chronic toxicity

Chronic toxicity, the development of adverse effects as a result of long term exposure to a contaminant or other stressor, is an important aspect of aquatic toxicology. Adverse effects associated with Chronic toxicity can be directly lethal but are more commonly sublethal, including changes in growth, reproduction, or behavior. Chronic toxicity is in contrast to acute toxicity, which occurs over a shorter period of time to higher concentrations. Various toxicity tests can be performed to assess the Chronic toxicity of different contaminants, and usually last at least 10% of an organism's lifespan. Results of aquatic Chronic toxicity tests can be used to determine water quality guidelines and regulations for protection of aquatic organisms. Chronic toxicity definition Chronic toxicity is the development of adverse effects as the result of long term exposure to a toxicant or other stressor. It can manifest as direct lethality but more commonly refers to sublethal endpoints such as decreased growth, reduced reproduction, or behavioral changes such as impacted swimming performance. Common aquatic Chronic toxicity tests Chronic toxicity tests are performed to determine the long term toxicity potential of toxicants or other stressors, commonly to aquatic organisms. Examples of common aquatic Chronic toxicity test organisms, durations, and endpoints include: Fathead minnow, Pimephales promelas, larval survival and growth Daphnia, Daphnia magna, 21-d survival and reproduction Green algae, Raphidocelis subcapitata, 72-h growth Amphipod, Hyalella azteca, 42-d survival, growth, and reproduction Application of Chronic toxicity test results Results from Chronic toxicity tests can be used to calculate values that can be used for determining water quality standards. These include: