resulting from pesticide interaction with soil microorganisms in aerobic (oxygen-rich) 

conditions in the laboratory. The fate of pendimethalin formed in or deposited on soil 

cannot be characterized without the requested data. The Agency is asking for a minimum 

environmental fate data set for the pendimethalin in order to estimate aquatic and 

terrestrial exposure. Without these data, exposure estimates will be based on 

conservative assumptions. 

2. Environmental Chemistry Methods and Associated Independent Laboratory Validation 

(soil and water) (850.6100): Independently validated analytical methods for residues in 

water, sediment, and soil (environmental chemistry methods) submitted by the registrant 

are used to evaluate analyses described in submitted environmental fate and ecological 

effects studies. Submitted analytical methods are also used by various Federal, State, 

Tribal, and local agencies to detect and monitor residues that are or are suspected to be in 

environmental compartments due to outdoor uses and accidental releases. Independent 

laboratory validations for submitted analytical methods are necessary to confirm that the 

methods are functional and to confirm the levels of detection and quantitation reported in 

registrant-prepared validations (MRIDs 45364705, 45364706, 45163802, and 45136801).

The available effects data are considered incomplete for the purposes of risk assessment. The 

following data gaps exist:

1. Avian acute oral toxicity (OCSPP guideline # 850.2100). Avian acute oral toxicity data 

are not available for passerines, which are required under the new 40 CFR Part 158.

2. Whole sediment chronic invertebrates (in prep OCSPP guideline #s 850.1760, 850.1770, 

and 850.1780)1. No acceptable chronic or sediment toxicity tests for freshwater or 

marine invertebrates have been submitted for pendimethalin to satisfy the Agency’s 

updated data requirements for outdoor uses in 40 CFR Part 158 (October 26, 2007). 

Chronic whole sediment tests on Hyalella azteca, Chironomus tentans, and Leptocheirus 

plumulosus are requested. 

3. Saltwater Aquatic Invertebrate Life Cycle (OCSPP guideline # 850.1350). No chronic 

invertebrate tests for marine invertebrates have been submitted for pendimethalin to 

satisfy the Agency’s data requirements for outdoor uses in 40 CFR Part 158). A chronic 

life cycle study on a saltwater invertebrate is requested. 

 1 As an alternative to recommending the conduct of 2 chronic (life cycle) sediment toxicity tests, EFED would also 

consider a tiered testing approach for sediment toxicity testing. In this approach, sediment toxicity testing would 

first be conducted with the aforementioned species using the 10-d (subchronic) sediment toxicity test guidelines 

(OSCPP 850.1735 and 850.1740). Then, pending a comparison of estimated environmental concentrations (EEC) in 

sediment and porewater with toxicity results from the 10-d sediment toxicity studies, the need for one or more 

chronic sediment toxicity studies would be determined. This tiered testing approach has the potential advantage of 

reducing the number of chronic (life cycle) studies that would be needed when results of the 10-d (subchronic) tests 

in conjunction with sediment EECs indicate chronic testing is not likely to alter risk assessment conclusions. In 

some cases, however, this tiered testing approach may result in the conduct of both a 10-d (subchronic) and a 

chronic (life cycle) study.
4. Saltwater Fish Early-Life Cycle (OCSPP guideline # 850.1400). No chronic fish tests for 

marine invertebrates have been submitted for pendimethalin to satisfy the Agency’s data 

requirements for outdoor uses in 40 CFR Part 158). A chronic life cycle study on a 

saltwater fish is requested. 

5. Vegetative vigor and seedling emergence (OSCPP guideline #s 850.4150 and 850.4250). 

No acceptable toxicity data are currently available to assess the risk of pendimethalin to 

non-target terrestrial plants. Since pendimethalin has many outdoor uses, vegetative vigor 

and seedling emergence studies are needed. In addition, four minor terrestrial plant 

incidents have been reported to the Agency involving pendimethalin. Phytotoxicity data 

are needed to assess the impact of pendimethalin on non-target terrestrial plants.

6. Aquatic plant growth (OSCPP quidline #s 850.4400 and 850.5400). No acceptable 

toxicity data are currently available to assess the risk of pendimethalin to non-target 

aquatic nonvascular and vascular plants. Since pendimethalin has many outdoor uses, 

aquatic plant growth toxicity studies are requested with either cypermethrin technical or a 

typical end-use product.

Additional detail on the current data gaps for environmental fate and effects is provided in 

Section 7.9. 
Problem Formulation for the Environmental Fate and 

Ecological Risk, Endangered Species, and Drinking 

Water Assessments in Support of the Registration 

Review of Pendimethalin

N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine

CAS Registry Number: 40487-42-1

PC Code: 108501

Prepared by:

Elizabeth Riley, Biologist

Ibrahim Abdel-Saheb, Ph.D, Environmental Scientist

U. S. Environmental Protection Agency

Office of Pesticide Programs

Environmental Fate and Effects Division

Environmental Risk Branch VI

1200 Pennsylvania Ave., NW

Mail Code 7507P

Washington, DC 20460

Reviewed by:

William P. Eckel, Senior Scientist

Stephen Carey, Biologist

August 30, 2012

Office of Chemical Safety 

and Pollution Prevention
2

Table of Contents 

1 PURPOSE ...................................................................................................................................................... 3

2 PROBLEM FORMULATION.............................................................................................................................3

2.1 NATURE OF REGULATORY ACTION ...........................................................................................................................3

2.2 PREVIOUS RISK ASSESSMENTS.................................................................................................................................3

3 STRUCTURE AND PHYSICAL/CHEMICAL PROPERTIES OF PARENT..................................................................6

3.1 OVERVIEW OF PESTICDE USAGE ..............................................................................................................................7

3.2 ENVIRONMENTAL FATE AND TRANSPORT ................................................................................................................12

4 RECEPTORS................................................................................................................................................. 17

4.1 AQUATIC AND TERRESTRIAL EFFECTS ......................................................................................................................17

4.1.1 Terrestrial Animals...............................................................................................................................17

4.1.2 Aquatic Animals...................................................................................................................................19

4.1.3 Plants...................................................................................................................................................22

4.2 INCIDENT DATABASE REVIEW................................................................................................................................23

4.3 ECOSYSTEMS POTENTIALLY AT RISK........................................................................................................................25

5 ASSESSMENT ENDPOINTS ........................................................................................................................... 25

6 CONCEPTUAL MODEL ................................................................................................................................. 26

6.1 RISK HYPOTHESIS ...............................................................................................................................................26

6.2 CONCEPTUAL DIAGRAM.......................................................................................................................................27

7 ANALYSIS PLAN........................................................................................................................................... 30

7.1 STRESSORS OF CONCERN......................................................................................................................................31

7.2 MEASURES OF EXPOSURE.....................................................................................................................................31

7.3 MEASURES OF EFFECT .........................................................................................................................................35

7.4 INTEGRATION OF EXPOSURE AND EFFECTS ...............................................................................................................36

7.5 DETERMINISTIC AND PROBABILISTIC ASSESSMENT METHODS ......................................................................................36

7.6 ENDANGERED SPECIES ASSESSMENTS .....................................................................................................................36

7.7 DRINKING WATER ASSESSMENT ............................................................................................................................37

7.8 ENDOCRINE DISRUPTOR SCREENING PROGRAM........................................................................................................37

7.9 PRELIMINARY IDENTIFICATION OF DATA GAPS..........................................................................................................38

7.9.1 Environmental Fate Data Gaps............................................................................................................38

7.9.2 Effects ..................................................................................................................................................39

8 LITERATURE CITED...................................................................................................................................... 45

9 FATE AND ECOTOXICITY BIBLIOGRAPHY ..................................................................................................... 46

APPENDIX A. PRD DATA REQUEST JUSTIFICATION TABLES ........................................................... 59

APPENDIX B. REPORTED PENDIMETHALIN ECOLOGICAL INCIDENT SUMMARIES IN THE EIIS 

DATABASE ....................................................................................................................................................... 63
3

1 Purpose

The purpose of this problem formulation is to provide the foundation for the ecological risk 

assessment being conducted for the registered uses of pendimethalin. As such, it articulates the 

purpose and objectives of the risk assessment, evaluates the nature of the problem, and provides 

a plan for analyzing the data and characterizing the risk (USEPA, 1998). Additionally, this 

problem formulation is intended to identify data gaps, uncertainties, and potential assumptions 

needed to address those uncertainties in characterizing the ecological risk associated with the 

registered uses of pendimethalin. 

2 Problem Formulation

2.1 Nature of Regulatory Action 

This report is the Environmental Fate and Effects Division’s (EFED) Problem Formulation for 

the Registration Review of pendimethalin. Previous risk assessments were completed for the use 

of this chemical, which serve as the basis for this document.

The Food Quality Protection Act (FQPA) of 1996 mandated the EPA to implement registration 

review (http://www.epa.gov/oppsrrd1/registration_review/). All pesticides distributed or sold in 

the United States generally must be registered by the EPA. The decision to register a pesticide is 

based on the consideration of scientific data and other factors showing that it will not cause 

unreasonable risks to human health, workers, or the environment when used as directed on 

product labeling. In addition, it must not be expected to cause unreasonable adverse effects to 

human health through the dietary and residential routes of exposure under the Federal Food Drug 

and Cosmetic Act (FFDCA). The registration review program is intended to ensure that, as the 

ability to assess risk evolves and as policies and practices change, all registered pesticides 

continue to meet the statutory standard of no unreasonable adverse effects to human health and 

the environment. Changes in science, public policy, and pesticide use practices will occur over 

time. Through the registration review program, the Agency periodically reevaluates pesticides to 

make sure that as change occurs, products in the marketplace can be used safely. 

As part of the implementation of the Registration Review program pursuant to Section 3(g) of 

the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), the Agency is conducting an 

evaluation to determine whether pendimethalin continues to meet the FIFRA standard for 

registration. This problem formulation for the environmental fate and ecological risk assessment 

chapter, in support of the registration review, is intended for the initial docket opening the public 

phase of the review process.

2.2 Previous Risk Assessments 

Pendimethalin was patented by American Cyanamid in 1972 and first registered in the United 

States in 1974. Pendimethalin is a dinitroaniline herbicide which selectively controls certain 

broadleaf weeds and grassy weed species in certain crop and non-crop areas. It is applied to soil 

pre-plant, pre-emergence, and post-emergence, with ground and aerial equipment. 

The Reregistration Eligibility Decision Document [RED], published in June 1997, concluded 

that uses of pendimethalin would not cause unreasonable risks to the environment, though risks 

were identified for listed and non-listed fish and aquatic invertebrates as well as terrestrial and 

aquatic plants and listed and non-listed birds and mammals. 
4

Pendimethalin is currently registered for use on a variety of agricultural crops, turf, and 

ornamentals. It can be broadcasted by air or ground and/or be banded as a directed spray or 

applied via irrigation equipment. Currently registered maximum single application rates of 

pendimethalin range from approximately 1 to 6 lb a.i./A with a seasonal application rates range 

from 4 to 6 lbai/A. Recent pendimethalin ecological risk assessments include the litigationrelated California red-legged frog (CRLF) assessment (USEPA, 2009) a Section 3 new use 

assessment for artichoke, asparagus, brassica subgroup 5a, and grapes (USEPA, 2007; DP 

334069) and a Section 3 new use assessment for edamame and cold- and warm-weather forage 

grass (USEPA, 2010; DP 378514). 

