UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

MEMORANDUM 

Date: October 31, 2013 

OFFICE OF 

CHEMICAL SAFETY AND 

POLLUTION PREVENTION 

SUBJECT: Proquinazid: Human Health Risk Assessment for the Tolerance on Imported 

Grapes 

PC Code: 044502 

Decision No.: 459391 

Petition No.: 1E7972 

Risk Assessment Type: Single Chemical 

TXRNo.: NA 

MRIDNo.: NA 

DP Barcode: 399842 

Registration No.: None 

Regulatory Action: Tolerance, No U.S. 

Registration 

Case No.: NA 

CAS No.: 189278-12-4 

40 CFR: 180.TBD 

FROM: Jessica Kidwell, Risk Assessor 

Marquea King, PhD, Toxicolo~·~~7J. 

Thurston Morton, Chemist 

Susan Hummel, Chemist 

RAB IV, Health Effects Division (HED) (7509P) 

THROUGH: Elissa Reaves, Branch Chief 

RAB IV, HED (7509P) 

Ray Kent, Chemist c--:? /\ 

Immediate Office, HED (7509P) ·- ~ \ 

Chris

RAB 

t

III, 

ine 

HE

Olin

D 

ger, 

(7509P) 

Branch Chief 

v~r--<- ~ / ~ ~ 

TO: Tony Kish and Rosemary Kearns, PM22 

Cynthia Giles-Parker, Branch Chief 

Fungicide Branch, Registration Division (7505P) 
Proquinazid Human Health Risk Assessment DP No. 399842 

1.0 Executive Summary ........................................................................................................... 4 

2.0 HED Recommendations .................................................................................................... 5 

2.1 

2.2 

2.2.1 

2.2.2 

2.2.3 

Data Deficiencies ............................................................................................................ 6 

Tolerance Considerations .............................................................................................. 6 

Enforcement Analytical Method ............................................................................... 6 

Recommended Tolerances ................................................................ ......................... 6 

Revisions to Petitioned-For Tolerances .................................................................... 7 

2.2.4 International Harmonization ..................................................................................... 7 

2.3 Label Recommendations ................................................................................................ 7 

3.0 Introduction ........................................................................................................................ 7 

3.1 Chemical Identity ........................................................................................................... 7 

3.2 Physical/Chemical Characteristics ............................................................................... 8 

3.3 Pesticide Use Pattern ............................................................... ....................................... 8 

3.4 Anticipated Exposure Pathways ................................................................................... 9 

3.5 Consideration of Environmental Justice ...................................................................... 9 

4.0 Hazard Characterization and Dose-Response Assessment ............................................ 9 

4.1 Toxicology Studies Available for Analysis ................................................................... 9 

4.2 Absorption, Distribution, Metabolism, & Elimination (ADME) ............................. 1 0 

4.2.1 Dermal Absorption ................................................................................................... 10 

4.3 Toxicological Effects .................................................................................................... 11 

4.4 FQPA Safety Factor for Infants and Children .......................................................... 12 

4.4.1 Completeness of the Toxicology Database .............................................................. 12 

4.4.2 Evidence of Neurotoxicity ........................................................................................ 12 

4.4.3 Evidence of Sensitivity/Susceptibility in the Developing or Young Animal.. ...... 13 

4.4.4 Residual Uncertainty in the Exposure Database ................................................... 13 

4.5 Toxicity Endpoint and Point of Departure (POD) Selections .................................. 13 

4.5.1 Dose-Response Assessment ...................................................................................... 13 

4.5.2 Recommendation for Combining Routes of Exposures for Risk Assessment ..... 14 

4.5.3 Cancer Classification and Risk Assessment Recommendation ............................ 14 

4.5.4 Summary of Points of Departure and Toxicity Endpoints Used in Human Risk 

Assessment ............................................................................................................................... 16 

5.0 Dietary Exposure and Risk Assessment.. ....................................................................... 17 

5.1 Metabolite/Degradate Residue Profile ....................................................................... 17 

5.1.1 Summary of Plant and Animal Metabolism Studies ............................................. 17 

5.1.2 Summary of Environmental Degradation .............................................................. 17 

5.1.3 Comparison of Metabolic Pathways ....................................................................... 17 

5.1.4 Residues of Concern Summary and Rationale ...................................................... 17 

5.2 Food Residue Profile .................................................................................................... 18 

5.3 Water Residue Profile .................................................................................................. 19 

5.4 Dietary Risk Assessment .............................................................................................. 19 

5.4.1 Description of Residue Data Used in Dietary Assessment.. .................................. 19 

5.4.2 Percent Crop Treated Used in Dietary Assessment .............................................. 19 

5.4.3 Acute Dietary Risk Assessment.. ............................................................................. 19 

5.4.4 Chronic Dietary Risk Assessment ........................................................................... 20 

5.4.5 Cancer Dietary Risk Assessment.. ........................................................................... 20 

5.4.6 Summary Table ......................................................................................................... 20 

Page 2 of49 
Proquinazid Human Health Risk Assessment DP No. 399842

Page 3 of 49

6.0 Residential (Non-Occupational) Exposure/Risk Characterization ............................. 20

7.0 Aggregate Exposure/Risk Characterization.................................................................. 20

8.0 Cumulative Exposure/Risk Characterization ............................................................... 21

9.0 Occupational Exposure/Risk Characterization ............................................................ 21

10.0 References......................................................................................................................... 21

Appendix A. Toxicology Profile and Executive Summaries .................................................. 22

A.1 Toxicology Data Requirements................................................................................... 22

A.2 Toxicity Profiles............................................................................................................ 23

A.3 Hazard Identification and Endpoint Selection .......................................................... 36

A.4 Executive Summaries................................................................................................... 37

Appendix B. Metabolism Summary Table ............................................................................... 48

Appendix C. Physicochemical Properties Table ...................................................................... 49
Proquinazid Human Health Risk Assessment DP No. 399842

Page 4 of 49

1.0 Executive Summary

Proquinazid is a new fungicide used to control powdery mildew on grapes. It acts primarily by 

preventing infection through disruption of secondary appressorial formation (parasitic fungi 

penetration into host tissues). The formulated product is referred to as Proquinazid 200 g/L EC, 

produced by DuPont Agricultural Products. This is the first food use for this chemical. 

Tolerances of 0.5 ppm for proquinazid residues on grapes and 1.0 ppm for proquinazid residues 

on raisins are proposed, but no registration is being proposed in the United States (U.S). Since 

the request is for an import tolerance only and there are no U.S. registrations being proposed, 

only dietary (food only) exposures are assessed. Occupational and residential risk assessments 

are not required. The present action is being conducted as a joint review with Health Canada’s 

Pesticide Management Regulatory Authority (PMRA). This risk assessment was reviewed by the 

Risk Assessment Review Committee (RARC) on July 10, 2013.

The database of experimental toxicology studies available for proquinazid provides a robust 

characterization of the hazard potential of this pesticide. There are no outstanding studies 

according to Part 158 data requirements for the current request for an import tolerance on grapes. 

However, HED has determined that a comparative thyroid assay in rats is required to assess the 

potential impact of proquinazid exposure on thyroid function in the young. The agency is 

requiring these data given the pivotal role of thyroid hormones in brain development.

The main target tissues for proquinazid are the thyroid and liver, with effects seen in several 

species. The lowest effect levels following exposure to proquinazid are based primarily on 

thyroid and liver effects in rats, liver toxicity in mice, and body weight decrements in dogs. 

Proquinazid was classified as “Suggestive Evidence of Carcinogenic Potential”. This 

determination was based on the treatment-related liver tumors observed in female rats. The 

thyroid follicular cell tumors observed in male rats and the cholangiocarcinomas observed in 

female rats were supported by mode of action data. No treatment-related tumors were observed 

in male or female mice. There is no mutagenicity concern from the in vivo or in vitro genetic 

toxicity assays. Proquinazid has no significant acute toxicity via the oral, dermal, or inhalation 

routes of exposure. It is not an eye or skin irritant and does not cause skin sensitization. Based on 

the results of a 28-day dermal study in rats (as well as the dermal LD50 study), proquinazid is 

poorly absorbed through the skin. No evidence of increased quantitative or qualitative 

susceptibility was seen in the proquinazid hazard database following in utero exposure with rats 

or rabbits in the prenatal developmental studies or in young rats in the 2–generation reproduction 

study. Decreased motor activity in both sexes was seen following acute oral exposure and no 

neurotoxic effects were seen in the subchronic study. 

Based on the current petition for an import tolerance on grapes, exposure is expected only from 

food through the oral route of exposure. Therefore, endpoints for acute and chronic dietary risk 

assessments only were selected at this time. The endpoint chosen for acute dietary exposure for 

the general population was from the acute neurotoxicity study in rats and was based on decreased 

motor activity. An acute dietary endpoint was not selected which was specific for Females 13-49 

years old since no developmental effects that could be attributed to a single exposure were 

identified in the proquinazid database. The endpoint chosen for chronic dietary exposure was 

from the chronic toxicity/carcinogenicity study in the rat and was based on a dose-related 
Proquinazid Human Health Risk Assessment DP No. 399842

Page 5 of 49

increase in non-neoplastic liver lesions and changes in the thyroid hormones and thyroid

pathology. Quantification of risk using a non-linear approach (i.e., reference dose (RfD)) will 

adequately protect for all chronic toxicity, including carcinogenicity, that could result from 

exposure to proquinazid. 

The FQPA Safety Factor (SF) was retained at 10X as a database uncertainty factor due to lack of 

a comparative thyroid assay. The objective of this study is to evaluate the potential for a 

chemical to alter thyroid homeostasis via reduction of circulating thyroid hormones because it is 

known that adverse effects on the thyroid affect development, especially of the nervous system. 

Effects on the thyroid (manifested as changes in hormones, weight and histopathology) 

following proquinazid exposure were consistently observed in adult animals (rats) following 

subchronic and chronic exposures. There is, however, no data regarding the potential effects of 

proquinazid on thyroid homeostasis in infants and children. This lack of characterization in the 

young creates uncertainty with regards to potential life stage sensitivities due to exposure to 

proquinazid, and raises the Agency’s level of concern. 

The acute reference dose (RfD) is derived from a Point of Departure (POD) of 50 mg/kg/day 

based on decreased motor activity at 100 mg/kg/day and an uncertainty factor of 1000, which 

includes 10x for interspecies extrapolation, 10x for intraspecies variability, and 10x database 

uncertainty factor. The chronic RfD is derived from a POD of 1.2 mg/kg/day based on liver and 

thyroid toxicity and an uncertainty factor of 300, which includes 3X for interspecies 

extrapolation, 10x intraspecies variation, and 10X database uncertainty factor. Since the POD for 

deriving the chronic RfD is based on thyroid toxicity, the 3X toxicodynamics part of the 10X 

interspecies extrapolation factor can be removed because of several important quantitative 

dynamic differences between rats and humans with respect to thyroid function. A reduction in 

the 10X interspecies extrapolation cannot be made for the acute dietary risk since the endpoint of 

concern is neurotoxicity.

Acute and chronic dietary analyses were performed using conservative assumptions (i.e., use of 

tolerance level residues and 100% crop treated). There is no drinking water exposure associated 

with the establishment of an import tolerance; therefore, the acute and chronic dietary exposure 

and risk assessments include food residues only. The acute dietary exposure estimates were less 

than HED’s level of concern (≤100% acute Population Adjusted Dose (PAD)) for the general 

U.S. population (3.8% aPAD) and all population sub-groups. The most highly exposed 

population subgroup was Children 1-2 years old with an estimated risk of 18% aPAD at the 95th

percentile. The resulting chronic exposure estimates were less than HED’s level of concern 

(≤100% chronic PAD) for general U.S. population (8.1% cPAD) and all population sub-groups. 

The most highly exposed population subgroup was Children 1-2 years old with an estimated risk 

of 47% cPAD. As noted above, quantification of risk using a non-linear approach (i.e., RfD) will 

adequately account for all chronic toxicity, including carcinogenicity, that could result from 

exposure to proquinazid.

2.0 HED Recommendations

HED concludes that there are no risk issues that would preclude establishing tolerances for the

residues of proquinazid, including its metabolites and degradates, in or on grapes and raisins. 
Proquinazid Human Health Risk Assessment DP No. 399842

Page 6 of 49

Additional data are needed as outlined in section 2.1 below. Specific tolerance recommendations 

are discussed in section 2.2.

2.1 Data Deficiencies

2.1.1 Toxicity Studies

There are no outstanding studies according to Part 158 data requirements for the current request 

for an import tolerance on grapes; however, HED has determined that a comparative thyroid 

assay in rats is required to generate specific data on the thyroid hormone levels to protect the 

developing nervous system from thyroid hormone disrupting chemicals. In the absence of this 

data, the 10X FQPA database uncertainty factor has been retained in this risk assessment for the 

uncertainty associated with the potential for enhanced sensitivity of the developing organism to 

prenatal or postnatal thyroid toxicity. This uncertainty may be addressed by submission of a 

comparative thyroid assay or a proposal describing an alternative approach that adequately 

addresses the issue of disruption of thyroid hormone homeostasis during development.

2.1.2. Residue Chemistry

There are no residue chemistry issues which would preclude setting the recommended 

tolerances.

2.2 Tolerance Considerations

2.2.1 Enforcement Analytical Method

An adequate analytical method is available to enforce the proposed tolerances for residues of 

proquinazid on grape commodities. The gas chromatography (GC) with electron capture 

detection (ECD) and GC with mass spectrometry (MS) for confirmation method AMR 4943-98

has been adequately validated and has undergone a successful independent laboratory validation

(ILV). It is considered adequately radiovalidated and has been reviewed by the Agency for 

appropriateness as an enforcement method. 

The limit of quantitation (LOQ) was reported as 0.01 ppm in grapes. The LOD was estimated to 

be ≤0.001 ppm (grape).

Proquinazid is completely recovered using the FDA PAM I multiresidue protocol E using 

GC/Electron Capture Detection (ECD), not recovered using protocol D, without Florisil cleanup, 

and variably recovered by protocol F. 

2.2.2 Recommended Tolerances

Currently there are no tolerances established for residues of proquinazid. Based on the HED 

Interim Guidance on Tolerance Expressions (Knizner, S., 05/27/2009), the following tolerance 

expression is recommended. 
Proquinazid Human Health Risk Assessment DP No. 399842

Page 7 of 49

Tolerances are established for residues of the fungicide, proquinazid, 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 

proquinazid [6-iodo-2-propoxy-3-propyl-4(3H)-quinazolinone] in or on the commodity.

Table 2.2.2. Tolerance Summary for Proquinazid. § 180.xxx

Commodity Current/Proposed 

Tolerance (ppm)

Recommended 

Tolerance (ppm)

Comments; Correct Commodity 

Definition

Grape 0.5 0.50

Raisin 1.0 1.0 Grape, raisin

2.2.3 Revisions to Petitioned-For Tolerances

The Agency is recommending that tolerances be set for the commodities requested by the 

petitioner at the levels requested, with the change in the commodity definition for raisins as 

specified in Table 2.2.2 above. The change in the commodity definition is recommended to be 

consistent with Agency naming-conventions for commodities and crop groups. No changes are 

recommended for the proposed tolerance levels, but the grape tolerance is changed to 0.50 to 

correct the number of significant figures.

2.2.4 International Harmonization

CODEX has not established any maximum residue limits (MRLs) for proquinazid. Canada has 

not established MRLs for proquinazid, but is concurrently planning to establish an MRL on 

grape at 0.50 ppm, and raisin at 1.0 ppm. Therefore, there are no issues related to international 

harmonization associated with this petition. 

2.3 Label Recommendations

Since this action is for tolerances without a U.S. registration, a discussion of labels is not 

pertinent to this risk assessment. 

3.0 Introduction

3.1 Chemical Identity

The structure and nomenclature for proquinazid are provided below in Table 3.1. 
Proquinazid Human Health Risk Assessment DP No. 399842

Page 8 of 49

Table 3.1. Proquinazid Nomenclature.

Compound

N

N

O

I

O

CH3

CH3

Common name Proquinazid

Company experimental name DPX-KQ926

IUPAC name 6-Iodo-2-propoxy-3-propyl-3H-quinazolin-4-one

CAS name 6-Iodo-2-propoxy-3-propyl-4(3H)-quinazolinone

CAS registry number 189278-12-4

Molecular weight 372.21 g/mole

End-use product (EP) TALENDO and TALIUS . 

3.2 Physical/Chemical Characteristics

The physical and chemical properties for proquinazid are detailed in Appendix C.

Proquinazid has a low vapor pressure (10-5Pa) and is, therefore, not a volatile pesticide. 

Proquinazid has fairly high water solubility and does not dissociate. It is very soluble in most 

organic solvents, both polar and nonpolar. Environmental fate properties are not available since 

no use is proposed in the U.S.

3.3 Pesticide Use Pattern

No U. S. registration is proposed at the present time for proquinazid. The registrant has provided 

a summary of the use pattern for the Agency’s consideration. The formulated product is referred 

to as Proquinazid 200 g/L EC, produced by DuPont Agricultural Products. Registrations have 

been proposed in the European Union and Australia.

Proquinazid 200 g/L EC is diluted in water and applied using broadcast air-assisted sprayers, 

variable geometry sprayers, ducted air-assisted sprayers and hand-held sprayers. The application 

use pattern is summarized in the table below. 

Table 3.3. Summary of Proposed Directions for Use Proquinazid 200 g/L EC

Formulation

[EPA Reg. No.],

a.i. 

Applic. Timing, Type, and 

Equip. 

Applic. Rate

(g ai/ha)

Max. 

Seasonal 

Applic. Rate

(g ai/A)

PHI

(days) Use Directions and Limitations 

Grapes

200 g/L EC

Foliar ground broadcast 

application in 100 L -500 L 

water.

75 300 60 14 day interval between 

applications.
Proquinazid Human Health Risk Assessment DP No. 399842

Page 9 of 49

3.4 Anticipated Exposure Pathways

The Registration Division has requested an assessment of human health risk to support the 

proposed new use of proquinazid on imported grapes. This request is for an import tolerance, 

therefore, humans may be exposed to proquinazid in food only. Since there is no U.S. use on 

grapes, there is no potential for residues to end up in drinking water or potential for domestic 

worker exposure to residues of proquinazid during the application to grapes. Lastly, there are no 

registered residential uses; therefore, there is no potential for domestic residential exposure to 

proquinazid.

3.5 Consideration of Environmental Justice

Potential areas of environmental justice concerns, to the extent possible, were considered in this 

human health risk assessment, in accordance with U.S. Executive Order 12898, "Federal Actions 

to Address Environmental Justice in Minority Populations and Low-Income Populations," 

(http://www.eh.doe.gov/oepa/guidance/justice/eo12898.pdf. As a part of every pesticide risk 

assessment, OPP considers a large variety of consumer subgroups according to well-established 

procedures. In line with OPP policy, HED estimates risks to population subgroups from pesticide 

exposures that are based on patterns of that subgroup’s food and water consumption, and 

activities in and around the home that involve pesticide use in a residential setting. Extensive 

data on food consumption patterns are compiled by the USDA under the National Health and 

Nutrition Survey/What We Eat in America (NHANES/WWEIA) and are used in pesticide risk 

assessments for all registered food uses of a pesticide. These data are analyzed and categorized 

by subgroups based on age and ethnic group. Additionally, OPP is able to assess dietary 

exposure to smaller, specialized subgroups and exposure assessments are performed when 

conditions or circumstances warrant. Whenever appropriate, non-dietary exposures based on 

home use of pesticide products and associated risks for adult applicators and for toddlers, youths, 

and adults entering or playing on treated areas postapplication are evaluated. Further 

considerations are currently in development as OPP has committed resources and expertise to the 

development of specialized software and models that consider exposure to bystanders and farm 

workers as well as lifestyle and traditional dietary patterns among specific subgroups.

4.0 Hazard Characterization and Dose-Response Assessment

4.1 Toxicology Studies Available for Analysis

The database of experimental toxicology studies available for proquinazid provides a robust 

characterization of the hazard potential of this pesticide. There are no outstanding studies 

according to Part 158 data requirements for the current request for an import tolerance on grapes. 

However, HED has determined that a comparative thyroid assay in rats is required to assess the 

potential impact of proquinazid exposure on thyroid function in the young (Dellarco et al. 2005). 

The agency is requiring these data given the pivotal role of thyroid hormones in brain 

development. In the absence of these data, the 10X FQPA database uncertainty factor has been 

retained.

The data from the following studies were used to evaluate the hazard potential of proquinazid:
Proquinazid Human Health Risk Assessment DP No. 399842

Page 10 of 49

-Developmental Rat Study 

-Developmental Rabbit Study

-Reproduction Rat Study

- Cancer Mouse Study

-Chronic/Cancer Rat Study

-28 Day Oral Mouse Study

-90 Day Rat Study

-90 Day and 1 year Dog Study

-Acute Neurotoxicity (ACN) Rat Study

-Subchronic Neurotoxicity (SCN) Rat Study

-28-day Dermal Rat Study

-Genotoxicity Studies 

-Immunotoxicity Study

-Metabolism and Pharmacokinetics

Although most of the acute studies submitted were conducted with proquinazid manufactured by 

the current production process, most of the other toxicology studies submitted were conducted 

with proquinazid manufactured by the old production process. As a result of these differences, 

bridging studies were conducted to compare the toxicity of materials produced by the two 

methods. These studies demonstrated that studies conducted with the current production process 

exhibited equivalent or lesser toxicity than the studies conducted with the old production process

(see section A.4.10).

4.2 Absorption, Distribution, Metabolism, & Elimination (ADME)

Proquinazid is extensively absorbed (86-89%) after a single oral administration in rats within 48 

hours. Peak plasma concentration was reached after 4-8h (1 mg/kg bw) or 6-10h (20 mg/kg bw). 

Proquinazid and metabolites are widely distributed in the body (highest tissue levels in adrenals, 

liver, kidneys, fat). Excretion is rapid and extensive, equally important via urine and feces, and 

with biliary excretion accounting for nearly all of the fecal excretion. There is no significant 

accumulation of [phenyl14C] proquinazid residues in tissues, as radioactive tissue concentrations 

after 7 consecutive doses are similar to those generated after a single dose. In addition, major 

metabolites in urine and feces are the same following single or multiple doses. There are no 

significant gender differences in the disposition or elimination of radioactive residues. The 

elimination half-life is 8-12 hours. Proquinazid is extensively metabolized (>98 % of dose), 

mainly through phenyl ring hydroxylation and hydroxylation at the propyl and propoxy side 

chains, as well as some hydrolysis of side chains. 

4.2.1 Dermal Absorption

Dermal exposure is not expected with an import tolerance.
Proquinazid Human Health Risk Assessment DP No. 399842

Page 11 of 49

4.3 Toxicological Effects

Proquinazid is a new fungicide with a novel pesticidal mode of action (MOA). It is highly active 

against powdery mildew diseases and acts by preventing secondary appressorial formation

(parasitic fungi penetration into host tissues), which is essential for successful infection by 

powdery mildew fungi. 

The liver and thyroid are the primary target organs for proquinazid. In rodents, body weight/body 

weight gain reductions, increased liver and thyroid organ weights, hypertrophy/hyperplasia, liver 

enzyme induction, and thyroid hormone changes were seen across varying durations and routes 

of exposure in rodents but not dogs. Effects seen in the toxicity studies where proquinazid was 

administered by the oral and dermal routes of exposures are qualitatively similar but the effects 

occur at much higher dose levels by the dermal route compared to the oral route, indicating 

relatively poor dermal absorption of the technical material.

In the 90-day oral rat study, the low dose effects of proquinazid are characterized primarily by 

altered thyroid hormones and associated follicular cell hypertrophy in the thyroid. Decrements in 

body weight and nutritional parameters, as well as histopathological changes in the liver 

(including hypertrophy) were observed at higher doses. In a 28-day oral rat study, hypertrophy of 

the thyroid and liver was completely reversible after a 6 week recovery period. In chronic rodent 

studies, non-neoplastic effects in both mice and rats included thyroid follicular hyperplasia and 

hypertrophy, with associated thyroid hormone changes (only investigated in rats), and some 

marked hepatic lesions, i.e., necrosis and hyperplasia (including oval cell hyperplasia in rats). In 

addition chronic exposure in rats led to increases in the incidence of liver and thyroid tumors.

Mechanistic investigations revealed that cytochrome P-450 content in rats and mice and 

peroxisome proliferation in mice were increased in the liver after 1 week, with lesser increases 

after exposure for 6 or 12 months. The mode of action (MOA) for the thyroid tumors in rats was 

based on early changes in liver enzyme regulation that lead to dysregulation of thyroid hormone 

homeostasis (↑thyroid stimulating hormone (TSH), ↓triiodothyronine (T3), ↓thyroxine (T4)), 

thyroid follicular hypertrophy/hyperplasia, and thyroid follicular adenoma formation. 

Proquinazid was classified as “Suggestive Evidence of Carcinogenic Potential”. This 

determination was based on the treatment-related liver tumors observed in female rats. The 

thyroid follicular cell tumors observed in male rats and the cholangiocarcinomas observed in 

female rats were supported by mode of action data. The hypothesized mode of action (i.e, nongenotoxic) for each tumor type (i.e., the thyroid and cholangiocarcinoma) was supported by 

adequate studies that clearly identified the sequence of key events, dose-response concordance,

and temporal relationship to the tumor types. No treatment-related tumors were observed in male 

or female mice. There is no mutagenicity concern from the in vivo or in vitro genetic toxicity 

assays. 

Proquinazid was not found to be immunotoxic.

No evidence of increased quantitative or qualitative susceptibility was seen following in utero

exposure to proquinazid with rats or rabbits in the prenatal developmental studies or in young 
Proquinazid Human Health Risk Assessment DP No. 399842

Page 12 of 49

rats in the 2-generation reproduction study. The 2-generation rat reproduction study resulted in 

no effects on reproduction or fertility. The offspring effects (decreases in F1 pup weight during 

lactation) occurred at the same dose which caused parental effects (thyroid hypertrophy, reduced 

body weight gain and food consumption). Evidence of developmental delays were observed in 

developmental toxicity studies in rabbits and rats and were characterized by reduced fetal weight 

and an increased incidence of retarded ossification and patent ductus arteriosus, respectively. 

These developmental effects occurred in the presence of maternal toxicity and were considered 

of equal toxicity. 

Decreased motor activity in both sexes was seen following acute oral exposure and no neurotoxic 

effects were seen in the subchronic study. 

4.4 FQPA Safety Factor for Infants and Children

No evidence of increased quantitative or qualitative susceptibility was seen following in utero

exposure to proquinazid with rats or rabbits in the prenatal developmental studies or in young 

rats in the 2-generation reproduction study. There is only limited evidence for neurotoxicity 

following oral exposures to proquinazid. Thyroid toxicity was seen following subchronic and 

chronic exposures to adult rats in multiple studies. There is, however, no data regarding the 

potential effects of proquinazid on thyroid homeostasis in the young animals. This lack of 

characterization creates uncertainty with regards to potential life stage sensitivities due to 

exposure to proquinazid, and raises the Agency’s level of concern. Therefore, the Agency is 

requiring a comparative thyroid assay in rats with proquinazid. This study will better address the 

concern for potential thyroid toxicity in the young. There are no residual uncertainties in the 

proquinazid residue database with regards to dietary exposure. Therefore, the FQPA Safety 

Factor is retained at 10X in the form of a database uncertainty factor (UFDB).

4.4.1 Completeness of the Toxicology Database

There are no outstanding studies according to Part 158 data requirements for the current request 

for an import tolerance on grapes; however, HED has determined that a comparative thyroid 

assay in rats is required as discussed above. The uncertainty for the lack of this study is 

addressed by retaining the FQPA Safety Factor of 10X as the database UFDB.

4.4.2 Evidence of Neurotoxicity

There is limited evidence for neurotoxicity following oral exposures to proquinazid. Following a 

single exposure, evidence for neurotoxicity at the LOAEL was limited to decreased motor 

activity in both sexes with no behavioral or neuropathology changes. At doses above the study 

LOAEL other effects including decreased grip strength and foot splay were observed. Following 

repeated (dietary) exposures, there were no treatment-related clinical signs of neurotoxicity, 

behavioral changes or neuropathology. Typically, if there is a concern for neurotoxicity, the 

Agency would require a developmental neurotoxicity study. However, in the case of 

proquinazid, since the evidence for neurotoxicity was limited and the thyroid was shown to be 

the target organ in adult rats raising the concern for thyroid toxicity in the young, the Agency is 

requiring a comparative thyroid assay. The comparative thyroid assay will better address this 

concern than a developmental neurotoxicity study.
Proquinazid Human Health Risk Assessment DP No. 399842

Page 13 of 49

4.4.3 Evidence of Sensitivity/Susceptibility in the Developing or Young Animal

No evidence of increased quantitative or qualitative susceptibility was seen following in utero

exposure to proquinazid with rats or rabbits in the prenatal developmental studies or in young 

rats in the 2-generation reproduction study. The 2-generation rat reproduction study resulted in 

no effects on reproduction or fertility. The offspring effects (decreases in F1 pup weight during 

lactation) occurred at the same dose which caused parental effects (thyroid hypertrophy, reduced 

body weight gain and food consumption). Evidence of developmental delays were observed in 

developmental toxicity studies in rabbits and rats and were characterized by reduced fetal weight 

and an increased incidence of retarded ossification and patent ductus arteriosus, respectively. 

These developmental effects occurred in the presence of maternal toxicity. For the rats, the 

developmental effects were seen in the presence of clear maternal toxicity, including a marked 

reduction in body weight gain after adjustment for uterine contents and were considered to be of 

equal severity. As stated above in the FQPA section, there is, however, no data regarding the 

potential effects of proquinazid on thyroid homeostasis in the young animals. This lack of 

characterization creates uncertainty with regards to potential life stage sensitivities due to 

exposure to proquinazid, and raises the Agency’s level of concern. Therefore, the Agency is 

requiring a comparative thyroid assay in rats with proquinazid.

4.4.4 Residual Uncertainty in the Exposure Database

There are no residual uncertainties in the proquinazid residue database with regards to dietary 

exposure. HED used conservative assumptions in the dietary exposure assessment, including 

tolerance level residues and 100% crop treated. No water, residential, or worker assessments are 

required for this action.

4.5 Toxicity Endpoint and Point of Departure (POD) Selections

4.5.1 Dose-Response Assessment

The specific toxicity endpoints and PODs are presented in Table 4.5.4.1. Based on the current 

petition for an import tolerance on grapes, exposure is expected only from food through the oral 

route of exposure. Therefore, endpoints for acute and chronic dietary risk assessments were only 

selected at this time. 

The endpoint chosen for acute dietary exposure for the general population was from the acute 

neurotoxicity study in rats (MRID 48696359). Decreased motor activity at a LOAEL of 100 

mg/kg/day (NOAEL=50 mg/kg/day) in females in the acute neurotoxicity study was considered a 

treatment-related effect and appropriate for endpoint selection. This was a single dose effect seen 

on day 1. While the dose-response for the decreased motor activity was fairly flat, the percentage 

decreases were statistically significant and >40% and were considered treatment-related and 

adverse for all doses ≥100 mg/kg/day. Furthermore, selection of an observation time of 1-3 hours 

post dosing on day one in the ACN was too early and not ideal since the ADME study showed a 

plasma tmax of 6-10 hours following a single dose of 20 mg/kg/day. If the endpoint was evaluated 

at the time of peak plasma concentration, a more robust response may have been seen. For this 

risk assessment the total uncertainty factor is 1000 (10X interspecies factor, 10X intraspecies 
Proquinazid Human Health Risk Assessment DP No. 399842

Page 14 of 49

variability, and 10X database uncertainty factor). The FQPA SF was retained at 10X as a 

database uncertainty factor for lack of a comparative thyroid study. An acute dietary endpoint 

was not selected specifically for Females 13-49 years old since no developmental effects that 

could be attributed to a single exposure were identified in the proquinazid database. The acute 

dietary risk assessment is a screening-level assessment. Children <6 years old and females 13-49 

years old are the population subgroups that require the 10X FQPA safety factor due to the 

potential for thyroid effects; however, the 10X FQPA safety factor has been applied to all 

population subgroups as a conservative assumption. In the future, if refinements are required for 

the acute dietary assessment, the subpopulations can be assessed separately; however, since the 

assessment is a screening-level and health-protective, this level of refinement is not required at 

this time. 

The endpoint chosen for chronic dietary exposure was from the chronic toxicity/carcinogenicity 

study in the rat (MRID 48696348). This was based on a dose-related increase in non-neoplastic 

liver lesions, changes in the thyroid hormones and thyroid pathology in females at a LOAEL of 

12 mg/kg/day (NOAEL = 1.2 mg/kg/day). Since the POD for the chronic dietary risk assessment 

is based on thyroid toxicity in adult rats, the interspecies uncertainty factor was reduced to 3X to 

account for the toxicodynamics differences between rats and humans. These differences stem 

from markedly longer half-life for T4 in humans than in rats (5-9 days vs 12 hrs) due to the

presence of thyroxin binding globulin in the humans resulting in slower metabolic degradation 

and clearance of thyroid hormones. Therefore, TSH levels in rats are ≈ 25-fold higher than in 

humans reflecting the increased activity of the thyroid-pituitary axis in rats to maintain thyroid 

hormone homeostasis. Thus, on a toxicodynamic basis, adult rats are more sensitive than adult 

humans. The combined total uncertainty factor for the chronic dietary risk assessment is, 

therefore, 300 (3X for interspecies extrapolation, 10x for intraspecies variation, and 10X 

database uncertainty factor). 

4.5.2 Recommendation for Combining Routes of Exposures for Risk Assessment

Since only oral exposure is anticipated for proquinazid, it is not relevant to this action to discuss 

combining routes of exposure at this time. 

4.5.3 Cancer Classification and Risk Assessment Recommendation

In accordance with the EPA's Final Guidelines for Carcinogen Risk Assessment (March, 2005), 

the CARC classified proquinazid as having “Suggestive Evidence of Carcinogenic Potential”

(CARC Report, Rowland, J and Middleton, K, 4/24/2013, TXR No. 0056645). This 

determination was based on the following: (i) treatment-related liver tumors were observed in 

female rats at doses that were considered adequate to assess carcinogenicity; (ii) treatmentrelated thyroid follicular cell tumors were observed in male rats; (iii) treatment-related 

cholangiocarcinomas were observed in female rats; (iv) no treatment-related tumors were 

observed in male or female mice at doses that were considered adequate to assess 

carcinogenicity; (v) there is no mutagenicity concern from the in vivo or in vitro genetic toxicity 

assays; and(vi) the hypothesized mode of action (i.e, non-genotoxic) for each tumor type (i.e., 

the thyroid and cholangiocarcinoma) was supported by adequate studies that clearly identified 
Proquinazid Human Health Risk Assessment DP No. 399842

Page 15 of 49

the sequence of key events, dose-response concordance, and temporal relationship to the tumor 

types. The mode of action met the criteria established by the Agency.

The overall weight-of-evidence was considered sufficient to demonstrate that proquinazid

thyroid follicular tumors are the result of an antithyroidal mode of action and rats are 

substantially more sensitive than humans to the development of thyroid follicular cell tumors in 

response to thyroid hormone imbalance.

Proquinazid induced cholangiocarcinomas in female rats only at doses that produced marked 

liver toxicity and oval cell hyperplasia microscopically. In contrast, in both male and female rats, 

doses that produced less severe or no hepatotoxicity or oval cell proliferation did not produce 

cholangiocarcinomas. Therefore, at high enough doses, proquinazid can cause these biochemical 

and histopathological effects in livers of rodents but is unlikely to be carcinogenic at doses below 

those causing these changes.

Quantification of risk using a non-linear approach (i.e., reference dose (RfD)) will adequately 

protect for all chronic toxicity, including carcinogenicity, that could result from exposure to 

proquinazid. 
Proquinazid Human Health Risk Assessment DP No. 399842

Page 16 of 49

4.5.4 Summary of Points of Departure and Toxicity Endpoints Used in Human Risk 

Assessment

Table 4.5.4.1 Summary of Toxicological Doses and Endpoints for Proquinazid for Use in Dietary Human 

Health Risk Assessments

Exposure/ 

Scenario

Point of 

Departure

Uncertainty/

FQPA Safety 

Factors

RfD, PAD, 

Level of 

Concern for 

Risk 

Assessment

Study and Toxicological Effects

Acute Dietary 

(General 

Population, 

including 

Infants and 

Children)

NOAEL= 50 

mg/kg/bw

UFA= 10x

UFH= 10x

FQPA UFDB = 

10x

Acute RfD = 

aPAD = 0.050

mg/kg/bw

Acute Neurotoxicity Study - Rat

(48696359)

LOAEL = 100 mg/kg/bw based on 

decreased motor activity seen in females 

on day 1

Chronic 

Dietary (All 

Populations)

NOAEL= 1.2 

mg/kg/day

UFA= 3x

UFH= 10x

FQPA UFDB = 

10x

Chronic RfD = 

cPAD = 0.004 

mg/kg/day

Chronic Toxicity/Carcinogenicity Study -

Rat (48696348)

LOAEL = 12 mg/kg/day based on 

increases in non-neoplastic liver lesions 

and changes in thyroid hormones and 

thyroid pathology

Cancer (oral, 

dermal, 

inhalation)

Classification: “Suggestive Evidence of Carcinogenic Potential”. 

A non-linear approach (i.e., reference dose (RfD) will adequately protect for all chronic toxicity, 

including carcinogenicity, that could result from exposure to proquinazid.

Point of Departure (POD) = A data point or an estimated point that is derived from observed dose-response data and 

used to mark the beginning of extrapolation to determine risk associated with lower environmentally relevant human 

exposures. NOAEL = no observed adverse effect level. LOAEL = lowest observed adverse effect level. UF = 

uncertainty factor. UFA = extrapolation from animal to human (interspecies). UFH = potential variation in 

sensitivity among members of the human population (intraspecies). UFDB = to account for the absence of key data 

(i.e., lack of a critical study). FQPA SF = FQPA Safety Factor. PAD = population adjusted dose (a = acute, c = 

chronic). RfD = reference dose. 
Proquinazid Human Health Risk Assessment DP No. 399842

Page 17 of 49

5.0 Dietary Exposure and Risk Assessment 

5.1 Metabolite/Degradate Residue Profile

5.1.1 Summary of Plant and Animal Metabolism Studies

The grape metabolism study is adequate to support a tolerance for proquinazid residues on 

grapes. The primary residue on grapes was the parent compound, proquinazid, present at 35-40% 

parent. No other metabolites were found at >10% of the residue. Approximately 60% of the total 

radioactive residues (TRR) was identified or characterized. Parent residues of proquinazid were 

shown to decline from 75% to 53% of the residue on grape foliage; however, no metabolites on 

grape leaves were reported. The proposed metabolic pathway for proquinazid in grapes primarily 

involves the loss of the iodine substituent to form IN-MM671, followed by O-dealkylation of the 

propoxy side chain to form IN-MM991 (see Appendix B for structures). These metabolites were 

further metabolized and incorporated into unextractable naturally occurring compounds 

associated with the lignin fraction of the plant.

Livestock metabolism data were not reviewed by the Agency and are not required to support the 

requested grape tolerance without U.S. registration. 

5.1.2 Summary of Environmental Degradation

Since there is no U.S. registration proposed for grapes, a discussion of the environmental fate 

parameters for proquinazid is not required at this time. 

5.1.3 Comparison of Metabolic Pathways

Only one plant metabolism study is available for proquinazid and no additional data are required 

at this time; therefore it is not possible to comment on comparative metabolic profiles in plants. 

Similarly, no livestock metabolism data are required; therefore it is not possible to draw 

conclusions with respect to similarities between ruminant, poultry and rat metabolic profiles. Of 

note, however, is the fact that the two metabolites identified in the grape metabolism study were 

not identified in the rat metabolism study. The metabolism pathways in rats and grapes appear to 

be different.

5.1.4 Residues of Concern Summary and Rationale

The residue of concern for proquinazid on grapes is proquinazid, per se (Table 5.1.4). For future 

tolerances and registrations of proquinazid, the registrant must continue to monitor for the 

metabolite IN-MM671 in field trials. Limited toxicity data indicate that IN-MM671 may have 

equal toxicity compared to the parent, although additional toxicity data for the metabolite could 

preclude this concern. However, based on the lack of IN-MM671 residues in exaggerated rate 

field trials in grapes at the 28-day pre-harvest interval (PHI), there is not likely to be any 

significant exposure and, therefore, this metabolite is not being included in the residue definition.

The two minor plant metabolites in grapes were not found as rat metabolites.
Proquinazid Human Health Risk Assessment DP No. 399842

Page 18 of 49

Table 5.1.4. Summary of Metabolites and Degradates to be included in the Risk 

Assessment and Tolerance Expression

Matrix Residues Included In Risk 

Assessment

Residues Included In 

Tolerance Expression

Plants Primary Crop-grapes Proquinazid Proquinazid

Rotational Crop* -- --

Livestock Ruminant -- --

Poultry -- --

Drinking Water -- Not Applicable since this is 

an import use

* Since no registration is being requested in the US at the present time, and grapes are not 

included in plant rotations, no rotational crop studies have been submitted nor are required for 

the use on grapes.

5.2 Food Residue Profile

DuPont Inc. has submitted residue data for proquinazid (KQ926) from grape field trials. Twentyeight trials were conducted in Europe during 1997 and 2001-2002 growing seasons.

In the European trials, the treated plots in each field received 4 to 6 foliar broadcast spray 

applications of proquinazid at a rate of 75 g a.i./ha, with a 14 day re-treatment interval (RTI) for 

a total rate of 375-450 g a.i./ha, amounting to Good Agricultural Practices (GAP) to 1.5x the 

maximum seasonal rate for GAP. In the Australian trials, four applications of proquinazid were 

made to grapes at a nominal rate of either 60 g a.i./ha or 179 g a.i./ha, with a 14 day RTI, for a 

total rate of either 240 g a.i./ha or 716 g a.i./ha. The actual total application rates in the 

Australian trials were 191-1648 g a.i./ha. The Australian trials differed so much from GAP that 

they were not further considered. 

Field trials were conducted at the proposed foliar use rate (GAP) and higher seasonal 

applications rates, except in Australia. Samples were analyzed by a validated analytical method 

and were found to be below the recommended tolerance, but quantifiable. Prior to analysis, the 

samples were stored in a manner in which residues of proquinazid and IN-MM671 were shown 

to be stable. In decline studies, residues were reported to decline with increasing PHI from 0 to 

28 days. No quantifiable residues were found of the metabolite, IN-MM671 in any of the field 

trials. In future field trials, the petitioner must continue to analyze for this metabolite.
Proquinazid Human Health Risk Assessment DP No. 399842

Page 19 of 49

Grape Field Trial Data are summarized in Table 5.2 below. The Australian trials are excluded 

from the summary because the use patterns in the Australian trials were not close to the 

registered single or seasonal application rate. It should be noted that residues in the Australian 

trials are much lower than the residues in the European trials.

TABLE 5.2. Summary of Residue Data from Grape Trials with Proquinazid.

Commodity Total Rate of Proquinazid

(g ai/ha)

PHI

(days)

Residue Levels (ppm)*

N Min. Max. Mean Median St. Dev.

Proquinazid

Grapes

300

(4 applications at 75 g ai/ha)

28 6 <0.01 0.25 0.14 0.13 0.08

375

(5 applications at 75 g ai/ha)

25-29 6 0.02 0.35 0.20 0.19 0.14

450

(6 applications at 75 g ai/ha)

28 16 0.02 0.37 0.13 0.12 0.09

* Based on average field trial residues.

The processing data indicated that residues of proquinazid may concentrate in raisins (2.6x), wet 

pomace (3.9x) and dry pomace (12.5x), but do not concentrate in juice (0.4x), wine (0.3x), or

must or must deposit/lees (<1x).

