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General tolerances have been established under 40CFR§180.205(a), and range from 0.01 ppm for 

egg and milk to 210 ppm for Animal feed, nongrass, group 18, hay. Tolerances with regional 

registration have been established under 40CFR§180.205(c) at 0.05 ppm for cassava, pigeon pea 

seed, tanier, tyfon, and true yam, and at 0.1 ppm for taro corm. 

The qualitative nature of paraquat residues in plant commodities is understood based upon 

studies depicting the metabolism of paraquat in carrots and lettuce following preemergence 

treatment and in potatoes and soybeans following desiccant treatment. The residue of concern in 

plants is the parent, paraquat. The qualitative nature of residues in livestock is adequately 

understood based on the combined results of studies conducted with ruminants (goats and cows), 

swine, and poultry. The residue of concern in eggs, milk, and poultry and livestock tissues is 

also parent paraquat.

An adequate spectrophotometric method, Method I of the Pesticide Analytical Manual (PAM) 

Vol. II, is available for enforcing tolerances for residues of paraquat in/on plant commodities. 

For the method, samples are heated at reflux with 0.5 M sulfuric acid and then applied to a cation 

exchange column. Paraquat residues are eluted with saturated ammonium chloride solution. 

Cotton seed samples are first subjected to Soxhlet extraction in hexane, and the hexane extract is 

refluxed with sulfuric acid and then applied to the cation exchange column. An aliquot of the 

column eluate is mixed with 0.2% (w/v) sodium hydrosulfite in 0.3 M sodium hydroxide, which 

reduces paraquat to a free radical. Residues are determined using a variable wavelength 

spectrophotometer, measuring the light absorption of the paraquat free radical. The validated 

limits of quantitation (LOQ) vary from 0.01 ppm up to 0.5 ppm.

PAM Vol. II lists a spectrophotometric method, designated as Method Ia (LOD = 0.005 ppm), as 

available for the enforcement of tolerances for paraquat residues in animal commodities. In 

addition, an adequate HPLC/UV method is available for the enforcement of tolerances for 

paraquat residues in livestock tissues and eggs (RAM 004/04, MRID 43226902; this method has 

not yet been published in PAM Vol. II); the reported LOQ is 0.005 ppm for livestock tissues and 

eggs. 

Adequate storage stability data are available indicating that residues of paraquat are stable under 

frozen storage conditions in/on representative examples of the following crop groups for at least 

18 months: non-oily grains, including corn grain; leafy vegetables, including corn forage, fodder, 

and silage; root crops; and fruits or fruiting vegetables. In addition, residues of paraquat have 

been found to be stable in/on cantaloupe stored frozen for up to 3.7 months, cucumber stored 

frozen for up to 4.0 months, summer squash stored frozen for up to 2.6 months, ginger root 

stored frozen for up to 2.4 months, and okra pod stored frozen for up to 7.3 months. It was

previously concluded that storage stability data for corn grain may be translated to oilseeds. 

The available ruminant and poultry feeding study data indicate that the tolerance 

recommendations of the RED Document (8/97) are appropriate, and that increased tolerances for 

livestock commodities are not needed to support the requested new uses. 
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The residue chemistry chapter of the RED (D217262, D. Miller, 7/28/95) concluded that no 

plantback restrictions or field rotational crop studies are required for paraquat based on an 

acceptable confined rotational crop study. 

Regulatory Recommendations and Residue Chemistry Deficiencies

Pending the submission of a revised Section F, there are no residue chemistry issues that would 

preclude granting a registration for paraquat on perennial tropical and sub-tropical fruit trees; or 

establishment of tolerances for residues of paraquat, as follows: 

Tolerances to be established under 40 CFR§180.205(a):

Atemoya ...............................................................................................................................0.05 ppm

Biriba....................................................................................................................................0.05 ppm

Canistel.................................................................................................................................0.05 ppm

Cherimoya ............................................................................................................................0.05 ppm

Custard Apple.......................................................................................................................0.05 ppm

Feijoa....................................................................................................................................0.05 ppm

Ilama.....................................................................................................................................0.05 ppm

Jaboticaba.............................................................................................................................0.05 ppm

Longan..................................................................................................................................0.05 ppm

Lychee ..................................................................................................................................0.05 ppm

