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About Legionella and Legionnaires Disease
Why is Legionella pneumophila a Risk?
There are many species of Legionella bacteria some of which cause pneumonia-like diseases of varying severity, collectively called Legionellosis. Legionella pneumophila is the most pathogenic species of Legionella causing a specific type of Legionellosis called Legionnaires' disease which is a potentially fatal type of pneumonia resulting in the death of approximately 12% of reported cases.
Initial symptoms include
- fever
- severe headache
- chills and muscle pain
Further symptoms may include
- a dry cough
- difficulty breathing
- diarrhoea
- vomiting
- confusion and delirium
Susceptible groups include:
- diabetics
- smokers
- people over 45
- the elderly
- alcoholics
- those with cancer
- chronic illnesses or immunosupression
How is Legionnaires' Disease Contracted?
Legionnaires' disease is contracted when Legionella pneumophila bacteria are inhaled and infect the lungs. The bacteria may be inhaled if they are present in tiny water droplets (aerosols) or in the air after the water has evaporated.
Who is Responsible for a Legionella Outbreak?
Employers are responsible for ensuring that, as far as is reasonably practicable, persons using or affected by their facilities are not exposed to risks to their health or safety - Health and Safety at Work Act 1974 and Control of Substances Hazardous to Health Regulations 2002.
EMU provides specialist survey, laboratory and consultancy services to support organisations involved in water quality management. Our expertise includes laboratory testing of environmental, treated, recreational and wastewaters for microbiological indicators. We support all our laboratory testing with sampling and survey services including swimming pool sampling, bathing water investigations, pollution studies, environmental monitoring and wastewater/UV disinfection performance tests. The combination of 14 years experience in water quality sampling and microbiological testing and stringent quality assurance credentials, is the foundation upon which the company's activities are based.
Specific guidance for employers can be found in the HSE leaflet. Legionnaires' disease: A guide for employers . Responsibilities under Health and Safety legislation extend to:
- Employers / managers
- Persons responsible for control of premises (e.g. landlord)
- Service providers (e.g. maintenance companies)
- Suppliers and Installers
What is Required Under Health and Safety Law?
The above regulations impose a requirement on responsible persons to:
- Identify and assess the risk of exposure to Legionella bacteria
- Prevent and control the risk
- Monitor the effectiveness of controls put in place
- Controls to reduce the risk from Legionella bacteria should be managed and monitored which includes ensuring that adequate microbiological testing is carried out.
Guidance on the legal requirements and specific controls for Legionella, including requirements for water quality monitoring are outlined in the HSE Approved Code of Practice L8 (ACOP) "Legionnaires' disease The control of Legionella bacteria in water systems"
Legionella Risk Assessment
The risk from Legionella depends on a number of factors:
- Suitable conditions for growth of Legionella bacteria(e.g. water temperature between 20 ° C-45 ° C, stagnant water, infrequently used outlets, debris/slime/scale etc)
- Presence of Legionella
- Release of aerosols
- Presence of (vulnerable) people to inhale aerosols
- Legionella bacteria are naturally present in environmental water sources e.g. rivers and reservoirs but usually in low numbers which pose a threat to human health.
As they are naturally present in water, Legionella bacteria frequently enter man-managed water systems which often provide suitable conditions for Legionella bacteria to colonise and multiply into potentially dangerous numbers. Legionella bacteria can multiply between 20°C - 45°C, are dormant below 20°C and will not survive above 60°C. Legionella bacteria benefit from the nutrients and protective conditions provided by algae, slimes, sludge, scale and other bacteria that often build up in water systems. Once Legionella bacteria have colonised a water system, risks associated with human exposure will depend on the likelihood of the production and inhalation of aerosols. High-risk water systems therefore include any plant or system containing water at temperatures between 20 ° C-45 ° C and likely to release fine sprays or aerosols. This means that any trade, business or premises that uses or stores water could be the source of Legionella pneumophila and the cause of an outbreak of Legionnaires disease.
Just a few examples of high-risk systems for which EMU supply Legionella testing services:
- Spa baths (including shop displays)
- Cooling towers and evaporative condensers
- Hot and cold water systems in large buildings (e.g. hotels, care homes, schools, shops and hospitals)
- Humidifiers and Air conditioning units
- Domestic hot and cold water systems
- Showers (including emergency showers)
- Sprinkler / hose systems (e.g. fire fighting equipment)
- Misting systems (e.g. horticulture, food retail)
- Machine coolant systems
- Dental equipment
- Car Washes
- Fountains and water features (including shop displays)
Prevention and Control of Risks
Where a risk has been identified, controls must be documented, implemented and managed by competent persons. In general, controls will be designed to:
- reduce the occurrence and exposure to aerosols or
- reduce colonisation/proliferation of bacteria e.g.