5.3 Water Residue Profile

An assessment of residues in drinking water is not required for this assessment because there is 

no drinking water exposure in the U.S. associated with the establishment of an import tolerance.

5.4 Dietary Risk Assessment

5.4.1 Description of Residue Data Used in Dietary Assessment

For the acute and chronic dietary analyses, tolerance level residues were used. Default 

processing factors were used for grape juice. The Agency considers these to be highly 

conservative assessments. 

5.4.2 Percent Crop Treated Used in Dietary Assessment

For the acute and chronic dietary analyses, a 100% crop treated assumption was used.

5.4.3 Acute Dietary Risk Assessment

The results of the acute dietary exposure analyses are reported in Table 5.4.6. The acute risk

estimates were less than HED’s level of concern (≤100% aPAD) for the general U.S. population 

(3.8% aPAD) and all population sub-groups. The most highly exposed population subgroup was 

Children 1-2 years old with an estimated risk of 18% aPAD at the 95th percentile.
Proquinazid Human Health Risk Assessment DP No. 399842

Page 20 of 49

5.4.4 Chronic Dietary Risk Assessment

The results of the chronic dietary exposure analyses are reported in Table 5.4.6. The resulting 

chronic risk estimates were less than HED’s level of concern (≤100% cPAD) for the general U.S. 

population (8.1% cPAD) and all population sub-group. The most highly exposed population 

subgroup was Children 1-2 years old with an estimated risk of 47% cPAD.

5.4.5 Cancer Dietary Risk Assessment

The Agency has determined that quantification of risk using a non-linear approach (i.e., 

reference dose (RfD)) will adequately protect for all chronic toxicity, including carcinogenicity 

that could result from exposure to proquinazid. As noted in Section 5.4.4, there are no chronic 

risks of concern for proquinazid.

5.4.6 Summary Table

Table 5.4.6. Summary of Dietary (Food Only) Exposure and Risk for Proquinazid

Population Subgroup

Acute Dietary

95th Percentile Chronic Dietary Cancer

Dietary 

Exposure 

(mg/kg/day)

%

aPAD

Dietary 

Exposure

(mg/kg/day)

% 

cPAD

Dietary 

Exposure

(mg/kg/day)

Risk

General U.S. Population 0.001890 3.8 0.000324 8.1

NA

All Infants (< 1 year old) 0.004074 8.2 0.000672 17

Children 1-2 years old 0.009079 18 0.001881 47

Children 3-5 years old 0.005852 12 0.001138 28

Children 6-12 years old 0.002913 5.8 0.000447 11

Youth 13-19 years old 0.000793 1.6 0.000147 3.7

Adults 20-49 years old 0.001333 2.7 0.000205 6.1

Adults 50-99 years old 0.001426 2.9 0.000237 5.9

Females 13-49 years old 0.001370 2.7 0.000214 5.4

6.0 Residential (Non-Occupational) Exposure/Risk Characterization

There are no residential uses for proquinazid and the food use is for imported grapes. As a result,

a residential exposure risks assessment in not required.

7.0 Aggregate Exposure/Risk Characterization

There are no proposed registrations for proquinazid in the U.S. Therefore, the only human 

exposure to proquinazid in the U.S. is from imported grapes and grape processed commodities 

treated with proquinazid. Dietary exposure is from food only. There is no potential drinking 

water or residential exposure resulting from use on grapes. Therefore, the only component of the 

aggregate risk assessment is food, and those risks are not of concern and have been detailed in 

Section 5.4.3 and 5.4.4, above. 
Proquinazid Human Health Risk Assessment DP No. 399842

Page 21 of 49

8.0 Cumulative Exposure/Risk Characterization

Unlike other pesticides for which EPA has followed a cumulative risk approach based on a 

common mechanism of toxicity, EPA has not made a common mechanism of toxicity finding as 

to proquinazid and any other substances and proquinazid does not appear to produce a toxic 

metabolite produced by other substances. For the purposes of this tolerance action, therefore, 

EPA has not assumed that proquinazid has a common mechanism of toxicity with other 

substances. For information regarding EPA’s efforts to determine which chemicals have a 

common mechanism of toxicity and to evaluate the cumulative effects of such chemicals, see the 

policy statements released by EPA’s Office of Pesticide Programs concerning common 

mechanism determinations and procedures for cumulating effects from substances found to have 

a common mechanism on EPA’s website at http://www.epa.gov/pesticides/cumulative/.

9.0 Occupational Exposure/Risk Characterization

This action is for imported grape and no U.S. registration is requested. An occupational exposure 

risk assessment is not required.

10.0 References

Dellarco, V. et al. 11/01/2005. Interim Guidance: Thyroid Disrupting Pesticides: Use of Rat 

Thyroid Data and Application of Uncertainty Factors for RfD Derivation. Prepared and 

Reviewed by the Hazard Science Policy Council.

OPP Guidance. 10/24/2005. Guidance for Thyroid Assays in Pregnant Animals, Fetuses 

and Postnatal Animals, and Adult Animals. Office of Pesticide Programs, Health Effects 

Division, Washington, DC. Cited in Dellarco, V. et al 2005

Hummel, S. 6/20/2013. D410206. Proquinazid-Petition for Establishment of Permanent 

Tolerances on Imported Grapes (1E7972). Summary of Chemistry and Residue Data.

Knizner, S. 05/27/2009. “Interim Guidance on Tolerance Expressions,” EPA Memorandum.

Morton, T. 10/30/2013. D410207. Proquinazid –Acute and Chronic Dietary (Food Only) 

Exposure and Risk Assessments for the Use on Imported Grapes. 

Rowland, J and Middleton, K. 4/24/2013. TXR No. 0056645. Proquinazid: Report of the Cancer 

Assessment Review Committee. 

Scollon, E. 5/29/2013. Email from Ed Scollon to Sue Hummel. Proquinazid ROCKS decision.

Van Alstine, J. 9/03/13. D399842. RARC Report: Summary of the RARC Meeting to Discuss 

the Proquinazid Human Health Risk Assessment for a Tolerance on Imported Grapes.
Proquinazid Human Health Risk Assessment DP No. 399842

Page 22 of 49

Appendix A. Toxicology Profile and Executive Summaries

A.1 Toxicology Data Requirements

The requirements (40 CFR 158.500) for the Food Use of Proquinazid are in Table A.1. Use of 

the new guideline numbers does not imply that the new (1998) guideline protocols were used.

Table A.1. Toxicology Data Requirements

Study Technical

Required Satisfied

870.1100 Acute Oral Toxicity.......................................................

870.1200 Acute Dermal Toxicity ..................................................

870.1300 Acute Inhalation Toxicity..............................................

870.2400 Primary Eye Irritation....................................................

870.2500 Primary Dermal Irritation ..............................................

870.2600 Dermal Sensitization......................................................

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

yes

870.3050 28-day oral (rodent).........................................

870.3100 Oral Subchronic (rodent)...............................................

870.3150 Oral Subchronic (nonrodent) .........................................

870.3200 21-Day Dermal ..............................................................

870.3250 90-Day Dermal ..............................................................

870.3465 90-Day Inhalation..........................................................

yes

yes

yes

yes

cr

cr

yes

yes

yes

yes

no

no

870.3700a Developmental Toxicity (rodent)...................................

870.3700b Developmental Toxicity (nonrodent).............................

870.3800 Reproduction .................................................................

yes

yes

yes

yes

yes

yes

870.4100a Chronic Toxicity (rodent) ..............................................

870.4100b Chronic Toxicity (nonrodent)........................................

870.4200a Oncogenicity (rat)..........................................................

870.4200b Oncogenicity (mouse)....................................................

870.4300 Chronic/Oncogenicity....................................................

n/a

yes

n/a

yes

yes

-

yes

-

yes

yes

870.5100 Mutagenicity—Gene Mutation - bacterial.....................

870.5300 Mutagenicity—Gene Mutation - mammalian................

870.5375 Mutagenicity—Structural Chromosomal Aberrations...

870.5395 Mutagenicity—Other Genotoxic Effects........................

yes

yes

yes

yes

yes

yes

yes

yes

870.6100a Acute Delayed Neurotox. (hen) .....................................

870.6100b 90-Day Neurotoxicity (hen)...........................................

870.6200a Acute Neurotox. Screening Battery (rat) .......................

870.6200b 90-Day Neuro. Screening Battery (rat)..........................

870.6300 Develop. Neuro..............................................................

no

no

yes

yes

cr

-

-

yes

yes

n/a

870.7485 General Metabolism ......................................................

870.7600 Dermal Penetration ........................................................

870.7800 Immunotoxicity .............................................................

yes

cr

yes

yes

yes

yes
Proquinazid Human Health Risk Assessment DP No. 399842

Page 23 of 49

Table A.1. Toxicology Data Requirements

Study Technical

Required Satisfied

Special Studies for Ocular Effects

Acute Oral (rat)...........................................................

Subchronic Oral (rat) ..................................................

Six-month Oral (dog)..................................................

Other Special Studies

Comparative Thyroid Assay (rat)......................

no

no

no

yes

-

-

-

no

n/a=not applicable

A.2 Toxicity Profiles

Table A.2.1 Table A.2.1 Acute Toxicity Profile – Proquinazid, TGAI 

Guideline No. Study Type MRID(s) Results Toxicity Category

870.1100 Acute oral, rat 48696329

LD50 = 4846 

mg/kg females

LD50 > 5000

mg/kg males

III 

870.1100 Acute oral, rat (IN-MM671, 

metabolite of DPX-KQ926) 48696330

LD50 = 2052 

mg/kg females

LD50 = 2890 

mg/kg males

III

870.1200 Acute dermal, rat 48696331 LD50 > 5000 

mg/kg

IV

870.1300 Acute inhalation, rat 48696332 LC50 > 5.2 mg/L IV

870.2400 Acute eye irritation, rabbit 48696333 irritation at 1 hr 

cleared by 24 hrs;

redness through 

72 hrs cleared by 

day 7;

discharge at 1 hr 

cleared by 24 hrs

III

870.2500 Acute dermal irritation, rabbit 48696334 very slight 

erythema through 

48 hrs cleared by 

72 hrs

IV

870.2600 Skin sensitization, guinea pig 48696335 Negative --
Proquinazid Human Health Risk Assessment DP No. 399842

Page 24 of 49

Table A.2.2 Subchronic, Chronic and Other Toxicity Profile

Guideline 

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.3050 28-Day oral 

toxicity (rat)

48696336 (2002)

Acceptable/Guideline

0, 10,30, 300, ppm 

0, 0.6, 1.9, 19, mg/kg/day

NOAEL = 30 ppm (1.9 mg/kg bw/day) in 

males

LOAEL = 300 ppm 19 mg/kg bw/day)

based on increased serum TSH and rT3, 

decreased serum T3 and T4, increased UDPglucuronyltransferase activity, decreased 5’-

deiodinase activity, and thyroid follicular cell 

hypertrophy; substance-related changes in 

thyroid hormones and UDPglucuronyltransferase activity at 30 ppm are 

considered to be adaptive, but not adverse 

findings. The reversibility of the increase in 

liver weight and hepatocellular hypertrophy, 

and absence of cell proliferation in the liver, is 

consistent with an adaptive response in the 

liver.

3000ppm was tested but all rats were killed on 

day 18 due to excessive bw decreases

870.3100 90-Day oral 

toxicity (rat)

Proquinazid

Note: bridging 

study with 

proquinazid from 

current 

manufacturing 

process

48696337 (2002)

Acceptable/Guideline

M: 0, 30, 100, 300, or 

2000 ppm

F: 0, 30, 100, 300, or 600 

ppm 

M: 0, 2, 6, 19, and 127 

mg/kg bw/day

F: 0, 2, 8, 24 and 50 

mg/kg bw/day 

NOAEL=30 ppm (2 mg/kg bw/day) in males 

NOAEL=100 ppm (8 mg/kg bw/day) in 

females.

LOAEL =100 ppm (6 mg/kg/bw/day) for males 

based on thyroid hypertrophy and hormonal 

changes associated with the thyroid 

LOAEL=300 ppm (24 mg/kg bw/day) for 

females based on decreases in white blood cell 

counts.

870.3100 90-Day oral 

toxicity (mouse)

N/A No study submitted. The applicant states that 

reports of 28-day and 90-day feeding studies 

with mice were not submitted because they 

were conducted on an early laboratory sample 

that is not representative of the current 

production process and add no additional 

information.
Proquinazid Human Health Risk Assessment DP No. 399842

Page 25 of 49

Table A.2.2 Subchronic, Chronic and Other Toxicity Profile

Guideline 

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.3150 90-Day oral 

toxicity (dog)

48696339 (1997)

48696340 (1998) 

Supplement No. 1

Acceptable/Guideline

0, 500, 2000, or 

4000/3000 ppm 

M: 0, 17, 62, and 87, 

mg/kg/day

F: 0, 18, 56, and 95

mg/kg/day

NOAEL = 2000 ppm

LOAEL = 4000/3000 ppm

Substance-related toxicity (ocular discharge, 

red ears and increased liver weight) was seen at 

all dose levels, i.e. ≥ at 500 ppm (> 17-18 

mg/kg bw/day). Although proquinazid is not 

classified as an eye irritant based on acute 

exposure of rabbits, the extent to which ocular 

discharge in this dog study was due to a local 

irritation rather than to a systemic effect is 

unclear. The presence of red ears at all doses 

and conjunctivitis in one top dose animal is 

consistent with an irritant response. However 

increased ocular discharge was also seen in the 

1-year dog study with dosing by capsule. 

870.3200 21/28-Day dermal 

toxicity (rat)

48696341 (2002)

Acceptable/Guideline

M/F: 100, 500, 1000, or 

2000 mg/kg bw/day

The NOAEL for systemic effects = 500 mg/kg 

bw/day for males and 100 mg/kg bw/day for 

females. 

In males, the LOAEL= 1000 mg/kg bw/day 

based on thyroid hypertrophy and increased 

liver weight and hepatocyte hypertrophy. 

In females, the LOAEL=500 mg/kg bw/day 

was based on based on decrements in body 

weight and nutritional parameters as well as 

increased liver weight and hepatic hypertrophy 

at 500 mg/kg bw/day and above.

The NOAEL for local dermal effects was 500 

mg/kg bw/day in male and female rats based on 

desquamation and/or erythema at the 

application site at 1000 mg/kg bw/day and 

above.

[It is notable that at the NOAEL of 100 mg/kg 

bw/day, the amount of proquinazid applied per 

cm2 can be calculated to be about 1.2 mg. ]
Proquinazid Human Health Risk Assessment DP No. 399842

Page 26 of 49

Table A.2.2 Subchronic, Chronic and Other Toxicity Profile

Guideline 

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.3700a Prenatal 

developmental in 

(rat)

Dosed from 

Gestation Days 7-

21

48696342 (1997)

Acceptable/Guideline

0, 5, 10, 30, or 60 mg/kg 

bw/day 

Maternal and developmental NOAEL in rats =

30 mg/kg/day.

