And what threat, if any, is there to the U.S. and other countries if a nuclear meltdown sends a plume of radiation into the atmosphere?
The carrier USS George Washington, which sits pier side in Yokosuka, Japan, has detected low levels of radiation. Some Navy crewman who have been assisting with search and rescue and humanitarian efforts have had low-level exposure, have gone through decontamination, and been given potassium iodide tablets. The US military says those steps were precautionary.
The images are disturbing. The unknown is always unnerving, and the fact that people who live within 20 miles of Japan's troubled nuclear plants have been either evacuated, or told to stay indoors has ratcheted up anxiety -- certainly in Japan and to an extent, also, across the Pacific in the U.S.
Some, particularly on the West Coast are visiting their local drug stores looking for potassium iodide pills, a preventative against radiation poisoning of the thyroid gland.
"The real thing is, How much radiation exposure would the U.S. get? ... I'm completely confident in saying it'd be totally insignificant if detected at all," said Dr. Elmer Lewis, Northwestern University nuclear engineer.
Dr. Lewis has spent much of his career teaching and analyzing the nuclear power field, and he says that the radiation health risk in Japan -- although it could change -- remains at present relatively low.
So the notion of a plume of radiation, so concentrated that it could travel 4,500 miles across the Pacific and arrive in any threatening form, would be a stretch.
We receive a certain amount of radiation -- naturally -- every day, from cosmic rays and from the earth. Chicago receives significantly less "background" radiation than, for instance, Denver because of its higher elevation
And we receive some radiation exposure from medical diagnostics.
The Chernobyl nuclear plant disaster in the Ukraine 25 years ago did cause deaths and long-term cancers, but there was no measurable release of radiation from Chernobyl that ever reached the U.S., though there was considerable anxiety then as there is today with the situation in Japan. "My own feeling about these accidents is that the worst-case scenario is the number of deaths to the public -- if any -- will be insignificant compared to the number of bodies washing up on the shore from the earthquake itself," said Dr. Lewis.
ABC7 checked with several drug stores Tuesday, and one pharmacist says he has received some inquiries about potassium iodide tablets, but his store, part of the Walgreens chain, doesn't routinely stock it.
Nine years ago, the Illinois State Department of Public Health dispensed the tablets to residents living within a 10-mile radius of the state's nuclear power plants. That came at a time when there was considerable concern about a possible terrorist strike. There is a shelf-life to potassium iodide, so that state supply was exhausted, and there are no immediate plans by the state to replenish it.