Thundiyil Josef G, Yuan Yan, Smith Allan H, Steinmaus Craig
Division of Occupational/Environmental Medicine, Division of Medical Toxicology, University of California, San Francisco, CA, USA.
Environ Res. 2007 Jul;104(3):367-73. doi: 10.1016/j.envres.2007.02.007. Epub 2007 Apr 24.
The issue of seasonal arsenic measurement variability poses consequences regarding the interpretation and frequency of well water measurements for both public health research and surveillance. In this study, we evaluated seasonal variability in arsenic concentration in 356 wells in western Nevada. River flow data obtained from US Geological Survey National Water Information System were used to classify seasons as wet or dry, and mean differences in arsenic well concentrations measured during these seasons were compared. Arsenic concentrations in these wells averaged 72.9 microg/L (range, non-detect to 3000 microg/L). The mean difference in arsenic concentrations between the wet and dry seasons was -3.3 microg/L (p = 0.78; average percent difference = 2.3%). Eighty wells (22%) had higher arsenic concentrations in the wet season, 75 wells (21%) had higher arsenic concentrations in the dry season and no difference was seen in 201 wells (56%). The mean differences in wells with arsenic levels of 0-10, 11-50, 51-200, > 200 microg/L were -1.4 microg/L(p=0.43), 9.2 microg/L(p=0.36), 15.1 microg/L(p=0.30), and -49.9 microg/L(p=0.59). In summary, although changes in arsenic concentrations were seen in some wells, clear trends in arsenic concentration over time were not associated with the wet and dry seasons. These findings provide evidence that, in our study area as a whole, little seasonal variability occurs in arsenic concentrations, and repeated assessments of arsenic concentrations based on season might add little value to the accuracy of health effects research or public health surveillance.
季节性砷含量测量的变异性问题，对公共卫生研究和监测中井水测量的解读及频率都产生了影响。在本研究中，我们评估了内华达州西部356口水井中砷浓度的季节性变化。利用从美国地质调查局国家水信息系统获得的河流水流量数据，将季节划分为湿润或干旱，并比较了这些季节中井水砷浓度的平均差异。这些水井中的砷浓度平均为72.9微克/升（范围为未检测到至3000微克/升）。湿润季节和干旱季节之间砷浓度的平均差异为-3.3微克/升（p = 0.78；平均百分比差异 = 2.3%）。80口水井（22%）在湿润季节砷浓度较高，75口水井（21%）在干旱季节砷浓度较高，201口水井（56%）未观察到差异。砷含量水平为0 - 10、11 - 50、51 - 200、> 200微克/升的水井中，平均差异分别为-1.4微克/升（p = 0.43）、9.2微克/升（p = 0.36）、15.1微克/升（p = 0.30）和-49.9微克/升（p = 0.59）。总之，尽管在一些水井中观察到了砷浓度的变化，但随着时间推移砷浓度的明显趋势与湿润和干旱季节并无关联。这些发现表明，在我们整个研究区域，砷浓度几乎没有季节性变化，基于季节对砷浓度进行重复评估，可能对健康影响研究或公共卫生监测的准确性贡献不大。
