UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

MEMORANDUM 

Date: 04-FEB-2016 

OFFICE OF 

CHEMICAL SAFETY AND 

POLL T ION PREVENTION 

SUBJECT: Triclopyr. Petition to Amend Tolerance Expressions to Include Triclopyr 

Choline Salt; and Petition to Remove Grazing Restrictions for Dairy Cattle. 

Summary of Analytical and Residue Chemistry Data. 

PC Codes: 1 16000, 1 1600 I, I 16002, 1 16004 

Decision No.: 488478 

Petition Nos.: 4F8249 & 4F8279 

Risk Assessment Type: NA 

TXR No.: NA 

MRIO No.: 4974 1901 

DP No.: 0419487 

Registration Nos.: 62719-37, 62719-53, 627 19-87, 

62719-552, 62719-637, 62719-AIT (687) 

Regulatory Action: Section 3 

Case No.: 2710 

CAS Nos.: 55335-06-3 , 572 13-69- 1, 64700-56-7, 

I 0483 73-85-8 

40 CFR: § 180.4 17 

From: Jennifer R. Tyler, Chemist C ~rc11 Risk Assessment Branch I (RAB 1) 

Through: 

To: 

Health Effects Division (HED, 7509P) 

Mindy Ondish, Risk Reviewer 

Reuben Baris, Product Manager 25 

Herbicide Branch (HB) 

Registration Division (RD, 7505P) 

Executive Summarv 

Dow AgroSc iences has submitted 1) a petition to amend the tolerance expressions for triclopyr to 

include a new formulation , triclopyr choline salt (PP# 4F8279); and 2) a petition to remove the 

grazing restriction for lactating dairy cattle, and establish a tolerance for residues in milk, fat 

(0.70 ppm) as well as increased tolerances for residues in milk (0.60 ppm), meat (0.08 ppm), fat 

(0.09 ppm), and meat byproducts (0. 7 ppm) (PP# 4F8249). The company submitted the results 

of a livestock feeding study in support of PP# 4F8249. 

Currently, pennanent tolerances are established for the combined residues of triclopyr per se, as 

a result of the application/use of butoxyethyl ester of triclopyr and triethylamine salt of triclopyr, 

in or on eggs; fish; grass forage and hay; milk; poultry fat, meat, and meat byproducts, except 

kidney; rice, grain and straw; and shellfish [ 40 CFR § 180.417 (a)(l )]. In addition, permanent 

tolerances are established for residues of triclopyr acetic ac id and its metabolite 3,5,6-trichloro-2-

pyridinol (TCP) as a result of the application/use of butoxyethyl ester of triclopyr and 

Page I of7 
Triclopyr Summary of Analytical Chemistry and Residue Data DP# 419487

Page 2 of 7

triethylamine salt of triclopyr, in or on the meat, fat, and meat byproducts of cattle, goats, hogs, 

horses, and sheep [40 CFR §180.417 (a)(2)].

Regulatory Recommendations and Residue Chemistry Deficiencies

Pending submission of a revised Section F (see requirements under Proposed Tolerances), there 

are no residue chemistry issues that would preclude granting the following:

PP# 4F8279: An updated tolerance expression in 40 CFR §180.417(a) to state:

40 CFR 180.417(a)(1): “Tolerances are established for residues of the herbicide 

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

below resulting from the application of the butoxyethyl ester of triclopyr, triethylamine 

salt of triclopyr, or choline salt of triclopyr. Compliance with the tolerance levels 

specified below is to be determined by measuring only triclopyr (2-[(3,5,6-trichloro-2-

pyridinyl)oxy]acetic acid).”

40 CFR 180.417(a)(2): Tolerances are established for residues of the herbicide triclopyr, 

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

resulting from the application of the butoxyethyl ester of triclopyr, triethylamine salt of 

triclopyr, or choline salt of triclopyr. Compliance with the tolerance levels specified 

below is to be determined by measuring the combined residues of triclopyr (2-[(3,5,6-

trichloro-2-pyridinyl)oxy]acetic acid) and its metabolite 3,5,6-trichloro-2-pyridinol 

(TCP), calculated as the stoichiometric equivalent of triclopyr.”

PP# 4F8249: The removal of the grazing restriction for lactating dairy cattle as well as the 

establishment of the following permanent tolerances:

Milk1 0.60 ppm

Meat*2 0.10 ppm

Fat*2 0.10 ppm

Meat byproducts*2 0.50 ppm

* of cattle, goat, hog, horse, and sheep. 1 40 CFR §180.417 (a)(1)

2 40 CFR §180.417 (a)(2)

860.1550 Proposed Tolerances

A summary of the recommended tolerances along with recommendations for commodity 

definitions are presented in Table 6. The petitioner is requested to submit a revised Section F to 

reflect the recommendations in Table 6. A human health risk assessment will be prepared as a 

separate document (DP# 426071).

Background

Triclopyr, triclopyr TEA, and triclopyr BEE products are used as selective herbicides to control 

broadleaf weeds and woody brush. Triclopyr products are registered for use on rice as well as a 

variety of non-agricultural sites including rights of way, pasture and rangelands, forests, and turf 

(including home lawns), golf courses, cemeteries, parks, lakes, bayous, ponds, reservoirs, 

marshes, roadsides, fence rows, canals, ditch banks, athletic fields, storage yards, industrial sites, 

trails, patios, camp areas, homes and cabins (outdoor), and christmas tree plantings. Triclopyr 
Triclopyr Summary of Analytical Chemistry and Residue Data DP# 419487

Page 3 of 7

products are formulated as soluble concentrates, emulsifiable concentrates, liquids (pressurized 

and ready-to-use), granules, wettable powders, and pellets.

PP# 4F8279

Dow AgroSciences has submitted a petition to amend the tolerance expressions for triclopyr to 

include a new formulation, triclopyr choline salt. The company proposes that the tolerance 

expression in 40 CFR §180.417(a) be updated to state:

40 CFR 180.417(a)(1): “Tolerances are established for residues of the herbicide triclopyr 

(2-[(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid), including its metabolites and degradates, 

in or on the commodities in the table below resulting from the application of the 

butoxyethyl ester of triclopyr, triethylamine salt of triclopyr, or triclopyr choline. 

Compliance with the tolerance levels specified below is to be determined by measuring 

only triclopyr.”

and,

40 CFR 180.417(a)(2): Tolerances are established for residues of the herbicide triclopyr 

(2-[(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid), including its metabolites and degradates, 

in or on the commodities in the table below resulting from the application of the 

butoxyethyl ester of triclopyr, triethylamine salt of triclopyr, or triclopyr choline. 

Compliance with the tolerance levels specified below is to be determined by measuring 

the combined residues of triclopyr and its metabolite 3,5,6-trichloro-2-pyridinol (TCP).”

In a memo dated 22-MAR-2012, HED reviewed a request to determine the bioequivalence 

between triclopyr and triclopyr choline salt, and agreed that bioequivalence was supported by the 

currently available information (Memo, G. Kramer, D399410). Therefore, HED recommends in 

favor of the request to amend the tolerance expressions for triclopyr to include triclopyr choline 

salt.

PP# 4F8249

49741901 der.doc

Dow AgroSciences has submitted a petition to remove the grazing restriction for lactating dairy 

cattle on several registered labels for triclopyr (see Table 1). 

Table 1. Summary of Existing and Proposed Grazing Restrictions for Triclopyr.

Use Site Formulation

(EPA Reg. No.)

Existing Use 

Directions and 

Limitations

Proposed Use Directions and 

Limitations

Land Grazed by 

Lactating Dairy Animals 

(Rangelands, Pastures, 

CRP Acres, Non-Crop 

Areas, Forestry)

TEA MUP (EPA Reg. No. 62719-53)

BEE MUP (EPA Reg. No. 62719-87)

Garlon® 3A (EPA Reg. No. 62719-37)

Remedy® Ultra (EPA Reg. No. 62719-552)

PastureGard® HL (EPA Reg. No. 62719-637)

Do not allow lactating 

dairy animals to graze 

treated areas until the 

next growing season.

PHI (hay): 14 days.

Grazing or harvesting green forage: 

There are no grazing or haying 

restrictions for livestock including 

dairy animals on treated area.

Haying (harvesting of dried forage): 

Do not harvest within 14 days after 

application.
Triclopyr Summary of Analytical Chemistry and Residue Data DP# 419487

Page 4 of 7

In addition, the company has also proposed the establishment of a tolerance for residues in milk, 

fat (0.70 ppm) as well as increased tolerances for residues in milk (0.60 ppm), meat (0.08 ppm), 

fat (0.09 ppm), and meat byproducts (0.7 ppm).

The ruminant feed items associated with triclopyr are grass forage and hay, and rice grain. Using 

residues from previously submitted magnitude of the residue studies on grass and rice, HED 

recalculated the maximum reasonable dietary burden (MRDB) for dairy cattle to include these 

commodities (see Table 2).

Table 2. Calculation of MRDB of Beef/Dairy Cattle for Triclopyr.

Feed 

Commodity Feedstuff Type1 % Dry Matter2 % Diet2 Residue (ppm)3 MRDB (ppm)4

Beef Cattle (R=15%; CC=80%; PC=5%)

Grass hay R 88 15 173 (highest 

residue)

29.489

Rice grain CC 88 20 0.109 (average 

residue)

0.025

Untreated PC/CC NA 65 NA -

Total 29.513

Dairy Cattle (R=45%; CC=45%; PC=10%)

Grass forage R 25 45 697 (highest 

residue)

1254.6

Rice grain CC 88 20 0.109 (average 

residue)

0.025

Untreated PC NA 35 NA -

Total 1255

1. CC = carbohydrate concentrate; R = roughage; PC = protein concentrate.

2. Table 1 (860.1000 OPPTS Test Guidelines; June 2008 Revisions of Livestock Diets Percents Reasonable Balanced Diets. 

3. Highest residue of 173 ppm used for grass hay [1974 Study cited on pg. 16 of Section E of petition; residues in grass forage were 

determined following application at 1.5 lb ae/A; residues were extrapolated to 2 lb ae/A (labeled rate)]. Highest residue of 697 ppm 

used for grass forage (MRID# 41961001). Average residue of 0.109 ppm used for rice grain [used in D275030 (Memo, W. Donovan;

16-APR-2002)].

4. Contribution = [tolerance /% DM (if cattle)] X % diet.

The company submitted the results of a new livestock feeding study in support of PP# 4F8249 

(MRID# 49741901), and the study is considered to be scientifically acceptable and adequate to 

support the proposed petition. In this study, lactating Friesian/Holstein dairy cattle were dosed 

orally with triclopyr for 28-29 consecutive days. The doses were administered on two occasions 

each day (AM and PM). The cows were divided into 5 treatment groups: control group (3 

cows); 50-ppm dose group (0.04x, 4 cows); 100 ppm dose group (0.08x, 4 cows); 500 ppm dose 

group (0.4x, 4 cows), and 1000 ppm dose group (0.8x, 16 cows). Twelve of the cows in the 

0.84x treatment group were used to generate depuration data (3, 7, 14, and 21 days). At the end 

of the dosing, these cows were transferred to the control diet to measure the decline in residues 

following withdrawal of triclopyr from the diet. Residues of triclopyr and the metabolite TCP in 

tissues (muscle, liver, kidney, subcutaneous fat, mesenteric fat, and perirenal fat) and milk 

(whole milk, skimmed milk, and cream) were determined using a high-performance liquid 

chromatography (HPLC)/mass spectrometry (MS)/MS method. The limit of detection (LOD)

and limit of quantitation (LOQ) for each analyte were 0.003 ppm and 0.01 ppm, respectively. 

