Em Fields On Brain Tumor Incidence - Chemicals And Cell Phones
..."In a series of studies, Hardell and colleagues have examined the relationship between the side of the head habitually used in operation of cellular and cordless phones and a possible relationship to the site of brain tumors ([Hardell et al., 2003]). The risk for ipsilateral (same side) use significantly increased the risk for astrocytoma for all types of phones, but use of the phone on the opposite side of the head was not associated with significantly increased risk. Overall, use of FM (analog) phones gave an increased risk, whereas digital and cordless phones did not increase risks significantly."...
This excellent piece of work by Dr Adey (so typical of this towering figure in EM and Cell research) should put to rest the debate on the dangers of Cell phones (obviously this applies to all the wireless stuff that is so much the rage these days as well) . While the danger cannot be avoided at least it can be minimized, to some extent, as per above. Those who insist on using them can further reduce their exposure by shortening transmissions (cutting out the 'gift of the gab') and listening more (pun intended)...which besides lessening the exposure should improve their listen skills (a much maligned attribute of our modern society)..
This paper is a must read for those interested in non thermal effects EMF (Electromagnetic Fields) particularly the collective cell/neuron response/behavior/properties to stimuli. It is an eye opener and very useful when dealing with vested interests who continually ignore non thermal effects to promote their wares with self serving rhetoric.
5. Influence of EM fields on brain tumor incidence in man and in animal models (10)
5.1. Epidemiological studies
Environmental EM fields may act jointly with exposure to environmental chemicals with known cancer-promoting actions in enhancing occupational brain tumor risks. Experimental evidence supports cell membranes as a site for joint actions of many chemical cancer promoters with EM fields ([Adey, 1992b]). The latter include pesticides, weedicides and electrical solvents. A case control study by the U.S. National Cancer Institute of brain tumor incidence in RF/microwave occupational exposures ([Thomas et al., 1987]) in the states of New Jersey, Pennsylvania and Louisiana concluded that all excess risk for primary brain tumors in white males aged over 30 years derived from jobs involving design, manufacture, installation and repair of electronic equipment (Risk Ratio=2.3, 95% CI=1.3,4.2). Cases were divided into cohorts with 5, 10, 15 and 20+ years of exposure. Risks of astrocytomas increased to ten-fold for those employed 20 years or more, when concurrent exposure to electrical and electronic solvents was involved. RRs were not increased in men exposed to RF/microwave fields, but who never worked in electrical or electronics jobs; leading the authors to emphasize concurrent exposures to soldering fumes, solvents and a variety of chemicals as possible co-factors with RF/microwave fields in tumor promotion.
In a case-control study of risk factors for gliomas and meningiomas in males in Los Angeles County, involving 272 men aged 2569 with primary brain tumors and 272 matched neighbor controls ([Preston-Martin et al., 1989]), glioma (but not meningioma) risk related to prior employment in jobs likely to involve high exposure to electric and magnetic fields (P<0.05). The risk was greatest for astrocytoma (OR for employment in such jobs for >5 years=4.3; CI=1.215.6). As in the study of microwave workers cited above, there was evidence of concurrent action of chemical factors. More glioma cases had worked in the rubber industry (discordant pairs 6/1), and more worked in hot processes using plastics (9/1).
[Savitz and Loomis (1995)] have linked work site magnetic field measurements to individual work histories in a cohort mortality study (138,905 men) at 5 large American electric power companies over a period of 36 years. Brain cancer risk increased by a factor of 1.94 per microtesla-year of magnetic field exposure in the previous 210 years, with a mortality rate ratio of 2.6 in the highest exposure category.
In a series of studies, Hardell and colleagues have examined the relationship between the side of the head habitually used in operation of cellular and cordless phones and a possible relationship to the site of brain tumors ([Hardell et al., 2003]). The risk for ipsilateral use significantly increased the risk for astrocytoma for all types of phones, but use of the phone on the opposite side of the head was not associated with significantly increased risk. Overall, use of FM (analog) phones gave an increased risk, whereas digital and cordless phones did not increase risks significantly.
