MEMORANDUM DATED 10-4-2012

From: Steve Funk, HED/RAB3
    To: Barbara Madden, MUT/RD


Subject:  Justification of the Cucurbit Group Tolerance (Inclusive of Cucumber Greenhouse Use)  
                    Flonicamid

Barbara and Sidney,

The rationale for increasing the cucurbit group tolerance to encompass cucumber from greenhouses as opposed to creating a separate tolerance for cucumber is summarized on page 24 of Appendix II of the Summary Document of 10/02/2012 (D396902.me1).

"The existing tolerance for cucurbit vegetables is 0.4 ppm.  This is based on the evaluation of  crop field trial data for summer squash, cantaloupe, and  cucumber (D290386, A. Acierto, 04/22/2005).  The highest residues were 0.17 ppm on squash, 0.34 ppm on cucumber, and 0.25 ppm on cantaloupe. The recommended tolerance of 1.5 ppm for cucurbit vegetables is appropriate for the representative commodities."

Here is a detailed explanation:

At the time that the original group tolerance of 0.4 ppm was established, no statistical procedure for estimation was used.  It was common practice to estimate the tolerance slightly above the highest field trial result.  Thus, estimates would have been 0.2 ppm (based on squash), 0.4 ppm (based on cucumber), and 0.3 ppm (based on cantaloupe).  The highest value (0.4 ppm) is adopted.   The guidance is that the lowest estimate and the highest estimate should not differ by more than a factor of 5X, , 0.4 / 0.2 = 2 X in this case.

The estimate for cucumber from the greenhouse cucumber trials is 1.5 ppm.  1.5 / 0.2 = 7.5, which is in excess of the 5X allowed.  The apparent conclusion would be that a group tolerance is not appropriate.  However, the new cucumber value is based on the use of the Organization of Economic Cooperation and Development  (OECD) calculation procedure.  In order to make an appropriate comparison, the field trial data reviewed in 2005 (D290386, 04/22/2005; MRID 45854808) were re-evaluated with the OECD calculator.  The findings are as follows:  


Flonicamid Cucurbit Field Trials Tolerance Estimates Based on OECD Procedure (2005 Data)
                                  Flonicamid
                                   Cucumber
                                 MRID 45854808
                             0.3 lb ai/A, 0 d PHI
 
 
Total number of data (n)
                                       6
Percentage of censored data
                                      0%
Number of non-censored data
                                       6
Lowest residue
                                     0.138
Highest residue
                                     0.324
Median residue
                                     0.220
Mean
                                     0.216
Standard deviation (SD)
                                     0.067
Correction factor for censoring (CF)
                                     1.000
 
                                        
Proposed MRL estimate
 
 
                                        
- Highest residue
                                     0.324
- Mean + 4 SD
                                     0.484
- CF x 3 Mean
                                     0.649
Unrounded MRL
                                     0.649
 
                                        
Rounded MRL
                                      0.7
 
                                        
 High uncertainty of MRL estimate.
[Small dataset]



                               Residues (mg/kg)
                                       n
                                     0.138
                                       1
                                     0.153
                                       1
                                     0.216
                                       1
                                     0.224
                                       1
                                     0.242
                                       1
                                     0.324
                                       1

                                  Flonicamid
                                  Cantaloupe
                                 MRID 45854808
                             0.3 lb ai/A, 0 d PHI
 
 
Total number of data (n)
                                       6
Percentage of censored data
                                      0%
Number of non-censored data
                                       6
Lowest residue
                                     0.138
Highest residue
                                     0.324
Median residue
                                     0.227
Mean
                                     0.219
Standard deviation (SD)
                                     0.068
Correction factor for censoring (CF)
                                     1.000
 
                                        
Proposed MRL estimate
 
 
                                        
- Highest residue
                                     0.324
- Mean + 4 SD
                                     0.489
- CF x 3 Mean
                                     0.656
Unrounded MRL
                                     0.656
 
                                        
Rounded MRL
                                      0.7
 
                                        
 High uncertainty of MRL estimate.
[Small dataset]

                               Residues (mg/kg)
                                       n
                                     0.138
                                       1
                                     0.153
                                       1
                                     0.216
                                       1
                                     0.238
                                       1
                                     0.242
                                       1
                                     0.324
                                       1






                                  Flonicamid
                                 Summer Squash
                                 MRID 4584808
                             0.3 lb ai/A, 0 d PHI
 
 
Total number of data (n)
                                       5
Percentage of censored data
                                      20%
Number of non-censored data
                                       4
Lowest residue
                                     0.040
Highest residue
                                     0.164
Median residue
                                     0.142
Mean
                                     0.123
Standard deviation (SD)
                                     0.048
Correction factor for censoring (CF)
                                     0.867
 
                                        
Proposed MRL estimate
 
 
                                        
- Highest residue
                                     0.164
- Mean + 4 SD
                                     0.317
- CF x 3 Mean
                                     0.321
Unrounded MRL
                                     0.321
 
                                        
Rounded MRL
                                      0.4
 
                                        
 High uncertainty of MRL estimate.
[Small dataset]

                               Residues (mg/kg)
                                       n
                                   < 0.04 
                                       1
                                     0.128
                                       1
                                     0.142
                                       1
                                     0.143
                                       1
                                     0.164
                                       1
 
The tolerance estimate values are 0.7 (based on cucumber), 0.7 (based on cantaloupe), and 0.4 ppm (based on summer squash).  The estimate for greenhouse cucumber is 1.5 ppm.  The difference between the highest and lowest estimates (1.5 /0.4 = 3.8X) is <5X.  Therefore, a cucurbit group tolerance of 1.5 ppm is possible.

Steve Funk
OPP/HED/RAB3, S-10318
tele:  1-703-305-5430
cell: 1-240-374-8439
fax: 1-703-305-0871
