2 

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 (EFED) has completed the preliminary problem 

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

assessments to be conducted as part of the registration review of dithiopyr. The problem 

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

and ecological risk assessments in support of Registration Review and provides an overview of 

the environmental fate, ecological effects, and potential risks associated with the use of dithiopyr 

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

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

Major findings include the following data needs and the uncertainty 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): Mysid chronic toxicity test 

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

 OCSPP Guideline 850.4500 (TGAI): Algal toxicity, 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 invertebrates freshwater and marine (TGAI) 

Justifications for these data needs as well as assumptions 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 between the half-lives calculated 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 likelihood that concentrations of dithiopyr in compost 

could reach a level that adversely affects non-target plants. 

2 Introduction 

Dithiopyr is a systemic pyridine herbicide that is applied 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 inhibiting the formation and 

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

Susceptible plant roots are stunted and fail to function in the presence 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 information 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 registration of dithiopyr as a new chemical 

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

latest Agency science policies and risk assessment methodologies. 

3 Use Characterization 

Dithiopyr is a selective herbicide that is applied pre-emergence and early post-emergence to 

control crabgrass and other susceptible annual grasses and broadleaf 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 course turf, industrial/construction 

areas (outdoor), mulch, nonagricultural rights-of-way/fencerows/hedgerows, agricultural 

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

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

(railroad), rose, and tree nuts. Dithiopyr is formulated as an emulsifiable concentrate, flowable 

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

powder. Application equipment includes back sprayer, foam applicator, granule applicator, 

handgun, sprayer, and spreader. The chemical profile produced by BEAD, located 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, application interval, application method) may result in conservative 

assumptions. 

4 Conclusions from Previous Risk Assessments 

4.1 Ecological Risk Assessments 

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

memorandum that described available environmental fate and ecological effects data was 

produced in 1991 to support the registration of dithiopyr as a new chemical (USEPA, 1991). No 

risk conclusions were made in the document. 

4.2 Drinking Water Exposure Assessments 

A drinking water assessment was not conducted in the past for 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 are appropriate to include in the drinking water 

assessment along with the parent dithiopyr. A total toxic residue (TTR) approach will be utilized 

in the drinking water assessment to account for these potential residues of concern. 
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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 the PF for prioritization and possibly to use as 

benchmark criteria. 

Dithiopyr is not identified as a cause of impairment for any water bodies listed as impaired under 

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

been developed for dithiopyr. Any data submitted 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 the environment (on soil and in 

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

shallow, clear surface waters (average half-life ~ 19 days), but does not photolyze on soil. Major 

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

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

stable to hydrolysis at pH 5 and 7 but exhibits some alkaline-based hydrolysis (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). Dithiopyr accumulated in fish with maximum 

concentration factors of 320x, 1400x, and 930x in edible 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. However, its primary degradation 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 environmental fate and transport 

properties of dithiopyr is summarized in Table 5-1.

Table 5-1. Chemical Properties and Environmental 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 C15H16S2NO2F5

Structure 

Molecular Mass 401.4 g/mole 
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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 m3/mol Calculated1

Octanol/water partition 

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

Dissociation Constant (pKa) -- 

Hydrolysis (t1/2) 

pH 5 = stable

pH 7 = stable 

pH 9 = 1053 days (2.9 years) 

40638627 

Aqueous Photolysis (t1/2) 

(pH 7) 

17.6 days 

20.6 days 40638628 

Soil Photolysis (t1/2) 444 days 

Aerobic Soil Metabolism (t1/2) 

 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 (Koc) 

(mL/g) 

2063 

1396 

3049 

1543 

2241 

1757 

40638630 

Terrestrial Field Dissipation 

(t1/2) 

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-m3/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 photolysis, and aerobic soil metabolism studies. Table 5-2

summarizes the transformation products of dithiopyr 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 showing up in the foam volatile traps. Batch 

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

mobile to mobile, with KOC values in four soils ranging from 3 to 29 L/kg OC (MRID 

