UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

	

OFFICE OF                  

PREVENTION, PESTICIDES AND 

TOXIC SUBSTANCES        

MEMORANDUM

DATE:  28-January-2010

SUBJECT:	Difenoconazole  FQPA Human Health Risk Assessment to Support
the Establishment of Import Tolerances on Mango and Waxapple (also known
as Wax jambu)

PC Code:	128847	DP Barcode:	371612

Decision No.:	413927	Registration No.:  	N/A

Petition No.:	PP#9E7573	Regulatory Action:	Section 3

Risk Assessment Type: 	Single Chemical/Aggregate	Case No.:	NA

TXR No.:	NA	CAS No.:	119446-68-3

MRID No.:	NA	40 CFR	§180.475



FROM:		Yan Donovan, Risk Assessor

		Registration Action Branch IV 

		Health Effects Division (HED); 7509P

		

THROUGH:	Ray Kent, Branch Chief

		Susan V. Hummel, Senior Chemist

		Registration Action Branch IV 

		Health Effects Division (HED); 7509P

TO:		Rosemary Kearns/Tony Kish (RM 22)

		Fungicide Branch

		Registration Division (7505P)



Table of Content

  TOC \o "1-3" \h \z \u    HYPERLINK \l "_Toc251834880"  1.0	Executive
Summary	  PAGEREF _Toc251834880 \h  3  

  HYPERLINK \l "_Toc251834881"  2.0	Ingredient Profile	  PAGEREF
_Toc251834881 \h  7  

  HYPERLINK \l "_Toc251834882"  2.1	Summary of Proposed Uses	  PAGEREF
_Toc251834882 \h  7  

  HYPERLINK \l "_Toc251834883"  2.2	Structure and Nomenclature	  PAGEREF
_Toc251834883 \h  8  

  HYPERLINK \l "_Toc251834884"  3.0	Hazard Characterization/Assessment	 
PAGEREF _Toc251834884 \h  9  

  HYPERLINK \l "_Toc251834885"  3.1	Hazard and Dose-Response
Characterization	  PAGEREF _Toc251834885 \h  9  

  HYPERLINK \l "_Toc251834886"  3.1.1	Toxicological Effects and
Dose-response	  PAGEREF _Toc251834886 \h  9  

  HYPERLINK \l "_Toc251834887"  3.2	FQPA Considerations	  PAGEREF
_Toc251834887 \h  12  

  HYPERLINK \l "_Toc251834888"  3.2.1.  Determination of Susceptibility	
 PAGEREF _Toc251834888 \h  13  

  HYPERLINK \l "_Toc251834889"  3.2.2.  Adequacy of Toxicity Database	 
PAGEREF _Toc251834889 \h  13  

  HYPERLINK \l "_Toc251834890"  3.2.3.  Degree of Concern Analysis:	 
PAGEREF _Toc251834890 \h  13  

  HYPERLINK \l "_Toc251834891"  3.2.4. FQPA Safety Factor Recommendation
  PAGEREF _Toc251834891 \h  13  

  HYPERLINK \l "_Toc251834892"  3.3	Endocrine Disruption	  PAGEREF
_Toc251834892 \h  14  

  HYPERLINK \l "_Toc251834893"  4.0	Public Health and Pesticide
Epidemiology Data	  PAGEREF _Toc251834893 \h  14  

  HYPERLINK \l "_Toc251834894"  5.0	Dietary Exposure/Risk
Characterization	  PAGEREF _Toc251834894 \h  14  

  HYPERLINK \l "_Toc251834895"  5.1	Pesticide Metabolism and
Environmental Degradation	  PAGEREF _Toc251834895 \h  15  

  HYPERLINK \l "_Toc251834896"  5.1.1	Metabolism in Primary Crops	 
PAGEREF _Toc251834896 \h  15  

  HYPERLINK \l "_Toc251834897"  5.1.2	Metabolism in Rotational Crops	 
PAGEREF _Toc251834897 \h  15  

  HYPERLINK \l "_Toc251834898"  5.1.3	Metabolism in Livestock	  PAGEREF
_Toc251834898 \h  15  

  HYPERLINK \l "_Toc251834899"  5.1.4	Analytical Methodology	  PAGEREF
_Toc251834899 \h  15  

  HYPERLINK \l "_Toc251834900"  5.1.5	Environmental Degradation	 
PAGEREF _Toc251834900 \h  16  

  HYPERLINK \l "_Toc251834901"  5.1.6	Comparative Metabolic Profile	 
PAGEREF _Toc251834901 \h  16  

  HYPERLINK \l "_Toc251834902"  5.1.7	Toxicity Profile of Major
Metabolites and Degradates	  PAGEREF _Toc251834902 \h  16  

  HYPERLINK \l "_Toc251834903"  5.1.8	Pesticide Metabolites and
Degradates of Concern	  PAGEREF _Toc251834903 \h  17  

  HYPERLINK \l "_Toc251834904"  5.1.9	Drinking Water Residue Profile	 
PAGEREF _Toc251834904 \h  17  

  HYPERLINK \l "_Toc251834905"  5.1.10	Food Residue Profile	  PAGEREF
_Toc251834905 \h  18  

  HYPERLINK \l "_Toc251834906"  5.1.11	International Residue Limits	 
PAGEREF _Toc251834906 \h  19  

  HYPERLINK \l "_Toc251834907"  5.2	Dietary Exposure and Risk	  PAGEREF
_Toc251834907 \h  19  

  HYPERLINK \l "_Toc251834908"  6.0	Residential (Non-Occupational)
Exposure/Risk Characterization	  PAGEREF _Toc251834908 \h  21  

  HYPERLINK \l "_Toc251834909"  6.1	Residential Handler Exposure and
Risk Characterization	  PAGEREF _Toc251834909 \h  21  

  HYPERLINK \l "_Toc251834910"  7.0	Aggregate Risk Assessments and Risk
Characterization	  PAGEREF _Toc251834910 \h  22  

  HYPERLINK \l "_Toc251834911"  7.1	Acute & Chronic Aggregate Risk	 
PAGEREF _Toc251834911 \h  22  

  HYPERLINK \l "_Toc251834912"  7.2	Short- and Intermediate-Term
Aggregate Risk	  PAGEREF _Toc251834912 \h  22  

  HYPERLINK \l "_Toc251834913"  8.0	Cumulative Risk
Characterization/Assessment	  PAGEREF _Toc251834913 \h  23  

  HYPERLINK \l "_Toc251834914"  9.0	Occupational Exposure/Risk Pathway	 
PAGEREF _Toc251834914 \h  24  

  HYPERLINK \l "_Toc251834915"  10.0	Data Needs and Label
Recommendations	  PAGEREF _Toc251834915 \h  24  

  HYPERLINK \l "_Toc251834916"  11.0	References:	  PAGEREF _Toc251834916
\h  26  

  HYPERLINK \l "_Toc251834917"  12.0	Tolerance Summary	  PAGEREF
_Toc251834917 \h  27  

  HYPERLINK \l "_Toc251834918"  13.0	Appendices	  PAGEREF _Toc251834918
\h  28  

  HYPERLINK \l "_Toc251834919"  Appendix 1: Acute Toxicity Data on
Difenoconazole Technical	  PAGEREF _Toc251834919 \h  28  

  HYPERLINK \l "_Toc251834920"  Appendix 2: Subchronic, Chronic and
Other Toxicity Profile	  PAGEREF _Toc251834920 \h  29  

  HYPERLINK \l "_Toc251834921"  Appendix 3.  Proposed Metabolic Pathway
for difenoconazole in Rats	  PAGEREF _Toc251834921 \h  49  

  HYPERLINK \l "_Toc251834922"  Appendix 4   Environmental Fate
Degradates	  PAGEREF _Toc251834922 \h  50  

 1.0	Executive Summary  TC \l1 "1.0	Executive Summary 

Difenoconazole is a broad spectrum fungicide belonging to the triazole
group of fungicides (Group 3).  It is currently registered in the U.S.
for use as a seed treatment on cereal grains, canola, and cotton and for
foliar applications to pome fruits, sugar beets, fruiting vegetables,
and tuberous and corm vegetables.  Tolerances for difenoconazole are
currently established under 40 CFR §180.475.  Difenoconazole acts by
blocking demethylation during sterol biosysnthesis which, in turn,
disrupts membrane synthesis.  

Proposed Uses

Under PP#9E7573, Syngenta Crop Protection, Inc. is proposing the
establishment of import tolerances for residues of difenoconazole
[1-[2-[2-chloro-4-(4-chlorophenoxy)phenyl]-4-methyl-1,3-dioxolan-2-ylmet
hyl]-1H-1,2,4-triazole] in/on Mango at 0.09 ppm and on waxapple at 1.5
ppm.  The end-use product (EP) for use on mangos grown in Brazil is
Score®, an emulsifiable concentrate (EC) formulation containing 250 g
ai/L.  Up to three foliar spray applications at a target rate of 0.11 lb
ai/A/application (0.125 kg ai/ha/application), with a 14-day retreatment
interval (RTI), may be made to mature mango trees for a total seasonal
rate of 0.33 lb ai/A (0.375 kg ai/ha) using ground equipment.  The
preharvest interval (PHI) is 7days.  The EP for use on waxapples grown
in Taiwan is a soluble concentrate (SC) formulation containing 12.5% w/v
difenoconazole and 20% w/v azoxystrobin.  The information for waxapple
use in Taiwan is incomplete, however, the submitted field trial data
will support up to eight foliar applications of a 125 g/L SC formulation
of difenoconazole at a target rate of 0.34 lb ai/A/application (0.39 kg
ai/ha/application), with 6- to 8-day RTI (re-entry interval), to mature
waxapple trees for a total seasonal rate of 2.74 lb ai/A (3.07 kg ai/ha)
and a 12-day PHI.  Applications may be made using ground equipment. 
Consistent with the submitted field trial data, applications should be
restricted to fruit protected with exclusion net bags or otherwise
bagged fruit.  The subject review addresses difenoconazole only.

Toxicity/Hazard

Difenoconazole possesses low acute toxicity by the oral, dermal and
inhalation routes of exposure.  It is not considered to be an eye or
skin irritant and is not a sensitizer.  Difenoconazole exhibits some
evidence of neurotoxicity in the database, but the effects are transient
or occur at doses exceeding the limit dose.  It is not mutagenic andit
is not a developmental or reproductive toxicant.  Chronic effects in
rats and mice are seen as cumulative decreases in body weight gains.  
No evidence of carcinogenicity was seen in rats.  Evidence for
carcinogenicity was seen in mice where liver tumors were induced at
doses which were considered to be excessively high for carcinogenicity
testing. Treatment-related non-neoplastic lesions were confined to the
liver. Tumors were observed in mice at 46 and 58 mg/kg/day ( males and
females, respectively); however, based on excessive toxicity observed at
the two highest doses, the absence of tumors at the lower doses and the
absence of genotoxic effects, HED’s Cancer Peer Review Committee
(CPRC) recommended for a cancer classification of C (possible human
carcinogen).  A margin-of-exposure (MOE) approach to risk assessment was
advocated by the CPRC in July 2007.  The FQPA Safety Factor (SF) is
reduced to 1x.

The toxicological database for difenoconazole is sufficient to conduct
this risk assessment.  However, in accordance with Part 158 Toxicology
Data requirements, an immunotoxicity study (870.7800) is required for
difenoconazole.

Endpoints and doses for risk assessment were selected for the following
scenarios:  Acute dietary (general population including infants and
children), chronic dietary, short-term dermal and short-term inhalation.

Dietary Exposure/Risk Assessment

HED has examined the residue chemistry database for difenoconazole and
concluded that field trial data for mango are adequate and reflect the
proposed use of Score® on mango in Brazil.  Assuming that the use
directions for waxapple in Taiwan, once fully elucidated, will comport
with the submitted field trial data, HED believes that there are no
residue chemistry issues that would preclude granting import tolerances
for residues of difenoconazole on mango in Brazil and waxapple in
Taiwan.  

Acute and chronic dietary (food + water) risk assessments were conducted
using the Dietary Exposure Evaluation Model - Food Consumption Intake
Database (DEEM-FCID(, ver. 2.03.  This model uses food consumption data
from the United States Department of Agriculture’s (USDA’s)
Continuing Surveys of Food Intakes by Individuals (CSFII; 1994-1996 and
1998).  

The unrefined acute analysis assumed tolerance-level residues, 100% crop
treated (CT), and default processing factors.  The resulting acute food
exposure estimates were less than HED’s level of concern (<100% of the
acute population-adjusted dose (aPAD)) at the 95th percentile of the
exposure distribution for the general U.S. population (7% aPAD) and all
population sub-groups; the most highly exposed population subgroup was
Children1-2 years old with 16% aPAD.  The somewhat refined chronic
analysis assumed tolerance-level residues for some commodities, field
trial residues for the majority of commodities, experimental processing
factor for some crops, and 100 % CT.  The resulting chronic food
exposure estimates were less than HED’s level of concern for the
general U.S. population (17% cPAD) and all population sub-groups; the
most highly exposed population subgroup was children 1-2 years old with
45% cPAD.  

   

A cancer dietary assessment was not conducted for difenoconazole because
the cancer NOAEL is higher than the chronic RfD; therefore, the chronic
dietary risk estimate is more protective.

Residential Exposure/Risk Assessment

No new residential uses are being requested at this time.  However,
adults and adolescents may be exposed to difenoconazole from its
currently registered use on ornamentals.  These risks have been
previously assessed.  It was concluded that residential pesticide
handlers will be exposed to short-term duration (1 - 30 days) only.  
The dermal and inhalation (short-term) residential exposure was assessed
for a homeowner mixer/loader/applicator wearing short pants and
short-sleeved shirts as well as shoes plus socks using a garden hose-end
sprayer, “pump-up” compressed air sprayer, or backpack sprayer.  The
margin of exposures (MOEs) are >100; therefore are not of concern.  With
respect to residential post-application exposures, current HED policy
(see ExpoSAC minutes from 8/19/99 and 10/11/01) specifies that no
significant post-application exposure is anticipated from ornamentals,
either by residents or professional applicators; therefore, no
residential post-application assessment was conducted.

Aggregate Risk Assessment

Acute and chronic aggregate exposures include food plus drinking water
exposures.  As stated above, acute and chronic aggregate risks are not
of concern.  Since a common endpoint has been identified for assessment
of short-term oral, dermal, and inhalation exposures, short-term
aggregate risk assessment combines chronic dietary (food and water)
exposure estimates with residential exposure estimates.  The proposed
residential scenarios result in exposure to only adults.   Aggregate
MOEs are ≥180 and are not of concern. 

Triazole metabolites

The requested uses of difenoconazole did not result in an increase in
dietary exposure estimates for free triazole or conjugated triazoles. 
Therefore, the last dietary exposure analyses for the triazole
metabolites (M. Negussie, 28 Oct. 2009) have not changed.

Occupational Handler and Postapplication Exposure/Risk Assessment

Not applicable since this is an import tolerance.

