Leukemia following occupational exposure to 60-Hz electric and magnetic fields among Ontario electric utility workers

Biological Effects of Magnetic Storms and ELF Magnetic Fields

Magnetic fields are a constant and essential part of our environment. The main components of ambient magnetic fields are the constant part of the geomagnetic field, its fluctuations caused by magnetic storms, and man-made magnetic fields. These fields refer to extremely-low-frequency (<1 kHz) magnetic fields (ELF-MFs). Since the 1980s, a huge amount of data has been accumulated on the biological effects of magnetic fields, in particular ELF-MFs. However, a unified picture of the patterns of action of magnetic fields has not been formed. Even though a unified mechanism has not yet been generally accepted, several theories have been proposed. In this review, we attempted to take a new approach to analyzing the quantitative data on the effects of ELF-MFs to identify new potential areas for research. This review provides general descriptions of the main effects of magnetic storms and anthropogenic fields on living organisms (molecular-cellular level and whole organism) and a brief description of the main mechanisms of magnetic field effects on living organisms. This review may be of interest to specialists in the fields of biology, physics, medicine, and other interdisciplinary areas.

Background radiation and cancer risks: A major intellectual confrontation within the domain of radiation genetics with multiple converging biological disciplines

This paper assesses the judgments of leading radiation geneticists and cancer risk assessment scientists from the mid-1950s to mid-1970s that background radiation has a significant effect on human genetic disease and cancer incidence. This assumption was adopted by the National Academy of Sciences (NAS) Biological Effects of Atomic Radiation (BEAR) I Genetics Panel for genetic diseases and subsequently applied to cancer risk assessment by other leading individuals/advisory groups (e.g., International Commission on Radiation Protection-ICRP). These recommendations assumed that a sizeable proportion of human mutations originated from background radiation due to cumulative exposure over prolonged reproductive periods and the linear nature of the dose-response. This paper shows that the assumption that background radiation is a significant cause of spontaneous mutation, genetic diseases, and cancer incidence is not supported by experimental and epidemiological findings, and discredits erroneous risk assessments that improperly influenced the recommendations of national and international advisory committees, risk assessment policies, and beliefs worldwide.

Eco-Geophysical and Geoecological Factors in Assessing the State of the Geological Environment Based on the Analysis of Spatial Databases of the Territory of the Republic of North Ossetia–Alania

The article considers the main sources of pollutionin the territory of the Republic of North Ossetia–Alania. A study of environmental geophysical factors in the city of Vladikavkaz was carried out at 126 points; indicators of noise pollution, electric fields and the level of gamma radiation were measured. A geoaccumulation index of heavy metals in soils and indices of carcinogenic and non-carcinogenic risks were calculated and corresponding maps were constructed. The obtained data supporting a high level of carcinogenic risk are consistent with a high level of cancer morbidity in the city, which indicates a close relationship between morbidity and the carcinogenic risk index. It has been determined that emissions from road transport are greater by an order of magnitude than stationary sources emissions, while there is a steady trend towards an increase in air pollution as a result of the increasing negative impact of motor vehicle emissions. It has been established that the most hazardous way for heavy metals to enter the human body from the soil is by inhalation. It has been determined that in areas where environmental pollution with heavy metals is higher, cancer morbidity is also higher.

Progress in the Knowledge, Application and Influence of Extremely Low Frequency Signals

This paper describes the characteristics of contributions made by researchers worldwide in the field of ELF (extremely low frequency) waves from 1957 to 2019. The data were collected through the Scopus database and processed with analytical and bibliometric techniques. The selection of the keywords is an essential step, because ELF has a very different meaning in some areas of medicine, where it is associated with a gene. A total of 12,436 documents were worked on in 12 thematic communities according to their collaborative relationships between authors and documents. Studies included authors publishing in the different thematic areas and the country where the USA stands first with more researchers in this theme than China and Japan. Documents were analyzed from the temporal perspective, their overall contribution, means of publication, and the language of the publication. Research requires extra effort and multidisciplinary collaboration to improve the knowledge, the application, and influence of these fields.

Occupational extremely low frequency magnetic fields (ELF-MF) exposure and hematolymphopoietic cancers - Swiss National Cohort analysis and updated meta-analysis

PURPOSE

Previous studies have examined risks of leukaemia and selected lymphoid malignancies in workers exposed to extremely low frequency magnetic fields (ELF-MF). Most studies evaluated hematolymphopoietic malignancies as a combined category, but some analyses suggested that effects may be contained to some specific leukaemia or lymphoma subtypes, with inconsistent results.

METHODS

We examined exposure to ELF-MF and mortality 1990-2008 from different types of hematolymphopoietic cancers in the Swiss National Cohort, using a job exposure matrix for occupations recorded at censuses 1990 and 2000. We analysed 3.1 million workers exposed at different levels to ELF-MF: ever-high, only-medium, only-low exposure using Cox proportional hazard models. We evaluated risk of death from acute myeloid leukaemia (AML), chronic myeloid leukaemia, lymphoid leukaemia, diffuse large B-cell lymphomas, follicular lymphoma, Waldenström's macroglobulinemia, multiple myeloma and Hodgkin lymphoma.

RESULTS

Mortality from hematolymphopoietic cancers was not associated with exposure to ELF-MF with the exception of an increase in ever-high exposed men of myeloid leukaemias (HR 1.31, 95% CI 1.02-1.67), and AML (HR 1.26, 95%CI 0.93-1.70). If workers had been high exposed during their vocational training and at both censuses, these HR increased to 2.24 (95%CI 0.91-5.53) and 2.75 (95%CI 1.11-6.83), respectively.

CONCLUSIONS

Our analysis provided no convincing evidence for an increased risk of death from a range of hematolymphopoietic cancers in workers exposed to high or medium levels of ELF magnetic fields. However, we observed an increased risk of acute myeloid leukaemia in workers exposed to high levels for a longer duration. Observed risks are in line with meta-analysed previous reports on ELF-MF exposure and AML risk, with a summary relative risk of 1.21 (95%CI 1.08-1.37).

The impact of electric fields on testis physiopathology, sperm parameters and DNA integrity-The role of resveratrol

This study investigated the long-term effects of electric fields (EF) which might cause physiopathological or morphological changes in the testis tissues of rats. We assumed that using resveratrol (RES) might reduce harmful effects of the EF. Thirty-two male Wistar Albino rats were randomly divided into four groups with eight animals in each; control, EF, EF + RES and RES. Malondialdehyde (MDA), superoxide dismutase, catalase, glutathione peroxidase and histopathological parameters were evaluated in testis tissue. Epididymal sperm count, motility and DNA damage were studied. Total testosterone, follicle-stimulating hormone, luteinising hormone, estradiol and growth hormone levels were evaluated in the plasma samples. EF caused statistically significant increase in MDA levels, body weight and DNA damage. A significant decrease was detected in sperm count and motility. The histopathological examination of the testes showed the germ cell decrease in the seminiferous epithelium with oedema and vascular congestion in the interstitial tissue. In immunohistochemical examination, the increase in the apoptotic cells number was detected. RES partially ameliorated biochemical, histopathological and immunohistochemical findings in the EF + RES group. These findings clearly demonstrated that EF can cause damage in rat testis. RES can ameliorate the damage caused by EF.

