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1.
Dielectric heaters and sealers present the most common source of occupational exposure to excessive radio frequency (RF) fields. These systems are used industrially to heat or melt dielectric materials. Nowadays, the effects of high frequency electromagnetic (EM) fields on the health have been discussed frequently but there are few health studies done for workers around dielectric heaters and sealers. In this study, the leakage fields around dielectric heaters and sealers (27.12?MHz) were measured in MKE--Mechanical and Chemical Industry Corporation, Gazi Rocket Factory and evaluated in terms of standards. It has been observed that operators exposed to same RF fields with occupational exposure limits. Many workers have health complaints, such as elevated body temperatures in the factory. Safe distances or areas for workers should be recommended in these systems. Protective measures could be implemented to minimize these exposures. Further measurements and occupational exposure studies of RF exposed women and men are needed to demonstrate the levels of exposed Radio Frequency Radiation (RFR). Precautions should therefore be taken either to reduce the leakage fields or minimise the exposed fields.  相似文献   

2.
Electromagnetic field exposure and health among RF plastic sealer operators   总被引:2,自引:0,他引:2  
Operators of RF plastic sealers (RF operators) are an occupational category highly exposed to radiofrequency electromagnetic fields. The aim of the present study was to make an appropriate exposure assessment of RF welding and examine the health status of the operators. In total, 35 RF operators and 37 controls were included. The leakage fields (electric and magnetic field strength) were measured, as well as induced and contact current. Information about welding time and productivity was used to calculate time integrated exposure. A neurophysiological examination and 24 h ECG were also carried out. The participants also had to answer a questionnaire about subjective symptoms. The measurements showed that RF operators were exposed to rather intense electric and magnetic fields. The mean values of the calculated 6 min, spatially averaged E and H field strengths, in line with ICNIRP reference levels, are 107 V/m and 0.24 A/m, respectively. The maximum measured field strengths were 2 kV/m and 1.5 A/m, respectively. The induced current in ankles and wrists varied, depending on the work situation, with a mean value of 101 mA and a maximum measured value of 1 A. In total, 11 out of 46 measured RF plastic sealers exceeded the ICNIRP reference levels. RF operators, especially the ready made clothing workers had a slightly disturbed two-point discrimination ability compared to a control group. A nonsignificant difference between RF operators and controls was found in the prevalence of subjective symptoms, but the time integrated exposure parameters seem to be of importance to the prevalence of some subjective symptoms: fatigue, headaches, and warmth sensations in the hands. Further, RF operators had a significantly lower heart rate (24 h registration) and more episodes of bradycardia compared to controls.  相似文献   

3.
The mortality experience of a cohort of Italian plastic-ware workers exposed to radiofrequency (RF)-electromagnetic fields generated by dielectric heat sealers was investigated. Follow-up extended from 1962 to 1992. The standardised mortality ratio (SMR) analysis was restricted to 481 women workers, representing 78% of the total person-years at risk. Mortality from malignant neoplasms was slightly elevated, and increased risks of leukemia and accidents were detected. The all-cancer SMR was higher among women employed in the sealing department, where exposure to RF occurred, than in the whole cohort. This study raises interest in a possible association between exposure to RF radiation and cancer risk. However, the study power was very small, and the possible confounding effects of exposure to solvents and vinyl chloride monomer (VCM) could not be ruled out. The hypothesis of an increased risk of cancer after radiofrequency exposure should be further explored by means of analytical studies characterised by adequate power and more accurate exposure assessment. Bioelectromagnetics 18:418–421, 1997. © 1997 Wiley-Liss, Inc.  相似文献   

