Two interesting excerpts from the Backscatter X-ray wikipedia page: The national radiation safety standard (see below) sets a dose per screening limit for the

Two interesting excerpts from the Backscatter X-ray wikipedia page: The national radiation safety standard (see below) sets a dose per screening limit for the general-use category. To meet the requirements of the general-use category a full-body x-ray security system must deliver less than the dose a person receives during 4 minutes of airline flight. TSA has set their dose limit to ensure a person receives less radiation from one scan with a TSA general-use x-ray security system than from 2 minutes of airline flight. And Fathers exposed to medical diagnostic x-rays are more likely to have infants who contract leukemia, especially if exposure is closer to conception or includes two or more X-rays of the lower gastrointestinal (GI) tract or lower abdomen.[36] In medical radiography the x-ray beam is adjusted to expose only the area of which an image is required, so that generally shielding is applied to the patient to avoid exposing the gonads,[37] whereas in an airport backscatter scan, the testicles of men and boys will be deliberately subjected to the direct beam, and radiation will also reach the ovaries of female subjects. Whilst the overall dose averaged over the entire body is lower in a backscatter X-ray scan than in a typical medical X-ray examination, because of the shielding of the gonads used in medical radiography this in itself does not mean that the dose to the testicles would be less in an airport scan.