UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

OFFICE OF CHEMICAL 

SAFETY AND 

POLLUTION 

PREVENTION 

PC Code: 080808 

OP Barcode: 428090 

Date: Oct. 28, 2015 

MEMORANDUM 

SUBJECT: 

TO: 

FROM: 

THRU: 

Preliminary Risk Assessment for Registration Review of Propazine 

Marianne Mannix, Chemical Review Manager 

A vivah Jakob. Team Leader 

Kelly Sherman, Branch Chief 

Risk Management and lmplemenration Branch 3 

Pesticide Re-evaluation Division (7508P) ) _ 

n t d ~ I I I r - ~ (o \ \.<_ij-j I 0 C(- 1 1 

Michelle Colletti. Chemist ~ l......h)-r ti \ Brian D. Kiernan, Biologist ~(/t_----1° 2.1 ! , Cl 111 

William P.Eckel, PhD., SeniorScicnccAdvisor . ~ fY ~ l()zrr f,~ Environmental Risk Branch 6 

Environmental Fate and Effects Division (7507P) 

Mark Corbin, Branch Chief -ji!JU Environmental Risk Branch 6 

Environmental Fate and Effects Division ( 507P) 

The Environmental Fate and Effects Division (EFED) has completed the preliminary 

environmental fate and ecological risk assessment (PRA) conducted in support of the 

Registration Review of the triazine herbicide, propazine (PC Code: 080808). Tllis assessment 

is based on propazine's currently registered use sites; sorghum (which is grown in several 

states) and container grown ornamentals. 

This document is an abbreviated PRA due to its re liance on the Section 3 New Use Risk 

Assessment for propazine on sorghum (DP 310326+) (EFED. 2006). minimal new data 

submissions, and because the use patterns have remained unchanged since the 2006 assessment. 

Risk conclusions in this assessment are similar to those in the 2006 assessment and the 

Registration Review Problem Formulation (DP 407225) (EFED (I), 20 13). For additional 

deta ils, please refer to those documents. 
Executive Summary and Introduction 

Propazine (2-chloro-4,6-bis(isopropylamino)-s-triazine) is in the Weed Science Society 

herbicide group 5 (s-triazine) and the Herbicide Resistance Action Committee (HRAC) group 

C 1, with the mechanism of action of inhibiting photosynthesis in photosystem II (PSII). 

Propazine is currently registered for preemergence application to control broadleaf and grass 

weeds in grain sorghum (Sorghum bicolor) plantings and for use on container grown 

ornamentals in greenhouses (per product label EPA Reg. No. 42750-148). This assessment 

assumes that the ornamental use is only used inside greenhouses, and causes minimal potential 

environmental exposure compared to the sorghum use. The risk assessment for sorghum is 

protective of any risks from green house use. 

Currently, there is one active end-use product registration for propazine (Propazine 4L; EPA 

Reg. No. 42750-148). Propazine may be applied aerially or by ground equipment at rates up to 

1.2 pounds of active ingredient per acre (lbs a.i./ A). 

Environmental fate studies suggest that propazine is expected to be persistent and mobile in most 

soils, and it is resistant to breakdown by hydrolysis and photolysis. If applied in an outdoor 

environment, propazine has a high potential to leach into ground water or reach surface waters 

by runoff. The end-use product label specifies that propazine may not be applied within 66 feet 

of the points where surface water runoff enters perennial or intermittent streams and rivers or 

within 200 feet around natural or impounded lakes and reservoirs. 

This preliminary risk assessment identifies potential risk to several taxa (in order of magnitude 

ofLOC exceedance): 

Mammals 

Potential chronic risk to mammals is identified, with exceedances of the LOC up to 25-

fold. 

Terrestrial Plants 

As expected with an herbicide, risk to terrestrial plants was identified, with exceedances 

of up 13-fold. 

Birds 

Potential chronic risk to birds is indicated using the LOAEC from the northern bobwhite 

quail study; a NOAEC is not available, but the magnitude of the LOC exceedance is 

expected to increase with the submission of new data. 

Aquatic plants 

Risk is indicated for listed aquatic vascular plants and for both listed and nonlisted 

aquatic nonvascular plants, with exceedances of up to nearly 7-fold. 

Three chlorotriazine herbicides have current registrations in the United States: propazine (6-

chloro-N,N'-bis(l-methylethyl)-1,3,5-triazine-2,4-diarnine), PC code 080808; atrazine (6-chloro2 
N-ethyi-N'-(1 -methylethyl)-1 ,3,5-triazine-2,4-diamine), PC code 080803; and simazine (6-

chloro-N,N'-diethyl-1 ,3,5-triazine-2,4-diamine), PC code 080807. These three chemicals differ 

only in number and/or position of methyl groups on moieties branched in identical positions off 

the triazine ring, thus are structurally nearly identical (Figure 1). Based upon the available 

guideline and non-guideline toxicity studies, these chlorotriazines result in similar herbicidal 

effects to terrestrial and aquatic plants. These molecules bind with a protein complex of the 

photosystem II in chloroplast photosynthetic membranes (Schulz et al., 1990). The result is an 

inhibition in the transfer of electrons through the light reactions of photosynthesis that in turn 

inhibits the formation and release of oxygen, production of adenosine triphosphate, and the 

fixation of carbon dioxide into sugars. 

In terrestrial animals, the guideline studies for all three chlorotriazines have shown similar 

effects at similar doses and concentrations (see atrazine PRA, docket EPA-HQ-OPP-20 13-0266 

and simazine, docket EPA-HQ-OPP-20 13-0251 ). These effects include food avoidance and/or 

reductions in frank weights or weight gain, although post-exposure recovery is frequently 

noted. The similarities of effects in mammalian studies have led OPP's Health Effects Division 

to consider atrazine, simazine, propazine, and their chlorotriazine degradates in a cumulative 

human health risk assessment (although the ecological assessments are not cumulative). Unlike 

atrazine, propazine and simazine do not have the wealth of non-guideline ecological effects data 

(e.g., mesocosms, amphibians, academic research) that have informed the atrazine registration 

review ecological risk assessment. The ecological risk assessment presented in this document is 

for the active ingredient propazine only. However, EPA considers it reasonable to assume that if 

a similar body ofliterature was available for propazine or simazine, risk conclusions similar to 

atrazine may be reached. 

3 
USE PATTERN 

Propazine was initially registered in 1958; however, all propazine registrations were canceled in 

1988. Propazine was subsequently registered for non-agricultural uses in 1998, and in 2007, it 

was registered for use on sorghum. Propazine is also registered for use in greenhouses on 

containerized ornamentals (shade trees, herbaceous plants, non-flowering plants, and woody 

shrubs and vines). A map by the US Department of Agriculture (USDA) of the sorghum 

production area is shown in Figure 1 below. Figure 1 depicts counties in the US with the highest 

acreage of sorghum production, and where propazine usage is expected to be high compared to 

other parts of the country; however, propazine may not be applied to all sorghum plantings. 

