RESUMEN
To establish a dose-response relationship between the strength of electromagnetic fields (EMF) and previously reported effects on the brain, we investigated the influence of EMF exposure by varying the signal intensity in three experimental sessions. The head of 15 healthy male subjects was unilaterally exposed for 30 min prior to sleep to a pulse-modulated EMF (GSM handset like signal) with a 10 g-averaged peak spatial specific absorption rate of (1) 0.2 W kg(-1), (2) 5 W kg(-1), or (3) sham exposed in a double-blind, crossover design. During exposure, subjects performed two series of three computerized cognitive tasks, each presented in a fixed order [simple reaction time task, two-choice reaction time task (CRT), 1-, 2-, 3-back task]. Immediately after exposure, night-time sleep was polysomnographically recorded for 8 h. Sleep architecture was not affected by EMF exposure. Analysis of the sleep electroencephalogram (EEG) revealed a dose-dependent increase of power in the spindle frequency range in non-REM sleep. Reaction speed decelerated with increasing field intensity in the 1-back task, while accuracy in the CRT and N-back task were not affected in a dose-dependent manner. In summary, this study reveals first indications of a dose-response relationship between EMF field intensity and its effects on brain physiology as demonstrated by changes in the sleep EEG and in cognitive performance.
Asunto(s)
Cognición/efectos de la radiación , Electroencefalografía/efectos de la radiación , Ondas de Radio , Fases del Sueño/efectos de la radiación , Vigilia/efectos de la radiación , Adulto , Estudios Cruzados , Método Doble Ciego , Humanos , Masculino , Pruebas Neuropsicológicas , Análisis y Desempeño de TareasRESUMEN
We investigated the effects of radio frequency electromagnetic fields on brain physiology. Twenty-four healthy young men were exposed for 30 min to pulse-modulated or continuous-wave radio frequency electromagnetic fields (900 MHz; peak specific absorption rate 1 W/kg), or sham exposed. During exposure, participants performed cognitive tasks. Waking electroencephalogram was recorded during baseline, immediately after, and 30 and 60 min after exposure. Pulse-modulated radio frequency electromagnetic field exposure reduced reaction speed and increased accuracy in a working-memory task. It also increased spectral power in the waking electroencephalogram in the 10.5-11 Hz range 30 min after exposure. No effects were observed for continuous-wave radio frequency electromagnetic fields. These findings provide further evidence for a nonthermal biological effect of pulsed radio frequency electromagnetic fields.
Asunto(s)
Cognición/efectos de la radiación , Electroencefalografía/efectos de la radiación , Ondas de Radio , Vigilia , Adulto , Humanos , Masculino , Pruebas Neuropsicológicas , Factores de TiempoRESUMEN
BACKGROUND: Radio-frequency electromagnetic fields (RF EMF) of mobile communication systems are widespread in the living environment, yet their effects on humans are uncertain despite a growing body of literature. OBJECTIVES: We investigated the influence of a Universal Mobile Telecommunications System (UMTS) base station-like signal on well-being and cognitive performance in subjects with and without self-reported sensitivity to RF EMF. METHODS: We performed a controlled exposure experiment (45 min at an electric field strength of 0, 1, or 10 V/m, incident with a polarization of 45 degrees from the left back side of the subject, weekly intervals) in a randomized, double-blind crossover design. A total of 117 healthy subjects (33 self-reported sensitive, 84 nonsensitive subjects) participated in the study. We assessed well-being, perceived field strength, and cognitive performance with questionnaires and cognitive tasks and conducted statistical analyses using linear mixed models. Organ-specific and brain tissue-specific dosimetry including uncertainty and variation analysis was performed. RESULTS: In both groups, well-being and perceived field strength were not associated with actual exposure levels. We observed no consistent condition-induced changes in cognitive performance except for two marginal effects. At 10 V/m we observed a slight effect on speed in one of six tasks in the sensitive subjects and an effect on accuracy in another task in nonsensitive subjects. Both effects disappeared after multiple end point adjustment. CONCLUSIONS: In contrast to a recent Dutch study, we could not confirm a short-term effect of UMTS base station-like exposure on well-being. The reported effects on brain functioning were marginal and may have occurred by chance. Peak spatial absorption in brain tissue was considerably smaller than during use of a mobile phone. No conclusions can be drawn regarding short-term effects of cell phone exposure or the effects of long-term base station-like exposure on human health.