4.
The World Health Organization (WHO), the International Commission on Non-Ionizing Radiation Protection (ICNIRP), and the German and Austrian Governments jointly sponsored an international seminar in November of 1996 on the biological effects of low-level radiofrequency (RF) electromagnetic fields. For purposes of this seminar, RF fields having frequencies only in the range of about 10 MHz to 300 GHz were considered. This is one of a series of scientific review seminars held under the International Electromagnetic Field (EMF) Project to identify any health hazards from EMF exposure. The scientific literature was reviewed during the seminar and expert working groups formed to provide a status report on possible health effects from exposure to low-level RF fields and identify gaps in knowledge requiring more research to improve health risk assessments. It was concluded that, although hazards from exposure to high-level (thermal) RF fields were established, no known health hazards were associated with exposure to RF sources emitting fields too low to cause a significant temperature rise in tissue. Biological effects from low-level RF exposure were identified needing replication and further study. These included in vitro studies of cell kinetics and proliferation effects, effects on genes, signal transduction effects and alterations in membrane structure and function, and biophysical and biochemical mechanisms for RF field effects. In vivo studies should focus on the potential for cancer promotion, co-promotion and progression, as well as possible synergistic, genotoxic, immunological, and carcinogenic effects associated with chronic low-level RF exposure. Research is needed to determine whether low-level RF exposure causes DNA damage or influences central nervous system function, melatonin synthesis, permeability of the blood brain barrier (BBB), or reaction to neurotropic drugs. Reported RF-induced changes to eye structure and function should also be investigated. Epidemiological studies should investigate: the use of mobile telephones with hand-held antennae and incidence of various cancers; reports of headache, sleep disturbance, and other subjective effects that may arise from proximity to RF emitters, and laboratory studies should be conducted on people reporting these effects; cohorts with high occupational RF exposure for changes in cancer incidence; adverse pregnancy outcomes in various highly RF exposed occupational groups; and ocular pathologies in mobile telephone users and in highly RF exposed occupational groups. Studies of populations with residential exposure from point sources, such as broadcasting transmitters or mobile telephone base stations have caused widespread health concerns among the public, even though RF exposures are very low. Recent studies that may indicate an increased incidence of cancer in exposed populations should be investigated further. Bioelectromagnetics 19:1–19, 1998. © 1998 Wiley-Liss, Inc.  相似文献   

5.
The 1998 International Commission for Non-Ionising Radiation (ICNIRP) Guidelines for human exposure to radiofrequency (RF) fields contain a recommendation to assess the potential impact of metallic implants in workers exposed up to the allowable occupational field limits. This study provides an example of how numerical electromagnetic (EM) and thermal modelling can be used to determine whether scattered RF fields around metallic implants in workers exposed to allowable occupational ambient field limits will comply with the recommendations of relevant standards and guidelines. A case study is performed for plane wave exposures of a 50 mm diameter titanium cranioplasty plate, implanted around 5-6 mm under the surface of the forehead. The level of exposures was set to the ambient power flux density limits for occupational exposures specified in the 1998 ICNIRP guidelines and the current 1999 IEEE C95.1 standard over the frequency range 100-3000 MHz. Two distinct peak responses were observed. There was a resonant response for the whole implant at 200-300 MHz where the maximum dimension of the implant is around a third of the wavelength of the RF exposure. This, however, resulted in relatively low peak specific energy absorption rate (SAR) levels around the implant at the exposure limits. Between 2100-2800 MHz, a second SAR concentrating mechanism of constructive interference of the wave reflected back and forth between the air-scalp interface and the scalp-plate interface resulted in higher peak SARs that were within the allowable limits for the ICNIRP exposures, but not for the IEEE C95.1 exposures. Moreover, the IEEE peak SAR limits were also exceeded, to a lesser degree, even when the implant was not present. However, thermal modelling indicated that the peak SAR concentrations around the implant did not result in any peak temperature rise above 1 degrees C for occupational exposures recommended in the ICNIRP guidelines, and hence would not pose any significant health risk.  相似文献   

6.
Potential health effects of static magnetic fields have received far less attention than, for example, power frequency or radiofrequency fields. Static fields are found in certain occupational settings, e.g. in the aluminium and chloralkali industries, in arc-welding processes, and certain railways systems. Magnetic resonance imaging (MRI) for medical diagnosis is another source. This paper summarizes the epidemiological evidence of static magnetic field exposure and long-term health effects. There are only a few epidemiological studies available, and the majority of these have focused on cancer risks. There are some reports on reproductive outcomes, and sporadic studies of other outcomes. Overall, few occupational studies have focused specifically on effects of static magnetic field exposure, and exposure assessment have consequently been poor or non-existent. Results from studies that have estimated static magnetic field exposure have not indicated any increased cancer risks, but they are generally based on small numbers of cases and crude exposure assessment. Control of confounding has been limited, and it is likely that the “healthy worker” effect have influenced the results. A few studies have reported results on reproductive outcomes among aluminium workers and MRI operators, but limitations in study designs prevent conclusions. A problem in epidemiological studies of static magnetic fields is that workers in exposed occupations are also exposed to a wide variety of other potentially harmful agents, including some known carcinogens. In conclusion, the available evidence from epidemiological studies is not sufficient to draw any conclusions about potential health effects of static magnetic field exposure.  相似文献   

