17 November 2014

Cancer from a mobile phone? Some say yes, many say no

Mobile phones have been implicated in the risk of cancer many times over the years. The first mobile phone to go on sale was Motorola's DynaTAC 8000X in 1984. It cost nearly US$4,000, and the phones did not become relatively common till the 1990s. Given that some types of cancer may take years to develop, it could well be that we will only see a jump in cancer rates due to mobile phone radiation 25 years on - or basically from around now. 

A new study published in Pathophysiology this October has again found that the radiation from mobile and cordless phones can cause problems, specifically for a type of brain tumour called a glioma. 

In the study, Mobile phone and cordless phone use and the risk for glioma – Analysis of pooled case-control studies in Sweden, 1997–2003 and 2007–2009, researchers led by Lennart Hardell, Professor, Department of Oncology, University Hospital, Örebro, Sweden analysed two studies on malignant brain tumours in 1,498 patients diagnosed from 1997 to 2003 and from 2007 to 2009 respectively. Scandinavian countries were very early adopters of mobile phones, so it is likely that people there have used mobile phones for longer than people elsewhere. The study found that:

  • Mobile phone use increased the risk of glioma, with those who have used the phones for over 25 years being at a much higher risk. 
  • Cordless phone usage also increased this risk but not to as great an extent. 
  • The highest risk was found for glioma in the temporal lobe, and First use of a mobile or cordless phone before the age of 20 gave a higher likelihood of getting glioma than other age groups.
The warnings keep recurring, but for every study that claims that mobile phones cause cancer of some kind, there seem to be many more which claim the opposite. The link has been debunked as far back as 1999. A 2006 study investigating whether mobile phones cause non-Hodgkins lymphoma, a type of cancer, is one of many studies to come up with nothing, for example.

But there seem to be a few studies which point to a risk of cancer from mobile phone radiation. The first are studies by Hardell. Another October 2014 study by Hardell in the International Journal of Environmental Research and Public Health notes that brain cancer victims who have a particular type of glioma called astrocytoma and who also use mobile phones or cordless phones tend to die earlier, for instance.

A second study is dated July 2014 and found in Occupational and Environmental Medicine. Part of the CERENAT study from France, very heavy users of mobile phones were more likely to get gliomas and tumours of the temporal lobe in the brain, researchers said. The study also found that those who use mobile phones because of their jobs and who use them in the city are more likely to be at risk.

Another cited source of a positive link between mobile phone usage and radiation comes from the Interphone study. A September 2011 report in Occupational and Environmental Medicine also noticed increased rates of glioma and meningioma (cancer of the meninges, a different part of the brain) for heavy mobile phone users (people who had used mobile phones for over seven years) in the Interphone study for Australia, Canada, France, Israel, New Zealand, especially for glioma. 

A further analysis was done on tumours in different parts of the brain, and heavy mobile phone users (people who had used mobile phones for more than 10 years) had more tumours in the part of the head most exposed to mobile phone radiation as compared to other parts of the head. The study stopped short of saying that mobile phones had caused this trend, and called for further research on the topic. 

Despite these indications a 2011 review of Interphone concluded that "Although there remains some uncertainty, the trend in the accumulating evidence is increasingly against the hypothesis that mobile phone use can cause brain tumors in adults."

Another 2011 analysis of Interphone acknowledged the data on tumours but said: "Elevated odds ratios observed at the highest level of cumulative call time could be due to chance, reporting bias or a causal effect."

Another possible hint of a problem is a study from Taiwan published October 2012. This study was not about mobile phone exposure through direct use of mobile handsets, but about radiation coming from mobile phone base stations. Researchers noted that children with under 15 who lived closer to mobile phone base stations had a higher risk of suffering from tumours, which they referred to as neoplasms. There was however no specific risk associated with brain tumours or with leukemia, and no mention of whether these tumours were benign or malignant. 

Other researchers have focused on vestibular schwannomas, also called acoustic neuromas. These are benign tumours that develop in the ear area, which might well be due to mobile phones held close to the ear when in conversation.

January 2014 study in Tumour Biology found that vestibular schwannomas, are much larger for mobile phone users than non-users. Tumours were more likely to be found in the side of the head that the user would place the phone, whereas if it were random, there should have been a 50:50 chance of tumours being on either side of the head. 

A review of the research on the subject in Surgical Neurology in 2009 found that subjects who used cell phones for at least 10 years had a 2.4-fold greater risk of developing acoustic neuromas on the same side of the head as they used the phone.

Japanese study published in 2006 found no link between acoustic neuromas and mobile phones however. While both sets of research studied what should be the same thing, it might not be apples to apples because people in Japan hadn't been using the phones for long enough, or the phones that were in use at the time weren't as powerful. Alternatively, it could also be that most people in Japan don't put their phones to their ears to use them, but may use handsets instead.

Parotid gland tumours are another logical possibility as parotid glands are near the ear, basically where a mobile phone would be held for a voice call. Parotid glands produce saliva, though they aren't the only glands to do so. Research has turned up no statistically significant links with mobile phones. This 2012 study in the European Journal of Cancer Prevention is typical, and the same result was mentioned in 2006. Hardell also studied the possibility in 2004 and came up with nothing. 

In 2011 however researchers noted that most victims of malignant epithelial parotid gland tumours were in cities as opposed to rural areas, where there would generally be fewer mobile phones in use. 

