50 Hz Magnetic Fields of 1 mT do not Promote Lymphoma Development in AKR/J Mice

Carcinogenicity of extremely low-frequency magnetic fields: A systematic review of animal studies

Possible carcinogenicity of extremely low frequency (ELF) magnetic fields (MFs), associated with the use and transmission of electricity, has been under scientific and public debate for decades. This review aims to provide an update on studies testing carcinogenicity of ELF MFs in experimental animals. Emphasis was placed on identifying possible connections between study characteristics and the results obtained. This review followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement, and the methodological quality of the studies was evaluated using the Risk of Bias Rating Tool for Human and Animal Studies developed by the National Toxicology Program's Office of Health Assessment and Translation (OHAT). Publication bias was assessed using the caliper test. Fifty-four eligible studies were identified. Despite poor ratings in certain aspects of the risk of bias evaluation, the quality of the studies was generally relatively good, with only four studies receiving the weakest rating. Overall, there was very little evidence that ELF MFs alone are carcinogenic. Evidence of co-carcinogenicity, from studies that have used ELF MFs in combination with other agents, remains inconclusive. A clear indication of publication bias was observed, though it is unlikely that this bias alone explains all reported MF-modified effects. Based on the current literature, future studies on co-carcinogenicity of ELF MFs should employ approaches other than classical initiation-promotion models. Additionally, well-designed studies to better understand the reported effects of ELF MFs and the underlying mechanisms are warmly welcomed.

Effects of extremely low frequency magnetic fields on animal cancer and DNA damage: A systematic review and meta-analysis

The objective of this systematic review and meta-analysis was to assess the carcinogenic effects of extremely low frequency magnetic fields (ELF-MF) by analyzing animal and comet assay studies. We have performed a global meta-analysis on all the animal studies on the relation between ELF-MF and cancer incidence and separate meta-analyses on the incidence of cancer, leukemia, lymphoma, breast cancer, brain cancer and DNA damage assessed with the comet assay. Of the 5145 references identified, 71 studies have been included in our systematic review and 22 studies in our meta-analyses. Our global meta-analysis indicated that ELF-MF exposure had no significant impact on the incidence of cancers in rodents (19 studies, OR = 1.10; 95% CI 0.91-1.32). However, our separate meta-analyses showed that ELF-MF increased the odds of developing leukemia in mice (4 studies, OR = 4.45; 95% CI 1.90-10.38) but not in rats. Our systematic review also suggests that ELF-MF can damage DNA in certain cell types like brain cells. Nevertheless, a meta-analysis on three comet assay studies indicated that ELF-MF did not increase DNA damage in neuroblastoma cells (SMD = -0.08; 95% CI -0.18-0.01). Overall, our results suggest that exposure to ELF-MF does not represent a major hazard for mammals and the carcinogenic effects of these magnetic fields could be limited to leukemia.

Magnetic Fields and Cancer: Epidemiology, Cellular Biology, and Theranostics

Humans are exposed to a complex mix of man-made electric and magnetic fields (MFs) at many different frequencies, at home and at work. Epidemiological studies indicate that there is a positive relationship between residential/domestic and occupational exposure to extremely low frequency electromagnetic fields and some types of cancer, although some other studies indicate no relationship. In this review, after an introduction on the MF definition and a description of natural/anthropogenic sources, the epidemiology of residential/domestic and occupational exposure to MFs and cancer is reviewed, with reference to leukemia, brain, and breast cancer. The in vivo and in vitro effects of MFs on cancer are reviewed considering both human and animal cells, with particular reference to the involvement of reactive oxygen species (ROS). MF application on cancer diagnostic and therapy (theranostic) are also reviewed by describing the use of different magnetic resonance imaging (MRI) applications for the detection of several cancers. Finally, the use of magnetic nanoparticles is described in terms of treatment of cancer by nanomedical applications for the precise delivery of anticancer drugs, nanosurgery by magnetomechanic methods, and selective killing of cancer cells by magnetic hyperthermia. The supplementary tables provide quantitative data and methodologies in epidemiological and cell biology studies. Although scientists do not generally agree that there is a cause-effect relationship between exposure to MF and cancer, MFs might not be the direct cause of cancer but may contribute to produce ROS and generate oxidative stress, which could trigger or enhance the expression of oncogenes.