The most recent review performed for pendimethalin was the Section 3 New Use registration for 

use on leaf lettuce, brassica leafy greens subgroup 5B, turnip greens, melon subgroup 9A, 

succulent soybean (edamame) and small fruit vine climbing subgroup 13-07E except grapes (DP 

391166 and DP 391167, March 20012). The screening-level risk assessment indicated that 

pendimethalin on these crops has the potential for direct acute effects to listed freshwater fish, 

estuarine/marine fish, estuarine/marine invertebrates, and aquatic vascular and non-vascular 

plants (including risk to non-listed aquatic non-vascular plants). With respect to terrestrial 

animals, direct acute and chronic effects to listed and non-listed birds and mammals are possible. 

In addition, acute and chronic effects to piscivorous birds and mammals via ingestion of 

pendimethalin residues in aquatic biota may be possible; however, depuration of pendimethalin 

was observed in the submitted blue gill sunfish study, which may reduce the potential for 

bioaccumulation. Risks to terrestrial plants are also predicted.

National Water Quality Assessment (NAWQA)

Pendimethalin is included in the NAWQA sampling and analysis program 

(http://infotrek.er.usgs.gov/apex/f?p=136:23:0:QUERY:NO:::, accessed 4/05/2012). It was 

measured in 21.28% of water samples as “code 82683, Pendimethalin_ water_ filtered_ (0.7 

micron glass fiber filter)_recoverable_micrograms per liter” and 0.7% of water samples as “code 

61665, 4-(Hydroxymethyl) pendimethalin_water_filtered_recoverable_micrograms per liter”. 

Pendimethalin was measured, with detection limits ranging from 0.004 to 0.022 ppb, in all 50 

states. Table 3.1 below gives the toal number of samples analyzed for water and the total number 

of pendimethalin detects in each state. 
5

Table 3.1. Number of NAWQA Water Samples analyzed for Pendimethalin and number of detects1

State No. of Water 

Samples

No. of Detects State No. of Water 

Samples

No. of Detects

AL 419 95 MO 209 13

AK 39 0 MT 94 1

AZ 229 35 NE >500 141

AR 118 3 NV 318 25

CA >500 >500 NH 82 0

CO >500 128 NJ >500 60

CT 214 3 NM 190 2

DE 87 0 NY 394 45

DC 4 1 NC 401 45

FL 419 4 ND 74 1

GA >500 128 OH 316 50

HI 56 1 OK 62 1

ID 380 3 OR 303 104

IL 449 104 PA >500 127

IN 430 122 RI 12 0

IA 407 36 SC 306 8

KS 180 1 SD 5 0

KY 13 1 TN 347 27

LA 388 74 TX >500 184

ME 77 0 UT 336 49

MD 293 48 VT 39 0

MA 219 12 VA 390 68

MI 232 14 WA >500 82

MN 430 15 WV 101 0

MS 187 89 WI 395 43

WY 99 1 1 Detection limits range from 0.004 to 0.022 ppb.

Aquatic Life Criteria and Aquatic Life Benchmarks

The Clean Water Act requires the Agency to publish water quality criteria that accurately reflect 

the latest scientific knowledge on the kind and extent of all identifiable effects on health and 

welfare which might be expected from the presence of pollutants in any body of water, including 

ground water. While these recommended criteria do not, in themselves, impose any 

requirements, states and authorized tribes can use them to develop water quality standards. The 

US EPA Aquatic Life Ambient Water Quality Criteria document may be found at 

http://www.epa.gov/waterscience/criteria/ (accessed 4/09/12). No criteria for pendimethalin

have been published.

Impaired Water Bodies

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

under section 303(d) of the Clean Water Act1. In addition, no Total Maximum Daily Loads 

 1 http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=885
6

(TMDL) have been developed for Pendimethalin2. More information on impaired water bodies 

and TMDLs can be found at the Agency’s website3. The Agency invites submission of water 

quality data for this pesticide. To the extent possible, data should conform to the quality 

standards in Appendix A of the OPP Standard Operating Procedure: Inclusion of Impaired 

Water Body and Other Water Quality Data in OPP’s Registration Review Risk Assessment and 

Management Process4 in order to ensure they can be used quantitatively or qualitatively in 

pesticide risk assessments.

For pendimethalin, OPP has published aquatic life benchmarks for freshwater species, based on 

the most sensitive species from the most recent risk assessments (refer to the following site 

http://www.epa.gov/oppefed1/ecorisk_ders/aquatic_life_benchmark.htm#benchmarks accessed 

4/09/12). The benchmarks are 69 ppb (fish acute), 6.3 ppb (fish chronic), 140 ppb (invertebrate 

acute), 14.5 ppb (invertebrate chronic), 5.2 ppb (non-vascular plant acute), and 12.5 ppb 

(vascular plant acute).

3 Structure and Physical/Chemical Properties of Parent

Table 4.1 provides some identification information for pendimethalin. The general structure of 

pendimethalin is provided in Figures 4-1.

Figure 4-1. The general structure of pendimethalin

Table 4.2 lists various important physicochemical characteristics of pendimethalin. 

 2 http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id=885&p_pollutant_group_name=PESTICIDES 3 http://www.epa.gov/owow/tmdl/

4 http://www.epa.gov/oppsrrd1/registration_review/water_quality_sop.htm.
7

TABLE 4.2. General Chemical Properties 

Fate Property Value (unit) MRID (or source) 

Trade and Other Names Prowl, Squadron 1997 RED

CAS Registry Number: 40487-42-1 1997 RED

Empirical Formula C13H19N3O4 1997 RED

Molecular Weight 281.31 

Foot Print Pesticide 

Database 

@http://sitem.herts.ac.

uk/aeru/footprint/en/in

dex.htm

Henry’s constant (atm-m3/mol) 4.04x 10-5 calculated

Vapor Pressure (mmHg) 3.0x10-5 MRID# 00153766 

Water Solubility (mg/L.) 0.275 MRID#46861302

Octanol-water partition coefficient (Log 

KOW) pH 7, 20oC

152, 000 (5.18)

Foot Print Pesticide 

Database 

@http://sitem.herts.ac.uk

/aeru/footprint/en/index.h

tm

Dissociation Constant (pKa) at 25o

C 2.8

Foot Print Pesticide 

Database 

@http://sitem.herts.ac.uk

/aeru/footprint/en/index.h

tm

Chemical Family Dinitroaniline 1997 RED

SMILES Code [O-][N+](=O)c1c(c(cc([N+]([O-

])=O)c1NC(CC)CC)C)C

Foot Print Pesticide 

Database 

@http://sitem.herts.ac.uk

/aeru/footprint/en/index.h

tm

Mode of Action of Herbicide

Pendimethalin is a selective herbicide registered for control of broadleaf weeds and grassy weed 

species on a variety of agricultural crops, turf, and ornamentals. Pendimethalin disrupts the 

process of mitosis in the growth of shoots and roots. It acts as a microtubule disruptor by 

inhibiting cell division and cell elongation in plants, and is generally applied early in the growing 

season. Adsorption of the herbicide takes place at the roots and shoots. Very little translocation 

occurs from the site of intake.

3.1 Overview of Pesticde Usage

Pendimethalin is applied as a liquid spray formulation. Pendimethalin can be applied either by 

aerial equipment or using ground equipment to a variety of agricultural and non-agricultural 

sites. It can be broadcasted by air or ground, and be banded as a directed spray or applied by 

irrigation equipment in various crops. It can also be left on the soil surface or incorporated. The 

use information presented in this problem formulation was obtained from the tables in the EFED 

Label Data Report dated 5/31/2012, from BEAD’s Chemical Profile for Registration Review 
8

(USEPA 2012), and from various evaluated labels. There are currently 83 Section 3 registered 

products as well as 20 Special Local Needs (SLN) registrations for pendimethalin. 

Pendimethalin has numerous uses. A summary of agricultural use patterns based on maximum 

application rate per crop group for pendimethalin is shown Table 4.3. 

Table 4.3. Summary of Agricultural Use Information for the Pendimethalin

Use Maximum 

Applic. Rate 

Maximum 

Seasonal Rate 

Maximum 

Number of 

Applications 

Minimum 

Retreatment 

Interval 

(days)

Citrus 6.00 lb a.i./A 6.00 lb a.i./A NS 30

Nut crops 6.00 lb a.i./A 6.00 lb a.i./A NS 30

Pome fruits 4.00 lb a.i./A 6.00 lb a.i./A NS NS

Stone fruits 4.00 lb a.i./A 4.00 lb a.i./A NS 30

Flavoring and spice crops 2.00 lb a.i./A 2.00 lb a.i./A NS NS

Fruiting vegetables 1.50 lb a.i./A 1.50 lb a.i./A NS NS

Leafy and stem 

vegetables 4.00 lb a.i./A 4.00 lb a.i./A 1 NS

Root crop vegetables 1.50 lb a.i./A NS NS NS

Forage grasses 4.00 lb a.i./A 4.00 lb a.i/A NS NS

Legumes 1.50 lb a.i./A NS NS NS

Grain crops 1.50 lb a.i./A 1.50 lb a.i./A NS NS

Sugarcane 4.00 lb a.i/A 6.00 lb a.i./A NS NS

Tobacco 1.50 lb a.i./A NS NS NS

Corn 2.00 lb a.i./A 2.00 lb a.i./A NS NS

Cotton 2.00 lb a.i./A NS NS NS

Olives 4.00 lb a.i./A 4.00 lb a.i/A NS 30

Peanuts 1.70 lb a.i./A NS NS NS

Sunflowers 1.50 lb a.i./A NS NS NS

Soybeans 2.00 lb a.i./A 2.00 lb a.i./A NS NS

Asparagus 4.00 lb a.i/A 4.00 lb a.i./A NS NS

Onions 1.89 lb a.i./A 5.92 lb a.i./A NS NS

Rice 1.00 lb a.i./A NS NS NS

Grapes 6.00 lb a.i./A 6.00 lb a.i./A NS 30

Strawberries 1.50 lb a.i./A 3.00 lb a.i./A NS NS

Figs 4.41 lb a.i./A NS NS NA

Loquat 4.00 lb a.i./A 4.00 lb a.i/A NS NS

Pomegranates 4.00 lb a.i./A 4.00 lb a.i/A NS 30

The agricultural usage of pendimethalin, from the Screening Level Usage Analysis (SLUA), is 

provided in Table 4.4. The table is arranged by crop in alphabetical order. According to the 

table, the major agricultural uses for pendimethalin are soybean (2.6 million lbs a.i. annually), 

cotton (1.7 million lbs a.i. annually) and corn (1.5 million lbs a.i. annually). 

Table 4.4. Screening-Level Estimates of Agricultural Uses of Pendimethalin 

(SLUA)5

Percent Crop Ttd.

Crop Lbs. A.I. Avg. Max.