When theory and observation collide: Can non-ionizing radiation cause cancer?

This paper attempts to resolve the debate about whether non-ionizing radiation (NIR) can cause cancer-a debate that has been ongoing for decades. The rationale, put forward mostly by physicists and accepted by many health agencies, is that, "since NIR does not have enough energy to dislodge electrons, it is unable to cause cancer." This argument is based on a flawed assumption and uses the model of ionizing radiation (IR) to explain NIR, which is inappropriate. Evidence of free-radical damage has been repeatedly documented among humans, animals, plants and microorganisms for both extremely low frequency (ELF) electromagnetic fields (EMF) and for radio frequency (RF) radiation, neither of which is ionizing. While IR directly damages DNA, NIR interferes with the oxidative repair mechanisms resulting in oxidative stress, damage to cellular components including DNA, and damage to cellular processes leading to cancer. Furthermore, free-radical damage explains the increased cancer risks associated with mobile phone use, occupational exposure to NIR (ELF EMF and RFR), and residential exposure to power lines and RF transmitters including mobile phones, cell phone base stations, broadcast antennas, and radar installations.

Effects on g2/m phase cell cycle distribution and aneuploidy formation of exposure to a 60 Hz electromagnetic field in combination with ionizing radiation or hydrogen peroxide in l132 nontumorigenic human lung epithelial cells

The aim of the present study was to assess whether exposure to the combination of an extremely low frequency magnetic field (ELF-MF; 60 Hz, 1 mT or 2 mT) with a stress factor, such as ionizing radiation (IR) or H2O2, results in genomic instability in non-tumorigenic human lung epithelial L132 cells. To this end, the percentages of G2/M-arrested cells and aneuploid cells were examined. Exposure to 0.5 Gy IR or 0.05 mM H2O2 for 9 h resulted in the highest levels of aneuploidy; however, no cells were observed in the subG1 phase, which indicated the absence of apoptotic cell death. Exposure to an ELF-MF alone (1 mT or 2 mT) did not affect the percentages of G2/M-arrested cells, aneuploid cells, or the populations of cells in the subG1 phase. Moreover, when cells were exposed to a 1 mT or 2 mT ELF-MF in combination with IR (0.5 Gy) or H2O2 (0.05 mM), the ELF-MF did not further increase the percentages of G2/M-arrested cells or aneuploid cells. These results suggest that ELF-MFs alone do not induce either G2/M arrest or aneuploidy, even when administered in combination with different stressors.

Extra-low-frequency magnetic fields alter cancer cells through metabolic restriction

BACKGROUND

Biological effects of extra-low-frequency (ELF) magnetic fields (MFs) have lacked a credible mechanism of interaction between MFs and living material.

OBJECTIVES

To examine the effect of ELF-MFs on cancer cells.

METHODS

Five cancer cell lines were exposed to ELF-MFs within the range of 0.025-5 µT, and the cells were examined for karyotype changes after 6 d.

RESULTS

All cancer cells lines lost chromosomes from MF exposure, with a mostly flat dose-response. Constant MF exposures for three weeks allow a rising return to the baseline, unperturbed karyotypes. From this point, small MF increases or decreases are again capable of inducing karyotype contractions (KCs). Our data suggest that the KCs are caused by MF interference with mitochondria's adenosine triphosphate synthase (ATPS), compensated by the action of adenosine monophosphate-activated protein kinase (AMPK). The effects of MFs are similar to those of the ATPS inhibitor, oligomycin. They are amplified by metformin, an AMPK stimulator, and attenuated by resistin, an AMPK inhibitor. Over environmental MFs, KCs of various cancer cell lines show exceptionally wide and flat dose-responses, except for those of erythroleukemia cells, which display a progressive rise from 0.025 to 0.4 µT.

CONCLUSIONS

The biological effects of MFs are connected to an alteration in the structure of water that impedes the flux of protons in ATPS channels. These results may be environmentally important, in view of the central roles played in human physiology by ATPS and AMPK, particularly in their links to diabetes, cancer and longevity.

Possible health benefits from reducing occupational magnetic fields

BACKGROUND

Magnetic fields (MF) from AC electricity are a Possible Human Carcinogen, based on limited epidemiologic evidence from exposures far below occupational health limits.

METHODS

To help formulate government guidance on occupational MF, the cancer cases prevented and the monetary benefits accruing to society by reducing workplace exposures were determined. Life-table methods produced Disability Adjusted Life Years, which were converted to monetary values.

RESULTS

Adjusted for probabilities of causality, the expected increase in a worker's disability-free life are 0.04 year (2 weeks) from a 1 microtesla (µT) MF reduction in average worklife exposure, which is equivalent to $5,100/worker/µT in year 2010 U.S. dollars (95% confidence interval $1,000-$9,000/worker/µT). Where nine electrosteel workers had 13.8 µT exposures, for example, moving them to ambient MFs would provide $600,000 in benefits to society (uncertainty interval $0-$1,000,000).

CONCLUSIONS

When combined with the costs of controls, this analysis provides guidance for precautionary recommendations for managing occupational MF exposures.

A meta-analysis of epidemiological studies on the relationship between occupational electromagnetic field exposure and the risk of adult leukemia

Since the first paper by Milham et al. suggested that occupational exposure to an electromagnetic field (EMF) could increase the risk of adult leukemia, many epidemiological studies on this problem have been published. In this report the method of meta-analysis was used to summarize the results from these papers quantitatively. The combined relative risk of all leukemia (RR=1.11), as well as acute lymphocytic leukemia (RR=1.38), acute myeloid leukemia (RR=1.07) and chronic lymphocytic leukemia (RR=1.14) increased but not significantly. So far, it is difficult to make a consistent conclusion about the relationship of the occupational exposure to EMF and adult leukemia. Further carefully designed case-control and cohort studies using the more valid means of exposure assessment are required.

Global electromagnetic toxicity and frequency-induced diseases: Theory and short overview

The development and implementation of electricity in the modern society have facilitated the survival of mankind in the present, modern ages. However, the health consequences of introducing electricity into the society are poorly studied. Studies of artificial light and non-ionizing radiation are generally low priorities on the agenda of public health organizations, and the reported existing data indicate that there are several unanswered questions to whether humans are negatively affected in electrified environments. This article discusses the potential aspects of the impact of electricity on human health and brain function and introduces a hypothesis. The article furthermore discusses the disturbance of sleep patterns caused by electrified environments, and the increasing absence of natural stimuli to the human brain causing chronic 'digital stress' facilitating pathophysiological development. A significant need to study adverse health effects from non-ionizing radiation and synthetic luminous environments from an environmental toxicological perspective is definitely urged.

