Elsevier

Environmental Pollution

Volume 267, December 2020, 115632
Environmental Pollution

Effects of different mobile phone UMTS signals on DNA, apoptosis and oxidative stress in human lymphocytes

https://doi.org/10.1016/j.envpol.2020.115632Get rights and content

Highlights

  • Comparatively analyzed genotoxic effects of UMTS signals at different frequency.

  • Significant role of UMTS carrier frequency (1977 MHz) in inducing DNA damage.

  • No association of UMTS exposure with apoptosis, TP53 mutations and PFG induction.

  • Prolonged exposure to microwave radiation may induce genotoxic effects.

Abstract

Different scientific reports suggested link between exposure to radiofrequency radiation (RF) from mobile communications and induction of reactive oxygen species (ROS) and DNA damage while other studies have not found such a link. However, the available studies are not directly comparable because they were performed at different parameters of exposure, including carrier frequency of RF signal, which was shown to be a critical for appearance of the RF effects. For the first time, we comparatively analyzed genotoxic effects of UMTS signals at different frequency channels used by 3G mobile phones (1923, 1947.47, and 1977 MHz). Genotoxicity was examined in human lymphocytes exposed to RF for 1 h and 3 h using complimentary endpoints such as induction of ROS by imaging flow cytometry, DNA damage by alkaline comet assay, mutations in TP53 gene by RSM assay, preleukemic fusion genes (PFG) by RT-qPCR, and apoptosis by flow cytometry. No effects of RF exposure on ROS, apoptosis, PFG, and mutations in TP53 gene were revealed regardless the UMTS frequency while inhibition of a bulk RNA expression was found. On the other hand, we found relatively small but statistically significant induction of DNA damage in dependence on UMTS frequency channel with maximal effect at 1977.0 MHz. Our data support a notion that each specific signal used in mobile communication should be tested in specially designed experiments to rule out that prolonged exposure to RF from mobile communication would induce genotoxic effects and affect the health of human population.

Introduction

For last few decades, the environment has been increasingly suffered from a new type of pollution created by electromagnetic radiations from wireless mobile communication (Blackman et al., 1979; Adey, 1993). This generated serious concerns regarding health of humans and safety of biota (Balmori, 2010). Different studies showed serious potential impact of electromagnetic radiation on our environment (Balmori, 2009; Lopatina et al., 2019). This electromagnetic pollution from mobile communication may affect not only human beings but also animals and birds (Balmori and Hallberg, 2007). In 2011, the International Agency for Research on Cancer (IARC), which is part of the World Health Organization, classified radiofrequency radiation (RF) including that from mobile phones as a possible carcinogen, group 2B (Baan et al., 2011). Long term mobile phone usage in different case control studies showed statistically significant association with increased risk of brain tumors (Wang and Guo, 2016; Bortkiewicz et al., 2017; Prasad et al., 2017; Yang et al., 2017).

As far as genotoxic effects are the most direct cause for carcinogenicity, available relevant studies were thoroughly reviewed in the IARC RF monograph (IARC, 2013). Diverse conclusions stemmed from these studies: in general, about half of studies found some RF genotoxicity (positive reports) while the other half have not (negative reports). This approximately similar numbers of positive and negative reports is in line with studies measuring some others biological endpoints of RF exposure (Huss et al., 2008; Apollonio et al., 2013; Cucurachi et al., 2013). While many studies on RF genotoxicity have been performed since the assessment of IARC in 2011, the balance between negative and positive studies did not change much (https://www.emf-portal.org/en/search/results?query=RF+genotoxicity&languageIds%5B%5D=en). However, results of all these studies are not directly comparable due to dependence of the RF effects on a number of critical physical parameters of exposure, which vary significantly between studies (Belyaev, 2010; IARC, 2013). While specific absorption rate (SAR) and power flux density (PD) are the main determinants for the thermal RF effects, several other physical parameters of exposure including frequency, modulation, polarization, duration of exposure and also different biological variables have long been known to be critical for non-thermal RF biological effects such as induced by exposure to various sources of mobile communication (Blackman, 1992, 2009; Adey et al., 1999; Belyaev et al., 2000).

Free radicals are a group of highly reactive molecules having unpaired electrons in the outer orbit. Most known free radicals are reactive oxygen species (ROS) derived from oxygen metabolism. Upon overproduction, these reactive species can damage various molecules including DNA leading to increased mutations, changed cell death and cell growth, and thus contributing to the multistage carcinogenesis process. About 90% of available studies have reported that RF exposure causes oxidative stress as revealed by increase in ROS, oxidized proteins, peroxidized lipids and fragmented DNA, see for review (Georgiou, 2010; Yakymenko et al., 2015). However, the relevance of RF-induced ROS to DNA damage was less investigated and some studies reported that RF-induced ROS was not followed by DNA damage (Durdik et al., 2019).

