The two-volume Handbook of Environmental Health has been a standard reference for over 23 years. The fourth edition continues to provide a basis for understanding the interactions between humans and the environment and how such interactions affect the health and welfare of individuals. Focusing on factors generally associated with the internal environment, Volume I provides a significant understanding of basic new environmental issues, energy, practical microbiology and chemistry, risk assessment, emerging infectious diseases, recent laws, emerging microorganisms, toxicology, epidemiology, human physiology, and the effects of the environment on humans.