The sixteenth century was a time of scientific and medical renaissance, an era in which traditional folk beliefs were being supplanted by critical scientific thought. During this period, the Swiss alchemist-physician Theophrastus Phillippus Au-reolus Bombastus von Hohenheim opined that “All substances are poisonous. There is nothing which isn't poisonous. The right dose differentiates a poison from a remedy” (http://www.biology.arizona.edu/chh/problem_sets/toxicology/01t.html), thus fostering current fundamentals of toxicology and pharmacology. From our perspective, passage of the 1972 amendments to the Federal Water Pollution Control Act (Clean Water Act) [1] rekindled social awareness of environmental toxicology. This public law, introduced by Senator Edmund Muskie of Maine, formally recognized the need to control the discharge of “toxic substances in toxic amounts,” acknowledging the realities of the concentration-response relationship and establishing a firm role for environmental toxicologists and chemists in water-quality regulation. Although much information on the laboratory toxicology of individual chemicals was available at the time, little was compiled on the toxicities of complex mixtures and their effects on receiving streams. The laboratories of regulatory agencies, industries, and academia began the task of defining the usefulness of aquatic toxicity testing methods to assess the effects of whole effluents on surface water biota. Because of the relatively high expense of life-cycle testing in the regulatory context, these analyses were generally limited to short-term lethality tests. Recognizing the need to synthesize and evaluate the practicality of this new information, the Society of Environmental Toxicology and Chemistry (SETAC), a professional organization with equal representation from government, academia, and business, convened the fifth in its series of Pellston Workshops in 1982 in Cody, Wyoming, USA, titling this effort Environmental Hazard Assessment of Effluents [2]. Researchers representing the broad constituency of SETAC met to present and review the knowledge gathered to that point and to place it in the context of environmental management. Recognizing that much of the toxicologic work accomplished to that point (and previous Pellston Workshops) had concentrated on the assessment of hazards of individual chemicals, this group attempted to evaluate the effectiveness of existing methods for predicting the hazards of mixed wastes. In this 1982 workshop, 55 participants reviewed the status of whole effluent toxicity (WET), including work performed over the previous several years, and proposed means to most effectively apply analytical and risk assessment methods to WET evaluation. Participants concluded that toxicologic assessment methods for single chemicals could be effectively adapted to assess whole effluents and that these procedures provided realistic tools to evaluate potential environmental impacts. A tiered regulatory assessment and response strategy was proposed to enhance the cost effectiveness of these approaches. While validating WET methods as important regulatory tools, the workshop concluded that these and a variety of other assessment techniques were needed to provide thorough assessment of environmental impact, including chemical specific approaches, bioaccumulation assessment, and field population surveys. During this period, many U.S. state regulatory agencies began to assess acute effluent toxicity by implementing WET limits or monitoring requirements through the National Pollutant Discharge Elimination System (NPDES). In 1984, a landmark paper by Mount and Norberg [3] led to a significant change in the approach to WET assessment. They proposed a short-term method to assess both lethal and sublethal toxicity of whole effluents, ambient waters, and single compounds to the cladoceran Ceriodaphnia over a significant portion of its life cycle. This concept sparked several years of discourse, which still continues, on the application of several short-term methods for the assessment of chronic toxicity. Significantly, the methods provided some of the first techniques that could cost-effectively evaluate sublethal chronic toxicity in NPDES compliance monitoring. As regulatory agencies began placing chronic toxicity limitations in NPDES permits, a number of questions about the technical adequacy and environmental relevance of assessment methods began to reach states and the U.S. Environmental Protection Agency (U.S. EPA). Awakened to these concerns, the U.S. EPA and several trade groups once again called on SETAC to provide a balanced review of these important questions. In September 1995, a group of invited experts met in Pellston, Michigan, USA, to provide this mid-course review. This meeting focused more specifically on the effectiveness and reliability of test methods [4-6] that were facing imminent promulgation in the United States Federal Register [7]. Questions persisted on whether these new tools were appropriate to the task, whether they were performing as designed, and whether their predictive capabilities were acceptable in the context of water-quality regulation. Workshop discussions and deliberations, spanning a period of several days, reaffirmed and built on the conclusions of the 1982 effort. The SETAC review concluded that currently available tools were acceptable to assess WET, but that technical refinements of the methods were possible and more nationally consistent implementation would add to the quality of the effort. The WET methods were considered to be effective tools for predicting instream impacts, but many factors were identified that could affect the success of this prediction, including the relative domination of a water body by an effluent, the consistency of exposure conditions, and the extrapolation of effects of surrogate species to other phylogenetic communities. It was recognized that plant species, sediment toxicity, genotoxicity, and