Submitted to: Food Additives & Contaminants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2012
Publication Date: 1/23/2013
Publication URL: http://handle.nal.usda.gov/10113/56704
Citation: Huwe, J.K., Archer, J.C. 2013. Dioxin congener patterns in commercial catfish from the United States and the indication of mineral clays as the potential source. Food Additives & Contaminants: Part A. 30(2):331-338. Interpretive Summary: The USDA is responsible for the safety of meat, poultry, egg, and catfish products sold in the United States. An initial assessment of chemical residues that may be present in commercially marketed catfish was conducted by the USDA from April 2008 to June 2010. One of the chemical residues measured in the catfish products was a class of environmental pollutants called "dioxins" made up of 17 individual compounds. Dioxins are hazardous chemicals formed as byproducts of industrial and natural processes which can spread through the environment and into our food supply. Animal based food products are the major route of exposure to dioxins for humans, and one way to reduce that exposure is to identify and remove the sources of dioxin before they enter the food chain. Different sources of dioxins can be identified by the unique fingerprint or pattern formed by the 17 individual compounds. In the catfish products marketed in the United States, the observed dioxin pattern indicated that a natural source, i.e. mineral clay, was the likely cause of dioxins in the catfish. Mineral clays are often used in catfish feeds to prevent caking or clumping, and dioxins have been found in certain mineral clays and numerous catfish feeds. Although the dioxin residues found in the catfish products were low and suggested minimal public health risks, care should be taken to use uncontaminated mineral clays or alternatives to mineral clays in catfish feeds to prevent the unwanted entrance of dioxins to the food supply.
Technical Abstract: Since 1991 the U.S. Department of Agriculture (USDA) has conducted annual surveys of pesticide residues in foods under the Agricultural Marketing Service’s Pesticide Data Program (PDP). To assess chemical residues in domestically marketed catfish products, 1479 catfish samples were collected during the 2008 to 2010 PDPs. A subset of 202 samples was analyzed for 17 toxic polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs). The average pattern of the individual PCDD/F congener concentrations in the catfish was rather unique in that it had almost no measurable amounts of PCDFs, but all PCDDs were present. This pattern was more dominant in the domestically produced catfish products than in the imported products (China/Taiwan). Comparison of the pattern to known sources of PCDD/Fs showed strong similarities to the pattern of PCDD/Fs found in kaolin clays which have often been used as anticaking agents in animal feeds. To investigate whether catfish feeds may be the source of the PCDD/Fs found in the catfish, archived catfish feed data from a U.S. Food and Drug Administration database were examined. In 61 out of 112 feed samples, the PCDD concentrations were fifty times higher than the PCDF concentrations and resembled the pattern found in the catfish products and in clays mined in the southeastern U.S. Although the source of PCDD/Fs in domestically marketed catfish products cannot be definitively established, mined clays products used in feeds should be considered a likely source and, given the wide concentration range of PCDD/Fs that has been found in clays, a critical control point for PCDD/Fs entrance to the food supply.