Cell phones and cell phone towers have been the subject of much concern in the media about potential health issues. There have been a number of highly sensational statements from certain individual scientists and doctors about the risk of cancer from cell phone use. Some have gone so far as to claim the cell phone use is as harmful to health as smoking. These wild claims are not supported by the scientific evidence.
In fact studies to date have found no solid evidence for any link between cell phone use and cancer. Two basic types of epidemiological studies are have been used for assessing the risk of cell phones causing brain cancer. These are case-control and the cohort studies. For cell phones case control studies, patients with brain cancer are identified. These patients are then either given a questionnaire, or are interviewed, and are asked to recall from memory how much they used their cell phones over their lifetimes. Their answers are compared with a control group that does not have brain cancer. This type of study is subject to a number of potential sources of error. The most serious is "recall bias". Patients with brain cancer who have heard that cell phones might cause brain cancer may unconsciously overstate their past use. The cancer may also have affected their memory. In fact a case control study is only as good as people's memory.
The cohort type of study is much more robust. In this type of study a large number of subjects are identified before they have any illness. Their cell phone use is monitored for a number of years. At the end of the study, the cell phone usage of subjects who develop brain cancer is compared with those who are healthy. One of the best studies to date was a "retrospective" cohort study of 420,000 cell phone users in Denmark. Some had been using their cell phones for over 15 years. Researchers had access to both their cell phone and their medical records. There was no possibility of recall bias. No evidence of increased risk for brain cancer was found (see study #2 below).
Another strong piece of evidence is the fact that there has been no increase in the rates of brain cancer in the population. The European SCENIHR and the US National Cancer Institute (NCI) have issued statements to this effect. The following quote was taken from the latest Jan. 2009 report "Health Effects of Exposure to EMF" by the SCENIHR advisory committee of the European Commission (P. 24, also see Fig. 1 above): "Altogether, the data collected until now provide no evidence of an increased brain tumor risk. This is consistent with the observation that no visible increases are seen in the age specific incidence rates of tumors of the central nervous system in the Nordic countries over the last decade" In a recent Bulletin (Sept 23, 2008) the NCI stated: "There was no upturn in the incidence of brain or other nervous system cancers between 1987 and 2005, according to data from NCI's Surveillance, Epidemiology and End Results program". Fig. 1 above taken from P. 24 of the SCENIHR report shows that the incidence of brain cancer has remained constant from 1985 to 2004 - which covers the entire period since cell phones were introduced. Fig 2 was generated from the latest data on brain cancer and other nervous system cancer from the NCI's SEER database and covers the years 1975 - 2007. The vertical axis is annual cases per 100,000 all races & sexes. Several new studies based on brain cancer incidence continue to show no correlation between cell phone use and brain cancer. See the section on New Papers below. Also see the following humorous take on the brain cancer incidence data.
New papers confirm that the incidence of brain cancer has not changed since the introduction of cell phones
The first is from the US and covers the period 1992 - 2006. The second is from the UK and covers the period from 1998 - 2007. The third is from Israel and covers the period from 1980 - 2009.
1. Brain cancer incidence trends in relation to cellular telephone use in the United States Inskip et al. Neuro-Oncology 12(11):1147-1151, 2010
2. TimeTrends (1998-2007) in Brain Cancer Incidence Rates in Relation to Mobile Phone Use in England Vocht et al. Article first published in Bioelectromagnetics online 28 Jan 2011.
3. Changes in Brain Glioma Incidence and Laterality Correlates with Use of Mobile Phones - a Nationwide Population Based Study in Israel, Barchana et al., Asian Pacific J Cancer Prevention 13 (11), 5857 - 5863. Quote from the conclusion: "The approach we used, though based on semi ecological data, is in-line with other observations and does not support the assumption that mobile phone use is a causative factor for brain gliomas".
