Following the incident at the Fukushima Dai-ichi nuclear plant during the March 2011 tsunami, majority of the 370,000 children living at the Fukushima prefecture in Japan are given regular ultrasounds.

In 2014, 25 children were diagnosed with "suspicious or malignant cases" of thyroid cancer. In August 2015, 137 children were found to have thyroid cancer. The rate is 20 to 50 times higher in Fukushima compared to the other areas' estimated average of one or two in every one million children diagnosed annually.

"This is more than expected and emerging faster than expected. This is 20 times to 50 times what would be normally expected, said lead author Toshihide Tsuda from the Okayama University in Japan.

Tsuda's analysis is based on the widespread public health survey conducted in Fukushima after the March 2011 nuclear accident caused by the tsunami. Part of the survey includes regular thyroid tests among children living in the prefecture.

Children's thyroids have an elevated growth rate compared to adults, which makes them more vulnerable to the radioactive iodine that could have been released during the accident at the nuclear plant. The World Health Organization report stated thyroid cancer as a potential health risk. However the published report also mentioned that linking cancer diagnosis to the accident would be difficult.

State officials have expressed that the high numbers were most likely caused by increased screenings in the Fukushima. However, the paper contradicted the government's line and indicated that thyroid cancer rates throughout Fukushima are highly prominent.

Other health officials also shared their skepticisms. Professor Geraldine Thomas from Imperial College London commented that Tsuda incorrectly compared the numbers of Fukushima screenings to numbers clinical cases of patients who already have thyroid cancer. Thomas studied thyroid cancer cases linked to the 1986 Chernobyl Nuclear Power Plant disaster in Ukraine.

Columbia University's Center for Radiological Research director David Brenner exposed another flaw in the study. Brenner commended that Tsuda's paper did not trace the patient's potential exposure. The paper simply related cancer risks to geological regions. The researchers didn't even make an effort in studying each child's radiation dose.

The research was published online in Epidemiology journal on Oct. 5, 2015.

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