Is cellphone and cordless phone radiation a risk factor for thyroid cancer?
The authors call for research on the effects on the thyroid gland from exposure to radiofrequency radiation and ionizing radiation.
Michael Carlberg, Lena Hedendahl, Mikko Ahonen, Tarmo Koppel, Lennart Hardell. Increasing incidence of thyroid cancer in the Nordic countries with main focus on Swedish data. BMC Cancer. 16:246. 2016. DOI 10.1186/s12885-016-2429-4
Background: Radiofrequency radiation in the frequency range 30 kHz–300 GHz was evaluated to be Group 2B, i.e. ‘possibly’ carcinogenic to humans, by the International Agency for Research on Cancer (IARC) at WHO in May 2011. Among the evaluated devices were mobile and cordless phones, since they emit radiofrequency electromagnetic fields (RF-EMF). In addition to the brain, another organ, the thyroid gland, also receives high exposure. The incidence of thyroid cancer is increasing in many countries, especially the papillary type that is the most radiosensitive type.
Methods: We used the Swedish Cancer Register to study the incidence of thyroid cancer during 1970–2013 using joinpoint regression analysis.
Results: In women, the incidence increased statistically significantly during the whole study period; average annual percentage change (AAPC) +1.19 % (95 % confidence interval (CI) +0.56, +1.83 %). Two joinpoints were detected, 1979 and 2001, with a high increase of the incidence during the last period 2001–2013 with an annual percentage change (APC) of +5.34 % (95 % CI +3.93, +6.77 %). AAPC for all men during 1970–2013 was +0.77 % (95 % CI −0.03, +1.58 %). One joinpoint was detected in 2005 with a statistically significant increase in incidence during 2005–2013; APC +7.56 % (95 % CI +3.34, +11.96 %). Based on NORDCAN data, there was a statistically significant increase in the incidence of thyroid cancer in the Nordic countries during the same time period. In both women and men a joinpoint was detected in 2006. The incidence increased during 2006–2013 in women; APC +6.16 % (95 % CI +3.94, +8.42 %) and in men; APC +6.84 % (95 % CI +3.69, +10.08 %), thus showing similar results as the Swedish Cancer Register. Analyses based on data from the Cancer Register showed that the increasing trend in Sweden was mainly caused by thyroid cancer of the papillary type.
Conclusions: We postulate that the whole increase cannot be attributed to better diagnostic procedures. Increasing exposure to ionizing radiation, e.g. medical computed tomography (CT) scans, and to RF-EMF (non-ionizing radiation) should be further studied. The design of our study does not permit conclusions regarding causality.
Keywords: Mobile phone, Cordless phone, Thyroid cancer, Swedish Cancer Register, NORDCAN, Radiofrequency electromagnetic fields, RF-EMF, Ionizing radiation, Incidence, Nordic countries
... Our results clearly indicate that the increasing incidence of thyroid cancer is mainly for the papillary type and may be caused by radiation. Both ionizing and non-ionizing radiation should be considered. Just recently, statistics from the Swedish Cancer Register have been made official on all new cancer cases for 2014 . For thyroid cancer there is a continuous increase in incidence in 2014 compared to 2013, by 12.1 % for men, (from 3.3 to 3.7), and by 11.2 % for women, (from 8.9 to 9.9; age standardized per 100,000 inhabitants).
A study of 18 cancer registers in the US showed an increased incidence of all thyroid cancers between 2000–2002 and 2010–2012 of 22.76 %. For papillary carcinoma of the thyroid, the incidence increased by 173.86 %. The increase included all sizes of papillary carcinoma, from those under one centimeter to those over 4 cm 
The impact of diagnostic changes during 2003–2007 on the rise in thyroid cancer incidence was studied in high-resource countries . The study included the
Nordic countries. It was postulated that diagnostic changes may account for ≥60 % of the cases in France, USA, Australia and the Republic of Korea, about 50 % in the Nordic countries and 30 % in Japan. It is noteworthy that the main increase in Sweden was found after that study period and thus cannot fully explain the results in our joinpoint analysis.
Increased exposure to thyroid-specific environmental carcinogens could be responsible, such as ionizing radiation (mostly medical radiation), increased iodine intake and chronic lymphocytic thyroiditis and environmental pollutants such as nitrates, heavy metals and other compounds largely used in the industrialized society . Other factors that have been suggested include eating habits, smoking, living in volcanic areas, xenobiotics and
One environmental factor that needs to be discussed in this context is the public’s increased exposure to the radiofrequency electromagnetic fields (RF-EMFs) due to the use of mobile and cordless phones. With the decreased subscription cost and innovations in technology, we have seen a large spread of mobile networking; mobile phones are not only used to make phone calls but also for using the internet. We have discussed that issue in relation to the increasing rate of brain tumors in the Swedish National Inpatient Register (IPR) and Causes of Death Register (CDR) . Moreover, there has been a rapid increase in the use of wireless phones during the last two decades. An estimate of 6.9 billion mobile phone subscriptions worldwide was reported at the end of 2014 by the International Telecommunication Union . Mobile phones were introduced in Sweden during the early 1980s, but the real increase of the use has taken place since the 1990s . Desktop cordless phones have been used since the end of the 1980s. There are no official statistics on that use, but almost all desktop phones on the market are now of the wireless type. While used, wireless phones emit RF-EMFs ....
... near-field OSA [organ-specific average] absorption caused by mobile phone and cordless phone sources was calculated. The eye lens, skin and thyroid
gland were the organs with the highest exposure other than the brain . It can be summarized that both with near-field and far-field exposure, the thyroid gland was among the organs with the highest exposure.
This study has shown an increasing incidence of thyroid cancer in Sweden and the Nordic countries. Better diagnostic imaging cannot solely account for the increase. Increased use of CT and PET-CT for medical examinations has elevated the population’s exposure to the ionizing radiation and should be considered as a risk factor. Exposure to RF-EMFs also merits in-depth investigation. The design of our study does not permit conclusions regarding causality.
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