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# REGISTRATION REVIEW

PROBLEM FORMULATION

Dithiopyr

CAS Number 97886-45-8

US EPA PC CODE 128994

Prepared by:

Robin Sternberg, Ph.D., Wildlife Biologist

Christopher M. Koper, M.S., Chemist

Environmental Risk Branch 1

Reviewed by:

Stephen Wente, Ph.D., Biologist

Michael Lowit, Ph.D., Ecologist

Environmental Risk Branch 1 U.S. Environmental Protection Agency

Office of Pesticide Programs

Environmental Fate and Effects Division

Environmental Risk Branch I

1200 Pennsylvania Ave., NW

Mail Code 7507P

Washington, DC 20460

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# 1 Executive Summary

The Environmental Fate and Effects Division (E FED) has completed the preliminary problem

formulation for the ecological risk, environmenta l fate, endangered species, and drinking water

assessments to be conducted as part of the re gistration review of d ithiopyr. The problem

formulation describes the methods planned to be used during the completion of drinking water

and ecological risk assessments in support of Re gistration Review and provides an overview of

the environmental fate, ecological effects, and poten tial risks associated w ith the use of dithiopyr

as well as uncertainties unique to risk assessmen t of dithiopyr. This document also identifies

additional studies that would be beneficial to the conduct of an ecological risk assessment.

Major findings include the fo llowing data needs and the uncer tainty described below:

 OCSPP Guideline 835.4200 (TGAI): Anaerobic soil metabolism

 OCSPP Guideline 835.4300 (TGAI) : Aerobic aquatic metabolism

 OCSPP Guideline 835.4400 (TGAI): Anaerobic aquatic metabolism

 OCSPP Guideline 835.1410 (TGAI): Volatility – laboratory

 OCSPP Guideline 850.1350 (TGAI): My sid chronic toxicity test

 OCSPP Guideline 850.4400 (TGAI): Aquatic pl ant toxicity test using Lemna spp.

 OCSPP Guideline 850.4500 (TGAI): Algal toxici ty, marine diatom and freshwater

diatom

 OCSPP Guideline 850.4550 (TGAI): Cyanobacteria ( Anabaena flos-aquae ) toxicity

 OCSPP Guideline 850.2100 (TGAI): Avian acute oral toxicity, passerine species

 Non-guideline honey bee acute oral toxicity (TGAI)

 Non-guideline larval honey bee acute oral toxicity (TGAI)

 Non-guideline whole sediment: Chronic inve rtebrates freshwater and marine (TGAI)

Justifications for these data needs as well as as sumptions that will be made in the absence of

these data are provided in Section 11

.

There is uncertainty as to whether exposure of non-target plants via components of compost

( e.g. , turf clippings) that have been treated with dithiopyr is an exposure pathway of concern.

Dithiopyr is a systemic herbicide; it is absorbed by the root and translocated upwards into the

shoot. However, there is a large difference be tween the half-lives cal culated from the aerobic

metabolism study and the field dissipation study (336-639 days and 0.6-97 days, respectively).

As a result, there is uncertainty as to the likeli hood that concentrations of dithiopyr in compost

could reach a level that advers ely affects non-ta rget plants.



# 2 Introduction

Dithiopyr is a systemic pyrid ine herbicide that is applie d pre-emergence and early postemergence to selectively control crabgrass and other susceptible annual grasses and broadleaf

weeds in established lawns and ornamental turf. Dithiopyr acts via inhi biting the formation and

function of microtubulin resulting in the disrupti on of normal cell division of susceptible plants.

Susceptible plant roots are stunted and fail to function in the presen ce of dithiopyr. Plants do not

# 4 grow and develop through their normal cycle of vegetative growth followed by reproduction

(flowering and seed setting).

EFED evaluated toxicity, exposure, and usage in formation to determine if sufficient data are

available and if further updates are needed to support Registration Review. A briefing

memorandum was produced in 1991 to support regi stration of dithiopyr as a new chemical

(USEPA, 1991); however, no risk conclusions were made. In addition, EFED considered the

latest Agency science policies a nd risk assessment methodologies.



# 3 Use Characterization

Dithiopyr is a selective herbic ide that is applied pre-emerge nce and early post-emergence to

control crabgrass and other sus ceptible annual grasses and broadl eaf weeds in established lawns

and ornamental turf. It is registered for non-food use on the following sites: airports/landing

fields, commercial/industrial lawns, fruits (unspecified), golf c ourse turf, industr ial/construction

areas (outdoor), mulch, nonagr icultural rights-of-way/fencer ows/hedgerows, agricultural

uncultivated areas/soils, shade trees, ornament als, paths/patios, paved areas (private

roads/sidewalks), recreation area lawns, recrea tional areas, residential lawns, rights-of-way

(railroad), rose, and tree nuts. D ithiopyr is formulated as an emul sifiable concentrate, flowable

concentrate, granule, ready-to-u se liquid, soluble concentrate (liquid and solid), and wettable

powder. Application equipment includes back sp rayer, foam applicator, granule applicator,

handgun, sprayer, and spreader. The chemical pr ofile produced by BEAD, lo cated in the docket,

lists the use patterns of maximum exposures for the current uses of dithiopyr. EFED will use

application scenarios that result in maximum exposure for a given use in the ecological risk

assessment. The absence of information on labels ( e.g. , maximum single and annual application

rates in lbs a.i./year, appli cation interval, application met hod) may result in conservative

assumptions.



# 4 Conclusions from Previous Risk Assessments

4.1 Ecological Risk Assessments

The Agency has not conducted a recent ecologica l risk assessment for dithiopyr. A briefing

memorandum that described available environm ental fate and ecologi cal effects data was

produced in 1991 to support the re gistration of dithiopyr as a ne w chemical (USEPA, 1991). No

risk conclusions were made in the document.

4.2 Drinking Water Exposure Assessments

A drinking water assessment wa s not conducted in the past fo r this chemical because the

registrations were for non-food uses (turf). A drinking water assessment will be conducted for

dithiopyr at the time of the preliminary risk assessment. The Health Effects Division (HED)

recommends the normal acid and the reverse acid ar e appropriate to include in the drinking water

assessment along with the parent dithiopyr. A tota l toxic residue (TTR) appr oach will be utilized

in the drinking water assessment to account fo r these potential residue s of concern.

# 5 4.3 Clean Water Act Programs

As part of the PF process, OPP and OW have an agreement that states would be able to use the

most sensitive aquatic endpoints identified in th e PF for prioritization and possibly to use as

benchmark criteria.

Dithiopyr is not identifie d as a cause of impairment for any wa ter bodies listed as impaired under

section 303(d) of the Clean Water Act. No To tal Maximum Daily Load (TMDL) criteria have

been developed for dithiopyr. Any data subm itted or otherwise located as part of the

Registration Review process may be used to update aquatic life benchmarks if applicable.



# 5 Environmental Fate and Transport

Dithiopyr (CAS No. 97886-45-8; PC code 128994) dissipates in th e environment (on soil and in

surface water) principally by aqueous photolysis and volatilization. Dithiopyr photolyzes in

shallow, clear surface waters (ave rage half-life ~ 19 days), but doe s not photolyze on soil. Major

aqueous photolysis degradates include the normal acid (27%) and the reverse acid (14%).

Dithiopyr is persistent under c onditions where it does not volatilize or photolyze. Dithiopyr is

stable to hydrolysis at pH 5 and 7 but exhibits some alkaline-based hydrol ysis (half-life of 1053

days) at pH 9. Dithiopyr slowly degrades in aerobic soil (average half-life of 505 days) to three

minor acids (normal, reverse, diacid). D ithiopyr accumulated in fish with maximum

concentration factors of 320x, 1400x, and 930x in ed ible tissues, non-edible tissues, and whole

fish, respectively. However, 92-94% of dithiopyr was eliminated from all tissues by day 14 of

the depuration period. Dithiopyr has a low potential for leaching because of its low solubility in

water and its high tendency to bind to soil. Howe ver, its primary degrad ation products are acids

which may have the potential to leach to ground water in vulnerable aquifers, such as those with

coarse-textured soils low in organic matter. A selection of environmen tal fate and transport

properties of dithiopyr is summarized in Table 5-1

.

