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Setting Context: Acceptable Radiation Exposure Levels & Potassium Iodide

March 18, 2011

NOTE: The below provides information as of March 18, 2011 and is based upon the medical expertise of: radiology, environmental health, and pediatric oncologist specialists at Seattle Children’s

On Radiation in the Pacific Northwest 

People are concerned about what the radiation situation in Japan means for the Pacific Northwest and other parts of the West Coast. According to the Washington State Department of Health (DOH) there is minimal risk to residents of Washington state: http://www.doh.wa.gov/Topics/japan-faq.htm. Current as of Mar. 18, the DOH says:

“We don’t expect significant levels of radioactivity in our state, and there’s no health risk. Japan is thousands of miles from our state, and if radioactivity from the reactors there is released to the upper atmosphere it would be thinned-out by the winds before it could reach us. We could see a very small increase in radiation levels — well below levels that would be a health concern. We’re working with federal, state, and local agencies in a coordinated effort to monitor radiation levels in the air and rainwater.” 

Seattle Children’s agrees with the DOH that there is virtually no risk of radiation in the Pacific Northwest from the nuclear reactor events in Japan. This is because concentrated radiation exposures (those likely to cause health effects) would be completely diffused by the time wind reaches our shores (even in the case of a full meltdown, nuclear specialists think the risk would effect a 100 mile radius around the plant). We are approximately 4300 miles away from Japan. To compare, Chernobyl’s radiation exposures extended to a 600-900 mile distance from the plant.

Here’s some background on acceptable radiation exposure levels to set context on the various radiation reports coming from Japan since the earthquake and tsunami. 

The average person in the U.S. gets around 620 Millirem (mrem) of radiation per year, according to the US Nuclear Regulatory Commission (Jan. 2011). Half of this is background radiation that comes from natural sources like soil and cosmic radiation. The rest comes from manmade sources, like x-rays. For context, a routine chest x-ray is about 10 mrem per film. In higher altitude areas like in Colorado, natural radiation exposure can be 1,000 mrem per year.

The annual radiation exposure limit for someone who works around radiation in the U.S. is 5,000 mrem. Occupational exposure limits for pregnant women are less, as the fetus is more sensitive to radiation, particularly through the first trimester. Pregnant women should consult with their physicians if they have any concern about radiation exposure to their fetus.

Excessive radiation in humans may result in some changes to cells in the body. An injured or damaged cell may be able to repair itself, so no lasting damage is seen. Cells that die may be able to replace themselves during normal biological processes. Lastly, a cell may incorrectly repair itself which can result in biophysical changes like genetic effects, or cancer. This last scenario is highly unlikely to occur unless dangerous levels of radiation is reached.

Radiation affects people in different ways, so it’s impossible to indicate what dose causes death. The US Nuclear Regulatory Commission website has more information about the biological effects of radiation.

On Potassium Iodide 

Seattle Children’s does not support taking potassium iodide as a precaution. Potassium iodide only protects against radioactive iodide which would only be necessary for those exposed to high concentrations very close to the plant. It can have harmful side effects, especially for those who already have thyroid problems. In addition, most people get some potassium iodide in their diet from foods like apples, tomatoes and chicken. Supplements that are not FDA approved do not require testing and there are no assurances that they contain what is labeled on the packaging.

Additional background on radiation levels can be found here:

About Seattle Children's Hospital

Consistently ranked as one of the best children’s hospitals in the country by U.S. News & World Report, Children’s serves as the pediatric and adolescent academic medical referral center for the largest landmass of any children’s hospital in the country (Washington, Alaska, Montana and Idaho). For more than 100 years, Children’s has been delivering superior patient care and advancing new treatments through pediatric research. Children’s serves as the primary teaching, clinical and research site for the Department of Pediatrics at the University of Washington School of Medicine. The hospital works in partnership with Seattle Children’s Research Institute and Seattle Children’s Hospital Foundation. For more information, visit http://www.seattlechildrens.org.

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