Four more leaks have been discovered in the contaminated water tanks inside the Fukushima Daiichi nuclear power plant, according to the Tokyo Electric Power Company (TEPCO) [ja]. The maximum radiation level found was “1,800 millisieverts per hour dose equivalent at 70 micrometer” in the bottom of the tank in B Group H3 Area.
So how horrific is “1,800 millisieverts per hour dose equivalent at 70 micrometer”? The New York Times says it is “enough to give a lethal dose in about four hours“, but an anonymous Japanese blogger who blogs at ex-skf.blogspot.jp has criticized mainstream media for purposefully omitting “dose equivalent” information to mislead readers by mixing up exposure to gamma radiation, which is highly penetrating and can travel deep into human tissue, and exposure to beta radiation, which is lighter and not as penetrating.
The blogger at ex-skf.blogspot.jp explains:
1,800 millisieverts/hour is “dose equivalent at 70 micrometer”, to show the beta radiation exposure at very close proximity for particular organs – skin, and eye lens.
The “1,800 millisieverts/hour that would kill a person in 4 hours” would be gamma radiation.
In this case, RO waste water is extremely high in beta nuclides including strontium but not so much at all in gamma nuclides. You wouldn't die just by being near this water for four hours.
1,800 millisieverts/hour dose equivalent is still very high, as the annual limit for equivalent dose for skin is 500 millisieverts. The same for lens is 300 millisieverts.
But to purposefully omit “dose equivalent” information from the original information from TEPCO and add sensational claim of killing one in four hours of exposure is another low for the media.