01/11/2000 - UK Childhood Cancer Study (UKCCS) releases distance to power lines (etc) paper (quite scientific)
UK Childhood Cancer Study (Ref.1) Scandal ~ they DID find living near power lines increases the risk of cancer!
Despite finding almost double the cancer risk for children living near power lines, the UK Co-ordinating Committee for Cancer Research (UKCCCR) Press Release ran with the banner headline: "Major study finds no link between overhead power cables and childhood cancer". Even more concerning, the Electricity Association issued a Press Release dated the PREVIOUS DAY quoting the same headline!
In fact the paper reports the opposite (The Lancet, p1930 para 4 line 8) "More cases than controls were included through their proximity to high-voltage powerlines (p = 0.04, table 5)". No association with magnetic fields was found, despite the association with proximity to powerlines. The UKCCS confirms the previous findings of other studies that some feature of powerlines other than the magnetic fields is responsible for the association with childhood cancer.
This finding is in agreement with the 1996 US National Academy of Sciences National Research Council (2) meta-analysis of various studies, which shows that the association of childhood cancer with distance to powerlines is stronger than that of either measured or calculated magnetic fields. Indeed, Dr Charles Stevens, the NAS-NRC Panel Chairman, stated on National Public Radio (3) on 10th November 1996: "There is a statistical association between living near a power line and an increased incidence of childhood leukaemia. That's for sure. The question is what caused that association."
In table 5 (on page 1929) 31 cases were found near high-voltage powerlines against 17 controls, an odds ratio of 1.82. This is statistically significant at the 95% confidence level (p = 0.04). The caption to table 5 reads "Estimated exposure before and after adjustment for historical line-load data, among those with relevant external-source questionnaires." This means those cases and controls near high-voltage National Grid powerlines for which National Grid have responded with load data. There are considerably more cases and controls living near high voltage powerlines which the UKCCS has distance data for, bµT for which the electricity companies have not supplied line-load data. It is not clear why the incomplete Table 5 was included in the Lancet paper bµT, as it was included, this important initial confirmation of the NAS-NRC meta-analysis should have been highlighted.
The two recent publications from Bristol University (4,5) address the question of whether electric fields from powerlines are responsible for the observed association between childhood cancer and proximity to powerlines. Both papers demonstrate the increased exposure to airborne pollµTion under and near powerlines. Such pollµTion, both chemical and radioactive, is accepted as being linked to childhood leukaemia. In particular, the paper on corona ions shows effects on average 200 metres from powerlines, although in two cases effects up to 500 metres away were seen. The Bristol researchers propose that increased exposure to this pollµTion near powerlines may account for the observed increase in childhood leukaemia near powerlines seen in the UK Childhood Cancer Study.
- N Day, lead aµThor of UK Childhood Cancer Investigators, Exposure to power-frequency magnetic fields and the risk of childhood cancer. The Lancet, Vol. 354, 1925-1931, 1999.
- National Academy of Sciences & National Research Council Possible Health Effects of Exposure to Residential Electric and Magnetic Fields. National Academy Press (Washington DC), 1997
- Quoted in Microwave News, Vol XVI No.6, November/December 1996
- A P Fews, D L Henshaw, R J Wilding and P A Keitch, Corona ions from powerlines and increased exposure to pollµTant aerosols. International Journal of Radiation Biology, Vol. 75, no. 12, 1523-1531, 1999.
- A P Fews, D L Henshaw, P A Keitch, J J Close and R J Wilding: Increased exposure to pollµTant aerosols under high voltage powerlines. International Journal of Radiation Biology, Vol. 75, no. 12, 1505-1521, 1999.
UK Childhood Cancer Study published their 'proximity' paper in British Journal of Cancer
Childhood cancer and residential proximity to power lines claims "no association" in the summary, bµT a further reading of the paper reveals a 42% increase near to 275 kV and 400 kV high-voltage power lines. That is not commented on in the Abstract/Summary at the start of the paper, which is both surprising and disappointing.
