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Presented by N.W. Pieterse
GAUTENG BRANCH WORKSHOP
24 NOVEMBER 2015
C FIELD RADIATION
• Introduction to EMF and UV Radiation.
• Definition of EMF Radiation.
• Key concepts related to EMF Radiation.
• Sources of EMF Radiation.
• Health effects related to EMF Radiation.
• Measurement methodology, Instrumentation and Special
• Standards and OEL’s related to EMF Radiation.
• Case Sudy.
• An electromagnetic field (also EMF or EM field) is a physical
field produced by moving electrically charged objects. It
affects the behavior of charged objects in the vicinity of the
• The electromagnetic field extends indefinitely throughout
space and describes the electromagnetic interaction.
• EMF has both electric and magnetic field components, which
stand in a fixed ratio of intensity to each other, and which
oscillate in phase perpendicular to each other and
perpendicular to the direction of energy and wave
• In a vacuum, electromagnetic radiation propagates at a
characteristic speed, the speed of light.
• Ohm's law states that the current through a conductor
(Atmosphere) between two points is directly proportional to the
potential difference across the two points. Introducing the
constant of proportionality, the resistance, one arrives at the usual
mathematical equation that describes this relationship:
• where I is the current through the conductor in units of amperes, V
is the potential difference measured across the conductor in units
of volts, and R is the resistance of the conductor in units of ohms.
More specifically, Ohm's law states that the R in this relation is
constant, independent of the current.
• Atmospheric Resistance = 377 ohm
• ELECTRIC FIELD STRENGTH (E): The magnitude of the
electric field vector expressed in V/m.
• MAGNETIC FIELD STRENGTH (H): The magnitude of the
magnetic field vector expressed in A/m.
• POWER DENSITY (S): Power per unit area normal to the
direction of propagation, expressed in mW/cm2.
• EMISSION: Radiation produced by a single radiofrequency
• INMISION: Radiation resulting from the contribution of all
radiofrequency sources whose fields are present in the
• OCCUPATIONAL EXPOSURE: A situation in which people
are subjected to electrical, magnetic or electromagnetic
fields, or to contact or induced currents associated with
electromagnetic fields of radiofrequencies.
• POPULATION OR NON-CONTROLLED EXPOSURE:
Situations in which the general public may be exposed or in
which people exposed in the course of their work may not
have been warned of the potential exposure and may not be
Cell Phone Towers Radio Towers High Voltage Power Lines
Transformer Station Mobile Military Radio Mast
Fixed Radar Antenna Mobile Radar Antenna
• Coupling to low-frequency electric fields. The interaction of
time-varying electric fields with the human body results in the
flow of electric charges (electric current), the polarization of
bound charge (formation of electric dipoles), and the
reorientation of electric dipoles already present in tissue.
• Coupling to low-frequency magnetic fields. The physical
interaction of time-varying magnetic fields with the human body
results in induced electric fields and circulating electric
• Biological effects and epidemiological studies (100 kHz–
300 GHz). Available experimental evidence indicates that the
exposure of resting humans for approximately 30 min to EMF
producing a whole-body SAR of between 1 and 4 W kg21 results
in a body temperature increase of less than 1 °C. Animal data
indicate a threshold for behavioural responses in the same
• Exposure to more intense fields, producing SAR values in
excess of 4 W kg21, can overwhelm the thermoregulatory
capacity of the body and produce harmful levels of tissue
• Electric Dipoles: In physics, the electric dipole moment is a
measure/moment of the separation of positive and negative electrical
charges in a system of electric charges, that is, a measure of the
charge system's overall polarity. An atom in which the centre of the
negative cloud of electrons has been shifted slightly away from the
nucleus by an external electric field constitutes an induced electric
• Data on human responses to high-frequency EMF that
produce detectable heating have been obtained from
controlled exposure of volunteers and from
epidemiological studies on workers exposed to sources
such as radar, medical diathermy equipment, and heat
sealers. They are fully supportive of the conclusions
drawn from laboratory work, that adverse biological
effects can be caused by temperature rises in tissue that
• Indirect effects of electromagnetic fields. In the
frequency range of about 100 kHz–110 MHz, shocks and
burns can result either from an individual touching an
ungrounded metal object that has acquired a charge in a
field or from contact between a charged individual and a
grounded metal object.
• Health effects closely related to the frequency and type of
• Recent studies indicated that exposure to EMF might be
related to leukaemia and other types of cancer.
