Cancer risk and electromagnetic fields

Axial Alignment of Carbon Nanotubes on Fibers To Enable Highly Conductive Fabrics for Electromagnetic Interference Shielding

Conductive coatings show great promise for next-generation electromagnetic interference (EMI) shielding challenges on textile; however, their stringent requirements for electrical conductivity are difficult to meet by conventional approaches of increasing the loading and homogeneity of conductive nanofillers. Here, the axial alignment of carbon nanotubes (CNTs) on fibers that were obtained by spontaneous capillary-driven self-assembly is shown on commercial cotton fabrics, and its great potential for EMI shielding is demonstrated. The aligned CNTs structurally optimize the conductive network on fabrics and yield an 81-fold increase in electrical conductivity per unit of CNT, compared with the disordered CNT microstructure. The high-efficiency electrical conductivity allows a several-micron-thick coating on insulating fabrics to endow an EMI shielding effectiveness of 21.5 dB in the X band and 20.8 dB in the Ku band, which meets the standard shielding requirement in commercial applications. It is among the minimum reported thicknesses for conductive nanocomposite coatings to date. Moreover, the coated fabrics with aligned CNTs possess a desirable stability upon bending, scratching, stripping, and even washing, which is attributed to the dense CNT packing in the aligned microarchitecture. This work presents the anisotropic structure on large areas by self-assembly, offering new opportunities for next-generation portable and wearable electronic devices.

Significant Differences in the Effects of Magnetic Field Exposure on 7,12-Dimethylbenz(a)anthracene-Induced Mammary Carcinogenesis in Two Substrains of Sprague-Dawley Rats

We have shown previously (S. Thun-Battersby et al., Cancer Res., 59: 3627-3633, 1999) that power-line frequency (50-Hz) magnetic fields (MFs) at micro T-flux densities enhance mammary gland tumor development and growth in the 7,12-dimethylbenz(a)anthracene (DMBA) model of breast cancer in female Sprague-Dawley (SD) rats. We also demonstrated that MF exposure results in an enhanced proliferative activity of the mammary epithelium of SD rats (M. Fedrowitz et al., Cancer Res., 62: 1356-1363, 2002), which is a likely explanation for the cocarcinogenic or tumor-promoting effects of MF exposure in the DMBA model. However, in contrast with our data, in a similar study conducted by Battelle in the United States, no evidence for a cocarcinogenic or tumor-promoting effect of MF exposure was found in the DMBA model in SD rats (L. E. Anderson et al., Carcinogenesis, 20: 1615-1620, 1999). Probably the most important difference between our and the Battelle studies was the use of different substrains of SD rats; the United States rats were much more susceptible to DMBA than the rats used in our studies. This prompted us to compare different substrains of SD outbred rats in our laboratory in respect to MF effects on cell proliferation in the mammary gland, susceptibility to DMBA-induced mammary cancer, and MF effects on mammary tumor development and growth in the DMBA model. The SD substrain (termed "SD1") used in all of our previous studies was considered MF-sensitive and used for comparison with another substrain ("SD2") obtained from the same breeder. In contrast with SD1 rats, no enhanced cell proliferation was determined after MF exposure in SD2 rats. MF exposure significantly increased mammary tumor development and growth in SD1 but not SD2 rats. These data indicate that the genetic background plays a pivotal role in effects of MF exposure. Different strains or substrains of rats may serve to evaluate the genetic factors underlying sensitivity to cocarcinogenic or tumor-promoting effects of MF exposure.

The effect of strong static magnetic field on lymphocytes

We investigated whether static electromagnetic fields (EMFs) at a flux density of 4.75 T, generated by an NMR apparatus (NMRF), could promote movements of Ca2+, cell proliferation, and the eventual production of proinflammatory cytokines in human peripheral blood mononuclear cells (PBMC) as well as in Jurkat cells, after exposure to the field for 1 h. The same study was also performed after activation of cells with 5 mg/ml phytohaemagglutinin (PHA). Our results clearly demonstrate that static NMRF exposure has neither proliferative, nor activating, nor proinflammatory effects on both normal and PHA activated PBMC. Moreover, the concentration of interleukin-1beta, interleukin-2, interleukin-6, interferon, and tumour necrosis factor alpha (TNFalpha) remained unvaried in exposed cells. Exposure of Jurkat cells statistically decreased the proliferation and the proliferation indexes, which 24 and 48 h after exposure were 0.7 +/- 0.29 and 0.87 +/- 0.12, respectively. Moreover, in Jurkat cells the [Ca2+]i was higher than in PBMC and was reduced significantly to about one half after exposure. This is consistent with the decrease of proliferation and with the low levels of IL-2 measured. On the whole, our data suggest that NMRF exposure failed to affect the physiologic behaviour of normal lymphomonocytes. Instead in Jurkat cells, by changing the properties of cell membranes, NMRF can influence Ca2+ transport processes, and hence Ca2+ homeostasis with improvement of proliferation.