Table 5-1. Chemical Properties and Enviro nmental Fate Parameters of Dithiopyr

Parameter Value Source/MRID #

Common name Dithiopyr

Product Chemistry CAS number 97886-45-8

Chemical name 3,5-Pyridinedicarbothioic acid,

2-(difluoromethyl)-4-(2-methylpropyl)-

6-(trifluoromethyl)-S,S-dimethyl ester

Chemical Class/Category Herbicide

Empirical formula C 15 

# H 16 

# S 2 

# NO 2 

# F 5



# Structure

Molecular Mass 401.4 g/mole

# 6 Parameter Value Source/MRID #

Water Solubility 1.4 mg/L at 25  C

Vapor pressure (25  C) 4.0 x 10 -6 

# mm Hg

Henry’s Law Constant 1.5 x 10 -6 

# atm m 3 

# /mol Calculated 1



# Octanol/water partition

coefficient (K

ow 

# ) 56,250 (log Kow = 4.75) Product Chemistry

Dissociation Constant (pKa) --

Hydrolysis (t 1/2 

# ) pH 5 = stable

pH 7 = stable

pH 9 = 1053 days (2.9 years) 40638627

Aqueous Photolysis (t 1/2 

# )

(pH 7) 17.6 days

20.6 days 40638628

Soil Photolysis (t 1/2 

# ) 444 days

Aerobic Soil Metabolism (t 1/2 

# ) 336 days (silt loam)

418 days (sandy loam)

490 days (clay soil)

523 days (silt loam)

625 days (sandy loam)

639 days (clay soil) 40638629

41001517

Soil Partition Coefficient (K

oc 

# )

(mL/g) 2063

1396

3049

1543

2241

1757 40638630

Terrestrial Field Dissipation

(t 1/2 

# ) 0.6 – 8.0 days

14 – 59 days

4 – 97 days 41001519

Bioaccumulation in Fish

(BCF) 320X in edible tissues

1400X for non-edible tissues

930X for whole fish

94% depuration rate (14 days) 41001518

1 

# = Henry’s Law (atm-m 3 

# /mole) = (VAPR/760)/(SOL/MWT), where VAPR is vapor pressure in torr, MWT is

molecular weight in g/mol, and SOL is the solubility in water in mg/L.



# 5.1 Transformation Products

The major organic degradates of dithiopyr in submitted environmental fate studies were the

normal and reverse acids (aqueous photolysis; MRID 40638628). A variety of minor degradates

were observed in the hydrolysis, soil photol ysis, and aerobic soil metabolism studies. Table 5-2

summarizes the transformation products of d ithiopyr and their maximum amounts formed.

Aerobic soil metabolism studies (MRID 40638629; MRID 41001517) show that dithiopyr is

volatile with 20 and 28% of the chemical show ing up in the foam volatile traps. Batch

equilibrium studies show dithi opyr’s acid degradates (normal, reverse, and diacid) are highly

mobile to mobile, with K OC 

# values in four soils ranging from 3 to 29 L/kg OC (MRID

41135601). Most environmental fate studies conducted with dithiopy r degradates have not been

submitted. Therefore, the behavior of these degradates is not well understood.7Table 5-2. Dithiopyr and Its Major Environmental DegradatesCode Name/SynonymChemical NameChemical StructureStudy TypeMRIDMaximum Formation(% Applied)DithiopyrMON-7200MON-15100CAS Name:3,5-Pyridinedicarbothioic acid,2-(difluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-S,S-dimethylesterMolecular Weight:401.4 g/molSMILES:CSC(=O)C1=C(N=C(C(C(=O)SC)=C1CC(C)C)C(F)(F)F)C(F)FParent structure shown for referenceNormal AcidCAS Name:2-(Difluoromethyl)-4-(2methylpropyl)-5-((methylthio)carbonyl)]-6-(trifluoromethyl)3-pyridinecarboxylic acidHydrolysis pH 9 406386272.0Aqueous Photolysis 4063862827.3Soil Photolysis 406386285.0Aerobic Soil Metabolism 406386295.9Aerobic Soil Metabolism 410015176.3Reverse AcidCAS Name:6-(Difluoromethyl)-4-(2-methylpropyl)-5-[(methylthio)carbonyl)]-2-(trifluoromethyl)-3-pyridinecarboxylic acidAqueous Photolysis 4063862814.2Aerobic Soil Metabolism 40638629 3.0Aerobic Soil Metabolism 41001517 5.0DiacidCAS Name:2-(Difluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl]-3, 5-pyridinedicarboxylic acidAqueous Photolysis 40638628 4.4Aerobic Soil Metabolism 40638629 5.0Aerobic Soil Metabolism 41001517 7.38Code Name/SynonymChemical NameChemical StructureStudy TypeMRIDMaximum Formation(% Applied)Degradate VCAS Name:3,5-bis(Methylthiocarbonyl)-2-formyl-4-(2-methylpropyl) -6-trifluoromethyl pyridineAqueous Photolysis 40638628 4.7Degradate VICAS Name:3-(Methylthiocarbonyl)-2-difluoromethyl-4-(2-methylpropyl) -6-trifluoromethylpyridineAqueous Photolysis 40638628 < 7.3CRDegradate VIICAS Name:3-{Methylthiocarbonyl)-2-formyl-4-(2-methyl-propyl)-6-trifluoromethylpyridineAqueous Photolysis 40638628 < 7.3CRVolatilesDithiopyrAerobic Soil Metabolism 4063862920.43Aerobic Soil Metabolism 4100151728.09CO2Carbon DioxideO=C=OAerobic Soil Metabolism 40638629 0.43Aerobic Soil Metabolism 41001517 0.58UnextractableResiduesAerobic Soil Metabolism 40638629 7.1Aerobic Soil Metabolism 4100151719.1CR= combined residues; aqueous photolysis study 40638628, degradate VIand VII together comprised 7.3% of the applied radioactivity.

# 9 

# 6 Receptors

Tables 6-1 and 6-2 provide a summary of toxicity endpoint s used to characterize the potential

acute and chronic ecological e ffects of dithiopyr to aquatic and terrestrial taxonomic groups,

respectively. No toxicity da ta are available for the major degradates of dithiopyr ( i.e. , normal

acid and reverse acid). In the absence of these data, the toxicity of th e major degradates to

terrestrial and aquatic organisms ar e assumed to be comparable to that of dithiopyr because they

