Table_1_A large and feasible national survey representative of population exposure to outdoor gamma radiation in urban areas.XLSX

BackgroundAlthough data on outdoor gamma radiation are available for many countries, they have generally been obtained with measurements performed in undisturbed environments instead of in urban areas where most of the population lives. Only one large national survey, with on-site measurements in urban areas, has been identified worldwide, probably due to high costs (e.g., personnel and instrumentation) and difficulties in selecting measuring points.
MethodsA campaign of outdoor gamma radiation measurements has been carried out in the entire Italian territory. All measurement points were selected at the infrastructures of an Italian telecommunications company as representatives of all the possible situations of outdoor exposure to gamma radiation for population in urban areas. Ten replicates of portable gamma (X) detectors carried out all the measurements.
ResultsApproximately 4,000 measurements have been performed. They are distributed across 2,901 Italian municipalities, accounting for 75% of the Italian population. The national population-weighted mean of the gamma ambient dose equivalent rate (ADER) is 117 nSv h−1, and it ranges from 62 to 208 nSv h−1 and from 40 to 227 nSv h−1 for 21 regions and 107 provinces, respectively. The average variability at the municipal level, in terms of the coefficient of variation (CV) is 21%, ranging from 3 to 84%. The impact of land coverage and the distance from a building on the outdoor gamma radiation level was assessed with complementary measurements, leading to differences ranging from −40 to 50% and to 50%, respectively.
ConclusionA representative campaign of outdoor gamma dose rate measurements has been performed in Italy, only in urban areas, to assess the exposure effect due to outdoor gamma radiation on the population. It is the largest national campaign in urban areas worldwide, with a total of 3,876 on-site measurements. The land coverage and the distance from surrounding buildings were recognized to strongly affect outdoor gamma radiation levels, leading to high variability within small areas. The collaboration with a company that owns a network of facilities on a national territory as dense as the residing population made this survey feasible and affordable. Other countries might adopt this methodology to conduct national surveys in urban environments.

背景
尽管全球多国已拥有室外γ辐射（gamma radiation）相关数据，但此类数据大多采集自未受干扰的自然环境，而非多数人口聚居的城市区域。目前全球范围内仅见1项针对城市区域开展现场测量的大型国家级调查，这一现状或源于高昂的成本（如人员与仪器投入）以及测点选取的重重困难。

方法
本研究在意大利全境范围内开展了室外γ辐射测量工作。所有测点均选取自某意大利电信公司的基础设施，以此作为意大利城市区域人口室外γ辐射暴露各类场景的代表性点位。全部测量工作均由10台便携式γ（X）探测器完成重复测量。

结果
本次研究共完成约4000次测量，覆盖意大利2901个市镇，覆盖人口占意大利总人口的75%。以人口加权计算的全国室外γ辐射周围剂量当量率（gamma ambient dose equivalent rate, ADER）平均值为117 nSv·h⁻¹；21个大区和107个省的该指标范围分别为62~208 nSv·h⁻¹与40~227 nSv·h⁻¹。在市镇尺度下，变异系数（coefficient of variation, CV）的平均水平为21%，区间跨度为3%~84%。本研究通过补充测量评估了土地覆盖类型以及与建筑物距离对室外γ辐射水平的影响，结果显示二者分别可导致辐射水平产生-40%~50%和50%的差异。

结论
本研究针对意大利城市区域开展了具有代表性的室外γ辐射剂量率测量工作，旨在评估室外γ辐射对人群的暴露影响。本次调查共计完成3876次现场测量，是目前全球范围内规模最大的城市区域国家级辐射测量项目。研究证实，土地覆盖类型与周边建筑物距离对室外γ辐射水平具有显著影响，可导致小尺度区域内辐射水平出现较高的变异性。本次调查能够得以顺利开展且成本可控，得益于与一家在全国范围内拥有与人口分布密度匹配的设施网络的电信企业的合作。其他国家可借鉴本研究方法，在城市环境中开展国家级辐射调查。