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31/01/2011 - January 2011 - Science Update

The following is a quick summary of another twenty papers that have come out over the last few months related to effects of electromagnetic radiation. Some of the papers are notable papers that have been published very recently, others are papers that were published a few months ago that have not yet made it to one of the Science Updates.


1. N Nieto-Hernandez R et al, (September 2010) Can exposure to a terrestrial trunked radio (TETRA)-like signal cause symptoms? A randomised double-blind provocation study, Occup Environ Med. 2010 Sep 23. [Epub ahead of print] [View Author's abstract conclusions] [View on Pubmed]
 

Objectives Concerns have been raised about possible health effects from radiofrequency fields pulsing at around 16 Hz. A radio system used by UK police (TETRA) employs signals which pulse at 17.6 Hz. We tested whether exposure to a continuous wave signal at 385.25 MHz or a TETRA-like signal resulted in symptoms among users reporting sensitivity to TETRA compared to users not reporting sensitivity to TETRA. Methods 60 sensitive and 60 non-sensitive users were exposed to three 50 min conditions: a signal with a 16 Hz component, a continuous wave condition and a sham condition. The mean radiated power for the 16 Hz and continuous wave conditions was 250 mW. The order of conditions was randomised and testing was conducted double-blind. Participants reported the severity of eight symptoms during and after each exposure, their mood state at the end of each exposure, and whether they could tell which sessions involved active signals. The study was registered in advance with the ISRCTN register. Results Exposure to the continuous wave signal increased ratings of headache in all participants, fatigue in non-sensitive participants and difficulty concentrating in sensitive participants. Paradoxically, it reduced sensations of itching in sensitive participants. These effects were not observed in the condition with 16 Hz pulsing, except for those relating to concentration. Adjusting for multiple comparisons removed most significant effects, but not those relating to itch. The results suggested that exposure to TETRA signals is not responsible for symptoms reported by some users, although exposure to a continuous wave signal may affect symptoms.


2. P Grigoriev YG et al, (December 2010) Confirmation studies of Soviet research on immunological effects of microwaves: Russian immunology results, Bioelectromagnetics. 2010 Dec;31(8):589-602. doi: 10.1002/bem.20605. Epub 2010 Sep 20 [View Author's abstract conclusions] [View on Pubmed]
 

This paper presents the results of a replication study performed to investigate earlier Soviet studies conducted between 1974 and 1991 that showed immunological and reproductive effects of long-term low-level exposure of rats to radiofrequency (RF) electromagnetic fields. The early studies were used, in part, for developing exposure standards for the USSR population and thus it was necessary to confirm the Russian findings. In the present study, the conditions of RF exposure were made as similar as possible to those in the earlier experiments: Wistar rats were exposed in the far field to 2450 MHz continuous wave RF fields with an incident power density in the cages of 5 W/m2 for 7 h/day, 5 days/week for a total of 30 days, resulting in a whole-body SAR of 0.16 W/kg. Effects of the exposure on immunological parameters in the brain and liver of rats were evaluated using the complement fixation test (CFT), as in the original studies, and an additional test, the more modern ELISA test. Our results, using CFT and ELISA, partly confirmed the findings of the early studies and indicated possible effects from non-thermal RF exposure on autoimmune processes. The RF exposure resulted in minor increases in formation of antibodies in brain tissue extract and the exposure did not appear to be pathological. In addition, a study was conducted to replicate a previous Soviet study on effects from the injection of blood serum from RF-exposed rats on pregnancy and foetal and offspring development of rats, using a similar animal model and protocol. Our results showed the same general trends as the earlier study, suggesting possible adverse effects of the blood serum from exposed rats on pregnancy and foetal development of intact rats, however, application of these results in developing exposure standards is limited.


