Year: 2018
Type: dissertation
Abstract: Humans are ubiquitously exposed to natural and manmade electromagnetic fields (EMFs).New applications keep emerging, especially in the intermediate frequency (IF) range and, despite research conducted over many decades, the risks to human health are still partly unclear, particularly whether there are risks to human health under the current exposure limits.Extremely low frequency (ELF) magnetic fields (MFs) and radiofrequency (RF) EMFs have been classified as possibly carcinogenic to humans by the International Agency for Research on Cancer, mainly based on associations observed in epidemiological studies.However, the causality of the associations is still unclear, largely because there are no generally accepted mechanisms for explaining carcinogenic effects at exposure levels present in the environment.A common property of many environmental carcinogens is their ability to cause harmful changes in the genome.Consequently, many studies have been conducted to assess the possible genotoxicity of EMFs, with inconclusive results.Recent research has revealed that exposure to ionizing radiation and several other environmental agents can result in induced genomic instability (IGI), a phenomenon that differs from direct genotoxicity studied by conventional methods.Induced genomic instability can be defined as de novo appearance of delayed damage observed in the progeny of exposed cells many cell generations after exposure.Previous data on the ability of EMFs to induce genomic instability are very limited.The general aim of this study is to investigate possible genome-damaging effects of EMFs and to increase understanding of the mechanisms of such effects.To this end, experiments were conducted to assess genotoxicity and IGI in cultured cells and animals exposed to ELF and IF MFs or RF EMFs.The aim of the ELF MF studies was to investigate genotoxicity and to test a mechanistic explanation for the effects of weak MFs (the radical pair mechanism) by studying interactions between E L F M F s a n d b l u e l i g h t .E x p e r i me n t s w i t h I F M F s a i me d a t e v a l u a t i n g t h e i r g e n o t o x i ci t y , e f f e ct s o n D N A r e p a i r , a n d I G I .G e n o t o x i ci t y a n d I G I w e r e a l s o studied in experiments with RF EMFs, and these experiments also aimed at testing possible differences between modulated and non-modulated RF signals.A common aim at all frequencies was to study the effects of combined exposure to EMFs and known genotoxic chemicals.The results indicated that exposure to 50 Hz 100 µT MFs for 24 h affected production of reactive oxygen species but did not increase micronuclei alone or in combination with menadione in human SH-SY5Y neuroblastoma cells.Combined exposure to blue light and ELF MFs was studied for the first time.The findings do not support the simple hypothesis that MF effects would be observed only in the presence of blue light, but interactions between blue light and ELF MFs were nevertheless observed.The finding that MF effects occurred without blue light indicates that MFs may affect light-independent radical reactions.These observations may be important for understanding the effects of weak MFs.The IF MF studies revealed that exposure to 7.5 kHz MFs up to 300 µT for 24 h in vitro or in vivo did not cause genotoxicity alone or in combination with chemicals.There was some evidence that IF MFs might actually reduce the level of genetic damage, and rather strong evidence that the relative cell number was increased after exposure to IF MFs.Furthermore, exposure to vertical or horizontal 7.5 kHz MF at 300 µT did not induce genomic instability alone or in combination with chemicals in rat primary astrocytes.The results indicate that exposure to IF MFs may actually decrease genomic instability.However, this was the first time that the induction of genomic instability by IF MFs was studied.Exposure of rat primary astrocytes to 872 MHz RF EMFs at 0.6 or 6 W/kg for 24 h did not cause genotoxicity alone and the results of combined exposure with chemicals were inconsistent.Modulation-dependent effects were not seen.Induction of genomic instability by RF EMFs was evaluated for the first time using 24-h exposure to 872 MHz GSM-modulated RF fields at 0.6 or 6 W/kg alone or in combination with menadione.No induction or enhancement of genomic instability in rat primary astrocytes was observed.In conclusion, the present study produced new information that is likely to be important for understanding the mechanisms of the biological effects of weak MFs.The results did not support genotoxicity or co-genotoxicity of IF or RF EMFs.No evidence for induction of genomic instability by RF or IF EMFs was found in this study that assessed such effects for the first time.
Author: Herrala, Mikko
Institution: University of Eastern Finland
Language: English
Subfield: Biophysics
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W7018561626