The Impact of the Low Frequency of the Electromagnetic Field on Human

Recently, there has been attention and controversial debate topic about the effect of low-frequency electromagnetic fields (EMFs) on human beings. The catalyst for public awareness initiated from the first epidemiological study in 1979 that reported an association between residential EMFs exposure and the incidence of childhood leukemia. For over 40 years, many epidemiological and laboratory investigations were conducted to identify the possible biological effects of low-frequency EMF. Several studies conducted at frequencies 50/60 Hz, which related to generating of electricity from electrical appliances. Experimental studies on low-frequency EMF have provided conflicting data under specific "in vivo" and "in vitro" environments. Some original papers have reported the damaging effect on DNA molecule in EMF-exposed cells. Other studies have suggested no such damage in EMF-exposed cells. Also, the conclusions from other studies were inconclusive. These conflicting findings may attribute to the differences in the apparatus used to generate electromagnetic fields, experimental design, exposure time, genetic endpoints, and biological materials such as cell lines and animal species, strain, and age. As DNA damage is frequently a prerequisite for cancer disease, this review provided an experimental body of evidence on the effect of EMF on genetic material.

Exposure of rats to extremely low-frequency electromagnetic fields (ELF-EMF) alters cytokines production

Investigations indicate a potential link between exposure to extremely low-frequency electromagnetic field (ELF-EMF) and some cancers. Carcinogenesis of ELF-EMF may be mediated by effect on the immune system. During an immune response, naïve T cells differentiate to effector type 1 helper T cells (T(H)1), T(H)2, or T(H)17 subsets according to existence of different cytokines and T(H)1 is important in defense against tumors. Therefore, it will be reasonable to test whether ELF-EMF can change cytokines like interferon gamma (IFN-γ), interleukin-4 (IL-4), IL-6, and IL-12 that regulate T(H)1/T(H)2/T(H)17 balance. Forty adult male rats were randomly separated into ELF-EMF-exposed and sham-exposed control groups. The ELF-EMF group was exposed to a flux density of 100 μT, frequency 50 Hz, 2 h/day for 3 months. The controls were placed in identical chamber without ELF-EMF. The results showed there were no significant differences between the mean mass of rats, thymuses, and spleens in ELF-EMF exposed group compared with controls. Serum IL-12 level was decreased from 418 ± 47 pg/ml in controls to 300 ± 23 pg/ml (p < 0.05) in ELF-EMF-exposed group. Phytohemagglutinin activated of in vitro production of IL-6 by the whole spleen culture (1356 ± 92 pg/ml) and total blood culture (418 ± 40 pg/ml) of ELF-EMF-exposed rats were higher (p < 0.001) comparing with controls (905 ± 74 pg/ml), (182 ± 26 pg/ml), respectively. However, the levels of IFN-γ, IL-4, and IL-6 of serum and IFN-γ, IL-4, and IL-12 in spleen culture and total blood culture of two groups were not significantly different. It seems that ELF-EMF may change T(H)1/T(H)2/T(H)17 balance toward down regulation of T(H)1 and upregulation T(H)17 type responses.

ELF magnetic fields: animal studies, mechanisms of action

Animal studies can contribute to addressing the issue of possible greater health risk for children exposed to 50-60 Hz extremely low frequency (ELF) magnetic fields (MFs), mostly in terms of teratological effects and cancer. Teratology has been extensively studied in animals exposed to ELF MFs but experiments have not established adverse developmental effects. Childhood leukaemia has been the only cancer consistently reported in epidemiological studies as associated with exposure to ELF MFs. This association has been the basis for the classification as "possibly carcinogenic to humans" by the International Agency for Research on Cancer in 2002. Animal experiments have provided only limited support for these epidemiological findings. However, none but one study used an animal model for acute lymphoblastic leukaemia (ALL), the main form of childhood leukaemia, and exposures to ELF MFs were not carried out over the whole pregnancy period, when the first hit of ALL is assumed to occur. Moreover, there are no generally accepted biophysical mechanisms that could explain carcinogenic effects of low-level MFs. The radical pair mechanism and related cryptochromes (CRY) molecules have recently been identified in birds and other non-mammalian species, as a sensor of the geomagnetic field, involved in navigation. The hypothesis has to be tested in mammalian models. CRY, which is part of the molecular circadian clock machinery, is a ubiquitous protein likely to be involved in cancer cell growth and DNA repair. In summary, we now have some clues to test for a better characterization of the interaction between ALL and ELF MFs exposure.