Effects on micronuclei formation of 60-Hz electromagnetic field exposure with ionizing radiation, hydrogen peroxide, or c-Myc overexpression

PURPOSE

Epidemiological studies have demonstrated a possible correlation between exposure to extremely low-frequency magnetic fields (ELF-MF) and cancer. However, this correlation has yet to be definitively confirmed by epidemiological studies. The principal objective of this study was to assess the effects of 60 Hz magnetic fields in a normal cell line system, and particularly in combination with various external factors, via micronucleus (MN) assays.

MATERIALS AND METHODS

Mouse embryonic fibroblast NIH3T3 cells and human lung fibroblast WI-38 cells were exposed for 4 h to a 60 Hz, 1 mT uniform magnetic field with or without ionizing radiation (IR, 2 Gy), H(2)O(2) (100 μM) and cellular myelocytomatosis oncogene (c-Myc) activation.

RESULTS

The results obtained showed no significant differences between the cells exposed to ELF-MF alone and the unexposed cells. Moreover, no synergistic effects were observed when ELF-MF was combined with IR, H(2)O(2), and c-Myc activation.

CONCLUSIONS

Our results demonstrate that ELF-MF did not enhance MN frequency by IR, H(2)O(2) and c-Myc activation.

Extremely low frequency electric fields and cancer: assessing the evidence

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.

An integrated job exposure matrix for electrical exposures of utility workers

Electric utility workers may be exposed to any combination of magnetic fields, electric fields, nuisance shocks (from spark discharges and continuous currents), imperceptible contact currents, and electrical injuries. Collectively these exposures are referred to as EMF Factors. Previous occupational exposure assessments have mainly characterized the magnetic field, with less attention to the electric field. Nuisance shocks and electrical injuries, though palpable, have received little to no attention. This article presents a prototype job exposure matrix that addresses exposure to all EMF Factors taking into account job category, work environment, and occupied environment. Exposures for all factors were classified into three ordinal levels for 22 job categories. Electric and magnetic field exposures were classified by the geometric mean of daily average of personal exposure measurements. Although relatively sparse, survey data on nuisance shocks were adequate for exposure assignment by job category and indicate that the frequency of these exposures has diminished over time. The least information was available for imperceptible contact currents that are associated with electric field exposures and small contact voltages. Data for electrical injuries by job category were derived from the Electric Power Research Institute Occupational Health Surveillance Database, with exposure assignments based on combined injury rates for flash burn and electric shock/electrocution. The highest exposures for all EMF Factors are essentially limited to four job categories that work on or close to electrical equipment: (1) cable splicers, (2) electricians, (3) line workers, and (4) substation operators.

50-Hz magnetic field induces EGF-receptor clustering and activates RAS

PURPOSE

In a previous study, we found that exposure to a 50 Hz magnetic field (MF) could activate stress-activated protein kinase (SAPK) and P38 mitogen-activated protein (MAP) kinase (P38 MAPK) in Chinese hamster lung (CHL) fibroblast cells, and simultaneous exposure to a 'noise' MF of the same intensity inhibited these effects. In order to explore the possible target sites and upstream signal transduction molecules of SAPK and P38 MAPK, and further validate the interference effects of 'noise' MF on 50 Hz MF, the effects of MF exposure on clustering of epidermal growth factor (EGF) receptors and Ras protein activation were investigated.

MATERIALS AND METHODS

CHL cells were exposed to a 50 Hz sinusoidal MF at 0.4 mT for different durations, and clustering of EGF receptors on cellular membrane and Ras protein activation were analyzed using immunofluorescence confocal microscopy and co-precipitation technology. EGF treatment served as the positive control.

RESULTS

The results showed that, compared with sham-exposed cells, exposure to a 50 Hz MF at 0.4 mT for 5 min slightly induced EGF receptor clustering, whereas exposure for 15 min enhanced receptor clustering significantly. Corresponding to receptor clustering, Ras protein was also activated after exposure to the 50 Hz MF. Exposure to a 'noise' MF (with frequency ranges from 30 - 90 Hz) at the same intensity and durations, did not significantly affect EGF receptor clustering and Ras protein. However, by superimposing the 'noise' MF, receptor clustering and Ras activation induced by 50 Hz MF were inhibited.

CONCLUSION

The results suggested that membrane receptors could be one of the most important targets where extremely low frequency (ELF) MF interacts with cells, and Ras may participate in the signal transduction process of 50 Hz MF. Furthermore, a 'noise' MF could inhibit these effects caused by ELF-MF.

A population-based job exposure matrix for power-frequency magnetic fields

A population-based job exposure matrix (JEM) was developed to assess personal exposures to power-frequency magnetic fields (MF) for epidemiologic studies. The JEM compiled 2,317 MF measurements taken on or near workers by 10 studies in the United States, Sweden, New Zealand, Finland, and Italy. A database was assembled from the original data for six studies plus summary statistics grouped by occupation from four other published studies. The job descriptions were coded into the 1980 Standard Occupational Classification system (SOC) and then translated to the 1980 job categories of the U.S. Bureau of the Census (BOC). For each job category, the JEM database calculated the arithmetic mean, standard deviation, geometric mean, and geometric standard deviation of the workday-average MF magnitude from the combined data. Analysis of variance demonstrated that the combining of MF data from the different sources was justified, and that the homogeneity of MF exposures in the SOC occupations was comparable to JEMs for solvents and particulates. BOC occupation accounted for 30% of the MF variance (p << 10(-6)), and the contrast (ratio of the between-job variance to the total of within- and between-job variances) was 88%. Jobs lacking data had their exposures inferred from measurements on similar occupations. The JEM provided MF exposures for 97% of the person-months in a population-based case-control study and 95% of the jobs on death certificates in a registry study covering 22 states. Therefore, we expect this JEM to be useful in other population-based epidemiologic studies.

Effects of extremely low-frequency electromagnetic fields on delayed chromosomal instability induced by bleomycin in normal human fibroblast cells

This study was carried out to examine the interaction of extremely low-frequency electromagnetic fields (ELF-EMF) on delayed chromosomal instability by bleomycin (BLM) in human fibroblast cells. A micronucleus-centromere assay using DNA probes for chromosomes 1 and 4 was performed and a 60-Hz ELF-EMF of 0.8 mT field strength was applied either alone or with BLM throughout the culture period. The frequencies of micronuclei (MN) and aneuploidy were analyzed at 28, 88, and 240 h after treatment with BLM. The coexposure of cells to BLM and ELF-EMF led to a significant increase in the frequencies of MN and aneuploidy compared to the cells treated with BLM alone. No difference was observed between field-exposed and sham-exposed control cells. The frequency of MN induced by BLM was increased at 28 h, and further analysis showed a persistent increase up to 240 h, but the new levels were not significantly different from the level at 28 h. BLM increased the frequencies of aneuploidy at 28, 88, and 240 h, and significantly higher frequency of aneuploidy was observed in the cells analyzed at 240 h compared to the cells examined at 28 h. No interaction of ELF-EMF on delayed chromosomal instability by BLM was observed. Our results suggest that ELF-EMF enhances the cytotoxicity of BLM. BLM might induce delayed chromosomal instability, but no effect of ELF-EMF was observed on the BLM-induced delayed chromosomal instability in fibroblast cells.