maintain the core pyridine stru cture of the parent.10Table 6-1. Summary of the Endpoints fromAquatic Toxicity Studies for DithiopyrTaxonStudy TypeTGAI/TEP(% a.i.)SpeciesToxicity Value, Effects, &Acute Toxicity Classification (If Applicable)Source& StudyClassificationFish(surrogate foraquatic-phaseamphibians)Acute: 96-hour, staticexposureTGAI (91.5)Rainbow trout(Oncorhynchus mykiss)LC50(95% C.I.) = 0.49 (0.37-0.65) mg a.i./L (mm)Probit slope (95% C.I.) = 4.8 (2.6-7.0)NOAEC = 0.19 mg a.i./L (mm)LOAEC = 0.27 mg a.i./L (mm)(NOAEC based on no mortality at≤0.19 mg/L)Highly toxicMRID 40638623AcceptableAcute: 96-hour, staticexposureTGAI (91.5)Bluegill sunfish(Lepomis macrochirus)LC50(95% C.I.) = 0.47 (0.33-0.83) mg a.i./L (mm)NOAEC = 0.20 mg a.i./L (mm)LOAEC = 0.33 mg a.i./L (mm)(NOAEC based on no mortality at≤0.20 mg/L)Highly toxicMRID 40638624AcceptableAcute: 96-hour exposure Fathead minnow(Pimephales promelas)To be determined MRID 44243701In reviewEarly life stage: 60-day,flow-through exposureTGAI (90.7)Rainbow trout(Oncorhynchus mykiss)NOAEC = 0.056 mg a.i./L (mm)LOAEC = 0.12 mg a.i./L (mm)(based on reduced length and wet weight at≥0.12 mg/L; alsoreduced survival at≥0.20 mg/L; concentration-dependent increasein the incidence of sublethal effects including loss of equilibrium,surfacing, exophthalmia, and distended abdomen)MRID 41001515AcceptableFull life cycle: 272-day,flow-through exposureTGAI (94.54)Fathead minnow(Pimephales promelas)To be determined MRID 44243701In reviewAcute: 96-hour, flowthrough exposureTGAI (94.3)Sheepshead minnow(Cyprinodonvariegatus)LC50> 2.164 mg a.i./L (mm)NOAEC = 0.604 mg a.i./L (mm)LOAEC = 0.987 mg a.i./L (mm)(0, 0, 0, 0, 5, 15, and 20% mortality in the negative control, solventcontrol, 0.342, 0.604, 0.987, 1.549, and 2.164 mg/L treatmentgroups; NOAEC based on sublethal effects: at 96 hours, erraticswimming at≥0.987 mg/L, loss of equilibrium at 1.549 mg/L)At most moderately toxicMRID 42402101Acceptable11TaxonStudy TypeTGAI/TEP(% a.i.)SpeciesToxicity Value, Effects, &Acute Toxicity Classification (If Applicable)Source& StudyClassificationEarly life stage(chronic)Estuarine/marine fish No dataChronic toxicity may be characterized using toxicity data forfreshwater fish (i.e., rainbow trout or fathead minnow)For example:Estimated chronic NOAEC(sheepshead minnow)= Acute LC50(sheepshead minnow)/ Acute-to-Chronic Ratio(rainbow trout)= (>2.164 mg/L) / 8.75≥0.247 mg/LWhere:Acute-to-Chronic Ratio(rainbow trout)= Acute LC50(rainbow trout)/ Chronic NOAEC(rainbow trout)= 0.49 mg/L / 0.056 mg/L= 8.75NAAquaticinvertebratesAcute limit test: 48-hour,static exposureTGAI (92.6)Water flea(Daphnia magna)EC50> 1.7 mg a.i./L (mm)(10% immobility at 1.7 mg/L; no sublethal effects)At most moderately toxicMRID 42050201AcceptableAcute: 48-hour, staticexposureForm. (12.6)Water flea(Daphnia magna)EC50= 5.2 mg a.i./L (mm)NOAEC = 2.0 mg a.i./L (mm)LOAEC = 4.6 mg/L (mm)(NOAEC based on no mortality at≤2.0 mg/L)Moderately toxicMRID 42050201AcceptableLife cycle (chronic): 21-day, flow throughexposureTGAI (92.2)Water flea(Daphnia magna)21-day NOAEC = 0.081 mg a.i./L21-day LOAEC = 0.19 mg a.i./L7-day EC50= 0.25 mg a.i./L(based on survival; 100% mortality by day 21 at 0.19 and 0.36mg/L)MRIDs 42333301& 42419801AcceptableSediment acute/chronic Sediment-dwellinginvertebrateNo data NA12TaxonStudy TypeTGAI/TEP(% a.i.)SpeciesToxicity Value, Effects, &Acute Toxicity Classification (If Applicable)Source& StudyClassificationAcute: 96-hour, flowthrough exposureTGAI (94.3)Eastern oyster(Crassostrea virginica)EC50(95% C.I.) = 0.158 (0.114-0.247) mg a.i./L (mm)NOAEC = 0.048 mg a.i./L (mm)LOAEC = 0.080 mg a.i./L (mm)Highly toxicMRID 42399401AcceptableAcute: 96-hour, flowthrough exposureTGAI (94.3)Mysid shrimp(Mysidopsis bahia)LC50= 0.586 mg a.i./L (mm)NOAEC = 0.173 mg a.i./L (mm)LOAEC = 305 mg a.i./L (mm)(NOAEC based on no mortality at≤0.173 mg/L ; lethargy at 48hours at≥0.467 mg/L; lethargy at all test concentrations at 72hours)Highly toxicMRID 42395001AcceptableLife cycle (chronic) Estuarine/marine invertebrateNo data NAAquaticvascular plantNA Duckweed(Lemna gibba)No data NAAquatic nonvascular plant:5-day, static exposureTGAI (94.3)Green alga(Selenastrumcarpicornutum)EC50= 20 μg a.i./L (mm)aNOAEC = 7.6 μg a.i./L (mm)(based on cell density)MRID 42246401AcceptableNA Freshwater diatom No data NAMarine diatom No data NACyanobacterium No data NAmm = mean measured; NA = not applicableaThe raw data for this study will be subjected tonew statistical analysis because the present EC50was determined using probit analysis rather than non-linearregression analysis.13Table 6-2. Summary of the Endpoints fromTerrestrial Toxicity Studies for DithiopyrTaxonStudy TypeTGAI/TEP(% a.i.)SpeciesToxicity Value, Effects, &Acute Toxicity Classification (If Applicable)Source& StudyClassificationBirds(surrogate forreptiles andterrestrialphaseamphibians)Acute oral: single dose,14-day observationTGAI (91.5)Bobwhite quail(Colinus virginianus)LD50> 2250 mg a.i./kg-bw (nom)NOAEL: Not specified(no mortality; 2 control birds with ruffled appearance from days10-14 ; at≥486 mg/kg-bw, 1-4 birds with ruffled appearanceand/or wing drop from days 0-3; at≥810 mg/kg-bw, 1 lethargicfemale on days 1-2; at 810 mg/kg-bw, 1 female with ruffledappearance on days 13-14)Practically non-toxicMRID 40638620AcceptableAcute oral Passerine species No data NASub-acute dietary: 5-dayexposure; 3-day postexposure observationTGAI (91.5)Bobwhite quail(Colinus virginianus)LC50> 5620 mg a.i./kg-diet (nom)NOAEC = 5620 mg a.i./kg-diet (nom)(no mortality or sublethal effects)Practically non-toxicMRID 40638622AcceptableSub-acute dietary: 5-dayexposure; 3-day postexposure observationTGAI (91.5)Mallard duck(Anas platyrhynchos)LC50>5620 mg a.i./kg-diet (nom)NOAEC = 3160 mg a.i./kg-diet (nom)LOAEC = 5620 mg a.i./kg-diet (nom)(no mortality; NOAEC based on reduction in body weight gainat 5620 mg/kg-diet)Practically non-toxicMRID 40638621AcceptableReproduction(chronic)TGAI (94.3)Bobwhite quail(Colinus virginianus)NOAEC = 1250 mg a.i./kg-diet (nom)LOAEC > 1250 mg a.i./kg-diet (nom)(no effects)MRID 42495601AcceptableReproduction(chronic)TGAI (94.3)Mallard duck(Anas platyrhynchos)NOAEC = 250 mg a.i./kg-diet (nom)LOAEC = 1250mg a.i./kg-diet (nom)(based on slight reductions in % viability [~9%] and 14-daysurvival/eggs set [~9.2%]a)MRID 42661001AcceptableTerrestrialinvertebratesAcute contact: singledose, 48-hour observationTGAI (91.5)Honey bee(Apis mellifera)LD50(95% C.I.) = 81 (53-256) μg a.i./bee (nom)NOAEL: Not specifiedPractically non-toxicMRID 40638626Acceptable14TaxonStudy TypeTGAI/TEP(% a.i.)SpeciesToxicity Value, Effects, &Acute Toxicity Classification (If Applicable)Source& StudyClassificationAcute dietary (oral)Honey bee(Apis mellifera)No data NALarval honey bee(Apis mellifera)No data NATerrestrialplantsSeedling emergenceTGAI (91.6)Most sensitive monocot:OnionIC25= 0.0026 lb a.i./AbIC05= To be determinedbNOAEC = 0.0031 lb a.i./Ab(based on dry weight)MRID 42244401AcceptableMost sensitive dicot:LettuceEC25= 0.0082 lb a.i./AbEC05= To be determinedbNOAEC = 0.023 lb a.i./Ab(based on height)Vegetative vigorTGAI (91.6)Most sensitive monocot:RyegrassEC25= 0.041 lb a.i./AbEC05= To be determinedbNOAEC = 0.074 lb a.i./Ab(based on dry weight)MRID 42244401AcceptableMost sensitive dicot:SoybeanIC25= 0.11 lb a.i./ANOAEC = 0.025 lb a.i./A(based on height)NA = not applicable ; nom = nominalareductions were not statistically significantbSince the NOAEC is greater than the EC25, the EC05will be determined via new statistical analysis of theraw data and used to estimate risk to listed monocots.

