Page 1 of 5

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF

CHEMICAL SAFETY AND

POLLUTION PREVENTION

MEMORANDUM

Date: March 25, 2011

SUBJECT: Tetrachlorvinphos. Response to Comment on Storage Stability Residue Data Deficiencies. 

PC Code: 083701/083702 DP Barcodes: D385359 & D386954

Decision No.: 359967 Registration No.: Not Applicable

Petition No.: Not Applicable Regulatory Action: Reregistration Follow-up

Risk Assessment Type: Not Applicable Case No.: 0321

TXR No.: Not Applicable CAS No.: 22248-79-9

MRID Nos.: 486378101 48319001 40 CFR: 180.252

FROM: Christine L. Olinger, Chemist

Risk Assessment Branch VII

Health Effects Division (7509P)

Office of Pesticide Programs

THRU: Donna S. Davis, Chemist

Michael S. Metzger, Chief,

Risk Assessment Branch VII

Health Effects Division (7509P)

Office of Pesticide Programs

TO: James Parker, CRM

Risk Management and Implementation Branch II

Pesticide Re-evaluation Division (7508P)

Office of Pesticide Programs

In response to deficiencies noted in a review of livestock magnitude of residue studies (C. 

Olinger; 10/7/10; D320848, D320858, D320859, and D381350) SRA International, on behalf of 

KMG Bernuth, has submitted data relating to the storage stability of tetrachlorvinphos residues 

in livestock tissues, eggs, and milk. The Pesticide Re-evaluation Division (PRD) has requested 

HED review of this information to satisfy the outstanding data deficiencies.

CONCLUSIONS

No additional storage stability data are needed to support the use of tetrachlorvinphos on poultry. 

The magnitude of residue study on poultry is adequate and there are no outstanding deficiencies 

with this study. The magnitude of residue requirement is considered satisfied for poultry.
Page 2 of 5

No storage stability data are available for livestock commodities. The samples from the 

ruminant magnitude of residue study that reflect the maximum current use pattern were stored 

less than thirty days, so storage stability data are not needed. Provided the registrant does not 

make changes to the current use pattern/application rates, no additional storage stability data are 

needed and the requirement for a magnitude of residue study for ruminants is satisfied. Should 

the registrant wish to revise the existing use patterns such that the magnitude of residue data 

from other treatment groups would be used for tolerance and/or risk assessment, additional 

storage stability data demonstrating stability of tetrachlorvinphos and its metabolites for at least 

two months would be required. 

DETAILED CONSIDERATIONS

HED identified the following deficiencies regarding the storage stability data as well as detailed 

information on storage intervals in the review of poultry and ruminant magnitude of residue 

studies (C. Olinger; 10/7/10; D320848, D320858, D320859, and D381350). 

 New storage stability studies should be conducted with quantifiable (i.e., fortified)

residues of all analytes in all cattle and poultry matrices. In addition, the registrant needs 

to submit information pertaining to dates of treatment, collection, extraction, and analysis 

to verify the maximum storage intervals of all samples collected from both the cattle and 

poultry studies.

 Although a companion storage stability study was included in support of the cattle study, 

the submitted data were deemed inadequate because of the study design. Selected 

samples of various matrices were re-assayed after the initial analysis. Considerable 

degradation may have occurred prior to the initial analysis of storage stability samples. 

Many of the matrices did not have quantifiable residues of one or more of the analytes at 

the time of initial analysis, so potential degradation upon storage cannot be accurately 

assessed. 

SRA International, on behalf of KMG Bernuth, has submitted additional information on the 

storage intervals for these studies, which is discussed below.

Data Submitted to Support MRID 47589301 Poultry Magnitude of Residue Study

The registrant has provided information on the storage intervals for samples from the original 

poultry study. SRA submitted storage interval information in two volumes, MRID Nos. 

486378101 and 48319001. A summary of the storage intervals is presented in Table 1 below.

Table 1. Storage Intervals for Samples from Tetrachlorvinphos Poultry Magnitude of Residue Study 1

Matrix Group(s) 2 Time 

Interval 3

No. Days 

Storage Matrix Group(s) 2 Time Interval 3

No. Days 

Storage

Eggs 1-4 -7 1-3 Eggs 1-4 78 11

Eggs 1-4 -1 1-2 Eggs 1-4 82 9

Eggs 1-4 1 2-3 Eggs 1-4 84 12-20

Eggs 1-4 3 2-3 Eggs 1-4 86 18

Eggs 1-4 5 2-3 Eggs 1-4 88 16

Eggs 1-4 8 1-3 Eggs 1-4 91 13
Page 3 of 5

Table 1. Storage Intervals for Samples from Tetrachlorvinphos Poultry Magnitude of Residue Study 1

