Chapter 9: Health effects of electric and magnetic fields
Introduction
733. The possible health effects of exposure to extremely low-frequency electric and magnetic fields (ELF EMF) associated with electric power were raised in approximately 960 of some 1244 submissions made in response to public notification of Transpower’s designation requirements and resource consent applications.
734. At the hearing, some expert witnesses and submitters referred to many scientific studies and reviews addressing a range of health outcomes, in particular cancer.
735. In this chapter, the Board discusses potential effects on human health in exposure to ELF EMF from the proposed transmission line, and the application of a precautionary or prudent avoidance approach.
Exposure guidelines
736. Professor A W Wood, biophysicist and member of the World Health Organization (WHO) Task Group for Environmental Health Criteria (EHC) 238; Dr D R Black, occupational medicine physician; and Dr E van Rongen, radiobiologist, Health Council of the Netherlands and member of the WHO Task Group for EHC 238, gave evidence outlining the two international exposure limit guidelines in place to protect against adverse effects of ELF EMF exposure. These are the ICNIRP guidelines (1998) and the Institute of Electrical and Electronic Engineers (IEEE) standard (2002). Dr van Rongen also gave evidence about the Health Council of the Netherlands guidelines (2000).
737. The guidelines base their limits on short-term immediate (ie, acute) health effects. They do not base their limits on epidemiological data of long-term or chronic effects of exposure because of insufficient evidence that there is a causal relationship with the observed effects, notably childhood leukaemia.
ICNIRP guidelines
738. The ICNIRP guidelines are more restrictive than the IEEE and Health Council guidelines, and are currently being revised.
739. In New Zealand, the Ministry of Health recommends use of the ICNIRP guidelines to protect against adverse effects of ELF EMF exposure.
740. The ICNIRP guidelines’ reference levels to protect the general public are 100 microtesla (µT) for magnetic fields and 5 kilovolts per metre (kV/m) for electric fields. These levels are based on established acute effects of exposure (retinal flashing, neurostimulation, perceptible microshocks) with the incorporation of a safety margin, and assume exposure of unlimited duration. The guidelines allow for higher levels of exposure for electrical workers due to their training and ability to take precautions to minimise exposure.
741. Transpower reported that it proposed to use the ICNIRP guidelines as if they were a standard, and would comply with the limits for general public protection.
Adequacy of the ICNIRP guidelines
742. Some submitters raised concerns about the adequacy of the ICNIRP guidelines to protect public health, claiming they are outdated, and that the limit values were too high.
743. In her evidence, Dr Bennet gave the opinion that recent exposure modelling studies suggest the exposure levels might be particularly inadequate for the fetus. In his rebuttal evidence, Dr van Rongen concluded that the findings were inconsistent and for electric fields only, and that a safety margin had been incorporated in the derivation of the ICNIRP limit.
744. Dr Bennet also endorsed the BioInitiative Report’s (2007) arguments and conclusion about the inadequacy of current exposure guideline limits. In his rebuttal evidence, Dr van Rongen, and in his evidence, Professor J M Elwood, cancer epidemiologist and public health physician, questioned the objectivity and authority of this report. In his rebuttal evidence, Professor Wood was critical of the BioInitiative Report’s failure to clearly differentiate between ELF and radiofrequency forms of EMF.
745. Dr R J McQueen, Professor of Electronic Commerce Technologies and Vice Chairman of New Era Energy Incorporated (NEE), included in his evidence an alternative guideline (McQueen et al, 2005) authored by himself and fellow submitters, Dr Smart and Dr Bennet. This proposed a limit of 0.1 µT for sensitive areas such as residences, schools, hospitals, childcare centres, work places with women of childbearing age, and playgrounds. According to these submitters, this would represent a designation width of 600 metres for a 400-kV transmission line.
746. In his oral submission, Dr McQueen asserted:
… we should be relying and looking at a health standard of somewhere around 0.4 microtesla as the level at which known health effects are caused1
747. He also asserted that some epidemiological studies show an effect at 0.1 µT.
748. Dr McQueen contended that the Board should determine whether 0.4 µT and not 100 µT should apply at designation boundaries. He also contended that no evidence had been reported by Transpower that showed a cut point of 100 µT below which there was no effect, and above which there was an effect.2
749. Dr McQueen acknowledged that the proposed alternative standard had not been peer reviewed.3
750. In addressing the Board in support of his submission, Dr Smart also contended that the ICNIRP guidelines were not satisfactory and that the exposure limit should be 0.1 µT.
751. In response to questions from the Board, Dr Smart acknowledged that the derivation of 600 metres had incorporated a safety margin.4
752. Dr Bennet supported a limit of 0.4 µT, but in her oral submission to the Board, she contended that the designation width should be 600 metres and may have to be wider.
753. In his evidence, Professor Wood stated that the cut points used in the epidemiological studies, such as 0.4 µT, are arbitrary and do not represent a threshold of effect. In contrast, 100 µT is based on a threshold of effect.
Conclusion
754. Policy 9 in the NPS is directly applicable to the Board’s Inquiry in achieving the purpose of the Act. It directs that provisions dealing with electric and magnetic fields associated with the network are to be based on the ICNIRP Guidelines for limiting exposure to time varying electric magnetic fields (up to 300 GHz) and recommendations from the WHO monograph EHC 238 (June 2007) or revisions thereof and any applicable New Zealand standards or national environmental standards.
