So what should you believe? Is the cell phone industry, like the tobacco industry in the past, covering up evidence for the harmful effects of cells phones?
It's not hard to find scare stories about cell phones and brain cancer. On the other hand, numerous randomized, double-blind studies have debunked extreme claims of negative health effects of EMF exposure.
So what should you believe? Is the cell phone industry, like the tobacco industry in the past, covering up evidence for the harmful effects of cells phones?
Let's start with the biology. Cancer generally requires mutation, i.e., DNA damage, and electromagnetic energy less energetic than high-energy UV does not have the capability to directly damage DNA. Cell phone signals, radio waves, WiFi - none of these have enough energy to break the chemical bonds that hold your DNA together.
This of course doesn't rule out indirect paths to brain cancer. Biology is messy, and there could easily be something more to this than the relationship between the wavelength and energy of photons. Perhaps cell phone signals influence some other (currently unknown) process going in your neurons, and that process ultimately results in DNA damage. Although there has been speculation about what such a process might be, there are no really obvious candidates, and currently there's not much evidence that unambiguously supports an indirect mechanism.
However, the absence of a known mechanism for a cell phone-cancer link doesn't mean that such a link doesn't exist. In the absence of a known mechanism, epidemiological studies might still be able to find such a link. Such studies are being conducted, but, overall, the results are inconclusive: some studies find an association between cell phones and cancer, others don't. There are a variety of methodological problems, like accurately surveying cell phone use over long time periods, that make answering this question tough. The biggest factor is time: current studies just haven't been carried on long enough, because 10 years ago cell phone use wasn't anything close to what it is now.
To get a feel for the evidence, take a look at the conclusions of some recent meta-analyses of cell phone-brain cancer studies:
Cellular phone use and brain tumor: a meta-analysis:
CONCLUSIONS: We found no overall increased risk of brain tumors among cellular phone users. The potential elevated risk of brain tumors after long-term cellular phone use awaits confirmation by future studies.
Epidemiologic evidence on mobile phones and tumor risk: a review:
Despite the methodologic shortcomings and the limited data on long latency and long-term use, the available data do not suggest a causal association between mobile phone use and fast-growing tumors such as malignant glioma in adults (at least for tumors with short induction periods). For slow-growing tumors such as meningioma and acoustic neuroma, as well as for glioma among long-term users, the absence of association reported thus far is less conclusive because the observation period has been too short
Long-term use of cellular phones and brain tumours: increased risk associated with use for > or =10 years:
Of the 16 case-control studies, 11 gave results for > or =10 years' use or latency period. Most of these results were based on low numbers. An association with acoustic neuroma was found in four studies in the group with at least 10 years' use of a mobile phone. No risk was found in one study, but the tumour size was significantly larger among users. Six studies gave results for malignant brain tumours in that latency group. All gave increased odd ratios (OR), especially for ipsilateral exposure. In a meta-analysis, ipsilateral cell phone use for acoustic neuroma was OR = 2.4 (95% CI 1.1 to 5.3) and OR = 2.0, (1.2 to 3.4) for glioma using a tumour latency period of > or =10 years. CONCLUSIONS: Results from present studies on use of mobile phones for > or =10 years give a consistent pattern of increased risk for acoustic neuroma and glioma. The risk is highest for ipsilateral exposure.
Mobile phone use and risk of glioma in adults: case-control study:
CONCLUSIONS: Use of a mobile phone, either in the short or medium term, is not associated with an increased risk of glioma. This is consistent with most but not all published studies. The complementary positive and negative risks associated with ipsilateral and contralateral use of the phone in relation to the side of the tumour might be due to recall bias.
Cellular phones, cordless phones, and the risks of glioma and meningioma (Interphone Study Group, Germany)
No excess of temporal glioma (p = 0.41) or meningioma (p = 0.43) was observed in cellular phone users as compared with nonusers. Cordless phone use was not related to either glioma risk or meningioma risk. In conclusion, no overall increased risk of glioma or meningioma was observed among these cellular phone users; however, for long-term cellular phone users, results need to be confirmed before firm conclusions can be drawn.
Time trends in brain tumor incidence rates in Denmark, Finland, Norway, and Sweden, 1974-2003:
From 1974 to 2003, the incidence rate of glioma increased by 0.5% per year (95% confidence interval [CI] = 0.2% to 0.8%) among men and by 0.2% per year (95% CI = -0.1% to 0.5%) among women and that of meningioma increased by 0.8% per year (95% CI = 0.4% to 1.3%) among men, and after the early 1990s, by 3.8% per year (95% CI = 3.2% to 4.4%) among women. No change in incidence trends were observed from 1998 to 2003, the time when possible associations between mobile phone use and cancer risk would be informative about an induction period of 5-10 years.
Mobile phone use and risk of tumors: a meta-analysis:
CONCLUSION: The current study found that there is possible evidence linking mobile phone use to an increased risk of tumors from a meta-analysis of low-biased case-control studies. Prospective cohort studies providing a higher level of evidence are needed.
Mobile phones and brain tumours: a review of epidemiological research
There are reports of small associations between MP-use ipsilateral to the tumour for greater than 10 years, for both acoustic neuroma and glioma, but the present paper argues that these are especially prone to confounding by recall bias. The reported associations are in need of replication with methods designed to minimise such bias before they can be treated as more than suggestive.
Unfortunately, we need to learn to make decisions in the presence of scientific uncertainty. Any cell-phone cancer links, if they exist, ought to become more clear within the next few as the long-term studies keep coming in. If a significant link isn't found by then, personally, I'll be satisfied, but my prediction is that, in the absence of a conclusive link, we'll continue to see debate and more studies that do little to resolve the question.
Read the feed:
/ 
Comments