Recommendations for Tolerances and Registration

Pending submission of a revised Section B for waxapple (see Section 10.0
 under Directions for Use) and a revised Section F (see requirements
under Proposed Tolerances), there are no residue chemistry issues that
would preclude granting import tolerances for residues of difenoconazole
resulting from the uses on mango in Brazil and waxapple in Taiwan:

Mango	0.07 ppm

Waxapple	1.5 ppm

Notes to PM:

With regards to the use on mangos in Brazil, HED notes that Mexico and
not Brazil is the largest importer of mangos into the U.S.  Since only
data from Brazil were submitted, the registrant should be made aware
that HED can not ascertain the adequacy of the recommended tolerance to
cover residues incurred in other geographical regions of South America
or Mexico from the same or similar use. 

An error was found in MRID 47760601, Section 1.3 Test Item, bottom of
Page 6 of 66.  The stated nominal/actual formulation content in Amistar
Top 325 SC of difenoconazole and azoxystrobin are reversed.  According
to the label, Amistar Top 325 SC contains 125 g/L of difenoconazole and
200 g/L azoxystrobin.  The MRID should be corrected. 

The registrant should be reminded that because difenoconazole is a
triazole compound, HED requires that samples from any metabolism,
feeding, field trial, and/or processing studies be analyzed for the
triazole metabolites triazolylalanine (TA), triazolyl acetic acid (TAA),
and 1,2,4-triazole (1,2,4-T).  Guidance has been issued concerning these
residue chemistry data requirements for the triazole-based metabolites
under DP# 327788 (4/25/06, M. Doherty) and data submitted in support of
future uses of difenoconazole will be accessed accordingly.

The registrant should be reminded that magnitude of the residue data for
papaya, as a representative crop of the tropical fruit crops group, have
been deemed adequate to support the same or substantially similar use on
mango (among other tropical fruits) and the establishment of a separate
mango tolerance.  An import tolerance is currently established under
§180.475(a)(1) for residues of difenoconazole in/on papaya at 0.3 ppm. 
  

Environmental Justice Considerations

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,"   HYPERLINK
"http://www.eh.doe.gov/oepa/guidance/justice/eo12898.pdf" 
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 Continuing
Survey of Food Intake by Individuals (CSFII) 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, season of
the year, ethnic group, and region of the country.  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.

Review of Human Research

This risk assessment relies in part on data from studies in which adult
human subjects were intentionally exposed to a pesticide or other
chemical.  These studies, which comprise the Pesticide Handlers Exposure
Database (PHED) and information from the Agricultural Re-Entry Task
Force (ARTF) and the Outdoor Residential Exposure Task Force (ORETF),
have been determined to require a review of their ethical conduct, have
received that review, and were considered appropriate (or ethically
conducted) for use in risk assessments.

2.0	Ingredient Profile  TC \l1 "2.0	Ingredient Profile 

2.1	Summary of Proposed Uses  TC \l2 "2.1	Summary of Proposed Uses 

(HED memo of B. Cropp-Kohlligian, 01/21/10, D366507)

A list of the end-use products (EPs) relevant to this import tolerance
petition is presented in Table 2.1a.  A summary of the use directions
for these EPs is presented in Table 2.1b.

Table 2.1a.   Summary of Difenoconazole End-Use Products Proposed for
Use on Mango and Waxapple.

Trade Name	Country	a.i. (% of formulation) 	Formulation Type	Proposed 
Crops	Target Pests	Label Date

Score® 	Brazil	25%

 (250 g ai/L)	EC	Mango	Powdery mildew and anthracnose	10/30/02

(Hao Jia Zan) 1

Azoxystrobin + Difenoconazole	Taiwan	12.5%	SC	Waxapple	Anthracnose
undated, Section B

1  The Taiwan end-use product is a soluble concentrate formulation
containing 12.5% w/v difenoconazole and 20% w/v azoxystrobin.

Table 2.1b.   Summary of Proposed Directions for Use of Difenoconazole.

Applic. Timing, Type, and Equip.	Product

[Formulation]

	Applic. Rate 

(lb ai/A)

[g ai/ha]	Max. No. Applic. per Season	Max. Seasonal Applic. Rate

(lb ai/A)

[g ai/ha]	PHI

(days)	Use Directions and Limitations

Mango

Foliar;

Ground

(500-1,000 L/ha spray volume)	Score®

[250 g  ai/L EC]	0.022-0.11

[25-125]	3	0.33

[375]	7	Applications must start immediately after the engorgement of
floral gems or before flowers bloom, using smallest dose in the first
applications to control powdery mildew and a larger dose to control
anthracnose; 14-day RTI.

Waxapple

Foliar;

equipment not specified (NS)	Hao Jia Zan

[12.5% w/v SC]	3,000x

dilution1	5	NS	30	Only to be applied during fluorescence; 7-day RTI.

1 The application rate could not be determined as the Section B only
reported the concentration to be applied.

2.2	Structure and Nomenclature  TC \l2 "2.2	Structure and Nomenclature 

The nomenclature of difenoconazole is summarized in Table 2.2a, and the
physicochemical properties of difenoconazole are summarized in Table
2.2b.  

Table 2.2a.   Difenoconazole Nomenclature.

Chemical structure	

Common name	  SEQ CHAPTER \h \r 1 Difenoconazole

Company experimental name	CGA-169374

IUPAC name
1-({2-[2-chloro-4-(4-chlorophenoxy)phenyl]-4-methyl-1,3-dioxolan-2-yl}me
thyl)-1H-1,2,4-triazole

CAS name
1-[[2-[2-chloro-4-(4-chlorophenoxy)phenyl]-4-methyl-1,3-dioxolan-2-yl]me
thyl]- 1H-1,2,4-triazole

CAS registry number	119446-68-3

End-use products (EP)	Score® - for mango grown in Brazil.

‘Hao Jia Zan Azoxystrobin + Difenoconazole’ - for waxapple grown in
Taiwan

Chemical structure of CGA-205375 livestock metabolite	



Table 2.2b	Physicochemical Properties of Difenoconazole.

Parameter	Value	Reference

Melting point	  SEQ CHAPTER \h \r 1 78.6 ºC	  SEQ CHAPTER \h \r 1 DP#s
172067 and 178394, 10/26/92, R. Lascola

pH	  SEQ CHAPTER \h \r 1 6-8 at 20 ºC (saturated solution)

	Density	  SEQ CHAPTER \h \r 1 1.37 g/cm3 at 20 ºC

	Water solubility	  SEQ CHAPTER \h \r 1 3.3 ppm at 20 ºC

	Solvent solubility		  SEQ CHAPTER \h \r 1 g/100 mL at 25 ºC:

n-hexane:	0.5

1-octanol:	35

toluene:	77

acetone:	88

ethanol:	89

	Vapor pressure	  SEQ CHAPTER \h \r 1 2.5 x 10-10 mm Hg at 25 ºC

	Dissociation constant, pKa	  SEQ CHAPTER \h \r 1 Reported as   SEQ
CHAPTER \h \r 1 <0 in MRID 42090003 which was previously reviewed in
DP#s 172067 and 178394; however, questions have arisen concerning this
value.  Re-examination of MRID 42090003 found that the product chemistry
data study to support the reported dissociation constant for the
technical grade of difenoconazole was not included.

Octanol/water partition coefficient, Log(KOW)	  SEQ CHAPTER \h \r 1 4.2
at 25 ºC	DP#s 172067 and 178394, 10/26/92, R. Lascola

UV/visible absorption spectrum	(max at about 200 and 238 nm
(in methanol at 26 ºC)	PMRA Proposed Regulatory Decision Document on
Difenoconazole, 4/14/99 (PRDD99-01)



3.0	Hazard Characterization/Assessment  TC \l1 "3.0	Hazard
Characterization/Assessment 

(For detailed discussion, refer to HED memo of M. Sahafeyan, 11/09/07,
D346591)

The toxicological database for difenoconazole is complete for the
purpose of this risk assessment.  However, a new data requirement for an
Immunotoxicity study is required. 

3.1	Hazard and Dose-Response Characterization  TC \l2 "3.1	Hazard and
Dose-Response Characterization 

For a complete list of studies considered, see Appendix 1 and 2 under
Section 13.0 of this document.

3.1.1	Toxicological Effects and Dose-response

Difenoconazole possesses low acute toxicity by the oral, dermal and
inhalation routes of exposure.  It is not considered to be an eye or
skin irritant and is not a sensitizer.  

In an acute neurotoxicity study in rats, reduced fore-limb grip strength
was observed on day 1 in males and clinical signs of neurotoxicity in
females at the limit dose of 2000 mg/kg. This effect in males is
considered as transient since it was not observed at later observation
points and toxicity in females was observed only at doses exceeding the
limit dose.  In a subchronic neurotoxicity study in rats decreased hind
limb strength was observed only in males, which was considered as
nonspecific in nature.  

It is not a developmental or reproductive toxicant.  Chronic effects in
the rat study are seen as cumulative decreases in body weight gains. 
Similarly, chronic feeding studies in mice showed decreased body-weight
gains in male and female mice at termination.  In mice,
treatment-related non-neoplastic lesions were confined to the liver and
were supported by clinical chemistry data at a level of 300 ppm (46 and
58 mg/kg/day for males and females, respectively).  No systemic toxicity
was observed at the limit dose in a 28-day dermal toxicity study in
rats.  A dermal absorption of 15.3% was observed through rat skin using
an in vivo method.

Difenoconazole is not mutagenic, and no evidence of carcinogenicity was
seen in rats. Evidence for carcinogenicity was seen in mice, where liver
tumors were induced at doses which were considered to be excessively
high for carcinogenicity testing.  Liver tumors were observed in mice at
300 ppm and higher; however, based on excessive toxicity observed at the
two highest doses of 2500 and 4500 ppm (females terminated after two
weeks due to excessive toxicity resulting in moribundity and death), the
absence of tumors at two lower doses of 10 and 30 ppm and the absence of
genotoxic effects, HED’s Cancer Peer Review Committee (CPRC)
recommended for a cancer classification of C (possible human
carcinogen).  A margin-of-exposure (MOE) approach in risk assessment was
advocated by the CPRC utilizing the no-observable-adverse-effects-level
(NOAEL) of 30 ppm (4.7 and 5.6 mg/kg/day in males and females,
respectively) and the lowest-observable-adverse-effects-level (LOAEL) of
300 ppm (46 and 58 mg/kg/day in males and females, respectively) from
the mouse study using only those biological endpoints which were
relevant to tumor development (i.e., hepatocellular hypertrophy, liver
necrosis, fatty changes in the liver and bile stasis) (Memo, Jess
Rowland and Esther Rinde, 27-JUL-1994; Memo, PV Shah, 1-March-2007, HED
Doc. No. 005453).

The doses and toxicological endpoints selected for various exposure
scenarios applicable to this risk assessment are summarized in Table
3.1.3a and Table 3.1.3b.

Table 3.1.3a.  Summary of Toxicological Doses and Endpoints for
Difenoconazole for Use in Dietary and Non-Occupational Human-Health Risk
Assessments.  

Exposure Scenario	Point of Departure	Uncertainty/FQPA Safety Factors
RfD, PAD, LOC for Risk Assessment	Study and Relevant Toxicological
Effects

Acute Dietary (All populations)	NOAEL = 25

mg/kg	UFA = 10X

UFH = 10X

UFFQPA = 1X 	aRfD = aPAD = 0.25 mg/kg/day	Acute Neurotoxicity Study in
Rats

LOAEL= 200 mg/kg in males based on reduced fore-limb grip strength in
males on day 1.

Chronic Dietary (All populations)	NOAEL = 0.96

mg/kg/day	UFA = 10X

UFH = 10X

UFFQPA = 1X	cRfD = cPAD = 0.01mg/kg/day	Combined chronic
toxicity/carcinogenicity (rat; dietary) LOAEL = 24.1/32.8 mg/kg/day
(M/F) based on cumulative decreases in body-weight gains.

Incidental Oral

Short- and Intermediate-Term (1-30 days and 1-6 months)	NOAEL = 1.25

mg/kg/day	UFA = 10X

UFH = 10X

UFFQPA = 1X 

	Residential LOC for MOE<100	Reproduction and fertility effects (rat;
dietary) Offspring LOAEL = 12.5 mg/kg/day based on reduction in
body-weight of F1 males.

Dermal

Short- and Intermediate- Term (1-30 days and 1-6 months)	Oral NOAEL =
1.25

mg/kg/day

Dermal Absorption factor=15.3%

	UFA = 10X

UFH = 10X

UFFQPA = 1X 

	Residential LOC for MOE<100	Reproduction and fertility effects (rat;
dietary) Offspring LOAEL = 12.5 mg/kg/day based on reduction in
body-weight gain of F0 females prior to mating, gestation and lactation.

Dermal

Long-Term (>6 months)	Oral NOAEL = 0.96

mg/kg/day

Dermal Absorption factor=15.3%	UFA = 10X

UFH = 10X

UFFQPA = 1X	Residential LOC for MOE<100	Combined chronic
toxicity/carcinogenicity (rat; dietary) LOAEL = 24.1/32.8 mg/kg/day
(M/F) based on cumulative decreases in body-weight gains.

Inhalation

(Short- and Intermediate-term)	Oral NOAEL = 1.25

mg/kg/day

100% inhalation absorption assumed	UFA = 10X

UFH = 10X

UFFQPA = 1X 

	Residential LOC for MOE<100	Reproduction and fertility effects (rat;
dietary) Offspring LOAEL = 12.5 mg/kg/day based on reduction in body
weight gain of F0 females prior to mating, gestation and lactation.

Inhalation

(Long- term)	Oral NOAEL = 0.96

mg/kg/day

100% inhalation absorption assumed	UFA = 10X

UFH = 10X

UFFQPA = 1X	Residential LOC for MOE<100	Combined chronic
toxicity/carcinogenicity (rat; dietary) LOAEL = 24.1/32.8 mg/kg/day
(M/F) based on cumulative decreases in body weight gains.

Cancer (oral, dermal, inhalation)	Difenoconazole is classified as a
Group C, possible human carcinogen with a non-linear (MOE) approach for
human risk characterization (CPRC Document, 7/27/94, Memo, P. V. Shah
dated March 3, 2007, HED Doc. No. 0054532).

Abbreviations: UF = uncertainty factor, UFA = extrapolation from animal
to human (interspecies), UFH = potential variation in sensitivity among
members of the human population (intraspecies), UFFQPA = FQPA Safety
Factor, NOAEL = no-observed-adverse-effect level, LOAEL =
lowest-observed-adverse-effect level, RfD = reference dose (a = acute, c
= chronic), PAD = population-adjusted dose, MOE = margin of exposure,
LOC = level of concern.

Table 3.1.3b.  Summary of Toxicological Doses and Endpoints for
Difenoconazole for Use in Occupational 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

Dermal

Short- and Intermediate- Term (1-30 days and 1-6 months)	Oral NOAEL =
1.25

mg/kg/day

Dermal Absorption factor=15.3%

	UFA = 10X

UFH = 10X

	Occupational LOC for MOE<100	Reproduction and fertility effects (rat;
dietary) Offspring LOAEL = 12.5 mg/kg/day based on reduction in
body-weight gain of F0 females prior to mating, gestation and lactation.

Dermal

Long-Term (>6 months)	Oral NOAEL = 0.96

mg/kg/day

Dermal Absorption factor=15.3%	UFA = 10X

UFH = 10X

	Occupational LOC for MOE<100	Combined chronic toxicity/carcinogenicity
(rat; dietary) LOAEL = 24.1/32.8 mg/kg/day (M/F) based on cumulative
decreases in body-weight gains.