755. The Board, therefore, has a duty to have particular regard to the ICNIRP guidelines.
756. The epidemiological evidence is discussed later in this chapter but the Board holds that, in the absence of a scientific consensus of a cause-and-effect relationship between chronic exposure to ELF EMF and a health outcome, there are no results that can be used as a basis for derivation of quantitative long-term exposure limits.
757. The Board also notes that although the WHO recommends a precautionary approach in EHC 238, it does not recommend that exposure limits are reduced to an arbitrary level to achieve precaution, and endorses the use of the ICNIRP and IEEE guidelines.
Strength of fields
758. The main issues of relevance to human health are the levels of the magnetic and electric fields caused by the proposed 400-kV-capable transmission line which would occur in its vicinity, including within dwellings, and at various distances from the line.
759. The strength of electric and magnetic fields reduces rapidly with increasing distance from their source; and unlike magnetic fields, electric fields are readily shielded by conducting objects such as vegetation and buildings.
760. Field exposures can be expressed in terms of instantaneous or time-averaged values. This section discusses the instantaneous values.
761. Mr M V Khot, Transpower’s Senior Development Engineer (Lines), and Mr A C Mitton, consultant electrical engineer, gave evidence that the ICNIRP reference levels for electric and magnetic fields would be met within the designation.
Electric fields
The overhead line
762. Mr Khot explained that for the overhead line the ICNIRP requirement of 5 kV/m for electric fields would be met by a minimum ground clearance for the conductors of about 12.7 metres. In addition, where the line crosses roads, the conductors would be at least 14 metres above, to minimise the possibility of a person experiencing a microshock from a vehicle parked directly under the line.
763. Mr Khot stated that the electric field strength is more or less constant, and only varies to the extent the line sags closer to or away from the ground. Maximum sag occurs in conditions of minimum wind and highest ambient temperature.
764. Since cross-examination did not cast doubt on the reliability of Mr Khot’s evidence, and no contradictory expert evidence was provided, the Board accepts his evidence of electric field strengths in relation to the overhead line.
The underground cable route and substations
765. In his evidence, Mr Mitton stated that there would be no electric field around the underground cables since they would be effectively screened by the conductor and insulation shields and cable sheath.
766. He gave evidence that the electric field strengths around the Whakamaru, Pakuranga and Otahuhu Substations at the security fence boundary, including where conductors enter the substations, would be below the 5 kV/m limit. As Brownhill would be a GIS substation, there would be an electric field only directly below where the conductors enter the substation; and this would be below 5 kV/m.
767. None of the submitters cross-examined Mr Mitton, nor called contradictory expert evidence. The Board accepts his evidence in relation to electric fields around underground cables and substations.
Magnetic fields
The overhead line
768. Mr Khot gave evidence that the magnetic field reduces as the cube of the distance laterally away from the line (ie, doubling of the distance from the line reduces the field strength eight times). The magnetic field is directly proportional to the current (and, therefore, to demand) on the line during various times of the day and year.
769. Magnetic field calculations were reported for normal operating conditions for summer and winter for the various levels of progressively increasing currents from 2012 to 2042 and beyond. The magnetic field level is predicted to increase in about 2030 because the current is expected to increase. When the line converts to 400-kV operation in about 2035, the current level would reduce, with a consequent reduction in magnetic field which would rise to about 2030 levels again from 2042.
770. Magnetic field strengths at the edge of the designation (32.5 metres from the centreline, approximately 1 metre above ground), in winter, were estimated to increase from 1.1 µT in 2012 to about 5.4 µT beyond 2042, and, in summer, from 1.0 µT in 2012 to about 4.6 µT in 2042 and beyond.
771. The magnetic field strengths were higher under the conductors with the highest, about a quarter of the 100 µT limit, beyond 2042.
772. These levels were calculated for normal operation under worst-case ambient and demand conditions, ie, with both circuits in service when the period of maximum load demand occurs on a hot still day.
773. In cross-examination by Dr McQueen, Mr Khot stated that validation studies had been done comparing calculated with measured magnetic fields under existing New Zealand transmission lines, and these studies had shown that calculated levels were very similar.5
774. In his oral submission, Dr McQueen questioned Transpower’s magnetic field calculations because they had been based on field strengths reducing in proportion to the cube of the distance from the proposed line. The basis for his assertion was two epidemiological studies which had suggested the impact of distance on magnetic fields was much lower.6,7 As no expert evidence was called, the validity of this assertion was unable to be tested. The Board, therefore, does not accept it.
775. Since cross-examination did not cast doubt on the reliability of Mr Khot’s evidence, and no contradictory expert evidence was provided, the Board accepts his evidence of magnetic field strengths in relation to the overhead line.
The underground cable route and substations
776. Mr Mitton gave evidence that magnetic field calculations near to the Brownhill-Pakuranga underground cable route (at ground level at the closest occupied dwellings and their boundaries, and directly above the cable tunnel) and around the substations (approximately 1 metre above ground at the closest occupied dwelling and security fence boundary including where conductors and cables enter the substation) would also be below the 100 µT limit. Levels at the closest dwelling to the substations were less than 0.1 µT.
777. Although well below the ICNIRP limit, magnetic field levels above underground cables would be higher in some locations than the highest calculated level under the conductors.
778. None of the submitters cross-examined Mr Mitton, nor called contradictory expert evidence. The Board, therefore, accepts his evidence in relation to magnetic fields around underground cables and substations.