1 Alfalfa 100,000 <1 <2.5

 5 Dated 01/21/2011
9

2 Almonds 500,000 20 45 3 Apples 40,000 5 20 4 Apricots 3,000 10 25 5 Asparagus 1,000 <2.5 5 6 Beans, Green 30,000 15 25 7 Cabbage 2,000 5 15 8 Caneberries + 7,000 20 20 9 Cantaloupes + <500 <1 <2.5

10 Carrots 20,000 20 60

11 Cherries 40,000 10 35

12 Corn 1,500,000 <2.55

13 Cotton 1,700,000 15 20

14 Cucumbers + 2,000 <2.55

15 Dry Beans/Peas 300,000 15 20

16 Fallow 10,000 <1 <2.5

17 Garlic 20,000 75 100

18 Grapefruit 20,000 10 20

19 Grapes 200,0005 30

20 Hazelnuts, Filberts 5,0005 15

21 Lemons 5,00055

22 Lima beans 10,000 40 50

23 Nectarines 5,000 10 10

24 Onions 100,000 65 80

25 Oranges 100,0005 15

26 Pasture 1,000 <1 <2.5

27 Peaches 20,0005 20

28 Peanuts 500,000 45 60

29 Pears 10,0005 20

30 Peas, Green 60,000 45 65

31 Pecans 20,000 <2.55

32 Peppers 7,000 10 25

33 Pistachios 100,000 25 60

34 Plums/prunes 30,000 10 25

35 Pomegranates* 30,000 N/C N/C

36 Potatoes 200,000 30 35

37 Pumpkins + 1,000 <2.55

38 Rice 100,0005 10

39 Sorghum 6,000 <1 <2.5

40 Soybeans 2,600,0005 10

41 Squash + <500 <2.5 <2.5

42 Strawberries 1,000 <2.55

43 Sugarcane 600,000 30 45
10

44 Sunflowers 400,000 15 25

45 Sweet Corn 50,000 10 15

46 Tangerine 4,000 5 5

47 Tobacco 100,000 40 45

48 Tomatoes 50,000 15 30

49 Walnuts 80,000 10 25

50 Watermelons + 5,000 5 10

51 Wheat 7,000 <1 <2.5

Sorted alphabetically. All numbers rounded.

<500 Less than 500 pounds of active ingredient

<2.5 Less than 2.5 percent of crop treated

<1 Less than 1 percent of crop treated

N/C Only Lbs. A.I. available

* CA data only (95% or more of U.S. acres in California)

SLUA data sources include: 

USDA-NASS (United States Department of Agriculture's National Agricultural Statistics Service) 

(pesticide usage data from 2001 to 2008)

Private Pesticide Market Research (pesticide usage data from 2001 to 2008)

 California DPR (Department of Pesticide Regulation) (data for 2000 to 2008)

BEAD provided agricultural information by state in its Pendimethalin Chemical Profile for 

Registration Review (USEPA 2012). The BEAD report states: “The states with the most 

agricultural usage in terms of pounds AI applied are California (19%), Texas (8%), Georgia 

(8%), Iowa (6%), Illinois (5%), and Louisiana (5%). In terms of total area treated the top states 

are Texas (11%), Georgia (10%), California (9%), Iowa (7%) and Illinois (5%).” 

Figure 4-2 shows the 2006-2010 estimated annual agricultural use of pendimethalin from the 

BEAD report.
11

Figure 4-2. Pendimethalin Usage by Crop Reporting District (2006-2010).6

The following labeling statements appear on all pendimethalin labels to avoid contamination of 

aquatic environments and endangered species from use on agricultural products. 

ENVIRONMENTAL HAZARD STATEMENTS 

• This product is toxic to fish. DO NOT apply directly to water, or to areas where surface 

water is present, or to intertidal areas below the mean high water mark. 

 6 This is a map of agricultural pesticide usage at the Crop Reporting District (CRD) level. CRDs are boundaries 

created by USDA NASS which are aggregates of counties (USDA, 2010). Pesticide usage is displayed as average 

pounds (for the years 2006-2010) per 1,000 acres offarmland in a CRD to normalize for the variation in farmland 

between CRDs. Farmland acreage was obtained from USDA (2007). Usage is based on private market surveys of 

pesticide use in agriculture (Proprietary Data, 2006-2010). The survey data are limited to the states that represent the 

top 80-90% of acreage for the individual crops, therefore, use may be occurring in regions outside the scope of the 

survey. CRDs showing no usage of pesticides may be due to either the lack of pesticide use in the region or nonparticipation in the agricultural surveys. In addition, across the years, there may be variations in the specific crops 

included in the CRD survey. This may result in a lower annual average for-the CRD.

Sources:

Proprietary Data. 2006-2010.

USDA, 2006-2010. NASS Crop Reporting Districts. Online:

http://www.ers.usda.govlbriefing/arms/resourceregions/resourceregions.htm#nass.

USDA,2007. Census of Agriculture. Online: http://www.agcensus.usda.gov/Publications/2007Iindex.asp.
12

• Drift and runoff from treated areas may be hazardous to aquatic organisms in adjacent 

aquatic areas. DO NOT contaminate water when disposing of equipment washwateres or 

rinsate.

ENDANGERED SPECIES PROTECTION

• If endangered plant species occur in proximity to the application sites, the following 

mitigations are required:

o If applied by ground, leave an untreated buffer zone of 200 feet. The product must 

be applied using low boom (20 inches above the ground) and ASAE fine to 

medium/coarse nozzles. 

o If applied by air, leave an untreated buffer zone of 170 feet. Must use straightstream nozzles (D-6 or larger): wind can be no more than 8 mph, and release 

height must be 15 feet or less. 

In addition to the agricultural uses described above, pendimethalin has numerous nonagriculatural uses (Table 4.5). 

Table 4.5. Summary of Non-Agricultural Use Information for the Pendimethalin

Use Maximum 

Applic. Rate 

Maximum 

Seasonal Rate 

Maximum 

Number of 

Applications 

Minimum 

Retreatment 

Interval 

(days)

Ornamental nurseries 4.41 lb a.i./A NS NS NS

Christmas tree 

plantations 4.41 lb a.i./A NS NS NS

Sod farms 3.50 lb a.i./A NS NS NS

Rangeland 3.50 lb a.i./A NS NS NS

Forestry 4.40 lbs a.i./A NS NS NS

Commercial/ industrial/ 

recreational lawns 3.96 lb a.i./A NS NS NS

Golf courses 3.50 lb a.i./A NS NS NS

Airports/ landing fields 3.50 lb a.i./A NS NS NS

Uncultivated 

agriculatural areas 

(fallow land)

3.00 lbs a.i/A 3.00 lbs a.i./A 1 NA

Rights-of-way/ 

fencerows/ hedgerows 4.41 lb a.i./A NS NS NS

Around commercial, 

industrial, institutional 

buildings

4.32 lb a.i./A NS NS NS

Around paved areas 4.41 lb a.i./A NS NS NS

Residential lawns 3.96 lb a.i./A NS NS NS

3.2 Environmental Fate and Transport

Table 4.6 summarizes the environmental fate/transport properties of pendimethalin. 

Table 4.6. Environmental fate/transport properties of pendimethalin

Study Value (units) Major Degradates Minor 

Degradates 

MRID # 
13

Hydrolysis Stable None 00106777 

Direct Aqueous 

Photolysis 

Dark corrected, continuous 

irradiation half-life 21 days; 12-

hour light/dark half-life 42 days. 

37 minor, unidentified 

degradates 2,6-dinitro-3,4-

dimethylaniline (9.3% of 

applied) 

00153763 

43808201 

Soil Photolysis Stable None 00153764 

Aerobic Soil 

Metabolism 

1322 days (log linear 

calculations)

2,6-dinitro3,4-xylidine 4-

[(1-ethylpropyl)amino]-2-

methyl-3,5-dinitrobenzyl 

alcohol 4-[(1-

ethylpropyl)amino]-2-

methyl-3,5-dinitro-o-toluic 

acid 

40185104 

Anaerobic Soil 

Metabolism 

Stable 98% parent at 60 days 2,6-dinitro3,4-xylidine 4-

[(1-ethylpropyl)amino]-2-

methyl-3,5-dinitrobenzyl 

alcohol 4-[(1-

ethylpropyl)amino]-2-

methyl3,5-dinitro-o-toluic 

acid 

40185105 

Anaerobic 

Aquatic 

Metabolism 

68-day half-life (upper 90th %ile

confidence bound on mean) 

None 40813501 

43154702 

Aerobic Aquatic 

Metabolism 

27 X 3 (81 days) None 47385201 

Kd-ads / Kd-des 

(mL/g) 

Koc- ads / Koc-des 

(mL/g) 

30 – 854 (U.S. soils) 61 – 285 

(Japanese soils) 

17,040 mL/g O.C. (U.S. soils) 

(avg of 5 values, 13000 – 29400) 

7011- 43863 mL/g o.c. 

(Japanese soils) 

N/A 00153765 

43041901 

Laboratory 

Volatility 

Volatilization half-life 12.5 days 

from moist loam soil 

None measured 

00153766 

Fish 

Bioaccumulation 

Bioconcentration factor BCF = 

5100, 35-day exposure 

4-[(1-ethylpropyl)amino]-2-

methyl-3,5-dinitrobenzyl 

alcohol (3.1%) 

00156726 

00158235

Degradation

Available structures of observed degradates are provided in Table 4.7. The alcohol metabolites 

3, 4, 5, and 7 are isomers and the acid metabolites 2 and 6 are isomers. Thus there are 3 groups 

of degradates; alcohols, acids and 2,6-dinitro-3,4-dimethylaniline (metabolite # 1). These 

degradates are considered minor. 

Table 4.7 . Chemical names and structures of pendimethalin metabolites

Number Structure Name
14

1

2,6-Dinitro-3,4-

dimethylaniline

2

acid

N-(1 -Ethylpropyl)-3,4-

dimethyl-2,6-dinitroaniline

3

alcohol

(4-[(1 -Ethylpropyl)amino]-2-

methyl-3,5-

dinitrophenyl)methanol

4

alcohol

3,5-Dinitrobenzyl alcohol 

metabolite

5

alcohol

2,4-Dinitrobenzyl alcohol 

metabolite

6

acid

4-[(l-ethylpropy1)aminol-3,5-

dinitro-o-touc acid
15

7

alcohol

4-[(1-ethyl-propyl)amino]-2-

methyl-3,5-dinitro benzyl 

alcohol

To explore the potential toxicity of the metabolites of pendimethalin to aquatic animals and 

plants, EFED employed the Ecological Structure Activity Relationships (Ecosar v1.0) program. 

Based on the structure of the parent compound, Ecosar predicts a degradate’s aquatic toxicity 

based on structural classes it belongs to. These toxicity values can then be compared to the 

available aquatic toxicity data for the parent chemical of interest in order to identify potential 

degradates of concern. Degradates that are predicted to have equal or greater toxicity than the 

parent may be of concern for risk assessment and may require additional data or inclusion in a 

Total Toxic Residue (TTR) approach if they occur in significant amounts in the environment to 

present a risk concern. 

Ecosar placed the parent compound pendimethalin in the dinitrobenzene class, with toxicity to 

aquatic organisms as the available data indicates for pendimethalin (Table 4.8). The prediction 

for pendimethalin matched the actual data very well, thus the dinitrobenzene class QSAR was 

used for degradates that Ecosar also identified asdinitrobenzenes. Ecosar automatically assumes 

that metabolites with an acid group are ten times less toxic. For the purposes of this comparison,

the 10x adjustment factor for the acid group being present was removed. Based on this 

comparison; 1) the alcohol metabolites have equal or greater toxicity to pendimethalin for 

chronic freshwater fish, acute freshwater invertebrates, acute and chronic estuarine/marine fish, 

and acute green algae; and 2) the acid metabolites and the dinitromethylamine metabolites all 

have lesser toxicity than the parent pendimethalin.

