Extremely-low frequency fields

Extremely-low frequency (ELF) electric and magnetic fields (EMF) are produced whenever electricity is generated (i.e. power stations), transmitted and distributed (i.e. power lines) or used (i.e. electric appliances). 

Extremely-low frequency (ELF) electric and magnetic fields (EMF) have frequencies between around 1 Hz up to 3 kHz. The frequency used in Ireland and throughout Europe is 50 Hz. ELF-EMF have long wavelengths (around 5,000 km at 50 Hz) and are considered fields rather than radiation, since their energy is not radiated far away from the source. This means that the electric and magnetic fields have independent characteristics and therefore need to be measured separately. 

Extremely Low Frequency Field

Electric fields are easily blocked by solid materials, including buildings and trees. Therefore, the levels of ELF electric fields at which the public may be exposed are very low, and generally are not a concern. ELF magnetic fields are not as easily shielded.  However, magnetic fields fall off rapidly with distance from the source.   

ELF magnetic field (microTesla, μT)
SourceDistance 1 (near)Distance 2 (far)
Overhead (AC) 110-400 kV transmission line 5-4.9 μT at 10 m <0.01 μT at 100 m
Overhead (AC) 10-60 kV distribution line 1-1.4 μT at ≤5 m ≈0.8 μT at 10 m
Underground (AC) power line 1-0.9μT at ≤5 m ≈0.03 μT at 10 m 
Hair dryer  ≈30 μT at 15 cm ≈0.1 μT at 30 cm
Electric stove  ≈3 μT at 15 cm ≈0.2 μT at 60 cm
Television set ≈0.7 μT at 30 cm ≈0.2 μT at 60 cm
Fluorescent bulb ≈0.1 μT at 15 cm ≈0.1 μT at 30 cm

Note: Tesla is the most frequent unit used for magnetic fields; 1 microTesla (μT10-6 Tesla.  Magnetic field estimates from EirGrid and HydroQuebec. The current recommended reference level for public exposure to ELF magnetic fields (at 50 Hz) is 100 µT (1999/519/EC).