Contact currents flow from/into a human body, when contacting an object such as a metal structure with a different electric potential due to electromagnetic field exposure, which should stimulate muscle and peripheral nerves. In this context, numerical analysis of electric fields induced by contact currents in a human body have been performed so far, while the effectiveness of computational methods for transient contact currents has not been investigated sufficiently. Therefore, further numerical analysis of induced quantities in specific tissues is required. In addition, a previous study reported that a threshold contact current in the child which elicits biological responses is lower than that in the adult. Thus, further investigation for human models with different dimensions is required. Our group analyzed the induced quantities in a Japanese adult male model due to transient contact currents from charged human body with the FDTD method. We considered Japanese adult female model and 3-year-old child model in addition to the adult model, and then analyzed the in-situ electric fields due to transient contact current from charged human body. As a result, it was found that the decay constant for contact current of the 3-year-old child model whose capacitance is low was higher than that of the adult models for the same charged voltage. It was also confirmed that in-situ electric field becomes large around the metal rod and small sectional area on the current path. In-situ electric fields of 3-year-old child model were found to be higher than that of the adult models, because cross-sectional area of the hand and forearm of child model does not change so much as compared to that of the adults.%接触電流は，電磁界曝露で電位ポテンシャルを持つ金属構造物に人体が接触したときに体内外へ流出入し，その際の体内誘導電流密度／電界が筋肉や末梢神経を刺激する恐れがある．こうした背景から，接触電流で体内に誘導される電流密度／電界に関する数値検討は行われているものの，報告例は十分ではない．また，特定組織における誘導量の更なる検討が求められている．加えて，接触電流による生体反応を引き起こす電流の閤値が成人に比べて子供の方が小さいとの報告もあり，異なる寸法の人体モデルに対する検討も求められる．筆者らの研究グループでは，日本人成人男性を対象とした解剖学的人体数値モデルを用いて，帯電人体からの過渡的な接触電流による体内誘導量のFDTD解析を行ってきた．本稿では，日本人成人男性モデルに加えて，日本人成人女性モデルおよび3歳小児モデルも解析の対象として，帯電人体からの過渡的な接触電流による誘導電界を解析した．解析の結果，同じ充電電圧による帯電人体からの接触電流は，人体容量の小さい3歳小児モデルが成人男女モデルに比べて減衰定数が大きいことがわかった．また，体内誘導電界は，金属棒付近および電流経路上の断面積の小さい箇所において大きくなることが確認できた．更に，3歳小児モデルにおける誘導電界は，成人男女モデルに比べて大きくなり，その主な理由は手から前腕部にかけて断面積の変化が小さいことが示唆された．
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