Updated and corrected, because yours truly mixed up millisieverts and microsieverts before he had his morning coffee and flew off the handle and accused CNBC and Thomson Reuters of being morons:
The average individual background radiation dose for Americans is 3 millisieverts/year, according to Wikipedia here. In microsieverts, that would come to 3000 in one year, the same dose a woman gets once a year from a mammogram in addition to the individual background radiation.
From all sources, the average American presently gets a dose of 6.2 mSv/year, or 6200 microsieverts in one year.
Taking a story from Thomson Reuters, CNBC this morning publishes this, entitled "Risks at Each Reactor of Japan's Stricken Plant Explained":
Radiation levels were higher than normal but not dangerous, Japan's Nuclear and Industrial Safety Agency said on Thursday.
They were measured at 338 microsieverts per hour at the west gate at 2000 GMT March 16 (5 am local time March 17). If a person stands outdoors for a year, they would be exposed to a radiation level of 400 microsieverts, the agency said.
The wind is blowing northwest-to-southeast, towards the Pacific Ocean, Japan Meteorological Agency said.
If 6200 microsieverts per year is normal for an American, 338 microsieverts per hour does not become out of the ordinary until after 18 hours of continuous exposure. But compressing into the course of two or three days the radiation exposure one gets normally in a year is nothing to sniff at.
Standing outside for a year equals 400 microsieverts? That's about 0.4 mSv/year.
Acute radiation exposure over one day begins near 250 millisieverts, with possible symptoms including nausea and appetite loss, and damage to the bone marrow, lymph nodes and the spleen. In microsieverts, this would be 250,000 IN ONE DAY. On Tuesday there was a brief time in which radiation levels at Fukushima reached way beyond 250 millisieverts to 400 mSv/hour, or 400,000 microsieverts. Very dangerous.
So I figured it out . . . before I died!
And apologies to Reuters, which I now realize had a good post on the milli/micro ins and outs here yesterday.