Ministry of Health’s view
779. In his evidence, Mr M D Gledhill, on behalf of the National Radiation Laboratory, Ministry of Health, considered that Transpower’s calculations were appropriate and that exposures would comply with the ICNIRP guidelines. He was not cross-examined on this matter.
Effect of line compacting
780. In evidence for the Hunua and Paparimu Residents’ Association Incorporated, Mr D A Parker supported use of compact towers for reasons that included reducing EMF strength. Although the Board accepts that line compacting reduces ELF EMF, the Board accepts that it is not practical for the proposed line because it would restrict live-line maintenance, and for voltage stability reasons. This is discussed fully in Chapter 13.
Exposure
781. Potential risk to human health can only occur if there is exposure to a hazard. The likelihood of an adverse health effect resulting from that exposure, combined with the magnitude of the adverse effect, determines the level of risk.
782. In relation to health, the key issue is whether there would be any adverse health effects from the levels of exposure caused by the proposed 400‑kV-capable line.
783. Submitters were concerned about exposure to those, particularly children, living close to the proposed line, and the intermittent exposure of those working or playing under the conductors (or above underground cables located in reserves) and in the close vicinity.
Proximity of schools
784. Some concern was expressed among submitters about the location of schools (such as Waerenga, Hunua, Horahora, Te Miro and Whitehall) in the vicinity of the proposed line.
785. In cross-examination, Mr Campbell stated that, as part of the ACRE process, selection of the final route had avoided proximity to schools.8 Ms Allan gave evidence that one of the factors in the selection of the western route in the Hunua area had been the proximity to Paparimu School of the alternative eastern route.9
786. The Board notes that the closest school to the proposed line, Hunua School, would be 380 metres from it. At that distance the magnetic field level would be the normal background level experienced in dwellings.
Sensitive population groups
787. In her evidence, Dr Bennet highlighted the potential vulnerability to ELF EMF of the fetus, children and the elderly. Dr Black gave evidence that the ICNIRP limits include a safety factor with the intention of protecting sensitive groups of the population.
788. In cross-examination by Dr McQueen, Dr Black stated that there was no evidence for the existence of sensitive population groups in the case of ELF EMF.10
789. The Board finds that no sensitive population groups to ELF EMF exposure have been identified; and that, in any event, the ICNIRP guidelines include a safety factor to protect such people.
Long-term versus short-term exposure
790. In his evidence, Professor Elwood stated that long-term average exposure levels to magnetic fields are the most relevant in terms of health effects.
791. This was explained further in cross-examination as follows:
McQueen: So, just to indicate again, Paragraph 22 in that line you say, ‘it is the long-term average exposure levels to magnetic fields, which are most relevant’. Other evidence you have given indicates that we don’t yet have a causal mechanism, but you state the mechanism here is long-term exposure. Can you just explain those conflicting views?
Elwood: There’s no conflict. I said the average exposure levels are most relevant. They are most relevant, because almost all the scientific information we have relates to average magnetic field exposure levels. That does not imply that...I’m not talking here about the...the, you know the biological mechanism, I do discuss that several other places...and I did emphasise in other places the few studies...or very few studies, which have looked at other parameters reflecting magnetic field exposure.
McQueen: I guess I was trying to understand more clearly the long-term average exposures, which we have...I think are the basis of most of the studies you’ve referred to, versus other mechanisms, which could be possible, such as, instantaneous exposures or other kinds of exposure processes?
Elwood: Well, other mechanisms are possible, but the amount of scientific information available on them is extremely little. So, the point of this paragraph is that if one is considering magnetic fields in the context of a power line, or any other submission, and you want to relate those fields to the existing scientific evidence of health effects, almost all of the material you’ll be dealing with relates to average magnetic field exposures.
McQueen: As opposed to the instantaneous?
Elwood: Yes.
McQueen: Thank you. Still in that same paragraph, the fourth line, you say that, ‘the field exposures from the new transmission lines will be very low at the edge of the easement and quite low even directly under the line’. What are the numbers that you’re using for those ‘very low’ and ‘quite low’ phrases?
Elwood: Well, this has been discussed in great detail by other witnesses, and I’ll defer to them in terms of the actual numbers. My understanding is, at the edge of the designation, the average field...or the...Most of the information we have from Transpower is on instantaneous or maximum exposures, which I think are less than about 30 microtesla, both at the edge and directly under the line, and obviously the long-term average exposure is going to be substantially less than those peak exposures. Because, to me, what is important is the average exposure of a person, and I don’t imagine that people are going to spend extensive time directly under the line.
McQueen: So, those terms ‘very low’ and ‘quite low’ would refer to 30 microtesla?
Elwood: No...no, they would refer to something considerably lower than that, because that 30 figure...and I defer to other witnesses to correct me on that, is a peak...is an instantaneous maximum exposure. So, if...I mean, if you say...well, someone lives near the line, you would ask how much time do they spend directly under it, which might be in the order of, you know, a tiny fraction of their annual exposure, and it’s only that component, which would contribute to their average magnetic exposure.11
792. Professor Elwood concluded from the evidence of Mr Khot about magnetic field strengths:
It seems unlikely that the levels of exposure to magnetic fields to which people will be exposed for a considerable time, for example inside homes, will be increased by the new transmission line.
Conclusion
793. The Board accepts the evidence of Mr Khot (discussed earlier in paragraphs 769-776) that the level of exposure from the proposed line would be low. It finds that time-averaged exposure (which is relevant to health effects) would be even lower.