The non-Hodgkin lymphomas: a review of the epidemiologic literature

The non-Hodgkin lymphomas (NHL) are a heterogeneous group of B-cell and T-cell neoplasms that arise primarily in the lymph nodes. NHL incidence rates in the US doubled between about 1970 and 1990, and stabilized during the 1990s. NHL accounts for approximately 3.4% of cancer deaths in the US. Although some of the observed patterns in NHL have been related to HIV/AIDS, these conditions cannot fully explain the magnitude of the changes; neither do changes in classification systems nor improved diagnostic capabilities. Studies of occupational and environmental exposures (e.g., pesticides, solvents) have produced no consistent pattern of significant positive associations. Inverse associations with ultraviolet radiation exposure and alcohol and fish intake, and positive associations with meat and saturated fat intake have been reported in several studies; additional studies are needed to confirm or refute these associations. Family history of NHL or other hematolympho-proliferative cancers and personal history of several autoimmune disorders are associated with increased risk of NHL, but are not likely to account for a large proportion of cases. HIV and other infectious agents, such as human herpesvirus 8 and Epstein-Barr, appear to be associated with differing types of NHL, such as some B-cell lymphomas. Future epidemiologic studies should evaluate associations by NHL type, enhance exposure information collected, and elucidate factors that may identify susceptible (or resistant) subpopulations because of genetic, immunologic or other characteristics. The extent to which the etiology of NHL types may differ is important to resolve in ongoing and future studies.

Occupational exposure to ionizing and non-ionizing radiation and risk of non-Hodgkin lymphoma

OBJECTIVE

To investigate the association between occupational exposure to ionizing, ultraviolet (UV), radiofrequency (RF) and extremely low frequency (ELF) radiation and risk of developing non-Hodgkin lymphoma (NHL) in a population-based case-control study.

METHODS

The study population consisted of 694 NHL cases, first diagnosed between 1 January 2000 and 31 August 2001, and 694 controls from two regions in Australia, matched by age, sex and region of residence. A detailed occupation history was first obtained using a lifetime calendar and a telephone interview. Exposure to radiation was then assessed using a Finnish job-exposure matrix (FINJEM). Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated from logistic regression models that included the matching variables as covariates.

RESULTS

For ionizing radiation, the ORs were close to unity. For UV and ELF radiation, the highest exposed group of workers had ORs of 1.32 (95% CI=0.96-1.81) and 1.25 (95% CI=0.91-1.72), respectively. For UV radiation there was a positive dose-response when exposure was lagged by 5 and 10 years (P for trend 0.04 for both lag periods). Workers in the upper tertile of exposure for RF radiation had an OR of 3.15 (95% CI=0.63-15.87), but the estimate was based on very small numbers.

CONCLUSIONS

Our results do not provide support for an association between NHL and occupational exposure to ionizing or ELF radiation. For UV radiation, our findings are consistent with a weak positive association. Further investigation focusing on UV and RF radiation and NHL is required.

Occupational exposure to low frequency magnetic fields and the risk of low grade and high grade glioma

OBJECTIVE

The purpose of this population-based case control study was to investigate a possible association between occupational exposure to low frequency magnetic fields and the risk of low grade glioma (LGG) and high grade glioma (HGG).

METHODS

The study population consisted of 414 histologically confirmed cases of glioma (LGG=110, HGG=304), first diagnosed between July 1987 and December 1991, and 421 controls from Melbourne, Australia, matched by age, sex and postcode of residence. A detailed occupational history was obtained for each subject. Exposure to low frequency magnetic fields was estimated using three different methods: self-report, expert hygienist review and a job exposure matrix (JEM).

RESULTS

Elevated but statistically non-significant risk estimates were found for all glioma and HGG when exposure was assessed by the expert hygienist. The odds ratios (OR) for the highest exposed group of workers when assessed by the expert hygienist were 1.4 (95% confidence interval, CI: 0.85-2.27) and 1.51 (95% CI: 0.90-2.53) for all glioma and HGG, respectively. There were inverse associations for the self-reported and JEM exposures for both LGG and HGG but these may reflect limitations in these exposure assessment methods.

CONCLUSIONS

Our results do not support a role for occupational exposure to low frequency magnetic fields in the development of either LGG or HGG.

Occupational exposure to power frequency magnetic fields and risk of non-Hodgkin lymphoma

OBJECTIVES

To investigate the risk of non-Hodgkin lymphoma (NHL) using a job-exposure matrix (JEM) to assess exposure to occupational magnetic fields at the power frequencies of 50/60 Hz.

METHODS

The study population consisted of 694 cases of NHL, first diagnosed between 1 January 2000 and 31 August 2001, and 694 controls from two regions in Australia, matched by age, sex and region of residence. A detailed occupational history was given by each subject. Exposure to power frequency magnetic fields was estimated using a population-based JEM which was specifically developed in the United States to assess occupational magnetic field exposure. The cumulative exposure distribution was divided into quartiles and adjusted odds ratios were calculated using the lowest quartile as the referent group.

RESULTS

For the total work history, the odds ratio (OR) for workers in the upper quartile of exposure was 1.48 (95% CI 1.02 to 2.16) compared to the referent (p value for trend was 0.006). When the exposure was lagged by 5 years the OR was 1.59 (95% CI 1.07 to 2.36) (p value for trend was 0.003). Adjusting for other occupational exposures did not significantly alter the results.

CONCLUSIONS

These findings provide weak support for the hypothesis that occupational exposure to 50/60 Hz magnetic fields increases the risk of NHL.

Occupation and malignant lymphoma: a population based case control study in Germany

AIMS

To identify occupations suspected to be associated with malignant lymphoma and to generate new hypotheses about occupational risks in a multicentre, population based case control study.

METHODS

Male and female patients with malignant lymphoma (n = 710) aged 18-80 years of age were prospectively recruited in six study regions in Germany. For each newly recruited lymphoma case, a sex, region, and age matched control was drawn from the population registers. Odds ratios and 95% confidence intervals for major occupations and industries were calculated using conditional logistic regression analysis, adjusted for smoking (in pack-years) and alcohol consumption. Patients with specific lymphoma subentities were additionally compared with the entire control group using unconditional logistic regression analysis.