Asunto(s)
Teléfono Celular , Cognición/efectos de la radiación , Campos Electromagnéticos/efectos adversos , Ondas de Radio/efectos adversos , Adulto , Relación Dosis-Respuesta en la Radiación , Método Doble Ciego , Femenino , Humanos , Masculino , Persona de Mediana Edad , Desempeño Psicomotor/efectos de la radiación , Calidad de Vida , Radiometría , Encuestas y CuestionariosRESUMEN
Possible biological effects of mobile phone microwaves were investigated in vitro. In this study, which was part of the 5FP EU project REFLEX (Risk Evaluation of Potential Environmental Hazards From Low-Energy Electromagnetic Field Exposure Using Sensitive in vitro Methods), six human cell types, immortalized cell lines and primary cells, were exposed to 900 and 1800 MHz. RNA was isolated from exposed and sham-exposed cells and labeled for transcriptome analysis on whole-genome cDNA arrays. The results were evaluated statistically using bioinformatics techniques and examined for biological relevance with the help of different databases. NB69 neuroblastoma cells, T lymphocytes, and CHME5 microglial cells did not show significant changes in gene expression. In EA.hy926 endothelial cells, U937 lymphoblastoma cells, and HL-60 leukemia cells we found between 12 and 34 up- or down-regulated genes. Analysis of the affected gene families does not point towards a stress response. However, following microwave exposure, some but not all human cells might react with an increase in expression of genes encoding ribosomal proteins and therefore up-regulating the cellular metabolism.
Asunto(s)
Teléfono Celular , Regulación hacia Abajo/efectos de la radiación , Microondas , Regulación hacia Arriba/efectos de la radiación , Línea Celular , HumanosRESUMEN
Mouse embryonic stem (ES) cells were used as an experimental model to study the effects of electromagnetic fields (EMF). ES-derived nestin-positive neural progenitor cells were exposed to extremely low frequency EMF simulating power line magnetic fields at 50 Hz (ELF-EMF) and to radiofrequency EMF simulating the Global System for Mobile Communication (GSM) signals at 1.71 GHz (RF-EMF). Following EMF exposure, cells were analyzed for transcript levels of cell cycle regulatory, apoptosis-related, and neural-specific genes and proteins; changes in proliferation; apoptosis; and cytogenetic effects. Quantitative RT-PCR analysis revealed that ELF-EMF exposure to ES-derived neural cells significantly affected transcript levels of the apoptosis-related bcl-2, bax, and cell cycle regulatory "growth arrest DNA damage inducible" GADD45 genes, whereas mRNA levels of neural-specific genes were not affected. RF-EMF exposure of neural progenitor cells resulted in down-regulation of neural-specific Nurr1 and in up-regulation of bax and GADD45 mRNA levels. Short-term RF-EMF exposure for 6 h, but not for 48 h, resulted in a low and transient increase of DNA double-strand breaks. No effects of ELF- and RF-EMF on mitochondrial function, nuclear apoptosis, cell proliferation, and chromosomal alterations were observed. We may conclude that EMF exposure of ES-derived neural progenitor cells transiently affects the transcript level of genes related to apoptosis and cell cycle control. However, these responses are not associated with detectable changes of cell physiology, suggesting compensatory mechanisms at the translational and posttranslational level.
