Migration Worst case, estimate

In order to use the migration equations, especially the generally accepted equation (7-51), values for the partition coefficient K of the migrant between P and L and the diffusion coefficient DP of the migrant in P are needed. For migrants with a high solubility in the foodstuff or simulant, the value K = 1 can be used and a worst case estimation is obtained in this way. 

FDA also concluded that establishing a 0.5 pg/kg dietary concentration as the threshold of regulation is appropriate because it corresponds to a migration level that is above the measurement limit for many of the analytical methods used to quantify migrants from food-contact materials. Thus, decisions are usually made based on dietary concentrations that result from measurable migration into food or food-simulating solvents rather than on worst-case estimates of dietary concentration based on the detection limits of the methods used in the analysis. 

It is assumed that the moisture content of the soil has been determined to be approximately 50% under worst-case conditions. Using this information and the results from vendor tests, it has been determined that a minimum dose of one part solidification reagent to two parts soil is required for the migration control of lead. Testing has shown that the optimum solidification reagent mixture would comprise ca. 50% fly ash and ca. 50% kiln dust. Thus, ca. 7000 t (6364 T) each of fly ash and cement kiln dust would be required. The reagents would be added in situ with a backhoe. As one area of the soil is fixed, the equipment could be moved onto the fixed soil to blend the next section. It may be anticipated that the soil volume would expand by ca. 20% as a result of the fixation process. This additional volume would be used to achieve the required slope for the cap. An RCRA soil/clay cap placed over the solidified material is necessary to prevent infiltration and additional hydraulic stress on the fixed soil. It is estimated that the fixation would reduce lead migration by 40% and that the fixed soil may pass the U.S. EPA levels for lead. 

Mass balance estimation of worst case styrene migration... 

Interpretation of result The calculated migration values here are realistic since results calculated using Eq. (14-4) cannot be larger than the mass balance result (Example 14-1). The calculated amount of styrene is still above the assumed sensory threshold limit of 0.1 mg/kg in the product for the worst case in step 4 but is equal to the estimation using the experimental diffusion coefficient in step 5. 

In the following Dp-values calculated with the refined Eq. (15-3) and partition coefficients KpF assumed to equal 1 are used for estimating worst case migration rates for additives from polyolefins with Eq. (7-51). These estimated values are compared with experimentally obtained migration values carried out under well defined conditions for several additives from HDPE and different PP-types (Table 15-3a) into olive oil (O Brian et al., 1999 and 2000). The results are summarized in Table 15-3b. 

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