Inhalation

(Short- and Intermediate-term)	Oral NOAEL = 1.25

mg/kg/day

100% inhalation absorption assumed

	UFA = 10X

UFH = 10X

	Occupational LOC for MOE<100	Reproduction and fertility effects (rat;
dietary) Offspring LOAEL = 12.5 mg/kg/day based on reduction in
body-weight gain of F0 females prior to mating, gestation and lactation.

Inhalation

(Long- term)	Oral NOAEL = 0.96

mg/kg/day

100% inhalation absorption assumed	UFA = 10X

UFH = 10X

	Occupational LOC for MOE<100	Combined chronic toxicity/carcinogenicity
(rat; dietary) LOAEL = 24.1/32.8 mg/kg/day (M/F) based on cumulative
decreases in body-weight gains.

Cancer (oral, dermal, inhalation)	Difenoconazole is classified as a
Group C, possible human carcinogen with a non-linear (MOE) approach for
human risk characterization (CPRC Document, 7/27/94, Memo, P. V. Shah
dated March 3, 2007, HED Doc. No. 0054532).

Abbreviations: UF = uncertainty factor, UFA = extrapolation from animal
to human (interspecies), UFH = potential variation in sensitivity among
members of the human population (intraspecies), UFFQPA = FQPA Safety
Factor, NOAEL = no-observed-adverse-effect level, LOAEL =
lowest-observed-adverse-effect level, RfD = reference dose (a = acute, c
= chronic), PAD = population-adjusted dose, MOE = margin of exposure,
LOC = level of concern.

3.2	FQPA Considerations  TC \l2 "3.3	FQPA Considerations 

3.2.1.  Determination of Susceptibility

The Hazard Identification Assessment Review Committee (HIARC) determined
that the available Agency Guideline studies indicated no increased
susceptibility of rats or rabbits to in utero and/or postnatal exposure
to difenoconazole. In the prenatal developmental toxicity studies in
rats and rabbits and the two-generation reproduction study in rats,
toxicity to the fetuses/offspring, when observed, occurred at equivalent
or higher doses than in the maternal/parental animals.  In the prenatal
developmental toxicity study in rats, maternal toxicity was manifested
as decreased body weight gain and food consumption at the LOAEL of 85
mg/kg/day; the NOAEL was 16 mg/kg/day.  The developmental toxicity was
manifested as alterations in fetal ossifications at 171 mg/kg/day; the
developmental NOAEL was 85 mg/kg/day.  In a developmental toxicity study
in rabbits, maternal and developmental toxicity were seen at the same
dose level (75 mg/kg/day).  Maternal toxicity in rabbits were manifested
as decreased in body weight gain and decreased in food consumption,
while developmental toxicity was manifested as decreased fetal weight. 
In a 2-generation reproduction study in rats, there were decreases in
maternal body weight gain and decreases in body weights of F1 males at
the LOAEL of 12.5 mg/kg/day; the parental systemic and off spring
toxicity NOAEL was 1.25 mg/kg/day.  

3.2.2.  Adequacy of Toxicity Database

There are no data gaps for the assessment of the effects of
difenoconazole following in utero and/or postnatal exposure.  The acute
and subchronic neurotoxicity studies in rats are available.  In an acute
neurotoxicity study in rats, reduced fore-limb grip strength was
observed on day 1 in males. This effect is considered as transient since
it was not observed at later observation points.  In a subchronic
neurotoxicity study in rats decreased hind limb strength was observed
only in males, which was considered as nonspecific in nature. 
Difenoconazole exhibits some evidence of neurotoxicity in the database,
but the effects are transient or occur at doses exceeding the limit
dose.  EPA concluded that difenoconazole is not a neurotoxic compound.
Based on the toxicity profile, and lack of neurotoxicity, a
developmental neurotoxicity study in rats is not required.

3.2.3.  Degree of Concern Analysis:

Since there is no evidence of susceptibility, there is no concern for
increased susceptibility due to exposure to difenoconazole.

3.2.4. FQPA Safety Factor Recommendation

		

The FQPA factor for increased susceptibility to infant and children is
reduced to 1x for the following considerations:

1) toxicology data base for difenoconazole is complete; 

2) there is no indication of increased susceptibility of rats or rabbit
fetuses to in utero and/or postnatal exposure in the developmental and
reproductive toxicity data; 

3) there are no concerns for neurotoxicity;

4) developmental neurotoxicity study is not required;

5) there are no residual uncertainties in the toxicology database.  

3.3	Endocrine Disruption tc \l2 "3.1	Endocrine Disruption 

As required under FFDCA section 408(p), EPA has developed the Endocrine
Disruptor Screening Program (EDSP) to determine whether certain
substances (including pesticide active and other ingredients) may have
an effect in humans or wildlife similar to an effect produced by a
“naturally occurring estrogen, or other such endocrine effects as the
Administrator may designate.”  The EDSP employs a two-tiered approach
to making the statutorily required determinations. Tier 1 consists of a
battery of 11 screening assays to identify the potential of a chemical
substance to interact with the estrogen, androgen, or thyroid (E, A, or
T) hormonal systems.  Chemicals that go through Tier 1 screening and are
found to have the potential to interact with E, A, or T hormonal systems
will proceed to the next stage of the EDSP where EPA will determine
which, if any, of the Tier 2 tests are necessary based on the available
data. Tier 2 testing is designed to identify any adverse endocrine
related effects caused by the substance, and establish a dose-response
relationship between the dose and the E, A, or T effect.

Between October 2009 and February 2010, EPA issued test orders/data
call-ins for the first group of 67 chemicals, which contains 58
pesticide active ingredients and 9 inert ingredients.  This list of
chemicals was selected based on the potential for human exposure through
pathways such as food and water, residential activity, and certain
post-application agricultural scenarios.  This list should not be
construed as a list of known or likely endocrine disruptors.

Difenoconazole is not among the group of 58 pesticide active ingredients
on the initial list to be screened under the EDSP.  Under FFDCA sec.
408(p) the Agency must screen all pesticide chemicals.  Accordingly, EPA
anticipates issuing future EDSP test orders/data call-ins for all
pesticide active ingredients. 

For further information on the status of the EDSP, the policies and
procedures, the list of 67 chemicals, the test guidelines and the Tier 1
screening battery, please visit our website:  http://www.epa.gov/endo/.

4.0	Public Health and Pesticide Epidemiology Data  TC \l1 "4.0	Dietary
Exposure/Risk Characterization 

Not relevant since these are new uses.

Dietary Exposure/Risk Characterization

  TC \l1 "4.0	Dietary Exposure/Risk Characterization 

 Pesticide Metabolism and Environmental Degradation

5.1.1	Metabolism in Primary Crops  TC \l3 "5.1.1	Metabolism in Primary
Crops 

The nature of the residue in plants is understood based on acceptable
plant metabolism studies reflecting foliar applications in canola,
grape, potato, tomato, and wheat and seed treatment in wheat.  Based on
the results of available plant metabolism studies, the petitioner has
proposed that difenoconazole is metabolized in plants by the
hydroxylation of the phenyl ring and/or cleavage of the dioxolane ring
followed by cleavage of the carbon-carbon bridge between the phenyl and
triazole rings.  The metabolic pathway appears to proceed by hydrolysis
of the ketal to the ketone followed by reduction of the ketone
(CGA-205374) to the alkanol (CGA 205375).  CGA 205375 can be conjugated
with sugars or the bridge linking the phenyl and triazole moieties is
cleaved.  HED concluded that the residue of concern for both tolerance
enforcement and risk assessment for crops included in this petition is
difenoconazole per se.   

5.1.2	Metabolism in Rotational Crops  TC \l3 "5.1.2	Metabolism in
Rotational Crops 

The nature of the residue in rotational crops is not adequately
understood because previously conducted studies did not reflect
sufficiently high application rates, and/or insufficient
characterization/identification of residues was achieved.  An additional
confined rotational crop study reflecting phenyl-ring labeling must be
conducted at 1x the proposed maximum seasonal foliar application rate
(0.46 lb ai/A).  An acceptable limited field rotational crop study is
available; these data will be reevaluated when the outstanding confined
rotational crop study is received.  In the meantime, this subject is not
relevant since this is an import tolerance.

5.1.3	Metabolism in Livestock  TC \l3 "5.1.3	Metabolism in Livestock 

The nature of the residue in livestock is understood based on acceptable
goat and hen metabolism studies.  The data were originally evaluated in
support of seed treatment uses only, and HED concluded that the residue
of concern in livestock commodities was difenoconazole per se.  When the
first foliar uses of difenoconazole on crop commodities were proposed
(DP# 340379), HED re-evaluated the livestock metabolism data and
concluded that the residues of concern for both tolerance setting and
risk assessment for livestock commodities are difenoconazole and
metabolite CGA-205375.

5.1.4	Analytical Methodology  TC \l3 "5.1.4	Analytical Methodology 

An adequate tolerance enforcement method, method AG-575B, is available
for crop commodities.  The method determines residues of difenoconazole
per se in/on crop commodities by gas chromatography with
nitrogen-phosphorus detection (GC/NPD).  The method limits of
quantitation (LOQs) are 0.01-0.05 ppm.  A confirmatory GC method with
mass-selective detection (MSD) is also available for crop commodities. 
Samples from the submitted the crop field trials were analyzed for
residues of difenoconazole using a high performance liquid
chromatography method with tandem mass spectrometry detection
(LC/MS/MS), Syngenta REM 147.08, or a similar method.  The methods are
adequate for data collection based on acceptable concurrent method
recoveries.  The LOQ was 0.01 ppm for difenoconazole in mango and
waxapple.

5.1.5	Environmental Degradation

In soil environment, difenoconazole is persistent and slightly mobile. 
Difenoconazole has low potential to reach ground water, except in soils
of high sand and low organic matter content.  It is likely to reach
surface sources of drinking water via spray drift and runoff.  In the
aquatic environment its main route of dissipation is partitioning into
the bottom sediment, and potentially relatively fast to slow aqueous
photolysis in clear water conditions.  

Major degradates include CGA 205375 which was found in lab accumulation
in fish at 51-64% applied dose, and in aerobic soil at 14.8%, in aerobic
aquatic at 11.6% and anaerobic aquatic at 12.6% of the applied dose, and
CGA 71019 (triazole) and CGA-142856 (TAA).  Since triazole and TAA are
common metabolites from a group of chemicals, they should be addressed
separately.   (See Appendix 4 for structures)

5.1.6	Comparative Metabolic Profile TC \l3 "5.1.6	Comparative Metabolic
Profile 

Rat metabolism studies (MRID 42090028 through 31, and 42710013
through14) indicated that difenoconazole was rapidly adsorbed and mainly
eliminated vis bile.   Three major urinary metabolites were isolated and
further identified as sulfate conjugates of CGA 205375, isomers of CGA
205375, and the hydroxyacetic metabolite of CGA 205375.  Further
metabolism formed free triazoles.   The proposed metabolic pathway in
rats is presented in Appendix 3.

Comparisons of the metabolisms indicated that the metabolic pathways in
plants, livestock, rats, and the environment are very similar or
identical, with the formation of CGA 205375 and then further metabolism
to form free triazole metabolites.

5.1.7	Toxicity Profile of Major Metabolites and Degradates TC \l3 "5.1.7
Toxicity Profile of Major Metabolites and Degradates 

Other than the triazole metabolites, no toxicity information is
available on the CGA 205375 metabolite.  Based on structural similarity,
it is assumed that the CGA 205375 shares the same toxicity as the
parent.

5.1.8	Pesticide Metabolites and Degradates of Concern TC \l3 "5.1.8
Pesticide Metabolites and Degradates of Concern 

The most recent MARC evaluation for difenoconazole was in 1994.  In
2007, HED reviewers re-evaluated the plant and livestock metabolism
studies based on new data submitted in conjunction with the new uses. 
It was concluded that the residue of concern for both tolerance
enforcement and risk assessment for currently registered crops is
difenoconazole per se.   For livestock, the residues of concern for both
tolerance setting and risk assessment for livestock commodities are
difenoconazole and its metabolite CGA-205375.   With the subject
petition, HED determined that previous conclusions on plants and
livestock stand.  As for drinking water assessment, HED tentatively
concludes that the residues of concern are parent and CGA 205375.   

5.1.9	Drinking Water Residue Profile TC \l3 "5.1.9	Drinking Water
Residue Profile 

Although the subject petition is for import tolerances and therefore
does not result in drinking water exposure, there are existing uses of
difenoconazole in the U.S.  The most recent drinking water assessment
was conducted for parent compound only.  The fate and transport database
for difenoconazole were sufficient to conduct the drinking water
assessment.    SEQ CHAPTER \h \r 1 The Tier II drinking water assessment
was performed using PRZM (v3.12.2; May 12, 2005)/EXAMS (v. 2.98.04.06;
April 25, 2005) modeling with index reservoir (IR) scenarios and percent
cropped area (PCA) adjustment factors.  The assessment was based on
difenoconazole uses on citrus fruits and grapes. These are major crops,
with difenoconazole maximum application rate to citrus fruits being the
highest of all agricultural uses, and grapes being the second highest.
An initial simulation analysis showed that grapes would produce the
highest EDWCs of all proposed crop uses with the same maximum
application rate of 0.46 lb ai/A hence grapes and citrus fruits were
modeled.   

Florida and California citrus fruit scenarios were modeled for citrus
fruits, and New York and California grapes scenarios were modeled for
grapes.   Default PCA of 0.87 was used for surface water models.  Among
all the registered and proposed new uses, the highest estimated drinking
water concentrations (EDWCs) from surface water sources were derived for
aerial applications of difenoconazole to New York grapes at the maximum
annual application rate of 0.46 lb ai/acre. The recommended peak and
mean estimated drinking water concentrations (EDWCs) for the human
health risk assessment are provided in Table 1. These estimates exceed
the previously EDWCs from 2007 drinking water assessment (D333319).

Table 1.  PCA Adjusted Difenoconazole EDWCs from Surface Water Sources.

Scenario	Application Type/Annual Fungicide Application Rate

(lb ai/A) )	Estimated Drinking Water Concentrations (µg/L)a



1 in 10 year annual peak	1 in 10 year annual mean	36 year annual mean



NY Grape	aerially applied

0.114 x  4  = 0.46	

15.8	

10.4	

7.62

a EXAMS EECs multiplied by 0.87, a default PCA factor.  

The highest SCI-GROW estimated drinking water concentration of
difenoconazole from shallow ground water sources is 1.23 x 10-2 µg/L
derived for the maximum proposed application rate to citrus fruit (0.50
lb ai/A), i.e. agricultural uses. Based on the previous drinking water
assessment, this estimate is lower than an estimate for non-agricultural
uses 1.28 x 10-2 µg/L, obtained for the maximum application rate for
ornamentals (0.52 lb ai/A; D333319).  These concentrations can be
considered as both the acute and chronic values.  

Currently, no data are available indicating whether water treatment
process will increase dissipation and/or will form degradation products
that may be more toxic than the parent.

5.1.10	Food Residue Profile  TC \l3 "5.1.10	Food Residue Profile 

(HED memo of B. Cropp-Kohlligian, 01/21/10, D366507) 

HED has examined the residue chemistry database for difenoconazole and
no major residue deficiencies will prevent the establishment of
permanent tolerances for the proposed uses.  For details on data
deficiencies, please see Section 10.0.

The nature of the residue in plants is understood based on acceptable
plant metabolism studies reflecting foliar applications in canola,
grape, potato, tomato, and wheat, and seed treatment in wheat.  HED
concludes that the residue of concern for both tolerance enforcement and
risk assessment for crops included in this petition is difenoconazole
per se.  The nature of the residue in livestock is understood based on
acceptable goat and hen metabolism studies.  The residues of concern for
both tolerance setting and risk assessment for livestock commodities are
difenoconazole per se and its metabolite CGA-205375.

An adequate tolerance enforcement method, method AG-575B, is available
for crop commodities.  The method determines residues of difenoconazole
per se in/on crop commodities by gas chromatography with
nitrogen-phosphorus detection (GC/NPD).  The method limits of
quantitation (LOQs) are 0.01-0.05 ppm.  A confirmatory GC method with
mass-selective detection (MSD) is also available for crop commodities. 
Samples from the submitted the crop field trials were analyzed for
residues of difenoconazole using a high performance liquid
chromatography method with tandem mass spectrometry detection
(LC/MS/MS), Syngenta REM 147.08, or a similar method.  The methods are
adequate for data collection based on acceptable concurrent method
recoveries.  The LOQ was 0.01 ppm for difenoconazole in mango and
waxapple.

The submitted field trial data for mango are adequate and reflect the
proposed use of Score® on mango in Brazil.  The residue data from the
trials conducted will support the proposed import tolerance of 0.09 ppm
for mango.  A Codex MRL for residues of difenoconazole per se has been
established at 0.07 ppm for mango.   To harmonization with the
established Codex MRL, HED recommends a tolerance of 0.07 ppm for mango.
 HED is unable to assess the adequacy of the submitted field trial data
for waxapple at this time because the use directions have not been fully
elucidated.  Syngenta is required to provide label use information as
detailed under ‘Directions for Use’ section.  Assuming that the use
directions for waxapple in Taiwan, once fully elucidated, will comport
with the submitted field trial data, HED tentatively recommends for the
proposed import tolerance of 1.5 ppm for waxapple.  

There are no feedstuffs associated with the foreign uses of
difenoconazole on mango in Brazil and waxapple in Taiwan.  Therefore, no
livestock enforcement methods, storage stability data, or feeding
studies are required to support this petition.

5.1.11	International Residue Limits TC \l3 "5.1.11	International Residue
Limits 

A Codex MRL for residues of difenoconazole per se has been established
at 0.07 ppm for mango.  Canadian and Mexican MRLs have been established
for difenoconazole; however, no MRLs have been established for mango. 
No Codex, Canadian, and Mexican MRLs have been established for residues
of difenoconazole in/on waxapple.   

5.2	Dietary Exposure and Risk TC \l2 "5.2  Dietary Exposure and Risk 

(HED memo of T. Morton, 01/21/10, D371613)

Residue Data used for Acute and Chronic Assessments:

The unrefined acute analysis assumed tolerance-level residues, 100% crop
treated (CT), and the available empirical or DEEM( (ver. 7.81) default
processing factors.  The somewhat refined chronic analysis assumed
tolerance-level residues for some commodities, average field trial
residues for the majority of commodities, the available empirical or
DEEM( (ver. 7.81) default processing factors, and 100 % CT.   

μg/L) was used for the acute dietary exposure assessment, while 1-in-10
year annual mean (10.4 μg/L) was used for chronic.   HED notes that
degradate CGA 205375 was not included in the drinking water assessment;
however, the relative amount of CGA 205375 is not significant in
comparison to the parent.

DEEM-FCID™ Program and Consumption Information

Difenoconazole acute and chronic dietary exposure assessments were
conducted using the DEEM-FCID( (ver. 2.03), which incorporates
consumption data from USDA’s CSFII (1994-1996 and 1998).  The 1994-96,
98 data are based on the reported consumption of more than 20,000
individuals over two non-consecutive survey days.  Foods “as
consumed” (e.g., apple pie) are linked to EPA-defined food commodities
(e.g., apples, peeled fruit - cooked; fresh or N/S; baked; or wheat
flour - cooked; fresh or N/S, baked) using publicly available recipe
translation files developed jointly by USDA/ARS and EPA.  For chronic
exposure assessment, consumption data are averaged for the entire U.S.
population and within population subgroups, but for acute exposure
assessment are retained as individual consumption events.  Based on
analysis of the 1994-96, 98 CSFII consumption data, which took into
account dietary patterns and survey respondents, HED concluded that it
is most appropriate to report risk for the following population
subgroups:  the general U.S. population, all infants (<1 year old),
children 1-2, children 3-5, children 6-12, youth 13-19, adults 20-49,
females 13-49, and adults 50+ years old.

Results and Discussion

The resulting acute food exposure estimates were less than HED’s level
of concern (<100% of the acute population-adjusted dose (aPAD)) at the
95th percentile of the exposure distribution for the general U.S.
population (7 % aPAD) and all population sub-groups; the most highly
exposed population subgroup was children1-2 years old with 16 % aPAD. 
The resulting chronic food exposure estimates were less than HED’s
level of concern (<100% of the chronic population-adjusted dose (cPAD))
for the general U.S. population (17 % cPAD) and all population
sub-groups; the most highly exposed population subgroup was children 1-2
years old with 45 % cPAD.   A cancer dietary assessment was not
conducted for difenoconazole because the cancer NOAEL is higher than the
chronic RfD; therefore, the chronic dietary risk estimate is more
protective.

Table 5.2a.  Summary of Acute Dietary Exposure and Risk for
Difenoconazole at the 95th Percentile. 



Population Subgroup	

aPAD (mg/kg/day)	

Exposure (mg/kg/day)	

%aPAD



General U.S. Population	

0.25	

0.017747	7



All Infants (< 1 year old)



0.0255139	10



Children 1-2 years old



0.039565	16



Children 3-5 years old



0.031818	13



Children 6-12 years old



0.017949	7



Youth 13-19 years old

0.008828	4



Adults 20-49 years old 



0.013083	5



Adults 50+ years old 



0.017255	7



Females 13-49 years old 



0.013281	5

The bolded %aPAD is the highest.

Table 5.2b.  Summary of Chronic Dietary Exposure and Risk for
Difenoconazole. 



Population Subgroup	

cPAD (mg/kg/day)	

Exposure (mg/kg/day)	

%cPAD



General U.S. Population	

0.01	

0.001709	17



All Infants (< 1 year old)



0.002445	25



Children 1-2 years old



0.004484	45



Children 3-5 years old



0.003624	36



Children 6-12 years old



0.002061	21



Youth 13-19 years old



0.001372	14



Adults 20-49 years old 



0.001376	14



Adults 50+ years old 



0.001548	16



Females 13-49 years old 



0.001402	14

The bolded %cPAD is the highest.

  

The requested uses of difenoconazole did not result in an increase in
dietary exposure estimates for free triazole or conjugated triazoles. 
Therefore, the last dietary exposure analyses for the triazole
metabolites (M. Negussie, 28 Oct. 2009) have not changed.

6.0	Residential (Non-Occupational) Exposure/Risk Characterization  TC
\l1 "5.0	Residential (Non-Occupational) Exposure/Risk Characterization 

(HED memo of M. Sahafeyan, 11/09/07, D346591)

6.1	Residential Handler Exposure and Risk Characterization  TC \l2 "5.1
Residential Handler Exposure and Risk Characterization 

No new residential uses are being requested at this time.  However,
adults and adolescents  may be exposed to difenoconazole from its
currently registered use on ornamentals.  These risks have been
previously assessed.  Below are the results from HED’s previous
assessment:

HED believes residential pesticide handlers will be exposed to
short-term duration (1 - 30 days) only.   The dermal and inhalation
(short-term) residential exposure was assessed for "homeowners"
mixer/loader/applicator wearing short pants and short-sleeved shirts as
well as shoes plus socks using garden hose-end sprayer, “pump-up”
compressed air sprayer, and backpack sprayer.  A MOE of 100 is adequate
to protect residential pesticide handlers from exposures to
difenoconazole.  MOEs are >100; therefore are not of concern.  A summary
of these exposures and risks is presented in Table 6.1.

Table 6.1 Summary of Exposure & Risk for Homeowners Applying
Difenoconazole.

Unit Exposure1

mg ai/lb handled	Applic. Rate2

lb ai/unit	Units Treated3	Avg. Daily Exposure4

mg ai/kg bw/day	Short-term

MOE5

Mixer/Loader/Applicator Using Garden Hose-end Sprayer

Dermal:

SS&SP  11 

Inhal.        0.017	0.13 lb ai/A	

0.5 A/day

	Dermal:

shrtsl&pants 0.00156

Inhal.            0.0000158	

790



Mixer/Loader/Applicator Using "Pump-Up" Compressed Air Sprayer

Dermal:

SS&SP   38 

Inhal         0.0027	0.13 lb ai/A	

0.5 A/day

	Dermal:

shrtsl&pants    0.00539

Inhal.            0.0000025	

230



Mixer/Loader/Applicator Using Backpack Sprayer

Dermal:

SS&SP  5.1  

Inhal.     0.03	0.13 lb ai/A	

0.5 A/day

	Dermal:

shrtslv&pants  0.000725

Inhal.               0.000028	

1,700



1.  Unit Exposures are taken from “PHED SURROGATE EXPOSURE GUIDE”,
Estimates of Worker Exposure from The Pesticide Handler Exposure
Database Version 1.1, August 1998.   Inhal. = Inhalation.  Units = mg
a.i./pound of active ingredient handled.  Unit exposures are also taken
from ORETF studies OMA 004,OMA006 and from the Draft Residential SOPs,
DECEMBER 1997.  SS & SP = short sleeved shirt and short pants.  LS & LP
= long sleeved shirt and long pants.

2.  Applic. Rate. = Taken from the  draft Inspire® label.

3.  Units Treated are taken the residential SOPs. 

4.  Average Daily Dose (ADD) = Unit Exposure * Applic. Rate * Units
Treated * absorption factor  (15.3 % for dermal) ( Body Weight (70 kg). 


5.  NOAEL = No Observable Adverse Effect Level (1.25 mg a.i./kg bw/day
for short-term  and intermediate-term dermal and inhalation).

6.  MOE = Margin of Exposure = No Observable  Adverse Effect Level
(NOAEL)  ( ADD.  ADD = dermal + inhalation.

With respect to residential post-application exposures, current HED
policy (see ExpoSAC minutes from 8/19/99 and 10/11/01) specifies that no
significant post-application exposure is anticipated from ornamentals,
either by residents or professional applicators; therefore, no
residential post-application assessment was conducted.

7.0	Aggregate Risk Assessments and Risk Characterization  TC \l1 "6.0
Aggregate Risk Assessments and Risk Characterization 

In accordance with the FQPA, HED must consider and aggregate (add)
pesticide exposures and risks from three major sources: food, drinking
water, and residential exposures.  In an aggregate assessment, exposures
from relevant sources are added together and compared to quantitative
estimates of hazard (e.g., a NOAEL or PAD), or the risks themselves can
be aggregated.  When aggregating exposures and risks from various
sources, HED considers both the route and duration of exposure.

7.1	Acute & Chronic Aggregate Risk  TC \l2 "6.1	Acute & Chronic
Aggregate Risk 

Acute and chronic aggregate exposures include food plus drinking water
exposures.  As demonstrated under Section 5.2.  Acute and chronic
aggregate risks are not of concern.

7.2	Short- and Intermediate-Term Aggregate Risk  TC \l2 "6.2	Short-Term
Aggregate Risk 

  Since the aggregate MOEs are ≥180, short-term aggregate exposure to
difenoconazole is not of concern. 

Table 7.2. Short-Term Aggregate Risk Calculations for Handlers

Population	Target Aggregate

MOE1	dietary 

MOE2	dermal + inhalation 

MOE3	agg. MOE

(dietary and residential)4

Youth 13-19 years old	100	910	230	180

Adults 20-49 years old

910

180

Adults 50+ years old

810

180

Females 13-49 years old

890

180

1	total uncertainty factor for all routes of exposure is 100x;
therefore, the target MOE is 100.

2	dietary MOE = short-term incidental oral NOAEL ( chronic dietary
exposure.

3	dermal MOE = short-term dermal NOAEL ((dermal + inhalation residential
exposure) (see text).

4 	aggregate MOE (dietary and residential) = 1(((1(MOEdietary) +
(1(MOEdermal) + (1(MOEinhalation)).

  tc \l1 "6.0  CUMULATIVE RISK 

8.0	Cumulative Risk Characterization/Assessment  TC \l1 "7.0	Cumulative
Risk Characterization/Assessment 

Difenoconazole is a member of the triazole-containing class of
pesticides.  Although conazoles act similarly in plants (fungi) by
inhibiting ergosterol biosynthesis, there is not necessarily a
relationship between their pesticidal activity and their mechanism of
toxicity in mammals.  Structural similarities do not constitute a common
mechanism of toxicity.  Evidence is needed to establish that the
chemicals operate by the same, or essentially the same, sequence of
major biochemical events (EPA, 2002).   In conazoles, however, a
variable pattern of toxicological responses is found.   Some are
hepatotoxic and hepatocarcinogenic in mice. Some induce thyroid tumors
in rats.  Some induce developmental, reproductive, and neurological
effects in rodents.  Furthermore, the conazoles produce a diverse range
of biochemical events including altered cholesterol levels, stress
responses, and altered DNA methylation.  It is not clearly understood
whether these biochemical events are directly connected to their
toxicological outcomes.  Thus, there is currently no evidence to
indicate that conazoles share common mechanisms of toxicity and EPA is
not following a cumulative risk approach based on a common mechanism of
toxicity for the conazoles.   For information regarding EPA’s
procedures for cumulating effects from substances found to have a common
mechanism of toxicity, see EPA’s website at
http://www.epa.gov/pesticides/cumulative.

Difenoconazole is a triazole-derived pesticide.  This class of compounds
can form the common metabolite 1,2,4-triazole and two triazole
conjugates (triazolylalanine and triazolylacetic acid).  To support
existing tolerances and to establish new tolerances for
triazole-derivative pesticides, including difenoconazole, U.S. EPA
conducted a human health risk assessment for exposure to 1,2,4-triazole,
triazolylalanine, and triazolylacetic acid resulting from the use of all
current and pending uses of any triazole-derived fungicide.  The risk
assessment is a highly conservative, screening-level evaluation in terms
of hazards associated with common metabolites (e.g., use of a maximum
combination of uncertainty factors) and potential dietary and
non-dietary exposures (i.e., high end estimates of both dietary and
non-dietary exposures).  In addition, the Agency retained the additional
10X FQPA safety factor for the protection of infants and children.  The
assessment includes evaluations of risks for various subgroups,
including those comprised of infants and children.  The Agency’s
complete risk assessment is found in the propiconazole reregistration
docket at http://www.regulations.gov, Docket Identification (ID) Number
EPA-HQ-OPP-2005-0497.

9.0	Occupational Exposure/Risk Pathway  TC \l1 "8.0	Occupational
Exposure/Risk Pathway 

Not applicable since this is a import tolerance.

