Table 16.3 - Typical exposure levels from some electric and magnetic field sources
Source: WHO (in press)
Field sources | Frequency range (Hz) | Magnetic flux density | ||
---|---|---|---|---|
Average level | Peak level | Electric field strength | ||
Earth | 0 | 50 µT |   | 130 V/m |
50 and 60 | 106 µT | 320 kV/m (thunderstorms) | ||
51000 |   | 10-40.5 V/m (atmospherics) | ||
Offices and households | 50 and 60 | 0.031 µT | 140 µT (at 30 cm distance from various appliances) | 2500 V/m (at 30 cm distance from various appliances) |
  | 0.612 µT (residences with electric heating) |   | ||
30 cm from a VDU | 50 | 0.8 µT | 518 µT | 301500 V/m |
High-voltage AC power transmission | ||||
Right under overhead transmission line (380 and 756 kV) | 50 and 60 | 1030 µT | 400 µT (during failure) | 310 kV/m |
25 m from midspan (380 kV) | 50 | 68 µT |   | 12 kV/m |
Railway transmission line (110 kV) | 16 2/3 | 1225 µT | 25 kV/m | |
Inside generating stations | 50 and 60 | 2040 µT | 270 µT | 516 kV/m |
Industry | ||||
Electrolytic processes | 0 and 50 | 110 mT | 50 mT |   |
Welding machines | 0 and 50 |   | 130 mT | |
Electric furnaces | 11000 | 25 mT | ||
Induction heating | 5010 000 | 16 mT | 25 mT | |
Medicine | ||||
Nuclear magnetic resonance imager | 0 | 15 mT (operator) | 2T, 6T/s (patient) |   |
30250 mT (operator, outside magnet) | ||||
Therapeutic equipment | 12, 15, 20, 50, 75 | 116 mT (patient) |   |