Monitoring of electromagnetic field exposure in an international context

Objectives: Electromagnetic field exposure to general people is a public health concern and a topic of debate globally. Electromagnetic field is non-ionizing part of electromagnetic spectrum that can further be divided into extremely low frequency (0- 10 MHz) EMF and radiofrequency (10-300 MHz) EMF based on frequency and corresponding wavelength. Both of these components are of a topic of public debate and a subject of on-going research. The most common sources of extremely low frequency fields are alternating current carried in wiring, household appliances, power lines, electrical wiring, and electrical equipment. Some common sources of radiofrequency fields are mobile phone handsets and mobile phone base stations. Hence the main goals of this thesis were to propose a validated 3D computer model for extremely low frequency magnetic field exposure assessment from overhead powerlines and to develop a novel method of assessing radiofrequency field exposure in different microenvironments. More specifically, this thesis was planned with four different objectives as below:
 To systematically review the radiofrequency electromagnetic field exposure situation in the European countries based on peer-reviewed articles on spot measurements, personal measurement with trained researchers, and personal measurement with volunteers studies.
 To test the suitability of microenvironmental measurement surveys with portable exposimeters for monitoring of radiofrequency electromagnetic field levels in various everyday microenvironments in Switzerland.
 To apply already tested radiofrequency electromagnetic field monitoring protocol to monitor radiofrequency electromagnetic field exposure from Switzerland to international microenvironments of Ethiopia, Nepal, South Africa, Australia and the United States of America
 To validate a 3D computer model, developed for the calculation of the absolute value of magnetic flux density from an overhead power line, with a 6 measurement campaign conducted every two months for a year time.
Methods: For the systematic review for radiofrequency electromagnetic field exposure in European countries, we systematically searched the ISI Web of Science for relevant literature published between 1st January, 2000 and 30th April, 2015 that assessed RF-EMF exposure levels by any of the methods; spot measurements, personal measurement with trained researchers and personal measurement with volunteers. For the non-ionizing radiation monitoring in Switzerland, we used ExpoM-RF device mounted on a backpack to assess radiofrequency electromagnetic field by walking through 51 different outdoor microenvironments from 20 different municipalities in Switzerland. Measurements were conducted between 25th March and 11th July 2014.
The non-ionizing radiation monitoring in international microenvironments used the tested protocol from non-ionizing radiation monitoring in Switzerland. The measurements in international microenvironments were taken using two different kinds of portable RF meter called “ExpoM-RF” and “EME Spy 201”. The measurements were conducted either by walking (Switzerland and Nepal) or driving a car with ExpoM-RF device mounted on its roof (Ethiopia, South Africa, Australia, and the United States of America) or mixed walking and driving (Ethiopia, South Africa, Australia). We selected 15 different microenvironments from Switzerland, 18 microenvironments from Ethiopia, 12 microenvironments from Nepal, and 17 microenvironments from South Africa, 24 microenvironments from Australia and 8 microenvironments from the United States of America. Each of the selected microenvironments was measure twice: between 10 March and 14 April 2017. For the powerline validation study, six measurements were taken every two month between January 2015 and December 2015 from two different locations on two different power lines in order to describe variation of extremely low frequency magnetic field exposure by different seasons of the year. The measurements were taken from the selected power lines for at least 48 hours from each line on each measurement day. The measurements were taken using EMDEX II, temperature logger, and ESTEC device.
Results: The systematic review yielded twenty one published studies that met our eligibility criteria of which 10 were spot measurements studies, 5 were personal measurement studies with trained researchers (microenvironmental), 5 were personal measurement studies with volunteers and 1 was a mixed methods study combining data collected by volunteers and trained researchers. The mean total RF-EMF exposure for spot measurements in European “Homes” and “Outdoor” microenvironments was 0.29 V/m and 0.54 V/m respectively. Among all European microenvironments in “Transportation”, the highest mean total RF-EMF 1.96 V/m was found in trains of Belgium during 2007 where more than 95% of exposure was contributed by uplink.
The non-ionizing radiation monitoring in Switzerland found mean RF-EMF exposure of 0.53 V/m in industrial zones, 0.47 V/m in city centers, 0.32 V/m in central residential areas, 0.25 V/m non-central residential areas, 0.23 V/m in rural centers and rural residential areas, 0.69 V/m in trams, 0.46 V/m in trains and 0.39 V/m in buses. Temporal correlation between first and second measurement of each path was high: 0.83 for total RF-EMF, 0.83 for all five mobile phone downlink bands combined, 0.54 for all five uplink bands combined and 0.79 for broadcasting.
The non-ionizing radiation monitoring internationally found mean RF-EMF exposure in all 5 countries varied between 0.94 V/m and 0.05 V/m. Mean total RF-EMF exposure was highest in Australia (0.94 V/m city centers) and lowest in South Africa (0.36 V/m in rural centers and rural residential areas). For outdoor areas major exposure contribution was from mobile phone base station. The mobile phone base stations contributed more than 65% in all measured microenvironments across the 5 countries.
The two components of the powerline validation study: feasibility study by a computer model and its validation by field measurement of extremely low frequency magnetic field found the estimated precision of the results to be of the order of 10 % to 25 %, and this large degree precision may be due to errors in the coordinates and heights. The both components of the study helped in identifying the input data necessary for large-scale modeling of magnetic fields from high-voltage power lines and how long-term temporal averages of the field can be computed.
Conclusion: The systematic review of radiofrequency electromagnetic field concluded that typical radiofrequency electromagnetic field exposure levels are substantially below regulatory limits. The non-ionizing radiation monitoring in Switzerland demonstrated that microenvironmental surveys using a portable device yields highly repeatable measurements, which allows monitoring time trends of RF-EMF exposure over an extended time period of several years and to compare exposure levels between different types of microenvironments. The non-ionizing radiation monitoring in international microenvironments further support the results from pilot study in Switzerland. The powerline validation study concluded the model agrees well with the measurement values, with average offsets in the range of a few percent. We also found that the precision of the results corresponds to the precision estimated during the pilot study.