Working with time-varying
Electro-Magnetic Fields
(EMF)
STFC Safety Code No 23
Rev. 1.3, Issued on December 2014
Note - This document may have been superseded by a more recent version.
Please check the SHE website for the most up-to-date version of this document
Note - This document may have been superseded by a more recent version.
Please check the SHE website for the most up-to-date version of this document
Revisions
1
Initial release
1.1
Update to action values
1.2
Amendments to audit checklist
1.3
Add Document retention policy Appendix
Issue Number: 1.3
Issue Date: 09/12/2014
February 2009
May 2011
May 2013
December 2014
Author: Graeme Finlan/P McIntosh/D Findlay
Page 2 of 15
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Working with time-varying Electro-Magnetic Fields (EMF)
Contents
1.
Purpose
2.
Scope
3.
Definitions
4.
Responsibilities
5.
4.1
Directors responsible for activities employing strong EMF sources
4.2
EMF Protection Advisers
4.3
Managers responsible for strong EMF radiation sources
4.5
STFC staff and tenants
4.5
SHE Group
4.6
Occupational Health Advisers
References
Appendices
Appendix 1: Summary of the effects of EMF Radiation
Appendix 2: Summary of ICNIRP Basic Restrictions and Investigation
Appendix 3: Principles of EMF Risk Control
Appendix 4: Training
Appendix 5: Audit checklist
Appendix 6:Document Retention Policy
Issue Number: 1.3
Issue Date: 09/12/2014
Author: Graeme Finlan/P McIntosh/D Findlay
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Working with time-varying Electro-Magnetic Fields (EMF)
1.
Purpose
The purpose of this code is to ensure that hazards associated with strong and timevarying electromagnetic fields (EMFs) up to a frequency of 300 GHz are managed so as
to minimise so far as is reasonably practicable the health and safety risks to staff and
others. Frequencies up to 300 GHz encompass the Radio Frequency (RF) and
microwave parts of the electromagnetic spectrum.
Devices generating EMFs are widely used at the STFC laboratories.
Typical
applications can be found in the radio frequency systems of particle accelerators, radars,
imaging systems and radio transmission systems. More general applications are found
in microwave ovens and communication devices. It has been recognised that
electromagnetic radiation from these devices may, under certain conditions, give rise to
health hazards. Since many of the alleged longer term risks are difficult to quantify and
subject to ongoing research, medical examination is unlikely to identify clinical findings
from exposure, and so establishing ‘safe’ levels of EMF exposure is not straightforward
(see Appendix 1).
This document is an interpretation of relevant laws and standards and cannot cover all
conceivable situations. The STFC intends, so far as is reasonably practicable, to comply
with the guidance issued by the International Commission on Non-Ionising Radiation
Protection (ICNIRP), which was adopted by the NRPB (now the Health Protection
Agency: Radiation Protection Division) in March 2004, see 5.
ICNIRP guidance is based on the interaction of EMFs with body tissues and refers to
direct and indirect health effects in establishing ‘Basic Restrictions’ (see Appendix 2).
Such values are typically based on quantities such as energy absorbed by the body
(Specific energy Absorption Rate [SAR]) which is not readily measurable. To provide
practical guidance, frequency-dependent ‘Reference levels’ have been developed
based on electric and magnetic field strengths and currents which can be more readily
measured.
The European Directive relating to EMFs, the Physical Agents Directive, introduced in
April 2004, has not yet been implemented within UK law. The present STFC code will
be reviewed when this Directive is implemented. The directive establishes a ‘Limit
Value’ corresponding to the aforementioned ICNIRP ‘Reference Level’ and a lower
‘Action Value’ which are employed in this code.
2.
Scope
This code establishes requirements for controlling the exposure of STFC staff, visitors,
facility users, tenants, contractors and the public to strong EMFs at all STFC sites. The
code applies to any equipment generating EMFs at or above the Action Limits defined by
this code.
Issue Number: 1.3
Issue Date: 09/12/2014
Author: Graeme Finlan/P McIntosh/D Findlay
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This code is intended to cover equipment specifically designed to produce strong EMFs
for example, high-power RF systems driving particle accelerators and radar sets.
