Legionnaires’ disease

Legionnaires’ disease is an airborne disease caught by inhaling small droplets of contaminated water. It is not contagious and is not known to spread directly from person to person. It cannot be caught by drinking contaminated water.

Legionella bacteria are common in natural water sources such as rivers, lakes and reservoirs, usually in low numbers. The risk of the disease is present when water is stored or re-circulated in man-made water systems. Contamination can develop and spread in purpose-built systems like cooling towers, evaporative condensers, hot and cold water systems and whirlpool spas, humidifiers, air-washers, emergency showers and indoor water fountains. Problems develop when bacteria spread quickly through water-based systems in warm temperatures (between 20oC to 45oC).

In 2012, the HSE updated its guidance Legionnaires’ disease: a brief guide for dutyholders. It explains the employer’s duty to ensure that a risk assessment of the water system is carried out by a competent person and kept up to date. Safety reps are entitled to see the risk assessment and the results of any monitoring and inspection. The risk assessment must include:

• management responsibilities, including the name of the competent person and a description of the system;

• any potential risk sources of the bacteria;

• any controls currently in place;

• monitoring, inspection and maintenance procedures;

• records of monitoring results, inspections and checks.

The employer’s primary obligation is to prevent the risk of legionella arising in the first place, for example by considering replacing a wet cooling tower with a dry air-cooled system.

Under the guidance, the employer must:

• ensure that the release of any water spray is properly controlled;

• avoid water temperatures and conditions that encourage the growth of micro-organisms;

• ensure water cannot stagnate anywhere in the system (keeping pipe work as short as possible, or removing redundant pipes);

• avoid materials that encourage the growth of Legionella;

• keep the system and the water clear; and

• treat water to kill legionella or to limit their ability to grow.

In July 2012, the HSE issued a safety notice telling businesses to do more to protect workers and members of the public from exposure to legionella after it identified common failings in legionella control from a review of outbreaks of Legionnaires’ disease over the past ten years. Two outbreaks in Edinburgh and Stoke-on-Trent in 2012 caused five deaths and left more than 120 other members of the public ill.

The HSE says its review findings confirmed that cooling towers and evaporative condensers are the most common source of significant outbreaks. Ninety per cent of outbreaks stem from failure to recognise potential legionella problems or to adopt effective control measures.

The notice also stressed the need for effective and consistent monitoring of water quality and the importance of responsibilities being assigned to named individuals with proper management oversight.

In September 2012, it issued a similar safety notice targeting companies and organisations that use hot and cold water systems for bathing and washing or in manufacturing processes, including leisure centres with spa pools and care homes. This stresses the need for measures to be in place to control identified legionella risks and for these to be reviewed regularly.

It also warned that organisations with cooling towers face checks to ensure they are managing legionella risks appropriately.

Figures released to the Chartered Institute of Environmental Health (CIEH) journal, Environmental Health News, following an information request showed that the number of legionella inspections carried out by the HSE had fallen by 44% over the past three years. The number of legionella inspections at cooling towers fell from 237 in 2010 to 134 in 2011.