Epidemiological studies of childhood cancer and magnetic fields
We provide here the abstracts for the major epidemiological studies of magnetic fields and childhood cancer. We have not included every single study. Instead, we have included the better quality, more reliable studies, using similar selection principles to those used by Ahlbom et al for their pooled analysis: essentially studies with measurements or calculations for 48 hours or longer. See also a recent study on survival from childhood leukaemia and a pooled analysis of night-time exposure.
|Ahlbom et al||2000|
|Greenland et al||2000|
|Dockerty et al||1998||New Zealand|
|Dockerty||1999||New Zealand (subsidiary analysis)|
|Feychting and Ahlbom||1993||Sweden|
|Draper et al||2005||UK|
|Green et al||1999||Canada|
|Green et al||1999||Canada (subsidiary analysis)|
|Kleinerman et al||2000||USA (subsidiary analysis)|
|Linet et al||1997||USA|
|McBride et al||1999||Canada|
|Olsen et al||1993||Denmark|
|Schuz et al||2001||Germany|
|Sermage-Faure et al||2013||France|
|Tynes and Haldorsen||1997||Norway|
|UKCCS||2000||UK (subsidiary analysis)|
|UKCCS||2002||UK (subsidiary analysis)|
|Verkasalo et al||1993||Finland|
British Journal of Cancer (2013), 1–8 doi: 10.1038/bjc.2013.128
Background: High-voltage overhead power lines (HVOLs) are a source of extremely low-frequency magnetic fields (ELF-MFs), which are classified as possible risk factors for childhood acute leukaemia (AL). The study was carried out to test the hypothesis of an increased AL incidence in children living close to HVOL of 225–400 kV (VHV-HVOL) and 63–150 kV (HV-HVOL).
Childhood cancer in relation to distance from high voltage power lines in England and Wales: a case-control study
Objective To determine whether there is an association between distance of home address at birth from high voltage power lines and the incidence of leukaemia and other cancers in children in England and Wales.
Br J Cancer 2000 Sep;83(5):692-8
Ahlbom A, Day N, Feychting M, Roman E, Skinner J, Dockerty J, Linet M, McBride M, Michaelis J, Olsen JH, Tynes T, Verkasalo PK.
Division of Epidemiology, National Institute of Environmental Medicine, Karolinska Institute, Sweden.
Previous studies have suggested an association between exposure to 50-60 Hz magnetic fields (EMF) and childhood leukaemia. We conducted a pooled analysis based on individual records from nine studies, including the most recent ones. Studies with 24/48-hour magnetic field measurements or calculated magnetic fields were included. We specified which data analyses we planned to do and how to do them before we commenced the work. The use of individual records allowed us to use the same exposure definitions, and the large numbers of subjects enabled more precise estimation of risks at high exposure levels. For the 3203 children with leukaemia and 10 338 control children with estimated residential magnetic field exposures levels < 0.4 microT, we observed risk estimates near the no effect level, while for the 44 children with leukaemia and 62 control children with estimated residential magnetic field exposures >/= 0.4 microT the estimated summary relative risk was 2.00 (1.27-3.13), P value = 0.002). Adjustment for potential confounding variables did not appreciably change the results. For North American subjects whose residences were in the highest wire code category, the estimated summary relative risk was 1.24 (0.82-1.87). Thus, we found no evidence in the combined data for the existence of the so-called wire-code paradox. In summary, the 99.2% of children residing in homes with exposure levels < 0.4 microT had estimates compatible with no increased risk, while the 0.8% of children with exposures >/= 0.4 microT had a relative risk estimate of approximately 2, which is unlikely to be due to random variability. The explanation for the elevated risk is unknown, but selection bias may have accounted for some of the increase. Copyright 2000 Cancer Research Campaign.
See also the main results table
Epidemiology 2000 Nov;11(6):624-34
Greenland S, Sheppard AR, Kaune WT, Poole C, Kelsh MA.
Department of Epidemiology, UCLA School of Public Health, Los Angeles, CA, USA.
