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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF

CHEMICAL SAFETY AND

POLLUTION PREVENTION

MEMORANDUM

Date: October 7, 2010

SUBJECT: Tetrachlorvinphos. Cattle Oral/Dermal and Poultry Dermal Studies. Summary of 

Residue Data Submitted in Support of Reregistration.

PC Codes: 083701/083702 DP Barcodes: D320848, D320858, D320859, and 381350

Decision Nos.: 359964, 359967, 386529 Registration No.: None

Petition No.: NA Regulatory Action: Other Reregistration

Risk Assessment Type: NA Case No.: 0321

TXR No.: NA CAS No.: 22248-79-9

MRID Nos.: 47193001, 47369201, and 47589301 40 CFR: §180.252

From: Christine L. Olinger, Chemist

Risk Assessment Branch VII

Health Effects Division (7509P)

Through: Donna S. Davis Chemist

Risk Assessment Branch VII

Health Effects Division (7509P)

Michael S. Metzger, Chief

Risk Assessment Branch VII

Health Effects Division (7509P)

To: James Parker

Risk Management and Implementation Branch I

Pesticide Re-evaluation Division (7508P)

This document was originally prepared under contract by Dynamac Corporation (1901 Research 

Boulevard, Suite 220; Rockville, MD 20850).
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Dynamac QC 

Reviewer:

Date: 04/01/2009

Sandra Hastings

Dynamac Program 

Manager:

Date: 04/01/2009

Danilo Martinez

The document has been reviewed by the Health Effects Division (HED) and revised to reflect 

current Office of Pesticide Programs (OPP) policies.
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

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Executive Summary

Tetrachlorvinphos is an insecticide registered for use as a feed-through (oral) larvicide for 

livestock and for direct treatment of beef cattle, dairy cattle, horses, poultry, swine, and livestock 

premises to control nuisance and public health pests such as flies. No plant uses of 

tetrachlorvinphos are currently registered.

EPA has completed its reregistration eligibility review and decisions on tetrachlorvinphos (EPA 

738-R-95-041, September 1995). The Residue Chemistry Science Chapter for Tetrachlorvinphos 

Reregistration Eligibility Decision (RED) was issued 7/6/94 (DP# 199644, F. Suhre). According 

to the Residue Chemistry Chapter, the formulations registered for use on animals include the 

granular (G), wettable powder (WP), impregnated material (Impr), dust (D), ready-to-use (RTU), 

and emulsifiable concentrate (EC). These formulations may be applied directly as a spray, 

backrubber solution, dust-bag, and dust. The G formulations are registered as feed supplements

to control fecal flies (oral larvicide); the D, WP and EC formulations are registered for animal 

premise treatments, and/or topical treatments.

In response to the Tetrachlorvinphos RED, KMG Bernuth, Inc., has submitted the results of 

magnitude of the residue studies on cattle and poultry as well as a storage stability study and a 

residue analytical method. These studies have been reviewed by HED. This document 

summarizes the adequacy of these data in fulfilling reregistration requirements. It is noted that 

the Tetrachlorvinphos RED also required a new magnitude of the residue study on swine which 

remains outstanding. The swine study was required in lieu of a swine metabolism study. For the 

purpose of this action, the end-use product labels registered to KMG Bernuth were re-examined. 

Based on the results of the reviewed studies, HED is requiring label revisions for certain 

products.

Tolerances for residues of tetrachlorvinphos are established under 40 CFR §180.252. The 

current tolerance expression is for the combined residues of tetrachlorvinphos [(Z)-2-chloro-1-

(2,4,5-trichlorophenyl)vinyl dimethyl phosphate] and its metabolites, 1-(2,4,5-trichlorophenyl)-

ethanol (free and conjugated forms), 2,4,5-trichloroacetophenone, and 1-(2,4,5-trichlorophenyl)-

ethanediol. Time limited tetrachlorvinphos tolerances are established for the animal 

commodities under 40 CFR §180.252 and were based on the available metabolism data. In the 

RED HED recommended time-limited tolerances to allow time for the registrant to submit new 

magnitude of residue studies. There are no Codex maximum residue limits (MRLs) established 

or proposed for residues of tetrachlorvinphos.

The qualitative nature of the residue in ruminants following oral or dermal dosing, and in poultry

following dermal application is adequately understood based on previously submitted studies. 

The Agency has determined that the residues of concern are tetrachlorvinphos, des-O-methyl 

tetrachlorvinphos, 1-(2,4,5-trichlorophenyl)ethanol (free and conjugated forms), 2,4,5-

trichloroacetophenone, and 1-(2,4,5-trichlorophenyl)ethanediol.

A gas liquid chromatography (GLC) method for the determination of tetrachlorvinphos per se in 

animal commodities is described in the Pesticide Analytical Method (PAM), Vol. II, as Method I. 

The registrant has submitted a method for the determination of tetrachlorvinphos and its 
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

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metabolites, which uses LC/MS/MS, LC/MS, GC/ECD, and GC/MS methods. An independent 

laboratory validation (ILV) must be submitted.

Samples collected from the animal studies were analyzed for all tetrachlorvinphos residues of 

concern using LC/MS/MS, LC/MS, GC/ECD or GC/MS methods. The limit of quantitation was 

0.01 ppm for each analyte and was defined as the lowest fortification level at which acceptable 

recovery data are obtained. The methods used for analysis of cattle matrices were adequately

validated by fortifying control matrices with each analyte at 0.01-0.6 ppm, while the method for 

the poultry matrices was validated at 0.01 and 0.1 ppm. 

No data pertaining to the behavior of regulated tetrachlorvinphos metabolites using FDA's 

multiresidue protocols have been submitted. As requested in the 1994 Residue Chemistry

Chapter, the regulated metabolites of tetrachlorvinphos should be analyzed using the FDA 

multiresidue protocols as appropriate to ascertain if the methods are capable of accurately

quantifying all residues of concern.

Samples collected from the magnitude of the residue study on cattle were stored frozen for up to 

50 days for milk and cream, 54 days for liver, fat, and kidney, and 63 days for muscle prior to 

residue analysis. Samples collected from the magnitude of the residue study on poultry were 

estimated (information regarding dates of sample collection and analysis was not provided) to be 

stored frozen for up to 144 days for eggs and 59 days for tissues prior to analysis. 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. A new storage stability study 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.

The submitted magnitude of the residue study on cattle is inadequate but upgradeable pending 

submission of supporting storage stability data. The residue data reflect a combination of two 

treatments: oral administration of tetrachlorvinphos for 29-31 days at actual rates of 1.512-1.555 

and 4.630 g ai/750 kg BW per day (6.3-6.5x and 19.3x, respectively, the maximum registered 

rate of 0.24 g ai/750 kg BW for feed-through treatment) and dermal spray treatments on three 

occasions, at ~14 day intervals, at actual rates of 10.111 and 19.166-19.493 g ai per animal per 

dose (~0.5 and 1.0x, respectively, the maximum registered rate of 18.9 g ai/animal for direct 

animal spray treatment). At the treatment regime approximating the registered uses (6.5x oral + 

1x dermal), the maximum total residues of concern (with the maximum residues of the parent in 

parentheses) were: 0.072 (0.036) ppm for milk, 0.078 (<0.01) ppm for cream, 0.158 (<0.01) ppm 

for liver, 0.278 (0.015) ppm for kidney, 0.272 (0.212) ppm for muscle, 0.842 (0.558) ppm for 

subcutaneous fat, and 0.747 (0.340) ppm for peritoneal fat. These data will support the registered

feed-through (oral) and direct animal spray uses of tetrachlorvinphos on cattle.

The submitted magnitude of the residue study on poultry is inadequate but upgradeable pending 
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

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submission of storage stability data/information. The residue data reflect 6-7 dermal spray

treatments of laying hens with an EC formulation, made at two-week retreatment intervals, at 

rates of 0.0908, 0.1816, or 0.5448 g ai/hen/application. These application rates, respectively, 

correspond to ~0.5x, 1.0x, or 2.9x the maximum registered direct spray treatment rate of 0.19 g 

ai/bird daily. At ~1.0x, the maximum total residues of concern (with the maximum residues of 

the parent in parentheses) were: 0.288 (0.026) ppm for egg, 0.517 (0.016) ppm for liver, 0.583 

(0.022) ppm for kidney, 0.396 (0.082) ppm for muscle, 19.405 (6.030) ppm for skin with fat, and 

1.298 (0.099) ppm for abdominal fat. 

No data were submitted reflecting application of tetrachlorvinphos as a backrubber treatment, 

direct animal dusting and/or premise spray treatment; also no data were submitted directly

reflecting the use of cattle ear tag uses which may still be registered to other companies. The 

OPPTS 860.1480 Guideline states that when a pesticide may be applied by more than one mode 

of treatment, separate studies are required; however, only oral and dermal spray studies were 

required in the TCVP RED. Because the oral and dermal treatments are expected to result in the 

highest residue levels, no additional data will be required to support backrubber or premise spray

treatments. Data from wetting sprays may be accepted in lieu of data from dust treatments.

Analytical standards for tetrachlorvinphos are currently available in the EPA National Pesticide 

Standards Repository; however, no reference standards are available for the metabolites which 

are also regulated (TCVPdeme, TCPEone, TCPEol, and TCPEdiol).