Mango ..................................................................................................................................0.05 ppm

Pawpaw ................................................................................................................................0.05 ppm

Pomegranate .........................................................................................................................0.05 ppm

Pulasan .................................................................................................................................0.05 ppm

Rambutan..............................................................................................................................0.05 ppm

Sapodilla...............................................................................................................................0.05 ppm

Sapote, black ........................................................................................................................0.05 ppm

Sapote, mamey .....................................................................................................................0.05 ppm

Sapote, white ........................................................................................................................0.05 ppm

Soursop.................................................................................................................................0.05 ppm

Spanish lime .........................................................................................................................0.05 ppm

Star apple..............................................................................................................................0.05 ppm

Starfruit.................................................................................................................................0.05 ppm

Sugar apple...........................................................................................................................0.05 ppm

Wax jambu ...........................................................................................................................0.05 ppm

860.1550 Proposed Tolerances

The proposed tolerances should be revised to reflect the correct commodity definitions as 

specified in Table 11.

860.1200 Directions for Use

The petitioner needs to propose maximum seasonal rates for perennial tropical and subtropical fruit trees. The proposed maximum seasonal rate must reflect the total of all 

types of applications. The available data will support the following maximum seasonal 

rates: 3.76 lb ai/A.
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Background

IR-4 has submitted a petition (PP#0E7748) to support uses on perennial tropical and sub-tropical 

fruit trees. The PC Code, nomenclature, and chemical structure of paraquat are listed below in 

Table 1. The physicochemical properties of paraquat are listed in Table 2. 

Table 1. Nomenclature of Paraquat Dichloride.

Compound

N

+

N

+

H C3

CH3

Cl

2

Common name Paraquat dichloride

IUPAC name 1,1’-dimethyl-4,4’-bypyridinium dichloride

CAS name 1,1’-dimethyl-4,4’-bypyridinium dichloride

CAS registry number 1910-42-5

(4685-14-7 for the cation)

End-use product (EP) 2.0 lb paraquat cation/gal SC (Gramoxone Inteon; EPA Reg. No. 100-1217)

Table 2. Physicochemical Properties of Technical Grade Paraquat Dichloride.

Parameter Value Reference

Melting point/range decomposes at ca. 340 °C Product Chemistry Chapter 

of the Paraquat Dichloride 

Update, 10/10/91

pH 6.4 at 20 °C

Density 1.5 g/cm3at 25 °C

Water solubility (20 °C) freely soluble in water:

618-620 g/L at pH 5.2, 7.2, and 9.2 

Solvent solubility (20 °C) <0.1 g/L in acetone, dichloromethane, 

toluene, ethyl acetate, and hexane;

143 g/L in methanol

Vapor pressure <<10-8kPa at 25 °C

Octanol/water partition coefficient, 

Log(KOW)

log KOW = -4.5 at 20 °C

Dissociation constant, pKa 0.95 (pure active ingredient) Product Chemistry Chapter 

of the Paraquat 

Reregistration Standard, 

11/25/85

UV/visible absorption spectrum Not available
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860.1200 Directions for Use

IR-4 has submitted copies of the registered label for a 2.0 lb paraquat cation/gal soluble 

concentrate (SC) formulation of paraquat dichloride (Gramoxone Inteon; EPA Reg. No. 100-

1217). The product proposed for amended use is presented in Table 3 below, and the proposed 

new use directions are presented in Table 4. 

Table 3. Summary of Proposed End-Use Product.

Trade Name Reg. 

No.

ai (% of 

formulation)

Formulation TypeTarget Crops Target Pests Label Date

Gramoxone 

Inteon

100-

1217

2 lb 

paraquat 

cation/gal

SC A variety of 

food/feed crops .

A variety of small 

annual weeds 

(broadleaves and 

grasses), and 

perennial weeds; also 

used as a harvest aid 

and desiccant.

Proposed 

supplemental label 

+ registered label

Table 4. Summary of Proposed Directions for Use of Gramoxone Inteon (100-1217).

Application Timing Application 

Rate 

(lb ai/A)

Max. No. 

Applic. 

per 

Season

RTI1

(days)

Max. 

