The CCRG (or “Draper”) study abstracts

BMJ. 2005 Jun 4;330(7503):1290.
Childhood cancer in relation to distance from high voltage power lines in England and Wales: a case-control study.Draper G, Vincent T, Kroll ME, Swanson J. 

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.
Design Case-control study.
Setting Cancer registry and National Grid records.
Participants 29081 children with cancer, including 9700 with leukaemia. Children were aged 0-14 years and born in England and Wales, 1962-95. Controls were individually matched for sex, approximate date of birth, and birth registration district. No active participation by cases or controls was required.
Main outcome measures Distance from home address at birth to the nearest high voltage overhead power line in existence at the time. Results Compared with those who lived >600 m from a line at birth, children who lived within 200 m had a relative risk of leukaemia of 1.69 (95% confidence interval 1.13 to 2.53); those born between 200 and 600 m had a relative risk of 1.23 (1.02 to 1.49). There was a significant (P<0.01) trend in risk in relation to the reciprocal of distance from the line. No excess risk in relation to proximity to lines was found for other childhood cancers.
Conclusions There is an association between childhood leukaemia and proximity of home address at birth to high voltage power lines, and the apparent risk extends to a greater distance than would have been expected from previous studies. About 4% of children in England and Wales live within 600 m of high voltage lines at birth. If the association is causal, about 1% of childhood leukaemia in England and Wales would be attributable to these lines, though this estimate has considerable statistical uncertainty. There is no accepted biological mechanism to explain the epidemiological results; indeed, the relation may be due to chance or confounding.

Ann N Y Acad Sci. 2006 Sep;1076:318-30
Power-frequency electric and magnetic fields in the light of Draper et al. 2005.Swanson J, Vincent T, Kroll M, Draper G. 

National Grid, London, WC2N 5EH, UK. john.swanson@physics.org

Power-frequency electric and magnetic fields are produced wherever electricity is used; exposure is ubiquitous. Epidemiologic studies find an association between children living in homes with the highest magnetic fields and childhood leukemia, but bias is a possible alternative to a causal explanation. A new study, Draper et al., looks at residence close to high-voltage power lines, one source of exposure to such fields, and its design avoids any obvious bias. It finds elevated childhood leukemia rates, but extending too far from the power lines to be straightforwardly compatible with the existing literature. This leads to an examination of alternative explanations: magnetic fields, other physical factors, such as corona ions, the characteristics of the areas power lines pass through, bias, and chance. The conclusion is that there is currently no single preferred explanation, but that this is a serious body of science that needs further work until an explanation is found.

J Radiol Prot. 2008 Mar;28(1):45-59. Epub 2008 Feb 26.
Methods used to calculate exposures in two epidemiological studies of power lines in the UK.Swanson J. 

Two epidemiological studies of cancer (one for children and one for adults) and proximity to high-voltage power lines are being performed in the UK. We describe the methods used to calculate exposure to magnetic fields in these studies. We used grid references derived from addresses for subjects and compared these to the grid references of pylons to calculate distances to power lines. We gathered relevant data on the power lines and used these to calculate magnetic fields. This required information on loads in the years from 1962 to the present. The only such information now available is a prediction of loads made for each year in advance, and the use of predictions rather than actual loads is the biggest source of error in these calculations. For a recent year, we compare the loads used in these studies with actual loads to assess the accuracy of our calculations. These calculations were performed by industry, and we describe the steps taken to ensure their trustworthiness, including conducting them all blind to the case-control status of the subjects.

British Journal of Cancer (2010) 103, 1122 – 1127
Childhood cancer and magnetic fields from high-voltage power lines in England and Wales: a case–control study 

ME Kroll, J Swanson, TJ Vincent and GJ Draper

BACKGROUND: Epidemiological evidence suggests 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.
METHODS: 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.
RESULTS: The estimated relative risk for each 0.2 mT 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.
CONCLUSION: 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 previously reported from this study.

Br J Cancer. 2012 Sep 11. doi: 10.1038/bjc.2012.359. [Epub ahead of print]
Case-control study of paternal occupation and childhood leukaemia in Great Britain, 1962-2006. 

Keegan TJ, Bunch KJ, Vincent TJ, King JC, O'Neill KA, Kendall GM, Maccarthy A, Fear NT, Mfg M.

Background: Paternal occupational exposures have been proposed as a risk factor for childhood leukaemia. This study investigates possible associations between paternal occupational exposure and childhood leukaemia in Great Britain.
Methods:The National Registry of Childhood Tumours provided all cases of childhood leukaemia born and diagnosed in Great Britain between 1962 and 2006. Controls were matched on sex, period of birth and birth registration subdistrict. Fathers' occupations were assigned to 1 or more of 33 exposure groups. Social class was derived from father's occupation at the time of the child's birth.
Results:A total of 16 764 cases of childhood leukaemia were ascertained. One exposure group, paternal social contact, was associated with total childhood leukaemia (odds ratio 1.14, 1.05-1.23); this association remained significant when adjusted for social class. The subtypes lymphoid leukaemia (LL) and acute myeloid leukaemia showed increased risk with paternal exposure to social contact before adjustment for social class. Risk of other leukaemias was significantly increased by exposure to electromagnetic fields, persisting after adjustment for social class. For total leukaemia, the risks for exposure to lead and exhaust fumes were significantly <1. Occupationally derived social class was associated with risk of LL, with the risk being increased in the higher social classes.
Conclusion:Our results showed some support for a positive association between childhood leukaemia risk and paternal occupation involving social contact. Additionally, LL risk increased with higher paternal occupational social class.

Br J Cancer. 2014 Mar 4;110(5):1402-8.

