..................................................................................................................................................................................................................
..................................................................................................................................................................................................................
Abstract
The published results available in 2005 were insufficient to draw firm conclusions concerning the possible non-thermal effects of radiofrequency fields on the blood-brain barrier (BBB). This critical review deals with 16 articles on this topic published since 2005. The methodological quality of these articles was not equivalent. We therefore analysed the underlying methodologies from both their biological and physical aspects. We conclude that recent studies provide no convincing proof of deleterious effects of RF on the integrity of the BBB, for specific absorption rates (SAR) up to 6 W/kg.
Summary
This summary of effects on the BBB is based on 16 research articles, including:
• Three studies in vitro:
Two of these studies [8,9] showed no effect of semi-chronic exposure to GSM or UMTS electromagnetic radiation for SAR values from 0.02 to 1.64 W/kg with validated dosimetry, but with incomplete dosimetry in one case. The third study [10] reported effects of RF at 915 MHz with modulation and an unusual exposure system, but without dosimetry to determine the SAR.
• Two studies in humans:
Two studies have reported weak variation of circulating protein concentrations in humans, but the methodologies of these methods include several major flaws, particularly as concerns the choice of parameter, making it impossible to interpretate the results. Indeed, the parameter used has not been validated, varies between individuals and is determined in the blood rather than in the CSF [22,23].
• Eleven studies in vivo:
Effects of exposure to RF on the permeability of the BBB and/or neuronal integrity have been sought in vivo, in conditions of acute, semi-chronic or chronic exposure, with a large range of SAR, extending from 0.0018 to 20 W/kg for GSM 900 or TDMA at 1439 MHz or 2450 MHz (continuous and modulated) signals.
The published results available in 2005 were insufficient to draw firm conclusions concerning the possible non-thermal effects of radiofrequency fields on the blood-brain barrier (BBB). This critical review deals with 16 articles on this topic published since 2005. The methodological quality of these articles was not equivalent. We therefore analysed the underlying methodologies from both their biological and physical aspects. We conclude that recent studies provide no convincing proof of deleterious effects of RF on the integrity of the BBB, for specific absorption rates (SAR) up to 6 W/kg.
Summary
This summary of effects on the BBB is based on 16 research articles, including:
• Three studies in vitro:
Two of these studies [8,9] showed no effect of semi-chronic exposure to GSM or UMTS electromagnetic radiation for SAR values from 0.02 to 1.64 W/kg with validated dosimetry, but with incomplete dosimetry in one case. The third study [10] reported effects of RF at 915 MHz with modulation and an unusual exposure system, but without dosimetry to determine the SAR.
• Two studies in humans:
Two studies have reported weak variation of circulating protein concentrations in humans, but the methodologies of these methods include several major flaws, particularly as concerns the choice of parameter, making it impossible to interpretate the results. Indeed, the parameter used has not been validated, varies between individuals and is determined in the blood rather than in the CSF [22,23].
• Eleven studies in vivo:
Effects of exposure to RF on the permeability of the BBB and/or neuronal integrity have been sought in vivo, in conditions of acute, semi-chronic or chronic exposure, with a large range of SAR, extending from 0.0018 to 20 W/kg for GSM 900 or TDMA at 1439 MHz or 2450 MHz (continuous and modulated) signals.
A review of 44 animal studies
Radiofrequency studies on tumorigenesis and the blood-brain barrier in lab animals support the conclusion of no adverse effects without significant tissue temperature increase
by Elder presented at: Electromagnetic Compatibility (APEMC), 2010 Asia-Pacific Symposium on Electromagnetic Compatiblity April 12 - 16, Beijing, China
This paper summarizes the weight of scientific evidence on whether or not exposure of laboratory animals to radiofrequency (RF) energy a) causes or promotes tumor development and b) affects the integrity of the blood-brain barrier (BBB). Forty-four studies of tumorigenesis were identified. In addition to the studies of spontaneous tumorigenesis in animals exposed to RF energy alone, 21 of the 44 studies investigated tumor promotion in animals exposed to RF energy in combination with chemicals [e.g., ethylnitrosurea (ENU) and 7,12-dimethylbenz[a]anthracene (DMBA)] and physical agents (e.g., x-rays and ultraviolet radiation) known to cause cancer. Evaluation of the results in all 44 studies on tumorigenesis showed no adverse effect of RF exposure up to two years in duration at dose rates up to 4 W/kg (10 times greater than the occupational safety limit) on carcinogenic processes (initiation, promotion and co-promotion). Other information in these studies on survival and body mass provides supporting evidence for the conclusion that RF exposure does not affect tumor development because a) 26 of 27 studies since 1983 reported no significant change on survival and b) all 27 studies reporting body mass observed no significant change in this health indicator. The weight of evidence of 44 animal tumorigenic studies supports the conclusion that RF exposure within current internationally accepted limits, when given alone or in combination with carcinogens, is unlikely to affect tumor development in human beings. Furthermore, the results showing a lack of RF effects on tumorigenesis, survival and body mass in live animals offer a strong challenge to studies reporting potential genotoxic and other health effects based on research with cells in culture and other biological samples exposed in vitro to RF energy. Another area of research has focused on whether or not RF exposure could affect the integrity of the blood-brain barrier (BBB) that protects the brain from potentially to- - xic molecules in the blood. A number of laboratories have confirmed that the permeability of the BBB can be affected if the temperature of the brain is increased significantly. The effect is a temperature effect because it does not matter whether the effect on the BBB was caused by exposing the animal to heated air, heated water or RF energy. Reports in the 1970s and more recent reports of changes in BBB permeability following exposure to levels of RF energy that would not significantly increase the brain temperature have failed the test of independent confirmation.
