Transmissible Spongiform Encephalopathy Agents: Safe Working and the Prevention of Infection: Annex C
ANNEX C
General principles of decontamination and waste disposal
Introduction
C1.
This annex has been updated to provide information on the general principles
of decontamination and waste disposal for transmissible spongiform
encephalopathies (TSEs). A list of selected guidelines and standards related
to decontamination and waste disposal is included as Table C4. Guidance on
decontamination and waste disposal in a healthcare setting can now be found
in Part 4 of this guidance. Guidance on decontamination and waste disposal
in a laboratory setting can now be found in Part 3 of this guidance.
The Decontamination Cycle for reusable medical equipment
C2.
ACQUISITION 1. Purchase 2. Loan CLEANING
TRANSPORT DISINFECTION At all stages:
Location Facilities Equipment Management Policies/Procedures
USE STORAGE INSPECTION PACKAGING TRANSPORT
STERILISATION
DISPOSAL
1. Scrap 2. Return to lender Decontamination and TSE agents
C3.
TSE agents are particularly resistant to standard physical and chemical
methods of inactivation and decontamination. Therefore, effective cleaning
is of great importance in the removal of these agents.
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Transmissible Spongiform Encephalopathy Agents: Safe Working and the Prevention of Infection: Annex C
C4.
Details of chemical and gaseous disinfectants and physical processes
commonly used for decontamination, and their effectiveness at reducing
infectivity, are outlined below. It should be noted that combinations of
some agents and/or processes could be effective, for example,
physical/chemical combinations such as autoclaving with sodium
hydroxide.
Chemical decontamination
C5.
Most chemical disinfectants are ineffective at reducing infectivity and
some, acting as protein fixatives, may stabilise the agent (see Table C1).
Table C1: Ineffective chemical disinfectants
Chemical disinfectants commonly
INEFFECTIVE at reducing infectivity
used
for
decontamination
that
are
Alcohols1
Ammonia
ß-propiolactone
Chlorine dioxide
Ethylene oxide
Formaldehyde and related compounds1
Glutaraldehyde and related compounds1 (e.g. orthophthalaldehyde [OPA])
Hydrochloric acid (Not reliably effective for practicable use)
Hydrogen peroxide
Iodophors
Peracetic acid
Aqueous solutions of phenol (≤90% phenol)
Sodium dichloroisocyanurate (e.g. ‘Presept’)2
10,000ppm sodium hypochlorite (Not reliably effective for practicable use)
1
These agents are strong fixatives, may stabilise infectivity and thereby decrease the
efficiency of the decontamination process
2
The rate of release of chlorine from this product is insufficient to ensure complete
inactivation of the agent
C6.
Sodium hypochlorite is considered to be effective at reducing infectivity but
only at concentrations (20,000ppm available chlorine for 1 hour) that pose
certain practical constraints. The following should be taken into account when
considering the use of sodium hypochlorite:
o
It must not be used on open surfaces i.e. benches due to the possible
release of chlorine gas
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Transmissible Spongiform Encephalopathy Agents: Safe Working and the Prevention of Infection: Annex C
C7.
o
It corrodes metal and steel
o
It is incompatible with formaldehyde, alcohols and acids
o
It is rapidly inactivated by protein residues
o
Concentrated stock dilutions last for only approximately 2-3 weeks
o
Diluted solutions are not stable and should be made up daily
Sodium hydroxide (2M for 1 hour) has a substantial effect. An increase in
temperature will increase effectiveness. The following should be taken into
account when considering the use of 2M sodium hydroxide:
C8.
o
It should not be used on aluminium or zinc
o
It will not cause fumes but is damaging to body tissue
o
It is an irritant and harmful as dust
Formic acid (96% for 1 hour) may be used for histological samples of human
or animal tissue that have previously been fixed in formalin. However, it
should not be used on tissue that has previously been exposed to phenol, as
this interacts deleteriously with formic acid.
C9.
Phenol (≥ 90% phenol) is highly effective at eliminating infectivity. Phenol is a
toxic, corrosive and irritant chemical which can be absorbed through mucous
membranes, wounds and intact skin, and should be used cautiously and with
the appropriate personal protective clothing.
Physical processes
Incineration
C10.
Incineration is effective at removing the infectious agent and eliminating
infectivity. Temperatures over 600ºC are likely to be practically effective, and
850ºC is commonly used in practice. Temperatures ≥1000 ºC can produce
sterility. The particle size of material to be combusted should be suitably small
to ensure efficient heat penetration to the centre.
Autoclaving
C11.
Autoclaving remains an important method of reducing infectivity. Different
strains of TSE are also known to vary in their sensitivity to heat.
C12.
The following holding times will reduce infectivity but cannot be relied upon to
completely eliminate infectivity (either porous load or gravity displacement):
•
121°C for 15 minutes
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Transmissible Spongiform Encephalopathy Agents: Safe Working and the Prevention of Infection: Annex C
C13.
