The Science (in brief)

Key details of the science informing the study are shown below. For more in-depth information about the evidence base and research agenda driving COSMOS please visit our Science page.

Mobile phones and other wireless technologies (e.g. tablets, laptops, cordless phones) are sources of electromagnetic fields (EMF). It is exposure to these electromagnetic fields when using a mobile phone that is the main scientific interest in this study. Electromagnetic fields can arise from natural sources (such as lightning, or from the Earth’s magnetic field) but it is EMF from man-made sources that we are interested in.

Mobile phones and EMF
Mobile phones make use of EMF by converting your voice or text into an electrical signal, which is then transmitted as radio waves and converted back into sound or text. However, to send a long-distance radio signal takes a lot more power than most phones are able to provide, and alone, a phone is only able to transmit a short distance. To get around this problem, mobile phone masts are used to pick up the weak signal and relay it onwards across a network of masts until it gets to its destination – all in a matter of milliseconds.
The electromagnetic spectrum
There are many different types of EMF, ranging from mostly harmless low frequency waves (non-ionizing radiation) to dangerous high frequency waves (ionizing radiation) that can damage cells and DNA. The frequency (measured in Hertz (Hz)) of radiation, is the number of waves that travel through a certain point in a given length of time. Depending on the frequency, these waves can be hundreds of metres long or smaller than an atom. However, even high frequency radiation has many uses, such as for medical X-Rays or nuclear power, as illustrated in the diagram below.
Mobile phones belong in the radio frequency (radio wave) part of the spectrum, which we primarily use for communications (e.g. TV and radio).
Ionizing and non-ionizing radiation
Ionizing radiation includes gamma rays, X-rays, and ultraviolet rays. These rays can break chemical bonds between atoms to produce ions – hence the term ‘ionizing’. Scientific evidence is clear that exposure to ionising radiation can cause cancer, with risk to health depending on the dose of ionising radiation received. Risks from low doses are actually small and ionising radiation is widely used in cancer therapy.
Non-ionising radiation includes radiowaves, microwaves, infrared and visible light. This type of radiation cannot break chemical bonds, but can cause heating.
Potential risks
We know that when we are exposed to radio frequency waves, some of the transmitted energy is absorbed into our heads and bodies. As there is still no clear answer as to whether there are any possible health effects from non-ionising radiation, studies that are investigating this area, such as COSMOS, are hugely important.

Evidence Base

Many reviews have concluded that there is no convincing evidence to date that mobile phones are harmful to health in the short term. However, the widespread use of mobile phones is a relatively recent phenomenon and it is possible that adverse health effects could emerge after ten years or more of prolonged use. The evidence base necessary to allow us to make firm judgments regarding use in the longer-term has not yet been accumulated, and this question can only resolved by monitoring the health of a large cohort of phone users over a long period of time.

IARC announcement
The current research agenda
Key reviews of research to date
IARC announcement
  • In May 2011 the International Agency for Research on Cancer (IARC) announced in a press release (1) that it had classified radiofrequency electromagnetic fields as possibly carcinogenic to humans (Group 2B).
  • The group reviewed the scientific literature and concluded that there was limited evidence of carcinogenicity among users of wireless telephones for glioma and acoustic neuroma, but inadequate evidence to draw conclusions for other types of cancers.
  • IARC concluded that a close watch should be kept for a link between mobile phones and cancer risk and that it is important that additional research be conducted into the long-term, heavy use of mobile phones.
  • A commentary on Mobile Phones and Cancer was also published in 2014, ‘Next Steps After the 2011 IARC Review’ (2), and the authors ‘made the call for more research’, recognising prospective cohort studies like COSMOS as essential for a valid assessment of exposure.
The current research agenda
  • In 2010, the World Health Organization (WHO) published a new research agenda for radiofrequency (RF) fields (3). This agenda sets out the priorities for health effects research relating to RF exposures, which include the use of mobile phones.
  • In terms of epidemiological research, the WHO agenda identifies the COSMOS study as one of the most important studies currently ongoing in this field, and the study continues to be classified as high priority in order to evaluate potential long-term risks of mobile phone use.
Key reviews of research to date
  • 2000 - The Stewart Report (4), a major report on mobile phones and health, was published by the UK Independent Expert Group on Mobile Phones.
  • 2005 – Following on from the Stewart Report, a further review of mobile phones and health was undertaken by the Advisory Group on Non-Ionizing Radiation (AGNIR) (5) and published by the National Radiological Protection Board (NRPB).
  • 2007 - The independent Mobile Telecommunications and Health Research programme (MTHR) (established in 2001 following the Stewart Report) published a report (6) describing research undertaken as part of its programme. None of the published research supported by MTHR demonstrates biological or adverse health effects produced by radiofrequency exposure from mobile phones.
  • 2009 - Reports reviewing mobile phones and health research were published by both The International Commission on Non-Ionizing Radiation Protection (ICNIRP) (7) and The Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR) (8). The report by ICNIRP concluded that studies published to date do not demonstrate an increased risk for any head tumour. However, the Commission notes that the observation period for slow-growing tumours has been too short for the absence of associations reported so far to be considered conclusive.