Flawed Israeli "study" on parotid tumors: No 4X increase
A recent letter to the Journal Epidmiology has generated publicity with the sensational claim that the number of parotid tumor cases quadrupled in Israel from 1970 - 2006. However this letter contains a number of serious flaws, that make any meaningful interpretation of cancer incidence impossible. This letter was submitted by a couple of individuals from the school of dentistry at Hebrew University, not by qualified epidemiologists. A letter such as this is not normally peer reviewed.There are several serious flaws with the way the data is presented. The data is presented as the total raw number of cases of parotid tumors per year in Israel, rather than the way an epidemiologist would; as an age adjusted incidence rate per 100,000. The authors themselves note that the population of Israel more than doubled in the study period. This fact alone would double the number of cases. In fact available statistics for all cancers in Israel show that the number of cases increased by 2.5X from 1980 - 2007 - which is 10 years less than the "study". Furthermore, there is no age adjustment in the "study".The authors mention yet another confounding factor that they did not factor into their graph, namely that the accuracy of diagnosis changed considerably during the study period. The "not otherwise specified" declined from 36% before 2001 to 13% during 2001 - 2006. This flaw could also inflate the number of cases by a large amount. When you add up all these confounding factors, it is impossible to conclude anything about the incidence rate of parotid tumors in Israel.
Does Cell Phone Use Alter Brain Activity?
A study entitled "Effects of Cell Phone Radiofrequency Signal Exposure on Brain Glucose Metabolism" has generated news headlines such as this story in the NY Times. This study purports to show that brain activity (technically glucose metabolism) increased in areas of the brain closest to a cellular telephone. There are a number of potential problems with this study. Some of these are covered in the following article: "Chatting on your cell phone may boost brain metabolism". The British National Health Service has also published a commentary on this study: Mobiles `increase brain activity'.
The study used PET scans to produce images of glucose metabolism through a "slice" of the brain. Changes in glucose metabolism were measured with a cell phone on for 50 minutes vs. being off. The size of the glucose increase reported in the study is quite small (35.7 vs 33.3 mol/100 g per minute). The authors report that other studies similar to theirs have had "yielded variable results". Some have "reported increases, decreases and increases, or no changes in CBF". Like all preliminary findings, these results must be repeatable to be accepted as real. There is a long history of preliminary false "positive" findings of cell phone EMF on biological processes that failed attempts at replication.
There are a couple of basic problems with the data underlying this study. The authors misreported the SAR value for this model of cell phone. The authors reported a SAR value of 0.901W/kg, according to the manufacturer's report the correct value for the right side of the head is 0.769W/kg. More importantly, it is highly unlikely that the cell phone was operating at peak power. Typically, a cell phone will operate at around 1% of peak power. The authors did not make any measurement of the actual SAR for this study. The map of the electric field shown in Fig 1 cannot be correct. The authors state that this was calculated: "using the far-field approximation, of a dipole field". This is a method that is more than 20 years old and is not considered valid for a cell phone next to the head. Experts in this area use much more advanced models for calculating field strength distribution maps. These deficiencies are indications that this study is poorly designed and that the authors did not consult with any experts in the testing of cell phones.
The authors of this study note that the increase in glucose activity seen here is actually less dramatic than that seen when the brain goes to work on a visual task. This indicates that the PET scan is very sensitive since even simple visual stimulation can increase brain metabolic activity. It is likely that temperature rise can also influence this activity. Numerical computations indicate that the steady state temperature increase in the brain due to cell phone EMF at the 1.6W/kg limit can be 0.1 C at the highest spot. But during a 50 minute phone call, it has been shown that there is a several degrees Celsius temperature rise on the cheek and ear after a 30 minute call due to the blocking of air circulation and also heating of the cell phone itself due to its internal power consumption. The heat conducted from the phone to the head can be significant. So another possible explanation for this result is that heat directly or indirectly due to the cell phone is what causes the slight change in metabolism.