•
134-137°C for 3 minutes
•
134-137°C for 18 minutes
•
Six successive cycles of 134-137°C for 3 minutes
The ‘Prion Cycle’ found on some benchtop vacuum autoclaves will also
reduce infectivity but will not eliminate infectivity entirely. See MHRA
Safety Notice ‘SN 2002(11): Benchtop vacuum steam sterilizers – the ‘prion
cycle’:
http://www.mhra.gov.uk/Publications/Safetywarnings/MedicalDeviceAlerts/Safetynoti
ces/CON008791
Radiation
C14.
Ionising, UV or microwave radiation at conventional doses are not effective at
reducing infectivity.
Other processes
C15.
A number of anti-prion technologies are currently in development. The
Engineering and Science Advisory Committee into the Decontamination of
Surgical Instruments including Prion Removal (ESAC-Pr) produced a report
on prion inactivating agents, written by their New Technologies Working
Group, in August 2008. This report provides advice on various anti-prion
technologies that are on, or close to coming on, the market, their applicability
to the current decontamination process for reusable medical equipment, and
the direction of future research needs. The report can be accessed here.
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Transmissible Spongiform Encephalopathy Agents: Safe Working and the Prevention of Infection: Annex C
Table C4: Selected guidelines and standards related to decontamination and
waste disposal
Name
93/42/EEC
The Medical
Devices
Directive
Date
published
1993
UK law
since 1998
Brief description
This Directive under European Law covers the placing on
the market and putting into service of Medical Devices
(other than active implantable and in vitro diagnostic
devices). Available here.
Essential requirements in the Directive are listed under
Annex 1. Two essential requirements under section 8 –
Infection and microbial contamination – are particularly
relevant:
“8.4: Devices delivered in a sterile state must have been
manufactured and sterilised by an appropriate validated
method.”
“8.5: Devices intended to be sterilised must be
manufactured in appropriately controlled (e.g.
environmental) conditions.”
Medical Devices
Regulations
2002
These UK Regulations are drawn from the Medical
Devices Directive 93/42/EEC
DH Estates and Facilities (formerly NHS Estates) Health Building Notes (HBN)
HBN provide advice to project teams designing and planning new buildings and
adapting/extending existing buildings. HBNs are available free to NHS staff who register with
the DH Knowledge and Information Portal http://estatesknowledge.dh.gov.uk/
HBN 13
2004
Design of Sterile
Service
Departments
This HBN provides guidance to help health planners,
estates and facilities managers, sterile services managers
and capital planning and design teams to plan and design
a sterile services department. It supersedes HBN 13
‘Sterile services departments’, published in 1992. In
Scotland, the relevant document is SHBN 13.
DH Estates and Facilities (formerly NHS Estates) Engineering Health Technical
Memoranda (HTM)
HTMs provide guidance for the design, installation and running of specialised building service
systems. HTMs are available free to NHS staff who register with the DH Knowledge and
Information Portal http://estatesknowledge.dh.gov.uk/
HTM 2010
Sterilization
1995
This HTM provides guidance on choice, specification,
purchase, installation, validation, periodic testing, operation
and maintenance of clinical and laboratory sterilizers. It is
intended primarily as a guide for technical personnel who
are specialists in sterilizing processes and procedures and
for those responsible for maintenance and testing. It is also
for staff who have responsibility for the day-to-day running
of sterilizers. In Scotland, the relevant document is SHTM
2010.
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Transmissible Spongiform Encephalopathy Agents: Safe Working and the Prevention of Infection: Annex C
HTM 2031
1997
HTM 2031 covers the nature of contamination in steam
supplies, regulatory requirements for steam quality, the
new “clean steam” specification, engineering measures for
the generation of clean steam, validation and periodic
testing of clean steam supplies and guidance on the
analysis of steam samples. It supplements the guidance on
steam quality in HTM 2010 ‘Sterilization’. In Scotland, the
relevant document is SHTM 2031.
1997
HTM 2030 gives guidance on the choice, specification,
purchase, installation, validation, periodic testing, operation
and maintenance of washer-disinfectors in use in the
National Health Service for processing medical devices,
laboratory ware and sanitary products. In Scotland, the
relevant document is SHTM 2030.
Part A 2007
This HTM, once fully published, will replace HTM 2010,
HTM 2031 and HTM 2030, amongst others. The HTM is in
four parts:
Clean Steam
HTM 2030
Washer
Disinfectors
HTM 01-01
Decontamination
of Medical
Devices
Part A – Management and Environment
Part B – Equipment
Part C – Sterilizers
Part D – Washer disinfectors
Parts B, C and D are currently in preparation and due to be
published in late 2009.