Maternal LOAEL = 60 mg/kg/day based on 

reduced body weight gain and food 

consumption, and clinical signs.

Developmental LOAEL= 60 mg/kg/day based 

on reduced fetal weight and increased incidence 

of two structural variations (retarded sternal 

ossification and patent ductus arteriosus).

Fetal effects were seen in the presence of 

markedly reduced maternal body weight gain.

870.3700b Prenatal 

developmental in 

(rabbit)

Dosed from 

Gestation Days 7-

28.

48696343 (1998)

Acceptable/Guideline

0, 1, 2.5, 5, or 10 mg/kg 

bw/day. 

The NOAEL in rabbits is 2.5 mg/kg bw/day for 

both maternal and developmental effects. 

Maternal LOAEL = 5 mg/kg/day based on 

decreased body weight gain and food 

consumption. 

Developmental LOAEL = 5 mg/kg/day based 

on decreased mean fetal weight 
Proquinazid Human Health Risk Assessment DP No. 399842

Page 27 of 49

Table A.2.2 Subchronic, Chronic and Other Toxicity Profile

Guideline 

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.3800 Reproduction and 

fertility effects

(rat)

48696344 (2002)

The acceptability of the

study has not been 

assessed due to a more 

recent study.

0,150, 300, 600 ppm

M0:0, 19, 17, 35

mg/kg/day

F0: 0, 11, 21, 44 

mg/kg/day

premating

Parental/Systemic NOAEL = not established

LOAEL = 150 ppm based on thyroid gland 

effects

Reproductive NOAEL = 300 ppm, 

LOAEL=600 ppm based on reductions in 

implantation site numbers and implantation 

efficiency 

Offspring NOAEL = 150 ppm 

LOAEL = 300 ppm based on reductions in 

pup weight. Reductions in pup viability were 

present at 600 ppm

The applicant states that the in-life phase of this 

study predates the January, 2001 update of 

OECD 416. During the conduct of this study, 

more detailed protocols for 2-generation 

reproduction studies were promulgated. Some 

endpoints included in these new guidelines 

were added to the study protocol for the F1

generation. However, not all additional 

endpoints could be included and sperm 

parameters, though included, were not 

considered valid due to methodological 

concerns. Therefore, the 2-generation study 

was repeated in accordance with more recent 

regulatory guidelines, see B.6.6.1.a.

870.3800 Reproduction and 

fertility effects

(rat)

48696345 (2003)

Acceptable/Guideline

0, 10, 30, 150, or 600 ppm 

M0: 0, 0.6, 1.8, 9, 35

mg/kg/day

F0: 0, 0.7, 2.3, 11, 44 

mg/kg/day

Premating

Parental/Systemic NOAEL = 30 ppm (2 

mg/kg bw/day) 

LOAEL = 150 ppm (9-11 mg/kg bw/day) 

based on thyroid hypertrophy in P1 and 

F1 males and females fed. 

Reproductive NOAEL = 600 ppm (35-44 

mg/kg bw/day), the highest concentration 

tested, based on absence of effects on 

reproductive parameters and reproductive 

organs.

LOAEL= Not established

Offspring NOAEL = 150 ppm (11 

mg/kg/day)

LOAEL = 600 ppm (44 mg/kg bw/day) based 

on a marginal reduction in total litter weight of 

F1 pups during lactation, which was likely 

secondary to maternal toxicity in P1 females.
Proquinazid Human Health Risk Assessment DP No. 399842

Page 28 of 49

Table A.2.2 Subchronic, Chronic and Other Toxicity Profile

Guideline 

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.4100b Chronic toxicity 

(dog)

48696346 (2002)

Acceptable/Guideline

0 (empty capsules), 15, 

60, or 180 mg/kg bw/day 

ppm. The dose level for 

the high dose group was 

60 mg/kg/day for Study 

Week 0, 120 mg/kg/day 

for Study Week 1, and 

180 mg/kg/day for the 

remainder of the study. 

NOAEL = 15 mg/kg bw/day (males)

LOAEL = 60 mg/kg bw/day (males) based 

reduced body weight gain. 

NOAEL = 60 mg/kg bw/day (females)

LOAEL =180 mg/kg bw/day (females) based 

on decreases in body weight and/or reductions 

in body weight gains

870.4200 Carcinogenicity

(mouse)

48696347 (2002)

Acceptable/Guideline

0, 5, 30, 200, or 2000 ppm 

Males: 0, 0.7, 4, 27, and 

282 mg/kg bw/day

Females: 0, 1.0, 6, 38, 

and 415 mg/kg bw/day

NOAEL = 30 ppm for males and females (4 

and 6 mg/kg/day, respectively). 

LOAEL= 200 ppm (27 and 38 mg/kg bw/day) 

based on non-neoplastic lesions in the liver. 

Non-neoplastic lesions were also present in the 

thyroid gland of male and female mice fed 

2000 ppm. Increased liver weight and 

hepatocyte hypertrophy at 2000 ppm was 

probably due, at least in part, to the observed 

induction of cytochrome P-450 and increase in 

peroxisome proliferation.

No treatment-related tumors in male or female 

mice

870.4300 Chronic Toxicity/

Carcinogenicity

(rat)

48696348 (2002)

Acceptable/Guideline

Males: 0, 10, 30, 300, 

1000 and 2000 ppm

Females: 0, 10, 30, 300, 

600 and 1200 ppm

Males: 0, 0.4, 1.2, 12, 43, 

and 92 mg/kg bw/day. 

Females: 0, 0.5, 1.4, 16, 

35 and 76 mg/kg bw/day. 

NOAEL = 30 ppm in males and females (1.2 

and 1.4 mg/kg/day, respectively)

LOAEL = 300 ppm (12 and 16 mg/kg bw/day) 

based on test substance-related increases in 

non-neoplastic liver lesions and changes in 

thyroid hormones and pathology.

Liver tumors and cholangiocarcinomas (with 

acceptable MOA data) in female rats.

Thyroid tumors (with acceptable MOA data) in 

male rats
Proquinazid Human Health Risk Assessment DP No. 399842

Page 29 of 49

Table A.2.2 Subchronic, Chronic and Other Toxicity Profile

Guideline 

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.5100 Bacterial Reverse 

Mutation

Proquinazid

48696349 (1998)

Acceptable/Guideline

Nominal concentrations of 

10, 50, 100, 500, 1000, 

2500, and 5000 μg/plate

Proquinazid (DPX-KQ926-75) was negative for 

mutagenic activity in the non activated and S9-

activated test systems in the in vitro bacterial 

gene mutation assay.

870.5100 Bacterial Reverse 

Mutation

Proquinazid

48696350 (1997)

Acceptable/Guideline

Nominal concentrations of 

10, 50, 100, 250, 500, 

1000, 2500, and 5000 

μg/plate were initially 

evaluated in Trial 1 using 

strains TA100 and E. 

Coli only.

Proquinazid (DPX-KQ926-45) was negative for 

mutagenic activity in the non activated and S9-

activated test systems in the in vitro bacterial 

gene mutation assay.

870.5100 Bacterial Reverse 

Mutation

Metabolite INMM671

48696351 (1999)

Acceptable/Guideline

Nominal concentrations of 

10, 50, 100, 500, 1000, 

2500, and 5000 μg/plate 

were evaluated in Trial 1. 

Nominal concentrations of 

10, 50, 100, 500, 750, 

1000, and 2500 μg/plate 

were evaluated in Trial 2. 

Metabolite IN-MM671 was negative for 

mutagenic activity in the non-activated and S9 

activated test systems in the in vitro bacterial 

gene mutation assay.

870.5300 In vitro

Mammalian Cell 

Gene Mutation

48696352 (1997)

Acceptable/Guideline

Initial assay 

(nonactivated): 1.5, 5.0, 

10, 15, 20, 30, or 40 

μg/mL.

Initial assay (activated): 5, 

15, 50, 60, 75, 100, or 125 

gμ/mL

Independent repeat assay 

(nonactivated): 10, 15, 20, 

25, 30, or 35 gμ/mL 

Independent repeat assay 

(activated): 25, 50, 55, 60, 

65, or 70 μg/mL 

Third assay (activated): 

40, 50, 60, 65, 70, 75, 90, 

or 100 μg/mL. 

The findings of this study were considered to

be uninterpretable. It was recommended that a 

mouse lymphoma assay conducted to 

internationally accepted standards be provided 

to address this endpoint. The applicant has now 

submitted such a study (48696353).
Proquinazid Human Health Risk Assessment DP No. 399842

Page 30 of 49

Table A.2.2 Subchronic, Chronic and Other Toxicity Profile

Guideline 

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.5300 In vitro Gene 

Mutation 

Mouse 

Lymphoma

48696353 (2005)

Acceptable/Guideline

Experiment 1: L5178 

TK+ mouse lymphoma 

cells (duplicate cultures 

per dose) were exposed 

for 3 h at 37 oC to the test 

substance at 

concentrations of 20 to 

180 μg/mL in the nonactivated test system. In 

the S9 activated test 

system, cultures were 

exposed for 3 hours at 37 

oC to concentrations of 45 

to 180 μg/mL. 

Experiment 2: Cultures 

were exposed for 24 h at 

37 C to the test substance 

at concentrations of 10 to 

140 g/mL in the nonactivated test system, and 

for 3 h at 37 C to 

concentrations of 45 

to180 g/mL in the S9 

activated test system.

Proquinazid was negative in the non-activated 

and S9-activated test systems in this mouse 

lymphoma assay.
Proquinazid Human Health Risk Assessment DP No. 399842

Page 31 of 49

Table A.2.2 Subchronic, Chronic and Other Toxicity Profile

Guideline 

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.5375 In vitro

Mammalian 

Chromosome 

Aberration 

48696354 (1999)

Acceptable/Guideline

Doses (2 replicates/dose) 

were as follows.

Non-activated initial 

assay:

79, 157, 313, 625*, 

1250*, 2500*, and 5000* 

μg/mL. 

S9-activated initial assay:

79*, 157*, 313*, 625*, 

1250*, 2500, and 5000 

μg/mL. 

Non-activated 

independent repeat assay:

79, 157, 313, 625*, 

1250*, 2500*, and 5000* 

μg/mL.

S9-activated independent 

repeat assay:

40, 79*, 157*, 313*, 

625*, 1250, 2500, and 

5000 μg/mL. 

[* = doses for which a 

cytogenetic evaluation 

was made]

Proquinazid (DPX-KQ926-45) was negative for 

structural and numerical chromosome

aberrations in the non-activated and S9-

activated test systems in the in vitro 

mammalian cytogenetics test using human 

peripheral blood lymphocytes. However the 

study was not completely adequate by current 

standards because there was no investigation of 

the effect of continuous exposure in the 

absence of metabolic activation (which could 

have limited to ability to detect any test 

substance induced structural and numerical 

aberrations). Also the study may have had 

limited sensitivity because the doses of 

proquinazid used had resulted in high levels of 

cytotoxicity and current positive control 

responses were relatively low. These study 

limitations have been confirmed by the UK 

Committee on Mutagenicity (see Appendix 6).

870.5395 Mammalian 

Erythrocyte 

Micronucleus 

48696355 (1999)

Acceptable/Guideline

0, 360, 720, or 1400 

mg/kg bw by single-dose 

oral gavage

Proquinazid (DPX-KQ926-45) did not induce 

an increase in micronuclei in bone marrow cells 

of mice and is considered negative in this in 

vivo assay. The clinical signs of toxicity seen in 

mice (especially ataxia and lethargy in the 

absence of diarrhea) are indicative of systemic 

exposure (and hence likely exposure of the 

bone marrow) to proquinazid and/or 

metabolites.

In the single dose ADME study with rats, with 

dosing of radiolabelled proquinazid by gavage 

(B.6.1.1a), radiolabel was found in bone 

marrow at similar levels to that plasma and 

blood. It is likely that radiolabel reaching the 

bone marrow is a mixture of parent and 

metabolites because metabolism of parent is 

extensive in rats, with biliary excretion being 

important. 
Proquinazid Human Health Risk Assessment DP No. 399842

Page 32 of 49

Table A.2.2 Subchronic, Chronic and Other Toxicity Profile

Guideline 

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.5395 Mammalian 

Erythrocyte 

Micronucleus 

48696356 (1999a)

Acceptable/Guideline

Male mice received 720, 

1440, or 2000 mg/kg bw 

by single-dose oral 

gavage. 

Doses in females were 

360, 720, or 1440 mg/kg 

bw. 

Proquinazid (DPKQ926-75) did not induce an 

increase in micronuclei in bone marrow cells of 

mice and is considered negative in this in vivo 

assay. The rapid appearance of clinical signs of 

toxicity in mice is indicative of rapid 

absorption and likely systemic exposure 

(including bone marrow) to proquinazid and/or 

metabolites.

In the single dose ADME study with rats, with 

dosing of radiolabelled proquinazid by gavage 

(B.6.1.1a), radiolabel was found in bone 

marrow at similar levels to that plasma and 

blood. It is likely that radiolabel reaching the 

bone marrow is a mixture of parent and 

metabolites because metabolism of parent is 

extensive in rats, with biliary excretion being 

important. 

870.5395 Mammalian 

Erythrocyte 

Micronucleus 

Metabolite INMM671

48696357 (1999b)

Acceptable/Guideline

Male and female mice 

received 0, 500, 1000, or 

2000 mg/kg by singledose oral gavage. 

IN-MM671 did not induce an increase in 

micronuclei in bone marrow cells of mice, and 

is considered negative in this in vivo assay.

870.5550 Unscheduled 

DNA Synthesis in 

Mammalian 

Cultured Cells

48696358 (1999)

Acceptable/Guideline

In both initial and 

independent repeat assays, 

the test substance was 

tested at eight dose levels, 

ranging from 3.9 to 500 

μg/mL, and fully 

evaluated for UDS at five 

dose levels of 7.8, 15.6, 

31.3, 63, and 125 μg/mL.

Proquinazid (DPX-KQ926-45) did not cause a 

significant increase in unscheduled DNA 

synthesis and was concluded to be negative in 

this assay.
Proquinazid Human Health Risk Assessment DP No. 399842

Page 33 of 49

Table A.2.2 Subchronic, Chronic and Other Toxicity Profile

Guideline 

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.6200a Acute 

neurotoxicity 

screening battery

48696359 (1997) 

Acceptable/Guideline

M/F: 0, 100, 500, 2000 

mg/kg/day

In order to establish a 

NOAEL for females, 12 

females/dose were 

similarly administered a 

single dose by oral gavage 

of: 0, 15, 30, or 50 

mg/kg/day

NOAEL = 100 mg/kg bw for males

LOAEL= 500 mg/kg bw for males based on 

decreased motor activity on the day of exposure

NOAEL =50 mg/kg bw for females

LOAEL = 100 mg/kg/day for females, based on 

decreased motor activity on the day of 

exposure. While the dose-response for the 

decreased motor activity in females was fairly 

flat, the percentage decreases were statistically 

significant and >40% and were considered 

treatment-related and adverse for all doses 

≥100 mg/kg/day. [While there was a 23% 

decrease in motor activity at 50 mg/kg/day, this 

was not statistically significant and was 

considered a NOAEL.]

