ECONOMICS OF SCREENING IN THE DETECTION OF ORGANICS IN GROUND-WATER

Screening may be defined as the use of efficient test procedures to determine and/or to quantify the presence or absence of contaminants in samples. In support of screening, many commercial laboratories offer price-breaks when analysis for only a few compounds are sought instead of a standard scan (such as those required under a governmental regulatory program). Screening is a step-wise or a decision tree approach to sampling and analysis. For a fixed number of compounds in a screen, a model to maximize the total expected number of positive determinations (detections) of organic compounds in ground water samples is developed and evaluated. This model is tested with extensive data on organic measurements obtained from ground-water samples at hazardous waste sites. The economic viability of the model is evaluated within the context of price-breaks in analytical services offered by commercial laboratories. For a set of price-break assumptions, screening is shown to be far superior in the detection of pesticide, acid, and base neutral compounds than in the detection of volatile organic compounds in ground water at hazardous waste sites. By incorporating relevant QA/QC costs, it is further shown that screening is a cost-effective alternative for all four groups of organic compounds. A few promising avenues for further research are also outlined.