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The Danish Cohort Cell Phone and Cancer Study


The Flawed Danish Cohort Cell Phone and Cancer Study Design Invalidates Conclusions



The Danish Cohort cell phone and cancer study was originally funded by Two Danish Telecom Companies and an industry-linked organization, the International Epidemiology Institute.

  • The Danish Cohort study was established with support from two Danish telecom operating companies—TeleDenmark Mobil (partially owned by SBC Communications, which is Denmark’s largest phone company) and Sonafon. This support is stated in the first 2001 Danish Cohort publication.
  • The study was conducted by the industry-friendly International Epidemiology Institute (IEI) known as an industry defense firm as IEI studies were funded by an industry making a product, found “no” or “unclear”  evidence of a problem and were used in legal battles.  Read more about IEI later on this webpage.
  • Co-author to the Danish Studies epidemiologist Christoffer Johansen also received  personal fees from industry in relation to his work on EMF and leukemia regarding powerline frequencies. “In the period 1994 to 2004, I have received funding from the Danish Energy Agency to investigate the risk of a number of diseases among Danes with employment with Danish electricity companies, as well as means to investigate the risk of cancer among children residing close to high voltage electrical installations.” A disclosure note from 2010 shows he has received personal industrial fees from the electric industry four times in the period 1994-2010- despite his status as a consulting consultant for the National Board of Health within the same topic. A report he co-authored was used by the electricity industry to assess the safety of a high voltage grid upgrade in Denmark.He also signed a disclosure for a contract in 2017.

    “I have for the last 20 years 1999, 2006 and 2010 conducted a review and assessment of scientific literature that highlights the connection between exposure to electromagnetic field and health effects for the advisory engineering firm COWI…I signed in 2017 a contract with COWI for an  update to this report and also informed the National Board of Health about that contract.” 2017 Disclosure

  • The Danish Cohort cell phone and cancer study has major design flaws that render the study’s conclusions invalid.
Danish Cohort Cell Phone and Cancer Study
Note: This webpage lists supporting published documentation for all statements. Scroll down to see citations.

A cohort of cell phone “exposed” persons was established based entirely on two Danish telecom operating companies’ cell phone subscriptions from 1982 to 1995. Health records were reviewed and the exposed groups risk was compared to the corresponding risk within the rest of the adult population—with follow-ups published in 2002 and 2007 and 2011. This study found no evidence of any increased risk of brain or nervous system tumors or any cancer among mobile phone subscribers.

  • The design of the study was financially supported by two Danish telecom operating companies TeleDenmark Mobil (partially owned by SBC Communications, which is Denmark’s largest phone company) and Sonafon.
  • A 2019 expose documents the telecom and electricity company industry funding to one of the key researchers- Christoffer Johansen.
  • Epidemiology Institute scientists have put forth years of “documentation” supporting  “no proof of harm” for  various industries—such as with the herbicide glyphosate, breast implants, menthol cigarettes, uranium mining, and others.

Corporate Users in the Control Group:

The study design was to divide people into two groups: one group was considered exposed to cell phone radiation, and the control group was considered unexposed to cell phone radiation. However, the starting cohort of 723,421 “exposed” people excluded corporate subscribers (people who used cell phones as part of their job). More than 200,000 corporate subscribers, who likely were heavy cell phone users, were placed in the control group, as if they were to be considered “unexposed” to cell phone radiation.

The supposedly unexposed control group was “contaminated” with these corporate cell phone users. The study authors even state, “Because we excluded corporate subscriptions, mobile phone users who do not have a subscription in their own name will have been misclassified as unexposed.”

Furthermore, because over two-thirds of the subscriptions began in 1994 and 1995, the majority of the cohort members had 2 years or less of subscription time.

Decade Long Users of Cell Phones In The “Unexposed” Group:

1995 was the cut-off year for establishing the cohort. The paper states, “individuals with a subscription in 1996 or later were classified as non-users.” Therefore, any person who bought a cell phone subscription after 1995 was placed in the control group. For example, say an individual within the study was diagnosed with brain cancer in 2007. If that person got their first phone in 1996 (one year after the Danish cohort cut-off) then that person would be considered as a non-exposed individual who developed brain cancer. Whereas, in reality, this individual was exposed to a cell phone for 11 years and developed brain cancer. In other words, all the individuals who acquired their first cell phone subscription after 1995 were misleadingly part of the “unexposed” control group.

