Toxic chemicals: Can what we don't know harm us?

The Chesapeake Bay Program began more than 20 years ago with assessments of a number of key areas, relying on measurements of habitats, plant and anim al populations, and physical and chemical conditions. This approach used wi ldlife as indicators of Bay "health" and of potential threats to human heal th. The extent of toxic chemical contamination was one of the assessment en dpoints in the original survey. When the initial assessment was completed i n 1983, the results of Bay-wide surveys indicated that several specific wat erways were contaminated. These waters, the Elizabeth River, Virginia, the James River, Virginia, and Baltimore Harbor, Maryland, were targeted for sp ecific actions to address the problems of historical and ongoing pollution. Over the past 10 years or more, data on some toxic chemical releases into and levels in the environment have been collected, but these data are limit ed in scope. Furthermore, these data are not used to assess threats to huma n health or more generally to nonhuman endpoints. New and existing data on environmental levels of chemicals and effects at low concentrations provide evidence that toxic chemicals may threaten both human and nonhuman health in the wider Bay system. (C) 2000 Academic Press.