7.
We estimate that there are about 100,000 workers from different disciplines, such as radiographers, nurses, anesthetists, technicians, engineers, etc., who can be exposed to substantial electromagnetic fields (compared to normal background levels) around magnetic resonance imaging (MRI) scanners. There is a need for well‐designed epidemiological studies of MRI workers but since the exposure from MRI equipment is a very complex mixture of static magnetic fields, switched gradient magnetic fields, and radiofrequency electromagnetic fields (RF EMF), it is necessary to discuss how to assess the exposure in epidemiological studies. As an alternative to the use of job title as a proxy of exposure, we propose an exposure categorization for the different professions working with MRI equipment. Specifically, we propose defining exposure in three categories, depending on whether people are exposed to only the static field, to the static plus switched gradient fields or to the static plus switched gradient plus RF fields, as a basis for exposure assessment in epidemiological studies. Bioelectromagnetics 34:81–84, 2013. © 2012 Wiley Periodicals, Inc.  相似文献   

8.
Radiofrequency electric and magnetic fields have been measured around 11 large broadcast stations and tall FM/TV towers in Sweden. The results show that operating personnel may be exposed to fields exceeding by several times the present standard for occupational exposure to RF radiation. Maintenance personnel are especially vulnerable to exposure when climbing energized towers. The present study indicates that the transmitters should be switched off during the performance of certain tasks on the tower. Safe passage of maintenance personnel near energized antennas of certain types is impossible without a drastic reduction of the transmitted power. In the stations, the RF leakage radiation was generally low, but when work was done with the cabinet doors of the transmitter open, high field strengths were found in the vicinity of the transmitter even though it was switched off. It was found that the transmitter acted as a tuned receiver of energy from the other transmitters.  相似文献   

9.
Physiological processes in organisms can be influenced by extremely low-frequency (ELF) electromagnetic energy. Biological effect studies have great importance; as well as measurement studies since they provide information on the real exposure situations. In this study, the leakage magnetic fields around a transformer were measured in an apartment building in Küçükçekmece, Istanbul, and the measurement results were evaluated with respect to the international exposure standards. The transformer station was on the bottom floor of a three-floor building. It was found that people living and working in the building were exposed to ELF magnetic fields higher than the threshold magnetic field value of the International Agency for Research on Cancer (IARC). Many people living in this building reported health complaints such as immunological problems of their children. There were child-workers working in the textile factories located in the building. Safe distances or areas for these people should be recommended. Protective measures could be implemented to minimize these exposures. Further residential exposure studies are needed to demonstrate the exposure levels of ELF magnetic fields. Precautions should, therefore, be taken either to reduce leakage or minimize the exposed fields. Shielding techniques should be used to minimize the leakage magnetic fields in such cases.  相似文献   

10.
We have plotted data from a number of studies on the range of radiofrequency (RF) field levels associated with a variety of environmental and occupational sources. Field intensity is shown in units of volts/meter (V/m) for electric field strength and amps/meter (A/m) for magnetic field strength. Duty factors, modulation frequencies, and modulation indices are also reported for some sources. This paper is organized into seven sections, each cataloging sources into appropriate RF frequency bands from very-low frequency (VLF) to super-high frequency (SHF), and covers frequencies from 10 kHz to 30 GHz. Sources included in this summary are the following: Coast Guard navigational transmitters, a Navy VLF transmitter, computer visual display terminals (VDTs), induction stoves or range tops, industrial induction and dielectric heaters, radio and television broadcast transmitters, amateur and citizens band (CB) transmitters, medical diathermy and electrosurgical units, mobile and handheld transmitters, cordless and cellular telephones, microwave ovens, microwave terrestrial relay and satellite uplinks, and police, air traffic, and aircraft onboard radars. For the sources included in this summary, the strongest fields are found near industrial induction and dielectric heaters, and close to the radiating elements or transmitter leads of high power antenna systems. Handheld transmitters can produce near fields of about 500 V/m at the antenna. Fields in the general urban environment are principally associated with radio and TV broadcast services and measure about 0.1 V/m root-mean-square (rms). Peak fields from air traffic radars sampled in one urban environment were about 10 V/m, 300 times greater than the rms value of 0.03 V/m when the duty factor associated with antenna rotation and pulsing are factored in. Bioelectromagnetics 18: 563–577, 1997. Published 1997 Wiley-Liss, Inc.
  • 1 This article is a US Government work and, as such, is in the public domain in the United States of America.
  •   相似文献   