We obtained original individual data from 15 studies of magnetic fields or wire codes and childhood leukemia, and we estimated magnetic field exposure for subjects with sufficient data to do so. Summary estimates from 12 studies that supplied magnetic field measures exhibited little or no association of magnetic fields with leukemia when comparing 0.1-0.2 and 0.2-0.3 microtesla (microT) categories with the 0-0.1 microT category, but the Mantel-Haenszel summary odds ratio comparing >0.3 microT to 0-0.1 microT was 1.7 (95% confidence limits = 1.2, 2.3). Similar results were obtained using covariate adjustment and spline regression. The study-specific relations appeared consistent despite the numerous methodologic differences among the studies. The association of wire codes with leukemia varied considerably across studies, with odds ratio estimates for very high current vs low current configurations ranging from 0.7 to 3.0 (homogeneity P = 0.005). Based on a survey of household magnetic fields, an estimate of the U.S. population attributable fraction of childhood leukemia associated with residential exposure is 3% (95% confidence limits = -2%, 8%). Our results contradict the idea that the magnetic field association with leukemia is less consistent than the wire code association with leukemia, although analysis of the four studies with both measures indicates that the wire code association is not explained by measured fields. The results also suggest that appreciable magnetic field effects, if any, may be concentrated among relatively high and uncommon exposures, and that studies of highly exposed populations would be needed to clarify the relation of magnetic fields to childhood leukemia.
Int J Cancer 2001 Mar 1;91(5):728-35
Schuz J, Grigat JP, Brinkmann K, Michaelis J.
Institute for Medical Statistics and Documentation, University of Mainz, Mainz, Germany. email@example.com
Our objective was to investigate whether exposure to residential power-frequency (50 Hz) magnetic fields above 0.2 microT increases a child's risk of leukaemia and to confirm or reject a finding from a previous German study on this topic, which reported increased leukaemia risk with exposure to stronger magnetic fields during the night. A population-based case-control study was used, covering the whole of the former West Germany. Residential magnetic fields were measured over 24 hr for 514 children with acute leukaemia identified by the German Childhood Cancer Registry and 1,301 control children taken from population registration files. Magnetic fields above 0.2 microT were relatively rare in Germany (only 1.5% of the study population). Childhood leukaemia and 24 hr median magnetic fields were only weakly related (OR = 1.55, 95% CI 0.65-3.67). A significant association was seen between childhood leukaemia and magnetic field exposure during the night (OR = 3.21, 95% CI 1.33-7.80). A dose-response-relationship was observed after combining the data of all German studies on magnetic fields and childhood leukaemia. The evidence for an association between childhood leukaemia and magnetic field exposure in our study comes from a measure of exposure during the night. Despite the large size of our study, the results are based on small numbers of exposed children. If the observed association stands, the effect on a population level in Germany would be small. Copyright 2001 Wiley-Liss, Inc.
Am J Epidemiol 1999 May 1;149(9):831-42
McBride ML, Gallagher RP, Theriault G, Armstrong BG, Tamaro S, Spinelli JJ, Deadman JE, Fincham S, Robson D, Choi W.
Cancer Control Research Programme, British Columbia Cancer Agency, Vancouver, Canada.
In a case-control study of childhood leukemia in relation to exposure to power-frequency electric and magnetic fields (EMF), 399 children resident in five Canadian provinces who were diagnosed at ages 0-14 years between 1990 and 1994 (June 1995 in British Columbia and Quebec) were enrolled, along with 399 controls. Exposure assessment included 48-hour personal EMF measurement, wire coding and magnetic field measurements for subjects' residences from conception to diagnosis/reference date, and a 24-hour magnetic field bedroom measurement. Personal magnetic fields were not related to risk of leukemia (adjusted odds ratio (OR) = 0.95, p for trend = 0.73) or acute lymphatic leukemia (OR = 0.93, p for trend = 0.64). There were no clear associations with predicted magnetic field exposure 2 years before the diagnosis/reference date or over the subject's lifetime or with personal electric field exposure. A statistically nonsignificant elevated risk of acute lymphatic leukemia was observed with very high wiring configurations among residences of subjects 2 years before the diagnosis/reference date (OR = 1.72 compared with underground wiring, 95% confidence interval 0.54-5.45). These results provide little support for a relation between power-frequency EMF exposure and risk of childhood leukemia.
