This lecture discusses various environmental health hazards and their effects. It covers four main types of hazards: physical, chemical, biological, and cultural. It then focuses on disease as a major topic in environmental health, explaining how diseases can have both genetic and environmental causes and discussing factors that influence disease transmission and evolution. The document also provides an overview of toxicology and examines specific toxicants, how they enter the environment and human bodies, their persistence and accumulation over time, and approaches to studying their health impacts.