To the Editor:
Samet and colleagues1 present the state of knowledge on mobile phones and cancer 2 years after the International Agency for Research on Cancer evaluation of radiofrequency radiation,2 which recommended a coordinated, strategic plan of epidemiologic research, experimental studies, and risk communication and management.
Samet and colleagues1 describe results of recent epidemiologic studies, including analysis of data from 5 INTERPHONE countries using estimates of cumulative energy at tumor location.3 They report the increased glioma risk among heaviest users but omit important findings: a dose-response for glioma among long-term users and, in case-only analyses minimizing recall bias by ignoring reported amount and laterality of use, an increased odds ratio (OR) among long-term users in the most exposed part of the brain.3 They also do not mention a similar OR in case-specular analyses of data from 7 other INTERPHONE countries.4
Recommendations stemming from previous case-control studies include the following: (1) further development of radiofrequency radiation exposure modeling, (2) bias modeling, and (3) parallel reanalysis of the INTERPHONE and Hardell studies. We fully support such recommendations. Despite limitations of the case-control design—which must be addressed—this design is the most powerful for investigating potential associations between radiofrequency radiation and brain tumors.
Prospective studies based on operator records are also recommended; although immune to recall bias, they are limited by statistical power (INTERPHONE captured a population of 50 million, hardly achievable in a cohort study), exposure assessment, and selection bias. Time-trend analyses are important for population surveillance but have limited power to detect risks of tumors arising only in the most exposed part of the brain, years after substantial exposure.2
Samet and colleagues1 also note the importance of developing and implementing a strategic research agenda and keeping the public well informed. The newly European Union–funded GERoNiMO project (geronimo.crealradiation.com) builds upon existing European resources (including large-scale cohort and case-control studies) to: (1) better understand health effects (and mechanisms) potentially associated with electromagnetic fields (EMF), including brain tumors, neurodegenerative, behavioral, and reproductive outcomes; (2) better characterize EMF exposure in the general population; (3) improve integration of EMF and health research into health risk assessment; and (4) underpin risk management policies. GERoNiMO focuses on radiofrequency radiation (from mobile phones and newer communication technologies) and increasingly ubiquitous intermediate frequency fields—alone and in combination with other environmental exposures. We anticipate that GERoNiMO will improve the integration, coherence, and coordination of EMF and health research, leading to improved evidence-based risk estimation, management, and communication.
Chelsea Eastman Langer
Michelle C. Turner
Centre for Research in Environmental Epidemiology (CREAL)
Universitat Pompeu Fabra (UPF)
Ciber Epidemiología y Salud Pública (CIBERESP)
1. Samet JM, Straif K, Schüz J, Saracci R. Commentary: Mobile Phones and Cancer: Next Steps After the 2011 IARC Review. Epidemiology. 2014;25:23–27
2. Baan R, Grosse Y, Lauby-Secretan B, et al.WHO International Agency for Research on Cancer Monograph Working Group. Carcinogenicity of radiofrequency electromagnetic fields. Lancet Oncol. 2011;12:624–626
3. Cardis E, Armstrong BK, Bowman JD, et al. Risk of brain tumours in relation to estimated RF dose from mobile phones: results from five Interphone countries. Occup Environ Med. 2011;68:631–640
4. Larjavaara S, Schüz J, Swerdlow A, et al. Location of gliomas in relation to mobile telephone use: a case-case and case-specular analysis. Am J Epidemiol. 2011;174:2–11