# 15 6.1 Ecological Incidents

A preliminary review on September 17, 2013, of th e Ecological Incident Information System

(EIIS, version 2.1), which is maintained by the Ag ency’s Office of Pesticide Programs, and the

Avian Monitoring Information System (AIMS), which is maintained by the American Bird

Conservancy, indica tes a total of 32 reported ecological incidents a ssociated with the use of

dithiopyr. These incidents are summarized in Table 6-3

.

All of the dithiopyr incide nts occurred between 1992 and 2009 and involved plants. The

certainty categories regardi ng the likelihood that the use of dithiopyr caused the 32 incidents

ranged from possible (2 incidents) to probabl e (30 incidents). One of the incidents was

considered a registered use at the time of the incident, 2 involved misuses (accidental), and the

legality of use was undetermined in 29 incidents. Two of the incidents involved additional

chemicals besides dithiopyr.

In the risk assessment, the incidents will be fu rther evaluated to determine if the reported

incidents represent current patterns of use for d ithiopyr. Examples of additional considerations

are mitigation ( e.g ., reduced application rates), product cance llations, and changes in use patterns

that have occurred since the date of the reported incident(s).

In addition to the incidents reco rded in EIIS and AIMS, additiona l incidents have been reported

to the Agency in aggregated incident reports. Pesticide registrants re port certain types of

incidents to the Agency as a ggregate counts of incidents occu rring per product per quarter.

Ecological incidents reported in aggregate reports include those cat egorized as ‘minor fish and

wildlife’ (W-B), ‘minor plant’ (P -B), and ‘other non-target’ (ONT ) incidents. ‘Oth er non-target’

incidents include reports of adve rse effects to insects and other terrestrial invertebrates. For

dithiopyr, registrants have reported 6 minor fish and wildlife incidents, 27 minor plant incidents,

and 0 other non-target incidents. Un less additional information on these aggregated incidents

becomes available, they will be assumed to be repr esentative of registered uses of dithiopyr in

the risk assessment.16Table 6-3. Summary of EcologicalIncidents Involving Dithiopyr as Documented inthe Ecological Incident Information SystemTaxonAffectedIncident IDUse SiteDateLegalityCertaintyStateCountyTotal MagnitudeProductOtherPesticidesInvolved?Plants I000133-001 Turf, golf course1992 Misuse (accidental) Probable TX Not specified Golfcourse greens Dimension NoPlants I000301-001 Turf, golf course 1992 Undetermined Probable AZ Not specified Not specified Dimension NoPlants I000301-002 Turf, golf course 1992 Undetermined Probable AZ Not specified 3 golf greens Dimension NoPlants I000301-003 Turf, golf course 1992 Undetermined Probable AZ Not specified 1 golf green Dimension NoPlants I000301-004 Turf, golf course 1992 Undetermined Probable IL Not specified 18 golf greens Dimension NoPlants I000301-005 Turf, golf course 1992 Undetermined Probable IN Not specified Unknown Dimension NoPlants I000301-006 Turf, golf course 1992 Undetermined Probable MI Not specified 17 golf greens Dimension NoPlants I000301-007 Turf, golf course 1992 Undetermined Probable MO Not specified 1 golf green Dimension NoPlants I000301-008 Turf, golf course 1992 Undetermined Probable NV Not specified 18 golf greens Dimension NoPlants I000301-009 Turf, golf course 1992 Undetermined Probable NC Not specified Golf greens, tees Dimension NoPlants I000301-010 Turf, golf course 1992 Undetermined Probable NC Not specified Golf greens Dimension NoPlants I000301-011 Turf, golf course 1992 Undetermined Probable OK Not specified Golf greens Dimension NoPlants I000301-012 Turf, golf course 1992 Undetermined Probable OH Not specified Golf fairway Dimension NoPlants I000301-013 Turf, golf course 1992 Undetermined Probable OH Not specified 18 golf greens Dimension NoPlants I000301-014 Turf, golf course 1992 Undetermined Probable OH Not specifiedGolf greens and teesDimension NoPlants I000301-015 Turf, golf course 1992 Undetermined Probable OH Not specified 18 golf greens Dimension NoPlants I000301-016 Turf, golf course 1992 Undetermined Probable OH Not specified 1 golf green Dimension NoPlants I000301-017 Turf, golf course 1992 Undetermined Probable PA Not specified 3 golf greens Dimension NoPlants I000301-018 Turf, golf course 1992 Undetermined Probable SC Not specified 18 golf greens Dimension NoPlants I000301-019 Turf, golf course 1992 Undetermined Probable SC Not specified 18 golf greens Dimension NoPlants I000301-020 Turf, golf course 1992 Undetermined Probable TX Not specified 18 golf greens Dimension NoPlants I000301-021 Turf, golf course 1992 Undetermined Probable TX Not specified 18 golf greens Dimension NoPlants I000301-022 Turf, golf course 1992 Undetermined Probable TX Not specified 18 golf greens Dimension NoPlants I000301-023 Turf, golf course 1992 Undetermined Probable TX Not specified Golf greens Dimension NoPlants I000301-024 Turf, golf course 1992 Undetermined Probable TX Not specified 18 golf greens Dimension NoPlants I000301-025 Turf, golf course 1992 Undetermined Probable TX Not specified Golf greens Dimension NoPlants I000301-026 Turf, golf course 1992 Undetermined Probable TX Not specified Golf greens Dimension NoPlants I003629-001 Turf, golf course 1992 Undetermined Probable VAChesapeake CityUnknown Dimension NoPlants I003629-004 Agricultural area NS Undetermined Probable NE Douglas Unknown Dimension NoPlants I016671-001 Right-of-way 2005 Registered use Possible CA Sutter 75 to 100 trees DimensionYes,chlorsulfuronPlants I020998-034 Not specified 2003 Undetermined Possible WA Chelan Not specifiedYes,diuronbromacilpicloramPlants I021002-002 Lettuce 2009 Misuse (accidental) Probable CA Salinas 125 acres Kerb* NoNS = not specified*Dithiopyr is not listed on the Kerb label. Upon investigation,Dow Agrosciences determined that a small portion of the Kerb package contained dithiopyr.

# 17 

# 7 Exposure Pathways of Concern

The environmental fate properties and use patterns of dithiopyr indicate th at direct spray, spray

drift, atmospheric deposition, and runoff represent potential transpor t mechanisms of dithiopyr to

aquatic and terrestrial organisms.

