Legionnaires' disease (1991)

[Music] [Applause] water is a basic substance of life it contains millions of of microscopic organisms one of which can be the bacterium Legionella in factories and hospitals and on the rooftops of hotels and offices we can create the right conditions for Legionella to multiply through industrial processes hot water systems and cooling towers it's not known exactly how systems can become come seeded with Legionella there is some evidence that the organism is washed into pip work during building construction it may also enter in low numbers through the Main's water supply Airborne droplets or particles containing lianella May contaminate reservoirs open tanks and cooling ponds once a system is contaminated and given the right temperature range intermittent use or stagnation Legionella will multiply and colonize that system the rate at which it multiplies is determined by water temperature between 20 and 45° C growth may be rapid but above 50° the organism will begin to die Towers like this are commonly used for industrial cooling systems and air conditioning and have been associated with outbreaks of Legionnaire's Disease within a square mile of any City Center there may be hundreds of units like this on rooftops there may be a health hazard if any of them are producing spray containing Legionella this may be carried long distances before becoming dilute enough to be harmless to contract legioner disease one must inhale the organism and it must penetrate deep into the lowest part of the lungs and to do so the organ M must be contained in a particle of less than 3,000 of a millimeter or 3 micromet in diameter now particles of that size can remain suspended in air for prolonged periods of time and scientifically we have a term for such a suspension which is an aerosol aerosols can be generated from water in a variety of ways simply turning on a tap May generate a shower rainfall or in the case of cooling towers the distribution system to spray or the trough and gutter distribution system an aerosol produces a range of droplet sizes larger ones fall to Earth fairly rapidly but smaller ones stay airborne and continue to evaporate down to an inhalable size that can cause infection legionaire disease is an infection caused by Legionella bacteria its main feature is pneumonia so that it presents with a fever chills headache aches and pains a cough soon develops usually a dry cough at first then patients may get difficulty with breathing and have chest pain they usually admitted to hospital towards the end of the first week of illness okay is that comfortable diagnosis of Legionnaire disease relies on Laboratory Testing to distinguish it from other forms of pneumonia confirming an outbreak takes time for water samples from the suspected source to be cultured this is a culture after 48 hours and this after 72 hours most cases of legionaire disease appear to be sporadic in other words no link is established with any other case of legionaire disease most spreaded cases um are indigenous in other words they're contracted in this country but each year up to a third of cases associated with travel abroad now each year in this country we detect between four and six outbreaks of legionary disease the most common source of an outbreak of legionary disease there a hot water system in a large building such as a hotel or hospital no cases of Legionnaire disease have been attributed to domestic Water Systems in large Buildings Hot Water Services are one of the main sources of Legionnaire disease Legionella can multiply in various parts of the system for example in storage tanks if there in a warm place like a roof space which is heated by the sun if the temperature rang is Right Legionella can multiply in calorifiers the large hot water cylinders and in the pipes if water stands for long periods when the system is used intermittently the best way to avoid risk in hot water systems is to store and circulate the water at the right temperature water should be stored at 60° C and reach the TAPS at 50° the system should be used frequently so that the water doesn't stand the storage tanks and calorifiers of hot water systems should be inspected annually it's good practice to drain water and other deposits from the bottom of calorifiers frequently to reduce the collection of sediment if there's a buildup of slime scum or other deposits they should be drained cleaned and disinfected cooling towers are the second most frequent source of outbreaks of Legionnaire's Disease a cooling tower is a heat exchange system warm water enters the tower at the top and is sprayed and splashed onto the packing material as the water falls air is blown or drawn upwards through the packing material cooling the water the air escapes from the top of the cooling tower taking with it some water as Aerosoles in order to reduce the Escape of Aerosoles drift eliminators are used the cooled water is collected in the pond and recirculated to the air conditioning system or industrial process where it acquires heat then it's returned to the top of the cooling tower although there's a lot of spray here in an induced draft cooling tower there is little history of these towers causing Legionnaire's Disease cooling towers produce Aerosoles and aerosols must be contained within the cooling tower because the conditions there are ideal for Legionella to multiply water is at about 30° C it collects dust from the incoming air leaves and other materials May settle in the pond providing food for the bacteria and rust and corrosion products May provide more food a slimy layer called a bofilm May build up on the surface of the tower which may shelter these organisms because of this regular cleaning and disinfection is necessary before scrubbing or using a hose the operator must put on suitable respiratory protective equipment then everything is cleaned to remove sludge scale rust biofilm and debris cleaning is done twice a year or more frequently on particularly Dusty industrial processes on a regular basis chemicals are added either manually or automatically to ensure the continued safe running of the system tests are performed to monitor the water quality and levels of chemicals and bacteria outbreaks of Legionnaire disease can affect people at work or the general public so there is great media interest several Committees of quiry have been set up by Parliament to investigate various aspects of Legionnaire's Disease and an approved code of practice has been published by the health and safety commission to give advice most of the time the risk of Contracting Legionnaire's Disease is low but given the right circumstances this can change rapidly to become a high risk the risk is controllable by following following a regular program of cleaning and maintenance the threat of Legionnaire disease can be contained [Music] [Applause] [Music] [Applause]