There’s something in the water

Legionnaires’ disease is one of those illnesses that most people will have heard of. But what exactly is it? A potentially fatal type of pneumonia caused by legionella bacteria, people can become infected by breathing in small droplets of water contaminated by the bacteria.
     
Anyone can be infected but some people are at higher risk, particularly those over 45, smokers and heavy drinkers, those suffering from chronic respiratory or kidney disease, and people whose immune system is impaired. It cannot be passed from one person to another.
     
The deadly legionella bacteria are common in rivers and ponds. Prevalent in the natural environment, they may contaminate and grow in other water systems such as cooling towers and hot and cold water services.
    
The bacteria can survive low temperatures and actually thrives at temperatures between 20-45°C if a supply of nutrients such as rust, scale and algae is present.

Managing Legionella
The most reliable way of killing legionella bacteria is by exposing it to high temperatures.
    
A spokesman for the Health and Safety Executive (HSE) said: “Under general health and safety law, employers must consider the risks from legionella that may affect their staff or members of the public and take suitable precautions.
    
“It is up to employers or those responsible for a workplace – such as a landlord – to identify and assess sources of risk.”
    
Managing legionella involves creating and implementing a system for dealing with the risks, identifying a responsible manager, keeping records and checking that what has been done is effective. Employers with a cooling tower on site may also have to notify the local authority.

• A series of simple questions give a rough indicator of whether more rigorous action is necessary.
• Are conditions present which will encourage bacteria to multiply? For example, is the water temperature between 20-45°C?
• Is it possible that water droplets will be produced and, if so, could they be dispersed over a wide area? For example, consider showers and aerosols from cooling towers.
• Is it likely that anyone particularly susceptible will come into contact with the contaminated water droplets?

Cooling towers, evaporative condensers and hot and cold water systems have all been associated with outbreaks. Other potential sources where precautions might be needed include humidifiers and spa baths.
    
If employers decide that the risks are insignificant, no further assessment is necessary although the assessment will need to be reviewed periodically to ensure that it reflects changes in the business.

Implementing controls
In a business where likely risks have been identified, safety law requires proper controls to be introduced. Risks from legionella in water systems can be controlled but careful planning, a successful management policy, competent staff and attention to proper control strategies are all essential.
    
The main advice to employers is to consider whether you can prevent the risk of legionella in the first place by looking at the type of water system being used. For example, it may be possible to replace a wet cooling tower with a dry air cooled system.
    
A written scheme will be needed that sets out how the risk from legionella will be controlled. It should cover:

• the system – an up-to-date plan or schematic diagrams are sufficient
• who is responsible for carrying out the assessment and managing its implementation
• the safe and correct operation of the system
• what control methods and other precautions you will be using
• what checks will be carried out on the control scheme and how often

The key point is to design, maintain and operate water services under conditions which prevent or control the growth and multiplication of legionella.
    
If employers have a cooling tower or evaporative condenser on site you must, under the Notification of Cooling Towers and Evaporative Condensers Regulations, notify the local authority in writing with details of where it is located – including when/if such devices are no longer in use.

An outbreak
Should the worst happen and a case of legionellosis be diagnosed in an employee who has worked on cooling towers or hot water systems that are likely to be contaminated with legionella, this must be notified under the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations (RIDDOR).
    
If there is an outbreak, local authorities have special plans for dealing with major outbreaks of infectious disease including legionellosis. These are usually investigated by an outbreak control team whose purpose is to protect public health and prevent further infection.
    
“Legionella is a serious illness that needs to be taken seriously by employers and others who have responsibilities,” a HSE spokesman said. “It is important that the health sector is familiar with both the risks and the legal requirements on them. It is unacceptable for employees and members of the public to be put at risk of legionella exposure.”

For more information
Web: www.hse.gov.uk/legionnaires/index.htm