1. Residential exposure to EMFs
Phoka Rathebe

2. Characteristics of EMFs
Electromagnetism- EMFs- Electric and Magnetic Fields.
EMFs- is considered non-ionising radiation. It is characterised in terms of frequencies (Hz or s) and wavelength (nm).
EMFs are created by movement of electrical current in the conductor.
RF fields (communication and medical devices) and Power Frequencies (50 Hz in South Africa and 60 Hz in European countries).
EMFs:
Extremely Low Frequencies
Low frequencies
High frequencies
Very high frequencies

3. EMFs in public spaces RF fields:
Signal towers and Medical devices (MRI)
Signal towers, cell phones and other communication devices- 10 KHz- 100 KHz- Low frequencies
MRI: 10 MHz- 300 MHz- low Frequencies and High frequencies.

4. Cont…
Power Frequencies: 3 to 3000 Hz (ELF Electric and Magnetic fields).
Railway lines- 11 kV
Power stations and substation- 756, 132 to 11 kV
Power lines- Overhead and underground (132 to 11 kV).
Home appliance- 3 KHz to 10 KHz

5. Cont… MRI scanners (1.5 T & 3.0 T Scanners):
Time-varying magnetic fields- Movement of workers in the MRI room.
Static Magnetic fields- Permanently present due to magnet bore.
RF fields- Produced by RF coil transmit.

6. Probability of exposure effects
ELF magnetic fields- vascular dementia and leukemia (average exposure > 3 microTesla).
Other forms of cancer cannot be caused by ELF magnetic fields has it has insufficient photon energy and electromotive force to dislodge electrons in the human body and also to break chemical bonds in the human cells.
Transient biological effects are not yet confirmed this is due to improper exposure assessments.

7. Cont….. RF fields: Thermal and non-thermal effects
Thermal: burning of less blood supplied organs due to insufficient blood flow to the tissues. This include effects on the testis and eyes.
In Testes- it slower the spermatogenesis (this happens when the internal temperature is lower by 2OC to the normal body temperature).
Excessive absorption of RF energy increases the tissue temperature which result in tissue burning (SAR- Absorbed RF energy per kilogram of tissue).

8. Cont…
Preterm delivery and abortion has been reported amongst pregnant patients who underwent MRI scan after the first trimester.
Non-thermal: the only known non-thermal effect is electromagnetic hypersensitivity. Exposure assessments are necessary to inform epidemiological studies in order to establish more non-thermal effects, which could range from transient to long-term exposure-related effects.

9. Cont….
Static magnetic fields: transient, ranging from vertigo, concentration difficulties, memory loss, nausea, severe headache etc.
Hypertension recently been reported amongst MRI workers who have more than 10 years experience in the MRI units.
Bleeding from uterus was reported amongst women who have uterus implant birth control (Intra Uterine Device (IDU) are made of ferromagnetic material which makes them easy to have ballistic effects).

10. Exposure assessments
Exposure to EMFs, particular magnetic fields is significantly based on the inverse-square law.
Inverse-square law- the closer the source the higher the exposure. In this case, exposure can only be mitigated through the use of reverberation chamber and faraday cage (MRI rooms). Faraday cages are lined with copper which presents unique absorption properties.

11. Cont….
Distance: decreases exposure significantly. E.g. if exposure at 3 m is 1.25 microTesla, at 2 m it will be 2.5 microTesla and 5 microTesla at 1 m.
Duration and frequency of exposure determines the probability of absorbed intensity. The longer the time you spend closer to the source, the higher the exposure.
Magnitude and absorbed magnitude: There is higher magnitude closer to the source, however, exposure levels present in the atmosphere cannot be a true indication of absorbed magnitude (dose) in the target organ.

12. Guidelines ICNIRP guidelines:
Static magnetic fields: ELV up to 2 T for workers and 200 mT for general public.
ELF magnetic fields: ELV of l 000 microTesla for workers and 200 microTesla for general public.
RF energy/ 0.2 microTesla and 4 W/kg in the event where exposure dosimeters are used.

13. Thank you