It is not intended to cover every piece of equipment that could conceivably emit
electromagnetic radiation. The following classes of normal domestic electrical equipment
are specifically excluded from this code by virtue of their exemption from ICNIRP
recommendations although their manufacture is subject to legislative emission
standards:
•
Cellular/mobile phones;
•
Personal mobile radios (“walkie-talkies”);
•
Microwave ovens used for heating food;
•
Video display terminals; and
•
Standard WiFi wireless internet systems.
As are 240V AC mains electricity infrastructures: substations; distribution boards;
building wiring etc.
Inevitably, what should and should not be covered by this code is a matter of technical
judgement of EMF Protection Advisors.
The hazards associated with strong static magnetic fields are addressed by a separate
SHE code.
3.
Definitions
3.1
Limit Value
The Limit Value is the frequency-dependent EMF field strength above which staff and
others should not be exposed (see Appendix 2, Table 1). Staff and others exposed to
EMFs above this level should be medically assessed by Occupational Health.
3.2
Action Value
The Action Value is the frequency-dependent EMF field strength above which formal
consideration through risk assessment and EMF surveying must be given to the health
and safety of staff and others exposed to EMFs. The frequency-dependent Action
Values are established at the recommended general public exposure field strengths
(see Appendix 2, Table 2).
4.
Responsibilities
4.1
Directors responsible for activities employing strong EMF sources shall:
4.1.1
Appoint in writing one or more suitably qualified and experienced EMF Protection
Advisers (EPAs) for those areas employing EMF generating equipment or devices (see
Appendix 4 for EPA training requirements). The letter of appointment should define the
geographic/equipment scope of their responsibility and should be recorded in SHE
Directory. It would be normal for the technical manager responsible for the day-to-day
operation of the equipment to be appointed the EPA.
4.2
EMF Protection Advisers (EPAs) shall:
4.2.1 Provide advice to management responsible for strong EMF sources on technical
modifications, changes to work practices or engineering controls that could eliminate
Issue Number: 1.3
Issue Date: 09/12/2014
Author: Graeme Finlan/P McIntosh/D Findlay
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EMF hazards or minimise their impact so far as reasonably practicable, including the use
of appropriate signage for all areas where field strengths are above Action Values.
4.2.2
Regularly survey the field strength of equipment generating strong EMFs that could
affect staff and others within their scope of responsibility and ensure that risk
assessment controls are appropriate. Specific consideration should be given to
undertaking EMF measurements following any changes that could reasonably be
expected to affect the field characteristics of equipment, for example following
maintenance/servicing or after modification. Surveys should be documented and identify
all areas above the Action and Limit Values.
4.2.3 Ensure that only monitoring equipment calibrated to recognised standards is used to
measure strong EMFs and to determine compliance with the limits specified in Appendix
2.
4.3
Managers responsible for strong EMF radiation sources shall:
4.3.1 Ensure that no equipment capable of radiating strong EMF radiation is brought on to
STFC sites without the approval of the relevant EPA, including equipment borrowed or
provided by others, so that managers can ensure that suitable precautions are taken
before the equipment is used.
4.3.2 Where equipment generating strong EMF radiation is designed and manufactured in
house, ensure that the Limit and Action Values are considered and that the appropriate
EPA is consulted before the equipment is brought into use.
4.3.3 Ensure that the advice of an EPA is sought and that documented risk assessments are
conducted for all work through which persons may be exposed to EMFs above ‘Action
Levels’ (see SHE Code 6: Risk Management) and that suitable controls are established
to minimise exposure. These controls should include undertaking a suitable and
documented EMF survey.
4.3.4 Where equipment generates EMFs above the Action Values (see Appendix 2) in places
to which personnel have access, ensure that suitable warning signage is in place and
that exposure is minimised through suitable engineering controls, work practices and
local operating instructions.
4.3.5 Ensure that all persons working in areas or with equipment where strong EMF radiation
can be generated, in particular EMFs above Action Values, are aware of the hazards
and of the need to follow the advice of the local EPA and local control measures.
4.3.6 Establish control measures to ensure the safety of all staff, visitors, facility users, and
contractors to areas where strong EMFs may exist (see Appendix 3). Individuals with
pacemakers or other medical implants should not be allowed to enter areas where
known EMF hazards exist. Warning signage should be located at all entrances to such
areas (see Appendix 3).
