NHK: Thyroid cancer found in 18 Fukushima children

[caraher]

62. Seems like many rational people did read your numbers as data-based estimates

I understand your general points - careful screening will certainly turn up tumors that would otherwise have gone unnoticed, so even an elevated rate doesn't necessarily suggest a causal link exists. But phantom power, for instance, clearly took your numbers to be real, and I didn't see much of a disclaimer when I read the post where you suggested a range of 15-20 for comparison purposes.

Anyway, I looked for some real numbers. (Actual values do matter!) Evidently, thyroid cancer is quite rare among those younger than 10 and picks up in adolescence, which makes it a little tricky to make an estimate that would apply to 360,000 screened "under age 18." The rates in my source are 15.4 per million for ages 15-19 and less than 1 per million for those under age 10. So if these were really young kids, I think 18 confirmed cases could represent a significant difference (though the cause may be obscure - what is the typical latency for a thyroid tumor caused by I-131 ingestion?).

Assuming the 360,000 are distributed equally among ages 0-18 and the rate of 15.4 million for the older end translates can be translated into something vaguely like 5 per million across the whole group (assume it's effectively 0 for the younger 2/3 and 15 per million for the eldest third) you'd still only expect maybe 2 cases from a population of 360,000. So if you ignore all the important disclaimers about the statistics of very small numbers, that's roughly an order of magnitude more than you'd expect.

A good complementary study, of course, would be to pick an unexposed population and see whether they also see an order of magnitude increase when submitted to the same kind of more-intense screening. But that might be a hard study to fund and organize. In any case, it's clear that the 18 cases do represent a spike above the rate one would expect from an ordinary population under no special scrutiny.