Re-entry scenarios

It is therefore advisable to group the various crop habitats and maintenance activities into "re-entry scenarios" and to determine whether standard values for the initial DFR shortly after the first application and generic transfer factors for the level of dermal exposure for each scenario can be developed. Investigations to this end have been carried out over the last two decades, primarily in the U.S. The generic transfer factors for a number of... 

Although a comprehensive survey of occupational and residential exposure data requirements across all regulatory jurisdictions is beyond the scope of this chapter, it is evident that the majority of jurisdictions require an assessment of exposure for conventional pesticides if the proposed use pattern indicates potential handler exposure (either occupational and residential) or agricultural re-entry exposure. The extent to which exposure assessments are required/conducted for residential re-entry scenarios or bystanders, however, is less uniform. Although most jurisdictions require/conduct assessments for residential re-entry scenarios (e.g. treated turf, carpeL etc.), exposure assessment methodology for other types of bystander exposure scenarios (e.g. residential exposure in agricultural areas, direct exposure to drift, exposures from the use of pesticides in schools, daycare centers and other public places) is less mature and requires further collaboration. 

In general, plant-protection products are biocidal active substances and are therefore by nature toxic to target organisms. At least some of them are also toxic to humans therefore, the safe use of plant-protection products presupposes, among other things, an evaluation of worker exposure during re-entry, an adequate risk assessment on the basis of the various practical scenarios in agriculture and horticulture, and, if necessary, specific instructions for worker protection on the product label. 

It is advisable, then, in a tiered approach to concentrate first on crops and activities (scenarios) that are considered to be relevant with respect to the expected level of exposure and to exclude those not relevant. Second, whether or not the toxicological properties of the product may lead to general restrictions on re-entry should be investigated. If both the likelihood of reentry and the hazard due to the toxicity of the compound cannot generally be neglected, a risk assessment over several steps should be carried out. The assessment may be based on surrogate data and "worst-case" assumptions at first and then refined, if necessary. One possible approach to a tiered evaluation procedure is presented in Figure 1. 

Modeling Residential Re-entry Dermal Exposures 157 Integrated Physical-Stochastic Dermal Model 158 Macro-Based Dermal Exposure Methodology 159 Scenario 1 159... 

In addition, when considering the appropriateness of the area dose levels in the dermal absorption study to the subpopulations under consideration in the risk assessment, it is important to recognize that different area dose levels may be experienced depending on the scenario. For instance, with an agricultural worker, the mixer/loader may be exposed to the concentrated product, the applicator to the diluted spray mixture and the re-entry worker to dried residues on vegetation. As such, it is possible that different dermal absorption values have to be used for each work-function scenario. 

As has been shown in the previous section, the CO2 temperature upon entry to the wellhead is a function of CO2 temperature in the pipeline and the wellhead pressure. The relationship between the CO2 temperature upon entry to wellhead and the CO2 temperature in the pipeline has been shown in Figure 10 and re-plotted in Figures 11a and 11b. Also shown in Figures 11a and 11b are the hydrate formation temperature for scenarios with and without hydrate inhibitor in the wellbore fluid. Note that the hydrate regime is marked as red-shaded for the case without hydrate inhibitor, whereas the phase change region is marked as yellow-shaded. 

---