About Legionnaires' disease

Legionnaires' disease guide for employers

Read the Legionnaires' disease - A Guide for Employers which is based on the Approved Code of Practice issued by the Government

Below, we have set out some detailed information on Legionnaires' disease.

Please use the links below.

  1. What is Legionnaires' disease?
  2. How is it caused?
  3. Legislation - health and safety law
  4. What sort of industries are affected by Legionnaires' disease?
  5. Which systems present the greatest risk?

What is Legionnaires' disease?

Legionnaires' disease is a potentially fatal form of pneumonia which can affect anybody, but which mainly affects those who are susceptible due to factors such as age and illness. 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.

How is it caused?

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 6ºC and 60ºC. Water temperatures in the range 20ºC to 45ºC seem to favour growth. The organisms do not appear to multiply below 20ºC and will not survive above 60ºC. 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 37ºC have greater virulence than the same legionella bacteria kept at a temperature below 25ºC.

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 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.

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.

What sort of industries are affected by Legionnaires' disease?
Under General Health and Safety Law, ALL employers must consider the risks from legionella that may affect their staff or members of the public and take suitable precautions. We are able to offer a UKAS accredited test for the detection of legionella, and will assist you in eliminating legionella contamination.

Contact us for a risk assessment today.

Which systems present the greatest risk?
The following systems present the greatest risk from Legionnaires' disease:
:: Cooling Tower systems
:: Evaporative Condenser Units
:: Hot and Cold Water Systems
:: Showerheads
:: Low usage outlets
:: Ultrasonic humidifiers / foggers and water misting systems
:: Spray humidifiers, air washers and wet scrubbers
:: Water softeners
:: Emergency showers and eye wash sprays
:: Sprinkler & Hose Reel systems
:: Lathe & Machine Tool coolant systems
:: Spa Baths
:: Horticultural misting systems
:: Dental Equipment
:: Car / Bus Washers
:: Indoor fountains & Water features

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