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Sources and Characteristics
Published in David H.F. Liu, Béla G. Lipták, Wastewater Treatment, 2020
Larry W. Canter, Negib Harfouche
Toxicity tests, the second category of biomonitoring, are less expensive and labor intensive than ecological surveys. Toxicity tests use indicator organisms in a controlled situation to examine water and effluent toxicity. The toxic effects of concern are death, immobilization, serious incapacitation, reduced fecundity, or reduced growth. Toxicity tests can be used to assess acute or chronic toxicity. Acute toxicity is a severe toxic effect resulting from a brief exposure, while chronic toxicity results from prolonged exposure. Tests for acute toxicity can be conducted within 24–96 hr, and chronic tests for toxicity are conducted usually in four or more days (Clesceri, Greenberg, and Trussell 1989).
Nomenclature and Terminology
Published in Jack Daugherty, Assessment of Chemical Exposures, 2020
Toxicity is an adverse effect on an organism. Acute toxicity is the effects resulting from a brief exposure while chronic toxicity is the adverse effects that follow a long term exposure. Cumulative toxicity are adverse effects due to repeated doses occurring as the result of a prolonged action. Subchronic toxicity is the adverse effects from repeated daily exposure for approximately ten percent of life time (about seven years).
Biocompatibility
Published in Marie B. Teixeira, Design Controls for the Medical Device Industry, 2019
The risk of a medical device causing systemic toxic reactions during short term, long term, or continuous application on or in the human body depends mainly on the risk that relevant quantities of toxic substances may be released from the product to become systemically available during its intended use. Systemic toxicity refers to the way the animal/human body is affected as a whole. In systemic toxicity testing, the animal is exposed to the test article or the extract of the test article. Four categories of systemic toxicity testing exist, and each is based upon the duration of exposure. These include: Acute toxicity = a toxic effect resulting from a single, short-term (24–72 hours) exposure to a chemical substance.Subacute toxicity = a toxic effect that results from a single dose or multiple doses to a chemical substance for 14–28 days (~1 month).Subchronic toxicity = a toxic effect resulting from prolonged exposure to a chemical substance for up to 90 days (1–3 months).Chronic toxicity = a toxic effect from continuous and prolonged exposure for over 90 days (typically 6–12 months).
Hazard characterization of silver nanoparticles for human exposure routes
Published in Journal of Environmental Science and Health, Part A, 2020
A number of studies have been conducted on AgNP toxicity in animal models. In the last decade, a number of these nanoparticle toxicity studies have gained attention due to increased public concern regarding the seemingly unlimited applications in the market. Acute toxicity studies determine metric values such as LD50 (lethal dose 50) (single dose or 14 days). A deeper analysis in subacute toxicity studies (28 days) further identified specific effects. The NOAEL (no observable adverse effect level) can be determined by subchronic toxicity studies (90 days). In Europe, the OECD (the organization for economic co-operation and development) guidelines provided protocols for studying chemical toxicity. OECD Guidelines (No. 401—413) have been used in identifying health effects of AgNPs through oral, dermal and inhalation pathways over different exposure periods. However, the evaluation of nanoparticle in the category of chemicals causes difficulty. Therefore, OECD has provided guidelines for characterizing physical and chemical properties for studying nanoparticles,[22] and updated related protocols to enable testing and characterization of the effects of nanomaterials.[23] In vivo toxicity studies have provided a means of hazard characterization by exploring dose-response relationships of pharmacokinetics and toxic performances on targeting tissues, which are shown in Figure 1.