    11.
    Radiofrequency (RF) radiation is used in a variety of workplaces. In addition to RF radiation, many workers are concurrently exposed to numerous chemicals; exposed workers include those involved with the microelectronics industry, plastic sealers, and electrosurgical units. The developmental toxicity of RF radiation is associated with the degree and duration of hyperthermia induced by the exposure. Previous animal research indicates that hyperthermia induced by an elevation in ambient temperature can potentiate the toxicity and teratogenicity of some chemical agents. We previously demonstrated that combined exposure to RF radiation (10 MHz) and the industrial solvent, 2-methoxyethanol (2ME), produces enhanced teratogenicity in rats. The purpose of the present research is to determine the effects of varying the degree and duration of hyperthermia induced by RF radiation (sufficient to maintain colonic temperatures at control [38.5], 39.0, 40.0, or 41.0 °C for up to 6 h) and 2ME (100 mg/kg) administered on gestation day 13 of rats. Focusing on characterizing the dose-response pattern of interactions, this research seeks to determine the lowest interactive effect level. Day 20 fetuses were examined for external and skeletal malformations. The results are consistent with previous observations. Significant interactions were observed between 2ME and RF radiation sufficient to maintain colonic temperatures at 41 °C for 1 h, but no consistent interactions were seen at lower temperatures even with longer durations. These data indicate that combined exposure effects should be considered when developing both RF radiation and chemical exposure guidelines and intervention strategies. Bioelectromagnetics 18:349–359, 1997. © 1997 Wiley-Liss, Inc.  相似文献   

    12.
    Ninety-three adult males working at AM broadcasting stations (0.738–1.503 MHz) or radio line stations volunteered for cardiological examinations. The examinations included routine electrocardiogram (ECG) at rest, analysis of heart rate variability (HRV), Holter 24-h ECG, and 24-h ambulatory blood pressure (ABP). Results of cardiological examinations were correlated with individual exposure to EM fields (maximum exposure levels during working shift, daily exposure dose, and cumulative lifetime exposure). Of the 93 subjects qualified for the study, 71 (76.3%) experienced occupational RF exposure, while the remaining 22 (23.7%) had no history of regular EM exposure. ECG abnormalities or pathological changes were recorded quite frequently (50–70%) in both exposed and control populations. There was no correlation with exposure levels. We found measurable effects in the HRV and ABP parameters in the EM-exposed population, but none could be assigned clinical significance. The results suggest that exposure of workers to EM fields can cause slight disturbances in autonomic cardiac regulation and slight dysregulation of circadian rhythms in workers exposed to EM fields exceeding 100–150 V/m.  相似文献   

    13.
    Much of the research and reviews on extremely low frequency (ELF) electric and magnetic fields (EMFs) have focused on magnetic rather than electric fields. Some have considered such focus to be inappropriate and have argued that electric fields should be part of both epidemiologic and laboratory work. This paper fills the gap by systematically and critically reviewing electric‐fields literature and by comparing overall strength of evidence for electric versus magnetic fields. The review of possible mechanisms does not provide any specific basis for focusing on electric fields. While laboratory studies of electric fields are few, they do not indicate that electric fields should be the exposure of interest. The existing epidemiology on residential electric‐field exposures and appliance use does not support the conclusion of adverse health effects from electric‐field exposure. Workers in close proximity to high‐voltage transmission lines or substation equipment can be exposed to high electric fields. While there are sporadic reports of increase in cancer in some occupational studies, these are inconsistent and fraught with methodologic problems. Overall, there seems little basis to suppose there might be a risk for electric fields, and, in contrast to magnetic fields, and with a possible exception of occupational epidemiology, there seems little basis for continued research into electric fields. Bioelectromagnetics 31:89–101, 2010. © 2009 Wiley‐Liss, Inc.  相似文献   