Possible health effects
Positive effects of power
794. There was no dispute that an adequate reliable supply of electricity to the upper North Island is essential to maintain infrastructure and the economy, and therefore to protect public health.
Adverse effects
795. A large volume of research, incorporating laboratory studies of cell cultures and animals and epidemiological studies of human populations, has been carried out to investigate whether exposure to ELF EMF causes adverse health effects. Several hundred of these studies were referred to, some in considerable detail, during the hearing.
796. There are recognised acute effects of exposure to fields of sufficient strength that arise from induced electric fields and currents. These are the basis of the reference levels in the ICNIRP guidelines.
797. In contrast, there is much international scientific debate about the long-term effects of exposure to fields which are below those at which acute effects are seen. This was the predominant area of health concern raised by submitters, and is discussed below.
Epidemiological studies
798. Among submitters, opinions differed about the nature of possible health effects from chronic ELF EMF exposure; but many highlighted the epidemiological association between magnetic fields and childhood leukaemia. Other effects mentioned were miscarriage, amyotrophic lateral sclerosis, adult brain cancer, adult leukaemia, suicide, depression, Alzheimer’s disease, childhood brain cancer, breast cancer, lung cancer, melanoma, osteosarcoma, and asthma. Many considered these relationships were causal.
799. Many submitters had gone to considerable effort in the preparation of their oral submissions. However, few submitters presented evidence to the Board, so the reliability of their information was unable to be tested through cross-examination.
800. Some submitters sought proof that no health effects would occur from the proposed line. Professor Elwood gave his opinion that it is impossible to prove the absence of a health effect such as childhood leukaemia. He outlined a weight-of-evidence approach to the assessment of high quality scientific studies to reach a conclusion that no effect was likely.
801. This was further addressed in cross-examination of Professor Wood:
McQueen: Paragraph 89, you’re addressing again issues raised by submitters, and you’re saying that, ‘EMF has not been proved to cause any disease’. That’s your evidence?
Wood: Yes.
McQueen: Has it been disproved?Wood: I think as in the answer that Dr Black gave yesterday, or maybe it was earlier today, it’s very difficult to prove a negative. I would say that there has been sufficient research done; now we’re talking in tens of thousands of research studies to form a view as to what the health risks are, and as I mentioned previously, the EHC was careful not to imply that EMF had shown to be causal, but nevertheless, as I said before, it had done its health risk assessment on the assumption that it was. So, really...it doesn’t really make any difference, because what they’re suggesting we do will be the same whether it’s proved or not proved. Because the magnitude of the effect is really quite small, the only question then is, if we do things that cost a lot of money, and then later it is disproved or there’s no convincing proof...of whether that money was spent in vain.12
802. In addressing the Board in support of his submission, Dr Smart contended that evidence is strongest for childhood leukaemia, miscarriage, amyotrophic lateral sclerosis (Lou Gehrig’s disease), adult brain cancer, adult leukaemia, suicide, and depression. In his evidence, Professor Elwood considered Dr Smart’s submission reported studies showing increased health risks, excluded those with different results, and selectively reported results from some studies.
803. Dr A Kilfoyle, senior medical registrar in haematology, gave evidence which focused on two pooled analyses and three case-control studies (one of which was included in the pooled analyses) showing increased risks of haematological cancer. She acknowledged there were negative studies that were not in her evidence, although some had been included in the pooled analysis. She also acknowledged that these studies did not support a change in the International Agency for Research on Cancer (IARC) classification above that of possible carcinogen for ELF magnetic fields.13
804. In her oral submission, Dr Kilfoyle acknowledged there is a lack of animal data, and that the mechanism by which EMF could cause cancer was uncertain. With regard to cancer, she stated:
Furthermore, it’s unclear if, in fact, it is electromagnetic fields, themselves, which exert the effect that is seen in the epidemiological studies.14
805. Dr McQueen’s evidence cited 12 papers, most of which he subsequently spoke to at the hearing. In his rebuttal evidence, Dr van Rongen stated that the list of papers did not contain any comprehensive weight-of-evidence reviews, and included several non-peer-reviewed papers.
806. In his rebuttal evidence, Professor Elwood identified a lack of balance in the review of studies in the evidence of Dr McQueen, Dr Kilfoyle and Dr Bennet. In the case of one study (Draper et al, 2005), referred to by all of these submitters, the submitters did not mention the study authors’ conclusion that their findings of increased childhood leukaemia risk at considerable distances from power lines did not fit the hypothesis of causation by magnetic fields.
807. Transpower submitted that there are no actual or potential public health issues associated with the proposed transmission line. 15
808. In his evidence Professor Elwood reviewed the epidemiological evidence related to possible health effects, in particular cancer, from long-term (or chronic) exposure. This included reports by independent expert review groups which gave a summative assessment of the overall weight of evidence based on individual studies, two pooled analyses which combined original data from nine and 13 childhood leukaemia, and magnetic fields studies respectively, and many individual studies.
809. When asked in cross-examination whether his choice of evidence from the original studies and reviews had been selective, Professor Elwood responded:
I’ve tried very hard not to be, I’ve as we said...we discussed earlier, I’ve put most emphasis on the studies, which I regard as having the strongest methodologies, irrespective of what the results say. So, I’ve tended to put emphasis on studies, which are large, and have excellent methods, and appropriate analysis. And, where possible, I’ve quoted directly from the authors’ own summaries or final conclusions, where that seems appropriate.16
Childhood leukaemia and residential magnetic fields
810. The relationship of most concern from the epidemiological studies is that between childhood leukaemia and residential magnetic fields.