Int J Cancer 1999 Jul 19;82(2):161-70
Green LM, Miller AB, Villeneuve PJ, Agnew DA, Greenberg ML, Li J, Donnelly KE.
Department of Public Health Sciences, University of Toronto, Canada. firstname.lastname@example.org
A population-based case-control study was conducted in Ontario, Canada, to assess the relation between the risk of childhood leukemia and residential exposure to magnetic fields. Participating subjects consisted of 201 cases, diagnosed at 0 to 14 years of age during 1985-1993, ascertained from the records at the Hospital for Sick Children (Toronto), and 406 individually matched controls. Where possible, point-in-time measurements of magnetic fields were made in all residences occupied by subjects during the period of inquiry in the defined catchment area. Three different classification schemes of wire code were assigned to each residence. Detailed information was collected by interviewer-administered questionnaires, which enabled risk estimates to be adjusted for socio-economic characteristics, medical history of parent(s) and child and environmental exposures. Inconsistent elevations in risk were associated with time-weighted averages of magnetic fields both inside and outside the home for subjects having residential point-in-time measurements that represented at least 70% of their etiological period. These risks increased in magnitude when analysis was restricted to children under 6 years of age at diagnosis or to those with acute lymphoblastic leukemia. For children younger than 6 years at diagnosis, outside perimeter measurements of the residence, > or = 0.15 microT, were associated with increased leukemia risk (OR = 3.45, 95% CI = 1.14-10.45). Evaluation of different exposure times for point-in-time magnetic field measurements and wire configuration suggested that exposures earliest in the etiological period were associated with greater risks for children diagnosed at a younger age (OR = 2.50, 95% CI = 1.14-5.49). Our findings did not support an association between leukemia and proximity to power lines with high current configuration.
Cancer Causes Control 1999 Jun;10(3):233-43
Green LM, Miller AB, Agnew DA, Greenberg ML, Li J, Villeneuve PJ, Tibshirani R.
Department of Public Health Sciences, University of Toronto, Ontario, Canada.
OBJECTIVES: To evaluate the risk of childhood leukemia in relation to residential electric and magnetic field (EMF) exposures. METHODS: A case control study based on 88 cases and 133 controls used different assessment methods to determine EMF exposure in the child's current residence. Cases comprised incident leukemias diagnosed at 0-14 years of age between 1985-1993 from a larger study in southern Ontario; population controls were individually matched to the cases by age and sex. Exposure was measured by a personal monitoring device worn by the child during usual activities at home, by point-in-time measurements in three rooms and according to wire code assigned to the child's residence. RESULTS: An association between magnetic field exposures as measured with the personal monitor and increased risk of leukemia was observed. The risk was more pronounced for those children diagnosed at less than 6 years of age and those with acute lymphoblastic leukemia. Risk estimates associated with magnetic fields tended to increase after adjusting for power consumption and potential confounders with significant odds ratios (OR) (OR: 4.5, 95% confidence interval (CI): 1.3-15.9) observed for exposures > or = 0.14 microTesla (microT). For the most part point-in-time measurements of magnetic fields were associated with non-significant elevations in risk which were generally compatible with previous research. Residential proximity to power lines having a high current configuration was not associated with increased risk of leukemia. Exposures to electric fields as measured by personal monitoring were associated with a decreased leukemia risk. CONCLUSIONS: The findings relating to magnetic field exposures directly measured by personal monitoring support an association with the risk of childhood leukemia. As exposure assessment is refined, the possible role of magnetic fields in the etiology of childhood leukemia becomes more evident.
N Engl J Med 1997 Jul 3;337(1):1-7
Linet MS, Hatch EE, Kleinerman RA, Robison LL, Kaune WT, Friedman DR, Severson RK, Haines CM, Hartsock CT, Niwa S, Wacholder S, Tarone RE.
Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Md 20892-7362, USA.
BACKGROUND: Previous studies found associations between childhood leukemia and surrogate indicators of exposure to magnetic fields (the power-line classification since known as "wire coding"), but not between childhood leukemia and measurements of 60-Hz residential magnetic fields. METHODS: We enrolled 638 children with acute lymphoblastic leukemia (ALL) who were under 15 years of age and were registered with the Children's Cancer Group and 620 controls in a study of residential exposure to magnetic fields generated by nearby power lines. In the subjects' current and former homes, data collectors measured magnetic fields for 24 hours in the child's bedroom and for 30 seconds in three or four other rooms and outside the front door. A computer algorithm assigned wire-code categories; based on the distance and configuration of nearby power lines, to the subjects' main residences (for 416 case patients and 416 controls) and to those where the family had lived during the mother's pregnancy with the subject (for 230 case patients and 230 controls). RESULTS: The risk of childhood ALL was not linked to summary time-weighted average residential magnetic-field levels, categorized according to a priori criteria. The odds ratio for ALL was 1.24 (95 percent confidence interval, 0.86 to 1.79) at exposures of 0.200 mu T or greater as compared with less than 0.065 mu T. The risk of ALL was not increased among children whose main residences were in the highest wire-code category (odds ratio as compared with the lowest category, 0.88; 95 percent confidence interval, 0.48 to 1.63). Furthermore, the risk was not significantly associated with either residential magnetic-field levels or the wire codes of the homes mothers resided in when pregnant with the subjects. CONCLUSIONS: Our results provide little evidence that living in homes characterized by high measured time-weighted average magnetic-field levels or by the highest wire-code category increases the risk of ALL in children.
Am J Epidemiol 2000 Mar 1;151(5):512-5
Kleinerman RA, Kaune WT, Hatch EE, Wacholder S, Linet MS, Robison LL, Niwa S, Tarone RE.
Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, MD 20892, USA.
In the National Cancer Institute/Children's Cancer Group case-control study of childhood acute lymphoblastic leukemia (1989-1993), living in a home with a high-voltage wire code was not associated with disease risk. To further investigate risk near power lines, the authors analyzed distance to transmission and three-phase primary distribution lines within 40 m of homes and created an exposure index of distance and strength of multiple power lines (408 case-control pairs). Neither distance nor exposure index was related to risk of childhood acute lymphoblastic leukemia, although both were associated with in-home magnetic field measurements. Residence near high-voltage lines did not increase risk.
Lancet 1999 Dec 4;354(9194):1967-8
Dockerty JD, Elwood JM, Skegg DC, Herbison GP.
A nationwide case-control study of childhood leukaemia in New Zealand included measurements of electric and magnetic fields in children's homes. There was no significant association between leukaemia and the time-weighted average of the 50 Hz magnetic or electric fields in the bedroom and living (or daytime) room combined.
Cancer Causes Control 1998 May;9(3):299-309
Dockerty JD, Elwood JM, Skegg DC, Herbison GP.
Department of Preventive and Social Medicine, University of Otago, Dunedin, New Zealand.
OBJECTIVES: To assess childhood cancer risks for electromagnetic field (EMF) exposures. METHODS: A case-control study was conducted in New Zealand. Cases (aged from zero to 14 years) were ascertained from national databases including the New Zealand Cancer Registry; 303 took part (participation rate, 88 percent). The 303 age- and gender-matched controls were selected randomly from birth records (participation, 69 percent). Mothers were interviewed about appliance exposures (all cases and controls), and 24-hour residential measurements of EMFs were made (leukemia cases and matched controls). RESULTS: For the various appliance exposures, there were some odds ratios (OR) above 1.0 and others below 1.0. For electric blanket use by the child before diagnosis, the adjusted ORs were: leukemia, 2.2 (95 percent confidence interval [CI] = 0.7-6.4); central nervous system cancers, ORs = 1.6 (CI = 0.4-7.1); and other solid cancers, OR = 2.4 (CI = 1.0-6.1). Leukemia risk was increased for the highest category of the mean measured bedroom magnetic field (> or = 0.2microT cf < 0.1 microT), with an adjusted OR of 15.5 (CI = 1.1-224). A gradient in OR with exposure was not shown (middle category: OR 1.4, CI = 0.3-7.6), and there was no association with exposure categorized into thirds based on controls' exposure. The adjusted OR for leukemia in relation to the measured daytime room magnetic field (> or = 0.2 microT cf < 0.1 microT) was 5.2 (CI = 0.9-30.8). CONCLUSIONS: This was a small study and multiple comparisons were made. The positive findings thus should be interpreted cautiously.