Seasonal 

Applic. Rate

(lb ai/A)

PHI

(days)

Use Directions and other 

Limitations

Perennial Tropical and Sub-tropical Fruit Trees (atemoya, biriba, black sapote, canistel, cherimoya, custard apple, 

feijoa, ilama, jaboticaba, longan, lychee, mamey sapote, mango, pawpaw, pomegranate, pulasan, rambutan,

sapodilla, soursop, Spanish lime, star apple, starfruit, sugar apple, wax jambu, white sapote)

Postemergence 

directed spray 

0.63-0.94 4 28 NS 14 Applications are to be 

directed between rows 

and made using ground 

equipment in a minimum 

of 10 gal/A. May be tank 

mixed with other 

postemergence directed 

herbicides. Do not graze 

treated area. Do not feed 

cover crops grown in 

treated areas to livestock.

1 RTI = Retreatment interval
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The supplemental label specifies that preemergence applications must be made prior to crop 

emergence and that postemergence applications (other than harvest aid or defoliation 

applications) should be made without contact to the crop. Intentional or accidental contact 

(including drift) with the crop may result in severe damage or loss of the crop.

The current product label prohibits application through any type of irrigation system. Preplant 

and postemergence applications are not to be made to soils lacking clay minerals (i.e., peat, 

muck, pure sand, and artificial planting media), and applications should always be made with 

either a nonionic surfactant or crop oil concentrate. The product may be tank mixed with 

photosynthetic inhibitor (PSI) herbicides at the use rates, limitations, etc. specified on the 

respective labels. All rotational crops may be planted immediately after the last application. 

Conclusions. The proposed use directions are adequate to allow evaluation of the available 

residue data relative to the proposed use. 

860.1300 Nature of the Residue - Plants

The residue chemistry chapter of the RED (D217262, D. Miller, 7/28/95) concluded that, for the 

purposes of reregistration and risk assessment, the qualitative nature of the residue in plants is 

adequately understood based on studies depicting the metabolism of paraquat in carrots and 

lettuce following preemergence treatment and in potatoes and soybeans following desiccant 

treatment. The residue of concern in plants is parent paraquat.

860.1300 Nature of the Residue - Livestock

The residue chemistry chapter of the RED (D217262, D. Miller, 7/28/95) concluded that for 

purposes of reregistration and risk assessment, the qualitative nature of the residue in animals is 

adequately understood based on the combined results of studies conducted with ruminants (goats 

and cows), swine, and poultry. The residue of concern in eggs, milk, and poultry and livestock 

tissues is parent paraquat.

860.1340 Residue Analytical Methods

Plant commodity method

PAM Vol. II lists a spectrophotometric method, designated as Method I (LOD = 0.01-0.06 ppm), 

as available for the enforcement of tolerances in plant commodities. Several modifications of 

Method I have been developed for analysis of specific crops, and these modified methods have 

been used for data collection. 

The RED Document (EPA 738-F-96-018, 8/97) reported that radiovalidation data had been 

provided for Method 1B of the enforcement method using radiolabeled samples. The Agency 

tentatively concluded that Method 1B adequately recovers paraquat cation residues from samples 

of potatoes and soybeans treated with [14C]paraquat. At the time of the RED document, the 

registrant had recently submitted representative spectra and other supporting raw data from the 

radiovalidation study (MRID 43954002). It was concluded that, upon the Agency’s review of 
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this additional information, the requirements for residue analytical methods for plant 

commodities would be considered fulfilled for reregistration purposes. HED has not conducted a 

formal review of the data. A preliminary review has been conducted, however, and the data are 

considered to be adequate for the purposes of these tolerance petitions.

Conclusions. The existing spectrophotometric method (Method I of PAM Vol. II) is adequate for 

collecting data on residues of paraquat in/on plant commodities. The method is adequate for 

tolerance enforcement purposes for these commodities.

Animal commodity method

PAM Vol. II lists a spectrophotometric method, designated as Method Ia (LOD = 0.005 ppm), as 

being available for the enforcement of tolerances in animal commodities. The registrant has 

submitted descriptions and adequate independent laboratory validation data for a highperformance liquid chromatography method (HPLC; designated as Method 4B) to determine 

paraquat residues in animal tissues and eggs. The method has been validated by the Analytical 

Chemistry Branch (ACB). The registrant was requested to make minor changes in the method 

write-up. A revised version of the method has been submitted (RAM 004/04; MRID 43226902)

and is now available for enforcement purposes. The reported LOQ is 0.005 ppm for livestock 

tissues and eggs.