811. A number of epidemiological studies show an association between increased childhood leukaemia, in the order of a doubling of the risk, and estimated 24-hour or longer average exposure levels above 0.3–0.4 µT in the child’s home. Professor Elwood explained that to establish causation, alternative explanations for the association such as bias, chance and the effect of other factors (or confounding) need to be excluded; and specific criteria such as consistency within, and among, studies and biological plausibility which are expected if a cause-and-effect relationship exists, identified.
812. Professor Elwood agreed with the conclusions of reports from the UK National Radiological Protection Board (2001, 2004), IARC (2002), ICNIRP (2003), US National Institute of Environmental Health Sciences (1999) and WHO (2007) that the interpretation of this association remains unclear and that current scientific evidence is insufficient to show that it reflects causation. His reasons were:
- a) the results for the highest exposure category are based on small numbers of subjects, and those who participated in the studies and had the highest exposure levels may be unrepresentative because of factors affecting participation in the studies
- b) it is possible that children with exposure to higher levels of electric and magnetic fields also have other exposures or characteristics which may give them an increased risk of cancer
- c) the third reason to treat these results with caution is that there is no consistent evidence from cell, animal, or other human studies that magnetic fields at these exposure levels are involved in the development of leukaemia or other cancers.
813. Professor Elwood disagreed with the conclusions of the California EMF Program, Department of Health Services report (2002) and two relevant chapters of the BioInitiative Report (2007), stating that they gave less weight to relevant animal and experimental evidence, and differed in some interpretations of epidemiological data. He contended that neither report was equivalent in authority to the reports cited in the paragraph above.
814. In his rebuttal evidence, Professor Elwood provided additional review of the BioInitiative Report. He concluded that the report is of much lower scientific quality than other available relevant reports. In his opinion, its epidemiological conclusions are likely to be biased since it had excluded many important studies, and, in some instances, had presented a misinterpretation of the results of studies.
815. He acknowledged that although magnetic fields might cause childhood leukaemia, this possibility required more research.
816. In his opinion, the most likely explanation for the association seen between childhood leukaemia and magnetic field exposures was:
…there may be an association between higher magnetic field exposures and other factors which themselves are relevant biological factors increasing the risk of childhood leukaemia.
Other health outcomes
817. Professor Elwood reported that evidence in regard to cancers in children, other than leukaemia, and cancer in adults (in particular brain and leukaemia), is inconsistent. The argument for any association with breast cancer had also recently been considerably weakened by some high-quality epidemiological studies.
818. The professor stated that he had not reviewed the information on neurological diseases, suicide or reproductive outcomes in detail in his evidence, but reported the WHO’s EHC conclusion that the evidence is inconsistent and inconclusive, and, therefore, considered inadequate.
819. Although he noted that weak evidence for associations between occupational magnetic field exposures and adult chronic lymphocytic leukaemia and amyotrophic lateral sclerosis were reported by one and three of the review groups respectively, Professor Elwood further stated:
All these groups have concluded that the scientific evidence does not establish that exposure to electric or magnetic fields is the cause of cancer or any other human disease.
Biophysical mechanisms, in vitro and animal studies
Biophysical mechanisms
820. In his evidence, Professor Wood stated that identification of a biophysical mechanism is of major importance, because of the weak evidence linking ELF magnetic fields and childhood leukaemia.
821. This witness gave evidence on some proposed direct mechanisms of ELF magnetic fields interaction with biological materials, and concluded that there is no generally accepted and plausible biophysical mechanism to account for the epidemiological finding of increased childhood leukaemia.
822. This was also the conclusion of the WHO’s EHC 238.
823. High-voltage power lines may produce electrically charged ions that are blown downwind as a result of corona discharge. These ions charge pollutant particles that pass through them, which could increase their deposition in the lungs and on skin, possibly affecting health. Some submitters (such as Dr McQueen, Dr Kilfoyle, and those using the standard submission form) stated that these “ionised particles” or corona ions could be responsible for the epidemiological findings of childhood leukaemia.
824. Professor Wood gave evidence that this indirect mechanism is speculative, and that the increased production of air ions through corona discharge has not been shown to lead to any disease. Lung and skin cancer have not been associated with ELF EMF in the major epidemiological studies.
825. In his evidence, Dr van Rongen (and Professor Wood in his rebuttal evidence) reported that the National Institute for Public Health and the Environment of the Netherlands (and the UK National Radiological Protection Board) had concluded that it was unlikely that corona ions would have more than a small effect, if any, on long-term health risks. This conclusion has also been reached by the WHO.
826. Mr Khot gave evidence that because a triplex sulphur conductor bundle has been proposed for the line, the surface voltage gradient would be low compared to many 220-kV lines. He stated that corona discharge, which is a function of the surface voltage gradient, is less likely to occur from the proposed line than from a line with a simplex conductor configuration such as the existing 110-kV ARI-PAK A line.
In vitro or laboratory studies
827. Professor Wood reported that, although there have been many studies on the effects of ELF EMF on biological tissue samples, most have been done at much higher magnetic field strengths than the epidemiological studies’ cut point of 0.3 µT. He added that the findings of those that are relevant to cancer initiation or progression are inconsistent.
