Table 1. Summary of the Health Protection Agency's review of the annual exposure of the UK population from all sources of ionising radiation.
| Source | Average annual dose (μSv) a | Total (%) |
|---|---|---|
| Natural | ||
| Cosmic | 330 | 12 |
| Gamma | 350 | 13 |
| Internal | 250 | 9.5 |
| Radonb | 1300 | 50 |
| Artificial | ||
| Medical (diagnostic only) | 410 | 15 |
| Occupational | 6 | 0.2 |
| Fallout | 6 | 0.2 |
| Discharges | 0.9 | <0.1 |
| Consumer products | 0.1 | <0.1 |
| Total (rounded) | 2700 | 100 |
Based on Hughes et al (2005).
a
Throughout this report the term ‘dose’ is used to indicate ‘committed effective dose’ unless otherwise specified. ‘committed effective dose’ is derived by considering the absorbed dose (in joules per kilogram) and then multiplying it by a weighting factor to take account of the type of radiation involved. For sources that do not involve a uniform dose to the whole body, the doses to specific organs are further weighted according to factors recommended by the International Commission on Radiological Protection (ICRP, 2007).
b
Assuming that living for a year in a home with a long-term average radon gas concentration of 20 Bq m−3 gives rise to a dose of about 1000 μSv.