There is uncertainty as to whether exposure of non-target plants via components of compost

( e.g. , turf clippings) that have been treated with dithiopyr is an exposure pathway of concern.

Dithiopyr is a systemic herbicide; it is absorbed by the root and translocated upwards into the

shoot. However, there is a large difference be tween the half-lives cal culated from the aerobic

metabolism study and the field dissipation study (336-639 days and 0.6-97 days, respectively).

As a result, there is uncertainty as to the likeli hood that concentrations of dithiopyr in compost

could reach a level that advers ely affects non-ta rget plants.

Drinking water and inhalation e xposure pathways were screen ed using the SIP (Screening

Imbibition Program) and STIR (Screening Tool for Inhalation Risk) screening methods and were

found to be exposure pathways of low concern (no LOC exceedances are expected). SIP and

STIR are described in detail at: http://www.epa.gov/oppefed1/m odels/terrestrial/index.htm

.



# 8 Analysis Plan

8.1 Stressors of Concern

8.1.1 Ecological Risk Assessment

The toxicities of the normal and reverse acids of dithiopyr to terrestria l and aquatic organisms

are assumed to be comparable to that of dithiopyr because they maintain the core pyridine

structure of dithiopyr. As a re sult, dithiopyr and its normal and reverse acid degradates will be

considered the stressors of ecological concern, a nd a total toxic residues (TTR) approach will be

used for terrestrial and aquatic modeling.

8.1.2 Drinking Water Exposure Assessment

The Health Effects Division (HED) recommends the normal acid and th e reverse acid be

included in the drinking water assessment along with the parent dithiopyr. A TTR approach will

be utilized in the drinking water assessment to account for these potential re sidues of concern.

8.2 Measures of Exposure

EFED will use standard available models to evaluate potential exposures to aquatic and

terrestrial organisms as described at http://www.epa.gov/pesticides/science/models_db.htm

. Because dithiopyr and its normal and reverse ac id degradates are assumed to have similar

toxicity to terrestrial and aquatic organisms, a TTR approach will be used for terrestrial and

aquatic modeling.

# 18 8.2.1 Available Monitoring Data

The Agency is aware of monitoring conducted by federal and state agenci es, and this route of

exposure will be considered in the assessment to th e extent that data on di thiopyr are available.

8.3 Measures of Effect

Toxicity data presented in Section 6 of this problem formulation w ill be used to calculate risk

quotients. Any additional information submitted by th e registrant or found in the open literature

prior to conduct of the risk assessment will also be considered. The open literature studies are

identified using EPA’s ECOTOXicology database (ECOTOX) 1 

# , which employs a literature

search engine for locating chemical toxicity data for aquatic life, terrestrial plants, and wildlife.

The evaluation of both sources of data can also provi de insight into the dir ect and indirect effects

of pesticides on biotic communities from loss of species that are sensitiv e to the chemicals and

from changes in structure and functional ch aracteristics of the affected communities.



# 9 Endangered Species Assessments

Consistent with the Agency’s responsibility under the Endangered Species Act (ESA), the

Agency will evaluate risks to federally-listed th reatened and/or endangere d (listed) species from

registered uses of pesticides in registration re view. The process for evaluating potential risks to

listed species is further described at

http://www.epa.gov/oppfead1/enda nger/litstatus/riskasses.htm

.



# 10 Endocrine Disruptors Screening Program

Dithiopyr was not included in th e first group of 67 chemicals issued an order to conduct Tier 1

EDSP testing. For additional info rmation the EDSP program, visit http://www.epa.gov/endo/

.



# 11 Preliminary Identification of Data Gaps

11.1 Environmental Fate

Table 11-1 identifies environmental fate studies by MRID that offer data for each guideline

requirement, study classifications, an d whether or not further data are needed in order to support

the risk assessment.

1 

# http://cfpub.epa.gov/

# 19 Table 11-1. Submitted Environmental Fate Data for Dithiopyr

OCSPP

Guideline Data

Requirement Source

MRID Classification Are Data

Needed to

Conduct the

Risk

Assessment? Justification and Assumptions EPA

Will Make in the Absence of Data

835.2120 Hydrolysis 4063 8627 Acceptable No --

835.2240 Aqueous

photolysis 40638628 Acceptable No --

835.2410 Soil photolysis 4 0638628 Acceptable No --

835.4100 Aerobic soil

metabolism 40638629

41001517 Acceptable

Acceptable No

No --

835.4200 Anaerobic soil

metabolism 

# -- -- Yes No anaerobic soil metabolism data

have been submitted. OCSPP

guidance recommends that these tests

be performed with four soils.

Because OCSPP uses an upper 90th

percentile estimate of soil metabolism

half-lives based on available study

data for modeling purposes, any

additional data can reduce uncertainty

related to the exposure assessment as

well as the half-life value used in

modeling. Stability will be assumed

in the absence of data.

835.4300 Aerobic aquatic

metabolism 

# -- -- Yes Data are needed for aerobic sedimentwater systems. Two different

sediments with varying organic

carbon content and texture are

recommended as described in the

OCSPP guidelines. Stability will be

assumed in the absence of data.

835.4400 Anaerobic

aquatic

metabolism 

# -- -- Yes Data are needed for anaerobic

sediment-water systems. Two

different sediments with varying

organic carbon content and texture are

recommended as described in the

OCSPP guidelines. Stability will be

assumed in the absence of data.

835.1230

835.1240 Adsorption/

Desorption and

Leaching 40638630

41135601 Acceptable

Acceptable No

No --

835.1410 Volatility –

Field 41615601 Supplemental Yes The registrant should submit

analytical data for the soil and turf

grass surfaces to confirm the

application rate and the rate of

volatilization. If this data cannot be

provided, a new study is requested.

# 20 OCSPP

Guideline Data

Requirement Source

MRID Classification Are Data

Needed to

Conduct the

Risk

Assessment? Justification and Assumptions EPA

Will Make in the Absence of Data

835.6100 Terrestrial field

dissipation 41001519 Acceptable No

-- Analytical

Method in soil 42456601

44559801 Acceptable

Acceptable No

No

165-4

(850.1730) Fish

bioconcentration 41001518 Acceptable No

--



# 11.2 Ecological Effects

Tables 11-2 and 11-3 identify ecological effects studies by MRID that offer data for each

guideline requirement, study classifi cations, and whether or not further data are needed in order

to support the risk assessment.

No toxicity data are available for the normal a nd reverse acid degradates of dithiopyr. Since

there is no evidence that these degradates ar e more toxic than dithiopyr, EFED does not

recommend requesting data for the normal and revers e acid degradates of dithiopyr at this time.

