Nowadays, almost all human beings are always surrounded by technology, and different intensities of electromagnetic field (EMF) exposure accompany them at home, in the workplace, at public facilities, etc. Mobile phones (MP) are an integral part of modern telecommunication systems and have become globally ubiquitous (2, 12, 21). Currently, mobile communication shapes daily life through better connectivity and intelligent smartphone services (19). However, many animal and human studies have emphasised the deleterious biological consequences of EMF exposure from MP for health. Others have nevertheless reported no significant influence. The debate about the effect on health of EMF exposure from MP used in close proximity to the body, especially the effect on the brain, opens a new reasearch avenue for scientists.
MP technology relies on the transmission of a radio frequency (RF) signal which generates an EMF (a type of non-ionising radiation). MP transmit and receive mainly at 800–1,800 MHz (5). Non-ionising radiation cannot cause ionisation; however, it has been shown to produce other biological effects, for instance by heating, altering chemical reactions, or inducing electrical currents in tissues and cells. The biological effects observed on the cardiovascular, endocrine, and immune systems and on the behaviour of animals seem to be thermal effects of acute exposure to EMF and microwave radiation (EMF radiation with a frequency in the range of 3,000 to 300,000 MHz), with negligible increases of 2°C needed to produce these effects (5, 21). As to any increased risk of developing cancer after exposure to EMF or microwave fields, the evidence for such an association is extremely weak.
Brain tissue consists of neuronal cell bodies, their processes (dendrites and axons, myelinated or not, which form either sparse branches and arborisations or dense fibre bundles), the interconnecting extracellular brain matrix, glial cells, blood vessels, and extracellular fluid. Each of these components may have a different influence on the local mechanical properties of the tissue, which, in turn, regulate a wide variety of very relevant mechanotransduction phenomena (4). Multiple vital neural cell processes are impacted by mechanical signals, and an abnormal mechanical environment can impair brain function and neurodevelopment and progress neurological disorders (4).
Rodents (mice and especially
The central nervous system is the main priority for EMF health research since MP usage involves close exposure or immediate contact with the head, and then the human brain is exposed to relatively high SAR of EMF when compared to other organs (5). Exposure to 900 MHz EMF has provided evidence of causation of blood-brain barrier damage, induction of glial reactivity, and initiation of biochemical modifications in the rat brain (17, 27). Xu
Until now, no solid evidence has been found of the effects of EMF exposure from MP on histomorphological characteristics in the brain, and therefore, we aimed to investigate the possible adverse effect applying two different exposure levels of EMF originating from MP in BALB/c strain mouse brain model.
After segmentation and measurement, the brain was immediately excised and fixed in 10% neutral formalin. Slices were cut in a horizontal plane with a thickness of approximately 300μm. The paraffin blocks were made using Pathcentre (Thermo Shandon, Runcorn, UK) and TES 99 (Medite Medizintechnik, Burgdorf, Germany) equipment. Serial 4-μm sections were prepared from each sample with an Accu-Cut SRM microtome (Sakura Finetek, Tokyo, Japan) and underwent routine haematoxylin and eosin (H&E) staining. Paraffin sections of 4 μm in thickness were prepared for analysis of the histological and histochemical staining.
The main findings of this study are presented in Tables 1 and 2 and supplemented with Figures 1–4. Accurate segmentation of the brain lobes (Table 1) clearly demonstrated that the OB was the greatest in size (excluding the OBC section, which is not a single lobe in the strict sense). The OB lobe in EMF groups I and II was respectively 0.80% and 1.40% larger than the control group. Similar results (increments of 0.97% and 3.88%, respectively) were recorded in the SC lobe in EMF groups I and II. The C lobe presented enlargement of 2.45% in EMF group I and 4.09% in EMF group II compared with the control. Analogous outcomes (1.83% and 4.09% greater size, respectively) were noticed in the MO lobe in EMF groups I and II in comparison to controls. The OBC section increased by 1.22% in EMF group II over the control animal size for this brain region, but it actually decreased by 1.10% in EMF group I. No significant differences between groups were observed analysing measurements of the IC lobe.