Short cycles of both static and pulsed electromagnetic fields have no effect on the induction of cytokines by peripheral blood mononuclear cells

We evaluated the effect of short cycles of static and pulsed electromagnetic field exposure on the eventual activation of peripheral blood mononuclear cells. The cells were subjected to three 15-min cycles of EMF, each exposure being followed by 105 min without a field, for a total of 6 hr. The results clearly demonstrate that the proliferative responses of both normal cells and cells stimulated with 1 microg/ml phytohemagglutinin were not distinguishable from control cells not exposed to EMF. Moreover, although the production of interleukin-2, interferon gamma and tumor necrosis factor alpha increased during the first 48 hr of incubation, the values remained unchanged with respect to controls. This indicates that brief exposure to an electromagnetic field has no significant effect on peripheral blood mononuclear cells. The comparison between biological activity and the cytokine antigen present in our samples indicated that the recovery of antigen corresponded to an equal recovery of biological activity, suggesting the absence of either qualitative differences in these proteins or the impairment of transcriptional and translational processes.

Suppression of heat-induced HSP-70 by simultaneous exposure to 50 mT magnetic field

Effect of extremely low frequency magnetic field (ELFMF) at 50 mT and 60 Hz on heat-induced expression of heat shock protein 70 (hsp-70) was examined in HL60RG cells. No increase in hsp-70 production was observed in the cells after exposure to 50 mT ELFMF alone. Simultaneous exposure to 50 mT ELFMF in combination with mild heat at 42 and 40 degrees C suppressed heat-induced hsp-70 expression. The suppression of hsp-70 occurred when cells were simultaneously exposed to both for longer periods of more than 5 h. However, the suppression of hsp-70 was not observed at a magnetic density of 5 and 0.5 mT. This result suggests that exposure to 50 mT ELFMF may act on a protection against the concomitant mild heat stress in HL60RG cells.

Ets1 oncogene induction by ELF-modulated 50 MHz radiofrequency electromagnetic field

We have analyzed gene expression in hemopoietic and testicular cell types after their exposure to 50 MHz radiofrequency (RF) non-ionizing radiation modulated (80%) with a 16 Hz frequency. The exposure system generates a 0.2 microT magnetic field parallel to the ground and a 60 V/m electric field orthogonal to the earth's magnetic field. Exposure conditions were selected so as to interfere with the calcium ion flow. Under these electromagnetic field (EMF) conditions, we observed an overexpression of the ets1 mRNA in Jurkat T-lymphoblastoid and Leydig TM3 cell lines. This effect was observed only in the presence of the 16 Hz modulation, corresponding to the resonance frequency for calcium ion with a DC magnetic field of 45.7 microT. We have also identified a putative candidate gene repressed after EMF exposure. The experimental model described in this paper may contribute to the understanding of the biological mechanisms involved in EMF effects.

Induction of stress proteins by electromagnetic fields in cultured HL-60 cells

HL-60 cells in culture were exposed for 2 h to a sinusoidal 0.1 or 1 mT (1 or 10 Gauss) magnetic field at 60 Hz and pulse labeled after exposure with radioactive isotopes by incubation by using either [(35)S]methionine, [(3)H]leucine, or [(33)P]phosphate. The radioactive labels were incorporated into cellular proteins through synthesis or phosphorylation. Proteins were extracted from electrostatically sorted nuclei, and the heat shock/stress proteins (sp) were analyzed for synthesis and phosphorylation by two-dimensional polyacrylamide gel electrophoresis. In the control cultures (no exposure to the magnetic field), sp 72c (cognate form) was faintly observed. A 0.1 mT exposure did not show sp metabolism to be different from that of the controls; however, after a 1 mT exposure of the HL-60 cells, sp 70i (inducible form) was synthesized ([(35)S]methionine incorporation). Sp 90 was not synthesized at either field level, but was phosphorylated ([(33)P]phosphate incorporation) in the 1 mT exposure. Sp 27 (isoforms a and b) was induced after a 1 mT exposure as reflected by labeling with [(3)H]leucine. These sps were not detected after a 0.1 mT exposure. After a 1 mT exposure and labeling with [(33)P], sp 27 isoforms b and c were phosphorylated whereas isoform 'a' was not observed. Sps 70i, 72c, and 90 were identified by commercial sp antibodies. Likewise, polypeptides a, b, and c were verified as sp 27 isoforms by Western blotting. Statistical evaluation of sp areas and densities, determined from fluorographs by Western-blot analysis, revealed a significant increase in sps 90 and 27a after a 1 mT magnetic field exposure. The 1 mT magnetic field interacts at the cellular level to induce a variety of sp species. Bioelectromagnetics 20:347-357, 1999. Published 1999 Wiley-Liss, Inc.

The design, construction and calibration of a carefully controlled source for exposure of mammalian cells to extremely low-frequency electromagnetic fields

Despite some epidemiological evidence for an association between increased risk of cancer and exposure to electromagnetic fields (EMFs), cancer causation by such exposure remains unproven. Furthermore, for reasons such as biological unresponsiveness of the chosen system, poor equipment design and experimental confounders, no reproducible effects on animals or mammalian cells in culture have been demonstrated following exposure to power frequency EMFs at levels normally encountered in residential settings (<10 to 1000 microT). The apparatus described here, designed specifically to perform large, well-controlled cell biology experiments, reduces extraneous variables to the absolute minimum, so that small effects cannot be ascribed to some cause unrelated to the experimental protocol. Our novel apparatus consists of two identical solenoids which, in use, only differ by whether the field-producing current is flowing or not; they do not influence one another in any way. They are supplied with conditioned air from a common tissue culture incubator, are completely screened from environmental a.c. fields with Mumetal shielding and can be operated under normal laboratory conditions. Furthermore, the arrangement is such that the investigator is unaware whether cells have, or have not, been exposed until after the results have been evaluated. We report the design, construction, calibration and potential uses of this source.

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.