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

submitted. Therefore, the behavior of these degradates is not well understood. 
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Table 5-2. Dithiopyr and Its Major Environmental Degradates 

Code Name/ Synonym Chemical Name Chemical Structure Study Type MRID Dithiopyr MON-7200 MON-15100 

CAS Name: 3,5-Pyridinedicarbothioic acid, 2-(difluoromethyl)-4-(2-methylpropyl)- 6-(trifluoromethyl)-S,S-dimethyl ester Molecular Weight: 401.4 g/mol SMILES: CSC(=O)C1=C(N=C(C(C(=O)SC)=C1CC(C)C)C(F)(F)F)C(F)F 

Parent structure shown 

Normal Acid CAS Name: 

2-(Difluoromethyl)-4-(2 methylpropyl)-5-((methylthio)carbonyl)]- 6-(trifluoromethyl)3-pyridinecarboxylic acid 

Hydrolysis pH 9 4063862

Aqueous Photolysis 4063862Soil Photolysis 4063862Aerobic Soil Metabolism 4063862Aerobic Soil Metabolism 4100151

Reverse Acid CAS Name: 

6-(Difluoromethyl)-4-(2-methylpropyl)-5-[(methylthio)carbonyl)]- 2-(trifluoromethyl)-3- pyridinecarboxylic acid 

Aqueous Photolysis 4063862

Aerobic Soil Metabolism 4063862Aerobic Soil Metabolism 4100151

Diacid CAS Name: 

2-(Difluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl] -3, 5-pyridinedicarboxylic acid 

Aqueous Photolysis 4063862Aerobic Soil Metabolism 4063862Aerobic Soil Metabolism 4100151
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Code Name/ Synonym Chemical Name Chemical Structure Study Type MRID Degradate V CAS Name: 

3,5-bis(Methylthiocarbonyl)-2-formyl-4-(2-methylpropyl) -6-trifluoromethyl pyridine 

Aqueous Photolysis 4063862

Degradate VI CAS Name: 

3-(Methylthiocarbonyl)-2-difluoromethyl-4-(2- methylpropyl) -6-trifluoromethylpyridine 

Aqueous Photolysis 4063862

Degradate VII CAS Name: 

3-{Methylthiocarbonyl)-2-formyl-4-(2-methyl-propyl) -6-trifluoromethylpyridine 

Aqueous Photolysis 4063862

Volatiles Dithiopyr Aerobic Soil Metabolism 4063862

Aerobic Soil Metabolism 4100151

CO2 Carbon Dioxide O=C=O Aerobic Soil Metabolism 4063862

Aerobic Soil Metabolism 4100151

Unextractable Residues 

Aerobic Soil Metabolism 4063862Aerobic Soil Metabolism 4100151

CR = combined residues; aqueous photolysis study 40638628, degradate VI and VII together comprised 7.3% of the applied radioactivity.
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6 Receptors 

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

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

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

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

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

maintain the core pyridine structure of the parent. 
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Table 6-1. Summary of the Endpoints from Aquatic Toxicity Studies for Dithiopyr 

Taxon Study Type 

TGAI/TEP  (% a.i.) 

Species Toxicity Value, Effects, & 

Acute Toxicity Classification (If Applicable)

Fish (surrogate for aquatic-phase amphibians) 

Acute: 96-hour, static exposure TGAI (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 toxic 

Acute: 96-hour, static exposure TGAI (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 toxic 

Acute: 96-hour exposure Fathead minnow 

(Pimephales promelas) 

To be determined 

Early life stage: 60-day, flow-through exposure TGAI (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; also reduced survival at ≥0.20 mg/L; concentration-dependent incrin the incidence of sublethal effects including loss of equilibri

surfacing, exophthalmia, and distended abdomen) 

Full life cycle: 272-day, flow-through exposure TGAI (94.54) 

Fathead minnow (Pimephales promelas) 

To be determined 

Acute: 96-hour, flowthrough exposure TGAI (94.3) 

Sheepshead minnow (Cyprinodon variegatus) 

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, socontrol, 0.342, 0.604, 0.987, 1.549, and 2.164 mg/L treatment groups; NOAEC based on sublethal effects: at 96 hours, erratiswimming at ≥0.987 mg/L, loss of equilibrium at 1.549 mg/L) At most moderately toxic 
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Taxon Study Type 

TGAI/TEP  (% a.i.) 

