Transcript Electromagnetic field and UV radiation in the workplace

ELECTROMAGNETIC
FIELD RADIATION IN
THE WORKPLACE
Presented by N.W. Pieterse
GAUTENG BRANCH WORKSHOP
25 NOVEMBER 2015
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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
Considerations.
• 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 field.
• 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 propagation.
• In a vacuum, electromagnetic radiation propagates at a
characteristic speed, the speed of light.
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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:
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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
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ELECTRIC FIELD STRENGTH (E): The magnitude of the electric field
vector expressed in V/m.
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MAGNETIC FIELD STRENGTH (H): The magnitude of the magnetic
field vector expressed in A/m.
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POWER DENSITY (S): Power per unit area normal to the direction of
propagation, expressed in mW/cm2.
• EMISSION: Radiation produced by a single radiofrequency source.
• INMISION: Radiation resulting from the contribution of all
radiofrequency sources whose fields are present in the place.
• 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 able to control it.
Cell Phone Towers
Transformer Station
Radio Towers
High Voltage Power Lines
Mobile Military Radio Mast
Microwave Antenna
Fixed Radar Antenna
Mobile Radar Antenna
• Coupling to low-frequency electric fields. The interaction of timevarying 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 currents.
• 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 wholebody SAR of between 1 and 4 W kg results in a body temperature
increase of less than 1 °C. Animal data indicate a threshold for
behavioural responses in the same SAR range.
• Exposure to more intense fields, producing SAR values in excess of 4
W kg , can overwhelm the thermoregulatory capacity of the body
and produce harmful levels of tissue heating.
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• 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 dipole.
• 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 exceed 1°C.
• 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 EMF
radiation.
• 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
implants.
• 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 Frequency):
• Commercial instruments and probes for measuring
radiofrequency
Non-tuneable
Tuneable
Interchangeable antennae
for measuring E or H field
(Isotropic)
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Near Field  measure E, H or both (must comply with MPE limits imposed).
Far Field  measure E or H and obtain S [S = E2/Z0 = H2*Z0] (must comply with
MPE limits imposed).
E=V/m
H=A/m
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377 ohm
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 frequency ranges
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
Exposures
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 exposure proportionally.
• Metal enclosures or EMF shielding can be used to shield
workers from EMF Radiation (depending on type of EM Fields).
• Ensure that all metal objects and structures in the vicinity of an
EMF source are properly earthed (Electrical Charge).
• 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.
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Personal
Alarm
Fence to Limit Access
RF Protective Suits
MEASUREME
NT
REFERENCE
No.
WORK AREA/PERSON
Measurement Welgedag Substation (6.6 kV
Position - 3
Substation
Yard
area).
Measurements were conducted in
central part of the yard at about 7m
underneath the 11 kV overhead
feed power line.
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FREQUENCY
RANGE
50 Hz
50 Hz
EMF (ELF) X
VECTOR MAX RMS
VALUE
EMF (ELF) Y
VECTOR MAX RMS
VALUE
EMF (ELF) Z
VECTOR MAX RMS
VALUE
310.7
777.5
789.3
1150
B-Field
0.5867
(Magnetic flux
Density) (µT)
TASKS AND COMMENTS
0.3048
0.3246
0.74
FIELD VECTOR
E-Field
Strength (V m1)
EMF (ELF)
MEAN
ISOTROPIC.
RMS VALUE
REFERENC
E VALUE
(UNPERTU
RBED RMS
VALUES
10,000 V
m-1
500 µT
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.
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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.
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Employees perform general maintenance, instrument checking and inspections near the 6.6 kV transformers.
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The employees work a 9.5-hour shift in the area performing such activities.
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No PPE was provided or worn by the employees while conducting the surveys in the mentioned area.
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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.
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No effective EMF shielding is provided for, serving as a barrier between the workers and the source in reducing exposure to EMF (ELF) Radiation.
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No persons with cardiac pacemakers or any other implanted electronic medical devices are employed in the area.
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