O'Connor, T.2010-02-152010-02-151990http://hdl.handle.net/1969.3/2147934 p.This report based on six years of results from the NS&T Program and other monitoring efforts, describes the spatial extent and severity of chemical contamination and changes in concentrations of contaminants over the last decade. While conclusions are always subject to new information, it appears that, on a national scale, high and biologically significant concentrations of contaminants measured in the NS&T Program are limited primarily to urbanized estuaries. In addition, levels of those contaminants have, in general, begun to decrease in the coastal U.S.polychlorinated biphenyls (PCBs)Book