Residues of triclopyr and TCP from the 1000-ppm dose group, including residues following a 3-

day depuration period, are summarized in Table 3. 
Triclopyr Summary of Analytical Chemistry and Residue Data DP# 419487

Page 5 of 7

Table 3. Triclopyr and TCP Residues in New Dairy Cattle Feeding Study at 1000-ppm Dose (MRID# 

49741901).

Matrix1

Triclopyr TCP Triclopyr + TCP

Average 

Residue 

(ppm)

Maximum 

Residue 

(ppm)

Average 

Residue 

(ppm)

Maximum 

Residue 

(ppm)

Average 

Residue 

(ppm)

Maximum 

Residue 

(ppm)

Whole Milk (Days 8-29) 0.071 0.216 - - - -

Whole Milk (+3 days)2 ND4 ND - - - -

Skimmed Milk (Day 22) 0.044 0.161 - - - -

Cream (Day 22) 0.028 0.095 - - - -

Muscle 0.353 0.610 1.18 1.36 1.54 1.97

Muscle (+3 days)2 ND4 ND <LOQ <LOQ <0.015 <0.015

Composite/Average Fat3 1.65 2.35 4.64 7.67 6.29 10.0

Composite/Average Fat 

(+3 days)2,3

0.018 0.023 0.045 0.050 0.064 0.073

Liver 1.14 1.76 15.5 16.6 16.6 17.5

Liver (+3 days)2 ND ND 0.197 0.249 <0.202 <0.254

Kidney 41.6 74.7 28.8 31.7 70.4 106

Kidney (+3 days)2 <LOQ <LOQ 0.153 0.181 <0.163 <0.191

1. Residue of concern in milk is triclopyr only. Residues of concern in all other livestock commodities are triclopyr and metabolite TCP.

2. Residue levels after 3 days of depuration.

3. Composite fat residue values were calculated as the average of the triclopyr concentration in the corresponding subcutaneous, 

mesenteric, and perirenal fat samples.

4. <LOQ = limit of quantitation (<0.01 ppm); ND = not detected (<0.003 ppm). For residues <LOQ, LOQ (0.01 ppm was used for 

calculation. For ND residues, 1/2 LOQ (0.005 ppm) used for calculations. 

Current triclopyr labels contain the following pre-slaughter interval: During the season of 

application, withdraw livestock from grazing treated grass at least 3 days before slaughter. 

Based on this restriction, coupled with the fact that the majority of the livestock dietary burden is 

from treated grass (>99% of the dietary burden) the company recommends using the residue data 

from the 3-day depuration period to determine appropriate tolerance levels for residues in/on 

livestock meat, fat, and meat byproducts. ChemSAC agreed with this proposal (18-NOV-2015 

ChemSAC Meeting Minutes). In addition, ChemSAC recommended the pre-slaughter interval 

listed on current triclopyr labels be amended to include a restriction against feeding treated grass 

to livestock at least 3 days before slaughter.

The anticipated residues for livestock commodities were determined using the Langmuir Model 

(see Table 5). The maximum percent residues remaining following the 3-day depuration period 

were then used, as appropriate, to the determined the appropriate tolerances for livestock 

commodities.

Table 5. Tolerance Calculation Proposal Using Langmuir Model and 3-Day Depuration Data.

Dose Level (ppm) Commodity

Milk Muscle Fat Liver Kidney

54.8 0.01 0.314 0.744 2.43 5.33

109.6 0.038 0.193 1.13 3.55 8.34

538.7 0.138 1.19 5.01 11.7 53.8

1057.4 0.517 1.97 10 17.5 106

Livestock Dietary Burden 

(ppm) Anticipated Residues1 (ppm)

Dairy Cattle 1255 0.56 2.2 12 19 126

Depuration from 0 to 3 days

Max % Remaining - 0.76 0.73 1.45 0.18

Dairy Cattle - 0.016 0.087 0.275 0.226

Tolerance 0.60 0.02 0.10 0.30 0.30

1. Residue of concern in milk is triclopyr only. Residues of concern in all other livestock commodities are triclopyr and metabolite TCP.
Triclopyr Summary of Analytical Chemistry and Residue Data DP# 419487

Page 6 of 7

Although previously submitted livestock feeding studies for triclopyr showed concentration of 

triclopyr in milk fat (MRID# 00071808), residues did not concentrate in milk fat in the current 

study. Based on the high residues in kidney and liver and ionic nature of triclopyr, HED has 

determined that a tolerance for milk fat is not required.

HED recommends the tolerances listed in Table 6. A summary of current U.S. tolerances and 

Canadian maximum residue limits (MRLs) for triclopyr can be found in Attachment 1. The 

recommended U.S. tolerances and Canadian maximum limits (MRLs) for milk is not 

harmonized. The removal of the grazing restriction necessitates higher tolerance level for milk. 

During Registration Review, HED will consider the possibility of harmonizing with Canada for 

the commodities with differing tolerances.

Table 6. Tolerance Summary for Triclopyr.

Commodity

Established 

Tolerance 

(ppm)

Proposed 

Tolerance 

(ppm)

Recommended 

Tolerance 

(ppm)

Canadian 

MRL (ppm)

Comments

Correct 

Commodity 

Definition

40 CFR §180.417 (a)(1)

Milk1 0.01 0.60 0.60 0.01

Milk, fat1 - 0.70 - -

40 CFR §180.417 (a)(2)

Meat2,3 0.05 0.08 0.10 0.1

Fat2,3 0.05 0.09 0.10 0.1

Liver2,3 0.5 - NA -

Kidney2,3 0.5 - NA -

Meat byproducts, except kidney 

and liver2,3

0.05 - NA -

Meat byproducts2,3 - 0.7 0.50 0.5

1 Triclopyr only.

2 Triclopyr and TCP.

3 Meat fat, liver, kidney, and meat byproducts of cattle, goats, horses, hogs, and sheep.

A revised Section F should be submitted to include the recommended tolerances listed in 

Table 6.

RDI: RAB1 Chemists (12/09/2015); G. Kramer (2/4/2016)

cc: J. Tyler

J. Tyler:S10943:PY-S:(703)305-5564:7509P:RAB1
Triclopyr Summary of Analytical Chemistry and Residue Data DP# 419487

Page 7 of 7

Attachment 1: Triclopyr International Residue Limit Status Sheet.

Summary of US and International Tolerances and Maximum Residue Limits.

Residue Definition:

US Canada Mexico1 Codex

US [40 CFR §180.417 (1) Tolerances for residues of 

the herbicide triclopyr per se, as a result of the 

application/use of butoxyethyl ester of triclopyr and 

triethylamine salt of triclopyr

3,5,6-trichloro-2-pyridyloxyacetic acid, 

including the metabolite 3,5,6-trichloro-2-

pyridinol

Milk: 3,5,6-trichloro-2-pyridyloxyacetic acid

None

Commodity Tolerance (ppm) /Maximum Residue Limit (mg/kg)

US Canada Mexico1 Codex

Egg 0.05

Fish 3.0

Grass, forage 700.0

Grass, hay 200.0

Milk 0.01 0.01

Poultry, fat 0.1

Poultry, meat 0.1

Poultry, meat byproducts, except kidney 0.1

Rice, grain 0.3

Rice, straw 10.0

Shellfish 3.5

US [40 CFR §180.417 (2) Canada Mexico1 Codex2

Livestock:

(2) Tolerances for the combined residues of the 

herbicide triclopyr ((3,5,6-trichloro-2-pyridinyl)oxy) 

acetic acid and its metabolite 3,5,6-trichloro-2-

pyridinol (TCP), as a result of the application/use of 

butoxyethyl ester of triclopyr or the triethylamine 

salt of triclopyr

3,5,6-trichloro-2-pyridyloxyacetic acid, 

including the metabolite 3,5,6-trichloro-2-

pyridinol

Milk: 3,5,6-trichloro-2-pyridyloxyacetic acid

None

Commodity Tolerance (ppm) /Maximum Residue Limit (mg/kg)

US Canada Mexico1 Codex2

Cattle, fat 0.05 0.1

Cattle, kidney 0.5 0.5

Cattle, liver 0.5 0.5

Cattle, meat 0.05 0.1

Cattle, meat byproducts, except kidney and liver 0.05 0.1

Goat, fat 0.05 0.1

Goat, kidney 0.5 0.5

Goat, liver 0.5 0.5

Goat, meat 0.05 0.1

Goat, meat byproducts, except kidney and liver 0.05 0.1

Hog, fat 0.05 0.1

Hog, kidney 0.5 0.5

Hog, liver 0.5 0.5

Hog, meat 0.05 0.1

Hog, meat byproducts, except kidney and liver 0.05 0.1

Horse, fat 0.05 0.1

Horse, kidney 0.5 0.5

Horse, liver 0.5 0.5

Horse, meat 0.05 0.1

Horse, meat byproducts, except kidney and liver 0.05 0.1

Sheep, fat 0.05 0.1

Sheep, kidney 0.5 0.5

Sheep, liver 0.5 0.5

Sheep, meat 0.05 0.1

Sheep, meat byproducts, except kidney and liver 0.05 0.1

Completed: M. Negussie; 02/19/2014

1 Mexico adopts US tolerances and/or Codex MRLs for its export purposes.
Triclopyr (PC Code I 16001 )/Dow AgroSciences 

B.7.8 Livestock Feeding Studies 

(Annex IIA 6.4; Annex IHA 8.4) 

8.7.8.1 Cattle 

Document ID: MRTD No. 49741901 

Report: Rawle, N. (2015) Triclopyr Livestock Feeding Study: Magnitude of the 

Residue in Milk, Muscle, Liver, Kidney and Fat of Lactating Dairy Cattle. 

Report Nos. CEMS-6356, 131285, CEMR 6356. Unpublished study 

prepared by Dow AgroSciences Danmark A/S. 672 p. 

Guidelines: EPA OCSPP Harmonized Test Guideline 860.1480 

Meat/Milk/Poultry/Eggs (August 1996) 

PMRA Regulatory Directive DJR98-02 - Residue Chemistry Guidelines, 

Section 8 - Meat/Milk/Poultry/Eggs 

OECD Guideline 505 Residues in Livestock (January 2007) 

GLP Compliance: No deviations from U.S. EPA regulatory requirements were reported 

which would have an impact on the validity of the study. 

Acceptability: The srudy is considered scientifically acceptable. The acceptability of this 

study for regulatory purposes is addressed in the forthcoming U.S. EPA 

Residue Chemistry Summary Document, DP# 419487. ~ 

Evaluator: Jennifer R. Tyler, Chemist ~~.-,.//...c;::>• _,_... Registration Action Branch I /Health Effects Division ~ / 

(RAB 1/HED, 7509P) 

Note: This Data Evaluation Record (DER) was originally prepared under contract by Versar, Inc. (6850 Versar Center. 

pringfield. VA 2215 I: submined I 2/30/ 15). The DER has been reviewed by 1-1 ED and revised to reflect current Office of 

Pesticide Programs (OPP) policies. 

EXECUTIVE SUMMARY 

Dow AgroSciences has submitted a cattle feeding study with triclopyr [2-[(3,5,6-trichloro-2-

pyridinyl)oxy ]acetic acid). In the study, four groups of dairy cows (4 cows/group) were dosed 

orally via gelatin capsule, twice daily after milking for 28-29 consecutive days, with triclopyr at 

1.646, 3.265, 15.905, and 34.391 mg/kg bw/day (Groups B, C, D, and E). Based on the average 

feed consumption, the actual mean daily dose levels were equivalent to 54.8, 109.6, 538.7, and 

1057.4 ppm in the diet (dry-weight basis). Twelve additional cows in Group E were dosed to 

obtain depuration data. One group of three control cows (Group A) received capsules containing 

no triclopyr. The in-life phase of the study was conducted at ADAS Drayton (Stratford-onAvon, Warwickshire, UK), and the analytical phase was conducted by CEM Analytical Services 

(CEMAS; Wokinghan1, Berkshire, UK). 