Lack of a co-promotion effect of 60 Hz circularly polarized magnetic fields on spontaneous development of lymphoma in AKR mice

The present study was conducted to investigate the possible effect of 60 Hz circularly polarized magnetic fields (MFs) as promoters of genetically initiated lymphoma in AKR mice. One hundred sixty female animals were divided into four different groups. They were exposed to four different intensities of circularly polarized MFs. Animals received exposure to 60 Hz circularly polarized MF at field strengths (rms-value) of 0 microT (sham control, T1, Group I), 5 microT(T2, Group II), 83.3 microT (T3, Group III), or 500 microT(T4, Group IV), for 21 h/day from the age of 4-6 weeks to the age of 44-46 weeks. There were no exposure-related changes in mean survival time, clinical signs, body weights, hematological values, micronucleus assay, gene expression arrays, analysis of apoptosis, and necropsy findings. At histopathological examination, lymphoma was seen in all the groups. The tumor incidence was 31/40(78%), 30/40(75%), 32/40(80%), and 31/40(78%) in sham control, 5, 83.3, and 500 microT groups, respectively. However, there were no differences in the tumor incidence between the sham control (T1) and circularly polarized MF exposure groups (T2-T4). In conclusion, there was no evidence that exposure to 60 Hz circularly polarized MF strengths up to 500 microT promoted lymphoma in AKR mice.

Changes of leukocyte adherence ability under the influence of magnetic field in the course of a treatment of patients with laryngeal and pharyngeal carcinoma

The authors were monitoring adherence ability of T lymphocytes in vitro in patients with laryngeal and pharyngeal carcinoma at the presence of tumor-specific and viral LDH antigen. The results were assessed and expressed in percent of non adherent T lymphocytes (NAL). First, NAL in patients before initiating the treatment was compared with NAL control group (voluntary blood donors). The ability of the adherence in T lymphocytes in the control group is statistically significantly higher. Further on, NAL in the course of a successful oncological treatment was monitored at the interval of 6 months following the treatment, and further on at yearly intervals. NAL level drops statistically significantly within 6 months and then hold on at levels with no statistical difference unlike the control group, however, the ability of T lymphocyte in patients to adhere remains statistically significantly lower. Statistically significantly higher levels of NAL are at the presence of LDH viral antigen. Further on, the authors were following the influence of magnetic sinusoidal field of power frequency (50 Hz) of a low induction (0.5, 0.1, and 0.05 mT) on NAL. NAL values under the influence of an experimental magnetic field before initiating the treatment as well as in the course of a successful oncological treatment are statistically significantly lower. It means that magnetic filed increases the adherence ability of T lymphocytes in patients with laryngeal and pharyngeal cancer in vitro.

Assessing the potential leukemogenic effects of 50 Hz magnetic fields and their harmonics using an animal leukemia model

To answer the still unresolved question of the possible leukemogenic effects of extremely low frequency magnetic fields (ELF-MFs) and of their harmonics on the incidence of B acute lymphoblastic leukemia in children, we used an animal model to explore the possible co-initiating or co-promoting effects of ELF-MFs on the development of leukemia. We used a rat model in which B acute lymphoblastic leukemia is chemically induced by a nitrosurea derivative. From the onset of the chemical treatment, the animals were also exposed to ELF-MFs (100 microT, sinusoidal 50 Hz MFs), with or without harmonics. The experiment was conducted on 280 rats. We compared body weight and survival time, percentage of bone marrow blast cells, cumulative incidence of leukemia and type of leukemia in the unexposed groups and in the groups exposed to 50 Hz MFs, with and without harmonics. The results showed no significant differences between exposed and unexposed rats for any of these parameters (p > 0.05). Significant changes in the leukemia type obtained after gamma-irradiation of the leukemia model, showed its sensitivity to a physical agent. Our results do not support the hypothesis that ELF-MFs, with or without harmonics, affect the development of B acute lymphoblastic leukemia in children.

Lymphoma development in mice chronically exposed to UMTS-modulated radiofrequency electromagnetic fields

There are public concerns regarding possible carcinogenic or cancer-promoting effects of electromagnetic fields (EMFs) from mobile phones and base stations. The objective of the present study was to investigate whether chronic exposure to EMFs of the UMTS (Universal Mobile Telecommunication System) influences the development of lymphoma in a lymphoma animal model, the AKR/J mouse. Unrestrained mice were chronically sham-exposed (n = 160) or exposed (n = 160) in identical exposure systems (radial waveguides) to a generic UMTS test signal (24 h per day, 7 days per week, 0.4 W/kg SAR). Additionally, 30 animals were kept as cage controls. Animals were checked visually each day and were weighed and palpated weekly to detect swollen lymph nodes. Starting at the age of 6 months, blood samples were taken from the tail every 2 weeks to perform differential leukocyte counts and to measure the hematocrit. Visibly diseased animals or those older than 43 weeks were killed humanely, and tissue slices were examined for metastatic infiltrations and lymphoma type. The study was performed in a blinded way. Cage control animals had a significantly lower growth rate than those kept in the radial waveguides. The number of ill animals, the mean survival time, and the severity code of the disease did not differ between the experimental groups. Therefore, the data show no negative effects from exposure and corroborate earlier findings in AKR/J mice exposed to GSM EMF (Sommer et al., BMC Cancer 4, 77-90, 2004).