The US Food and Drug Administration (FDA) has released an updated regulation that redefines the acceptable concentration levels of a carcinogen allowed in food-producing animals.
The regulation, Regulation of Carcinogenic Compounds in Food-Producing Animals, changes two definitions in particular: "So" and "Sm."
So previously referred to the concentration level of carcinogens in an animal's diet that is equal to a 1/1,000,000 risk of the animal developing cancer over the course of its lifetime as estimated through cancer bioassays and extrapolation procedures. FDA explained it used So to provide a rough approximation of a product's cancer risk to humans.
The definition of Sm is closely related to this definition, and is the concentration of carcinogens found in the edible tissues of an animal.
In its Federal Register notice, FDA said it is looking to change both definitions to accommodate a more nuanced presentation of the risks associated with the acceptable levels of carcinogens found in animals.
Under the new final rule, So would be defined as, "The concentration of a residue of carcinogenic concern in the total human diet that represents no significant increase in the risk of cancer to the human consumer," and secondarily as, "The concentration of test compound in the total diet of test animals that corresponds to a maximum lifetime risk of cancer in the test animals of 1 in 1 million."
FDA noted this change in definition would also allow the agency's Center for Veterinary Medicine (CVM) to consider the use of certain drugs in animals that might cause cancer in animals, but not in humans.
Accordingly, the definition of Sm will be changed to mean, "The concentration of a residue of carcinogenic concern in a specific edible tissue corresponding to no significant increase in the risk of cancer to the human consumer." This, too, will allow for CVM to shift the focus of its efforts to the risk of cancer in humans, rather than in animals.
The Delaney Clause and DES Proviso
FDA said the change in definitions was necessary to comply with the so-called "Delaney Clause," which stipulates that any product that causes cancer in humans cannot be used in food-producing animals. The only exception, known as the Diethylstilbestrol (DES) Proviso, allows FDA to approve products known to be a human carcinogen if it does not harm an animal and is not found as a residue in the animal's tissue. The new definitions conform to the DES Proviso and allows FDA to avoid development of a, "Second, alternate, set of terminology."