MECADOX

Comments:

The Committee's 36th meeting did not establish an ADI because as carbadox and some of its metabolites (desoxycarbadox and hydrazine) were genotoxic hepatocarcinogens in rats; but, the metabolite found in tissues, quinoxaline-2-carboxylic acid (QCA), was not carcinogenic or mutagenic. The Committee did not use linear extrapolation to estimate a ‘virtually safe dose’ for carbadox and its metabolites of carcinogenic concern, owing to the substantial inherent uncertainties involved. However, the Committee concluded that residues resulting from use of carbadox in pigs were acceptable, based on information demonstrating no detectable residues of carbadox or its carcinogenic metabolites in tissues and provided that the recommended maximum residue limits of 0.03 mg/kg (liver) and 0.005 mg/kg (muscle) as QCA, were not exceeded. Carbadox was reviewed by the present Committee primarily on the basis of new information on residue levels. The results of a recent study of residues of carbadox in pigs indicated longer persistence of substantial amounts of desoxycarbadox in liver at the time when the concentration of the marker residue, QCA, fell below the MRL and to the end of the experiment 15 days after withdrawal. Based on the new data demonstrating the presence of carcinogenic residues in animal products and the uncertainty in the residue data, the previously-established MRL levels for carbadox were withdrawn.

MRL Comment:

MRLs withddrawn because the Committee could not determine the amounts of residues of carbadox and its metabolites in food that represented an acceptable risk to consumers.

MRL Code:

MRL

Intake:

Not calculated

Meeting:

60

Report: 

Tox Monograph: 

Residues: 

Previous Years: