Nuclear security

A safe dose of radiation? Opinions vary wildly

Radiation is everywhere. Some naturally occurs in gases, such as radon, released from the ground. Some comes from the sun. And some is man-made in the form of X-rays, radio waves and nuclear power.

The average annual radiation dose of a person living in the United States is 6.2 millisieverts. This includes 2.4 millisieverts per year of natural or background radiation, according to theNational Council on Radiation Protection and Measurements, an advisory group. A millisievert is a measure of radiation absorbed into living tissue.


The Chernobyl emergency workers who died within a month of the accident received doses of around 6,000 millisieverts. Tens of thousands of evacuated residents received doses of 490 millisieverts. The typical dose of a CT scan is about 10 millisieverts, according to Radiology Info.

Over a short time, a 1,000-millisievert dose causes acute radiation sickness; a 10,000-millisievert dose would be fatal within a few weeks.