    14.
    There is a paucity of information regarding the long-term health effects associated with exposure to static magnetic fields. Perceptual and other acute effects have been demonstrated above a threshold of about 2 T, and these form the basis for human exposure standards at present. Exposures well above this threshold are increasingly becoming more common as the technology associated with magnetic resonance imaging advances. Therefore, priority should be given to assessing the health risks associated with exposures to such fields. Studies should include a prospective cohort study investigating cancer risks of workers and patients exposed to fields in excess of 2 T, a study investigating effects on human cognitive performance from repeated exposures, and a molecular biology study investigating acute changes in genomic responses in volunteers exposed to fields of up to 8 T. Studies investigating the effects of long-term exposure on cancer, and on neurobehavioural development are also recommended using animals, where the use of transgenic models is encouraged. In addition, dosimetric studies should be conducted using high-resolution male, female and pregnant voxel phantoms, as should theoretical studies investigating the local currents induced in the eye and in the heart by movement during exposure. Finally, studies are recommended to investigate further the ability of static magnetic fields to significantly affect radical pair reactions in biological systems.  相似文献   

    15.
    We evaluated the methods and results of nine cohort studies dealing with the biological effects on human health from exposure to radiofrequencies/microwaves, published between 1980 and 2002. The size of the cohorts varied between 304 (3,362 person years) and nearly 200,000 persons (2.7 million person years). As exposures were defined: dielectric heaters in a plastic manufacturing plant, working with radio devices (professional and amateur), production of wireless communication technologies, radar devices of the Canadian police, radar units used by the military as well as artificially produced electromagnetic pulses similar to those after a nuclear explosion. In all studies (except one that used a qualitative job-exposure-matrix) either the duration of occupational work as an approximation to actual exposure was determined or a simple yes/no differentiation was used based on a definition of high-exposed and/or low-exposed (occupational) groups. Either total mortality, cancer mortality, cancer incidence or other outcomes were estimated. In most of the studies, an increased risk for various types of cancer was found in exposed study participants, although in different organs. The overall results were, however, inconsistent. The most important limitations of the studies were the lack of measurements referring to past and current exposures and, thus, the unknown details on actual exposure, the use of possibly biased data as well as the lack of adjustment for potential confounders and the use of indirect standardization techniques. Due to these limitations and the inconsistencies of the results it has to be concluded that the studies give no evidence of high frequency emissions causing cancer.  相似文献   

    16.
    Biological effects and health implications of radio frequency (RF) electromagnetic fields have been a subject of scientific investigation for more than 50 years. It has become a focus of attention because of the expanded use of RF radiation in the frequency range between 300 MHz and 6 GHz for wireless communication over the past decade. Another cause for the attention is the uncertainty of some observed responses and lack of understanding of the mechanism of interaction of RF electromagnetic fields with biological systems. At present, considerable efforts are devoted to developing and revising RF exposure standards. Each of these efforts should aim to make explicit the philosophy and process by which they reason and decide guidelines for deeming exposure as safe. Furthermore, the reconciliation of philosophies of protection will definitely be an asset, in practice, to those interested in international harmonization of RF exposure standards.  相似文献   

    17.
    Data are presented on ankle-specific SARs and foot currents as a function of strengths of radio-frequency electromagnetic fields encountered by operators of dielectric heaters. The determination of foot currents was based on near-field exposures in which reactive coupling dominates, and which can result in substantial SARs in exposed workers. The operators were located less than one wavelength from--usually within one meter of--the dielectric heaters, which generated fields at frequencies from 6.5 to 65 MHz. At distances normally assumed by workers, maximal strengths of electric fields ranged from 10(4) to 2.4 x 10(6) V2/m2; maximal strengths of magnetic fields ranged from 5.0 x 10(-3) to 33.3 A2/m2. Currents through both feet to ground were measured while operators stood where they normally worked. Maximal currents ranged from 3 to 617 mA, rms. Nearly 27 percent of the dielectric heaters induced foot currents that exceeded the 200-mA limit that has been proposed for a new ANSI C95.1 standard. Twenty percent of the heaters induced foot currents that exceeded 350 mA. SARs in ankles were calculated from foot currents, and they approximated 5 W/kg at 100 mA, 29 W/kg at 250 mA, and 57 W/kg at 350 mA. The maximal SAR in the ankle was approximately 176 W/kg at 617 mA.  相似文献   