Cows were milked twice daily, prior to dosing (PM and AM) and samples were collected for 

analysis on Study Days -1(pre-dosing),2, 6, 8, 10, 14, 18, 22, 26, and 28 or 29. In addition, 

milk was collected from the depuration cows on Study Days 29, 31 , 33, 35, 38, 40. 42, 45, 48, 

and49(1,3, 5, 7, 10, 12, 14, 17, 20,and21 daysafterthefinaldose). Extra milk collected on 

Days 22 and 26 (proportional composite of previous day PM and that day AM sample) was used 

for preparation of cream and skim milk samples. Animals that were not included in the 

depuration study were sacrificed - 3-6 hours after the final dose on Study Days 28 (Groups C and 

E) and 29 (Groups B and D). Samples of liver, kidney, fat (subcutaneous, mesenteric, and 

MRlD# 49741901 Page I of24 
Triclopyr [PC Code 116001]/Dow AgroSciences

MRID# 49741901 Page 2 of 24

perirenal), and muscle (composite of hind leg or flank, loin, and diaphragm) were collected from 

each cow. 

Samples were stored frozen (≤-18 °C) at the test facility, during shipping, and at the analytical 

laboratory until analysis. Maximum storage durations were: 57 days (1.9 months) for whole 

milk; 79 days (2.6 months) for skim milk; 152 days (5.0 months) for cream; 111 days (3.7 

months) for triclopyr and 150 days (4.9 months) for 3,5,6-trichloro-2-pyridinol (TCP) for liver; 

99 days (3.3 months) for kidney; 98 days (3.2 months) for fat; and 106 days (3.5 months) for 

muscle. The intervals between extraction and analysis were not reported. To support sample 

storage durations, a concurrent storage stability study was conducted with the feeding study 

reflecting three storage intervals: 0; 30, 32, or 63; and 105-171 days for samples of whole milk, 

skim milk, cream, and all tissues fortified with both analytes. The data demonstrate that residues 

of triclopyr and TCP [3,5,6-trichloro-2-pyridinol] are stable for up to: 168 days in whole milk; 

110 days in skim milk; 153 days in cream; 171 days in liver; 105 days in kidney; 159 days in 

fats; and 160 days in muscle. These data are adequate to support the study.

Samples were analyzed for residues of triclopyr and metabolite TCP using two high-performance 

liquid chromatography methods with tandem mass-spectrometry detection (LC/MS/MS) based 

on the methods described in Dow AgroSciences Study ID 130961 for whole milk, skim milk,

and tissues and in Study ID 120588 for cream. The limit of quantitation (LOQ; determined as 

the lowest level of method validation, LLMV) was 0.01 ppm for each analyte in each bovine 

matrix; the combined LOQ was 0.02 ppm. The methods were adequate for data collection based 

on acceptable concurrent recovery data from samples fortified with each analyte at: 0.01-1.0 

ppm for whole milk, skim milk, and cream; 0.01-20 ppm for liver; 0.01-75 ppm for kidney; 0.01-

10 ppm for fat; and 0.01-2.0 ppm for muscle. The fortification levels used in concurrent method 

recovery were adequate to bracket expected residue levels (within an order of magnitude for fat). 

Concurrent recoveries were corrected for apparent residues in controls; residues in the treated 

samples were not corrected for residues in controls. Quantifiable residues of TCP were 

converted to parent equivalents by the study reviewer using a molecular weight conversion factor 

of 1.3 (MW triclopyr 256.46 ÷ MW TCP 198.44).

Combined residues of triclopyr and TCP were below the LOQ in all samples of cream and near 

or below the LOQ in whole milk and skim milk (residues ranged <0.02-<0.037 ppm) at the 54.8-

ppm dose level. At the 109.6- and 538.7-ppm dose levels, combined residues in whole milk 

plateaued by Study Days 6-8; at the 1057.4-ppm dose level, residues of triclopyr plateaued by 

Day 8, but residues of TCP continued to increase through the study. Residues of TCP in milk 

exceeded those of triclopyr at the 109.6-, 538.7-, and 1057.4-ppm dose levels, respectively, by 

up to 3.2x (average 1.9x), 18x (average 8.8x), and 15x (average 6.1x). Combined residues of 

triclopyr and TCP at the 109.6-, 538.7-, and 1057.4-ppm dose levels, respectively, were: <0.026-

0.065, 0.094-0.377, and 0.184-0.602 ppm in whole milk; <0.029-0.049, 0.123-0.314, and 

<0.235-0.615 ppm in skim milk; and <0.02-<0.028, <0.069-0.177, and <0.114-0.339 ppm in 

cream.

Quantifiable residues triclopyr and TCP were observed in tissues at all dosing levels, with the 

highest residues observed in kidney, then liver, and the lowest residues observed in muscle. 

Ratios of residues in tissues to those in feed were relatively consistent across feeding levels 

except for those in liver, which declined steadily with increasing feeding level. Residues of TCP 

exceeded those of triclopyr in liver (average 15-26x), fat (1.6-4.0x), and muscle (1.7-3.7x) but 
Triclopyr [PC Code 116001]/Dow AgroSciences

MRID# 49741901 Page 3 of 24

were lower than those of triclopyr in kidney (0.3-0.8x). Combined residues of triclopyr and TCP 

at the 54.8-, 109.6-, 538.7-, and 1057.4-ppm dose levels, respectively, were: 0.929-2.43, 2.46-

3.55, 10.3-11.7, and 14.3-17.5 ppm in liver; 2.77-5.33, 6.46-8.34, 28.2-53.8, and 48.3-106 ppm 

in kidney; 0.058-0.744, 0.130-1.13, 1.26-5.01, and 3.25-10.0 ppm in composite fat (calculated by 

the petitioner as the average of analyte concentrations in the corresponding samples of individual 

fats); and 0.040-0.134, 0.147-0.193, 0.975-1.19, and 1.29-1.97 ppm in muscle.

The depuration study indicated that following removal of the test substance from the diet, residue 

levels decreased in milk and all tissues, with residues decreasing most rapidly in milk and muscle 

and least rapidly in liver. Combined residues of triclopyr and TCP in whole milk and muscle 

decreased to below the LOQ (<0.02 ppm) by Study Day 31 (Depuration Day 3). Combined 

residues were near or below the LOQ in kidney by Study Day 42 (Depuration Day 14) and in fats 

by Study Day 49 (Depuration Day 21). Average combined residues were <0.031 ppm in liver by 

Study Day 49. 

Linear-regression analysis demonstrated a generally linear relationship between dose level and 

resulting residues in milk and tissues, with a better correlation observed for TCP than for 

triclopyr.

I. MATERIALS AND METHODS

A. MATERIALS

Table B.7.8.1-1. Nomenclature for Triclopyr and Compounds of Interest.

Common name Triclopyr

Identity [(3,5,6-Trichloro-2-pyridinyl)oxy]acetic acid

CAS no. 55335-06-3

Company experimental name Not applicable

Other synonyms (if applicable) Not applicable

Metabolite TCP

Identity 3,5,6-trichloro-2-pyridinol
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MRID# 49741901 Page 4 of 24

B. STUDY DESIGN

1. Test Procedure

Four groups of dairy cows (4 cows/group) were dosed orally via gelatin capsule, twice daily after 

milking for 28-29 consecutive days, with triclopyr at 1.646, 3.265, 15.905, and 34.391 mg/kg 

bw/day (Groups B, C, D, and E). Based on the average feed consumption, the actual mean daily 

dose levels were equivalent to 54.8, 109.6, 538.7, and 1057.4 ppm in the diet (dry-weight basis). 

Twelve additional cows in Group E were dosed to obtain depuration data. One group of three 

control cows (Group A) received capsules containing no triclopyr. The in-life phase of the study 

was conducted at ADAS Drayton (Stratford-on-Avon, Warwickshire, UK)

Livestock

Table B.7.8.1-2. Description of Livestock Used in the Feeding Study.

Species Breed Age

(Years)

Weight at 

Study Initiation 

(kg)

Health Status Description of Housing/Holding Area

Bos taurus Friesian/

Holstein

3.5-7.5 526-828

(Study Day -1)

All health issues were 

relatively minor and 

typical for cows of this 

age

Individual stalls (3.75 m x 3.45 m)

Natural light with artificial lighting as necessary, 

naturally ventilated. Min/max temperatures & 

R.H. were recorded daily but were not reported.

Diet

Table B.7.8.1-3. Test Animal Dietary Regime.

Composition of Diet Feed Consumption1

(Avg. kg/cow/wk)

Water Acclimation Period Predosing

Grass silage (ad libitum);

Pelleted dairy compound: ~11 

kg/day split into 3 feedings

Group A: 18.06-20.58

Group B:17.95-19.93

Group C: 18.71-20.90

Group D: 17.75-19.71

Group E: 19.02-21.21

Ad libitum 14 days None

1 The petitioner noted that cows in all groups had slightly lower intake in week three compared to the rest of the study. The level 

of dosing did not seem to affect food intakes.

Treatment

Table B.7.8.1-4. Dosing Regime.

Treatment Group

(Cow #s)

Treatment 

Type

Level of 

Administered Dose 

(mg/kg bw/day)

Residue 

Intake in Diet

(ppm)

Vehicle Timing/ Duration

(days)

Group A (1, 2, 3) Oral 0 0 Gelatin capsule N/A

Group B (4, 5, 6, 7) 1.646 54.8 29

Group C (8, 9, 10, 11) 3.265 109.6 28

Group D (12, 13, 14, 15) 15.905 538.7 29

Group E (16, 17, 18, 19)1 34.391 1057.4 28 1 Group E also contained cows (20, 21, 22), (23, 24, 25), (26, 27, 28), and (29, 30, 31) for the depuration study.
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MRID# 49741901 Page 5 of 24

Sampling

Table B.7.8.1-5. Sample Collection.

Milk Collected Urine, Feces, Cage 

Wash Collected

Interval From Last 

Dose to Sacrifice

Tissues Harvested and Analyzed

Milk was collected twice daily. Milk 

collected in the PM was combined with 

milk collected the following morning to 

generate daily samples.

Skim milk and cream were generated 

from milk samples collected as above on 

Study Days 22 and 26

Not collected Feeding study:

3-5.5 hours

Depuration study:

3-21 days

Liver

Kidney

Fat (subcutaneous, mesenteric, perirenal)

Muscle

(comprised of equal pieces of hind leg or 

flank, loin, and diaphragm muscle)

Sample Handling and Preparation

Milk was collected twice daily, prior to dosing (PM and AM) on Study Days -1 (pre-dosing), 2, 

6, 8, 10, 14, 18, 22, 26, and 28. In addition, milk was collected from the depuration cows on 

Study Days 29, 31, 33, 35, 38, 40, 42, 45, 48, and 49 (1, 3, 5, 7, 10, 12, 14, 17, 20, and 21 days 

after the final dose). For each cow, milk from the PM collection was stored refrigerated (5 ± 3 

°C) overnight until it was composited with the following day’s AM sample to produce a daily 

sample. The composited samples were then stored frozen (<-18 °C). Average milk yields for 

the respective dose levels (0-1057.4 ppm) were: 24.4, 23.3, 22.4, 24.4, and 26.2 kg/day. Extra 

milk collected on Days 22 and 26 (proportional composite of previous day PM and that day AM 

sample) was centrifuged to separate cream and skim milk.

