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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF

CHEMICAL SAFETY AND

POLLUTION PREVENTION

MEMORANDUM

Date: April 5, 2011

SUBJECT: Tetrachlorvinphos. Request for Waiver of a Swine Magnitude of Residue Study

PC Code: 083701/083702 DP Barcode: D320857

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.: None 40 CFR: 180.252

FROM: Christine L. Olinger, Chemist

Risk Assessment Branch VII

Health Effects Division (7509P)

Office of Pesticide Programs

THRU: Alexandra LaMay, Biologist

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

Tetrachlorvinphos is an organophosphate insecticide used as a direct animal treatment and feed 

through on poultry, ruminants, and swine. In a recent review of poultry and ruminant magnitude 

of residue (MOR) studies HED reiterated the reregistration requirement to also conduct a 

magnitude of residue study in swine (C. Olinger; 10/7/10; D320848, D320858, D320859, and 

D381350). HED had previously recommended for this study in the Residue Chemistry Chapter 

to the Reregistration Eligibility Decision (RED) (F. Suhre, DP Barcode D199644, 7/6/94) and 

the HED Chapter to the RED (C. Swartz, 12/8/99, D261626). In response, SRA International, on 

behalf of the Tetrachlorvinphos Task Force (TCVPTF), has requested a waiver of this study. 

The Pesticide Re-evaluation Division (PRD) has requested HED review of this submission.
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REGISTRANT WAIVER REQUEST

KMG-Bernuth, Inc. (KMG) has performed and submitted to the Agency two MOR studies, one 

in dairy cows (MRID No. 47193001) and one in poultry (MRID No. 4758301) as well as nature 

of the residue (NOR) studies in both animal species. The metabolite profile was identified and 

quantified in animals as a result of these studies. 

TCVPTF believes that the ruminant study would likely produce higher residues than a swine 

study, since the material would likely remain in a ruminant digestive system longer than swine. 

According to their submission, it is well-documented that residence time in swine intestines is 

significantly shorter relative to that in a ruminant; a swine study would not be expected to 

provide any more meaningful information than can be inferred from the existing feeding studies. 

In addition, the TCVPTF has stated that both the NOR and MOR studies demonstrated the very

poor absorption of TCVP following both oral and dermal administration. This poor absorption is 

designed into Rabon Oral Larvicide products (by requiring [specifying] a very large particle size) 

because product efficacy is predicated upon TCVP passing through the animal and being 

excreted intact in order for it to be effective. 

HED RECOMMENDATION

HED has considered the product use information, existing guidance, and the registrant’s 

submission. The magnitude of residue data show that most of the residues are found as a result 

of the dermal treatment; residues from livestock treated only with the feed through were 

substantially less than the residues from both dermal and feed-through treatment. This is 

consistent with the registrant’s discussion on the poor oral absorption. The application rates for 

ruminants and swine are generally comparable as noted in Table 1 at the end of this review (and 

is copied from the 10/7/10 review). Note that in residue monitoring of livestock from 2001-2009 

USDA Food Safety and Inspection Service (FSIS) has never detected residues of 

tetrachlorvinphos per se and the USDA Pesticide Data Program (PDP) has detected 

tetrachlorvinphos twice in milk at very low levels.

Residues in swine are not likely to be higher than the residues in ruminants. Therefore, HED 

recommends for the waiver of the swine magnitude of residue study and will translate the 

ruminant data to swine. The recommended tolerance levels for swine (hog) meat, meat byproducts, and fat may be found in Table 2.

Table 1. 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. 
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Table 1. 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 

Brahman-cross 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 
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Table 1. Summary of Registered Directions for Use of Tetrachlorvinphos. 1

Application 

Type/Mode

Formulation

[EPA Reg. No.] Application Rate Use Directions and Limitations

spray solution made by 

diluting 1 gal of 23% EC in 

50 gal of water

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. 

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 2. Tolerance Reassessment Summary for Tetrachlorvinphos for Hog Commodities.

Commodity Established

Tolerance 1

(ppm)

Maximum 

Residues 2

(ppm)

Reassessed 

Tolerance 3

(ppm)

Comments; 

Correct Commodity Definition

Hog, 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

Hog, fat (of which no more 

than 0.6 ppm is 

tetrachlorvinphos per se)

Hog, kidney (of which no more than 

0.05 ppm is tetrachlorvinphos per se)

1.0 -- Remove See hog, meat byproducts

Hog, liver (of which no more than 0.05 

ppm is tetrachlorvinphos per se)

0.5 -- Remove See hog, meat byproducts

Hog, meat (of which no more than 2.0 

ppm is tetrachlorvinphos per se)

2.0 0.27 (0.21) 

muscle

0.3 Hog, meat (of which no more 

than 0.2 ppm is 

tetrachlorvinphos per se)
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Table 2. Tolerance Reassessment Summary for Tetrachlorvinphos for Hog Commodities.

Commodity Established

Tolerance 1

(ppm)

Maximum 

Residues 2

(ppm)

Reassessed 

Tolerance 3

(ppm)

Comments; 

Correct Commodity Definition

Hog, meat byproducts, except kidney 

and liver

1.0 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 Hog, meat byproducts (of 

which no more than 0.6 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).