Japan radiation levels uncertain: Should evacuation zone be bigger?
Difficulties in measuring radiation are increasing confusion in Japan. The government must weigh incomplete and sometimes contradictory data before making decisions.
Kyodo News / AP
Conflicting data on radiation levels is making it difficult to judge the dangers posed by the damaged Fukushima Daiichi nuclear plant – and heightening anxiety among average Japanese.
On Thursday, store shelves across Tokyo were bare of bottled water one day after authorities warned that the level of radioactive iodine in tap water was twice the allowable level for infants. But follow-up tests conducted Thursday showed the iodine level had fallen back below acceptable limits.
Some nearby cities were showing elevated levels of radioactive iodine 131 in their municipal water supplies, however. And new estimates from Japan’s Nuclear Safety Technology Center seemed to indicate that atmospheric radiation levels might be too high for infants at some spots outside the 12-mile evacuation zone surrounding the Fukushima Daiichi nuclear complex.
“There is continuing scattered information about contamination exposures that is not entirely consistent,” said Edward Lyman, a senior staff scientist at the Union for Concerned Scientists, a nuclear watchdog group in Washington. “Confusion seems to be growing.”
Given the scale of the crisis, such confusion is to be expected, said Dr. Lyman. Similar problems would occur anywhere multiple reactors suffered total power blackouts and apparent fuel rod damage.
Why is it so hard to measure radiation? It is not like measuring temperature, or barometric pressure, or some other easily-discernable weather variable. Emissions from Fukushima have been a mix of different kinds of radioactive materials, which disseminate into the atmosphere differently, and travel in the air in different ways.