L8 - Approved Code of Practice (ACoP) & Guidance
"Legionnaires' disease: The control of legionella
bacteria in water systems"
In the UK the Health and Safety Executive’s Approved
Code of Practice (ACoP) and Guidance document titled "Legionnaires'
disease: The control of legionella bacteria in water systems"
(L8) gives practical advice on how to comply with UK health and
safety law with respect to the control of Legionella bacteria. This
Code is important in that it has a special legal status. If you
are prosecuted for a breach of health and safety law, and it is
proved that you did not follow the relevant provisions of the Code,
you would need to demonstrate that you have complied with the law
in some other way or a Court would find you at fault.
The document also contains guidance issued
by the Health and Safety Commission and Health and Safety
Executive. Following the guidance is not compulsory and organisations
are free to take other action. However, if you do follow the
guidance you would normally be doing enough to comply with
the law.
Accepta have negotiated special permission from the copyright
owners of the Approved Code of Practice, L8 document, the
Controller of HMSO and the Queen’s Printer for Scotland,
to reproduce the Code in full. Consequently, we are proud
to be serialising the Code in our Accepta newsletter. |
Legionella Bacteria |
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Approved Code of Practice (ACoP) and Guidance
"Legionnaires' disease: The control of legionella
bacteria in water systems" (L8)
Introduction
1 - This Approved Code of Practice gives practical advice on
the requirements of the Health and Safety at Work etc Act 1974
(HSWA) and the Control of Substances Hazardous to Health Regulations
1999 (COSHH) concerning the risk from exposure to legionella bacteria.
In particular it gives guidance on sections 2, 3, 4 and 6 (as
amended by the Consumer Protection Act 1987) of HSWA and regulations
6, 7, 8, 9 and 12 of COSHH. The Code also gives guidance on compliance
with the relevant parts of the Management of Health and Safety
at Work Regulations 1999 (MHSWR).
2 - This publication replaces two separate documents: the 1995
Approved Code of Practice and the technical guidance, HSG70. This
has allowed information to be consolidated, with the aim of making
it easier to read and understand the duties under the law. Since
the last revision, the Health and Safety Executive (HSE) and others
have funded research to assess the efficacy of new and alternative
control strategies. This new document incorporates the findings
of that research and explains how such strategies can be used
safely and effectively.
3 - This Code applies to the risk from legionella bacteria (the
causative agent of legionellosis including Legionnaires’
disease) in circumstances where the Health and Safety at Work
etc Act 1974 applies.
4 - To comply with their legal duties, employers and those with
responsibilities for the control of premises should:
(a) identify and assess sources of risk
– this includes checking whether conditions are present
which will encourage bacteria to multiply, e.g. is the water
temperature between 20–45°C; there is a means of creating
and disseminating breathable droplets, eg the aerosol created
by a shower or cooling tower; and if there are susceptible people
who may be exposed to the contaminated aerosols (see paragraphs
23–38);
(b) prepare a scheme for preventing or
controlling the risk;
(c) implement, manage and monitor precautions
– if control measures are to remain effective, then regular
monitoring of the systems and the control measures is essential
(see paragraphs 61–65). Monitoring of general bacterial
numbers can indicate whether microbiological control is being
achieved (see paragraphs 124–129 and 183–184). Sampling
for legionella is another means of checking that a system is
under control (see paragraphs 130–131 and 185–189);
(d) keep records of the precautions;
and
(e) appoint a person to be managerially
responsible.
5 - The Code and guidance also set out the responsibilities of
suppliers of services such as water treatment and maintenance
as well as the responsibilities of manufacturers, importers, suppliers
and installers.
Background to the Disease & Organisms
6 - Legionnaires’ disease is a potentially fatal form of
pneumonia which can affect anybody, but which principally affects
those who are susceptible because of age, illness, immunosuppression,
smoking etc. It is caused by the bacterium Legionella pneumophila
and related bacteria. Legionella bacteria can also cause less
serious illnesses which are not fatal or permanently debilitating
(see Box 1). The collective term used to cover the group of diseases
caused by legionella bacteria is legionellosis.
7 - On average there are approximately 200–250 reported
cases of Legionnaires’ disease each year in the United Kingdom
(UK). It is thought, however, that the total number of cases of
the disease may be generally underestimated. About half of cases
are associated with travel abroad. Infections which originate
in the UK are often sporadic, for which no source of infection
is traced. However, clusters of cases also occur and outbreaks
have been associated with cooling tower systems and hot and cold
water systems in factories, hotels, hospitals and other establishments.
Box 1: Legionellosis
(including Legionnaires’ disease)
- Legionnaires’ disease was first
identified following a large outbreak of pneumonia among people
who attended an American Legion Convention in Philadelphia
in 1976. A previously unrecognised bacterium was isolated
from lung tissue samples which was subsequently named Legionella
pneumophila.
- It is normally contracted by inhaling
legionella bacteria, either in tiny droplets of water (aerosols),
or in droplet nuclei (the particles left after the water has
evaporated) contaminated with legionella, deep into the lungs.