Animals that were not included in the depuration study were sacrificed ~3-6 hours after the final 

dose on Study Days 28 (Groups C and E) and 29 (Groups B and D). For the depuration study, 

three cows were terminated on each of Study Days 31, 35, 42, and 49 (Depuration Days 3, 7, 14, 

and 21). Samples of liver, kidney, fat (subcutaneous, mesenteric, and perirenal), and muscle 

were collected from each cow. Tissue samples were placed in frozen storage (<-18 °C) within 3 

hours of collection.

The petitioner stated that no adverse treatment-related effects were observed on body weight, 

feed consumption, or milk production, and that no treatment-related behavioral reactions or 

systemic signs of toxicity were noted. Gross necropsies showed no effects that appeared to be 

treatment-related.

Samples were shipped frozen by ground transport within 1-20 days of collection to the analytical 

laboratory (CEMAS), where they were stored frozen (≤-18 °C) until preparation for analysis. 

Samples of liver, kidney, and fat were prepared for analysis by homogenizing in the presence of 

dry ice; dry ice was not needed for homogenization of muscle samples, and no preparation was 

needed for whole milk, skim milk, or cream. 

2. Description of Analytical Procedures

Samples were analyzed for residues of triclopyr and metabolite TCP using two LC/MS/MS

methods, based on the methods described in Dow AgroSciences Study ID 130961 for whole 

milk, skim milk, and tissues and in Study ID 120588 for cream. Brief descriptions of the 

methods, including modifications for method 120588 were included in the submission.
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MRID# 49741901 Page 6 of 24

Briefly, samples of milk, skim milk, and tissues were extracted with methanol:2.5 N NaOH 

(90:10, v:v). An aliquot of the extract was acidified with 1.0 N HCl, then purified through a 

reverse-phase polymeric solid phase extraction (SPE) column. Residues were eluted with 

acetonitrile (ACN)/water/1 N HCl, and the eluate was diluted with a solution containing stable 

isotope standards of triclopyr and TCP in water:acetic acid (99.9:0.1, v:v) for analysis by 

LC/MS/MS.

Samples of cream were extracted with water:ACN (1:1, v:v) and QuEChERS extraction salts 

(MgSO4:NaCl:sodium citrate:disodium citrate sesquihydrate (4:1:1:0.5, w:w:w:w)), and the 

ACN phase was placed in a freezer overnight to precipitate fat. An aliquot of the resulting 

extract was centrifuged if necessary and combined with water/0.1% acetic acid and stable isotope 

internal standard solution. The mixture was filtered (0.45 μm) for analysis by LC/MS/MS.

The methods monitor the following ion transitions for quantitation of triclopyr and TCP, 

respectively: m/z 254.1 → 196.0 and m/z 197.7 → 106.8. The methods do not provide for 

conversion of metabolite residues to parent equivalents; therefore, quantifiable residues of TCP 

were converted to parent equivalents by the study reviewer using a molecular weight conversion 

factor of 1.3 (MW triclopyr 256.46 ÷ MW TCP 198.44).

The LOQ (determined as the LLMV) was 0.01 ppm for each analyte in each bovine matrix; the 

combined LOQ was 0.02 ppm. The limit of detection (LOD) for each analyte was 0.003 ppm.

II. RESULTS AND DISCUSSION

Method performance was evaluated during method validation and by use of concurrent recovery 

samples. For method validation, samples of skim milk, cream, and muscle were fortified with 

each analyte at 0.01 and 0.10 ppm; for concurrent recoveries, samples were fortified with each 

analyte at: 0.01, 0.10, 0.50, and 1.0 ppm for whole milk; 0.01, 0.10, and 1.0 ppm for skim milk 

and cream; 0.01, 0.10, 1.0, 10, and 20 ppm for liver; 0.01, 0.10, 1.0, 10, and 75 ppm for kidney; 

0.01, 0.1, 0.5, 1.0, 5.0 and/or 10 ppm for fat; and 0.01, 0.10, and 2.0 ppm for muscle. Recoveries 

were generally within the acceptable range of 70-120%; therefore, the methods were considered 

valid for the analysis of triclopyr and TCP residues in bovine matrices (Table B.7.8.1-6). The 

fortification levels bracketed the measured residues (within an order of magnitude for fat). 

Concurrent recoveries were corrected for apparent residues in controls.

The detector response was linear for all matrices (coefficient of determination, r2 ≥0.9968) 

within the range of 0.05-10 ng/mL. Representative chromatograms of control samples, fortified 

samples, and treated samples were provided. The control chromatograms generally had no peaks 

of interest above the chromatographic background. The fortified sample chromatograms 

contained only the analyte of interest, and peaks were symmetrical and well defined. Apparent 

residues in controls were below the LOQ (<0.01 ppm) for each analyte in all control samples of 

whole milk, skim milk, cream, kidney, fat, and muscle. Residues of triclopyr were below the 

LOQ in all control samples of liver; however, apparent residues of TCP were observed at 0.023-

0.048 ppm. To investigate whether TCP may have formed during storage or when samples were 

thawed for preparation or analysis, retain samples were analyzed with extra precautions taken to 

keep them as cold as possible; however, TCP was also found in control retain samples. The 

petitioner concluded that it was “unclear what was responsible for the TCP residues in control 

liver.” The reported residue values were not corrected for apparent residues in controls. 
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MRID# 49741901 Page 7 of 24

Quantifiable residues of TCP were converted to parent equivalents by the study reviewer using a 

molecular weight conversion factor of 1.3 (MW triclopyr 256.46 ÷ MW TCP 198.44).

Table B.7.8.1-6. Summary of Method Validation and Procedural/Concurrent Recoveries of Triclopyr and 

TCP from Bovine Matrices.

Matrix Analyte Fortification 

Level 

(ppm)

Sample 

size (n)

Quantitation1 Confirmation1

Recoveries2

(%)

Mean ± Std. 

Dev. (%)

Recoveries2

(%)

Mean ± Std. 

Dev. (%)

Method Validation

Skim milk Triclopyr 0.01-0.10 10 78-88 83 ± 3.6 80-87 83 ± 2.5

TCP 0.01-0.10 10 71-90 85 ± 6.4 73-87 82 ± 5.4

Cream Triclopyr 0.01-0.10 10 95-108 101 ± 3.6 96-105 101 ± 2.6

TCP 0.01-0.10 10 71-86 76 ± 6.9 70-86 77 ± 7.9

Muscle Triclopyr 0.01-0.10 10 72-88 83 ± 5.5 73-85 81 ± 4.3

TCP 0.01-0.10 10 76-90 82 ± 6.4 73-85 79 ± 4.5

Concurrent Recoveries

Whole milk Triclopyr 0.01-1.0 86 70-112 93 ± 7.9

TCP 0.01-1.0 71 69, 69; 71-111 86 ± 11

Skim milk Triclopyr 0.01-1.0 19 88-105 97 ± 5.5

TCP 0.01-1.0 19 71-104 86 ± 11

Cream Triclopyr 0.01-1.0 16 97-109 102 ± 3.6

TCP 0.01-1.0 16 66; 72-95 83 ± 8.8

Liver Triclopyr 0.01-20 25 92-106 97 ± 3.3

TCP 0.1-20 15 72-97 84 ± 7.2

Kidney Triclopyr 0.01-75 25 83-112 105 ± 7.8

TCP 0.01-75 25 72-120; 121, 127 98 ± 17

Fat, 

subcutaneous 

Triclopyr 0.01-5.0 12 71-90 83 ± 5.7

TCP 0.01-5.0 12 73-99 84 ± 8.4

Fat, mesenteric Triclopyr 0.01-10 21 86-108 98 ± 5.4

TCP 0.01-10 21 70-100 86 ± 8.6

Fat, perirenal Triclopyr 0.01-10 12 89-107 98 ± 5.2

TCP 0.01-10 12 87-113 102 ± 7.2

Muscle Triclopyr 0.01-2.0 21 88-110 98 ± 5.5

TCP 0.01-2.0 21 69, 69; 70-94 82 ± 8.0

1 The methods monitor the following ion transitions for quantitation of triclopyr and TCP, respectively: m/z 254.1 → 196.0 and 

m/z 197.7 → 106.8; confirmation transitions were not reported. 2 Concurrent recoveries were corrected for apparent residues in controls; values include fresh fortification recoveries for storage 

stability.

Samples were stored frozen (≤-18 °C) at the test facility, during shipping, and at the analytical 

laboratory until analysis. Maximum storage durations were: 57 days (1.9 months) for whole 

milk; 79 days (2.6 months) for skim milk; 152 days (5.0 months) for cream; 111 days (3.7 

months) for triclopyr and 150 days (4.9 months) for TCP for liver; 99 days (3.3 months) for 

kidney; 98 days (3.2 months) for fat; and 106 days (3.5 months) for muscle (Table B.7.8.1-7a). 

The intervals between extraction and analysis were not reported. To support sample storage 

durations, a concurrent storage stability study was conducted with the feeding study reflecting

three storage intervals: 0; 30, 32, or 63; and 105-171 days for samples of whole milk, skim milk, 

cream, and all tissues fortified with both analytes (Table B.7.8.1-7b). The data demonstrate that 

residues of triclopyr and TCP are stable for up to: 168 days in whole milk; 110 days in skim 

milk; 153 days in cream; 171 days in liver; 105 days in kidney; 159 days in fats; and 160 days in 

muscle. These data are adequate to support the study. The petitioner also investigated the 
Triclopyr [PC Code 116001]/Dow AgroSciences

MRID# 49741901 Page 8 of 24

storage stability of residues of triclopyr in extracts of milk and tissues stored refrigerated (4 °C) 

for 7-8 days. The results indicated that residues were stable for all matrices.

Table B.7.8.1-7a. Summary of Storage Conditions.

Matrix Analyte Storage 

Temperature (°C)

Actual Storage Duration1 Interval of Demonstrated Storage 

Stability2

Whole milk Triclopyr & TCP ≤-18 8-57 days (0.3-1.9 months) 168 days

Skim milk Triclopyr & TCP 75-79 days (2.5-2.6 months) 110 days

Cream Triclopyr & TCP 148-152 days (4.9-5.0 months) 153 days

Liver Triclopyr 90-111 days (3.0-3.7 months) 171 days

TCP 129-150 days (4.2-4.9 months)

Kidney Triclopyr & TCP 78-99 days (2.6-3.3 months) 105 days

Fats Triclopyr & TCP 71-98 days (2.3-3.2 months) 159 days

Muscle Triclopyr & TCP 85-106 days (2.8-3.5 months) 160 days 1 Interval from collection/sacrifice to extraction. The intervals between extraction and analysis were not reported. 2 Based on a concurrent storage stability study (refer to Table B.7.8.1-7b).

Table B.7.8.1-7b. Stability of Triclopyr and TCP Residues in Bovine Matrices During Frozen Storage (≤-18 

°C).

Commodity Analyte Spike 

Level

(ppm)

Storage 

Interval

(days)

Fresh Fortification 

Recoveries (%)

[Avg.]