Species Toxicity Value, Effects, & 

Acute Toxicity Classification (If Applicable)

Early life stage (chronic) 

Estuarine/marine fish No data 

Chronic toxicity may be characterized using toxicity data for freshwater fish (i.e., rainbow trout or fathead minnow) For example: Estimated chronic NOAEC(sheepshead minnow)

= Acute LC50(sheepshead minnow) / Acute-to-Chronic Ratio(rainbow trou

= (>2.164 mg/L) / 8.75 

≥ 0.247 mg/L 

Where: Acute-to-Chronic Ratio(rainbow trout)

= Acute LC50(rainbow trout) / Chronic NOAEC(rainbow trout)

= 0.49 mg/L / 0.056 mg/L = 8.75 

Aquatic invertebrates 

Acute limit test: 48-hour, static exposure TGAI (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 toxic 

Acute: 48-hour, static exposure Form. (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 toxic 

Life cycle (chronic): 21-day, flow through exposure TGAI (92.2) 

Water flea(Daphnia magna) 

21-day NOAEC = 0.081 mg a.i./L 21-day LOAEC = 0.19 mg a.i./L 7-day EC50 = 0.25 mg a.i./L 

(based on survival; 100% mortality by day 21 at 0.19 and 0.36 mg/L) 

Sediment acute/chronic Sediment-dwelling 

invertebrate 

No data 
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Taxon Study Type 

TGAI/TEP  (% a.i.) 

Species Toxicity Value, Effects, & 

Acute Toxicity Classification (If Applicable)

Acute: 96-hour, flow through exposure TGAI (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 toxic 

Acute: 96-hour, flow through exposure TGAI (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 hours at ≥0.467 mg/L; lethargy at all test concentrations at 72 hours) Highly toxic 

Life cycle (chronic) Estuarine/ 

marine invertebrate 

No data 

Aquatic vascular plant 

NA Duckweed 

(Lemna gibba) 

No data 

Aquatic nonvascular plant: 5-day, static exposure 

TGAI (94.3) 

Green alga (Selenastrum carpicornutum) 

EC50 = 20 μg a.i./L (mm)aNOAEC = 7.6 μg a.i./L (mm) (based on cell density) 

NA Freshwater diatom No data 

Marine diatom No data Cyanobacterium No data 

 mm = mean measured; NA = not applicable a The raw data for this study will be subjected to new statistical analysis because the present EC50 was determined using probit analysis 

regression analysis. 
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Table 6-2. Summary of the Endpoints from Terrestrial Toxicity Studies for Dithiopyr 

Taxon Study Type 

TGAI/TEP  (% a.i.) 

Species Toxicity Value, Effects, & 

Acute Toxicity Classification (If Applicable)

Birds (surrogate for reptiles and terrestrialphase amphibians) 

Acute oral: single dose, 14-day observation TGAI (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 10-14 ; at ≥ 486 mg/kg-bw, 1-4 birds with ruffled appearancand/or wing drop from days 0-3; at ≥810 mg/kg-bw, 1 lethafemale on days 1-2; at 810 mg/kg-bw, 1 female with ruffled appearance on days 13-14) Practically non-toxic 

Acute oral Passerine species No data Sub-acute dietary: 5-day exposure; 3-day postexposure observation TGAI (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-toxic 

Sub-acute dietary: 5-day exposure; 3-day postexposure observation TGAI (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 gat 5620 mg/kg-diet) Practically non-toxic 

Reproduction (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) 

Reproduction (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-day survival/eggs set [~9.2%]a) 

Terrestrial invertebrates 

Acute contact: single dose, 48-hour observation TGAI (91.5) 

Honey bee (Apis mellifera)

LD50 (95% C.I.) = 81 (53-256) μg a.i./bee (nom) 

NOAEL: Not specified Practically non-toxic 
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Taxon Study Type 

TGAI/TEP  (% a.i.) 