Regulatory Recommendations and Residue Chemistry Deficiencies

The submitted magnitude of the residue studies on cattle and poultry are inadequate but 

upgradeable. Since a swine magnitude of residue study has not been submitted, the existing time 

limited tolerances based on the goat metabolism study should remain until the new study has 

been submitted. The poultry and cattle tolerances will need modification; refer to Table 9 for 

tolerance reassessment summary.

It is noted that the metabolite des-O-methyl tetrachlorvinphos is not included in the current 

tolerance expression as determined by the Agency; therefore 40 CFR §180.252 should be 

amended to include the TCVPdeme metabolite. HED recommends that the tolerance definition 

should be modified as follows.

Tolerances are established for residues of the insecticide tetrachlorvinphos, 

including its metabolites and degradates, in or on the commodities in the table 

below. Compliance with the tolerance levels specified below is to be determined 

by measuring only the sum of tetrachlorvinphos [(Z)-2-chloro-1-(2,4,5-

trichlorophenyl)vinyl dimethyl phosphate) and its metabolites chloro- 1 -(2,4,5-

trichlorophenyl)-vinylmonomethyl phosphate, 1-(2,4,5-trichlorophenyl)-ethanol 

(free and conjugated forms), 2,4,5-trichloroacetophenone, and 1-(2,4,5-

trichlorophenyl)-ethanediol, calculated as the stoichiometric equivalent of 

tetrachlorvinphos, in or on the commodity.

A list of the outstanding residue chemistry deficiencies is presented below. 
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

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860.1200 Directions for Use

• Based on the magnitude of the residue study on cattle, the product labels with direct 

animal spray uses on cattle (EPA Reg. Nos. 61483-43 and 61483-50) should be amended 

to specify a maximum of three applications, with two-week retreatment intervals, at 19 g 

ai/animal/dose. The product label for Ravap (EPA Reg. No. 61483-50) should also be 

amended to provide conversion factors to allow calculation of direct animal spray

treatment rate in terms of g ai/animal. 

• Based on the magnitude of the residue study on poultry, the product labels with direct 

animal spray uses on poultry (EPA Reg. Nos. 61483-43 and 61483-50) should be 

amended to specify a maximum of seven applications (with two-week retreatment

intervals) at 0.18 g ai/hen/application. Note that the label should specify the weight or 

volume of the product to be applied.

860.1340 Residue Analytical Methods

• An Independent Laboratory Validation (ILV) must be submitted for the proposed 

tolerance enforcement method. 

860.1360 Multiresidue Methods

• No data pertaining to the behavior of regulated tetrachlorvinphos metabolites using FDA's 

multiresidue protocols have been submitted. As requested in the 1994 Residue Chemistry

Chapter, the regulated metabolites of tetrachlorvinphos should be analyzed by the FDA 

multiresidue protocols as appropriate to ascertain that the methods are capable of 

accurately quantifying all residues of concern. See Decision Tree for MRM in Appendix 

II-2 of PAM Vol. I for more information.

860.1380 Storage Stability

• 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.

860.1480 Meat, Milk, Poultry, and Eggs

• A magnitude of the residue study on swine is required.

860.1650 Submittal of Analytical Reference Standards

• The registrant must submit reference standards for the TCVP regulated metabolites

(TCVPdeme, TCPEone, TCPEol, and TCPEdiol) to the Analytical Chemistry Lab.
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

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Background

The chemical names and structures of the regulated residues are presented in Table 1. The 

physicochemical characteristics of the technical grade of tetrachlorvinphos are presented in Table 

2.

Table 1. Test Compound Nomenclature.

Compound

P

O

O

H3CO

OCH3

Cl

Cl Cl

Cl

Common name Tetrachlorvinphos

Company experimental name TCVP

IUPAC name (Z)-2-chloro-1-(2,4,5-trichlorophenyl) vinyl dimethyl phosphate

CAS registry number 22248-79-9

End-use products registered to 

KMG Bernuth, Inc.

Rabon 50 WP Insecticide (EPA Reg. No. 61483-43, 50% WP);

Rabon 3% Insecticide Dust EPA Reg. No. 61483-45, 3% D); 

Rabon 97.3 Oral Larvicide (EPA Reg. No. 61483-47, 97.3% G); 

Rabon 7.76 Oral Larvicide Premix (EPA Reg. No. 61483-48, 7.76% G); and

Ravap EC Livestock, Poultry & Premise Insecticide Spray (EPA Reg. No. 61483-50, 23% 

EC)

Compound

P

O

O

HO

OCH3

Cl

Cl Cl

Cl HO

CH3

Cl Cl

Cl

Common name TCVPdeme TCPEol

Chemical name des-O-methyl tetrachlorvinphos 1-(2,4,5-trchlorophenyl)ethanol

Compound

O

CH3

Cl Cl

Cl

HO

Cl Cl

Cl

OH

Common name TCPEone TCPEdiol

Chemical name 2,4,5-trichloroacetophenone 1-(2,4,5-trichlorophenyl)ethanediol

Table 2. Physicochemical Properties of the Technical Grade Test Compound: Tetrachlorvinphos.

Parameter Value Reference 1

Melting point/range 94.5 oC (MRID 41222503)

pH 5.5; 1% solution (MRID 41222503)

Density 0.83 g/mL (MRID 41222503)

Water solubility (25°C) 0.00116 g/100g (MRID 41222503)
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

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Table 2. Physicochemical Properties of the Technical Grade Test Compound: Tetrachlorvinphos.

Parameter Value Reference 1

Solvent solubility (mg/100mg at 25°C)

chloroform 80

methanol 21

acetone 44

hexane 0.8

toluene 28

(MRID 41222503)

Vapor pressure (25°C) 2.6 x 10-7 mm Hg (MRID 41222503)

Dissociation constant, pKa non-ionizable (MRID 41222503)

Octanol/water partition coefficient, Log(KOW) 3350 average KOW at 25 oC (MRID 41222503)

UV/visible absorption spectrum Not available

1 Cited reference was reviewed under CB No. 7468, 4/3/91, R. Perfetti.

860.1200 Directions for Use

A search of EPA’s PPLS database conducted 02/04/2009 identified five tetrachlorvinphos enduse products registered to KMG Bernuth, Inc. for use as an oral larvicide for livestock or direct 

treatment of beef cattle, lactating cattle, horses, poultry, swine, and livestock premises. These 

products are listed in Table 3A. Only those end-use products registered to the technical 

registrant, KMG-Bernuth, are considered in this table.

Table 3A. List of Tetrachlorvinphos End-Use Products Registered to KMG Bernuth, Inc.

Trade Name EPA Reg. No. Acceptance Date ai (% of formulation) Formulation Type

Rabon 50 WP Insecticide 61483-43 4/17/2006 50% WP

Rabon 3% Insecticide Dust 61483-45 10/23/2008 3% D

Rabon 97.3 Oral Larvicide 61483-47 09/18/2007 97.3% G

Rabon 7.76 Oral Larvicide Premix 61483-48 05/04/2006 7.76% G

Ravap EC Livestock, Poultry & 

Premise Insecticide Spray 1

61483-50 11/30/2007 23% EC

1 Also contains 5.3% dichlorvos.

The tetrachlorvinphos products listed above may be applied directly to livestock via various 

methods or used as a feed-through (oral supplement). It may also be applied to their living 

quarters. A summary of the directions for use for ruminants, poultry, and swine, which are the 

subject of the residue data reviewed herein, are presented in Table 3B. Example calculations for 

application rates are presented in Table 3C for the product, Rabon 50 WP Insecticide (EPA Reg. 

No. 61483-43), that leads to the maximum application rate.

Table 3B. Summary of Registered Directions for Use of Tetrachlorvinphos.

1

Application 

Type/Mode

Formulation

[EPA Reg. No.]

Application Rate Use Directions and Limitations

Cattle, Beef

Direct animal spray 50% WP

[61483-43]

0.5-1.0 gal of 0.35-0.5% 

solution/animal;

(equivalent to a maximum 

rate of 18.9 g ai/animal) 

Apply as a low pressure coarse spray 

and apply only to point before runoff. 

No retreatment restrictions are 

specified. There is no withholding 

period from last application to 

slaughter. 
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

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Table 3B. Summary of Registered Directions for Use of Tetrachlorvinphos.

1

Application 

Type/Mode

Formulation

[EPA Reg. No.]

Application Rate Use Directions and Limitations

23% EC

[61483-50]

0.5-1.0 gal of a spray 

solution per animal with 

spray solution made by 

diluting 1 gal of 23% EC in 

75 to 200 gal of water

(equivalent to 11 g 

ai/animal)

Do not treat more often than every 10 

days. Do not apply to calves under 6 

months of age. Brahman and Brahmancross cattle should not be treated as 

they may show hypersensitivity to 

organophosphate pesticides. Do not 

apply in combination with other 

organophosphate pesticides (e.g., 

trichlorfon). There is no withholding 

period from last application to

slaughter.

Feed through (oral) 7.76% G

[61438-48]

70 mg/100 lb BW/day

(equivalent to 0.24 g ai/750 

kg BW)

For use as an oral larvicide in cattle 

feeds to prevent the development of 

flies in the manure of treated cattle. 

Concentrate must be mixed with feed.

