The paper describes taxonomies and safety and security challenges posed by the integration of process control systems and information and communication technology (ICT). Taxonomies and safety and security in process control and ICT are explored, to establish a framework to be used. A description of key challenges of integration is given related to technology, organization and knowledge. Issues from several known incidents are documented, including the Deepwater Horizon accident. A set of specific key issues to be explored are defined related to knowledge, organizational issues and technology. A set of guidelines to be used are suggested and a HAZOP process to explore challenges are described. Results from several reviews of integration between process control systems and information and communication technology are given.