The current labeled maximum single application rate on sorghum is 1.2 lbs a.i./A. Only a single 

application of propazine is permitted per year for use on sorghum and should not be applied if 

atrazine has or will be applied to the same area in the same growing season. Applications can be 

made by aerial, ground equipment, and by t-band application. Propazine, per the currently 

accepted label, is not registered for use on sorghum in the states of California or Florida. In 

addition, the application of propazine on sorghum, as specified by the label, prohibits use on 

sand and loamy sand soils. 

Acres 

l«<l>l""'"' 

·;;:.t(.,O SGOO·t~ 

I)OO).,ll t!ll 

1!>.00). 4') t'.O 

S)OO) . 

Sorghum 2013 

Pl:llltod Acros by County 

for Selected St:ltos 

USDA -ft~ : ._,,,, ..... "" 

Figure 1: Sorghum planted acres in 2013. Source: USDA National Agricultural Statistics 

Service, 2013. 

4 
CONCEPTUAL MODEL 

A conceptual model for propazine was included in the 2006 Section 3 New Use Assessment to 

consider all potential routes of exposure (OP 31 0326+) (EFED, 2006). This preliminary risk 

assessment expands on the risk conclusions of the 2006 New Use Assessment but makes no 

changes to the conceptual model or diagrams. 

Risk Hypothesis 

The following risk hypothesis is presumed for this preliminary risk assessment: 

Based on the mobility and persistence of propazine, the mode of action, and the nature of 

the use patterns, propazine has the potential to cause reductions in survival, reproduction 

and growth impairment for both aquatic and terrestrial animal and plant species. 

ENVIRONMENTAL FATE 

Propazine is expected to be moderately persistent and mobile in most soils, and it is resistant to 

breakdown by hydrolysis, photolysis, or biodegradation. Table 1 below summarizes the 

physical and chemical properties of propazine. Further description of the physicochemical 

properties ofpropazine are available in the 2006 Ecological Risk Assessment (OP 310326+) 

(EFED, 2006) 

Table l. Physical and Chemical Properties of Propazine 

Property Value Reference 

Common name Propazine 

Chemical name CAS: 6-chloro-N,N' -bis( 1-methylethyl)-

I ,3,5- triazine-2,4-diam ine 

IUPAC: 2 -ch loro-4 ,6-bi s(isopropy lam i no )-s-triazine 

CAS number 139-40-2 

Chemical Structure 

0', ~ Cl\ 

J)~A;:Cl\ Molecular formula C9Ht6C1Ns Product Chemistry 

Molecular weight 229.71 Product Chemistry 

Physical state Crystalline solid Product Chemistry 

Melting point 2 12-2 14°C Product Chemistry 

Vapor pressure 2.9 x I 0·

8 nun Hg at 20°C Product Chemistry 

Water solubility 8.6 mg/L water at 20°C Product Chemistry 

Henry's Law Constant 1.02 x I 0·9 atm.m3/mol {Worthing, 1983) (calculated) Product Chemistry 

LogKow 2.91 (Montgomery. 1993), Product 

Chemistry 

pKa 1.85 at 22°C (Montgomery, 1993), Product 

Chemistry 

5 
Studies suggest that propazine is stable to both abiotic processes of hydrolysis and aqueous 

photolysis. Propazine is also fairly stable under aerobic and anaerobic aquatic metabolism 

with half-lives ranging from 146 to 1240 days (extrapolated past the end of the study) and 69.3 

to 122 days respectively. Batch equilibrium experiments suggest that propazine is mobile, 

with Freundlich K<t values ranging from 0.34 to 3.19 in two separate studies involving 8 soil 

textures. The Koc values ranged from 65 to 268 in these same studies. 

The mobility of propazine is also noted in the supplemental terrestrial field dissipation studies, 

suggesting that propazine persists in the upper 6 inches and may leach to ground water. It has 

also been reported in the literature that if released to soil, propazine will persist longer in dry or 

cold conditions or other conditions which inhibit biological and chemical activity (Worthing, 

1983). Therefore, it is very likely that the use of propazine may result in groundwater and/or 

surface water contamination in areas where soils are highly permeable, the water table is 

shallow, or where there is irrigation and/or high rainfall which promote runoff. Volatility and 

air photolysis are not expected to be major routes of dissipation due to the low vapor pressure 

(2.9 x 1 o-s torr at 20°C). Table 2 below summarizes the environmental fate and transport 

properties of propazine. 

Table 2. Summary of Environment~) Fate and Transport Properties fo~ Propazine 

Parameter 

Hydrolysis half-life (25°C, pH 5, 7, & 

Aqueous photolysis half-life (25°C) 

Aerobic aquatic metabolism half-life 

(20°C) 

Anaerobic aquatic metabolism halflife (20°C) 

Persistence in Soil 

Soil photolysis half-life (25°C) 

Aerobic soil metabolism half-life 

(25°C) 

Anaerobic soil metabol ism half-life 

(200C) 

Mobility 

Organ ic carbon partitioning 

coefficient(Koc. L·kg-1/Kd) 

Value SWCC Model Reference 

Input (MRID #) 

Persistence in Water 

Stable 0 43689802 

Stable (24-hr irradiation xenon arc lamp; 211 0 44184805 days dark control) 

Golden Lake Sandy Loam- 1240 days1 

2380 days2 

(DFOP) @20°C 

48125802 

Goose River Clay Loam - 146 days 1 (DFOP) 

Golden Lake Sandy Loam- 122 days1 (SFO) 177 days2 

48125803 

Goose River Clay Loam- 69.3 days1 (SFO) @20°C 

Stable 44184806 

KY Sandy Loam- 423 Days1 (SFO) 1269 days3 44184807 

8 Weeks (loamy sand soil) 00153713 

83/0.34 (loamy sand); 123/ 1.14 (sandy loam); 

00152997 158/2.69 (loam); 65/3.1 9 (clay loam) 

125 3 

268/0.67 (sand); 128/ 1.28 (sandy loam); 

43689804 96/1 .30 (silty clay); 79/ 1.35 (loam) 

6 
Parameter 

Field Dissipation 

Terrestrial field dissipation half-life 

Value 

2-hydroxy-propazille 145/ 1.45 (sandy loam); 

329/0.28 (sand); 78/ 1.33 (loam); 342/4.57 

(silty clay) 

NC (Wilson Co) 1.2 lb ai/A- bare ground 

sandy loam (0-6") and sandy clay loam (6-

12") 