It has been suggested that oxidative stress could be a key factor for RF-related incidence of brain tumors and childhood leukemias (De Iuliis, Newey et al., 2009). However, no studies are available to test whether mutations related to brain tumors and childhood leukemias are induced by exposure to RF signals used by mobile phones. In particular, different frequency channels of UMTS signals used in 3G technology have not been tested so far.

Tumor suppressor gene TP53 encoding p53 protein is the most commonly mutated gene in human cancers including brain tumors (Kandoth et al., 2013; Bouaoun et al., 2016). Somatic TP53 mutations have been detected in up to 20% of acute myeloid leukemia (AML), often associated with a complex karyotype, resulting into inferior survival rates (Grossmann et al., 2012; Rucker et al., 2012). Recent data suggested that somatic TP53 mutations may represent early leukemogenic events, possibly by initiating mutations acting as mediators of resistance in this type of leukemia (Lal et al., 2017).

Other early primary genetic abnormalities in the origination of acute childhood leukemia are chromosomal translocations in hematopoietic cells resulting in so-called preleukemic fusion genes (PFG). Two chromosomal translocations with corresponding PFG are frequent in pediatric acute lymphoid leukemia (ALL): t(12;21) (p13;q22) TEL-AML1 (24-26%) and t(4;11)(q21;q23) MLL-AF4 (∼5%). MLL-AF9 belongs to the most frequent PFG for acute myeloid leukemia (AML). In this study, for the first time, we applied several complementary techniques to validate whether exposure of human lymphocytes to RF at different UMTS frequency channels induce ROS, DNA damage, apoptosis, TP53 mutations and most frequent PFG.

Section snippets

Chemicals

Reagent grade chemicals were obtained from Sigma (St. Louis, MI, USA) and Merck (Darmstadt, Germany).

Ethical considerations

The Ethics Committee of Children’s Hospital in Bratislava has approved this study. All UCB samples were provided with an informed consent from a parent for study participation.

Cells

In vitro cultures of human lymphocytes were used to investigate the effect of RF exposure. Cells were isolated from UCB and cell aliquots were cryopreserved in liquid nitrogen by Dr. M. Kubes (Eurocord, Slovakia) as

DNA damage

UCB cells from three different probands were exposed to UMTS RF at different frequencies (1923, 1947.47, or 1977 MHz) for 1 h and 3 h. Upon RF exposure, DNA damage was analyzed by alkaline comet assay. The representative photomicrographs of cells with damaged DNA are shown in Fig. 1A & B. Blood lymphocytes are known to be very sensitive to apoptosis, for instance induced by regular freeze and thaw process. Apoptotic cells were differentiated from viable cells according to the appropriate

Discussion

In the present investigation, we analyzed non-thermal effects of RF from 3G mobile phone at different UMTS frequency channels on human lymphocytes. We used complimentary biomarkers to assess DNA damage by alkaline comet assay, ROS by imaging flow cytometry, apoptosis by flow cytometry, p53 mutations by RSM method, and induction of PFG by RT-qPCR method. Comet assay is a very sensitive technique which can detect damage in DNA at single cell level and widely accepted in genonotoxicity studies

Conclusion

We found relatively small but statistically significant induction of DNA damage in dependence on UMTS frequency channel with maximal effect at 1977 MHz through alkaline comet assay. We concluded that UMTS RF exposure at the 1923 and 1977 MHz frequency did not induce ROS, apoptosis, selected TP53 mutations and PFG, but inhibited a bulk RNA expression. Our data support a notion that each specific signal used in mobile communication should be tested in specially designed experiments to rule out

Statement from authors

All of the authors have read and approved the paper and it has not been published previously nor is it being considered by any other peer-reviewed journal.

Author contributions

I.B. and S.G. conceived the experiments; S.G., P.K., M.D., M.S., L.J., E.M., conducted the experiments; S.G., P.K., M.D., M.S., I.B. analyzed the results; S.G and I.B. wrote the manuscript.

Declaration of competing interest

S.G., P.K., M.D., M.S., L.J., E.M., report no conflict of interest. IB provided expert opinions in the Cell Phone Litigation on link between microwave radiation from mobile phones/base stations and human health.

Acknowledgements

The authors are thankful to Dr. M. Kubes, Eurocord-Slovakia, Bratislava, Slovak Republic, for providing UCB MNC and Mgr. L. Zastko for measurements of SMF. This study was supported by the Slovak Research and Development Agency (APVV-15-0250); the Vedecká grantová agentúra (VEGA) Grant Agency (2/0089/18) of the Slovak Republic, and the Structural Funds of EU (Protonbeam, ITMS: 26220220200).

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