There is evidence that the disease may also be contracted
by inhaling legionella bacteria following ingestion of contaminated
water by susceptible individuals. Person-to-person spread
of the disease has not been documented. Initial symptoms of
Legionnaires’ disease include high fever, chills, headache
and muscle pain. Patients may develop a dry cough and most
suffer difficulty with breathing. About one third of patients
infected also develop diarrhoea or vomiting and about half
become confused or delirious. Legionnaires’ disease
can be treated effectively with appropriate antibiotics.
- The incubation period is between
2–10 days (usually 3–6 days). Not everyone exposed
will develop symptoms of the disease and those that do not
develop the ‘full blown’ disease may only present
with a mild flu-like infection.
- Infection with legionella bacteria
can be fatal in approximately 12% of reported cases. This
rate can be higher in a more susceptible population; for example,
immunosuppressed patients or those with other underlying disease.
Certain groups of people are known to be at higher risk of
contracting Legionnaires’ disease; for example, men
appear more susceptible than women, as do those over 45 years
of age, smokers, alcoholics, diabetics and those with cancer
or chronic respiratory or kidney disease.
- The disease is usually diagnosed
by a combination of tests. The organism may be cultured from
the patient’s sputum, bronchial washings or lung tissue.
Alternatively, tests are used to measure the presence of antibodies
in the blood and, increasingly, tests are available to measure
specific antigens in the patient’s urine.
- L. pneumophila is also responsible
for a short feverish form of the illness without pneumonia,
known as Pontiac fever. Its incubation period is typically
between 2–3 days. Another species of legionella, L.
micdadei, is responsible for a similar form of the illness
without pneumonia called Lochgoilhead fever after an outbreak
in Lochgoilhead, Scotland. The incubation period can be up
to 9 days. A high percentage of those exposed to this agent
tend to be affected. However, there have been no recorded
deaths associated with either Pontiac or Lochgoilhead fevers.
- To date, approximately 40 species
of the legionella bacterium have been identified. L. pneumophila
causes about 90% of cases. Sixteen different serogroups of
L. pneumophila have been described; however, L. pneumophila
serogroup 1 is most commonly associated with cases of Legionnaires’
disease in the UK.
- L. pneumophila serogroup 1 can be
further sub-divided to distinguish between strains most commonly
associated with Legionnaires’ disease. Additionally,
‘genetic fingerprinting’ methods such as Restriction
Fragment Length Polymorphism (RFLP) and Amplified Fragment
Length Polymorphism (AFLP) can be valuable tools in the investigation
of outbreaks. Such methods of typing can sometimes provide
a means of linking the organisms isolated from patients to
the sources of cases of outbreaks.
8 - Cases of Legionnaires’ disease have occurred among
staff in the workplace (factories, offices, shops and hospitals);
visitors (delivery drivers) and members of the public (patients,
hotel guests or passers-by).
Natural History of the Legionella
Bacterium
9 - Legionella bacteria are common and can be found naturally
in environmental water sources such as rivers, lakes and reservoirs,
usually in low numbers. Legionella bacteria can survive under
a wide variety of environmental conditions and have been found
in water at temperatures between 6°C and 60°C. Water temperatures
in the range 20°C to 45°C seem to favour growth. The organisms
do not appear to multiply below 20°C and will not survive
above 60°C. They may, however remain dormant in cool water
and multiply only when water temperatures reach a suitable level.
Temperatures may also influence virulence; legionella bacteria
held at 37°C have greater virulence than the same legionella
bacteria kept at a temperature below 25°C.
10 - Legionella bacteria also require a supply of nutrients to
multiply. Sources can include, for example, commonly encountered
organisms within the water system itself such as algae, amoebae
and other bacteria. The presence of sediment, sludge, scale and
other material within the system, together with biofilms, are
also thought to play an important role in harbouring and providing
favourable conditions in which the legionella bacteria may grow.
A biofilm is a thin layer of micro-organisms which may form a
slime on the surfaces in contact with water. Such biofilms, sludge
and scale can protect legionella bacteria from temperatures and
concentrations of biocide that would otherwise kill or inhibit
these organisms if they were freely suspended in the water.
11 - As legionella bacteria are commonly encountered in environmental
sources they may eventually colonise manufactured water systems
and be found in cooling tower systems, hot and cold water systems
and other plant which use or store water. To reduce the possibility
of creating conditions in which the risk from exposure to legionella
bacteria is increased, it is important to control the risk by
introducing measures which:
(a) do not allow proliferation of the
organisms in the water system; and
(b) reduce, so far as is reasonably practicable,
exposure to water droplets and aerosol.
Extracted from "Approved Code of Practice (ACoP)
and Guidance "Legionnaires' disease: The control of legionella
bacteria in water systems" (L8)" © Crown copyright
This document is continued in the next issue of Accepta's newsletter.....
Additional Information & Technical
Support
For further information, technical support and advice on all aspects
of Legionella and legislative compliance please call Accepta on
+44 (0) 161 877 2334 or e-mail info@accepta.com.
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