*Not suitable for half-life calculation 

TX (Armstrong Co) 1.2 lb ai/A- bare 

ground loamy sand (0-6" and 6- 12") 

T ~=52 days ( 186-day study) 

1

Half-lives recalculated using PestDF 0.8.13 (EFED ( I), 2015) 2 90th percentile confidence bound on the mean half-life value (EFED (2), 2015) 3 EFED Input Parameter Guidance (EFED (2), 20 15) 

··No time 0 sample was reported for Terrestrial Field Dissipation Study (442873 14) 

Degradates: 

SWCC Model 

Input 

Reference 

(MRID#) 

44287313 

44287314 

44184809 

The 2006 Section 3 New Use ofpropazine for sorghum (DP 31 0326+) did not include 

degradates in its analysis. Potential degradates (see below) that propazine has in common with 

atrazine and simazine are DEA and DACT. DIA is not a degradate of propazine. Because of 

the greater stability of parent propazine, relative to atrazine and simazine, inclusion of 

degradates would not change the conclusions of the risk assessment. 

One major degradate, hydroxy-propazine, was not included in the 2006 sorghum new use 

assessment because hydroxy degradates were determined to not be of toxicological concern in 

the assessments for atrazine and simazine; also, no environmental fate data were available. 

Because of long parent half-lives in soil and aquatic systems, this assessment considers this as 

an uncertainty but will not model a total toxic residues approach. 

7 
G-30027 

Atrazine 

ATZ 

G-30033 

Desethylatrazille 

DEA 

G-30028 

Propazine 

PRZ 

G-28279 

Oesisopropylatrazitte 

DLA 

G-27692 

S imazin e 

SIZ 

G-28273 

Diatuiuocltloroarrazine 

DACT 

Figure 2. Structures of s-chlorotriazines parents and transformation products. 

ECOLOGICAL EFFECTS 

Aquatic 

Fish and Invertebrates: Aquatic effects data, as reported in previous documents, are 

summarized in Table 3 below. Although the LC50s for aquatic fish and invertebrates are near 

or above the solubility limit of propazine, sublethal effects (such as loss of equilibrium) were 

observed in all the acute studies. 

An acute exposure study with the rainbow trout (MRID 47452301; Acceptable), not previously 

described, resulted in the lowest frank endpoint for fish at a concentration similar to previously 

reported non-definitive values. In that 96-h study, rainbow trout (Oncorhynchus mykiss) were 

exposed to propazine at mean-measured concentrations of limit of quantitation ( <0.0266 mg 

a.i./L, negative and solvent controls), 0.56, 1.19, 2.28, 4.51 and 8.26 mg a.i./L under static 

conditions. The 96-h LCso was 5.00 mg a.i./L. The observed NOAEC value, based on sublethal effects, was 2.28 mg a.i/L. Sublethal effects included fish laying on bottom of test 

chamber and discoloration at 4.51 mg a.i./L. Based on the results of this study, propazine is 

classified as moderately toxic to freshwater fish on an acute exposure basis. 

Aquatic Plants: Studies for all four required taxa of nonvascular aquatic plants have been 

submitted; while the most sensitive endpoint is shown, other taxa are affected at similar 

concentrations. Growth of the aquatic vascular plant, Lemna gibba, is also inhibited by 

exposure to propazine. 

8 
Table 3. Summary of the Most Sensitive Endpoints from Aquatic Toxicity Studies for 

p ropazme. 

Taxonomic Study Surrogate Species Toxicity Value Acute Source 

Group Type Toxicity (Study 

Classification classification) 

Rainbow Trout LCso =5.0 mg 

Acute (Oncorhynchus ai/L (observed Moderately 47452301 

NOAEC: 2.3 toxic (Acceptable) mykiss) mg ai/L) 

NOAEC = 0.56 

Freshwater fish 1 

Chronic mg ai/L 

(Early 

Fathead Minnow LOAEC = 1.23 48036205 

Life- (Pimephales mg ai/L -- (Acceptable) promelas) Endpoint: Stage) reduction in 

!rrOWth 

ECso > 5.32 mg 

Acute Water Flea ai/L (observed Moderately 44287305 

(Daphnia magna) NOAEC: 5.32 toxic (Supplemental) 

mg ai!L) 

Freshwater NOAEC = 

invertebrates 0.047 mg ai/L 

LOAEC = 0.091 44327602 

Chronic Water Flea mg ai/L -- (Acceptable) 

Endpoint: 

reduction in 

growth 

Sheepshead LCso >3.87 mg 

Acute Minnow ai/L (observed Moderately 48036204 

(Cyprinodon NOAEC: 2.0 1 toxic (Acceptable) 

variegatus) mg ai/L) 

NOAEC = 1.34 

Estuarine/marine mg ai/L 

fish Sheepshead LOAEC = 2.59 

Chronic Minnow mg ai/L 44 184802 

(36 day) (Cyprinodon Endpoint: -- (Supplemental) 

variegatus) embryo survival 

and hatching 

success 

Mysid LCso = 4.2 mg 

Acute (Americamysis a ilL (observed Moderately 44 18480 1 

NOAEC: 0.586 toxic (Acceptable) bahia) mg ai/L) 

Estuarine/marine NOAEC = 

invertebrates 0.266 mg ai/L 

Chronic Mysid LOAEC = 0.474 44 184803 

(28 day) (A mericamysis mg ai!L -- (Supplemental) bahia) Endpoint: 

reduction in 

growth 

NOAEC = 

Aquatic plants Vascular Duckweed 0.022 mg ai/L 44287309 

(Lemna gibba) lCso =0.1 mg -- (Acceptable) 

a ilL 

9 
Taxonomic Study Surrogate Species Toxicity Value Acute Source 

Group Type Toxicity (Study 

Classification classification) 

Freshwater diatom NOAEC = 

Non- (Navicula 0.0065 mg ai!L 44287310 

vascular ICso = 0.0248 -- (Acceptable) pe/liculosa) mg ai/L . . 1 Freshwater fish may be surrogates for aquatic-phase amphibians . 

Terrestrial 

Terrestrial animal effects data are summarized in Table 4 below. Terrestrial plant toxicity data 

are summarized in Table 5. 

Birds: Propazine is classified as practically nontoxic to terrestrial birds from acute dose-based 

or dietary-based exposure; however, an acute oral study for passerines is not available for 

propazine. Sublethal effects (decreased weights) were noted in both the bobwhite quail and the 

mallard duck acute oral and subacute dietary studies, suggesting chemical-induced anorexic 

response at 430 mg a.i/kg-bw and up. Additionally, adult female weight gain was 

significantly affected in both mallard duck and bobwhite quail reproduction studies, with 

significant effects at the lowest dose in the bobwhite study. Therefore, an avian NOAEC is 

unavailable for the risk assessment. 