by Elder presented at: Electromagnetic Compatibility (APEMC), 2010 Asia-Pacific Symposium on Electromagnetic Compatiblity April 12 - 16, Beijing, China
This paper summarizes the weight of scientific evidence on whether or not exposure of laboratory animals to radiofrequency (RF) energy a) causes or promotes tumor development and b) affects the integrity of the blood-brain barrier (BBB). Forty-four studies of tumorigenesis were identified. In addition to the studies of spontaneous tumorigenesis in animals exposed to RF energy alone, 21 of the 44 studies investigated tumor promotion in animals exposed to RF energy in combination with chemicals [e.g., ethylnitrosurea (ENU) and 7,12-dimethylbenz[a]anthracene (DMBA)] and physical agents (e.g., x-rays and ultraviolet radiation) known to cause cancer. Evaluation of the results in all 44 studies on tumorigenesis showed no adverse effect of RF exposure up to two years in duration at dose rates up to 4 W/kg (10 times greater than the occupational safety limit) on carcinogenic processes (initiation, promotion and co-promotion). Other information in these studies on survival and body mass provides supporting evidence for the conclusion that RF exposure does not affect tumor development because a) 26 of 27 studies since 1983 reported no significant change on survival and b) all 27 studies reporting body mass observed no significant change in this health indicator. The weight of evidence of 44 animal tumorigenic studies supports the conclusion that RF exposure within current internationally accepted limits, when given alone or in combination with carcinogens, is unlikely to affect tumor development in human beings. Furthermore, the results showing a lack of RF effects on tumorigenesis, survival and body mass in live animals offer a strong challenge to studies reporting potential genotoxic and other health effects based on research with cells in culture and other biological samples exposed in vitro to RF energy. Another area of research has focused on whether or not RF exposure could affect the integrity of the blood-brain barrier (BBB) that protects the brain from potentially to- - xic molecules in the blood. A number of laboratories have confirmed that the permeability of the BBB can be affected if the temperature of the brain is increased significantly. The effect is a temperature effect because it does not matter whether the effect on the BBB was caused by exposing the animal to heated air, heated water or RF energy. Reports in the 1970s and more recent reports of changes in BBB permeability following exposure to levels of RF energy that would not significantly increase the brain temperature have failed the test of independent confirmation.
Sample Study: Brain Blood Barrier
Effect of long-term mobile communication microwave exposure on vascular permeability in mouse brain.
Finnie JW et al., Pathology 2002 Aug:34(4): 344 - 7
Veterinary Services Division, Institute of Medical and Veterinary Science, Adelaide, South Australia, Australia.
Abstract
AIMS: To study the effect of long-term exposure to global system for mobile communication (GSM) radiofrequency fields on vascular permeability in murine brains.
METHODS: Using a purpose-designed exposure system at 900 MHz, mice were given a 60-minute far-field, whole body exposure on each of 5 days per week for 104 weeks at specific absorption rates (SAR) of 0.25, 1.0,2.0 and 4.0 W/kg. Control mice were sham-exposed or permitted free movement in a cage to evaluate any stress-related effects. Albumin immunohistochemistry was used to detect increased vascular permeability and the efficacy of the vascular tracer was confirmed with a positive control group exposed to a clostridial toxin known to increase vascular permeability in the brain.
RESULTS: In all exposed and control groups, albumin extravasation was minimal, often leptomeningeal, and was deemed insignificant as a maximum of three capillaries or venules in a given brain showed leakage from the very many blood vessels present in the three coronal brain sections.
