The radiation risk is clearly defined for Japan, but is there a risk for the rest of the world, including the west coast of the United States? Fortunately for the United States, its distance from Japan will dilute most radiation coming from the Japanese nuclear power plants. Even if the radiation was caught up in the fast moving jet stream, your thyroid is safe.
According to nuclear experts and physicians, there are minimal health risks presented to Hawaii, Alaska, or the western United States residents. X-Rays, CT scans and even flying on an airplane exposes us to more radiation than anything potentially coming from the tragedy in Japan.
The answer from the scientific community has been overwhelmingly no.... there is no health risk for the United States. Across the board, nuclear experts and physicians have explained that there is no reason to worry.
The reason is because of the immense distance the Pacific ocean puts between our two countries. Even if large amounts of radiation were released and got caught in winds traveling across the ocean, by the time it would reach the United States, it would be so diluted as to not cause any effect. Glenn Braunstein, director of the Thyroid Cancer Center at Cedars-Sinai Medical Center in Los Angeles noted that someone would probably get more radiation while flying from New York to Los Angeles than they would ever get from the radiation from Japan's power plants.
That's the most likely scenario, but what about a worst-case scenario? If radiation particles got caught in high-level jet stream winds and were allowed to travel across the ocean in a more concentrated fashion? Edward Morse, a nuclear engineer at the University of California, Berkeley noted that the sensitive monitoring equipment we have in the US would indeed pick it up two to three days after release in Japan, but again, the levels would not be high enough to cause an impact on anyone's health, they'd simply be observable.
So really, don't worry about radiation! X-rays, CT scans, and flying on an airplane will give you more radiation than anything happening in Japan. In fact, paranoia about radiation fears can actually hurt you MORE than the radiation itself! Any of you who bought potassium iodide tablets because you thought you'd prevent thyroid cancer? Dr. Jonathan E. Fielding, Los Angeles County’s public health chief thinks that's an overreaction. “We want to urge you not to take potassium iodide unnecessarily […] It's definitely not recommended as a precautionary medication.”
The state of Illinois department of health chimed in and was more blunt, stating that people who are taking it could actually be putting their health at risk. The side effects of potassium iodide include nausea and vomiting, skin rashes, fatigue and tiredness, and even tingling in the hands and feet. It's not worth it to put your body through that for a threat that doesn't exist.
So America: You're safe. Time to focus on what's really important, and that's helping the people of Japan recover from this tragedy. The Red Cross, Save the Children, and UNICEF have all set up funds. Please donate whatever you can.