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Greenland, S. |
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Title |
Multiple-bias modelling for analysis of observational data (with discussion) |
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Journal Article |
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Year |
2005 |
Publication |
Journal of the Royal Statistical Society: Series A (Statistics in Society) |
Abbreviated Journal |
J Royal Statistical Soc A |
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Volume |
168 |
Issue |
2 |
Pages |
267-306 |
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Abstract |
Conventional analytic results do not reflect any source of uncertainty other than random error, and as a result readers must rely on informal judgments regarding the effect of possible biases. When standard errors are small these judgments often fail to capture sources of uncertainty and their interactions adequately. Multiple-bias models provide alternatives that allow one systematically to integrate major sources of uncertainty, and thus to provide better input to research planning and policy analysis. Typically, the bias parameters in the model are not identified by the analysis data and so the results depend completely on priors for those parameters. A Bayesian analysis is then natural, but several alternatives based on sensitivity analysis have appeared in the risk assessment and epidemiologic literature. Under some circumstances these methods approximate a Bayesian analysis and can be modified to do so even better. These points are illustrated with a pooled analysis of case–control studies of residential magnetic field exposure and childhood leukaemia, which highlights the diminishing value of conventional studies conducted after the early 1990s. It is argued that multiple-bias modelling should become part of the core training of anyone who will be entrusted with the analysis of observational data, and should become standard procedure when random error is not the only important source of uncertainty (as in meta-analysis and pooled analysis). |
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0964-1998 |
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WP2 Exposure measurements |
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CBM.UAM @ ccobaleda @ |
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57 |
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Kheifets, L.; Ahlbom, A.; Crespi, C.M.; Draper, G.; Hagihara, J.; Lowenthal, R.M.; Mezei, G.; Oksuzyan, S.; Schuz, J.; Swanson, J.; Tittarelli, A.; Vinceti, M.; Wunsch Filho, V. |
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Title |
Pooled analysis of recent studies on magnetic fields and childhood leukaemia |
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Journal Article |
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Year |
2010 |
Publication |
British Journal of Cancer |
Abbreviated Journal |
Br J Cancer |
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Volume |
103 |
Issue |
7 |
Pages |
1128-1135 |
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Keywords |
Child; Child, Preschool; Electromagnetic Fields/*adverse effects; Environmental Exposure/adverse effects; Female; Humans; Leukemia, Radiation-Induced/*epidemiology; Male; Risk |
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BACKGROUND: 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. METHODS: 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. RESULTS: 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 muT, 0.2-0.3 muT and >/=0.3 muT, compared with <0.1 muT, 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. CONCLUSIONS: 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. |
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Department of Epidemiology, UCLA School of Public Health, 650 Charles Young Drive, Los Angeles, CA 90095, USA. kheifets@ucla.edu |
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0007-0920 |
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WP2 Exposure measurements & WP9 Epidemiology |
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PMID:20877339 |
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CBM.UAM @ ccobaleda @ |
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58 |
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Maslanyj, M.P.; Mee, T.J.; Renew, D.C.; Simpson, J.; Ansell, P.; Allen, S.G.; Roman, E. |
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Investigation of the sources of residential power frequency magnetic field exposure in the UK Childhood Cancer Study |
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Journal Article |
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2007 |
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Journal of Radiological Protection : Official Journal of the Society for Radiological Protection |
Abbreviated Journal |
J Radiol Prot |
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27 |
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1 |
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41-58 |
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Child; Electric Power Supplies; Electric Wiring; Electromagnetic Fields/*adverse effects; Environmental Exposure/*adverse effects; Housing; Humans; Leukemia, Radiation-Induced/*etiology; Magnetics/adverse effects; Public Health |
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There is an unexplained association between exposure to the magnetic fields arising from the supply and use of electricity, and increase in risk of childhood leukaemia. The UK Childhood Cancer Study (UKCCS) provides a large and unique source of information on residential magnetic field exposure in the UK. The purpose of this supplementary study was to investigate a sample of UKCCS homes in order to identify the particular sources that contribute to elevated time-averaged exposure. In all, 196 homes have been investigated, 102 with exposures estimated on the basis of the original study to be above 0.2 microT, and 21 higher than 0.4 microT, a threshold above which a raised risk has been observed. First, surveys were carried out outside the property boundaries of all 196 study homes, and then, where informed consent had been obtained, assessments were conducted inside the properties of 19 homes. The study found that low-voltage (LV) sources associated with the final electricity supply accounted together for 77% of exposures above 0.2 microT, and 57% of those above 0.4 microT. Most of these exposures were linked to net currents in circuits inside and/or around the home. High-voltage (HV) sources, including the HV overhead power lines that are the focus of public concern, accounted for 23% of the exposures above 0.2 microT, and 43% of those above 0.4 microT. Public health interest has focused on the consideration of precautionary measures that would reduce exposure to power frequency magnetic fields. Our study provides a basis for considering the options for exposure mitigation in the UK. For instance, in elevated-exposure homes where net currents are higher than usual, if it is possible to reduce the net currents, then the exposure could be reduced for a sizeable proportion of these homes. Further investigations would be necessary to determine whether this is feasible. |
