Denise Wallace

Does short-term exposure to mobile phone base station signals increase symptoms in individuals who report sensitivity to electromagnetic fields? A double-blind randomized provocation study

Background Individuals with idiopathic environmental illness with attribution to electromagnetic fields (IEI-EMF) believe they suffer negative health effects when exposed to electromagnetic fields from everyday objects such as mobile phone base stations. Objectives This study used both open provocation and double-blind tests to determine if sensitive and control individuals experience more negative health effects when exposed to base station-like signals compared with sham. Methods Fifty-six self-reported sensitive and 120 control participants were tested in an open provocation test. Of these, 12 sensitive and 6 controls withdrew after the first session. The remainder completed a series of double-blind tests. Subjective measures of well-being and symptoms as well as physiological measures of blood volume pulse, heart rate, and skin conductance were obtained. Results During the open provocation, sensitive individuals reported lower levels of well-being in both the global system for mobile communication (GSM) and universal mobile telecommunications system (UMTS) compared with sham exposure, whereas controls reported more symptoms during the UMTS exposure. During double-blind tests the GSM signal did not have any effect on either group. Sensitive participants did report elevated levels of arousal during the UMTS condition, whereas the number or severity of symptoms experienced did not increase. Physiological measures did not differ across the three exposure conditions for either group. Conclusions Short-term exposure to a typical GSM base station-like signal did not affect well-being or physiological functions in sensitive or control individuals. Sensitive individuals reported elevated levels of arousal when exposed to a UMTS signal. Further analysis, however, indicated that this difference was likely to be due to the effect of order of exposure rather than the exposure itself.

Selective target processing: Perceptual load or distractor salience?

Perceptual load theory (Lavie, 1995) states that participants cannot engage in focused attention when shown displays containing a low perceptual load, because attentional resources are not exhausted, whereas in high-load displays attention is always focused, because attentional resources are exhausted. An alternative “salience” hypothesis holds that the salience of distractors and not perceptual load per se determines selective attention. Three experiments were conducted to investigate the influence that target and distractor onsets and offsets have on selective processing in a standard interference task. Perceptual load theory predicts that, regardless of target or distractor presentation (onset or offset), interference from ignored distractors should occur in low-load displays only. In contrast, the salience hypothesis predicts that interference should occur when the distractor appears as an onset and would occur for distractor offsets only when the target was also an offset. Interference may even occur in highload displays if the distractor is more salient. The results supported the salience hypothesis.

Short-term exposure to mobile phone base station signals does not affect cognitive functioning or physiological measures in individuals who report sensitivity to electromagnetic fields and controls.

Individuals who report sensitivity to electromagnetic fields often report cognitive impairments that they believe are due to exposure to mobile phone technology. Previous research in this area has revealed mixed results, however, with the majority of research only testing control individuals. Two studies using control and self-reported sensitive participants found inconsistent effects of mobile phone base stations on cognitive functioning. The aim of the present study was to clarify whether short-term (50 min) exposure at 10 mW/m(2) to typical Global System for Mobile Communication (GSM) and Universal Mobile Telecommunications System (UMTS) base station signals affects attention, memory, and physiological endpoints in sensitive and control participants. Data from 44 sensitive and 44 matched-control participants who performed the digit symbol substitution task (DSST), digit span task (DS), and a mental arithmetic task (MA), while being exposed to GSM, UMTS, and sham signals under double-blind conditions were analyzed. Overall, cognitive functioning was not affected by short-term exposure to either GSM or UMTS signals in the current study. Nor did exposure affect the physiological measurements of blood volume pulse (BVP), heart rate (HR), and skin conductance (SC) that were taken while participants performed the cognitive tasks.

Do TETRA (Airwave) base station signals have a short-term impact on health and well-being? A randomized double-blind provocation study.

Background “Airwave” is the new communication system currently being rolled out across the United Kingdom for the police and emergency services, based on the Terrestrial Trunked Radio Telecommunications System (TETRA). Some police officers have complained about skin rashes, nausea, headaches, and depression as a consequence of using their Airwave handsets. In addition, a small subgroup in the population self-report being sensitive to electromagnetic fields (EMFs) in general. Objectives We conducted a randomized double-blind provocation study to establish whether short-term exposure to a TETRA base station signal has an impact on the health and well-being of individuals with self-reported “electrosensitivity” and of participants who served as controls. Methods Fifty-one individuals with self-reported electrosensitivity and 132 age- and sex-matched controls participated in an open provocation test; 48 sensitive and 132 control participants went on to complete double-blind tests in a fully screened semianechoic chamber. Heart rate, skin conductance, and blood pressure readings provided objective indices of short-term physiological response. Visual analog scales and symptom scales provided subjective indices of well-being. Results We found no differences on any measure between TETRA and sham (no signal) under double-blind conditions for either controls or electrosensitive participants, and neither group could detect the presence of a TETRA signal at rates greater than chance (50%). When conditions were not double blind, however, the self-reported electrosensitive individuals did report feeling worse and experienced more severe symptoms during TETRA compared with sham. Conclusions Our findings suggest that the adverse symptoms experienced by electrosensitive individuals are due to the belief of harm from TETRA base stations rather than to the low-level EMF exposure itself.

Perceived Comfort and Blinding Efficacy in Randomised Sham-Controlled Transcranial Direct Current Stimulation (tDCS) Trials at 2 mA in Young and Older Healthy Adults

Background tDCS studies typically find that: lowest levels of comfort occur at stimulation-onset; young adult participants experience less comfort than older participants; and participants’ blinding seems effective at low current strengths. At 2 mA conflicting results have been reported, questioning the effectiveness of blinding in sham-controlled paradigms using higher current strengths. Investigator blinding is rarely reported. Objective Using a protocol with 30 min of 2 mA stimulation we sought to: (a) investigate the level of perceived comfort in young and older adults, ranging in age from 19 to 29 years and 63 to 76 years, respectively; (b) test investigator and participant blinding; (c) assess comfort over a longer stimulation duration; (d) add to the literature on protocols using 2 mA current strength. Methods A two-session experiment was conducted where sham and active stimulation were administered to the frontal cortex at the F8/FP1 sites in a within-subjects manner. Levels of perceived comfort were measured, using a visual analogue scale, at the start and end of stimulation in young and older adults. Post-stimulation, participants and investigators judged whether or not active stimulation was used. Results Comfort scores were lower at stimulation onset in both age groups. Older adults reported: (i) more comfort than young participants overall; (ii) comparable levels of comfort in sham and active stimulation; (iii) significantly more comfort than the young participants during active stimulation. Stimulation mode was correctly identified above chance in the second of the two sessions; 65% of all participants correctly identified the stimulation mode, resulting in a statistical trend. Similarly, the experimenter correctly identified stimulation mode significantly above chance, with 62% of all investigator judgements correct across 120 judgements. Conclusions Using 2 mA current strength over 30 minutes, tDCS stimulation comfort is lower at stimulation onset in young and older adults and, overall, lower for young participants. Investigators and participants may be able to identify active stimulation at above chance levels, although accuracy never exceeded 65% for either participants or the experimenter. Further research into blinding efficacy is recommended.

Aggregated data from two double-blind base station provocation studies comparing individuals with idiopathic environmental intolerance with attribution to electromagnetic fields and controls.

Data from two previous studies were aggregated to provide a statistically powerful test of whether exposure to electromagnetic fields (EMFs) produced by telecommunication base stations negatively affects well-being in individuals who report idiopathic environmental illness with attribution to electromagnetic fields (IEI-EMF) and control participants. A total of 102 IEI-EMF and 237 controls participated in open provocation trials and 88 IEI-EMF and 231 controls went on to complete double-blind trials in which they were exposed to EMFs from a base station emitting either a Global System for Mobile Communication and Universal Mobile Telecommunications System or a Terrestrial Trunked Radio Telecommunications System signal. Both experiments included a comparison sham condition. Visual analog and symptom scales measured subjective well-being. Results showed that IEI-EMF participants reported lower levels of well-being during real compared to sham exposure during open provocation, but not during double-blind trials. Additionally, participants reported lower levels of well-being during high compared to low load trials and this did not interact with radiofrequency-EMF exposure. These findings are consistent with a growing body of literature indicating there is no causal relationship between short-term exposure to EMFs and subjective well-being in members of the public whether or not they report perceived sensitivity to EMFs.

Mobile Phone Base Stations: Eltiti et al. Respond.

Three letters have questioned the validity of the conclusions drawn in our recent article on the short-term effects of GSM (global system for mobile communication) and UMTS (universal mobile telecommunications system) base station signals (Eltiti et al. 2007). Most of the concerns are founded in misunderstandings of the study, and we hope to clarify these issues here. We assessed whether people could detect the presence of a 10-mW/m2 signal over a 50-min period (not 10 μW as claimed by Zinelis). This level of exposure is roughly equivalent to standing within 60 m of a mobile phone base station and was based on prior scientific evidence (Mann et al. 2000). We also measured a range of variables within three classes of response: physiological response, self-reported well-being, and actual symptoms experienced.

When you can, scale up: Large-scale study shows no effect of tDCS in an ambiguous risk-taking task

Background: A wide range of neuroimaging and neuromodulation studies have shown that the dorsolateral prefrontal cortex (DLPFC) plays a pivotal role in decision‐making. Of particular interest is the question of its role in decision‐making when conditions are uncertain and whether manipulating this neural substrate through neuromodulation changes subsequent risk‐taking behaviour. Previous work using the Balloon Analogue Risk Task (BART) suggests that bilateral tDCS stimulation of the DLPFC reduces risk‐taking behaviour but unilateral stimulation has no effect. However, participant numbers have been limited and may have biased the estimate of the size of the effect of the stimulation on task performance. Objectives/hypothesis: We aimed to test the robustness and generalizability of these previous findings by using a very similar methodology but with a much larger sample. Methods: During both 20‐ and 30‐min tDCS stimulation at 2 mA, we administered the BART to about 200 participants assigned to bilateral DLPFC stimulation of either right anodal/left cathodal, left anodal/right cathodal or sham (Study 1 and Study 2); and to unilateral stimulation conditions (Study 2): right anodal, left anodal or sham with the referent electrode over the contralateral supraorbital region. Results: In the first bilateral study, we found that risk‐taking was greater for participants in the right anodal/left cathodal stimulation group compared to those who received left anodal/right cathodal stimulation, but not compared to sham. The results obtained in the bilateral and unilateral stimulation protocols implemented in Study 2 yielded no evidence of any effect of stimulation. Combining the data from both studies, we found no statistically significant differences between mean performances of the nine stimulation groups. Indeed, all 95% confidence intervals for the nine means overlapped, suggesting that these randomly vary around a common population mean. Conclusions: This study showed that there was no detectable effect of tDCS stimulation on risky decision‐making under ambiguity, compared to sham stimulation. Hence, using a much larger sample, we did not replicate previous work reporting a reduction in risky decision‐making by bilateral stimulation of the DLPFC compared to sham. When the results of our bilateral and unilateral stimulation studies were combined, it emerged that the most likely explanation for the apparent significant results in our bilateral stimulation study was random variation in performance. This outcome is a further reminder of the need for appropriately sized samples to potentially achieve reliable outcomes in brain modulation studies. HIGHLIGHTSWe aimed to assess whether neuromodulation affects risk taking.tDCS applied to the dorsolateral prefrontal cortex does not affect risk taking.Previous significant effects are likely to reflect random variation.

Symptom Presentation in Idiopathic Environmental Intolerance With Attribution to Electromagnetic Fields: Evidence for a Nocebo Effect Based on Data Re-Analyzed From Two Previous Provocation Studies

Individuals with idiopathic environmental illness with attribution to electromagnetic fields (IEI-EMF) claim they experience adverse symptoms when exposed to electromagnetic fields (EMFs) from mobile telecommunication devices. However, research has consistently reported no relationship between exposure to EMFs and symptoms in IEI-EMF individuals. The current study investigated whether presence of symptoms in IEI-EMF individuals were associated with a nocebo effect. Data from two previous double-blind provocation studies were re-analyzed based on participants’ judgments as to whether or not they believed a telecommunication base station was “on” or “off”. Experiment 1 examined data in which participants were exposed to EMFs from Global System for Mobile Communication, Universal Mobile Telecommunications System, and sham base station signals. In Experiment 2, participants were exposed to EMFs from Terrestrial Trunked Radio Telecommunications System and sham base station signals. Our measures of subjective well-being indicated IEI-EMF participants consistently reported significantly lower levels of well-being, when they believed the base station was “on” compared to “off”. Interestingly, control participants also reported experiencing more symptoms and greater symptom severity when they too believed the base station was “on” compared to “off”. Thus, a nocebo effect provides a reasonable explanation for the presence of symptoms in IEI-EMF and control participants.