    18.
    Cellular effects of electromagnetic fields   总被引:3,自引:0,他引:3  
    Studies at the cellular level are needed to reveal the cellular and molecular biological mechanisms underlying the biological effects and possible health implications of non-ionising radiation, such as extremely low frequency (ELF) magnetic fields (MFs) and radiofrequency (RF) fields. Our research group has studied the effects of 50 Hz ELF MFs (caused by power lines and electric devices) and 872 MHz or 900 MHz RFs (emitted by mobile phones and their base stations) on cellular ornithine decarboxylase activity, cell cycle kinetics, cell proliferation, and necrotic or apoptotic cell death. For RFs, pulse-modulated (217 Hz modulation frequency corresponding a global system for mobile communication-type signal) or continuous wave (unmodulated) signals were used. To expose the cell cultures to MFs or RFs, specially developed exposure systems were used, where levels of electromagnetic field exposure and the conditions of cell culture could be precisely controlled. A coexposure approach was used in many studies, i.e. the cell cultures were exposed to other stressors in addition to MFs or RFs. Ultraviolet radiation, serum deprivation, or fresh medium addition, were used as co-exposures. The results presented in this short review show that the effects of mere MFs or RF on cell culture models are quite minor, but that various co-exposure approaches warrant additional study.  相似文献   

    19.
    We discuss initial magnetic field strength measurements made around radiofrequency (RF) induction heaters. These measurements were made with a monitor developed for the National Institute for Occupational Safety and Health (NIOSH) by the National Bureau of Standards (NBS). The monitor has a dynamic range of .01 to 10,000 A2/m2, a frequency range of 300 kHz to 100 MHz, an isotropic response (+/- .3 dB) with three mutally orthogonal loop antennas that have the ability to measure and display each of three orthogonal magnetic field components, a high probe burnout protection level of 20,000 A2/m2, and an accuracy of +/- 1.0 dB at 13 calibration frequencies. The portable survey monitor was used to measure the magnetic field strengths in the vicinity of 16 RF induction heaters. Typically these induction heaters are operated continuously for several hours. The maximum field strengths (without duty factor correction) ranged from 15 to 4,500 A2/m2 and were measured 5 to 51 cm from the loop applicators of the induction heaters. At locations commonly occupied by workers (ie, approximately 30 to 76 cm from heaters), the fields ranged from .01 to 300 A2/m2 (without duty factor correction).  相似文献   

    20.
    Fifth generation networks (5G) will be associated with a partial shift to higher carrier frequencies, including wavelengths comparable in size to insects. This may lead to higher absorption of radio frequency (RF) electromagnetic fields (EMF) by insects and could cause dielectric heating. The yellow fever mosquito (Aedes aegypti), a vector for diseases such as yellow and dengue fever, favors warm climates. Being exposed to higher frequency RF EMFs causing possible dielectric heating, could have an influence on behavior, physiology and morphology, and could be a possible factor for introduction of the species in regions where the yellow fever mosquito normally does not appear. In this study, the influence of far field RF exposure on A. aegypti was examined between 2 and 240 GHz. Using Finite Difference Time Domain (FDTD) simulations, the distribution of the electric field in and around the insect and the absorbed RF power were found for six different mosquito models (three male, three female). The 3D models were created from micro-CT scans of real mosquitoes. The dielectric properties used in the simulation were measured from a mixture of homogenized A. aegypti. For a given incident RF power, the absorption increases with increasing frequency between 2 and 90 GHz with a maximum between 90 and 240 GHz. The absorption was maximal in the region where the wavelength matches the size of the mosquito. For a same incident field strength, the power absorption by the mosquito is 16 times higher at 60 GHz than at 6 GHz. The higher absorption of RF power by future technologies can result in dielectric heating and potentially influence the biology of this mosquito.  相似文献   

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