HTM 01-02
In preparation
Pathology
Decontamination
HTM 01-04
In preparation
Laundry
Decontamination
HTM 01-05
Dental
Decontamination
2009
This guidance has been produced to reflect a reasonable
and rational response to emerging evidence around the
effectiveness of decontamination in primary care dental
practices, and the possibility of prion transmission through
protein contamination of dental instruments.
Available here.
HTM 01-06
In preparation, due to be published in late 2009
Endoscope
Decontamination
HTM 01-07
In preparation
Primary Care
Decontamination
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Transmissible Spongiform Encephalopathy Agents: Safe Working and the Prevention of Infection: Annex C
HTM 07-01
2006
Safe
management of
healthcare waste
This document is a best practice guide to the management
of healthcare waste. Healthcare waste refers to any waste
produced by, and as a consequence of, healthcare
activities. For the purposes of this document, this guidance
also applies to offensive/hygiene and infectious waste
produced in the community from non-NHS healthcare
sources.
The document replaces the Health Services Advisory
Committee’s (1999) guidance document ‘Safe disposal of
clinical waste’ and takes into account the changes in
legislation governing the management of waste, its
storage, carriage, treatment and disposal, and health and
safety. This guidance document was produced by DH,
supported by the Environment Agency, Defra, HSE, the
Department for Transport, Welsh Health Estates and
Health Facilities Scotland.
Device Bulletins (DB)
The Medicines and Healthcare Products Regulatory Agency (MHRA) produce Device
Bulletins that contain guidance and information on medical devices of a more general
management interest. They are written as a result of experience gained from adverse incident
investigations, contacts with manufacturers and users, and other sources of information.
DB 2002(05)
2002
This Bulletin (due for update and revision) is intended to
offer advice and guidance to both users and manufacturers
of devices and reprocessing equipment. It draws together
existing advice, with particular reference to disinfectant
contact times. Personnel with responsibility for
decontamination and infection control may base their
processing procedures on this information. Available here.
2002
This Bulletin (due for update and revision) provides
guidance on the purchase, operation and maintenance of
all types of benchtop steam sterilizers. The guidance is
intended for potential purchasers, and all current owners
and users of benchtop steam sterilizers. Available here.
Decontamination
of Endoscopes
DB 2002(06)
Benchtop steam
sterilizers:
guidance on
purchase,
operation and
maintenance
Other relevant guidance
The Glennie
framework
2001
The first report from the Sterile Services Provision Review
Group, NHS Scotland. This Group, led by John Glennie,
Chief Executive of Borders General Hospital NHS Trust,
undertook a review of sterile service provision across NHS
Scotland. Available here.
Infection control
in dentistry
2003
This advice sheet condenses current knowledge and
recommendations on infection control for the dental
practitioner. It was developed with the DH in England and
is consistent with current infection control policies in the
NHS. Its production and distribution to dentists in the UK
has been financed by the DH. It is commonly known as the
A12 document. Available here.
British Dental
Association
advice sheet
A12
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Transmissible Spongiform Encephalopathy Agents: Safe Working and the Prevention of Infection: Annex C
“MAC Manual”
Sterilization,
Disinfection and
Cleaning of
Medical
Equipment:
Guidance on
Decontamination
from the
Microbiology
Advisory
Committee to
the Department
of Health
Part 1 –
2002
Part 2 –
2005
Part 3 –
2006
This publication, known as the MAC Manual, has been
prepared and endorsed by the MHRA's Microbiology
Advisory Committee to provide advice on all aspects of
decontamination. Available here.
Part 1 – Principles (2002 revision currently under review) this part provides the general principles of
decontamination, illustrated by some examples of basic
decontamination equipment.
Part 2 – Protocols – this part contains the protocols for
decontamination using cleaning, disinfection and
sterilization processes. The introduction provides general
guidance on the need for systems of work for the
decontamination of medical devices and equipment both
prior to clinical use and before inspection, service or repair.
A general protocol for handling items to be maintained or
repaired is then provided, and detailed protocols for
cleaning, disinfection and sterilization follow this.
Part 3 – Procedures – Section 1 provides an overview of
what the European Directives for medical devices mean for
users. Section 2 provides general procedures to be
followed for particular groups of equipment including:
Standards and
Practice
2007
•
Endoscopes
•
Dental equipment
•
Ophthalmic instruments
•
Surgical instruments
•
Ventilators
•
Miscellaneous items
The Institute of Decontamination Sciences (IDSc), formerly
the Institute of Sterile Services Management, has
produced a revised third edition of this guidance, which
sets out in detail the operational, technical and managerial
requirements of decontamination services and provides a
useful resource for anyone working in or around
decontamination. The revised 3rd edition has been
extensively updated to include the latest legislative
framework referencing the work of the Healthcare
Commission, ISO 13485 and the revised HBN13.
A hardcopy of ‘Standards and Practice’ is free to full
members of the Institute. Non-members can purchase
hardcopies of the guidance. More information available
here.
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