Asunto(s)
Apoptosis , Campos Electromagnéticos , Embrión de Mamíferos/citología , Embrión no Mamífero , Neuronas/efectos de la radiación , Células Madre/citología , Células Madre/efectos de la radiación , Transcripción Genética/efectos de la radiación , Proliferación Celular , Ensayo Cometa , ADN/química , Daño del ADN , Regulación hacia Abajo , Péptidos y Proteínas de Señalización Intracelular/metabolismo , Modelos Biológicos , Neuronas/metabolismo , Biosíntesis de Proteínas , Procesamiento Proteico-Postraduccional , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , ARN Mensajero/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Factores de Tiempo , Regulación hacia Arriba , Proteína X Asociada a bcl-2/metabolismo , Proteinas GADD45RESUMEN
The transverse electromagnetic (TEM) cell system developed by Litovitz et al. and utilized by Penafiel et al. for the exposure of cells in T25 flasks at 835 MHz has been reevaluated for the purpose of replicating the studies published by Penafiel. The original setup has been reconstructed as closely as possible, with improvements enabling blinded exposures, forced cooling and better repeatable positioning of the flasks, as well as tight exposure and environmental parameter control. The signal unit can simulate the original signal but also enables various other exposure schemes. The setup has been evaluated for four T25 flasks filled with 5 and 10 ml of cell medium by experimental and numerical means. Comparing E field, SAR and temperature measurements resulted in good agreement: <0.4 dB (4.5%) for E field and 0.48 dB (10.5%) for SAR. The overall average SAR within the medium is 6.0 W/kg at 1 W input power with a standard deviation of less than 52%. The temperature increase was determined to be 0.13 degrees C/(W/kg). This can be reduced to 0.045 degrees C/(W/kg) by applying active air flow cooling. The comparison of SAR values from temperature measurements with the corresponding simulated values resulted in excellent agreement. These results do not correspond to the previous study reporting an average SAR within the medium of 2.5 W/kg at an input power of 0.96 W.
Asunto(s)
Técnicas de Cultivo de Célula/instrumentación , Fenómenos Fisiológicos Celulares/efectos de la radiación , Exposición a Riesgos Ambientales/análisis , Análisis de Falla de Equipo , Radiometría/instrumentación , Técnicas de Cultivo de Célula/métodos , Diseño de Equipo , Dosis de Radiación , Radiometría/métodos , Reproducibilidad de los Resultados , Sensibilidad y EspecificidadRESUMEN
For in vitro studies on the effect of extremely low frequency (ELF) magnetic field exposures in different laboratories, a programmable, high precision exposure system enabling blinded exposures has been developed and fully characterized. It is based on two shielded 4 coil systems that fit inside a commercial incubator. The volume of uniform B field exposure with 1% field tolerance is 50% larger compared to a Merrit 4 coil system with the same coil volume. The uncertainties for the applied magnetic fields have been specified to be less than 4%. The computer controlled apparatus allows signal waveforms that are composed of several harmonics, blind protocols, monitoring of exposure and environmental conditions and the application of B fields up to 3.6 mT root-mean-square amplitude. Sources of artifacts have been characterized: sham isolation >43 dB, parasitic incident E fields <1 V/m, no recognizable temperature differences in the media for exposure or sham state, and vibrations of the mechanically decoupled dish holder <0.1 m/s(2) (= 0.01 g), which is only twice the sham acceleration background level produced by the incubator and fan vibrations.
Asunto(s)
Técnicas de Cultivo de Célula/instrumentación , Fenómenos Electromagnéticos/instrumentación , Radiometría/instrumentación , Transductores , Técnicas de Cultivo de Célula/métodos , Campos Electromagnéticos , Fenómenos Electromagnéticos/métodos , Ambiente Controlado , Diseño de Equipo , Análisis de Falla de Equipo , Dosis de RadiaciónRESUMEN
Conflicting results have recently emerged from human provocation studies that addressed the possible health hazards of radio frequency (RF) field exposure from mobile phones. Different findings may have resulted from exposures that are poorly defined and difficult to compare. The aim of this study was to develop guidelines to facilitate the development of exposure systems for human volunteer studies which lead to reproducible results and which provide maximum relevance with respect to the assessment of the safety of mobile technology. The most important exposure parameters are discussed such as the signal, field distribution, and field strength, as well as the minimum requirements for the setup and dosimetry.
