16/12/2008 - Gene for ELF EMF susceptibility?

Researchers from the Jiao Tong University School of Medicine in Shanghai, China, have found genetic markers that demonstrate a 4-fold increase in risk of childhood leukaemia if they also live within 100 metres of powerlines or transformers compared to their neighbours with a fully functioning version of this gene.

This doesn't give a biological mechanism (for which there are a number of theories requiring further research ^{[Henshaw 2002, Henshaw & Reiter 2005, Binhi 2008, Blank 2008]}), but what it does give is a marker for biological susceptibility. This has been suspected with most causes of cancer (that the issue is multi-causal and multi-factorial - i.e. for each of the many causes there are many factors) but previously there has been no evidence of this for ELF electromagnetic fields. This research strongly supports the association between living proximity to powerlines and childhood leukaemia^{[Ahlbom 2000, Greenland 2000]}, but more importantly it also provides the beginnings of a possibility that people may be able to screen themselves for susceptibility. This is potentially groundbreaking as it allows some level of preventative action for those looking at purchasing a house near existing overhead powerlines, and could also provide peace of mind for those already living near powerlines if they are tested and found not to have the marker.

There is one remaining aspect that is of interest: At the moment there is about a 1 in 1,800 chance for any given child of being diagnosed with leukaemia within the first 14 years of the their life. 5% of children (if we are to assume that the British average similar to the Shanghai population studied) have this genetic marker. Taking the Ahlbom and Greenland figure of approximately a 2-fold risk increase for living near powerlines, the risk for those without the marker (but living near powerlines) will be the x in (95x + 5y) / 100 = 2. As we know that the marker increases the risk 4-fold, this can be expressed as (95x + 20x) / 100 = 2, or 115x = 200. The increased risk is therefore approximately 1.7-fold for those without the marker and 7 for those with the marker! This means that having the marker and living within 100m of powerlines increases the risk of being diagnosed with leukaemia within the first 14 years of the child's life is more like 1 in 250, a considerably higher risk than for the majority of the British population.

The researchers conclude that the risk of developing childhood leukaemia is significantly elevated (p < 0.01) for children with XRCC1 EX9+16A genotypes who also live within 100 metres of a powerline or substation transformer and/or who are exposed to power-frequency magnetic field levels above 0.14 microtesla.

Three UK Ministers (from DH, DCLG and DECC) meet on Wednesday this week to decide the UK Government's response to the first SAGE Report. It has taken them 18 months to reach this point and hold this meeting. This new report on childhood leukaemia, together with last month's research from Switzerland showing a doubling in Alzheimer's Disease for people living within 50 metres of powerlines^{[Huss 2008]}, means that they should recommend an immediate moratorium on new buildings or new powerlines within 60 metres of each other as suggested by SAGE. Until further research is done this could be a time-limited moratorium for, say, 5 years. The 60 metres distance was based on a typical distance where the magnetic field has reduced to 0.4 microtesla or less. Using a cut-point of 0.14 uT would increase this distance to more like 100 metres.

The Cross Party Inquiry on Powerlines and Leukaemia also reported in 2007. They recommended a moratorium on "new build". Five MPs (Dr Howard Stoate MP, Michael Connarty MP, Dr Ian Gibson MP, Sandra Gidley MP and Nick Hurd MP) considered in detail the evidence for an association between Electric and Magnetic Fields (EMF) from High Voltage Overhead Transmission Lines (HVOTL) and an increased risk of childhood leukaemia and determine what should be done. The members of the Inquiry held 5 meetings during 2006 and 2007, taking oral and written evidence from a broad range of witnesses.

The researchers found the increased incidence extending down to magnetic field levels below 0.1 microtesla. This has implications for house wiring and the use and location of appliances and electronics products in child bedrooms.

Excellent further information is presented on the Microwaves News web site.

There has also been criticism levelled at the statistical methods employed by the study, in that the chance of finding increased risk is going to be unreasonably high purely due to trying to look at too many things at once (thus increasing the chance of finding individual points of data with increased significance).

Either way, whilst not being authorative or definitive in itself, this study provides a potential avenue for funding exploratory research into a plausible genetic susceptibility that may help elucidate the association between residential proximity to overhead powerlines and childhood leukaemia.

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