In 2011 the the Fukushima-Daiichi Nuclear Power Plant (NPP) was hit by a magnitude 9.0 earthquake and 50 minutes later a massive tsunami.
All infrastructure in Tohoku region of Japan was crippled, thousands of lives were lost and nearly half a million people were displaced. In total, 14 nuclear reactors across four nuclear plants were hit by the earthquake and tsunami, but three reactors at the Fukushima-Daiichi NPP melted down and another leaked radioactive material into the atmosphere.
After reactors one, two and three melted down and reactor four released radioactive materials into the atmosphere, concerns over thyroid cancer spread among survivors of the disasters.
Amid these fears and concerns the Fukushima Health Management Survey (FHMS) began massive routine thyroid ultrasounds for those exposed to radiation from the NPP before being evacuated. In a study published by Clinical Oncology in December 2015, researchers examined the data from the thyroid ultrasound examinations.
During the first survey, over 300,000 children under the age of 18 were screened over a period of three years, from October 2011 to March 2014.
The children were grouped into four categories: A1, A2, B and C. Children that were grouped in category A1 had no thyroid nodules or cysts. Children grouped in category A2 had nodules that were less than 5 mm or cysts that were less than 20 mm.
The children in category B had nodules that were larger than 5mm and cysts that were larger than 20 mm. The children in category C needed immediate care. Fifty-one percent of the children fell into category A1, 47 percent in category A2 and less than 1 percent of the children were classified as category B. No children were grouped in category C.
The children with nodules and cysts greater than those in category A2 underwent further examination. Of the 2294 children in group B, 113 were diagnosed with thyroid cancer or suspected cancer and were treated accordingly.
During the second survey, participation dropped under 50 percent of the initial 300,000 to just 170,000 children. In this survey, the percentage of children with nodules and/or cysts in category A2 grew from 47 percent to 57 percent. Category A1 dropped from 51 percent to 41 percent and categories B and C remained the same.
In the study it was suggested that the discovery of thyroid cancers and growths had less to do with radiation exposure and more to do with the massive screenings.
The early results of cancers and growths found in the study were met with worries that Fukushima’s children had been victims of previous exposure from the NPP. This caused outrage among exposed residents, some of who demanded more frequent ultrasounds for their children to monitor possible cancer risks.
To quell fears, the Ministry of Environment directed the Japan association of Breast and Thyroid Sonology (JABTS) to perform the same study across the Aomori, Yamanashi and Nagasaki prefectures using the same methods and protocols.
The studies concluded that the children in the other prefectures, which are not close to the Fukushima-Daiichi NPP, had a higher instance of being grouped in category A2.
In the study it was suggested that the discovery of thyroid cancers and growths had less to do with radiation exposure and more to do with the massive screenings. Meaning that harmless growths and nodules were found which otherwise would have not caused any health problems.
Because they were found, treatment, which some believe to have been unnecessary, was issued.
The researchers in the study do not believe that the cause of the cancers is due to radiation exposure from the Fukushima-Daiichi NPP disaster…
Thyroid cancer caused by radiation exposure does not typically occur until four to five years post exposure. This has been observed in nuclear incidents throughout history, including the Chernobyl accident and the atomic bombs dropped on Hiroshima and Nagasaki.
The researchers in the study do not believe that the cause of the cancers is due to radiation exposure from the Fukushima-Daiichi NPP disaster, but did suggest the continuation of the thyroid ultrasound examination.
March 11, 2016 marks the fifth year since the Great East Japan Earthquake and the Tohoku tsunami.
Suzuki, S. 2015. Childhood and Adolescent Thyroid Cancer in Fukushima after the Fukushima Daiichi Nuclear Power Plant Accident: 5 Years On. Clinical Oncology , Volume 28 , Issue 4 , 263-271DOI: http://dx.doi.org/10.1016/j.clon.2015.12.027