RESULTS

The following economic/industrial sectors were positively associated with lymphoma: food products, beverages, tobacco; paper products, publishing and printing; and metals. Chemicals; real estate, renting, and business activities were negatively associated with lymphoma diagnosis. The authors observed an increased overall lymphoma risk among architects; maids; farmers; glass formers; and construction workers. Shoemaking and leather goods making was negatively associated with the lymphoma diagnosis (although based on small numbers). In the occupational group analysis of lymphoma subentities, Hodgkin's lymphoma was significantly associated only with rubber and plastic products making; diffuse large B cell lymphoma risk was considerably increased among metal processors; follicular lymphoma showed highly significant risk increases for several occupational groups (medical, dental, and veterinary workers; sales workers; machinery fitters; and electrical fitters); and multiple myeloma showed a particularly pronounced risk increase for farmers as well as for agriculture and animal husbandry workers.

CONCLUSIONS

The results partly confirm previously defined occupational risks. Occupational risk factors for follicular lymphomas might differ from the overall risk factors for malignant lymphoma.

Effect of melatonin on the induction of foci of aberrant crypts in the colon by azoxymethane in rats

OBJECTIVE

A program of research was established on the question whether melatonin played a chemopreventive role in the development of foci of aberrant crypts in the intestinal tract of male rats. Male F344 rats were injected i.p. with an aqueous solution of 15 mg/kg azoxymethane (AOM) on day 50 and day 57, and a group was also injected i.p with 0.5 mg melatonin in 0.5 ml of 10% ethanol solution 5 times per week beginning at age 47 days. Foci and multiplicity of aberrant crypts were determined after 8 weeks. These groups of animals were kept in light daily from 4∶30 to 16∶30.

RESULTS

In the group receiving AOM and the melatonin injections, there were fewer foci of aberrant crypts in the colon and the average number of crypts was lower after 8 weeks, compared to the group on AOM alone.

CONCLUSIONS

Melatonin inhibited the formation of foci of aberrant crypts in the descending colon of rats. Also, it reduced the number of aberrant crypts per focus from foci with 3 and more aberrant crypts.

Occupational exposure to electromagnetic fields and acute leukaemia: analysis of a case-control study

AIMS

To investigate whether the risk of acute leukaemia among adults is associated with occupational exposure to electromagnetic fields.

METHODS

Probable occupational exposure to electromagnetic fields at higher than typical residential levels was investigated among 764 patients diagnosed with acute leukaemia during 1991-96 and 1510 sex and age matched controls. A job exposure matrix was applied to the self reported employment histories to determine whether or not a subject was exposed to electromagnetic fields. Risks were assessed using conditional logistic regression for a matched analysis.

RESULTS

Study subjects considered probably ever exposed to electromagnetic fields at work were not at increased risk of acute leukaemia compared to those considered never exposed. Generally, no associations were observed on stratification by sex, leukaemia subtype, number of years since exposure stopped, or occupation; there was no evidence of a dose-response effect using increasing number of years exposed. However, relative to women considered never exposed, a significant excess of acute lymphoblastic leukaemia was observed among women probably exposed to electromagnetic fields at work that remained increased irrespective of time prior to diagnosis or job ever held.

CONCLUSION

This large population based case-control study found little evidence to support an association between occupational exposure to electromagnetic fields and acute leukaemia. While an excess of acute lymphoblastic leukaemia among women was observed, it is unlikely that occupational exposure to electromagnetic fields was responsible, given that increased risks remained during periods when exposure above background levels was improbable.

Teratogenic effect of broad-band electromagnetic field on neonatal mice (Mus musculus)

Pregnant mice (Mus musculus), strain Swiss Webster, were exposed to a continuous electromagnetic field (12.8V/m) beginning in the third week of pregnancy. Histological and hematological analysis showed gender specific responses in 21 day-old mice after in-utero and post-natal continuous exposure. Automated lymphocyte percentage and total white blood cell counts were significantly elevated in exposed 21 day-old female mice compared to control mice. Lymphoma-like cells were seen in higher numbers in exposed 21 day-old male mice. Megaloblastic changes, such as hypersegmented neutrophils, were observed in exposed mice. The blood from control neonatal mice was more viscous than that of exposed mice, enough to interfere with making a blood smear. The adult female mice showed no significant differences in the above hematologic parameters between exposed and control groups. Histological study showed the following pathological changes in the adrenal cortex: degeneration/necrosis in the zona glomerulosa; hypertrophy in zona reticularis; degeneration/necrosis, intracytoplasmic inclusions and inflammation in the zona fasciculata/reticularis, more prominent in exposed female neonates; and lipidosis in the zona fasciculata. In the adrenal medulla: atrophy was more common in exposed female neonates; and intracytoplasmic inclusions and vacuolation were more common in exposed male neonates. Cystic proliferations were found in the cortical area of the thymus. In the medulla of the thymus, there was vacuolation, inflammation, or eosinophilic intracytoplasmic inclusions in exposed adults. Behavioral differences occurred in both neonates and adult females. Control neonates were able to manipulate through a maze more quickly than exposed neonates; and control adult females displayed more thorough grooming behavior than exposed mothers, and maintained more distance between the nest and dropping location than did the exposed group.

Testicular toxicity effects of magnetic field exposure and prophylactic role of coenzyme Q10 and L-carnitine in mice

The protective effect of L-carnitine or coenzyme Q10 (CoQ10) against high magnetic field (20 mT) induced testicular toxicity in mice were evaluated. Animals were injected with L-carnitine (200 mg kg(-1), i.p.) or CoQ10 (200 mg kg(-1), p.o.) 1h before exposure to fractionated doses (30 min per day, three times per week for 2 weeks) or acute dose (3h) of magnetic field. Total sperm count, motility, daily sperm production, and testicular LDH-X activity as well as histopathological examination were investigated. Exposure of mice to fractionated doses of magnetic field caused a significant decrease in sperm count, motility, daily sperm production, and LDH-X activity, which was more pronounced than that of acute dose. Moreover, a marked testicular histopathological changes were observed after exposure to fractionated doses of magnetic field. Pretreatment of mice with L-carnitine or CoQ10 1h before exposure to magnetic field caused a significant recovery of mice testes damage induced by high magnetic field (20 mT).

Does our electricity distribution system pose a serious risk to public health?

Elevated magnetic field exposures are associated with increased childhood leukaemia risk. A link with breast and other cancers has been postulated via modified melatonin activity. Other illnesses have been linked to electricity distribution, by association or mechanistic considerations. For selected illnesses, this paper estimates the annual number of excess cases that might occur near high-voltage powerlines in the UK. Within 150m of powerlines, magnetic field exposures above 0.1 microT are postulated to result in 9000 excess cases of depression in adults and 60 cases of suicide. Electric field effects can mediate increased exposure to air pollution. Within 400m of powerlines, this may result annually in 200-400 excess cases of lung cancer, 2000-3000 cases of other illnesses associated with air population and 2-6 cases of childhood leukaemia. Seventeen cases of non-melanoma skin cancer might occur by exposure directly under powerlines.

