Shock
According to the United States Environmental Protection Agency (EPA), a person standing directly under a high voltage power line could receive a mild shock when touching something that conducts electricity. This is directly related to the large amount of electricity passing overhead. The EPA recommends not standing under those lines, and in general, staying as far away from the lines as possible. If exposure is unavoidable then limit the time.
Legal Restrictions
There are no federal standards which prohibit or regulate exposure to EMF. According to the EPA about seven states set minimum right-of-way distances for the high voltage power lines in order to limit exposure. Power companies have to obtain the right to construct those towers over property and those rights prohibit any structures from being placed in the right-of-way. In general, there is no reason for a person other than a power company employee to be under the lines. Since the impact on the magnetic field diminishes with distance the EPA advice of staying as far away as possible remains valid.
Health Effects
Controversy exists over whether or not exposure to magnetic fields, particularly those generated by high voltage power lines, cause health problems. The EPA states that the evidence is weak and inconclusive and thus insufficient to support a cause and effect finding.