3. P Lowden A et al, (January 2011) Sleep after mobile phone exposure in subjects with mobile phone-related symptoms, Bioelectromagnetics. 2011 Jan;32(1):4-14 [View Author's abstract conclusions] [View on Pubmed]
 

Several studies show increases in activity for certain frequency bands (10-14 Hz) and visually scored parameters during sleep after exposure to radiofrequency electromagnetic fields. A shortened REM latency has also been reported. We investigated the effects of a double-blind radiofrequency exposure (884 MHz, GSM signaling standard including non-DTX and DTX mode, time-averaged 10 g psSAR of 1.4 W/kg) on self-evaluated sleepiness and objective EEG measures during sleep. Forty-eight subjects (mean age 28 years) underwent 3 h of controlled exposure (7:30-10:30 PM; active or sham) prior to sleep, followed by a full-night polysomnographic recording in a sleep laboratory. The results demonstrated that following exposure, time in Stages 3 and 4 sleep (SWS, slow-wave sleep) decreased by 9.5 min (12%) out of a total of 78.6 min, and time in Stage 2 sleep increased by 8.3 min (4%) out of a total of 196.3 min compared to sham. The latency to Stage 3 sleep was also prolonged by 4.8 min after exposure. Power density analysis indicated an enhanced activation in the frequency ranges 0.5-1.5 and 5.75-10.5 Hz during the first 30 min of Stage 2 sleep, with 7.5-11.75 Hz being elevated within the first hour of Stage 2 sleep, and bands 4.75-8.25 Hz elevated during the second hour of Stage 2 sleep. No pronounced power changes were observed in SWS or for the third hour of scored Stage 2 sleep. No differences were found between controls and subjects with prior complaints of mobile phone-related symptoms. The results confirm previous findings that RF exposure increased the EEG alpha range in the sleep EEG, and indicated moderate impairment of SWS. Furthermore, reported differences in sensitivity to mobile phone use were not reflected in sleep parameters.


4. N Bourthoumieu S et al, (September 2010) Cytogenetic Studies in Human Cells Exposed In Vitro to GSM-900 MHz Radiofrequency Radiation Using R-Banded Karyotyping, Radiat Res. 2010 Sep 20. [Epub ahead of print] [View Author's abstract conclusions] [View on Pubmed]
 

Abstract It is important to determine the possible effects of exposure to radiofrequency (RF) radiation on the genetic material of cells since damage to the DNA of somatic cells may be linked to cancer development or cell death and damage to germ cells may lead to genetic damage in next and subsequent generations. The objective of this study was to investigate whether exposure to radiofrequency radiation similar to that emitted by mobile phones of second-generation standard Global System for Mobile Communication (GSM) induces genotoxic effects in cultured human cells. The cytogenetic effects of GSM-900 MHz (GSM-900) RF radiation were investigated using R-banded karyotyping after in vitro exposure of human cells (amniotic cells) for 24 h. The average specific absorption rate (SAR) was 0.25 W/kg. The exposures were carried out in wire-patch cells (WPCs) under strictly controlled conditions of temperature. The genotoxic effect was assessed immediately or 24 h after exposure using four different samples. One hundred metaphase cells were analyzed per assay. Positive controls were provided by using bleomycin. We found no direct cytogenetic effects of GSM-900 either 0 h or 24 h after exposure. To the best of our knowledge, our work is the first to study genotoxicity using complete R-banded karyotyping, which allows visualizing all the chromosomal rearrangements, either numerical or structural.


5. P Ulku R et al, (September 2010) Extremely Low-Frequency Magnetic Field Decreased Calcium, Zinc and Magnesium Levels in Costa of Rat, Biol Trace Elem Res. 2010 Sep 25. [Epub ahead of print] [View Author's abstract conclusions] [View on Pubmed]
 

Electromagnetic field (EMF) can affect cells due to biochemical change followed by a change in level of ions trafficking through membrane. We aimed to investigate possible changes in some elements in costa of rats exposed to long-term extremely low-frequency magnetic field (ELF-MF). Rats were exposed to 100 and 500 µT ELF-MF, which are the safety standards of public and occupational exposure for 2 h/day during 10 months. At the end of the exposure period, the samples of costa were taken from the rats exposed to ELF-MF and sham. The levels of elements were measured by using atomic absorption spectrophotometry (AAS) and ultraviolet (UV) spectrophotometry. Ca levels decreased in the ELF-500 exposure group in comparison to sham group (p < 0.05). Statistically significant decrease was found in Mg levels in the ELF-500 exposure group in comparison to sham and ELF-100 exposure groups (p < 0.05). Zn levels were found to be lower in the ELF-500 exposure group than those in the sham and ELF-100 exposure groups (p < 0.05). No significant differences were determined between groups in terms of the levels of P, Cu and Fe. In conclusion, it can be maintained that long-term ELF-MF exposure can affect the chemical structure and metabolism of bone by changing the levels of some important elements such as Ca, Zn and Mg in rats.