A subacute dietary study (MRID 49635701) with zebra finch (Taeniopygia guttata) was recently 

submitted and is currently under review. The study was submitted in response to the registration 

review DCI requiring an avian acute oral toxicity study with a passerine. A dietary study was 

conducted due to regurgitation observed in the range-finding study. Based on a preliminary 

review of the study report, the birds were exposed to mean-measured dietary concentrations of 0 

(control), 326,712, 1560, 3190, and 5290 mg ai/kg-diet with an LCso of2837 mg a.i.lkg-diet. 

Based on this, propazine would be considered slightly toxic to passerines on a subacute dietary 

basis. 

From the study report: Abnonnal behaviors were observed from Day I through Day 8 of the study, at 

the 712 mg a.i./kg feed treatment level through the 5920 mg a.i./kg feed treatment level, and included 

asthenia, piloerection, hypoactivity and lethargy. Mortality reached 80% and 90% of birds exposed to 

the test substance at 3190 and 5920 mg a. i./kg feed, respectively. Mortality did not occur at any other 

treatment level, nor among the controls. All treatment groups experienced a significant reduction in body 

weight during the exposure period compared to the control group. Birds at the 326 and 712 mg a.i./kg 

feed treatment levels recovered near-control body weights during the post-exposure period and over the 

entire course of the study. However, net body weight gain among birds at the 1560 and 3190 mg a. i./kg 

feed treatment levels remained significantly lower than the controls during the post-exposure period and 

over the course ofthe entire study. In similar fashion, average daily feed consumption was significantly 

lower at all treatment levels compared to the control, and remained slightly lower (thought statistically 

significant) than the control in the 3190 mg a. i./kg feed treatment group during the post-exposure period. 

There remains an avian effects data gap for propazine: an avian reproduction study with the 

bobwhite quail (OCSPP Guideline 850.2300). The study was required through the registration 

review data call-in issued on April 30, 2014, but data have not yet been submitted to EPA. 

10 
Mammals: Propazine is classified as practically nontoxic to mammals on an acute exposure 

basis, but effects from chronic exposure (adult toxicity and reproduction effects) were observed 

as low as 50 mg ailkg-bw/day. 

Terrestrial invertebrates: Propazine is classified as practically nontoxic to honeybees on an 

acute contact basis. However, propazine use may be of exposure concern for pollinators visiting 

plants that are contaminated by direct application or spray drift. The complete suite of honey bee 

adult and larvae studies have not been submitted for propazine, and these data are needed to 

fulfill EPA's recent policy on pollinator protection1

• A Tier I study on the toxicity of residues on 

foliage (OCSPP 850.3030) is not needed since results of the honey bee acute contact LDso is 

>96.7 )lg a.i./bee, well above the 11 )lg a.i./bee trigger criterion. The following Tier I, II and lii 

honey bee studies, yet to be submitted for propazine, are required2: 

o Honeybee adult acute oral toxicity study (following OECD 237, Tier I) 

o Honeybee larval acute oral toxicity study (following OECD 237, Tier I) 

o Honeybee adult 1 0-day chronic oral (special study; Tier I) 

o Honeybee larval chronic oral toxicity study (Tier I) 

o Semi-field testing for pollinators (special study, Tier II) 

o Field testing for pollinators (OCSPP 850.3040, Tier III) 

o Field trial of residues in pollen and nectar (special study, Tier Ill) 

Terrestrial plants: As expected with an herbicide, propazine adversely affects plants. Effects 

were seen in both the seedling emergence and vegetative vigor studies and in both monocots and 

dicots. For some species in these studies, NOAECs were not determined; in these cases the 

IC05 will be used to estimate risk to listed plant species. 

1 (Guidance for Assessing Pesticide Risks to Bees, 06.23.2014; signed by Donald Brady, Director, EFED; 

hnp://www2.epa.gov/siteslproductionllilesf20 14-06/document pollinator risk assessment guidance 06 19 1-t.odO 

2 The need for higher Tier semi-field and full field pollinator studies for propazine will be determined after review 

of these Tier I studies. 

11 
Table 4. Summary of the Most Sensitive Endpoints from Terrestrial Animal Toxicity 

Studies 

Taxonomic Study Type Surrogate Species Toxicity Value Acute Toxicity Source (Study 

G roup Classification classification) 

LDso > 1640 mg 

Bobwhite quail ai/kg-bw Acute Practically non- 44287301 (Co/inus Observed NOAEC = 244 

virginianus) mg ai/kg-bw based on toxic (Acceptable) 

weight 

LCso > 4930 mg 

ai/kg-diet 

Bobwhite quail Effects on weight/food Practically non- 44287302 

(Colinus virginianus) consumption were toxic (Acceptable) observed at all dietary 

Sub-acute 

concentrations (LOAEC 

Birds dietary 

578 mg ai!kg-diet) 

LCso = 2837 mg ai/kgZebra fmch diet (observed NOAEC Slightly toxic 4963570 1 

(Taeniopygia guttata) not determined based on (under review) 

weight) 

NOAEC <262 mg 

ai/kg-diet 

Chron ic Bobwhite quail LOAEC = 262 mg 48036201 

ai/kg-diet Endpoint: -- (Supplemental) 

adult fema le body 

weight gain 

Acute Oral Laboratory rat LDso :::._5050 mg Practically non- 43474101 

(Rattus norvegicus) ai/kg-bw toxic (Acceptable) 

NOAEL=5 mg 

J. Morales et at. 

0 323271 12/ 13/2005 

Mammals ai/kg/day LOAEL = Propazine. Revised HED 

Chronic Laboratory rat (Rattus 50mg -- Risk Assessment for the norvegicus) ai/kg/day Endpoint: rTolerance Reassessment 

parental toxicity and Eligibility Decision reproductive effects Document (TRED) 

Insects Acute contact 

Honey bee (A pis LDso > 96.7 f,lg ai/bee Practically non- 00036935 

mellifera) toxic (Supplemental) 

12 
Table 5. Plant endpoint summary by species (MRID 44184804; Acceptable) 

Seedling Emergence 

NOAEC Species Endpoint (lbs a.i.!A) 

Com None 2.4 

Oat Biomass 0.0191 

Onion Biomass 0.00871

.2 

Ryegrass Biomass 0.077 

Wheat Biomass 0.01 

Cabbage Biomass 0.0491 

Cucumber Emergence 0.0421 

Lettuce Biomass 0.0047 

Radish Biomass 0.077 

Soybean Biomass 0.59 

Tomato Biomass 0.0391 

1

1Cos used as a NOAEC not determined. 

2Bold indicates most sensitive. 

