Human monitoring as a supplement to or replacement for environmental monitoring of toxic substances in the workplace has become an increasingly important issue within the last decade, leading to Congressional hearings, governmental studies, and scientific conferences around the world. Just as the purposes for undertaking human monitoring are diverse and sometimes conflicting, so too are the concerns-- medical, legal, and ethical-- such testing has generated.

The authors begin by providing precise characterizations of the types of monitoring now in use and a clear account of the legal basis...