Low frequency (LF) EMFs (sometimes called ELF fields) occurs around electrical wiring and appliances, including wiring in the walls; also pylons and near substations.
Studies suggest effects of prolonged exposure to LF EMFs include sleep difficulties, concentration problems, damage to cell regulation and growth, hormone production, enzyme production, and disturbance of brain wave rhythms.
LF EMFs do reduce considerably with distance form the source, are mainly hazardous to health when there is prolonged exposure in one place, therefore solutions to this problem are generally focused around removing or shielding sources close to beds.