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Gepubliceerd: vrijdag 21 november 2014 08:43

Personal exposure meters underestimate the exposure of humans to non-ionizing radiation in indoor environments.

de Miguel-Bilbao et al. Assessment of human body influence on exposure measurements of electric field in indoor enclosures. Bioelectromagnetics. 2014 Nov 14. (PubMed)

Personal exposure meters (PEMs) used for measuring exposure to electromagnetic fields (EMF) are typically used in epidemiological studies. As is well known, these measurement devices cause a perturbation of real EMF exposure levels due to the presence of the human body in the immediate proximity. This paper aims to model the alteration caused by the body shadow effect (BSE) in motion conditions and in indoor enclosures at the Wi-Fi frequency of 2.4 GHz.

It has been found that the influence of the presence of the human body can be characterized as an angle of shadow that depends on the dimensions of the indoor enclosure.

In conclusion, the perturbation caused by BSE in PEMs readings cannot be compensated for by correction factors. Although the mean value is well adjusted, BSE causes changes in CDF that would require improvements in measurement protocols and in the design of measuring devices to subsequently avoid systematic errors.

This study demonstrates that ignoring the BSE is a systematic error that underestimates the real exposure of humans to non-ionizing radiation in indoor environments.

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Bioelectromagnetics. 2014 Nov 14. doi: 10.1002/BEM.21888. [Epub ahead of print]

Assessment of human body influence on exposure measurements of electric field in indoor enclosures.

de Miguel-Bilbao S1, García J, Ramos V, Blas J.

Abstract

Personal exposure meters (PEMs) used for measuring exposure to electromagnetic fields (EMF) are typically used in epidemiological studies. As is well known, these measurement devices cause a perturbation of real EMF exposure levels due to the presence of the human body in the immediate proximity. This paper aims to model the alteration caused by the body shadow effect (BSE) in motion conditions and in indoor enclosures at the Wi-Fi frequency of 2.4 GHz. For this purpose, simulation techniques based on ray-tracing have been carried out, and their results have been verified experimentally. A good agreement exists between simulation and experimental results in terms of electric field (E-field) levels, and taking into account the cumulative distribution function (CDF) of the spatial distribution of amplitude. The Kolmogorov-Smirnov (KS) test provides a P-value greater than 0.05, in fact close to 1. It has been found that the influence of the presence of the human body can be characterized as an angle of shadow that depends on the dimensions of the indoor enclosure. The CDFs show that the E-field levels in indoor conditions follow a lognormal distribution in the absence of the human body and under the influence of BSE. In conclusion, the perturbation caused by BSE in PEMs readings cannot be compensated for by correction factors. Although the mean value is well adjusted, BSE causes changes in CDF that would require improvements in measurement protocols and in the design of measuring devices to subsequently avoid systematic errors.

KEYWORDS:

PEM; body shadow effect; exposure assessment; radiofrequency electromagnetic fields (RF-EMF)