Stored Sample 

Recoveries (%)

Mean 

Recovery (%)

Corrected % 

Recovery1

Whole milk Triclopyr 0.10 0 87, 83, 85 [85] 86, 87, 87 87 102

32 96, 93, 95 [95] 101, 100, 103 101 107

168 80, 82, 81 [81] 81, 78, 80 80 98

TCP 0.10 0 77, 78, 73 [76] 83, 78, 80 80 106

32 78, 71, 73 [74] 81, 80, 78 80 108

168 69, 69, 77 [72] 65, 71, 65 67 93

Skim milk Triclopyr 0.10 0 88, 91, 88 [89] 90, 88, 90 89 100

32 100, 104, 102 [102] 106, 107, 97 103 101

110 100, 102, 100 [101] 99, 97, 98 98 97

TCP 0.10 0 76, 82, 77 [78] 77, 77, 76 77 98

32 76, 75, 75 [75] 82, 85, 73 80 106

110 71, 77, 78 [75] 72, 74, 80 75 100

Cream Triclopyr 0.10 0 99, 103, 104 [102] 102, 103, 104 103 101

63 102, 100, 103 [102] 112, 113, 109 111 110

153 107, 104, 111 107 105

TCP 0.10 0 66, 73, 72 [70] 75, 73, 76 75 106

63 75, 75, 80 [77] 76, 71, 71 73 95

153 74, 78, 75 76 98

Liver Triclopyr 0.10 0 97, 95, 98 [97] 96, 97, 99 97 101

30 97, 94, 100 [97] 112, 105, 108 108 112

171 99, 97, 97 [98] 92, 89, 92 91 93

TCP 0.10 0 73, 72, 76 [74] 77, 79, 77 78 105

30 85, 82, 83 [83] 100, 94, 89 94 113

171 83, 81, 83 [82] 63, 60, 64 62 76

Kidney Triclopyr 0.10 0 90, 83, 89 [87] 90, 86, 82 86 98

30 101, 101, 103 [102] 96, 107, 105 103 101

105 108, 110, 111 [110] 108, 108, 105 107 98

TCP 0.10 0 75, 72, 84 [77] 78, 71, 71 73 95
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MRID# 49741901 Page 9 of 24

Table B.7.8.1-7b. Stability of Triclopyr and TCP Residues in Bovine Matrices During Frozen Storage (≤-18 

°C).

Commodity Analyte Spike 

Level

(ppm)

Storage 

Interval

(days)

Fresh Fortification 

Recoveries (%)

[Avg.]

Stored Sample 

Recoveries (%)

Mean 

Recovery (%)

Corrected % 

Recovery1

30 79, 79, 81 [80] 81, 83, 83 82 103

105 81, 80, 83 [81] 75, 78, 80 78 95

Fat Triclopyr 0.10 0 99, 98, 94 [97] 98, 101, 95 98 101

32 92, 95, 98 [95] 103, 103, 105 104 109

159 100, 97, 100 [99] 100, 99, 100 100 101

TCP 0.10 0 81, 81, 86 [83] 87, 87, 84 86 104

32 72, 70, 73 [72] 76, 76, 85 79 110

159 89, 85, 86 [87] 81, 80, 78 80 92

Muscle Triclopyr 0.10 0 110, 89, 98 [99] 88, 92, 90 90 91

32 88, 91, 91 [90] 95, 97, 94 95 106

160 92, 95, 96 [94] 97, 99, 99 98 104

TCP 0.10 0 86, 87, 88 [87] 87, 82, 82 84 96

32 71, 76, 70 [72] 77, 75, 76 76 105

160 88, 81, 83 [84] 78, 80, 83 80 96

1 Corrected for recovery in freshly fortified samples.

The results from the submitted feeding study are presented in Tables B.7.8.1-8 (whole milk, skim 

milk, and cream), B.7.8.1-9 (tissues), B.7.8.1-10 (residue summary), and B.7.8.1-11 (depuration 

results). Combined residues of triclopyr and TCP were below the LOQ in all samples of cream 

and near or below the LOQ in whole milk and skim milk (residues ranged <0.02-<0.037 ppm) at 

the 54.8-ppm dose level. At the 109.6- and 538.7-ppm dose levels, combined residues in whole 

milk plateaued by Study Days 6-8; at the 1057.4-ppm dose level, residues of triclopyr plateaued 

by Day 8, but residues of TCP continued to increase through the study (see Figure B.7.8.1-1). 

Residues of TCP in milk exceeded those of triclopyr at the 109.6-, 538.7-, and 1057.4-ppm dose 

levels, respectively, by up to 3.2x (average 1.9x), 18x (average 8.8x), and 15x (average 6.1x). 

Combined residues of triclopyr and TCP at the 109.6-, 538.7-, and 1057.4-ppm dose levels, 

respectively, were: <0.026-0.065, 0.094-0.377, and 0.184-0.602 ppm in whole milk; <0.029-

0.049, 0.123-0.314, and <0.235-0.615 ppm in skim milk; and <0.02-<0.028, <0.069-0.177, and 

<0.114-0.339 ppm in cream.

Quantifiable residues triclopyr and TCP were observed in tissues at all dosing levels, with the 

highest residues observed in kidney, then liver, and the lowest residues observed in muscle. 

Ratios of residues in tissues to those in feed were relatively consistent across feeding levels 

except for those in liver, which declined steadily with increasing feeding level. Residues of TCP 

exceeded those of triclopyr in liver (average 15-26x), fat (1.6-4.0x), and muscle (1.7-3.7x) but 

were lower than those of triclopyr in kidney (0.3-0.8x). Combined residues of triclopyr and TCP 

at the 54.8-, 109.6-, 538.7-, and 1057.4-ppm dose levels, respectively, were: 0.929-2.43, 2.46-

3.55, 10.3-11.7, and 14.3-17.5 ppm in liver; 2.77-5.33, 6.46-8.34, 28.2-53.8, and 48.3-106 ppm 

in kidney; 0.058-0.744, 0.130-1.13, 1.26-5.01, and 3.25-10.0 ppm in composite fat (calculated by 

the petitioner as the average of analyte concentrations in the corresponding samples of individual 

fats); and 0.040-0.134, 0.147-0.193, 0.975-1.19, and 1.29-1.97 ppm in muscle.

The depuration study indicated that following removal of the test substance from the diet, residue 

levels decreased in milk and all tissues, with residues decreasing most rapidly in milk and muscle 
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MRID# 49741901 Page 10 of 24

and least rapidly in liver. Combined residues of triclopyr and TCP in whole milk and muscle 

decreased to below the LOQ (<0.02 ppm) by Study Day 31 (Depuration Day 3). Combined 

residues were near or below the LOQ in kidney by Study Day 42 (Depuration Day 14) and in fats 

by Study Day 49 (Depuration Day 21). Average combined residues were <0.031 ppm in liver by 

Study Day 49. 

Linear-regression analysis demonstrated a generally linear relationship between dose level and 

resulting residues in milk and tissues, with a better correlation observed for TCP than for 

triclopyr; see Figures B.7.8.1-2 (whole milk), B.7.8.1-3 (liver); B.7.8.1-4 (kidney); B.7.8.1-5 

(subcutaneous fat); and B.7.8.1-6 (muscle).

Table B.7.8.1-8. Whole Milk, Skim Milk, and Cream Residue Data From Ruminant Feeding Study with 

Triclopyr.

Animal ID # Collection 

Time

(study day)

Feeding 

Level 

(ppm)

Residues1 (ppm parent equivalents)

Triclopyr TCP Combined [Avg.]2

Whole milk

4, 5, 6, 7 2 54.8 (0.003), (0.008), (0.004), ND ND, (0.005), (0.006), 

(0.004)

<0.02, <0.02, <0.02, <0.02 

[<0.02]

6 (0.003), (0.006), (0.003), 

(0.004)

(0.006), (0.01), (0.009), 

(0.006)

<0.02, <0.02, <0.02, <0.02 

[<0.02]

83 ND, (0.003), ND, ND (0.004), (0.008), (0.008), 

(0.003)

<0.02, <0.02, <0.02, <0.02 

[<0.02]

10 (0.004), (0.006), (0.004), ND (0.005), 0.014, (0.009), 

(0.004)

<0.02, <0.024, <0.02, 

<0.02 [<0.021]

14 (0.004), (0.007), (0.004), 

(0.003) 

(0.004), 0.016, (0.008), 

(0.004)

<0.02, <0.026, <0.02, 

<0.02 [<0.021]

18 (0.005), (0.008), (0.007), 

(0.004)

(0.006), 0.018, (0.01), 

(0.005)

<0.02, 0.028, <0.02, <0.02 

[<0.022]

22 ND, (0.003), (0.004), (0.004) (0.006), 0.021, (0.008), 

(0.004)

<0.02, <0.031, <0.02, 

<0.02 [<0.023]

26 (0.004), (0.004), (0.004), 

(0.003)

(0.008), 0.022, (0.01), 

(0.005)

<0.02, <0.032, <0.02, 

<0.02 [<0.023]

29 (0.003), (0.008), (0.005), 

(0.004)

(0.006), 0.016, (0.007), 

(0.005)

<0.02, <0.026, <0.02, 

<0.02 [<0.021]

83, 9, 10, 11 2 109.6 (0.008), (0.007), 0.012, 

(0.006)

(0.007), 0.016, 0.013, 

(0.009)

<0.02, <0.026, 0.025, 

<0.02 [<0.023]

6 (0.007), (0.007), 0.022, 

(0.006)

0.016, 0.027, 0.023, 0.019 <0.026, <0.037, 0.045, 

<0.029 [<0.034]

83 (0.005), (0.005), 0.012, 

(0.004)

0.018, 0.027, 0.019, 0.017 <0.028, <0.037, 0.031, 

<0.027 [<0.031]

10 (0.007), (0.006), 0.014, 

(0.006)

0.016, 0.030, 0.017, 0.016 <0.026, <0.040, 0.031, 

<0.026 [<0.030]

14 (0.007), (0.006), 0.022, 

(0.007)

0.017, 0.028, 0.016, 0.017 <0.027, <0.038, 0.038, 

<0.027 [<0.032]

18 (0.01), 0.013, 0.038, 0.011 0.018, 0.039, 0.027, 0.019 <0.028, 0.052, 0.065, 

0.030 [<0.044]

22 (0.008), (0.008), 0.015, 0.013 0.018, 0.025, 0.025, 0.017 <0.028, <0.035, 0.040, 

0.030 [<0.033]

26 (0.008), (0.008), 0.015, 0.011 0.021, 0.032, 0.027, 0.030 <0.031, <0.042, 0.042, 

0.041 [<0.039]

28 0.015, 0.010, 0.030, 0.016 0.022, 0.031, 0.026, 0.028 0.037, 0.041, 0.056, 0.044

[0.045]

12, 13, 14, 

15

2 538.7 0.057, 0.037, 0.019, 0.034 0.045, 0.080, 0.083, 0.032 0.102, 0.117, 0.102, 0.066

[0.097]
Triclopyr [PC Code 116001]/Dow AgroSciences

MRID# 49741901 Page 11 of 24

Table B.7.8.1-8. Whole Milk, Skim Milk, and Cream Residue Data From Ruminant Feeding Study with 

Triclopyr.

