Ongoing Project on Magnetic Field Exposure Assessment

The European Commission in the frame of INCO-COPERNICUS Program is sponsoring a 3-year (1997-2000) multi-disciplinary international project "Improvement of methods of exposure assessment for magnetic fields from electric traction with regard to coronary heart diseases".
Recently electrified transport modes came into consideration in studies of health related issues of MFs. It was found that railway employees had increased risk in some specific kind of cancer. Adverse effects on general health, while raising less public concern than enhanced cancer risks, could nevertheless have an even greater impact on the safety of trains by affecting the nervous and cardiovascular system and thus the performance of transport operators.
Being still obscure the mechanisms through which MFs might produce adverse health effects, the characteristics of MFs to be measured for testing their linkage to biological responses/diseases are unclear. In most studies MF exposures are generally characterised only in terms of root-mean square (rms) of the field strength, a time-weighted average field-strength parameter.
There is little or no systematic information on such characteristics as the frequency content, including intermittent components, frequency-magnitude dependence and 3-dimensional distribution of these characteristics. Meanwhile biological and epidemiological studies of possible effects of MFs indicate that there is not a well established dose-response relationship when "dose" is the time-weighted average field strength (TWA). Frequency-intensity "windows", intermittence, presence of DC field and polarisation can be important. The project studies exposure parameters other than the customary considered TWA. A portable wave-form capture system MVC-2 (torsion-type magnetometer) has been used for continuous registration of static and variable MFs along 3 orthogonal axes. This computer-based device, with sampling rate up to 200 Hz, allows to capture a field profile and to characterise field magnitudes over time and frequency. In so doing all information characterising intensity, frequency domain and geometry is catured.

The main activity of the project is focused on the following tasks:

• Development of extensive archive of MF records in different kind of electrified railroad systems. Measurement survey in Russian DC and in Swiss AC (16,67Hz) electric trains is underway.

• Examination of the hypothesis whether MFs from electric traction constitute a mortality risk for coronary heart diseases among engine drivers population. The cohort data of the Swiss Federal Railway (18,000 members) in the years 1972-1993 serves as a main body to answer this question.
• Development of MF patterns typical for Russian and Swiss electric trains based on thorough analysis of specific features of transport MF: complex multi-frequency spectra, including intermittent components and quasi-static fields, variable amplitude-frequency dependence, polarisation.

• These patterns will be used to study the biological response of nervous and cardiovascular systems in animals and humans exposed to simulated transport-like MF. To generate complex train MF, a special exposure facility has been developed: three sets of mutually orthogonal coils fed by amplifiers and computer-driven current.

• Results of epidemiological and biological studies will provide information for identifying an appropriate exposure metrics which takes into account specific features of transport MF.

For the realisation of this project a transnational collaboration of various experts (physicists, dosimetric and medical specialists, biologists, epidemiologists) from Belgium, Italy, Russia, Switzerland and Ukraine has been established.

Dr. G. Villoresi, (coordinator of the project) CNR, Italy
Dr. N. Ptitsyna, (co-coordinator for Eastern countries) SPbFIZMIRAN, Russia