Direct animal 

dusting

3% D

[61483-45]

1.7-3.4 g ai/animal Apply to the upper portions of the 

back, neck, and poll by hand dusting or 

self-treating dust bag. Repeat as 

necessary.

Cattle, Lactating

Direct animal spray 23% EC

[61483-50]

0.5 gal of a spray solution 

per animal with the spray 

solution made by diluting 1 

gal of 23% EC in 200 gal 

of water

(equivalent to 4 g 

ai/animal)

Repeat as necessary (general label 

directions specify do not apply more 

than once a day). Do not apply to 

calves under 6 months of age. No milk 

discard is required. Care should be 

taken that the spray does not come in 

direct contact with the cow’s teats 

unless they are washed with an 

approved cleansing solution and dried 

before milking. Apply the spray at 

least 20 minutes prior to milking or 

after milking has been completed.

Feed through (oral) 97.3% G

[61483-47]

7.76% G

[61438-48]

70 mg/100 lb BW/day

(equivalent to 0.24 g ai/750 

kg BW

For use as an oral larvicide in cattle 

feeds to prevent the development of 

flies in the manure of treated cattle. 

Concentrate must be mixed with feed.

Direct animal 

dusting

3% D

[61483-45]

1.7-3.4 g ai/animal Apply to the upper portions of the 

back, neck, and poll by hand dusting or 

self-treating dust bag. Repeat as 

necessary.

Poultry

Direct animal spray 50% WP

[61483-43]

1.0 gal of 0.5% 

solution/100 birds 

(equivalent to a maximum 

rate of 0.19 g ai/bird)

Spray the vent and fluff of wire cages 

from below. Repeat when necessary 

but do not repeat more than every 14 

days. 

23% EC

[61483-50]

1.0 gal of a spray solution 

per 100 birds with the 

spray solution made by 

diluting 1 gal of 23% EC in 

50 gal of water
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

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Table 3B. Summary of Registered Directions for Use of Tetrachlorvinphos.

1

Application 

Type/Mode

Formulation

[EPA Reg. No.]

Application Rate Use Directions and Limitations

Direct animal 

dusting

3% D

[61483-45]

0.03 lb ai/300 birds For individual treatment of poultry in 

wire cages. Direct dust to vent and 

fluff area. Group treatment may be 

preferred. Dust should reach skin. 

Wire rungs and corners should also be 

treated.

Swine

Direct animal spray 50% WP

[61483-43]

0.25 to 0.5 gal of 0.5% 

solution/animal

(equivalent to a maximum 

rate of 9.5 g ai/animal)

Apply as a low pressure coarse spray 

and apply only to point before runoff. 

Repeat in 2 weeks if necessary. There 

is no withholding period from last 

application to slaughter. 

Feed through (oral) 7.76% G

[61438-48]

22.7 mg/1000 lb BW;

0.077 g ai/750 kg BW

For use as an oral larvicide in swine 

feeds to prevent the development of 

flies in the manure of treated cattle. 

Concentrate must be mixed with feed.

Direct dusting of 

animal 

3% D

[61483-45]

2.6-3.4 g ai/animal Apply by conventional hand or power 

duster to each animal with special 

attention given to the neck and around 

the ear. 

Horses

Feed through 

(animal supplement)

7.76% G

[61438-48]

5.4 mg ai/100 lb BW/day For use as an oral larvicide in horse 

feeds to prevent the development of 

flies in the manure of treated cattle. 

Concentrate must be mixed with feed. 

The product is not to be used for horses 

designed for slaughter.

1Note: Application rates for backrubber and premise treatments are not included in this table as they are likely to 

lead to lower exposure than the direct application via sprays and dusts. Only the use directions from products 

registered by the technical registrant, KMG-Bernuth, are included.

Table 3C. Calculation of Application Rates for Direct Animal Spray (EPA Reg. No. 61483-43)1

Pounds

Product

Percent of ai 

in Product

Volume 

Water, 

Gallons

Solution

Percentage

Volume 

Applied to 

Animal, Gallons

Application 

Rate, lb 

ai/animal2

Application 

Rate, g 

ai/animal 3

0.5 50 9 0.35 1 0.03 13.6

0.5 50 6 0.5 1 0.0417 18.9

0.5 50 6 0.5 0.5 0.021 9.5

2 50 36 0.35 1 0.0278 12.6

2 50 25 0.5 1 0.04 18.2

4 50 75 0.35 1 0.0267 12.1

4 50 50 0.5 1 0.04 18.2

8 50 150 0.35 1 0.0267 12.1

8 50 100 0.5 1 0.04 18.2

1 The lb product, % ai, volume values were obtained directly from the label.

2 Calculated by the following formula: (lb product x % ai in product x volume applied to animal)/volume water in 

spray solution.

3 Calculated by the following formula: lb ai/animal x 454 g/lb.

Conclusions. The end-use product labels of KMG Bernuth, Inc. were examined and are deemed 

adequate to allow evaluation of the residue data relative to the registered animal use patterns. 
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

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Based on the magnitude of the residue study on cattle, the product labels with direct animal spray

uses on cattle (EPA Reg. Nos. 61483-43 and 61483-50) should be amended to specify a 

maximum of three applications, with two-week retreatment intervals, at 19 g ai/animal/dose. The

product label for Ravap (EPA Reg. No. 61483-50) should also be amended to provide conversion 

factors to allow calculation of direct animal spray treatment rate in terms of g ai/animal. 

Based on the magnitude of the residue study on poultry, the product labels with direct animal 

spray uses on poultry (EPA Reg. Nos. 61483-43 and 61483-50) should be amended to specify a 

maximum of seven applications (with two-week retreatment intervals) at 0.18 g

ai/hen/application. Note that the labels should state the amount of product (weight or volume) to 

be applied to the animal so the applicator will not have to calculate the amount of product 

equivalent to 0.18 g ai/animal.

860.1300 Nature of the Residue - Plants

There are no registrations or tolerances for plant commodities, so these studies are not required 

for tetrachlorvinphos.

860.1300 Nature of the Residue - Livestock

Residue Chemistry Memo: DP# 243528, 3/11/98, D. Miller

Residue Chemistry Memo: DP# 206721, 9/21/94, D. Miller (Addendum to RED)

Residue Chemistry Chapter to Tetrachlorvinphos RED (DP# 199644, 7/6/94, F. Suhre)

Residue Chemistry Memo: J. Abbotts, No DP#, 4/93, Results of Metabolism Committee Meeting

The qualitative nature of the residue in ruminants following oral or dermal dosing, and in poultry

following dermal application is adequately understood based on previously submitted studies. 

The Agency has determined that the residues of concern are tetrachlorvinphos, des-O-methyl 

tetrachlorvinphos, 1-(2,4,5-trichlorophenyl)ethanol (free and conjugated forms), 2,4,5-

trichloroacetophenone, and 1-(2,4,5-trichlorophenyl)ethanediol.

The metabolism of tetrachlorvinphos in ruminants and poultry differs somewhat. The 

metabolites des-O-methyl tetrachlorvinphos and 1-(2,4,5-trichlorophenyl)ethanediol are found 

only in hens, and the metabolite 1-(2,4,5-trichlorophenyl)ethanol is found only in goats 

(following both oral and dermal administration). The difference in metabolic profiles between 

goats and swine, both mammals, would be expected to be less significant than the difference 

between goat and hens. Therefore, the requirements for swine metabolism studies have been 

waived, provided that a magnitude of the residue study with swine is conducted including 

analysis of all residues of concern.

The HED Metabolism Committee has determined that the residues of concern are 

tetrachlorvinphos, des-O-methyl tetrachlorvinphos, 1-(2,4,5-trichlorophenyl)ethanol (free and 

conjugated forms), 2,4,5-trichloroacetophenone, and 1-(2,4,5-trichlorophenyl)ethanediol. Timelimited tolerances for livestock commodities, based on feed-through and direct dermal uses on 

livestock, were estimated by the Agency from the acceptable metabolism data. Permanent 

tolerances are to be established when adequate magnitude of the residue data for ruminants, 

swine and poultry are available.
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

Page 12 of 28

860.1340 Residue Analytical Methods

Residue Chemistry Chapter to Tetrachlorvinphos RED (DP# 199644, 7/6/94, F. Suhre)

DER Reference List: 47369201.der.doc

Tolerance Enforcement Methods

Analytical methods for plant commodities are not required because there are no tetrachlorvinphos

end-use products registered for use on any plant commodity.

The registrant has submitted a method for tolerance enforcement of livestock commodities

(MRID 47369201, 2007). This method involves the extraction of TCVP and its four major 

metabolites from tissues, milk and cream using acetonitrile and the removal of lipid interferences 

using partition with hexane and a C18 solid phase extraction (SPE) cartridge. TCVP, 

TCVPdeme and TCPEdiol are isolated on the C18 cartridge and are quantified using liquid 

chromatography with mass spectrometric detection (LC-MS). TCPEone and TCPEol are further 

cleaned up with an ENVI-CARB cartridge before quantitation using gas chromatography with 

electron capture detection (GC-ECD). Conjugated TCPEol and TCPEdiol are extracted from the 

initial acetonitrile extract using saturated sodium chloride solution and liberated by hydrolyzing 

overnight under acidic conditions. Further clean up is performed using an ENVI-CARB 

cartridge prior to quantitation by GC-ECD (TCPEol) or LC-MS (TCPEdiol). 

