Epidemiology • Volume 27, Number 3, May 2016
Letters
To the Editor: suda et al. analyzed the incidence of thyroid ultrasound screening, referring to the interim results of Fukushima Health Management Survey, and reported that the highest incidence rate was observed in the central middle district of Fukushima Prefecture (prevalence, 605 per million), when compared with Japanese annual incidence. They concluded that an excess of thyroid cancer had been detected by ultrasound among children and adolescents in Fukushima after the accident at the Fukushima Dai-ichi Nuclear Power Plant.1 We recently conducted thyroid ultrasound screening, using the same procedures as the Fukushima Health Management Survey, in 4,365 children aged 3–18 years from three Japanese prefectures, and confirmed one patient with papillary thyroid cancer (prevalence, 230 per million).2 Furthermore, we recently reviewed findings of thyroid ultrasound screening conducted in Japan.3 In one survey, 9,988 students underwent thyroid screening and four students (including one foreign student) were subsequently diagnosed with thyroid cancer (prevalence, 300 per million). In another study at Okayama University that examined 2,307 students, three patients with thyroid cancer were found (prevalence, 1,300 per million), while at Keio High School, of 2,868 female students examined, one was found to have thyroid cancer (prevalence, 350 per million). These results show that the prevalence of thyroid cancer detected by advanced ultrasound techniques in other areas of Japan does not differ meaningfully from that in Fukushima Prefecture. We should also note that it is important to evaluate carefully the relationship between the incidence of
T
The author reports no conflicts of interest. Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved. ISSN: 1044-3983/16/2703-0e18 DOI: 10.1097/EDE.0000000000000464
e18 | www.epidem.com
thyroid cancer and exposure doses. In fact, measured values of thyroid doses in more than 1,000 children in Fukushima just after the accident were less than 15 mSv in 99% of children 0–14 years old, with the maximum doses around 35 mSv.2 We must of course evaluate carefully the incidence of thyroid cancer and age at the time of the Fukushima accident. After the accident at Chernobyl in 1986, childhood thyroid cancer increased dramatically because of internal radiation exposure to I-131 through the intake of contaminated milk.4 In Chernobyl, many patients were younger than 10 years old, whereas in Fukushima, no children were under 5 years old and only a few were under 10. We should pay careful attention before making any definitive statements without accurate dose estimations. Based on the experiences in Chernobyl and other nuclear disasters, we need to continue our efforts at appropriate, scientific evaluation of the health conditions in Fukushima. Noboru Takamura Department of Global Health, Medicine and Welfare Atomic Bomb Disease Institute Nagasaki University Nagasaki, Japan [email protected]
To the Editor: suda et al.1 evaluated the prevalence of thyroid cancer among children and adolescents after the Fukushima accident in zones of different level of radiation contamination. Based on the numbers in their Table 1, I calculated the means of thyroid cancer prevalence in three zones of radiation contamination (low, middle, high); the least contaminated area (Northeastern, Western, Southeastern, Iwaki City), the combined four districts with intermediate contamination (North middle, Central middle, Koriyama City, South middle), and the nearest area to the crippled reactor (Fig.). The error bars in the Figure indicate 95% confidence intervals. It is hard to see any association of thyroid cancer prevalence with radiation contamination. This makes it difficult to accept that radiation has caused an increase of thyroid cancer among children and adolescents in Fukushima Prefecture during 2011–2014. After Chernobyl, a sharp rise of thyroid cancers in children from Belarus was observed in 1990; during 1987–1991, the annual numbers of newly detected cancers were 4, 5, 6, 29, and 55, respectively.2 In Fukushima, therefore, an increase of thyroid cancers is likely not expected to occur before 2015.
T
Alfred Körblein Nürnberg, Germany [email protected]
REFERENCES 1. Tsuda T, Tokinobu A, Yamamoto E, Suzuki E. Thyroid cancer detection by ultrasound among residents age 18 year and younger. Epidemiology. 2016;27:316–322. 2. Nagataki S, Takamura N. A review of the Fukushima nuclear reactor accident: radiation effects on the thyroid and strategies for prevention. Curr Opin Endocrinol Diabetes Obes. 2014;21:384–393. 3. Hayashida N, Imaizumi M, Shimura H, et al. Thyroid ultrasound findings in a follow-up survey of children from three Japanese prefectures: Aomori, Yamanashi, and Nagasaki. Sci Rep. 2015;5:9046. 4. Health Effects of the Chernobyl accident and Special health care programmes. Report of the UN Chernobyl Forum. Expert Group “Health”. Available at: http://www.who.int/ ionizing_radiation/chernobyl/WHO%20 Report%20on%20Chernobyl%20Health%20 Effects%20July%2006.pdf#search=%27He alth+Effects+of+the+Chernobyl+accident+a nd+Special+health+care+ptogrammes%27. Accessed October 12, 2015.
REFERENCES 1. Tsuda T, Tokinobu A, Yamamoto E, Suzuki E. Thyroid cancer detection by ultrasound among residents ages 18 years and younger in Fukushima, Japan: 2011 to 2014. Epidemiology. 2016;27:316–322. 2. Kazakov VS, Demidchik EP, Astakhova LN. Thyroid cancer after Chernobyl. Nature. 1992;359:21.
The author reports no conflicts of interest. Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved. ISSN: 1044-3983/16/2703-0e18 DOI: 10.1097/EDE.0000000000000463
© 2016 Wolters Kluwer Health, Inc. All rights reserved.