870.6200b Subchronic 

neurotoxicity 

screening battery

Combined 

subchronic (90-

day) feeding study 

and subchronic 

neurotoxicity 

study (proquinazid 

from previous 

manufacturing 

process)

48696338 (2003)

Acceptable/Guideline

M: 0, 30, 100, 300, 

2000ppm 

0, 2, 6, 19, 135 mg/kg/day

F: 0, 30, 100, 600ppm

0, 2, 8, 23, 50 mg/kg/day

Neurotoxicity

NOAEL = 2000 ppm (135 mg/kg bw/day) in 

males and 600 ppm (50 mg/kg bw/day) in 

females, HDT

LOAEL= not observed

(systemic toxicity of proquinazid (DPXKQ926-45)

NOAEL = 30 ppm (2 mg/kg bw/day) in males 

and 100 ppm (8 mg/kg bw/day) in females 

LOAEL= 100 ppm (6 mg/kg bw/day) in males 

and at 300 ppm (23 mg/kg bw/day) in females 

based on hormonal and morphological changes 

(hypertrophy) in the thyroid; decrements in 

body weight and nutritional parameters, as well 

as microscopic and clinical pathological 

changes in the liver, were also present at higher 

doses.
Proquinazid Human Health Risk Assessment DP No. 399842

Page 34 of 49

Table A.2.2 Subchronic, Chronic and Other Toxicity Profile

Guideline 

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

870.7485 Metabolism and 

pharmacokinetics

(rat)

48696360 (1999)

Acceptable/Guideline

M/F: 1mg/kg/ 7days

Male and female rats were dosed with 

approximately 1 mg/kg of [phenyl14C(U)]

proquinazid for 7 consecutive days and 

sacrificed at approximately 4.4-6.1, 24-25, 48-

49, and 169-170 hours after the last dose. The 

concentration of radioactivity in tissues 

declined rapidly following the last dose. Tissue 

residue concentrations were generally lower 

than plasma concentrations with the exception 

of liver, kidney, and fat. There appeared to be 

little potential for bioaccumulation. Extensive 

metabolism of proquinazid was observed. The 

most abundant metabolites in urine and feces 

were the same as observed in the single dose 

study. A small percentage of 14C-proquinazid

(up to 6%) was deiodinated and excreted as a 

ring hydroxylated product.

870.7485 Metabolism and 

pharmacokinetics

(rat)

48696361 (1998)

Acceptable/Guideline

M/F: 1 and 20 mg/kg/day

Proquinazid was virtually completely absorbed 

at the 1 and 20 mg/kg doses. There was 

extensive metabolism, based on very low 

excretion of parent compound and extensive 

excretion of metabolised dose in urine and 

feces. Biliary excretion accounted for 

essentially all of the fecal excretion. The 

elimination half-life for total radioactive 

residues was 8-12 hours, and by 7 days post 

dosing little potential for accumulation of 

residues was seen (<1% of the dose in the 

body). Major biotransformations observed 

were the loss of side chains and 

hydroxylation/oxidation both at the phenyl ring 

and side chains

870.7800 Immunotoxicity

(mouse)

48778901 (2012)

Acceptable/Guideline

0, 50, 200, 600, or 1200 

ppm ( 0, 4, 14, 42, or 82 

mg/kg/day)

The systemic toxicity LOAEL is 1200 ppm (82 

mg/kg/day) based on decreases in terminal 

body weight, body weight gain, food 

consumption and food efficiency. The NOAEL 

for systemic toxicity is 600 ppm (42 

mg/kg/day).

The immunotoxicity NOAEL is 1200 ppm (82 

mg/kg/day), the highest dose tested. The 

LOAEL was not established.
Proquinazid Human Health Risk Assessment DP No. 399842

Page 35 of 49

Table A.2.2 Subchronic, Chronic and Other Toxicity Profile

Guideline 

No. 

Study Type MRID No. (year)/ 

Classification /Doses

Results

Nonguideline

Special 

Studies

Scientific 

Advisory Panel 

Review of 

Thyroid

48696364 (2003) The colloid alteration was shown to occur at 

doses where alterations in thyroid hormone 

homeostasis were minimal or absent, as well as 

in control rats. Furthermore, this change was 

not observed in mice or dogs even at high 

doses. Therefore, as with changes in other

thyroid parameters, the rat appears to be 

uniquely susceptible to the colloid alteration 

described in these studies. Based on these 

observations, the SAP considered the colloid 

changes in rats not to be relevant to humans.

Nonguideline

Special 

Studies

Scientific 

Advisory Panel 

Review of Liver

48696365 (2003) The precise mechanisms for the development of 

proliferative cholangiofibrotic lesions in the 

liver, as well as the precise cell of origin, have 

not been definitively determined. However, it 

is clear that significant hepatotoxicity is a 

prerequisite for the eventual development of 

cholangiofibrotic lesions including intestinaltype cholangiocarcinomas in the liver. Such 

hepatotoxicity was evident in association with 

cholangiofibrotic lesions in female rats fed high 

dietary concentrations of proquinazid [RMS: 

these tumors were seen at > 600ppm i.e. at >35 

mg/kg bw/day which is a moderate, not high, 

dose level]
Proquinazid Human Health Risk Assessment DP No. 399842

Page 36 of 49

A.3 Hazard Identification and Endpoint Selection

A.3.1 Acute Reference Dose (aRfD) - Females age 13-49

An endpoint was not selected for Females 13-49 years old since no developmental effects that 

could be attributed to a single exposure were identified in the proquinazid database.

A.3.2 Acute Reference Dose (aRfD) - General Population

Study selected: Acute neurotoxicity study (rat)

MRID No.: 48696359

Dose and Endpoint for Risk Assessment: NOAEL = 50 mg/kg/day based on decreased motor 

activity seen at the LOAEL of 100 mg/kg/day in females on day 1.

Comments about Study/Endpoint/Uncertainty Factors: Decreased motor activity in the acute 

neurotoxicity study was considered a treatment-related effect and appropriate for endpoint 

selection. This is a single dose effect seen on day 1. While the dose-response for the decreased 

motor activity was fairly flat, the percentage decreases were statistically significant and >40% 

and were considered treatment-related and adverse for all doses ≥100 mg/kg/day. The selection 

of an observation time of 1-3 hours post dosing on day one in the ACN was considered to be 

suboptimal since the ADME study showed a plasma tmax of 6-10 hours following a single dose of 

20 mg/kg/day. If the endpoint had been evaluated at the time of peak plasma concentration, a 

more robust response may have been seen. The total UF is 1000 (10X for interspecies 

uncertainty factor, 10X for intraspecies variability, and a 10X FQPA database uncertainty 

factor).

aRfD = aPAD = 50 mg/kg/day = 0.050 mg/kg/day

 1000

A.3.3 Chronic Reference Dose (cRfD) `

Study Selected: Chronic toxicity/carcinogenicity study (rat)

MRID No.: 48696348

Dose and Endpoint for Risk Assessment: NOAEL = 1.2 mg/kg/day (males) based on test 

substance-related increases in non-neoplastic liver lesions and changes in thyroid hormones and 

pathology seen at LOAEL = 12 mg/kg/day (males).

Comments about Study/Endpoint/Uncertainty Factors: This study was selected since the 

database reveals that the rodent is the most sensitive species and effects to the liver and thyroid 

are considered the most sensitive endpoints. The duration of 2 years and route of exposure

through feed is also appropriate. It is a robust endpoint that is protective of adverse effects 
Proquinazid Human Health Risk Assessment DP No. 399842

Page 37 of 49

observed in other studies, including cancer effects. The NOAEL (1.2 mg/kg/day) is similar to the 

NOAEL observed in the rat reproduction study (2 mg/kg/day). The total UF is 300 (an 

interspecies scaling factor of 3x, lowered from 10X for pharmacodynamics (rats eliminate 

thyroxine (a thyroid hormone) at a higher rate than humans), an intraspecies variability factor of 

10X, and a 10X FQPA database uncertainty factor). 

cRfD = cPAD = 1.2 mg/kg/day = 0.004 mg/kg/day

 300

A.4 Executive Summaries

A.4.1 Subchronic Toxicity

870.3050 28-Day Oral Toxicity – Rat

This executive summary and classification determination was prepared by the EPA reviewer. 

The purpose of these studies was to investigate the toxicity of DPX-KQ926 technical to male rats 

when administered via the diet for 28 consecutive days (MRID 48696336). Young adult male 

Crl:CD (IGS)BR rats were administered diets containing 0, 10, 30, 300, or 3000 ppm 

proquinazid (adjusted for purity of 97.03%) for 28 days. Rats were about 10 weeks old at the 

start of dosing. The test substance was dissolved in acetone and then mixed in the diet. There 

were 100 rats per concentration, with generally different subsets of rats being used for hormonal 

analysis, for cell proliferation and for biochemistry/histopathology at each concentration. 

Satisfactory data were provided for homogeneity, stability and achieved concentration of the 

active ingredient in the diet. Due to excessive body weight depression in the 3000 ppm dose 

group, all rats in that group were killed on Test Day 18 and did not contribute further to the 

study. The mean daily intake of proquinazid was 0.6 1.9 and 19 mg/kg/day for the 10, 30, and 

300 ppm dose groups, respectively. The increase of liver weight and hepatocellular hypertrophy 

was considered adaptive. The NOAEL was 30 ppm (1.9 mg/kg bw/day) based on the spectrum of 

adverse effects (increased serum TSH and rT3, decreased serum T3 and T4, increased UDPglucuronyltransferase activity, decreased 5’-deiodinase activity, and thyroid follicular cell 

hypertrophy) that was observed at the LOAEL of 300 ppm (19 mg/kg bw/day).

This 28-day oral toxicity study in the rat is classified as acceptable/guideline.

870.3100 90-Day Oral Toxicity – Rat

This executive summary and classification determination was prepared by the EPA reviewer. 

The purpose of these studies was to investigate the toxicity of DPX-KQ926-75 technical to both 

female and male rats when administered via the diet for 90+ consecutive days (MRID 

48696337). Young adult Crl:CD (SD) IGS BR rats (10 rats/sex/concentration) were 

administered diets containing proquinazid (DPX-KQ926-75) at concentrations of 0, 30, 100, 300, 

or 2000 ppm for males, and 0, 30, 100, 300, or 600 ppm for females for approximately 104 days. 

Mean daily intakes were: males: 0, 2, 6, 19, and 127 mg/kg bw/day and females: 0, 2, 8, 24 and 

50 mg/kg bw/day. The follicular cell hypertrophy of the thyroid in the absence of persistent 
Proquinazid Human Health Risk Assessment DP No. 399842

Page 38 of 49

changes in thyroid hormones is not considered to be a non-adverse response and hence 

concluded that the NOAEL was 30 ppm (2 mg/kg bw/day) in males and 100 ppm (8 mg/kg 

bw/day) in females. The LOAELs were based on thyroid hypertrophy coupled with hormonal 

changes associated with the thyroid at 100 ppm (6 mg/kg/ bw/day) and above for males and on 

decreases in white blood cell counts at 300 ppm (24 mg/kg bw/day) and above for females. 

Decrements in body weight and nutritional parameters were also present at higher doses, together 

with hepatocyte hypertrophy (but no clear evidence of hepatocellular damage). At 30 ppm, 

increased severity of altered colloid in the thyroid of males is not considered an adverse effect.

This 90-day oral toxicity study in the rat is classified as acceptable/guideline.

870.3100 90-Day Oral Toxicity - Mouse

No study was submitted. The applicant states that reports of 28-day and 90-day feeding studies 

with mice were not submitted because they were conducted on an early laboratory sample that is 

not representative of the current production process and add no additional information.

870.3150 90-Day Oral Toxicity – Dog

This executive summary and classification determination was prepared by the EPA reviewer. 

The purpose of these studies was to investigate the toxicity of DPX-KQ926 technical to through 

dietary administration to dogs for 90-days (MRIDs 48696339 and48696340). Proquinazid was 

offered to beagle dogs (4/sex/concentration) in 400g of food for 1-2h/day at concentrations of 0, 

500, 2000, or 4000/3000 ppm; these concentrations were corrected for purity of 97%. Due to 

decreased food consumption and body weight loss, the 4000 ppm groups received basal diet 

during Study Week 5 and resumed test substance administration during Study Week 6 at 3000 

ppm. Originally, ‘dry’ proquinazid was mixed with the diet but because of poor homogeneity 

from week 3 proquinazid was added to acetone before being mixed in the diet; satisfactory 

homogeneity data were then achieved. Satisfactory data were provided for stability and achieved 

concentration of the a.i. in the diet. The mean daily intakes were: males: 0, 17, 62, and 87 mg/kg 

bw/day and females: 0, 18, 56, and 95 mg/kg bw/day. The clinical findings included: decreases 

in body weight, body weight gain at dietary concentrations of 3000/4000 ppm (LOAEL) and 

above. Other findings, including eye discharge and decreased food consumption may have been 

due to local effects (ocular irritation) or decreased palatability rather than systemic toxicity, 

respectively, therefore, the NOAEL for systemic toxicity was found to be 2000 ppm.

This 90-day oral toxicity study in the dog is classified as acceptable/guideline and is considered 

supplemental.

870.3200 21/28-Day Dermal Toxicity – Rat

This executive summary and classification determination was prepared by the EPA reviewer. 

The purpose of this study was to investigate the toxicity of DPX-KQ926 technical to male rats 

when applied via the dermal route for 28 consecutive days (MRID 48696341). In a 28-day 

dermal study, proquinazid was moistened with deionised water to form a paste and applied to the 

shaved, intact dorsal skin of male and female Crl: CD (SD)BR rats (10/sex/dose) for 28 daily 
Proquinazid Human Health Risk Assessment DP No. 399842

Page 39 of 49

(consecutive) applications. The rats were exposed to the test substance, applied under gauze and 

self-adhesive bandages, for 6 hours per day. Exposure doses were 100, 500, 1000, or 2000 

mg/kg bw/day (adjusted for a purity of 96.4%). There were also control animals (10/sex).

