As the nuclear crisis continues in northeastern Japan, the government is telling people near the damaged Fukushima-Daiichi reactors to stay indoors. The US government is warning Americans already in Japan to stay at least 80 kilometers away from the reactor site. Meanwhile, many people in the U.S., China and Russia are reportedly stocking up on potassium iodide pills to protect themselves against any wind-borne radiation. While there are many uncertainties about the public health situation in Japan, much is known about the health effects of radiation. Carol Pearson reports.