Species Toxicity Value, Effects, & 

Acute Toxicity Classification (If Applicable)

Acute dietary (oral) Honey bee 

(Apis mellifera) 

No data 

Larval honey bee (Apis mellifera) 

No data 

Terrestrial plants 

Seedling emergence TGAI (91.6) 

Most sensitive monocot: Onion 

IC25 = 0.0026 lb a.i./Ab

IC05 = To be determinedb

NOAEC = 0.0031 lb a.i./Ab

(based on dry weight) 

Most sensitive dicot: Lettuce 

EC25 = 0.0082 lb a.i./Ab

EC05 = To be determinedb

NOAEC = 0.023 lb a.i./Ab

(based on height) 

Vegetative vigor TGAI (91.6) 

Most sensitive monocot: Ryegrass 

EC25 = 0.041 lb a.i./Ab

EC05 = To be determinedbNOAEC = 0.074 lb a.i./Ab

(based on dry weight) 

Most sensitive dicot: Soybean 

IC25 = 0.11 lb a.i./A 

NOAEC = 0.025 lb a.i./A (based on height) 

NA = not applicable ; nom = nominal a reductions were not statistically significant b Since the NOAEC is greater than the EC25, the EC05 will be determined via new statistical analysis of the raw data and used to estimat
15 

6.1 Ecological Incidents 

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

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

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

Conservancy, indicates a total of 32 reported ecological incidents associated with the use of 

dithiopyr. These incidents are summarized in Table 6-3. 

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

certainty categories regarding the likelihood that the use of dithiopyr caused the 32 incidents 

ranged from possible (2 incidents) to probable (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 further evaluated to determine if the reported 

incidents represent current patterns of use for dithiopyr. Examples of additional considerations 

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

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

In addition to the incidents recorded in EIIS and AIMS, additional incidents have been reported 

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

incidents to the Agency as aggregate counts of incidents occurring per product per quarter. 

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

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

incidents include reports of adverse 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. Unless additional information on these aggregated incidents 

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

the risk assessment. 
16 

Table 6-3. Summary of Ecological Incidents Involving Dithiopyr as Documented in the Ecological Incident Inform