Br J Cancer 2000 Dec;83(11):1573-80
In the United Kingdom Childhood Cancer Study, a population-based case-control study covering the whole of England, Scotland and Wales, measured power-frequency magnetic fields were not found to be associated with risk for any malignancy. To examine further the risk associated with residential proximity to electricity supply equipment, distances to high-voltage lines, underground cables, substations and distribution circuits were collected for 3380 cases and 3390 controls. Magnetic field exposure from this equipment was calculated using distance, load and other circuit information. There was no evidence that either proximity to electrical installations or the magnetic field levels they produce in the UK is associated with increased risk of childhood leukaemia or any other cancer. Odds ratios of 0.73 (95% CI = 0.42-1.26) for acute lymphoblastic leukaemia, 0.75 (95% CI = 0.45-1.25) for all leukaemias, 1.08 (95% CI = 0.56-2.09) for central nervous system cancers and 0.92 (95% CI = 0.64-1.34) for all malignancies were obtained for residence within 50 m of an overhead line. When individuals with a calculated magnetic field exposure > or = 0.2 microT were compared to those in a reference category of exposure <0.1 microT, odds ratios of 0.51 (95% CI = 0.11-2.33) for acute lymphoblastic leukaemia, 0.41 (95% CI = 0. 09-1.87) for total leukaemia, 0.48 (95% CI =0.06-3.76) for central nervous system cancers and 0.62 (95% CI = 0.24-1.61) for all malignancies were obtained. Copyright 2000 Cancer Research Campaign.
Lancet 1999 Dec 4;354(9194):1925-31
BACKGROUND: Previous studies have suggested an association between exposure to power-frequency electromagnetic fields (EMF) and the development of childhood malignant disease, especially leukaemia and tumours of the central nervous system. We investigated the relation between all childhood cancer and exposure to power-frequency magnetic fields. METHODS: The UK Childhood Cancer Study was a population case-control study covering the whole of England, Wales, and Scotland. All children with a confirmed malignant disorder were potentially eligible. For each case, we matched two controls on date of birth and sex, randomly chosen from the list of the Family Health Services Authority in England and Wales or Health Board in Scotland. In the main study, 3838 cases and 7629 controls were interviewed. The EMF part of the study included only one control per case, and household EMF measurements and school measurements where relevant were taken on 2226 matched pairs. These measurements, adjusted for historical line load and appliance fields, were used to estimate average exposure in the year before the date of diagnosis, or an equivalent date for controls. Analyses were by conditional logistic regression, incorporating a census-derived deprivation index used as a measure of socioeconomic status. FINDINGS: For children with mean exposures of more than 0.2 microT compared with children with mean exposures of less than 0-1 microT, the adjusted odds ratios were 0.92 (95% CI 0.47-1.79) for acute lymphoblastic leukaemia, 0.90 (0.49-1.63) for all leukaemia, 0.46 (0.11-1.86) for central-nervous-system tumours, 0.97 (0.46-2.05) for other malignant disease, and 0.87 (0.56-1.35) for all malignant disease combined. Higher exposures (>0.4 microT) were recorded for only 17 (<0.4%) individuals (eight cases, nine controls). INTERPRETATION: This study provides no evidence that exposure to magnetic fields associated with the electricity supply in the UK increases risks for childhood leukaemia, cancers of the central nervous system, or any other childhood cancer.
