ASABE Technical Library - Abstract
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Toxicological Issues
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: No Citation available.Authors: Ray, Chittaranjan
Keywords: Pesticides, Toxicological, Dose, Pharmacokinetics, Health advisories, Noncarcinogenic, Carcinogenic, Ecotoxicological, Exposures, Metabolites, Drinking water, Health advisories
Once a contaminant (e.g., a pesticide or its metabolite) is present in the environment, the primary exposure routes for it to gain entry into the human body are inhalation, ingestion, and dermal contact. Using these routes, the contaminant passes through the digestive track, blood and lymph system, and lungs; interacts with body organs; and finally is eliminated through exhaled air, urine, or feces or is partly stored in fat, bone, and other tissue. LaGregaet al. (1994) provide a description of the process and fraction of a contaminant passing through each of these pathways within the body. Irrespective of the route, the chemical must move across the body barrier to enter the blood stream; this transport process is referred to as absorption. An administrative dose is the amount of toxic chemical to which the body is exposed; this is called an intake or uptake dose. The amount reaching a target organ is known as the target or effective dose. This dose is dependent on how the bodys system interacts with the chemical. Upon reaching the blood stream, the chemicals can move throughout the body using the circulatory system. Based upon their affinity for various tissues, they can accumulate in the body for extended periods of time. Polarity of the chemical and the affinity between the chemical structure and the storage tissue are the main factors affecting storage in the body. Storage is one of the defense mechanisms of the body; however, dieting, stress, and other use of fat reserves can induce the rapid release of stored substances to cause toxic effects. Once a chemical reaches an organ, three events (other than storage) can take place: (1) biotransformation, (2) elimination, and (3) formation of a complex involving the chemical and the receptor. Chemical metabolites are formed by the enzymatic action of various organs; however, some of the resulting metabolites may be more toxic than the parent compounds. For polar compounds, most metabolites and chemicals that do not get stored in the body may pass out of the body in urine, bile, feces, or secretions. For non-polar and non-volatile compounds, elimination is difficult unless the parent compound is metabolized to a more polar compound.
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