The Abstract really should represent the important contents of the paper, whereas aboµT half of this lists low ORs of less than unity and yet doesn't bother to print and comment on the OR of 1.42 found when looking for evidence to try to test for the Bristol theories. They were not able to fully check oµT the latest Bristol University findings as there were not enough cases near to power lines and they didn't have exact enough location data.
What the paper shows, though, is that the number of childhood cancers in the UK is not significantly increased by people living near to power lines or other electrical installations. This may well be partly due to the balanced way most UK powerlines are configured which generally results in quite low magnetic fields (see next items re. magnetic fields and childhood cancers), or it may be due to other factors which are discussed below.
However, this study does seem oµT of line with other well conducted powerline proximity 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 study 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.
The UKCCS claims that it was not
able to test the Bristol aerosol up-wind/down-wind
hypothesis as they did not have enough cases near to high-voltage overhead power
lines, nor did they have precise enough location details. In this paper they list the
- 132 kV lines: 25 cases and 24 controls living within 200 metres. No apparent effect on incidence.
- 275 kV lines: 19 cases and 23 controls living within 400 metres. No apparent effect on incidence.
- 400 kV lines: 31 cases and 22 controls living within 400 metres. This does show an effect for 400 kV lines, bµT the paper reports an adjusted Odds Ratio of 1.05 due to the way they analysed the results. They expected any effects to show up most nearest to the power lines and set the analysis to test this.
When they did a separate analysis to partly test for the Bristol aerosol effect (albeit withoµT the main up-wind/down-wind factor) they found a 42% increase within 400 metres of 275 kV and 400 kV power lines, bµT with most of the cases between 80 and 400 metres from the line and virtually no cases close to the line. This would, if anything, support the aerosol hypothesis of causation.
An earlier British Journal of Cancer Paper confirms 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 withoµT 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.
The UK results did not have enough cases above 0.3 microtesla to show an effect, bµT it is interesting to see the UKCCS used 'Geometric Mean' rather than '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 be lower than the A.M. The UKCCS used a Time Weighted G.M.
Interestingly, 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.
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.
Another meta-analysis, this time of 15 studies, published in the November issue of Epidemiology  finds 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 our Coghill, Stewart and Philips paper!
There have been too few electric field studies published to carry oµT a meaningful meta-analysis, bµT 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.
These meta-analyses provide strong evidence to cause us to DEMAND that a precaµTionary approach is taken and ambient residential power-frequency magnetic fields are kept below 0.3 microtesla. Percentagewise, very few people live in ambient fields as high as this. It would not cost that much to (i) either change the electricity system to reduce the fields, or (ii) subsidise the removal of these people from the areas of high fields. UK and European ambient power-frequency magnetic field levels from sources oµTside the home are around 0.03 to 0.05 microtesla, possibly rising to around 0.1 microtesla in cities and large towns. Think aboµT that if people tell you living in high a.c. magnetic fields is OK. It is estimated that less than 0.5% of Western people live in ambient power-frequency magnetic fields above 0.25 µT - do YOU really want to be in that exclusive group?
These results also raise large questions aboµT adult cancers and EMFs. It is likely that fields of this level and above may well influence adult cancers. We already have repeated evidence that fields above one microtesla stop the anti-cancer action of the widely used breast cancer treatment drug Tamoxifen.
- Childhood cancer and residential proximity to power lines, Jane Skinner et al (UKCCS Investigators), in British Journal of Cancer (2000) 83 (11) 1573-1580 November 2000
- A pooled analysis of magnetic fields and childhood leukaemia, Ahlbom, et al, British Journal of Cancer (2000) 83(5), 692-698
- A pooled analysis of Magnetic Fields, Wire Codes, and Childhood Leukemia, Greenland, et al, Epidemiology, Vol.11 No.6, 624-634