In memoriam of David P. Rall.

As a scientist, administrator, and diplomat, David P. Rall pioneered the effort to identify and understand the elements that make up the human environment and their consequences for human health. As an intellectual and aggressive activist, he educated scientists, governments, and the world community to the critical need to address the existence of environmental agents and their consequences for human health. As a leader he marshalled some of the best minds and hearts of his time to the cause of world health through a safe and clean environment. And as a visionary he provided the goals of environmental health science and the direction to guide both current and future generations. His death on September 28 brought to a close a chapter in the evolution of our understanding of the interconnectedness of human health and the environment, a chapter he was largely responsible for writing.