The main finding in this 28-day dermal study in rats, hypertrophy of thyroid and liver, and 

reduced body weight gain. The NOAEL for systemic effects was 500 mg/kg bw/day for males 

and 100 mg/kg bw/day for females. In males, a LOAEL of 1000 mg/kg bw/day based on thyroid 

hypertrophy and increased liver weight and hepatocyte hypertrophy. In females, the LOAEL 

was 500mg/kg bw/day was based on body weight decrements, nutritional parameters, increased 

liver weight, and hepatic hypertrophy at the LOAEL and doses greater than that. Male and 

female rats both showed desquamation and/or erythema at the application site at 1000mg/kg 

bw/day and above with a NOAEL of 500 mg/kg bw/day for local dermal effects.

This 28-day dermal toxicity study in the rat is classified as acceptable/guideline.

A.4.2 Prenatal Developmental Toxicity

870.3700a Prenatal Developmental Toxicity Study – Rat

This executive summary and classification determination was prepared by the EPA reviewer. 

Proquinazid was administered by oral gavage to mated Crl:CD (SD)BR female rats (25/dose 

group) on Gestation Days 7-21(MRID 48696342). Gavage doses in 0.5% methyl cellulose 

vehicle were 0, 5, 10, 30, or 60 mg/kg bw/day. The maternal and developmental NOAEL was 30 

mg/kg bw/day based on the evidence of delayed fetal development (reduced weight and an 

increased incidence of retarded ossification and patent ductus arteriosus) seen in the presence of 

clear maternal toxicity (including a marked reduction in body weight gain after adjustment for 

uterine contents, reduced food consumption and clinical signs) with a LOAEL of 60 mg/kg 

bw/day. 

This prenatal developmental toxicity study in the rat is classified as acceptable/guideline.

870.3700b Prenatal Developmental Toxicity Study – Rabbit

This executive summary and classification determination was prepared by the EPA reviewer. 

Proquinazid was administered by oral gavage to time-mated Hra:(NZW)SPF female rabbits 

(22/dose group) on Gestation Days 7-28 (MRID 48696343). Gavage doses in 0.5% methyl 

cellulose vehicle were 0, 1, 2.5, 5, or 10 mg/kg bw/day. In rabbits, decreased fetal weight was 

seen in the presence of maternal toxicity (reduction in body weight gain after adjustment for 

uterine contents). The NOAEL was 2.5 mg/kg bw/day for both maternal and developmental 

endpoints, while the LOAELs for both were 5 mg/kg bw/day with maternal effects being 

decreased body weight gains and food consumption and the developmental effects were 

decreased mean fetal weight. 

This prenatal developmental toxicity study in the rabbits is classified as acceptable/guideline.
Proquinazid Human Health Risk Assessment DP No. 399842

Page 40 of 49

A.4.3 Reproductive Toxicity

870.3800 Reproduction and Fertility Effects - Rat

This executive summary and classification determination was prepared by the EPA reviewer.

During the conduct of the 2002 study, a more detailed protocol for 2-generation reproduction 

studies was promulgated. Therefore, the 2-generation study (2003) was repeated in accordance 

with more recent regulatory guidelines (MRID 48696345). A two-generation reproduction study 

was conducted with proquinazid (DPX-KQ926-85) involving the production of one set of litters 

in each generation. Throughout this study, Crl:CD (SD)IGS BR rats (30/sex/concentration) were 

fed diets containing 0, 10, 30, 150, or 600 ppm proquinazid. Proquinazid was dissolved in 

acetone before being mixed with diet. Following at least 70 days of diet administration 

(premating), the P1 and F1 generation males and females were co-housed within their respective 

treatment groups, to produce F1 and F2 litters, respectively. Dams were allowed to deliver and 

rear their offspring until weaning (Postpartum Day 21). At weaning, 30 F1 rats/sex/group were 

randomly selected as the F1 parental generation and were given the same concentration level as 

their respective P1 generation sires and dams. F1 and F2 litters were culled to 4 pups/sex/litter 

(litter size permitting) on Postnatal Day 4; all remaining pups were discarded without further 

evaluation. No deaths and no test substance-related clinical signs were observed. Thyroid 

hypertrophy in P1 and F1 males and females occurred at the lowest dose tested (9-11 mg/kg 

bw/day). . Increased incidence/severity of altered colloid in thyroid at 10 and 30 ppm is not

considered to be an adverse finding. There were no effects on reproductive parameters and 

reproductive organs. Pup growth and development was effected with a marginal reduction in 

total litter weight of F1 pups during lactation at 44 mg/kg bw/day.

The parental/systemic NOAEL was 30 ppm (2 mg/kg bw/day). The parental/systemic 

LOAEL was 150 ppm (9-11 mg/kg bw/day) based on thyroid hypertrophy in P1 and F1 males 

and females fed. 

The reproductive NOAEL was 600 ppm (35-44 mg/kg bw/day), the highest concentration 

tested, based on absence of effects on reproductive parameters and reproductive organs. The 

reproductive LOAEL was not established. 

The offspring NOAEL was 150 ppm (11 mg/kg/day). The offspring LOAEL was 600 ppm (44 

mg/kg bw/day) based on a marginal reduction in total litter weight of F1 pups during lactation, 

which was likely secondary to maternal toxicity in P1 females.

The repeated 2-generation reproduction study in the rats is classified as acceptable/guideline.

A.4.4 Chronic Toxicity

870.4100a (870.4300) Chronic Toxicity – Rat

See 870.4300.
Proquinazid Human Health Risk Assessment DP No. 399842

Page 41 of 49

870.4100b Chronic Toxicity – Dog

This executive summary and classification determination was prepared by the EPA reviewer. 

The purpose of this study was to investigate the toxicity of DPX-KQ926 technical to beagle dogs 

administered via the diet for 1 year (MRID 48696346). Proquinazid was administered to beagle 

dogs (5/sex/concentration) at doses of 0 (empty capsules), 15, 60, or 180 mg/kg bw/day for 

54 consecutive weeks. The dose level for the high dose group was 60 mg/kg/day for Study 

Week 0, 120 mg/kg/day for Study Week 1, and 180 mg/kg/day for the remainder of the study. 

Concentrations were corrected for purity of 97%. A NOAEL of 15 mg/kg bw/day is proposed 

for males based on reduced body weight gain seen at a LOAEL of 60 mg/kg bw/day. A NOAEL 

of 60 mg/kg/day for females was based on decreases in body weight and/or reductions in body 

weight gains at a LOAEL of 180 mg/kg/day. 

This 1-year chronic toxicity study in the dog is classified as acceptable/guideline

A.4.5 Carcinogenicity

870.4200a Carcinogenicity Study – rat

See 870.4300.

870.4200b Carcinogenicity (feeding) – Mouse

In a carcinogenicity study (MRID 48696347), proquinazid (94.1-98.4% a.i.; Batch No. KQ926-

45) was administered in the diet to Crl:CD-1 (ICR) BR mice (70/sex/group) for up to 80 weeks 

at concentrations of 0, 5, 30, 200, or 2000 ppm (equivalent to 0/0, 0.7/1.0, 4/6, 27/38, and 

282/415 mg/kg bw/day in males/females). The NOAEL in mice was 30 ppm for males and 

females (4 and 6 mg/kg/day, respectively). This LOAEL was based on non-neoplastic lesions in 

the liver at 200 ppm (27 and 38 mg/kg bw/day). Non-neoplastic lesions were also present in the 

thyroid gland of male and female mice fed 2000 ppm. Increased liver weight and hepatocyte 

hypertrophy at 2000 ppm was probably due, at least in part, to the observed induction of 

cytochrome P-450 and increase in peroxisome proliferation. No treatment-related tumors were 

observed in male or female mice.

This study is classified as acceptable/guideline and satisfies the guideline requirements.

870.4300 Chronic Toxicity/Carcinogenicity (feeding) - Rat

In a 2 year combined chronic toxicity/carcinogenicity feeding study in rats (MRID 48696348), 

proquinazid (93.1-96.5% a.i.; Batch No. KQ926-45) was administered in the diet to 

Crl:CD (SD)BR rats (80/sex/group) at concentrations of males/females 0/0, 10/10, 30/30,

300/300, 1000/600, or 2000/1200 ppm (equivalent to 0/0, 0.4/0.5, 1.2/1.4, 12/16, 43/35, and 

92/76 mg/kg bw/day in males/females). The NOAEL in rats was 30 ppm in males and females 

(1.2 and 1.4 mg/kg/day, respectively) based on test substance-related increases in non-neoplastic 

liver lesions and changes in thyroid hormones and pathology at a LOAEL of 300 ppm (12 and 16 

mg/kg bw/day). 
Proquinazid Human Health Risk Assessment DP No. 399842

Page 42 of 49

Proquinazid was oncogenic, causing thyroid tumors (follicular cell adenomas in males at 1000 

ppm and above) and liver tumors (hepatocellular adenomas in females at 600 ppm and above).

The thyroid tumors had acceptable mode of action (MOMA) data. In females at 600 ppm and 

above there was treatment related incidence and acceptable MOA data for cholangiocarcinomas.

This study is classified as acceptable/guideline and satisfies the guideline requirements.

A.4.6 Mutagenicity

870.5100 Bacterial Reverse Mutation

The purpose of these studies was to investigate the in vitro toxicity of DPX-KQ926-45, -75, and 

metabolite IN-MM671. IN-MM671 was evaluated for mutagenicity in Salmonella typhimurium

strains TA97a, TA98, TA100, TA1535, and in Escherichia coli strain WP2 uvrA (pKM101) with 

and without an exogenous metabolic activation system (10% Aroclor -induced rat liver S9 (v/v), 

4.0 mg/mL protein). Nominal concentrations of 10, 50, 100, 500, 1000, 2500, and 5000 g/plate 

were evaluated in Trial 1. Nominal concentrations of 10, 50, 100, 500, 750, 1000, and 2500 

g/plate were evaluated in Trial 2. The two 2 independent trials used standard plate 

incorporation methods. The highest dose level in Trial 1 was set based on the limit dose for this 

test system, and in Trial 2 based on cytotoxicity observed in Trial 1. The test substance was 

administered to the test system as a solution in dimethyl sulfoxide (DMSO). Proquinazid (DPXKQ926-45); (DPX-KQ926-75); and Metabolite IN-MM671 were all negative for mutagenic 

activity in the non-activated and S9-activated test systems in the in vitro bacterial gene mutation 

assay (MRIDs 48696349, 48696350, 48696351)

These bacterial reverse mutation studies (in vitro) are classified as acceptable/guideline.

870.5300 Gene Mutation

Proquinazid was tested in the CHO/HPRT mutation assay with and without an exogenous 

metabolic activation system (Aroclor1254 -induced rat liver S9). An initial, independent repeat 

and third mutagenesis assay were conducted. The third assay (S9 activated test system only) was 

conducted due to the lack of toxicity observed in the independent repeat assay. The test 

substance was dissolved in acetone at a maximum concentration of 500 mg/mL. The purpose of 

these studies was to investigate the in vitro toxicity of DPX-KQ926-45 and L5178 mouse 

lymphoma cells. The findings of the initial study (MRID 48696352) were considered by the UK 

Committee on Mutagenicity to be not interpretable. Upon recommendation a mouse lymphoma 

assay conducted to internationally accepted standards and provided to address this endpoint. 

Proquinazid was negative in the non-activated and S9-activated test systems in this mouse 

lymphoma assay (MRID 48696353).

This gene mammalian mutation study (in vitro) is classified as acceptable/guideline.
Proquinazid Human Health Risk Assessment DP No. 399842

Page 43 of 49

870.5375 Chromosome Aberration

Proquinazid (DPX-KQ926-45) was tested in the in vitro mammalian cytogenetic test using 

human peripheral blood lymphocytes (from 3 adult males and 3 adult females) both with and 

without an exogenous metabolic activation system (Aroclor -induced rat liver S9). The purpose 

of these studies was to investigate the in vitro toxicity of Proquinazid (DPX-KQ926-45) and was 

found to be negative for structural and numerical chromosome aberrations in the non-activated 

and S9-activated test systems in the in vitro mammalian cytogenetics test using human peripheral 

blood lymphocytes. 

This mammalian chromosomal aberration study (in vitro) is classified as acceptable/guideline.

870.5395 Mammalian Erythrocyte Micronucleus

Proquinazid was evaluated for its ability to induce micronucleated polychromatic erythrocytes 

(MNPCEs) in the bone marrow of Cr1: CD-1 (ICR)BR mice (5/sex/dose/sample time, with 

5/sex extra at the top dose). Male and female mice received 0, 360, 720, or 1400 mg/kg bw by 

single-dose oral gavage. Proquinazid (DPX-KQ926-45) did not induce an increase in 

micronuclei in bone marrow cells of mice and is considered negative in this in vivo assay. The 

clinical signs of toxicity seen in mice (especially ataxia and lethargy in the absence of diarrhea) 

are indicative of systemic exposure (and hence likely exposure of the bone marrow) to 

proquinazid and/or metabolites (MRID 48696355). 

Proquinazid was evaluated for its ability to induce micronucleated polychromatic erythrocytes 

(MNPCEs) in the bone marrow of Cr1:CD-1 (ICR)BR mice (5/sex/dose/sampling time, with an 

extra 5/sex at the top dose). Male mice received 720, 1440, or 2000 mg/kg bw by single-dose 

oral gavage. Doses in females were 360, 720, or 1440 mg/kg bw. The highest dose level was set 

based on a previous mouse micronucleus study conducted with the technical material DPXKQ926-45 and a range finding study conducted with the current batch of technical material. The 

test substance was suspended in corn oil at a top concentration of 200 mg/mL. Proquinazid 

(DPKQ926-75) did not induce an increase in micronuclei in bone marrow cells of mice and is 

considered negative in this in vivo assay. The rapid appearance of clinical signs of toxicity in 

mice is indicative of rapid absorption and likely systemic exposure (including bone marrow) to

proquinazid and/or metabolites (MRID 48696356).

IN-MM671 was evaluated for its ability to induce micronucleated polychromatic erythrocytes 

(MNPCEs) in the bone marrow of Cr1:CD-1 (ICR)BR mice (5/sex/dose/sampling time, with an 

extra 5/sex at the top dose ). Male and female mice received 0, 500, 1000, or 2000 mg/kg by 

single-dose oral gavage. The highest dose level was set based on the limit dose for this test 

system. The test substance was dissolved in corn oil at concentrations of 51.0, 103.3, and 205.0 

mg/mL after adjusting for purity. Cyclophosphamide (40 mg/kg) was used as the positive 

control. IN-MM671 did not induce an increase in micronuclei in bone marrow cells of mice, and 

is considered negative in this in vivo assay (MRID 48696357).
Proquinazid Human Health Risk Assessment DP No. 399842

Page 44 of 49

These mammalian erythrocytes micronucleus studies (in vivo) are classified as 

acceptable/guideline.

