Vistnes A I, Ramberg G B, Bjørnevik L R, Tynes T, Haldorsen T
Institute of Physics, University of Oslo, Norway.
Bioelectromagnetics. 1997;18(1):47-57.
The aim of this work was to study the exposure to magnetic fields of children living at different distances from a power line and to evaluate how well theoretical calculations compared with actual exposure. Personal exposure instruments were carried for 24 h by 65 schoolchildren living 28-325 m from a 300 kV transmission line; the current load was 200-700 A. About half of the children attended a school far from the power line, whereas the other half attended a school located about 25 m from the line. Exposure to magnetic fields was analyzed for three categories of location: at home, at school, and at all other places. Time spent in bed was analyzed separately. The results indicated that children who lived close to a power line had a higher magnetic field exposure than other children. The power line was the most important source of exposure when the magnetic field due to the line was greater than about 0.2 microT. Exposure at school influenced the 24 h time-weighted average results considerably in those cases where the distance between home and power line was very different from the distance between school and power line. The calculated magnetic field, based on line configuration, current load, and distance between home and power line, corresponded reasonably well with the measured field. However, the correlation depends on whether home only or 24 h exposure is used in the analysis and on which school the children attended. The calculated magnetic field seems to be a reasonably good predictor of actual exposure and could be used in epidemiological studies, at least in Norway, where the electrical system normally results in less ground current than in most other countries.
这项工作的目的是研究居住在距输电线不同距离处的儿童所接触的磁场，并评估理论计算与实际接触情况的吻合程度。65名居住在距一条300 kV输电线路28 - 325米处的学童携带个人接触仪器24小时；电流负荷为200 - 700安培。大约一半的儿童就读于远离输电线的学校，而另一半就读于距离线路约25米的学校。对三类场所的磁场接触情况进行了分析：在家中、在学校以及在所有其他场所。在床上度过的时间单独进行了分析。结果表明，居住在靠近输电线处的儿童比其他儿童有更高的磁场接触量。当线路产生的磁场大于约0.2微特斯拉时，输电线是最重要的接触源。在家庭与输电线之间的距离与学校与输电线之间的距离差异很大的情况下，学校的接触情况对24小时时间加权平均结果有相当大的影响。基于线路配置、电流负荷以及家庭与输电线之间的距离计算出的磁场与实测磁场相当吻合。然而，这种相关性取决于分析中是仅使用在家中的情况还是24小时接触情况，以及儿童就读的是哪所学校。计算出的磁场似乎是实际接触情况的一个相当好的预测指标，并且可用于流行病学研究，至少在挪威是这样，在挪威，电力系统通常产生的接地电流比大多数其他国家少。