Copyright © 2016 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Letters
To the Editor: suda et al. analyzed the incidence of thyroid ultrasound screening, referring to the interim results of Fukushima Health Management Survey, and reported that the highest incidence rate was observed in the central middle district of Fukushima Prefecture (prevalence, 605 per million), when compared with Japanese annual incidence. They concluded that an excess of thyroid cancer had been detected by ultrasound among children and adolescents in Fukushima after the accident at the Fukushima Dai-ichi Nuclear Power Plant.1 We recently conducted thyroid ultrasound screening, using the same procedures as the Fukushima Health Management Survey, in 4,365 children aged 3–18 years from three Japanese prefectures, and confirmed one patient with papillary thyroid cancer (prevalence, 230 per million).2 Furthermore, we recently reviewed findings of thyroid ultrasound screening conducted in Japan.3 In one survey, 9,988 students underwent thyroid screening and four students (including one foreign student) were subsequently diagnosed with thyroid cancer (prevalence, 300 per million). In another study at Okayama University that examined 2,307 students, three patients with thyroid cancer were found (prevalence, 1,300 per million), while at Keio High School, of 2,868 female students examined, one was found to have thyroid cancer (prevalence, 350 per million). These results show that the prevalence of thyroid cancer detected by advanced ultrasound techniques in other areas of Japan does not differ meaningfully from that in Fukushima Prefecture. We should also note that it is important to evaluate carefully the relationship between the incidence of
T
The author reports no conflicts of interest. Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved. ISSN: 1044-3983/16/2703-0e18 DOI: 10.1097/EDE.0000000000000464
e18 | www.epidem.com
thyroid cancer and exposure doses. In fact, measured values of thyroid doses in more than 1,000 children in Fukushima just after the accident were less than 15 mSv in 99% of children 0–14 years old, with the maximum doses around 35 mSv.2 We must of course evaluate carefully the incidence of thyroid cancer and age at the time of the Fukushima accident. After the accident at Chernobyl in 1986, childhood thyroid cancer increased dramatically because of internal radiation exposure to I-131 through the intake of contaminated milk.4 In Chernobyl, many patients were younger than 10 years old, whereas in Fukushima, no children were under 5 years old and only a few were under 10. We should pay careful attention before making any definitive statements without accurate dose estimations. Based on the experiences in Chernobyl and other nuclear disasters, we need to continue our efforts at appropriate, scientific evaluation of the health conditions in Fukushima. Noboru Takamura Department of Global Health, Medicine and Welfare Atomic Bomb Disease Institute Nagasaki University Nagasaki, Japan [email protected]
To the Editor: suda et al.1 evaluated the prevalence of thyroid cancer among children and adolescents after the Fukushima accident in zones of different level of radiation contamination. Based on the numbers in their Table 1, I calculated the means of thyroid cancer prevalence in three zones of radiation contamination (low, middle, high); the least contaminated area (Northeastern, Western, Southeastern, Iwaki City), the combined four districts with intermediate contamination (North middle, Central middle, Koriyama City, South middle), and the nearest area to the crippled reactor (Fig.). The error bars in the Figure indicate 95% confidence intervals. It is hard to see any association of thyroid cancer prevalence with radiation contamination. This makes it difficult to accept that radiation has caused an increase of thyroid cancer among children and adolescents in Fukushima Prefecture during 2011–2014. After Chernobyl, a sharp rise of thyroid cancers in children from Belarus was observed in 1990; during 1987–1991, the annual numbers of newly detected cancers were 4, 5, 6, 29, and 55, respectively.2 In Fukushima, therefore, an increase of thyroid cancers is likely not expected to occur before 2015.
T
Alfred Körblein Nürnberg, Germany [email protected]
REFERENCES 1. Tsuda T, Tokinobu A, Yamamoto E, Suzuki E. Thyroid cancer detection by ultrasound among residents age 18 year and younger. Epidemiology. 2016;27:316–322. 2. Nagataki S, Takamura N. A review of the Fukushima nuclear reactor accident: radiation effects on the thyroid and strategies for prevention. Curr Opin Endocrinol Diabetes Obes. 2014;21:384–393. 3. Hayashida N, Imaizumi M, Shimura H, et al. Thyroid ultrasound findings in a follow-up survey of children from three Japanese prefectures: Aomori, Yamanashi, and Nagasaki. Sci Rep. 2015;5:9046. 4. Health Effects of the Chernobyl accident and Special health care programmes. Report of the UN Chernobyl Forum. Expert Group “Health”. Available at: http://www.who.int/ ionizing_radiation/chernobyl/WHO%20 Report%20on%20Chernobyl%20Health%20 Effects%20July%2006.pdf#search=%27He alth+Effects+of+the+Chernobyl+accident+a nd+Special+health+care+ptogrammes%27. Accessed October 12, 2015.
REFERENCES 1. Tsuda T, Tokinobu A, Yamamoto E, Suzuki E. Thyroid cancer detection by ultrasound among residents ages 18 years and younger in Fukushima, Japan: 2011 to 2014. Epidemiology. 2016;27:316–322. 2. Kazakov VS, Demidchik EP, Astakhova LN. Thyroid cancer after Chernobyl. Nature. 1992;359:21.
The author reports no conflicts of interest. Copyright © 2016 Wolters Kluwer Health, Inc. All rights reserved. ISSN: 1044-3983/16/2703-0e18 DOI: 10.1097/EDE.0000000000000463
© 2016 Wolters Kluwer Health, Inc. All rights reserved.
Copyright © 2016 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
