Health symptoms and cognitive function in Swiss adolescents in relation to mobile phone use and radiofrequency electromagnetic field exposure

Introduction and Background
Within the last 15 years the use of mobile phones has increased remarkably in adults as well as in adolescents. This increase has been accompanied by a growing public concern that radio frequency electromagnetic fields (RF-EMF), which are emitted from such devices, might be associated with adverse health effects or cognitive function in adolescents. In particular, young people have become the focus of increased attention since the lifetime exposure will be longer than that of present-day adults. Potential effects of RF-EMF on health and cognitive function in adolescents are of high public interest since the use of mobile phones is an essential part of the daily life of adolescents.
To date, epidemiological research in this field is scarce and the Research Agenda of the World Health Organization (WHO) considers additional research in this age group as a high research priority. There have been several studies so far that investigated whether health, cognitive function and behavior in adolescents are affected by RF-EMF exposure from mobile phones. The majority of these studies however had some methodological limitations such as a cross-sectional study design and self-reported mobile phone use data. Additionally, there is not only RF-EMF emitted by mobile phones, but there are a lot of other RF-EMF sources in our everyday life which have to be considered when dealing with RF-EMF exposure. No study so far has ever tried to differentiate between effects due to RF-EMF radiation and to non-radiation related effects, which are mediated by regularly using the mobile phone and other wireless devices.
Objectives
The aim of the work for this thesis was to evaluate how adolescents’ perceived health and how cognitive function are affected by various aspects of mobile phone use and other wireless devices including radiofrequency electromagnetic field exposure.
Methods
In the framework of the HERMES (Health Effects Related to Mobile phonE use in adolescentS) study, 439 students aged 12 to 17 years and attending 7th, 8th or 9th grade in schools in Central Switzerland were recruited to participate in the baseline investigation, which was conducted from June 2012 until February 2013. During a school visit the adolescents filled in a questionnaire with questions, amongst others, on health symptoms, use of mobile phones and other wireless devices, socio-demographics, and other relevant covariables and two cognitive tests using a standardized, computerized cognitive testing system were performed. Additionally a questionnaire for the parents was distributed. The questionnaire for the parents included questions, amongst others, on the behavior of their children, on socio-economic factors, on wireless technology at home and on child development. This procedure was repeated one year later with the same study participants (participation rate: 96.8%).
From 234 study participants objectively recorded mobile phone use data from the three Swiss mobile phone operators for the time period up to six months prior to the baseline investigation until follow-up was received.
A subgroup of 95 study participants took part in personal measurements. The adolescents carried a portable measurement device, a so-called exposimeter, and kept a diary on a timeactivity diary application installed on a mobile phone in flight-mode for about three consecutive days. Far-field exposure from fixed site transmitters (radio and TV broadcast transmitters and mobile phone base stations) at home and in school was modelled using a geospatial propagation model. RF-EMF dose measures were computed for the brain and the whole body by combining questionnaire data with objectively recorded mobile phone use data, personal measurements and propagation model outputs.
Results
We could demonstrate that mobile phone use during night is common among adolescents. In a cross-sectional design, poor perceived health was shown when adolescents were being awakened by an incoming text message or call during night. Similar results were found when considering objectively recorded mobile phone use during night. The cognitive tests on concentration capacity and memory performance were not related to mobile phone use during night.
An integrative exposure surrogate combining exposure from near-field (use of wireless devices) and far-field (environmental sources) RF-EMF sources to one single whole body and brain exposure measure was developed. Most relevant contributors for the brain dose, based on self-reported mobile phone call duration, were calls on the mobile phone (on average 93.3%) followed by calls with the cordless phones (4.2%). For the whole body dose, calls on the mobile phone (on average 66.9%), the use of computer/laptop/tablet connected to WLAN (12.0%) and data traffic on mobile phones over WLAN (8.1%) counted for the most part. Less important for the dose measures were exposure from radio and TV broadcast transmitters (brain dose: 0.1%; whole body dose: 0.3%) and mobile phone base stations (brain dose: 0.6%; whole body dose: 2.0%).
By applying these RF-EMF dose measures to the prospective HERMES cohort study, we investigated whether adolescents’ perceived health and cognitive function such as memory performance are affected by the use of mobile phones or other wireless devices per se or by RF-EMF exposure. We observed that rather the use of mobile phones or other wireless devices than RF-EMF exposure affect adolescents’ health. In contrast we found that memory performance was more strongly associated with RF-EMF exposure than with the use of mobile phones or other wireless devices per se. This may indeed indicate that RF-EMF exposure affect memory performance in adolescents.
Using the geospatial propagation model we observed highest total exposure from fixed site transmitter to be 376 µW/m2 (=0.38 V/m), which easily complies with current ICNIRP guidelines, as well as with the precautionary reference levels for Switzerland, which are 10 times lower than the ICNIP’s. We observed an association between RF-EMF exposure from fixed site transmitters and tiredness in Swiss adolescents whereas other health symptoms were not related. The observed associations however have to be interpreted with caution and might represent a chance finding.
Conclusions and Outlook
In the HERMES study we we used the most comprehensive exposure assessment methods considering most relevant RF-EMF sources and exposure relevant behaviors. The integrative RF-EMF dose measures for the brain and the whole body are worldwide unique and have not been applied ever before.
We were able to demonstrate that rather the use of mobile phones or other wireless devices than RF-EMF exposure affect the health of adolescents. In contrast we found that memory performance was more strongly associated with RF-EMF exposure than with the use of mobile phones or other wireless devices per se.
Based on the results we conclude that precautionary measures to reduce the mobile phone use and thus personal exposure to RF-EMF should be applied.
Due to the massive growth in connecting devices, exposure assessment in the near future will become even more complex but also inevitably necessary in order to establish evidence-based management measures and effective health risk communication programs.