The method was validated by SRA International using quintuplet sets of control samples of 

bovine muscle, bovine liver, bovine kidney, bovine fat, milk and cream fortified with TCVP, 

TCVPdeme, TCPEol, TCPEone and TCPEdiol at 10 and 100 ppb. Individual recoveries from 

fortified samples ranged from 70% to 110%. Standard deviations for each crop/spiking level 

were no higher than 15%. 

An independent laboratory validation (ILV) trial has not been submitted to HED for review and

radiovalidation data were not provided with this method validation trial. Since the extraction 

scheme is similar to those employed in the metabolism study, and the tissues from the 

metabolism study are not likely still available, the requirement for radiovalidation data is waived.

Data Collection Methods

Egg, milk and tissue samples from the cattle and poultry magnitude of the residue studies were 

analyzed for residues of tetrachlorvinphos, (TCVP), des-O-methyl tetrachlorvinphos 

(TCVPdeme), 1-(2,4,5-trichlorophenyl)ethanol (TCPEol; free and conjugated), 2,4,5-

trichloroacetophenone (TCPEone), and 1-(2,4,5-trichlorophenyl)ethanediol (TCPEdiol; free and 

conjugated) using LC/MS, LC/MS/MS, GC/ECD, or GC/MS methods. Briefly, samples were 

initially extracted with acetonitrile (ACN), and lipid interferences were removed by partitioning 

with hexane and C18 solid phase extraction (SPE) cartridge.
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

Page 13 of 28

TCVP, TCVPdeme, and TCPEdiol were isolated on a C18 cartridge and quantified using LC/MS 

or LC/MS/MS. Separate LC conditions were used for each analyte. Quantitation of TCVP 

residues was performed using an electrospray interface in the positive ion mode. Quantitation of 

TCVPdeme residues was performed using an electrospray interface in the negative or positive 

ion mode. Quantitation of TCPEdiol residues was performed using LC/MS with an electrospray

interface in the negative ion mode.

TCPEone and TCPEol were further cleaned up by Envicarb cartridge before quantitation using 

GC/ECD or GC/MS. Conjugated TCPEol and TCPEdiol were extracted from the initial 

acetonitrile extract using a saturated sodium chloride solution and liberated by hydrolyzing 

overnight under acidic conditions. Further clean-up is performed by Envicarb cartridge prior to 

quantitation by GC/ECD or GC/MS (TCPEol) or LC/MS (TCPEdiol).

The LOQ was 0.01 ppm for each analyte and was defined as the lowest fortification level at 

which acceptable recovery data are obtained. The estimated limit of detection (LOD) was 0.002 

ppm for TCVP (and TCVPdeme in poultry matrices), 0.005 ppm for TCPEdiol, and 0.0025 ppm 

for all other analytes. Concurrent method recoveries were within the acceptable range of 70-

120%.

Conclusions. A tolerance enforcement method has been submitted, but the requirement for an 

ILV remains outstanding. Samples collected from the animal studies were analyzed for all 

tetrachlorvinphos residues of concern using LC/MS/MS, LC/MS, GC/ECD, or GC/MS methods. 

The limit of quantitation was 0.01 ppm for each analyte and was defined as the lowest 

fortification level at which acceptable recovery data are obtained. The methods used for analysis 

of cattle matrices were adequately validated by fortifying control matrices with each analyte at 

0.01-0.6 ppm. However, the poultry methods were only verified at fortification levels of 0.01 

and 0.1 ppm. Adequate dilutions were used, so no further validation data are required.

860.1360 Multiresidue Methods

Residue Chemistry Chapter to Tetrachlorvinphos RED (DP# 199644, 7/6/94, F. Suhre)

The FDA PESTDATA database dated 8/93 (PAM Vol. I, Appendix II) indicates that 

tetrachlorvinphos is completely recovered (>80%) using FDA multiresidue method protocol D 

(section 232.4) but is not recovered using protocol E (Sections 211.1/231.1 and 212.1/232.1, 

fatty and nonfatty matrices). No data pertaining to the behavior of regulated tetrachlorvinphos 

metabolites using FDA's multiresidue protocols have been submitted. As requested in the 1994 

Residue Chemistry Chapter, the regulated metabolites of tetrachlorvinphos should be analyzed by

the FDA multiresidue protocols as appropriate to ascertain if the methods are capable of 

accurately quantifying all residues of concern. See Decision Tree for MRM in Appendix II-2 of 

PAM Vol. I for more information.
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

Page 14 of 28

860.1380 Storage Stability

Sample Storage Conditions and Intervals

The integrity of samples collected from the animal studies was maintained by appropriate 

handling and freezer storage. Sample storage conditions and durations are summarized in Table 

4.

Table 4. Summary of Storage Conditions.

Matrix Storage Temperature

(°C)

Actual Storage Duration Interval of Demonstrated Storage Stability

Cattle Study (MRID 47193001)

Milk -20 <30-50 days None.

Cream <30-50 days

Liver <30-54 days

Kidney <30-54 days

Muscle <30-64 days

Fat, Subcutaneous <30-54 days

Fat, Peritoneal <30-54 days

Poultry Study (MRID 47589301)

Egg -20 144 days None.

Tissues 59 days

Storage Stability Data

Residue Chemistry Chapter to Tetrachlorvinphos RED (DP# 199644, 7/6/94, F. Suhre)

DER Reference List: 47193001.de2.doc

The 1994 Residue Chemistry Chapter reported that storage stability studies have been conducted 

for the parent compound using fortified samples of milk and animal tissues. Residues of the 

tetrachlorvinphos per se are stable for 25 days at 0 °C in milk, for 31 days at 0 °C in milk fat, for 

3 days at room temperature in muscle, for 4 days at room temperature in kidney, for 5 days at 

room temperature in liver, and for 11 days at room temperature in fat.

The registrant submitted additional storage stability data for the parent and all residues of 

concern along with the cow feeding study (MRID 47193001). HED has reviewed the companion 

study, and the Executive Summary of the Data Evaluation Records is reproduced below.

SRA International, Inc., on behalf of KMG Bernuth, Inc., has included supporting storage 

stability data in the amended final report of a dairy cattle feeding study with tetrachlorvinphos. 

To generate data on the stability of weathered tetrachlorvinphos residues of concern in milk,

cream, liver, kidney, muscle, and fat, selected samples of these matrices were re-assayed after the 

initial analysis. Initial residue analyses of samples from the cattle feeding study were made after 

the collected samples were stored frozen for up to 50 days for milk and cream, 54 days for liver, 

fat, and kidney, and 63 days for muscle; the registrant reported that the majority of samples were 

stored for less than 30 days. Samples were re-analyzed at the following intervals after the initial 

analysis: 74 and 112 days for milk, 70 and 84 days for cream, 57 days for liver, 60 days for 

kidney, 68 days for muscle, and 63 and 65 days for fat.
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

Page 15 of 28

Milk and tissue samples were analyzed for residues of tetrachlorvinphos, TCVPdeme, TCPEol, 

TCPEone, and TCPEdiol using LC/MS, LC/MS/MS, or GC/ECD methods. The validated LOQ 

was 0.01 ppm for each analyte. The adequacy of the method for data collection was verified by

fortifying untreated samples of milk and tissues with TCVP and its metabolites at 0.01 and 0.1 

ppm. Additional untreated samples of muscle were fortified with TCVP at 0.5 ppm and 

peritoneal fat were fortified with TCVP and TCPEol each at 0.6 ppm. Concurrent method 

recoveries were within the acceptable range of 70-120%. 

Considerable variability in the sample results was observed. Initial analysis for some analytes 

showed nondetectable residues, but residues were quantifiable at later intervals (TCPEol -

conjugated). For some matrices extensive degradation was observed, but extensive increases 

were observed for other matrices (e.g., free TCPEol). The registrant concluded that overall 

results for total TCVP-derived residues did not indicate any consistent or significant losses 

outside the expected limits of analytical variation. HED does not concur with the registrant’s 

conclusion. The samples were stored for at least 50 days prior to the initial assay. Considerable 

degradation may have occurred prior to the initial analysis. 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.

Conclusions. Storage durations of cattle and hen samples collected from the magnitude of the 

residue studies are not supported by adequate storage stability data. Although a companion 

storage stability study was submitted in support of the cattle study, the data were deemed 

inadequate because considerable degradation may have occurred prior to the initial analysis of 

storage stability samples. New storage stability studies should be conducted with quantifiable 

(i.e., fortified) residues of all analytes in cattle and poultry matrices according to 860.1380. In 

addition, the registrant needs to submit information pertaining to dates of treatment, collection, 

extraction, and analysis to verify the maximum storage intervals from collection to extraction and 

analysis of all samples from both the cattle and poultry studies.

860.1400 Water, Fish, and Irrigated Crops

This guideline is not applicable to tetrachlorvinphos as the only use is on livestock.

860.1460 Food Handling

This guideline is not applicable to tetrachlorvinphos as the only use is on livestock.

860.1480 Meat, Milk, Poultry, and Eggs

Residue Chemistry Chapter to Tetrachlorvinphos RED (DP# 199644, 7/6/94, F. Suhre)

New ruminant, swine, and poultry magnitude of the residue studies were requested in the 1994 

Residue Chemistry Chapter. The Chapter concluded that no residue data are required for horses 

provided that all applicable labels prohibit treatment of horses destined for slaughter. 