6. - Kroll ME et al, (September 2010) Childhood cancer and magnetic fields from high-voltage power lines in England and Wales: a case-control study, Br J Cancer. 2010 Sep 28;103(7):1122-7 [View Author's abstract conclusions] [View on Pubmed]
 

Epidemiological evidence suggests that chronic low-intensity extremely-low-frequency magnetic-field exposure is associated with increased risk of childhood leukaemia; it is not certain the association is causal. We report a national case-control study relating childhood cancer risk to the average magnetic field from high-voltage overhead power lines at the child's home address at birth during the year of birth, estimated using National Grid records. From the National Registry of Childhood Tumours, we obtained records of 28,968 children born in England and Wales during 1962-1995 and diagnosed in Britain under age 15. We selected controls from birth registers, matching individually by sex, period of birth, and birth registration district. No participation by cases or controls was required. The estimated relative risk for each 0.2 µT increase in magnetic field was 1.14 (95% confidence interval 0.57 to 2.32) for leukaemia, 0.80 (0.43-1.51) for CNS/brain tumours, and 1.34 (0.84-2.15) for other cancers. Although not statistically significant, the estimate for childhood leukaemia resembles results of comparable studies. Assuming causality, the estimated attributable risk is below one case per year. Magnetic-field exposure during the year of birth is unlikely to be the whole cause of the association with distance from overhead power lines that we previously reported.


7. - Schmiedel S, Blettner M, (September 2010) The association between extremely low-frequency electromagnetic fields and childhood leukaemia in epidemiology: enough is enough?, Br J Cancer. 2010 Sep 28;103(7):931-2 [View Author's abstract conclusions] [View on Pubmed]
 

In summary, epidemiological studies have repeatedly shown positive results for this association. However, a causal biological mechanism for carcinogenicity of EMF-ELF has not yet been found, despite intense research (WHO, 2007, Chapter 11.3.6). Thus, the epidemiological results stand alone. The International Agency for Research on Cancer (IARC) has categorised ELF magnetic fields in 2002 as being possibly carcinogenic (IARC, 2002) only on the basis of concordant findings in epidemiologic studies. The categorisation was not changed by the World Health Organization (WHO, 2007, Chapter 11.5), which included more recent studies. We believe epidemiology cannot provide any further evidence. On the basis of current knowledge on possible causal mechanisms and epidemiological methods, better insights into this association cannot be expected. Hence, a point in the discussion by Greenland et al (2000) that 'possibly [y] measures only reflect effects of some biologically relevant exposure that is missing from [y] data.' is still valid after 10 years, despite many additional published studies.


8. P Yan J et al, (December 2010) Effects of extremely low-frequency magnetic field on growth and differentiation of human mesenchymal stem cells, Electromagn Biol Med. 2010 Dec;29(4):165-76. Epub 2010 Oct 5 [View Author's abstract conclusions] [View on Pubmed]
 

Human Mesenchymal Stem Cells (hMSCs) were exposed to a developed extremely low-frequency (ELF) magnetic fields (50 Hz ,20 mT ELF) system to evaluate whether exposure to (ELF) magnetic fields affects growth, metabolism, and differentiation of hMSCs. MTT method was used to determine the growth and metabolism of hMSCs following exposure to ELF magnetic fields. Na(+)/K(+) concentration and osmolality of extracellular were measured after exposured culture. Alkaline phosphatase (ALP) assay and Calcium assay, ALP staining, and Alizarin red staining were performed to evaluate the osteogenic differentiation of hMSCs under the ELF magnetic field exposure. In these experiments, the cells were exposed to ELF for up to 23 days. The results showed that exposure to ELF magnetic field could inhibit the growth and metabolism of hMSC, but have no significant effect on differentiation of hMSCs. These results suggested that ELF magnetic field may influence the early development of hMSCs related adult cells.


9. - Joseph W, Verloock L, (November 2010) Influence of mobile phone traffic on base station exposure of the general public, Health Phys. 2010 Nov;99(5):631-8 [View Author's abstract conclusions] [View on Pubmed]
 

The influence of mobile phone traffic on temporal radiofrequency exposure due to base stations during 7 d is compared for five different sites with Erlang data (representing average mobile phone traffic intensity during a period of time). The time periods of high exposure and high traffic during a day are compared and good agreement is obtained. The minimal required measurement periods to obtain accurate estimates for maximal and average long-period exposure (7 d) are determined. It is shown that these periods may be very long, indicating the necessity of new methodologies to estimate maximal and average exposure from short-period measurement data. Therefore, a new method to calculate the fields at a time instant from fields at another time instant using normalized Erlang values is proposed. This enables the estimation of maximal and average exposure during a week from short-period measurements using only Erlang data and avoids the necessity of long measurement times.