Environmental Fate and Exposure 

Vegetative Vigor 

IC2s NOAEC (lbs Endpoint (lbs a.i.!A) a. i./A) 

>2.4 None 2.5 

0.050 Biomass 0.0022 

0.035 Biomass 0.075 

0.83 Biomass 0.075 

0.14 Biomass 0.02 

0.098 Biomass 0.011 

0.12 Biomass 0.0471 

0.016 Biomass 0.075 

0. 16 Biomass 0.075 

0.97 Biomass 0.038 

0.18 Biomass 0.038 

IC2s 

(lbs 

a. i./A) 

>2.5 

0.11 

0.096 

0.17 

0.046 

0.1 3 

0.10 

0.10 

0.22 

0.66 

0.15 

The current risk assessment uses the Surface Water Concentration Calculator (SWCC) version 

1.1 06, which uses PRZM (version 5.0+) and the VVWM (variable volume water model), a 

replacement for the older EXAMS model, for Tier 2 surface water assessments. The Tier 2 

assessment reports the highest peak, 21-day and 60-day average estimated environmental 

concentrations (EEC) for propazine that are expected to occur once every ten years. The 

estimates are generated using 30-years of meteorological data, encompassing the years from 

1961 to 1990. For further information on these models see: 

http://www.epa.gov/oppefedl /models/water/index.htm. 

Scenario Selection 

Similar to modeling conducted for the 2006 New Use Assessment, the agricultural use of 

propazine for broadleaf weed control in sorghum was simulated in this risk assessment with the 

sorghum crop scenarios for Kansas and Texas. Note that the non-standard Texas sorghum 

scenario was developed for the cumulative assessment for the organophosphate insecticides 

(2002) and is used in this assessment to provide spatial context to the EECs generated using the 

standard Kansas sorghum scenario. 

The environmental fate input parameters used in the SWCC model are listed in Table 1. The 

spray drift fraction was calculated using AgDrift version 2.1.1 using EFED Guidance on 

Modeling Offsite Deposition of Pesticides via Spray Drift for Ecological and Drinking Water 

Assessments (EFED (2), 2015). The propazine end-use product label specifies that propazine 

may be applied preplanting, after the soil is plowed; and preemergence, at or immediately after 

planting before weeds and sorghum emerge. Application dates for modeling in SWCC are at 

13 
planting, preemergence. Additional input parameters are provided in Table 6. 

Table 6: Additional SWCC Input Parameters 

Maximum 

Use Site Rate (lbs Interval Date Spray Drift Application 

a. i./A) fraction Efficiency 

At Plant 0.0078 0.99 (ground) 

I application I (Relative to (ground) 

Sorghum 1.2 season' planting date in 0.95 (aerial) 

0.03 14 SWCC) (aerial) 

1 While the label specifies per season, multiple planting seasons per year are doubtful for sorghum. 

Table 7. Estimated Environmental Concentrations (EEC) of propazine residues for 

sorghum in the Standard Pond with the SWCC model. 

The simulations used the maximum labeled number of applications (I) and maximum application rate (1.2 lb. 

a. i .I Nappi ication). 

1-in-1 0 year Propazine Concentration (J.tg/L) 

Scenario -State Crop Peak 21- Day 60-Day 

KS - Sorghum 

Aerial Spray 36.3 35.7 35.1 

Ground Spray 32.5 32.0 31.5 

TX - Sorghum (OP) 

Aerial Spray 42.8 41.7 40. 1 

Ground Spray 40.8 39.8 38.2 

Monitoring Data 

Monitoring data for propazine were downloaded from the Water Quality Portal database 

(http://waterqualitydata.us/) on April 10, 2015. The Water Quality Portal integrates data from 

the USGS National Water Information System (NWIS), EPA's STORET data warehouse, and 

USDA ARS STEWARDS platform. A total of38,217 records were analyzed for propazine. The 

organizations in Table 8 below contributed to the monitoring data ranging in date from 1977 to 

2015; however, only monitoring data from the 1990's forward were included in the following 

summary. The contributors include state and federal agencies and Indian tribes. At least nine 

states and four tribes are represented. 

14 
Table 8: Monitoring Data for Propazine 

Sampling Organization 

Number of records in 

STORET 

Kansas Dept. of Health and Environment 17,622 

Iowa Dept. Natural Resources 13,387 

Minnesota Dept. Agriculture 3,344 

Indiana STORET data 978 

Iowa Geological Survey 738 

Upper Sioux Community 529 

Arkansas Dept. Environmental Quality 456 

National Park Service Water Resources Div. 382 

US Army Corps of Engineers, Omaha District 357 

Kentucky Div. of Water 271 

California SWMP 255 

Minnesota Pollution Control Agency 80 

EPA Region 7 36 

US Fish & Wildlife, NM Ecol. Services Field Office 34 

Flandreau Santee Sioux 31 

Lower Sioux Lndian Community (MN) 10 

Fort McDowell Yavapai 5 

New Mexico Env. Dept./ SWQB 2 

TOTAL RECORDS 38,217 

Propazine was detected in 271 samples (0.7%); a further 361 samples are listed as detects, but 

appear to be reported as detection limits (0.05 ug!L or lower). Of the samples with detectable 

propazine, 5 exceeded 1 ug/L, 8 samples were between 0.5 to 1.0 ug!L, 22 samples were 0.25 to 

0.5 ug/L, and 595 were 0.25 ug!L or less. 

Of the 35 samples measuring 0.25 ug!L or higher, 20 were in Kansas, 9 were in Iowa, and 2 were 

taken by the US Army Corps of Engineers. No monitoring data were retrieved from the Water 

Quality Portal for Texas, which is expected to be a major use area for propazine on sorghum. 

Water bodies with detections above 1 ug/L were all in Kansas, and included Little Arkansas 

River at Valley Center, Indian Creek at Kansas City, Missouri, Smoky Hill River at Elkader, and 

Delaware River near Half Mound. Concentrations in these water bodies ranged from 1.1 to 5.6 

ug!L. The highest detection in Iowa (0.53 ug/L) was at Boyer River near Missouri Valley. 

All of the monitoring concentrations in the STORET data were less than the SWCC modeled 

EECs. 

The USGS National Water Quality Assessment (NA WQA) Program also contains propazine 

monitoring data (http://cida.usgs.gov/nawqa_queries_public/jsp/mxmaster.jsp) and was accessed 

on April 10,2015. The NAWQA database has 1,733 records from 16 states from the years 1992 

to 2003 (Table 9). 