10.0	Data Needs and Label Recommendations  TC \l1 "9.0	Data Needs and
Label Recommendations 

Residue Chemistry

860.1200 Directions for Use - Waxapple

Syngenta must submit a complete description of the use of difenoconazole
on waxapple grown in Taiwan (a translated label or complete Section B). 
As required by the NAFTA Guidance Document on Data Requirements for
Tolerances on Imported Commodities in the United States and Canada
(December 2005), it is necessary to submit copies of registered/approved
label(s) translated to English.  The information must include, but is
not limited to, the maximum single application rate, the maximum annual
application rate, application timing (as it relates to plant growth
stage), retreatment interval, application tank-mix preparation, volume
of spray mix per unit area, application equipment, and the preharvest
interval.  The application rates should be expressed in units of pounds
of active ingredient per acre (or kilograms per hectare).

Syngenta must submit a complete description of the use of difenoconazole
on waxapple grown in Taiwan consistent with the use profile of the
submitted field trial data (MRID 47760601).  The submitted field trial
data will support eight foliar applications of a 125 g/L suspension
concentrate (SC) formulation of difenoconazole at a target rate of 0.39
kg ai/ha/application (0.34 lb ai/A/application), with 6- to 8-day
retreatment intervals, for a total rate of 3.07 kg ai/ha (2.74 lb ai/A)
and a 12-day PHI.  Applications may be made using ground equipment in
2,000 L/ha spray volumes (214 gal/A which is considered a dilute spray
volume), without an adjuvant.  

Consistent with the submitted field trial data, applications should be
restricted to fruit protected with exclusion net bags or otherwise
bagged fruit.

860.1550 Proposed Tolerances

The proposed tolerances should be revised to reflect the recommended
tolerance levels and correct commodity definitions as specified in Table
12.0.  

Toxicity

Immunotoxicity study (870.7800)

In accordance with Part 158 Toxicology Data requirements, an
immunotoxicity study (870.7800) is required for difenoconazole.  In the
absence of specific immunotoxicity studies, EPA has evaluated the
available difenoconazole toxicity data to determine whether an
additional database uncertainty factor is needed to account for
potential immunotoxicity.  There are no indications in the available
studies that organs associated with immune function, such as the thymus
and spleen, are affected by difenoconazole, and difenoconazole does not
belong to a class of chemicals (e.g., the organotins, heavy metals, or
halogenated aromatic hydrocarbons) that would be expected to be
immunotoxic.  Therefore, EPA does not believe that conducting
immunotoxicity testing will result in a point of departure lower than
those already selected for difenoconazole risk assessment, and an
additional database uncertainty factor is not needed to account for the
lack of this study.

ORE

none



11.0	References:  TC \l1 "10.0 References: 

1.	HED memo of B. Cropp-Kohlligian, 01/28/10, “Difenoconazole.  Import
Tolerance Request on Mango and Waxapple (also known as Wax jambu). 
Summary of Analytical Chemistry and Residue Data.  D371612.

2.	HED memo of T. Morton, 01/21/10, “Difenoconazole.  Acute and
Chronic Aggregate Dietary Exposure and Risk Assessments for the Section
3 Registration Request for Mango and Wax Apple.  D371613.

3.	EFED  memo of  I. Maher, 05/28/09,  Difenoconazole (Parent Only)
Drinking Water Assessment in Support of New Use Registration Action for
Bulb Vegetables, Brassica (Cole) Leafy Vegetables, Cucurbit Vegetables,
Citrus Fruit, Grapes, and Tree Nuts”.

12.0	Tolerance Summary

The proposed tolerances should be revised to reflect the recommended
tolerance levels and correct commodity definitions as specified in Table
12.0.

Table 12.0.    Tolerance Summary for Difenoconazole.

Commodity	Proposed Tolerance (ppm)	Recommended Tolerance

(ppm)	Comments; 

Correct Commodity Definition

Mango, fruit	0.09	0.07	Mango

Waxapple, fruit	1.5	1.5	Wax  jambu



  TC \l1 "11.0	Tolerance Summary 

13.0	Appendices  TC \l1 "12.0	Appendix: Toxicity Profile 

Appendix 1: Acute Toxicity Data on Difenoconazole Technical

Table 13.0a	Acute Toxicity Profile - Difenoconazole

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

870.1100	Acute oral rat	42090006	LD50  = 1450 mg/kg	III

870.1200	Acute dermal rat	42090007	LD50 > 2010 mg/kg	III

870.1300	Acute inhalation rat	42090008	LC50 > 3.3 mg/L	III

870.2400	Acute eye irritation rabbit	42090009	Mild ocular irritation
reversible in 7 days	III

870.2500	Acute dermal irritation rabbit	42090010	Slight irritation	IV

870.2600	Skin sensitization mouse	42090011, 42710004	Negative	N/A

 TC \l2 "A.2  Toxicity Profiles 

  TC \l2 "12.2	Appendix 2.: Acute Toxicity Data on Pyraclostrobin
Technical 

Appendix 2: Subchronic, Chronic and Other Toxicity Profile

  TC \l2 "12.3	Appendix 3.: Subchronic, Chronic and Other Toxicity
Profile 

Table 13.0b	Subchronic, Chronic and Other Toxicity Profile of
Difenoconazole

Guideline No. 	Study Type	MRID No. (year)/ Classification /Doses	Results

870.3100

	90-Day oral toxicity (rat)	42090022 (1987)

Acceptable/guideline

0, 20, 200, 750, 1500 or 3000 ppm

0, 1, 10, 37.5, 75 and 150 mg/kg/d	NOAEL = 20 ppm (1 mg/kg/day)

LOAEL = 200 ppm (10 mg/kg/day) based on the 10% decrease in body weight
in the 200 ppm females (as well as a negative trend in feed consumption)
and Increases in absolute liver weights in both sexes



870.3100

	90-Day oral toxicity (mouse)	42090021 (1987)

Minimum/guideline

0, 20, 200, 2500, 7500 or 15,000 ppm 

M: 0, 2.9, 30.8, 383.6, 1125 and 2250 mg/kg/d

F: 0, 4.1, 41.5, 558.9, 1125 and 2250 mg/kg/d	NOAEL = 20 ppm (2.9
mg/kg/day)

LOAEL = 200 ppm (30.8 mg/kg/day) based on body weight changes & liver
histopathology.

870.3150	26-Week oral toxicity	42090012 (1987)

Minimum/ guideline

0, 100, 1000, 3000 or 6000 ppm

M: 0, 3.6, 31.3, 96.6 and 157.8 mg/kg/d

F: 0, 3.4, 34.8, 110.6 and 203.7 mg/kg/d	NOAEL = 3000 ppm (31.3
mg/kg/day in males/34.8 mg/kg/day in females)

LOAEL = 6000 ppm (96.6 mg/kg/day in males/110.6 mg/kg/day in females),
based primarily on microscopic examination of CGA 169374-related
lenticular cataracts.

870.3200

	21/28-Day dermal toxicity (rat)	42090013 (1987)

Minimum/ guideline

0, 10, 100 and 1000 mg/kg/d	NOAEL = 10 mg/kg/day

LOAEL = 100 mg/kg/day based on statistically significant decrements in
body weight, body weight gain, and food consumption.

870.3200

	21/28-Day dermal toxicity (rat)	46950310 (2000)

Acceptable/ guideline

0, 10, 100 and 1000 mg/kg/d	NOAEL (systemic) = 1000 mg/kg/day

LOAEL (systemic) was not determined.

NOAEL (dermal) = 100 mg/kg/day

LOAEL (dermal) = 1000 mg/kg/day based on hyperkeratosis at the skin
application site.

870.3700a

	Prenatal developmental in (rat)	42090016, 42710007 (1987)

Minimum/ guideline

0, 2, 20, 100 or 200 mg/kg/d from GD 6-15 (nominal doses  differed
widely from theoretical, this required altering NOAEL/LOAEL values)
Maternal NOAEL = 16 mg/kg/day

LOAEL = 85 mg/kg/day based on decreased body weight gain and food
consumption.

Developmental NOAEL = 85 mg/kg/day

LOAEL = 171 mg/kg/day based on alterations in fetal ossification.

870.3700b

	Prenatal developmental in (rabbit)	42090017, 42710008 (1987)

Minimum/ guideline

0, 1, 25 or 75 mg/kg/d from GD 7-19

	Maternal NOAEL = 25 mg/kg/day

LOAEL = 75 mg/kg/day based on decreased body weight gain and food
consumption.  

Developmental NOAEL = 25 mg/kg/day

LOAEL = 75 mg/kg/day based on nonsignificant increases in
postimplantation loss and resorptions/doe and a significant decrease in
fetal weight.

870.3800

	Reproduction and fertility effects

(rat)	42090018 (1988)

Minimum/ guideline

0, 25, 250 or 2500 ppm

0, 1.25, 12.5 and 125 mg/kg/d

	Parental/Systemic NOAEL = 25 ppm (1.25 mg/kg/day) 

LOAEL = 250 ppm (12.5 mg/kg/day) based on reductions (statistically
nonsignificant) in body weight gain which appear to be part of a
dose-related trend days 70-77 prior to mating, days 0-7 of gestation,
and days 7-14 of lactation

Reproductive NOAEL = 25 ppm (1.25 mg/kg/day)

LOAEL = 250 ppm (12.5 mg/kg/day) based on a significant reduction in the
body weight of F1 male pups at day 21 in the 250 ppm group.

870.4100b

	Chronic toxicity

(dog)	42090012, 42710005 (1988)

Minimum/ guideline

0, 20, 100, 500 or 1500 ppm

M: 0, 0.71, 3.4, 16.4 and 51.2 mg/kg/d

F: 0, 0.63, 3.7, 19.4 and 44.3 mg/kg/d	NOAEL = 100 ppm (3.4 mg/kg/day in
males/3.7 mg/kg/day in females)

LOAEL = 500 ppm (16.4 mg/kg/day in males/19.4 mg/kg/day in females),
based on significant inhibition of body weight gain in females.



870.4200

	Carcinogenicity

(rat)	42090019, 42710010 (1989)

Minimum/ guideline

0, 10, 20, 500 or 2500 ppm

M: o, 0.48, 0.96, 24.12 and 123.7 mg/kg/d

F: 0, 0.64, 1.27, 32.79 and 169.6 mg/kg/d	NOAEL = 20 ppm (0.96 mg/kg/day
in males/1.27 mg/kg/day in females)

LOAEL = 500 ppm (24.1 mg/kg/day in males/ 32.8  mg/kg/day in females)
based on reductions in cumulative body weight gains in the 500 and 2500
ppm groups.

No evidence of carcinogenicity

870.4300

	Carcinogenicity

(mouse)	42090015, 42710006 (1989)

Minimum/ guideline

0, 10, 30, 300, 2500 or 3000 ppm

M: 0, 1.51, 4.65, 46.29, 423.1 and 818.9 mg/kg/d

F: 0, 1.9, 5.63, 57.79 and 512.6 mg/kg/d	NOAEL = 30 ppm (4.7 mg/kg/day
in males/5.6 mg/kg/day in females)

LOAEL = 300 ppm (46.3 mg/kg/day in males/57.8 mg/kg/day in females)
based on reductions in the cumulative body weight gains in the 300, 2500
& 4500 ppm groups. 

Evidence of carcinogenicity (liver adenoma/carcinoma in both sexes)

870.5100	In vitro bacterial gene mutation (Salmonella typhimurium/ E.
coli)/ mammalian activation gene mutation assay	42090019, 42710010
(1989)

Minimum/ guideline

340 - 5447 μg/plate;

85 - 1362 μg/plate (repeat assay with TA1537 and TA98)

	There were sufficient and valid data to conclude that CGA 169374
technical was negative in the microbial gene mutation assay.

870.5300	in vitro mammalian cell gene mutation assay in mouse lymphoma
cells

	42090024 (1986)

Unacceptable/ guideline	No conclusion can be reached from the three
nonactivated and two S9 activated mouse lymphoma forward mutation assays
conducted with difenoconazole technical. The study was seriously
compromised.

870.5375	In vitro Mammalian Cytogenetics (chromosomal aberrations) assay
in Chinese hamster CHO cells	46950319 (2001)

Acceptable/ guideline

0, 21.99, 27.49, or 34.36 µg/mL (-S9)

0, 34.36, 53.69 or 67.11 µg/mL (+S9)	There was evidence of a weak
induction of structural chromosomal aberrations over background in the
presence of S9-mix.



870.5375	In vitro Mammalian Cytogenetics (chromosomal aberrations) assay
in Chinese hamster CHO cells	46950321 (2001)

Acceptable/ guideline

0, 26.3, 39.5 or 59.3 µg/mL (-S9)

0, 11.7 or 17.6 µg/mL (+S9)	There was evidence of a weak induction of
structural chromosomal aberrations over background.



870.5375	In vitro Mammalian Cytogenetics (chromosomal aberrations) assay
in human lymphocytes	46950323 (2001)

Acceptable/ guideline

0, 5, 30 or 75 µg/mL (-S9)

0, 5, 30 or 62 µg/mL (+S9)	There was no evidence of structural
chromosomal aberrations induced over background.



870.5385 	In vivo mammalian chromosomal aberration test Assay in Mice
42090023 (1986)

Unacceptable/guideline

250, 500 or 1000 mg/kg	There was no evidence of a cytotoxic effect on
the target organ or significant increase in the frequency of nuclear
anomalies (micronuclei). However, the study was compromised.

870.5395 	In vivo mammalian cytogenetics - erythrocyte micronucleus
assay in mice	41710011 (1992)

Acceptable/guideline

Doses up to 1600 mg/kg	Mice bone marrow - No increase in micronucleated
polychromatic erythrocytes occurred with CGA-1 69374 (91.2% a.i).

870.5550	Unscheduled DNA Synthesis in Mammalian Cells in Culture

	4210012 (1992)

Acceptable/ guideline

μg/mL

	CGA-i69374 tech. (92.2% a.i.) was considered to be negative in the
unscheduled DNA synthesis assay in rat primary hepatocytes as measured
by an autoradiographic method at concentrations up to 50.0 μg/mL.

870.5550	Unscheduled DNA Synthesis in Mammalian Cells in Culture

	42090027 (1985)

Unacceptable/ guideline

0.25-31.25 μg/mL

	No conclusion can be reached from the unscheduled DNA synthesis (UDS)
primary rat hepatocyte assay conducted with difenoconazole technical at
concentrations ranging from 0.25 to 31.25 μg /mL. The sensitivity of
the study was severely compromised.

870.5550	Unscheduled DNA Synthesis in Mammalian Cells in Culture
42090026 (1985)

Unacceptable/ guideline

0.08-10 μg/mL	No conclusion can be reached from the unscheduled DNA
synthesis (UDS) human fibroblast assay conducted with difenoconazole
tech. at conc. ranging from 0.08 to 10 μg /mL. 

870.6200a

	Acute neurotoxicity screening battery	46950327 (2006)

Acceptable/ guideline

0, 25, 200 or 2000 mg/kg/d	NOAEL (M) = 25 mg/kg/day

LOAEL (M) = 200 mg/kg/day based on reduced fore-limb grip strength in
males on day 1 and increased motor activity on Day 1.  

NOAEL (F) = 200 mg/kg/day

LOAEL (F) = 2000 mg/kg/day based on decreased body weight, the following
clinical signs: upward curvature of the spine, tip-toe gait, decreased
activity, piloerection and sides pinched in and decreased motor
activity.

870.6200b

	Subchronic neurotoxicity screening battery	46950329 (2006)

Acceptable/ guideline 

0, 40, 250, or 1500 ppm  M; 0, 2.8, 17.3 or 107.0 mg/kg/d 

F: 0, 3.2, 19.5, or 120.2 mg/kg/d	NOAEL (M) = 40 ppm (2.8 mg/kg/day)

LOAEL (M) = 250 ppm (17.3 mg/kg/day) based on decreased hind limb
strength.  

NOAEL (F) = 250 ppm (19.5 mg/kg/day)

LOAEL (F) = 1500 (120.2 mg/kg/day) based on decreased body weight, body
weight gain and food efficiency. 

870.7485

	Metabolism and pharmacokinetics

(rat)	42090028 (1990)

Acceptable/ guideline

14 daily doses of  0.5 or 300 mg/kg	The absorption, distribution,
metabolism, and excretion of CGA 169374 were studied in groups of male
and female Sprague-Dawley rats. Animals were administered a single oral
gavage dose of 0.5 or 300 mg/kg [14C]CGA- 169374, or 0.5 mg/kg unlabeled
GGA-169374 by gavage for 14 days followed by a single gavage dose of 0.5
mg/kg [14C)CGA-169374 on day 15. The test compound was labeled with C14
at either the phenyl or triazole ring.

870.7485

	Metabolism and pharmacokinetics

(rat)	42090031 (1988)

Acceptable/ guideline

0.5 or 300 mg/kg

	These studies indicate that distribution, metabolism, and elimination
of CGA-169374 were not sex related. There was a slight dose difference
in the metabolism and elimination of CGA-169374. In phenyl and triazole
labeling studies, fecal excretion of radioactivity was higher in the
high dose animals compared to the low dose animals, and an additional
metabolite was found in the feces of the high dose animals compared to
the low dose animals. There was no major difference in the distribution
and excretion of radioactivity with labeling at the phenyl and triazole
ring positions, however, there were some different metabolites
identified. The studies also showed that administration of 0.5 and 300
mg/kg CGA- 169314 did not induce any treatment related clinical effects.

870.7485

	Metabolism and pharmacokinetics

(rat)	420710013, 42710014 (1990)

Acceptable/ guideline

0.5 or 300 mg/kg

	These two studies described the absorption, distribution, and excretion
as the pharmacokinetics and isolated and identified urinary metabolites.
Issues raised in the previous supplementary studies were answered. In
conjunction with these studies, the previous studies are upgraded.

870.7485

	Metabolism and pharmacokinetics

(rat)	42090029 (1987)

Acceptable/ guideline

	[14C]CGA-169374 was rapidly and extensively distributed. metabolized,
and excreted in rats for all dosing regimens. The extent of absorption
is undetermined pending determination of the extent of biliary
excretion. The 4-day recoveries were 97.4- 107.75% of the administered
dose for all dosing groups. The elimination of radioactivity in the
feces (78.06- 94.61% of administered dose) and urine (8.48-21.86%) were
almost comparable for all oral dose groups, with slightly higher
radioactivity found in the feces of the high dose group than the low
dose groups. This was probably due to biliary excretion, poor absorption
or saturation of the metabolic pathway. The radioactivity In the blood
peaked at about 24-48 hours for all dosing groups. Half-lives of
elimination appear to be approximately 20 hours for the low dose groups
and 33 - 48 hours for the high dose group. The study results also
indicate that CGA-1 69374 and/or its metabolites do not bioaccumulate to
an appreciable extent following oral exposure since all the tissues
contained negligible levels (<1%) of radioactivity 7 days postexposure.

870.7485

	Metabolism and pharmacokinetics

(rat)	42090030 (1987)

Acceptable/ guideline

	The metabolism of CGA-169374 appears to be extensive because the
metabolites accounted for most of the recovered radioactivity in the
excreta. Three major metabolites were identified in the feces (i.e., A,
B, and C). Two of the metabolites were separated into isomers (i.e., A1,
A2, B1, and B2). Metabolite C was detected only In the high dose groups,
indicating that metabolism of CGA-169374 is dose related and involves
saturation of the metabolic pathway. Free triazole metabolite was
dete6ted in the urine of triazole labeled groups and its byproduct was
detected In the liver of phenyl labeled groups only. Other urinary
metabolites were not characterized.



Table A.1.3.	Subchronic, Chronic and Other Toxicity Profile of
Difenoconazole Metabolites 

Guideline No. 	Study Type	MRID No. (year)/ Classification /Doses	Results

870.5100	In vitro Bacterial Gene Mutation (Salmonella typhimurium/ E.
coli)/ mammalian activation gene mutation assay	46950314 (1991)

Unacceptable/ guideline

0, 31.3, 62.5, 125, 250, 500 or 1000 µg/plate in strains TA100 and
TA1537 (-S9)

0, 31.3, 62.5, 125, 250, 500 or 1000 µg/plate in all strains (+S9)

0, 62.5, 125, 250, 500, 1000 or 2000 µg/plate in strains TA1535, WP2
uvrA and TA98 (-S9)

0, 62.5, 125, 250, 500, 1000 or 2000 µg/plate in strains WP2 uvrA (+S9)
The number of revertants per plate was not increased over the concurrent
solvent control value at any test material concentration, with or
without S9-mix, in any tester strain. The solvent and positive controls
induced the appropriate responses in the corresponding strains. There
was no evidence of induced mutant colonies over background.

Tested: CGA-189138 (metabolite of difenoconazole)

870.5100	In vitro Bacterial Gene Mutation (Salmonella typhimurium/ E.
coli)/ mammalian activation gene mutation assay	46950315 (1991)

Unacceptable/ guideline

0, 156, 313, 625, 1250, 2500 or 5000 µg/plate ((S9)	The number of
revertants per plate was not increased over the concurrent solvent
control value at any test material concentration, with or without
S9-mix, in any tester strain. The solvent and positive controls induced
the appropriate responses in the corresponding strains. There was no
evidence of induced mutant colonies over background.

Tested: CGA205374 (metabolite of difenoconazole)

870.5100	In vitro Bacterial Gene Mutation (Salmonella typhimurium/ E.
coli)/ mammalian activation gene mutation assay	46950317 (1991)

Unacceptable/ guideline

0, 2.50, 5.00, 10.0, 20.0, 40.0 or 80.0 µg/plate in all strains (-S9)

0, 5.00, 10.0, 20.0, 40.0, 80.0 or 160 µg/plate in strains TA100 and
TA1535 (+S9)

0, 10.0, 20.0, 40.0, 80.0, 160 or 320 µg/plate in strains WP2 uvrA and
TA1537 (-S9)

0, 2.50, 5.00, 10.0, 20.0, 40.0, or 80.0 µg/plate in strain TA98 (+S9)
The number of revertants per plate was not increased over the concurrent
solvent control value at any test material concentration, with or
without S9-mix, in any tester strain. The solvent and positive controls
induced the appropriate responses in the corresponding strains. There
was no evidence of induced mutant colonies over background.

Tested: CGA205375 (metabolite of difenoconazole)



EXECUTIVE SUMMARIES OF SOME STUDIES:

STUDY TYPE: 28-Day Dermal Toxicity – Rat
(OPPTS 870.3200 [§82-2] (rodent); OECD 410).

CITATION:	Gerspach, R. Difenoconazole: 28-Day Repeated Dose Dermal
Toxicity Study in Rats. Novartis Crop protection AG Toxicology
(Switzerland). Novartis Report Number: 993072; Syngenta Report Number:
T002728-06. July 11, 2000, MRID 46950310 and MRID 46950311. Unpublished.

EXECUTIVE SUMMARY:  In a 28-day dermal toxicity study (MRID 46950310)
CGA 169374 Technical (91.8% a.i., Batch No. P807002) was applied to the
shaved skin of ten male and ten female rats at dose levels of 0, 10, 100
and 1000 mg/kg bw/day. There were no treatment-related effects on body
weight or food consumption. Non clinical signs of toxicity were noted
including specific indicators of neurotoxicity. The dose level of 1000
mg/kg bw/day caused hyperkeratosis at the skin application site. A high
incidence of follicular cell hypertrophy of the thyroid was observed in
males and females of control and all treatment groups and variations
with dose are not considered treatment-related. Minimal inconsequential
changes were noted on clinical chemistry parameters in high dose males
that were not relevant toxicologically. The incidence and severity was
increased in animals in the highest dose group. There was an increase in
the absolute (12%) and relative (16%) weight of the liver in males in
the high dose group accompanied by an increased incidence of slight
hepatocellular hypertrophy (7/10) compared to controls (2/10).  Females
in the high dose group also had an increase in the relative weight of
the liver (10%) with an increased incidence of slight hepatocellular
hypertrophy (7/10) compared to controls (1/10). These effects are
consistent with adaptive responses of the liver.

A systemic LOAEL for male and female rats was not established. The NOAEL
for male and female rats is 1000 mg/kg bw/day.

A dermal irritation LOAEL for male and female rats is 1000 mg/kg bw/day
based on hyperkeratosis at the skin application site. The dermal NOAEL
for male and female rats is 100 mg/kg bw/day.

This 28-day dermal toxicity study in the Fischer 344 rat is
Acceptable/Guideline and satisfies the guideline requirement for a
28-day dermal toxicity study (OPPTS 870.3200; OECD 410) in the rat.

STUDY TYPE:	Acute Neurotoxicity - Rats OPPTS 870.6200a [§81-8]; OECD
424.

CITATION:	Pinto, P.J. (2006) Difenoconazole Technical (CGA169374): 
Acute Neurotoxicity Study in Rats. Central Toxicology Laboratory
(Cheshire, UK). Laboratory report number AR7517-REG-R1, July 28, 2006.
MRID 46950327. Unpublished.

	Pinto, P.J. (2006) Difenoconazole Technical (CGA169374):  Preliminary
Acute Neurotoxicity Study in Rats. Central Toxicology Laboratory
(Cheshire, UK). Laboratory report number AR7518-REG, June 16, 2006. MRID
46950325. Unpublished.

EXECUTIVE SUMMARY:  In an acute neurotoxicity study (MRID 46950327),
groups of fasted Alpk:APfSD Wistar-derived rats (10/sex/dose), at least
42 days old, were given a single oral dose of difenoconazole technical
(CGA169374) (94.3% w/w, batch/lot # WM806228) in 1% w/v aqueous
carboxymethylcellulose (CMC) at doses of 0, 25, 200, or 2000 mg/kg bw
and observed for 14 days.  Dose levels selected for this study were
based on the results of a preliminary acute neurotoxicity study (MRID
46950325).  Neurobehavioral assessment (functional observational battery
and motor activity testing) was performed on 10 animals/sex/group on
days -7, 1, 8, and 15.  Body weight and food consumption were measured
weekly throughout the study.  At study termination, 5 animals/sex/group
were euthanized and perfused in situ for neuropathological examination;
brain weight was recorded from these animals.  Of the perfused animals,
5 animals/sex from the control and high dose groups were subjected to
histopathological evaluation of brain and peripheral nervous system
tissues. 

There were no unscheduled deaths at any dose level. Weight change on the
day of dosing by the control, low-, mid-, and high-dose groups was -2.1,
-1.0, -7.8, and -18.3 g, respectively, for males and 0.0, 2.1, -3.8, and
-13.0 g, respectively, for females.  Body weight for females had
recovered to control levels by day 8.  Food consumption for males given
2000 mg/kg was approximately 20% less than control during week 1 only
(p<0.01).  Food consumption for these animals recovered to control
levels during week 2.  There were no differences from control for
females at any dose level or for males at the lower dose levels.  These
effects on body weight and food consumption were not toxicologically
significant.

At 2000 mg/kg, a number of adverse clinical signs were observed on day 1
(at the time of peak effect), including: upward curvature of the spine
(8 males, 9 females); tip-toe gait (3, 8); decreased activity (6, 7);
piloerection (3, 5); sides pinched in (3, 7); and subdued (1, 0). 
Females were affected more than males.  All treatment-related clinical
signs observed on day 1 showed complete recovery by day 5 (males) or day
7 (females).  

↓23%) and high-dose (↓26%) males on day 1.  Females dosed with 2000
mg/kg had lower motor activities on day 1 (37%), at the time of peak
effect, and on day 8 (31%).  Males dosed with 200 or 2000 mg/kg had
higher motor activities than the controls on day 1, 50% and 55%,
respectively, at the time of peak effect.

There were no effects on brain weight at any dose level. 
Neuropathological examination of the central and peripheral nervous
system showed no effects of treatment at doses of 2000 mg/kg in both
sexes.

The LOAEL for acute neurotoxicity of difenoconazole technical
(CGA169374) in male rats is 200 mg/kg bw based on reduced fore-limb grip
strength in males on day 1 and increased motor activity on Day 1.  The
NOAEL is 25 mg/kg bw. 

The LOAEL for acute neurotoxicity of difenoconazole technical
(CGA169374) in female rats is 2000 mg/kg bw based on decreased body
weight, the following clinical signs: upward curvature of the spine,
tip-toe gait, decreased activity, piloerection and sides pinched in  and
decreased motor activity. The NOAEL is 200 mg/kg bw. 

This acute neurotoxicity study is classified as Acceptable/Guideline and
satisfies the guideline requirement for an acute neurotoxicity study in
rats (870.6200; OECD 424).    SEQ CHAPTER \h \r 1 Positive control data
have been submitted for review and were considered acceptable.

STUDY TYPE:	Subchronic Neurotoxicity, OPPTS 870.6200b [§82-7] feeding -
rat; (OECD 424).

CITATION:	Pinto, P J. (2006). Difenoconazole technical (CGA 169374)
subchronic neurotoxicity study in rats, final report.  Central
Toxicology Laboratory, Alderley Park, Macclesfield, Cheshire, UK SK 10
4TJ.  Report number PR1330-REG-R1.  July 28, 2006.  MRID 46950329.
Unpublished. 

	Pinto, P.J. (2006). Difenoconazole technical (CGA 169374) 28-day
dietary rangefinding study in rats, final report.  Central Toxicology
Laboratory, Alderley Park, Macclesfield, Cheshire, UK SK 10 4TJ.  Report
number KR1606-REG.  June 13, 2006.  MRID 46950326. Unpublished. 

 

	Alexander, O. (2006)  Difenoconazole technical (CGA 169374) subchronic
neurotoxicity study in rats – study profile.  Syngenta Crop
Protection, Inc., 410 Swing Road, P.O. Box 18300, Greensboro, NC
27419-8300.  Report number PR1330-REG-R1.  September 19, 2006.  MRID
46950330. Unpublished. 

EXECUTIVE SUMMARY:  In a subchronic neurotoxicity study (MRID 46950329)
difenoconazole technical (94.5% w/w, batch no. WM806228) was
administered to groups of 12 male and 12 female Alpk:APfSD
(Wistar-derived) rats at concentrations of 0, 40, 250, or 1500 ppm in
the diet for 90 days.  Respective dose levels corresponded to 0, 2.8,
17.3 or 107.0 mg/kg bw/day for males and 0, 3.2, 19.5, or 120.2 mg/kg
bw/day for females.  Neurobehavioral assessment (functional
observational battery and motor activity testing) was performed in 12
animals/sex/group pretest and during weeks 2, 5, 9, and 14. 
Cholinesterase activity was not determined.  At study termination, 5
animals/sex/group were euthanized and perfused in situ for
neuropathological examination.  Of the perfused animals, 5/sex from the
control group and 5/sex from the 1500 ppm group were subjected to
histopathological evaluation of brain and peripheral nervous system
tissues. 

only in females [7%]), and food efficiency was significantly reduced in
males by 21% (p≤0.05) and in females by 21% (ns).  Lower dose groups
were unaffected.  Absolute liver weight in males and females in the 1500
ppm group was increased over respective control weight by 38% and 45%. 
Liver was not weighed in lower dose groups.  The increase in liver
weight was considered a normal response to chemical treatment.