10. - Verschaeve L et al, (December 2010) In vitro and in vivo genotoxicity of radiofrequency fields, Mutat Res. 2010 Dec;705(3):252-68. Epub 2010 Oct 16 [View Author's abstract conclusions] [View on Pubmed]
 

There has been growing concern about the possibility of adverse health effects resulting from exposure to radiofrequency radiations (RFR), such as those emitted by wireless communication devices. Since the introduction of mobile phones many studies have been conducted regarding alleged health effects but there is still some uncertainty and no definitive conclusions have been reached so far. Although thermal effects are well understood they are not of great concern as they are unlikely to result from the typical low-level RFR exposures. Concern rests essentially with the possibility that RFR-exposure may induce non-thermal and/or long-term health effects such as an increased cancer risk. Consequently, possible genetic effects have often been studied but with mixed results. In this paper we review the data on alleged RFR-induced genetic effects from in vitro and in vivo investigations as well as from human cytogenetic biomonitoring surveys. Attention is also paid to combined exposures of RFR with chemical or physical agents. Again, however, no entirely consistent picture emerges. Many of the positive studies may well be due to thermal exposures, but a few studies suggest that biological effects can be seen at low levels of exposure. Overall, however, the evidence for low-level genotoxic effects is very weak.


11. P Kolodziejczyk L et al, (2010) Extremely low frequency magnetic field and the hatching rate of Fasciola hepatica eggs, the fecundity and survival of liver fluke-infected snail, Lymnaea truncatula, Folia Biol (Krakow). 2010;58(3-4):157-61 [View Author's abstract conclusions] [View on Pubmed]
 

Eggs of Fasciola hepatica were exposed for 10 days to extremely low frequency magnetic field (ELFMF) at the frequency of 50 Hz and density of 2 mT (rms). The results show an accelerated hatching of F. hepatica eggs in relation to control (non-exposed) group. The host snails, Lymnaea truncatula, were divided into three groups; those of groups I and II were infected with the miracidia of F. hepatica hatched from control egg culture, whereas those of group III were infected with miracidia hatched from eggs affected by ELFMF. Thereafter, snails of groups II and III were exposed to ELFMF for 53 days, whereas those of group I were not exposed. At day 14 post infection, a significant decrease was observed in the number of cocoons laid by snails of group III, compared with control. Also, significant mortality in group III snails was observed 42 days post infection. The increased mortality and a lower number of cocoons laid by group III snails have probably resulted from enhanced stimulation of metacercarial parthenogenetic reproduction in consequence of infecting the molluscs with miracidia reared under ELFMF.


12. N Lee KY et al, (October 2010) Effects of combined radiofrequency radiation exposure on the cell cycle and its regulatory proteins, Bioelectromagnetics. 2010 Oct 28. [Epub ahead of print] [View Author's abstract conclusions] [View on Pubmed]
 

The aim of this study was to investigate whether single or combined radio frequency (RF) radiation exposure has effects on the cell cycle and its regulatory proteins. Exposure of MCF7 cells to either single (837 MHz) or combined (837 and 1950 MHz) RF radiation was conducted at specific absorption rate values of 4 W/kg for 1?h. During the exposure period, the chamber was made isothermal by circulating water through the cavity. After RF radiation exposure, DNA synthesis rate and cell cycle distribution were assessed. The levels of cell cycle regulatory proteins, p53, p21, cyclins, and cyclin-dependent kinases were also examined. The positive control group was exposed to 0.5 and 4 Gy doses of ionizing radiation (IR) and showed changes in DNA synthesis and cell cycle distribution. The levels of p53, p21, cyclin A, cyclin B1, and cyclin D1 were also affected by IR exposure. In contrast to the IR-exposed group, neither the single RF radiation- nor the combined RF radiation-exposed group elicited alterations in DNA synthesis, cell cycle distribution, and levels of cell cycle regulatory proteins. These results indicate that neither single nor combined RF radiation affect cell cycle progression.