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Health Protection Agency, Radiation Protection Division, Centre for Radiation, Chemical and Environmental Hazards, Chilton, Didcot, UK. myron.maslanyj@hpa-rp.org.uk |
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0952-4746 |
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WP2 Exposure measurements |
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PMID:17341803 |
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CBM.UAM @ ccobaleda @ |
Serial |
59 |
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Author |
Ke, X.Q.; Sun, W.J.; Lu, D.Q.; Fu, Y.T.; Chiang, H. |
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Title |
50-Hz magnetic field induces EGF-receptor clustering and activates RAS |
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Journal Article |
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Year |
2008 |
Publication |
International Journal of Radiation Biology |
Abbreviated Journal |
Int J Radiat Biol |
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Volume |
84 |
Issue |
5 |
Pages |
413-420 |
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Keywords |
Animals; Cell Membrane/metabolism; Cluster Analysis; Cricetinae; *Electromagnetic Fields; Fibroblasts/metabolism; *Genes, ras; Glutathione Transferase/metabolism; Immunoprecipitation; Microscopy, Confocal; Microscopy, Fluorescence; Receptor, Epidermal Growth Factor/*chemistry/metabolism; Signal Transduction/radiation effects; p38 Mitogen-Activated Protein Kinases/metabolism; ras Proteins/*metabolism |
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Abstract |
PURPOSE: In a previous study, we found that exposure to a 50 Hz magnetic field (MF) could activate stress-activated protein kinase (SAPK) and P38 mitogen-activated protein (MAP) kinase (P38 MAPK) in Chinese hamster lung (CHL) fibroblast cells, and simultaneous exposure to a 'noise' MF of the same intensity inhibited these effects. In order to explore the possible target sites and upstream signal transduction molecules of SAPK and P38 MAPK, and further validate the interference effects of 'noise' MF on 50 Hz MF, the effects of MF exposure on clustering of epidermal growth factor (EGF) receptors and Ras protein activation were investigated. MATERIALS AND METHODS: CHL cells were exposed to a 50 Hz sinusoidal MF at 0.4 mT for different durations, and clustering of EGF receptors on cellular membrane and Ras protein activation were analyzed using immunofluorescence confocal microscopy and co-precipitation technology. EGF treatment served as the positive control. RESULTS: The results showed that, compared with sham-exposed cells, exposure to a 50 Hz MF at 0.4 mT for 5 min slightly induced EGF receptor clustering, whereas exposure for 15 min enhanced receptor clustering significantly. Corresponding to receptor clustering, Ras protein was also activated after exposure to the 50 Hz MF. Exposure to a 'noise' MF (with frequency ranges from 30 – 90 Hz) at the same intensity and durations, did not significantly affect EGF receptor clustering and Ras protein. However, by superimposing the 'noise' MF, receptor clustering and Ras activation induced by 50 Hz MF were inhibited. CONCLUSION: The results suggested that membrane receptors could be one of the most important targets where extremely low frequency (ELF) MF interacts with cells, and Ras may participate in the signal transduction process of 50 Hz MF. Furthermore, a 'noise' MF could inhibit these effects caused by ELF-MF. |
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Department of Hygiene of Children and Adolescents, Zhejiang University School of Medicine, Hangzhou, China |
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0955-3002 |
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WP5 In vitro |
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PMID:18464070 |
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CBM.UAM @ ccobaleda @ |
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62 |
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Author |
Schuz, J.; Grigat, J.P.; Stormer, B.; Rippin, G.; Brinkmann, K.; Michaelis, J. |
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Title |
Extremely low frequency magnetic fields in residences in Germany. Distribution of measurements, comparison of two methods for assessing exposure, and predictors for the occurrence of magnetic fields above background level |
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Journal Article |
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Year |
2000 |
Publication |
Radiation and Environmental Biophysics |
Abbreviated Journal |
Radiat Environ Biophys |
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39 |
Issue |
4 |
Pages |
233-240 |
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Child; *Electromagnetic Fields; *Environmental Exposure/analysis; Environmental Monitoring/*methods; Germany; *Housing; Humans; Models, Statistical; Odds Ratio; Risk Factors; Time Factors |
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We examined the results of 1,835 magnetic field measurements in German residences conducted between November 1997 and September 1999. The measurements were part of an epidemiological study on the relationship between magnetic fields and childhood leukemia. We performed a fixed-location measurement of the magnetic field at 50 Hz and 16 2/3 Hz (frequency of the German railway system) over 24 h in the child's bedroom in the residence of each study participant. In addition, we conducted a second 24 h-measurement in the living room at 50 Hz, and spot measurements while walking through all rooms of the respective dwelling. Median 50 Hz magnetic fields above 0.2 muT were found to be infrequent in Germany (only 1.4% of all residences). Fields produced by high-voltage power lines (123-420 kV) were lower than expected: the median magnetic field was above 0.2 muT in only 8 (32.0%) of 25 residences located 50 m or closer to a high-voltage power line indicating that power lines in Germany are usually run well below the maximum power load. We found that magnetic fields were correlated with the type of residence and higher magnetic fields were measured in apartment buildings. There was also some evidence for a positive correlation between magnetic fields and traffic density and an inverse association between magnetic fields and family net income. The 24 h-magnetic field measurements correlated well with the spot measurements (r>0.7). However, when dichotomized with a cut-off point of 0.2 muT, there was only a poor agreement between the two measurement methods. A loss of the strength of the association after categorization was also observed when comparing the arithmetic mean and median of the same 24 h-measurement. In summary, these analyses give a valuable overview of magnetic field distributions in German residences. |
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Institut fur Medizinische Statistik und Dokumentation, University of Mainz, Germany. schuez@imsd.uni-mainz.de |
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ISSN |
0301-634X |
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WP2 Exposure measurements |
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PMID:11200967 |
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CBM.UAM @ ccobaleda @ |
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61 |
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