The International Agency for Research on Cancer (IARC), a part of the World Health Organisation (WHO), recently published a report warning that there might be an elevated risk of certain types of brain tumour in heavy cell phone users. I was surprised to say the least, given that I've previously referenced the WHO as an authority when the swine flu vaccine scaremongering was at its peak a couple of years back. Personally, I'm pretty confident that my cell phone isn't going to kill me unless I walk under a bus while tweeting. Let me explain, using a little biology, physics and common sense.
Cancers happen when an otherwise healthy cell is reprogrammed by a genetic mutation to behave as a cancerous cell. This mutation can occur either by chemical interaction or by EM radiation. The effecting agent is described as a mutagenic agent. EM radiation does this by dislodging electrons in a chromosome which ionise the molecule, allowing it to accept other atoms or molecules which in turn induce a mutation in the chromosome, sometimes leading to cancer. In this case, the effecting agent is described as a carcinogenic agent. (Note: These mutation mechanisms have been around since life first arose on Earth and are fundamental to evolution; they are NOT a result of our technology running amok.)
The IARC claim is that there is a link between cellphone radiation and two types of brain cancer. For this to happen, cellphone radiation would need to be able to ionise the DNA molecule in order to introduce a mutation. This requires a certain amount of energy that cellphone radiation simply doesn't carry. It is non-ionising radiation. To understand more about this, let's take a look at what we mean when we talk about electromagnetic radiation. Below is the electromagnetic spectrum, the range of electromagnetic radiation from longwave radio through visible light all the way up to gamma rays, increasing in energy from right to left. As the frequency of the light increases, the energy it carries also increases.
How do we know this? (Bear with me here, we'll get to cellphones shortly!) Albert Einstein won a Nobel Prize for discovering the Photoelectric Effect which, essentially, says that light above a certain frequency falling on a metal induces a current. This happens because the energy in the light's photons is sufficient to cause electrons in the metal to move. He showed that red light won't induce a current, but blue light will. Max Planck later found a relationship between the frequency of light and the energy of its photons. As we can see above, red light has a frequency of 700nm (7*10^ -7m), blue light 400nm (4*10^ -7m). It's clear from Planck's discovery that blue light is more energetic than red.
Now, back to cellphones. Where does this radiation figure on the spectrum? Look at where red light is on the spectrum. Go below it, you find Infra-red, then below it again you find the microwave region, a range of wavelengths from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz (0.3 GHz) and 300 GHz. Cellphones typically operate in the low end of the microwave region, overlapping with the high end of UHF radio frequencies, usually below 2Ghz. Obviously, this is well below the level of ionising radiation, which is beyond the UV region of the spectrum, in x-ray and gamma-ray territory. It can't be carcinogenic.
Cancers happen when an otherwise healthy cell is reprogrammed by a genetic mutation to behave as a cancerous cell. This mutation can occur either by chemical interaction or by EM radiation. The effecting agent is described as a mutagenic agent. EM radiation does this by dislodging electrons in a chromosome which ionise the molecule, allowing it to accept other atoms or molecules which in turn induce a mutation in the chromosome, sometimes leading to cancer. In this case, the effecting agent is described as a carcinogenic agent. (Note: These mutation mechanisms have been around since life first arose on Earth and are fundamental to evolution; they are NOT a result of our technology running amok.)
The IARC claim is that there is a link between cellphone radiation and two types of brain cancer. For this to happen, cellphone radiation would need to be able to ionise the DNA molecule in order to introduce a mutation. This requires a certain amount of energy that cellphone radiation simply doesn't carry. It is non-ionising radiation. To understand more about this, let's take a look at what we mean when we talk about electromagnetic radiation. Below is the electromagnetic spectrum, the range of electromagnetic radiation from longwave radio through visible light all the way up to gamma rays, increasing in energy from right to left. As the frequency of the light increases, the energy it carries also increases.
Now, back to cellphones. Where does this radiation figure on the spectrum? Look at where red light is on the spectrum. Go below it, you find Infra-red, then below it again you find the microwave region, a range of wavelengths from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz (0.3 GHz) and 300 GHz. Cellphones typically operate in the low end of the microwave region, overlapping with the high end of UHF radio frequencies, usually below 2Ghz. Obviously, this is well below the level of ionising radiation, which is beyond the UV region of the spectrum, in x-ray and gamma-ray territory. It can't be carcinogenic.
So why all the hoopla from the WHO? The IARC report states the following results:
"Results:
The evidence was reviewed critically, and overall evaluated as being limited among users of wireless telephones for glioma and acoustic neuroma, and inadequate to draw conclusions for other types of cancers. The evidence from the occupational and environmental exposures mentioned above was similarly judged inadequate. The Working Group did not quantitate the risk; however, one study of past cell phone use (up to the year 2004), showed a 40% increased risk for gliomas in the highest category of heavy users (reported average: 30 minutes per day over a 10‐year period).
'Limited evidence of carcinogenicity': A positive association has been observed between exposure to the agent and cancer for which a causal interpretation is considered by the Working Group to be credible, but chance, bias or confounding could not be ruled out with reasonable confidence.
'Inadequate evidence of carcinogenicity': The available studies are of insufficient quality, consistency or statistical power to permit a conclusion regarding the presence or absence of a causal association between exposure and cancer, or no data on cancer in humans are available. "
What does this mean then? A correlation has been observed, but as skeptics are fond of saying, correlation does not equal causation. It would appear the IARC are playing the "let's keep an eye on this just in case" card. As far as I'm concerned there's nothing new here. Might there be an issue? Maybe. But it's unlikely. Cellphones have been in mass consumption for over 15 years now and there doesn't appear to be any increase in brain tumours, according to studies done in several countries. I'll be here waiting for the evidence, and if it comes I'll be the first to change my mind.
Some links:
A list of other items in the same "2B Possibly Carcinogenic" category:
PZ Meyers on the IARC report:
Phil Plait weighs in:
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