Residential distance at birth from overhead high-voltage powerlines: childhood cancer risk in Britain 1962-2008

Bunch KJ, Keegan TJ, Swanson J, Vincent TJ, Murphy MFG

Background: We extend our previous study of childhood leukaemia and proximity to high-voltage powerlines by including more recent data and cases and controls from Scotland, by considering 132-kV powerlines as well as 275 and 400 kV, and by looking at greater distances from the powerlines.
Methods: Case–control study using 53 515 children from the National Registry of Childhood Tumours 1962–2008, matched
controls, and calculated distances of mother’s address at child’s birth to powerlines at 132, 275 and 400 kV in England, Wales and Scotland.
Results: Our previous finding of an excess risk for leukaemia at distances out to 600m declines over time. Relative risk and confidence interval for leukaemia, 0–199m compared with >1000 m, all voltages: 1960s 4.50 (0.97–20.83), 2000 s 0.71 (0.49–1.03), aggregate over whole period 1.12 (0.90–1.38). Increased risk does not extend beyond 600 m, but may be present, albeit less strongly, for 132 kV lines.
Conclusion: A risk declining over time is unlikely to arise from any physical effect of the powerlines and is more likely to be the
result of changing population characteristics among those living near powerlines.

J Radiol Prot. 2014 Oct 17;34(4):N81-N86. [Epub ahead of print]

Relative accuracy of grid references derived from postcode and address in UK epidemiological studies of overhead power lines.

Swanson J, Vincent TJ, Bunch KJ.

In the UK, the location of an address, necessary for calculating the distance to overhead power lines in epidemiological studies, is available from different sources. We assess the accuracy of each. The grid reference specific to each address, provided by the Ordnance Survey product Address-Point, is generally accurate to a few metres, which will usually be sufficient for calculating magnetic fields from the power lines. The grid reference derived from the postcode rather than the individual address is generally accurate to tens of metres, and may be acceptable for assessing effects that vary in the general proximity of the power line, but is probably not acceptable for assessing magnetic-field effects.

J. Radiol. Prot. 34 (2014) 873–889

Childhood cancer and exposure to corona ions from power lines: an epidemiological test

J Swanson1 , K J Bunch2 , T J Vincent2 and M F G Murphy2

1 National Grid, 1–3 Strand, London WC2N 5EH, UK

2 formerly Childhood Cancer Research Group, University of Oxford, New Richards Building, Old Road Campus, Headington, Oxford OX3 7LG, UK

Received 12 June 2014, revised 12 September 2014, accepted for publication 1 October 2014

Abstract

We previously reported an association between childhood leukaemia in Britain and proximity of the child’s address at birth to high-voltage power lines that declines from the 1960s to the 2000s. We test here whether a ‘corona-ion hypothesis’ could explain these results. This hypothesis proposes that corona ions, atmospheric ions produced by power lines and blown away from them by the wind, increase the retention of airborne pollutants in the airways when breathed in and hence cause disease. We develop an improved model for calculating exposure to corona ions, using data on winds from meteorological stations and considering the whole length of power line within 600 m of each subject’s address. Corona-ion exposure is highly correlated with proximity to power lines, and hence the results parallel the elevations in leukaemia risk seen with distance analyses. But our model explains the observed pattern of leukaemia rates around power lines less well than straightforward distance measurements, and ecological considerations also argue against the hypothesis. This does not disprove the corona-ion hypothesis as the explanation for our previous results, but nor does it provide support for it, or, by extension, any other hypothesis dependent on wind direction.

Journal of Radiological Protection 2015 Sep;35(3):695-705.

Magnetic fields and childhood cancer: an epidemiological investigation of the effects of high-voltage underground cables
K J Bunch, J Swanson, T J Vincent, M F G Murphy

Epidemiological evidence of increased risks for childhood leukaemia from magnetic fields has implicated, as one source of such fields, high-voltage overhead lines. Magnetic fields are not the only factor that varies in their vicinity, complicating interpretation of any associations. Underground cables (UGCs), however, produce magnetic fields but have no other discernible effects in their vicinity. We report here the largest ever epidemiological study of high voltage UGCs, based on 52,525 cases occurring from 1962-2008, with matched birth controls. We calculated the distance of the mother’s address at child’s birth to the closest 275 or 400 kV AC or high-voltage DC UGC in England and Wales and the resulting magnetic fields. Few people are exposed to magnetic fields from UGCs limiting the statistical power. We found no indications of an association of risk with distance or of trend in risk with increasing magnetic field for leukaemia, and no convincing pattern of risks for any other cancer. Trend estimates for leukaemia as shown by the odds ratio (and 95% confidence interval) per unit increase in exposure were: reciprocal of distance 0.99 (0.95-1.03), magnetic field 1.01 (0.76-1.33). The absence of risk detected in relation to UGCs tends to add to the argument that any risks from overhead lines may not be caused by magnetic fields.

J. Radiol. Prot. 36 (2016) 437–455
Epidemiological study of power lines and childhood cancer in the UK: further analyses
K J Bunch, J Swanson, T J Vincent and M F G Murphy

We report further analyses from an epidemiological study of childhood cancer and residence at birth near high-voltage power lines in the UK. These results suggest that the elevated risks for childhood leukaemia that we previously found for overhead power lines may be higher for older age at diagnosis and for myeloid rather than lymphoid leukaemia. There are differences across regions of birth but not forming any obvious pattern. Our results suggest the decline in risk we previously reported from the 1960s to the 2000s is linked to calendar year of birth or of cancer occurrence rather than the age of the power lines concerned. Finally, we update our previous analysis of magnetic fields to include later subjects.