Examination of the 7.76% G oral larvacide label (EPA. Reg. No. 56493-35), a product registered 

to the technical registrant, shows that it has been amended to prohibit treatment of horses

intended for slaughter. It is possible that other registrants may have uses on horses; the product 
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

Page 16 of 28

labels of these other registrants need to be examined to ensure that such restrictions are 

established.

Protocols for the conduct of the required animal studies were reviewed by HED in memos dated 

06/01/99 (DP# 246716, S. Hummel) and 8/27/01 (DP# 277227, M. Metzger). The results of the 

new ruminant and poultry magnitude of the residue studies have now been submitted. HED has 

reviewed these studies, and the Executive Summaries of the Data Evaluation Records are 

reproduced below. The requirements for a swine study remain outstanding.

Cattle Oral/Dermal Study

DER Reference List: 47193001.de1.doc

SRA International, Inc., on behalf of KMG Bernuth, Inc., has submitted the amended final report 

of a dairy cattle feeding study with tetrachlorvinphos. The study was designed to quantify the 

residues of tetrachlorvinphos and its four significant metabolites in the milk and tissues of dairy

cows following oral administration of tetrachlorvinphos for 29-31 days and concurrent topical 

(spray) application of tetrachlorvinphos on three occasions at two-week intervals. A summary of 

the five treatment groups is presented in Table 5. Groups of lactating dairy cows received 

tetrachlorvinphos incorporated twice daily into the concentrate feed in oil suspensions at target 

levels equivalent to 1.155 or 3.465 g ai/750 kg body weight per day for 29-31 days. In addition, 

doses of tetrachlorvinphos were administered by the dermal route on three occasions, at ~14 day

intervals, as a solution in water at target levels equivalent to 6.055 and 12.11 g ai per animal per 

dose. An untreated animal was also included to provide control data.

Table 5. Treatment Parameters Used in the Cattle Study.

Group Treatment Target and (Actual) Exposure Level 1 Cow numbers

Oral Dermal

1 Control -- -- 1

2 Oral 1.155 (1.553) -- 2, 3, 4/16

3 Oral + Dermal 1.155 (1.512) 6.055 (10.111) 5, 6, 7

4 Oral + Dermal 1.155 (1.555) 12.11 (19.166) 8, 9, 10

5 Oral + Dermal 3.465 (4.630) 12.11 (19.493) 11, 12, 13, 14, 15

1 Dose levels are in g ai/750 kg body wt/day for oral doses and g ai/animal/dose for dermal doses.

Milk was collected twice daily. A portion of the milk collected on days 14 and 28/29 were 

separated into skim milk and cream. One cow from each group was sacrificed after 29, 30, or 31 

consecutive days of treatment. The following tissues were collected at sacrifice for analysis: 

subcutaneous fat, muscle, peritoneal fat, liver, and kidney.

Two cows from treatment group 5 were used in a depuration study to determine how quickly

residues in tissues dissipate. Milk was collected from both animals on days 30, 34, 36, and from 

the remaining cow on days 38 and 43 after the first dose. On study day 37 and 44, (7 and 14 days 

without treatment), the depuration animals were sacrificed, and samples of liver, kidney, muscle, 

subcutaneous fat, and peritoneal fat were collected for analysis.

Milk and tissue samples were analyzed for residues of tetrachlorvinphos, TCVPdeme, TCPEol, 
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

Page 17 of 28

TCPEone, and TCPEdiol using LC/MS, LC/MS/MS, or GC/ECD methods. The validated 

method LOQ was 0.01 ppm for each analyte. The adequacy of the method for data collection 

was verified by fortifying untreated samples of milk and tissues with TCVP and its metabolites at 

0.01 and 0.1 ppm. Additional untreated samples of muscle were fortified with TCVP at 0.5 ppm 

and peritoneal fat were fortified with TCVP and TCPEol each at 0.6 ppm. Concurrent method 

recoveries were within the acceptable range of 70-120%.

Prior to residue analysis, samples of milk and cream were stored frozen for up to 50 days; liver, 

fat, and kidney samples for up to 54 days; and muscle samples for up to 64 days. It is noted that 

only the storage intervals exceeding 30 days were documented in the report. The storage stability

data (refer to 47193001.de2) submitted in conjunction with this study are inadequate. Additional 

data are required to support the study.

The results show that in milk, quantifiable residues occurred as TCVP and TCPEol. TCVP was 

not present in any samples from Group 2 (oral treatment only), but was found in all groups 

treated both orally and dermally (Groups 3, 4, and 5) on Days 1 and 2, with the highest 

concentrations occurring in Group 5. No other quantifiable residues of TCVP occurred except on

Day 30 in the two animals maintained for depuration. No residues were generally detectable in 

any groups on Days 7-14 and Days 24-28.

In cream, quantifiable residues occurred mainly as free TCPEol, with some low quantifiable 

residues for TCPEone in Group 5 only. Residues of TCVP and other metabolites were below the 

LOQ in all treatment groups.

In tissues, TCVP-derived residues were overall highest in subcutaneous and peritoneal fat Lower 

residues occurred in kidney and muscle, and the lowest residue concentrations were found in 

liver. Residues generally showed some correlation with exposure levels. In the two depuration 

animals, tissue residues declined after cessation of dosing, reaching levels below the LOQ by 14 

days of withdrawal in all tissues except subcutaneous fat, in which a low quantifiable residue of 

TCVP only was measured.

The maximum individual residues of TCVP, TCVPdeme, TCPEone, TCPEol (free and 

conjugated), and TCPEdiol (free and conjugated) as well as the maximum total residues in milk 

and tissues from the dairy cattle feeding study are presented in Table 6 below.

Table 6. Maximum Individual/Combined Residues in Milk and Tissues of Dairy Cattle.

Matrix

Residues (ppm) 1

TCVP TCVPdemeTCPEone TCPEol 

(free)

TCPEol

(conj.)

TCPEdiol

(free)

TCPEdiol

(conj.)

Total 2

(TCVP 

equiv.)

Group 2

Milk <0.01 <0.01 <0.01 0.014 <0.01 <0.01 <0.01 0.014

Cream <0.01 <0.01 <0.01 0.020 <0.01 <0.01 <0.01 0.034

Liver <0.01 0.012 <0.01 <0.01 <0.01 <0.01 <0.01 0.032

Kidney <0.01 <0.01 <0.01 <0.01 0.044 <0.01 <0.01 0.081

Muscle <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 ND

Fat, subcutaneous <0.01 <0.01 <0.01 0.012 <0.01 <0.01 <0.01 0.020

Fat, peritoneal <0.01 <0.01 <0.01 0.024 <0.01 <0.01 <0.01 0.044
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

Page 18 of 28

Table 6. Maximum Individual/Combined Residues in Milk and Tissues of Dairy Cattle.

Matrix

Residues (ppm) 1

TCVP TCVPdemeTCPEone TCPEol 

(free)

TCPEol

(conj.)

TCPEdiol

(free)

TCPEdiol

(conj.)

Total 2

(TCVP 

equiv.)

Group 3

Milk 0.032 <0.01 <0.01 0.015 <0.01 <0.01 <0.01 0.063

Cream <0.01 <0.01 <0.01 0.035 <0.01 <0.01 <0.01 0.077

Liver <0.01 0.031 <0.01 0.017 <0.01 <0.01 <0.01 0.070

Kidney <0.01 0.012 <0.01 0.052 0.039 <0.01 <0.01 0.168

Muscle 0.128 0.021 <0.01 <0.01 <0.01 <0.01 <0.01 0.158

Fat, subcutaneous 0.343 0.072 <0.01 0.115 <0.01 <0.01 <0.01 0.485

Fat, peritoneal 0.203 0.024 0.028 0.139 <0.01 <0.01 <0.01 0.485

Group 4

Milk 0.036 <0.01 <0.01 0.022 <0.01 <0.01 <0.01 0.072

Cream <0.01 <0.01 <0.01 0.036 <0.01 <0.01 <0.01 0.078

Liver <0.01 <0.01 0.010 0.056 <0.01 <0.01 <0.01 0.158

Kidney 0.015 <0.01 <0.01 0.075 0.069 <0.01 <0.01 0.278

Muscle 0.212 0.034 <0.01 0.015 <0.01 <0.01 <0.01 0.272

Fat, subcutaneous 0.558 0.111 <0.01 0.098 <0.01 <0.01 <0.01 0.842

Fat, peritoneal 0.340 0.040 0.027 0.198 <0.01 <0.01 <0.01 0.747

Group 5

Milk 0.040 <0.01 <0.01 0.018 <0.01 <0.01 <0.01 0.080

Cream <0.01 <0.01 0.016 0.217 <0.01 <0.01 <0.01 0.380

Liver <0.01 0.070 0.011 0.035 <0.01 <0.01 <0.01 0.122

Kidney 0.019 0.018 0.023 0.085 0.131 <0.01 <0.01 0.419

Muscle 0.474 0.112 <0.01 0.021 <0.01 <0.01 <0.01 0.625

Fat, subcutaneous 0.534 0.144 0.011 0.153 <0.01 <0.01 <0.01 0.859

Fat, peritoneal 0.318 0.032 0.028 0.246 <0.01 <0.01 <0.01 0.725

1 

 LOQ = 0.01 ppm for each analyte. 