860.1360 Multiresidue Methods

The FDA PESTDATA database (dated 11/01) does not have an entry for paraquat. The residue 

chemistry chapter of the RED (D217262, D. Miller, 7/28/95) concluded that the existing FDA 

multiresidue methods are not likely to recover residues of paraquat because of its ionic nature.

860.1380 Storage Stability

This guideline is not relevant to the current petition.

860.1400 Water, Fish, and Irrigated Crops

This guideline is not relevant to the current petition.

860.1460 Food Handling

This guideline is not relevant to the current petition.

860.1480 Meat, Milk, Poultry, and Eggs

This guideline is not relevant to the current petition.
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860.1500 Crop Field Trials

No residue field trial data have been submitted for this petition.

The following was taken from the minutes of the 10/1/2008 ChemSAC meeting.

3. Paraquat on Tropical Fruits (IR-4 via M. Doherty):

IR-4 is requesting that EPA allow tolerances and registrations on all perennial tropical fruit crops 

based on surrogate data and current registrations. Specifically, IR-4 requests 0.05 ppm tolerances 

and registrations for the following perennial tropical and semi-tropical fruit trees: sugar apple, 

cherimoya, atemoya, custard apple, ilama, soursop, birba, lychee, longan, Spanish lime, 

rambutan, pulasan, star apple, black sapote, mango, sapodilla, canistel, mamey sapote, feijoa, 

jaboticaba, wax jambu, starfruit (carambola), pawpaw, pomegranate, and white sapote. 

The proposed use pattern for the perennial tropical fruit crops will be the same as for the 

following currently labeled perennial crops: avocado, acerola, banana, papaya, guava, coffee, 

tree nuts, fig, citrus fruit, pome fruit, olive, persimmon, and stone fruit (Gramoxone label), which 

all have a tolerance of 0.05 ppm. 

Passionfruit, a tropical fruit crop, is an exception with a tolerance of 0.2 ppm. Passionfruit 

differs from the rest in that it is a vine which drops ripe fruit to the ground; much of the fruit is 

harvested by picking it up off the ground. 

The ChemSAC had no objection to the proposal. 

860.1520 Processed Food and Feed

This guideline is not relevant to the current petition.
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860.1650 Submittal of Analytical Reference Standards

The registrant must submit paraquat dichloride analytical reference standards when required to:

Theresa M. Cole

US EPA National Pesticide Standard Repository

Environmental Science Center

701 Mapes Road

Fort Meade, MD 20755-5350

Cole.Theresa@epa.gov

(410) 305-2907

An analytical standard for paraquat dichloride is currently available in the National Pesticide 

Standards Repository (Charles Stafford, electronic communication, 3/22/2011). 

860.1850/1900 Confined/Field Accumulation in Rotational Crops

This guideline is not relevant to the current petition.

860.1550 Proposed Tolerances

HED previously determined that the residue of concern for paraquat in/on plant and animal 

commodities is paraquat per se (D217262, D. Miller, 7/28/95). Because there are currently no 

registered products containing paraquat dimethyl sulfate, the tolerance expression listed under 40 

CFR§180.205(a) and §180.205(c) should be revised to remove reference to the bis(methyl 

sulfate) salt of paraquat. 

In 2009 HED issued guidance on tolerance expressions (S. Knizner, 2009). We now conclude 

the tolerance expression should be as follows: Tolerances are established for residues of 

paraquat, 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 

paraquat dichloride and calculated as the paraquat cation.

A summary of the recommended tolerances for the current petition is given in Table 6. 

