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02/11/2000 - NRPB response to UKCCS plus Powerwatch comments relating to increased child leukaemia (quite scientific)

Further developments have taken place following the 14th November 2001 NRPB statement, which we believe was seriously flawed. Mrs Maureen Asbury is a member of the Trentham Environmental Action Campaign, a group of people living in fields of several microtesla directly under a 132 kV power line. Dr John Stather (NRPB) wrote a very misleading letter to Mrs Asbury. She complained to the Chairman of the NRPB (Sir Walter Bodmer), copying it to Govt.Ministers. She has now had a reply from Dr Stather's boss, the NRPB Director, Professor Roger Clarke.

The letter from Professor Clarke expressed regrets that Dr Stather's letter "did not contain the latest information". He said that the NRPB posted an additional information sheet to their web site on 28th November that discusses the new British Journal of Cancer meta-analysis. In this, the NRPB now admit that living in magnetic fields of 0.4 µT or more doubles the risk of leukaemia. (95% confidence interval 1.27-3.13) Adjustment for factors such as socio-economic status and type of dwelling did not change the results appreciably.

The NRPB try to minimise the implications of this result by adding a completely gratuitous and misleading fact "the leukaemia risk is small nationally (less than 1 in 20,000 per year)." The risk is small only due to the fact that few people live in such fields. For people like Mrs Asbury, who unwillingly live in EMF pollution of several microtesla, the implications of the BJC meta-analysis are enormous.

The NRPB have not withdrawn or modified the earlier flawed statement which we comment on below.

Professor Nic Day, the lead researcher for the UKCCS EMF analyses, has now been appointed to the Board of the NRPB and has also been awarded a CBE in the New Year Honours. We offer our congratulations. UK EMF research is increasingly looking incestuous.

We believe that the following NRPB Response Statement is scientifically and morally flawed

NRPB: The first results of the EMF part of the case-control UK Childhood Cancer Study (UKCCS) were published in 1999 [1]. The main conclusion of the analysis was that there was no evidence that exposure to magnetic fields associated with the electricity supply in the UK augments risk for childhood leukaemia, cancers of the central nervous system, or any other childhood cancer.

Powerwatch CommentsIt was admitted in the study that very few of the UK children had been in magnetic flux levels in the high exposure categories. Indeed a COMMENTARY by Mike Repacholi, Head of the WHO EMF Programme, and Anders Ahlbom, in the same issue of the Lancet (page 1918) stated "The UKCCS provides evidence only for exposures up to 0.2 microtesla."

It also stated "Reviews of epidemiological studies conducted by the US National Research Council [NRPB Ref 4], WHO [A], and the National Institute of Environmental Health Sciences (NIEHS) [B] have suggested that there is a weak link between exposure to power-frequency magnetic fields and childhood leukaemia, with an odds ratio of about 1.5. Using the International Agency for Research on Cancer criteria for classifying potential carcinogens, an international working group convened by the NIEHS [B] rated exposure to power-frequency fields as a category 2B, a possible human carcinogen."

The 1999 NIEHS Report to US Congress [C] stated: "The NIEHS concludes that ELF-EMF exposure cannot be recognized as entirely safe..... because virtually everyone in the US uses electricity and is therefore routinely exposed to ELF-EMF, passive regulatory action is warranted such as continued emphasis on educating both the public and the regulated community on means aimed at reducing exposures."

NRPB: Recently an important subsidiary analysis has been carried out which focuses on the relationship between childhood cancer and living near to power lines [2]. The results, published in the British Journal of Cancer, are consistent with those based on measurements in the first analysis. There was no evidence that either residential proximity to electrical installations, or the magnetic field levels they produce, is associated with increased risk of childhood leukaemia or any other cancer.

Powerwatch CommentsThis is NOT correct. A full reading of the paper shows that an analysis of incidence within 400 metres of 275 and 400 kV overhead power lines found an increased Odds Ratio of 1.42, an increased association of 42%.

NRPB: The UKCCS was set up in the early 1990s at a time when previous studies had suggested an association between exposure to power frequency electromagnetic fields (EMF) and the development of childhood malignant disease, especially leukaemia and cancers of the central nervous system [3]. The main analysis [1] was based on residential and school measurements of magnetic flux density.

Powerwatch CommentsIt should be noted that the UKCCS used a 'Geometric Mean' rather than the much more commonly used 'Arithmetic Mean' (AM = normal average). Geometric Mean is an unusual metric and is the nth root of all the numbers multiplied together. It tends to ignore relatively few large values whereas one single zero will take the GM to zero! The more usual Arithmetic Mean is the normal 'average' where you add all the 'n' numbers up together and then divide by 'n'.  Most EMF studies have used A.M. or a time-weighted mean (for areas where the child spent time) and virtually none have used G.M. which always tends to give a lower result than the A.M.

The UKCCS used a Time Weighted G.M. that would have probably under-estimated the exposure of children living near to high voltage power lines. A mid-1990's UK National Grid paper by John Swanson and David Renew looked at A.M and G.M for two populations - those living within 100 m from 132 kV or above overhead power lines and those who lived further away. Note: uT = microtesla.

For the further away group the results were: P(5%) 0.012 µT, G.M.= 0.036 µT, A.M.=0.051 µT, P(95%)=0.141 µT
For those living within 100 m the results were: P(5%) 0.025 µT, G.M.=0.153 µT, A.M.=0.973 µT, P(95%)=6.453 µT

So, for those living close to overhead power lines, G.M. seems to us to be especially inappropriate as it loses the peaks - in this case by a factor of 973/153 or divided by a factor of 6.4.