Taxon Affected 

Incident ID Use Site Date Legality Certainty State County Total Magnitude 

Plants I000133-001 Turf, golf course 1992 Misuse (accidental) Probable TX Not specified Golf course greens Plants I000301-001 Turf, golf course 1992 Undetermined Probable AZ Not specified Not specified Plants I000301-002 Turf, golf course 1992 Undetermined Probable AZ Not specified 3 golf greens Plants I000301-003 Turf, golf course 1992 Undetermined Probable AZ Not specified 1 golf green Plants I000301-004 Turf, golf course 1992 Undetermined Probable IL Not specified 18 golf greens Plants I000301-005 Turf, golf course 1992 Undetermined Probable IN Not specified Unknown Plants I000301-006 Turf, golf course 1992 Undetermined Probable MI Not specified 17 golf greens Plants I000301-007 Turf, golf course 1992 Undetermined Probable MO Not specified 1 golf green Plants I000301-008 Turf, golf course 1992 Undetermined Probable NV Not specified 18 golf greens Plants I000301-009 Turf, golf course 1992 Undetermined Probable NC Not specified Golf greens, tees Plants I000301-010 Turf, golf course 1992 Undetermined Probable NC Not specified Golf greens Plants I000301-011 Turf, golf course 1992 Undetermined Probable OK Not specified Golf greens Plants I000301-012 Turf, golf course 1992 Undetermined Probable OH Not specified Golf fairway Plants I000301-013 Turf, golf course 1992 Undetermined Probable OH Not specified 18 golf greens Plants I000301-014 Turf, golf course 1992 Undetermined Probable OH Not specified Golf greens and tees Plants I000301-015 Turf, golf course 1992 Undetermined Probable OH Not specified 18 golf greens Plants I000301-016 Turf, golf course 1992 Undetermined Probable OH Not specified 1 golf green Plants I000301-017 Turf, golf course 1992 Undetermined Probable PA Not specified 3 golf greens Plants I000301-018 Turf, golf course 1992 Undetermined Probable SC Not specified 18 golf greens Plants I000301-019 Turf, golf course 1992 Undetermined Probable SC Not specified 18 golf greens Plants I000301-020 Turf, golf course 1992 Undetermined Probable TX Not specified 18 golf greens Plants I000301-021 Turf, golf course 1992 Undetermined Probable TX Not specified 18 golf greens Plants I000301-022 Turf, golf course 1992 Undetermined Probable TX Not specified 18 golf greens Plants I000301-023 Turf, golf course 1992 Undetermined Probable TX Not specified Golf greens Plants I000301-024 Turf, golf course 1992 Undetermined Probable TX Not specified 18 golf greens Plants I000301-025 Turf, golf course 1992 Undetermined Probable TX Not specified Golf greens Plants I000301-026 Turf, golf course 1992 Undetermined Probable TX Not specified Golf greens Plants I003629-001 Turf, golf course 1992 Undetermined Probable VA Chesapeake City Unknown Plants I003629-004 Agricultural area NS Undetermined Probable NE Douglas Unknown Plants I016671-001 Right-of-way 2005 Registered use Possible CA Sutter 75 to 100 trees Plants I020998-034 Not specified 2003 Undetermined Possible WA Chelan Not specified Plants I021002-002 Lettuce 2009 Misuse (accidental) Probable CA Salinas 125 acres 

NS = not specified *Dithiopyr is not listed on the Kerb label. Upon investigation, Dow Agrosciences determined that a small portion of the Kerb package containe
17 

7 Exposure Pathways of Concern 

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

drift, atmospheric deposition, and runoff represent potential transport 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 between the half-lives calculated 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 likelihood that concentrations of dithiopyr in compost 

could reach a level that adversely affects non-target plants. 

Drinking water and inhalation exposure pathways were screened 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/models/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 terrestrial and aquatic organisms 

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

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

considered the stressors of ecological concern, and 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 the 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 residues 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 acid 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 agencies, and this route of 

exposure will be considered in the assessment to the extent that data on dithiopyr are available. 

8.3 Measures of Effect 

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

quotients. Any additional information submitted by the 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 provide insight into the direct and indirect effects 

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

from changes in structure and functional characteristics 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 threatened and/or endangered (listed) species from 

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

listed species is further described at 

http://www.epa.gov/oppfead1/endanger/litstatus/riskasses.htm. 

10 Endocrine Disruptors Screening Program 

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

EDSP testing. For additional information 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, and 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 40638627 Acceptable No -- 

835.2240 Aqueous 

photolysis 

40638628 Acceptable No -- 

835.2410 Soil photolysis 40638628 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 classifications, and whether or not further data are needed in order 

to support the risk assessment. 

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

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

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

In the absence of these data, the toxicity of the normal and reverse acid degradates of dithiopyr to 

terrestrial and aquatic organisms are assumed to be comparable to that of dithiopyr. 
21 

Table 11-2. Submitted Aquatic Ecological Effects Data for Dithiopyr OCSPP Guideline 

Data Requirement 

Source MRID 

Classification Data 

Gap?

Are Data 

Needed to 

Conduct the 

Risk 

Assessment? 

