At 05:39 PM 3/18/2011, Mike Miller wrote:
>What's normal?

The worldwide average background exposure is about 250 millirems (2.5
millisieverts) a year.  People in Denver get about twice that because
of the altitude.  Various places get more, some a lot more.  Granite
is radioactive, so is coal and seawater so people in New Hampshire
get a slightly higher exposure.

A chest or abdomen CT scan delivers somewhat over twice the average
yearly background dose, whereas a static chest xray adds only a very tiny dose.

Yours,
David