Assessment Methods

development of risk assessments and supporting documentation for regulatory agencies and environmental and engineering companies. Williams authored the cover story, %sessmg Risk: Toxicity in Perspective," in our August 1993 issue. A s a companion document to the Human Health Evaluation Manual, EPA published the Environmental Evaluation Manuall in 1989 as a part of its Risk Assessment Guidance for Super-fund. This document was intended to address one of the requirements of Sections 121(b)(l) and (d) of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), namely, that selected remedial actions at Super-fund sites be protective of human health and the environment. Like the Human Health Evaluation Manual, the Environmental Evaluation Manual was developed for the Remedial Investigation/ Feasibility Study (RI/FS) process at Superfund sites, and thus to serve as an aid in the selection of remedial alternatives at such sites. Despite the fact that the manuals were published at nearly the same time and EPA guidance in these two areas appeared almost simultaneously , the common practice of environmental or ecological risk assessment has not occurred, Unlike the human health risk assessment for which definitive endpoints (for example, cancer) and species (man) are targeted, ecological end-points and species of concern are ill-defined. Toxicologists and other environmental scientists now are beginning to acquire a better understanding of the effects of chemicals on aquatic species and terrestrial wildlife, and to develop standardized methods for the assessment