Effects of microwave and radio frequency electromagnetic fields on lichens

The effects of electromagnetic fields on lichens were investigated. Field experiments of long duration (1–3 years) were combined with laboratory experiments and theoretical considerations. Samples of the lichen species Parmelia tiliacea and Hypogymnia physodes were exposed to microwaves (2.45 GHz; 0.2, 5, and 50 m W/cm²; and control). Both species showed a substantially reduced growth rate at 50 m W/cm². A differentiation between thermal and nonthermal effects was not possible. Temperature measurements on lichens exposed to microwaves (2.45 GHz, 50 m W/cm²) showed a substantial increase in the surface temperature and an accelerated drying process. The thermal effect of microwave on lichens was verified. The exposure of lichens of both species was repeated near a short-wave broadcast transmitter (9.5 MHz, amplitude modulated; maximum field strength 235 V/m, 332 mA/m). No visible effects on the exposed lichens were detected. At this frequency, no thermal effects were expected, and the experimental results support this hypothesis. Theoretical estimates based on climatic data and literature showed that the growth reductions in the initial experiments could very likely have been caused by drying of the lichens from the heating with microwaves. The results of the other experiments support the hypothesis that the response of the lichens exposed to microwaves was mainly due to thermal effects and that there is a low probability of nonthermal effects. © 1996 Wiley-Liss, Inc.     

Determination of the duty cycle of WLAN for realistic radio frequency electromagnetic field exposure assessment

Wireless Local Area Networks (WLANs) are commonly deployed in various environments. The WLAN data packets are not transmitted continuously but often worst-case exposure of WLAN is assessed, assuming 100% activity and leading to huge overestimations. Actual duty cycles of WLAN are thus of importance for time-averaging of exposure when checking compliance with international guidelines on limiting adverse health effects. In this paper, duty cycles of WLAN using Wi-Fi technology are determined for exposure assessment on large scale at 179 locations for different environments and activities (file transfer, video streaming, audio, surfing on the internet, etc.). The median duty cycle equals 1.4% and the 95th percentile is 10.4% (standard deviation SD = 6.4%). Largest duty cycles are observed in urban and industrial environments. For actual applications, the theoretical upper limit for the WLAN duty cycle is 69.8% and 94.7% for maximum and minimum physical data rate, respectively. For lower data rates, higher duty cycles will occur. Although counterintuitive at first sight, poor WLAN connections result in higher possible exposures. File transfer at maximum data rate results in median duty cycles of 47.6% (SD = 16%), while it results in median values of 91.5% (SD = 18%) at minimum data rate. Surfing and audio streaming are less intensively using the wireless medium and therefore have median duty cycles lower than 3.2% (SD = 0.5–7.5%). For a specific example, overestimations up to a factor 8 for electric fields occur, when considering 100% activity compared to realistic duty cycles.     

Exposure to extremely low frequency magnetic fields in an urban area

Magnetic field levels were studied in an urban area—the city of Cáceres (Spain). The study included systematic spot measurements throughout the city, an analysis of the temporal variation of the magnetic field, and the incorporation of the data into a geographic information system. The levels detected were at most 7.3% of the ICNIRP reference levels, and the highest fields were found in the oldest neighborhoods. Considered overall, the ELF magnetic flux density levels determined in the present study were between those found in residential and in working environments. Knowledge of the levels of such fields in urban areas is therefore fundamental in evaluating the population’s overall exposure, especially for people who work outdoors.     

Behavioral effects in monkeys exposed to extremely low frequency electromagnetic fields

Several experiments with rhesus and squirrel monkeys on the influence of extremely low frequency (ELF) electromagnetic fields found no effects on behavior. Magnetic fields of 0.3 and 1.0 mT with electric fields of below 1 to 29 V/m at frequencies of 7, 10, 15, 45, 60 and 75 Hz were used. Small differences in ambulatory activity and response rate were occasionally observed, but no consistent effects between or within animals on any measures were obtained. No effects on reaction time, interresponse time, match-to-sample performance, and blood constituents were observed. Such previously reported effects may not be a consequence of ELF values alone, but are probably related to other environmental variables.Presented at the Seventh International Biometeorological Congress, 17–23 August 1975, College Park, Maryland, USA.     