Animal ID # Collection 

Time

(study day)

Feeding 

Level 

(ppm)

Residues1 (ppm parent equivalents)

Triclopyr TCP Combined [Avg.]2

6 0.024, 0.027, 0.011, 0.013 0.105, 0.173, 0.164, 0.068 0.129, 0.200, 0.175, 0.081

[0.146]

83 0.020, 0.138, (0.005), (0.008) 0.129, 0.239, 0.168, 0.110 0.149, 0.377, <0.178, 

<0.120 [<0.206]

10 (0.007), 0.016, 0.013, 0.018 0.098, 0.177, 0.142, 0.076 <0.108, 0.193, 0.155, 

0.094 [<0.138]

14 0.015, 0.020, (0.007), 0.015 0.112, 0.193, 0.162, 0.083 0.127, 0.213, <0.172, 

0.098 [<0.152]

18 0.036, 0.016, 0.024, 0.039 0.141, 0.256, 0.174, 0.140 0.177, 0.272, 0.198, 0.179

[0.206]

22 0.037, 0.025, 0.014, 0.029 0.112, 0.199, 0.198, 0.115 0.149, 0.224, 0.212, 0.144

[0.182]

26 0.027, 0.029, 0.012, 0.025 0.131, 0.244, 0.220, 0.114 0.158, 0.273, 0.232, 0.139

[0.200]

29 0.028, 0.024, 0.011, 0.013 0.163, 0.233, 0.185, 0.110 0.191, 0.257, 0.196, 0.123

[0.192]

16, 17, 18, 

19 (20, 21, 

22, 23, 24, 

25, 26, 27, 

28, 29, 30, 

31)4

2 1057.4 0.118, 0.059, 0.312, 0.051 0.147, 0.110, 0.171, 0.145 0.265, 0.169, 0.483, 0.196

[0.278]

6 0.059, 0.018, 0.147, 0.028 0.317, 0.181, 0.335, 0.318 0.376, 0.199, 0.482, 0.346

[0.351]

8 0.058, 0.041, 0.138, 0.051 0.309, 0.182, 0.331, 0.306 0.367, 0.223, 0.469, 0.357

[0.354]

10 0.024, 0.035, 0.107, 0.053 0.213, 0.149, 0.289, 0.176 0.237, 0.184, 0.396, 0.229

[0.262]

14 0.041, 0.023, 0.156, 0.037, 

0.092, 0.172, 0.051, 0.041, 

0.094, 0.041, 0.114, 0.102, 

0.297, 0.039, 0.040, 0.029

0.317, 0.168, 0.273, 0.341, 

0.309, 0.265, 0.417, 0.262, 

0.324, 0.208, 0.385, 0.304, 

0.045, 0.142, 0.239, 0.279

0.358, 0.191, 0.429, 0.378,

0.401, 0.437, 0.468, 0.303, 

0.418, 0.249, 0.499, 0.406, 

0.342, 0.181, 0.279, 0.308

[0.353]

18 0.097, 0.019, 0.198, 0.040 0.355, 0.190, 0.287, 0.286 0.452, 0.209, 0.485, 0.326

[0.368]

22 0.032, 0.022, 0.216, 0.101, 

0.517, 0.130, 0.089, 0.059, 

0.074, 0.119, 0.087, 0.167, 

0.039, 0.069, 0.075, 0.033

0.473, 0.230, 0.386, 0.379, 

0.469, 0.375, 0.512, 0.342, 

0.424, 0.211, 0.429, 0.381, 

0.371, 0.226, 0.339, 0.395

0.505, 0.252, 0.602, 0.480, 

0.986, 0.505, 0.601, 0.401, 

0.498, 0.330, 0.516, 0.548, 

0.410, 0.295, 0.414, 0.428

[0.486]

26 0.065, 0.034, 0.104, 0.035 0.465, 0.222, 0.362, 0.433 0.530, 0.256, 0.466, 0.468

[0.430]

28 0.061, 0.046, 0.096, 0.052, 

0.128, 0.055, 0.031, 0.032, 

0.084, 0.066, 0.179, 0.122, 

0.044, 0.037, 0.032, 0.044

0.455, 0.256, 0.408, 0.420, 

0.349, 0.350, 0.710, 0.476, 

0.470, 0.230, 0.443, 0.403, 

0.258, 0.240, 0.309, 0.419

0.516, 0.302, 0.504, 0.472, 

0.477, 0.405, 0.741, 0.508, 

0.554, 0.296, 0.622, 0.525, 

0.302, 0.277, 0.341, 0.463

[0.457]

Skim milk

4, 5, 6, 7 22 54.8 ND, ND, (0.004), (0.003) (0.009), 0.027, 0.017, 

(0.006)

<0.02, <0.037, <0.027, 

<0.02 [<0.026]

26 (0.004), ND, (0.004), (0.003) (0.009), 0.022 (0.010), 

(0.005)

<0.02, <0.032, <0.02, 

<0.02 [<0.023]

8, 9, 10, 11 22 109.6 (0.007), (0.006), 0.015, 0.012 0.025, 0.039, 0.034, 0.025 <0.035, <0.049, 0.049, 

0.037 [<0.042]

26 (0.005), (0.007), 0.014 (0.007) 0.021, 0.032, 0.025, 0.019 <0.031, <0.042, 0.039, 

<0.029 [<0.035]
Triclopyr [PC Code 116001]/Dow AgroSciences

MRID# 49741901 Page 12 of 24

Table B.7.8.1-8. Whole Milk, Skim Milk, and Cream Residue Data From Ruminant Feeding Study with 

Triclopyr.

Animal ID # Collection 

Time

(study day)

Feeding 

Level 

(ppm)

Residues1 (ppm parent equivalents)

Triclopyr TCP Combined [Avg.]2

12, 13, 14, 

15

22 538.7 0.029, 0.014 (0.009), 0.019 0.163, 0.300, 0.237, 0.142 0.192, 0.314, <0.247, 

0.161, [<0.228]

26 0.014, 0.013 (0.005), 0.013 0.137, 0.292, 0.218, 0.110 0.151, 0.305, <0.228, 

0.123 [<0.202]

16, 17, 18, 

19

22 1057.4 0.017, (0.008), 0.161, 0.058 0.536, 0.278, 0.454, 0.467 0.553, <0.288, 0.615, 

0.525 [<0.495]

26 0.029, (0.006), 0.045, 0.020 0.470, 0.225, 0.376, 0.405 0.499, <0.235, 0.421, 

0.425 [<0.395]

Cream

4, 5, 6, 7 22 54.8 ND, ND, ND, ND (0.004), (0.009), (0.006) 

ND

<0.02, <0.02, <0.02, <0.02

[<0.02]

26 ND, ND, ND, ND (0.004), (0.009), (0.005), 

(0.003)

<0.02, <0.02, <0.02, <0.02

[<0.02]

8, 9, 10, 11 22 109.6 (0.003) ND, (0.007), (0.005) (0.009), 0.017, 0.018, 

(0.01)

<0.02, <0.027, <0.028, 

<0.02 [<0.024]

26 ND, (0.004), (0.007), (0.003) (0.009), 0.016, 0.017, 

(0.009)

<0.02, <0.026, <0.027, 

<0.02 [<0.023]

12, 13, 14, 

15

22 538.7 0.012, 0.011 (0.008), (0.009) 0.070, 0.165, 0.124, 0.059 0.082, 0.176, <0.134, 

<0.069 [<0.115]

26 (0.008), 0.011 (0.007), (0.007) 0.077, 0.166, 0.126, 0.059 <0.087, 0.177, <0.136, 

<0.069, [<0.117]

16, 17, 18, 

19

22 1057.4 0.015 (0.007), 0.095, 0.032 0.242, 0.121, 0.244, 0.234 0.257, <0.131, 0.339, 

0.266 [<0.248]

26 0.020 (0.005), 0.025, 0.016 0.244, 0.104, 0.220, 0.208 0.264, <0.114, 0.245, 

0.224 [<0.212] 1 ND = not detected (<LOD). The LOD was 0.003 ppm, and the LOQ was 0.01 ppm for each analyte. Values between the LOD 

and LOQ are reported in parenthesis. Quantifiable residues of TCP were converted to parent equivalents using a molecular 

weight conversion factor of 1.3 (MW triclopyr 256.46 ÷ MW TCP 198.44). Combined residues and averages were calculated by 

the study reviewer using the LOQ for all residues reported as <LOQ. 2 Combined residues of triclopyr and TCP. 3 Day 8 milk samples for cows in dose groups 54.8, 109.6, and 538.7 reflecting AM milk sampling only.

4 Samples for cows 20-31 in the dose group 1057.4 were taken on days 14, 22, and 28 days only.

Table B.7.8.1-9. Tissue Residue Data From Ruminant Feeding Study with Triclopyr.

Animal 

Identification #

Collection 

Time

Feeding 

Level 

(ppm)

Residues1 (ppm parent equivalents)

Triclopyr TCP Combined [Avg.]2

Liver

4, 5, 6, 7 Sacrifice 54.8 0.084, 0.094, 0.086, 

0.075

1.28, 2.34, 1.29, 0.854 1.37, 2.43, 1.38, 0.929

[1.53]

8, 9, 10, 11 109.6 0.199, 0.119, 0.137, 

0.080

3.14, 3.43, 2.32, 3.31 3.34, 3.55, 2.46, 3.39

[3.18]

12, 13, 14, 15 538.7 0.562, 0.958, 0.301, 

0.727

9.71, 9.93, 11.43, 9.80 10.27, 10.89, 11.73, 10.53

[10.85]

16, 17, 18, 19 1057.4 1.764, 1.102, 0.903, 

0.795

15.63, 13.24, 16.62, 16.40 17.39, 14.34, 17.52, 17.20

[16.61.]

Kidney

4, 5, 6, 7 Sacrifice 54.8 2.935, 3.713, 2.960, 

2.293

0.943, 1.62, 0.806, 0.478 3.88, 5.33, 3.77, 2.77

[3.94]

8, 9, 10, 11 109.6 5.667, 5.372, 4.902, 

3.481

2.43, 2.97, 1.99, 2.98 8.10, 8.34, 6.89, 6.46

[7.45]
Triclopyr [PC Code 116001]/Dow AgroSciences

MRID# 49741901 Page 13 of 24

Table B.7.8.1-9. Tissue Residue Data From Ruminant Feeding Study with Triclopyr.

Animal 

Identification #

Collection 

Time

Feeding 

Level 

(ppm)

Residues1 (ppm parent equivalents)

Triclopyr TCP Combined [Avg.]2

12, 13, 14, 15 538.7 19.696, 37.819, 14.031, 

26.713

17.3, 16.0, 14.1, 13.4 36.98, 53.82, 28.16, 40.13

[39.77]

16, 17, 18, 19 1057.4 74.654, 31.272, 36.205, 

24.253

30.9, 31.7, 28.8, 24.0 105.51, 62.97, 65.01, 

48.28 [70.44]

Fat, subcutaneous

4, 5, 6, 7 Sacrifice 54.8 0.077, 0.141, 0.028, 

0.036

0.181, 0.377, 0.067, 0.043 0.258, 0.518, 0.095, 0.079

[0.238]

8, 9, 10, 11 109.6 0.223, 0.138, 0.172, 

0.035

0.392, 0.609, 0.408, 0.134 0.615, 0.747, 0.580, 0.169

[0.528]

12, 13, 14, 15 538.7 0.209, 0.712, 0.481, 

0.374

1.33, 2.04, 2.97, 1.64 1.54, 2.75, 3.45, 2.01 

[2.44]

16, 17, 18, 19 1057.4 0.556, 0.819, 0.738, 

0.464

1.64, 3.18, 3.40, 2.18 2.20, 4.00, 4.14, 2.64

[3.25]

Fat, mesenteric

4, 5, 6, 7 Sacrifice 54.8 0.085, 0.145, 0.038, 

0.026

0.158, 0.439, 0.070, 0.028 0.243, 0.584, 0.108, 0.054

[0.247]

8, 9, 10, 11 109.6 0.163, 0.198, 0.134, 

0.014

0.397, 0.876, 0.266, 0.062 0.560, 1.07, 0.400, 0.076

[0.528]

12, 13, 14, 15 538.7 0.268, 1.321, 0.700, 

0.255

1.66, 2.93, 3.34, 0.632 1.92, 4.25, 4.04, 0.887

[2.77]

16, 17, 18, 19 1057.4 1.157, 1.463, 2.213, 

0.472

2.81, 4.55, 8.39, 2.40 3.97, 6.01, 10.61, 2.88

[5.87]

Fat, perirenal

4, 5, 6, 7 Sacrifice 54.8 0.256, 0.399, 0.148, 

0.016

0.350, 0.729, 0.136, 0.025 0.606, 1.13, 0.284, 0.041, 

[0.515]