4.3.7 Ensure that all instances where staff or others are exposed to EMFs greater than the
relevant Limit Values (see Appendix 2) are reported according to SHE Code 5: Incident
reporting and investigation to SHE Group, and that any staff or others exposed to EMFs
above the Limit Value are referred to Occupational Health for medical assessment..
4.4
STFC staff and tenants shall:
Issue Number: 1.3
Issue Date: 09/12/2014
Author: Graeme Finlan/P McIntosh/D Findlay
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4.4.1 Comply with any local operating instructions relating to equipment which is capable of
exposing staff and others to strong electromagnetic fields.
4.4.2 When responsible for visitors, facility users or contractors, ensure that the
visitors/users/contractors comply with relevant local operating instructions and that the
visitors/users/contractors make STFC staff aware of any devices/equipment they bring
on to STFC sites capable of exposing personnel to strong electromagnetic fields.
4.4.3 When responsible for visitors, contractors or facility users in an area where strong EMFs
are present, ensure that their attention is drawn to notices warning that no one with a
pacemaker or other implanted medical device should be allowed into the area.
4.4.4 Report all incidents relating to strong EMFs to SHE Group (see STFC SHE Code 5,
Incident Reporting and Investigation).
4.5
SHE Group shall:
4.5.1 Maintain an STFC register of EPAs and their areas of responsibility.
4.6
Occupational Health advisers shall:
4.6.1 Undertake medical assessments of those exposed to EMFs above the Limit Value and
establish health assessments for those working in strong EMFs.
4.6.2 Provide advice for persons who have implanted medical devices such as cardiac
pacemakers about the hazards of exposure to strong EMFs.
5.
References
5.1
This document should be read in conjunction with the NRPB Publication ‘Review of the
scientific evidence for limiting the exposure to electromagnetic fields (0-300GHz)’:
Documents of the NRPB Volume 15 Number 3: 2004 which is available from SHE
Group.
5.2
ICNIRP Guidelines for Limiting Exposure to time-varying Electric, Magnetic, and
Electromagnetic Fields (up to 300 GHz).
5.3
Use of the ICNIRP EMF Guidelines
5.4
The US Federal Communications Commission (FCC) have undertaken investigations
into the Biological Effects and Potential Hazards of Radio Frequency Electro Magnetic
Fields see:
http://www.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet56/oet56e
4.pdf, http://www.fcc.gov/oet/dockets/et93-62/ and 1982 ANSI standard (ANSI C95.11982), which “permitted exclusion from compliance with the MPE limits if the localized
specific absorption rate (SAR) of a low-power device could be shown to be 8
watts/kilogram (8W/kg) or less, or if the input power of the radiating device at
frequencies between 300 kHz and 1 GHz was 7 watts or less”. This (potential)
exemption has not be recognised in the UK by the HPA in their guidelines
Issue Number: 1.3
Issue Date: 09/12/2014
Author: Graeme Finlan/P McIntosh/D Findlay
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Appendices
Appendix 1: Summary of the effects of EMF Radiation
EMF radiation can be absorbed by body tissue and can give rise to temperature increases in
exposed tissue. Many other possible biological effects of electromagnetic fields have been
postulated although it is generally accepted that the most significant effects, and those best
understood to date, are thermal. Normally blood vessels dilate to allow the excess heat to be
removed by blood flow. The main risk is therefore to parts of the body with poor blood supply,
such as the lens of the eye.
Exposure of the head to pulsed radiation such as radar can result in an apparent audible sound
such as a chirp or a buzz in some individuals although this is not considered to be harmful.
The effects of low-level microwave exposure (<1 mW/cm2) are the subject of ongoing research
with some suggestions that such levels may cause reversible disturbances of the central
nervous system, like headaches, emotional instabilities, and changes in the
electroencephalogram, and alterations in blood chemistry. However, such phenomena have not
been sufficiently investigated and the link between low level EMF exposure and health effects
has not been proven.
Electrically conducting materials such as spectacle frames or medically implanted metal objects
(screws, valves and plates) may become hot when exposed to strong EMF or RF fields, leading
to damage of the surrounding tissue. Burns can occur when the EMF induced current enters
the body through contact between a small area of the body (such as a finger) and an electrical
conductor.