The proposed tolerances should be revised to reflect the correct commodity definitions as 

specified in Table 6.
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Table 6. Tolerance Summary for Paraquat Dichloride

Commodity Tolerance (ppm) Comments (correct commodity 

definition) Established Proposed Recommended

Tolerances to be established under 40 CFR '180.205(a):

Atemoya -- 0.05 0.05

Biriba -- 0.05 0.05

Black sapote -- 0.05 0.05 Sapote, black

Canistel -- 0.05 0.05

Cherimoya -- 0.05 0.05

Custard apple -- 0.05 0.05

Feijoa -- 0.05 0.05

Ilama -- 0.05 0.05

Jaboticaba -- 0.05 0.05

Longan -- 0.05 0.05

Lychee -- 0.05 0.05

Mamey sapote -- 0.05 0.05 Sapote, mamey

Mango -- 0.05 0.05

Pawpaw -- 0.05 0.05

Pomegranate -- 0.05 0.05

Pulasan -- 0.05 0.05

Rambutan -- 0.05 0.05

Sapodilla -- 0.05 0.05

Soursop -- 0.05 0.05

Spanish lime -- 0.05 0.05

Star apple -- 0.05 0.05

Starfruit -- 0.05 0.05

Sugar apple -- 0.05 0.05

Wax jambu -- 0.05 0.05

White sapote -- 0.05 0.05 Sapote, white

Codex/International MRL Harmonization

The Codex Alimentarius Commission has established several maximum residue limits (MRLs) 

for paraquat residues in various commodities. The Codex and U.S. tolerances are in harmony 

with respect to MRL/tolerance expression; both regulate the parent paraquat cation only. The 

Agency cannot harmonize with the Codex MRL of 0.01 ppm since some commodities which the 

proposed US tolerance is translated from contained residues of > 0.01 ppm. A comparison of the 

Codex MRLs and the proposed U.S. tolerances is presented in the following table. To the extent

possible, U.S. tolerances have been harmonized with Codex, Canadian, and Mexican MRLs. 

No Canadian or Mexican MRLs have been established for paraquat. Registered food/feed uses 

of paraquat exist in Canada. These uses presumably fall under the PMRA General MRL of 0.1 

mg/kg. Regulation B.15.002(1) of the Canadian Food and Drugs Regulations (FDR) establishes 

0.1 ppm as the General Maximum Residue Limit. This regulation states that a food is adulterated
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if it contains residues of a pesticide at a level greater than 0.1 ppm unless a specific MRL has 

been established in Table II, Division 15 of the FDR.
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International Residue Limits 

Paraquat Dichloride (060601; 3/9/2011)

Summary of US and International Tolerances and Maximum Residue Limits 

Residue Definition:

US Canada Mexico2 Codex3

40 CFR 180.205:

Plant: paraquat (1,1′-dimethyl-4,4′-

bipyridinium-ion) derived from application of 

either the bis(methyl sulfate) or the dichloride 

salt (both calculated as the cation) 

None Paraquat cation

Commodity1 Tolerance (ppm) /Maximum Residue Limit (mg/kg)

US Canada Mexico2 Codex

Atemoya 0.05 0.01 (*) Assorted tropical and 

subtropical fruits-inedible peel 

(Includes all except-Atemoya, 

Biriba, Jaboticaba, Starfruit 

and Wax Jambu).

Biriba 0.05

Black sapote 0.05

Canistel 0.05

Cherimoya 0.05

Custard apple 0.05

Feijoa 0.05

Ilama 0.05

Jaboticaba 0.05

Longan 0.05

Lychee 0.05

Mamey sapote 0.05

Mango 0.05

Pawpaw 0.05

Pomegranate 0.05

Pulasan 0.05

Rambutan 0.05

Sapodilla 0.05

Soursop 0.05

Spanish lime 0.05

Star apple 0.05

Starfruit 0.05

Sugar apple 0.05

Wax jambu 0.05

White sapote 0.05

Completed: M. Negussie; 3/10/2011

1

Includes only commodities of interest for this action. Tolerance values should be the HED recommendations and 

not those proposed by the applicant.

2 Mexico adopts US tolerances and/or Codex MRLs for its export purposes.

3 * = absent at the limit of quantitation; Po = postharvest treatment, such as treatment of stored grains. PoP = 

processed postharvest treated commodity, such as processing of treated stored wheat. (fat) = to be measured on the 

fat portion of the sample. MRLs indicated as proposed have not be
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References

Paraquat Dichloride. (061601) Product Chemistry Chapter and Residue Chemistry Chapter for

the Reregistration Eligibility Document: CBRS No. 15906; Rereg. Case No. 0262, D217262,

D. Miller, 7/28/95