Public health's response to a changed world: September 11, biological terrorism, and the development of an environmental health tracking network.

Historically, the importance of public health has often been recognized during or as a result of major tragedy. The attacks that occurred in the United States in 2001 are no exception. These events have raised awareness of our vulnerability and the need for emergency preparedness, the need for a flexible and sustainable public health infrastructure, and the importance of linkages between environmental exposures and health outcomes. The authors encourage the public health community, along with policymakers, to develop a national environmental health tracking system that can improve our overall public health capacity and prepare us to investigate the critical issues of the day, whether they be emerging infectious diseases, terrorist attacks, or chronic illnesses.