May 18, 2016

Comparative dosimetry for children and rodents exposed to extremely low-frequency magnetic fields

Yijian Gong, Myles Capstick, Clemens Dasenbrock, Maren Fedrowitz, Cesar Cobaleda, Isidro Sanchez-Garcia, and Niels Kuster, Bioelectromagnetics, Volume 37, Issue 5, pp. 310–322, July 2016, online May 13, 2016

We describe a method to correlate E-fields induced by exposure to extremely low frequency magnetic fields in laboratory mice and rats during in vivo experiments to those induced in children. Four different approaches of mapping relative dose rates between humans and rodents are herein proposed and analyzed. Based on these mapping methods and volume averaging guidelines published by the International Commission on Non-Ionizing Radiation Protection (ICNRP) in 2010, maximum and median induced field values for whole body and for tissues of children and rodents were evaluated and compared. Median induced electric fields in children younger than 10 years old are in the range 5.9–8.5 V/m per T (±0.4 dB). Maximum induced electric fields, generally in the skin, are between 48 V/m and 228 V/m per T (±4 dB). To achieve induced electric fields of comparable magnitude in rodents, external magnetic field must be increased by a factor of 4.0 (±2.6 dB) for rats and 7.4 (±1.8 dB) for mice. Meanwhile, to achieve comparable magnetic field dose in rodents, ratio is close to one. These induced field dose rates for children and rodents can be used to quantifiably compare experimental data from in vivo studies with data on exposure of children from epidemiological studies, such as for leukemia.

The scientific and technical impact of the study can be summarized as:

  • Methods for specific mapping of ELF-MF exposures of immature rodents to human children to allow quantifiable comparisons of in vivo experiments are assessed.
  • For magnetic fields, the dose correlation between rodents and children is essentially the external MF at the location of the target tissue.
  • For E-fields induced in tissues or organs, differences in the morphologies and anatomies of individual tissues or organs between rodents and humans require more complex correlation assessment than ratios based on straightforward weight-based scaling.
  • A more accurate approach to the ratio problem that takes the mapping method, growth rate, and various uncertainty factors into consideration is described.
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