Alicia Antolín

Electrical stimulation vs thermal effects in a complex electromagnetic environment

Studies linking exposure to low levels of radiofrequencies with adverse health effects, notwithstanding their present apparent inconsistency, have contributed to a steady improvement in the quality of evaluating that exposure. In complex electromagnetic environments, with a multitude of emissions of different frequencies acting simultaneously, knowledge of the spectral content is fundamental to evaluating human exposure to non-ionizing radiation. In the present work, we quantify the most significant spectral components in the frequency band 0.5-2200 MHz in an urban area. The measurements were made with a spectrum analyzer and monopole, biconical, and log-periodic antennas. Power density levels were calculated separately for the medium wave, short wave, and frequency modulation radio broadcasting bands, and for the television and GSM, DCS, and UMTS mobile telephony bands. The measured levels were compared with the ICNIRP reference levels for exposure to multiple frequency sources for thermal effects and electrical stimulation. The results showed the criterion limiting exposure on the basis of preventing electrical stimulation of peripheral nerves and muscles to be stricter (exposure quotient 24.7 10(-4)) than that based on thermal considerations (exposure quotient 0.16 10(-4)). The bands that contribute most to the latter are short wave, with 46.2%, and mobile telephony with 32.6% of the total exposure. In a complex electromagnetic environment, knowledge of the radiofrequency spectrum is essential in order to quantify the contribution of each type of emission to the publics exposure. It is also necessary to evaluate the electrical effects as well as the thermal effects because the criterion to limit exposure on the basis of the effect of the electrical stimulation of tissues is stricter than that based on thermal effects.

Estimation of Uncertainties in Electric Field Exposure From Medium-Frequency AM Broadcast Transmitters

International guidelines for limiting exposure to electromagnetic fields set out basic restrictions and reference levels to protect human health. To ensure compliance with these guidelines, standard measurement procedures must be used, and assessments of the uncertainties in the measurements must be reported. Nevertheless, neither the exposure restrictions nor the technical assessment standards specify how the measurement and computation of the uncertainties should be considered. This paper analyzes the following two sources of uncertainties that are not often considered in the assessment of exposure to electromagnetic fields: 1) repeatability and 2) spatial interpolation. For this purpose, electric field measurements were made in an area in which three medium-wave radio broadcasting transmitters are located. Systematic random sampling was performed with a spectrum analyzer and a monopole-type antenna, and geostatistical techniques were used to construct contour maps of the electromagnetic radiation and its associated uncertainties. The results suggest that, in handling uncertainties in assessments of human exposure to electromagnetic fields based on spatial interpolation from point measurements, based on medium-frequency amplitude modulation broadcast transmitters, the additive approach (i.e., the uncertainty is added to the results of the assessment before the exposure level is compared to the relevant limit) is the most appropriate.

Exposure to high-frequency electromagnetic fields (100 kHz-2 GHz) in Extremadura (Spain).

The last decade has seen a rapid increase in peoples exposure to electromagnetic fields. This paper reports the measurements of radiofrequency (RF) total power densities and power density spectra in 35 towns of the region of Extremadura, Spain. The spectra were taken with three antennas covering frequencies from 100 kHz to 2.2 GHz. This frequency range includes AM/FM radio broadcasting, television, and cellular telephone signals. The power density data and transmitting antenna locations were stored in a geographic information system (GIS) as an aid in analyzing and interpreting the results. The results showed the power density levels to be below the reference level guidelines for human exposure and that the power densities are different for different frequency ranges and different size categories of towns.

Medium wave exposure characterisation using exposure quotients

One of the aspects considered in the International Commission on Non-Ionizing Radiation Protection guidelines is that, in situations of simultaneous exposure to fields of different frequencies, exposure quotients for thermal and electrical stimulation effects should be examined. The aim of the present work was to analyse the electromagnetic radiation levels and exposure quotients for exposure to multiple-frequency sources in the vicinity of medium wave radio broadcasting antennas. The measurements were made with a spectrum analyser and a monopole antenna. Kriging interpolation was used to prepare contour maps and to estimate the levels in the towns and villages of the zone. The results showed that the exposure quotient criterion based on electrical stimulation effects to be more stringent than those based on thermal effects or power density levels. Improvement of dosimetry evaluations requires the spectral components of the radiation to be quantified, followed by application of the criteria for exposure to multiple-frequency sources.

Optimization and comparison of three spatial interpolation methods for electromagnetic levels in the AM band within an urban area

Abstract A comparative study was made of three methods of interpolation – inverse distance weighting (IDW), spline and ordinary kriging – after optimization of their characteristic parameters. These interpolation methods were used to represent the electric field levels for three emission frequencies (774 kHz, 900 kHz, and 1107 kHz) and for the electrical stimulation quotient, QE, characteristic of complex electromagnetic environments. Measurements were made with a spectrum analyser in a village in the vicinity of medium‐wave radio broadcasting antennas. The accuracy of the models was quantified by comparing their predictions with levels measured at the control points not used to generate the models. The results showed that optimizing the characteristic parameters of each interpolation method allows any of them to be used. However, the best results in terms of the regression coefficient between each models predictions and the actual control point field measurements were for the IDW method. HighlightsInterpolation methods were used to represent the electric field levels in a village.Temporal variation values were less than spatial variations detected in the area.Inverse distance weighting, spline, and ordinary kriging were compared.The accuracy was quantified comparing the predictions with levels at control points.The best fits between predicted and measured values corresponded to the IDW model.

Spectral analysis to assess exposure to extremely low frequency magnetic fields in cars

A type of contamination that has been little studied in cars comes from the extremely low frequency (ELF) magnetic fields generated by the vehicles electrical devices and the magnetized metal in the tyres. The magnetic fields in cars are frequently analysed with broadband meters sensitive to a frequency range above 30Hz. This has the disadvantage that they neither detect the magnetic field of the spinning tyres nor give any information on the spectral components, which makes it impossible to adequately assess exposure. The objective of the present study was to perform spectral analyses of ELF magnetic fields in cars, to identify their frequencies, and to assess exposure based on the ICNIRP regulatory guidelines. To do this, a meter and a spectrum analyser sensitive to magnetic fields in the 5Hz-2kHz frequency range were used. Spectra were acquired for different seats, heights, and speeds, and spatially averaged exposure coefficients were calculated. The results indicated that the main emissions were detected in the 5-100Hz range, where the wheel rotation frequencies and their harmonics are found. The intensity of the rest of the emissions were negligible in comparison. The exposure quotient increases with speed, and is approximately twice as great at foot level as at head level. The magnetic field levels are lower than the reference levels (the maximum represents 3% of the ICNIRP standard), but higher than those found in residential environments and than the cut-off threshold used by the IARC to classify ELF magnetic fields in Group 2B.