In the absence of these data, the toxicity of the no rmal and reverse acid degradates of dithiopyr to

terrestrial and aquatic organisms are assumed to be comparable to that of dithiopyr.21Table 11-2. Submitted Aquatic Ecological Effects Data for DithiopyrOCSPPGuidelineDataRequirementSourceMRIDClassificationDataGap?Are DataNeeded toConduct theRiskAssessment?Justification and Assumptions EPA Will Make in the Absence of Data850.1010 Freshwaterinvertebrateacute toxicity42050201 Acceptable No No --850.1025850.1035850.1045850.1055Saltwaterinvertebrateacute toxicity42399401(mollusk)Acceptable No No --42395001(mysid)Acceptable850.1075 Freshwater fishacute toxicity40638623(cold water)AcceptableNo No --40638624(warm water)Acceptable850.1075 Saltwater fishacute toxicity42402101 Acceptable No No --850.1300 Freshwaterinvertebratelife cycle4233330142419801Acceptable No No --850.1350 Saltwaterinvertebrateslife cycleNo data NA YesYesAquatic invertebrate life cycle toxicity data for an estuarine/marineinvertebrate are required under 40 CFR Part 158 if the product is expectedto enter the environment in significant concentrations because of itsexpected use or mobility patterns or if the acute LC50is <1 mg/L (i.e.,mysid LC50= 0.586 mg/L; MRID 42395001). A study has not beensubmitted for this data requirement.A guideline-compliant estuarine/ marineinvertebrate life cycle test isneeded. Dithiopyr is more acutely toxic to estuarine/marine invertebrates(i.e.,M. bahia) than to freshwater invertebrates (i.e.,D. magna). Inaddition, an acute-to-chronic ratio derived from data forD. magnacannotbe used to estimate a chronic toxicity value forM. bahiabecause the acute22OCSPPGuidelineDataRequirementSourceMRIDClassificationDataGap?Are DataNeeded toConduct theRiskAssessment?Justification and Assumptions EPA Will Make in the Absence of Datatoxicity value forD. magnais non-definitive.In the absence of these data, estuarine/marine invertebrate chronic toxicitydata for surrogate pesticides – starting with data for closely relatedpesticides (e.g., pyridine herbicides) and proceeding to data for lessrelated pesticides – may be used tocharacterize the chronic toxicity ofdithiopyr to estuarine/marine invertebrates.850.1400 Freshwater fishearly-life stage41001515 Acceptable No No--850.1400 Saltwater fishearly-life stageNo data NA Yes No In the absence of these data, an acute-to-chronic ratio derived fromtoxicity data for freshwater fish may be used to estimate the chronictoxicity of dithiopyr to estuarine/marine fish. This methodology mayyield a conservative estimate of the chronic toxicity of dithiopyr toestuarine/marine fish given the non-definitive acute toxicity endpoint forsheepshead minnow.850.1500 Fish life cycle 44243701(freshwater)In review No No --NonguidelineWholesediment:chronicinvertebratesfreshwater andmarineNo data NA YesYesChronic sediment invertebrate toxicity data are required under 40 CFRPart 158 if:i.the estimated environmental concentration (EEC) in sediment is> 0.1 of the acute LC50/EC50values;ii.the half-life of the pesticide in sediment if > 10 days in either theaerobic soil or aquatic metabolism studies and if any of thefollowing exist:A.The soil partition coefficient (Kd) is≥50B.The log Kow is≥3.C.The Koc is≥1,000.Preliminary modeling via PRZM/EXAMSaindicates peak and 21-daypore water EECs of ~10 μg/L which is approximately 0.1 of the EC50forEastern oyster (i.e., 158 μg/L); the half-lives of dithiopyr in the aerobicsoil metabolism studies are all >300 days; and the log Kow and Koc of23OCSPPGuidelineDataRequirementSourceMRIDClassificationDataGap?Are DataNeeded toConduct theRiskAssessment?Justification and Assumptions EPA Will Make in the Absence of Datadithiopyr are 4.75 and >1300 mL/g, respectively.Chronic sediment tests with the midgeChironomus dilutus, freshwateramphipodHyalella azteca, and/or estuarine/marine amphipodLeptocheirus plumulosusare recommended. A tiered approach usingtoxicity data from sub-chronic (10-day) sediment toxicity tests with thethree species may be used to determine which species should undergochronic toxicity testing.In the absence of these data, sediment-dwelling invertebrate chronictoxicity data for surrogate pesticides – starting with data for closelyrelated pesticides (e.g., pyridine herbicides) and proceeding to data forless related pesticides – may be used to characterize the chronic toxicity ofdithiopyr to sediment-dwelling invertebrates.850.4400 Aquatic planttoxicity testusingLemnaspp.No data NA YesYesA study withLemnaspp. has not been submitted. A guideline-complianttest withLemnais needed.In the absence of these data,Lemnatoxicity data for surrogate pesticides –starting with data for closely related pesticides (e.g., pyridine herbicides)and proceeding to data for less related pesticides – may be used tocharacterize the acute toxicity of dithiopyr to aquatic vascular plants.850.4500 Algal toxicity 42246401(green alga)AcceptableNoYesStudies with a marine diatom and a freshwater diatom have not beensubmitted. Guideline-compliant algaltoxicity tests with a freshwaterdiatom and a marine diatom are needed.In the absence of these data, diatom toxicity data for surrogate pesticides –starting with data for closely related pesticides (e.g., pyridine herbicides)and proceeding to data for less related pesticides – may be used tocharacterize the acute toxicity ofdithiopyr to freshwater and marinediatoms.No data(marinediatom)NAYesNo data(freshwaterdiatom)NA Yes850.4550 Cyanobacteria No data NA YesYesA study with cyanobacteria has not been submitted. A guideline-24OCSPPGuidelineDataRequirementSourceMRIDClassificationDataGap?Are DataNeeded toConduct theRiskAssessment?Justification and Assumptions EPA Will Make in the Absence of Datatoxicity compliant cyanobacteria toxicity test is needed.In the absence of these data, cyanobacteria toxicity data for surrogatepesticides – starting with data for closely related pesticides (e.g., pyridineherbicides) and proceeding to data for less related pesticides – may beused to characterize the acute toxicity ofdithiopyr to cyanobacteria.NA = not applicableaPRZM/EXAMS scenario PA Turf; first application date: June 01; broadcast aerial application modeled as 95% application efficiency and 5% spray drift; 3applications @ 0.5208 lb a.i./acre; 30-day application intervalTable 11-3. Submitted Terrestrial Ecological Effects Data for DithiopyrOCSPPGuidelineDataRequirementSourceMRIDClassificationDatagap?Are DataNeeded toConduct theRiskAssessment?Justification and Assumptions EPA Will Make in the Absence ofData850.2100 Avian oraltoxicity40638620(upland game)Acceptable YesYesAcute oral toxicity data for a passerine species are required under thenew 40 CFR Part 158. A study has not been submitted for this datarequirement.A guideline-compliant passerine acute oral toxicity test is needed.Acute oral toxicity data are onlyavailable for one avian species (i.e.,bobwhite quail). Sublethal effects were noted in the acute oral studywith bobwhite quail. Passerine birds may utilize metabolic pathwaysthat are different from larger birds and therefore be more sensitive todithiopyr. Furthermore, passerines exhibit behavioral responses topesticide dosing that are potential indicators of reduced fitness in thefield (e.g., regurgitation of contaminateddiet) even when directbiochemically-mediated lethal toxicity is not apparent.In the absence of these data, passerine toxicity data for surrogatepesticides – starting with data for closely related pesticides (e.g.,No data(passerine)NA25OCSPPGuidelineDataRequirementSourceMRIDClassificationDatagap?Are DataNeeded toConduct theRiskAssessment?Justification and Assumptions EPA Will Make in the Absence ofDatapyridine herbicides) and proceeding to data for less related pesticides –may be used to characterize the acutetoxicity of dithiopyr to passerinespecies.850.2200 Avian dietarytoxicity40638622(upland game)Acceptable No No --40638621(waterfowl)Acceptable850.2300 Avianreproduction42495601(upland game)Acceptable NoNo --42661001(waterfowl)Acceptable850.3020 Honey bee acutecontact toxicity40638626 Acceptable No No --NonguidelineHoney bee acuteoral toxicityNo data NA NAYesThe “White Paper in Support of the Proposed Risk Assessment Processfor Bees” as submitted to the FIFRA Scientific Advisory Panel2proposes a screening-level risk assessment process that includes acutecontact and oral toxicity tests with adult bees and an acute oral toxicitytest with larval bees. Larval andadult honey bee acute oral toxicitydata are not available.In the absence of these data, honey bee oral toxicity data for surrogatepesticides – starting with data for closely related pesticides (e.g.,pyridine herbicides) and proceeding to data for less related pesticides –may be used to characterize the oral toxicity of dithiopyr to honey bees.NonguidelineLarval honeybee acute oraltoxicityNo data NA NAYes850.4100 SeedlingEmergence and42244401 Acceptable No No --2http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2012-0543-000426OCSPPGuidelineDataRequirementSourceMRIDClassificationDatagap?Are DataNeeded toConduct theRiskAssessment?Justification and Assumptions EPA Will Make in the Absence ofDataSeedlingGrowth850.4150 VegetativeVigor42244401 Acceptable No No --NA = not applicable

# 27 

# 12 References

USEPA. 1991. Briefing Memorandu m: Registration of Dithiopyr (DIMENSION Turf Herbicide

(MON-15151), DIMENSION Turf Herbicide (MON-15104), and MON-15100 Herbicide (a

Manufacturing and Formulating Use Product).



