ENA - the Energy Networks Association - is the industry body for UK energy transmission and distribution licence holders and operators. It runs a programme of EMF research on behalf of its members, which complements other electricity industry research on EMFs.
The two main programmes of work supported at present are:
- Ongoing maintenance of the database of electricity industry workers that has formed the basis of several epidmeiological studies
- Work at Lawson Health Research Institute in Canada on better understanding the thresholds for the acute effects of EMFs that exposure limits are based on.
We also summarise here the previous studies it has supported (most recent first).
16 Dose Response
Status
Approved 28 February 2008. The analysis is now complete and a paper has been submitted to a journal for publication in fulfilment of the project requirements.
Purpose
Up to now epidemiology studies of childhood leukaemia and exposure to magnetic fields have assumed a threshold model whereby there is a certain risk at fields above a certain level and no risk below that level. The study will investigate the impact of other dose-response relationships on the calculation of risk ratios in residential EMF epidemiology. It will be carried out by Prof Leeka Kheifets at the University of California at Los Angeles.
Results
We will add a summary of the results here as soon as the paper is published.
15 Improved Modelling of Induced Currents in the Retina at ELF Frequencies
Status
Approved 28 February 2008. Contract terminated early
Purpose
The induced current in the retinal is sometimes the critical organ when considering compliance with current-density exposure limits. The retina is a thin layer of nervous tissue extending over much of the periphery of the eye, and earlier dosimetry, having a resolution determined by the 2 mm voxels, does not model the eye adequately. For this project a good finite-element model of the retina will be developed and then the model will be applied to calculate the electric and magnetic fields to ensure that the current density basic restrictions is not exceeded in the eye. The research will be carried out by Peter Wainwright of the Health Protection Agency.
Results
The study started during July 2008. The project was proceeding well with acquisition of models and modelling software . Sadly, the researcher doing the work (Peter Wainwright) died unexpectedly at the end of March 2009 and therefore it was necessary to agree to the termination of the contract. HPA, the contracting organisation recognises the importance of the work but they are not in a position to continue it for the time being. It is hoped that they will be able to consider a new project when their team has been rebuilt and their expertise in finite element modelling has been re-established.
14 Maintenance and SMR Analysis of Mortality Cohort Database - Third Contract 2007/11
Status: Approved 10 Nov 2006; Cancer-incidence extension approved Oct 2008. In progress.
Purpose
The "mortality cohort" is a database of employees of the electricity industry which can be used for epuidemiological studies - see more detail on the studies which have been performed. The contract with the University of Birmingham will run for 5 years (2007 to 2011), providing for computerising and checking of quarterly returns (death-certificates for new deaths within the cohort) obtained from the Office for National Statistics. The contract includes a one-off payment in 2007 for a pilot study into obtaining cancer registrations for bladder cancer for a sample of 1000 cohort members.
Results
The digitisation of death certificates has been completed to a high standard. ONS initially provided cancer registrations data for bladder cancer cases. It was then agreed to obtain cancer registrations for the whole cohort, and this contract with the University of Birmingham was modified to extend the cohort to include cancer registration data.
The contract now includes obtaining cancer registration data for all members of the cohort and reporting in 2010 on proportional incidence ratios for cancers within the cohort.
13 Electric Field Analysis
Status
Approved 24 November 2005. The study is completed and published.
Purpose
Although the majority of evidence for ELF points to magnetic rather than electric fields, electric fields are raised in some quarters as an alternative explanation capable of explaining inconsistencies in the data on childhood leukaemia. Professor Kheifets of UCLA worked with John Swanson and David Renew from National Grid to prepare a comprehensive review of the literature focussing on electric fields. The project is complete and the paper has been published.
