Power lines and risks on human health Literature review and synthesis Marielle André – IWMI, International Water Management Institute May 2009

Sketch of the problem

Introduction Exposure to extremely low frequency fields The use of electricity has become an integral part of everyday life. Whenever electricity flows, both electric and magnetic fields (EMF) exist close to the lines that carry electricity, and close to appliances. On initial consideration, it is not obvious that EMF would pose any hazard to human health. In particular, this radiation has insufficient energy to damage DNA directly, and therefore in principle should not be capable of initiating cancers. But since the late 1970s, questions have been raised whether exposure to these extremely low frequency (ELF) electric and magnetic fields (EMF) produces adverse health consequences. Since then, much research has been done, leading to very controversial results.

1979, first suspicion Concern about a possible danger has arisen in the last 20 years, however, and has initially been brought to prominence by a report in 1979 of an epidemiologic study in Denver by Wertheimer and Leeper (Wertheimer N, Leeper E. (1979). Electrical wiring configurations and childhood cancer. Am J Epidemiol 109:273–284). They found a relation between risk of childhood leukemia and a proxy measure of degree of exposure to EMF radiation from electricity transmission lines. Since that study, there has been a burgeoning of research in this area. The most intensive epidemiologic effort has concerned childhood malignancy, especially leukemia, but there has also been considerable research on possible occupational associations with cancer in adults, on cardiovascular and neurological/ psychological diseases in adults, and on reproductive outcomes. This research has been 1

accompanied by public apprehension about the possibility that exposures to EMF, particularly for children, might be a cause of malignancy.

Possible risks on human health Most of the studies about the effects of EMF on human health concern childhood leukemia. Others scientists have been focusing on different health effects as psychological or cardiovascular symptoms. The following table synthesise the topics examined in the different papers related to electromagnetic fields. * Lymptomes * Brain and nervous system tumors * Leukemia Adult cancer * Leukemia * Breast cancer OTHER END POINTS Neurodegenerative disease * Amyotrophic lateral sclerosis * Alzheimer's disease Suicide and Depression Cardiovascular diseases Reproductive effects

CANCER

Childhood cancer

Short-term effects There are established biological effects from acute exposure at high levels (well above 100 μT) that are explained by recognized biophysical mechanisms. External ELF magnetic fields induce electric fields and currents in the body which, at very high field strengths, cause nerve and muscle stimulation and changes in nerve cell excitability in the central nervous system. However, these levels are much higher than average residential power-frequency magnetic fields in homes (about 0.07 μT in Europe; 0.11 μT in North America). Potential long-term effects Much of the scientific research examining long-term risks from ELF magnetic field exposure has focused on childhood leukaemia. In 2002, IARC (International Agency for Research on Cancer) published a monograph classifying ELF magnetic fields as "possibly carcinogenic to humans". This classification is used to denote an agent for which there is limited evidence of carcinogenicity in humans and less than sufficient evidence for carcinogenicity in experimental animals (other examples include coffee and welding fumes). This classification was based on pooled analyses of epidemiological studies demonstrating a consistent pattern of a two-fold increase in childhood leukaemia associated with average exposure to residential power-frequency magnetic field above 0.3 to 0.4 μT. The Task Group concluded that additional studies since then do not alter the status of this classification. However, the epidemiological evidence is weakened by methodological problems, such as potential selection bias. In addition, there are no accepted biophysical mechanisms that would suggest that low-level exposures are involved in cancer development. Thus, if there were any 2

effects from exposures to these low-level fields, it would have to be through a biological mechanism that is as yet unknown. Additionally, animal studies have been largely negative. Thus, on balance, the evidence related to childhood leukaemia is not strong enough to be considered causal. Childhood leukaemia is a comparatively rare disease with a total annual number of new cases estimated to be 49,000 worldwide in 2000. Average magnetic field exposures above 0.3 μT in homes are rare: it is estimated that only between 1% and 4% of children live in such conditions. If the association between magnetic fields and childhood leukaemia is causal, the number of cases worldwide that might be attributable to magnetic field exposure is estimated to range from 100 to 2400 cases per year, based on values for the year 2000, representing 0.2 to 4.95% of the total incidence for that year. Thus, if ELF magnetic fields actually do increase the risk of the disease, when considered in a global context, the impact on public health of ELF EMF exposure would be limited. ICNIRP literature review

In 2001, the ICNIRP (International Commission for Non-Ionizing Radiation Protection) reviewed epidemiologic literature on EMF and risks of chronic disease (Ahlbom, A.; Cardis, E., Green; A.; Linet, M.; Savitz, D.; Swerdlow, A. (2001). Review of the Epidemiologic Literature on EMF and Health, ICNIRP Standing Committee on Epidemiology). They conclude that: a) The quality of epidemiologic studies on this topic has improved over time and several of the recent studies on childhood leukemia and on cancer associated with occupational exposure are close to the limit of what can realistically be achieved in terms of size of study and methodological rigor. b) Exposure assessment is a particular difficulty of EMF epidemiology, in several respects: • The exposure is imperceptible, ubiquitous, has multiple sources, and can vary greatly over time and short distances. • The exposure period of relevance is before the date at which measurements can realistically be obtained and of unknown duration and induction period. • The appropriate exposure metric is not known and there are no biological data from which to impute it. c) In the absence of experimental evidence and given the methodological uncertainties in the epidemiologic literature, there is no chronic disease for which an etiological relation to EMF can be regarded as established. d) There has been a large body of high quality data for childhood cancer, and also for adult leukemia and brain tumor in relation to occupational exposure. Among all the outcomes evaluated in epidemiologic studies of EMF, childhood leukemia in relation to postnatal exposures above 0.4 μT is the one for which there is most evidence of an association. The relative risk has been estimated at 2.0 (95% confidence limit: 1.27–3.13) in a large pooled analysis. This is unlikely to be due to chance but, may be, in part, due to bias. This is difficult to interpret in the absence of a known mechanism or reproducible experimental support. In the large pooled 3