2

 Total residues, in TCVP equivalents, were calculated by the registrant. To convert to TCVP equivalents, assay results were 

multiplied by the following factors: TCVPdeme = 1.04; TCPEone = 1.64; TCPEol = 1.62.

Conclusions. The submitted magnitude of the residue study on cattle is inadequate but 

upgradeable pending submission of supporting storage stability data. The residue data reflect a 

combination of two treatments: oral administration of tetrachlorvinphos for 29-31 days at actual 

rates of 1.512-1.555 and 4.630 g ai/750 kg BW per day (6.3-6.5x and 19.3x, respectively, the 

maximum registered rate of 0.24 g ai/750 kg BW for feed-through treatment) and dermal spray

treatments on three occasions, at ~14 day intervals, at actual rates of 10.111 and 19.166-19.493 g 

ai per animal per dose (~0.5 and 1.0x, respectively, the maximum registered rate of 18.9 g 

ai/animal for direct animal spray treatment). Among the combination of treatment regimes used 

in the study, the oral treatment at 1.555 g ai/750 kg BW per day (6.5x) plus dermal spray

treatments at 19.166 g ai per animal (~1.0x) may be used to estimate residue exposure for the 

purpose of tolerance reassessment (see Table 9). At this treatment regime (labeled as Group 4 in 

the study), the maximum total residues of concern (with the maximum residues of the parent in 

parentheses) were: 0.072 (0.036) ppm for milk, 0.078 (<0.01) ppm for cream, 0.158 (<0.01) ppm 

for liver, 0.278 (0.015) ppm for kidney, 0.272 (0.212) ppm for muscle, 0.842 (0.558) ppm for 

subcutaneous fat, and 0.747 (0.340) ppm for peritoneal fat. These data will support the registered

feed-through (oral) and direct animal spray uses of tetrachlorvinphos on cattle.
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

Page 19 of 28

No data were submitted reflecting application of tetrachlorvinphos as a backrubber treatment, 

direct animal dusting and/or premise spray treatment; also no data were submitted directly

reflecting the use of cattle ear tag uses which may still be registered to other companies. The 

OPPTS 860.1480 Guideline states that when a pesticide may be applied by more than one mode 

of treatment, separate studies are required; however, only oral and dermal spray studies were 

required in the TCVP RED. Because the oral and dermal treatments are expected to result in the 

highest residue levels, no additional data will be required to support backrubber or premise spray

treatments. Data from wetting sprays may be accepted in lieu of data from dust treatments.

Poultry Dermal Study

DER Reference List: 47589301.der.doc

SRA International, Inc. has submitted the results of a magnitude of the residue study with 

tetrachlorvinphos. Groups of 12 hens were topically (dermally) treated with an aqueous solution 

of a 23% EC formulation of tetrachlorvinphos. A total of 6-7 applications were made at twoweek intervals at 0.0908, 0.1816, or 0.5448 g ai/hen/application (0.5x, 1x, or 3x the nominal 

rate). Another group was treated with water only as the control group. A fifth group of hens was 

treated at 1.816 g ai/hen/application (10x nominal rate), but because of moderate to severe signs 

of toxicity/intolerance indicative of acute cholinergic effects attributed to the test substance, this 

treatment level was discontinued and excluded from the study.

Eggs were collected daily on a group basis. Hens were sacrificed following the last application 

(0-day) from all groups. Subgroups of four hens from a second group of 12 hens, treated at the 

nominal 3x rate, were sacrificed 7, 14, or 21 days following the last application, for residue 

depuration. The following tissues were collected at sacrifice for analysis: abdominal fat, liver, 

kidneys, muscle (breast/leg composite), and skin with underlying subcutaneous fat. Group 

application rates and sacrifice times are summarized below in Table 7.

Table 7. Treatment Parameters Used in the Poultry Study.

Group Treatment Number of 

Doses

Exposure Level

(g ai/hen/dose)

Sacrifice

(DALA)1

Hen #

1 Control 7

(water only)

-- 0 201-205, 208, 211-216 (n=12)

2 Dermal (Nx1) 7 0.1816 0 218-220, 222-228, 230, 231 (n=12)

3 Dermal (Nx3) 7 0.5448 0 233, 235, 236, 238-245, 248 (n=12)

3R Dermal

(Nx3)

7 0.5448 7 246, 247, 252, 253 (n=4)

14 251, 256, 259, 262 (n=4)

21 257, 261, 263, 264 (n=4)

4 Dermal (Nx0.5) 6 0.0908 0 267-274, 277-280 (n=12)

1 Days after last treatment (DALA).

Egg and tissue samples were analyzed for residues of tetrachlorvinphos, TCVPdeme, TCPEol, 

TCPEone, and TCPEdiol using LC/MS, LC/MS/MS, or GC/MS methods. The validated method 

LOQ was 0.01 ppm for each analyte. The adequacy of the method for data collection was 

verified by fortifying untreated samples of eggs and tissues with TCVP and its metabolites at 
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

Page 20 of 28

0.01 and 0.1 ppm. Concurrent method recoveries were within the acceptable range of 70-120%. 

The fortification levels encompassed most residues found in hen eggs and tissues; however, 

residues exceeding an order of magnitude of the highest fortification level in the concurrent 

method validation, were observed for TCVP, TCVPdeme, and TCPEol (free) in skin with fat and 

abdominal fat.

The registrant did not provide study dates, but based on the start, sacrifice and experimental end 

dates, samples may have been stored for up to 144 days (4.7 months) for eggs and 59 days (1.9 

months) for tissues. The registrant did not address storage issues, and no supporting storage 

stability data were provided.

TCVP-derived residues showed a linear dose response with the dosing level. Conjugated 

residues of TCPEol and TCPEdiol were each below the method LOQ (<0.01 ppm) in all samples 

of egg and hen tissues (muscle, kidney, liver, skin with fat, and abdominal fat) from all treatment 

rates.

TCVP-derived residues occurred in eggs from all treatment groups in a cyclical pattern of 

accumulation and depletion after each application. Residues of TCVP and the metabolites 

TCVPdeme, TCPEone, TCPEol (free) and TCPEdiol (free) were detected, with TCPEdiol 

accounting for the highest levels in eggs. With comparison of the high and low values observed 

after successive applications to the hens, residues appear to plateau in eggs after the third or 

fourth treatment. Residues in eggs appear to decline after the final application, but quantifiable 

residues (free TCPEol and TCPEdiol) were still present in eggs following 21 days of withdrawal.

TCVP-derived residues occurred in tissues from all treatment groups, and TCVP and the 

metabolites TCVPdeme, TCPEone, TCPEol (free) and TCPEdiol (free) were detected in all 

matrices, except for TCPEone which was not quantifiable in liver. Residues were highest in skin 

with subcutaneous fat by a significant margin (~30x higher) than those observed in abdominal 

fat, which bore the next highest levels of residues. Similar lower levels were observed in liver 

and muscle, and the lowest residue levels were found in kidney. The principal residues in hen 

tissues were free TCPEol and free TCPEdiol in liver and kidney; TCVP and TCVPdeme in 

muscle and skin with fat; and free TCPEol in abdominal fat. The registrant states that since 

similar levels of the parent and TCVPdeme were found in skin with fat, the results represent 

incurred residues and not simply residual contamination with the test substance. Overall residues 

of TCVP, TCVPdeme, TCPEone, TCPEol (free) and TCPEdiol (free) declined in hen tissues 

collected following longer withdrawal periods; however, quantifiable residues were still present 

in all tissues following 21 days of withdrawal.

The maximum individual residues of TCVP, TCVPdeme, TCPEone, TCPEol (free and 

conjugated), and TCPEdiol (free and conjugated) as well as the maximum total residues in eggs 

and tissues from the laying hen dermal dosing study are presented below in Table 8.
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

Page 21 of 28

Table 8. Maximum Individual/Combined Residues in Poultry Eggs and Tissues.

Matrix

Residues (ppm) 1

TCVP TCVPdemeTCPEone TCPEol 

(free)

TCPEol

(conj.)

TCPEdiol

(free)

TCPEdiol

(conj.)

Total 2

(TCVP 

equiv.)