Low frequency RF radiation below a few MHz may interact with the body through electrical
charges induced on ungrounded or poorly grounded metallic objects such as vehicles, wires or
fences. When a person comes in contact with such an object a current can pass to ground
through the body. The current depends on the total charge which in turn depends on the
frequency and field strength as well as the geometry and capacitance of the object and the
person's impedance to ground.
Interference with Implantable Medical Devices such as Pacemakers and Implantable
Cardioverter Defibrillators (ICDs)
EMFs can interfere with the proper operation of pacemakers and ICDs. Electric field
interference with pacemakers has been observed at levels as low as 1½–2kV/m. However,
modern dual-chamber pacemakers appear unaffected at levels as high as 20kV/m.
The European Committee for Electro-technical Standardization (CENELEC) are in the process
of producing a standard for the “Assessment, measurement and calculations of human
exposure at the workplace bearing Active Implantable Medical Devices (AMIDs) in electric,
magnetic and electromagnetic fields with frequencies from 0 to 100 GHz”.
Further information can be found in references presented in section 5.
Issue Number: 1.3
Issue Date: 09/12/2014
Author: Graeme Finlan/P McIntosh/D Findlay
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Appendix 2: Summary of ICNIRP Basic Restrictions and Investigation
Levels
The following Tables, with technical definitions, are taken from the publication ‘Guidelines for
Limiting Exposure to time-varying Electric, Magnetic and Electromagnetic Fields (up to 300
GHz)’ (see Section 5, References).
To facilitate their use a summary chart presents the electric and magnetic field strengths as
commonly measured and presented by EMF meters for Action and Limit Values. The basis for
the frequency dependent data presented in these tables is the Specific energy Absorption Rates
(SAR) of these EMFs for human exposure.
Table 1: Reference Levels [Limit Values] for Occupational Exposure to Time-Varying
Electric and Magnetic Fields (Unperturbed RMS Values)
Table 2: Reference Levels [Limit Values] for General Public Exposure to Time-Varying
Electric and Magnetic Fields (Unperturbed RMS Values)
Issue Number: 1.3
Issue Date: 09/12/2014
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Summary chart of the data presented in Tables 1 and 2, electric and magnetic field strengths,
as function of EMF frequency.
Electric field strengths
Magnetic field strengths
Key
Red
Blue
Solid line
Dashed line
Electric field strength
Magnetic field strength
Limit Value for occupational exposure
Action Value – established at the recommended general public exposure field strengths
Technical definitions
Specific energy Absorption (SA)
The energy absorbed per unit mass of biological tissue, (SA) expressed in Joules per kilogram (J/kg); specific energy
absorption is the time integral of specific energy absorption rate.
Specific energy Absorption Rate (SAR)
The rate of energy absorption per unit body mass, usually expressed in Watts per kilogram (W/kg); SAR is the
dosimetric measure that has been widely adopted at frequencies above about 100 kHz.
Issue Number: 1.3
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Appendix 3: Principles of EMF Risk Control
In view of the potential hazards of exposure to EMF radiation a number of control measures
should be considered. These are presented below:
a)
It must be ensured as far as reasonably practicable that where equipment likely to
generate a strong EMF radiation is purchased or borrowed, that the supplier provides
details of the likely EMF output characteristics and recommended control measures.
Such data should already be provided if the equipment is CE–marked, but nevertheless
it is recommended that the equipment is re-tested locally to confirm its EMF output.
b)
The immediate vicinity of unmanned, high-power sources of EMF radiation (e.g. radiotransmitters) shall be suitably fenced off to prevent unauthorized access.
c)
Equipment generating strong EMF radiation shall be positioned as far away as
reasonably practicable from areas normally occupied by staff and others.
d)
There shall be no unnecessary metal objects near any radiating EMF device.
presence of such objects may result in high-intensity fields in certain locations.
e)
Shielding or screening of equipment shall be carried out as necessary to reduce EMF
radiation exposure.
f)
Equipment generating high-power microwaves shall not be tested without an appropriate
load connected to its output. The power generated should never be allowed to radiate
freely into occupied areas.