The following is from a commentary on this study by the British National Health service: "Any increased activity in the brain cells due to thinking, for example, could have led to this difference, and the wide confidence interval suggests that the difference in metabolism could have been as low as 0.67/33.3 μmol/100 g per minute or 2%." "It is possible that the participants could tell if the phone was on or off or receiving a call even if they were set to silent. For example, the phone that was turned on may have been warmer. This was not tested or reported by the researchers. This is important because knowing whether the phone was making a call could have influenced the underlying brain activity."
The lack of control for heat is another indication of poor study design. The authors should have at least repeated the tests with a heat source that was equivalent to the active cell phone in order to control for this variable. The physics of the effects of cell phone EMF is well understood. Heating is the only plausible effect. The small direct and indirect heating effects from cell phones do not cause harm. The glucose change may simply be the body's response to this heat. The authors of this study concede that their findings are "of unknown clinical significance". In other words, assuming that their findings are correct, it is not clear that there are any harmful effects on health.
Included below are links to a number of studies and documents related to cell phones.
1. New Danish Cell Phone study: There was no substantial change in brain tumor incidence among adults 5 to 10 years after cell phone usage sharply increased, according to a new brief communication published online December 3 in the Journal of the National Cancer Institute. These findings are essentially the same as those from the NCI and SCENIHR cited above. Study summary.
2. Danish Cell Phone Study: This "retrospective" cohort study was published in the Dec. 6, 2006 issue of the Journal of the National Cancer Institute. This is probably the most reliable epidemiological study on cell phones and cancer to date. From the abstract: The widespread use of cellular telephones has heightened concerns about possible adverse health effects. The objective of this study was to investigate cancer risk among Danish cellular telephone users who were followed for up to 21 years. Methods: This study is an extended follow-up of a large nationwide cohort of 420 095 persons whose first cellular telephone subscription was between 1982 and 1995 and who were followed through 2002 for cancer incidence. Conclusions: We found no evidence for an association between tumor risk and cellular telephone use among either short-term or long-term users. Moreover, the narrow confidence intervals provide evidence that any large association of risk of cancer and cellular telephone use can be excluded.
3. The Interphone series of case control studies are an international collaborative effort coordinated by the IARC to assess the health risks of cell phones. Groups from 13 countries including Australia, Canada, Denmark, Finland, France, Germany, Israel, Italy, Japan, New Zealand, Norway, Sweden and the UK are conducting a series case-control studies for a variety of cancers. The results to date for the Interphone series of studies do not show any clear increased health risk. However research is ongoing for long term use greater than 10 years. The final report has been delayed. There has been much speculation in the media fueled by alarmists about this study. One of the researchers participating in the Interphone study stated recently that: "the study has not yet confirmed whether or not there is an increased risk of cancer from mobile phone use." "There is ... absolutely no information circulating at the moment that is accurate and correct with respects to the results of that study." It is important to understand that a difficulty with this type of study is that it relies on brain cancer patients to recall how much they used their cell phones over their lifetimes. Patients who have brain cancer, and have heard media reports of a possible association between cell phones and brain cancer, may unconsciously overstate their cell phone use and skew the results. This is what is termed recall bias. The Danish cell phone study is much more robust because it used actual cell phone records.
News: The final Interphone Study has just been released See our special web page.
Statements about cell phones & health from public health authorities
The following is a list of links to statements issued by the public health authorities of various countries about cell phones and health. The message from each of them is essentially the same. There is no significant evidence to date of harmful health effects due to cell phones. However research is on going for longer term use. It should be noted that available statistics for the US and Canada (up to 2007) show a slight decrease in the annual number of newly diagnosed malignant brain tumors.
1. The American Cancer Society statement on cell phones & health.
2. US FDA statement on cell phones & health.
3. US National Cancer Institute NCI statement on cell phones & health and a recent update: Cell Phones and Brian Cancer: What do we know?