Asunto(s)
Teléfono Celular , Exposición a Riesgos Ambientales , Proyectos de Investigación , Medición de Riesgo , Absorción , Método Doble Ciego , Campos Electromagnéticos/efectos adversos , Exposición a Riesgos Ambientales/clasificación , Humanos , Dosis de Radiación , Ondas de Radio/efectos adversos , Reproducibilidad de los Resultados , Medición de Riesgo/clasificación , Seguridad , TemperaturaRESUMEN
A novel integrated thermistor probe for temperature evaluations in radiofrequency-heated environments was realized. The probe's sensitive area is based on a highly resistive 50 microm x 100 microm layer of amorphous germanium processed on a glass tip. The small dimensions allow measurements with a distance as close as 150 microm from solid boundaries. Due to its high temperature resolution of 4 mK and its short response time of the order of 10 ms, the sensor is very well suited for dosimetric measurements in strong absorption gradients. The influence of radiofrequency (RF) electric fields on the signal is minimized due to the high resistance of the sensor and the leads. The probe was successfully used to determine the highly nonuniform absorption distribution resulting from the RF exposure of cell cultures placed in Petri dishes.
Asunto(s)
Ondas de Radio , Radiometría/instrumentación , Termografía/instrumentación , Termómetros , Transductores , Carga Corporal (Radioterapia) , Campos Electromagnéticos , Diseño de Equipo , Análisis de Falla de Equipo , Radiometría/métodos , Efectividad Biológica Relativa , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Temperatura , Termografía/métodosRESUMEN
Effects of electromagnetic fields (EMF) simulating exposure to the Global System for Mobile Communications (GSM) signals were studied using pluripotent embryonic stem (ES) cells in vitro. Wild-type ES cells and ES cells deficient for the tumor suppressor p53 were exposed to pulse modulated EMF at 1.71 GHz, lower end of the uplink band of GSM 1800, under standardized and controlled conditions, and transcripts of regulatory genes were analyzed during in vitro differentiation. Two dominant GSM modulation schemes (GSM-217 and GSM-Talk), which generate temporal changes between GSM-Basic (active during talking phases) and GSM-DTX (active during listening phases thus simulating a typical conversation), were applied to the cells at and below the basic safety limits for local exposures as defined for the general public by the International Commission on Nonionizing Radiation Protection (ICNIRP). GSM-217 EMF induced a significant upregulation of mRNA levels of the heat shock protein, hsp70 of p53-deficient ES cells differentiating in vitro, paralleled by a low and transient increase of c-jun, c-myc, and p21 levels in p53-deficient, but not in wild-type cells. No responses were observed in either cell type after EMF exposure to GSM-Talk applied at similar slot-averaged specific absorption rates (SAR), but at lower time-averaged SAR values. Cardiac differentiation and cell cycle characteristics were not affected in embryonic stem and embryonic carcinoma cells after exposure to GSM-217 EMF signals. Our data indicate that the genetic background determines cellular responses to GSM modulated EMF. Bioelectromagnetics 25:296-307, 2004.
Asunto(s)
Campos Electromagnéticos , Embrión de Mamíferos/efectos de la radiación , Embrión no Mamífero , Expresión Génica/efectos de la radiación , Genes p53 , Células Madre/efectos de la radiación , Animales , Diferenciación Celular/efectos de la radiación , División Celular/efectos de la radiación , Línea Celular , Embrión de Mamíferos/citología , Embrión de Mamíferos/metabolismo , Citometría de Flujo , Miocardio/citología , Tolerancia a Radiación/genética , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Células Madre/metabolismoRESUMEN
The diffusion of extremely low-frequency (50 Hz) electromagnetic fields (ELF-EMF) in the human environment raises the question of the induction of biological effects of EMF on mammalian cells. We used the model of mouse pluripotent embryonic stem (ES) cells, which have the capacity to develop in vitro into cells of all lineages, to analyse non-thermal effects of ELF-EMF. Wild type (wt) and p53-deficient ES cells were exposed under controlled conditions to ELF-EMF signals simulating power-line (50 Hz) magnetic field (PL-MF) exposure. Different flux densities of 0.1 mT, 1.0 mT or 2.3 mT and intermittency schemes with various ON/OFF cycles were applied for 6 h or 48 h during the first stages of cell differentiation. Transcript levels of regulatory genes, such as egr-1, p21, c-jun, c-myc, hsp70 and bcl-2, were analysed by semi-quantitative RT-PCR immediately after exposure or after a recovery time of 18 h. Intermittent PL-MF exposure to 5 min ON/30 min OFF cycles at a flux density of 2.3 mT for 6 h resulted in a significant up-regulation of c-jun, p21 and egr-1 mRNA levels in p53-deficient, but not in wild-type cells. No significant effects were observed in both cell systems by PL-MF at lower flux densities, longer exposure time or after 18 h recovery time. Our data indicate that 5 min ON/30 min OFF intermittent PL-MF exposure is capable of evoking non-thermal responses in ES cells, dependent on the cellular p53 function. The nature of the biological responses triggered by PL-MF is discussed.
