MTHR - Mobile Telecommunications and Health Research

Epidemiology Workshop

Chair: Professor P Elliott

Professor Elliott welcomed the speakers and the representatives of the epidemiological research groups funded under the MTHR programme to the workshop.

Dr Leeka Kheifets, the Head of the Radiation Programme at the World Health Organisation (WHO) presented an overview of EMF epidemiological studies. She noted that although some previous studies had focused on brain cancers these had suffered from several limitations: crude dosimetry, low usage and adequate latency period. It was suggested that future research should focus on a wider range of end points and that the success of future studies would be dependent on improved exposure assessment, which would need to be updated as new communications technology is developed, and methodological work. A comparison of previous radiofrequency and extremely low frequency (ELF) epidemiological studies was presented. Dr Kheifets suggested that ELF epidemiological studies benefited from more sophisticated exposure analysis, a broader range of outcomes, more studies and more consistent results compared to the radiofrequency studies. A discussion on dosimetry methodology followed; this included the suitability of personal dosimetry meters in different situations.

Professor Hamnerius from Chalmers University of Technology, Sweden gave a presentation on exposure to radiofrequency radiation from mobile phones. The factors affecting exposure from mobile phones were discussed, these factors include; the phone model, the method of power control employed and whether the network uses discontinuous transmission (DTX). Further details on the impact of power control on the mobile phone user’s exposure to radiofrequency radiation were given. This included a description of a Swedish study that compared the proportion of time that a mobile phone operates at maximum power in rural and urban areas. It was noted that mobile phones in rural areas operated at maximum power for 40% of the time whilst in urban environments the phone operated at maximum power 20% of the time. In addition, it was estimated that efficient power control could reduce the power emitted by the mobile phone by as much as 100 times. It was noted that all the networks use full power for a significant proportion of the time. If this can be fully characterised then it was suggested that calculated exposures could be adjusted accordingly to improve the accuracy of exposure assessments. It was estimated that DTX reduced the average power emitted by the mobile phone by 20 – 40%. If a network does not use DTX it was suggested that the duration of a phone call, which could be established by using the billing records, could be used as an approximation for exposure assessment. The assessment could be improved if data on the phone model, area of use and network characteristics were available.

Progress reports on the MTHR funded projects: “A case-control study of brain tumour and acoustic neuromas in relation to use of mobile phones” and “UK case control study of adult brain tumours” were presented to the workshop. It was noted that the Nordic group that Professor Swerdlow had hoped to collaborate with had no further funding. The workshop discussed whether, as young children now use mobile phones this age group should be included in the study. It was concluded that as childhood and adult cancers were histologically different and the long latency would result in very low number of cases in younger age groups, it would not be practical to include children in the project.

A progress report on “Cohort study of mobile phone users (pilot study)” was given. The need for a cohort study of sufficient size and duration was discussed as was the technique of using a pilot study to develop and test methods for a cohort study in this area. The research group was keen to explore funding opportunities for a full cohort study. In addition, Anders Ahlbom from the Karolinska Institute, Sweden presented work on exposure assessments in mobile phone cohorts. The relative importance of individual factors in exposure analysis was discussed. Relevant factors include: total calling time, number of calls, environment, time of day, phone model, the use of hands free kits and whether the mobile phone user is stationary or mobile.

A progress report on the MTHR funded project “A case study of leukaemia in relation to use of mobile phones” was presented. The potential for overmatching cases and controls in epidemiological studies was discussed.

Validation of data was discussed by the workshop. The accuracy of self-reported phone use was an important issue. The difficulty in recruiting volunteers for projects could be a major problem due to low participation rates. Alternative strategies for recruiting controls could include the use of friends and family, although such arrangements would need careful consideration.

Summaries of the closed sessions of the MTHR Research Seminar - 11th of November 2002