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Biomedical subjects

M H Repacholi

Publications and source records attributed to M H Repacholi.

At least 19 recordsLinked to original sources
PubMed2003

WHO's health risk assessment of ELF fields.

The World Health Organization (WHO), the International Commission on Non-Ionizing Radiation Protection (ICNIRP), WHO's scientific collaborating centres (including the UK's National Radiological Protection Board (NRPB)) and over 50 participating Member States are participants of WHO's International EMF Project. As part of WHO's health risk assessment process for extremely low frequency fields (ELF), this workshop was convened by NRPB to assist WHO in evaluating the potential health impacts of electrical currents and fields induced by ELF in molecules, cells, tissues and organs of the body. This paper describes the process by which WHO will conduct its health risk assessment. WHO is also trying to provide information on why exposure to ELF magnetic fields seems to be associated with an increased incidence of childhood leukaemia. Are there mechanisms that could lead to this health outcome or does the epidemiological evidence incorporate biases or other factors that need to be further explored?

Child↗
PubMed2002

Health and safety implications of exposure to electromagnetic fields in the frequency range 300 Hz to 10 MHz.

An international seminar on health effects of exposure to electromagnetic fields (EMF) in the frequency range from 300 Hz to 10 MHz (referred to as the Intermediate Frequency (IF) range) was held in Maastricht, Netherlands, on 7-8 June 1999. The seminar, organized under the International EMF Project, was sponsored jointly by the World Health Organization (WHO), the International Commission on Non-Ionizing Radiation Protection (ICNIRP), and the Government of the Netherlands. This report does not attempt to summarize all of the material presented at the conference, but focuses on sources of exposure, biophysical and dosimetric considerations pertinent to extrapolating biological data from other frequency ranges to IF and identifies potential health concerns and needs for developing exposure guidelines. This paper is based on presentations at the conference and reports of working groups consisting of the speakers and other experts. It concludes with recommendations for further research aimed at improving health risk assessments in this frequency range.

Biophysics↗
PubMed2001

Health risks from the use of mobile phones.

Widespread concerns have been raised about the possibility that exposure to the radiofrequency (RF) fields from mobile telephones or their base stations could affect people's health. Such has been the rapid growth of mobile telecommunications that there will be about one billion mobile phone users before 2005. Already there are more mobile than fixed-line users. Developing countries are establishing mobile telecommunications rather than the more expensive fixed-line systems. Thus, if there is any impact on health from mobile telephones, it will affect everyone in the world. The World Health Organization (WHO) established the International EMF Project in 1996 to evaluate the science, recommend research to fill any gaps in knowledge and to conduct formal health risk assessments of RF exposure once recommended research had been completed. In addition, the UK government established an independent expert group to review all the issues concerning health effects of mobile telephones and siting of base stations. Cancer has been suggested as an outcome of exposure to mobile telephones by some scientific reports. This paper reviews the status of the science and WHO's programme to address the key issues. In addition, the main conclusions and recommendations of the UK expert group will be summarised.

Brain↗
PubMed1999

Interaction of static and extremely low frequency electric and magnetic fields with living systems: health effects and research needs.

An international seminar was held June 4-6, 1997, on the biological effects and related health hazards of ambient or environmental static and extremely low frequency (ELF) electric and magnetic fields (0-300 Hz). It was cosponsored by the World Health Organization (WHO), the International Commission on Non-Ionizing Radiation Protection (ICNIRP), the German, Japanese, and Swiss governments. Speakers provided overviews of the scientific literature that were discussed by participants of the meeting. Subsequently, expert working groups formulated this report, which evaluates possible health effects from exposure to static and ELF electric and magnetic fields and identifies gaps in knowledge requiring more research to improve health risk assessments. The working groups concluded that, although health hazards exist from exposure to ELF fields at high field strengths, the literature does not establish that health hazards are associated with exposure to low-level fields, including environmental levels. Similarly, exposure to static electric fields at levels currently found in the living and working environment or acute exposure to static magnetic fields at flux densities below 2 T, were not found to have demonstrated adverse health consequences. However, reports of biological effects from low-level ELF-field exposure and chronic exposure to static magnetic fields were identified that need replication and further study for WHO to assess any possible health consequences. Ambient static electric fields have not been reported to cause any direct adverse health effects, and so no further research in this area was deemed necessary.

Animals↗
PubMed1998

Low-level exposure to radiofrequency electromagnetic fields: health effects and research needs.

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.

Animals↗
PubMed1998

A test of lymphoma induction by long-term exposure of E mu-Pim1 transgenic mice to 50 Hz magnetic fields.

E mu-Pim1 transgenic mice expressing a dysregulated Pim1 oncogene in their lymphoid cells were used to test whether exposure to 50 Hz magnetic fields can increase the frequency of malignant lymphoma in mice of a strain predisposed to develop such tumors spontaneously at low incidence. Specific-pathogen-free female mice were allocated randomly into groups of approximately 100 at 6-8 weeks of age and then exposed for 20 h/day for up to 18 months to sinusoidal magnetic fields of 0, 1, 100 or 1000 microT, or 1000 microT pulsed 15 min on and 15 min off. Additional E mu-Pim1 mice were injected with ethylnitrosourea (50 mg/kg body weight) as positive controls for enhanced lymphomagenesis; these yielded a cumulative incidence of lymphoma of 60% in 9 months. A lethal, transgene-dependent renal glomerular disease occurred at a frequency that varied from 9% to 19% among the groups, but the increase was statistically significant only at the 1000-microT exposure. Lymphoblastic and non-lymphoblastic (predominantly follicular) lymphomas were seen in 26 to 35% of the exposed mice, but at no significantly higher incidence than the 29% found in the sham-exposed mice. Hence we conclude that the lymphoma-prone mice did not reveal any tumorigenic effect of long-term exposure to 50 Hz magnetic fields.

