Public Health Sciences Division, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, PO Box 19024, M4-C308, Seattle, Washington, USA.
Environ Health. 2010 Jan 28;9:4. doi: 10.1186/1476-069X-9-4.
Tap water may be an important source of exposure to arsenic and nitrate. Obtaining and analyzing samples in the context of large studies of health effects can be expensive. As an alternative, studies might estimate contaminant levels in individual homes by using publicly available water quality monitoring records, either alone or in combination with geographic information systems (GIS).
We examined the validity of records-based methods in Washington State, where arsenic and nitrate contamination is prevalent but generally observed at modest levels. Laboratory analysis of samples from 107 homes (median 0.6 microg/L arsenic, median 0.4 mg/L nitrate as nitrogen) served as our "gold standard." Using Spearman's rho we compared these measures to estimates obtained using only the homes' street addresses and recent and/or historical measures from publicly monitored water sources within specified distances (radii) ranging from one half mile to 10 miles.
Agreement improved as distance decreased, but the proportion of homes for which we could estimate summary measures also decreased. When including all homes, agreement was 0.05-0.24 for arsenic (8 miles), and 0.31-0.33 for nitrate (6 miles). Focusing on the closest source yielded little improvement. Agreement was greatest among homes with private wells. For homes on a water system, agreement improved considerably if we included only sources serving the relevant system (rho = 0.29 for arsenic, rho = 0.60 for nitrate).
Historical water quality databases show some promise for categorizing epidemiologic study participants in terms of relative tap water nitrate levels. Nonetheless, such records-based methods must be used with caution, and their use for arsenic may be limited.
自来水可能是砷和硝酸盐暴露的一个重要来源。在对健康影响进行大型研究的背景下，获取和分析样本可能会很昂贵。作为替代方案，研究可以通过使用公共水质监测记录，单独或结合地理信息系统 (GIS)，来估计个别家庭的污染物水平。
我们在砷和硝酸盐污染普遍但通常处于中等水平的华盛顿州检验了基于记录的方法的有效性。从 107 个家庭（中位数为 0.6μg/L 砷，中位数为 0.4mg/L 硝酸盐氮）中采集样本进行实验室分析，作为我们的“金标准”。使用 Spearman 的 rho 检验，我们将这些测量值与仅使用家庭街道地址以及在指定距离（半径）范围内最近和/或历史上来自公共监测水源的测量值（从半英里到 10 英里不等）进行比较。
随着距离的缩短，一致性有所提高，但我们能够估计摘要测量值的家庭比例也随之下降。当包括所有家庭时，对于砷（8 英里），一致性为 0.05-0.24，对于硝酸盐（6 英里），一致性为 0.31-0.33。将注意力集中在最近的水源上并没有带来多大改善。对于拥有私人水井的家庭，一致性最高。对于使用供水系统的家庭，如果仅包括为相关系统服务的水源，则一致性会有很大提高（对于砷，rho = 0.29，对于硝酸盐，rho = 0.60）。
历史水质数据库在根据自来水中硝酸盐的相对水平对流行病学研究参与者进行分类方面显示出一定的前景。尽管如此，此类基于记录的方法必须谨慎使用，其对砷的使用可能受到限制。
