(Above text links to U.S. Department of State Current Travel Alerts Web page)
The situation in Japan changes frequently and it is important for all travelers to the area to be informed, and to know where to access reliable sources of information. Generally, if one is in Tokyo or south and west of there, the risk of air contamination is very small. The other risks have to do with contamination of the food and water supply. It is important for people to know where food was grown, harvested and processed; this information should be on labels. One should inquire about this issue if there is no clear labeling, and if you cannot be sure, you should not eat or drink such products.
Children, pregnant women and nursing mothers should take more precautions than healthy adults. Internationally reputable sources of reliable and updated information concerning the situation in Japan include:
International Atomic Energy Association (IAEA)
World Health Organization (WHO)
FAQs: Japan nuclear concerns: Travel Advice
Centers for Disease Control (CDC)
2011 Earthquake, Tsunami, and Radiation Release in Japan: Travel Information
EPA data on ionizing radiation measurements
Common isotopes involved in nuclear accidents include I-131, Cesium, and Plutonium. These isotopes differ in their half lives from 7-8 days to hundreds of years; this difference in half life, affects the potential for both environmental and human impact. In addition to the rate of decay (half life), the other thing that affects the potential for environmental and human impact after a nuclear accident is the rate and distance of dispersion throughout the environment into air, water, and soil.
The average annual dose of ionizing to persons residing in the United States is approximately 3.6 mSv (milliseverts). The majority of this dose (55 percent is due to exposure to radon products from the earth and construction materials, with man-made sources of radiation (eg, medical imaging studies), cosmic radiation, and natural radiation from endogenous sources (eg, the naturally occurring radioactive isotope of potassium, potassium-40) contributing the the majority of the other 45 percent (2).
Examples of the ranges of exposures that might be seen following medical imaging procedures include the following:
Estimation of the dose associated with death in 50 percent of those similarly exposed (ie, the LD 50) have been made in various scenarios. As an example, virtually all survivors of the explosion of a nuclear device at Hiroshima had estimated exposures of less than 3000 mSv. Depending on the incident, estimates for the LD 50 have ranged from 1400 mSv among atomic bomb survivors in Japan to 4500 mSv following uniform total-body exposure to ionizing radiation (6,7). This is very unlikely in the current situation.
Several factors/principles determine the seriousness of health impact of ionizing radiation. These include:
The following observations have been made concerning the effects of ionizing radiation on human tissue:
Material adapted from:
Dainiak, N. MD, FACP. (March 29, 2010). Biology and clinical features of radiation injury in adults. In Biology and clinical features of radiation injury in adults. Retrieved March 31, 2011, from http://www.uptodate.com/contents/biology-and-clinical-features-of-radiation-injury-in-adults?source=search_result&selectedTitle=1~150.
2. National Research Council, Committee on the Biological effects of Ionizing Radiation. Health Effects of Exposure to Low Levels of Ionizing Radiation, BEIR V. Washington, DC: National Academy Press 1990.
3. Fazel R, Krumholz HM, Wang Y, et al. Exposure to low-dose ionizing radiation from medical imaging procedures. N Engl J Med 2009; 361:849.
4. McKetty MH. Study of radiation doses to personnel in a cardiac catheterization laboratory. Health Phys 1996; 70:563.
5. Brix G, Lechel U, Glatting G, et al. Radiation exposure of patients undergoing whole-body dual-modality 18F-FDG PET/CT examinations. J Nucl Med 2005; 46:608.
6. Rotblat, J. Acute mortality in nuclear war. In: The Medical Implications of Nuclear War, Soloman, F, Marston, RQ (Eds), Institute of Medicine, National Academy of Sciences, Washington, DC 1986.
7. Mole RH. The LD50 for uniform low LET irradiation of man. Br J Radiol 1984; 57:355.
8. Reeves GI. Radiation injuries. Crit Care Clin 1999; 15:457.
9. Bentzen SM. Preventing or reducing late side effects of radiation therapy: radiobiology meets molecular pathology. Nat Rev Cancer 2006; 6:702.
10. Barnett GC, West CM, Dunning AM, et al. Normal tissue reactions to radiotherapy: towards tailoring treatment dose by genotype. Nat Rev Cancer 2009; 9:134.
11. Dainiak N. Hematologic consequences of exposure to ionizing radiation. Exp Hematol 2002; 30:513.