Animal studies
828. Professor Wood also reported that data from animal studies on adverse health effects of ELF EMF are similarly inconsistent.
Conclusion on mechanisms, in vitro and animal studies
829. Professor Wood gave his opinion that lack of a credible biophysical mechanism and inconsistent animal and laboratory data make it unlikely that magnetic or electric fields are a direct cause of adverse health effects.
830. Cross-examination of Professor Wood did not leave question in the Board’s mind about the acceptability of his evidence; and there was no contradictory expert evidence. The Board, therefore, accepts his opinions.
Conclusion on possible health effects
831. In summary, the Board considers that cross-examination of Dr Black, Professor Elwood, Professor Wood and Dr van Rongen did not establish that their evidence on possible health effects, in particular their conclusions, was unreliable.
832. In the absence of expert epidemiological or biophysical evidence to the contrary, the Board accepts that although childhood leukaemia is associated with chronic exposure to magnetic fields above 0.3–0.4 µT, there is insufficient evidence that this relationship is causal. The Board considers that the strength of current scientific evidence for other potential health effects is considerably less.
Likely public health impact
833. In response to questions from the Board, Professor Elwood stated that even if the relationship between ELF EMF exposure and childhood leukaemia was eventually found to be causal, given the rarity of the disease, it would be unlikely that an additional case of leukaemia would be attributable to exposure from the transmission line.
I have made an estimation, which is, if there were… and I think this is a very high figure… if there were one thousand children exposed to very high magnetic fields from any source, this doubling of risk would mean that we would have one extra case of leukaemia in twenty years. I think, that thousand number is actually likely to be very high. If there were only a hundred exposed, we’re talking about one case of leukaemia in two hundred years.17
834. Dr Black also gave evidence that, if the relationship is assumed to be causal, the likelihood of a case of childhood leukaemia occurring is extremely low, given the field strengths and size of the population exposed.
835. The Board considers that the impact of childhood leukaemia on the individual child and the family/whānau or community would be severe. However, it notes that it is a rare disease. In the absence of contradictory expert evidence, it accepts that, even if the relationship is causal and a child’s long-term average exposure is sufficiently high (ie, above 0.3–0.4 µT), a child is very unlikely to develop leukaemia as a direct consequence of living close to the proposed line.
Cumulative effect of magnetic fields
836. Some submitters (such as Hon M W R Storey, Ms D Allen, Mrs F Aldridge and Mrs D Levesque) raised concerns about the cumulative effect on health arising from the existing and proposed transmission lines in some locations (Hunua area, Waiterimu Valley), but presented no evidence on this matter.
837. The Board notes that the relevant issue with respect to a potential cumulative effect from multiple overhead lines is the total current (not total voltage) which results in a net magnetic field.
838. In response to written submissions, Professor Wood gave evidence that multiple power lines can lead to enhancement or reduction of magnetic fields depending on their configuration. He commented that an advantage of having three phases in three sets of conductors, as is proposed, is that the net current would be zero, and the magnetic fields would be considerably reduced. In a two-circuit system, reverse phasing of the second circuit leads to further reduction.
839. Mr Khot, also in response to written submissions, stated that electric and magnetic fields from lines do not necessarily add up, since they may not be in phase. Only the fields produced from those lines that are exactly in phase would result in a field strength that is a sum of the constituent fields. Fields that are not in phase lead to some cancellation of the fields.
840. There was no cross-examination of either of these witnesses relating to this subject.
841. No information was presented to the Board as to what the total worst-case magnetic field level may be in areas where the proposed line is in close proximity to existing lines. However, based on the evidence of Mr Khot on the maximum magnetic field levels from the proposed line, the Board judges that if the lines are in phase, the increase to existing magnetic field levels would be small.
Indirect health effects
Perceptible electric shocks
842. Dr Black gave evidence that a discharge current may lead to a perceptible electric shock when touching unearthed metallic objects in the transmission line corridor that have been charged by the electric field from the overhead conductors. He stated that these objects are generally readily identified and, if necessary, remedied.
Noise
843. Some submitters raised concerns about audible noise from the line, from substations and during construction. Sources of potential noise from the proposed line were identified in the evidence of Mr Khot as corona discharge, the 100-Hz hum and wind. These, along with substation and construction noise, are discussed more fully in Chapter 11.
844. In terms of adverse effects on health, noise may result in annoyance, sleep disturbance and impact on general well-being.
845. Mr G W F Warren, an independent acoustical consultant, gave evidence that, at the edge of the designation, predicted corona discharge noise from the conductors in wet conditions when the line is operating at 400 kV, would be well below the level at which adverse effects – including sleep disturbance – are caused.18 The predicted noise level would also comply with daytime and night-time noise limits in all relevant district plans.
846. Accepting that, the Board finds that the design of the proposed line and the proposed conditions would adequately avoid, remedy or mitigate actual and potential health effects of noise.
Health consequences of the grid upgrade proposal
847. A number of submitters (including Dr Bennet, Ms S Jones, Mr J Melis, Mrs F Aldridge, Mr T Shergold, Mrs G McCulloch, Mr G and Mrs D Smith, Ms L Bilby, Ms J Colliar, and Mr B and Mrs J Burwell) raised stress to individual landowners, and in some instances, communities, from the grid upgrade proposal.
