Gosh - typo error detected by plastic surgeon. The end of my career. Sorry, should indeed be 6000. The silly lumping is the ICRP's proposals not mine!
Wiggy - the problem is what is the dose of radiation for a chest X Ray. In 1920 it was 10,000 mrem. By 1960 it had fallen to 1000 mrem. Today it is 2-5 mrem and new equipment can cut this further.
A transatlantic flight exposes you to 0.238 mrem per hour and some studies have recorded annual exposure of 219 mrem so at first glance it would seem that flying is far worse than an X ray, but to put it in perspective one CT scan can be up to 1500 mrem and the safe annual exposure for healthcare workers is 2000 mrem per year so flying is well within the safe level
In fact the background exposure we get at sea level is 300 mrem per year and rises to 1500 mrem per year at 10,000 feet. Radon gas adds 200 mrem per year.