Jukka Juutilainen

Relationship between Field Strength and Abnormal Development in Chick Embryos Exposed to 50 Hz Magnetic Fields

Chick embryos were exposed to sinusoidally oscillating 50 Hz magnetic fields during their first 2 days of development. In the first series of experiments magnetic field strengths of 0.1, 0.3, 1 and 10 A/m were used. The percentage of abnormal embryos (% AE) was 16 per cent in the sham-exposed control group. % AE was increased at 1 A/m (29 per cent) and 10 A/m (32 per cent), but not at 0.1 A/m (16 per cent) or 0.3 A/m (14 per cent). In the second series of experiments field strengths of 0.4, 0.6, 0.9 and 1.35 A/m were used. % AE was 17 per cent in the control group, 10 per cent at 0.4 A/m, 19 per cent at 0.6 A/m, 17 per cent at 0.9 A/m and 36 per cent at 1.35 A/m. Only the 1.35 A/m group was significantly different from the controls. The results of this study suggest that exposure of chick embryos to a 50 Hz magnetic field causes abnormal development, and that no abnormalities are induced below a threshold between 0.9 and 1 A/m.

In vitro and in vivo genotoxicity of radiofrequency fields

There has been growing concern about the possibility of adverse health effects resulting from exposure to radiofrequency radiations (RFR), such as those emitted by wireless communication devices. Since the introduction of mobile phones many studies have been conducted regarding alleged health effects but there is still some uncertainty and no definitive conclusions have been reached so far. Although thermal effects are well understood they are not of great concern as they are unlikely to result from the typical low-level RFR exposures. Concern rests essentially with the possibility that RFR-exposure may induce non-thermal and/or long-term health effects such as an increased cancer risk. Consequently, possible genetic effects have often been studied but with mixed results. In this paper we review the data on alleged RFR-induced genetic effects from in vitro and in vivo investigations as well as from human cytogenetic biomonitoring surveys. Attention is also paid to combined exposures of RFR with chemical or physical agents. Again, however, no entirely consistent picture emerges. Many of the positive studies may well be due to thermal exposures, but a few studies suggest that biological effects can be seen at low levels of exposure. Overall, however, the evidence for low-level genotoxic effects is very weak.

Mobile Phone Radiation and the Developing Brain: Behavioral and Morphological Effects in Juvenile Rats

Abstract Kumlin, T., Iivonen, H., Miettinen, P., Juvonen, A., van Groen, T., Puranen, L., Pitkäaho, R., Juutilainen, J. and Tanila, H. Mobile Phone Radiation and the Developing Brain: Behavioral and Morphological Effects in Juvenile Rats. Radiat. Res. 168, 471–479 (2007). The increasing use of mobile phones by children and teenagers has raised concerns about their safety. Addressing such concerns is difficult, because no data are available on possible effects from long-term exposure to radiofrequency (RF) fields during the development of the nervous system. Possible morphological and functional changes were evaluated in the central nervous system of young male Wistar rats exposed to 900 MHz mobile phone signal for 2 h/day on 5 days/week. After 5 weeks of exposure at whole-body average specific energy absorption rates of 0.3 or 3.0 W/kg or sham exposure, six rats per group were examined histologically, and the remaining 18 rats per group were subjected to behavioral tests. No degenerative changes, dying neurons, or effects on the leakage of the blood-brain barrier were detected. No group differences were observed in the open-field test, plus maze test or acoustic startle response tests. In the water maze test, however, significantly improved learning (P = 0.012) and memory (P = 0.01) were detected in rats exposed to RF fields. The results do not indicate a serious threat to the developing brain from mobile phone radiation at intensities relevant to human exposure. However, the interesting finding of improved learning and memory warrants further studies.

Enhancement of chemically induced reactive oxygen species production and DNA damage in human SH-SY5Y neuroblastoma cells by 872 MHz radiofrequency radiation