"The results suggest a possible dose-response relationship of cellular phone use with epithelial parotid gland malignancy," they note in the abstract on the International Journal of Oral and Maxillofacial Surgery.

Hardell himself has also investigated testicular cancer as men may place their phones in trouser pockets, close to this part of the body. He found no link in this 2007 study in the International Journal of Andrology.

A large portion of the research is about searching out people who already have cancer and then asking them to recall how long they've used mobile phones. Rather than test people directly on something that may potentially be harmful, another portion of the research has focused on exposing rats to various electromagnetic fields to see what happens. The rats chosen are genetically predisposed to develop different types of cancer or also exposed to carcinogens. If using mobile phones can cause cancer, it could be assumed that the rats would then develop cancer very quickly, and even more quickly in the presence of a carcinogen. 

Researcher AM Sommer has exposed found that neither UMTS (published 2007) nor GSM-900 (published 2004), both bandwidth frequencies used by mobile phones, could be blamed for cancer. FM frequencies used to simulate mobile phone radiation in an April 2000 study had no effect at all on rats studied over two years, with or without the help of a carcinogen called ethylnitrosourea (ENU). Yet another two-year study on 900 rats, published in 2000, exposed to differing amounts of 860 MHz radiation in continuous and pulsed wave formats, delivered 0.5cm from the rat's nose, also drew a blank for tumours of any kind. Breast cancer was studied in rats which were exposed to 900 MHz radiation continuously for three years. Again, the radiation did not cause tumours to develop faster or more of them, said authors of the 2002 paper.

What separate research did find in 2010 however is that lung tumours do develop if mice exposed to UMTS fields are also pre-treated with ENU. The finding may indicate that radio frequencies may not in themselves cause cancer but can accelerate it if a person is also exposed to a carcinogen. Or, given the wealth of negative links, there may just have been something wrong with this particular study.

The research so far which has turned up next to nothing includes: 

A massive long-term study in the UK, the Mobile Telecommunications and Health Research Programme (MTHR), which said in 2012 that there is no evidence that TETRA radio signals affected people. Of course, while there are TETRA-based mobile phones, most mobile phones today use the GSM standard so this may not be relevant.

A meta analysis of the research in Bioelectromagnetics in April 2012, which has found no link between mobile phone use and cancers of the areas of the head which receive the most radiation from a phone.

Some things may even improve. A May 2014 study done on primary school children in Iran that simulated a 10-minute GSM-900 mobile call found that short term memory actually improved after exposure. And mice exposed to GSM phone radiation were subsequently more resistant to e. coli infections, according to a study reported in July 2013 in Dose Response.

The World Health Organization points out that electromagnetic fields produced by mobile phones are classified by the International Agency for Research on Cancer as "possibly carcinogenic" to humans because of the studies that do point to a problem. 

When many results are negative it is still uncertain whether the next study could also be negative, hence the classification. It could mean that mobile phones don't cause cancer at all, which is why there are so many negative results. Or it could mean that mobile phones do cause cancer, but under very specific circumstances which haven't been fully explored yet. 

It should also be noted that there are many different types of cancer. Mobile phones may not cause some types of cancer, but could possibly be responsible for others. It could be that researchers haven't found the cancers that're being caused by mobile phones yet.

Researchers are also assuming that people get cancer close to where they receive the most radiation. This might not be the case. 

And just as cancer is not one homogeneous entity, neither are mobile phones, nor the radiation they give off. The types of radio frequencies they use vary from country to country too. In a sense, none of the studies are truly apples-to-apples because they are likely to be studying people who are using completely different phones; the mobile phone signals could vary across cities and different frequencies are used in different countries. The phone may be very close to the body or quite far from it depending on whether handsfree kits or Bluetooth headsets are being used, affecting the amount of radiation delivered. Proximity to a base station might also matter.

All this research presumes that we are still making a lot of voice calls through the mobile network, and also making them through placing our mobile phones to our ears. In actual fact we may be using Wi-Fi, or using our phones to communicate in other ways. And when we use our phones for voice calls, we may be employing Bluetooth or basic hands-free kits.

Since we tend to spend more time holding our mobile phones in our hands, wouldn't we be more at risk of getting tumours of the hand? It turns out that tumours of the hand are very rare. One type of cancer, called soft tissue sarcoma, can occur but is not linked to mobile phones. It is however likely to be fatal. Another possibility would be that smartphones are a recent development and it may take another decade or more to see any cancers develop. Alternatively, the cancer cells could start in the hand but travel to other parts of the body.

But if you are expecting a glioma at any moment, another study from Taiwan may put things in context. Published November 2013, the researchers surveyed the number of malignant brain tumours in the whole of Taiwan from 2000 to 2009. According to the National Cancer Registry of Taiwan, there were just four incidences and four deaths during this period, against 23 million registered mobile phone numbers in Taiwan. It was not clear from the abstract if this referred to eight different cancer victims, or four victims who subsequently passed away; but either way the risk appears small.

It should also be noted that radiation can come from other sources, like electrical appliances, and we are all bathed in radio frequencies for all kinds of communications, including TV signals and shortwave radio. 

The WHO only plans to conduct a formal risk assessment of all studied health outcomes from radio frequency fields exposure by 2016. In the meantime, individual users have to decide for themselves if the research so far shows enough of a risk to take precautions. They can choose to make shorter calls, avoid placing their mobile phones close to their bodies, or invest in handsfree kits if they are worried, for example.