BMJ 1993 Oct 9;307(6909):891-5
Olsen JH, Nielsen A, Schulgen G.
Danish Cancer Society, Division for Cancer Epidemiology, Copenhagen.
OBJECTIVE--To investigate whether residence before and after birth near 50 Hz high voltage installations increases a child's risk of cancer and whether risk correlates with the strength of the magnetic field. DESIGN--A population based case-control study. SETTING--Denmark. SUBJECTS--1707 children under the age of 15 with leukaemia, tumour of the central nervous system, or malignant lymphoma diagnosed in 1968-86 and 4788 children taken from the central population register. MAIN OUTCOME MEASURES--Proximity before and after birth to existing or former 50-400 kV electrical transmission connections and substations and associated historical electromagnetic fields calculated on the basis of current load on line, phase ordering of line, and distance from the dwelling. RESULTS--A significant association was seen between all major types of childhood cancer combined and exposure to magnetic fields from high voltage installations of > or = 0.4 microT (odds ratio 5.6). At > or = 0.25 microT no significant association was seen (odds ratio 1.5). A possible association was also seen with cases of Hodgkin's disease separately at > or = 0.1 microT. CONCLUSIONS--On the basis these results and additional descriptive data on electricity consumption and incidence of childhood cancer in Denmark since the 1940s it was concluded that the proportion of childhood cancer possibly caused by 50 Hz electromagnetic fields must be small.
Am J Epidemiol 1993 Oct 1;138(7):467-81
Feychting M, Ahlbom A.
Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden.
A case-control study was conducted to test the hypothesis that exposure to magnetic fields of the type generated by high-voltage power lines increases cancer incidence in children. The study base consisted of everyone under age 16 years who had lived on a property located within 300 meters of any of the 220 and 400 kV power lines in Sweden during the period 1960-1985. Subjects were followed from their entry into the study base through 1985. A total of 142 cancer cases were identified through a record linkage to the Swedish Cancer Registry. There were 39 leukemia and 33 central nervous system tumor cases. A total of 558 controls were selected at random from the study base. Exposure was assessed by spot measurements and by calculations of the magnetic fields generated by the power lines, taking distance, line configuration, and load into account. Information about historical loads on the power lines was used to calculate the magnetic fields for the year closest in time to diagnosis. When historical calculations were used as exposure assessment for childhood leukemia with cutoff points at 0.1 and 0.2 microtesla (microT), the estimated relative risk increased over the two exposure levels and was estimated at 2.7 (95% confidence interval (CI) 1.0-6.3) for 0.2 microT and over; p for trend = 0.02. When the upper cutoff point was shifted to 0.3 microT, the relative risk was 3.8 (95% CI 1.4-9.3); p for trend = 0.005. These results persisted when adjustment for potential confounding factors was made. For central nervous system tumor, lymphoma, and all childhood cancers combined, there was no support for an association.
Am J Epidemiol 1997 Feb 1;145(3):219-26
Tynes T, Haldorsen T.
Cancer Registry of Norway, Institute of Epidemiological Cancer Research, Oslo, Norway.
The aim of the nested case-control study reported here was to test the hypothesis that exposure to electromagnetic fields of the type generated by high-voltage power lines increases the incidence of cancer in children aged 0-14 years. The study population comprised children who during at least one of the years 1960, 1970, 1980, 1985, 1987, or 1989 had lived in a census ward crossed by a high-voltage power line. The cases were diagnosed from 1965 to 1989 and were matched to controls by year of birth, sex, and municipality. Exposure to electric and magnetic fields was calculated by means of computer programs in which power line characteristics and distance were taken into account. No association was found between exposure to time-weighted average exposure to magnetic fields and cancer at all sites, brain tumors, lymphoma, or leukemia. Cancer at other sites showed elevated odds ratios in the two highest exposure categories in some, but not all, measures of exposure. This study provides little support for an association between children's exposure to magnetic fields and cancer and no support for an association between leukemia and such exposure, but no firm conclusions can be drawn owing to the small numbers involved.