4. US Centers for Disease Control CDC statement on cell phones and health.
5. Health Canada information document on Safety and Safe Use of Cellular Phones.
6. The SCENIHR advisory committee of the European Commission has published an updated 83 page report dated Jan. 2009 entitled Health Effects of Exposure to EMF. The following is a quote from the Abstract P. 4. "It is concluded from three independent lines of evidence (epidemiological, animal and in vitro studies) that exposure to RF fields is unlikely to lead to an increase in cancer in humans. However, as the widespread duration of exposure of humans to RF fields from mobile phones is shorter than the induction time of some cancers, further studies are required to identify whether considerably longer-term (well beyond ten years) human exposure to such phones might pose some cancer risk."
7. The SCENIHR advisory committee of the European Commission has published summary for the public on the issue of EMF & health dated March 2007. The following is a quote concerning cell phones and cancer risk: "Research indicates that a person who has used a mobile phone for up to 10 years does not have a higher risk of brain tumors or other cancers in the skull. This also appears to be the case for someone who has used a mobile phone for more than 10 years but more research is needed to confirm this."
8. The Health Council of the Netherlands published a 96 page report on Mobile Phones, an evaluation of health effects. The following statement is taken from the Executive Summary: "Mobile telecommunication has developed considerably in recent years: to date over half the population of the Netherlands posses a mobile telephone. Nevertheless, concerns also grow, particularly as to whether exposure to electromagnetic fields from antennas and mobile telephones can adversely affect health. In this advisory report, the Electromagnetic Fields Committee of the Health Council of the Netherlands provides, on the basis of the scientific literature, an overview of various aspects that may play a role. The Committee comes to the conclusion that there is at present no reason for concern. However, since mobile telephony leads to widespread electromagnetic field exposure and relatively little knowledge exists on, especially, long term effects; it indicates areas for further research."
Papers by Hardell et al.
Hardell et al. have been the authors of a number of studies that claim to have found an increased risk of certain brain cancers associated with long term use of cell phones. Hardell himself is one of the lead authors of the Bio-Initiative Report. Some of the Hardell et al. studies have been criticized in the scientific community because of "recall bias". All of Hardell's studies are of the case control type. Patients who have been diagnosed with brain cancer fill in a questionnaire in which they are asked to remember how much they used their cell phones. The US FDA had this to say about Hardell et al.'s methodology: "The results reported by Hardell et al. are not in agreement with results obtained in other long term studies. Also, the use of mailed questionnaire for exposure assessment and lack of adjustments for possible confounding factors makes the Hardell et al. study design significantly different from other studies." The SCENIHR scientific advisory group to the European Commission stated that this study was: "non-informative because of inappropriate exclusion criteria and combination of studies". Another scientific consortium advising the European Commission, the EMF-NET issued a formal statement criticizing the same recent Hardell et al. paper in which they questioned its statistical methods.
Hardell et al.'s latest study, just published in the journal Pathophysiology, appears to use a methodology that is similar to their previous studies. The new Hardell et al. paper actually criticizes the Interphone series of studies, which is an international collaborative effort coordinated by the IARC to assess the health risks of cell phones. It even suggests that cancer patients in the Interphone studies underestimated their use of cell phones, whereas in Hardell et al.'s studies they did not. This clearly indicates the main problem with this type of study, namely recall bias. The results to date for the Interphone studies do not show any increased health risk. The latest Hardell et al. paper also excluded two very important studies from their meta analysis. These studies did an objective analysis of the medical records of 420,000 cell phone users in Denmark and found no evidence for any increased cancer risk. These Danish studies did not use subjective questionnaires. Hardell himself has earned fees as an "expert" witness in litigation against cell phone companies. In 2002 his testimony in a lawsuit which sought $800M in damages for a single brain cancer patient was resoundingly rejected by the judge for lacking in scientific credibility.
It should be noted that Hardell et al. have promoted their studies in the mass media with the claim that they have been published in scientific peer reviewed journals. The implication is that their studies have a high degree of scientific credibility. It should be noted that there are literally thousands of scientific journals. There are wide differences in editorial standards and credibility among the various journals. Just because a study is published in a "peer reviewed" journal, does not necessarily mean that its findings are valid. Hardell et al.'s papers have been strongly criticized by a number of public health bodies. They are not generally accepted by the scientific community.
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