Everyone receives natural background radiation. UNSCEAR gives a world average of about 2.4 mSv per year, more than half of it from inhaled radon; the 2023 national report gives about 3.1 mSv for China. Medical exposure is the largest man-made source. A chest X-ray is about 0.1 mSv and a CT examination about 2–8 mSv.
Reviewed 2026-09-24
Doses compared
- Flight of about 2,000 km0.01 mSv
- One chest X-ray0.1 mSv
- Man-made sources, China average per year0.21 mSv
- Public dose limit per year (GB 18871)1 mSv
- Natural background, world average per year2.4 mSv
- Natural background, China average per year3.1 mSv
- One CT examination2–8 mSv
- Occupational limit, 5-year average per year (GB 18871)20 mSv
Where natural background comes from
| Component (world average) | mSv per year |
|---|---|
| Inhalation, mainly radon and its progeny | 1.26 |
| Terrestrial gamma radiation (external) | 0.48 |
| Cosmic radiation | 0.39 |
| Ingestion (food and water) | 0.29 |
| Total | 2.4 |
UNSCEAR 2008. Typical values range from about 1 to 13 mSv depending on location. For China, the 2023 national report gives about 0.9 mSv external and 2.23 mSv internal exposure.
Man-made sources
Man-made sources include medical diagnosis and therapy, nuclear power, past weapons testing and industrial, agricultural and research uses. Medical exposure dominates. UNSCEAR 2008 gives a global average of about 0.6 mSv per year from man-made sources; the corresponding figure cited for China is about 0.21 mSv.
Building materials
Natural stone can contain radionuclides; granite is more likely to than marble. China’s GB 6566-2010 classifies building materials into classes A, B and C: class A is unrestricted, class B should not be used for interior finishes of homes, hospitals, schools and similar buildings, and class C only for exterior use.
References
- UNSCEAR 2008 Report, Volume I: Sources of Ionizing Radiation
- 生态环境部辐射环境监测技术中心《2023 年全国辐射环境质量报告》
- GB 6566-2010 建筑材料放射性核素限量
- 新莱福防辐射产品手册（2024-09 V1）科普章节
- IAEA — Radiation, People and the Environment (2004)
This encyclopedia is for general and engineering reference and is not medical advice. Consult radiation protection or medical professionals for individual exposure assessment.