Morphometrical data of mouse brain
Lobe | Control | EMF group I | EMF group II |
---|---|---|---|
(n = 10) | (n = 10) | (n = 10) | |
M ± SD (mm) | M ± SD (mm) | M ± SD (mm) | |
OB | 5.00 ± 0.13 | 5.04 ± 0.11 | 5.07 ± 0.08 |
95% CI | 4.91–5.09 | 4.96–5.12 | 5.01–5.13 |
P | 0.0999973 | 0.0889386 | 0.0917641 |
SC | 2.06 ± 0.11 | 2.08 ± 0.11 | 2.14 ± 0.11 |
95% CI | 1.98–2.14 | 2.00–2.16 | 2.06–2.22 |
P | 0.0999993 | 0.0889386 | 0.0917651 |
IC | 1.98 ± 0.04 | 1.98 ± 0.04 | 1.99 ± 0.03 |
95% CI | 1.95–2.01 | 1.95–2.01 | 1.97–2.01 |
P | 0.0836604 | 0.081163 | 0.0800674 |
C | 2.44 ± 0.16 | 2.50 ± 0.14 | 2.54 ± 0.08 |
95% CI | 2.33–2.55 | 2.40–2.60 | 2.48–2.60 |
P | 0.1241794 | 0.1266725 | 0.1280379 |
MO | 1.09 ± 0.10 | 1.11 ± 0.13 | 1.15 ± 0.14 |
95% CI | 1.02–1.16 | 1.02–1.20 | 1.05–1.25 |
P | 0.0320313 | 0.0317181 | 0.0324736 |
OBC | 16.43 ± 2.03 | 16.25 ± 2.12 | 16.63 ± 2.07 |
95% CI | 15.44–17.43 | 14.78–17.72 | 15.19–18.06 |
95% CI – confidence interval; P – value; OB – olfactory bulb; SC – superior colliculus in the septum; IC – interior colliculus in the septum; C – cerebellum; MO – medulla oblongata; OBC – olfactory bulb– cerebellum; EMF – electromagnetic field; M ± SD – mean and standard deviation of mean
Analysis of brain weight
Group | N | Body weight, g | Brain weight, mg | RBW |
---|---|---|---|---|
M ± SD | M ± SD | |||
Control | n = 10 | 24.00 ± 0.00 | 193 ± 12.52 | 0.22 |
95%CI | 24.00–24.00 | 184.04–201.38 | ||
EMF I | n = 10 | 21.77 ± 2.87 | 202 ± 15.63 | 0.23 |
95%CI | 19.99–23.57 | 189.02–211.38 | ||
EMF II | n = 10 | 18.59 ± 3.35 | 207 ± 16.36 | 0.26 |
95%CI | 16.52–20.66 | 195.49–218.91 |
95% CI – confidence interval; N – number of animals; RBW – relative brain weight index; EMF – electromagnetic field; M ± SD – mean and standard deviation of mean
Segmentation of different mouse brain lobes in groups is shown in Fig.1. The OB size in EMF group I was 0.59% higher than that in the control group, whereas notable changes in OB size did not appear in EMF group II. The SC size among all groups was similar. The IC lobe presented decrements of 20.35% and 20.56% (P <0.05) in EMF group I and EMF group II, respectively, compared with the control. Increments of 0.53% in group I and 0.42% in group II were recorded in the size of the C lobe. Similar were the findings (increments of 0.20% and 0.29%, respectively) for the size of the MO lobe in EMF groups I and II.
The analysis of average body weight, brain weight, and RBW of the mice is comprised in Table 2. Brain weight decreased from that of the control group by 4.66% and 7.25% in EMF groups I and II, respectively, whereas RBW increased by 4.50% and 18.18%.
Histopathological lesions are shown in Figs 2–4. Shrinkage of pyramidal neurons, the presence of mild perivascular and perineuraloedema, and some vacuolation of neurons and glial cells derived from mouse great hemispheres were observed in EMF group I. Furthermore, reduction of Purkinje cells, vacuolisation of neurons and glial cells, and interstitial oedema in the cerebellum were also detected in EMF group II.
Blettner and Berg (5) referred to extensive debates having persisted for decades regarding the effect of EMF exposure from MP on public health, and a large number of studies have been performed to assess potential adverse effects of that exposure. Experimental investigation suggests that RF fields are not tumour initiators and that if they were related to carcinogenicity, this would be by tumour promotion or by increasing the uptake of carcinogens in cells.
In our study, employment of two different exposure levels of EMF originating from MP had a noxious effect on mouse cortex gradients and architecture. The results obtained revealed that EMF emitted from MP changed some brain region morphological characteristics, and this affected synaptic connections and reduced microglial activation in the hippocampus.
Large observational studies performed by Singh
Our study results proved that 72 h EMF exposure from MP (3 cm away from body) invoked changes in the brain map of BALB/c mice, especially in the olfactory bulb, interior colliculus in the septum, and cerebellum. These changes can accelerate the rate of neuronal dysfunction associated with brain pathology.
Perepelkina
Lessard-Beaudoin
The outcomes of the study by Saikhedkar
In our study, we found neurodegenerative changes in the brain. The reason for these changes may be oxidative stress or hyperthermia due to the effect of the EMF. In our case, gliocytes were frequently degenerated. It is commonly known that these cells are the main phagocytes in the brain; they are responsible for the immune response. Only in one case did we find foci of brain tissue calcination. Degenerative cells usually undergo calcination, but in our study, a very brief period of EMF wave exposure was applied, therefore such an explanation may not be correct. Notwithstanding this, according to Rafiqi
This study is an analysis of complex findings associated with brain cortex changes which had never been investigated before. An understanding of the aspects analysed in this article contributes to effective protection against deleterious biological consequences of MP EMF exposure for public health.
In conclusion, different exposure levels of EMF from MP over 72 h affected mouse brains and had a negative influence on segmentation parameters of mouse brain structures. These findings suggested that EMF equipment operating at a 3 cm distance from the cage may induce appreciable morphological changes in the brain. The research outcomes enrich knowledge of neurobiological mechanisms of brain scaling, neurodegerative changes, and integration of brain mapping algorithms and recommend using the mouse as an experimental model in neuroscientific, medical, or pharmacological studies. Moreover, the findings gained have potential to yield solutions improving public health.