The paper discusses the use of spark source mass spectrometry (SSMS) for elemental analysis by the U.S. EPA's Industrial Environmental Research Laboratory as part of its phased approach to environmental source assessment. The assessment is an evaluation of the physical, chemical, and biological characteristics of industrial process streams. The first phase, Level 1, is a screening that emphasizes completeness of detection of elements and classes of organic materials. SSMS was chosen for Level 1 analysis because it is most economical for 73 elements within adequate limits of detection. Another important consideration is that SSMS doesn't require dissolution. The trigger levels that indicate whether the next assessment phase is necessary are based on the requirement that the Level 1 data be precise within a factor of 3. Therefore, SSMS analysis should provide elemental composition within the limits of 3 with a reasonable level of confidence. Results of a recent Level 1 analytical laboratory audit, to evaluate the reliability of SSMS in meeting the assessment goals, indicate that SSMS generally fulfills the Level 1 requirements for reliability within cost limitations. Be, Te, Co, Mn, and Sc did not meet these requirements. Further studies have been initiated to improve analyses of these elements.