13. P Masuda H et al, (January 2011) Local exposure of the rat cortex to radiofrequency electromagnetic fields increases local cerebral blood flow along with temperature, J Appl Physiol. 2011 Jan;110(1):142-8. Epub 2010 Oct 28 [View Author's abstract conclusions] [View on Pubmed]
 

Few studies have shown that local exposure to radiofrequency electromagnetic fields (RF) induces intensity-dependent physiological changes, especially in the brain. The aim of the present study was to detect reproducible responses to local RF exposure in the parietal cortex of anesthetized rats and to determine their dependence on RF intensity. The target cortex tissue was locally exposed to 2-GHz RF using a figure-eight loop antenna within a range of averaged specific absorption rates (10.5, 40.3, 130, and 263 W/kg averaged over 4.04 mg) in the target area. Local cerebral blood flow (CBF) and temperatures in three regions (target area, rectum, and calf hypodermis) were measured using optical fiber blood flow meters and thermometers during RF exposure. All parameters except for the calf hypodermis temperature increased significantly in exposed animals compared with sham-exposed ones during 18-min exposures. Dependence of parameter values on exposure intensity was analyzed using linear regression models. The elevation of local CBF was correlated with temperature rise in both target and rectum at the end of RF exposure. However, the local CBF elevation seemed to be elevated by the rise in target temperature, but not by that of the rectal temperature, in the early part of RF exposure or at low-intensity RF exposure. These findings suggest that local RF exposure of the rat cortex drives a regulation of CBF accompanied by a local temperature rise, and our findings may be helpful for discussing physiological changes in the local cortex region, which is locally exposed to RF.


14. N Masuda H et al, (January 2011) Lack of effect of 50-Hz magnetic field exposure on the binding affinity of serotonin for the 5-HT 1B receptor subtype, Brain Res. 2011 Jan 12;1368:44-51. Epub 2010 Nov 1 [View Author's abstract conclusions] [View on Pubmed]
 

There is some concern that exposure to extremely low-frequency magnetic fields (MF) causes adverse health effects via signal transduction pathways. Two previous studies reported that exposure to 50-Hz MF decreased the binding affinity of the 1B receptor subtype of serotonin (5-HT) in rat brain membranes. The aim of this study was to investigate whether the exposure to MF affects binding to the 5-HT(1B) receptor and a physiological function associated with 5-HT(1B) receptor activation. Rat brain crude membrane fractions, including 5-HT(1B) receptor and C6-glial cells transfected with human 5-HT(1B) receptor gene, were exposed to 50-Hz MF at 1 mT using Merritt coils under temperature-regulated conditions. In the rat crude membrane, there was no significant difference in the affinity constant of [(3)H]-5-HT between exposed (K(d): 0.92 ± 0.38 nM) and sham-exposed (K(d): 1.00 ± 0.32 nM). The lack of affinity change after exposure was also confirmed using a chemical agonist of the 5-HT receptor, [(3)H]-5-carboxytryptamine (K(d): 0.59 ± 0.06 nM for exposed and 0.71 ± 0.08 nM for sham). Similar negative results in terms of affinity constant were obtained on the human 5-HT(1B) receptor in C6-glial cells. In addition, forskolin-stimulated cAMP production was inhibited by 5-HT administration in a dose-dependent manner in C6-glial cells, but exposure did not modify the inhibitory response. This study thus failed to confirm the previous results and findings suggest that exposure to MF below the current occupational limit does not affect the physiological function involved in 5-HT(1B) receptor subtypes.


15. - Joseph W et al, (October 2010) Comparison of personal radio frequency electromagnetic field exposure in different urban areas across Europe, Environ Res. 2010 Oct;110(7):658-63 [View Author's abstract conclusions] [View on Pubmed]
 

Only limited data are available on personal radio frequency electromagnetic field (RF-EMF) exposure in everyday life. Several European countries performed measurement studies in this area of research. However, a comparison between countries regarding typical exposure levels is lacking. This study is designed to compare for the first time mean exposure levels and contributions of different sources in specific environments between different European countries. In five countries (Belgium, Switzerland, Slovenia, Hungary, and the Netherlands), measurement studies were performed using the same personal exposure meters. The pooled data were analyzed using the robust regression on order statistics (ROS) method in order to allow for data below the detection limit. Mean exposure levels were compared between different microenvironments such as homes, public transports, or outdoor. Exposure levels were of the same order of magnitude in all countries and well below the international exposure limits. In all countries except for the Netherlands, the highest total exposure was measured in transport vehicles (trains, car, and busses), mainly due to radiation from mobile phone handsets (up to 97%). Exposure levels were in general lower in private houses or flats than in offices and outdoors. At home, contributions from various sources were quite different between countries. Highest total personal RF-EMF exposure was measured inside transport vehicles and was well below international exposure limits. This is mainly due to mobile phone handsets. Mobile telecommunication can be considered to be the main contribution to total RF-EMF exposure in all microenvironments.


