Contact currents occur when a person touches conductive surfaces at different electric potentials. In the low frequency to intermediate frequency, the flow of current from an object to the body may result in die stimulation of peripheral nerves and the temperature elevation, which depends on the frequency of current. Therefore, the reference level is regulated in terms of injected current in the international guidelines/standard. Contact current which does not produce induced quantities exceeding the basic restriction is used as a reference level. Some recent studies conducted dosimetry for contact current but only at extremely low frequencies. In our previous study we proposed a quasi-static finite-difference tune-domain (FDTD) method which has a feature in its capability for handling realistic structures and source at reasonable computational resources. This method extends a conventional FDTD method to solve quasi-static problems by choosing an appropriate waveform in voltage source. The present study first discusses an applicability of the quasi-static FDTD method for a human body in MHz region. Then the relationship between the basic restriction and reference level for contact current is discussed based on our computational results.%電磁界ばく露により異なる電位ポテンシャルを持つ金属に人体が接触するとき，接触亀流が生じ，体内に誘導された電界により生体影響を引き起こすとされる.ICNIRP (国際非電離放射線防護委員会）ガイドラインおよびIEEE/ICES規格では，電磁界ばく露と同様，接触亀流に対する参考レベルを股けている.近年では，数値解析により，参考レベルと体內誘導量の許容値である基本制限の関係の確認が行われている.人体のような不均質か つ複雑な構造を取り扱うにはFDTD (Finite Difference Time Domain)法が有効であるが，低周波においては膨大な操り返し計算が必要になる.そのため，筆者らは.波源（入射電圧源）をステップ形状とし，橾り返し回数を削減する準静的FDTD法を提案している.本稿では，まず，MHz带における準静的FDTD法の有効性について検討する.次に，参考レベルの接触電流を注入した場合の体内誘導電界および局所SAR (Specific Absorption Rate)と基本制限を比較する.
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