The properties of human body phantoms used in calculations of electromagnetic fields exposure by wireless communication handsets or hand-operated industrial devices

According to international guidelines, the assessment of biophysical effects of exposure to electromagnetic fields (EMF) generated by hand-operated sources needs the evaluation of induced electric field (E _in) or specific energy absorption rate (SAR) caused by EMF inside a worker's body and is usually done by the numerical simulations with different protocols applied to these two exposure cases. The crucial element of these simulations is the numerical phantom of the human body. Procedures of E _in and SAR evaluation due to compliance analysis with exposure limits have been defined in Institute of Electrical and Electronics Engineers standards and International Commission on Non-Ionizing Radiation Protection guidelines, but a detailed specification of human body phantoms has not been described. An analysis of the properties of over 30 human body numerical phantoms was performed which has been used in recently published investigations related to the assessment of EMF exposure by various sources. The differences in applicability of these phantoms in the evaluation of E _in and SAR while operating industrial devices and SAR while using mobile communication handsets are discussed. The whole human body numerical phantom dimensions, posture, spatial resolution and electric contact with the ground constitute the key parameters in modeling the exposure related to industrial devices, while modeling the exposure from mobile communication handsets, which needs only to represent the exposed part of the human body nearest to the handset, mainly depends on spatial resolution of the phantom. The specification and standardization of these parameters of numerical human body phantoms are key requirements to achieve comparable and reliable results from numerical simulations carried out for compliance analysis against exposure limits or within the exposure assessment in EMF-related epidemiological studies.     

Exposure to non-ionizing electromagnetic fields emitted from mobile phones induced DNA damage in human ear canal hair follicle cells

The aim of this study was to investigate effect of radiofrequency radiation (RFR) emitted from mobile phones on DNA damage in follicle cells of hair in the ear canal. The study was carried out on 56 men (age range: 30–60 years old)in four treatment groups with n = 14 in each group. The groups were defined as follows: people who did not use a mobile phone (Control), people use mobile phones for 0–30 min/day (second group), people use mobile phones for 30–60 min/day (third group) and people use mobile phones for more than 60 min/day (fourth group). Ear canal hair follicle cells taken from the subjects were analyzed by the Comet Assay to determine DNA damages. The Comet Assay parameters measured were head length, tail length, comet length, percentage of head DNA, tail DNA percentage, tail moment, and Olive tail moment. Results of the study showed that DNA damage indicators were higher in the RFR exposure groups than in the control subjects. In addition, DNA damage increased with the daily duration of exposure. In conclusion, RFR emitted from mobile phones has a potential to produce DNA damage in follicle cells of hair in the ear canal. Therefore, mobile phone users have to pay more attention when using wireless phones.     

Effects of protracted exposure to low intensity radio frequency fields on CHO cells in culture

This study was performed in order to investigate the biological effects of chronic exposure to low intensity radio frequency fields. By using CHO cells in culture, it was possible to extend exposure to several cell generations. The RF field consisted of a 27 MHz magnetic field (6 A/m), which produces a specific absorption rate of 1 W/kg. Exposure was continued for two to five days. The cells were then studied with respect to certain cell biological parameters: vital staining, plating efficiency, growth rate, volume and physical properties of the intracellular water, as measured by NMR. Scanning electron microscopy studies were also performed. A significant difference between exposed and control cells was found only with respect to intracellular water. A 10% decrease in line width which may indicate a corresponding increase in the spin-spin relaxation time was noted after exposure. A change in the colony forming pattern was also observed in thin cultures after two days of exposure.     

