What is Legionnaires’ disease?
Legionnaires’ disease is a potentially
fatal pneumonia caused by legionella bacteria.
It is the most well-known and serious form of
a group of diseases known as legionellosis. Other
similar (but usually less serious) conditions
include Pontiac fever and Lochgoilhead fever.
Infection is caused by breathing in small droplets
of water contaminated by the bacteria. The disease
cannot be passed from one person to another. Everyone
is potentially susceptible to infection but some
people are at higher risk eg those over 45 years
of age, smokers and heavy drinkers, those suffering
from chronic respiratory or kidney disease, and
people whose immune system is impaired.
Where is legionella found?
Legionella bacteria are common in natural water
courses such as rivers and ponds. Since legionella
are widespread in the environment, they may contaminate
and grow in other water systems such as cooling
towers and hot and cold water services. They survive
low temperatures and thrive at temperatures between
20°C- 45°C if the conditions are right,
eg if a supply of nutrients is present such as
rust, sludge, scale, algae and other bacteria.
They are killed by high temperatures.
What are my duties under the law?
Under general health and safety law, you have
to consider the risks from legionella that may
affect your staff or members of the public and
take suitable precautions. As an employer or a
person in control of the premises (eg a landlord),
you must:
-
identify and assess sources
of risk;
-
prepare a scheme (or course
of action) for preventing or controlling the
risk; implement and manage the scheme - appointing
a person to be managerially responsible, some-
times referred to as the ‘responsible
person’;
-
keep records and check that
what has been done is effective; and, if appropriate,
notify the local authority that you have a cooling
tower(s) on site
-
If a person working under your
control and direction is treated as self- employed
for tax and national insurance purposes, they
may nevertheless be your employee for health
and safety purposes. You may need therefore
to take appropriate action to protect them.
-
If you do not wish to employ
workers on this basis, you should seek legal
advice. Ultimately each case can only be decided
on its own merits by a court of law.
Assessing the risk
The risk assessment is your responsibility as the
employer or person in control of the premises. You
may be able to carry out the assessment yourself
but, if not, you should call on help and advice
from within your own organisation or if this is
not available, from outside sources, eg consultancies.
You need to find out if your water systems (including
the equipment associated with the system such as
pumps, heat exchangers, showers etc) are likely
to create a risk.
Ask yourself the following:
Are conditions present which will encourage bacteria
to multiply? For example - is the water temperature
between 20-45°C ?
Is it possible that water droplets will be produced
and, if so, could they be dispersed over a wide
area? For example, consider showers and aerosols
from cooling towers; and, Is it likely that anyone
particularly susceptible will come into contact
with the contaminated water droplets?
Which systems present the greatest risk?
Cooling towers, evaporative condensers and hot
and cold water systems have been associated with
outbreaks. Other potential sources where precautions
might be needed include humidifiers and spa baths.
If you decide that the risks are insignificant,
your assessment is complete. You need take no further
action other than to review the assessment periodically
in case anything changes in your system.
Preventing or controlling the risk
If a risk is identified which cannot be prevented,
you must introduce proper controls. Risks from legionella
in water systems can be controlled but careful planning,
a successful management policy, competent staff
and attention to proper control strategies are all
essential.
You should consider whether you can prevent the
risk of legionella in the first place by looking
at the type of water system you need. For example,
is it possible to replace a wet cooling tower with
a dry air cooled system?
You need to prepare a written scheme which sets
out how you intend to control the risk from legionella.
You should describe
- your system - an up-to-date plan or schematic
diagrams are sufficient;
- who is responsible for carrying out the assessment
and managing its implementation;
- the safe and correct operation of your system;
- what control methods and other precautions you
will be using; and, the checks that will be carried
out on the control scheme and how often these
checks will be carried out.
The key point is to design, maintain and operate
your water services under conditions which prevent
or control the growth and multiplication of legionella.
You should:
- ensure that the release of water spray is properly
controlled;
- avoid water temperatures and conditions that
favour the growth of legionella and other micro-
organisms;
- ensure water cannot stagnate anywhere in the
system by keeping pipe lengths as short as possible
or by removing redundant pipework;
- avoid materials that encourage the growth of
legionella;
- keep the system and the water in it clean; and,
- treat water to either kill legionella (and other
micro-organisms) or limit their ability to grow.
Keeping the water in a cooling tower system clean
will not only control legionella, but also lead
to other advantages. By reducing scale and fouling,
you are also ensuring that the cooling process is
operating efficiently - scaling
reduces the effectiveness of biocide treatment
and fouling can lead to loss of plant performance.
What water treatment methods can I use?
Cooling towers/systems are often treated using
biocides. But there are other treatment strategies
available such as ultra violet (UV) irradiation,
copper/silver ionisation and ozone.
In hot and cold water systems legionella has traditionally
been controlled by storing hot water above 60°C
and distributing it at above 50°C - and keeping
cold water below 20°C if possible. Other methods
which are used include copper/silver ionisation
and chlorine dioxide.
One way of controlling legionella is to keep water
hot, which you may be doing for other reasons already.
For example, nursing homes and residential care
homes tend to keep water hot for reasons other than
controlling legionella, including kitchen and laundry
use, to ensure proper boiler operation, or to take
account of long pipe runs.
