When scientists speak of radiation, they speak not only of single doses but also of cumulative doses.
See for example, this research from the University of Iowa showing that “cumulative radon exposure is a significant risk factor for lung cancer in women".
And see these studies on the health effects cumulative doses of radioactive cesium. (As I noted on March 29th, the radioactive cesium fallout from Japan already rivals Chernobyl. And the amount of radioactive fuel at Fukushima dwarfsChernobyl).
Admittedly, the damage from huge single doses may be greater than the same cumulative dose from many small exposures. But the smaller doses can still add up.
Remember, the radiation from CT scans and x-rays are external emitters - the radiation emanates from outside the body. In contract, internal emitters keep emitting their radiation inside the body. Therefore, the cumulative effect of multiple small doses of radiation from internal emitters could be even more dramatic, depending on the half life, metabolic pathways and other properties of the particular radioactive particle.
As the European Committee on Radiation Risk notes:
Cumulative impacts of chronic irradiation in low doses are ... important for the comprehension, assessment and prognosis of the late effects of irradiation on human beings ...
And see this.
A military briefing written by the U.S. Army for commanders in Iraq states:
Hazards from low level radiation are long-term, not acute effects... Every exposure increases risk of cancer.
(Military briefings for commanders often contain less propaganda than literature aimed at civilians, as the commanders have to know the basic facts to be able to assess risk to their soldiers.)
The briefing states that doses are cumulative, citing the following military studies and reports:
- ACE Directive 80-63, ACE Policy for Defensive Measures against Low Level Radiological Hazards during Military Operations, 2 AUG 96
- AR 11-9, The Army Radiation Program, 28 MAY 99
- FM 4-02.283, Treatment of Nuclear and Radiological Casualties, 20 DEC 01
- JP 3-11, Joint Doctrine for Operations in NBC Environments, 11 JUL 00
- NATO STANAG 2473, Command Guidance on Low Level Radiation Exposure in Military Operations, 3 MAY 00
- USACHPPM TG 244, The NBC Battle Book, AUG 02
One of the Giant's of Radiation Exposure Science Warned of Cumulative Low-Dose Exposures
American reporter Dahr Jamail reports today for Al Jazeera: