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Electromagnetic Fields in Biological Systems
the conductor. One was the case of exposure to uniform 10 kV/m electric fields, and the
other three were different magnetic field exposures including nonuniform conditions.
This result showed that for pregnant workers, the induced current densities might be
greater than the basic restrictions of occupational exposure recommended by ICNIRP,
10 mA/m 2 , and the induced current densities for their fetuses might be greater than the
basic restrictions of public exposure.
Dimbylow and Findlay (2010) pointed out that the analysis of the interaction of ELF
EMF with the body has used adult voxel models in standard standing posture, and
changes in posture and size of the body can alter the distribution of the induced current
densities. From these speculations, the effects of body posture, anatomical variations, age
difference, and pregnancy on the induced current densities from 50 Hz electric and magnetic fields were considered in an extensive ensemble of voxel models. For the calculations, there were six adult models, eight child models, and seven pregnant female models
including NAOMI at various stages of gestation. The SPFD method was used to calculate
the induced current densities from uniform 50 Hz magnetic fields, and the quasistatic
potential equation was applied to calculate the induced current densities for 50 Hz electric fields. The maximum value of 0.32 mA/m 2 for 1 kV/m occurred in the Virtual Family
female, Ella. The authors showed that this value would require an external 6.25 kV/m
to produce basic restriction of 2 mA/m 2 for public exposure. For magnetic fields, the
maximum value from all the models was 7.0 mA/m 2 per mT in TARO. This corresponds
to an external 0.286 mT to produce the basic restriction of 2 mA/m 2 for public exposure.
Hart and Gandhi (1998) compared the cardiac-induced endogenous fields and 60 Hz
electric and magnetic field induced exogenous fields in an anatomical human body
model. The endogenous fields due to the beating of the heart were computed, and the
magnitude of the naturally produced electric field and current densities inside the body
were estimated. The endogenous electric field and current densities in most of the tissues
in the frequency band of 40–70 Hz were found to be considerably smaller than those
induced in human body by 60 Hz electric and magnetic fields.
Andreuccetti, Priori, and Zoppetti (2009) proposed the simplified procedure for dosimetric evaluations of ELF sources with complex waveforms. This procedure is based on
the use of equivalent field intensity at an arbitrarily chosen reference frequency and allows
summarizing into a single-frequency dosimetric evaluation with some approximations.
Zoppetti and Andreuccetti (2009a,b) reviewed open problems in assessing compliance
the with 2004/40/EC Directive (EU 2004). The problem is the applicability of the numerical technique to check the compliance with exposure limit values at the ELF region. To
endorse the 2004/40 EC Directive, current densities must be averaged over a cross-section of 1 cm 2 at every point of the exposed tissue, which is introduced by ICNIRP (1998a).
The shape of the averaging surface is not specified. According to ICNIRP (1998b), the
target tissue for averaging is the tissues of the CNS. This guideline introduces reference
levels for external fields and basic restrictions for internal induced quantities and current densities. The current densities can be generally calculated using different types of
methods with high-resolution numerical body models cited in this chapter. Zoppetti and
Andreuccetti (2009a,b) pointed out, as open problems, that neither ICNIRP or the EU
Directive define the surface averaging procedure nor indicate how to proceed when the
tissue for 1 cm 2 averaging does not belong to the CNS. The basic restrictions may permit