Even the major international Interphone study, which has relied heavily on industry-funded research, has had to conclude that the risk increases after 10 years' use.
So why has it taken so long to discover this fact, which is now almost indisputable? For many years, any discovery of a health hazard with mobile phones has been countered by other studies that have contradicted the findings. This 'push-me, pull-you' dance has created a fog of uncertainty, within which the mobile phone industry has continued to grow exponen-tially, while paying across billions of pounds and dollars to governments.
Now, however, independent research appears to have made sense of the science, bringing us one step closer to the truth.
A new study, which can be found online ahead of print, has pooled the results of 23 previous studies investigating mobile phones and the risk of tumours. This 'meta-analysis', by an American-Korean team, involved nearly 38,000 sub-jects and examined whether mobile phone users have a higher risk of malignant (cancerous) or benign tumours of, for example, the brain or head and neck.
Although the study found no overall link between mobile phones and tumour risk, on closer examina-tion, the researchers were able to discern a clear pattern. When they analyzed only the high-quality studies, excluding those that were less methodologically rigorous, the team found a "significant positive association"-in other words, a harmful connection between mobiles and tumours (J Clin Oncol, 2009; Oct 13; Epub ahead of print).
As study co-author Dr Joel M. Moskowitz told the Los Angeles Times, "I went into this really dubious that anything was going on . . . Overall, you find no difference. But when you start teasing the studies apart and doing these subgroup analyses, you do find there is reason to be concerned."
Indeed, according to the high-quality studies, mobile phone users had a 10-30 per cent greater risk of tumours compared with those who rarely or never used such phones. Also, the risk was highest among those who had used mobiles for 10 years or more.
In contrast, the poorer-quality studies found either no association, a negative association or even a "protective effect".
Interestingly, the high-quality studies were mostly conducted by oncologist Dr Lennart Hardell and his team in Orebro, Sweden, and were independent of industry funding, whereas the low-quality studies tended to come from the INTERPHONE project, a 13-country investigation that is partly funded by the Mobile Manufacturers Forum and the Global System for Mobile Communication Association (see box, page 8).
Although it's been maintained that the INTERPHONE study investi-gators are not influenced by funding sources, the "distinct pattern" evident in the US-Korean meta-analysis is likely to be more than just a coincidence.
While the Hardell studies found a harmful effect from mobile phones, the INTERPHONE studies curiously found a protective effect. Could it be that the study sponsors are influencing the design of the study to affect the results?
Although this is pure speculation, it is worth mentioning that most of the INTERPHONE studies were not blinded-the researchers knew which subjects had tumours and which did not. This is an important design flaw that may affect any findings. On the other hand, all of the studies by Hardell were blinded, making them much more reliable.
Getting what you pay for
This is not the first time that mobile-phone researchers have observed the so-called 'funding effect'-a result biased by the source of funding. In 2007, Dr Anke Huss and her team at the University of Berne, Switzerland, conducted a systematic review to determine the relationship between the source of funding and the results of studies into the health effects of mobile-phone use. They found that studies paid for by the mobile-phone industry were 10 times more likely to report no adverse effects compared with studies funded by public agencies or charities (Environ Health Perspect, 2007; 115: 1-4).
Dr Henry Lai, based at Washington University in Seattle, has observed a similar pattern of skewing. His database of biological studies conducted on mobile phones reveals a clear funding bias: the industry-funded studies found an effect in 28 per cent of the studies whereas the independently funded studies found an effect 67 per cent of the time.
As one researcher has put it, "The probability that this is a chance finding is extraordinarily minute" (Pathophysiology, 2009; 16: 137-47).
Not surprisingly, this is a com-mon phenomenon in scientific research, and numerous books and papers have been written about it. As Professor Lisa Bero of the University of California at San Francisco notes, "Industry groups are likely to communicate risks in a way that minimizes harm and reduces the chance that their products are regulated or restricted in any way" (Public Health Rep, 2005; 120: 200-8).
In particular, the bias observed in the mobile-phone studies echoes the findings of investigations into the influence of the tobacco industry on the research it funded. In a study by Bero, for example, which analyzed review articles published in the 1980s and 1990s on the health effects of passive smoking, whether or not a harmful effect was reported was strongly related to the authors' affiliations.
"The only factor associated with concluding that passive smoking is not harmful was whether an author was affiliated with the tobacco industry," the study said (JAMA, 1998; 279: 1566-70).
