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Managing Legionella

Legionella is the name of a bacteria that is found in fresh water in all areas of the world (such as lakes and springs). It is common for this bacterium to be found in fresh water, albeit in small quantities, but it can be fatal to humans if water droplets that are contaminated with Legionella bacteria are ingested. The risk of this increases when Legionella bacteria multiply so that higher levels are found in the source water.

In fresh water supplies, the conditions are rarely favourable for Legionella bacteria to multiply into higher numbers (which is why the number of bacteria in natural water is low). The bacteria live and grow in water with an optimum temperature of 35 degrees Celsius, but can also survive temperatures ranging from 20 to 50 degrees Celsius.

This is why any hot or cold-water system must be properly maintained to prevent desirable conditions for Legionella to grow; creating a higher risk of someone developing Legionnaires’ disease. As well as hot and cold-water systems, Legionella can be found in cooling towers, evaporative condensers, air conditioning, spas and whirlpools, and humidifiers.

Legionella bacteria are the cause of Legionnaires’ disease, which is a pneumonia-like illness that, if left untreated, can cause fatal damage to the lungs. Legionnaires’ disease can commonly create flu-like symptoms in its sufferers, which can be cured with antibiotics. However, some people may continue to experience problems after treatment.

Those with weakened immune systems are at increased risk of the severe pneumonia that it can cause. Those groups that are at an increased risk of developing pneumonia from Legionella bacteria include smokers, heavy drinkers, older adults, and those with respiratory diseases.

Legionnaires’ disease was first discovered in America following a large outbreak of pneumonia in the 1970s. The species of Legionella bacteria that causes Legionnaires’ disease is the species L. pneumophila. Another milder illness that the bacteria are commonly associated with is Pontiac fever.

In England it is thought that Legionnaires’ disease is underreported, with up to 250 cases of the disease reported each year. However, this excludes cases that are reported with the person being exposed to Legionella bacteria outside of England.

When a person develops Legionnaires’ disease, they are likely to have a fever, headaches, muscle aches, and fatigue. As the infection worsens, the respiratory system will begin to suffer, causing pneumonia-like symptoms. These symptoms include shortness of breath, chest tightening and pain, and breathing difficulties. This is where the disease can become fatal and the person should seek immediate healthcare.

Water that could be carrying legionella

How to control Legionella

If you are responsible for the health and safety of a building it is extremely important that you control the water supply and system to prevent Legionella from multiplying. The first step in doing this is by thoroughly risk assessing your water system. This will identify any potential issues that you may have with your water system so that you can create a management plan to address these issues to ensure that they do not develop into a risk of Legionnaires’ disease.

Further details of Legionella management plans will be explained in the next section. Legionella bacteria can be found in water systems and aerosols.  World Health Organisation (WHO) report that Legionnaires’ disease is most commonly transmitted through aerosols.

This means that the bacteria could be in the air in tiny water droplets which could be inhaled by someone. For example, the water droplets in a steamy washroom could contain Legionella, and if a person were to enter that room, they could breathe in the bacteria from the air. This makes it crucial for thorough maintenance and cleaning of all water facilities. [Legionella cannot be spread directly from one person to another].

Legionella management is also included in Food Safety Management Systems. In the food industry there are many hazards that must be considered and controlled, such as Campylobacter, personal hygiene, and Legionella bacteria. Kitchen’s use water every day so should ensure that their systems are not contaminated.

If a business has been closed for a period of time, the appropriate risk management actions should apply (which will be explained towards the end of this guide to managing Legionella). Food Standards Agency also shared guidance for food businesses to reopen safely after a period of closure.

What is a Legionella management plan?

All public buildings should have a water management plan to help reduce the risk of Legionella spreading in the water system and through to any facilities. The Legionella management plan should include all areas in your building that Legionella bacteria have the potential to multiply, so that steps can be taken to reduce that risk. Each plan will be different because each building is different, so will therefore carry different risks.

It should include a series of steps that need to be regularly reviewed including:

  • Establishing a water management team.
  • Identifying and recording the water systems of your building.
  • Highlighting where Legionella could develop.
  • Identifying appropriate actions to apply to these risk areas and how they will be monitored.
  • Working out a contingency plan to use when controls are not met.
  • Continually reviewing progress of the plan.
  • Documenting and communicating the activities and actions arising from the plan.

Your Legionella management plan must be completed by an appointed person who is competent in understanding water systems and Legionella risks. The person appointed must understand the management of the estate as an employer or person in control of the premises.

Water management team checking the water systems for legionella

Legislative controls for Legionella

There are a number of pieces of legislation that make Legionella risk assessments compulsory for any workplace or business using water services.

The main legislative controls for Legionella include:

Health and Safety at Work etc. Act 1974

The Health and Safety at Work etc. Act 1974 makes a Legionella risk assessment a legal requirement. It creates duties that apply to the risks from exposure to Legionella bacteria that would arise due to work activities; thus, protecting the workforce. As well as risk assessments, the Act also requires employers to access the relevant specialists to be able to apply the law effectively.

