Radiation: How much is too much?

To put the reports coming out of Japan in perspective, the NRC limits occupational radiation exposure for adults working with radioactive material to 50,000 microsieverts a year.

The Federation of Electric Power Companies of Japan said that on Monday morning, a radiation level of 3,130 microsieverts per hour was recorded at the Fukushima Daiichi Nuclear Power Station, about six times the legal limit. Later in the morning, a radiation level of 326 micro sievert was recorded there…

But high doses are dangerous. The U.S. Environmental Protection Agency says exposure to five to 10 rems of radiation will alter a person’s blood chemistry, while 55 rems will also bring on nausea. and fatigue. (One rem is equal to 10,000 microsieverts.)