CONCLUSIONS: These results suggest that prolonged exposure to mobile telephone-type radiation produces negligible disruption to blood-brain barrier integrity at the light microscope level using endogenous albumin as a vascular tracer.
Finnie JW et al., Pathology 2002 Aug:34(4): 344 - 7
Veterinary Services Division, Institute of Medical and Veterinary Science, Adelaide, South Australia, Australia.
Abstract
AIMS: To study the effect of long-term exposure to global system for mobile communication (GSM) radiofrequency fields on vascular permeability in murine brains.
METHODS: Using a purpose-designed exposure system at 900 MHz, mice were given a 60-minute far-field, whole body exposure on each of 5 days per week for 104 weeks at specific absorption rates (SAR) of 0.25, 1.0,2.0 and 4.0 W/kg. Control mice were sham-exposed or permitted free movement in a cage to evaluate any stress-related effects. Albumin immunohistochemistry was used to detect increased vascular permeability and the efficacy of the vascular tracer was confirmed with a positive control group exposed to a clostridial toxin known to increase vascular permeability in the brain.
RESULTS: In all exposed and control groups, albumin extravasation was minimal, often leptomeningeal, and was deemed insignificant as a maximum of three capillaries or venules in a given brain showed leakage from the very many blood vessels present in the three coronal brain sections.
CONCLUSIONS: These results suggest that prolonged exposure to mobile telephone-type radiation produces negligible disruption to blood-brain barrier integrity at the light microscope level using endogenous albumin as a vascular tracer.
Sample Study: Genotoxicity/carcinogenicity in rats
GSM and DCS wireless communication signals: combined chronic toxicity/carcinogenicity study in the Wistar rat
Smith et al. Radiat Res. 2007 Oct;168(4):480-92
RCC Ltd, CH-4452 Itingen, Switzerland. paul.smith@convance.com
Abstract
A total of 1170 rats comprised of 65 male and 65 female Han Wistar rats per group were exposed for 2 h/day, 5 days/ week for up to 104 weeks to GSM or DCS wireless communication signals at three nominal SARs of 0.44, 1.33 and 4.0 W/kg. A preliminary study confirmed that the highest exposure level was below that which was capable of causing a measurable increase in the core temperature of the rat. Additional groups for each modulation were sham exposed, and there was also an unrestrained, unexposed (cage) control group. Fifteen male and 15 female rats per group were killed after 52 weeks. From the remaining 50 male and 50 female rats per group, surviving animals were killed after 104 weeks. Evaluations during the study included mortality rate, clinical signs, recording of palpable masses, body weight, food consumption, ophthalmoscopic examination, and clinical pathological investigations. Terminal investigations included organ weight measurement and macroscopic and microscopic pathology examinations. There was no adverse response to the wireless communication signals. In particular, there were no significant differences in the incidence of primary neoplasms, the number of rats with more than one primary neoplasm, the multiplicity and latency of neoplasms, the number of rats with metastases, and the number of benign and malignant neoplasms between the rats exposed to wireless communication signals and rats that were sham exposed.
Smith et al. Radiat Res. 2007 Oct;168(4):480-92
RCC Ltd, CH-4452 Itingen, Switzerland. paul.smith@convance.com
Abstract
A total of 1170 rats comprised of 65 male and 65 female Han Wistar rats per group were exposed for 2 h/day, 5 days/ week for up to 104 weeks to GSM or DCS wireless communication signals at three nominal SARs of 0.44, 1.33 and 4.0 W/kg. A preliminary study confirmed that the highest exposure level was below that which was capable of causing a measurable increase in the core temperature of the rat. Additional groups for each modulation were sham exposed, and there was also an unrestrained, unexposed (cage) control group. Fifteen male and 15 female rats per group were killed after 52 weeks. From the remaining 50 male and 50 female rats per group, surviving animals were killed after 104 weeks. Evaluations during the study included mortality rate, clinical signs, recording of palpable masses, body weight, food consumption, ophthalmoscopic examination, and clinical pathological investigations. Terminal investigations included organ weight measurement and macroscopic and microscopic pathology examinations. There was no adverse response to the wireless communication signals. In particular, there were no significant differences in the incidence of primary neoplasms, the number of rats with more than one primary neoplasm, the multiplicity and latency of neoplasms, the number of rats with metastases, and the number of benign and malignant neoplasms between the rats exposed to wireless communication signals and rats that were sham exposed.
Except where noted all images on this web site are taken from the Wikipedia commons
All trademarks are the property of their respective owners Copyright 2009 EMF & Health
All trademarks are the property of their respective owners Copyright 2009 EMF & Health