15 
T ba l e 9 . NAWQAP ropazme M om 't orm. g R esu It s 

State Year Total Records Detects Concentration Range (J..lg/L) 

AR 1996 - 1998 Ill 5 0.06 - 0.27 

CT 1993 I 0 -- GA 1993 5 0 -- lA 1995 - 2003 523 38 0.04 - 0.36 

IN 1991 - 1992 27 0 -- LA 1995 - 1997 91 7 0.05 - 0.85 

MD 1991 3 0 --

MN 1997 - 1998 39 0 --

MO 1996 - 1998 45 6 0.06 - 0. 19 

MS 1995 - 1997 191 17 0.05 - 0.11 

NE 1992 - 1999 416 79 0.05 - 1.08 

NY 1996 - 2000 13 0 -- OH 2002 3 0 -- TN 1996 - 1998 72 0 --

WI 1994 6 0 --

Data provided by the Texas Commission on Environmental Quality to the EPA for groundwater 

monitoring returned 493 results from the years 1985 to 2013. Seventy of the samples were 

detects with a range of 0.019 to 87.7 J..lg/L. The majority of propazine detections in groundwater 

over 1.0 J..lg/L occurred after 2004. 

Data provided by the State of Colorado to the EPA for monitoring returned 138 results from the 

year 201 0. Four of the samples were detects with a range of 0.021 to 0.5 J..lg/L with a detection 

limit of 0.02 J..lg/L. 

Data provided by the Washington State Department of Agriculture to the EPA for monitoring 

returned 3,244 results from the years 2003 to 2012. Sixteen of the samples were greater than 

0.05 1-lg/L with a range of 0.05 to 0.25 J..lg/L. 

The State of Wisconsin also provided monitoring data to the EPA, returning 2,23 1 results for the 

years ranging from 1999 to 2011. Results ranged from 0.0075 to 635.2 1-lg/L, and detection 

limits were not reported. 

None of the monitoring data listed above is a result of water sampling targeted to propazine use. 

That coupled with a less robust sample frequency would suggest that the monitoring results are 

most likely missing the peak concentrations of propazine. Some detections of propazine appear 

to be outside of the typical sorghum growing regions. It is likely that some ground water 

detections were the result of spills outside sorghum growing areas. Finally, propazine was not 

registered for use on sorghum until 2007, so any detections before that time may be due to 

previous, cancelled uses. 

16 
Risk Characterization 

This risk assessment was conducted primarily for the use on sorghum. The labeled use for 

containerized greenhouse ornamentals, if it is for outdoor use, would present a similar risk 

profile as the sorghum use, for terrestrial organisms. 

Regarding aquatic organisms, it is unlikely that propazine would be used on outdoor ornamentals 

in an area as extensive as a collection of sorghum fields. Thus, the results of the sorghum risk 

assessment are likely to be protective of the ornamental use. 

Risk to Aquatic Organisms 

For this assessment, parent-only EECs were calculated based on the sorghum modeling 

scenarios and the most sensitive of the existing toxicity data by taxa. Based on this preliminary 

assessment, using upper-bound exposure estimates, there are no exceedances for aquatic animal 

taxa (Table 10). This includes aquatic-phase amphibians, for which fish serve as surrogates. 

While there are amphibian-specific data for atrazine which indicate potential sublethal effects at 

low exposure concentrations (low ppb ), it is unclear to what degree those data represent 

propazme. 

Table 10. RQs for fish and aquatic invertebrates (based on the most sensitive endpoints) 

~ or propazme use on sorgl h um. 

Acute Chronic 

Fish Invertebrates Fish Invertebrates 

KS-Sorghum 

Aerial Spray 0.007 <0.007 0.06 0.75 

Ground Spray 0.006 <0.006 0.06 0.68 

TX-Sorghum (OP) 

Aerial Spray 0.01 2 <0.012 0.07 0.89 

Ground Spray 0.011 <0.011 0.07 0.85 

There are no exceedances for non-listed aquatic vascular plants from the use on sorghum; 

however, RQs for listed aquatic vascular plants exceed the LOC of 1.0 by a factor of roughly 

two (Table 11). The RQs for non-listed nonvascular aquatic plants exceed the LOC by almost a 

factor of two. RQs for listed aquatic nonvascular species exceed the LOC by almost 7-fo1d, but 

there are currently no aquatic nonvascular species listed. Because there are no ESA-listed 

aquatic nonvascular plants, no direct effects are anticipated. However, as with any direct 

effect to plants, indirect effects to other taxa are possible. 

17 
T a bl e 11 . RQ s t or aquatic p. ants t or t h e propazme use on sor~l h urn. 

Vascular Nonvascular 

Nonlisted Listed Nonlisted Listed 

KS - Sorghum 

Aerial Spray 0.36 1.61 1.5 5.6 

Ground Spray 0.32 1.5 1.3 5.0 

TX- Sorghum (OP) 

Aerial Spray 0.43 1.9 1.7 6.6 

Ground Spray 0.41 1.8 1.6 6.3 

1 Bold indicates exceedance of LOC 

It is important to note that while endpoints from the guideline studies for propazine result in 

relatively marginal exceedances for nonvascular plants, data for atrazine in open literature 

suggest that other species may be considerably more sensitive to chlorotriazines. To the extent 

that the same holds true for propazine, broad effects to aquatic communities of primary 

producers (phytoplankton) may be expected. For an in-depth discussion of these potential 

impacts, please see the atrazine draft ecological risk assessment (atrazine docket - EPA-HQOPP-20 13-0266). 

Risk to Terrestrial Organisms 

It is important to note that the risks identified here, as indicated by RQs relative to the LOCs, are 

based on the most sensitive endpoints and upper-bound exposure scenarios. If it becomes useful 

for risk management to provide refmements to these risk estimates (beyond those in the Section 

3 New Use assessment, DP Barcodes 0310326, 0249944, 0249945, 11103/06), they can be 

provided. 

Despite the avian acute lethality endpoints being non-definitive (i.e. greater than) values, 

sublethal effects on body weight were observed in the studies. Therefore, for frame of 

reference, RQ-values were calculated using the highest concentrations tested. The highest 

RQ-value is 0.28, which would exceed the listed species LOC. However, given that this 

RQ is based on sublethal effects and not a frank LDso, acute risk to avian species is 

expected to be )ow. 

Additionally, a recently submitted passerine subacute dietary study (described previously) which 

resulted in a frank endpoint is used provisionally. A dietary study was conducted based on 

regurgitation observed in the range-finding study. This study was submitted in lieu of the 

guideline acute oral study with passerines based on EFED Guidance (Brady 2014): "Guidance for 

Reviewing OCSPP 850.2100 Avian Oral Toxicity Studies Conducted with Passerine Birds". 

