Legionnaires disease

Legionnaires’ disease is a form of pneumonia caused by the bacterium Legionella pneumophila. This bacterium causes an acute infectious respiratory process which can potentially be fatal for some. Sometimes a lesser non-fatal infection can occur called Pontiac fever or Lochgoilhead fever that resemble acute influenza. Legionellosis is the collective name given to the pneumonia-like illness caused by legionella bacteria. Legionella pneumophila  is normally found in rivers, lakes and reservoirs, but in low numbers. However, the bacterium can also be found in purpose-built water systems such as cooling towers, evaporative condensers, hot water systems and whirlpool spas used in domestic and commercial premises. The bacterium doesn’t live very well below 20°C and will not survive above 60°C. In addition, these organisms favour nutrients (that may be found in non-maintained water systems) e.g. presence of sludge, scale or fouling.  Stored and/or re-circulated water and aerosols created by a cooling tower may also favour its’ growth. The risk of legionellosis arises when the bacterium grows in increasing amounts in domestic and commercial contained water systems. Anybody can catch legionnaires’ disease, simply by inhaling small droplets of water which may be suspended in the air which can be spread through humidifiers, water misting systems, high pressure water cleaning machines and, by contact with soil contaminated with the bacteria. As well as affecting the general public, it can also affect workers, especially maintenance technicians of air-conditioning or water supply systems. Work professionals affected can also include those that might be involved in using suspended water systems,  such as vehicle washers, healthcare workers, dental workers, workers in industrial wastewater treatment plants, among others. The bacterium is not known to be transmitted person to person.

During infection, the bacterium invades lung epithelial cells and replicates intracellularly. Some people can be infected and show only mild or no symptoms at all. Others develop flu – like systems which include high temperature, changes in temperature, coughs, muscle pains and headache. In severe cases there may be pneumonia which can be fatal. Everybody is susceptible to infection, however the elderly, heavy smokers, heavy drinkers, those with an impaired immune system and those suffering from chronic respiratory diseases are particularly at risk. Treatment includes antibiotics such as levofloxacin and azithromycin.

Duties under the Health and Safety at Work etc Act 1974, the Control of Substances Hazardous to Health Regulations 1999 (COSHH) and the Health and Safety at Work Regulations 1999 concern the risk from exposure to legionella bacteria in the workplace. Employers are responsible under these acts and other regulations to maintain a safe working environment for workers. Specifically, the COSHH Regulations provide a way of controlling  the risk from a range of hazardous substances including biological agents. Employers who have cooling towers and evaporative condensers on their premises are required, under the Notification of Cooling Towers and Evaporative Condensers Regulations 1992, to notify their local authority.


  • If, after carrying out a risk assessment in the workplace, there is reasonably foreseeable risk, the water systems or parts of them need to be avoided where it is practicable. If working with the water systems cannot be avoided, then there should be a written provision for controlling the risk from exposure, which, should be properly managed. This plan should have a remedial action plan in the event that the scheme is not effective. The plan should also contain instructions for the safe working of the water systems.
  • A system would be set in place where there is reduced exposure to water droplets, avoidance of water temperatures that favour the growth of the bacterium, avoidance of water stagnation and of materials that might inadvertently provide nutrients to the bacteriums’ growth. There should also be use of safe water treatment techniques and safe working of the water system.
  • Risk of exposure may be reduced by using a dry cooling plant, and risks reduced by  changes to engineering protocols and cleaning protocols.
  • The plan should include details on the physical treatment program, for example, the use of temperature to control the system and on the chemical treatment programme. Also, the health and safety information for storage, handling, use and disposal of chemicals, cleaning and disinfecting procedures, information on shutdown procedures and operating cycles needs to be included.
  • Routine testing of water quality and bacterial numbers should be part of the scheme.
  • Records should be kept of any accidents, results and exposures.


Sources   wikipedia    hse   osha

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