- Avoiding water temperatures between 20 ° C-45 ° C
- Avoiding stagnation
- Avoiding the build up of biofilms / sediments
- Disinfection or water treatment.
Controls must be monitored and recorded to demonstrate that they are effective. This will involve inspecting the water system (e.g. for physical damage or sediment build up) and checking performance (e.g. routine temperature testing). Monitoring will also include microbiological testing of water quality as well as chemical / physical parameters. Routine sampling and microbiological testing of water quality is commonly used to demonstrate effectiveness of controls against the proliferation of Legionella bacteria in water systems.
For effective monitoring, the persons responsible must ensure:
- Sampling is carried out by trained persons in accordance with appropriate procedures
- Testing is carried out by a regulated, accredited laboratory.
Legionella Risks from Spas
An increasing number of Legionella outbreaks in recent years have been associated with Spa pools. The risk of exposure from spa pools is not just to bathers. Legionnaires' disease has been contracted by maintenance/attendance staff and even members of the public from demonstration or show room spas.
Spa pools are a high-risk systems for the following reasons:
- Operational temperatures are optimal for Legionella
- High-velocity jets and air injection agitate the water producing of aerosols
- Recirculation of water which is not changed between bathers (whirlpool baths which discharge water after each use do not pose such a high risk).
- High bather loading in a relatively small volume of water
Numerous microorganisms which are potentially harmful to humans can occur in spas. Non-enteric infections are easily transmitted e.g. viruses, fungi and bacteria which can lead to skin, ear and other infections as well as infections linked to faecal contamination of the water by bathers. Disinfection ensures that bacteria and viruses are eliminated and hence pose no risk to users. Health and Safety legislation requires specific routine testing for indicator bacteria in swimming pools and spas. Failure to do so may result in outbreak of illness or infection, closure and liability to prosecution. The presence of indicator bacteria however are not a good indication of the risk from Legionella and therefore regular sampling and testing specifically for Legionella is required for spas. Legionella samples taken from spas will require the addition of a neutralising agent and should be taken from the main pool as well as the balance-tank.
Legionella in Hot and Cold Systems
Over recent years the association of Legionella outbreaks with hot and cold water systems has reduced probably due to improved maintenance. Hot and cold water systems however, present a foreseeable risk from Legionella. Water storage tanks can accumulate deposits that support bacterial growth, including Legionella, which is then distributed around the pipe work. Maintained at optimal temperatures, Legionella bacteria can grow in infrequently used outlets, peripheral parts of the domestic water system or dead legs. Problems most frequently occur in hospitals, care homes, rejuvenation centres etc due to the exposure to vulnerable people.
Hot and cold water system controls against Legionella may include detailed specification of the water system, maintenance to reduce build up of sediments/scale, prevention of stagnation, removal/flushing of deadlegs and infrequently used outlets, use of high temperatures to kill Legionella or introduction of biocides/disinfection. As part of the routine hot and cold water system inspection, temperature monitoring of all hot and cold outlets should be carried out and documented. Legionella testing for aerobic colony counts in hot and cold water systems is not routinely required, however, testing for Legionella should be carried out on systems where immunocompromised people/patients are at risk, or when an outbreak is suspected/reported. Testing may be required on a weekly basis for systems where control measures are compromised. Guidance on the use of Legionella testing and interpretation of results for hot and cold water systems is provided in HSE ACOP L8.
Legionella Testing for Cooling Towers
Cooling towers are recognised as high-risk water systems and require routine monitoring of water quality including microbiological parameters. Total Viable Counts in samples from cooling towers should be less than 10,000 cfu/ml and Legionella typically less than 100 cfu/litre. Detailed guidance is provided in the HSE ACOP L8.
Legionella in Air Conditioning Units
An increasing number of incidents of Legionella are associated with air conditioning units, including the recent outbreak at an arts centre in Barrow-in-Furness which has resulted in the prosecution of the councillor responsible for maintenance contracts. Microbiological testing is recommended where there is a risk of exposure to aerosols to the public or employees.
Legionella Testing for Humidifiers
Humidifiers can present significant risks from Legionella when water is maintained above 20 ° C within a resevoir / tank which is not adequately maintained or cleaned. Significant contamination of such systems has been reported and therefore risk assessment, documented maintenance and monitoring is required for humidifers and air washers. A recent case involved the death of two people after contracting Legionella from a Buffet unit at a hotel in Cardiff. The Managing Director of the installation company faced manslaughter charges and the hotel and maintenance manager were also charged with breeches of Health and Safety.
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Registered Address: 1 Mill Court, The Sawmills, Durley, Southampton, Hampshire, SO32 2EJ