Gene expression of cytokine receptors in HL60 cells exposed to a 50 Hz magnetic field

The effects of a 50 Hz extremely low frequency (ELF) sinusoidal magnetic field (MF) on the expression of genes relating to cytokine receptors were studied in HL60 cells. Transcription levels of tumor necrosis factor receptor (TNFR) p55 and p75, interleukin-6 receptor-alpha (IL-6Ralpha) and transforming growth factor-beta receptor 1 (TGFbetaR1) were quantified in cells exposed to an intensity of 0.1 or 0.8 mT for periods ranging from 30 min to 72 h. Cells treated with 10 nM of phorbol 12-myristate 13-acetate (PMA) for 8 h served as a positive control. Gene expression values were assessed by the ribonuclease protection assay (RPA) and normalized to those of the noninducible gene GAPDH. The results showed that MF exposure at 0.1 and 0.8 mT for 72 h increased TNFR p75 and IL-6Ralpha mRNA expression in HL60 cells. No significant change in gene expression levels of TNFR p55 and TGFbetaR1 was observed under any of the exposure conditions. In addition, we report here for the first time that IL-6Ralpha mRNA expression can be suppressed by PMA in HL60 cells.

Brain cancer and occupational exposure to magnetic fields among men: results from a Canadian population-based case-control study

BACKGROUND

The relationship between occupational exposure to magnetic fields and brain cancer in men was investigated using population-based case-control data collected in eight Canadian provinces. Emphasis was placed on examining the variations in risk across different histological types.

METHODS

A list of occupations was compiled for 543 cases and 543 controls that were individually matched by age. Occupations were categorized according to their average magnetic field exposure through blinded expert review (<0.3, 0.3-<0.6, and > or = 0.6 microT). In total, 133 cases (14%) and 123 controls (12%) were estimated to have at least one occupation whereby magnetic field exposures exceeded 0.3 microT. Odds ratios (OR) were generated using conditional logistic regression, and were adjusted for suspected occupational risk factors for brain cancer.

RESULTS

A non-significantly increased risk of brain cancer was observed among men who had ever held a job with an average magnetic field exposure >0.6 microT relative to those with exposures <0.3 microT (OR = 1.33, 95% CI : 0.75-2.36). A more pronounced risk was observed among men diagnosed with glioblastoma multiforme (OR = 5.36, 95% CI : 1.16-24.78). Moreover, a cumulative time weighted index score of magnetic field exposure was significantly related to glioblastoma multiforme (P = 0.02). In contrast, magnetic field exposures were not associated with astrocytoma or other brain cancers.

CONCLUSIONS

Our findings support the hypothesis that occupational magnetic field exposure increases the risk of glioblastoma multiforme.

A population-based prospective cohort study of personal exposure to magnetic fields during pregnancy and the risk of miscarriage

To study the effect of magnetic fields on the risk of miscarriage, we conducted a population-based prospective cohort study among pregnant women within a large health maintenance organization. All women with a positive pregnancy test at less than 10 weeks of gestation and residing in the San Francisco area were contacted for participation in the study. We conducted in-person interviews to obtain information on risk factors for miscarriage and other potential confounders. All participants were also asked to wear a magnetic field-measuring meter for 24 hours and to keep a diary of their activities. Pregnancy outcomes were obtained for all participants by searching the health maintenance organization's databases, reviewing medical charts, and telephone follow-up. We used the Cox proportional hazard model for examining the magnetic field-miscarriage association. A total of 969 subjects were included in the final analyses. Although we did not observe an association between miscarriage risk and the average magnetic field level, miscarriage risk increased with an increasing level of maximum magnetic field exposure with a threshold around 16 milligauss (mG). The rate ratio (RR) associated with magnetic field exposure > or = 16 mG (vs <16 mG) was 1.8 [95% confidence interval (CI) = 1.2-2.7]. The risk remained elevated for levels (in tertiles) of maximum magnetic field exposure > or = 16 mG. The association was stronger for early miscarriages (<10 weeks of gestation) (RR = 2.2, 95% CI = 1.2-4.0) and among "susceptible" women with multiple prior fetal losses or subfertility (RR = 3.1, 95% CI = 1.3-7.7). After excluding women who indicated that their daily activity pattern during the measurements did not represent their typical daily activity during pregnancy, the association was strengthened; RR = 2.9 (95% CI = 1.6-5.3) for maximum magnetic field exposure > or = 16 mG, RR = 5.7 (95% CI = 2.1-15.7) for early miscarriage, and RR = 4.0 (95% CI = 1.4-11.5) among the susceptible women. Our findings provide strong prospective evidence that prenatal maximum magnetic field exposure above a certain level (possibly around 16 mG) may be associated with miscarriage risk. This observed association is unlikely to be due to uncontrolled biases or unmeasured confounders.

Dosimetry in models of child and adult for low-frequency electric field

Induced electric field and current density in a child's body exposed to a 60-Hz electric field are calculated and compared with those for an adult's body. Because of the different proportions of the child body relative to those of the adult body, differences in the induced electric field and current density values in various organs are observed. These results are interpreted in terms of international guideline limits, and hypotheses regarding plausible interactions.

Effects of low frequency electromagnetic fields on expression of lymphocyte subsets and production of cytokines of men and women employed in a museum

The objective of this study was to analyse the immune response to electromagnetic fields (ELMFs) in seven men and eight women employed in a museum. The workers were exposed in a room to an ELMFs (range 0.2-3.6 microT and 40-120 V/m) induced by 50 Hz electricity for 20 h a week. Control groups consisted of 47 women and 39 men with a similar percentage of atopic subjects, age (range 30-51 years) and smoking habits of the workers included in the study. Levels of blood lead (Pb) and urinary trans-trans muconic acid, a metabolite of benzene (markers of exposure to traffic and smoking) of the control and exposed groups were similar. Lymphocyte subsets were determined in men and women using conjugated antibodies. Serum interleukin (IL) 4 and interferon gamma and their 'in vitro' production by peripheral mononuclear blood cells (PMBCs) stimulated by phytohemoglutinin (PHA), as well as blastogenesis of PMBCs induced by PHA, were determined in women only. ELMF-exposed women showed a significant reduction in the percentage of B and NK CD3(-)-CD25+ lymphocytes and a slight reduction of CD16(+)-56+ NK lymphocytes. They also showed significantly lower levels of interferon gamma in serum, or produced in the supernatants by PMBCs both spontaneously and stimulated by PHA, while they did not show significant changes in serum and 'in vitro' produced IL-4, or in blastogenesis of PMBCs. Men working in the museum showed, in relation to the controls, a statistically significant reduction in both number and percentage of CD16(+)- CD56+ and CD3(-)-CD25+ lymphocyte subsets. On the whole, this investigation demonstrates a reduction of blood NK lymphocytes and of the production of interferon gamma in workers exposed to low frequency ELMFs. Recent studies have shown that stress and poor lifestyle induce the reduction of blood cytotoxic activities possibly acting on nervous functions. This may suggest that ELMFs reduces blood NK lymphocytes by combined effects on the immune and nervous systems.

Case-cohort analysis of brain cancer and leukemia in electric utility workers using a refined magnetic field job-exposure matrix

BACKGROUND

The potential association between occupational electric and magnetic field exposure and cancer is well documented in the literature, but there is uncertainty regarding a causal relation.

