Keeping you safe - Legionella

Legionella acquired its name after a July, 1976 outbreak of a then-unknown "mystery disease" sickened 221 persons, causing 34 deaths. The outbreak was first noticed among people attending a convention of the American Legion - an association of U.S. military veterans. The convention in question occurred in Philadelphia during the U.S. Bicentennial year. This epidemic among U.S. war veterans, occurring in the same city as – and within days of the 200th anniversary of – the signing of the Declaration of Independence, was widely publicised and caused great concern in the United States. On January 18, 1977 the causative agent was identified as a previously unknown bacterium, subsequently named Legionella.

What is Legionnaires’ disease?
Legionnaires’ disease is a potentially fatal pneumonia caused by legionella bacteria. It is the most well-known and serious form of a group of diseases known as legionellosis. Other similar (but usually less serious) conditions include Pontiac fever and Lochgoilhead fever.

Infection is caused by breathing in small droplets of water contaminated by the bacteria. The disease cannot be passed from one person to another.

Everyone is potentially susceptible to infection but some people are at higher risk, eg those over 45 years of age, smokers and heavy drinkers, those suffering from chronic respiratory or kidney disease, and people whose immune system is impaired.

Legionella bacteria are common in natural water courses such as rivers and ponds. Since legionella are widespread in the environment, they may contaminate and grow in other water systems such as cooling towers and hot and cold water services.

They survive low temperatures and thrive at temperatures between 20-45°C if the conditions are right, eg if a supply of nutrients is present such as rust, sludge, scale, algae and other bacteria. They are killed by high temperatures.

Under general health and safety law, you have to consider the risks from legionella that may affect your staff or members of the public and take suitable precautions. As an employer or a person in control of the premises (eg a landlord), you must:

■ prepare a scheme (or course of action) for preventing or controlling the legionella risk;

■ implement and manage the scheme – appointing a person to be managerially responsible, sometimes referred to as the ‘responsible person’;

■ keep records and check that what has been done is effective; and

■ if appropriate, notify the local authority that you have a cooling tower(s) on site (see ‘Other duties’).

The risk assessment is your responsibility as the employer or person in control of the premises. You may be able to carry out the legionella assessment yourself but, if not, you should call on help and advice from within your own organisation or, if this is not available, from outside sources, eg consultancies.

You need to find out if your water systems (including the equipment associated with the system such as pumps, heat exchangers, showers etc) are likely to create a risk.

■ 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?

If a legionella risk is identified which cannot be prevented, you must introduce proper controls.

Risks from legionella in water systems can be controlled but careful planning, a successful legionella management policy, competent staff and attention to proper legionella control strategies are all essential.

You should consider whether you can prevent the risk of legionella in the first place by looking at the type of water system you need. For example, is it possible to replace a wet cooling tower with a dry air cooled system?

You need to prepare a written scheme which sets out how you intend to control the risk from legionella. You should describe:

■ legionella testing your system – an up-to-date plan or schematic diagrams are sufficient;

■ who is responsible for carrying out the legionella test and managing its implementation;

■ what control methods and other precautions you will be using; and

■ what legionella checks will be carried out on the control scheme and how often.

■ ensure that the release of water spray is properly controlled;

■ avoid water temperatures and conditions that favour the growth of legionella bacteria and other micro-organisms;

■ ensure water cannot stagnate anywhere in the system by keeping pipe lengths as short as possible or by removing redundant pipework;

■ treat water to either kill legionella (and other micro-organisms) or limit their ability to grow.

You need to appoint someone to take responsibility for managing the control scheme that you have put in place.

The ‘responsible person’ needs to be competent – that is, they need to have sufficient knowledge and experience of your system to enable them to manage and control the scheme effectively.

If there are several people responsible for managing the system and/or control scheme, for example because of shift-work patterns, you need to make sure that everyone knows what they are responsible for and how they fit into the overall management of the system.

If you decide to employ contractors to carry out legionella water treatment or other work, it is still the responsibility of the appointed person to ensure that the treatment is carried out to the required standards

If you employ five or more people you must record the significant findings of your risk assessment. This means writing down the significant findings of the assessment and details of any monitoring or checking carried out.

If you have fewer than five employees you do not need to write anything down, although it is useful to keep a written record of what you have done.

You also need to keep records of your written scheme and who is responsible for managing that scheme. You should also keep the results of your routine legionella testing. You need to keep these records for a minimum of five years.