Group 4 (0.5x)

Egg <0.01 0.019 <0.01 0.021 <0.01 0.066 <0.01 0.154

Liver <0.01 0.018 <0.01 0.031 <0.01 0.145 <0.01 0.284

Kidney <0.01 0.020 <0.01 0.083 <0.01 0.077 <0.01 0.292

Muscle 0.029 0.077 <0.01 0.014 <0.01 0.025 <0.01 0.165

Skin with fat 4.393 13.314 0.401 0.940 <0.01 0.038 <0.01 20.462

Fat, abdominal 0.039 0.021 0.069 0.247 <0.01 0.083 <0.01 0.699

Group 2 (1x)

Egg 0.026 0.034 0.010 0.037 <0.01 0.114 <0.01 0.288

Liver 0.016 0.024 <0.01 0.076 <0.01 0.238 <0.01 0.517

Kidney 0.022 0.051 0.015 0.150 <0.01 0.175 <0.01 0.583

Muscle 0.082 0.169 0.011 0.030 <0.01 0.047 <0.01 0.396

Skin with fat 6.030 9.857 0.668 1.489 <0.01 0.094 <0.01 19.405

Fat, abdominal 0.099 0.028 0.139 0.474 <0.01 0.149 <0.01 1.298

Group 3 (3x)

Egg 0.065 0.089 0.014 0.097 <0.01 0.230 <0.01 0.584

Liver 0.131 0.120 <0.01 0.184 <0.01 0.882 <0.01 1.865

Kidney 0.056 0.047 0.020 0.227 <0.01 0.238 <0.01 0.848

Muscle 1.017 0.726 0.020 0.068 <0.01 0.090 <0.01 2.045

Skin with fat 44.761 42.477 0.971 2.398 <0.01 0.191 <0.01 94.099

Fat, abdominal 0.753 0.101 0.296 1.158 <0.01 0.250 <0.01 3.265

1 

 LOQ = 0.01 ppm for each analyte. 

2

 Total residues, in TCVP equivalents, were calculated by the registrant. To convert to TCVP equivalents, assay results were 

multiplied by the following factors: TCVPdeme = 1.04; TCPEone = 1.64; TCPEol = 1.62; TCPEdiol = 1.516.

Conclusions: The submitted magnitude of the residue study on poultry is inadequate but 

upgradeable pending submission of additional method validation data, storage stability

data/information, and label revisions to specify appropriate retreatment intervals. The residue 

data reflect 6-7 dermal spray treatments of laying hens with an EC formulation, made at twoweek retreatment intervals, at 0.0908, 0.1816, or 0.5448 g ai/hen/application. These application 

rates, respectively, correspond to ~0.5x, 1.0x, or 2.9x the maximum registered direct spray

treatment rate of 0.19 g ai/bird daily. At ~1.0x, the maximum total residues of concern (with the 

maximum residues of the parent in parentheses) were: 0.288 (0.026) ppm for egg, 0.517 (0.016) 

ppm for liver, 0.583 (0.022) ppm for kidney, 0.396 (0.082) ppm for muscle, 19.405 (6.030) ppm 

for skin with fat, and 1.298 (0.099) ppm for abdominal fat. These data will support the registered 

direct animal spray use of tetrachlorvinphos on poultry and may be used to estimate residue 

exposure for the purpose of tolerance reassessment (see Table 9). 

No data are available to support the remainder of poultry uses registered to KMG Bernuth such 

as direct animal dusting and premise spray treatment. However, because the dermal treatments 

are expected to result in the highest residue levels, no additional data will be required to support 

premise spray treatments. Data from wetting sprays on poultry may be accepted in lieu of data 

from dust treatments. 
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

Page 22 of 28

860.1500 Crop Field Trials

860.1520 Processed Food and Feed

860.1850 Confined Accumulation in Rotational Crops

860.1900 Field Accumulation in Rotational Crops

No tetrachlorvinphos end-use products are currently registered for use on any plant commodity. 

Therefore, no field residue data, processing data, or confined/field rotational crop studies are 

required. Previous tolerances on crops have been revoked.

860.1650 Submittal of Analytical Reference Standards

An analytical standard for tetrachlorvinphos is currently available in the EPA National Pesticide 

Standards Repository (personal communication with Theresa Cole, ACB, 8/31/10) with an 

expiration date of 2/01/2011. No reference standards are available for the metabolites which are 

also regulated (TCVPdeme, TCPEone, TCPEol, and TCPEdiol). Analytical reference standards 

of the TCVPdeme, TCPEone, TCPEol, and TCPEdiol must be supplied and supplies replenished 

as requested by the Repository. The reference standards should be sent to the Analytical 

Chemistry Lab, which is located at Fort Meade, to the attention of either Theresa Cole or Thuy

Nguyen at the following address:

USEPA

National Pesticide Standards Repository/Analytical Chemistry Branch/OPP

701 Mapes Road

Fort George G. Meade, MD 20755-5350

(Note that the mail will be returned if the extended zip code is not used.)

860.1550 Tolerance Reassessment

Residue Chemistry Memo: DP# 243528, 3/11/98, D. Miller

The HED Metabolism Committee has determined that the residues of concern are 

tetrachlorvinphos, des-O-methyl tetrachlorvinphos, 1-(2,4,5-trichlorophenyl)ethanol (free and 

conjugated forms), 2,4,5-trichloroacetophenone, and 1-(2,4,5-trichlorophenyl)ethanediol. The 

current tolerance expression under 40 CFR §180.252 includes all of these residues except des-Omethyl tetrachlorvinphos. To allow separate risk assessments for cholinesterase inhibition 

(involving parent only), the tolerances for each animal commodity also specify the maximum 

residues of tetrachlorvinphos per se from the total residues. The revised tolerance definition 

should be modified as follows, to be consistent with the Tolerance Expression Guidance issued 

5/27/09 (S. Knizner).

Tolerances are established for residues of the insecticide tetrachlorvinphos, 

including its metabolites and degradates, in or on the commodities in the table 

below. Compliance with the tolerance levels specified below is to be determined 

by measuring only the sum of tetrachlorvinphos [(Z)-2-chloro-1-(2,4,5-

trichlorophenyl)vinyl dimethyl phosphate) and its metabolites chloro- 1 -(2,4,5-

trichlorophenyl)-vinylmonomethyl phosphate, 1-(2,4,5-trichlorophenyl)-ethanol 

(free and conjugated forms), 2,4,5-trichloroacetophenone, and 1-(2,4,5-
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

Page 23 of 28

trichlorophenyl)-ethanediol, calculated as the stoichiometric equivalent of 

tetrachlorvinphos, in or on the commodity.

The time-limited tolerances for livestock commodities under §180.252(a), based on feed-through 

and/or direct dermal uses on livestock, were estimated by the Agency from the acceptable 

metabolism data. A tolerance for poultry skin could not be estimated at that time because this 

matrix was not included in the hen metabolism study. HED recommended time-limited 

tolerances to allow time for the registrant to submit new feeding/dermal studies to determine 

permanent tolerances.

The submitted magnitude of the residue study on cattle is inadequate but upgradeable pending 

submission of supporting storage stability data and label revisions. The reviewed data will 

support the registered feed-through (oral) and direct dermal uses. HED has concluded that the 

oral and dermal data represent the worst-case and no additional data will be required to support 

other uses such as backrubber treatment and premise spray treatment.

The submitted magnitude of the residue study on poultry is inadequate but upgradeable pending 

submission of additional method validation data, storage stability data/information, and label 

revisions. The reviewed data will support the registered direct animal uses. HED has concluded 

that the dermal data represent the worst-case and no additional data will be required to support 

premise spray treatments.

The established/needed tolerances for hog commodities cannot be reassessed at this time as a 

magnitude of the residue study on swine is outstanding.

A summary of tolerance reassessment is detailed in Table 9. 
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

Page 24 of 28

Table 9. Tolerance Reassessment Summary for Tetrachlorvinphos.

Commodity Established

Tolerance 1

(ppm)

Maximum 

Residues 2

(ppm)

Reassessed

Tolerance 3

(ppm)

Comments; 

Correct Commodity Definition

Cattle, fat (of which no more than 0.1 

ppm is tetrachlorvinphos per se)

0.2 0.84 (0.56) 

subcutaneous 

fat;

0.75 (0.34) 

peritoneal fat

1.0 Cattle, fat (of which no more 

than 0.6 ppm is 

tetrachlorvinphos per se)

Cattle, kidney (of which no more than 

0.05 ppm is tetrachlorvinphos per se)

1.0 -- Remove

Cattle, liver (of which no more than 0.05 

ppm is tetrachlorvinphos per se)

0.5 -- Remove

Cattle, meat (of which no more than 2.0 

ppm is tetrachlorvinphos per se)

2.0 0.27 (0.21) 

muscle

0.3 Cattle, meat (of which no more 

than 0.2 ppm is 

tetrachlorvinphos per se)

Cattle, meat by products, except kidney 

and liver

1.0 -- Remove See cattle, meat byproducts

Cattle, meat by products None 0.16 (<0.01) 

liver;

0.28 (0.015) 

kidney;

0.84 (0.56) 

subcutaneous 

fat;

0.75 (0.34) 

peritoneal fat;

0.27 (0.21) 

muscle

1.0 Cattle, meat byproducts (of 

which no more than 0.6 ppm is 

tetrachlorvinphos per se) 4

Egg (of which no more than 0.05 ppm is 

tetrachlorvinphos per se)

0.2 0.288 (0.026) 0.3 Egg (of which no more than 

0.03 ppm is tetrachlorvinphos 

per se)

Hog, fat (of which no more than 0.1 ppm 

is tetrachlorvinphos per se)

0.2 TBD 5 TBD

Magnitude of the residue data 

in hog remains outstanding.