Br J Cancer 2002 Nov 18;87(11):1257-66
Skinner J, Mee TJ, Blackwell RP, Maslanyj MP, Simpson J, Allen SG, Day NE, Cheng KK, Gilman E, Williams D, Cartwright R, Craft A, Birch JM, Eden OB, McKinney PA, Deacon J, Peto J, Beral V, Roman E, Elwood P, Alexander FE, Mott M, Chilvers CE, Muir K, Doll R, Taylor CM, Greaves M, Goodhead D, Fry FA, Adams G, Law G; United Kingdom Childhood Cancer Study Investigators.
Strangeways Research Laboratory, University of Cambridge, Wort's Causeway, Cambridge CB1 8RN, UK.
The United Kingdom Childhood Cancer Study, a population-based case-control study covering the whole of Great Britain, incorporated a pilot study measuring electric fields. Measurements were made in the homes of 473 children who were diagnosed with a malignant neoplasm between 1992 and 1996 and who were aged 0-14 at diagnosis, together with 453 controls matched on age, sex and geographical location. Exposure assessments comprised resultant spot measurements in the child's bedroom and the family living-room. Temporal stability of bedroom fields was investigated through continuous logging of the 48-h vertical component at the child's bedside supported by repeat spot measurements. The principal exposure metric used was the mean of the pillow and bed centre measurements. For the 273 cases and 276 controls with fully validated measures, comparing those with a measured electric field exposure >/=20 V m(-1) to those in a reference category of exposure <10 V m(-1), odds ratios of 1.31 (95% confidence interval 0.68-2.54) for acute lymphoblastic leukaemia, 1.32 (95% confidence interval 0.73-2.39) for total leukaemia, 2.12 (95% confidence interval 0.78-5.78) for central nervous system cancers and 1.26 (95% confidence interval 0.77-2.07) for all malignancies were obtained. When considering the 426 cases and 419 controls with no invalid measures, the corresponding odds ratios were 0.86 (95% confidence interval 0.49-1.51) for acute lymphoblastic leukaemia, 0.93 (95% confidence interval 0.56-1.54) for total leukaemia, 1.43 (95% confidence interval 0.68-3.02) for central nervous system cancers and 0.90 (95% confidence interval 0.59-1.35) for all malignancies. With exposure modelled as a continuous variable, odds ratios for an increase in the principal metric of 10 V m(-1) were close to unity for all disease categories, never differing significantly from one.
BMJ 1993 Oct 9;307(6909):895-9
Verkasalo PK, Pukkala E, Hongisto MY, Valjus JE, Jarvinen PJ, Heikkila KV, Koskenvuo M.
Department of Public Health, University of Helsinki, Finland.
OBJECTIVE--To investigate the risk of cancer in children living close to overhead power lines with magnetic fields of > or = 0.01 microteslas (microT). DESIGN--Cohort study. SETTING--The whole of Finland. SUBJECTS--68,300 boys and 66,500 girls aged 0-19 years living during 1970-89 within 500 m of overhead power lines of 110-400 kV in magnetic fields calculated to be > or = 0.01 microT. Subjects were identified by record linkages of nationwide registers. MAIN OUTCOME MEASURES--Numbers of observed cases in follow up for cancer and standardised incidence ratios for all cancers and particularly for nervous system tumours, leukaemia, and lymphoma. RESULTS--In the whole cohort 140 cases of cancer were observed (145 expected; standardised incidence ratio 0.97, 95% confidence interval 0.81 to 1.1). No statistically significant increases in all cancers and in leukaemia and lymphoma were found in children at any exposure level. A statistically significant excess of nervous system tumours was found in boys (but not in girls) who were exposed to magnetic fields of > or = 0.20 microT or cumulative exposure of > or = 0.40 microT years. CONCLUSIONS--Residential magnetic fields of transmission power lines do not constitute a major public health problem regarding childhood cancer. The small numbers do not allow further conclusions about the risk of cancer in stronger magnetic fields.