5.2. Animal models of brain tumor promotion
There are few accepted animal models of spontaneous malignant central nervous system (CNS) tumors, although there has been increasing use of the Fischer 344 rat, with a reported incidence of spontaneous malignant tumors as high as 11%. Two life term studies using this rat model have compared exposures to the North American Digital Standard (NADC) digital phone field using 11
Time Division Multiple Access (TDMA) modulation pulsed at 50 "packets/sec, with comparable exposures to the older type of FM (analog) phone fields ([Adey et al., 1999]; [Adey et al., 2000]). Rats were exposed in utero to a single dose of the short-lived neurocarcinogen ethylnitrosourea (ENU), and thereafter, exposed intermittently to either TDMA or FM fields for 23 months.
In the TDMA study, when compared with rats receiving ENU but unexposed, rats that died from a primary CNS tumor before termination of the study showed a significant reduction in tumor incidence (P<0.015). A similar but non-significant reduction in spontaneous tumor incidence occurred in rats field-exposed but not receiving ENU (P<0.08). In the balanced design of this experiment, consistent non-significant differences in survival rates were noted between the four rat groups, with higher death rates in a progression: sham/field:sham/sham:ENU/field:ENU/sham. By contrast in the FM study, no field-related effects were observed in number, incidence or types of either spontaneous or ENU-induced CNS tumors.
These observations of an apparent protective effect against ENU-induced and spontaneous CNS tumors are not isolated. Low dosage of X-rays in fetal rats at the time of ENU dosage sharply reduce subsequent incidence of induced tumors ([Warkany et al., 1976]), through activation of AT (alkylguanine-DNA-alkyltransferase) enzymes that participate in DNA repair ([Stammberger et al., 1990]). Other studies with nonionizing (microwave) fields also suggest their actions in mechanisms of DNA repair. Modulation of levels of single-strand breaks in brain cell DNA has been reported following low-level, long-term microwave exposure in mice ([Sarkar et al., 1994]) and in acute experiments in rats ([Lai and Singh, 1995]).
6. Summary: intrinsic and induced electric fields as threshold determinants in central nervous tissue; the potential role of cell ensembles
The intact nervous system might be expected to be more sensitive to induced electric fields and currents than in vitro preparations, due to a higher level of spontaneous activity and a greater number of interacting neurons. However, these fields induced in the body are almost always much lower than those capable of stimulating peripheral nerve tissue ([Saunders and Jefferys, 2002]). Weak electric field effects, below action potential thresholds, have been demonstrated in in vitro brain slice preparations ([Faber and Korn; 1989]; [Jefferys, 1995]}.Behavioral sensitivities in sharks and rays may be as low as 0.5 nV/mm for tissue components of electrical fields in the surrounding ocean ([Kalmijn, 1971]), or 100 times below measurable thresholds of individual electroreceptor organs ([Valberg et al., 1997]).
Research in sensory physiology supports the concept that some threshold properties in excitable tissues may reside in highly cooperative properties of a population elements, rather than in a single detector ([Adey,1998, 2003a, 2003b]). Seminal observations in the human auditory system point to a receptor vibrational displacement of 10-11m, or approximately the diameter of a single hydrogen atom ([Bialek, 1983]; [Bialek and Wit, 1984]). It is notable that suppression of intrinsic thermal noise allows the ear to function as though close to 0 degree K, suggesting system properties inherent in the detection sequence. Human olfactory thresholds for musk occur at 10-11 M, with odorant molecules distributed over 240 mm2 ([Adey, 1959]). Human detection of single photons of bluegreen light occurs at energies of 2.5 eV ([Hagins, 1979]). In another context, pathogenic bacteria, long thought to function independently, exhibit ensemble properties by a system recognizing (12) colony numbers as an essential step preceding release of toxins. These quorum sensing systems may control expression of virulence factors in the lungs of patients with cystic fibrosis ([Erickson et al., 2002]).
Although far from a consensus on mechanisms mediating these low-level EMF sensitivities, appropriate models are based in nonequilibrium thermodynamics, with nonlinear electrodynamics as an integral feature. Heating models, based in equilibrium thermodynamics, fail to explain a wide spectrum of observed nonthermal EMF bioeffects in central nervous tissue. The findings suggest a biological organization based in physical processes at the atomic level, beyond the realm of chemical reactions between biomolecules. Much of this signaling within and between cells may be mediated by free radicals of the oxygen and nitrogen species. Emergent concepts of tissue thresholds to EMF sensitivities address ensemble or domain functions of populations of cells, cooperatively "whispering together " in intercellular communication, and organized hierarchically at atomic and molecular levels.
7. See Also Search Neuroscion Bibliographic References
posted by Chris Gupta on Wednesday October 20 2004
updated on Saturday September 24 2005
URL of this article:
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