Mobile phones classed as ‘possibly carcinogenic’

The WHO’s cancer agency IARC has said mobile phones “possibly” cause cancer. Flickr

Mobile phones are “possibly carcinogenic to humans”, according to a new report by the World Health Organisation’s cancer agency, the International Agency for Research on Cancer (IARC).

The IARC classified mobile phones as Group 2B, putting them in the same category as lead and petrol, “based on an increased risk for glioma, a malignant type of brain cancer, associated with wireless phone use.”

Group 1 agents, which definitely cause cancer, include asbestos and tobacco, while Group 2A, which includes anabolic steroids, are “probably carcinogenic”.

Dr. Jonathan Semet, Chairperson of the IARC Working Group, said the finding was based on compelling evidence, including several epidemiological studies.

“They are case-control studies, like the so-called INTERPHONE study. Another study in Sweden provided most compelling evidence,” he said.

“The working group members were also struck by the need for further research to fill in the gaps. More people are using mobile phones… nearly five billion people worldwide. As the numbers continue to grow, people will be exposed for longer and longer… there’s a need for further research and tracking.”

The working group included 31 scientists from 14 countries and reviewed published, peer-reviewed studies on the potential links between cancer and devices that emit electromagnetic fields. That includes mobile phones, wi-fi, bluetooth, television and radio signals and microwaves.

Martin Gledhill, Senior Advisor at New Zealand’s National Radiation Laboratory said the finding should be treated with caution.

“It should be noted that the data on which this conclusion is based mostly arises from older technology phones. Newer technologies (3G/XT/CDMA) produce much lower exposures than these phones,” he said.

Concerned mobile phone users could reduce the risk by using the phone where signal strength is higher, which means it transmits with less power, make short calls or switch to CDMA or 3G phones.

“Tests of hands-free kits have generally found that they reduce exposures to the head by up to 98%. To reduce exposure to all parts of the body, the phone should be placed away from the body when making a call,” he said, in comments released by New Zealand’s Science Media Centre.

The following comments were gathered by the UK Science Media Centre:

Prof Malcolm Sperrin, Director of Medical Physics & Clinical Engineering at Royal Berkshire Hospital,

This statement is a welcome authoritative analysis of the current understanding of the relationship between health and electromagnetic spectrum exposure; particularly that from mobile phones. In my opinion the categorisation as 2b is appropriate since the justification for such a risk indicator respects the anecdotal evidence that cancers may be associated with phone usage.

That being said, it is vitally important to fully understand that there is no definitive correlation between phone usage and the development of cancers that can be inferred from current studies or hypothetical tissue interactions with electromagnetic fields of the type under observation. Where there is ground for further studies, the statistics of the findings is sufficiently marginal simply to provide grounds for additional research and not to establish a link. It is only at high usage over long periods of time that such equivocal data is suspected.

The publication of more data along with a comprehensive justification of any conclusions is eagerly awaited especially in relation to children.

It should also be stated that electromagnetic field exposure is not new – witness the regular usage of radio and other waves for many decades with no convincing health detriment at low powers. The social and technological benefits also need to be emphasised.

The following comments and Q&A were gathered the Canadian Science Media Centre:

Mary McBride, Distinguished Scientist, Cancer Control Research, BC Cancer Agency, Clinical Associate Professor, University of British Columbia

The 2B classification suggests that there is limited evidence that radiofrequency fields may increase the risk of developing cancer but that other explanations are also possible. Overall, I agree with the classification. Cell phone utilisation is widespread and increasing globally and the risk of brain tumours is not to be ignored. There have been isolated studies that show increased risk of cancer but it is useful to appreciate that the evidence is limited – some aspects of research suggest that lo-frequency radiation would not affect cancer risk at all.

I don’t think it’s appropriate to make public health decisions on the possibility of cancer. There have been very limited positive results and a large number of results indicating that low-frequency radiation has no affect. Even after millions of dollars have been spent on research, we still have not been able to explain why cell phones would affect cancer risk.

I think the 2B classification is the appropriate conclusion based on the science – which is not at all consistent. There are different explanations for the experimental and observational results, but the risk is not something you would want to ignore.

We also have to keep in mind that cell phone technology is changing – current phones emit less radiation than older ones and there is also a higher proportion of text messages to calls. But at the same time, a lot more people are using phones much more often.

I know that in determining the classification the IARC used all three types of data – human observation, animal experimentation, and mechanistic studies in the laboratory. The limitation of mechanistic studies is that although they can show a change in action, a change in cells, they cannot show whether they will affect health, which is why you need to combine them with human studies. The problem is that observational human studies are susceptible to different kinds of bias. The IARC committee was working with mostly the same set of information as we had when the I results were released last year, when glioma was identified as the only outcome with an increased risk from cell phone use.

One thing we haven’t seen in any of the studies, and why the classification is 2B and not 2A (probably carcinogenic) is a dose response. A dose response would be an increase in risk of cancer which was linked to an increase in low-frequency radiation. For example, the more you use cell phones, the higher the risk you will develop brain tumours. That sort of dose response is required to determine whether an agent, like cell phone use, actually causes a health problem, like glioma, a serious brain tumour. While there was a statistical relationship in the large INTERPHONE study, the results don’t have the characteristics of a causal relationship, in particular since there was no evidence of dose response.

With cancer you are looking at causes being either a promoter or an initiator. If a cause (like cell phone use) is a promoter, you would expect to see evidence of cancer a few years after exposure. If it was an initiator, it would act as an early trigger – not necessarily causing cancer but acting as an enabler for other agents to cause cancer. In this case it could take decades to show affects.

So far, laboratory studies have shown that low-frequency radiation does not have the capability to act as an initiator and so it has always been assumed that if cell phone use caused cancer, it would be as a promoter and you would see the outcome sooner rather than later. This has not been the case; however, we still need to explore whether RF fields might act as cancer promoters.

We need more results from individuals who have been followed for 20-plus years. We should continue mechanistic studies to determine whether cell phones are an initiator or promoter, and we also need more human observations. The IARC and the Canadian group at the University of Ottawa are continually evaluating the literature. Researchers are also looking at types of brain tumour other than glioma.

The IARC indicated there was some evidence that low-frequency radiation was genotoxic, does that mean that children of people with brain tumours could be susceptible to cancer without ever being exposed to that form of radiation?

There was one study that demonstrated genotoxicity but no other lab has been able to reproduce the results.

Dr Kurt Straif, Head, IARC Monographs Program

It’s not clearly established at the moment that mobile phones do cause cancer in humans.

It’s always a tricky question what to do as a consumer. As I mentioned, we don’t make recommendations…but there are clearly some ideas for lowering exposure, and this could be taken forward by the consumers – for example, the highest exposure is from voice calls. If you use text messaging or headsets, this will lower the exposure.

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