Legionella …. unlikey but high severity
The bacterium, Legionella pneumophilia, is responsible for two important workplace conditions, Legionnaires’ Disease and Pontiac Fever.
Did you know?
• The bacteria are just 1 micron in size, 1 millionth of a metre.
• They can exist in the air even if the water they were emitted in dries out.
• It is hot and cold water systems which present the highest risk now not cooling towers.
• The bacteria are so small they remain airborne were they can be inhaled.
• Fresh water and mains water may contain legionella bacteria but at levels of less than 100 cultures per litre are considered safe. Start to worry if they reach 100,000!
• In warm conditions the bacteria can rapidly multiply.
• Having water temperatures of 60oC can reduce cultures from over 100,000 to less than 100 in just ten minutes
• Males are at greatest risk
• Those with suppressed immune systems are also at risk
• Most cases in the UK are acquired in the community rather than in healthcare premises.
The first identified outbreak of Legionnaires’ Disease occurred among people who had attended a Pennsylvanian State Convention of the American Legionnaires in 1976. Delegates subsequently suffered respiratory illness and the bacterium Legionella pneumophilia was isolated from lung specimens.
Legionella also causes Pontiac Fever is a shorter, more feverish illness, without the complications of pneumonia.
L. pneumophilia is one species of a genus of bacteria grouped under the name Legionella. They are rod-shaped organisms, widespread in natural water sources and found in rivers, lakes, streams, mud and soil as well as man-made water systems. To date, at least 34 different species of legionella are recognised. L. pneumophilia is apparently the most pathogenic and is the species most commonly associated with disease outbreaks.
The ecology of Legionella in water systems is not fully understood but the following conditions have been found to affect its rate of growth:
Water temperatures in the range of 25-45°C favour growth. It is uncommon to find proliferation below 20°C and it does not survive above 60°C. Organisms may remain dormant in cool water, multiplying only when the temperature reaches a certain level.
The presence of sediment, sludge, scale and organic material can act as a source of nutrients.
Commonly encountered organisms in water systems, such as algae, amoebae and other bacteria, may serve as an additional nutrient source for Legionella. Algal slime may provide a stable habitat for multiplication and survival.
Incorporation of Legionella in slime on surfaces in contact with water can protect the organisms from concentrations of biocides which would otherwise kill or inhibit those organisms freely suspended in water.
Legionnaires’ Disease is a type of pneumonia. As well as affecting the lungs it may also have serious effects on other organs of the body. Infection is caused by inhaling airborne droplets or particles containing viable legionella, which are small enough to pass deep into the lungs and be deposited in the alveoli.
Relevant Legal Requirements
• HASAWA S2, S3 & S4
• Management of Health and Safety at Work Regs 1999
• Water Supply (Water Fittings) Regulations 1999
• Water Supply (Water Quality) Regulations 2000
• COSHH 2002
• The COSHH ACOP L8 covers the standards expected to control the risk of legionella in buildings.
The Approved Code requires employers to manage risk by:
• Identifying and assessing sources of risk.
• Preparing a scheme for preventing or controlling the risk.
• Implementing and managing precautions.
• Keeping records of the precautions taken.
The risk assessment should take account of:
• The potential for drop formation
• Water temperature
• The risk to those who inhale droplets
• The means of preventing and controlling risk.
• The source of water in use
• The sources of contamination within the building
• Plant operating parameters
• Foreseeable but unusual operating conditions e.g. Breakdown
If the employer has 5 or more employees the assessment must be recorded.
In addition a written scheme must be in place, this must include:
• Up-to-date plan (schematic) of the entire plant or system
• Description of correct and safe operation of the system
• Precautions to be taken
• Checks to be carried out to ensure controls are working
• Action to be taken if it is shown that controls are not effective
Legionella bacteria may be found present in:-
• Cooling Towers
• Domestic hot & cold water systems
• Water features incl. fountains
• Equipment producing aerosols, mists or droplets from stored water sources including showers & humidifiers
• Equipment holding / circulating water at 20 – 45⁰ C
• Water tanks & baths
• Rarely used taps & showers (even at home)
• Dentistry tools
• Oil / water emulsions for lubricating lathes
Who is at risk?
Males are more likely to be affected than females by a ratio of 3 to 1.
Most reported cases occur in the 40 to 70 year age group.
Smokers, alcoholics and patients with cancer, chronic respiratory or kidney disease. Immunosuppressed patients.
Initial symptoms include high fever, chills, headache and muscle pain. A dry cough soon develops and most patients suffer difficulty with breathing. About a third of patients also develop diarrhoea or vomiting and about half become confused or delirious.
The problem continues
Yes again this year the coroner has ordered Basildon hospital to review its arrangements to prevent legionella after the death of a patient. They were prosecuted previously in 2007 for legionella contamination issues. The Health & Safety Executive will now be investigating possible breaches.