Bowlt C, Howe J R
Department of Radiation Biology, Medical College of St. Bartholomew's Hospital, London.
Health Phys. 1992 Dec;63(6):686-91. doi: 10.1097/00004032-199212000-00010.
Using a series of daily measurements of 125I in the drinking water of North Surrey, England, from November 1988 through May 1990, the accumulated activities in the thyroids of adults drinking such water were calculated on the assumption that the fraction of ingested iodine taken up by the thyroid was f = 0.3 and the tap water consumption was C = 600 L y-1. These figures were compared with measured values of 125I activities in 42 thyroids taken at necropsy from residents in the North Surrey area who were dying during this same time period. Eight thyroids (19%) had measured activities greater than predicted, so they were named the self-defining critical group. After comparing the thyroid with the drinking water activity, the current generalized derived limit for 125I in the drinking water may be too high by a factor of 2. The reason for this appears to be the use of f = 0.3 which is the mean value for the "normal" population. Models involving critical groups should use values of parameters different from the mean. In the present case, making f = 0.6 would remove the discrepancy between measurement and prediction and would be in reasonable accord with measured distributions of f.
利用1988年11月至1990年5月期间对英格兰北萨里地区饮用水中¹²⁵I进行的一系列每日测量数据，在假设甲状腺摄取的摄入碘比例为f = 0.3且自来水消耗量为C = 600 L·y⁻¹的情况下，计算了饮用这种水的成年人甲状腺中的累积活度。将这些数值与在同一时期死亡的北萨里地区居民尸检时采集的42个甲状腺中¹²⁵I活度的测量值进行了比较。八个甲状腺（19%）的测量活度高于预测值，因此它们被命名为自我定义的临界组。在将甲状腺活度与饮用水活度进行比较后，目前饮用水中¹²⁵I的通用导出限值可能高了2倍。出现这种情况的原因似乎是使用了f = 0.3，这是“正常”人群的平均值。涉及临界组的模型应使用与平均值不同的参数值。在当前情况下，将f设为0.6将消除测量值与预测值之间的差异，并且与f的测量分布合理相符。
