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Radiation levels at the Fukushima Daiichi nuclear plant have been reported to significantly increase on Tuesday during a fire near reactor No. 4. Fortunately, these levels dropped rapidly after the fire was extinguished. The measured unit, in millisieverts, is difficult to put into perspective in our daily lives. How do these levels compare to a whole body CT scan?
In an article in The New York Times {graphic above} today, these levels are put into perspective.
As you can see, there is only one data point significantly above 10 millisieverts (per hour), the amount equivalent to a whole body CT scan. Let us hope that such management of radiation levels continues.
UPDATE MARCH 18:
The New York Times has revised their graphic, clarifying that the “typical radiation doses are cumulative, not per hour.” {For example, doses from a whole body CT scan.} This revision was made after I submitted the following letter on March 16 to their Editor {they may have heard from many readers on this point}:
The Times coverage of health risks associated with the Fukushima nuclear power plant has helped clarify numerous conflicting reports in the media. The graphic, however, could be misleading, since different units are used: radiation levels at the plant are a rate (millisieverts, mSv, per hour) and typical radiation doses are shown as a single point in time (e.g., whole body CT scan). When corrected as a rate per hour, whole body CT scans are greater (about 720 mSv) than even the highest level measured at the plant (400 mSv.) We must compare apples to apples!
Note that my estimated value of 720 mSv per hour for a whole body CT scan was calculated after conferring with a radiologist, who informed me:
The six milisievert CT scan takes about 15-30 seconds. If you leave the scanner on constantly for 5-10 minutes skin erythema and epilation can be seen as it was in the Cedars Sinai/ University of Alabama CT perfusion scans that got so much press last year.
Reporter Denise Grady of The New York Times shared some useful information in this article:
Another device, a sodium iodide detector, can be held an inch or so from the neck to check for radioactive iodine in the thyroid gland; if it detects any, the person may be given iodide pills.
In photographs from Japan, health workers appear to be screening members of the public with both Geiger counters and sodium iodide detectors.
If there is a suspicion that someone has been exposed to a large dose of radiation, the first test that doctors are likely to perform is a complete blood count, Dr. Vetter said. Abnormalities in the count — fewer white cells than would be expected, for example — can show up within a day or so, and give a ballpark estimate of how bad the exposure was.
“In Japan, it’s very unlikely that a member of the public would get a dose of radiation that would result in a decrease in any blood cells,” Dr. Vetter said. “If anyone got that kind of dose, it’s likely people who are working in the nuclear plants themselves.”
People with significantly lowered blood counts from radiation can be given drugs to stimulate their bone marrow to make more blood cells. Those drugs were not available in 1986, when a nuclear power plant in Chernobyl, Ukraine, blew up. Other drugs can be used to help rid the body of certain radioactive isotopes. But if the exposure was so high that the drugs do not help, people may need to be treated in the hospital — put into isolation and given antibiotics to protect them from infection, and possibly blood transfusions as well. A bone marrow transplant may be a last resort, but, Dr. Vetter said, “the patient is in real trouble at that point.”
Crops can be contaminated by fallout, which can cling to surface of plants at first and later be taken up by their roots.
Radioactive iodine has a half-life of only eight days — the time it takes for half of it to decay or disappear — so most of it is gone within about two months. But radioactive forms of the particulate cesium persist much longer, and in the regions affected by Chernobyl, they are still the main threats to human health and will be for decades.
Wild mushrooms, berries and animals have been found to be contaminated with cesium in areas contaminated by Chernobyl, and that is expected to last for decades. Lakes and freshwater fish may also be contaminated, but experts say ocean fish are less of a worry because the contaminants are more dispersed and diluted in the ocean than in lakes.
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