Exposure Information Was Inadequate To Characterize An Individual’s Total RF Exposure:

  • No information was gathered on how often or for how long each day an individual used a cell phone over the years investigated by the study. The information on cell phone exposure for those in the “exposed”  group was merely the starting date of their cell phone subscription and the length of the cell phone subscription. Consequently, individuals who rarely used their cell phone and others who were heavy cellphone users were placed into the same “exposed” group.
  • No information was gathered on cordless landline phone use. Cordless phones expose the user’s brain to radiofrequency radiation, and cordless home phone use has exponentially increased over the years. Dr. Hardell’s Swedish studies gathered data on this exposure by analysing information on home cordless phone use in addition to cell phone use. However, in the Danish Cohort, these cordless phone radiofrequency exposures were not included in the analysis, and thus persons who used a cordless phone for multiple hours a day over the span of ten years could be considered “unexposed”.
  1. The Danish Cohort Cell Phone and Cancer Study has been heavily criticized by scientists worldwide.
    Scientists have criticized the study’s flawed design from the beginning. After the 2006 update was published, scientists (Anders Ahlbom, Maria Feychting, Elisabeth Cardis and Paul Elliott) wrote a letter to the Journal of the National Cancer Institute (JNCI) criticizing the research because a “large proportion of the population started to use mobile phones after the cohort was defined and thus are included in the reference population” and that the “same problem applies also to corporate users, who are not included as subscribers in the study.” They conclude, “All these circumstances would dilute any excess risk, were it to exist, and push the estimate toward the null.”The 2011 Danish Cohort publication was heavily criticized by Devra Davis, Denis Henshaw, Ron Herberman, Margaret Meade Glaser, Vini Khurana, Dariusz Leszczynski, Philippe Charlier, Allan H. Frey, Lloyd Morgan and Alasdair Philips in several letters to the editor, and all pointed out serious flaws in the design of the study that invalidate the conclusion made by the Danish Study authors.Dariusz Leszczynski, Research Professor at Finland’s Radiation and Nuclear Safety Authority, wrote a 2011 letter to the British Medical Journal  outlining the “several design flaws that should prevent the authors from any conclusions concerning the impact of mobile phone use on the development of brain cancer.” Leszczynski published an opinion in The Scientist magazine entitled Scientific Peer Review in Crisis. The case of the Danish Cohort“ asking “How is it possible that the British Medical Journal allowed such a poor quality peer review?” and “Why, once alerted to serious design flaws by readers, have BMJ editors not taken any action?…”Dr. Christopher Portier, former Director of the Environmental Toxicology Program (ETP) at the United States NIEHS and Associate Director of the United States National Toxicology Program (NTP), commented on the Danish Cohort in his plenary lecture at the BioEM 2015 Conference, pointing out the “Serious problem with exposure misclassification of the Danish Cohort” in his slide presentation. According to  Dariusz Leszczynski, who was present at the meeting, Portier considered the Danish Cohort “useless for any decision making because of the serious misclassification of “exposures.”
  2. In light of these shortcomings, in 2011 the World Health Organization International Agency for the Research on Cancer (IARC) minimized the Danish Cohort findings in their evaluation of cell phone radiation cancer risk. The Danish Cohort design flaws were cited as a reason to give less weight to the Danish study in comparison to the Interphone study and Hardell’s efforts. IARC’s Robert Bann wrote that the Danish cohort exclusion of the corporate subscribers “seems remarkable” and “could have resulted in considerable misclassification in exposure assessment.”

The Danish Cohort Cell Phone and Cancer Study cannot be used as proof of no evidence.


John Boice PhD, scientific director of the IEI, was lead researcher of the Danish study, and as of 2017 he is President of the National Council on Radiation Protection and Measurements (NCRP). NCRP’s 1986 Report No. 086 – Biological Effects and Exposure Criteria for Radiofrequency Electromagnetic Fields was key to the development of US radiofrequency radiation guidelines, and NCRP staunchly supports the opinion that low-level radiation is not harmful. In 2014, NCRP officers pressured the US Center for Disease Control staff to retract cautionary recommendations about reducing exposure to cell phone radiation emissions.

IEI has consistently supported industry and is often funded to research health effects, by funds from the same companies that created the product or exposure being investigated. In 2007, the American Journal of Industrial Medicine published an article by Dr. Lennart Hardell, who documents the conflicts of interest and connections to the cellphone industry of the privately-owned IEI. IEI’s pro-industry stance is well known, and IEI scientists have put forth years of “documentation” that supports the “no proof of harm” stance claimed by various industries—such as with the herbicide glyphosate, breast implants, menthol cigarettes, uranium mining, and others. Until October 15, 2000, IEI listed “Corporate Counseling” and “Litigation Support” among the list of services published on its website.

