There are still around 300 reported cases of Legionnaires’ disease in the UK every year.
Meanwhile, around 120,000 people are thought to have died in the US since the cause of the disease was established there more than 30 years ago.
However, the problem is probably far more serious because so many cases go unreported. Sufferers display the same symptoms as pneumonia victims, which means that many who die from legionella infection are lost among the general pneumonia statistics.
It is more than 10 years since the notorious outbreak in Barrow-in-Furness, Cumbria, that killed seven people and hospitalised another 180. Despite the huge public outcry and legal furore that followed, incidents of Legionnaires’ disease in workplaces, hotels, hospitals and other public buildings are still occurring on a regular basis. Why is this?
Notorious
Poor design and/or maintenance of cooling towers and building water systems is a major reason behind outbreaks. The more complex a water distribution system, the more likely it is to provide areas where the bacteria can grow. Long pipe runs are notorious for harbouring legionella bugs, because water remains undisturbed there for long periods; stagnant water can be a dangerous harbour for the bacteria that leads to Legionnaires’ disease.
The bacteria that cause the disease — legionella pneumophila — occur naturally in water and earth, but will proliferate and spread in stagnant hot water systems if the conditions are right. Scientists are concerned that the bacteria could be mutating. Some types have been reported as more resistant to the high water temperatures that previously used to kill the bacteria, which in other cases is multiplying in ever-lower temperatures.
FM QUICK FACTS
300
The number of reported cases of Legionnaires’ disease in the UK every year
120,000
The number of people thought to have died in the US since the cause of the disease was established there more than 30 years ago
Poor water temperature control is an increasingly difficult area, particularly with the increase in the number of lower temperature water heating systems fed by renewable systems. Lack of awareness of the potential risks and inadequate staff training will exacerbate any of these technical problems.
The growing emphasis on saving energy has led to more building operators switching off and/or turning down hot water systems overnight and at weekends to save money and cut carbon emissions. This can lower the temperature of the stored hot water into the ‘danger zone’ between 20C and 50C, which legionella bacteria enjoy. The optimum temperature for proliferation is around 37C.
The increasing use of solar thermal heating systems can also, if the system is not properly controlled and maintained, result in more hot water being stored in just this temperature range. Safety concerns about hot water scalding have also led to an increase in blending valve installations, which can lower hot water temperatures into the legionella zone.
Also, some strains of the bacteria are able to survive the low-level dosing of chlorine dioxide that is used as a cheaper alternative to more comprehensive maintenance regimes.
In general, the big threat is poor maintenance and monitoring. Budgetary pressures have forced many facilities managers and building operators to reduce the frequency and thoroughness of system checks. In many instances, even the vital initial risk assessment is not being carried out.
A regular programme of inspection and maintenance of air conditioning, water holding and water supply systems carried out by competent people is essential to reduce health risks. Clusters of cases are often traced back to poorly maintained cooling tower systems, air conditioning plants or hot and cold water systems.
Building operators are legally liable and the Health & Safety Executive (HSE) has been unstinting in its efforts to track down the source of outbreaks and the people responsible for failing to maintain systems in a safe condition.
FMs are advised to maintain records that prove they have taken the right steps, including:
- Risk assessment
- Basic principles of control
- Risk factors
- Programme of control
- Evidence of monitoring, records and training
Risks can be dramatically reduced by setting up a programme of regular inspection and maintenance of susceptible plant and equipment, including regular cleaning and disinfection. This does not need to be expensive — the major cost is in human time spent checking and remaining vigilant.
Stagnant water is where the bacteria grows most prolifically, so those parts of hot and cold water systems that are only used intermittently should be regularly flushed and cleaned. The HSE recommends that this is done weekly with shower heads and hoses cleaned quarterly.
Taps and showers are the main route used by the bacteria to get into the air close to potential victims in the form of a breathable aerosol. The HSE also recommends that cold water storage tanks be cleaned periodically and the water drained from hot water cylinders to check for debris or signs of corrosion.
Legal obligations for building owners and occupiers are set out in a single document, published by the Health and Safety Commission (HSC), called Legionnaires’ disease — the control of legionella bacteria in water systems. This is an HSC Approved Code of Practice (ACoP), commonly referred to as L8.
It is the building owner’s responsibility to put a proper control strategy in place that includes a system for managing the maintenance of water systems, regular monitoring with the records kept for five years, and training for everyone in the management chain, with their skills updated periodically.
Maintenance staff should regularly check the temperature at which water is being stored. Standard advice is to keep hot water above 60C, but as the potential bacteria mutations show, it is important to remain vigilant.
Avoiding complacency is the key. Legionella bacteria is all around us — it occurs naturally — but it becomes a threat to health when we provide it with conditions in which it can proliferate and then be distributed in a breathable form into an occupied area.
The overall threat is the same, but the potential sources are changing. Remain vigilant.