The funding effect could also explain why the research on mobile phones is so inconsistent. Indeed, some claim that many of the tobacco industry's techniques for manipulating data on risk-such as publishing only the findings that support their position while criticizing or suppressing those that don't-are also being employed by the mobile-phone industry. This means that, to answer the question of whether or not mobile phones are harmful to health, it all depends on who you ask.
The repeated facts
As it's difficult to trust the results of industry-funded research on mobile phones, it's crucial that we look at what the independent researchers have to say. Alarmingly, the message is highly consistent, and suggests that there's clearly cause for concern.
Much of the research is from Dr Hardell and his colleagues, and repeatedly shows that using mobile or cordless phones for 10 years or more significantly increases the risk of brain tumours.
Most recently, the group found a threefold greater risk of astrocyto-mas (tumours that start in the star-shaped glial cells) on the same side of the head as the phone is held among those using mobiles for more than 10 years. What's more, the risk of a brain tumour was highest-five times more likely compared with controls-among those who first started using a mobile under the age of 20. Similar results were found for acoustic neuroma, a tumour that affects the auditory (hearing) nerve (Int J Oncol, 2009; 35: 5-17).
Other significant findings by the Hardell group are that:
u for every 100 hours of mobile-phone use, the risk of brain cancer increases by 5 per cent (Int J Occup Saf Ergon, 2007; 13: 63-71);
u for every year of mobile phone use, the risk of brain cancer increases by 8 per cent (Int J Occup Saf Ergon, 2007; 13: 63-71); and
u after 10 or more years of digital mobile-phone use, there is a 280-per-cent greater risk of brain cancer (Int Arch Occup Environ Health, 2006; 79: 630-9);
According to a detailed report by the International EMF Collabora-tive, which reviewed Hardell's research (see Cellphones and Brain Tumours: 15 Reasons for Concern, Science, Spin and the Truth Behind INTERPHONE, at www.radiation research.org/pdfs/15reasons.asp), their findings are precisely what would be expected if mobiles lead to brain tumours; in particular:
u the higher the cumulative hours of mobile-phone use, the higher the risk (Int J Occup Saf Ergon, 2007; 13: 63-71);
u the greater the number of years since first mobile phone use, the greater the risk (Int J Occup Saf Ergon, 2007; 13: 63-71);
u the more power radiated from the mobile phone during use, the more the risk (Occup Environ Med, 2005; 62: 390-4);
u the greater the exposure (phone use on the same side of the head as the tumour), the greater the risk (Int Arch Occup Environ Health, 2006; 79: 630-9); and
u the younger the user, the higher the risk (Arch Environ Health, 2004; 59: 132-7).
Such consistency increases the credibility of their findings.
In contrast, most of the INTER-PHONE studies found that mobile-phone use protected against brain tumours. However, as Professor Bruce Armstrong, principal investi-gator of the Australian arm of the INTERPHONE study, stated in his keynote address to the Australian Centre for Radiofrequency Bio-effects Research (ACRBR) annual meeting in November, 2008, "Does anyone here know why mobile use protects against brain tumours . . . Does that sound plausible? Do you think it is at all likely, particularly to that extent? No! So, immediately, it tells you there is something wrong here, there's a problem here."
Indeed, 11 major design flaws have been identified, which may have compromised the study's results (see box, page 8).
Nevertheless, even the industry-funded INTERPHONE studies have found data that support the Hardell group's findings in some respects.
A results update, published online in October 2008, reported a "significantly increased risk" of some brain tumours "related to the use of mobile phones for a period of 10 years or more" in some studies. Findings in France and Germany show that those who started using a mobile a decade or more ago were roughly twice as likely to have a glioma. In addition, analysis of the pooled data from the Nordic countries and the UK showed a raised glioma risk with 10 or more years of mobile use, albeit only with 'ipsilateral use', when the phone was used on the same side of the head as where the tumour started.
For meningioma (tumours of the meninges, the membrane surround-ing the brain), six out of seven studies found a rise in risk when mobile-phone use started 10 or more years ago, while two of seven studies into acoustic neuroma reported similar patterns. One study found that ipsilateral mobile-phone use for 10 years or more resulted in a fourfold higher risk of acoustic neuroma (www.iarc.fr/en/research-groups/ RAD/INTERPHONE8oct08.pdf).
So, although the independent and industry-funded studies tend to be contradictory, in general, they appear to agree that long-term mobile use (10 years or more) is associated with an increased risk of brain tumours, particularly when that use is on the same side of the head as where the tumour develops.
This makes sense, as cancer usually takes years after the initial exposure to manifest, and it is also likely that the side of the brain on which the phone is usually held will have the highest radiation exposure and be the most vulnerable (Int J Oncol, 2009; 35: 5-17).
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