Aquatic toxicology is the study of the effects of manufactured chemicals and other anthropogenic and natural materials and activities on aquatic organisms at various levels of organization, from subcellular through individual organisms to communities and ecosystems. Aquatic toxicology is a multidisciplinary field which integrates toxicology, aquatic ecology and aquatic chemistry. This field of study includes freshwater, marine water and sediment environments. Common tests include standardized acute and chronic toxicity tests lasting 24–96 hours (acute test) to 7 days or more (chronic tests). These tests measure endpoints such as survival, growth, reproduction, that are measured at each concentration in a gradient, along with a control test. Typically using selected organisms with ecologically relevant sensitivity to toxicants and a well-established literature background. These organisms can be easily acquired or cultured in lab and are easy to handle.
History While basic research in toxicology began in multiple countries in the 1800s, it was not until around the 1930s that the use of acute toxicity testing, especially on fish, was established. Due to the wide use of the organochlorine pesticide DDT and its linkage to causing fish death, the field of aquatic toxicology grew. At first, studies focused mainly on oysters and mussels, as they could not move away from the toxic environment. The results of these studies eventually led to the implementation of programs that monitor concentrations of aquatic pollutants in oysters and mussels, such as the Mussel Watch program of the National Oceanic and Atmospheric Administration (NOAA). Over the next two decades, the effects of chemicals and wastes on non-human species became more of a public issue and the era of the pickle-jar bioassays began as efforts increased to standardize toxicity testing techniques. In the United States, the passage of the Federal Water Pollution Control Act of 1947 marked the first comprehensive legislation for the control of water pollution and was followed by the Federal Water Pollution Control Act in 1956. In 1962, public and governmental interests were renewed, in large part due to the publication of Rachel Carson's Silent Spring, and three years later the Water Quality Act of 1965 was passed, which directed states to develop water quality standards. Public awareness, as well as scientific and governmental concern, continued to grow throughout the 1970s and by the end of the decade research had expanded to include hazard evaluation and risk analysis. In the subsequent decades, aquatic toxicology has continued to expand and internationalize so that there is now a strong application of toxicity testing for environmental protection. Aquatic toxicology is continuing to evolve as risk assessment is becoming more practiced in the field. The field is gaining popularity as it has begun to link the effects of pollutants on marine animals to humans who eat fish and other marine life.
Aquatic toxicity tests Aquatic toxicology tests (assays): toxicity tests are used to provide qualitative and quantitative data on adverse (deleterious) effects on aquatic organisms from a toxicant. Toxicity tests can be used to assess the potential for damage to an aquatic environment and provide a database that can be used to assess the risk associated within a situation for a specific toxicant. Aquatic toxicology tests can be performed in the field or in the laboratory. Field experiments generally refer to multiple species exposure, but single species can be caged for a set duration, and laboratory experiments generally refer to single species exposure. A dose–response relationship is most commonly used with a sigmoidal curve to quantify the toxic effects at a selected end-point or criteria for effect (i.e. death or other adverse effect to the organism). Concentration is on the x-axis and percent inhibition or response is on the y-axis. The criteria for effects, or endpoints tested for, can include lethal and sublethal effects (see Toxicological effects). There are different types of toxicity tests that can be performed on various test species. Different species differ in their susceptibility to chemicals, most likely due to differences in accessibility, metabolic rate, excretion rate, genetic factors, dietary factors, age, sex, health and stress level of the organism. Common standard test species are the fathead minnow (Pimephales promelas), daphnids (Daphnia magna, D. pulex, D. pulicaria, Ceriodaphnia dubia), midge (Chironomus tentans, C. riparius), rainbow trout (Oncorhynchus mykiss), sheepshead minnow (Cyprinodon variegatu), zebra fish (Danio rerio), mysids (Mysidopsis), oyster (Crassotreas), scud (Hyalalla Azteca), grass shrimp (Palaemonetes pugio) and mussels (Mytilus galloprovincialis). As defined by ASTM International, these species are routinely selected on the basis of availability, commercial, recreational, and ecological importance, past successful use, and regulatory use. A variety of acceptable standardized test methods have been published. Some of the more widely accepted agencies to publish methods are: the American Public Health Association, US Environmental Protection Agency (EPA), ASTM International, International Organization for Standardization, Environment and Climate Change Canada, and Organisation for Economic Co-operation and Development. Standardized tests offer the ability to compare results between laboratories. There are many kinds of toxicity tests widely accepted in the scientific literature and by regulatory agencies. The type of test used depends on many factors: Specific regulatory agency conducting the test, resources available, physical and chemical characteristics of the environment, type of toxicant, test species available, laboratory vs. field testing, end-point selection, and time and resources available to conduct the assays are some of the most common influencing factors on test design.
Exposure systems Exposure systems are four general techniques the controls and test organisms are exposed to the dealing with treated and diluted water or the test solutions.
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