ASTM E3358-23a Standard Guidelines for Site Screening and Initial Characterization of Perfluorinated and Polyfluoroalkyl Substances provides a set of standard methods for identifying and assessing contamination of perfluorinated and polyfluoroalkyl substances (PFAS). The guidelines describe in detail how to conduct on-site screening, sample collection and preliminary characterization in environmental pollution investigations to help relevant personnel identify the source, distribution and concentration level of PFAS pollution. This standard provides a technical basis for environment monitoring, threat and risk assessment and pollution remediation, and ensures the accuracy and conformity of detection methods. It has important practical significance for practitioners in the fields of environment protection, public health, etc., and helps to develop more scientific and effective control measures.