THE SCIENTIFIC DETERMINATION OF REPORTING LIMITS AND EXPERIMENTAL CONFIRMATION OF A CALCULATION MODEL USING LABORATORY QUALITY CONTROL DATA

The State of California, Department of Health Services Division of Drinking Water and Environmental Monitoring (DHS-DDWEM), has used Detection Limit for Reporting (DLR) to establish the lower reporting limit for regulatory reports. The DLR refers to the minimum level at or above which any analytical finding of a contaminant in drinking water shall be reported to the State of California. DLR values are set by regulation.Initiated by DDWEM in February 1999, a technical review committee consisting of members of DHS and the regulated community of laboratories was convened to establish a more scientific and reproducible basis for the establishment of DLRs. A Statewide study by laboratories certified for drinking water was conducted to refine the criteria and establish numerical values. Concentration ranges for the statewide study were established using a statistical model and laboratory QC data together with EPA Performance Evaluation Study data. This paper will discuss the outcome of the study and how the calculation model can be used to simplify the determination of detection, reporting, and quantitation limits.