Legionella Testing and Risk Assessment
Under Approved Code of Practice L8 Legionnaires’ disease – The control of Legionella bacteria in water systems, it is a legal requirement ‘to identify and assess the risk of exposure to legionella bacteria from work activities and water systems on the premises and any necessary precautionary measures.’ In other words, any workplace with water services must have a risk assessment and the regulations even apply to some domestic properties such as for Housing Associations, where maintenance staff may be exposed.
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Legionella Risk Assessments should be reviewed on a regular basis and a new assessment is required if any of the following apply:
» it is more than two years since the last risk assessment
» there have been changes to the water systems
» the building use has changed
» there is new information about risks or control measures
» checks indicate that control measures are no longer effective
» a case of Legionnaires’ disease/legionellosis is associated with the system.
Healthy Buildings International are registered with The Legionella Control Association and work to the recommended code of conduct for Risk Assessment.
The Legionella Testing and Risk Assessment service may include some or all of the following:
» Production of a list of water services plant and outlets.
» Inspection of plant to assess condition and compliance with Approved Code of Practice (ACoP) L8 and Water Bye-Law requirements.
» Production of water system schematics.
» Samples for the presence of legionella bacteria from various locations within the down service water systems e.g. showers, taps etc or from evaporative cooling systems.
» Samples for microbial analysis, using dip slides, from various locations within the down service water systems e.g. showers, taps, tanks etc or from evaporative cooling systems.
» Temperature measurements will be taken from various locations within the down service water systems e.g. showers, taps, tanks etc or from evaporative cooling systems.
» pH measurements will be taken from various locations within the down service water systems e.g. showers, taps, tanks etc or from evaporative cooling systems.
» Measurement of conductivity from evaporative cooling systems.
» Identification of sources of risk.
» Numerical assessment of level of risk at the sources identified using HBI’s unique algorithm.
» Review of the existing System of Legionella Control to assess compliance with ACoP L8 requirements.
» Creation of System of Legionella Control on Records For Buildings, HBI’s web-based management system.
In July, 1976 in Philadelphia an outbreak of pneumonia affected 221 people, killing 34. Many were members of the American Legion attending a convention in the Bellevue-Stratford Hotel. The causative organism, Legionella pneumophila, is widely distributed in nature and although positively identified and named only several months after the outbreak of the illness that gave the disease its name, legionnaires' disease, it has probably been causing infections in humans for hundreds of years.
There are now identified more than 30 species of legionella and at least 14 serogroups of Legionella pneumophila, however the Pontiac sub-type (MAb2) of Legionella pneumophila Serogroup One is responsible for more than 90% of known infections. In recent years up to 300 cases of legionnaires' disease are reported each year in England and Wales alone.
Legionella species occur naturally in soil, rivers and lakes and have the ability to successfully colonise man-made water handling and storage systems, which often provide ideal conditions of nutrition and temperature for their proliferation. Legionella infection is not transmissible from person to person; it is caused by the inhalation of water aerosols containing the bacteria by susceptible individuals. The numbers of organisms required to induce infection is not known but will vary according to age, general health and other predisposing factors.
The potential for legionella to become a hazard to the health of large numbers of people is greatly enhanced by conventional water and air conditioning engineering methods as used in re-circulating cooling towers, air conditioning chill coils and humidifiers, water storage and distribution systems and other aquatic systems such as whirlpool spa baths.
Cooling Towers and Water Storage Systems
The single isolation of these bacteria from a water system does not mean that the disease will necessarily manifest itself but if the contaminated water becomes an aerosol the risk of human infection is greatly increased. Thus if man-made water systems produce jets, sprays or mists, as with cooling towers, showers and some types of humidifiers, it is important to minimise the chances of legionella colonising the water reservoirs, storage tanks and other aquatic systems serving them. Certainly cooling towers are of particular importance for their operating temperatures are at an optimum level, they are designed to aerosolise the water and they are easily and frequently contaminated by wind-blown dusts and soil particles which can carry with them disease producing micro-organisms including legionella
The presence of these bacteria in water systems is therefore of prime importance to engineers, building managers and hygienists. The organisms can be controlled in such systems by the application of biocides and their detection and identification plays a vital role both in initial assessment of the water system and subsequent treatment effectiveness and ongoing water quality monitoring.
The Health & Safety at Work Act 1974 (HSWA) and Control of Substances Hazardous to Health Regulations 1988 (COSHH) include for the risks from hazardous micro-organisms, including legionella. Under the Regulations risk assessments and the adoption of appropriate precautions are required to be made. Furthermore, the Approved Code of Practice and Guidance L8 (Legionnaires' disease. The control of legionella bacteria in water systems), (the ACoP), sets out statutory requirements for dealing with such risk. The ACoP applies to the risk from legionella bacteria in any circumstances where the HSWA applies. In order to comply with their legal duties, as detailed in the ACoP, employers and those with responsibility for the control of premises should:
» identify and assess sources of risk, (the ACoP dictates that persons responsible for undertaking the risk assessment need to have access to competent help and advice);
» prepare a scheme for preventing or controlling the risk;
» implement, manage and monitor precautions;
» keep records of the precautions; and
» appoint a person to be managerially responsible.
Identification and Assessment of Risk
At the time of water sampling HBI Field Technicians evaluate all the relevant factors affecting the condition of the water source, such as, system design, accessibility to airborne contamination, exposure to light, circulation rate, pH, temperature, droplet formation, water treatment programme, etc.
Testing the sample will then identify if the source is safe or contaminated at the time of sampling. Assessment of the hazards then permits high-risk sources to be identified and ensures that responsible means of implementing precautions are undertaken.
As the likelihood of future contamination can be predicted this also allows maintenance regimes and water treatment protocols to be established on the basis of need rather than on guesswork.
The HBI sampling protocol is designed to ensure accuracy, avoid ambiguity, and protect client confidentiality and to aid in diagnosis of contaminated water systems.
Water from cooling towers, spray-type humidifiers and other air conditioning associated equipment present the greatest degree of risk and a routine sampling procedure from their water storage reservoirs and from other water systems can be set up. This allows management to have up-to-date reports on the status of their building water systems and gives confidence that maintenance standards are being met. Tenants, staff and building users can then be assured that all reasonable precautions are being taken to avoid the spread of legionnaires' disease.
Furthermore, immediately prior to routine cleaning and maintenance, cooling towers and humidifiers can be tested for the presence of legionella. If it is found to be present then the necessary water treatment can be done, quickly verified for its effectiveness and engineering staff assured that they will not be exposed to microbial hazards as they carry out the work.
Hot and cold water services and other water systems can similarly be appraised for risk and a suitable system of maintenance, cleaning and testing implemented.
Because of its widespread presence in nature and its ability to thrive in man made water systems it is unlikely that legionella can be completely or permanently eradicated from these potentially hazardous systems. However, by suitable design, maintenance, treatment and testing of building water systems it is possible to control the conditions which allow this and other bacteria, fungi and protozoans to multiply, thus keeping the incidence of disease outbreaks associated with such systems at a minimum. Any Proactive Monitoring System applied to buildings and their water systems should therefore include regular monitoring for the presence of legionella at appropriate outlets.
The increased public awareness environmental health issues and the acceptance of the legislation now approved have ensured that risk assessment and appropriate preventative maintenance steps, should now be considered as the norm for every building.