Hog, kidney (of which no more than 0.05 

ppm is tetrachlorvinphos per se)

1.0 TBD TBD

Hog, liver (of which no more than 0.05 

ppm is tetrachlorvinphos per se)

0.5 TBD TBD

Hog, meat (of which no more than 2.0 

ppm is tetrachlorvinphos per se)

2.0 TBD TBD

Hog, meat byproducts, except kidney and 

liver

1.0 TBD TBD

Milk, fat (reflecting negligible residues 

in whole milk and of which no more than 

0.05 ppm is tetrachlorvinphos per se)

0.05 0.072 (0.036) 

for milk;

0.078 (<0.01) 

for cream

0.1 Milk (of which no more than 

0.04 ppm is tetrachlorvinphos 

per se)

Poultry, fat (of which no more than 7.0 

ppm is tetrachlorvinphos per se)

7.0 1.298 (0.099) 

abdominal fat

1.4 Poultry, fat (of which no more 

than 0.1 ppm is 

tetrachlorvinphos per se)

Poultry, liver (of which no more than 

0.05 ppm is tetrachlorvinphos per se)

2.0 Remove See poultry, meat byproducts
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

Page 25 of 28

Table 9. Tolerance Reassessment Summary for Tetrachlorvinphos.

Commodity Established

Tolerance 1

(ppm)

Maximum 

Residues 2

(ppm)

Reassessed

Tolerance 3

(ppm)

Comments; 

Correct Commodity Definition

Poultry, meat (of which no more than 3.0 

ppm is tetrachlorvinphos per se)

3.0 0.40 (0.082) 

muscle

0.4 Poultry, meat (of which no 

more than 0.1 ppm is 

tetrachlorvinphos per se)

Poultry, meat byproducts, except liver 2.0 -- Remove See poultry, meat byproducts

Poultry, meat byproducts None 0.52 (0.016) 

liver;

0.58 (0.022)

kidney;

0.40 (0.082) 

muscle;

19.41 (6.03)

skin with fat;

1.30 (0.099) 

abdominal fat

20 Poultry, meat byproducts (of 

which no more than 6.0 ppm is 

tetrachlorvinphos per se) 4

1

 Time-limited tolerances; current tolerance expression is for the combined residues of tetrachlorvinphos [(Z)-2-

chloro-1-(2,4,5-trichlorophenyl)vinyl dimethyl phosphate] and its metabolites, 1-(2,4,5-trichlorophenyl)-ethanol 

(free and conjugated forms), 2,4,5-trichloroacetophenone, and 1-(2,4,5-trichlorophenyl)-ethanediol; should also 

include des-O-methyl tetrachlorvinphos.

2

 Total residues of tetrachlorvinphos and its metabolites, TCVP-deme, TCPEone, TCPEol (free and conjugated 

forms), and TCPEdiol (free and conjugated), expressed in terms of parent equivalents; the value in parentheses 

represents the maximum residues of the parent tetrachlorvinphos.

3

 Reassessed tolerance is based on the maximum residue from the respective magnitude of the residue study; the 

maximum residues of the parent tetrachlorvinphos are reported in the corrected commodity definition.

4

 According to the 18 July 2007 Minutes of the HED ChemSAC meeting, the guidance document will be revised to 

include language detailing the use of the highest residue data for any tissue (liver, kidney, fat, skin or muscle) to 

determine the tolerance for meat byproducts. A single tolerance on “meat byproducts” will be recommended based 

on that highest residue, and individual tolerances will no longer be set on liver, kidney, or meat byproducts (except 

liver and kidney).

5 TBD = to be determined. 

Codex and Canadian MRL Harmonization

There are no Codex maximum residue limits (MRLs) established or proposed for residues of 

tetrachlorvinphos. Canada has established MRLs for plant and animal commodities. Canada’s 

residue definition is 2-chloro-1-(2,4,5-trichlorophenyl) vinyl dimethyl phosphate and its low 

melting isomer. A summary of U.S. and international tolerances and maximum residue limits is 

presented in Table 10. At this time the Agency cannot harmonize with the Canadian MRL since 

the new magnitude of residue data support the different tolerances. HED has not examined the 

Canadian registrations; different use patterns may account for the different residue levels. 
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

Page 26 of 28

Table 10. Summary of U.S. and International Tolerances and Maximum Residue Limits.

Commodity

U.S. Tolerances, 40 CFR §180.252 1

Codex MRL Canada’s MRL 2

Established U.S. 

Tolerance, ppm

Reassessed U.S. 

Tolerance, ppm 

Milk, fat 

(reflecting 

negligible 

residues in 

whole milk)

0.5 (of which not 

more than 0.05 ppm

is tetrachlorvinphos 

per se)

milk: 0.1 (of which not 

more than 0.04 ppm is 

tetrachlorvinphos per se)

None None

Fat, cattle 0.2 (of which not 

more than 0.1 ppm

is tetrachlorvinphos 

per se)

1.0 (of which not more 

than 0.8 ppm is 

tetrachlorvinphos per se)

None 1.5 3

Muscle meat of cattle and 

hog: 2.0 (of which 

not more than 2.0

ppm is 

tetrachlorvinphos 

per se)

meat of cattle: 0.3 (of 

which not more than 0.2

ppm is tetrachlorvinphos 

per se)

None 1.5 3

Kidney kidney of cattle and 

hog: 1.0 (of which 

no more than 0.05 

ppm is 

tetrachlorvinphos 

per se)

meat byproducts of cattle: 

1.0 (of which no more 

than 0.6 ppm is 

tetrachlorvinphos per se)

None 1.5 3

Liver liver of cattle and 

hog: 0.5 (of which 

no more than 0.05 

ppm is 

tetrachlorvinphos 

per se)

None 1.5 3

Meat byproducts meat byproducts, 

except kidney and 

liver of cattle and 

hog: 1.0

None 1.5 3

Poultry 0.75 poultry fat: 1.4 (of which 

not more than 0.1 ppm is 

tetrachlorvinphos per se)

None 0.75 4

Eggs 0.2 (of which not 

more than 0.05 ppm

is tetrachlorvinphos 

per se)

0.3 (of which not more 

than 0.03 ppm is 

tetrachlorvinphos per se)

None None

Poultry, muscle meat of poultry: 

3.0 (of which not 

more than 3.0 ppm 

is tetrachlorvinphos 

per se)

meat of poultry: 0.4 (of 

which not more than 0.1

ppm is tetrachlorvinphos 

per se)

None 0.75 4
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

Page 27 of 28

Table 10. Summary of U.S. and International Tolerances and Maximum Residue Limits.

Commodity

U.S. Tolerances, 40 CFR §180.252 1

Codex MRL Canada’s MRL 2

Established U.S. 

Tolerance, ppm

Reassessed U.S. 

Tolerance, ppm 

Poultry, liver 2.0 (of which not 

more than 0.05 ppm

is tetrachlorvinphos 

per se)

meat byproducts of 

poultry: 20 (of which not 

more than 6.0 ppm is 

tetrachlorvinphos per se)

None 0.75 4

Poultry, meat 

byproducts

meat byproducts, 

except liver, of 

poultry: 2.0

None 0.75 4

Poultry, fat 7.0 (of which not 

more than 7.0 ppm

is tetrachlorvinphos 

per se)

1.4 (of which not more 

than 0.1 ppm is 

tetrachlorvinphos per se)

None 0.75 4

Apples None None None 10

Grapes None None None 10

1

 Current US residue definition is tetrachlorvinphos, des-O-methyl tetrachlorvinphos, 1-(2,4,5-

trichlorophenyl)ethanol (free and conjugated forms), 2,4,5-trichloroacetophenone, and 1-(2,4,5-

trichlorophenyl)ethanediol. 

Hog U.S. tolerances cannot be reassessed at this time (the magnitude of the residue in hogs study is outstanding); 

because the current tolerances for hog are time limited, hog tissues were not included in the tolerance and MRL 

comparison summary.

2 Canada residue definition is 2-chloro-1-(2,4,5-trichlorophenyl) vinyl dimethyl phosphate and its low melting 

isomer.

3

 Meat, meat byproducts and fat of cattle and hogs, calculated on the fat content.

4

 Meat, meat byproducts and fat of poultry, calculated on the fat content.

References

DP#: 199644

Subject: Tetrachlorvinphos (Case 0321, Chemical 083701). Product Chemistry Chapter 

and Residue Chemistry Chapter for the Reregistration Eligibility Decision 

Document

From: F. Suhre

To: L. Propst

Dated: 07/6/94

MRIDs: None

DP#: 206721

Subject: Tetrachlorvinphos. Addendum to RED. PTRL Response to EPA Review of 

Nature of Residue Study (MRID Nos. 42828801-03). Request Dated August 11, 

1994. CBRS No. 14227; Case No. 0321.

From: D. Miller

To: D. McNeilly

Dated: 09/21/94
Tetrachlorvinphos Summary of Analytical Chemistry and Residue Data DP#s: 320848 & 320858

Page 28 of 28

MRIDs: None

DP#: 243528

Subject: Tetrachlorvinphos (083701). Development of Tolerance Estimates for Revised 

HED Chapter.

From: D. Miller

To: K. Boyle

Dated: 03/11/98

MRIDs: None

DP#: 246716

Subject: Tetrachlorvinphos (Case 0321, Chemical 083701). Protocol for Combined 

Oral/Dermal Livestock Studies

From: S. Hummel

To: D. Fuller and C. Swartz

Dated: 06/01/99

MRIDs: None

DP#: 277227

Subject: Tetrachlorvinphos. Livestock Feeding Study Protocols. Response to Questions 

from Boehringer Ingelheim

From: M. Metzger

To: D. Fuller

Dated: 08/27/01

MRIDs: None

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