No increased sensitivity in brain activity of adolescents exposed to mobile phone-like emissions

https://doi.org/10.1016/j.clinph.2013.01.010Get rights and content

Abstract

Objective

To examine the potential sensitivity of adolescents to radiofrequency electromagnetic field (RF EMF) exposures, such as those emitted by mobile phones.

Methods

In a double-blind, randomized, crossover design, 22 adolescents aged 11–13 years (12 males) underwent three experimental sessions in which they were exposed to mobile phone-like RF EMF signals at two different intensities, and a sham session. During exposure cognitive tasks were performed and waking EEG was recorded at three time-points subsequent to exposure (0, 30 and 60 min).

Results

No clear significant effects of RF EMF exposure were found on the waking EEG or cognitive performance.

Conclusions

Overall, the current study was unable to demonstrate exposure-related effects previously observed on the waking EEG in adults, and also provides further support for a lack of an influence of mobile phone-like exposure on cognitive performance.

Significance

Adolescents do not appear to be more sensitive than adults to mobile phone RF EMF emissions.

Highlights

► The current study examined the potential sensitivity of adolescents to mobile phone-like electromagnetic field exposures. ► Unlike previous studies conducted on adults, no significant effects of exposure were found. ► Results suggest that contrary to popular belief, adolescents are not more sensitive to mobile phone emissions.

Introduction

There has been increasing interest in recent years regarding whether radiofrequency electromagnetic fields (RF EMF), such as those emitted by mobile phones, have an influence on brain activity. Previous research has indeed shown that pulse-modulated RF EMFs characteristic of those emitted by mobile phones affect the electroencephalogram (EEG) during both sleep and waking in adults (e.g. Borbély et al., 1999, Croft et al., 2002, Curcio et al., 2005, Huber et al., 2000, Loughran et al., 2005, Regel et al., 2007a, Reiser et al., 1995, van Rongen et al., 2009). In particular, the alpha frequency range during waking and the alpha and spindle frequency ranges during sleep have been the most commonly reported areas influenced by such exposures to RF EMF. However, despite this increasing evidence of a repeatable mobile phone-induced effect on brain activity in adults, very little research exists regarding the presence and/or magnitude of this effect in children and adolescents.

Mobile phones are a dominant component of modern telecommunications technology and constitute the main source of RF EMF exposure for children and adolescents. In 2006 the World Health Organization (WHO) released a research agenda specifically relating to RF EMF in which investigations on potential effects on the EEG and cognition in children were identified as a high priority research need. A subsequent research agenda from the WHO stated that there have only been few such studies since this initial recommendation and therefore highlighted that further RF EMF provocation studies on children of different ages were still required (WHO, 2010). In addition, it was also suggested that neurobiological mechanisms and possible thresholds and dose–response relationships should also be investigated.

During normal mobile phone use, i.e., when operated at the head, some of the emitted RF EMF penetrates into the head tissues where it is absorbed. The distribution of the induced fields depends on the design of the phone, its position at the head and the brain anatomy (tissue distribution and dielectric parameters). Christ et al. (2010a) showed that local maximum averaged absorption is similar between children and adults but that the locally induced fields in certain subregions of the children’s brain (specifically the cortex, hippocampus and hypothalamus) can be significantly higher (on average by about a factor of two) compared to adults due to anatomical reasons.

In general, the maximum specific absorption rate (SAR) of the brain tissues of adults and children is considerably below the basic restrictions of 2 W/kg (by more than a factor of two for children and a factor of four for adults). These restrictions were proposed by the International Commission on Non-Ionizing Radiation Protection (1998) as safety limits for the general population and have since been adopted by most countries. However, despite these restrictions it remains that effects on brain physiology still occur in adults at exposures well below the currently accepted safety guidelines (for review, see van Rongen et al., 2009). In regards to the possibility of effects on children and adolescents this becomes especially important for several reasons. Children start to use mobile phones extensively in early adolescence and they might be particularly sensitive to RF EMF as maturational cortical changes are ongoing throughout development (Segalowitz et al., 2010, Whitford et al., 2007).

In view of the higher brain exposure of children, it surprising that very few studies have investigated in younger cohorts the influence observed on the EEG in adults, or even the inconsistent effects reported on cognitive performance (for review, see van Rongen et al., 2009). Therefore, the current experiment aimed to determine whether RF EMF exposure also influences the waking EEG and/or cognitive performance in adolescents and to establish a possible dose–response relationship.

Section snippets

Participants

Twenty-two young, healthy, right-handed adolescents (12 males) aged 11–13 years (mean age 12.3 ± 0.8 years) participated in this experiment. Pubertal status was assessed and determined as reported by the parents using the standardized Tanner staging system (adapted from Carskadon and Acebo, 1993), and only one female in the sample had reached menarche. Participants with a history of neurologic or psychiatric disorders were excluded from the study. Additionally, all subjects were medication and drug

Waking EEG

Spectral analysis of the waking EEG revealed significant main effects of ‘condition’ (p < 0.05) at 6 Hz and between 12 and 13.5 Hz. Post-hoc paired t-tests revealed higher power in the 12 Hz frequency bin following the low SAR exposure condition immediately (0 min) after exposure (p < 0.05). Data for the left occipital derivation are shown in Fig. 1. No further significant differences between the exposure conditions were observed and the relative EEG spectra were similar for both hemispheres.

Discussion

The present study was designed to further extend previously reported effects of RF EMF on healthy adults by looking at potential effects in younger subjects, and determine whether adolescents are indeed more sensitive to such exposures. For brain exposures higher than the maximum exposure during normal usage of a mobile phone (i.e., 1.4 W/kg versus <1 W/kg), we were unable to demonstrate any exposure related effects on the waking EEG or cognitive performance. These results not only suggest that

Acknowledgements

The authors thank Sarah Münst and Iva Jelezarova for their assistance in the sleep laboratory, and Karl Wüthrich and Dr. Roland Dürr for technical support. This study was supported by the Swiss National Science Foundation (National Research Programme 57: ‘Non-Ionizing Radiation – Health and Environment’).

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