Matrix Group(s) 2 Time 

Interval 3

No. Days 

Storage Matrix Group(s) 2 Time Interval 3

No. Days 

Storage

Eggs 1-4 12 2 Eggs 1-4 95 15

Eggs 1-4 15 2-4 Eggs 1-4 98 12

Eggs 1-4 17 2-4 Eggs 1-4 101 9

Eggs 1-4 19 2-4 Eggs 1-4 105 5

Eggs 1-4 22 1-4 Muscle 1-4 0 14

Eggs 1-4 26 2 Muscle 3R 7 22

Eggs 1-4 29 2-4 Muscle 3R 14 15

Eggs 1-4 31 3-4 Muscle 3R 21 8

Eggs 1-4 33 3-4 Liver 1-4 0 18

Eggs 1-4 36 1-4 Liver 3R 7 22

Eggs 1-4 40 2 Liver 3R 14 15

Eggs 1-4 43 2-6 Liver 3R 21 8

Eggs 1-4 45 3-10 Kidney 1-4 0 27

Eggs 1-4 47 3-10 Kidney 3R 7 22

Eggs 1-4 50 1-19 Kidney 3R 14 15

Eggs 1-4 54 2-17 Kidney 3R 21 8

Eggs 1-4 57 4-6 Skin/Fat 1-4 0 20

Eggs 1-4 59 4-10 Skin/Fat 3R 7 26

Eggs 1-4 61 6-10 Skin/Fat 3R 14 19

Eggs 1-4 64 11-19 Skin/Fat 3R 21 12

Eggs 1-4 68 9-17 Abdominal Fat 1-4 0 25

Eggs 1-4 70 12 Abdominal Fat 3R 7 26

Eggs 1-4 71 4-11 Abdominal Fat 3R 14 19

Eggs 1-4 73 4 Abdominal Fat 3R 21 12

Eggs 1-4 75 6

1 MRID No. for poultry magnitude of residue study is MRID 47589301; storage intervals are reported in MRID Nos. 

48378101 48319001.

2 Groups are described in MRID 47589301.

3 Time intervals for eggs are days after study initiation. Negative numbers refer to number of days prior to first 

application. Time intervals for tissues refer to days after sacrifice.

The Agency generally requires storage stability data when samples from magnitude of residue 

studies are stored for more than 30 days. Since all samples were stored for less than 30 days, no 

storage stability data are needed to support the poultry magnitude of residue study. There are no 

outstanding deficiencies for the poultry magnitude of residue study and the magnitude of residue 

requirement for poultry has been satisfied.

Data Submitted to Support MRID 47193001 Ruminant Magnitude of Residue Study

The registrant provided storage intervals for the samples from the original ruminant study. In 

addition, the registrant submitted an inadequate storage stability study to support the ruminant 

magnitude of residue study. In response to the deficiencies identified in the October 2010 review

the registrant submitted detailed information on storage intervals from the magnitude of residue 

study (MRID Number pending). 

The magnitude of residue study included five different treatment groups, which are described in 

Table 2 below. Treatment group 4 represents the current maximum label rate for both the feedthrough and dermal treatment uses. A summary of the storage intervals from treatment group 4 

is presented in Table 3 below.
Page 4 of 5

Table 2. Summary of Treatment Groups from Ruminant Magnitude of Residue Study

Group Treatment Description

1 Control

2 Nominal 1x rate Oral Only

3 Nominal 1x rate Oral; Nominal 0.5x rate Dermal

4 Nominal 1x rate Oral; Nominal 1x rate Dermal

5 Nominal 3x rate Oral; Nominal 0.5x rate Dermal

Table 3. Storage Intervals for Samples from Tetrachlorvinphos Ruminant

Magnitude of Residue Study (Group 4 Only)1

Matrix Cow No.2 Time Interval

(Days)3

No. Days 

Storage

Milk 8-10 -7 9

Milk 8-10 -1 3

Milk 8-10 1 6

Milk 8-10 2 7

Milk 8-10 4 16

Milk 8-10 7 26

Milk 8-10 10 20

Milk 8-10 14 9

Milk 8-10 17 8

Milk 8-10 21 7

Milk 8-10 24 11

Milk 8-10 28 14

Skim Milk 8-10 14 25

Skim Milk 8-10 29 15

Cream 8-10 14 23

Cream 8-10 29 22

Muscle 8 0 23 (63)4

Muscle 9 0 22 (62)

Muscle 10 0 21 (61)

Peritoneal Fat 8 0 28

Peritoneal Fat 9 0 27

Peritoneal Fat 10 0 26

Subcutaneous Fat 8 0 23 (63)

Subcutaneous Fat 9 0 22 (62)

Subcutaneous Fat 10 0 21 (61)

Kidney 8 0 31

Kidney 9 0 30

Kidney 10 0 29

Liver 8 0 34

Liver 9 0 33

Liver 10 0 32

1 MRID No. for ruminant magnitude of residue study is MRID 47193001; storage intervals are reported in email 

sent 3/23/11; MRID number pending.

2 Cow identification numbers are described in MRID 47193001.

3 Time intervals for milk are days after study initiation. Negative numbers refer to number of days prior to first 

application. Time interval for tissues refers to days after sacrifice.

4 Number of days storage prior to TCPEdiol analysis (where different from other analytes) is shown in parentheses
Page 5 of 5

The samples from treatment group 4 represent the application rates and retreatment intervals that 

represent current product labels. Almost all samples were analyzed within 30 days; all were 

analyzed within 34 days with the exception of the analyses for one metabolite, TCPEdiol, in 

muscle and subcutaneous fat. HED does not need additional storage stability data to support this 

treatment group since samples were analyzed within 30 days or slightly later. Although some 

samples were analyzed for one metabolite after two months of storage, most samples were 

analyzed within an appropriate interval for this metabolite and residues were non-detectable. 

Since significant exposure is not expected, a storage stability study for this metabolite will not be 

required to support treatment group 4.

However, samples from other treatment groups were stored up to two months. The data from 

these groups have not been used directly in tolerance and/or risk assessment, but have only been 

used for risk characterization. Should the registrant amend use directions such that these data 

would be needed for tolerance assessment, storage stability data would be required.