Approaches to the chemical characterization of aqueous wastes and gas phase fugitive emissions are reported. Characterization studies are directed toward known hazardous materials or toward chemical class fractions and components deemed likely hazards from bioactivity data obtained in the development of screening methodologies. Analytical techniques include multicomponent gas chromatographic profiling with element selective detectors, blind assays using biological activity data, chemical class fractionation for specific compound type characterization and use in bioassay studies, and many conventional methods of chemical identification. Specific studies have included: (1) characterization of occupational exposure to polynuclear aromatic hydrocarbons (PAH) in fugitive emissions; (2) determination of correlations between PAH content and bioactivity for several materials; (3) analyses of volatile components in headspace gases; (4) analyses of real and synthetic stack gas mixtures; (5) characterization of aqueous by-products from oil shale retorting, coal liquefaction, and petroleum refining; and (6) development of bioassay inhalation devices. (ERA citation 02:023950)