g)
Safety procedures to be followed by operators of equipment generating strong EMF
radiation shall include the following requirements:
•
•
•
•
The
Replacement components, in particular, waveguides, gaskets, flanges, etc., must
be such that the equipment’s EMF radiation characteristics remain acceptable;
Testing of an EMF-radiating device either before or after completion of repair
work must be carried out in accordance with this SHE code work and should
normally be carried out after protective shields, waveguides and other
components have been put back in their designated locations as far as
reasonably practicable;
Adjustments of voltages, replacement or dismantling of EMF-radiation-generating
components or refitting waveguides should be undertaken by people trained and
competent to undertake such tasks (see Appendix 4); and
Maintenance staff and operators of EMF radiation generating devices shall be
suitably aware of the potential hazards of EMF radiation.
h)
Managers responsible for new or existing EMF-radiating-equipment subjected to
modification/maintenance should ask the relevant EPA to undertake EMF surveys with
appropriate test equipment.
i)
Warning signs as shown below indicating the presence of EMF radiation shall be posted
as appropriate where exposure above Action Values may occur. Warning signs can be
obtained from SHE Group.
Issue Number: 1.3
Issue Date: 09/12/2014
Author: Graeme Finlan/P McIntosh/D Findlay
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j)
Warning signs, as shown below, prohibiting individuals with pacemakers or similar
devices from entering areas where EMFs exist shall be posted at all entrances. Warning
signs can be obtained from SHE Group.
k)
EMF-generating equipment may present additional hazards such as X-ray emission and
electrical dangers which will have to be evaluated separately (see SHE codes specific to
these additional hazards).
Issue Number: 1.3
Issue Date: 09/12/2014
Author: Graeme Finlan/P McIntosh/D Findlay
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Appendix 4: Training
Role
Manager of
area/activities in
which EMF
hazards exist
EMF Protection
Advisor (EPA)
Issue Number: 1.3
Initial Training
Refresher
Health Protection Agency
(HPA) ,”EMF Safety
Awareness”, 1 day
training.
Training in undertaking
EMF strength
measurements – generally
provided by
providers/manufacturers
of measuring equipment.
Detailed familiarisation
with the content of this
code.
(HPA) ,”EMF
Safety
Awareness”
Issue Date: 09/12/2014
Frequency
Comments
5 yearly
Author: Graeme Finlan/P McIntosh/D Findlay
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Appendix 5: Audit Checklist
Ref
Item
1
(Section 4.1.1)
Have Directors appointed in writing
EPAs for all equipment/areas
generating strong EMFs?
2
Have documented EMF surveys been
undertaken for all equipment
generating strong EMFs? Have these
been repeated following significant
change/modification or maintenance
of the equipment?
3
(Section 4.2.3)
Is EPA EMF survey meter within
calibration date and calibrated to a
recognised EMF standard?
4
(Section 4.3.4)
Are EMF warning signs located in all
areas where EMF strength exceeds
the Action Value?
5
(Section 4.3.3)
Have documented Risk Assessments
been conducted for all
equipment/areas where EMF exceed
Action Values?
6
(Section 4.3.5)
Are staff working in areas above the
Action Value aware of the effects of
EMF exposure?
7
(Section 4.3.7)
(Section 4.4.4)
Are SHE incidents involving EMF
reported?
8
(Section 4.3.7)
(Section 4.6.1)
Have medical assessments been
conducted for all staff exposed to
EMFs above the Limit Value?
9
(Section 4.4.3)
Are controls in place to prevent the
exposure of staff and others with
implanted medical devices to EMFs?
Is warning signage visible at the
entrances to such areas?
10
(Section 4.3.5)
(Section 4.4.1)
(Section 4.4.2)
Are staff aware of and following local
operating instructions established to
control exposure to EMFs?
Issue Number: 1.3
Issue Date: 09/12/2014
Rating
Comments
Author: Graeme Finlan/P McIntosh/D Findlay
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Appendix 6: Document Retention Policy
Records
Established
EMF Surveys
Responsible
Location of
Record
records
Keeper
Comments/Justifications
Current + 50 Years
Line
Management
Local Record
Systems
Probably 50 Years from Date of
last entry – health issues
Most Recent
Director
SHE Directory
Appointment Letter
Minimum
Retention Period
Appointments:
EMF Protection
Advisor
Issue Number: 1.3
Issue Date: 09/12/2014
Author: Graeme Finlan/P McIntosh/D Findlay
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