Last reviewed 31 August 2015

Justin Tyas examines a case in which a hospital trust was ordered to pay over £88,000 in fines and costs for failing to control the risks from legionella bacteria. A joint investigation by the police and the Health and Safety Executive (HSE) identified failings that may have hastened the death of an elderly patient.


Legionellosis is a collective term for diseases caused by legionella bacteria including the most serious, Legionnaires’ disease. The bacterium got its name after a 1976 outbreak, when many people who went to a Philadelphia convention of the American Legion suffered from this disease, a type of pneumonia (lung infection). Although this type of bacterium was around before 1976, the disease is now more prevalent.

Legionnaires’ disease is a potentially fatal form of pneumonia and everyone is susceptible to infection. People become infected when they inhale aerosols from a contaminated water source. The risk increases with age but some people are at higher risk including:

  • individuals over 45 years of age

  • smokers and heavy drinkers

  • people suffering from chronic respiratory or kidney disease

  • individuals with diabetes, lung and heart disease

  • anyone with an impaired immune system.

Legionella bacteria are widespread in natural water systems, eg rivers and ponds. However, the conditions are rarely right for people to catch the disease from these sources. Outbreaks of the illness occur from exposure to legionella growing in purpose-built systems where water is maintained at a temperature high enough to encourage growth, such as hot and cold water systems, spa pools, cooling towers, etc.

Certain conditions increase the risk of legionella, such as if:

  • the water temperature in all or some parts of the system is between 20°C and 45°C, which is suitable for bacteria growth

  • it is possible for breathable water droplets to be created and dispersed, eg via an aerosol created by a cooling tower, or water outlets

  • water is stored and/or recirculated

  • there are deposits providing a source of nutrients for the organism, eg rust, sludge, scale, organic matter and biofilms.

The joint HSE/police investigation identified a history of problems. A vulnerable patient died eight days after her urine tested positive for the legionella bacteria antigen. At the inquest into the patient’s death, it was found that she died of natural causes, and that the legionella pneumonia appeared to have been successfully treated, however, the inquest found that the infection may have hastened her death.

Statutory requirements

Duties under the Health and Safety at Work, etc Act 1974 (HSWA) extend to risks from legionella bacteria, which may arise from work activities. The Management of Health and Safety at Work Regulations 1999 provide a broad framework for controlling health and safety at work. More specifically, the Control of Substances Hazardous to Health Regulations 2002 provide a framework of actions designed to assess, prevent or control the risk from bacteria like legionella. In terms of the control of legionella bacteria in water systems, the HSE has issued an Approved Code of Practice (ACOP), L8, with supporting guidance.

The ACOP is aimed at duty holders, including employers, persons in control of premises and those with health and safety responsibilities for others, to help them comply with their legal duties in relation to legionella. The ACOP provides a comprehensive approach to control which includes the requirements for the following.

Risk assessment

A suitable and sufficient assessment must be carried out to identify and assess the risk of exposure to legionella bacteria from work activities and water systems on the premises and any precautionary measures needed.

The duty holder is responsible for ensuring the risk assessment is carried out. The duty holder is either:

  • the employer, or self-employed person, where there is a risk from their undertaking to themselves or others; or

  • the person who is in control of premises or water systems.

Managing the risk: management responsibilities, training and competence

Duty holders need to take reasonable steps to ensure that any control measures are properly used and applied. They are also required to have arrangements in place for the management of health and safety, to have access to competent health and safety advice and to provide employees with suitable and sufficient information, instruction, and training.

If the assessments show there is a foreseeable risk and it is reasonably practicable to prevent or control exposure, the duty holder should appoint a competent person or persons, known as the “responsible person” to take day-to-day responsibility for controlling any identified risk from legionella bacteria.

The control scheme

Duty holders are required to prevent, or where this is not reasonably practicable, adequately control exposure to legionella bacteria. They are also required to maintain, examine and test control measures and, at suitable intervals review and, if necessary, revise those measures. A written scheme for controlling the risk from exposure should be properly implemented and managed. Suitable records of examinations, tests and repairs of control measures must be maintained.

Review of control measures

For precautions to remain effective, the condition and performance of the system will need to be monitored. The appointed responsible person should oversee and manage this.

Duties and responsibilities of those involved in the supply of water systems

To ensure they are safe and without risks to health, additional technical guidance (HSG274) is provided by the HSE in three parts.

  1. Evaporative cooling system.

  2. Hot and cold water systems.

  3. Other risk systems.


The Hospital Trust was fined £50,000 with costs of £38,705 after pleading guilty to breaching s.3(1) of HSWA.

Section 3(1) of HSWA states: “It shall be the duty of every employer to conduct his undertaking in such a way as to ensure, so far as is reasonably practicable, that persons not in his employment who may be affected thereby are not thereby exposed to risks to their health or safety.”


The joint investigation by the HSE and the police identified a history of failures by the Hospital Trust to manage the risk from legionella bacteria in hot and cold water systems.

Although the Trust was monitoring legionella and water temperatures across its various sites at the time of the patient’s death, a total of 114 positive legionella tests and a further 651 records of water temperatures outside the required parameters were not adequately acted upon.

Chlorine dioxide (an oxidising biocide/disinfectant) dosing units were fitted at five sites but inspectors found that they routinely failed to deliver the dosage required to be effective. High legionella readings were found at other sites. In addition, inspectors found that at one site the water temperature often failed to reach 60°C, the temperature required to kill legionella bacteria.

One of the major contributors to the serious control failures was the fact that staff did not have sufficient instruction, training and supervision to be able to make informed decisions and take appropriate action.

Lessons learned

The risks from legionella bacteria in hot and cold water systems are well known. The intervention of the HSE and the police following the death of the vulnerable patient resulted in a new management system to effectively control legionella.

All duty holders have a responsibility to control the risks from hot and cold water systems. There is suitable management as well as technical guidance to support organisations including the responsible persons nominated to manage schemes of control. Risks that cannot be eliminated will require robust systems of control, including effective monitoring, and action taken, where necessary, based upon the informed decisions by competent persons.

Healthcare providers such as Hospital Trusts must be especially vigilant and robust in terms of the systems they have in place. Due to the nature of vulnerable patients in their care, they are at an even greater risk from potentially fatal legionella bacteria.