16. P Li P et al, (August 2009) Maternal occupational exposure to extremely low frequency magnetic fields and the risk of brain cancer in the offspring, Cancer Causes Control. 2009 Aug;20(6):945-55. Epub 2009 Feb 18 [View Author's abstract conclusions] [View on Pubmed]
 

This stude was designed to examine the contribution of maternal occupational exposure to extremely low frequency magnetic fields (ELF-MF) shortly before and during pregnancy on the incidence of childhood brain tumors. A total of 548 incident cases and 760 healthy controls recruited between 1980 and 2002 from two Canadian provinces (Québec and Ontario) were included in this study, and their mothers were interviewed. Quantitative occupational ELF-MF exposure in microTesla units was estimated using individual exposure estimations or a job exposure matrix. We used three metrics to analyze exposure: cumulative, average, and maximum level attained. Using the average exposure metric measured before conception, an increased risk was observed for astroglial tumors (OR = 1.5, 95% CI = 1.0-2.4). During the entire pregnancy period, a significantly increased risk was observed for astroglial tumors as well as for all childhood brain tumors with the average metric (OR = 1.6, 95% CI = 1.1-2.5 and OR = 1.5, 95% CI = 1.1-2.2, respectively). Based on job titles, a twofold risk increase was observed for astroglial tumors (OR = 2.3, 95% CI = 0.8-6.3) and for all childhood brain tumors (OR = 2.3, 95% CI = 1.0-5.4) among sewing machine operators. Results are suggestive of a possible association between maternal occupational ELF-MF exposure and certain brain tumors in their offspring.


17. P Sohrabi MR et al, (2010) Living near overhead high voltage transmission power lines as a risk factor for childhood acute lymphoblastic leukemia: a case-control study, Asian Pac J Cancer Prev. 2010;11(2):423-7 [View Author's abstract conclusions] [View on Pubmed]
 

This study aimed to investigate association of living near high voltage power lines with occurrence of childhood acute lymphoblastic leukemia (ALL). Through a case-control study 300 children aged 1-18 years with confirmed ALL were selected from all referral teaching centers for cancer. They interviewed for history of living near overhead high voltage power lines during at least past two years and compared with 300 controls which were individually matched for sex and approximate age. Logistic regression, chi square and paired t-tests were used for analysis when appropriate. The case group were living significantly closer to power lines (P < 0.001). More than half of the cases were exposed to two or three types of power lines (P < 0.02). Using logistic regression, odds ratio of 2.61 (95% CI: 1.73 to 3.94) calculated for less than 600 meters far from the nearest lines against more than 600 meters. This ratio estimated as 9.93 (95% CI: 3.47 to 28.5) for 123 KV, 10.78 (95% CI: 3.75 to 31) for 230 KV and 2.98 (95% CI: 0.93 to 9.54) for 400 KV lines. Odds of ALL decreased 0.61 for every 600 meters from the nearest power line. This study emphasizes that living close to high voltage power lines is a risk for ALL.


18. - Mezei G et al, (May 2008) Residential magnetic field exposure and childhood brain cancer: a meta-analysis, Epidemiology. 2008 May;19(3):424-30 [View Author's abstract conclusions] [View on Pubmed]
 