However, care is needed where water runs hot. The
risks of scalding should be assessed and appropriate
measures taken to prevent burns, eg warning notices
and thermostatic mixing valves on taps.
Can I reduce my water temperatures if I
am using another method of controlling legionella?
It depends. If you don’t need the hot water
for other reasons, then using another effective
treatment method means that you can reduce water
temperatures. There is specific advice on this issue
in hospitals and you should refer to this - it recommends
keeping the water hot and not reducing the temperature
(see Further Information section).
But whatever treatment method you use, you need
to make sure you know: what the effective level
of control is for your system, eg temperature and
concentration of biocides; if the treatment method
can cope with changes in the system, eg variations
in the amount of water used throughout the day;
and, how you are going to measure the effectiveness
of the treatment method; for example, if you are
using temperature as a control method you can take
the temperature of the water coming out of the taps.
Should I take samples to test for legionella?
It depends. Sampling and testing for the presence
of legionella bacteria is just one way of checking
that your system is under control. But it is not
a simple test - sampling and detecting legionella
requires specialist help. Further details on how
to sample and the frequency of sampling in both
cooling towers and hot and cold water systems can
be found in Part 2 of the ACOP and guidance.
Managing the risk
You need to appoint someone to take responsibility
for managing the control scheme that you have put
in place. The ‘responsible person’ needs
to be competent - that is, they need to have sufficient
knowledge and experience of your system to enable
them to manage and control the scheme effectively.
If there are several people responsible for managing
the system and/or control scheme, for example because
of shift- work patterns, you need to make sure that
everyone knows what they are responsible for and
how they fit into the overall management of the
system. If you decide to employ contractors to carry
out water treatment or other work, it is still the
responsibility of the appointed person to ensure
that the treatment is carried out to the required
standards. And remember, before you employ a contractor,
you should be satisfied that they can do the work
you want to the standard that you require. A Code
of Conduct for service providers has been prepared
to help you with this.
What records do I need to keep?
If you employ five or more people you must record
the significant findings of your risk assessment.
This means writing down the significant findings
of the assessment and details of any monitoring
or checking carried out. If you have fewer than
five employees you do not need to write anything
down, although it is useful to keep a written record
of what you have done. You also need to keep records
of your written scheme and who is responsible for
managing that scheme. You should also keep the results
of your routine monitoring. You need to keep these
records for a minimum of five years.
Does anybody else have to do anything about
legionella?
Yes. Anyone who is involved in the supply of water
systems and their com- ponents (eg designers, manufacturers,
water treatment companies and suppliers) has to
make sure that such equipment is designed and made
in such a way that it is safe to use at work and
that it can be easily cleaned and maintained. They
should tell you what risks might be present and
how you can operate and maintain the system safely.
If you are using products or services, for example,
for water treatment, the suppliers must make sure
that these are effective at controlling legionella
and that they can be used safely at work. They should
also tell you if, while they are treating your system,
they find any problems which could pose a significant
risk of legionella exposure.
Do I have any other duties?
Yes. If you have a cooling tower or evaporative
condenser on site you must, under the Notification
of Cooling Towers and Evaporative Condensers Regulations,
notify the local authority in writing with details
of where it is located. You must also tell them
when/if such devices are no longer in use. Notification
forms are available from your local Environmental
Health Department. If you have a case of legionellosis
in an employee who has worked on cooling towers
or hot water systems that are likely to be contaminated
with legionella, you have to report this under the
Reporting of Injuries, Diseases and Dangerous Occurrences
Regulations.
What happens when there is an outbreak?
Local authorities have special plans for dealing
with major outbreaks of infectious disease including
legionellosis. These are usually investigated by
an Outbreak Control Team whose purpose is to protect
public health and prevent further infection. HSE
or the local authority Environmental Health Department
may also be involved in investigating compliance
with health and safety legislation.
Where can I get further information?
More detailed guidance on your duties can be found
in the Approved Code of Practice and guidance Legionnaires’
disease: The control of legionella bacteria in water
systems Approved Code of Practice and guidance L8
(Third edition) HSE Books 2000 ISBN 0 7176 1772
6. Part 1 of this publication contains advice on
your duties under the law. Part 2 contains guidance
on technical aspects of the assessment and control
of legionella risks.
You may also find the following helpful:
Controlling legionella in nursing and residential
care homes INDG253 HSE Books 1997 (single copy free)
The control of legionellae in healthcare premises:
A Code of Practice. Good practice guide Health Technical
Memorandum 2040 ISBN 0 11 321683 1 NHS Estates 1993
The control of legionellosis: A recommended code
of conduct for service providers. Water Management
Society/ British Association for Chemical Specialities,
1999
Health and safety in care homes HSG220 HSE Books
2001 ISBN 0 7176 2082 4
You can also obtain advice from:
environmental health departments of local authorities;
your local HSE office; professional bodies and organisations
such as the Chartered Institute of Building Service
Engineers (CIBSE), the Building Services Research
and Information Association (BSRIA); and, associations
such the Water Manage- ment Society (WMS) or the
British Association for Chemical Specialities (BACS).
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