Investigating out-of-specification test results of mass concentration of total suspended particulates in air based on metrological concepts—a case study

Abstract

A metrological approach is used for investigating out-of-specification (OOS) test results of total suspended particulate matter (TSP) mass concentrations in ambient air. As a case study, 496 test results of mass concentration of TSP in ambient air were obtained according to methods of the Environmental Protection Agency, USA. The samples, collected in 2009, came from the same geographic proximity in three stone quarries located in Israel. Twenty of the test results were OOS test results that exceeded the upper limit specified in the national air quality regulations. Investigation of the OOS test results indicated the fact that only 10% of these results (two out of 20) can be decidedly interpreted as witnesses of violations of the national air quality regulations. The other 90% were probably metrologically related, i.e., compatible with the national air quality regulations when considering the measurement uncertainty associated with the test results. Probabilities of future OOS test results and global risks of the stone producer and the consumer, who is defined as an inhabitant near a quarry, were estimated. Acceptance limits, resembling “warning and action lines” used in quality control charts, for air test results were calculated by taking into account the measurement uncertainty.