[Code of Federal Regulations] [Title 21, Volume 6] [Revised as of April 1, 2007] From the U.S. Government Printing Office via GPO Access [CITE: 21CFR556.100] [Page 349] TITLE 21--FOOD AND DRUGS CHAPTER I--FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) PART 556_TOLERANCES FOR RESIDUES OF NEW ANIMAL DRUGS IN FOOD--Table of Subpart B_Specific Tolerances for Residues of New Animal Drugs Sec. 556.100 Carbadox. A tolerance of 30 parts per billion is established for residues of quinoxaline-2-carboxylic acid (marker residue) in liver (target tissue) of swine. [63 FR 13337, Mar. 19, 1998]