 18 to 27% relative to the control values.  At week 14, hind-limb grip
strength in males in the 250 ppm group was significantly (p≤0.05)
reduced by 20% relative to the control values.  FOB observations in
females were unaffected by treatment.  Motor activity was unaffected in
both sexes at all observation times.  Brain weight was unaffected by
treatment and there were no treatment-related neuropathological lesions.
 

The LOAEL in male rats is 250 ppm in the diet (17.3 mg/kg bw/day), based
on decreased hind limb strength.  The NOAEL is 40 ppm (2.8 mg/kg
bw/day).

The LOAEL in female rats is 1500 ppm in the diet (120.2 mg/kg bw/day),
based on decreased body weight, body weight gain and food efficiency. 
The NOAEL is 250 ppm  (19.5 mg/kg bw/day).

The study is classified as Acceptable/Guideline and does satisfies the
guideline requirement for a subchronic neurotoxicity study in rats
(870.6200b).  Positive control data have been submitted for review and
were considered acceptable.

STUDY TYPE:      Rodent In Vivo Dermal Penetration Study – Rat
OPPTS 870.7600 [§85-2]; OECD none.

CITATION:	Hassler, S. (2003) Difenoconazole 250 EC (A7402G): Dermal
absorption of [Triazole-U-14C] CGA 169374 formulated as Score® 250 EC
(A-7402G) in the rat (in vivo). Syngenta Crop Protection AG, Health
Assessment/Animal Metabolism CH-4002 Basel, Switzerland. Syngenta Number
T002729-06, May 6, 2003. MRID 46950333. Unpublished.

EXECUTIVE SUMMARY:  In a dermal penetration study (MRID 46950333),
[Triazole–U-14C] CGA 169374 (radiolabled: batch # 50.2-1 and 50.2-2
contained 98 and 99.3% a.i., respectively; nonradiolabeled: batch # AMS
255/3 contained 99.3% a.i.) formulated as Score® 250 EC (A-7402G) was
administered to 16 male HanBrl: WIST (SPF) rats/dose to a skin area of
10 cm2 at nominal dose levels of 0, 0.005, 0.0125, and 2.5 mg/cm2 skin. 
The 2.5 mg/cm2 dose was repeated because of a high variability in the
results of the washing procedure.  Measured dose levels were 0.005,
0.0130, 2.4, and 2.6 mg/cm2 for the low, mid, and high dose and high
dose repeat groups, respectively.   Exposure duration was 6 hours and
animals were monitored for 6, 24, 48, or 72 hours.  The remaining
discussion of dermal penetration at the high dose will include only the
“high-dose repeat” data (i.e., the results of the first high-dose
exposure will not be discussed).  Recovery of the applied dose was
acceptable with group means ranging from 95.44 to 103.67%.  Results were
not adjusted for incomplete recovery of the applied dose.  The majority
of the applied dose was recovered in the skin wash, accounting for
49-69%, 73-78%, and 76-86% of the low, mid, and high dose, respectively.
 The amount of the applied dose retained at the application site was
8-12%, 3-5%, and 2-5% of the low, mid, and high dose, respectively.  At
the low and mid dose, the major part of the radioactivity remaining in
the skin was associated with the stratum corneum (7-11% and 2-5%,
respectively), while only 1-2% of the high dose was recovered in the
upper skin layer.  Dermal absorption (sum of blood, carcass, urine,
feces, skin test site, gastrointestinal tract, untreated skin, and
cagewash) accounted for 15-38%, 7-15%, and 3-11% of the low, mid, and
high doses, respectively.  Of the test substance systemically absorbed,
excretion into the feces was generally the primary route of elimination,
accounting for up to 18%, 8%, and 2% of the low, mid, and high doses,
respectively.  Of the radioactivity remaining in the animal 72 hours
after application, the gastrointestinal tract contained 3.0%, 1.4%, and
0.3% of the low, mid, and high doses, respectively, and the carcass
contained 1.5%, 0.7%, and 1.1%, respectively.  Blood concentrations
during and after the exposure period were at or below the limits of
determination. Based on the limited blood concentration data available,
maximum blood concentrations were measured between 6-8 hours after dose
application.  

 

Based on the amount of radioactivity entering the systemic circulation
within 6 hours of exposure, the calculated penetration rates at the low,
mid, and high doses were 0.013, 0.162, and 30.4 µg cm-2 h-1,
respectively.  The penetration rates increased somewhat proportionally
with the increase of the test substance concentration at the three dose
levels (1:26:5100 for the concentration ratio of the dose levels versus
1:12:2300 for the ratio of the penetration values).

This study in the rat is unacceptable/guideline and does not satisfy the
guideline requirement for a dermal penetration study (870.7600) in rats.
 Major deficiencies include uncertainty in the ability of the laboratory
to perform the experiment, and only one exposure duration was tested (6
hours), despite minimum Guideline recommendations for durations of 1,
10, and 24 hours.  See “Study Deficiencies” for listing of numerous
minor deficiencies. 

STUDY TYPE:	In Vitro Dermal Penetration Study – Rat and Human
OPPTS 870.7600 [§85-2]; OECD none.

CITATION:	Hassler, S. (2003) Difenoconazole 250 EC (A7402G): The
percutaneous penetration of [Triazole-U-14C] CGA 169374 formulated as
Score® 250 EC (A-7402G) through rat and human split-thickness skin
membranes (in vitro). Syngenta Crop Protection AG, Health
Assessment/Animal Metabolism CH-402 Basel, Switzerland. Syngenta Number
T002730-06, April 9, 2003. MRID 46950332. Unpublished.

EXECUTIVE SUMMARY:  In an in vitro percutaneous penetration study (MRID
46950332), [Triazole–U-14C] CGA 169374 (98% a.i., batch number 50.2-1)
mixed with nonradiolabeled CGA 169374 (batch number AMS 255/3 containing
99.3% a.i.) formulated as SCORE 250® (A-7402) was applied to skin
membranes prepared from rat [male HanBrl: WIST (SPF)] and human
(cadaver) abdominal skin. Percutaneous absorption at low, mid, and high
doses of 0.5, 12.5, or 2500 µg/cm2 (actual applied doses of 0.5, 12, or
2345 µg/cm2) was assessed over 24 hours.  

Results clearly indicate that transfer of [Triazole–U-14C] CGA 169374
across skin membrane was notably greater for the rat skin membrane than
for human skin membrane as shown by flux values that were 10-, 12-, and
32-fold greater for the low, mid, and high concentrations, respectively.
 A concentration-dependent absorption was also indicated by greater flux
values with increasing concentration: flux values at the low, mid, and
high doses for the rat skin membranes were 0.020, 0.455, and 26.2
ug/cm2, respectively, and for human skin membranes were 0.002, 0.037,
and 0.822 ug/cm2, respectively.  The increasing flux values resulted in
greater absolute amounts of test article being transferred across the
skin membranes with increasing concentration: values at the low, mid,
and high doses for the rat skin membranes were 0.35, 7.7, and 539.2
ug/cm2, respectively, and for human skin membranes were 0.04, 0.84, and
15.6 ug/cm2, respectively.  However, the percutaneous absorption was
decreased, indicating saturated kinetics (absorption values at the low,
mid, and high doses expressed as percent of applied dose for the rat
skin membranes were 71%, 64%, and 23%, respectively, and for human skin
membranes were 8%, 7%, and 0.7%, respectively).  

This in vitro percutaneous absorption study in the rat is
acceptable/nonguideline, but does not satisfy the guideline requirement
for a dermal penetration study (870.7600) in rats. The study is a
specialty study and was designed to provide only supplemental
information to the OPPTS 870.7600 requirement.  Results of this study
provide information on the differences in dermal absorption between rat
and human skin membranes. 

STUDY TYPE: In vitro Mammalian Cytogenetics (chromosomal aberrations)
assay in Chinese hamster CHO cells; OPPTS 870.5375 [§84-2]; OECD 473

CITATION:	Lloyd, M. (2001) Difenoconazole Technical: Induction of
chromosome aberrations in cultured Chinese hamster ovary (CHO)cells. 
Covance Laboratories Ltd., Otley Road, Harrogate, North Yorkshire HG3
1PY, England. Laboratory Project ID: Covance Number 252/293, Syngenta 
Number T002874-06, December 11, 2001. MRID 46950319. Unpublished

EXECUTIVE SUMMARY:  In a mammalian cell cytogenetics assay (Chromosomal
aberrations) (MRID 46950319), Chinese hamster CHO cells in culture were
exposed to CGA 169374 Technical (94.3% w/w, Lot No. WM806228) in DMSO
for three hours at concentrations of 0, 21.99, 27.49, or 34.36 µg/mL
without metabolic activation (S9-mix) and at concentrations of 0, 34.36,
53.69 or 67.11 µg/mL with S9-mix.  Cells were harvested 17 hours
following the end of exposure.  Cells were exposed in a second
confirmatory study for three hours at concentrations of 0, 21.99, 27.49
or 34.36 µg/mL without S9-mix and for three hours at concentrations of
0, 34.36, 53.69, 67.11 or 83.89 µg/mL with S9-mix.  Cells were
harvested 17 hours following exposure.  Cells were evaluated for the
presence of structural chromosomal aberrations and for numerical
aberrations (polyploidy, endoreduplication and hyperploidy).  The
S9-fraction was obtained from Aroclor 1254 induced male Sprague-Dawley
rat liver. 

CGA 169374 Technical was tested up to cytotoxic concentrations as
evidenced by a dose-related reduction in mitotic activity seen with and
without S9-mix.  There was a statistically significant increase in the
percentage of cells with structural chromosomal aberrations at a CGA
169374 Technical concentration of 34.36 µg/mL without S9-mix in the
first study.  The slides were rescored to determine if aberrations at
the fragile X site were present.  Aberrations at the fragile X site are
not likely relevant to clastogenicity.  Aberrations at the fragile X
site were not found but the values obtained on rescoring were within the
historical solvent control range.  There was no clear reason given why
the percent of aberrant cells was lower when the slides were rescored.
Possibly the distribution of cells on the slides was uneven. The
increase at this dose without S9-mix was not seen in the confirmatory
assay and thus the increase was not considered biologically significant.
 A statistically significant increase in the percent of aberrant cells
was seen in the first study at 67.11 µg/mL with S9-mix.  The
statistical significance remained upon rescoring and all values exceeded
the historical solvent control range.  No statistically significant
increase was seen at this or a higher concentration in the confirmatory
study with S9-mix.  The failure to see a significant increase in the
percent of aberrant cells in the confirmatory study makes the results
equivocal.  The solvent and positive controls (4-Nitroquinoline 1-oxide
without S9-mix and cyclophosphamide with S9-mix) induced the appropriate
responses.  There was evidence of a weak induction of structural
chromosomal aberrations over background in the presence of S9-mix.

This study is classified as Acceptable/Guideline and satisfies the
guideline requirement for OPPTS 870.5375; OECD 473 for in vitro
cytogenetic mutagenicity data.

STUDY TYPE:	In vitro Mammalian Cytogenetics (chromosomal aberrations)
assay in Chinese hamster CHO cells; OPPTS 870.5375 [§84-2]; OECD 473

CITATION:	Ogorek, B. (2001) Difenoconazole Technical: Cytogenetic test
on Chinese hamster cells in vitro. Syngenta Crop Protection AG, Health
Assessment 2 Stein/Genetic Toxicology, CH-4332 Stein, Switzerland.
Laboratory Project ID: Syngenta AG Test Number 20013013, Syngenta Number
T002875-06, December 3, 2001. MRID 46950321. Unpublished

EXECUTIVE SUMMARY:  In a mammalian cell cytogenetics assay (Chromosomal
aberrations) (MRID 46950321), Chinese hamster CHO cells in culture were
exposed to CGA 169374 Technical (94.3% w/w, Lot No. WM806228) in DMSO
for three hours at concentrations of 0, 26.3, 39.5 or 59.3 µg/mL
without metabolic activation (S9-mix) and at concentrations of 0, 11.7
or 17.6 µg/mL with S9-mix.  Cells were harvested 18 hours following the
end of exposure.  Cells were exposed in a second confirmatory study for
21 hours at concentrations of 0, 2.3, 5.2 or 11.7 µg/mL without S9-mix
and for three hours at concentrations of 0, 7.8, 11.7 or 17.6 µg/mL
with S9-mix.  Cells were harvested immediately following the 21-hour
exposure and 18 hours after the three-hour exposure.  Cells were
evaluated for the presence of structural chromosomal aberrations and for
polyploidy.  The S9-fraction was obtained from Aroclor 1254 induced male
HanIbm:WIST(SPF) rat liver. 

CGA 169374 Technical was tested up to cytotoxic concentrations as
evidenced by a dose-related reduction in mitotic activity seen with and
without S9-mix.  There was a statistically significant increase in the
percentage of CHO cells with structural chromosomal aberrations at a CGA
169374 Technical concentration of 59.3 µg/mL without S9-mix in the
original study when aberrations at the fragile X site were included but
not when they were excluded.  Aberrations at the fragile X site are not
likely relevant to clastogenicity.  No statistically significant
increase in the percent of aberrant cells was seen in the original study
with S9-mix.  An increase in the percent of aberrant cells was seen in
the confirmatory study at 17.6 µg/mL with S9-mix and the increase was
statistically significant (p≤0.001) when aberrations at the fragile X
site were excluded.  The value of 6.5% aberrant cells exceeded the value
of >6% set as a criterion for a positive effect in the testing
laboratory.  The failure to see a significant increase in the percent of
aberrant cells in the original study makes the results equivocal.  No
statistically significant increase in the percentage of aberrant cells
was seen at any of the three test material concentrations without S9-mix
in the confirmatory study.  The solvent and positive controls (Mitomycin
C without S9-mix and Cyclophosphamide with S9-mix) induced the
appropriate responses.  There was evidence of a weak induction of
structural chromosomal aberrations over background.

This study is classified as Acceptable/Guideline and satisfies the
guideline requirement for OPPTS 870.5375; OECD 473 for in vitro
cytogenetic mutagenicity data.  

STUDY TYPE:	In vitro Mammalian Cytogenetics (chromosomal aberrations)
assay in human lymphocytes; OPPTS 870.5375 [§84-2]; OECD 473

CITATION:	Fox, V. (2001) Difenoconazole Technical: In vitro cytogenetic
assay in human lymphocytes. Central Toxicology Laboratory, Alderley
Park/Macclesfield, Cheshire, UK SK10 4TJ. Laboratory Project ID: CTL
Number SV1090, Syngenta Number T002876-06, August 29, 2001. MRID
46950323. Unpublished

sted immediately following the 20-hour exposure and 17 hours after the
three-hour exposure.  Cells were evaluated for the presence of
structural chromosomal aberrations.  The S9-fraction was obtained from
Phenobarbital + β-naphthoflavone induced male Sprague-Dawley rat liver.


