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No link between childhood cancer and mobile phone base stations or masts

Posted Jun 23 2010 12:00am

Mobile phone base stations do not increase the risk of childhood cancer, even if a child’s mother lived close to a mast when pregnant. That’s the message from the largest study looking at the health effects of mobile phone base stations in the UK.

The new research, published in the British Medical Journal , should provide reassurance to parents, especially expectant mothers, who are worried about living close to such stations.

The authors concluded:

“In summary, we found no association between risk of childhood cancers and mobile phone base station exposures during pregnancy. The results of our study should help to place any future reports of cancer clusters near mobile phone base stations in a wider public health context.”

What did the study find?

The results come from a large study of British children aged 0-4. The research team, led by Paul Elliott at Imperial College London looked at 1,397 children under five who were diagnosed with cancer between 1999 and 2001. They specifically focused on cancers of the brain and central nervous system, leukaemia, and non-Hodgkin lymphoma.

Each child was compared with four children of the same sex who were born on the same day but didn’t have cancer.

Elliott’s team worked out the home address of every child at their time of birth and gathered information about any mobile phone base stations that were close by. For each antenna, they took detailed information from the four mobile phone operators who were active at the time.

After crunching all this information, the team found no association between mobile phone base stations and risk of cancer. The distance between a child’s birth address and the nearest phone base station did not affect their risk of cancer. The total power output of all the base stations within a 700 metre radius did not affect their risk of cancer. The power density (a measure of power over a given area) of all stations within 1400 metres did not affect their risk of cancer.

It is worth stressing that the team did a large study covering all of Britain, they measured the effect of base stations in three different ways, and they considered a wide range of childhood cancers. And despite all of that, they didn’t find a single statistically significant result – not even a hint that mobile phone base stations could affect the risk of childhood cancer.

Who funded the study?

It’s also worth talking about sources of funding. This study was funded by an independent body called the UK Mobile Telecommunications Health Research Programme (MTHR). The MTHR was set up in 2001 to fund research into any possible health effects of mobile phones, following a recommendation by an independent expert group called the Stewart Committee.

The group is jointly funded by the UK Department of Health and the mobile telecommunications industry. It says, “In order to ensure that none of the funding bodies can influence the outcome of the MTHR Programme, it is run by an independent programme management committee .” This is a common theme in this area of research – industry funding has always been mediated by an independent third party, such as the International Union for Cancer Control .

What are the limitations of the study?

The study uses a child’s birth address to estimate the exposures that their pregnant mothers would have received from nearby base stations. That seems like a reasonable assumption, but it’s obviously not as good as directly measuring such exposures firsthand. It doesn’t account for emissions from other sources of radiofrequency fields such as cordless phones. And it’s possible that mothers may have moved house during their pregnancy.

And because the study focused on early childhood cancers, it has nothing to say about any longer-term effects of base station emissions. However, we should also note that childhood leukaemia is most common in the first 5 years of life so longer-term studies are unlikely to say anything different for this type of cancer.

Does this fit with previous research?

Yes. As we have said before, there is no strong evidence that mobile phone radiation can increase the risk of cancer. The majority of studies in people have not found a link between mobile phones and brain cancer, although weaknesses in these studies mean that more research needs to be done.

National trends also argue against such a link. The incidence of brain cancers in countries around the world has not significantly increased, despite the skyrocketing rise in mobile phone use over the last few decades. However, brain cancers can take many years to develop, so it is possible that such trends would only start rising after more time.

Most importantly, there is still no consistent or convincing explanation for how mobile phones or their base stations could actually increase the risk of cancer. The ‘radiofrequency radiation’ that they emit does not have enough energy to damage DNA directly. Many other possible explanations have been investigated but no consistent pattern has emerged.

Base station exposures are even less likely to affect our health than phones themselves as their emissions are many times weaker.  These extremely low emissions are between 1,000 and 10,000 times lower than values set in international guidelines .

However, until now, it was hard to say anything conclusive because very few studies had looked at this issue. There were also concerns around exposures for babies and children since they would get a greater dose for their size and their developing nervous systems are possibly more sensitive.

This new study should help to address these concerns and it adds some valuable evidence to this area. In a related article, John Bithell from the Childhood Cancer Research Group in Oxford says,

“Moving away from a mast, with all its stresses and costs, cannot be justified on health grounds in the light of current evidence. [This] is also supported by experimental evidence, which has so far failed to show any biological effects… that might lead us to worry about the impact on health.”

What about cancer clusters?

There have been a few reports of clusters of cancer around mobile phone base stations, but all of these have been based on very small numbers of affected people. With such small numbers, it is entirely possible that such clusters are coincidences. Just through chance, you would expect some cases of childhood cancer in any country to happen close together, and some of these might be near a visible mast. In such situations, it is tricky to work out whether the mast was directly involved.

This is a common problem, often known as the Texan sharpshooter effect. Imagine a Texan who fires his gun at a barn door. After he has fired a hundred shots, he finds the closest cluster of bullet holes, draws a bulls-eye around them, and claims to be a sharpshooter. It would certainly seem that way to a passer-by but we know it was just down to chance.

This is why scientists need to do large studies that look at the effects of base stations and masts in a large number of people, often across an entire region or country.

- Ed

PS – The excellent NHS Choices Behind the Headlines site have also covered this study

Photo by Harald Hubich at Wikipedia

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