848. During the hearing, it was also evident to the Board that a number of submitters were experiencing varying degrees of stress as a direct consequence of the proposal. For some, this related to their outright opposition to the proposal; while for others, to significant uncertainty surrounding the potential impact on current land-use activities, particularly during the construction phase, and easement agreements; to changes made over time to aspects such as tower location and height, tree removal and building relocation; the perception of health risks from exposure to ELF EMF; the possibility of stigma effects resulting from the line; and communication difficulties with Transpower.
849. It is a regrettable consequence of a project of such magnitude that it would inevitably cause some stress to affected landowners and occupiers. The Board acknowledges that the period since the announcement of the grid upgrade proposal in 2004 has been one of distress and uncertainty for a number of landowners, occupiers and communities. For some, this stress may continue, particularly during the construction period as their familiar environment changes.
850. The Board notes the proposed consent condition which offers free counselling to those directly affected by the designation crossing their properties.
851. The Board considers in the case of the overhead line that, as an exercise of social responsibility, the offer of free counselling should also be extended to those who occupy adjacent property, as, in some instances, the impact may be as great as (or greater than) on the occupier of the land which the designation crosses, due to their proximity to a tower(s).
Precautionary approach/prudent avoidance
852. A number of submitters stated that the Board should take into account a precautionary approach, or the precautionary principle with respect to the effects of ELF EMF on health.
853. Given that ELF magnetic fields are a possible carcinogen, for some submitters a precautionary approach meant the proposed line should not proceed.
Width of the designation
854. If the Board is to approve the proposed line, some submitters supported an increase in the designation width to reduce future health risks. The majority of these submitters stated that the width should be 600 metres.19
855. In their oral submissions, Dr Smart and Dr McQueen asserted that 600 metres is necessary to avoid exposures above 0.1 µT (and, therefore, possible health effects, in particular childhood leukaemia).
856. In her evidence, Dr Bennet contended that a 600-metre and possibly wider designation is necessary, and that protection against 0.4 µT and possibly lower, is needed.
857. Mr Davidson gave evidence supporting the SAGE report’s (2007) recommendation for a width of 120 metres or 0.4 µT. This was also supported by Ms H Polley in her oral submission to the Board. Mr J Scott suggested prohibiting dwellings within 400 metres.
The Stakeholder Advisory Group on ELF EMFs (SAGE) Report
858. The aim of the SAGE process was to make practical recommendations for precautionary measures in relation to ELF EMFs to the United Kingdom (UK) Government.
859. The Group considered the best available option to significantly reduce exposure would be to increase the separation of dwellings and schools from overhead lines. Based on a magnetic field level of 0.4 µT, this would represent a distance of 60 metres from the centre line for a new 400-kV line.
860. The Group did not recommend implementation of that option (which also included the same restriction on construction of new dwellings and schools), as they could not agree on whether it was supported by cost-benefit analysis, due to differing views among its members on the possible health effects which formed the basis for considering precautionary measures. As a result, the SAGE report’s conclusion was to urge the UK government to make a clear decision on whether to implement it or not.
861. Mr Gledhill and Professor Wood, in their evidence, both noted the UK Health Protection Agency’s response on the SAGE report to the UK Minister for Public Health that the decision to implement this option should be weighed against other health benefits obtainable from the same resources, as it was not supported by cost-benefit analysis, even assuming a causal link between magnetic field exposure and childhood leukaemia.
862. As already noted at Chapter 4 paragraph 268, the Board is not aware that the UK Government has made a decision on this matter.
Undergrounding
863. Other submitters supported undergrounding the entire line as a precautionary measure. In his evidence, Professor Wood stated that for people concerned about levels above 0.4 µT, those concerns would still apply with undergrounding, as there would be a strip about 43-metres wide above an underground cable where the peak field would exceed 0.4 µT.20
Precautionary approach
864. In cross-examination, Dr Black stated:
… to meet the precautionary principle, you’ve got to have a real effect; something that could actually…if it happened, it would be significant. And, therefore, if you apply precaution generically, it will ultimately result in improvement.21
865. This witness proceeded to explain application of the precautionary principle as follows:
…WHO and also the European Union have done some really good work on this, and one of the things that everybody pretty much comes up with, is that any action is got to be.. I think the word is proportional. …So, if something was, you know, a very significant hazard, then you could actually spend quite a lot of money on it. If something is less of a hazard or less likely, that would… you would have a graded approach to it. That’s my understanding of the way in which the precautionary principle is applied.22
866. Under cross-examination, Dr Black gave his opinion that increasing the designation width, ie, application of the precautionary principle, is not required:
McQueen: Just to clarify that in my mind, if we were looking at the precautionary principle in the context of the proposed 400-kV line … … Would that perhaps overall…say, doubling of the easement width, which might come in at, let’s say, something like five percent or four percent of the overall project cost…would that all go to that category of precautionary principle?
Black: Well, no, because…I don’t honestly think it would, because I … I can’t see how it would, even hypothetically, provide any benefit to anybody, in terms of health effects.23
867. In rebuttal evidence, Professor Elwood responded to the proposed 600-metres designation width as follows:
Given the current uncertainty in the human health evidence, one likely scenario is that no benefits to human health would accrue from making this change.
868. In his evidence, Dr van Rongen described the precautionary approach taken in the Netherlands, where the Government has recommended to local authorities that the annual time-weighted average exposure of children in dwellings, schools, creches, and daycare centres is limited to below 0.4 µT for new lines or changes to existing lines.
869. Transpower submitted that a precautionary approach is inherent in the RMA, and relevant case law demonstrates its application.
