On the 25th and 26th of July 2006 an international expert workshop was held at the Federal Office for Radiation Protection (BfS) in Neuherberg as part of the German Mobile Telecommunication Research Programme (DMF). The workshop focused on research projects which were aiming at the determination of everyday exposure from electromagnetic fields. In addition to mobile communication, the projects also investigated the exposure from new technologies (e.g. digital radio and television, WLAN, wireless DECT telephones). It was therefore possible to cover a wide range of technical applications of electromagnetic fields that play an important role in everyday life. Furthermore, the contributions of dosimetry to the biological projects within the DMF were discussed.

This workshop was the first in a series of five international workshops on the various research focal points within the DMF. The overall evaluation of all research projects in the middle of 2008 will also include international participation.

The programme can be found in the flyer.

Special thanks go to the rapporteur of the workshop, Dr. Simon Mann from the Health Protection Agency, UK, who compiled a detailed report.

The following presentations are also available for download as a PDF file.

The discussions in each session focused on the following questions:

1. What has been achieved by the projects?
2. Where do we still have knowledge gaps?
3. Can we define minimum standards for future work?
4. Are there findings that have an impact on guidelines or on standard settings?

After discussions with the workshop participants, the following conclusions were agreed upon:

1. What has been achieved by the projects?

• When using mobile phones a temperature increase in the skin of human beings up to 3 - 5°C is possible. Previous findings, that this is due to reduced convection and not high frequency electromagnetic exposure, have been confirmed.
• When using customary transmitters close to the body temperature increases in inner organs of the head or the trunk of the order of 0.1°C and below have been observed.
• Substantial progress has been made in understanding real exposure from transmitters in situations relevant for daily life. Open questions remain in complex mixed scenarios such as for example combined exposures from sources far away and very close to the body.
• The exposure assessment for EPI-Studies around cellular base stations is - in general - a very challenging task that is still not solved to full satisfaction. Computational methods can help to pre-select persons with potentially high or low exposures. Difficulties arise with accommodating broadcast transmitters, historical exposures and personal devices (phones etc.) in a total exposure metric. Some of those difficulties can possibly be tackled by means of newly developed devices for personal exposure determination.
• An improved understanding of general public exposures in well defined scenarios has been achieved. Open questions remain in complex scenarios as for example at workplaces with high-field sources.
• Although, there are contrasting examples, new technologies and applications in general tend to increase public exposure. On average hoewever, exposure of the public is still well below current limits.
• Cooperation between disciplines in health related studies has been improved further. State of the art dosimetric capabilities have been used to characterise exposure systems during these projects.

2. Where do we still have knowledge gaps?

• The status of development of models for children and pregnant women is promising while models for obese people and babies are still missing. Tools to change the postures of models are needed, in particular in case of evaluations of specific exposure scenarios of workers. Issue for discussion during the final workshop:
  Whether safety standards should be based on a “median” person, a 95th percentile person, or some other standard person is of fundamental importance.
• Newly developed personal dose meters have to be investigated in detail and further improved. Parameters like accuracy, isotropicity, crosstalk, sensitivity etc. are of interest in this context.
• This seems to be an issue for the final workshop:
  Pre market “monitoring” of maximal and typical exposures of emerging new technologies should be addressed by national authorities and used for information of the general public.
• Efforts in microdosimetry on the cellular level and modelling of complex exposure scenarios in in-vitro research are worth doing. These aspects are of importance especially in research concerning non thermal effects.

3. Can we define minimum standards for future work?

• Minimal requirements have been defined for in vitro, in vivo and human studies. However, specifying standards could lead to an unnecessary restriction impeding innovative solutions. Depending on biological requirements deviations from standards are acceptable as long as all exposure conditions can be defined and reproduced in terms of the relevant exposure metric.
• Higher homogeneity is needed (and possible) for in-vitro experiments; a value of 30% or better is recommended.
• For compliance testing simple dosimetric models can be used. However, a detailed technical rationale demonstrating the conservatism of simple dosimetric models used for compliance testing should be documented. For scientific research projects more exact models are needed.
• Temperature has to be assessed and controlled in all biological experiments, as it could confound the results of experiments. SAR is the central dosimetric quantity.

4. Are there findings that have an impact on guidelines or on standard settings?

• There is no direct impact on guidelines or on standard settings for the general public. The findings are relevant for compliance testing e.g. by indicating high exposure conditions. Results from some studies on localised SARs raise questions about the temperature rises that could occur at occupational basic restriction values. Guidelines should be reviewed in this respect. This needs to be discussed at the final workshop.
• From the viewpoint of dosimetry, guidelines in the high frequency range should still be based on the SAR concept. Temperature as a basic quantity was not recommended, because:
  • SAR can be calculated more precisely than temperature (thermal calculations are not equally sophisticated, metabolism and blood circulation should be included more precisely).
  • Non-thermal effects still can not be completely excluded.
  • More knowledge on thermo physiology is needed.
  This is also an issue for the final discussion
• Concerning the averaging mass for the SAR limitation 1 g mass is more conservative than 10 g, but for thermal consideration 10 g seems to be conservative enough at least for frequencies covered by the projects of this workshop (400 MHz – 5 GHz).
• Averaging over contiguous tissue elements should be preferred compared to averaging over a cube. Practicability, however, would favour the cube as averaging volume. For reviewing guidelines this issue requires further deliberation.
• For compliance measurements in the vicinity of GSM and UMTS base stations proposals for measurement standards taking into account the demands of the 26. BImSchV have been developed.

The original English text "Conclusions from the DMF Workshop on Dosimetry" can be Downloaded as PDF-file.