Like the other avian studies, weight loss was noted as a sublethal effect at all test concentrations, 

though recovery was ultimately noted in the lowest concentration. Based on the LCso = 2837 mg 

ailkg-diet, the highest dietary-based RQ is 0.1, which is exactly at the listed species LOC. The 

study authors provided a conversion to a dose (LDso 329 mg ai/kg-bw), which is used here for 

characterization purposes only, as there is low confidence in such a conversion. Using this 'dose', 

the highest RQ-value would be 1.38, almost three times the nonlisted LOC. However, this study 

18 
is under review and, again, these values are reported here provisionally. 

Consistent with the sublethal effects on weight noted in the acute studies, effects on weight were 

noted in the avian reproduction studies. Given the lack of a NOAEC, risk to birds from chronic 

exposure cannot be reliably estimated. Using the LOAEC from the available bobwhite study 

(262 mg ai!kg-diet), the dietary RQ-value for chronic exposure to birds is 1.1, marginally 

exceeding the LOC. A frank no-effect value from the requested study (Registration Review data 

call-in) would result in a greater exceedance of unknown magnitude. As a point of reference, 

simazine's bobwhite NOAEC is 100 mg ailkg-diet (MRID 00163134). If that endpoint were 

relevant to propazine, the highest RQ would be 2.88. 

Propazine has no known acute effect on mammals, and the likelihood of acute risk is 

considered to be low. However, decreased body weights were observed on both parental 

and reproductive endpoints in the three-generation rat study. Based on these effects, 

mammalian chronic RQs exceed the LOC by factors up to 25-fold. These 

exceedances are based on on-field exposure estimates; off-field exposure, particularly 

from spray drift has not been explored for this assessment. 

No effects on honeybees were observed in the available acute contact study, and therefore no 

RQs are calculated. However, as described previously, the full suite of pollinator toxicity 

studies are not available for propazine. 

As expected with an herbicide, RQs exceed the LOC for sensitive plant species. The RQs 

reported in Table 12 reflect the most sensitive species from the available studies (see Table 4). 

Given the spray drift RQ resulting from the screening level model TerrPlant are roughly 

equivalent to 200 feet off the site of application (based on comparison to AgDRJFT defaults), 

effects to sensitive terrestrial plants, particularly listed species, should be expected well off the 

site of application. As reported in Table 13, exceedances from ground spray application are 

considerably reduced. 

A refinement utilizing the AgDRlFT model could explore the distances off field for which effects 

are expected for each species tested, but given the sensitivities across species (see Table 5), these 

distances should be expected generally consistent across sensitive species. 

Table 12. Maximum expected terrestrial plant RQs for the use on sorghum (aerial 

application). 

I Plant T~ee I Listed Status I Dry I Sem i-Ag uatic I sera~ Drift 

Monocot non-listed 2.06 5.14 1.71 

Monocot listed 8.28 20.69 6.90 

Dicot non-listed 4.50 11.25 3.75 

Dicot listed 15.32 38.30 12.77 

I *If RQ > 1.0, the LOC is exceeded, resulting in potential for risk to that plant group. 

19 

I 
Table 13. Maximum expected terrestrial plant RQs for the use on sorghum (ground 

application). 

Plant Type Listed Status Dry Semi-Aquatic Spray Drift 

Monocot non-listed 0.69 3.77 0.34 

Monocot listed 2.76 15.17 1.38 

Dicot non-listed 1.50 8.25 0.75 

Dicot listed 5.11 28.09 2.55 

*If RQ > 1.0, the LOC is exceeded, resulting in potential for risk to that plant group. 

EPA generally uses a 25% inhibition in growth, either biomass or height, to assess potential risk 

to plant species. A population of plants that experience a 25% or greater inhibition in growth 

early in the growing season may recover, depending on the plant, but this level of effect may 

have lasting consequences on the affected plants. 

Plants whose growth is interrupted during their active growth period may not recover. Plants 

may be insufficiently competitive for resources, such as sunlight or water, due to their decreased 

growth. Early season interruption in growth may also result in fewer absolute seed numbers or 

in numbers of viable seed (i.e. reproductive effects). In communities where propazine exposures 

occur, relatively insensitive species may outcompete sensitive species, leading to shifts in 

community composition and subsequently shifts in community function. Such changes may 

result in a cascade of ecological effects on higher order species and/or edaphic functionality 

(such as decreased interception of excess nutrients). 

The plants used in guideline testing are generally crop species selected specifically for their ease 

of husbandry in laboratory settings. As a rule, it is best to consider each species tested as 

representative of a potential sensitivity in the universe of plants that may be exposed, such that 

sensitivity of, for example, soybean represents not only soybean, but plants with a sensitivity 

similar to soybean. What those species of similar sensitivity are is not usually known. Further, 

to what degree the species chosen for testing are representative of the range in potential plant 

sensitivities found in the general ecosystem is uncertain. 

Not just plant species are likely to be affected; plant biodiversity provides a number of 

ecosystem services, including providing habitat for pollinators and beneficial insect 

predators. Recently, a great deal of research has been directed at the effect of plant diversity and 

associated insect populations (Freemark and Boutine, 1995; Isaacs et a/. 2009; Mortensen et al., 

2012. Norris and Kogan, 2000; Norris and Kogan, 2005). Similar disruptions in habitat or food 

sources may occur for higher order animals (e.g. birds and mammals) in areas proximal to use 

sites. As changes in plant communities occur due to differences in species sensitivity, 

subsequent loss of preferred feed or shelter for animals can be expected. In this way, animals can 

be affected by use of these herbicides. Affected animals might be at any trophic level, and may 

particularly affect organisms with obligate relationships to specific plant species. 

Incidents 

The ecological incident information system (EllS) is an OPP database that houses ecological 

incidents that have been reported to the Agency. When available, EIIS includes date and 

20 
location of an incident, type and magnitude of effects observed in various species, use(s) of 

pesticides known or suspected of contributing to the incident, and results of any chemical residue 

analysis or other analyses conducted during incident investigation. EIIS incidents are 

categorized according to the certainty that the incident resulted from pesticide exposure. The 

Avian Monitoring System (AIMS) is a database administered by the American Bird Conservancy 

that contains publicly available data on reported avian incidents involving pesticides. Many of 

the incidents listed in this database are also in the EllS. 

As of September 2015, there are no reported incidents for propazine in the EllS database. There 

are also no incidents reported in the AIMS database nor are there any aggregate incidents 

reported. 

The absence of reported incidents should not be construed as the absence of incidents. Incident 

reports for non-target organisms typically provide information only on mortality events and plant 

damage. Sublethal effects in organisms such as abnormal behavior, reduced growth and/or 

impaired reproduction are rarely reported, except for phytotoxic effects in terrestrial plants. 

