23 October 2019

The UK electricity industry maintains a cohort of around 82,000 staff from the 1970s. This cohort looks at cause of death for any associations with occupational risk factors including EMFs. This study expanded on previous published results, including cancer incidence data up to the end of 2015. The key findings were:

• excesses for male workers for mesothelioma (asbestos related cancer), skin cancer and prostate cancer;

• overall cancer morbidity slightly lower than expected in males and as expected in females;

• excesses for female workers for cancer of the smaller intestine, nasal cancer, and breast cancer

Overall, no association between occupation EMF exposure and cancer has been found. Excesses of specific cancer types have been observed and can be explained by asbestos or sun exposure. Further information about the study can be found here.

Quite a lot of this site is devoted to explaining the scientific evidence on a possible connection between magnetic fields and childhood leukaemia.  We summarise how quite a few studies over the years have reported statistical associations.

A new paper (published February 2019) has looked systematically at how the reported association, or relative risk, has changed over time. It includes 41 studies (believed to be all that have been published). It concludes that the reported risk has declined over time, from a bit over 2 to about 1.5, but is still present and still statistically significant:

Journal of Radiological Protection
Changes over time in the reported risk for childhood leukaemia and magnetic fields
John Swanson, Leeka I Kheifets and Ximena Vergara
Abstract There have been many studies from 1979 to the present reporting raised risks for childhood leukaemia with exposure to power-frequency magnetic fields. There are also suggestions that the reported risk has been decreasing. We examine trends in the risk over time from all available studies. For 41 studies, we combine reported risks using inverse-variance weighting, drawing risk estimates from previous pooled analyses where possible for greater consistency. We examine the cumulative risk for studies published up to each successive calendar year for all studies and for various subsets, and test for a trend over the period. The cumulative relative risk has indeed declined, for our most rigorous analysis from a maximum 2.44 in 1997 to 1.58 in 2017, but not statistically significantly when tested as a linear trend. We find suggestions of higher risks in studies looking at higher exposures and in studies with better quality exposure assessment. We conclude that there is a decline in reported risk from the mid-1990s to now, which is unlikely to be solely explained by improving study quality but may be due to chance, and an elevated risk remains.

Multiple media have picked up on a Facebook story about children getting small shocks from the metal chains of the swings in a children’s playground under an overhead line in Kent.

Microshocks are a known phenomenon when the electric field from a power line induces small charges on conducting objects.  If you touch such an object, it can discharge to you through a tiny spark called a microshock.  This is very similar to when you acquire a charge through walking across a nylon carpet then touch a metal object, and just like those static shocks, it can be disconcerting but is not regarded as harmful.

We have not investigated this specific instance.  But we would guess that the metal chains are charging up.  The swings in question have a wooden frame, and normally, these would screen the electric field to some extent.  In the long spell of hot dry weather we had this summer, these would dry out, reducing or removing any screening effect.  Also, the drier it is, the more pronounced microshocks are anyway, because humidity in the air can help charge to leak away.

So (although, as we say, we haven’t investigated this specific instance), we are not too surprised by what is being described – it sounds fairly explicable in terms of what we know about microshocks – but it will possibly only have happened in the hot dry weather we’ve had, and we don’t think it would pose any serious health or safety risk.  These microshocks – or any other microshocks you may experience under overhead lines – do not indicate any fault with the line. You are not about to be electrocuted with thousands of volts!

Links to some of the media coverage:

• https://www.dailymail.co.uk/news/article-6148627/Staff-dismantle-playground-swings-children-suffer-electric-shocks.html
• https://www.mirror.co.uk/news/uk-news/playground-built-beneath-overhead-power-13203007
• https://www.kentonline.co.uk/tunbridge-wells/news/probe-as-children-jolted-at-power-line-playground-189291/

(also discussed on the Jeremy Vine show, BBC Radio 2, Monday 10 September starting at about 1230)

And on this site, more on

• microshocks
• another specific way microshocks can be experienced, riding a bicycle under an overhead line

Two new epidemiological studies were published at the end of May 2018.

One was a pooled analysis of 11 separate international studies of childhood leukaemia and proximity to power lines.  This confirmed a suggestion of a small elevation close to the highest voltage lines, but did not find the same effects as previously reported in the UK occurring in other countries.

Prompted by this, the CCRG in the UK published a further analysis, which found yet more quirky features of the findings.  This doesn’t mean that they are wrong, but it does strongly suggest that they are not a direct effect of the power line and are more likely to be some sort of indirect socioeconomic or demographic effect.

