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For the record

The IARC classifies mobile phone radiation as a 'possible' cancer risk: what does this mean?

On 1st June 2011, the International Agency for Research into Cancer announced their classification of whether the radiation emitted by mobile phones and WiFi increases the risk of cancer. The announcement was widely reported in the press - including BBC, the Guardian, The Telegraph - but what does this classification mean?

The IARC - part of the World Health Organisation - classifications are made by a panel of experts who consider the whole body of available research to assess whether there is sufficient scientific evidence that something is likely to cause cancer. This is assigned a rank on a scale of 1 to 4 - for example, they have classified the radiation from mobile phones as group 2B, described as anything which ‘possibly’ causes cancer in humans. The IARC working group published their assessment of the scientific evidence which led to this classification in The Lancet Oncology on 22nd June 2011.

As Ed Yong, Cancer Research UK’s head of health information, says: “The WHO’s verdict means that there is some evidence linking mobile phones to cancer but it is too weak to draw strong conclusions from. The vast majority of existing studies have not found a link between phones and cancer, and if such a link exists, it is unlikely to be a large one”.

Cancer Research UK have written a very good description of the IARC classification system, explaining what the current evidence says about the association between mobile phones and cancer risk. There has been discussion in the media about studies looking at a possible link between mobile phone use and gliomas (a type of brain tumour).  This blog looks in detail at the methods and conclusions of these studies, placing them in context with other research in the area to give an overall picture of what we know. Cancer Research UK concludes that “so far, the published studies do not show that mobile phones could increase the risk of cancer”.

NHS Choices also have a Behind the Headlines piece which clarifies what the new classification really means.

The rationale the IARC use to decide upon a classification are:

Group 1

‘carcinogenic to humans’

(highest risk)

includes anything for which strong evidence of an increased risk of cancer in humans, and a plausible mechanism, exists

examples: tobacco, alcohol, asbestos

Group 2A

 ‘probably carcinogenic’

limited evidence in humans but strong evidence of an increased risk of cancer from animal studies, where the mechanism in humans is likely to be similar

examples: UV radiation, diesel engine exhaust

Group 2B

‘possibly carcinogenic’

limited evidence of increased risk of cancer in both humans and animals, or evidence only of a potential mechanism

examples: coffee, styrene, DDT 

Group 3

‘not classifiable’

there are currently insufficient scientific studies to assess the likelihood of something causing cancer – often this means that further research is needed

examples: cholesterol, hydrogen peroxide

Group 4

‘probably not carcinogenic’

there is strong evidence to suggest that something does not cause cancer

examples: there is only 1 example, caprolactam, as the IARC focus on potential risks


For more information on the status of evidence on radiation and health, read our short guide Making Sense of Radiation.

Author: Sense About Science

Document type: For The Record

Published: 1 June 2011

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