Membrane potential and currents of isolated heart muscle cells exposed to pulsed radio frequency fields

The influence of radio frequency (RF) fields of 180, 900, and 1800 MHz on the membrane potential, action potential, L-type Ca(2+) current and potassium currents of isolated ventricular myocytes was tested. The study is based on 90 guinea-pig myocytes and 20 rat myocytes. The fields were applied in rectangular waveguides (1800 MHz at 80, 480, 600, 720, or 880 mW/kg and 900 MHz, 250 mW/kg) or in a TEM-cell (180 MHz, 80 mW/kg and 900 MHz, 15 mW/kg). Fields of 1800 and 900 MHz were pulsed according to the GSM-standard of cellular phones. The specific absorption rates were determined from computer simulations of the electromagnetic fields inside the exposure devices by considering the structure of the physiological test arrangement. The electrical membrane parameters were measured by whole cell patch-clamp. None of the tested electrophysiological parameters was changed significantly by exposure to RF fields. Another physical stimulus, lowering the temperature from 36 degrees C to 24 degrees C, decreased the current amplitude almost 50% and shifted the voltage dependence of the steady state activation parameter d(infinity) and inactivation parameter f(infinity) of L-type Ca(2+) current by about 5 mV. However, at this lower temperature RF effects (900 MHz, 250 mW/kg; 1800 MHz, 480 mW/kg) on L-type Ca(2+) current were also not detected.     

Extremely low frequency pulsed electromagnetic fields increase cell proliferation in lymphocytes from young and aged subjects

The effect of the in vitro exposure to extremely low frequency pulsed electromagnetic fields (PEMFs) on the proliferation of human lymphocytes from 24 young and 24 old subjects was studied. The exposure to PEMFs during a 3-days culture period or during the first 24 hours was able to increase phytohaemagglutinin-induced lymphocyte proliferation in both groups. Such effect was greater in lymphocytes from old people which showed a markedly reduced proliferative capability and, after PEMF exposure, reached values of 3H-TdR incorporation similar to those of young subjects. The relevance of these data for the understanding and the reversibility of the proliferative defects in cells from aged subjects and for the assessment of risk related to the environmental exposure to PEMFs has to be considered.     

Noninvasive methodology for analyzing the response of the system to electromagnetic fields of industrial frequency

Characteristics of the main biochemical components in surface structures and whole cells of unicellular green algae D. tertiolecta and T. viridis before and after the influence of an electromagnetic field (EMF) of industrial frequency were obtained by the method of noninvasive analysis in nonpolarized light. We showed fundamental differences in response to the influence of EMF among cells of algae cultures, which manifest themselves in changes in the main biochemical components and their concentration gradients. These changes led to the transformation of metabolism.     

Effects of high frequency electromagnetic fields on micronucleus formation in CHO-K1 cells

To investigate the effects of high frequency electromagnetic fields (HFEMFs), we assessed the frequency of micronucleus (MN) formation induced by chromosomal breakage or inhibition of spindles during cell division in Chinese hamster ovary (CHO)-K1 cells, using the cytokinesis block micronucleus method. The MN frequency in cells in the inner, middle and outer wells of an annular culture plate was determined for the following four conditions: (1) CHO-K1 cells were exposed to a HFEMF for 18 h at average specific absorption rates (SARs) of 13, 39 and 50 W/kg with input power 7.8 W, and were compared with a sham-exposed control; (2) the cells were also exposed to a HFEMF at SARs of 78 and 100 W/kg with input power 13 W, and were compared with a sham-exposed control; (3) the cells were treated with bleomycin alone or with bleomycin followed by exposure to a HFEMF for 18 h at SARs of 25, 78 and 100 W/kg, and were compared with a bleomycin-treated positive control. The cells treated with bleomycin alone were compared with sham-exposed controls; and (4) As a high temperature control, CHO-K1 cells were incubated at 39 degrees C for 18 h. In study (1), the MN frequency of cells exposed to a HFEMF at a SAR of up to 50 W/kg was not different to that in sham-exposed cells. In study (2), there were statistically significant increases in the MN frequencies of cells in the middle and outer wells of the annular culture plate caused by exposure to a HFEMF at 100 and 78 W/kg, respectively. In study (3), the MN frequencies of cells in the middle (100 W/kg) and outer wells (78 W/kg) of the annular culture plate were statistically higher than that caused by bleomycin-treatment alone. In study (4), there was a statistically significant increase of MN frequency in the cells treated by heat at 39 degrees C.These results indicate that cells exposed to a HFEMF at a SAR of 78 W/kg and higher form MN more frequently than sham-exposed cells, while exposure to a HFEMF at up to 50 W/kg does not induce MN formation. In addition, a HFEMF at a SAR of 78 W/kg and higher may potentiate MN formation induced by bleomycin-treatment.     

