METABOLIC VARIABLES AFFECTING THE EFFICACY, SAFETY, AND FATE OF AGRICULTURAL CHEMICALS
Location: Animal Metabolism-Agricultural Chemicals Research
Title: Fate of Chlorate Salts Excreted From Animals
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: July 22, 2008
Publication Date: December 20, 2009
Citation: Smith, D.J., Oliver, C.E., Hakk, H., Anderson, R.C., Larsen, G.L. 2009. Fate of Chlorate Salts Excreted from Animals. In: "Veterinary Pharmaceuticals in the Environment." J. Coats, K. Henderson, Eds. American Chemical Society Symposium Series 1018, Washington, D.C. Pp. 27-44.
Interpretive Summary: Sodium chlorate has historical uses in products as diverse as weed killers and toothpaste. At present, the main uses of chlorate are for water treatment plants, for use in bleaching pulp wood for paper production, and by the agricultural industry as a weed killer and crop drying agent (desiccant). Because chlorate salts selectively kill human pathogens that inhabit the gastrointestinal tracts of food animals (cattle, sheep, poultry, and swine), it is being developed as a pre-harvest food safety tool. Even though chlorate salts may be beneficial for improving human health through the reduction of pathogens on food, its fate and effects in and on the environment must also be considered. Studies are reviewed indicating that chlorate is converted to a nutrient (chloride) in animals and in the environment. In addition, the rate of chlorate conversion to chloride is very rapid in manure systems and can be rapid in soils if the conditions are right. In animal systems having manure disposal processes such as lagoons or composting, the likelihood that chlorate salts could survive without conversion to chloride ion is low.
Colonization of food animals with human pathogens such as E. coli O157:H7 and Salmonella has been a bane to the food animal industry for years. In the United States, E. coli O157:H7 is considered an adulterant, and meat animal products contaminated with the pathogen must be disposed at great cost to the producer. A new pre-harvest food safety technology, based upon the oral administration of chlorate salts to food animals, selectively eliminates gram negative pathogens such as E. coli O157:H7 and Salmonella species in economically important livestock species. Residue trials have demonstrated that chlorate salts are rapidly and extensively eliminated as parent chlorate in the excreta of cattle, swine, and broilers. Under proposed dosing regimens, environmental burdens of excreted chlorate could be significant, especially in areas of intensive food animal production. Chlorate is highly water soluble and its transport through soil columns was not restricted by a variety of soils composed of mixtures of loams, clays, or sands. In soil column studies, chlorate was sparingly converted to chloride ion by a few soil types, but in batch studies utilizing a mixture of soil, urine, and feces, chlorate was rapidly reduced to 16 chloride under both aerobic and anaerobic conditions. Rapid reduction under in vitro conditions implies a short environmental half-life of chlorate for most animal production waste management systems.