We conducted a meta-analysis of studies on magnetic field exposure and childhood brain tumors to evaluate homogeneity in the results, to examine reasons for heterogeneity, and to derive a summary effect estimate. Comparison of results from studies of childhood brain cancer and childhood leukemia may also help to assess the potential for selection bias in childhood leukemia studies. We included results from 13 studies. Using an inverse variance-weighted method, summary effect estimates were calculated separately for distance, wire codes, and measured and calculated magnetic fields. Sensitivity analyses were conducted to assess the influence of individual studies, the potential for selection bias, and the possibility of publication bias. With the exception of wire-code studies, results were compatible with homogeneity across studies. The summary odds ratios (95% confidence intervals) were 0.88 (0.57-1.37) for distance <50 m and 1.14 (0.78-1.67) for calculated or measured magnetic fields above 0.2 microT. For measured or calculated exposures above 0.3 or 0.4 microT, the summary odds ratio was 1.68 (0.83-3.43), with no differences by method of exposure assessment. No single study had a substantial effect on the summary estimates. There was no indication of publication bias. With the exception of high cut-point analyses (0.3/0.4 microT), where the possibility of a moderate risk increase cannot be excluded, no increase in childhood brain cancer risk was evident for any of the exposure metrics.


19. P Feizi AA, Arabi MA, (January 2007) Acute childhood leukemias and exposure to magnetic fields generated by high voltage overhead power lines - a risk factor in Iran, Asian Pac J Cancer Prev. 2007 Jan-Mar;8(1):69-72 [View Author's abstract conclusions] [View on Pubmed]
 

Many investigators have studied the effects of Extremely Low Frequency-Magnetic Fields generated by ordinary and domestic power lines, as a risk factor in acute leukaemias of children, but there are limited information available regarding very high voltage overhead power lines. Children in developing countries sometimes live very close to such structures and we have registered several patients with acute leukaemias appearing in clusters. In the present study we have analyzed 60 consecutively diagnosed patients with acute leukaemias, and 59 matched controls in a provincial capital city in North-Western Iran. After provision of consent, a detailed form was filled in, and a visit to the present (or previous) residential areas of both groups was arranged. The locations of the very high voltage power lines (123, 230, 400 kilo volts), were noted in each area, if present, and their distances from the houses under study were detected. The expected intensities of the Magnetic Fields (B) were calculated having the mean intensity of the electrical current and other line characteristics, by means of relevant equations. Fourteen patients in the case group (23.5%) were living near the high voltage power lines in distances < or = 500 meters. (Mean B = 0.6 microTeslas, microT). In the control group at the same distance, the figure was 2 children (3.3%) (Mean B = 0.35 microT). Statistically, the likelihood of leukaemia was increased considerably in this distance (Odds ratio (OR) = 8.67, 95% Confidence Interval (CI) = 1.74- 58.4, P value= 0.001). On the other hand 15 pts (25 %) in the leukaemia group were experiencing Magnetic fields above 0.45 microT in comparison to 5 in the control group ( 8.5% )(OR = 3.60, 95% CI = 1.11-12.39, P = 0.01). More children in developing countries like Iran live close to very high voltage lines, and they experience relatively more harmful effects from the Magnetic Fields, in comparison with children in developed countries. Residence near very high voltage overhead power lines, in distances < or = 500 meters, and Magnetic Fields >0.45 microT, should be considered a risk factor for the pathogenesis of acute leukaemias in children.


20. - Kheifets L et al, (September 2010) Pooled analysis of recent studies on magnetic fields and childhood leukaemia, Br J Cancer. 2010 Sep 28;103(7):1128-35 [View Author's abstract conclusions] [View on Pubmed]
 

Previous pooled analyses have reported an association between magnetic fields and childhood leukaemia. We present a pooled analysis based on primary data from studies on residential magnetic fields and childhood leukaemia published after 2000. Seven studies with a total of 10,865 cases and 12,853 controls were included. The main analysis focused on 24-h magnetic field measurements or calculated fields in residences. In the combined results, risk increased with increase in exposure, but the estimates were imprecise. The odds ratios for exposure categories of 0.1-0.2 µT, 0.2-0.3 µT and =0.3 µT, compared with <0.1 µT, were 1.07 (95% CI 0.81-1.41), 1.16 (0.69-1.93) and 1.44 (0.88-2.36), respectively. Without the most influential study from Brazil, the odds ratios increased somewhat. An increasing trend was also suggested by a nonparametric analysis conducted using a generalised additive model. Our results are in line with previous pooled analyses showing an association between magnetic fields and childhood leukaemia. Overall, the association is weaker in the most recently conducted studies, but these studies are small and lack methodological improvements needed to resolve the apparent association. We conclude that recent studies on magnetic fields and childhood leukaemia do not alter the previous assessment that magnetic fields are possibly carcinogenic.