• More on the various pooled analyses including this one
• More on the CCRG studies
• More on, specifically, this latest CCRG analysis

See also more on the evidence on childhood leukaemia generally.

The UK media have been running a story about a paper setting out the views of Professor Mel Greaves on the causes of childhood leukaemia, specifically how it is related to inadequate exposure to infections early in childhood. See a page on this site about these theories.

Childhood leukaemia is the disease that is most often linked to possible exposure to magnetic fields.  See more on the evidence for that.  Clearly, the more we understand about the causes, the better we will be able to understand whether EMFs play a role or not.

Sample media story

Some of the reporting mentions the issue of power lines and leukaemia.  This whole site is devoted to providing as objective and factual a view of that issue as we can.

The Society for Radiological Protection is the UK’s professional body for radiation issues including non-ionising radiation or EMFs.  They have just published a guide to how to judge the quality of EMF scientific publications.

We have some other material on this site already in the same general area about publication and research ethics.

A new study has been published looking at brain cancer rates in the UK.  It is normally said that brain cancer rates are not changing much over time.  This study identifies one type which seems to have increased, from 1995 to 2015 – glioblastoma multiforme – with decreases in other sorts to give the limited overall change.

The paper itself mentions several possible causes for an increase without being specific.  The accompanying press release (issued by MobileWise), however, focuses in on a possible link to mobile phone use, and that aspect was picked up by some of the media.

See:

• The study itself
• A sample of the media coverage: Daily Telegraph, Daily Mail, Sun

The relevance to power lines and substations

Radio-frequency magnetic fields (such as are emitted by mobile phones) are a different physical phenomenon to power-frequency electric and magnetic fields (emitted by power lines and substations).  The evidence on possible health effects has to be considered completely separately, so this new work has no direct relevance to power frequencies.

This website is concerned with power frequencies – we have just some basic information on radiofrequencies.

For brain cancer, there is little evidence linking them to power-frequency EMFs – that has been the conclusion of all the authoritative review bodies.

Looking at trends over time in a disease and comparing it to changes in an exposure is a perfectly valid (if limited) technique. It’s been done for power frequencies, on childhood leukaemia, with the conclusion that changes over time don’t seem to correlate, reducing the evidence for a causal link in that case.

A large epidemiological study of childhood cancer and power lines in California has been underway for the last few years.  It published its results for distance to the power lines in 2016 and has just published results for calculated magnetic fields.

It finds a modest elevated risk for calculated fields: relative risk 1.52.  That is consistent with their findings for distance.  They conclude:

Our large, statewide, record-based case–control study of childhood leukemia in California does not in itself provide clear evidence of risk associated with greater exposure to magnetic fields from power lines, but could be viewed as consistent with previous findings of increased risk.

See also:

• more detail on the California study
• the evidence overall on childhood leukaemia, and in particular the pooled analyses that summarise the previous findings

A new study has been published looking at Motor Neurone Disease in a large occupational dataset in the Netherlands.  It reports positive associations with magnetic fields.  This is a different finding to a recent UK study, which concentrated on workers in the electricity industry and used more sophisticated exposure assessment methods, which did not find associations.

See more on both studies and on the evidence on neurodegenrative disorders generally.

The Charity Children with Cancer ran a three-day conference in London 5-7 September 2016, and linked to that conference, there were stories in the media about the increase in incidence rates for cancer in children, teenagers and young adults, and what might be causing these increases.

see e.g. the Sunday Telegraph.

Power lines were one of the possible factors mentioned.

The Childhood Cancer and Leukaemia Group then published a response.

There seems to be agreement that childhood cancer rates probably are going up, though uncertainty as to how much of that is simply better diagnosis.  There are very few definitely known causes, but various suggested or possible causes, with varying strengths of evidence.  One of those possible causes is magnetic fields, from high-voltage power lines or other uses of electricity, or perhaps some other factor associated with the power lines other than magnetic fields.  This site is devoted to presenting the evidence on this subject.  But, specifically on the trends over time, this has been looked at in some detail.  Although exposures to magnetic fields and childhood leukaemia rates have both increased, the big increases in each were at different times (exposures had their biggest increase after the second war, leukaemia rates before), so this does not really provide any evidence in support of a causal link.

See more detail on:

the evidence on childhood leukaemia generally

time trends in particular