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 much 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.
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 20-45C; there is a means of creating and disseminating breathable droplets, e.g. the aerosol created by a shower or cooling tower; and if there are susceptible people who may be exposed to the contaminated aerosols.
(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. Monitoring of general bacterial numbers can indicate whether microbiological control is being achieved. Sampling for legionella is another means of checking that a system is under control.
keep records of the precautions and appoint a person to be managerially responsible.
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 and organisms

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. The collective term used to cover the group of diseases caused by legionella bacteria is legionellosis. 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. 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

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 6C and 60C. Water temperatures in the range 20C to 45C seem to favour growth. The organisms do not appear to multiply below 20C and will not survive above 60C. 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 help at 37C have greater virulence than the same legionella bacteria kept at a temperature below 25C.
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, amoebac 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 favorable 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.
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 it is reasonably practicable, exposure to water droplets and aerosol.

Legislation: health and safety law

Duties under the HSWA extend to risks from legionella bacteria which may arise from work activities. The MHSWR provide a broad framework for controlling health and safety at work. As well as requiring risk assessments, they also require employers to have access to competent help in applying the provisions of health and safety law; to establish procedures to be followed by any worker if situations presenting serious and imminent danger were to arise; and for co-operation and co-ordination where two or more employers or self-employed persons share a workplace.
Only the courts can give an authoritative of law in considering the application of these Regulations and guidance to people working under another's direction. The following should be considered: if people working under the control and direction of others are treated as self-employed for tax and national insurance purposes, they may nevertheless be treated as their employees for health and safety purposes. It may, therefore, be necessary to take appropriate action to protect them. If any doubt exists about who is responsible for the health and safety of a worker, this could be clarified and included in the terms of contract. However, it should be remembered that a legal duty under section 3 of HSWA cannot be passed on by means of a contract and there will still be duties towards others under section 3 of HSWA. If such workers are employed on the basis that they are responsible for their own health and safety, legal advice should be sought before doing so.

More specifically, the COSHH Regulations provide a framework of actions designed to control the risk from a range of hazardous substances including biological agents. The essential elements of COSHH are:
Risk assessment:
Prevention of exposure or substitution with a less hazardous substance if this is possible, or substitution of a process or method with a less hazardous one;
Control of exposure where prevention or substitution is not reasonably practicable;
Maintenance, examination and testing of control measures, e.g. automatic dosing equipment for delivery of biocides and other treatment chemicals; provision of information, instruction and training for employees; and
Health surveillance of employees (where appropriate, and if there are valid techniques for detecting indications of disease), where exposure may result in an identifiable disease or adverse health effect.
The Reporting of injuries, Diseases and Dangerous Occurrences Regulations 995 (RIDDOR) require employers and others, e.g. the person who has control of work and premises, to report to HSE, accidents and some diseases that arise out of or in connection with work. Cases of legionellosis are reportable under RIDDOR if a doctor notifies the employer and if the employee's current job involves work on or near cooling systems that use water or hot water service systems in the workplace. Further details can be obtained in HSE guidance.
Those who have, to any extent, control of premises have a duty under the Notification of Cooling Towers and Evaporative Condensers Regulations 1992 to notify the local authority in writing with details of 'noticeable devices'. These can consist of cooling towers and evaporative condensers, except when they contain water that is not exposed to the air and the water and electricity supply are not connected. Although the requirement is to notify the local authority, the Regulations are enforced by the relevant authority for the premises concerned. Forms are available from local authorities or the local HSE office. If a tower becomes redundant and is decommissioned or dismantled, this should also be notified. The main purpose of these Regulations is to help in the investigation of outbreaks.
The Safety Representatives and Safety Committees Regulations 1977 and the Health and Safety (Consultation with Employees) Regulations 1996 require employers to consult trade union safety representatives, other employee representatives, or employees where there are no representatives, about health and safety matters. This includes changes to the work that may affect their health and safety at work, arrangements for getting competent help, information on the risks and controls, and the planning of health and safety training. Further information and details of additional guidance can be found in a free HSE leaflet.

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