This two volume set (LNCS 8025-8026) constitutes the refereed proceedings of the Fourth International Conference on Digital Human Modeling and Applications in Health, Safety, Ergonomics and Risk Management, formerly International Conference on Digital Human Modeling, DHM 2013, held as part of the 15th International Conference on Human-Computer Interaction, HCII 2013, held in Las Vegas, USA in July 2013, jointly with 12 other thematically similar conferences. The total of 1666 papers and 303 posters presented at the HCII 2013 conferences was carefully reviewed and selected from 5210 submissions. These papers address the latest research and development efforts and highlight the human aspects of design and use of computing systems. The papers accepted for presentation thoroughly cover the entire field of Human-Computer Interaction, addressing major advances in knowledge and effective use of computers in a variety of application areas. This two-volume set contains 91 papers. The papers in this volume focus on the following topics: driving and aviation safety, human factors and digital human modeling in healthcare, and safety of the human environment.