 2, 3, 4 and 6 (as amended by the Consumer Protection Act 1987) of HSWA and regulations 6, 7, 8, 9 and 12 of COSHH. The Code also gives guidance on compliance with the relevant parts of the Management of Health and Safety at Work Regulations 1999 (MHSWR).

2 - This publication replaces two separate documents: the 1995 Approved Code of Practice and the technical guidance, HSG70. This has allowed information to be consolidated, with the aim of making it easier to read and understand the duties under the law. Since the last revision, the Health and Safety Executive (HSE) and others have funded research to assess the efficacy of new and alternative control strategies. This new document incorporates the findings of that research and explains how such strategies can be used safely and effectively.

3 - This Code applies to the risk from legionella bacteria (the causative agent of legionellosis including Legionnaires’ disease) in circumstances where the Health and Safety at Work etc Act 1974 applies.

4 - To comply with their legal duties, employers and those with responsibilities for the control of premises should:

(a) identify and assess sources of risk – this includes checking whether conditions are present which will encourage bacteria to multiply, e.g. is the water temperature between 20–45°C; there is a means of creating and disseminating breathable droplets, eg the aerosol created by a shower or cooling tower; and if there are susceptible people who may be exposed to the contaminated aerosols (see paragraphs 23–38);

(b) prepare a scheme for preventing or controlling the risk;

(c) implement, manage and monitor precautions – if control measures are to remain effective, then regular monitoring of the systems and the control measures is essential (see paragraphs 61–65). Monitoring of general bacterial numbers can indicate whether microbiological control is being achieved (see paragraphs 124–129 and 183–184). Sampling for legionella is another means of checking that a system is under control (see paragraphs 130–131 and 185–189);

(d) keep records of the precautions; and

(e) appoint a person to be managerially responsible.

5 - The Code and guidance also set out the responsibilities of suppliers of services such as water treatment and maintenance as well as the responsibilities of manufacturers, importers, suppliers and installers.

Background to the Disease & Organisms

6 - Legionnaires’ disease is a potentially fatal form of pneumonia which can affect anybody, but which principally affects those who are susceptible because of age, illness, immunosuppression, smoking etc. It is caused by the bacterium Legionella pneumophila and related bacteria. Legionella bacteria can also cause less serious illnesses which are not fatal or permanently debilitating (see Box 1). The collective term used to cover the group of diseases caused by legionella bacteria is legionellosis.

7 - On average there are approximately 200–250 reported cases of Legionnaires’ disease each year in the United Kingdom (UK). It is thought, however, that the total number of cases of the disease may be generally underestimated. About half of cases are associated with travel abroad. Infections which originate in the UK are often sporadic, for which no source of infection is traced. However, clusters of cases also occur and outbreaks have been associated with cooling tower systems and hot and cold water systems in factories, hotels, hospitals and other establishments.

Box 1: Legionellosis (including Legionnaires’ disease)

Legionnaires’ disease was first identified following a large outbreak of pneumonia among people who attended an American Legion Convention in Philadelphia in 1976. A previously unrecognised bacterium was isolated from lung tissue samples which was subsequently named Legionella pneumophila.

It is normally contracted by inhaling legionella bacteria, either in tiny droplets of water (aerosols), or in droplet nuclei (the particles left after the water has evaporated) contaminated with legionella, deep into the lungs. There is evidence that the disease may also be contracted by inhaling legionella bacteria following ingestion of contaminated water by susceptible individuals. Person-to-person spread of the disease has not been documented. Initial symptoms of Legionnaires’ disease include high fever, chills, headache and muscle pain. Patients may develop a dry cough and most suffer difficulty with breathing. About one third of patients infected also develop diarrhoea or vomiting and about half become confused or delirious. Legionnaires’ disease can be treated effectively with appropriate antibiotics.

The incubation period is between 2–10 days (usually 3–6 days). Not everyone exposed will develop symptoms of the disease and those that do not develop the ‘full blown’ disease may only present with a mild flu-like infection.

Infection with legionella bacteria can be fatal in approximately 12% of reported cases. This rate can be higher in a more susceptible population; for example, immunosuppressed patients or those with other underlying disease. Certain groups of people are known to be at higher risk of contracting Legionnaires’ disease; for example, men appear more susceptible than women, as do those over 45 years of age, smokers, alcoholics, diabetics and those with cancer or chronic respiratory or kidney disease.

The disease is usually diagnosed by a combination of tests. The organism may be cultured from the patient’s sputum, bronchial washings or lung tissue. Alternatively, tests are used to measure the presence of antibodies in the blood and, increasingly, tests are available to measure specific antigens in the patient’s urine.

 L. pneumophila is also responsible for a short feverish form of the illness without pneumonia, known as Pontiac fever. Its incubation period is typically between 2–3 days. Another species of legionella, L. micdadei, is responsible for a similar form of the illness without pneumonia called Lochgoilhead fever after an outbreak in Lochgoilhead, Scotland. The incubation period can be up to 9 days. A high percentage of those exposed to this agent tend to be affected. However, there have been no recorded deaths associated with either Pontiac or Lochgoilhead fevers.

To date, approximately 40 species of the legionella bacterium have been identified. L. pneumophila causes about 90% of cases. Sixteen different serogroups of L. pneumophila have been described; however, L. pneumophila serogroup 1 is most commonly associated with cases of Legionnaires’ disease in the UK.

 L. pneumophila serogroup 1 can be further sub-divided to distinguish between strains most commonly associated with Legionnaires’ disease. Additionally, ‘genetic fingerprinting’ methods such as Restriction Fragment Length Polymorphism (RFLP) and Amplified Fragment Length Polymorphism (AFLP) can be valuable tools in the investigation of outbreaks. Such methods of typing can sometimes provide a means of linking the organisms isolated from patients to the sources of cases of outbreaks.

8 - Cases of Legionnaires’ disease have occurred among staff in the workplace (factories, offices, shops and hospitals); visitors (delivery drivers) and members of the public (patients, hotel guests or passers-by).

Natural History of the Legionella Bacterium

9 - Legionella bacteria are common and can be found naturally in environmental water sources such as rivers, lakes and reservoirs, usually in low numbers. Legionella bacteria can survive under a wide variety of environmental conditions and have been found in water at temperatures between 6°C and 60°C. Water temperatures in the range 20°C to 45°C seem to favour growth. The organisms do not appear to multiply below 20°C and will not survive above 60°C. They may, however remain dormant in cool water and multiply only when water temperatures reach a suitable level. Temperatures may also influence virulence; legionella bacteria held at 37°C have greater virulence than the same legionella bacteria kept at a temperature below 25°C.

10 - Legionella bacteria also require a supply of nutrients to multiply. Sources can include, for example, commonly encountered organisms within the water system itself such as algae, amoebae and other bacteria. The presence of sediment, sludge, scale and other material within the system, together with biofilms, are also thought to play an important role in harbouring and providing favourable conditions in which the legionella bacteria may grow. A biofilm is a thin layer of micro-organisms which may form a slime on the surfaces in contact with water. Such biofilms, sludge and scale can protect legionella bacteria from temperatures and concentrations of biocide that would otherwise kill or inhibit these organisms if they were freely suspended in the water.

11 - As legionella bacteria are commonly encountered in environmental sources they may eventually colonise manufactured water systems and be found in cooling tower systems, hot and cold water systems and other plant which use or store water. To reduce the possibility of creating conditions in which the risk from exposure to legionella bacteria is increased, it is important to control the risk by introducing measures which:

(a) do not allow proliferation of the organisms in the water system; and

(b) reduce, so far as is reasonably practicable, exposure to water droplets and aerosol.