# 13 Bibliography:

Environmental Fate Studies

40638627 Pantano, L. (1988) The Hydrolysis of MON-7200/15100, 3,5-Pyridine-dicarbothioic Acid, 2-

(Difluoromethyl)-4-(2-methylpropyl)-6- (trifluorome thyl)-,S,S-dimethyl Ester: Laboratory Project

No. MSL-7690: R.D. No. 866. Unpublished study prepared by Monsanto Agricultural Co. 62 p.

40638628 Klemm, G.; Nadeau, R.; Solsten, R. (1988) The Photolysis of MON- 7200, 3,5-Pyridinedicarbothioic Acid, 2-(Difluoromethyl)-4-(2- methylpropyl)-6-(trifluoromethyl)-,S,S-dimethyl

Ester, in Water and in Soil: Laboratory Project No. MSL-7049: R.D. No. 866. Unpublished study

prepared by Monsanto Agricultural Co. 85 p.

40638629 Pantano, L.; Sing, Y. (1988) The Aerobic Soil Metabolism of MON- 7200/15100, 3,5-Pyridinedicarbothioic Acid, 2-(Difluoromethyl)- 4-(2-m ethylpropyl)-6-(trifluoromethyl)-,S,S-dimethyl

Ester: Laboratory Project No. MSL-7781: R.D. No. 866. Unpublished study prepared by

Monsanto Agricultural Co. 88 p.

40638630 Sing, Y. (1988) Adsorption/Desorption Studies of MON-7200/15100: Laboratory Project No.

MSL-7778: R.D. No. 866. Unpublished study prepared by Monsanto Agricultural Co. 73 p.

41001517 Patano, L.; Sing, Y. (1989) The Aerobic Soil Metabolism of MON-7200/15100 3,5-

Pyridinedicarbothioic Acid, 2-(difluoro- methyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-S,Sdimethyl Ester: Study No. MSL-7781: Study No. MSL-8551. Unpublished study prepared by

Monsanto Co. 102 p.

41001518 Forbis, A.; Chott, K. (1989) Uptake, Depuration, and Bioaccumulation of ?Carbon 14|-MON7200/15100 to Bluegill Sunfish ( Lepomis macrochirus ): Laboratory Project No. MSL-8347-48:

R.D. No. 900. Unpublished study prepared by Analytical Bio-Chemistry Laboratories, Inc. in

cooperation with Monsanto Agricultural Co. 459 p.

41001519 Adams, S. (1989) Terrestrial Field Soil Dissipation Study for the Determination of MON-15100

and Its Major Soil Metabolites Following Broadcast Application of MON-15126, MON-15120

and MON-15172. Unpublished study prepared by Monsanto Agricultural Co. 3549 p.

41135601 Sing, Y.; George, C. (1989) Adsorption/Desorption Studies of Metabolites of MON7200/15100

(Dithiopyr): Monoacid-I, Monoacid-II AND dIACID: Project No. 204400/MSL-8243; R.D. No.

932. Unpublished study prepared by Monsanto Agricultural Co. 118 p.

41615601 Fleschar, E.; Mueth, M.; Gustafson, D. et al. (1990) Volatilization of Dithiopyr Residues

Following Applications to Turfgrass. Lab Project Number: MSL/9686. Unpublished study

prepared by Mon- santo Agricultural Company. 215 p.

42275512 McLanahan, R. (1990) Hydrolysis Studies of MON 13200: Lab Project Number: MSL 9711: RD

1063. Unpublished study prepared by Monsanto Agricultural Co. 69 p. Mon 13200 = Thiazopyr

PC Code 129100

# 28 42275513 McLanahan, R. (1991) Adsorption/Desorption Studies of MON 13200 AND MON 13200

Monoacid: Lab Project Number: MSL 11388. Unpublished study prepared by Monsanto Agric.,

Co. 135 p.

42275514 Oppenhuizen, M.; Allin, J.; Cowell, J. (199 1) Terrestrial Field Soil Dissipation Study of MON

13200 and its Major Soil Metabolites: Lab Project Number: MSL 11223: 88-85-R-1. Unpublished

study prepared by Monsanto Agric., Co., and Amer ican Agric., Services, In c. 1039 p. Mon 13200

= Thiazopyr

42275515 Lange, B.; George, C.; Logusch, E. (1992) Confined Rotational Crop Study of MON 13200

Herbicide Part I: In Field Portion Part II: Quantitation, Characterization and Identification of

MON 13200 and its Metabolites in Rotational Crops: Lab Project Number: MSL 11135: EF-89-

08: MSL 11136. Unpublished study prepared by Monsanto Agricultural Co., and Pan-Agricultural

Labs., Inc. 226 p. Mon 13200 = Thiazopyr

42275516 Burgess, D. (1989) Part I: Uptake, Depuration and Bioconcentration of ?carbon 14|-MON 13200

by Bluegill (Lepomis macrochirus): Lab Pr oject Number: MSL 9580: 38096: RD 1063.

Unpublished study prepared by Analytical Bio-chemistry Labs., Inc. 453 p. Mon 13200 =

Thiazopyr

42275547 Hopkins, W. (1992) Results of the Analyses of Water Samples for MON 13200: Lab Project

Number: ML-88-352: EHL 88233: RD 1063. Unpublished study prepared by Monsanto Environ.,

Health Lab. 17 p.

42395101 Lundry, D.; Howe, R. (1992) Anaerobic Aquatic Metabolism Study of MON 15100: Lab Project

Number: MSL-11841. Unpublished study prepared by Monsanto Co. 144 p.

42456601 Manning, J. (1992) Terrestrial Field Soil Diss ipation Study for the Determination of Dithiopyr and

Identified Soil Metabolites Following Broadcast Application of Dimension Turf Herbicide to Bare

Ground: Lab Project Number: MSL-12059: 39578: 39622. Unpublished study prepared by

Monsanto Co. and ABC Labs. 557 p.

42456602 Rollie-Taylor, M. (1990) Storage Stability of MON 15100 and Its Major Metabolites in Frozen

Soil: Lab Project Number: MSL- 10139: 1121. Unp ublished study prepared by Monsanto Ag Co.

102 p.

42892501 Takano, R. (1993) Dictran Water Monitoring Interim Report: 1993 Trial: Lab Project Number:

ESJ-006. Unpublished study prepared by Monsanto Japan Ltd. 8 p.

43043301 Fleschar, E.; Mueth, M.; Gustafson, D. (199 3) Response to Agency Reviews of the Previously

Submitted Study: Volatilization of Dithiopyr Residues Following Applications to Turfgrass:

MRID 41615601: Lab Project Number: MSL-9686: 1012. Unpublished study prepared by

Monsanto Agricultural Group. 54 p.

44559802 Carbone, J. (1998) Dithiopyr Use on Turf: A Validation Trial of LEACHP Using the Maidstone

Lysimeters: Lab Project Number: 98R-1023. Unpublished study prepared by Rohm and Haas

Company. 86 p.

44559803 Parsons, R. (1998) Toxicological Evaluation of New York Lysimeter Data. Unpublished study

prepared by Rohm and Haas Company. 10 p.