Results
The Abstract of the published study reads:
"Much of the research and reviews on extremely low frequency (ELF) electric and magnetic fields (EMFs) have focused on magnetic rather than electric fields. Some have considered such focus to be inappropriate and have argued that electric fields should be part of both epidemiologic and laboratory work. This paper fills the gap by systematically and critically reviewing electric-fields literature and by comparing overall strength of evidence for electric versus magnetic fields. The review of possible mechanisms does not provide any specific basis for focusing on electric fields. While laboratory studies of electric fields are few, they do not indicate that electric fields should be the exposure of interest. The existing epidemiology on residential electric-field exposures and appliance use does not support the conclusion of adverse health effects from electric-field exposure. Workers in close proximity to high-voltage transmission lines or substation equipment can be exposed to high electric fields. While there are sporadic reports of increase in cancer in some occupational studies, these are inconsistent and fraught with methodologic problems. Overall, there seems little basis to suppose there might be a risk for electric fields, and, in contrast to magnetic fields, and with a possible exception of occupational epidemiology, there seems little basis for continued research into electric fields."
12 Future Direction of CEGB Cohort
Status
Approved 24 November 2005. Completed and reported.
Purpose
The electricity industry mortality cohort has been used for several studies and its population is ageing. For this project Professor Kheifets at UCLA carried out a review of the technical issues that would need to be addressed to ensure the continued usefulness of the cohort. The review dealt with issues such as the ongoing acquisition of death certificates, updating of work histories and exposure assessments. It also gave consideration to what future studies using the cohort would be worth while.
Results
This work is now complete and a report has been prepared by Dr Kheifets. The recommendations were to undertake additional methodological analyses of the data to gain new insights from existing data (which were listed), continue with planed update of the cohort with death outcomes over the next 5 years, future work should put an emphasis on within cohort comparisons to avoid the health worker effect, and to support international effort to address rare outcomes (e.g. ALS).
11 Workshop on Occupational Epidemiology within the Electricity Utility Industry
Status
Approved 24 November 2005. Workshop held on 14-15 September 2006.
Purpose
The workshop was planned to bring together researchers and research managers of previous studies within the industry internationally, including epidemiologists and exposure-assessment experts. The object was to review the previous research, ascertain the status of existing databases and develop further research priorities in the area of occupational epidemiology and exposure assessment.
The scientific organisation and invitations to participants were arranged by Leeka Kheifets, Professor of Epidemiology at UCLA School of Public Health, and the practical arrangements were made by Peter Coyle at ENA.
Results
The workshop was held at the Malmaison Hotel in Edinburgh, on 14-15 September, and was successful at achieving its objectives. The conclusions will be used for planning the next phase of the work using the cohort.
There were 24 attendees including epidemiologists, occupational physicians and exposure assessment experts as well as researchers and research managers, representing all of the largest previous occupational electricity utility studies. Affiliations included universities, in Europe and North America, the electricity utility industry, EPRI and NIEHS.
The conclusions were reported as follows:
There was an overall high level of agreement among the participants regarding the interpretation and significance of the existing epidemiologic evidence, future research priorities and collaborative research possibilities. It was agreed that it is worth doing more research on the priority areas identified. International collaboration and pooling of cohort data is now likely to be the best way forward and there was agreement by all those who attended and involved with previously studied cohorts. This could be achieved through shared protocols, exposure metrics and analytic approaches. This bodes well for the ultimate success of data pooling activities, in particular, where shared interests and commitment are essential.
Coordinated updates of the various cohorts with a common exposure assessment and data analysis methods would create a large database for the powerful examination of uncommon diseases and future issues. Although potentially worthwhile it appears to be quite difficult at this time. Practical proposals to advance current knowledge included an ALS study, methodological work in exposure assessment and statistical analysis.
Although not part of the original contract, a paper for publication for the peer-reviewed literature has been prepared jointly by a number of attendees at the workshop, led and coordinated by Dr Kheifets. The paper was published by the Journal Occupational and Environmental Medicine.
Its conclusion is that, although the epidemiologic evidence suggests excess risk with occupational EMF exposure for some health outcomes, there is no outcome for which the combined evidence is strong or consistent enough to support the conclusion that a health hazard exists.
