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Guidelines for Interpretation of the Biological Effects of Selected Constituents in Biota, Water, and Sediment November 1998 NIATIONAL RRIGATION WQATER UALITY P ROGRAM INFORMATION REPORT No. 3 United States Department of the Interior Bureau of Reclamation Fish and Wildlife Service Geological Survey Bureau of Indian Affairs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ntroduction The guidelines, criteria, and other information in The Limitations of This Volume this volume were originally compiled for use by personnel conducting studies for the It is important to note five limitations on the Department of the Interior's National Irrigation material presented here: Water Quality Program (NIWQP). The purpose of these studies is to identify and address (1) Out of the hundreds of substances known irrigation-induced water quality and to affect wetlands and water bodies, this contamination problems associated with any of volume focuses on only nine constituents or the Department's water projects in the Western properties commonly identified during States. When NIWQP scientists submit NIWQP studies in the Western United samples of water, soil, sediment, eggs, or animal States—salinity, DDT, and the trace tissue for chemical analysis, they face a elements arsenic, boron, copper, mercury, challenge in determining the sig-nificance of the molybdenum, selenium, and zinc. Financial analytical results. How much of a given and time restraints do not allow chemical constituent is “normal” in the tested consideration of other contaminants at this medium? How much is unusually high? What time. adverse effects—if any—may result from the reported concentration? Studies that address (2) For the most part, these are only guide- these questions are myriad: they are widely lines, merely reports of toxic effects that scattered in the literature, they use many were noted for certain concentrations in different approaches and testing protocols, and particular circumstances. Individual they yield greatly varying—and sometimes constituents may be more or less toxic at contradictory— results. The chapters in this other sites or for other species, depending volume are intended to: (1) identify the most on many factors. Some of these com- important, most relevant studies for several plicating factors are described in the “constituents of concern” that are commonly following section on data interpretation, encountered in environments affected by which readers are urged to review before irrigation drainage; (2) present a sampling of attempting to apply these guidelines. notable results from these studies in tables organized according to tested medium; (3) (3) Caution is particularly appropriate in using explain further, in the accompanying text, the the summary tables (the first numbered significance of these results; and (4) give full table in each of the chapters). These are and accurate references to the original studies, designed to give only a general indication of for those who desire more detailed information. concentrations that may be troublesome in various types of media. In some cases the Although this volume is targeted for scientific “no effect” and “threshold” values for a specialists, it may also be of interest to class of organisms have been distilled from government officials, farmers, ranchers, hundreds of individual studies of the conservationists, reporters, and anyone else diverse species that make up the class. In interested in the environmental health of other cases, we have had to rely on only a freshwater ecosystems. These readers may find handful of studies to set tentative values the glossary in Appendix II especially helpful. for the entire class. Readers should make no final, formal decisions regarding the toxicity of 1 National Irrigation Water Quality Program Guidelines a particular compound to a particular individual constituents to be more or less toxic species without consulting the more at other sites or for other species. This section detailed information presented later in each describes some of the better known factors that chapter and, when possible, the original may complicate the interpretation of toxicity studies. data. (4) Results from many recent studies could not be included here. Most of the research for Unnatural Laboratory Settings these chapters was completed by mid-1996, and only the literature pub-lished prior to Most laboratory studies test toxicity under that time was system-atically surveyed. completely unnatural conditions: they test the During subsequent review and preparation effect of a single compound on a single species, of this volume, more recent results that delivered by only one pathway under carefully came to our attention were added controlled conditions. In the wild, organisms opportunistically, not systematically. are exposed to many different chemical and physical agents simultaneously. (See (5) Legally enforceable standards are not “Interactions,” below.) presented here, with two exceptions. The U.S. Environmental Protection Agency has Generally, laboratory specimens in an established “maximum contaminant levels,” experimentally contaminated environment are applicable only to drinking water, for most given food from outside, uncontaminated of these constituents, and the U.S. Food sources, whereas wild creatures must eat food and Drug Administration has “action levels that has grown in the same environment and for human consumption” for two of them that may have accumulated, through (DDT and mercury). These legal standards bioconcentration, lethal levels of whatever are noted near the end of each chapter, in toxins are present. Thus, for instance, fish or the section “Regulatory standards.” Note, waterfowl could end up dying in areas where however, that even in those sections, values waterborne toxin concentrations are at levels identified as “goals” or “criteria” do not that caused no harm to laboratory specimens. have the force of law. On the other hand, most laboratory specimens Individual States may set legal standards that are are taken from uncontaminated populations, stricter than those of the Federal Government, which have no previous history of exposure to and many have chosen to do the toxin being tested. In the wild, organisms so. State standards are too variable and living in a contaminated environment may have voluminous to be listed here; however, acclimated or adapted to the toxin, especially if Appendix I lists addresses and phone numbers the contamination developed gradually. In this for the offices responsible for water quality case, one might find fish and waterfowl thriving standards in each of the 17 Western States. in areas where waterborne concentrations are at levels experimentally determined to be lethal. The Need for Caution in Laboratory specimens are rarely threatened by Interpreting Toxicological Data predators or challenged by others of their own kind in mating competitions, whereas their The contents of this report are described as undomesticated cousins deal with both conflicts. These conflicts can add to the overall stress on guidelines, rather than rules or standards, the organisms, making them more susceptible to because toxicological effects vary greatly in toxic effects. Conversely, the higher metabolic natural ecosystems. Many variables can cause 2 Introduction rates of creatures in conflict may help them In some cases, two substances that interact dispose of toxins more readily. antagonistically at first may eventually become synergistic with increasing concentrations. For These differences between natural and instance, some interactions may transform a laboratory environments mean that measure- toxic compound to a less toxic, but also less ments collected in natural settings are generally soluble, form. These low-solubility compounds preferable to laboratory measure-ments for may then accumulate in the liver, the kidneys, or predicting toxic effects in natural systems. In other bodily organs, eventually overtaxing the cases where natural studies are lacking, though, capacity of these storage sites. Physical damage the laboratory studies may provide the only may occur to organs storing too useful guidance to possible toxic effects. many solids. Moreover, only in controlled laboratory studies can the effects of individual variables be However, our understanding of biogeo-chemical studied, by holding all other factors constant. interactions is still rudimentary. The potential combinations of trace elements are essentially infinite, and research thus far has defined the Interactions additive, antagonistic, and synergistic effects of only a few simple com-binations. Some The toxicity of an element or compound may be compounds cause toxic effects by interfering in either reinforced or weakened through its essential chemical metabolic pathways, yet interaction with other substances. In toxi- different chemical species of the same two cology

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