NRPB: Exposure was estimated for the year preceding the date of diagnosis (or an equivalent date for controls) by weighting the measurements by the time spent in bed, at school and elsewhere, as determined during interview. Exposure estimates were adjusted for appliance and power line historical fields as necessary. The study found no association between measured power-frequency magnetic field exposure and risk for any malignancy [1].

Powerwatch Comments The results from the UKCCS do seem out of line with other well conducted powerline studies and there may be reasons for this. One might be that they only considered the home of the child for the year prior to diagnosis, whereas another (as yet unpublished) part of the UKCCS that is looking at the molecular genetics of the heel blood of newly born infants, has been finding genetic marker abnormalities that are associated with leukaemia AT BIRTH, i.e. usually quite a few years before the child actually develops leukaemia. So the relevant exposure period MAY be where the mother lived for the year BEFORE the birth of her child, rather than the year before the child was diagnosed with leukaemia.

NRPB: Several previous epidemiological studies have used distance from power lines as a crude marker of exposure [4]. Some have shown associations with childhood cancer; others have not. A recent view put forward is that either distance is a more stable surrogate for historical magnetic field exposure or that it may be a proxy measure for some unknown 'causal exposure' factor, less closely related to average measured magnetic fields [4]. During the course of the original study, details of external sources such as high voltage lines, underground cables, substations and some types of distribution circuits, were collected for the homes of most cases and one control per case. Home addresses and grid references were provided on questionnaires sent to electricity companies, masked with respect to case-control status. The details have provided study investigators with the opportunity to examine the postulated association between disease and distance. The effect of magnetic fields calculated from power lines alone has also been examined, using categories selected beforehand to be the same as those used for the measured analysis [1].

NRPB: The results are consistent with the previously reported results based on measured magnetic fields [1]. The study found no evidence that proximity to electrical installations, or the magnetic field levels they produce, is associated with increased risk of childhood leukaemia or any other cancer [3].

Powerwatch Comments This is a repeat of an earlier statement, and is still NOT correct. A full reading of the paper shows that an analysis of incidence within 400 metres of 275 and 400 kV overhead power lines found an increased Odds Ratio of 1.42, an increased association of 42%.

NRPB: All homes with external source information were examined, giving 3380 cases and 3390 controls, as compared to the 2226 case-control pairs in the measurement based analysis [1]. The proximity study included the great majority of eligible households (85% of interviewed cases) so the possible effect of participation bias was small. Restricting the analysis to those children who had lived in the same home for all the year of interest (approximately 90% of study subjects) made little difference to the results.

Powerwatch Comments As stated above, exposure during the year prior to diagnosis may not be the correct time frame.

Also not mentioned by the NRPB in their Response Statement, was another recent British Journal of Cancer Paper [D] that confirmed high power-frequency magnetic fields ARE associated with a doubling of childhood leukaemia. A major meta-analysis of the original data from a large number of competent studies, including the UKCCS, of 3,203 children with leukaemia and 10,338 children without showed that the few (62) children exposed to residential power-frequency magnetic fields above 0.4 microtesla (4mG) have twice the chance of developing leukaemia compared with the unexposed control children. Relative Risk = 2.0 (1.27-3.13), p=0.002 showing a very high level of confidence in the result.

Another not mentioned recent meta-analysis, this time of 15 studies, published in the November issue of Epidemiology [E], found a 1.7 fold increase in childhood leukaemia at 0.3 microtesla. This didn't include the UKCCS results ~ in fact the only UK paper was the Coghill, Stewart and Philips paper that the NRPB always chose to publicly ignore.

There have been too few electric field studies published to carry out a meaningful meta-analysis, but electric fields are also under suspicion. The Coghill study and a few US studies have found significant associations with low levels of a.c. electric fields. Against UK NRPB advice, the UKCCS did add the measurement of electric fields to the second part of the study (with funding provided by the Foundation for Children with Leukaemia), and we await the now overdue results of this with interest.

References (NRPB 1 to 4, plus additional Powerwatch Refs 5 to 9)

  1. UK Childhood Cancer Study Investigators. Exposure to power frequency magnetic fields and the risk of childhood cancer. The Lancet, 354, 1925-1931 (1999)
  2. UK Childhood Cancer Study Investigators. Childhood cancer and residential proximity to power lines. British Journal Cancer, 83, No. 11, 1573 -1580 (2000)
  3. UK Childhood Cancer Study Investigators. The UK Childhood Cancer Study: objectives, materials and methods. British Journal Cancer, 82, No. 5, 1073-1102 (2000)
  4. NAS-NRC. Possible health effects of exposure to residential electric and magnetic fields. National Academy Press, Washington DC (1997)
  5. Interaction of static and Extremely Low Frequency electric and magnetic fields with living systems: health effects and research needs, Repacholi MH and Greenebaum B, Bioelectromagnetics 1999, 20: 133-160
  6. Assessment of health effects from exposures to power-line frequency electric and magnetic fields, NIEHS Working Group Report: NIH Publication 98-3981. Research Triangle Park; NIEHS 1998
  7. Health Effects from Exposure to Power-Line Frequency Electric and Magnetic Fields, NIEHS/NIH Pub. 99-4493, prepared in response to the 1992 US Energy Policy Act (PL 102-486, Section 2118)
  8. A pooled analysis of magnetic fields and childhood leukaemia, Ahlbom, et al, British Journal of Cancer (2000) 83(5), 692-698.
  9. A pooled analysis of Magnetic Fields, Wire Codes, and Childhood Leukemia, Greenland, et al, Epidemiology, Vol.11 No.6, 624-634.