health professionals questions which are based upon the totality of evidence rather than the ?ndings of any single study. The series volumes are not the outcome of a symposium. Rather, each editor has the potential to examine a chosen area with a broad perspective, both in subject matter and in the choice of chapter authors. The editor(s), whose training(s) is (are) both research and practice oriented, has(ve) the opportunity to develop a primary objective for their book, de?ne the scope and focus, and then invite the leading authorities to be part of their initiative. The authors are encouraged to provide an overview of the ?eld, discuss their own research, and relate the research ?ndings to potential human health consequences.