8, 9, 10, 11 109.6 0.266, 0.517, 0.201, 

0.050

0.521, 1.04, 0.335, 0.096 0.787, 1.56, 0.536, 0.146

[0.757]

12, 13, 14, 15 538.7 0.209, 2.749, 1.482, 

0.275

1.27, 4.57, 6.07, 0.604 1.48, 7.32, 7.55, 0.879

[4.31]

16, 17, 18, 19 1057.4 4.274, 2.742, 4.103, 

0.828

5.58, 6.92, 11.2, 3.39 9.85, 9.66, 15.32, 4.22

[9.76]

Fat, composite3

4, 5, 6, 7 Sacrifice 54.8 0.139, 0.228, 0.071, 

0.026

0.230, 0.516, 0.090, 0.032 0.369, 0.744, 0.161, 0.058

[0.333]

8, 9, 10, 11 109.6 0.217, 0.284, 0.169, 

0.033

0.437, 0.843, 0.336, 0.097 0.654, 1.13, 0.505, 0.130

[0.604]

12, 13, 14, 15 538.7 0.229, 1.594, 0.888, 

0.301

1.419, 3.181, 4.125, 0.959 1.65, 4.77, 5.01, 1.26

[3.17]

16, 17, 18, 19 1057.4 1.996, 1.675, 2.351, 

0.588

3.343, 4.884, 7.669, 2.657 5.34, 6.56, 10.02, 3.25

[6.29]

Muscle

4, 5, 6, 7 Sacrifice 54.8 0.026, 0.038, 0.033, 

0.019

0.045, 0.096, 0.047, 0.021 0.071, 0.134, 0.080, 0.040

[0.081]

8, 9, 10, 11 109.6 0.066, 0.039, 0.050, 

0.027

0.127, 0.140, 0.111, 0.120 0.193, 0.179, 0.161, 0.147

[0.170]

12, 13, 14, 15 538.7 0.188, 0.356, 0.161, 

0.281

0.885, 0.832, 0.840, 0.694 1.07, 1.19, 1.00, 0.975

[1.06]

16, 17, 18, 19 1057.4 0.610, 0.276, 0.291, 

0.233

1.361, 1.018, 1.229, 1.131 1.97, 1.29, 1.52, 1.36

[1.54]

1 Quantifiable residues of TCP were converted to parent equivalents using a molecular weight conversion factor of 1.3 (MW 

triclopyr 256.46 ÷ MW TCP 198.44). Combined residues and averages were calculated by the study reviewer. 2 Combined residues of triclopyr and TCP. 3 Calculated by the petitioner as the average of analyte concentrations in the corresponding samples of individual fats.
Triclopyr [PC Code 116001]/Dow AgroSciences

MRID# 49741901 Page 14 of 24

Table B.7.8.1-10. Summary of Residue Data From Ruminant Feeding Study with Triclopyr.

Matrix Feeding 

Level (ppm)

Residues of Triclopyr and TCP (ppm parent equivalents)1 Tissue 

Residue:Feeding 

Level Ratio2 n Min. Max. Median Mean Std. Dev.

Triclopyr

Whole milk3

(Days 8, 10, 14, 

18, 22, 26, 29)

54.8 28 <0.01 <0.01 0.01 0.01 NA

109.6 28 <0.01 0.038 0.01 0.013 0.007

538.7 28 <0.01 0.138 0.019 0.024 0.024

1057.4 64 0.019 0.517 0.059 0.084 0.077

Skim milk 54.8 8 <0.01 <0.01 0.01 0.01 NA

109.6 8 <0.01 0.015 0.01 0.011 0.002

538.7 8 <0.01 0.029 0.014 0.015 0.006

1057.4 8 <0.01 0.161 0.025 0.044 0.050

Cream 54.8 8 <0.01 <0.01 0.01 0.01 NA

109.6 8 <0.01 <0.01 0.01 0.01 NA

538.7 8 <0.01 0.012 0.01 0.011 0.001

1057.4 8 <0.01 0.095 0.018 0.028 0.028

Liver 54.8 4 0.075 0.094 0.085 0.085 0.008 0.0017

109.6 4 0.080 0.199 0.128 0.134 0.050 0.0018

538.7 4 0.301 0.958 0.645 0.637 0.277 0.0018

1057.4 4 0.795 1.76 1.00 1.14 0.434 0.0017

Kidney 54.8 4 2.29 3.71 2.95 2.98 0.581 0.0677

109.6 4 3.48 5.67 5.14 4.86 0.969 0.0517

538.7 4 14.0 37.8 23.2 24.6 10.2 0.0702

1057.4 4 24.3 74.7 33.7 41.6 22.6 0.0706

Fat, composite4 54.8 4 0.026 0.228 0.105 0.116 0.088 0.0042

109.6 4 0.033 0.284 0.193 0.176 0.106 0.0026

538.7 4 0.229 1.59 0.595 0.753 0.634 0.0030

1057.4 4 0.588 2.35 1.84 1.65 0.761 0.0022

Muscle 54.8 4 0.019 0.038 0.030 0.029 0.008 0.0007

109.6 4 0.027 0.066 0.045 0.046 0.017 0.0006

538.7 4 0.161 0.356 0.235 0.247 0.089 0.0007

1057.4 4 0.233 0.610 0.284 0.353 0.173 0.0006

TCP

Whole milk3

(Days 8, 10, 14, 

18, 22, 26, 29)

54.8 28 <0.01 0.022 0.01 0.012 0.003

109.6 28 0.016 0.039 0.021 0.023 0.006

538.7 28 0.076 0.256 0.152 0.158 0.051

1057.4 64 0.045 0.710 0.328 0.328 0.110

Skim milk 54.8 8 <0.01 0.027 0.010 0.014 0.007

109.6 8 0.019 0.039 0.025 0.027 0.007

538.7 8 0.110 0.300 0.191 0.200 0.073

1057.4 8 0.225 0.536 0.429 0.401 0.105

Cream 54.8 8 <0.01 <0.01 0.01 0.01 NA

109.6 8 <0.01 0.018 0.013 0.013 0.004

538.7 8 0.059 0.166 0.100 0.106 0.046

1057.4 8 0.104 0.244 0.227 0.202 0.057

Liver 54.8 4 0.854 2.34 1.29 1.44 0.632 0.0427

109.6 4 2.32 3.43 3.22 3.05 0.500 0.0313

538.7 4 9.71 11.4 9.86 10.2 0.813 0.0212

1057.4 4 13.2 16.6 16.0 15.5 1.55 0.0157

Kidney 54.8 4 0.478 1.62 0.875 0.962 0.480 0.0296
Triclopyr [PC Code 116001]/Dow AgroSciences

MRID# 49741901 Page 15 of 24

Table B.7.8.1-10. Summary of Residue Data From Ruminant Feeding Study with Triclopyr.

Matrix Feeding 

Level (ppm)

Residues of Triclopyr and TCP (ppm parent equivalents)1 Tissue 

Residue:Feeding 

Level Ratio2 n Min. Max. Median Mean Std. Dev.

109.6 4 1.99 2.98 2.70 2.59 0.476 0.0272

538.7 4 13.4 17.3 15.1 15.2 1.76 0.0321

1057.4 4 24.0 31.7 29.8 28.8 3.43 0.0300

Fat, composite4 54.8 4 0.032 0.516 0.160 0.217 0.216 0.0094

109.6 4 0.097 0.843 0.386 0.428 0.311 0.0077

538.7 4 0.959 4.13 2.30 2.42 1.49 0.0077

1057.4 4 2.66 7.67 4.11 4.64 2.22 0.0073

Muscle 54.8 4 0.021 0.096 0.046 0.052 0.031 0.0018

109.6 4 0.111 0.140 0.123 0.124 0.012 0.0013

538.7 4 0.694 0.885 0.836 0.813 0.083 0.0016

1057.4 4 1.02 1.36 1.18 1.18 0.146 0.0013

Combined triclopyr + TCP

Whole milk3

(Days 8, 10, 14, 

18, 22, 26, 29)

54.8 28 <0.02 <0.032 0.02 0.022 0.003

109.6 28 <0.026 0.065 0.036 0.036 0.010

538.7 28 0.094 0.377 0.177 0.182 0.062

1057.4 64 0.181 0.986 0.412 0.412 0.140

Skim milk 54.8 8 <0.02 <0.037 0.02 0.024 0.007

109.6 8 <0.029 0.049 0.038 0.039 0.007

538.7 8 0.123 0.314 0.210 0.215 0.071

1057.4 8 <0.235 0.615 0.462 0.445 0.131

Cream 54.8 8 <0.02 <0.02 0.02 0.02 NA

109.6 8 <0.02 <0.028 0.023 0.023 0.004

538.7 8 <0.069 0.177 0.110 0.116 0.046

1057.4 8 <0.114 0.339 0.251 0.230 0.074

Liver 54.8 4 0.929 2.43 1.37 1.53 0.639 0.0443

109.6 4 2.46 3.55 3.36 3.18 0.491 0.0324

538.7 4 10.3 11.7 10.7 10.9 0.636 0.0217

1057.4 4 14.3 17.5 17.3 16.6 1.52 0.0166

Kidney 54.8 4 2.77 5.33 3.82 3.94 1.06 0.0973

109.6 4 6.46 8.34 7.49 7.45 0.912 0.0761

538.7 4 28.2 53.8 38.6 39.8 10.6 0.0999

1057.4 4 48.3 106 64.0 70.4 24.5 0.1002

Fat, composite4 54.8 4 0.058 0.744 0.265 0.333 0.303 0.0136

109.6 4 0.130 1.13 0.579 0.604 0.412 0.0103

538.7 4 1.26 5.01 3.21 3.17 1.99 0.0093

1057.4 4 3.25 10.0 5.95 6.29 2.84 0.0095

Muscle 54.8 4 0.040 0.134 0.075 0.081 0.039 0.0024

109.6 4 0.147 0.193 0.170 0.170 0.020 0.0018

538.7 4 0.975 1.19 1.04 1.06 0.095 0.0022

1057.4 4 1.29 1.97 1.44 1.54 0.304 0.0019

1 n = No. of samples. For calculation of median, mean, and standard deviation, the LOQ (0.01 ppm for each analyte) was used 

for residues reported as ND or <LOQ. NA = Not applicable 2 Referred to as the transfer coefficient (TC) or transfer factor (Tf); to be used in the calculation of residues anticipated at the 

dietary burden. The maximum factor for each tissue is bolded. 3 Data for whole milk are summarized for days after residues had reached a plateaus (based on 538.7-ppm dose level). 4 Calculated by the petitioner as the average of analyte concentrations in the corresponding samples of individual fats.
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Figure B.7.8.1-1. Combined Residues of Triclopyr and TCP in Whole Milk as a Function 

of Time. 

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0 5 10 15 20 25 30

Average Combined Residue (ppm)

Study Day

54.8-ppm Dose Group

109.6-ppm Dose Group

538.7-ppm Dose Group

1057.4-ppm Dose Group
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Figure B.7.8.1-2. Linear Regression of Triclopyr and TCP in Whole Milk vs. Dosing Level.
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Figure B.7.8.1-3. Linear Regression of Triclopyr and TCP in Liver vs. Dosing Level.
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Figure B.7.8.1-4. Linear Regression of Triclopyr and TCP in Kidney vs. Dosing Level.
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Figure B.7.8.1-5. Linear Regression of Triclopyr and TCP in Subcutaneous Fat vs. Dosing 

Level.
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Figure B.7.8.1-6. Linear Regression of Triclopyr and TCP in Muscle vs. Dosing Level.
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Depuration Period

Table B.7.8.1-11. Summary of Residues of Triclopyr in Whole Milk and Tissues of Cattle From the 

Depuration Study: 1057.4-ppm Feeding Level.