METHODS

Using data from a completed cohort study, we sought to refine the job-exposure matrix in a case-cohort analysis by regrouping jobs into more homogeneous groups, but without making additional measurements. From the original cohort, we selected the 164 men who died of leukemia, 145 men who died of brain cancer, and a random subcohort of 800 men (0.6% of the cohort). Erroneous job assignments were corrected and job groups were subdivided based on differences in work environments or tasks performed.

RESULTS

Magnetic field exposure remained unrelated to leukemia mortality and positively associated with brain cancer mortality based on both cumulative and average magnetic field indices. Although not monotonic across the middle intervals, increased risk of brain cancer was found in relation to career exposure, with risk ratios of 1.8 (95% CI = 0.7-4.7) and 2.5 (95% CI = 1.0-6.3) in the uppermost categories for cumulative and average exposure, stronger for exposure 2-10 years past.

CONCLUSIONS

Improvements in exposure assignment based only on reassignment of job titles to occupational categories had little impact on the measured associations of magnetic fields with leukemia or brain cancer.

Alternate indices of electric and magnetic field exposures among Ontario electrical utility workers

Epidemiologic studies examining the risk of cancer among occupational groups exposed to electric fields (EF) and or magnetic fields (MF) have relied on traditional summaries of exposure such as the time weighted arithmetic or geometric mean exposure. Findings from animal and cellular studies support the consideration of alternative measures of exposure capable of capturing threshold and intermittent measures of field strength. The main objective of this study was to identify a series of suitable exposure metrics for an ongoing cancer incidence study in a cohort of Ontario electric utility workers. Principal components analysis (PCA) and correlational analysis were used to explore the relationships within and between series of EF and MF exposure indices. Exposure data were collected using personal monitors worn by a sample of 820 workers which yielded 4247 worker days of measurement data. For both EF and MF, the first axis of the PCA identified a series of intercorrelated indices that included the geometric mean, median and arithmetic mean. A considerable portion of the variability in EF and MF exposures were accounted for by two other principal component axes. The second axes for EF and MF exposures were representative of the standard deviation (standard deviation) and thresholds of field measures. To a lesser extent, the variability in the exposure variable was explained by time dependent indices which consisted of autocorrelations at 5 min lags and average transitions in field strength. Our results suggest that the variability in exposure data can only be accounted for by using several exposure indices, and consequently, a series of metrics should be used when exploring the risk of cancer owing to MF and EF exposure in this cohort. Furthermore, the poor correlations observed between indices of MF and EF reinforce the need to be take both fields into account when assessing the risk of cancer in this occupational group.

Leukemia in electric utility workers: the evaluation of alternative indices of exposure to 60 Hz electric and magnetic fields

BACKGROUND

Epidemiological studies have inconsistently demonstrated a positive relationship between magnetic and/or electric fields and leukemia. Although exposure to both 60 Hz electric and magnetic fields can be characterized in many ways, to date, risk assessment has been performed by using only a limited number of exposure indices.

METHODS

The associations between adult leukemia and indices of electric and magnetic fields were explored within a nested case-control study of 31,453 Ontario electric utility workers.

RESULTS

The percentage of time spent above electric field thresholds of 20 and 39 V/m was predictive of leukemia risk after adjusting for duration of employment and the arithmetic mean exposure to both electric and magnetic fields (P<0.05). Duration of employment was strongly associated with an increased risk of leukemia. Those who had worked for at least 20 years, and were in the highest tertiles of percentage of time spent above 10 and 20 V/m had odds ratios of 10.17 (95% CI = 1.58-65.30) and 8.23 (95% CI = 1. 24-54.43), respectively, when compared to those in the lowest tertile. Nonsignificant elevations in risk were observed between indices of magnetic fields and leukemia.

CONCLUSIONS

Our results support the hypothesis that electric fields act as a promoting agent in the etiology of adult leukemia. Exposure assessment based on alternate indices of electric and magnetic fields should be incorporated into future occupational studies of cancer.

Non-Hodgkin's lymphoma among electric utility workers in Ontario: the evaluation of alternate indices of exposure to 60 Hz electric and magnetic fields

OBJECTIVES

To examine associations between non-Hodgkin's lymphoma (NHL) and exposures to 60 Hz magnetic and electric fields in electric utility workers with a series of indices that capture a variety of aspects of field strength.

METHODS

The study population consisted of 51 cases of NHL and 203 individually matched controls identified from within a cohort of male electric utility workers in Ontario. Odds ratios were calculated for several exposure indices with conditional logistic regression models. Aspects of exposure to electric and magnetic fields that were modelled included: the percentage of time spent above selected threshold field intensities, mean transitions in field strength, SD, and the arithmetic and geometric mean field intensities.

RESULTS

For the most part, there was a lack of an association between exposure indices of magnetic fields and the incidence of NHL. Subjects in the upper tertile of percentage of time spent above electric field intensities of 10 and 40 V/m had odds ratios of 3.05 (95% confidence interval (95% CI) 1. 07 to 8.80) and 3.57 (1.30 to 9.80), respectively, when compared with those in the lowest tertile. Moreover, the percentages of time spent above these electric field thresholds were significant predictors of case status over and above the association explained by duration of employment and the arithmetic or geometric mean exposure.

CONCLUSIONS

These data suggest that exposures above electric field threshold intensities of 10 and 40 V/m are important predictors of NHL. Consequently, the findings support the hypothesis that electric fields may play a promoting part in the aetiology of this cancer. Further occupational studies that include assessment of exposure to electric fields and measures of field strength above similar threshold cut off points are needed to confirm these findings.

Possible mechanisms by which electric fields from power lines might affect airborne particles harmful to health

Power lines produce alternating electric fields and modify static electric fields in their vicinity. These electric fields, if large enough, can alter the concentration or transport of airborne particles (including particles harmful to health), for example by causing deposition of charged particles, polarisation of neutral particles, or by production of ions. It has been suggested that this could lead to adverse health effects being associated with power lines. Theoretical considerations and experimental evidence relevant to eight separate postulated mechanisms involving power lines and airborne particles are examined. On theoretical grounds, none should lead to any adverse health effect, primarily because the effects produced are very small and are swamped by air currents or by gravity, and because people spend limited time in the relevant conditions. The experimental evidence also weighs against any adverse health effects. Further, even if significant health effects were produced, they would be different from those suggested by existing epidemiology concerning power lines.

Comparative analyses of the studies of magnetic fields and cancer in electric utility workers: studies from France, Canada, and the United States

OBJECTIVES

To summarise and to facilitate comparison of three major studies of electric utility workers that examined the relation between quantitative measurements of occupational exposure to magnetic fields and risk of brain cancer and leukaemia. These studies have been interpreted as providing conflicting evidence.

