CVM MEMO
CVMM-19
MONITORING FOR RESIDUES IN FOOD ANIMALS
FOOD AND DRUG ADMINISTRATION, CENTER FOR VETERINARY MEDICINE COMMUNICATIONS AND EDUCATION BRANCH, HFV-121, 301/594-1755
D.H.H.S. Pub. No. (FDA) 94-6001
Revised March 1994
U.S. Department of Health and Human Services
Public Health Service Food and Drug Administration
7500 Standish Place, HFV-12, Rockville, Maryland 20855
The use of drugs to control and treat animal disease and to promote faster, more efficient growth of livestock is a common practice. An estimated 80 percent of U.S. livestock and poultry receive some animal drugs during their lifetime. Improper use of animal drugs may cause residues in the edible tissues of slaughtered animals that could be hazardous to consumers. To protect the public, the Food and Drug Administration (FDA) and the U.S. Department of Agriculture (USDA), through its Food Safety and Inspection Service (FSIS), cooperate in a program to monitor the use of these animal drugs, identify improper use and take action to prevent future illegal use by a producer.
FDA requires animal drug manufacturers to show that each new animal drug is safe and effective for its intended use before it is approved for marketing. To ensure food safety the Agency sets a tolerance and withdrawal time for the product. For drugs approved for use in food-producing animals, additional toxicology residue and metabolism studies are required. Manufacturers also must submit a reliable assay method for detecting drug residues in edible tissues of slaughtered animals and in milk. These analytical methods are reviewed by FDA and FSIS before the drug is approved.
FDA establishes tolerances to include a safety factor to assure that the drug will have no harmful effects on consumers of the food product. The Agency first determines the level at which the drug does not produce any measurable effect in laboratory animals. From this, the Agency determines an acceptable daily intake (ADI), the drug tolerance and withdrawal times are then determined so that the concentration of drug residues in edible tissues are below the ADI. Depending on the drug, "safety factors" of between 100-fold to 2,000 fold are included in the calculations used to set the tolerances.
USDA regularly monitors tissue samples from slaughtered animals for many individual chemical compounds including:
Antimicrobials: Sulfonamides, penicillins, streptomycin, tetracyclines, erythomycin, neomycin, gentamicin, and tylosin;
Other drugs: Coccidiostats, growth promotants, antiparasitics, and other special purpose drugs;
Pesticides and industrial chemicals: Chlorinated hydrocarbon pesticides, organophoshates, plus others on an "as needed" basis.
The main goal of USDA's National Residue Program is to protect consumers from adulterated meat and poultry products. The program is divided into three major activities: Monitoring, Surveillance, and Exploratory phases.
Monitoring
Monitoring is designed to provide profile information on the occurrence of residue violations in specified animal populations on an annual national basis. The focus of monitoring is on violations; therefore, only compounds with established safe limits, tolerances, or action levels are considered. Compounds are selected for monitoring based on risk profiles and the availability of laboratory methodology that is suitable for regulatory purposes. Monitoring information is obtained through a statistically-based selection of random samples from healthy appearing animals under inspection.
In addition to profile information, monitoring provides a basis for further action. In particular, the results are used to identify producers and others in the marketing chain who market animals with violative concentrations of residues. Other auxiliary uses of the data are to indicate prevalence and concentrations of residues, to evaluate residue trends, and to identify problems within the industry for which educational or other corrective efforts may be needed. Thus, monitoring not only gathers information, but also assists in deterring practices that lead to violative residues.
Tolerances and action levels represent the maximum residue concentrations safe for daily consumption over a lifetime. To help livestock producers and marketers avoid exceeding FDA residue tolerances, FSIS notifies the individual producer or other responsible party whenever a tissue sample is found to be above the established tolerance. FSIS tests animals from subsequent flocks or herds to assure that residues in food products from that particular source remain below the legally permissible levels.
When an illegal residue is detected, FSIS reports the violation to the appropriate FDA district office. The district office may then, following compliance program guidelines, conduct an investigation. FDA investigators (or State officials in certain cases) visit the various premises and individuals handling the animal prior to and at slaughter, such as the farm or feed lot, the auction market, the livestock hauler or dealer, and the slaughterhouse. The investigation is aimed at determining the cause of the residue and identifying those responsible. Under the law, an animal is considered as food in the production unit and is subject to FDA regulations.
Surveillance
Surveillance is designed to investigate and control the movement of potentially adulterated products. The sampling is often purposely biased and is directed at particular carcasses or products in response to information from monitoring or other sources (e.g., industry members or a State agency), or from observations during ante-mortem or post-mortem inspection indicating that adulterating concentrations of residue may be present. In-plant testing procedures may be performed by the inspector, or samples may be submitted to an FSIS laboratory for analysis. Depending upon the weight of evidence that led to the testing, products may be retained until test results indicate the appropriate regulatory disposition. Laboratory testing of surveillance samples is completed as rapidly as possible and takes precedence over monitoring samples.
No matter in which phase of the program an illegal drug residue is found, FDA can conduct a follow-up investigation and FSIS can detain future shipments from the affected producer while tissue samples are analyzed. FDA follow-up investigation may lead to enforcement action when appropriate or necessary.
Exploratory
Exploratory projects are conducted for a variety of reasons, but these activities, whatever their objective, have in common the fact that test results are not ordinarily used to take regulatory action or to trigger follow-up surveillance testing.
Exploratory projects generally fall within the following two types:
Studies on the occurrence of residues for which no safe limits (i.e., tolerances or action levels) have been established or in a species not approved for use of a particular drug.
There are many chemicals (e.g., trace metals, industrial chemicals, and mycotoxins) that may be inadvertently present in animal tissues yet have no established safe concentrations. Their consistent presence in food (and the resulting need for a tolerance or action level to protect public health) has not been established. FSIS, with input from FDA, may conduct studies to develop information on the frequency and concentrations at which such residues occur.
These studies may be nationwide or limited to specific geographic areas. Sample collection may be random and statistically based, or biased to obtain "worst case" information. The results are given either to the Environmental Protection Agency (EPA) or the FDA, which have responsibility for establishing tolerances for contaminants in food under the Federal Food, Drug, and Cosmetic Act. Exploratory programs planned on a limited scale may be expanded if preliminary results cause greater concern and make acquiring comprehensive information more urgent.
Other projects as appropriate.
These may be designed for various purposes, such as evaluating new methods and approaches to monitoring, or supplementing the information used in considering a compound for monitoring.
Federal/State Agency Cooperation
Three Federal agencies--FDA, FSIS and the EPA--have an agreement that outlines each agency's responsibilities in the national residue reduction effort.
Illegal residues in animals are investigated by FDA; however, the dynamics of the Tissue Residue Program are such that no one agency can accomplish the goal of residue reduction and subsequent enhancement of consumer confidence. To this aim, the Center has participated in joint FDA and State cooperative work-sharing programs and awarded contracts for States to perform residue follow-up investigations on first time residue violators. If pesticide residues are determined to be due to direct application or environmental contamination, this information is furnished to the appropriate EPA regional office, which works with FDA and FSIS to help correct the problem. In cases of drug or pesticide residues in animals caused by contaminated feed, FSIS and FDA join forces to correct the problem. In either case, FSIS assumes primary responsibility for the wholesomeness of the meat supply, EPA has the responsibility to assure that pesticides are used according to label directions, and FDA has final authority for enforcement of the laws governing use of animal drugs and acceptability of medicated feeds.
Thus, FSIS, in their enforcement of Federal regulations, frequently must condemn food intended for human consumption. FDA, through the federal courts, has enjoined producers and livestock from sending animals to slaughter containing illegal drug residues. In past years, FSIS has condemned animals for a variety of pesticide and drug residues and FDA must seek other legal remedies. While FDA does not usually take punitive action for a first offense, it may do so if intent or prior knowledge of a residue violation can be documented. If found guilty, offenders may face criminal prosecution with fines or imprisonment as provided for under the law.
Summary
FDA and FSIS review the feasibility and effectiveness of a drug firm's proposed residue detection method.
FSIS monitors food animals for tissue residues of drugs, pesticides, and environmental contaminants.
Animals with illegal residues will be condemned by FSIS. Producers of these animals may be subject to detention of future shipments until they can prove their animals are in compliance with applicable tolerances. Repeated residue incidents may lead to legal sanctions.
Illegal drug residues detected by FSIS are reported to FDA, the livestock producer, or other responsible individual, and, where appropriate, State authorities.
FDA, or the appropriate State agency, may initiate an on-site investigation of a suspect producer. If the evidence shows a flagrant violation of the law, criminal charges may be filed against the producer.
The convicted animal drug abuser may be fined and possibly imprisoned for his crimes.
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