Residue studies

On plant surfaces, as in soils, numerous studies have demonstrated that endosulfan is oxidized to endosulfan sulfate. Initial residues of endosulfan on treated vegetables generally range from 1 to 100 mg/kg. However, residue levels typically decrease to less than 20% of initial levels within 1 week after treatment (NRCC 1975). Residues of endosulfan isomers are generally negligible after 2-3 weeks the a-isomer is much less persistent than the P-isomer. In most plant residue studies, endosulfan sulfate residue levels tend to increase relative to the parent isomers and other metabolites and appear to be very persistent (Coleman and Dolinger 1982). 

Sukul P, Chakravarty A, Pal S, et al. 1988. Residue studies on endosulfan and aldrin in paddy. 

In preparation for a registration submission, applicants should conduct a residue study on each edible crop through supervised field trials. Residue data should be prepared for each use pattern and formulation type to be labeled. 

Crop and crop grouping. Residue studies have to be conducted with each target crop proposed for registration one variety of the target crop is acceptable. 

Site/location selection. Residue studies are conducted at two or more sites for each target crop. Trial sites should be selected from typical growing areas for the target crop and should include different environmental conditions that might affect the levels of pesticide residues. 

Raw agriculture commodity requirements. Residues on all parts of crops that can be consumed are analyzed without preparation (e.g., washing and peeling, etc.) in the residue studies. There are no requirements on the residue data on processing foods. 

Residue decline study requirements. All residue studies should provide a decline study that shows the dissipation pattern of the residues for at least three different sampling times and shows the MRL. Typical sampling times are suggested to be a pre-harvest interval (PHI) of 1, 3, 7, 14, 21, 28 (30), 45, 60 days, etc. Especially for daily harvested crops such as tomato, cucumber, eggplant and bell pepper, a PHI of 1 day should be selected. 

Sample preparation by contract research organization. In Japan, GLP for field residue study work has not yet been established and sample preparation for residue studies by private companies is not authorized. Contract research organizations are limited to prefectural research institutes and MAFF-recognized local research institutes, mainly neutral organizations, such as the Japan Plant Protection Association (JPPA). 

The following considerations are critical in the selection and preparation of residue study test sites ... 

The number of fruit trees required for a field residue trial may be as small as a single tree, but it is often more than one tree per plot. Two treatments may not be applied to the same fruit tree. If crops are grown both in greenhouses and in an open field, residue studies must also be conducted in a greenhouse. 

End-use formulation products are used as test materials in the field residue study. Test materials are supplied by the sponsor company. 

Description of the different types of field crop residue studies... 

The type of field residue study being conducted will determine the amount of test site information required and the rigor required to obtain this information. 

The test substance used in a field residue study must be clearly defined and properly identified to ensure that the correct chemicals are used for the study. This process is called test substance characterization (40 CFR 160.105). The characterization of a test substance includes confirming the test substance is what was intended and that the test substance represents the actual commercial product that will be marketed. The test substance may be acquired from either a commercial production run or from... 

The movement of the test substance during the course of a Held residue study must be tracked to assure that the integrity of the test substance is maintained [40 CFR 160.185(a)(10)]. The COC can be accomplished in a number of ways. In the simplest situation, every person signs their name on a piece of paper that accompanies the test substance when they handle the test substance. Eventually the COC will list the names of all those who handled the test substance during the course of the study. Shipment, receipt, weighing, and final disposition of the test substance container must all be tracked and promptly recorded if an unbroken COC is to be present at the end of the trial. The completed COC becomes an essential part of the field residue trial record. 

The records required for field residue study authentication are the same records that would be required to reconstruct the study. Although this total volume of information is a necessary part of the GLP study record, the field summary report is a small fraction of that record. The field summary report is simply the information the EPA reviewers wish to see as they consider the data and determine how well they represent the crop situation for which the pesticide tolerance is being requested. At the current time, the field summary report should contain the information requested on pp. 48 and 49 of OPPTS 860.1500. The summary report for each test site in a study will typically form an appendix in the final study report. This information must be accurately extracted from the raw data notebook or field record and must be audited by... 

General issues and considerations in conducting residue studies in Europe... 

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