METABOLIC VARIABLES AFFECTING THE EFFICACY, SAFETY, AND FATE OF AGRICULTURAL CHEMICALS
Location: Animal Metabolism-Agricultural Chemicals Research
Title: Total radioactive residues and residues of [36Cl]chlorate in market size broilers.
Submitted to: Journal of Agriculture and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 15, 2007
Publication Date: June 16, 2007
Citation: Smith, D.J., Byrd, J.A., Anderson, R.C. 2007. Total radioactive residues and residues of [36Cl]chlorate in market size broilers. Journal of Agricultural and Food Chemistry 55:5898-5903.
Interpretive Summary: Each year thousands of US consumers become ill because they have eaten food products that are contaminated with pathogenic bacteria. Intense efforts have been made during the last decade to eliminate pathogenic contamination from food animals. To date, no single strategy to eliminate pathogens from food animal products has been widely accepted. A new pre-harvest food safety strategy has been developed that has been shown to greatly reduce, or even eliminate gram-negative pathogens from several food animal species. Use of this new food or water additive has not been approved by regulatory organizations because it is not known whether residues present in edible tissues of treated animals represent a health risk. The purpose of this study was to determine the effect that the dose of a new chlorate-based compound has on residues of chlorate in edible tissues of market broilers. For all of the doses tested, chlorate residues in edible tissues fell well below amounts that are estimated to be safe to consumers. Further research on the chlorate-based product is warranted because it could have a significant impact on lowering the incidence of harmful bacteria on meat products and because residues of the product fall below levels that regulatory agencies have estimated to be safe.
The oral administration of chlorate salts reduces the numbers of Gram-negative pathogens in gastrointestinal tracts of live food animals. Although the efficacy of chlorate salts has been demonstrated repeatedly, the technology cannot be introduced into commercial settings without first demonstrating that chlorate residues, and metabolites of chlorate remaining in edible tissues, represent a negligible risk to consumers. Typically a first step in this risk assessment is to quantify parent compound and to identify metabolites remaining in edible tissues of animals treated with the experimental compound. The objectives of this study were to determine the pathway(s) of chlorate metabolism in market broilers and to determine the magnitude of chlorate residues remaining in edible tissues. To this end, twelve broilers (6 wks; 2.70 ± 0.34 kg) were randomly assigned to three treatments of 7.4, 15.0, and 22.5 mM of sodium [36Cl]chlorate dissolved in drinking water (n=4 broilers per treatment). Exposure to chlorate, dissolved in drinking water, occurred at 0- and 24-hours (250 mL per exposure), feed was withdrawn at hour 38, water removed at hour 48, and birds were slaughtered at hour 54 (16 hours after feed removal and 8 hours after water removal). Radioactivity was rapidly eliminated in excreta with 69 to 78% of the total administered radioactivity being excreted by slaughter. Total radioactive residues were proportional to dose in all edible tissues with chloride ion comprising greater than 98.5% of the radioactive residue for the tissue (9.4 – 97.8 ppm chlorate equivalents). Chlorate residues were typically greatest in the skin (0.33 - 0.82 ppm), gizzard (0.1 – 0.137 ppm), and dark muscle (0.05 – 0.14 ppm). Adipose, liver, and white muscle tissue contained chlorate concentrations from 0.03 to 0.13 ppm. In contrast, chlorate concentrations in excreta eliminated during the 6-hour period prior to slaughter ranged from 53 to 71 ppm. Collectively these data indicate that broilers rapidly convert chlorate residues to an innocuous metabolite, chloride ion, and that chlorate residues in excreta remain fairly high during the time around slaughter. Because the target tissue of chlorate is the lower gastrointestinal tract, the relatively high distribution of parent chlorate to inedible gastrointestinal tissues and low distribution to edible tissues is favorable for the biological activity, and for food safety considerations. These data, when used in conjunction, with a toxicological assessment of chlorate can be used to determine a likely risk/benefit ratio for chlorate.