bioaccu-mulation were likely being underassessed by currently implemented state and national programs. In areas such as lakes, estuaries, and ocean outfalls, where waste dispersion and dilution are least understood, the more popular and simple steady-state dilution models were considered inadequate for accurate effects predictions. Finally, WET methods were not considered sufficient by themselves to make environmental hazard assessments. Other chemical-specific and bioassess-ment methods were still needed to understand the variety of stress mechanisms that affect any given receiving stream [8]. Following the 1995 Pellston meeting, SETAC held a public forum to discuss conclusions and recommendations on the adequacy of WET methods. Shortly thereafter, the U.S. EPA held a WET stakeholders workshop to receive input on current implementation of WET methods and recommended improvements. The U.S. EPA-sponsored SETAC WET Experts Advisory Panels were formed from this activity. Relying on the conclusions of the two Pellston WET Workshops and accounting for questions received from stakeholders, the WET Advisory Panels quickly developed WET training opportunities to provide basic information that could be transferred to a broad audience. These courses were crafted specifically to address the perceived need to educate both regulated and regulatory communities on the goals and methods of WET regulation. A public solicitation of questions about WET was followed with electronic publication (SETAC WET Experts Advisory Panels link; http://setac.org) of Frequently Asked Questions. Compilations of WET literature are being readied for distribution by electronic media, and additional workshops are being planned to highlight the evolution of knowledge about toxicity identification and reduction. The application of WET to NPDES permits has had a positive effect on the point-source discharge of toxic substances in toxic amounts in the United States. In 1986, Eagleson, Tedder, and Ausley [9] reported that 25% of effluents from NPDES facilities tested for WET were predicted to be acutely toxic instream. Since application of WET limits to permits in 1987, facilities compliant with all limits (acute and chronic) have been greater than 90% in any given month. However, the twenty-first century will dawn with the need to control more diffuse sources of pollutants. Although, in some areas, we have won battles of controlling quality of discharge, quantity of point-source and nonpoint-source pollutants continues to escalate in proportion to our population and our activities that disturb the land. What does the future hold? How can we remold our tools to evaluate and predict system-scale effects and their sources? What considerations will be necessary to assess ambient water column and sediment toxicity? How can we track toxicity to its source? How can we evaluate the persistence and fate of toxicity through the course of a watershed? The requirement to generate total maximum daily load plans in the water-quality regulatory framework of the United States is ever increasing. Although most of these plans to date have been required or performed on conventional pollutants and individual toxicants, such as biochemical oxygen demand, nutrients, and individual metals, the day will come when effects and control models for complex toxicant interactions are demanded. We must move beyond effluent testing to evaluation of watersheds on an ecosystem scale. Is it time for another Pellston WET Workshop? The Pellston Workshops have proven to be immensely effective at gathering acknowledged experts from diverse fields and sectors and in establishing scientific consensus on the more contentious aspects of WET, including its role in environmental regulation. However, the serious gap between state-of-the-art science and the regulatory arena still remains. Current litigation of WET regulation in the United States continues to raise the same questions that were asked and answered at the Pellston Workshops. These questions are not, for the most part, issues of law, but rather of fundamental science. How variable are the analyses? How should concentration–response curves be utilized? One of our most difficult tasks will be making the results of these more broadly known and accepted as definitive information, both in government and in the courts. The 1977 United States Congress gave us that implicit mandate. This will require us, as environmental toxicologists and chemists, to sometimes leave behind the relative comfort of our laboratories and venture into the world of legal, governmental, and political turmoil to be certain that our voices are appropriately heard and that the knowledge we have gained plays an important part in the betterment of our environment. The Pellston WET Workshops provided a unique venue to convene government, business, and academic scientists to deliberate cooperatively the best ways to utilize aquatic toxicity tools in a regulatory context. This process has worked so well that the U.S. EPA progressively has acted to capture the spirit of Pellston through the WET Experts Advisory Panels cooperative agreement with the SETAC Foundation for Environmental Education. We should continue to emphasize the usefulness of this process for weaving responsibly objective science into society. It is not surprising that much of the research published in this issue focuses on what we will have to face in the coming years. The downstream issues of watershed-scale bioassess-ment versus effluent toxicity, sediment toxicology, nonpoint-source runoff of agricultural and urban pollutants, and complex and ubiquitous toxicants are all addressed. With these we find the familiar treatment of methodologic concerns, data variability, and interpretation. The continued scrutiny of these variables will provide the bridge between our current understanding and the use of science and its evolving applications.
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