Summary of NRPB EMF report March 2001 - what it does and does not say relevant to powerlines. See also revolt news78 (response to the report). Please read (T as the symbol for microTesla.
1. The core report is Documents of the NRPB vol. 12 no. 1 2001, "ELF Electromagnetic Fields and the Risk of Cancer", ISBN 0-85951-456-0 price £30. It is the Report of the NRPB's Advisory Group on Non-ionising Radiation (AGNIR), chaired by Sir Richard Doll. It was published 6.3.01 together with a Press Release and a Response Statement (R3/2001) from the NRPB Board.
2. Chapter 7, Conclusions, ends with a "General Conclusion" on page 164, which is included in full in the Press Release: "Laboratory experiments have provided no good evidence that extremely low frequency electromagnetic fields are capable of producing cancer, nor do human epidemiological studies suggest that they cause cancer in general. There is, however, some epidemiological evidence that prolonged exposure to higher levels of power frequency magnetic fields is associated with a small risk of leukaemia in children. In practice, such levels of exposure are seldom encountered by the general public in the UK. In the absence of clear evidence of a carcinogenic effect in adults, or of a plausible explanation from experiments on animals or isolated cells, the epidemiological evidence is currently not strong enough to justify a firm conclusion that such fields cause leukaemia in children. Unless, however, further research indicates that the finding is due to chance or some currently unrecognised artefact, the possibility remains that intense and prolonged exposures to magnetic fields can increase the risk of leukaemia in children."
3. In my view that summary is very heavy-handed spin, to suppress concerns as much as possible. Some reasons for that view are: (a) starting with the negative and the oft-spun phrase "no good evidence", when in fact there is a mass of meaningful evidence giving grounds for concern; (b) use of the negative suggestion about "cancer in general", when the key evidence is positive specifically for childhood leukaemia; (c) the use of the word "seldom" for exposures which are regularly and reliably encountered by people living very close to powerlines; "seldom" suggests only on very rare occasions in time (see OED), not just that it affects a small minority of people; the fact that a significant number of people (albeit a small minority) is chronically exposed is suppressed; (d) the use of the word "plausible" to the exclusion of reasonable hypotheses which are compatible with the known evidence and with scientific principles, but do not have a full explanation verified by experiments; it would be more accurate to refer to the lack of a "convincing" explanation; (e) the use of "the possibility remains" to avoid admitting exposure is the most likely cause of the observed increased incidence (compare with the 1996 statement on BSE-CJD where the evidence was much less, and with the recognition in the body of the report that it is unlikely to be by chance).
4. The conclusions on residential exposure are given in Chapter 7 section 13, which says that the "recent large and well conducted studies ... taken in conjunction ... suggest that relatively heavy average exposures of 0.4 (T or more are associated with a doubling of the risk of leukaemia in children under 15 years of age. The evidence is, however, not conclusive." It goes on to say "In the UK, very few children (perhaps 4 in 1000) are exposed to 0.4 (T or more".
5. The Response Statement says there are about 500 (new) cases of childhood leukaemia in the UK each year, of which only about 2 would be extra cases due to exposure above 0.4 (T if there were a causal effect. For the few so exposed, "this would imply an increase in the annual risk of leukaemia in childhood from about 1 in 20,000 to 1 in 10,000 and would correspond to an increase in the overall risk of leukaemia to age 15 years from 1 in 1400 to 1 in 700".
6. Most of the exposure above 0.4 (T comes from domestic sources, only about a quarter of it from power lines, according to the Response Statement. So only about 1 case every two years would be caused by powerlines through this level of exposure. Nevertheless, although they are a small minority, many people live close to powerlines and would be exposed above this level.
7. Some important things omitted, or barely mentioned, by the report are: (a) electric field exposure, which has been of concern above 10 V/m, though does not have the same statistical strength as the combined studies for magnetic field; a much larger proportion of people is likely to be exposed at this level, from domestic sources rather than powerlines; Roger Coghill advances evidence pointing to perhaps 30% of people so exposed, which would suggest a much larger share of the 500 childhood leukaemias per year if it were causal; the UKCCS is supposed to be reporting its analysis of electric fields and cancer but it has not appeared yet; (b) contaminated aerosol particles from powerlines, which if shown to affect significant numbers of people would contaminate the controls in epidemiological studies to date, thereby causing them to under-estimate any association of powerlines with cancer; Chapter 2 (50) gives passing mention to the work of Fews, Henshaw et al and Chapter 8 (2) recommends further research; (c) illness other than cancer, briefly excluded in section 15 of the introduction, while section 1 of Conclusions says that possible association with neurological disease is being considered separately; the terms of reference of the AGNIR (on page 5 of the report) are "to review work on the biological effects of NIR relevant to human health and to advise on research priorities", not just cancer; (d) free radicals, mentioned in Chapter 3 (25) "since there are many cellular defence mechanisms against free radicals such a mechanism would be expected to operate only if there were inherent defects in the repair systems. The results of Lai and Singh should therefore be considered with some caution." Chapter 8 (2) recommends further research.
8. Chapter 2 section 4 accepts, for power supply frequency fields, "Man-made fields are many thousands of times greater than natural fields arising from either the Sun or the Earth." - a refreshing change from the false comparisons with natural static fields. Section 29 says "The geometric mean background field for the UK was estimated to be in the range 36-39 nT" - i.e. residential domestic fields are typically about a tenth the 0.4(T level of concern, so powerline magnetic fields really stand out against both natural and domestic background levels.
9. The report does give a substantial review of ELF sources and measurements, cellular studies, animal and volunteer studies, and epidemiological studies (residential and occupational) as far as they are relevant to ELF and cancer. It's a useful explanatory survey, despite omissions mentioned, and it recommends further research in several specified areas. It is possible the very limited positive conclusions of health risks are, if not the tip of the iceberg, still not the whole story.