Isabelle Magne

Methodology of a study on the French population exposure to 50 Hz magnetic fields

The characterisation of population exposure to a 50-Hz magnetic field (MF) is important for assessing health effects of electromagnetic fields. With the aim of estimating and characterising the exposure of the French population to 50-Hz MFs, two representative samples of the population were made. A random selection method based on the distribution of households in different regions of France was used. The samples were carried out starting from a random polling of telephone numbers of households (listed, unlisted fixed phones and cell phones only). A total of 95,362 telephone numbers were dialed to have 2148 volunteers (1060 children and 1088 adults). They all agreed to carrying an EMDEX II meter, measuring and recording MFs, and to filling out a timetable for a 24-hour period. In this article, the methodology of the sample selection and the collection of all necessary information for the realisation of this study are presented.

Exposure of children to extremely low frequency magnetic fields in France: Results of the EXPERS study

The assessment of magnetic field exposure in children is an important point in the context of epidemiological issues. EXPERS is the first study ever carried out measuring personal exposure to extremely low frequency magnetic fields at a national scale, involving 977 French children with 24 h personal measurements. Descriptive statistical analyses were performed for all the children, and only for children where no alarm clock was identified, as in some cases this requirement of the measurement protocol was not respected. The proportion of children with a 24 h arithmetic mean of ≥0.4 μT was 3.1% when considering all children and 0.8% when excluding alarm clocks. The alarm clocks were the main variable linked to the child exposure measurements. Magnetic field exposure increased when the home was located close to a high voltage power line. However, none of the 0.8% of children living at <125 m to a 225 kV line or <200 m to a 400 kV overhead line had a personal exposure of >0.4 μT. A multiple correspondence analysis showed the difficulty to build a statistical model predicting child exposure. The distribution of child personal exposure was significantly different from the distribution of exposure during sleep, questioning the exposure assessment in some epidemiological studies.

Computation of Pacemakers Immunity to 50 Hz Electric Field: Induced Voltages 10 Times Greater in Unipolar Than in Bipolar Detection Mode

Thisstudy aims to compute 50 Hz electric field interferences on pacemakers for diverse lead configurations and implantation positions. Induced phenomena in a surface-based virtual human model (standing male grounded with arms closed, 2 mm resolution) are computed for vertical exposure using CST EM® 3D software, with and without an implanted pacemaker. Induced interference voltages occurring on the pacemaker during exposure are computed and the results are discussed. The bipolar mode covers 99% of the implanted pacing leads in the USA and Europe, according to statistics. The tip-to-ring distance of a lead may influence up to 46% of the induced voltage. In bipolar sensing mode, right ventricle implantation has a 41% higher induced voltage than right atrium implantation. The induced voltage is in average 10 times greater in unipolar mode than in bipolar mode, when implanted in the right atrium or right ventricle. The electric field threshold of interference for a bipolar sensing mode in the worst case setting is 7.24 kV·m−1, and 10 times higher for nominal settings. These calculations will be completed by an in vitro study.

Electric field induced in the human body by uniform 50 Hz electric or magnetic fields: bibliography analysis and method for conservatively deriving measurable limits.

Health guidelines for electric and magnetic fields in the low frequency range define exposure limits for electric and magnetic fields in terms of induced electric field in the human body, which is not directly measurable, requiring use of dosimetry. However many parameters, such as human models, calculation codes and post-processing methods influence the calculation results. Based upon many published papers and therefore covering a wide range of these influence parameters, this paper proposes a method for conservatively deriving measurable levels of electric and magnetic fields equivalent to the basic restrictions. Following this method, we found that, regarding exposure to uniform fields, the ICNIRP 2010 occupational basic restrictions are equivalent to a 2 mT and 7 mT magnetic field and to a 35 kV m-1 and 35 kV m-1 electric field at 50 Hz when applied respectively to the central and peripheral nervous system.

Characterization of Children’s Exposure to Extremely Low Frequency Magnetic Fields by Stochastic Modeling

In this study, children’s exposure to extremely low frequency magnetic fields (ELF-MF, 40–800 Hz) is investigated. The interest in this thematic has grown due to a possible correlation between the increased risk of childhood leukemia and a daily average exposure above 0.4 µT, although the causal relationship is still uncertain. The aim of this paper was to present a new method of characterizing the children’s exposure to ELF-MF starting from personal measurements using a stochastic approach based on segmentation (and to apply it to the personal measurements themselves) of two previous projects: the ARIMMORA project and the EXPERS project. The stochastic model consisted in (i) splitting the 24 h recordings into stationary events and (ii) characterizing each event with four parameters that are easily interpretable: the duration of the event, the mean value, the dispersion of the magnetic field over the event, and a final parameter characterizing the variation speed. Afterward, the data from the two databases were divided in subgroups based on a characteristic (i.e., children’s age, number of inhabitants in the area, etc.). For every subgroup, the kernel density estimation (KDE) of each parameter was calculated and the p-value histogram of the parameters together was obtained, in order to compare the subgroups and to extract information about the children’s exposure. In conclusion, this new stochastic approach allows for the identification of the parameters that most affect the level of children’s exposure.

Implantable cardioverter-defibrillators exposed to low frequency magnetic fields

This paper presents a numerical modeling study of electromagnetic interference (EMI) in implantable cardioverter-defibrillators (ICDs), exposed to low frequency magnetic fields. Initially, an analysis of the standards that consider interference in ICDs was performed, to determine the level of induced voltage that may occur when the device is exposed to such magnetic fields. A Helmholtz coil was used to generate a uniform magnetic field. The magnetic field exposure was performed for the frontal position (front to back). This position presents the worst case scenario. The induced electric fields and voltage were investigated in both a simple homogenous block (brick) and in an anatomical model (virtual phantom). The ICDs sensitivity parameters were adjusted to minimum values (e.g. 0.2 mV for ventricular detection). This maximum sensitivity corresponds experimentally to the worst-case EMI scenarios. The results showed that magnetic fields above 5000 μT were required for the ICD to possibly present a dysfunction in the homogenous block, while they were only 1400μT in the anatomical model. These results could be informative for any proposed standards concerning the safety of ICDs (CENELEC, INCIRP) for workers as well as for the general public.

Quelle conduite tenir après l’implantation d’un défibrillateur cardiaque chez un travailleur exposé aux champs magnétiques ?

Determining fitness to work after implantation of a cardiac defibrillator in a worker exposed to magnetic fields. An EDF worker potentially exposed to high-intensity 50 Hz magnetic fields had a cardiac defibrillator implanted. Theoretically its operation could be disturbed by magnetic field exposure at work. We use this case study to present an approach to evaluating work safety and the worker’s fitness in such situations. The protocol consisted of measuring the magnetic field at the different places where the worker performed his job duties, in his presence, and simultaneously monitoring the operation of the device. The Medtronic device was programmed in bipolar mode. Throughout the workplace, the maximal magnetic field intensity measured at the device level was 650 μT. No dysfunction was recorded in bipolar mode. Following these measurements and device controls, the worker was declared fit and resumed his previous job. Two years later, no incident has been reported.