  The human dosimetry for electromagnetic field exposure is an essential task
to develop exposure guidelines/standards for human safety as well as product
safety assessment. At frequencies from a few hundred Hz to 10 MHz, the adverse
effect to be protected is the stimulation of the peripheral nervous system. The
in situ electric field in the skin is used as a surrogate of nerve activation.
In the low-frequency dosimetry, a high but inaccurate in situ electric field
has been reported at positions where a skin-to-skin contact exists, whose
relation to the stimulation is controversial. One of the reasons for high
electric fields may be attributable to the current resolution of anatomical
models. In this study, we first evaluate the stimulation threshold at postures
of skin-to-skin contact experimentally for different hand/finger positions to
represent skin touching/non-touching scenarios. We confirm that the
skin-to-skin contact does not lower the threshold current of magnetic
stimulation devices needed to induce pain. Second, a new method is proposed for
hand modeling to configure different finger positions using static hand models
with similar postures to the experiments. We compute the in situ electric field
at skin-to-skin contact for the different hand posture scenarios that indicate
an excessive raise of the electric field in skin-to-skin regions that is not
justified by the experiments. The comparison suggests that a high in situ
electric field in the skin would be caused by poor modeling of the skin layers,
which is not enough to represent in a resolution of the order of a millimeter.
This skin-to-skin contact should not be considered to set the restriction in
the international exposure guidelines/standards as well as product safety
assessment.