The objective of the study was to investigate effects of 872 MHz radiofrequency (RF) radiation on intracellular reactive oxygen species (ROS) production and DNA damage at a relatively high SAR value (5 W/kg). The experiments also involved combined exposure to RF radiation and menadione, a chemical inducing intracellular ROS production and DNA damage. The production of ROS was measured using the fluorescent probe dichlorofluorescein and DNA damage was evaluated by the Comet assay. Human SH-SY5Y neuroblastoma cells were exposed to RF radiation for 1 h with or without menadione. Control cultures were sham exposed. Both continuous waves (CW) and a pulsed signal similar to that used in global system for mobile communications (GSM) mobile phones were used. Exposure to the CW RF radiation increased DNA breakage (p<0.01) in comparison to the cells exposed only to menadione. Comparison of the same groups also showed that ROS level was higher in cells exposed to CW RF radiation at 30 and 60 min after the end of exposure (p<0.05 and p<0.01, respectively). No effects of the GSM signal were seen on either ROS production or DNA damage. The results of the present study suggest that 872 MHz CW RF radiation at 5 W/kg might enhance chemically induced ROS production and thus cause secondary DNA damage. However, there is no known mechanism that would explain such effects from CW RF radiation but not from GSM modulated RF radiation at identical SAR.

Effects of radiofrequency electromagnetic fields on the human nervous system

The effects of exposure to radiofrequency electromagnetic fields (EMF), specifically related to the use of mobile telephones, on the nervous system in humans have been the subject of a large number of experimental studies in recent years. There is some evidence of an effect of exposure to a Global System for Mobile Telecommunication (GSM)-type signal on the spontaneous electroencephalogram (EEG). This is not corroborated, however, by the results from studies on evoked potentials. Although there is some evidence emerging that there may be an effect of exposure to a GSM-type signal on sleep EEG, results are still variable. In summary, exposure to a GSM-type signal may result in minor effects on brain activity, but such changes have never been found to relate to any adverse health effects. No consistent significant effects on cognitive performance in adults have been observed. If anything, any effect is small and exposure seems to improve performance. Effects in children did not differ from those in healthy adults. Studies on auditory and vestibular function are more unequivocal: neither hearing nor the sense of balance is influenced by short-term exposure to mobile phone signals. Subjective symptoms over a wide range, including headaches and migraine, fatigue, and skin itches, have been attributed to various radiofrequency sources both at home and at work. However, in provocation studies a causal relation between EMF exposure and symptoms has never been demonstrated. There are clear indications, however, that psychological factors such as the conscious expectation of effect may play an important role in this condition.

Effects of 100-Hz magnetic fields with various waveforms on the development of chick embryos.

SummaryChick embroys were exposed during their 52 first hours of development to 100-Hz magnetic fields. Sinusoidal, square and pulsed waveforms were used at average field strengths from 0.1 A/m to 80 A/m. After exposure, the embryos were examined for abnormalities and classified by the developmental stages. When bipolar oscillations (oscillating at both sides of the zero-level) were used, the percentage of abnormal embryos was significantly increased above 1 A/m. In exposure to unipolar square waves, no significant effect on the percentage of abnormalities could be demonstrated. The developmental stage was possibly affected by unipolar square waves at 0.1 A/m, all other field strengths and wave-forms being apparently ineffective.

Do extremely low frequency magnetic fields enhance the effects of environmental carcinogens? A meta-analysis of experimental studies.

Purpose: This paper is a meta-analysis of data from in vitro studies and short-term animal studies that have combined extremely low frequency magnetic fields with known carcinogens or other toxic physical or chemical agents. Materials and methods: The data was analyzed by systematic comparison of study characteristics between positive and negative studies to reveal possible consistent patterns. Results: The majority of the studies reviewed were positive, suggesting that magnetic fields do interact with other chemical and physical exposures. Publication bias is unlikely to explain the findings. Interestingly, a nonlinear ‘dose-response’ was found, showing a minimum percentage of positive studies at fields between 1 and 3 mT. The radical pair mechanism (magnetic field effects on recombination of radical pairs) is a good candidate mechanism for explaining the biphasic dose-response seen in the present analysis. Conclusions: Most of the studies reviewed used magnetic fields of 100 μT or higher, so the findings are not directly relevant for explaining the epidemiological findings suggesting increased risk of childhood leukemia above 0.4 μT. However, confirmed adverse effects even at 100 μT would have implications for risk assessment and management, including the need to reconsider the exposure limits for magnetic fields. There is an obvious need for further studies on combined effects with magnetic fields.