METHODS

A common analytical approach was applied to data from the five cohorts included in the three studies based on original data from four of the cohorts, and published data from one additional cohort. A nested case-control design with conditional logistic regression was used to estimate the relative risk/10 microtesla-years (microT-years) for each of the contributing cohorts and for the combined data. The homogeneity of these estimates among the studies was also evaluated.

RESULTS

Apparent inconsistencies in the findings of these studies can be explained by statistical variation. Overall, the studies suggest a small increase in risk of both brain cancer and leukaemia. Different methodological choices had little impact on the results. Based on a combined analysis of data from all five studies, the relative risk/10 microT-years was 1.12 (95% confidence interval (95% CI) 0.98 to 1.28) for brain cancer, and 1.09 (95% CI 0.98 to 1.21) for leukaemia.

CONCLUSIONS

The combined estimates seem to provide the best summary measures of the data from all studies. However, fluctuations in risks among studies may reflect real differences, and the exposure measurements in different studies may not be entirely comparable.

Chronic toxicity/oncogenicity evaluation of 60 Hz (power frequency) magnetic fields in F344/N rats

A 2-yr whole-body exposure study was conducted to evaluate the chronic toxicity and possible oncogenicity of 60 Hz (power frequency) magnetic fields in rats. Groups of 100 male and 100 female F344/N rats were exposed continuously to pure, linearly polarized, transient-free 60 Hz magnetic fields at flux densities of 0 Gauss (G) (sham control), 20 milligauss (mG), 2 G, and 10 G; an additional group of 100 male and 100 female F344/N rats received intermittent (1 hr on/1 hr off) exposure to 10 G fields. Mortality patterns, body weight gains throughout the study, and the total incidence and number of malignant and benign tumors in all groups exposed to magnetic fields were similar to those found in sex-matched sham controls. Statistically significant increases in the combined incidence of C-cell adenomas and carcinomas of the thyroid were seen in male rats chronically exposed to 20 mG and 2 G magnetic fields. These increases were not seen in male rats exposed continuously or intermittently to 10 G fields or in female rats at any magnetic field exposure level. No increases in the incidence of neoplasms, which have been identified in epidemiology studies as possible targets of magnetic field action (leukemia, breast cancer, and brain cancer), were found in any group exposed to magnetic fields. There was a decrease in leukemia in male rats exposed to 10 G intermittent fields. The occurrence of C-cell tumors at the 2 lower field intensities in male rats is interpreted as equivocal evidence of carcinogenicity; data from female rats provides no evidence of carcinogenicity in that sex. These data, when considered as a whole, are interpreted as indicating that chronic exposure to pure linearly polarized 60 Hz magnetic fields has little or no effect on cancer development in the F344/N rat.

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.

Acute promyelocytic leukaemia: epidemiology and risk factors. A report of the GIMEMA Italian archive of adult acute leukaemia. GIMEMA Cooperative Group

Acute promyelocytic leukaemia (APL) exhibits peculiar epidemiological, clinical, cytogenetic and molecular features, compared to the other acute myeloid leukaemias (AML). Data on epidemiology and occupational risk factors for APL desumed from the GIMEMA archive are reported and compared with those of the other AML. An exploratory case-case study was designed on AML patients from 56 haematology centres in Italy. Overall, 4296 patients older than 15 yr with a new diagnosis of acute leukaemia were recorded between July 1992 and July 1997. Of these, 335 were classified as APL, and 2894 as other AML. The median age of APL patients was 43 compared to 59 yr for the other AML (p < 0.00001). In order to identify peculiar risk factors for APL development, different parameters were compared in the 2 groups. After adjusting by age no significant differences were observed with regard to education, lifetime prevalence of cancer among siblings and previous diseases in the patient's history. Occupational exposure as a possible risk factor for APL showed no increased risk compared to other AML among farmers, builders and leather workers. A significant association was found in electricians (OR=4.4, 95% CI=2.0-9.7) and a weak association was found in wood workers (OR=3.2, 95% CI=0.8-10.8). The proportion of APL with respect to other AML was significantly higher in the north east of Italy compared to the rest of the country (OR=1.7, 95% CI=1.3-2.2). These data confirm the younger age of APL patients compared to the other AML. A possible role of electromagnetic fields is suggested by the higher risk of APL in electrical workers and in the more industrialized areas of the country.

The 1.5 GHz electromagnetic near-field used for cellular phones does not promote rat liver carcinogenesis in a medium-term liver bioassay

We have recently established that local exposure to a 929.2 MHz electromagnetic near-field, used for cellular phones, does not promote rat liver carcinogenesis in a medium-term bioassay system. In the present study, a 1.439 GHz electromagnetic near-field (EMF), another microwave band employed for cellular phones in Japan, was similarly investigated. Time division multiple access (TDMA) signals for the Personal Digital Cellular (PDC) Japanese cellular telephone standard system were directed to rats through a quarter-wavelength monopole antenna. Numerical dosimetry showed that the peak SARs within the liver were 1.91-0.937 W/kg, while the whole-body average specific absorption rates (SARs) were 0.680-0.453 W/kg, when the time-averaged antenna radiation power was 0.33 W. Exposure was for 90 min a day, 5 days a week, over 6 weeks, to male F344 rats given a single dose of diethylnitrosamine (200 mg/kg, i.p.) 2 weeks previously. At week 3, all rats were subjected to a two-thirds partial hepatectomy. At week 8, the experiment was terminated and the animals were killed. Carcinogenic potential was scored by comparing the numbers and areas of the induced glutathione S-transferase placental form (GST-P)-positive foci in the livers of exposed (48) and sham-exposed rats (48). Despite increased serum levels of corticosterone, adrenocorticotropic hormone (ACTH) and melatonin, the numbers and the areas of GST-P-positive foci were not significantly altered by the exposure. These findings clearly indicated that local body exposure to a 1.439 GHz EMF, as in the case of a 929.2 MHz field, has no promoting effect on rat liver carcinogenesis in the present model.

Biological responses to electromagnetic fields

Electrification in developed countries has progressively increased the mean level of extremely low-frequency electromagnetic fields (ELF-EMFs) to which populations are exposed; these humanmade fields are substantially above the naturally occurring ambient electric and magnetic fields of approximately 10(-4) Vm(-1) and approximately 10(-13) T, respectively. Several epidemiological studies have concluded that ELF-EMFs may be linked to an increased risk of cancer, particularly childhood leukemia. These observations have been reinforced by cellular studies reporting EMF-induced effects on biological systems, most notably on the activity of components of the pathways that regulate cell proliferation. However, the limited number of attempts to directly replicate these experimental findings have been almost uniformly unsuccessful, and no EMF-induced biological response has yet been replicated in independent laboratories. Many of the most well-defined effects have come from gene expression studies; several attempts have been made recently to repeat these key findings. This review analyses these studies and summarizes other reports of major cellular responses to EMFs and the published attempts at replication. The opening sections discuss quantitative aspects of exposure to EMFs and the incidence of cancers that have been correlated with such fields. The concluding section considers the problems that confront research in this area and suggests feasible strategies.