Federally Threatened afld Efldangered (Listed) Species Concem s 

In November 2013, the EPA, along with the U.S. Fish & Wildlife Service (USFWS), the 

National Marine Fisheries Service (NMFS) (collectively, the Services), and the U.S. Department 

of Agriculture (USDA) released a summary of their joint Interim Approaches for assessing risks 

to listed species from pesticides. The Interim Approaches were developed jointly by the 

agencies in response to the National Academy of Sciences' (NAS) recommendations and reflect 

a common approach to risk assessment shared by the agencies as a way of addressing scientific 

differences between the EPA and the Services. The NAS report outlines recommendations on 

specific scientific and technical issues related to the development of pesticide risk assessments 

that EPA and the Services must conduct in connection with their obligations under the 

Endangered Species Act (ESA) and FIFRA. 

The joint Interim Approaches were released prior to a stakeholder workshop held on November 

15, 2013. In addition, the EPA presented the joint Interim Approaches at the December 2013 

Pesticide Program Dialogue Committee (PPDC) and State-FIFRA Issues Research and 

Evaluation Group (SFIREG) meetings, and held a stakeholder workshop in April2014, allowing 

additional opportunities for stakeholders to comment on the Interim Approaches. As part of a 

phased, iterative process for developing the Interim Approaches, the agencies will also consider 

public comments on the Interim Approaches in connection with the development of upcoming 

Registration Review decisions. The details of the joint Interim Approaches are contained in the 

white paper "Interim Approaches for National-Level Pesticide Endangered Species Act 

Assessments Based on the Recommendations of the National Academy of Sciences April 2013 

Report," dated November 1, 2013. 

Given that the agencies are continuing to develop and work toward implementation of the 

Interim Approaches to assess the potential risks of pesticides to listed species and their 

designated critical habitat, this preliminary risk assessment for propazine does not contain a 

complete ESA analysis that includes effects determinations for specific listed species or 

21 
designated critical habitat. Although EPA has not yet completed effects determinations for 

specific species or habitats, for this preliminary assessment EPA conducted a brief screeninglevel assessment for all taxa of non-target wildlife and plants that assumes for the sake ofthe 

assessment that listed species and designated critical habitats may be present in the vicinity of 

the application of propazine. This screening level assessment will allow EPA to focus its future 

evaluations on the types of species where the potential for effects exists once the scientific 

methods being developed by the agencies have been fully vetted. This screening-level risk 

assessment for propazine indicates potential risks of direct effects to listed birds, mammals, and 

terrestrial plants when used on sorghum. Listed species of birds, mammals, and terrestrial plants 

may also be affected through indirect effects because of the potential for direct effects on listed 

and non-listed species upon which such species may rely. Potential direct effects on listed birds, 

mammals, and terrestrial plants from the use of propazine may be associated with modification 

of Primary Constituent Elements (PCEs) of designated critical habitats, where such designations 

have been made. Once the agencies have fully developed and implemented the scientific 

methods necessary to complete risk assessments for endangered and threatened (listed) species 

and their designated critical habitats, these methods will be applied to subsequent analyses for 

propazine as part of completing this registration review. 

Endocrine Disruptor Screening Program (EDSP) 

As required by FIFRA and the Federal Food, Drug, and Cosmetic Act (FFDCA), EPA reviews 

numerous studies to assess potential adverse outcomes from exposure to chemicals. Collectively, 

these studies include acute, subchronic and chronic toxicity, including assessments of 

carcinogenicity, neurotoxicity, developmental, reproductive, and general or systemic toxicity. 

These studies include endpoints which may be susceptible to endocrine influence, including effects 

on endocrine target organ histopathology, organ weights, estrus cyclicity, sexual maturation, 

fertility, pregnancy rates, reproductive loss, and sex ratios in offspring. For ecological hazard 

assessments, EPA evaluates acute tests and chronic studies that assess growth, developmental and 

reproductive effects in different taxonomic groups. As part of the Problem Formulation for 

Registration Review (0407225; May, 2013), EPA reviewed these data and selected the most 

sensitive endpoints for relevant risk assessment scenarios from the existing hazard 

database. However, as required by FFDCA section 408(p), propazine is subject to the endocrine 

screening part of the Endocrine Disrupter Screening Program (EDSP). 

EPA has developed the 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 II 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 theE, A, or T effect. 

22 
Under FFDCA section 408(p), the Agency must screen all pesticide chemicals. 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. A second list of chemicals 

identified for EDSP screening was published on June 14, 2013[1] and includes some pesticides 

scheduled for registration review and chemicals found in water. Neither of these lists should be 

construed as a list of known or likely endocrine disrupters. Propazine is not on List 1. For 

further information on the status of the EDSP, the policies and procedures, the lists of chemicals, 

future lists, the test guidelines and Tier 1 screening battery, please visit our website[2]. 

[I) See hnp://www.regulations.gov/#!documentDetaii;D- EPA-1-10-0 PPT-2009-0477-0074 for the fmal second list 

of chemicals. 

[2] Available: http://www.epa.gov/endo/ 

23 
References: 

Freemark, K., and C. Boutin. 1995. Impacts of agricultural herbicide use on terrestrial wildlife 

in temperate landscapes - a review with special reference to North-America. Agric. 

Ecosyst. Environ. 52, 67- 91. 

Isaacs, R., Tuell, J., Fiedler, A., Gardiner, M., Landis, D., 2009. Maximizing arthropod-mediated 

ecosystem services in agricultural landscapes: the role of native plants. Front. Ecol. 

Environ. 7, 196-203. 

Mortensen, D.A., Egan, J.F., Maxwell, B.D., Ryan, M.R., Smith, R.G., 2012. Navigating a 

critical juncture for sustainable weed management. Bioscience 62, 75-85.Norris, R.F., 

Kogan, M., 2000. Interactions between weeds, arthropod pests, and their natural enemies 

in managed ecosystems. Weed Sci. 48, 94- 158. 

Norris, R.F., Kogan, M., 2000. Interactions between weeds, arthropod pests, and their natural 

enemies in managed ecosystems. Weed Sci. 48,94- 158. 

Norris, R.F., Kogan, M., 2005. Ecology of interactions between weeds and arthropods. Annu. 

Rev. Entomol. 50, 479-503. 

USEPA 2006. Ecological Risk Assessment for the Section 3 New Use on Sorghum: Propazine. 

DP barcodes 310326, 249944, 249945. United States Environmental Protection Agency, 

Office ofPesticide Programs, Washington, DC. 

USEPA 2013. Registration Review: Problem Formulation for Environmental Fate and 

Ecological Risk, Endangered Species, and Drinking Water Assessments for Propazine 

(Case 230). DP Barcode D407225. United States Environmental Protection Agency, 

Office of Pesticide Programs, Washington, DC. 

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