Proliferation, Oxidative Stress and Cell Death in Cells Exposed to 872 MHz Radiofrequency Radiation and Oxidants

Abstract Höytö, A., Luukkonen, J., Juutilainen, J. and Naarala, J. Proliferation, Oxidative Stress and Cell Death in Cells Exposed to 872 MHz Radiofrequency Radiation and Oxidants. Radiat. Res. 170, 235–243 (2008). Human SH-SY5Y neuroblastoma and mouse L929 fibroblast cells were exposed to 872 MHz radiofrequency (RF) radiation using continuous waves (CW) or a modulated signal similar to that emitted by GSM mobile phones at a specific absorption rate (SAR) of 5 W/kg in isothermal conditions. To investigate possible combined effects with other agents, menadione was used to induce reactive oxygen species, and tert-butylhydroperoxide (t-BOOH) was used to induce lipid peroxidation. After 1 or 24 h of exposure, reduced cellular glutathione levels, lipid peroxidation, proliferation, caspase 3 activity, DNA fragmentation and viability were measured. Two statistically significant differences related to RF radiation were observed: Lipid peroxidation induced by t-BOOH was increased in SH-SY5Y (but not in L929) cells, and menadione-induced caspase 3 activity was increased in L929 (but not in SH-SY5Y) cells. Both differences were statistically significant only for the GSM-modulated signal. The other end points were not significantly affected in any of the experimental conditions, and no effects were observed from exposure to RF radiation alone. The positive findings may be due to chance, but they may also reflect effects that occur only in cells sensitized by chemical stress. Further studies are required to investigate the reproducibility and dose response of the possible effects.

Incidence of leukaemia and brain tumours in finnish workers exposed to ELF magnetic fields

SummaryThe relative incidence of leukaemia, acute myeloid leukaemia (AML) and central nervous system (CNS) tumours among workers presumably exposed to extremely low frequency (ELF) magnetic fields (MFs) was studied. The study population consisted of all male industrial workers in Finland aged 25 to 64 years during 1971–1980 according to the Population Census in 1970. The occupations were grouped into three exposure categories according to the probability of exposure. The category of “probable” exposure included electrical occupations and the category of “possible” exposure included occupations where electric motors or welding are common. All other occupations were included to the category of “no exposure”. Cancer incidence rates in different occupational groups during 1971–1980 were obtained after linking the census records with the national death certificates and the files of the Finnish Cancer Registry. The adjusted relative risks (with 95% confidence limits) in the categories of “probable” and “possible” exposure were for all leukaemia 1.9 (1.0–3.5) and 1.4 (1.1–1.8), for AML 1.5 (0.5–4.7) and 1.4 (0.9–2.1), and for CNS tumours 1.3 (0.7–2.3) and 1.3 (1.0–1.6), respectively. The results are concordant with earlier studies suggesting elevated risk among workers exposed to ELF magnetic fields.

Effects of mobile phone radiation on X-ray-induced tumorigenesis in mice.

Abstract Heikkinen, P., Kosma, V-M., Hongisto, T., Huuskonen, H., Hyysalo, P., Komulainen, H., Kumlin, T., Lahtinen, T., Lang, S., Puranen, L. and Juutilainen, J. Effects of Mobile Phone Radiation on X-Ray-Induced Tumorigenesis in Mice. Radiat. Res. 156, 775–785 (2001). The increased use of mobile phones has raised the question of possible health effects of such devices, particularly the risk of cancer. It seems unlikely that the low-level radiofrequency (RF) radiation emitted by them would damage DNA directly, but its ability to act as a tumor promoter is less well characterized. In the current study, we evaluated the effect of low-level RF radiation on the development of cancer initiated in mice by ionizing radiation. Two hundred female CBA/S mice were randomized into four equal groups at the age of 3 to 5 weeks. The mice in all groups except the cage-control group were exposed to ionizing radiation at the beginning of the study and then to RF radiation for 1.5 h per day, 5 days a week for 78 weeks. One group was exposed to continuous NMT (Nordic Mobile Telephones)-type frequency-modulated RF radiation at a frequency of 902.5 MHz and a nominal average specific absorption rate (SAR) of 1.5 W/kg. Another group was exposed to pulsed GSM (Global System for Mobile)-type RF radiation (carrier-wave frequency 902.4 MHz, pulse frequency 217 Hz) at a nominal average SAR of 0.35 W/kg. The control animals were sham-exposed. Body weight, clinical signs, and food and water consumption were recorded regularly. Hematological examinations and histopathological analyses of all lesions and major tissues were performed on all animals. The RF-radiation exposures did not increase the incidence of any neoplastic lesion significantly. We conclude that the results do not provide evidence for cancer promotion by RF radiation emitted by mobile phones.