Justification and Assumptions EPA Will Mak

 850.1010 Freshwater 

invertebrate acute toxicity 

42050201 Acceptable No No -- 

850.1025 850.1035 850.1045 850.1055 

Saltwater invertebrate acute toxicity 

42399401 (mollusk) 

Acceptable No No -- 

42395001 (mysid) 

Acceptable 

 850.1075 Freshwater fish 

acute toxicity 

40638623 (cold water) 

Acceptable No No -- 

40638624 (warm water) 

Acceptable 

 850.1075 Saltwater fish 

acute toxicity 

42402101 Acceptable No No -- 

 850.1300 Freshwater 

invertebrate life cycle 

42333301 42419801 

Acceptable No No -- 

 850.1350 Saltwater 

invertebrates life cycle 

No data NA Yes Yes Aquatic invertebrate life cycle toxicity data for 

invertebrate are required under 40 CFR Part 158 to enter the environment in significant concentrexpected use or mobility patterns or if the acute 

mysid LC50 = 0.586 mg/L; MRID 42395001). A 

submitted for this data requirement.

A guideline-compliant estuarine/ marine inverteneeded. Dithiopyr is more acutely toxic to estu(i.e., M. bahia) than to freshwater invertebrates 

addition, an acute-to-chronic ratio derived from 

be used to estimate a chronic toxicity value for M
22 

OCSPP Guideline 

Data Requirement 

Source MRID 

Classification Data 

Gap?

Are Data 

Needed to 

Conduct the 

Risk 

Assessment? 

Justification and Assumptions EPA Will Maktoxicity value for D. magna is non-definitive. 

In the absence of these data, estuarine/marine indata for surrogate pesticides – starting with data pesticides (e.g., pyridine herbicides) and proceerelated pesticides – may be used to characterize 

dithiopyr to estuarine/marine invertebrates. 

 850.1400 Freshwater fish 

early-life stage 

41001515 Acceptable No No -- 

 850.1400 Saltwater fish 

early-life stage 

No data NA Yes No In the absence of these data, an acute-to-chronic 

toxicity data for freshwater fish may be used to toxicity of dithiopyr to estuarine/marine fish. Tyield a conservative estimate of the chronic toxiestuarine/marine fish given the non-definitive asheepshead minnow. 

 850.1500 Fish life cycle 44243701 

(freshwater) 

In review No No -- 

Nonguideline Whole sediment: 

chronic invertebrates freshwater and marine 

No data NA Yes Yes Chronic sediment invertebrate toxicity data are 

Part 158 if: 

i. the estimated environmental concentra

> 0.1 of the acute LC50/EC50 values; 

ii. the half-life of the pesticide in sedimen

aerobic soil or aquatic metabolism studfollowing exist: A. The soil partition coefficient (Kd) B. The log Kow is ≥ 3. C. The Koc is ≥ 1,000. 

Preliminary modeling via PRZM/EXAMSa indi

pore water EECs of ~10 μg/L which is approxim

Eastern oyster (i.e., 158 μg/L); the half-lives of 

soil metabolism studies are all >300 days; and t
23 

OCSPP Guideline 

Data Requirement 

Source MRID 

Classification Data 

Gap?

Are Data 

Needed to 

Conduct the 

Risk 

Assessment? 

Justification and Assumptions EPA Will Makdithiopyr are 4.75 and >1300 mL/g, respectivelyChronic sediment tests with the midge Chironomamphipod Hyalella azteca, and/or estuarine/marLeptocheirus plumulosus are recommended. A toxicity data from sub-chronic (10-day) sedimenthree species may be used to determine which schronic toxicity testing. In the absence of these data, sediment-dwelling toxicity data for surrogate pesticides – starting wrelated pesticides (e.g., pyridine herbicides) and 

less related pesticides – may be used to charactedithiopyr to sediment-dwelling invertebrates. 

850.4400 Aquatic plant 

toxicity test using Lemna

spp. 

No data NA Yes Yes A study with Lemna spp. has not been submitte

test with Lemna is needed. 

In the absence of these data, Lemna toxicity datstarting with data for closely related pesticides (and proceeding to data for less related pesticidecharacterize the acute toxicity of dithiopyr to aq

850.4500 Algal toxicity 42246401 

(green alga) 

Acceptable No Yes Studies with a marine diatom and a freshwater d

submitted. Guideline-compliant algal toxicity t

diatom and a marine diatom are needed. In the absence of these data, diatom toxicity datstarting with data for closely related pesticides (and proceeding to data for less related pesticidecharacterize the acute toxicity of dithiopyr to frediatoms. 