CGA 169374 Technical was tested up to cytotoxic concentrations as
evidenced by a dose-related reduction in mitotic activity seen with and
without S9-mix.  No statistically significant increases in the
percentage of cells with structural aberrations, excluding gaps, over
the solvent control values were seen at any test material concentration
with or without S9-mix in the first experiment or without S9-mix in the
second experiment.  A statistically significant increase over the
solvent control value was seen at 5µg/mL with S9-mix in the second
experiment; however, the increase was not considered biologically
significant because the value (4.00%) was within the historical solvent
control range, the values at the two higher concentrations were not
significantly increased and no increase was seen in the first
experiment. The solvent and positive controls (Mitomycin C without
S9-mix and Cyclophosphamide with S9-mix) induced the appropriate
responses.  There was no evidence of structural chromosomal aberrations
induced over background.

This study is classified as Acceptable/Guideline and satisfies the
guideline requirement for OPPTS 870.5375; OECD 473 for in vitro
cytogenetic mutagenicity data.

DIFENOCONAZOLE METABOLITES:

STUDY TYPE:	In vitro Bacterial Gene Mutation (Bacterial system,
Salmonella typhimurium and Escherichia coli)/ mammalian activation gene
mutation assay; OPPTS 870.5100 [§84-2]; OECD 471 (formerly OECD 471
& 472).

CITATION:	Nakajima, M. (1991) CGA189138 (metabolite of difenoconazole):
reverse mutation assay of CGA189138. Biosafety Research Center; Foods,
Drugs and Pesticides (An-Pyo Center); 582-2, Arahama Shioshinden;
Fukude-Cho Iwata-Gun.; Shizuoka 437-12; Japan. Laboratory Project ID:
BRC Number 1809, October 21, 1991.  MRID 46950314.  Unpublished.

EXECUTIVE SUMMARY:  In a reverse gene mutation assay in bacteria (MRID
46950314), strains TA98, TA100, TA1535 and TA1537 of S. typhimurium and
strain WP2 uvrA of E. coli were exposed to CGA-189138, a metabolite of
difenoconazole, (97.8% a.i., lot number 910806) dissolved in DMSO in two
independent assays using a 20-minute preincubation procedure and
duplicate plating. In the first mutagenicity assay, which was
alternatively called the pilot assay and the dose-finding assay,
concentrations of 0, 51.2, 128, 320, 800, 2000 or 5000 µg/plate were
tested with and without S9-mix. In the second assay, which was called
the main assay, concentrations of 0, 31.3, 62.5, 125, 250, 500 or 1000
µg/plate were tested in the absence of S9-mix in strains TA100 and
TA1537 and in the presence of S9-mix in all Salmonella strains;
concentrations of 0, 62.5, 125, 250, 500, 1000 or 2000 µg/plate were
tested in the absence of S9-mix in strains TA1535, WP2 uvrA and TA98 and
in the presence of S9-mix in strain WP2 uvrA. The S9 fraction was
obtained from phenobarbital and 5,6-benzoflavone-induced male
Sprague-Dawley rat liver.

CGA-189138 was tested at concentrations up to the limit concentration
for the assay in the pilot assay, and many of the higher concentrations
tested in both assays showed cytotoxicity and sometimes also
insolubility. In the absence of S9-mix in the pilot assay, the test
material was cytotoxic, as judged by stereomicroscopic examination of
the bacterial lawns, at concentrations of 800 µg/plate and higher in
strains TA100 and TA1537 and at concentrations of 2,000 µg/plate and
higher in strains TA1535, WP2 uvrA and TA98. In the presence of S9-mix
in the pilot assay, the test material was cytotoxic at concentrations of
800 µg/plate and higher in all four Salmonella strains and at
concentrations of 2,000 µg/plate and higher in strain WP2 uvrA. In the
absence of S9-mix in the main assay, the test material was cytotoxic at
concentrations of 500 µg/plate and higher in strain TA100, at
concentrations of 1,000 µg/plate and higher in strains TA1535 and TA98,
and at the maximum concentrations tested in strains WP2 uvrA and TA1537.
In the presence of S9-mix in the main assay, the test material was
cytotoxic at concentrations of 500 µg/plate and higher in strains
TA100, TA1535 and TA1537 and at the maximum concentrations tested in
strains WP2 uvrA and TA98. At cytotoxic concentrations there was often
also a marked decrease in the number of revertant colonies found. In the
pilot assay, precipitation of the white powdery test material was
observed on the surface of the agar plates at the time of colony
counting at concentrations of 5,000 µg/plate in the absence of S9-mix
and at concentrations of 2,000 µg/plate and above in the presence of
S9-mix. In the main assay, such precipitation was observed only in the
presence of S9-mix and at the highest concentration tested in strain WP2
uvrA. The number of revertants per plate was not increased over the
concurrent solvent control value at any test material concentration,
with or without S9-mix, in any tester strain. The solvent and positive
controls induced the appropriate responses in the corresponding strains.
There was no evidence of induced mutant colonies over background.

This study is classified as Unacceptable/Guideline and does not
satisfies the requirements for Test Guideline OPPTS 870.5100; OECD 471
for in vitro mutagenicity (bacterial reverse gene mutation) data.  Five
strains of S. typhimurium were not used in the assay.  The study can not
be upgraded.

STUDY TYPE:	In vitro Bacterial Gene Mutation (Bacterial system,
Salmonella typhimurium and Escherichia coli)/ mammalian activation gene
mutation assay; OPPTS 870.5100 [§84-2]; OECD 471 (formerly OECD 471
& 472).

CITATION:	Nakajima, M. (1991) CGA205374 (metabolite of difenoconazole):
reverse mutation assay of CGA205374. Biosafety Research Center; Foods,
Drugs and Pesticides (An-Pyo Center); 582-2, Arahama Shioshinden;
Fukude-Cho Iwata-Gun.; Shizuoka 437-12; Japan. Laboratory Project ID:
BRC Number 1746, August 14, 1991.  MRID 46950315.  Unpublished.

EXECUTIVE SUMMARY:  In a reverse gene mutation assay in bacteria (MRID
46950315), strains TA98, TA100, TA1535 and TA1537 of S. typhimurium and
strain WP2 uvrA of E. coli were exposed to CGA-205374, a metabolite of
difenoconazole, (99.3% a.i., lot number 9106054) dissolved in DMSO in
two independent assays using a 20-minute preincubation procedure and
duplicate plating. In the first mutagenicity assay, which was
alternatively called the pilot assay and the dose-finding assay,
concentrations of 0, 51.2, 128, 320, 800, 2000 or 5000 µg/plate were
tested with and without S9-mix. In the second assay, which was called
the main assay, concentrations of 0, 156, 313, 625, 1250, 2500 or 5000
µg/plate were tested with and without S9-mix. The S9 fraction was
obtained from phenobarbital and 5,6-benzoflavone-induced male
Sprague-Dawley rat liver.

CGA-205374 was tested at concentrations up to the limit concentration
for the assay, but the effective concentrations tested were limited by
insolubility. Evidence of cytotoxicity, which was collected by
stereomicroscopic examination of the bacterial lawns, was seen only in
strain TA1537 at the maximum concentration tested, and then only in the
main assay in the presence of S9-mix. The test material was quite
insoluble, with cloudiness of the preincubation mixture being observed
even at 128 µg/plate. The white powdery precipitate of the test
material was observed on the surface of the agar plates at the time of
colony counting at concentrations of 320 µg/plate and higher in the
pilot assay in the absence of S9-mix and at concentrations of 800
µg/plate and higher in the presence of S9-mix.  In the main assay, this
precipitate was noted at concentrations of 313 µg/plate and higher both
in the presence and absence of S9-mix. This precipitate became heavy
enough to make it difficult to observe the bacterial lawn at
concentrations of 1250 µg/plate or higher in the absence of S9-mix and
at the concentration of 5000 µg/plate in the presence of S9-mix. The
number of revertants per plate was not increased over the concurrent
solvent control value at any test material concentration, with or
without S9-mix, in any tester strain. The solvent and positive controls
induced the appropriate responses in the corresponding strains. There
was no evidence of induced mutant colonies over background.

This study is classified as Unacceptable/Guideline and does not
satisfies the requirements for Test Guideline OPPTS 870.5100; OECD 471
for in vitro mutagenicity (bacterial reverse gene mutation) data.  Five
strains of S. typhimurium were not used in the assay.  The study can not
be upgraded.

STUDY TYPE:	In vitro Bacterial Gene Mutation (Bacterial system,
Salmonella typhimurium and Escherichia coli)/ mammalian activation gene
mutation assay; OPPTS 870.5100 [§84-2]; OECD 471 (formerly OECD 471
& 472).

CITATION:	Nakajima, M. (1991) CGA205375 (metabolite of difenoconazole):
reverse mutation assay of CGA205375. Biosafety Research Center; Foods,
Drugs and Pesticides (An-Pyo Center); 582-2, Arahama Shioshinden;
Fukude-Cho Iwata-Gun.; Shizuoka 437-12; Japan. Laboratory Project ID:
BRC Number 1747, August 14, 1991.  MRID 46950317.  Unpublished.

EXECUTIVE SUMMARY:  In a reverse gene mutation assay in bacteria (MRID
46950317), strains TA98, TA100, TA1535 and TA1537 of S. typhimurium and
strain WP2 uvrA of E. coli were exposed to CGA-205375, a metabolite of
difenoconazole, (99.8% a.i., lot number 9106055) dissolved in DMSO in
two independent assays using a 20-minute preincubation procedure and
duplicate plating. In the first mutagenicity assay, which was
alternatively called the pilot assay and the dose-finding assay,
concentrations of 0, 51.2, 128, 320, 800, 2000 or 5000 µg/plate were
tested with and without S9-mix. In the second assay, which was called
the main assay, concentrations of 0, 2.50, 5.00, 10.0, 20.0, 40.0 or
80.0 µg/plate were tested in the absence of S9-mix in all strains;
concentrations of 0, 5.00, 10.0, 20.0, 40.0, 80.0 or 160 µg/plate were
tested in the presence of S9-mix in strains TA100 and TA1535;
concentrations of 0, 10.0, 20.0, 40.0, 80.0, 160 or 320 µg/plate were
tested in the presence of S9-mix in strains WP2 uvrA and TA1537; and
concentrations of 0, 2.50, 5.00, 10.0, 20.0, 40.0, or 80.0 µg/plate
were tested in the presence of S9-mix in strain TA98. The S9 fraction
was obtained from phenobarbital and 5,6-benzoflavone-induced male
Sprague-Dawley rat liver.

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ations tested in strains TA1535 and WP2 uvrA. At cytotoxic
concentrations there was often also a marked decrease in the number of
revertant colonies found. Because cytotoxicity was excessive at most
concentrations, the pilot assay provided only slight useful information
on mutagenesis in most strains. In the pilot assay, the needle
crystalline precipitate of the test material was observed on the surface
of the agar plates at the time of colony counting at concentrations of
800 µg/plate and above in the absence of S9-mix and at concentrations
of 2,000 µg/plate and above in the presence of S9-mix. No precipitation
was observed at any of the much lower concentrations tested in the main
assay. The number of revertants per plate was not increased over the
concurrent solvent control value at any test material concentration,
with or without S9-mix, in any tester strain. The solvent and positive
controls induced the appropriate responses in the corresponding strains.
There was no evidence of induced mutant colonies over background.

This study is classified as Unacceptable/Guideline and does not
satisfies the requirements for Test Guideline OPPTS 870.5100; OECD 471
for in vitro mutagenicity (bacterial reverse gene mutation) data.  Five
strains of S. typhimurium were not used in the assay.  The study can not
be upgraded.

Appendix 3.  Proposed Metabolic Pathway for difenoconazole in Rats

 Appendix 4   Environmental Fate Degradates

Table 13.0c.  Summary of Difenoconazole Major Degradates and Maximum
Percent Formation Observed in the Laboratory and Field Studies.

Degradate 1 	Max Degradate Concentration (% of applied) and Time (days)
to Max Concentration	Analyzed Degradates

	Lab Accumulation

in Fish	Aqueous Photolysis 2,3,4	

Aerobic Soil	Anaerobic Aquatic	Aerobic Aquatic 	

TFD  5	Ground 

Water 

CGA 205375 	51-64%	3.8% (4) 	14.8% (360)*	12.6% (175)	11.6% (90)	4.5%
(121)A

5.3% (364)B

3.5% (123)C

6.9% (182) D	

No study



CGA 205374 

1.1% (14)	2.1 % (272)	0.8% (247)



	CGA 71019

	20.6% (190) 	35.9% (350)*



	CGA-142856

41.8% (30)4*





	CGA-107069/

CGA-71019

12.27% (30) 4*

12.9% (9) 4





	1 Refer to Table I-2 for name and structure; 2 Difenoconazole was
stable under hydrolysis; 3 No meaningful amount of degradates were
formed in soil 

photolysis study (≤ 0.2% and only single replicates); 4 In sterile
natural water (MRID 46950105 and MRID 42245128); 5 % of the total
applied difenoconazole, based on 

four applications; A under bare soil conditions in GA (MRID 46950126); B
under potato production condition in ND (MRID 46950129); C under a bare
plot of loam soil 

in CA (MRID 46950129); D in CA bare loamy sand soil (MRID 42245140); and
* The max concentration was observed in the last sampling interval. 

Table 13.0d.  Chemical Structures of Difenoconazole and Degradation
Products Detected in Submitted Environmental Fate Studies.

Name(s)	Structure	Known Chemical and Fate Parameters

CGA-169374

Difenoconazole

1-[2-[2-Chloro-4-(4-chlorophenoxy)phenyl]-4-methyl-1,3-dioxolan-2-ylmeth
yl]-1H-1,2,4-triazole.

1-[[2-[2-Chloro-4-(4-chlorophenoxy)phenyl]-4-methyl-1,3-dioxolan-2-yl]me
thyl]-1H-1,2,4-triazole.

1-(2-[4-(4-Chlorophenyoxy)-2-chlorophenyl-(4-methyl-1,3-dioxolan-2-yl)-m
ethyl])-1H-1,2,4-triazole.







	CGA-205374 [CGA-176459]

1-[2-Chloro-4-(4-chlorophenoxy)-phenyl]-2-[1,2,4]triazol-1-yl-ethanone

1-[2-Chloro-4-(4-chlorophenoxy)phenyl]-2-(1H-1,2,4-triazol-1-yl)-ethanon
e



	CGA-205375 [CGA-211391]

1-[2-Chloro-4-(4-chlorophenoxy)-phenyl]-2-[1,2,4]triazol-1-yl-ethanol 

alpha-[2-Chloro-4-(4-chlorophenoxy)phenyl]-1H-1,2,4-triazole-1-ethanol.

	Mobility data available

CGA-142856

[1,2,4]Triazol-1-yl-acetic acid

1H-1,2,4-Triazole-1-acetic acid.

	DW assessment completed in 2006

CGA-71019

1-H-(1,2,4)-Triazole 

1H-1,2,4-Triazole

4H-[1,2,4]Triazole

	DW assessment completed in 2006

CGA-107069

1-H-(1,2,4)-Triazole-1-methanol 







	CGA-131013

2-Amino-3-[1,2,4]triazol-1-yl-propionic acid

alpha-Amino-1H-1,2,4-triazole-1-propanoic acid



	

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