Matrix Animal ID # Study 

Day

Depuration 

Day

Residues1 (ppm parent equivalents)

Triclopyr TCP Combined [Avg]2

Whole milk 20, 21, 22, 23, 24, 

25, 26, 27, 28, 29, 

30, 31

29 1 0.036, 0.032, 0.017, 

0.014, 0.037, 0.030, 

0.061, 0.080, 0.027, 

0.025, 0.021, 0.027

0.278, 0.289, 0.644, 

0.278, 0.381, 0.184, 

0.393, 0.358, 0.202, 

0.178, 0.279, 0.385

0.314, 0.321, 0.661, 

0.292, 0.418, 0.214, 

0.454, 0.438, 0.229, 

0.203, 0.300, 0.412 

[0.355]

20, 21, 22, 23, 24, 

25, 26, 27, 28, 29, 

30, 31

31 3 ND, ND, ND, ND, 

ND, ND, ND, ND, 

ND, ND, ND, ND

(0.004), (0.004), 

(0.008), (0.005), 

(0.007), (0.006), 

0.016, (0.005), 

(0.004), (0.003), 

(0.006), (0.007)

<0.02, <0.02, <0.02, 

<0.02, <0.02, <0.02, 

<0.026, <0.02, <0.02, 

<0.02, <0.02, <0.02

[<0.02]

23, 24, 25, 26, 27, 

28, 29, 30, 31

33 5 ND, ND, (0.004), 

ND, ND, ND, ND, 

ND, ND

ND, ND, ND, ND, 

ND, ND, ND, ND, 

ND

<0.02, <0.02, <0.02, 

<0.02, <0.02, <0.02, 

<0.02, <0.02, <0.02

[<0.02]

23, 24, 25, 26, 27, 

28, 29, 30, 31

35 7 ND, ND, ND, ND, 

ND, ND, ND, ND, 

ND,

ND, ND, ND, ND, 

ND, ND, ND, ND, 

ND

<0.02, <0.02, <0.02, 

<0.02, <0.02, <0.02, 

<0.02, <0.02, <0.02, 

[<0.02]

26, 27, 28, 29, 30, 

31

38 10 ND, ND, ND, ND, 

ND, ND

ND, ND, ND, ND, 

ND, ND

<0.02, <0.02, <0.02, 

<0.02, <0.02, <0.02

[<0.02]

26, 27, 28, 29, 30, 

31

40 12 ND, ND, ND, ND, 

ND, ND

ND, ND, ND, ND, 

ND, ND

<0.02, <0.02, <0.02, 

<0.02, <0.02, <0.02

[<0.02]

26, 27, 28, 29, 30, 

31

42 14 ND, ND, ND, ND, 

ND, ND

ND, ND, ND, ND, 

ND, ND

<0.02, <0.02, <0.02, 

<0.02, <0.02, <0.02

[<0.02]

29, 30, 31 45 17 ND, ND, ND ND, ND, ND <0.02, <0.02, <0.02

[<0.02]

29, 30, 31 48 20 ND, ND, ND ND, ND, ND <0.02, <0.02, <0.02

[<0.02]

29, 30, 31 49 21 ND, ND, ND ND, ND, ND <0.02, <0.02, <0.02

[<0.02]

Liver 20, 21, 22 31 3 ND, ND, ND 0.163, 0.180, 0.249 <0.173, <0.190, 

<0.259

[<0.207]

23, 24, 25 35 7 ND, ND, ND 0.039, 0.066, 0.032 <0.049, <0.076, 

<0.042 [<0.056]

26, 27, 28 42 14 ND, ND, ND 0.039, 0.054, 0.032 <0.049, <0.064, 

<0.042

[<0.052]

29, 30, 31 49 21 ND, ND, ND 0.028 (0.008), 0.023 <0.038, <0.020, 

<0.033

[<0.031]
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Table B.7.8.1-11. Summary of Residues of Triclopyr in Whole Milk and Tissues of Cattle From the 

Depuration Study: 1057.4-ppm Feeding Level.

Matrix Animal ID # Study 

Day

Depuration 

Day

Residues1 (ppm parent equivalents)

Triclopyr TCP Combined [Avg]2

Kidney 20, 21, 22 31 3 (0.007), (0.005), 

(0.004)

0.181, 0.100, 0.178 <0.191, <0.110, 

<0.188

[<0.163]

23, 24, 25 35 7 (0.004) 0.011 (0.004) 0.017, 0.032, 0.017 <0.027, 0.043, <0.027

[<0.032]

26, 27, 28 42 14 (0.003) ND, (0.004) (0.007), (0.006), 

(0.005)

<0.02, <0.02, <0.02

[<0.02]

29, 30, 31 49 21 ND, ND, ND (0.004), (0.004), 

(0.004)

<0.02, <0.02, <0.02

[<0.02]

Fat, 

subcutaneo

us

20, 21, 22 31 3 0.015, 0.038, 0.031 0.036, 0.083, 0.076 0.051, 0.121, 0.107

[0.093]

23, 24, 25 35 7 0.015, 0.017, (0.004) 0.018, 0.030, ND 0.033, 0.047, <0.02

[<0.033]

26, 27, 28 42 14 0.011, (0.009), 0.015 0.017, 0.017, (0.009) 0.028, 0.027, <0.025

[<0.027]

29, 30, 31 49 21 ND, ND, 0.014 (0.005), ND, 0.023 <0.02, <0.02, 0.037

[<0.026]

Fat, 

mesenteric

20, 21, 22 31 3 0.024, 0.024, (0.006) 0.041, 0.045, 0.027 0.065, 0.069, <0.037

[<0.057]

23, 24, 25 35 7 0.022, 0.018, (0.005) 0.026, 0.022, ND 0.048, 0.040, <0.02

[<0.036]

26, 27, 28 42 14 0.032, (0.009), 0.022 0.032, (0.006), 

(0.009)

0.064, <0.02, <0.032

[<0.039]

29, 30, 31 49 21 0.018, ND, ND 0.022, ND, ND 0.040, <0.02, <0.02

[<0.027]

Fat, 

perirenal

20, 21, 22 31 3 0.013, (0.008), 

(0.006) 

0.032, 0.023, 0.047 0.045, <0.033, <0.057 

[<0.045]

23, 24, 25 35 7 (0.007), 0.012, 

(0.009)

(0.009), 0.018

ND

<0.02, 0.030, <0.02

[<0.023]

26, 27, 28 42 14 0.012, (0.008), 

(0.004)

(0.008), ND, (0.005) <0.022, <0.02, <0.02

[<0.021]

29, 30, 31 49 21 ND, ND, ND ND, ND, ND <0.02, <0.02, <0.02

[<0.02]

Fat, 

composite3

20, 21, 22 31 3 0.017, 0.023, 0.014 0.036, 0.050, 0.050 0.053, 0.073, 0.064

[0.064]

23, 24, 25 35 7 0.015, 0.016, (0.006) 0.018, 0.023, ND 0.033, 0.039, <0.02

[<0.031]

26, 27, 28 42 14 0.018, (0.009), 0.014 0.019, (0.006), 

(0.008) 

0.037, <0.02, <0.024

[<0.027]

29, 30, 31 49 21 (0.006), ND, (0.005) (0.007), ND, (0.006) <0.02, <0.02, <0.02

[<0.02]

Muscle 20, 21, 22 31 3 ND, ND, ND (0.005), (0.005), 

(0.009) 

<0.02, <0.02, <0.02

[<0.02]

23, 24, 25 35 7 ND, (0.003) ND ND, (0.004) ND <0.02, <0.02, <0.02

[<0.02]

26, 27, 28 42 14 (0.003), ND, ND (0.003), ND, ND <0.02, <0.02, <0.02

[<0.02]

29, 30, 31 49 21 ND, ND, ND ND, ND, ND <0.02, <0.02, <0.02

[<0.02] 1 ND = Not detected (<LOD). The LOD was 0.003 ppm, and the LOQ was 0.01 ppm for each analyte. Values between the LOD 

and LOQ are reported in parenthesis. Quantifiable residues of TCP were converted to parent equivalents using a molecular 

weight conversion factor of 1.3 (MW triclopyr 256.46 ÷ MW TCP 198.44). Combined residues and averages were calculated by 

the study reviewer using the LOQ for all residues reported as <LOQ. 2 Combined residues of triclopyr and TCP.
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MRID# 49741901 Page 24 of 24

3 Calculated by the petitioner as the average of analyte concentrations in the corresponding samples of individual fats.

III. CONCLUSIONS

The cattle feeding study is considered to be scientifically acceptable. Combined residues of 

triclopyr and TCP were below the LOQ in all samples of cream and near or below the LOQ in 

whole milk and skim milk (residues ranged <0.02-<0.037 ppm) at the 54.8-ppm dose level. At 

the 109.6- and 538.7-ppm dose levels, combined residues in whole milk plateaued by Study 

Days 6-8; at the 1057.4-ppm dose level, residues of triclopyr plateaued by Day 8, but residues of 

TCP continued to increase through the study. Residues of TCP in milk exceeded those of 

triclopyr at the 109.6-, 538.7-, and 1057.4-ppm dose levels, respectively, by up to 3.2x (average 

1.9x), 18x (average 8.8x), and 15x (average 6.1x). Combined residues of triclopyr and TCP at 

the 109.6-, 538.7-, and 1057.4-ppm dose levels, respectively, were: <0.026-0.065, 0.094-0.377, 

and 0.184-0.602 ppm in whole milk; <0.029-0.049, 0.123-0.314, and <0.235-0.615 ppm in skim 

milk; and <0.02-<0.028, <0.069-0.177, and <0.114-0.339 ppm in cream.

Quantifiable residues triclopyr and TCP were observed in tissues at all dosing levels, with the 

highest residues observed in kidney, then liver, and the lowest residues observed in muscle. 

Ratios of residues in tissues to those in feed were relatively consistent across feeding levels 

except for those in liver, which declined steadily with increasing feeding level. Residues of TCP 

exceeded those of triclopyr in liver (average 15-26x), fat (1.6-4.0x), and muscle (1.7-3.7x) but 

were lower than those of triclopyr in kidney (0.3-0.8x). Combined residues of triclopyr and TCP 

at the 54.8-, 109.6-, 538.7-, and 1057.4-ppm dose levels, respectively, were: 0.929-2.43, 2.46-

3.55, 10.3-11.7, and 14.3-17.5 ppm in liver; 2.77-5.33, 6.46-8.34, 28.2-53.8, and 48.3-106 ppm 

in kidney; 0.058-0.744, 0.130-1.13, 1.26-5.01, and 3.25-10.0 ppm in composite fat (calculated by 

the petitioner as the average of analyte concentrations in the corresponding samples of individual 

fats); and 0.040-0.134, 0.147-0.193, 0.975-1.19, and 1.29-1.97 ppm in muscle.

The depuration study indicated that following removal of the test substance from the diet, residue 

levels decreased in milk and all tissues, with residues decreasing most rapidly in milk and muscle 

and least rapidly in liver. Combined residues of triclopyr and TCP in whole milk and muscle 

decreased to below the LOQ (<0.02 ppm) by Study Day 31 (Depuration Day 3). Combined 

residues were near or below the LOQ in kidney by Study Day 42 (Depuration Day 14) and in fats 

by Study Day 49 (Depuration Day 21). Average combined residues were <0.031 ppm in liver by 

Study Day 49. 

Acceptable methods were used for residue quantitation, and adequate storage stability data have 

been submitted to support sample storage durations and conditions. 

REFERENCES

None.