No data (marine diatom) 

NA Yes 

No data (freshwater diatom) 

NA Yes 

850.4550 Cyanobacteria No data NA Yes Yes A study with cyanobacteria has not been submit
24 

OCSPP Guideline 

Data Requirement 

Source MRID 

Classification Data 

Gap?

Are Data 

Needed to 

Conduct the 

Risk 

Assessment? 

Justification and Assumptions EPA Will Mak

toxicity compliant cyanobacteria toxicity test is needed. 

In the absence of these data, cyanobacteria toxic

pesticides – starting with data for closely related herbicides) and proceeding to data for less relatused to characterize the acute toxicity of dithiop

NA = not applicable a PRZM/EXAMS scenario PA Turf; first application date: June 01; broadcast aerial application modeled as 95% application efficie

applications @ 0.5208 lb a.i./acre; 30-day application interval 

Table 11-3. Submitted Terrestrial Ecological Effects Data for DithiopyrOCSPP Guideline 

Data Requirement 

Source MRID 

Classification Data 

gap? 

Are Data 

Needed to 

Conduct the 

Risk 

Assessment?

Justification and Assumptions EPA Will MData 

 850.2100 Avian oral 

toxicity 

40638620 (upland game) 

Acceptable Yes Yes Acute oral toxicity data for a passerine specie

new 40 CFR Part 158. A study has not been requirement. A guideline-compliant passerine acute oral toAcute oral toxicity data are only available for bobwhite quail). Sublethal effects were noted with bobwhite quail. Passerine birds may utilthat are different from larger birds and therefodithiopyr. Furthermore, passerines exhibit bepesticide dosing that are potential indicators ofield (e.g., regurgitation of contaminated diet) 

biochemically-mediated lethal toxicity is not In the absence of these data, passerine toxicity pesticides – starting with data for closely rela

No data (passerine) 

NA 
25 

OCSPP Guideline 

Data Requirement 

Source MRID 

Classification Data 

gap? 

Are Data 

Needed to 

Conduct the 

Risk 

Assessment?

Justification and Assumptions EPA Will MData pyridine herbicides) and proceeding to data fomay be used to characterize the acute toxicity species.

 850.2200 Avian dietary 

toxicity 

40638622 (upland game) 

Acceptable No No -- 

40638621 (waterfowl) 

Acceptable 

 850.2300 Avian 

reproduction 

42495601 (upland game) 

Acceptable No No -- 

42661001 (waterfowl) 

Acceptable 

 850.3020 Honey bee acute 

contact toxicity 

40638626 Acceptable No No -- 

Nonguideline Honey bee acute oral toxicity No data NA NA Yes The “White Paper in Support of the Proposed 

for Bees” as submitted to the FIFRA Scientifi

proposes a screening-level risk assessment prcontact and oral toxicity tests with adult bees test with larval bees. Larval and adult honey data are not available. In the absence of these data, honey bee oral topesticides – starting with data for closely rela

pyridine herbicides) and proceeding to data fomay be used to characterize the oral toxicity o

Nonguideline Larval honey bee acute oral 

toxicity 

No data NA NA Yes 

850.4100 Seedling 

Emergence and 

42244401 Acceptable No No -- 

2 http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPP-2012-0543-0004
26 

OCSPP Guideline 

Data Requirement 

Source MRID 

Classification Data 

gap? 

Are Data 

Needed to 

Conduct the 

Risk 

Assessment?

Justification and Assumptions EPA Will MData 

Seedling Growth 

850.4150 Vegetative 

Vigor 

42244401 Acceptable No No -- 

NA = not applicable
27 

12 References 

USEPA. 1991. Briefing Memorandum: 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- (trifluoromethyl)-,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-methylpropyl)-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. (1991) 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 American Agric., Services, Inc. 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 Project 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 Dissipation 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. Unpublished 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. (1993) 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 Laboratories, 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 Laboratories, 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 Bio-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 Deposition 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.