• EMF radiation might interfere with pacemakers and medical
• Exposure to EMF radiation in the microwave range might
cause damage to the retina.
• Induced current may cause tissue damage in areas
surrounding metal implants (Case in the DoD).
• Research on-going regarding Electromagnetic field
Radiation’s Health Effects.
• Identify the Frequency (Hz) and Wavelength (λ)of the
EMF source or sources that will be assed.
• Calculate the near and far fields (3 λ).
• Determine whether measurements will be done within
the near of far field (few cm’s to km’s depending on
frequency and wavelength).
• Consider interference from other sources (Same
• Commercial instruments and probes for measuring
measuring E or H
Near Field measure E, H or both (must comply with MPE limits
Far Field measure E or H and obtain S [S = E2/Z0 = H2*Z0] (must
comply with MPE limits imposed).
If uncertain measure both.
Imission: use of broadband instruments (non-tunable electromagnetic
radiation detectors), with isotropic E and H measurement probes
Emission: use of narrowband instruments (field intensity meters, tunable
spectrum analyzers, etc.), with antennae suitable for measurement
All instruments, antennae and probes must have a calibration certificate
(manufacturer or laboratory accredited in country of origin).
Record the value of the measurement, plus the uncertainties specified
(manufacturer), plus the error of the method used.
NIOSH: Manual for Measuring Occupational Electric and Magnetic Field
6 min Moving Average.
• Points of measurement:
• General in house areas with only a single source - Take measurement
at workstation if EMF Exposure at a workstation need to be measured.
• General in house areas with multiple sources - Divide area into square
meter squares. Take measurements in the middle of each square to
determine areas of high radiation (Map).
• Omni-directional systems (Antennas – Environmental/Community):
a minimum of 16 points
• Directional systems (Antennas – Environment/Community):
a minimum of 4 points in direction of max. propagation
12 remaining points according to character of radiation lobe.
• Inverse square law also applies to EM Fields. By
increasing the distance from the source will decrease
• Metal enclosures or EMF shielding can be used to shield
workers from EMF Radiation (depending on type of EM
• Ensure that all metal objects and structures in the vicinity
of an EMF source are properly earthed (Electrical
• Prevent workers with implanted medical devices or metal
implants to perform work near any EMF sources.
• Reduce exposure time exposed to EMF radiation.
• Conduct regular assessments in all high risk areas to
determine the efficacy of control measures.
• Conduct regular medical surveillance.
EMF (ELF) X
EMF (ELF) Y
EMF (ELF) Z
Position - 3
Welgedag Substation (6.6 kV
Substation Yard area).
Measurements were conducted in
central part of the yard at about 7m
underneath the 11 kV overhead
feed power line.
50 Hz E-Field
Strength (V m-
310.7 777.5 789.3 1150 10,000 V
50 Hz B-Field
0.5867 0.3048 0.3246 0.74 500 µT
TASKS AND COMMENTS
The calculated mean isotropic RMS value (derived from the max field strengths on the X, Y and Z vectors) for the E-Field at 11.50% of the Reference Value did not exceed the Reference Value of
10,000 V m-1 (@50 Hz) as prescribed by the ICNIRP Guidelines. It is unlikely that health effects related to E-Fields at the current frequency (50 Hz). The calculated E-Field Isotropic RMS value exceeds
the 1 kV m-1 action level for cardiac pacemakers, suggested by the ACGIH.
The calculated mean isotropic RMS value (derived from the max field strengths on the X, Y and Z vectors) of the B-Field at 0.148 % of the Reference Value did not exceed the Reference Value of 500
µT (@ 50 Hz) as prescribed by the ICNIRP Guidelines for the frequency established. It is unlikely that health effects related to B-Fields for the 50 Hz frequency might develop. The calculated B-Field
Isotropic RMS value did not exceed the 100 µT action level for cardiac pacemakers, suggested by the ACGIH.
Employees perform general maintenance, instrument checking and inspections near the 6.6 kV transformers.
The employees work a 9.5-hour shift in the area performing such activities.
No PPE was provided or worn by the employees while conducting the surveys in the mentioned area.
The source of exposure is the 11,000 V AC (50 Hz) feed cables/conductors and the transformer, situated in the close vicinity where maintenance is conducted.
No effective EMF shielding is provided for, serving as a barrier between the workers and the source in reducing exposure to EMF (ELF) Radiation.
No persons with cardiac pacemakers or any other implanted electronic medical devices are employed in the area.