Lead in drinking water: Sampling variability and analytical issues

Accurate quantification of lead in potable water samples is necessary for determining compliance with regulatory standards and for evaluating consumer health risks. Recently, the occurrence of particulate lead in drinking water received increased scrutiny, because it was implicated in "spikes" of lead in water that caused childhood lead poisoning. In addition, very high variability in water lead has been reported at certain taps due to sporadic release of lead particles, dependent on flow rate and other as yet unspecified parameters. EPA sampling protocols for lead in water, which were designed for regulatory compliance purposes, might not quantify the portion of lead particles present in water samples that will not dissolve in relatively weak acid (pH < 2.0) after 16 hours of holding time. Laboratory and field data will demonstrate that most of these problems can be overcome by using a stronger acid preservation step. Another set of problems, which arise from misunderstandings regarding the actual details of EPA approved sampling protocols and methodologies, could be addressed by reconciling previous guidance documents. Given the complexities of the problems associated with particulate lead occurrence relative to consumer health risks, it is recommended that additional research be conducted to squarely address concerns. Specifically, the EPA lead in water compliance protocol is not designed to measure water-lead health risks for problematic taps in homes of individual consumers.