The 4th International Conference on Selenium in the Environment and Human Health was held 18-21 October 2015 in São Paulo, Brazil. This conference provided an effective scientific communication platform for researchers in different disciplines worldwide to elucidate and better understand those complex roles of Se as both essential nutrient and environmental contaminant. This proceedings volume includes 98 peer-reviewed extended abstracts prepared by Se researchers from 28 countries. These most recent Se research studies address inter-relationships between the geological and atmospheric environment, agricultural food and selenium-biofortified food crops, human and animal health impacts, and genetic, biochemical, and cell and molecular activities. This book presents a unique myriad of Se research to further our international understanding of the role of Se in the context of biochemistry, food chain transfer, and health-related issues.