As an example of this corporate commissioned science, IEI scientists Boice and McLaughlin published a study on the mortality of aircraft manufacturing workers and found “no clear evidence” (First in 1999 with a 2011 follow up). This study was funded by Lockheed Martin Corporation at a time when the aerospace firm faced “a slew of claims” related to health concerns.  Lockheed Martin already had paid $60 million to residents and $33 million to workers in confidential out-of-court settlements.  The company still claimed there was “no evidence.” Similarly,  after a  1999  University of California at Los Angeles  cohort study of workers at Boeing’s Rocketdyne/Atomics International facilities found a significantly elevated risk of lung cancer among workers, Boeing chose IEI and Boice to  lead  a  study  (funded by Boeing and the US Air Force) to confirm these findings. IEIs follow up study  failed to find “no convincing evidence”.  IEI has been referred to as a classic “Product Protection Firm”—a term used in the book Doubt Is Their Product.



Hardell, Lennart, Michael Carlberg and David Gee. “Chapter 21: Mobile phones and brain tumour risk: early warnings, early actions?” In “Late lessons from early warnings: science, precaution, innovation.” European Environment Agency, 2012.

Söderqvist, Fredrik, Michael Carlberg, and Lennart Hardell. “Review of four publications on the Danish cohort study on mobile phone subscribers and risk of brain tumors.” Reviews on Environmental Health, vol. 27, no. 1, 2012, pp. 51-8.

  • Results: The nationwide Danish cohort study on mobile phone subscribers and risk of brain tumors, including at best 420,095 persons (58% of the initial cohort), is the only one of its kind. In comparison with previous investigations, i.e., case-control studies, its strength lies in the possibility to eliminate non-response, selection, and recall bias. Although at least non-response and recall bias can be excluded, the study has serious limitations related to exposure assessment. In fact, these limitations cloud the findings of the four reports to such an extent that render them uninformative at best. At worst, they may be used in a seemingly solid argument against an increased risk – as reassuring results from a large nationwide cohort study, which rules out not only non-response and recall bias but also an increased risk as indicated by tight confidence intervals.
  • Conclusion: Although two of the most comprehensive case-control studies on the matter both have methodological limitations that need to be carefully considered, type I errors are not the only threats to the validity of studies on this topic – the Danish cohort study is a textbook example of that.

Hardell L., et al. “Secret ties to industry and conflicting interests in cancer research.” American Journal of Industrial Medicine, vol. 50, no. 3, 2007, pp. 227–33.

“Another example of industry ties to research, but not one where there was a failure to disclose, involves the potential association between cellular phones and brain tumors. In 2002 the Swedish Radiation Protection Authority (SSI) hired two US epidemiologists to review published epidemiological studies on the relationship between the use of cellular telephones and cancer risk. They were Dr. John D. Boice, Jr. and Dr. Joseph K. McLaughlin from the private company International Epidemiology Institute (IEI).”

“A number of research projects have taken place at the Karolinska Institute, Stockholm with participation of Boice and McLaughlin, with a funding model through IEI. One of the studies was published in British Medical Journal [Nyre´n et al., 1998] with Adami as a co-author. A cohort of Swedish women with breast implants was studied with regard to connective tissue disease. No risk was found. Thanks to strict rules of stating conflicts of interest in the British Medical Journal it can be seen that the project was initiated by IEI, and that the funding from IEI was on behalf of Dow Corning, producer of silicon breast implants.” Hardell L., et al 2007

Levis, Angelo G., et al. “Mobile phones and head tumours. The discrepancies in cause-effect relationships in the epidemiological studies – how do they arise?” Environmental Health, vol. 10, no. 59, 2011.

  • “Conclusions: Our analysis of the literature studies and of the results from meta-analyses of the significant data alone shows an almost doubling of the risk of head tumours induced by long-term mobile phone use or latency.”
  • “Furthermore, other negative studies quoted in the present article have been supported by the mobile phone industry, for example the two Muscat studies [36,37] (Cellular Industry Telecommunications Association via the Wireless Technology Research) [19,62], the Johansen study [59] (TeleDanmark Mobil, Sonofon and the International Epidemiology Institute, a private company operating as a cell-phone industry adviser), and the Morgan study [58] (Motorola).”

Philips A, and G. Lamburn. “Updated study contains poor science and should be disregarded.” BMJ, vol. 343, 2011.

Ahlbom, Anders, et al. “Re: Cellular telephone use and cancer risk: update of a nationwide Danish cohort study.” Journal of the National Cancer Institute, vol. 99, no. 8, 2007, pp. 655.

Kundi, Michael. “Re: Cellular Telephone Use and Cancer Risk: Update of a Nationwide Danish Cohort.” Journal of the National Cancer Institute, Letter to the Editor, 2006.

Leszczynski, Dariusz. “Re: Use of mobile phones and risk of brain tumours: update of Danish cohort study.” BMJ, vol. 343, 2011.

