Radiation Protection Bureau, Health Canada, 775 Brookfield Road, Ottawa, K1A1C1, Ontario, Canada.
Radiation Protection Bureau, Health Canada, 775 Brookfield Road, Ottawa, K1A1C1, Ontario, Canada.
J Environ Radioact. 2022 Mar;243:106811. doi: 10.1016/j.jenvrad.2022.106811. Epub 2022 Jan 8.
External sources of radiation originate from cosmic rays and natural radioactive elements, principally K and decay products in the uranium and thorium decay series occurring in the ground. People are exposed to terrestrial radiation and cosmic rays everywhere and at all times. To assess Canadians' external exposure to natural radiation, five years (2016-2020) of real-time environment monitoring data recorded by Health Canada's Fixed Point Surveillance (FPS) network were analysed for 36 monitoring stations across Canada. Absorbed dose rates in air from terrestrial radiation vary geographically and seasonally. Absorbed dose rates due to cosmic rays depend strongly on the elevation and vary with solar activities. The population-weighted annual outdoor ambient dose equivalent rates are 20 nSv/h for terrestrial radiation and 52 nSv/h for cosmic rays. Considering that, on average, Canadians spend 89% of their time indoors and 11% of the time outdoors, the population-weighted annual effective doses were calculated as 443 μSv (54 μSv outdoors and 389 μSv indoors), with 20.6% (91 μSv) from terrestrial radiation and 79.4% (352 μSv) from cosmic rays.
外照射的辐射源来自宇宙射线和天然放射性核素，主要是存在于土壤中的铀和钍衰变系列中的 K 和衰变产物。人们随时随地都受到陆地辐射和宇宙射线的照射。为了评估加拿大民众所受到的天然辐射外照射，对加拿大卫生部固定点监测网络（FPS）在 2016 年至 2020 年五年间记录的环境实时监测数据进行了分析，这些数据来自加拿大各地的 36 个监测站。陆地辐射引起的空气中吸收剂量率在地理上和季节上存在差异。宇宙射线引起的吸收剂量率强烈依赖于海拔高度，并且随太阳活动而变化。人群加权的年户外环境当量剂量率分别为陆地辐射 20 nSv/h 和宇宙射线 52 nSv/h。考虑到加拿大民众平均 89%的时间在室内度过，11%的时间在户外，因此计算出人群加权的年有效剂量为 443 μSv（户外 54 μSv，室内 389 μSv），其中陆地辐射占 20.6%（91 μSv），宇宙射线占 79.4%（352 μSv）。
