Occupational Exposure of Dentists to Extremely-low-frequency Magnetic Field

Objective： To compare occupational exposure to extremely-low-frequency magnetic field (ELF-MF) between dentists practicing in dental clinics and those employed in hospitals. Methods： Thirty-two dentists who worked at clinics (n=15) and 33 dentists employed at hospital dental departments (n=7) voluntarily provided their informed consent to participate in this measurement study. The study dentists were requested to wear an ELF-MF dosimeter for some 3 h at work to determine their personal exposure. Spot measurements taken at a number of locations in each dental office were used to indicate the work environment exposure level. Additionally, ELF-MF emitted from common dental equipment was also measured. All measurements were performed with EMDEX Lite meters. Results： The average environmental exposure to ELF-MF is higher in clinic dental offices than in hospital dental departments (0.55 vs. 0.15μT, p=0.008). Personal dosimetry showed that on average, clinic dentists spent 35.71 and 19.39% of their time at exposures above 0.3 and 0.4μT at work, respectively. The corresponding figures for hospital dentists were 19.61 and 13.92%. Additionally, ELF-MF was greater than 0.4μT at 30 cm from all selected equipment, but the ELF-MF generally diminished as the distance from dental equipment increased. Uultraviolet air sterilization system produced 3 times as much ELF-MF as other dental equipment. Conclusions： This study suggests the possibility of over-exposure of dentists to power frequency ELF-MF. Additionally, certain dental equipment may produce ELF-MF levels greater than 0.4μT in areas where dentists usually work when treating patients.