Davis, Devra, Ronald Herberman and Yael Stein. “Re:Not enough data excluding cellphones’ morbidity.” Review of Use of mobile phones and risk of brain tumours: update of Danish cohort study, by Schuz, et al. BMJ, vol. 343, 2011.

Henshaw, Denis. “Mobile phone radiation could be detected by the human brain.” Review of Use of mobile phones and risk of brain tumours: update of Danish cohort study, by Frei, et al. BMJ, vol. 343, 2011.

Khurana, Vini. “Danish cohort study: Questions regarding selection, exposure, and tumour incidence.” Review of Use of mobile phones and risk of brain tumours: update of Danish cohort study, by Frei, et al. BMJ, vol. 343, 2011.

Frey, Allan H. “On the Safety of Cell Phone Radiation.” Review of Use of mobile phones and risk of brain tumours: update of Danish cohort study, by Frei, et al. BMJ, vol. 343, 2011.

Morgan, Lloyd L. “The Danish Cellphone Subscriber Study on the Risk of Cancer Among Subscribers Is Fundamentally Flawed.” Review of Use of mobile phones and risk of brain tumours: update of Danish cohort study by Frei, et al. BMJ, vol. 343, 2011.

Reviews of “Use of mobile phones and risk of brain tumours: update of Danish cohort study” by Frei, et al. BMJ, vol. 343, 2011.



Scientists have repeatedly documented the flaws of the Danish Cohort Cell Phone and Cancer Study design and the financial ties between industry and the Danish Cohort Study. According to Dr. George Carlo—the epidemiologist who formerly headed the $28 million Wireless Technology Research program—“John Boice and his colleagues have been on the cell phone industry payroll, and for big money, since the late 1990’s. The money laundering vehicle is the International Epidemiology Institute…” Please see examples below.

Nilsson, Mona. “The EU-report SCENIHR a scientific fraud paving the way for business as usual.” 2015.

Slesin, Louis. “The Danish Cohort Study: The Politics and Economics of Bias.” Microwave News, 2011.

Leszczynski, Dariusz. “Scientific Peer Review in Crisis. The case of the Danish Cohort“. The Scientist, 2013.

“Critical Comments by Leading Experts on Danish Study Claiming to Find No Link Between Cell Phone Use and Brain Tumors.” Electromagnetic Health, 2011.

Carlo, George. “Dr. George Carlo’s Response to the Danish Study.” EMF Health.

Clapp, Dick. “Food Fight over Conflict of Interest Article.” The Pump Handle, 2007.

“The Danish Cohort Study:The Politics and Economics of Bias.” Microwave News, 2011.


Morris, Jim. “Toxic Smoke and Mirrors: Overexposure to manganese has caused Parkinson’s-like symptoms for thousands of welders. So why does the welding industry still get a free chemical pass?” Mother Jones, 2008.

Guccione, Jean. “Burbank Pollution Dogs Lockheed Years Later.” Los Angeles Times, 05 Oct. 2000.

Leovy, Jill. “Residents Voice Fears of Health Risks Due to Lockheed Cleanup.” Los Angeles Times, 27 June 1997.

“Rocketdyne Worker Health Study: International Review Board and Other Human Subjects Committee Approvals, Appendix I.” International Epidemiology Institute, 13 July 2005.

Davis, Scott, et al. “Follow-On Rocketdyne Worker Health Study: Science Committee Summary.” 19 March 2005.


Johansen, Christoffer, et al. “Cellular telephones and cancer—a nationwide cohort study in Denmark.” Journal of the National Cancer Institute, vol. 93, no. 3, 2001, pp. 203-7.

Schüz, Joachim, et al. “Cellular telephone use and cancer risk: update of a nationwide Danish cohort.” Journal of the National Cancer Institute, vol. 98, no. 23, 2006, pp. 1707-13.

Schüz J, et al. “Risks for central nervous system diseases among mobile phone subscribers: a Danish retrospective cohort study.” PLoS One, vol. 4, no. 2, 2009, e4389.

Schüz J, and C. Johansen. “A comparison of self-reported cellular telephone use with subscriber data: agreement between the two methods and implications for risk estimation.” Bioelectromagnetics, vol. 28, no. 2, 2007, pp. 130-6.

Schüz J, et al. “Long-term mobile phone use and the risk of vestibular schwannoma: a Danish nationwide cohort study.” American Journal of Epidemiology, vol. 174, no. 4, 2011, pp. 416-22.

Frei, Patrizia, et al. “Use of mobile phones and risk of brain tumours: update of Danish cohort study.” BMJ, vol. 343, 2011, d6387.