在撰写本文时，根据美国环境保护局（USEPA）协议计算的方法检测限（MDL）是饮用水监测中检测限的官方衡量标准。一些公用事业和水检测实验室发现，他们无法定期实现公布的MDL，这一发现得到了51家饮用水实验室调查的证实，该调查还发现MDL存在显著差异。MDLs的传播表明，实验室可能无法可靠地检测低浓度的污染物，这对饮用水合规性监测造成了严重问题。这篇文章确定了那些可能会受到外部控制的因素，这些因素会导致实验室性能的更大一致性，以及关于检测限的更好信息。 包括11个参考文献、表格、图表。

At the time of this article, the method detection limit (MDL) calculated according to a US Environmental Protection Agency (USEPA) protocol is the official measure of detection limits in drinking water monitoring. Some utilities and water testing laboratories find that they cannot routinely achieve published MDLs, a finding confirmed by a survey of 51 drinking water laboratories which also found substantial variation in MDLs. The spread in MDLs suggests that laboratories may not reliably detect contaminants at low concentrations which poses a serious problem in drinking water compliance monitoring. This article identifies those factors that might be amenable to external control and lead to greater uniformity in laboratory performance and better information on detection limits. Includes 11 references, tables, figures.