870.5550 Unscheduled DNA Synthesis

The purpose of these studies was to investigate the in vitro toxicity of Proquinazid (DPXKQ926-45) and was found to not cause a significant increase in unscheduled DNA synthesis and 

was concluded to be negative in this assay. DPX-KQ926-45 was tested in the unscheduled DNA 

synthesis (UDS) assay using primary cultures of rat hepatocytes. In both initial and independent 

repeat assays, the test substance was tested at eight dose levels, ranging from 3.9 to 500 g/mL, 

and fully evaluated for UDS at five dose levels of 7.8, 15.6, 31.3, 63, and 125 g/mL. The 

highest dose level was set based on the limit dose for this test system, and cytotoxicity data from 

a range finding experiment. For both the initial and repeat assays, the test substance was 

administered to the test system as a solution in acetone at a maximum concentration of 500 

mg/mL. Proquinazid (DPX-KQ926-45) did not cause a significant increase in unscheduled DNA 

synthesis and was concluded to be negative in this assay (MRID 48696358).

This unscheduled DNA synthesis in mammalian cultured cell study (in vitro) is classified as 

acceptable/guideline.

A.4.7 Neurotoxicity

870.6200 Acute Neurotoxicity Screening Battery

This executive summary and classification determination was prepared by the EPA reviewer. 

The purpose of these studies was to investigate the toxicity of DPX-KQ926 technical to rats in an 

acute neurotoxicity screening battery (MRID 48696359). Proquinazid was administered to 

Crl:CD BR rats (12 rats/sex/dose) by single-dose gavage as a suspension in 0.5% methyl 

cellulose in water. Dose volumes were 10 mL/kg bw. Dose levels (adjusted for purity) in both 

sexes were: 0, 100, 500, or 2000 mg/kg bw . In order to establish a NOAEL for females, 12 

females/dose were similarly administered a single dose by oral gavage of: 0, 15, 30, or 50 mg/kg 

bw. 

The NOAEL for neurotoxicity was 100 mg/kg bw for males and 50 mg/kg bw for females based 

on decreased motor activity on the day of exposure at the LOAEL of 500 mg/kg bw and above in 

males and at 100 mg/kg bw and above in females. While the dose-response for the decreased 

motor activity in females was fairly flat, the percentage decreases were statistically significant 

and >40% and were considered treatment-related and adverse for all doses ≥100 mg/kg/day.

While there was a 23% decrease in motor activity in females at 50 mg/kg/day, this finding was 

not toxicologically relevant and considered a NOAEL because it was (i) not statistically 

significant (i.e., within the standard deviation) and (ii) within the normal variability historically 

observed for motor activity in adult rats (typically the variability is 20-53%) reported in studies 

from labs worldwide (Moser et al., 2007). Females in the 2000 mg/kg group had increased 

incidences of hunched posture and staining of the skin in various locations. On Test Day 8, hind 

limb grip strength and foot splay were significantly decreased in 2000 mg/kg bw females, and 
Proquinazid Human Health Risk Assessment DP No. 399842

Page 45 of 49

foot splay was significantly decreased in 2000 mg/kg bw males and females. Affected rats 

appeared to completely recover by Test Day 15.

This acute neurotoxicity screening battery in the rat is classified as acceptable/guideline.

870.6200 Subchronic Neurotoxicity Screening Battery

This executive summary and classification determination was prepared by the EPA reviewer. 

The purpose of these studies was to investigate the toxicity of DPX-KQ926-45 and -75 technical 

to rats when administered via the diet for 90 consecutive days as well as the subchronic 

neurotoxic effects (MRID 48696338). In a combined subchronic toxicity study and subchronic 

neurotoxicity study, Crl:CD BR rats (22 rats/sex/concentration) were administered diets 

containing 0, 30, 100, 300, or 2000 ppm proquinazid (DPX-KQ926-45) for males or 0, 30, 100, 

300, or 600 ppm for females for approximately 90 days. The mean daily intakes were: males: 0, 

2, 6, 19, and 135 mg/kg bw/day and females: 0, 2, 8, 23, and 50 mg/kg bw/day. Within each 

dose group, 10 rats were designated as the toxicity subgroup and 12 rats were designated as the 

neurotoxicity subgroup. 

The NOAEL for the systemic toxicity of proquinazid (DPX-KQ926-45) was 30 ppm (2 mg/kg 

bw/day) in males and 100 ppm (8 mg/kg bw/day) in females based on hormonal and 

morphological changes (hypertrophy) in the thyroid at a LOAEL of 100 ppm (6 mg/kg bw/day) 

in males and at 300 ppm (23 mg/kg bw/day) in females. Decrements in body weight and 

nutritional parameters, as well as microscopic and clinical pathological changes in the liver, were 

also present at higher doses. The NOAEL for neurotoxicity was 2000 ppm (135 mg/kg/day) in 

males and 600 ppm (49.7 mg/kg/day) in females, the highest dietary concentrations tested.

Under the conditions of the later study with a newer manufacturing process, the NOAEL values

in the 90-day feeding study with proquinazid (DPX-KQ926-75) was the same with a NOAEL of 

30 ppm (2 mg/kg bw/day) in males and 100 ppm (8 mg/kg bw/day) in females based on thyroid 

hypertrophy and hormonal changes associated with the thyroid at a LOAEL of 100 ppm (6 

mg/kg/bw/day) and above for males and on decreases in white blood cell counts at 300 ppm (24 

mg/kg bw/day) and above for females. Decrements in body weight and nutritional parameters 

were also present at higher doses, together with hepatocyte hypertrophy (but no clear evidence of 

hepatocellular damage).

This combined 90-day oral toxicity study and subchronic neurotoxicity screening battery in the 

rat are classified as acceptable/guideline.

870.6300 Developmental Neurotoxicity Study

A.4.8 Metabolism

870.7485 Metabolism – Rat

This executive summary and classification determination was prepared by the EPA reviewer. 

The purpose of these studies was to investigate the toxicity of DPX-KQ926 technical to rats in 
Proquinazid Human Health Risk Assessment DP No. 399842

Page 46 of 49

both a single dose and a repeat dose study of 7 consecutive days (MRIDs 48696360 and 

48696361). Experiments were conducted in male and female Sprague-Dawley CVF+ rats 

using the radiolabel [phenyl14C(U)]proquinazid (DPX-KQ926) at gavage doses of 1 mg/kg and 

20 mg/kg, and a dose volume of 4 ml/kg. Single dose: Proquinazid was virtually completely 

absorbed at the 1 and 20 mg/kg doses. There was extensive metabolism, based on very low 

excretion of parent compound and extensive excretion of metabolised dose in urine and feces. 

Biliary excretion accounted for essentially all of the fecal excretion. The elimination half-life for 

total radioactive residues was 8-12 hours, and by 7 days post dosing little potential for 

accumulation of residues was seen (<1% of the dose in the body). Major biotransformations 

observed were the loss of side chains and hydroxylation/oxidation both at the phenyl ring and 

side chains. Repeat dose: Male and female rats were dosed with approximately 1 mg/kg of 

[phenyl14C(U)]proquinazid for 7 consecutive days and sacrificed at approximately 4.4-6.1, 24-

25, 48-49, and 169-170 hours after the last dose. The concentration of radioactivity in tissues 

declined rapidly following the last dose. Tissue residue concentrations were generally lower 

than plasma concentrations with the exception of liver, kidney, and fat. There appeared to be 

little potential for bioaccumulation. Extensive metabolism of proquinazid was observed. The 

most abundant metabolites in urine and feces were the same as observed in the single dose study. 

A small percentage of 14C-proquinazid (up to 6%) was deiodinated and excreted as a ring 

hydroxylated product.

This metabolism and pharmacokinetics studies in the rat are classified as acceptable/guideline.

A.4.9 Immunotoxicity

870.7800 Immunotoxicity

In an immunotoxicity study (MRID No. 48778901), Proquinazid (95%, Lot No. 30041) was 

administered in the diet to female Crl:CD(SD) rats (10/group) at concentrations of 0, 50, 200, 

600, or 1200 ppm (equivalent to 0, 4, 14, 42, or 82 mg/kg/day, respectively) for 28 days. A group 

of 10 females in the positive control group received intraperitoneal injection of 

Cyclophosphamide at a dose of 25 mg/kg/day during Days 23-27. On Day 23, animals in all 

groups were immunized with a suspension of sheep red blood cells (SRBC) by intravenous 

injection (4 x108SRBC/animal, 0.5 mL/animal dose volume). Animals were sacrificed on Day 

28. All animals were evaluated for mortality, clinical signs, body weight changes, food 

consumption, water consumption, organ weights and gross pathology. Immunotoxicity was 

assessed for all animals by using an enzyme-linked immunosorbent assay (ELISA); brain, spleen 

and thymus weights were determined at necropsy. There were no effects of test substance 

treatment on mortality, clinical signs, food consumption, water consumption, spleen or thymus 

weights, or gross pathology. At the highest dose 1200 ppm (82 mg/kg/day), final body weight 

(test day 28) and overall body weight gains, food consumption, and food efficiency (test days 0-28) 

were reduced compared to the control. The systemic toxicity LOAEL is 1200 ppm (82 mg/kg/day) 

based on decreases in terminal body weight, body weight gain, food consumption and food 

efficiency. The NOAEL for systemic toxicity is 600 ppm (42 mg/kg/day).

This immunotoxicity study is classified acceptable/guideline and satisfy the guideline

requirements.
Proquinazid Human Health Risk Assessment DP No. 399842

Page 47 of 49

A.4.10 Additional information on batch variability

The toxicity tests summarized in this document were conducted with one of three specific 

batches of the technical material (DPX-KQ926-45, DPX-KQ926-75, and DPX-KQ926-85). A 

complete battery of mammalian toxicity studies was originally conducted with DPX-KQ926-45. 

During the course of the development of proquinazid the manufacturing process was modified 

and improved. Batches DPX-KQ926-75 and DPX-KQ926-85 are equivalent with respect to 

purity and impurity profile (see the Product Chemistry section, for full technical composition), 

and are representative of the commercial product produced by the current, improved 

manufacturing process. These technical materials are 98.3% and 97.7% (w/w) proquinazid, 

respectively. As there were differences in the purity and impurity profiles of technical material 

produced by the old and current methods, selected bridging studies were conducted to 

demonstrate the equivalent or lesser toxicity of material produced using the current method to 

that produced under the original process. These bridging studies (conducted with DPX-KQ926-

75) were a 90-day feeding study in rats, a bacterial reverse mutation test and an in vivo mouse 

micronucleus assay. These studies demonstrated that DPX-KQ926-75 exhibited equivalent or 

lesser toxicity to DPX-KQ927-45 and that like DPX-KQ927-45, is not likely to be genotoxic. 

Based on the results of these bridging studies, the remaining genotoxicity studies, as well as the 

chronic studies, the 90-day dog study, and the developmental and neurotoxicity studies 

conducted with DPX-KQ926-45 were not repeated using the current process material, thus 

greatly diminishing the use of animals. However, a complete battery of acute toxicity studies and 

a 2-generation reproductive study were conducted with the current process material (either DPXKQ926-75 or -85). The original two-generation reproduction study in rats was conducted with 

material produced by the previous process, DPX-KQ926-45, and was initiated prior to 

promulgation of the most recent (22 January, 2001) version of the OECD 416 guidelines for twogeneration reproduction toxicity studies. However, during the conduct of the study, some end 

points included in the 2001 update were included for the F

1 

(but not the P

1

) generation. The 

repeat two-generation reproduction study was conducted with test material representative of the 

current manufacturing process. In addition, this study was necessary in order to evaluate specific 

developmental and reproductive endpoints required in the updated OECD 416 guidelines that 

were not covered by the original study. Metabolism studies were conducted using a batch of 

pure proquinazid (DPX-KQ926-21, 99.2% w/w proquinazid).

Comparison of the results of 90-day studies in rats with proquinazid produced by the old method 

(batch KQ926-45) and the current method (batch KQ926-75) shows that the toxicity of the 

materials is mostly equivalent with respect to the thyroid effects, which generally form the basis 

of the NOAELs in rats. Also although liver weights were affected to a similar extent, other 

effects on the liver (clinical pathology and microscopic findings both sexes) were more 

pronounced with batch KQ926-45. Hence there are indications for the lesser toxic potential of 

proquinazid manufactured by the current process. Although a reduction in white blood cells in 

females (due primarily to reduced numbers of lymphocytes) was seen only with proquinazid 

manufactured by the new process, the toxicological significance of this finding is uncertain as 

there were no correlative effects on the histology of lymphoid organs (spleen, lymph node or 

thymus) or bone marrow. Taken together, these 90-day studies indicate similar target organs for 

the test materials produced by the former and current processes.
Proquinazid Human Health Risk Assessment DP No. 399842

Page 48 of 49

Appendix B. Metabolism Summary Table

Table B.1. Tabular Summary of Proquinazid Metabolites and Degradates

Chemical Name (other 

names in parenthesis) 

and Structure

Matrix Percent TRR (PPM) 1

Matrices - Major Residue 

(>10%TRR)

Matrices - Minor Residue 

(<10%TRR)

Parent Grapes 35-39% (0.08-0.09 ppm)

Grape Vines 52-75% 

IN-MM671 Grapes 3-8% (00.01 ppm)

Grape Vines --

IN-MM991 Grapes 2-3% (<0.01 ppm)

Grape Vines --

The final row of the table should have a concise summary of relevant parameters.

Crop 1; MRID No.48696316; Application Rate : 3 applications at 200 g ai/ha; Level of exaggeration compared to 

label rate (4x single application rate; 3x seasonal application rate); timing 30 day intervals (14 days on label); preharvest interval: samples collected 0, 14 and 29 days after the last application, compared to 60 day PHI on label.
Proquinazid Human Health Risk Assessment DP No. 399842

Page 49 of 49

Appendix C. Physicochemical Properties Table

Table 3.2. Physicochemical Properties of the Technical Grade Proquinazid.

Parameter Value Reference

Melting point/range 61.5 °C – 62 °C 48696308

pH 6.48 48696308

Density 1.57 g/mL 48696308

Water solubility (25°C) 0.97 mg/L 48696313

Solvent solubility (g/100 mL at 20°C to 

25°C)

Acetone >250 g/kg

Acetonitrile 154 g/L

Dichloromethane >250 g/kg

Dimethylformamide >250 g/kg

Ethyl acetate >250 g/kg

n-hexane >250 g/kg

methanol 136 g/L

1-octanol >250 g/kg

o-xylene >250 g/kg

48696313

Vapor pressure (25°C) 9 x 10-5 Pa 48696315

Dissociation constant, pKa No dissociation between pH 2.4 and 11.6 48696313

Octanol/water partition coefficient, log 

POW (25°C)

5.5 48696314

UV/visible absorption spectrum No absorbance maxima (λmax) above 325 

nm at pH <2, 7, and >10 buffer at 

concentrations of 12 and 19 μg/mL

48696312