10 Mortality from Neurodegenerative Diseases and Occupational Exposure to EMFs
Status
Approved 24 November 2005. Completed and published
Purpose
This was a study to investigate the mortality from Alzheimer’s disease, motor neurone disease (i.e. amyotrophic lateral sclerosis) and Parkinson’s disease in relation to EMF exposure using the electricity industry mortality cohort. These were the cause of death for 218 of the 21,888 people who had died up to 2004 in the cohort of 84,000 CEGB workers that was used for the study. It had been used in the previous studies of brain cancer, leukaemia and cardiovascular disease in relation to occupational exposure to magnetic fields.
The study was carried out by Prof Tom Sorahan, Professor of Occupational Epidemiology at the Institute of Occupational and Environmental Medicine at the University of Birmingham, working with Professor Leeka Kheifets, Professor of Epidemiology at UCLA School of Public Health, who was formerly the manager of the EPRI EMF research program and then manager of the WHO EMF programme.
The principal exposure for analysis was magnetic fields, using the detailed exposure assessment developed by National Grid for the previous studies using the cohort.
It is hoped to develop methods for assessing exposure to electric field and for assessing the severity and prevalence of electric shocks within the cohort with a view to reanalysing the data for these exposures as a follow on study.
Results
Based on serial mortality rates for England and Wales, deaths from Alzheimer’s disease and motor neurone disease were unexceptional. There was an excess of deaths from Parkinson’s disease of borderline significance. No statistically significant trends were shown for risks of any of these diseases to increase with lifetime cumulative exposure to magnetic fields (RR per 10mT.y with 95% confidence interval: Alzheimer’s disease 1.10 (0.90 to 1.33); motor neurone disease 1.06 (0.86 to 1.32); Parkinson’s disease 0.88 (0.74 to 1.05))
These results have been published.
9 Depression Near Power Lines
Status
Approved 13 July 2005. Subsequently discontinued
Purpose
This study of depression near power lines was intended to be conducted by the Institute of Psychiatry at the Maudsley Hospital and part of Kings College, London. The researchers were to produce an application for joint funding from the Department of Health’s latest call for research projects. However the project with that particular research group was not able to be be pursued and was discontinued. We hope still to be able to support a study in this area in future.
8 High-Field Homes
Status
Approved September 2001; increased funding agreed March 2004; final report issued November 2005. Completed and published.
Purpose
A 21-month study of the causes of the high exposure of the UKCCS cases and controls with exposures assessed as being greater than 0.2 µT. The project was funded jointly with the DTI with the DTI contribution being about twice the industry contribution. The work was be done primarily by the NRPB and Leukaemia Research Fund with some assistance being provided by EMF expertise within National Grid, and information about the electricity system close to the home being provided by ENA member companies.
Results
The study has been published. It identified that of homes with fields above 0.4 µT, roughly half come from high-voltage power lines and roughly half from low-voltage sources. These results are analysed further here.
7 WHO Environmental Health Criteria Document
Status
Approved July 2002. Completed.
Purpose
The WHO revised its environmental health criteria document relating to EMFs and cancer and other health effects. It estimated the process will cost $500,000. At the request of WHO, the ENA contributed £40,000 to the cost, spread over the four years, 2002 to 2005.
Results
The electricity industry's contribution to WHO conferred no influence whatsoever over the results.
For full details of WHO's EHC published in 2008 see here.
6 Adult Cancers Near Power Lines
Status
Approved July 2001. Research conducted by Small Areas Health Statistics Unit at Imperial College, London. In progress but now overdue. Funded jointly with DH; the contract with the researchers is with DH, with a separate contract between the electricity industry and DH to provide funding.
Purpose
A study of cancer incidence among adults living near 275 kV and 400 kV overhead lines in the UK. Analyses include analysis of incidence of disease with distance from the line and with exposure to magnetic field. It includes analyses to compare incidence of lung cancer upwind and downwind of the lines as a test of the hypothesis that corona ions from the line attaching to pollution particles thereby increase the incidence of disease in the downwind exposed population.
This study is the adult counterpart to the CCRG studies of childhood cancer.
Results
No results available yet.