Effects of extremely low frequency electromagnetic fields on intracellular calcium transients in cardiomyocytes

Abstract

Calcium transients play an essential role in cardiomyocytes and electromagnetic fields (EMF) and affect intracellular calcium levels in many types of cells. Effects of EMF on intracellular calcium transients in cardiomyocytes are not well studied. The aim of this study was to assess whether extremely low frequency electromagnetic fields (ELF-EMF) could affect intracellular calcium transients in cardiomyocytes. Cardiomyocytes isolated from neonatal Sprague-Dawley rats were exposed to rectangular-wave pulsed ELF-EMF at four different frequencies (15?Hz, 50?Hz, 75?Hz and 100?Hz) and at a flux density of 2?mT. Intracellular calcium concentration ([Ca²⁺]_i) was measured using Fura-2/AM and spectrofluorometry. Perfusion of cardiomyocytes with a high concentration of caffeine (10?mM) was carried out to verify the function of the cardiac Na⁺/Ca²⁺ exchanger (NCX) and the activity of sarco(endo)-plasmic reticulum Ca²⁺-ATPase (SERCA2a). The results showed that ELF-EMF enhanced the activities of NCX and SERCA2a, increased [Ca²⁺]_i baseline level and frequency of calcium transients in cardiomyocytes and decreased the amplitude of calcium transients and calcium level in sarcoplasmic reticulum. These results indicated that ELF-EMF can regulate calcium-associated activities in cardiomyocytes.     

Increase in radiation-induced HPRT gene mutation frequency after nonthermal exposure to nonionizing 60 Hz electromagnetic fields

It is widely accepted that moderate levels of nonionizing electric or magnetic fields, for example 50/60 Hz magnetic fields of about 1 mT, are not mutagenic. However, it is not known whether such fields can enhance the action of known mutagens. To explore this question, a stringent experimental protocol, which included blinding and systematic negative controls, was implemented, minimizing the possibility of observer bias or experimental artifacts. As a model system, we chose to measure mutation frequencies induced by 2 Gy gamma rays in the redox-sensitive hypoxanthine-guanine phosphoribosyl transferase (HPRT) gene in Chinese hamster ovary cells. We tested whether a 12-h exposure to a 60 Hz sinusoidally oscillating magnetic-flux density (Brms = 0.7 mT) could affect the mutagenic effects of ionizing radiation on the HPRT gene locus. We determined that the magnetic-field exposure induced an approximate 1.8-fold increase in HPRT mutation frequency. Additional experiments at Brms = 0.23 and 0.47 mT revealed that the effect was reduced at lower flux densities. The field exposure did not enhance radiation-induced cytotoxicity or mutation frequencies in cells not exposed to ionizing radiation. These results suggest that moderate-strength, oscillating magnetic fields may act as an enhancer of mutagenesis in mammalian cells.     

Effect of electromagnetic radiation of radio frequency (340 and 800 MHz) on liposomes from dimyristoyl lecithin

Using the liposomes prepared from dimyristoyl lecithin at temperature below that of phase transition, its was shown that the annealing of liposomes by 340- and 800-MHz microwave radiation required less integral heating of the samples, than it should be expected from the experiments on heating the samples in a thermostat.