Exposure Modelling of Extremely Low-Frequency Magnetic Fields from Overhead Power Lines and Its Validation by Measurements

3D GIS for surface modelling of magnetic fields generated by overhead power lines and their validation in a complex urban area

Residential exposure to magnetic fields generated by overhead high-voltage power lines, continues to be a matter of social concern and, for the scientific community, a challenge to model this exposure accurately enough to reliably detect even small effects in large populations complexes. In any expression of the magnetic field intensity, the source-receiver distance is a determining variable, especially in an environment closer to the electrical installation and critical with the existence of significant unevenness in the terrain. However, MF exposure studies adopt, due to their complexity, simplifications of reality where even sometimes the terrain relief and the buckling of the line are not considered. The application of 3D techniques with Geographic Information Systems (GIS) allows us to address this problem. This article presents a model for generating magnetic field intensity surfaces from high-precision terrain elevation data. The series expansion of the Biot-Savart law to an infinite rectilinear conductor with variable height according to the catenary described by the cables using ArcGIS software is applied to calculate the magnetic field. For the validation, 69 control points (1035 field measurements) were used in a free urban area and another 28 points (420 field measurements) in a built-up urban area with complex relief. Good estimates were obtained, although with differences in both areas. With MAPE 9.65% and 19.51%, R2 = 0.922 and 0.949, RMSE = 0.154 and 0.094 μT, respectively. Furthermore, 86% of the points were correctly classified according to usual exposure percentiles. However, the use of a 5 m resolution digital terrain model to obtain high-precision elevation data was an indispensable condition for the good performance of our model. The result as a continuous surface of magnetic field values at the real elevation of the ground can contribute significantly to the development of new environmental and public health studies.

Health-Related Electromagnetic Field Assessment in the Proximity of High Voltage Power Equipment

With respect to health issues, this paperpresents the results of an electromagnetic field (EMF) assessment in the proximity of a high voltage power station located in South Transylvania, Romania. The main parameters taken into account are, according to all standards and recommendations, the RMS (Root Mean Square) value of low frequency (0–300 Hz) electrical field strength E (in kV/m) and magnetic flux density B (in µT). Measurements were performed near all critical pieces of equipment (transformers, switches, busbars, overhead lines), according to the EMF European Directive. Some measurements were made as a function of distance from the HV (high-voltage) equipment, others as a time variation. The main objective was to verify that specific limits are met and, if necessary, to identify protective measures. Finally, safe exposure times for personnel operating at these sites were determined. In the future, detailed maps of EMF variations will be made available to the power companies.

Exposure to Static and Extremely-Low Frequency Electromagnetic Fields and Cellular Free Radicals

This paper summarizes studies on changes in cellular free radical activities from exposure to static and extremely-low frequency (ELF) electromagnetic fields (EMF), particularly magnetic fields. Changes in free radical activities, including levels of cellular reactive oxygen (ROS)/nitrogen (RNS) species and endogenous antioxidant enzymes and compounds that maintain physiological free radical concentrations in cells, is one of the most consistent effects of EMF exposure. These changes have been reported to affect many physiological functions such as DNA damage; immune response; inflammatory response; cell proliferation and differentiation; wound healing; neural electrical activities; and behavior. An important consideration is the effects of EMF-induced changes in free radicals on cell proliferation and differentiation. These cellular processes could affect cancer development and proper growth and development in organisms. On the other hand, they could cause selective killing of cancer cells, for instance, via the generation of the highly cytotoxic hydroxyl free radical by the Fenton Reaction. This provides a possibility of using these electromagnetic fields as a non-invasive and low side-effect cancer therapy. Static- and ELF-EMF probably play important roles in the evolution of living organisms. They are cues used in many critical survival functions, such as foraging, migration, and reproduction. Living organisms can detect and respond immediately to low environmental levels of these fields. Free radical processes are involved in some of these mechanisms. At this time, there is no credible hypothesis or mechanism that can adequately explain all the observed effects of static- and ELF-EMF on free radical processes. We are actually at the impasse that there are more questions than answers.

Proximity to overhead power lines and childhood leukaemia: an international pooled analysis

BACKGROUND

Although studies have consistently found an association between childhood leukaemia risk and magnetic fields, the associations between childhood leukaemia and distance to overhead power lines have been inconsistent. We pooled data from multiple studies to assess the association with distance and evaluate whether it is due to magnetic fields or other factors associated with distance from lines.

METHODS

We present a pooled analysis combining individual-level data (29,049 cases and 68,231 controls) from 11 record-based studies.

RESULTS

There was no material association between childhood leukaemia and distance to nearest overhead power line of any voltage. Among children living < 50 m from 200 + kV power lines, the adjusted odds ratio for childhood leukaemia was 1.33 (95% CI: 0.92-1.93). The odds ratio was higher among children diagnosed before age 5 years. There was no association with calculated magnetic fields. Odds ratios remained unchanged with adjustment for potential confounders.

CONCLUSIONS

In this first comprehensive pooled analysis of childhood leukaemia and distance to power lines, we found a small and imprecise risk for residences < 50 m of 200 + kV lines that was not explained by high magnetic fields. Reasons for the increased risk, found in this and many other studies, remains to be elucidated.