Researchers know from tests and calculations that very strong fields can interfere with the signals sent through the central nervous system. These are called known acute effects. The fields required are much stronger than the ones normally encountered at electricity supply installations (stronger than end 1000 µT). The effects range from mild and temporary cases of swimming eyes to serious disturbance of the heart rhythm (the latter only when fields are extremely strong). An effect is acute when it occurs immediately a person is exposed to the fields. In many instances, the effect is transitory, but extremely strong fields can cause permanent damage.

As such, several international organisations recommend specific exposure limits with regard to strong electric and magnetic fields, and the EU has adopted a directive to reduce field sizes in the workplace.

When we talk about long-term effects we mean diseases that may occur after a person has been exposed for a longer period of time. It could also be diseases occurring long after the exposure took place. Many types of cancer have a so-called 'latent period', ie the time between exposure and manifestation of the disease. The latent period for some forms of cancer can be both 10 and 20 years. Demographic studies must therefore always go way back in time to provide an accurate picture.

The numerous scientific studies conducted did not demonstrate that electric or magnetic fields of a given strength do in fact cause any long-term effects, and for that reason neither the World Health Organization (WHO) nor the International Commission on Non-Ionizing Radiation Protection (ICNIRP) recommends exposure limits due to long-term effects.