46603001 Adams, S. (1989) Validation of an Analytical Method for Determination of MON 15100 Residues

in Soil. Project Number: MSL/9009. Unpublished study prepared by EPL Bio-Analytical Services.

26 p.

# 29 46883818 Cowell, J.; Adams, S.; Kunstman, J.; et al . (1993) Comparison of Foliar Dissipation and Turf

Dislodgeable Residue Sampling Techniques. P. 100-112 in ACS Symposium Series: # 522

Pesticides in Urban Environments; April 5-10 , 1992, San Francisco, CA. Washington, D.C.:

American Chemical Society.

47116703 Cowell, J.; Adams, A.; Kunstman, J.; et al . (1993) Comparison of Foliar Dissipation and Turf

Dislodgeable Residue Sampling Techniques. pp. 100-112 in Pesticides in Urban Environments:

Fate and Significance by K. Racke and A. Leslie. Washington, D.C: American Chemical Society.



# Ecological Effects Studies

40638620 Grimes, J.; Jaber, M. (1987) MON 7200: An Acute Oral Toxicity Study with the Bobwhite:

Laboratory Project No. 139-235/WL-87-87: R.D. No. 866. Unpublished study prepared by

Wildlife International Ltd. 67 p.

40638621 Grimes, J.; Jaber, M. (1987) MON 7200: A Dietary LC50 Study with the Mallard: Laboratory

Project No. 139-234/WL-87-85: R.D. No. 866. Unpublished study prepared by Wildlife

International Ltd. 82 p.

40638622 Grimes, J.; Jaber, M. (1987) MON 7200: A Dietary LC50 Study with the Bobwhite: Laboratory

Project No. 139-233/WL-87-86: R.D. No. 866. Unpublished study prepared by Wildlife

International Ltd.

40638623 Bowman, J. (1987) Acute Toxicity of MON 7200 to Rainbow Trout ( Salmo gairdneri ):

Laboratory Project No. 36025/AB-87-90: R.D. No. 866. Unpublished study prepared by

Analytical Bio-Chemistry La boratories, Inc. 82 p.

40638624 Bowman, J. (1987) Acute Toxicity of MON 7200 to Bluegill Sunfish ( Lepomis macrochirus ):

Laboratory Project No. 36024/AB-87-89: R.D. No. 866. Unpublished study prepared by

Analytical Bio- Chemistry La boratories, Inc. 76 p.

40638626 Hoxter, K.; Jaber, M. (1987) MON 7200: An Acute Contact Toxicity Study with the Honey

Bee: Laboratory Project No. 139-236/WL-87- 84: R.D. No. 866. Unpublished study prepared

by Wildlife International Ltd. 20 p.

41001515 McAllister, W. (1988) Early Life Stage Toxicity of MON-7200 to Rainbow Trout ( Salmo

gairdneri ) in a Flow-through System: Laboratory Project No. AB-87-334/ABC 36552.

Unpublished study prepared by Analytical Bi o-Chemistry Laboratories, Inc. 969 p.

42050201 Blasberg, J.; Bucksath, J. (1991) Acute Toxicity of Dithiopyr Technical and MON 15151

Formulation to Daphnia magna : Lab Project Number: AB-90-582/39173: AB-90-583/39174.

Unpublished study prepared by ABC Labs, Inc. 951 p.

42244401 Canez, V.; White, T. (1992) Tier 2 Non-Target Phytotoxicity of Dithiopyr (MON 15100) to

Terrestrial Plants: Lab Project Number: 0695-91-3/BL91-470: 0695-91-2/BL91-469.

Unpublished study prepared by Pan-Agricultural Labs, Inc. 443 p.

42246401 Thompson, S. (1992) MON 7200: A 5-Day Toxicity Test with the Freshwater Alga

( Selenastrum capricornutum ): Lab Project Number: WL-91-10/139A-116. Unpublished study

prepared by Wildlife International, Ltd. 50 p.

42333301 Blasberg, J.; Hicks, S.; Bucksath, J. (1992) Chronic Toxicity Study of MON 7200 to Daphnia

magna under Flow-through Test Conditions: Lab Project Number: AB-91-376/39666.

Unpublished study prepared by ABC Labs, Inc. 43 p.

42395001 Swigert, J.; Smith, G. (1992) MON 7200: A 96-hour Flow-through Acute Toxicity Test with

the Saltwater Mysid ( Mysidopsis bahia ): Lab Project Number: WL-91-8. Unpublished study

prepared by Wildlife International, Ltd. 48 p.

# 30 42399401 Swigert, J.; Smith, G. ( 1992) Mon 7200: A 96-Hour Shell De position Test with the Eastern

Oyster ( Crassostrea virginica ): Lab Project Number: WL-91-9/139A-113A. Unpublished study

prepared by Wildlife Intl. 48 p.

42402101 Swigert, J. (1992) MON 7200: A 96-Hour Flow-through Acute Toxicity Test with the

Sheepshead Minnow ( Cyprinodon variegatus ): Lab Project Number: WL-91-7/139A-115.

Unpublished study prepared by Wildlife Intl. 47 p.

42419801 Blasberg, J. (1992) Supplemental Information in Response to Agency Reviews of the

Previously Submitted Study: Chronic Toxicity Study of MON 7200 to Daphnia magna under

Flow-through Test Conditions: Lab Project Number: AB-91-376/39666: RD 1100.

Unpublished study prepared by ABC Labs and Monsanto Company, Ag Group. 21 p.

42495601 Beavers, J.; Sipler, O.; Lynn, S.; et al. (1992) MON 7200: A One-generation Reproduction

Study with the Bobwhite ( Colinus virginianus ): Part I--In-life and Reproduction Observations:

Part II--Residue Determination of MON 7200 in Avian Tissue and Eggs: Lab Project Number:

WL-91-5/139-281: ML-91-456/91212: 1123. Unpublished study prepared by Monsanto

Agricultural Group. 225 p.

42495602 Beavers, J.; Sipler, O.; Lynn, S.; et al. (1992) MON 7200: A One-generation Reproduction

Study with the Mallard ( Anas platyrhynchos ): Part I--In-life and Reproduction Observations:

Part II--Residue Determination of MON 7200 in Avian Tissue and Eggs: Lab Project Number:

WL-91-6/139-282: ML-91-456/91212: 1124. Unpublished study prepared by Monsanto

Agricultural Group. 225 p.

42658901 Beavers, J.; Sipler, O.; Lynn, S.; et al. (1992) MON 7200: A One-Generation Reproduction

Study with the Bobwhite ( Colinus virginianus ): Part I--In-Life and Reproduction Observations:

Part II--Residue Determination of MON 7200 in Avian Tissue and Eggs: Supplement to MRID

42495601: Lab Project Number: WL-91-5/139-281: WL-91-456/91212: 1123. Unpublished

study prepared by Wildlife International, Ltd. and Monsanto Agricultural Group. 27 p.

42661001 Beavers, J.; Sipler, O.; Lynn, S.; et al. (1992) MON 7200: A One- generation Reproduction

Study with the Mallard ( Anas platyrhynchos ): Part I--In-life and Reproduction Observations:

Part II--Residue Determination of MON 7200 in Avian Tissue and Eggs: Addendum No. 1:

Lab Project Nos.: WL-91-6/139-282; ML-91-456/ 91212; 1124. Unpublished study prepared by

Wildlife International. 27 p.

44243701 Dionne, E. (1997) Dithiopyr Technical--The Chronic Toxicity to the Fathead Minnow

( Pimephales promelas ) During a Full Life-Cycle Exposure: Final Report: Lab Project Number:

96-11-6788: 86.0995.6191.122: 95RC-0188. Unpublished study prepared by Springborn Labs,

Inc. 573 p.