Animals↗
PubMed1997

Radiofrequency field exposure and cancer: what do the laboratory studies suggest?

Significant concern has been raised about possible health effects from exposure to radiofrequency (RF) electromagnetic fields, especially after the rapid introduction of mobile telecommunications systems. Parents are especially concerned with the possibility that children might develop cancer after exposure to the RF emissions from mobile telephone base stations erected in or near schools. These questions have followed scientific reports suggesting that residence near high voltage power lines may to be associated with an increased childhood leukemia risk. Epidemiologic studies have been plagued by poor RF exposure assessment and differences in methodology. There are no high-quality epidemiologic studies that can be used to evaluate health risks from RF exposure. Laboratory studies in this area have been somewhat confusing. Some animal studies suggest that RF fields accelerate the development of sarcoma colonies in the lung, mammary tumors, skin tumors, hepatomas, and sarcomas. A substantial RF-induced increase in lymphoma incidence in transgenic mice exposed for up to 18 months has also been reported. In contrast, other studies have not found carcinogenic effects. These conflicting results indicate the need for more well-conducted studies on laboratory animals, supplemented with high-quality in vitro studies to identify effects that need further research in vivo, and to characterize any acting mechanisms, especially at low RF field levels. This paper provides a review of the laboratory studies and indicates what conclusions about RF-induced cancer can be drawn.

Animals↗
PubMed1997

Lymphomas in E mu-Pim1 transgenic mice exposed to pulsed 900 MHZ electromagnetic fields.

Whether radiofrequency (RF) fields are carcinogenic is controversial; epidemiological data have been inconclusive and animal tests limited. The aim of the present study was to determine whether long-term exposure to pulse-modulated RF fields similar to those used in digital mobile telecommunications would increase the incidence of lymphoma in E mu-Pim1 transgenic mice, which are moderately predisposed to develop lymphoma spontaneously. One hundred female E mu-Pim1 mice were sham-exposed and 101 were exposed for two 30-min periods per day for up to 18 months to plane-wave fields of 900 MHz with a pulse repetition frequency of 217 Hz and a pulse width of 0.6 ms. Incident power densities were 2.6-13 W/m2 and specific absorption rates were 0.008-4.2 W/kg, averaging 0.13-1.4 W/kg. Lymphoma risk was found to be significantly higher in the exposed mice than in the controls (OR = 2.4. P = 0.006, 95% CI = 1.3-4.5). Follicular lymphomas were the major contributor to the increased tumor incidence. Thus long-term intermittent exposure to RF fields can enhance the probability that mice carrying a lymphomagenic oncogene will develop lymphomas. We suggest that such genetically cancer-prone mice provide an experimental system for more detailed assessment of dose-response relationships for risk of cancer after RF-field exposure.

Animals↗
PubMed1990

Cancer from exposure to 50/60 Hz electric and magnetic fields--a major scientific debate.

Millions of dollars are presently being spent on both laboratory and epidemiological studies to determine if an association exists between the exposure of humans to 50/60 Hz electromagnetic fields and cancer incidence. This review discusses findings from both of these areas of study and focuses attention on their relevance to the electromagnetic field-cancer debate. So far, the conflicting results from epidemiology have succeeded only in raising the concerns of both occupationally exposed groups and the general public. A few hypotheses have suggested possible mechanisms by which fields could exert biological effects. However the studies on which these hypotheses are based require substantiation and further, there is insufficient evidence to indicate if the biological effects observed in these studies have any relevance to human health. It will be at least another three to five years before there are results from large scale human studies presently being designed or undertaken. From an objective review of existing scientific data it can only be concluded that exposure to 50/60 Hz electric and magnetic fields at levels occurring in our environment have not been established to lead to cancer in humans. Sufficient gaps in our knowledge exist however to recommend that research continue, especially in areas identified in the text. To assist the casual reader of this subject the complex issues of cancer initiation and promotion are considered.

Animals↗
PubMed1983

Operator exposure to radiofrequency fields near a hyperthermia device.

Radiofrequency-induced hyperthermia has recently gained acceptance in cancer therapy. One of a few commercially available systems is the Magnetrode, a device operating at 13.56 MHz with an output power up to 1000 W. Heating of the prescribed part of the patient's body is accomplished by one of the coil electrodes. To assess exposure to the operator of the device, the intensities of the electric and magnetic fields in the vicinity of three Magnetrode coils were measured, while a human phantom or a human being was in the coil. Exposure to the device operator is compared with the recommendations of the Canadian safety code and the recent ANSI recommendations.

Diathermy↗
PubMed1982

Exposure to the operator and patient during short wave diathermy treatments.

Short-wave diathermy is one of the most popular treatment modalities used to relieve pain through localized heating. In Canada its use in hospitals is as frequent as that of ultrasonic therapy devices and about 10 times more popular than microwave diathermy. Intensities of the electric and magnetic fields around applicators of 7 different diathermy units were measured at the operator position and at various untreated areas of the patient during 11 treatment regimes using 5 types of applicators. Exposure to the operator in the normal operating position, behind the device console, usually does not exceed the limits recommended by the Canadian Federal Government. The intense fields around the applicators and the cables extend up to 0.5 m and are a source of potential overexposure to the operator.

Ambulatory Care Facilities↗