Refinery Stream Composition Da ta — Update to Speciation Data in API 4723 Since the publication of API 4723 in 2002, new regulatory requirements have resulted in many changes in refi nery processes that may have altered process stream compositions. Changing feedstocks, new pr ocess additives, and new catalysts may also have affe cted the concentrations of chemical species present in specific process streams. Based on an assessment of the range and depth of more recent stream speciation data, the Petroleum Envi ronmental Research Forum (PERF) elected to update the stream speciati on profiles in API 4723 using more recent composition sampling. The upda ted profiles are provided in this report. PERF members believe that the newer data are more representative due to improved sampling and analytica l techniques and that these newer analyses better reflect changes in refi nery operations over recent years. A large database of records was collat ed for the current study, representing information from 25 refineries. The original study reported on 24 ch emical species and the current study provides data on 89 species. The or iginal study reported on 65 refinery process streams and the current project provides data on 68 process streams. The material contained in t h i s r e p o r t w i l l b e o f u s e i n e s t i m a t i n g t h e emissions of specific chem ical species, preparing permit applications, and performing other environmental asse ssments. API, PERF, and the project participants make no claims as to the suitability or acceptability of the stream composition data reported herein for specific reporting or regulatory purposes