Reply #8: The radiation exposure is relatively small

[salvorhardin]

The effective radiation dose from a mammogram is about 0.7 mSv, which is about the same as the average person receives from background radiation in three months. Federal mammography guidelines require that each unit be checked by a medical physicist every year to ensure that the unit operates correctly. See the Safety page for more information about radiation dose.
http://www.radiologyinfo.org/en/info.cfm?PG=mammo&bhcp=1#part_nine

The actual risk is dependent on age since younger women are more sensitive to radiation-induced cancers. And of course, false positives are likely to result in additional exposures.