When life changed -- Collecting dust at Ground Zero -- Freeing the WTC dust -- The path to research and sample analysis -- Timing is everything for exposure -- A scientific framework -- The presence of lead -- What was in that WTC dust? -- Into the unknown : exposure and health -- Talking and writing : to what end? -- WTC dust sticks like glue -- Exposure science in future catastrophes -- Final thoughts -- Appendix A. Presentation of the detailed data set on the compounds measured in the WTC dust samples -- Appendix B. Original members of the WTC Technical Panel -- Appendix C. Comments on WTC Signature Study and Peer Review from Greg Meeker, Paul Lioy, and Mort Lippmann, November 3, 2005.