UK Research Team

Professor Paul Elliott
Professor Paul Elliott
Principal Investigator, Head of Department of Epidemiology
Professor Paul Elliott, MBBS, PhD, FMedSci, trained in clinical medicine and epidemiology as a Wellcome Trust Clinical Fellow at St Mary's Hospital London and the London School of Hygiene & Tropical Medicine.

He studied for his PhD in Epidemiology on the INTERSALT Study under the mentorship of Professor Geoffrey Rose. He remained at the London School working as a lecturer, then senior lecturer and reader in epidemiology before becoming Head of the Environmental Epidemiology Unit at LSHTM 1990. In 1995 he was appointed to the Chair in Epidemiology and Public Health Medicine at Imperial College London. He heads what is now the Department of Epidemiology and Biostatistics in the School of Public Health. The Department has expanded significantly during recent years to encompass a wide-ranging programme of health research and extensive collaborations with honorary and visiting staff. Paul Elliott is also Director of the MRC-PHE Centre for Environment and Health which sits within the Department and includes the Small Area Health Statistics Unit (SAHSU). He is also an honorary consultant in public health medicine in the Directorate of Primary Care and Public Health of the Imperial College Healthcare NHS Trust and the academic lead for the Biobanking research theme for the Imperial NIHR Biomedical Research Centre. He was recently appointed as the Academic Health Sciences Centre's (AHSC) Director of Information Governance.

Professor Mireille B Toledano
Professor Mireille B Toledano
Co-Principal Investigator, Reader in Epidemiology
Professor Mireille Toledano is a reader in epidemiology at Imperial College London and an investigator of the MRC-HPA Centre for Environment and Health specialising in environmental and spatial epidemiology.

She was awarded her undergraduate degree from University College London, a Master's degree in environmental epidemiology from the London School of Hygiene and Tropical Medicine, and her PhD from Imperial College London. She is currently a Fellow of the Higher Education Academy and a co-author of the Oxford Handbook series ‘Epidemiology for Clinicians’. Much of her work to date has focused on early life environmental exposures, including leading the environment theme of the new UK-wide Life Study and collaborative projects with various birth cohorts across Europe, assessing exposure at individual level through questionnaire data, biomarkers, and global metabonomic profiling. She also has over 10 years expertise in spatial epidemiology and the use of routinely collected data and geographical information systems (GIS) for small area health studies at the SAHSU. Her work in this field has included studies of birth outcomes and water disinfection by-products, waste incineration, and air and noise pollution, as well as investigations of cancer trends and clustering, in particular for primary liver tumours. Her special interest is in the field of non-ionizing radiation epidemiology, having worked on several major projects including national studies of adult cancers near overhead power lines and childhood cancers in proximity to mobile phone base stations.

International Team

Denmark Denmark Study Centre: Danish Cancer Society Research Center Number of participants: around 30,000 Principal Investigator: Dr Aslak Harbo Poulsen Email: Website:
Finland Finland Study Centre: School of Public Health at Tampere University Number of participants: around 15,000 Principal Investigator: Professor Anssi Auvinen Email:
France France Study Centre: International Agency for Research on Cancer (IARC) Number of participants: around 50,000 Principal Investigator: Dr Joachim Schüz Email:
Netherlands Netherlands Study Centre: Institute for Risk Assessment Sciences at Utrecht University Number of participants: around 90,000 Principal Investigator: Professor Hans Kromhout Email:
Sweden Sweden Study Centre: Karolinska Institute Number of participants: around 50,000 Principal Investigator: Professor Maria Feychting Email: Website:


Cohort profile: UK COSMOS – a UK cohort for study of environment and health
Sep 2015
Toledano MB, Smith RB, Chang I, Douglass M, Elliott P
International Journal of Epidemiology September 2015
How to Establish and Follow up a Large Prospective Cohort study in the 21st Century - Lessons from UK COSMOS
Jul 2015
Toledano MB, Smith RB, Brook JP, Douglass M, Elliott P
PLOS-ONE July 2015
Validation of exposure assessment and assessment of recruitment methods for a prospective cohort study of mobile phone users (COSMOS) in Finland: A pilot study
Mar 2011
Heinävaara S, Tokola K, Kurttio P, Auvinen A
Environmental Health, March 2011
An international prospective cohort study of mobile phone users and health (Cosmos): design considerations and enrolment
Feb 2011
Schüz J, Elliott P, Auvinen A, Kromhout H, Poulsen AH, Johansen C, Olsen JH, Hillert L, Feychting M, Fremling K, Toledano MB, et al.
Cancer Epidemiology, February 2011


There are currently no vacancies on the UK COSMOS team. Please check back later.


Press Release No. 208 - 31 May 2011.2
Commentary: Mobile Phones and Cancer: Next Steps After the 2011 IARC Review
WHO Research Agenda for Radiofrequency Fields.
Health Effects from Radiofrequency Electromagnetic Fields.
Mobile Telecommunications and Health Research Programme: report 2007.
Exposure to high frequency electromagnetic fields, biological effects and health consequences.
Health Effects of Exposure to EMF.
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