USDA Symbol Food Safety and Inspection Service
United States Department of Agriculture
Washington, D.C. 20250-3700

News and Information

July 13, 1997

To District Managers:

Guidance for Reprocessing of Broilers Exposed to Dioxin-Contaminated Feed

This document and the attached calculations provide guidance for plants that may choose to reprocess broilers. These methods, if properly applied, can be used in lieu of laboratory testing.

Dioxin compounds are known to accumulate in the fatty tissues of animals and are not uniformly distributed throughout the edible tissue. That is why dioxin laboratory tests are often done on fatty tissue and reported as parts per trillion on a lipid (fat) basis and then converted to an edible tissue basis. For this reason, when fat and skin are removed from chickens, most of the dioxin is removed as well, and edible tissue levels may be below the level of concern. FDA scientists have determined that the level of concern for dioxin contamination in animals and animal products is 1 part per trillion for the dioxin congener, 2,3,7,8 TCDD.

FSIS scientists have calculated levels of TCDD in raw, skinless chicken parts processed from birds exposed to dioxin-contaminated feed. These calculations are based on maximum exposure to the feed and 100% absorption of the dioxin from the feed, and the levels of TCDD in soybean meal and feed are based on data from EPA (see attached).

Actual levels of TCDD found in 2 of 80 poultry samples during the Joint EPA/USDA poultry survey were almost half of the calculated "worst case" value of 8.7 ppt edible tissue. This means that, if no information is available on the level of TCDD in broilers up to 56 days old, a skinless chicken breast would be below the 1 ppt level of concern. Therefore, without laboratory data, FSIS will permit the processing and distribution of skinless chicken breast. If plants choose this option, they should be aware that other parts are not suitable for human or animal food and must be disposed of accordingly.

If laboratory data are available, a plant can estimate the level of dioxin present in any raw, skinless chicken part, based on the attached information. For example, if the lipid based value of their sample is 16 ppt TCDD, the edible tissue value would be 2.4 ppt. The plant can then multiply the attached TCDD values for raw, skinless chicken parts by 2.4/8.7 (or 0.28); in other words, their estimated levels of TCDD would be proportional to those calculated for the "worst case". For this particular example, the estimated values would be 0.19 ppt (0.7 X 0.28) for breast meat, 0.53 ppt for drumsticks, 0.62 ppt for thigh meat, and 0.56 for wings. Should any estimated values be at or above 1 ppt TCDD, chicken parts cannot be used as human or animal food.

FSIS is gathering information on other poultry classes, including turkeys, and will provide guidance on the re-processing of those products as soon as it becomes available. In addition, FSIS has information to determine the suitability of products based on actual history of feed. Questions concerning this information should be directed to the Technical Center at 402-221-7400.

/s/ Carol M. Seymour
Acting Deputy Administrator
Field Operations

CALCULATION OF DIOXIN LEVELS IN PROCESSED TISSUES OF BROILERS-FRYERS

If broiler-fryers are fed a feed mixture which includes as components 20% Soybean Meal containing approximately 15 ppt 2,3,7,8 tetracholodibenzodioxin1 (TCDD), and an average of approximately 2% added fat containing 8.3 ppt TCDD2 for 40 days, chickens will have been exposed3 to approximately 12,800 pg. If they retain all of the TCDD to which they are exposed (i.e., 100% absorption, no elimination due to metabolism or other mechanisms), they will have a TCDD level of 8.7 ppt on a whole bird (edible tissue) basis, which calculates to approximately 57 ppt on a fat basis.

This calculated level of 57 ppt is almost twice as high as that found in any bird analyzed for TCDD (29 ppt on a fat basis).4

Virtually all of the TCDD will be in located in the skin and large fat deposits of the birds, with much smaller (absolute) amounts found within breast, thigh, or leg meat (muscle tissues).

The TCDD found within the muscle tissues will, again, be found within fatty material located within those muscles. According to Agriculture Handbook 8, Composition of Foods, raw skinless breast meat contains 1.24% fat; raw skinless drumsticks 3.42% fat; raw skinless leg meat, 3.81% fat; raw skinless thigh meat, 3.91% fat, and raw skinless wing meat, 3.54% fat.

Starting from the fat basis level of TCDD (57 ppt), TCDD levels in the five raw, skinless meat tissues may be calculated:

raw skinless breast meat 1.24% fat 0.7 ppt edible basis
raw skinless drumsticks 3.42% fat 1.9 ppt edible basis
raw skinless leg meat 3.81% fat 2.2 ppt edible basis
raw skinless thigh meat 3.91% fat 2.2 ppt edible basis
raw skinless wing meat 3.54% fat 2.0 ppt edible basis

Based on the above calculation, skinless breast meat from broiler-fryers that have been exposed to what are the now known highest levels of TCDD in chicken feed, will contain less than 1 ppt TCDD.

It should be noted that this calculated level is almost twice the level in skinless breast meat that would be present (based on calculation) in skinless breast meat originating from the analyzed chicken with the highest TCDD level found (29 ppt on a fat basis).

An added margin of safety would be obtained by hand trimming all visible fat from the chicken breasts. All fat and skin removed from chicken breasts can not be used for either human or animal food purposes, must be disposed of according to EPA regulations.

No other meat tissues from broiler-fryers appear, after removal of skin, to produce edible product that is below 1 ppt TCDD.


1 The highest reported soy bean meal sample contaminated with dioxins contained 14.68 ppt of 2,3,7,8-TCDD, and had a total toxic equivalency factor (Teq) of 21.75 ppt.

2 Two feed grade fat samples (this product is obtained from rendering "offal" and is added to chicken feed) samples were analyzed. One sample contained 8.25 ppt of TCDD (Teq=11.62 ppt); the other contained 8.13 ppt of TCDD (Teq=11.13 ppt).

3 Broiler-fryers are brought to slaughter at approximately 39-42 days, and have a live weight of approximately 2 kg. They consume approximately 4 kg of feed. After processing, they have a retail carcass weight of approximately 1.5 kg.

4 It appears as if approximately 50% of the TCDD presented to poultry in feed is actually retained by the birds. The fact that samples of litter from growing houses have been analyzed and found to contain between 2 and 5.9 ppt TCDD strongly suggests that less than 100% of ingested TCDD is retained, but there is insufficient data to determine what percentage is excreted.

For further information related to calculations, please contact:

Dr. Michael K. Hoffman, telephone 202-501-7332, fax 202-501-7639.

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