Studies indicate thyroid cancer latency much less than four years

Some of the Chernobyl research indicates that the latent period of thyroid cancer was much shorter than what has been recently stated by experts. The implications about the present cases of thyroid cancer in Fukushima are obvious.

(revised on 2014/03/10)

Last month there was an important finding about thyroid cancer research in the blog written by Paul Langley. He points out a serious contradiction in the claims that prominent “health physicists” have been making about the cases of thyroid cancer that have appeared in Fukushima since the nuclear accident. At the time he wrote this, I expected the news to go viral, but I’ve seen scant mention of it on social networks, and of course, the mass media did not notice it.
The reason for this oversight may be that Paul Langley’s blog posts are superb, but long and heavy on detail. Casual readers may have passed over important information without recognizing its significance. So I will try to summarize the main points and post the most interesting citations.
After the second anniversary of the Fukushima Daiichi catastrophe, a sharp increase in childhood thyroid cancer was recorded in Fukushima Prefecture. Health officials hesitated to attribute the cause to the nuclear accident because they said that it was simply too early to be finding cases of thyroid cancer. The Chernobyl studies all indicated, they said, that the mean latency period was at least four years. Experts in health physics outside Japan also repeated this claim. They seemed to wish that no one would remember their middle school math lessons and point out that a mean indicates that in the sample many values were higher and lower than the mean. Thus it is not surprising that thyroid cancer cases would appear much earlier than four years after the accident. A high number of early cases should be cause for alarm because it would indicate many more are yet to come by the mean time of onset.
Paul Langley found several studies that stated the latency period was much shorter than four years. According to these studies, an increase in the rate of thyroid cancer incidence is exactly what one would expect to find two years after a nuclear accident. One of the authors was none other than Shinichi Yamashita himself, the former head of the Fukushima Prefectural Health Management Survey Review Committee.
Paul Langley, quoting an article in The Japan Times, noted that this committee has stated that Chernobyl data shows that the latency period for thyroid cancer is 4–5 years, and that the progression of disease was slow in the case of the Chernobyl children.
Paul then found this quote from a 1998 research paper of which Dr. Yamashita was one of the authors:

“The high incidence of childhood thyroid cancer in Belarus is suspected to be due to radiation exposure after the Chernobyl reactor accident…  All of the preceding thyroid carcinomas developed after longer latency periods, whereas tumors arising in the Chernobyl population began developing with surprising rapidity and short latency.” (Shirahige et. al.)

Other research papers say:

“… absence of marked latency period is another feature of radiation-induced thyroid cancers caused in Belarus as a result of this accident.” (Malko)

“[the latent period for thyroid cancer is] 2.5 years, based on low estimates used for lifetime risk modeling of low-level ionizing radiation studies.” (Howard)

So about that latency period, which is it? 1 year, 2. 5 years, 4 years or 5 years, and does it really matter anyway? The denial of a causal relationship is the worst sort of deflection and quibbling by people who are highly motivated to avoid the truth. Japanese authorities claim that the high number of cancer cases found in Fukushima is a result of having used very sensitive equipment, with very close attention paid to a particular group. They imply that the same rate of thyroid cancer would be found in any other group subjected to the same intense analysis, but they refuse to carry out such a comparison in a region far away from Fukushima. This is typical of official studies of radiological disasters. Hundreds of studies are done, except the ones which seem most likely to produce results unfavorable to institutions which would be legally responsible for damages to health and property.


Howard, John. “Minimum Latency & Types or Categories of Cancer” Administrator World Trade Center Health Program, 9.11 Monitoring and Treatment, Revision: May 1, 2013.

Kyodo. “Thyroid cancer found in 12 minors in Fukushima.” The Japan Times, June 6, 2013.

Malko, Mikhail V. “Chernobyl Radiation-induced Thyroid Cancers in Belarus.”
Joint Institute of Power and Nuclear Research, National Academy of Sciences of Belarus. 2002.

Shirahige Y, Ito M, Ashizawa K, Motomura T, Yokoyama N, Namba H, Fukata S, Yokozawa T, Ishikawa N, Mimura T, Yamashita S, Sekine I, Kuma K, Ito K, Nagataki S.Childhood thyroid cancer: comparison of Japan and Belarus. Endocrine Journal, 1998 Apr;45(2):203-9.

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