analysis only 0.8% of all children were exposed above 0.4 μT. Further studies need to be designed to test specific hypotheses such as aspects of selection bias or exposure. On the basis of epidemiologic findings, evidence shows an association of amyotrophic lateral sclerosis with occupational EMF exposure although confounding is a potential explanation. Breast cancer, cardiovascular disease, and suicide and depression remain unresolved. Limits and difficulties of epidemiologic studies In most of the studies related to EMF and human health, the difficulties of exposure assessment are discussed. It concern: - Knowledge on relevant metric and relevant period of exposures - Retrospective exposure assessments - Completeness of exposure characterization.

Possible effects of magnetic fields on animals In 2008, a German and Czech researchers team found that cows and deer tended to align themselves north-south when grazing or resting (Begall, S., Červený, J., Neef, J., Vojtěch, O., and Burda, H. (2008). Magnetic alignment in grazing and resting cattle and deer. PNAS 2008, 105:13451-13455.). The findings, collated from satellite pictures and ground-level observation, suggested large mammals were influenced by Earth's magnetic field, like birds, turtles and salmon are. Six month later, the same researchers say the behaviour of cows and roe deer under high-voltage power lines, or within 50 metres either side of them, is an exception to the general rule. They say it is physically measurable that high-voltage power lines locally change the Earth's magnetic field. A scientist from the organisation Sense About Science said it seemed unlikely because the magnetic fields from power lines are so weak in comparison with the Earth.

Discussion Overall, despite 20 years of extensive epidemiologic investigation of the relation of EMF to risk of chronic disease, there are still epidemiologic questions that need to be resolved. To be of value, however, future studies of these questions must be of high methodological quality, of sufficient size and with sufficient numbers of highly exposed subjects, and must include appropriate exposure groups and sophisticated exposure assessment. Especially for childhood leukemia, little is to be gained from further repetition of investigation of risks at moderate and low exposure levels, unless such studies can be designed to test specific hypotheses, such as selection bias or aspects of exposure not previously captured. In addition there is a need for studies in humans of possible physiological effects of EMF that might relate to risks of chronic disease.

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References Wertheimer N, Leeper E. (1979). Electrical wiring configurations and childhood cancer. Am J Epidemiol 109:273–284. Begall, S., Červený, J., Neef, J., Vojtěch, O., and Burda, H. (2008). Magnetic alignment in grazing and resting cattle and deer. PNAS 2008, 105:13451-13455. Ahlbom, A.; Cardis, E., Green; A.; Linet, M.; Savitz, D.; Swerdlow, A. (2001). Review of the Epidemiologic Literature on EMF and Health, ICNIRP Standing Committee on Epidemiology. WHO - World Health Organisation (2007). Electromagnetic fields and public health. Fact sheet n°322, June 2007. IARC Working Group on the Evaluation of Carcinogenic Risks to Humans (2002). Nonionizing radiation, Static and extremely low frequency electric and magnetic fields. IARC, Lyon. ICNIRP - International Commission on Non-Ionizing Radiation Protection (2003). Exposure to static and low frequency electromagnetic fields, biological effects and health consequences (0100 kHz). Bernhardt JH et al., eds. Oberschleissheim, ICNIRP 2003. ICNIRP – International Commission on Non-Ionizing Radiation Protection (1998). Guidelines for limiting exposure to time varying electric, magnetic and electromagnetic fields (up to 300 GHz). Health Physics 74(4), 494-522.

Annexe : Articles concerning potential risks of EMF found in BBC-News website. Date

Title

References

02/12/1999 Pylons 'treble cancer particles'

Professor Denis Henshaw, University of Bristol

03/12/1999 Pylons safe, says 'definitive' research

Sir Richard Doll, Lancet medical journal

03/12/1999 Battle lines drawn in pylon debate 15/03/2000 Electromagnetic fields 'raise suicide risk'

Dr Edwin van Wijngaarden

05/03/2001 Fresh pylon link to child cancer

National Radiological Protection Board's investigation

06/03/2001 Watchdog confirms pylon cancer link

NRPB

19/12/2001 Electromagnetic fields 'raise cancer risk'

International Commission on Non-Ionizing Radiation Protection

01/05/2003 UK plans to lower EMF limits

NRPB

10/06/2003 Fresh debate over pylon cancer risk 09/02/2004 Electromagnetic field 'creates toxic gas'

Dr Steve Goheen, journal Bioelectromagnetics

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