LEGIONNAIRES DISEASE - (LEGIONELLOSIS)

Legionnaires’ disease (LD) is a virulent from of pneumonia, which can be fatal. People in good health can be come infected but older people who smoke, chronic drinkers and people who suffer from cancer; diabetes, chronic respiratory problems or kidney diseases are particularly at risk. Breathing in water droplets contaminated with legionella bacteria contracts LD. These are found in many recalculating, hot and cold water systems. Outbreaks of LD have occurred in or large building complexes such as factories, hospitals, hotels and offices.

The Hazard - Legionnaires’ disease is the most serious of the group of diseases collectively known as “legionellosis” infection occurs through the inhalation of water droplets contaminated with legionella bacteria. Infection can occur where the water temperature is between 20¥C and 45¥C and there is algae, rust, scale, sludge or other organic matter for nutrients: there also has to be a means of creating breathable droplets. Symptoms include high fever, chills, headaches and severe muscular ache; as the disease progresses sufferers also develop a cough and experience chest pains and difficulty in breathing: in some cases diarrhoea and vomiting may occur.

Particular hazards include:

• Water/air conditioning systems incorporating a cooling tower - these generate fine water droplets; there is the potential for wide dispersal and the infection of large numbers of people as air conditioning systems are usually sited on roofs;
  
• Hot and cold water systems; showers and spa baths have been associated with infection;
  
• Healthcare settings; nursing and residential care homes; where patients and residents are particularly susceptible to infection.

Dealing with the hazards - employers must carry out an assessment of all significant risks to health and safety in the workplace and put into place measures to prevent or control those risks, (Regulation 3 of the Management of Health and Safety at Work Regulations (1999)). Hot water should be stored at a temperature high enough to kill bacteria. The Health and Safety Executive (HSE) recommends storing at 60¥C and circulating at 50¥C (thermostatically controlled taps should be installed where there is a risk of scalding; scalding is a significant risk in nursing, care homes and schools for example).

The Health and Safety Commission (HSC) published in Jan ’01 a new Approved Code of Practice (ACoP) and guidance - Legionnaires' disease: The control of legionella bacteria in water systems.

The significant changes to the guidance are:

• The guidance recommends that dip slides used to monitor total microbiological activity in wet cooling systems now be carried out weekly not monthly;
  
• It is now recommended that routine sampling for legionella be included as part of a monitoring regime for wet cooling tower systems;
  
• The term ‘high efficiency drift eliminator’ has been replaced by ‘effective drift eliminator’; and
  
• More extensive guidance is provided on the commissioning and operation of systems.

Copies of The Control of legionella bacteria in water systems: Approved Code of Practice and Guidance, ISBN 0 7176 1772 6, price £8.00, ref. L8, are available from HSE Books.

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