5 Maintenance of Mortality Cohort Database - Second Contract - 2003/06
Status
Approved July 2002. Completed.
Purpose
A contract with the University of Birmingham Institute of Occupational Health to provide routine storage and maintenance for the mortality cohort. This included obtaining regular updates on deaths within the cohort from the Office of National Statistics.
Results
Maintenance of the cohort under this contract is now complete. Maintenance continues under the Third Contract – see item 14 above.
4 Maintenance and SMR Analysis of Mortality Cohort Database – First Contract – 2002
Status
Approved July 2001. Completed.
Purpose
A contract with the University of Birmingham Institute of Occupational Health to provide routine storage and maintenance for the mortality cohortfor the calendar year 2002. This included obtaining regular updates on deaths within the cohort from the Office of National Statistics. This contract covered two non-routine items: the transfer of the cohort maintenance from British Energy and eliminating the backlog that has accumulated; and the preparation and publication of a Standardised Mortality Ratio (SMR) analysis based on deaths received up to the end of 2002.
Results
The Standardised Mortality Ratio analyses provides a SMR value for a comprehensive list of causes of death for the 25% of the electricity industry cohort, set up in the 1970s, who have died so far. Separate analyses are given for men (18,800 deaths) and women (1,100 deaths), for staff who worked in power stations, in transmission and at non-operational locations.
Overall mortality was significantly below that expected based on national rates (Males: Obs 18,773, Exp 22,497.9, SMR 83, Females: Obs 1,122, Exp 1,424.9, SMR 79) Statistically significant deficits of deaths were also found in most of the major disease groupings. However significant excesses were found in male power station workers for cancer of the pleura (Males: Obs 129, Exp 30.3, SMR 426) and in non-operational locations for cancer of the brain (Males: Obs 55, Exp 36.0, SMR 153). There was also a non-significant excess of deaths from cancer of the breast in male power station workers (Obs 10, Exp 5.3, SMR 190).
Further details of this study
3 Validation of Death Certification of Sudden Cardiac Death
Status
Approved 13 July 2000. Completed and published August 2006.
Purpose
An assessment of the accuracy of current death certification practice for sudden and acute cardiovascular disease. One of the possible reasons for a false association between magnetic field exposure and arrhythmia-related heart disease could be due to errors in reporting the form of heart disease on death certificates.
Results
The aim of the study was to assess the accuracy of current death certification practice for sudden and acute cardiovascular disease. Medical reports and post mortem reports were obtained for a sample of 400 deaths occurring in selected Health Authorities in the West Midlands during the year 2000. These were distributed to two participating doctors, of differing background (pathologist, A&E specialist, GP, cardiologist) who assigned cause of death. Where their diagnoses differed a panel met to reach a consensus. These diagnoses were compared with the death certificate diagnoses and misclassifications calculated.
Conclusion: The process of identifying underlying cause of death, and in particular between “acute” and “chronic” causes, is an inaccurate one.
Further details of this study
2 Cardiovascular Disease and Occupational Exposure to Magnetic Fields
Status
Approved 13 July 2000. Completed and published January 2004.
Purpose
Analysis of cardiovascular disease mortality and magnetic field exposure using the electricity-industry mortality cohort and the advanced exposure assessment protocol developed by National Grid. This is a replication of a similar study published by Savitz in 1999 which showed an association between death from arrhythmia-related heart disease and occupational exposure to magnetic fields.
Results
There are no discernible excess risks of mortality from cardiovascular diseases as a consequence of occupational exposure to magnetic fields in UK electricity generation and transmission workers.
1 Brain Cancer and Occupational Exposure to Magnetic Fields
Status
Approved 13 July 2000. Completed and published October 2001.
Purpose
Analysis of brain cancer mortality and magnetic field exposure using the electricity industry mortality cohort and the advanced exposure assessment protocol developed by National Grid.
Results
Conclusion: There are no discernible excess risks of brain tumours as a consequence of occupational exposure to magnetic fields in United Kingdom electricity generation and transmission workers.
Further details of this study
See also:
- research by National Grid
- ongoing research in general