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 µT2­5 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 1­100025 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)