| Splitting more than hairs|
Background radiation is the small dose of ionizing radiation that everyone receives from natural radioactive elements present in the environment and from various human activity.
The average annual dose of background radiation is about 3 mSv, but varies a lot depending on the location. Convincing evidence of increased risk of cancer is available for acute doses higher than 100 mSv ("acute" means during a few hours, not in a year). For lower doses the evidence is inconclusive. Some scientists think that risk of cancer is proportional to radiation dose - this is called the linear no-threshold (LNT) hypothesis. Others think that there is a threshold below which there are no effects. Yet another group thinks that small doses of radiation are beneficial - this is called radiation hormesis. Currently the scientific consensus is in favor of the LNT model, but not overwhelmingly so.
- Radon gas in buildings - about 50%
- Direct irradiation from the ground and buildings
- Cosmic radiation - about 10%, significantly more for aircraft crew
- Medical procedures, such as X-ray, computed tomography, scintigraphy and radiotherapy - 10 to 15% in the developed countries
- Food and drink
- Fallout from atmospheric nuclear testing in the 50s and 60s - about 0.3%
- CRT television/computer monitors, which are still preferred for some applications. They can be more energy efficient than flat-panels if used the right way (having most of the screen dark most of the time)
- Household smoke detectors
- Coal-burning power-plant emissions, roughly 3.3x the radiation dosage one would receive living the same distance from a nuclear plant generating the same number of watts of electricity.
- Nuclear power - less than 0.01%