Occupational 50-Hz magnetic field exposure and human heart rate: A case report

In an office room located above the building's transformer station, a durable slowing of heart rate (48 bpm) and frequent ventricular extrasystoles were observed in a woman, 47 years old, a few months after she changed the location of her office. Her prior baseline heart rate was 80 bpm. All the cardiological investigations were normal. ELF electric field was low: 4-5 V/m. Average ELF magnetic flux density at the workplace was 23 mu T with peaks to 31.4 mu T. The worker had a long-term exposure period (40 h/week for 22 months). The slowing phenomenon decreased after termination of the exposure (60 bpm). The ventricular extrasystoles remained 1 year after the end of the exposure but were fewer and no longer polymorphous. The criteria of a possible link between the appearance of cardiac rhythm disorders and the ELF magnetic exposure are analyzed. With a review of the literature, this clinical case seems to satisfy to some degree the biological plausibility, the temporal relationship, and the experimental evidence.