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What is Legionella?

Legionella is the abbreviated name for the Legionella pneumophila bacteria that is responsible for the illness commonly known as Legionnaires’ Disease.

Legionella bacteria are commonly found naturally in low concentrations in rivers, lakes and reservoirs where they do not cause any harm.

Legionella bacteria can also be found in purpose built water systems including cooling towers, evaporative condensers, hot and cold-water systems and whirlpool spas. In these types of water systems, the water can be at an optimum temperature for the Legionella bacteria to grow.

Conditions which increase the risk of Legionella being present and causing a risk to health include:

• Water being stored in any part of the system at temperatures between 20°C and 45°C
• Stagnation or low flow
• The presence of materials and nutrients that could harbour or support the bacteria’s growth – e.g. rust, sludge, scale and organic matter and where there is the potential for aerosols to be produced by the water system

What is Legionnaires’ Disease?
Legionnaires’ Disease is a pneumonia-like illness contracted by inhalation deep into the lungs of Legionella bacteria in tiny droplets of water (aerosols). There is no evidence of person-to-person spread of the disease. The incubation period for Legionnaires’ Disease is generally two to ten days following exposure (in rare cases up to 20 days). Symptoms usually begin with high fever, chills, headache and muscle pain. A dry cough and breathing difficulties are also common, and some patients also suffer diarrhoea, vomiting and delirium/confusion. Legionnaires’ Disease can usually be treated successfully with antibiotics. However, it can be fatal. The UK Health Security Agency (UKSHA) advises that Legionnaire’s Disease is usually fatal in 10% of cases. Anyone can contract Legionnaires’ Disease. However, several sectors of the population appear to be at greater risk – individuals aged 45 and over, heavy drinkers and smokers, those with chronic respiratory or kidney disease and the immuno-compromised.

Legal Duty holders
Employers, the self-employed, or the person in control of a premises (including landlords with maintenance responsibility for their supplied water system) will be duty holders in terms of the health risks of Legionella under HSE ACoP L8, the Health and Safety at Work Act 1974 and/or the Management of Health and Safety at Work Regulations 1999.

The duty holder in control of the premises has a responsibility under HSE ACoP L8 to ensure a ‘suitable and sufficient’ risk assessment is carried out for all site water systems.

Identifying and Assessing Sources of Risk for Legionella
The duty holder is responsible for the undertaking of a risk assessment to identify sources and risks for exposure to Legionella. It is vital to understand what water systems are present, the equipment associated with the system such as cold water storage tanks, pumps, calorifiers, heat exchangers, showers (list not exhaustive) and all the component parts. The risk assessment must identify whether the system is likely to create a risk of exposure to Legionella and whether:

• Water is stored or re-circulated in any part of the water system
• The water temperature in all or any part of the system is between 20°C and 45°C
• There are sources of nutrients for Legionella bacteria, such as algae, rust, sludge, scale or organic matter
• There is a potential for water stagnation or low flow, e.g. dead legs
• Water droplets are capable of being produced and they could be dispersed, e.g. showers, or aerosols from cooling towers
• Susceptible individuals are present (e.g. employees, residents, customers, visitors)

The risk assessment should be carried out by a competent person, and this could be the employer or person in control of the premises, or it could be an external contractor. Whoever carries out the risk assessment must be competent in identifying and assessing the risks of exposure to Legionella bacteria, and determining the necessary control measures. The significant findings of the risk assessment should be documented. Employees should also be consulted, and the risk assessment should be reviewed regularly or after any significant changes to the water system.

Managing and Controlling the Risk of Legionella
Where the risk assessment identifies a reasonably foreseeable risk of exposure to Legionella bacteria, the duty holder must appoint a competent person either within the organisation or via an external party to take responsibility for the supervision and implementation of suitable control measures.

Ideally, the risk of exposure to Legionella should be prevented altogether. However, realistically, such prevention may not always be possible. It is therefore essential to design, maintain and operate water services under conditions that prevent or adequately control the growth of Legionella and reduce exposure to any aerosol.

Any identified risk must be effectively managed by the implementation of effective control measures. Control measures should be specific to each water system and focus on controlling the conditions which favour the growth of bacteria. Regular checks should be made on the effective implementation of these control measures.

The HSE’s Approved Code of Practice (ACoP) L8 recommends that appropriate site-specific control measures should include the following:

• Avoid water temperatures between 20°C and 45°C and conditions that favour the growth of Legionella bacteria and other microorganisms
• Avoid water stagnation which may encourage the growth of biofilm which supports Legionella growth
• Avoid the use of materials that harbour bacteria and other microorganisms or provide nutrients for microbial growth
• Control the release of water spray
• Maintain the cleanliness of the water system and the water in it
• Use effective water treatment techniques
• Take action to ensure the correct and safe operation and maintenance of the water system

Record Keeping
Documented records must be kept of the significant findings of the risk assessment. Records should include details of the:

• Person(s) responsible for carrying out the risk assessment
• Significant findings of the risk assessment
• Written control scheme and details of its implementation
• Results of any inspection, test or check carried out, and dates
• Details of whether the system is operating or not

Details of whether the system is operating or not Records should be kept for the time for which they remain current and for at least two years thereafter. Inspection records should be kept for five years