870. The Board accepts Transpower’s submission, relying on the case law cited.24
871. The WHO’s EHC 238 recognises the place for a precautionary approach to magnetic field exposure. Policy 9 of the NPS directs the Board that provisions dealing with electric and magnetic fields associated with the network are to be based on recommendations from this monograph.
872. Recommendations in EHC 238 include that, provided that the health, social and economic benefits of electric power are not compromised, implementing very low-cost precautionary procedures to reduce exposure are reasonable and warranted.
Prudent avoidance
873. A prudent avoidance approach supports taking reasonable low- or no-cost measures to avoid or minimise ELF EMF exposure, given the uncertainty as to possible health effects.
874. The Ministry of Health recommends adoption of a prudent avoidance approach.
875. Transpower submitted that as part of its adoption of a conservative stance to ensure that the ICNIRP limits would be met, it had also adopted a prudent avoidance approach by use of measures to minimise EMF exposure. These measures included the 65-metre width of the designation, location of the line in an area of low population density, reverse phasing of the conductors, burial of the cables at 1.5 metres, and the use of a trefoil cable configuration.25
876. In his evidence, Professor Wood concluded that some level of precaution is warranted in view of the epidemiological association of magnetic fields with childhood leukaemia; and that it would be appropriate to incorporate this precaution in the design and routing of the transmission line.
877. Dr Black gave his opinion that a precautionary approach hardly, if at all, applies in the context of the proposed line. However, he considered that design aspects of the line are consistent with a precautionary approach, and no further mitigation is necessary.
Conclusion on precautionary approach and prudent avoidance
878. The Board has considered the recommendations of the WHO’s EHC 238 (p13) in relation to a precautionary approach that are relevant to the scope of its Inquiry.
879. The Board notes the measures that have been incorporated in the design of the transmission line, and that under the proposed easement agreement, no dwelling or other building would be located in the designation. The Board considers that to prevent the possibility that dwellings may be located in the designation at some future time, a condition to that effect should be imposed on the designations for the overhead line.
880. The Board finds that additional precautionary measures would be of uncertain public health benefit, and are not necessary to further minimise ELF EMF exposure from the transmission line.
881. The Board is influenced in its conclusion by Transpower’s evidence that the magnetic field strength for normal operation under worst-case conditions would not exceed 30 µT directly under the overhead line, and would be less than 6 µT at the edge of the designation (32.5 metres from the centre line). The magnetic field at the edge of the designation is likely to be experienced long term, and hence is of relevance to human health, if dwellings are on the designation boundary. The Board expressly recognises that extent of adverse effects for the purposes of section 319(2) of the RMA.
Conclusions on health effects
882. The Board has assessed the evidence before it, considered the extent to which the evidence is reliable, and what weight should be given to it. It has taken into account whether the evidence falls into the category of high-quality epidemiological studies and/or animal or in vitro evidence, and whether there is expert consensus. While the differing views of submitters, and the high level of concern among some about health effects are acknowledged, some effects attributed to ELF EMF exposure were hypotheses: no evidence was presented to support them and they were not able to be tested in cross-examination.
883. The Board accepts that the time-averaged exposure which is of relevance to health effects would be considerably lower than the maximum of about 6 µT which has been calculated at the edge of the overhead line designation in worst-case conditions.
884. The Board finds that there is weak epidemiological evidence of a potential adverse health effect of low probability which has a high potential impact, namely childhood leukaemia from long-term ELF EMF exposure above 0.3–0.4 µT. This epidemiological evidence is accepted by the main expert review groups such as the WHO. However, there is no evidence that this relationship between ELF EMF and childhood leukaemia is causal. The evidence for other potential adverse health effects is weaker.
885. The Board does not consider that this weak epidemiological evidence of association is a reason for declining the designations, or refusing the resource consents.
886. The Board has come to its conclusion on the basis of the evidence before it about ELF EMF exposure and health effects, and not on the basis of the possibility that research might (or might not) in the future produce findings that have not been observed by research to date.
887. In summary, the Board finds that there would not be significant risk to human health from operation of the grid upgrade in compliance with the proposed conditions.
Endnotes
1. Transcript 22/07/08, p 30–31.
2. Transcript 22/07/08, p 30.
3. Transcript 22/07/08, p 33.
4. Transcript 11/09/08, p 31.
5. Transcript 10/04/08, p12–13.
6. Draper et al, 2005; Lowenthal et al, 2007
7. Transcript 22/07/08, p 16–19.
8. Transcript 3/04/08, p 40.
9. The existing ARI-PAK A line which is very close to Paparimu School will be dismantled as part of the grid upgrade proposal.
10. Transcript 5/05/08, p49.
11. Transcript 9/05/08, p 7–8.
12. Transcript 6/05/08, p 49.
13. Transcript 23/09/08, p 57.
14. Transcript 23/09/08, p 52.
15. Transpower opening submissions, para 592.
16. Transcript 9/05/08, p 33.
17. Transcript 9/05/08, p 35.
18. Predicted corona discharge noise is 35 dBA at the designation edge and 20–25 dBA inside a bedroom with an open window at the designation edge.
19. A standard submission form which included the reference to 600 metres was used by over 300 submitters.
20. Transcript 6/05/08, p 19.
21. Transcript 5/05/08, p 36.
22. Transcript 5/05/08, p 37.
23. Transcript 5/05/08, p38.
24. Transpower opening submissions, para 572–588.
25. The width of the designation was primarily determined by conductor swing.