Asunto(s)
Campos Electromagnéticos , Embrión de Mamíferos/citología , Regulación de la Expresión Génica/efectos de la radiación , Células Madre Pluripotentes/efectos de la radiación , Animales , Células Cultivadas , Genes Reguladores , Ratones , Células Madre Pluripotentes/metabolismo , Proteína p53 Supresora de Tumor/fisiologíaRESUMEN
In two previous studies we demonstrated that radiofrequency electromagnetic fields (RF EMF) similar to those emitted by digital radiotelephone handsets affect brain physiology of healthy young subjects exposed to RF EMF (900 MHz; spatial peak specific absorption rate [SAR] 1 W/kg) either during sleep or during the waking period preceding sleep. In the first experiment, subjects were exposed intermittently during an 8 h nighttime sleep episode and in the second experiment, unilaterally for 30 min prior to a 3 h daytime sleep episode. Here we report an extended analysis of the two studies as well as the detailed dosimetry of the brain areas, including the assessment of the exposure variability and uncertainties. The latter enabled a more in depth analysis and discussion of the findings. Compared to the control condition with sham exposure, spectral power of the non-rapid eye movement sleep electroencephalogram (EEG) was initially increased in the 9-14 Hz range in both experiments. No topographical differences with respect to the effect of RF EMF exposure were observed in the two experiments. Even unilateral exposure during waking induced a similar effect in both hemispheres. Exposure during sleep reduced waking after sleep onset and affected heart rate variability. Exposure prior to sleep reduced heart rate during waking and stage 1 sleep. The lack of asymmetries in the effects on sleep EEG, independent of bi- or unilateral exposure of the cortex, may indicate involvement of subcortical bilateral projections to the cortex in the generation of brain function changes, especially since the exposure of the thalamus was similar in both experiments (approx. 0.1 W/kg).
Asunto(s)
Encéfalo/efectos de la radiación , Campos Electromagnéticos/efectos adversos , Frecuencia Cardíaca/efectos de la radiación , Microondas/efectos adversos , Modelos Biológicos , Radiometría/métodos , Sueño/efectos de la radiación , Adulto , Encéfalo/fisiología , Simulación por Computador , Electroencefalografía/efectos de la radiación , Exposición a Riesgos Ambientales/efectos adversos , Exposición a Riesgos Ambientales/análisis , Frecuencia Cardíaca/fisiología , Humanos , Masculino , Dosis de Radiación , Sueño/fisiologíaRESUMEN
Several authors have reported that the meniscus as occurring at the walls of Petri dishes and flasks (solid-liquid interface) can significantly affect the SAR distribution in the entire dish and flask, while others have ignored this effect. In this study, this effect has been comprehensively analyzed by numerical means supported by theoretical considerations. The focus is on E polarization, which results in the most homogeneous exposure for monolayer cell cultures and therefore is the most often applied polarization in exposure setups for risk assessment studies. This includes setups based on TEM cells, waveguides, radial transmission lines (RTL), and HF chambers. The conclusion of this study is that the meniscus and its size have a significant effect on the strength and homogeneity of the induced SAR distribution. Hence, the meniscus needs to be accounted for in the determination of the averaged SAR as well as in the uncertainty assessment. It has also been demonstrated that a voxel size of less than 0.2 mm is needed to predict the SAR values for a monolayer of cells accurately.