Why is a Legionella Risk Assessment Important?

Man coughing outdoorsLegionnaires’ disease, a potentially serious health disorder, is triggered by a bacterium known as Legionella which is commonly found in water and other aquatic environments. This bacterium is most active when the water contains enough nutrients to encourage its development and multiplication and the water temperature is between 20 to 45 degrees Celsius.

A Legionnaires risk assessment is fundamental for lowering the risks of exposure to Legionella bacteria and contracting Legionnaires’ disease from contaminated water in the workplace. Individuals are vulnerable to contracting this potentially fatal bacterial disease by breathing in water droplets suspended in the air that contains legionella bacteria. Contamination can occur in hot & cold water systems, aquatic settings, wet air-conditioning units, spas and hot water baths, and atomizers.

Dangers of legionella infection

Legionella bacterium is responsible for a type of pneumonia known as Legionellosis. It can affect any individual once they have inhaled the Legionella bacteria. Most cases of Legionella infection can be treated with antibiotics; however, some cases of the infection are fatal (typically 10-15%). Individuals with the long-term respiratory ailments or kidney disorders, elderly people, smokers, people with weakened immune systems, and heavy drinkers are particularly susceptible to the effects of Legionnaires’ disease.

Identifying sources of legionella

A detailed review of the water systems used in a building or facility and then identifying all possible sources of danger resulting from Legionella contamination are the basic steps in determining the legionella threat in a workplace. The potential for bacterial infection is greater in man-made water systems. With elevated water temperatures of between 20 to 45 degrees Celsius, nutrients, and organic matter commonly found in water systems, the bacteria if left untreated can grow in hot tubs, water tanks and pipes to cause problems. Settings where water droplets are formed in the air (an aerosol) such as in showers and in cooling towers are considered to be higher risk with the potential to expose people to Legionella bacteria.

How to assess the legionella risks

The potential threat of exposure to Legionella and a subsequent outbreak of Legionnaires’ disease can be greatly decreased by identifying the likely bacterial sources, understanding the risks involved and setting out a plan how to manage them to prevent the growth and proliferation of legionella. This work can be carried out by Legionella specialist companies such as Legionella Control International who have specific expertise in such specialized areas of water safety and engineering risk management.

How Legionnaires’ disease can be controlled

Legionnaires’ disease is a serious lung disease that can in some cases be fatal. It is caused by the legionella bacterial organisms that usually live in common water bodies like rivers and lakes, or are found in mud and soil. These microscopic organisms can live in man-made water systems and may duplicate there to cause contamination of the water supply.
Controlling the risks associated with Legionnaires’ disease includes routine cleaning, disinfection and monitoring of the water systems. Some of the preventive steps are illustrated here:
• Since legionella bacteria thrives in warm stagnant water, the temperature of the cold water in the system should be kept below 20ºC, and the hot water above 50ºC, higher in hospitals and healthcare settings where the hot water temperatures should be at least than 55ºC.
• Since legionella can grow in water that is contaminated with algae, slime, rust, amoebae, lime scale, corrosion products, and biofilm or other organic substance and bacteria, keeping it clean and free of such contamination will also make a difference.
• Water should never be allowed to stagnate as legionella can flourish in water that remains static for long periods. Anything that will allow such stagnation should be removed from the water systems where possible.

Controlling Legionnaires’ disease in cooling water systems

All man-made water systems have the potential to become contaminated with Legionella bacteria and expose people to the dangers of Legionnaires’ disease. To manage these risks many countries have laws and guidelines that must be followed to protect the safety and health of people. These activities involve commissioning, on-going operations, maintenance, cleaning and disinfection, and other routine procedures.
• There should be periodic checks for microbial growth done by testing the water quality.
• The cooling water systems should be designed in a way that facilitates their regular cleaning and disinfection.
• Water sprays should be carefully managed, treated and released far from where they can cause problems for people in the surrounding areas.
• The water in each cooling system must be kept moving and biocide chemicals should be added to control the growth and development of microbial contamination, scaling and corrosion.
• Cooling towers must be managed and regularly assessed at least once a month with pertinent water treatment, microbiological tests, and cleaning and disinfection schedules.

Controlling Legionnaires’ in air conditioning systems

Air conditioning systems can pose an increased threat level and must be managed properly.
• Air conditioning and cooling systems should be designed properly, commissioned, operate effectively, serviced, cleaned and disinfected regularly.
• There must be an effective facility for the systems to exhaust away from public areas and simple and convenient access to the service the air filters.
• The air channels must be designed so that they do not collect humidity. There should also be an arrangement for easy maintenance access.
• When evaporative coolers are not in use, they should be drained and stored dry.
• In order to limit blockages and contamination, heat exchange coils must have corrosion-resistant fixings.