The following sections are of particular importance in relation to Legionella:

i. Section 2 places a duty on employers to ensure that their workforce is as safe as practicably possible.

ii. Section 3 ensures that non-employees who may be affected by work activities do not have their health and safety compromised.

iii. Section 4 places a duty on anyone responsible for the work setting to ensure that the premises does not endanger people using it.

Management of Health and Safety at Work Regulations 1999

The Management of Health and Safety at Work Regulations 1999 is a key piece of legislation that works in conjunction with the Health and Safety at Work etc. Act 1974. It helps to ensure that health and safety at work is maintained.

It requires workplaces to create policies that aim to prevent health and safety issues and places autonomy on workplaces to ensure that work employees read and understand the policies to help keep themselves and others safe. A lack of compliance with the Management of Health and Safety at Work Regulations 1999 can result in a fine of up to £20,000.

Control of Substances Hazardous to Health Regulations 2002

The Control of Substances Hazardous to Health Regulations 2002 (COSHH) control the risk of hazardous substances harming people. In relation to Legionella, it places a duty on workplaces to identify sources of Legionella, define necessary measures for Legionella prevention, and define the means of control.

Public health legislation also places a duty on medical professionals to report suspected cases of Legionnaires’ disease, in order to protect the public.

Duty holder and responsibilities

The health and safety legislation detailed above creates the requirement for a duty holder to be responsible for making improvements to health and safety issues (including a responsibility for the control of Legionella).

A duty holder refers to a person (or people) who is in charge of the building. It gives them obligations to control the levels of bacteria in water systems to ensure that conditions to not reach those that are optimum for Legionella to grow.

Their specific responsibilities in relation to Legionella prevention include:

  • Identify and assess sources of risk.
  • Prepare a written scheme for preventing or controlling the risk.
  • Implement, manage and monitor precautions.
  • Keep accurate records of precautions, actions and monitoring.
  • Appoint a team to help ensure compliance with these measures.

If duty holders do not feel competent in their requirements, they should seek the help of specialists to support them in their role as well as use autonomy to do their own learning about keeping their workplace safe from Legionella.

Spa facilities that should be cleaned regularly

Risk management

Risk management is the process of identifying, assessing, managing and reducing risks to a business. A risk is a harmful event that could jeopardise your business goals and safety, so a risk management plan foreshadows and protects your business from unfortunate events from happening. By using a risk management plan your business will save money and protect its future by avoiding potential threats.

A greater understanding of specific risks enables a greater risk management system to be put in place. That is why there are specific duty holders named in various forms of legislation to take charge of particular risks.

Having multiple duty holders covering a wide range of risks means that each duty holder can become an expert in their own risk areas, and make a more effective risk management plan. Below we have listed some of the common themes to be mindful of when considering your risk management plan for Legionnaire’s disease prevention.

Control water temperature

Ensuring that water temperature is controlled is the main way of minimising the risk of Legionella bacteria contaminating water systems. This is because Legionella bacteria breed at their optimal temperatures of 20-50 degrees Celsius, so avoiding those temperatures would play an active role in Legionella prevention.

Hot water should be stored at over 60 degrees Celsius and distributed at a minimum of over 50 degrees Celsius (as these temperatures are outside of the bacteria’s optimum growth range). Cold water should be stored and distributed at under 20 degrees Celsius to also prevent optimum temperatures for bacteria breeding.

To ensure that these temperatures are maintained, a health and safety representative for your building should regularly inspect and clean the water system. If your water outlets are not used frequently, then you should ensure that these are flushed weekly.

Stagnant water

Stagnant water is also a large risk for Legionella growth and should also be included in your risk assessment. Stagnant water is water that has been left to sit for hours or more without any disturbance. It can become smelly and discoloured, but even water without these characteristics could be stagnant. Using a specialist to keep on top of cleaning your water system can help to prevent stagnant water from building up.

Cleaning air conditioning systems

Another control of Legionnaire’s disease prevention is through air conditioning. Air conditioning units are a source of water droplets in the air which can cause Legionella bacteria to spread by aerosol. This can be spread at a fast rate because the water droplets will be invisible in the air and easily inhaled. If your air conditioning unit uses source water it should be included on your risk assessment, considering how often it is used and how often it should be cleaned to prevent Legionella.

Spa facilities

If you have a wellness business that includes facilities such as a spa, swimming pool, or hot tub, the facilities should be cleaned regularly when they are in use. If there is ever a period where your business facilities are not in use, the water should be drained and facilities cleaned. Then, before you intend to open these facilities again, they should be disinfected.

Legionella is an extremely harmful bacteria that can be fatal to humans. It is invisible to the naked eye, and is an easy part of your business that can become neglected. Understanding your business’s water supply and maintenance can mitigate any risks of Legionella from developing in your workplace and can protect the lives of your employees.

There should always be careful consideration of the responsibilities of the duty holder and supporting members to ensure that the relevant hygiene and maintenance measures can be maintained. That way your responsibilities to health and safety at work can be easily managed.

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About the author

Maria Reding

Maria Reding

Maria has a background in social work and marketing, and is now a professional content writer. Outside of work she enjoys being active outdoors and doing yoga. In her spare time she likes to cook, read and travel.



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