Benchmarking the Current Codex Alimentarius International Estimated Short-Term Intake Equations and the Proposed New Equations

The International Estimated Short-Term Intake IESTI equations are used during the establishment of Codex Maximum Residue Limits. A recent proposal to revise the equations sparked international debate regarding selection of residue inputs and the appropriate level of consumer protection. The 49th Codex Committee on Pesticide Residues meeting recommended benchmarking the IESTI equations against distributions of actual exposures. Using publicly available data and models, this work compares dietary exposures for strawberries, tomatoes, and apples at five levels of refinement to place these equations into context relative to real-world exposures. Case studies were based on availability of robust USDA PDP monitoring data, which is uniquely suited to refine dietary exposures for a population. Benchmarking dietary exposure involves several decision points. Alternate methodology choices are not expected to impact the large margins observed between the probabilistic estimates and the IESTI equations or to change the overall conclusion that existing IESTI equations are conservative and health-protective.

New method for removing type 2 copper from Rhus laccase

A new procedure is described for preparing tree laccase that is missing the type 2 copper. The derivative has only about 5% of the activity of the native enzyme, and some, or all, of the residual activity could be due to traces of holoprotein. The type 1 copper is fully oxidized in the purified type-2-depleted protein, while the type 3 site is reduced to the extent of at least 85%. However, the type 3 coppers can be reoxidized by treatment with excess H2O2. Reconstitution is achieved by incubation with Cu(I), and the remetalated protein exhibits the activity and the spectral properties of the native enzyme. The type 2 copper is removed by dialysis against a redox buffer containing ferri- and ferrocyanide ions as well as EDTA. More than 25% of the total copper is removed from laccase during the procedure, but the type-2-depleted fraction is readily isolated by means of an ion-exchange column. The practical advantages of this procedure are described. Finally, the simplicity of the method raises hopes that the mechanism of depletion can be defined.