Table 4.8. Ecosar v1.0 Analysis of Pendimethalin and its Degradates

Endpoint Parent 

data 

(ppm)

QSAR

(ppm)

3/4/5/7 

ecosar1

(ppm)

2/6 ecosar2

(ppm)

1 ecosar3

(ppm)

QSAR 

class

-- Dinitrobenzen

es (dnb)

dnb Dnb-acid Dinitroaromatic amine

FW fish 

acute

0.138 0.125 1.167 6.202 6.877

FW fish 

chronic

0.0063 0.004 0.018 * 0.119 0.661

Daphnia 

acute

0.280 0.697 7.746 38.971 5.049

Daphnia 

chronic

0.0145 0.020 0.120 0.733 0.529

Green 

algae 

No data 0.209 0.495 * 4.034 23.495

(neutral 
16

acute organic 

QSAR)

SW fish 

acute

0.710 0.618 1.732 * No 

prediction

No 

prediction

SW fish 

chronic

No data 0.053 0.162 * No 

prediction

No 

prediction

1 Degradates 3, 4, 5, and 7 are alcohol metabolites

2 Degradates 2 and 6 are acid metabolites

3 Degradate 1 is a dinitrodimethylaimine metabolite

Values with an asterisk (*) indicate degradates that are within a factor of 3 of 

parent toxicity (actual data or QSAR) and may be in included as part of the 

Total Toxic Residue (TTR). Values for the acid metabolites (dnb-acid 2 and 6) 

presented have had the 10x adjustment factor for the acid group being present 

removed. 

Fate in the Terrestrial Environment

Pendimethalin dissipates in the environment by sorption to soil, metabolization by microbes, and 

by volatilization into air. Microbes can degrade pendimethalin to many non-significant (<l0 % 

of applied radio activity) degradates. Also, the volatilization can be significant because 

pendimethalin has very limited water solubility, relatively high vapor pressure, and a high log 

Kow. Persistence in the terrestrial environment will decrease with increasing temperature, 

moisture, or decreasing soil organic carbon because the extent of sorption of pendimethalin is 

related to soil organic content. Pendimethalin residues in field studies are tightly bound to soil 

and sediment particles, which is consistent with the laboratory mobility studies.

Pendimethalin degraded in one soil and under aerobic soil conditions with a half-life of 1322 

days. Terrestrial field dissipation data that are consistent with laboratory data have also been 

provided. In an Indiana field dissipation study, the half-lives ranged from 84-147 days. 

However, in field dissipation studies in Louisiana (LA) and Mississippi (MS), the half-lives 

ranged from 4 to 82 days, with most studies containing half-lives of <20 days. The difference in 

half-lives between LA/MS and Indiana can be attributed to the soil and climatic differences 

between the two locations. No leaching was observed in the field dissipation studies, which is 

consistent with the results of laboratory studies.

Pendimethalin has been detected in air, rain, and snow, according to a compilation of studies by 

Majewski and Capel (1995). Pendimethalin was analyzed in at least ten sites, with detection 

values of 100 to 1,500 ng/L (rain), 0.64 to 3.6 mg/m3 (air), and 1,370 to 3,620 ng/L (fog).

Fate in the Aquatic Environment

Pendimethalin is stable to sterile hydrolysis, soil photolysis, and anaerobic soil metabolism but

degrades slowly by aqueous photolysis with a calculated half-life of 17 days. 

Pendimethalin is stable to sterile hydrolysis, but degrades slowly due to anaerobic aquatic

metabolism with a half-life of 68 days (upper 90 percentile confidence bound on mean) and, due 

to aqueous photolysis, with a calculated half-life of 17 days. Aqueous residues of parent 

pendimethalin and its degradates bind to sediment in anaerobic aquatic metabolism and soil 

mobility studies. Pendimethalin degraded under aerobic aquatic conditions (MRID 47385201) 

with a half-life of 27 days.
17

The half-life in the aquatic field dissipation study (MRID 44527601) was 15 days, and virtually 

all residues were present in the top layer of soil once the rice field was flooded.

Pendimethalin accumulated readily in bluegill sunfish with bioconcentration factors (BCFs) of

1400X in edible portions, 5800X in non-edible portions, and 5100X in whole fish. Of labeled 

14C-pendimethalin taken up by fish, depuration of 87-91% of the 14C-residues occurred by 14 

days post exposure.

4 Receptors

4.1 Aquatic and Terrestrial Effects

The receptor is the biological entity that is exposed to the stressor (EPA, 1998). Due to the 

outdoor uses of pendimethalin, the types of receptors that may be exposed include both aquatic 

and terrestrial receptors, such as birds, reptiles, mammals, amphibians, freshwater and 

estuarine/marine fish, non-target terrestrial and aquatic invertebrates and terrestrial and aquatic 

plants. The stressors in this case are pendimethalin. Spray drift and runoff exposures are 

expected for both ground and aerial applications of pendimethalin. Consistent with the process 

described in the Overview Document (USEPA, 2004), this problem formulation uses a surrogate 

species approach in its evaluation of pendimethalin. Toxicological data generated from 

surrogate test species, which are intended to be representative of broad taxonomic groups, are 

used to extrapolate to potential effects on a variety of species (receptors) included under these 

taxonomic groupings. 

Tables 5.1 and 5.2 provide a summary of the taxonomic groups and the surrogate species tested 

to help understand potential acute and chronic ecological effects of pendimethalin to these nontarget taxonomic groups. 

4.1.1 Terrestrial Animals

A summary of the most sensitive endpoints from the available toxicity studies conducted with 

terrestrial species is presented in Table 5.1. 

Table 5.1 Summary of most sensitive endpoints from submitted terrestrial toxicity studies for pendimethalin. 

Species 

(common 

name)

Taxa 

Represented Endpoint Concentration

Test 

Substance 

(% a.i.)

Reference/ 

Classification

Acute 

Toxicity 

Classification

Rattus 

norvegicus

(Laboratory 

Rat)

Mammals

LD50 1050 mg a.i./kg-bw TGAI

MRID# 

00026657

Acceptable

Slightly Toxic

NOAEL 52 mg a.i./kg/day

TGAI

MRID# 

41725203

Acceptable

Not 

LOAEL 125 mg a.i./kg/day Applicable

Mallard duck

(Anas 

platyrhynchos)

Birds, 

terrestrialphase LD50 1421 mg a.i./kg bw TGAI

MRID# 

00059739

Acceptable

Slightly Toxic
18

Table 5.1 Summary of most sensitive endpoints from submitted terrestrial toxicity studies for pendimethalin. 

Species 

(common 

name)

Taxa 

Represented Endpoint Concentration

Test 

Substance 

(% a.i.)

Reference/ 

Classification

Acute 

Toxicity 

Classification

Bobwhite quail 

(Colinus 

virginianus)

amphibians, and 

reptiles

LC50 4187 mg a.i./kg diet TGAI

MRID# 

00059739 

Acceptable

Practically 

non-toxic

Mallard duck

(Anas 

platyrhynchos)

NOAEL 141 mg a.i./kg-diet TGAI MRID# 

44907601

Acceptable

Not 

Applicable

LOAEL 1410 mg a.i./kg-diet TGAI Not 

Applicable

Apis mellifera

(Honey bee)

Terrestrial 

invertebrates

Contact

LC50

>49.7 μg a.i./bee TGAI

MRID#

0009980

Acceptable

Practically 

non-toxic

Mammals

The Agency’s rat acute oral assessment endpoint for risk assessment purpose shows the LD50 to 

be 1250 mg/kg (male) and 1050 mg/kg (female) (MRID 00026657). Pendimethalin is 

considered to be slightly toxic to mammals on an acute oral basis. 

A 2-generation reproduction study (MRID 41725203) with pendimethalin was reviewed by 

HED. The parental systemic NOAEL was 25 mg/kg/day (500 ppm), based on decreased body 

weight gain and food consumption at the LOAEL of 125 mg/kg/day (2500 ppm). The 

reproductive/offspring NOAEL is 25 mg/kg/day (500 ppm), based on decreases in the number of 

pups born and pup weight at the LOAEL of 125 mg/kg/day (2500 ppm). Parental and 

reproductive NOAELs and LOAELs were based on a generic ratio (1:20) of dietary intake of 

chemical. 

The HED Cancer Peer Review Committee classified pendimethalin as a “Group C” (possible 

human) carcinogen, based on thyroid follicular cell adenomas in rats. The committee 

recommended a non-quantitative approach (non-linear, RfD approach) since mode of action 

studies are available that demonstrate that the thyroid tumors are due to a thyroid-pituitary 

imbalance, and also since pendimethalin was shown to be non- mutagenic in mammalian somatic 

cells and germ cells. 

Birds

Two sub-acute LC50 dietary avian studies and one acute LD50 oral acute avian study using the 

technical pendimethalin were submitted to the Agency. For the LC50 dietary studies, the LC50

for the bobwhite quail is 4187 ppm and the mallard duck is >4640 ppm. For the acute LD50 for 

the mallard, the LD50 is 1421 mg/kg-bw. 

The endpoint selected for the assessment is the bobwhite quail’s LC50 of 4187 ppm (MRID 

00026674) and the mallard’s LD50 of 1421 mg/kg-bw (00059739). 

Pendimethalin technical is categorized as slightly toxic on a subacute dietary and acute oral basis 

to birds. No avian studies using formulated product have been submitted to the Agency. 
19

Two avian reproduction studies were submitted to the Agency. No treatment related effects were 

observed in the bobwhite quail and the LOAEL is greater than 1410 ppm. The mallard duck 

study (MRID 44907601) showed the parameter of 14-day survivor bodyweight was reduced at 

1410 ppm. The NOAEL for the mallard study is 410 ppm. No other treatment related effects 

were observed. This study is classified as acceptable. 

Terrestrial Invertebrates 

Only one acute oral bee toxicity study (MRID 00051271 or 00108773) was submitted to the 

Agency. This study was authored by Dr. Atkins in 1974. The species tested is the honey bee, 

Apis mellifera. The LD50 acute oral is greater than 49.8 μg/bee with no mortality observed at the 

highest tested dose. Pendimethalin is classified as practically non-toxic to the honey bee. 

4.1.2 Aquatic Animals

A summary of the most sensitive endpoints from the available toxicity studies conducted with 

aquatic animals is presented in Table 5.2. 

5.2. Summary of most sensitive endpoints from submitted aquatic toxicity studies for pendimethalin. 

Exposure 

Scenario Species Exposure Duration

Toxicity 

Reference 

Value

Effects Reference Toxicity 

Category

Freshwater Fish

Acute Rainbow 

trout

(Oncorhynch

us mykiss)

96 hours LC50 = 138 μg 

a.i./L

Mortality MRID 00046291

Acceptable

Highly Toxic

Chronic Fathead 

minnow

(Pimephales 

promelas)

288 days NOAEC = 6.3

μg a.i./L

LOAEC = 9.8 

μg ai/L

Reduced egg 

production

MRID 00037940

Acceptable

NA

Freshwater Invertebrates

Acute Daphnia 

magna

96 hours EC50 = 280

μg a.i./L

Mortality MRID 00059738

Acceptable

Very Highly 

Toxic

Chronic Daphnia 

magna

21 days NOAEC = 14.5 

μg a.i./L

LOAEC = 17.2 

μg ai/L

Reduced 

production of 

young

MRID 00100504

Supplemental

NA

Benthic Organisms

Acute Midge

(Chironomus 

riparius)

10 days NOAEC > 203 

mg a.i./kg

No effects MRID 47891601

Supplemental

NA

Estuarine/Marine Fish

Acute Sheepshead 

minnow

(Cyprinidon 

96 hours LC50 = 710 μg 

a.i./L

Mortality MRID 00131774

Acceptable

Very Highly 

Toxic
20

5.2. Summary of most sensitive endpoints from submitted aquatic toxicity studies for pendimethalin. 

Exposure 

Scenario Species Exposure Duration

Toxicity 

Reference 

Value

Effects Reference Toxicity 

Category

variegates)

Chronic No data available

Estuarine/Marine Invertebrates

Acute Eastern 

Oyster

Crassostrea 

virginica

96 hours LC50 = 210 μg 

a.i./L

Mortality MRID 00131772

Acceptable

Very Highly 

Toxic

Chronic No data available

Freshwater Fish

Three acute freshwater studies using technical grade pendimethalin are available (MRIDs

00037778, 0003778, and 00046291). Species studied include the bluegill sunfish, rainbow trout, 

and channel catfish with LC50 values of 199 ppb, 138 ppb and 418 ppb respectively. In addition, 

seven acute freshwater studies using formulated product are available (MRIDs 00037927, 

00037927, 00037927, 00037927, 00037927, 00037927, and 00131773). Species studied include 

the bluegill sunfish, rainbow trout, and channel catfish and LC50 values ranged from 520 ppb 

formulation to 94,400 ppb formulation (220 ppb and 28,747 ppb active ingredient, respectively), 

indicating that the formulated products are less toxic to freshwater fish than the technical grade 

pendimethalin. The available data suggests that pendimthalin is very highly toxic to freshwater 

fish on an acute basis. 

One chronic freshwater fish study (MRID00037940) was submitted to the Agency. This study is 

a Fathead minnow (Pimephales promelas) full life cycle study using technical grade 

pendimethalin. The 288-day NOAEC is 6.3 ppb (0.0063 ppm). The NOAEC is based on 

reduction of egg production. The LOAEC = 9.8 ppb (0.0098 ppm) is based on reduction of egg 

production. Reduced hatchability was also observed at 22 and 43 ppb. 

Estuarine/Marine Fish

There is one study available on the acute toxicity of technical grade pendimethalin and the 

formulation AC 92, 533 to the sheepshead minnow (Cyprinodon variegatus, MRID 00131774; 

Acceptable). The study reported a 96-hour LC50 value of 707 ppb (C.I. 552-907 ppb) for 

technical grade pendimethalin and a 96-hour LC50 value of 1700 ppb (C.I. 1230-3560 ppb) for 

the formulation. 

Chronic data on the toxicity of pendimethalin to estuarine/marine fish are not available. This is 

identified as a data gap. 

Freshwater Invertebrates

Three acute freshwater invertebrate studies were submitted to the Agency: two studies using the 

waterflea Daphnia magna and one using crayfish, Procambarus simulans (MRIDS 00059738, 

00071123, and 00153772 respectively).
21

A Daphnia magna study using technical grade pendimethalin had an EC50 of 280 ppb (C.I. 230-

330) and is considered to be an acceptable study. The other Daphnia magna study used the 

formulation containing 45.6% active ingredient with the EC50 = 5.1 ppm (5100 ppb) formulation. 

This study is considered to be acceptable for formulated study. 

The crayfish study is categorized as supplemental due to the precipitate being observed in 

concentrations of 1.0 ppm and more; the dissolved O2 concentration is less than 40% of 

saturation; and DMSO was used as a solvent which tends to increase mortalities rather than 

decrease them. This EC50 for this study is greater than 1.0 ppm (1000 ppb). 

Acute toxicity of pendimethalin technical to freshwater invertebrates is categorized as highly 

toxic and moderately toxic. Pendimethalin formulation is categorized as moderately toxic. 

One chronic freshwater invertebrate study (MRID 00100504) was submitted to the Agency. This 

study is a Daphnia magna life cycle study using a technical grade pendimethalin. The 21-day 

NOAEC is 14.5 ppb (0.0145 ppm). The NOAEC is based on reduced production of Daphnia. 

LOAEC = 0.0172 ppm (17.2 ppb). Mortality was observed in the study with 100% mortality at 

the 2 highest dose levels of 35.8 and 74.2 ppb. No appreciable mortality observed at 3 lowest 

concentration levels of 4.3, 8.2, and 14.5 ppb. Reduction of productivity of 50% occurred at 

22.1 and 17.5 ppb concentration levels. 

Estuarine/Marine Invertebrates

Two acute freshwater invertebrate studies are available for pendimethalin. An acceptable study 

with the eastern oyster (Crassostrea virginica, MRID 00131772) used technical grade and 

formulated pendimethalin (AC 92, 533). The study reported a 48-hour EC50 value of 210 ppb 

(C.I. 160-340 ppb) for technical grade pendimethalin and a 48-hour EC50 value of 450 ppb for 

the formulation, indicating that pendimethalin is highly toxic to oysters. 

In addition, an acceptable study tested the toxicity of technical grade pendimethalin and the 

formulation AC92, 533 to pink shrimp (Penaeus duorarum, MRID 00131775). The study had a 

96-hour LC50 value of 1.6 ppm (C.I. 1.2-2.2 ppm) for technical grade pendimethalin and a 96-

hour LC50 value of 11 ppm (C.I. 8.9-16 ppm) for the formulated product. This study suggests 

that pendimethalin is moderately toxic to pink shrimp. 

Chronic data on the toxicity of pendimethalin to estuarine/marine invertebrates are not available. 

This is identified as a data gap. 

Benthic Invertebrates 

A 28-day spiked sediment study (MRID 47891601) for the non-biting midge (Chironomus 

riparius) has been submitted and reviewed. Although the study is scientifically sound based on 

methods described in the non-guideline OECD Guideline 218 (“Sediment-Water Chironomid 

Toxicity Test Using Spiked Sediment”), it is classified as ‘supplemental’ because NOAEC and 

LOAEC values were not established, and the highest test concentration was well below the limit 

concentration of 1,000 mg a.i./kg sediment. Based on the results of the study, no treatmentrelated effects on mortality, emergence, or development rates were observed at the highest meanmeasured treatment level in sediment of 203 mg a.i./kg dw. In addition, total organic carbon 

(TOC) was not reported in this study. Without information on TOC it is not possible to 

determine whether the lack of treatment related effects were due to a relative insensitivity to the 

test substance or whether pendimethalin bound to the available organic carbon such that is was 
22

not bioavailable for the test organism. Concentrations of pendimethalin were measured in 

sediment, overlying water, and pore water at 0 and 28 days. In general, concentrations of 

pendimethalin remained largely associated with the sediment phase; the highest pendimethalin 

concentration in overlying water was measured at 80 μg a.i./L, and no quantifiable levels (<50 

μg a.i./L) were detected in pore water. Given pendimethalin’s propensity to partition to 

sediment, the lack of sediment toxicity data for benthic invertebrates has been identified as a data 

gap and a source of uncertainty for estimation of risk to benthic organisms in previous ecological 

risk assessments.

4.1.3 Plants

Tier II terrestrial plant toxicity testing was conducted with the TGAI, rather than the TEP as 

required by the non-target plant protection data requirements specified in 40 CFR Part 158. 

These data will be needed for ESA effects determination. Based on the available Tier II seedling 

emergence and vegetative vigor toxicity data for the TGAI, ryegrass and lettuce are the most 

sensitive monocot and dicot plants, respectively. However, ryegrass is the most sensitive in the 

vegetative vigor test as compared to the seedling emergence test, and lettuce shows similar 

sensitivity in both tests. It is important to note that all ten test species showed effects >25% in 

the seedling emergence test, whereas two of the ten test species (including radish and cucumber, 

both dicots) showed no effect in the vegetative vigor test at the highest treatment level of 4.0 lbs 

a.i./A. This study did not test the maximum application rate for currently registered uses of 

pendimethalin. In addition, use of the TGAI data may underestimate toxicity to plants as the 

TEP may include adjuvants or surfactants that increase the toxicity of the parent compound. The 

most sensitive EC25 and NOAEC values for ryegrass and lettuce, based on the available TGAI 

data, are bolded in Table 5.3. 

Table 5.3. Summary of Tier II Terrestrial Plant Toxicity Data for Pendimethalin.

Crop Species EC25 (lbs a.i./A) NOAEC (lbs a.i./A) Most sensitive 

parameter

Seedling Emergence

Monocots Oat 1.0 0.25 Plant height

Ryegrass 0.02 0.01 Dry weight

Corn 0.68 0.5 Plant height

Onion 0.08 0.06 Dry weight

Dicots Soybean 4.7 2.0 Dry weight

Lettuce 0.09 0.063 Dry weight

Radish 0.86 0.13 Plant height

Tomato 0.2 0.13 Dry weight

Cucumber 2.4 0.25 Plant height

Cabbage 0.44 0.25 Plant height

Vegetative Vigor

Monocots Oat 0.78 0.5 Dry weight

Ryegrass 0.034 0.0008 Dry weight

Corn 2.8 2.0 Plant height

Onion 0.56 0.5 Plant height

Dicots Soybean 0.27 0.13 Dry weight

Lettuce 0.10 0.003 Dry weight

Radish >4.0 4.0 NA

Tomato 0.5 0.13 Dry weight

Cucumber >4.0 4.0 NA
23

Cabbage 4.8 2.0 Dry weight

Aquatic plant toxicity data submitted to the Agency show a range of EC50 values from 5.2 ppb to 

>174 ppb. The most sensitive species tested are the green algae and marine diatom and the least 

sensitive species is the cyanobacteria (blue-green algae). With respect to aquatic vascular and 

non-vascular plants (Table 5.4), duckweed (Lemna gibba) and the marine diatom (Skeletonema 

costatum) are most sensitive to pendimethalin with respective EC50 values of 5.6 μg a.i./L and 

0.7 μg a.i./L. 

Table 5.4. Summary of Most Sensitive Aquatic Plant Toxicity Data for Pendimethalin.

Species Acute Toxicity

120-hr 

LC50

(μg a.i./L)

14-day EC50

(μg a.i./L)

NOAEC

(μg a.i./L)

Endpoints

(MRID)

Duckweed

Lemna gibba -- 12.5 5.6 Reduced Frond Number

(42137101)

Marine diatom

Skeletonema costatum 5.2 -- 0.7 Growth Inhibition(42372205)

ECOTOX

In addition to submitted data, available open literature will be used to evaluate the potential 

direct effects of pendimethalin to the terrestrial receptors identified in this section. This includes 

toxicity data on the technical grade active ingredient, and when available, formulated products. 

At this time, a full and complete ECOTOX search has not been performed, but will be conducted 

prior to the final risk assessment. The open literature studies will be identified through EPA’s 

ECOTOX database (http://cfpub.epa.gov/ecotox/), which employs a literature search engine for 

locating chemical toxicity data for aquatic life, terrestrial plants, and wildlife. The evaluation of 

data can also provide insight into the direct and indirect effects of pendimethalin on biotic 

communities from loss of species that are sensitive to the chemical and from changes in structure 

and functional characteristics of the affected communities. 

Open literature toxicity data for other ‘target’ insect species (not including bees, butterflies, 

beetles, and non-insect invertebrates including soil arthropods and worms), which include 

efficacy studies, are not currently considered in deriving the most sensitive endpoint for 

terrestrial insects. Efficacy studies do not typically provide endpoint values that are useful for 

risk assessment (such as NOAEC, EC50, etc.), but rather are intended to identify a dose that 

maximizes a particular effect (such as EC100). Therefore, efficacy data and non-efficacy 

toxicological target insect data will not be included in the ECOTOX open literature search. 

4.2 Incident Database Review 

A review of the Ecological Incident Information System (EIIS, v. 2.1) and Aggregate Incident 

databases for ecological incidents involving pendimethalin was completed on April 11, 2012. 

This database consists of exposure incident reports submitted to the EPA from 1994 to present. 

A search for incidents involving pendimethalin was also conducted in the American Bird 

Conservancy’s Avian Incident Monitoring System (AIMS). 
24

The reports are listed in order of certainty, from highly probable to unrelated. Incidents listed in 

EIIS are categorized by the likelihood that a particular pesticide is associated with that particular 

incident. These classifications include highly probable, probable, possible, unlikely, or 

unrelated. “Highly probable” incidents usually require carcass residues or clear circumstances 

regarding the exposure. “Probable” incidents include those where residue information was not 

available or circumstances were less clear than those for “highly probable”. “Possible” incidents 

occur when multiple chemicals may have been involved and the contribution of an individual 

chemical is not obvious. An “unlikely” incident classification is given when a given chemical is 

considered nontoxic to the type of organism involved or the chemical was analyzed and not 

detected in samples. The “unrelated” category is used for incidents confirmed not to involve 

pesticides. 

The number of reports listed in the EIIS database is believed to be only a small fraction of the 

total incidents involving organism mortality and damage caused by pesticides. Few resources 

are assigned to incident reporting. Reporting by states is only voluntary, and individuals 

discovering incidents may not be informed on the procedure of reporting these occurrences. 

Additionally, much of the database is generated from registrant-submitted incident reports. In 

addition, incident reports for non-target organisms typically provide information only on 

mortality events and plant damage incidents. Except for phytotoxic effects in terrestrial plants, 

sublethal effects for organisms such as reduced growth or impaired reproduction are rarely 

reported. Because of these logistical difficulties, EIIS is most likely a minimal representation of 

all pesticide-related ecological incidents.

Registrants are legally required to provide detailed reports of only “major” ecological incidents 

involving pesticides, while “minor” incidents are reported aggregately. Based on 40 CFR 

§159.184, an ecological incident is considered major and must be submitted to the Agency by the 

registrant if any of the following criteria are met:

Fish or wildlife:

(A) Involves any incident caused by a pesticide currently in Formal Review7 for ecological 

concerns. 

(B) Fish: Affected 1,000 or more individuals of a schooling species or 50 or more 

individuals of a non-schooling species. 

(C) Birds: Affected 200 or more individuals of a flocking species, or 50 or more individuals 

of a songbird species, or 5 or more individuals of a predatory species. 

(D) Mammals, reptiles, amphibians: Affected 50 or more individuals of a relatively 

common or herding species or 5 or more individuals of a rare or solitary species. 

(E) Involves effects to, or illegal pesticide treatment (misuse) of a substantial tract of 

habitat (greater than or equal to 10 acres, terrestrial or aquatic). 

Plants: 

(A) The effect is alleged to have occurred on more than 45 percent of the acreage 

exposed to the pesticide.

The EIIS database contained 70 major incidents involving pendimethalin. The reports 

included 65 terrestrial plant incidents, 2 fish incidents, and 1 avian incidents. In respect to 

the likelihood that pendimethalin caused the reported incidents, the certainty ranged from 

 7 Formal Review means Special Review, Rebuttable Presumption Against Registration (RPAR), FIFRA 

section 6(c) suspension proceeding, or FIFRA section 6(b) cancellation proceeding, whether completed or 

not.
25

unlikely to highly probable. The majority of reported incidents were identified as probable or 

highly probable. 27 of the incidents resulted from registered uses, 4 were misuses, and the 

remaining use patterns are unknown. A summary of ecological incidents involving 

pendimethalin included in the EIIS database are listed in Appendix B.

The AIMS database contains 2 avian incidents involving pendimethalin, both of which are 

also captured in EIIS.

All other incidents are classified as ‘minor’. All ecological incidents classified as ‘minor’ only 

need to be aggregately reported as quarterly counts of incidents by the registrant(s). Ecological 

incidents reported in aggregate reports include those categorized as ‘minor fish and wildlife’ (WB), ‘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 

pendimethalin, the registrants have reported 4 minor fish and wildlife incidents, 1,035 

minor plant incidents, and 3 “other non-target” incdents. Unless additional information on 

these aggregated incidents becomes available, they will be assumed to be representative of 

registered uses of pendimethalin in the risk assessment.

4.3 Ecosystems Potentially at Risk 

Pendimethalin may be applied on a variety of food/feed crops, including (but not limited to), 

citrus, nut crops, pome fruits, stone fruits, flavoring and spice crops, fruiting vegetables, leafy 

and stem vegetables, root crop vegetables, seed and pod vegetables, forage grasses and legumes, 

grain crops, fruits trees, and soybeans. In addition, it may be used on numerous non-food sites 

(e.g. ornamentals, christmas tree plantations, and turf). Thus, the ecosystems at risk may be 

extensive in scope, and as a result it may not be possible to identify specific ecosystems during 

the development of a baseline risk assessment. In general terms, terrestrial ecosystems 

potentially at risk due to the use of pendimethalin could include the treated field and areas 

immediately adjacent to the treated field that may receive drift or runoff. Areas adjacent to the 

treated field could include cultivated fields, fencerows and hedgerows, meadows, fallow fields or 

grasslands, woodlands, riparian habitats and other uncultivated areas. Current label directions 

for pendimethalin require vegetative buffer strips and impose limitations to reduce the potential 

for spray drift to impact areas adjacent to the treated field. However, due to the potential 

persistence of pendimethalin under certain circumstances, it is expected to drift and/ or runoff 

due to application to food crops and certain non-crop sites, resulting in possible exposure to 

aquatic ecosystems. Aquatic ecosystems potentially at risk due to the use of pendimethalin 

include water bodies adjacent or downstream from the treated field and might include 

impounded bodies such as ponds, lakes and reservoirs, or flowing waterways such as streams or 

rivers. For uses in coastal areas, aquatic habitat also includes marine ecosystems, such as 

estuaries. 

5 Assessment Endpoints

Assessment endpoints are defined as “explicit expressions of the actual environmental value that 

is to be protected.” Defining an assessment endpoint involves two steps: 1) identifying the 

valued attributes of the environment that are considered to be at risk; and 2) operationally 

defining the assessment endpoint in terms of an ecological entity (i.e., a community of fish and 
26

aquatic invertebrates) and its attributes (i.e., survival and reproduction). Therefore, selection of 

the assessment endpoints is based on valued entities (i.e., ecological receptors), the ecosystems 

potentially at risk, the migration pathways of pesticides, and the routes by which ecological 

receptors are exposed to pesticide-related contamination. The selection of clearly defined 

assessment endpoints is important because they provide direction and boundaries in the risk 

assessment for addressing risk management issues of concern. Changes to assessment endpoints 

are typically estimated from the available toxicity studies, which are used as the measures of 

effects to characterize potential ecological risks associated with exposure to pesticides, such as 

pendimethalin.

To estimate exposure concentrations, the ecological risk assessment considers applications at the 

maximum application rate to fields that have vulnerable soils. The most sensitive toxicity 

endpoints are used from surrogate test species to estimate treatment-related direct effects on 

acute mortality and chronic reproductive, growth and survival assessment endpoints. Toxicity 

tests are intended to determine effects of pesticide exposure on birds, mammals, fish, terrestrial 

and aquatic invertebrates, and plants. These tests include short-term acute, sub-acute, and 

reproduction studies and are typically arranged in a hierarchical or tiered system that progresses 

from basic laboratory tests to applied field studies. The toxicity studies are used to evaluate the 

potential of a pesticide to cause adverse effects, to determine whether further testing is needed, 

and to determine the need for precautionary label statements to minimize the potential adverse 

effects to non-target animals and plants.

An open literature search will be conducted to determine any relevant endpoints. The search will 

focus on survival, growth and reproductive effects for aquatic and terrestrial effects of 

pendimethalin. More sensitive endpoints from acceptable open literature studies will be included 

in the ecological risk assessment.

6 Conceptual Model

For a pesticide to pose an ecological risk, it must reach ecological receptors in biologically 

significant concentrations. An exposure pathway is the means by which a pesticide moves in the 

environment from a source to an ecological receptor. For an ecological pathway to be complete, 

it must have a source, a release mechanism, an environmental transport medium, a point of 

exposure for ecological receptors, and a feasible route of exposure.

A conceptual model provides a written description and visual representation of the predicted 

relationships between pendimethalin, potential routes of exposure, and the predicted effects for 

the assessment endpoint. A conceptual model consists of two major components: risk hypothesis 

and a conceptual diagram (USEPA, 1998).

6.1 Risk Hypothesis

Risk hypotheses are specific assumptions about potential adverse effects (i.e., changes in 

assessment endpoints) and may be based on theory and logic, empirical data, mathematical 

models, or probability models (USEPA 1998). For this assessment, the risk is stressor-initiated, 

where the stressor is the release of pendimethalin into the environment. The following risk 

hypotheses are presumed for this screening-level assessment:
27

Pendimethalin, when used outdoors in accordance with registered labels, may lead to offsite movement of the compound via agricultural and urban runoff, spray drift, and eroded 

soil leading to exposure of nontarget plants and animals. Based on information on the 

environmental fate, mode of action, direct toxicity, and potential indirect effects, EFED 

assumes that registered uses of pendimethalin have the potential to cause reduced 

survival, growth, and reproduction to non-target terrestrial and/ or aquatic animals and 

plants.

The conceptual model is a generic graphic depiction of the risk hypothesis. It includes the 

potential pesticide or stressor (pendimethalin and possible metabolites, as well as synergists), the 

source of the pesticide and/or transport pathways, exposure media, exposure point, biological 

receptor types, and attributable changes.

6.2 Conceptual Diagram

The conceptual model is a generic graphic depiction of the risk hypothesis. Based on an 

examination of the physicochemical properties of pendimethalin, the fate and disposition in the 

environment, and mode of application, a conceptual model was developed that represents the 

possible relationships between the stressors, ecological receptors, and the assessment endpoints. 

Through a preliminary iterative process of examining available data, the conceptual model (i.e., 

the representation of the risk hypothesis) may be refined to reflect the likely exposure pathways 

and the organisms that are most relevant and applicable to this assessment (Figures 7-1a and 7-

1b). They include the potential pesticide or stressor (pendimethalin, but the presence of 

toxicologically important metabolites and/ or synergists cannot be ruled out), the sources and/ or 

transport pathways, exposure media and exposure points, biological receptor types and attribute 

changes.

In order for a chemical to pose an ecological risk, it must reach ecological receptors in 

biologically significant concentrations. An exposure pathway is the means by which a pesticide 

moves in the environment from a source to an ecological receptor. For an ecological exposure 

pathway to be complete, it must have a source, a release mechanism, an environmental transport 

medium, a point of exposure for ecological receptors, and a feasible route of exposure. The 

assessment of ecological exposure pathways, therefore, includes an examination of the source 

and potential migration pathways for constituents, and the determination of potential exposure 

routes.

Under the possible uses of pendimethalin, the sources and mechanisms of release of the 

compounds are from ground or aerial spray. Note that this conceptual model considers 

agricultural applications as well as non-agricultural applications. Surface runoff from the areas 

of application is assumed to depend on factors such as topography, irrigation, and rainfall events. 

Direct deposition may result in contamination of food items that may be consumed by terrestrial 

organisms. Spray drift results in contaminated adjacent areas, including bodies of water. 

Leaching to groundwater is not considered an important source because pendimethalin shows

low mobility in a variety of soils. Pendimethalin appears to have the potential for volatilization, 

with a vapor pressure and vapor pressure of ~3.0 E-5

torr and Henry’s Law constant of ~8.6 E-7

atm/m3

-mol. In addition, pendimethalin has been detected in air, rain and snow according to a 

compilation of studies by Majewski and Capel (1995).
28

For aquatic receptors, the major point of exposure is through direct contact with the water 

column, sediment, and pore water (gill/integument) contaminated with spray drift (from spray 

application) and/or runoff and flow (e.g., piped storm drains) from treated areas. Indirect effects 

to aquatic organisms (both fish and aquatic invertebrates) can also occur through impact to 

various food chains. The representative aquatic receptors are certain freshwater and estuarine/ 

marine fish, invertebrates, and, in certain cases, aquatic plants. The major point of exposure for 

terrestrial animals is consumption of food contaminated with residues such as grass, foliage, and 

small insects. For plants, the point of exposure is direct contact or root uptake. The 

representative terrestrial receptors are mammals, birds and terrestrial plants. The attribute 

changes used to assess risk to terrestrial receptors depend on the type of test (e.g., reduced 

survival, growth, or reproduction for animals and seedling emergence and vegetative vigor for 

plants). It should be noted, that these species do not cover all the possible species in the animal 

and plant kingdoms; certain taxa are considered as surrogates for other taxa. For example, fish 

are considered surrogates for aquatic phase amphibians.

This conceptual model also shows information about the potential for biomagnification for 

pendimethalin (see piscivorous birds and mammals in Fig. 7-1b). The reported value of log 

octanol/ water partition coefficient of 5.18 suggests that pendimethalin has the potential to 

bioaccumulate in aquatic organisms assuming that chemical metabolism is negligible. Maximum 

BCFs for pendimethalin are 5100x for bluegill sunfish, 100x for catfish and negligible for the 

guppy. Depuration appeared to be moderately slow, with ~10-15% of the initial residues 

remaining after 14 days. Thus, it appears that there is potential for bioaccumulation/ 

bioconcentration in aquatic organisms and biomagnification in terrestrial organisms.

Pendimethalin has a solubility of 0.275 mg/L and a high log KOW of 5.2. These properties 

suggest that the chemical could partition with the sediments and particulate suspended in bodies 

of water. Pendimethalin has the potential to accumulate in the sediments, especially after 

repeated exposures (applications), where it could persist. Such sediments could serve as 

repositories of the chemical for extended periods of time and could potentially be toxic to 

sediment dwelling organisms, affecting the food chain. These issues will also be assessed in the 

risk assessment for pendimethalin.
29

Figure 7-1a. Aquatic conceptual model depicting stressors, exposure pathways, and 

potential effects to aquatic organisms from the use of pendimathalin on agricultural and 

non-agricultural sites 

1 Includes flow across vegetation and vegetated drainage systems (e.g., swales) and flow across 

impervious surfaces and through impervious (piped) storm drains.

2 Immobilization is considered equivalent to mortality in toxicity tests for aquatic invertebrates.

Dotted lines indicate exposure pathways that have a low likelihood of contributing to ecological 

risk.
30

Figure 7-1b. Terrestrial conceptual model depicting stressors, exposure pathways, and 

potential effects to terrestrial organisms from the use of pendimethalin on agricultural and 

non-agricultural sites 

Dotted lines indicate exposure pathways that have a low likelihood of contributing to ecological 

risk. 

1 Includes flow across vegetation and vegetated drainage systems (e.g., swales) and flow across 

impervious surfaces and through impervious (piped) storm drains.

 

7 Analysis Plan 

In order to address the risk hypothesis, the potential for adverse effects on the environment is 

estimated. Usage, environmental fate and transport, and ecological effects of pendimethalin are 

characterized and integrated to assess the risks. This is accomplished using a risk quotient (ratio 

of exposure concentration to effects concentration) approach. Although risk is often defined as 

the likelihood and magnitude of adverse ecological effects, the risk quotient-based approach does 

not provide a quantitative estimate of likelihood and/ or magnitude of an adverse effect. 
31

However, as outlined in the Overview Document (USEPA 2004), the likelihood of effects to 

individual organisms from particular uses of a chemical is estimated using the probit doseresponse slope and either the level of concern (discussed below) or the actual calculated risk 

quotient value. 

This analysis plan will be revisited and may be revised depending on the data available in the 

open literature and the information submitted by the public or the registrant in response to the 

opening of the Registration Review docket.

7.1 Stressors of Concern

The focus of this assessment is on the parent material, pendimethalin. However, the Agency will 

review open literature to identify degradate(s) of potential toxicological concern (e.g. 3,5-

dinitrobenzyl alcohol metabolite, 2,4-dinitrobenzyl alcohol metabolite). 

Toxicity data for environmental mixtures of pendimethalin with other pesticides (those mixtures 

occurring in the environment following application), if available, may be presented as part of the 

ecological risk assessment. Pendimethalin may be applied in tank mixtures with other products 

approved for use on registered crops. It is expected that the toxic effect of pendimethalin, in 

combination with other pesticides used in the environment, is likely to be a function of many 

factors including, but not necessarily limited to (1) the exposed species, (2) the co-formulants in 

the mixture, (3) the ratio of pendimethalin and co-formulants concentrations, (4) differences in 

the pattern and duration of exposure among formulants, and (5) the differential effects of other 

physical/ chemical characteristics of the receiving waters (e.g. organic matter present in sediment 

and suspended water). A discussion of implications of the available pesticide mixture effects 

data on the confidence of risk assessment conclusions will be addressed in the risk description of 

the final ecological assessment.

7.2 Measures of Exposure

In order to estimate risks of pendimethalin exposures in aquatic and terrestrial environments, all 

exposure modeling and resulting risk conclusions will be made based on maximum application 

rates for the current use patterns. Available monitoring data will also be considered when 

describing potential environmental exposure to non-target organisms.

Measures of exposure are based on aquatic and terrestrial models that predict estimated 

environmental concentrations of pendimethalin using maximum labeled application rates and 

methods, as well as any mitigation measures specifically indicated on the label. 

Additional information on the terrestrial exposure models and screening tools employed in EPA 

ecological risk assessments for pesticides can be found at 

http://www.epa.gov/oppefed1/models/terrestrial/.

More information on aquatic pesticide exposure models can be found at

http://www.epa.gov/oppefed1/models/water/index.htm.
32

Dietary exposure to terrestrial organisms

Measures of exposure for terrestrial mammals, birds, reptiles and amphibians similarly 

incorporate maximum proposed use rates but rely less on fate properties. Terrestrial exposures 

are estimated using a number of methods. For pendimethalin, acute and chronic terrestrial

exposure estimates are derived directly from empirically determined observations of pesticide 

residues on various terrestrial food items. The Kenaga nomogram, as modified by Fletcher et al, 

(Kenaga and Hoerger, 1972; Fletcher et al, 1994) is used to relate pesticide application rates to 

residues on terrestrial food items. The surface residue concentration (ppm) is estimated by 

multiplying the application rate (pounds active ingredient per acre) by a value specific to each 

food item. For numerous applications for a given use, the exposure model incorporates a firstorder decay rate dependent on the foliar dissipation half-life of the chemical. In the absence of 

foliar dissipation data, a default foliar dissipation half-life of 35 days is used.

Inhalation, drinking water and dermal exposure

Two screening tools were utilized to assess the potential for exposure of pendimethalin to 

terrestrial organisms via inhalation and drinking water exposure. The Screening Tool for 

Inhalation Risk (STIR v.1.0, November 19, 2010) was used to calculate an upper bound estimate 

of exposure using vapor pressure and molecular weight of pendimethalin for vapor phase 

exposure, as well as the maximum application rate and method of application for spray drift. 

STIR incorporates results from several toxicity studies including acute oral and inhalation rat 

toxicity (oral LD50 = 1050 mg/kg-bw and LC50 >320 mg/L, respectively) as well as the most 

sensitive acute oral avian toxicity endpoint (mallard duck, LD50 = 1421 mg ai/kg bw). Based on 

the results of the STIR model, inhalation exposure alone was determined not to be a potential 

pathway of concern for avian and mammalian species on an acute basis. 

Inhalation exposure via spray drift and vapor-phase of pendimethalin alone does not appear to be 

of concern. The analysis of the inhalation route in STIR does not consider that aggregation with 

other exposure pathways such as dietary, dermal, or drinking water may contribute to a total 

exposure that has a potential for effects to non-target animals. However, the Agency does 

consider the relative importance of other routes of exposure in situations where data indicate that 

pesticide exposures through other routes may be potentially significant contributors to wildlife 

risk (US EPA, 2004).

The Screening Imbibition Program (SIP v.1.0, Released June 15, 2010) was used to calculate an 

upper bound estimate of exposure using pendimethalin solubility (0.3 mg/L), the most sensitive 

acute and chronic avian oral toxicity endpoint (mallard duck, LD50 = 1421 mg ai/kg bw and 

NOEL = 141 mg/kg-diet, respetively) and the most sensitive acute and chronic mammalian 

toxicity endpoints (oral LD50 = 1050 mg/kg-bw and NOAEL = 500 mg/kg-bw, respectively). 

Drinking water exposure alone was determined not to be a potential pathway of concern for 

avian and mammalian species on an acute or chronic basis. 

Although drinking water exposure alone does not appear to be of concern, this does not take into 

account that when aggregated with other exposure pathways (dietary food sources, dermal, 

inhalation) drinking water may contribute to a total exposure that has a potential for effects on 

non-target animals and should be explored further. Because there is a high degree of 

conservatism in the SIP 1.0 exposure estimate, there is limited expectation that use scenarios not 

triggering a SIP 1.0 concern would contribute significantly to aggregate risks from water plus 
33

diet when a refined water exposure model is incorporated in the actual quantitative risk 

assessment.

Although not available at this time, the Agency is actively pursuing modeling techniques to 

account for dermal exposure via direct application of spray and by incidental contact with 

contaminated vegetation, soil and water.

Exposure to terrestrial plants

TerrPlant is used by EFED as a Tier 1 model for screening level assessments of pesticides. The 

purpose of TerrPlant is to provide screening level estimates of exposure to terrestrial plants from 

single pesticide applications. The model does not consider exposures to plants from multiple 

pesticide applications. TerrPlant derives pesticide EECs in runoff and in drift. RQs are 

developed for non-listed and listed species of monocots and dicots inhabiting dry and semiaquatic areas which are adjacent to treatment sites. Once suitable terrestrial plant data are 

submitted to the Agency, this model will be used to determine the potential risks to terrestrial 

plants following applications of pendimethalin. 

Aquatic exposure modeling

The models used to predict aquatic EECs are the Pesticide Root Zone Model coupled with the 

Exposure Analysis Model System (PRZM/EXAMS). PRZM (v.3.12.2, May 2005) and EXAMS 

(v.2.98.4.6, April 2005) are simulation models coupled with the input shell PE5.pl (August, 

2007) to generate daily exposures and 1-in-10 year EECs of pendimethalin, that may occur from 

spray drift and runoff to surface water bodies adjacent to application sites. PRZM simulates 

pesticide application, movement and transformation on an agricultural field and the resultant

pesticide loadings to a receiving water body via runoff, erosion and spray drift. The EXAMS 

model simulates the fate of the pesticide and resulting concentrations in the water body. The 

standard scenario used for ecological pesticide assessments assumes application to a 10-hectare 

agricultural field that drains into an adjacent 1-hectare water body that is 2 meters deep (20,000 

cubic meters volume) with no outlet. PRZM/ EXAMS is used to estimate screening-level 

exposure of aquatic organisms to pendimethalin and/ or its transformation products, should they 

be of concern. The measure of exposure for aquatic species is the 1-in-10 year return peak or 

rolling mean concentration. The 1-in-10 year peak is used for estimating acute exposures of 

direct effects to aquatic organisms. The 1-in-10-year 60-day mean is used for assessing chronic 

exposure to fish and aquatic-phase amphibians. The 1-in-10-year 21-day mean is used for 

assessing aquatic invertebrate chronic exposure.

At the present time, EFED considers the use of the impervious scenario (a PRZM modeling 

scenario) as the most suitable available modeling approach for simulating runoff from 

impervious surfaces such as roads, sidewalks, patios and parking lots. The PRZM impervious 

scenario may be used in the Tier 2 coupled aquatic models PRZM/EXAMS along with the 

residential or other suitable scenario such as rights-of-way (ROW) to obtain EECs. The 

conceptual model for the residential scenario integrates simultaneous modeling of the individual 

use scenario with an impervious scenario. This approach assumes that no watershed is 

completely covered by either the 1⁄4 acre lot (the basis for the residential scenario) or 

undeveloped land (the basis for the ROW scenario) for residential and ROW use patterns; 

therefore, differential amounts of runoff will occur within the watershed. The impervious 

scenario was developed to represent the paved areas within a watershed not including roads, 
34

parking lots, sidewalks, and buildings outside the 1⁄4 acre lot (the 1⁄4 acre lot scenario accounts for 

impervious surfaces such as buildings within the represented area). By modeling a separate 

scenario for impervious surfaces, it is also possible to estimate that amount of exposure that 

could occur when the pesticide is oversprayed onto this surface. Using two scenarios in tandem 

requires post-processing of the modeled output in order to derive a weighted EEC that represents 

the contribution of both the pervious (i.e., residential and ROW scenarios) and the impervious 

surfaces.

In general, incorporation of impervious surfaces into the exposure assessment results in 

increasing runoff volume in the watershed, which tends to reduce overall pesticide exposure. For 

the purposes of risk assessment alternate assumptions for percent impervious surfaces, 

percentage of use site treated, and percentage of overspray may be considered in order to 

characterize the assumptions of the ecological risk assessment in the context of the individual 

exposure assessment and risk conclusions. For example, previously tested assumptions used in 

the endangered species assessments may be considered for characterization (i.e., 10% and 30% 

impervious surfaces, 10% lot treated, and 0%, 1% and 10% overspray) unless other relevant 

values can be determined (i.e., modeling may be completed for the impervious surface with 0%, 

1% and 10% overspray to provide lower and upper bound values). The results of these alternate 

modeling exercises may be discussed in the assessment.

Given the aquatic toxicity of pendimethalin and its likelihood to occur in sediment, the Agency 

will also consider the potential exposures resulting from benthic/ sediment concentrations. Pore 

water concentrations are commonly used to predict toxicity of non-ionic substances in sediments 

and characterize exposure to organisms that spend time in or near sediments (Di Toro et al.

1991; US EPA 2002). PRZM/ EXAMS estimates 1-in-10-year peak and 21-day mean EECs for 

pore water.

Since pendimethalin has uses on rice, the screening-level Tier 1 Rice Model v.1.0 will be utilized 

to obtain estimated exposure concentrations (EECs) related to that use. The Tier I Rice Model 

v1.0 relies on an equilibrium partitioning concept to provide conservative estimates of 

environmental concentrations resulting from application of pesticides to rice paddies. When a 

pesticide is applied to a rice paddy, the model assumes that it will instantaneously partition 

between a water phase and a sediment phase. Among the assumptions of this model, the 

degradation of the pesticide and the mass transfer from the aqueous phase to the sediment are not 

considered. Also, volatilization and other dissipation processes are not considered. If LOCs are 

exceeded using the Tier 1 rice model, estimates may be made using a provisional model, 

Pesticides in Flooded Applications Model (PFAM), to better characterize the risk. 

Extent of Exposure

Two spray drift models, AgDisp and AgDRIFT, are used to assess exposures of aquatic and 

terrestrial organisms to pendimethalin deposited in terrestrial and aquatic habitats by spray drift. 

AgDrift (version 2.01; dated 5/24/2001) is the model most commonly used to simulate spray 

drift into terrestrial and aquatic environments. AgDisp (version 8.13; dated 12/14/2004) (Teske 

and Curbishley, 2003) is used when a parameter needs to be modeled that is not available in 

AgDrift. Spray drift analysis will be an important part of the analysis in defining the potential 

area of effects for endangered species.

Bioaccumulation
35

The potential for bioaccumulation for the chemical is assessed using the KABAM model, as well 

the results from bioconcentration in fish studies (e.g., the bioconcentration factors). This model 

is parameterized using relevant reviewed registrant-submitted environmental fate and transport 

data.

As indicated in Table 3.1 and its associated text in Section 3, pendimethalin has the potential to 

bioconcentrate in aquatic organisms and there is also some potential to biomagnify in terrestrial 

organisms. The potential for bioaccumulation of pendimethalin will also be examined in the risk 

assessment. Because pendimethalin has a fairly high log KOW (5.18) and the chemical may be 

persistent in water (aqueous photolysis half-life of 42 days) and sediments (>10 days for aquatic 

metabolism), there could be a potential for bioaccumulation. The maximum bioconcentration 

factor is 5100x for whole fish and the depuration rate is fairly slow (MRIDs 00156726 and 

00158235). 

Bioaccumulation will be assessed using the results from bioaccumulation in fish studies, as well 

as the KABAM model (KOW (based) Aquatic BioAccumulation Model, version 1.0, 2009), 

adjusting for biotransformation rates. KABAM is used to estimate potential bioaccumulation of 

hydrophobic organic pesticides in freshwater aquatic ecosystems and risks to mammals and birds 

consuming aquatic organisms which have bioaccumulated these pesticides. Monitoring data and 

biotransformation rates in terrestrial species will also be evaluated, to assess the potential for 

bioaccumulation in terrestrial food webs.

7.3 Measures of Effect

Ecological effects data are used as measures of direct and indirect effects to biological receptors. 

Data are typically obtained from registrant-submitted studies or from literature studies identified 

by ECOTOX. The ECOTOX database provides more ecological effects data in an attempt to 

bridge existing data gaps. ECOTOX is a source for locating single chemical toxicity data and 

potential chemical mixture toxicity data for aquatic life, terrestrial plants, and wildlife.

ECOTOX was created and is maintained by the USEPA, Office of Research and Development, 

and the National Health and Environmental Effects Research Laboratory's Mid-Continent 

Ecology Division.

The acute measures of effect used for animals in this assessment are the LD50, LC50 and EC50. 

LD stands for "Lethal Dose", and LD50 is the amount of a material, given all at once, that is 

estimated to cause the death of 50% of the test organisms. LC stands for “Lethal Concentration” 

and LC50 is the concentration of a chemical that is estimated to kill 50% of the test organisms. 

EC stands for “Effective Concentration” and the EC50 is the concentration of a chemical that is 

estimated to produce a specific effect in 50% of the test organisms. Endpoints for chronic 

measures of exposure for listed and non-listed animals are the NOAEL/NOAEC and NOEC. 

NOAEL stands for “No Observed-Adverse-Effect-Level” and refers to the highest tested dose of 

a substance that has been reported to have no harmful (adverse) effects on test organisms. The 

NOAEC (i.e., “No-Observed-Adverse-Effect-Concentration”) is the highest test concentration at 

which none of the observed effects were statistically different from the control. For non-listed 

plants, only acute exposures are assessed (i.e., EC25 for terrestrial plants and EC50 for aquatic 

plants); for listed plants either the NOAEC or EC05 is used.
36

At the time of the risk assessment, updated information on the potential effects of pentimethalin 

on non-target animals will also collected from the Ecological Incident Information System 

(EIIS), Aggregrate Incident Reports and the Avian Monitoring Information System (AIMS). 

Where available, sub-lethal effects observed in both registrant-submitted and open literature 

studies will be evaluated qualitatively. Such effects may include behavioral changes (e.g., 

lethargy and changes in coloration). Quantitative assessments of risks, though, are limited to 

those endpoints that can be directly linked to the Agency’s assessment endpoints of impaired 

survival, growth and reproduction.

The assessment of risk for direct effects to non-target organisms makes the assumption that the 

toxicity of pendimethalin to birds is similar to that of pendimethalin’s toxicity to terrestrial-phase 

amphibians and reptiles. The same assumption is made for fish and aquatic-phase amphibians. 

7.4 Integration of Exposure and Effects

Risk characterization is the integration of exposure and ecological effects to determine the 

potential ecological risk from the use of pesticides and the likelihood of direct and indirect 

effects to non-target organisms in aquatic and terrestrial habitats. The exposure and toxicity 

effects data are integrated in order to evaluate the risks of adverse ecological effects on nontarget species. For the assessment of risks, the risk quotient (RQ) method is used to compare 

exposure and measured toxicity values. EECs are divided by acute and chronic toxicity values. 

The resulting RQs are then compared to the Agency’s Levels of Concern (LOCs) (USEPA 

2004). These criteria will be used to indicate when pendiemthalin uses, as directed on the label, 

have the potential to cause adverse direct or indirect effects to non-target organisms. In addition, 

incident data from the EIIS will be considered as part of the risk characterization.

7.5 Deterministic and Probabilistic Assessment Methods

The quantitative assessment of risk will primarily depend on the deterministic point-estimate 

based approach described in the risk assessment. An effort may also be made to further 

qualitatively describe risk using probabilistic tools that the Agency has developed. These tools 

have been reviewed by FIFRA Scientific Advisory Panels 

(http://www.epa.gov/scipoly/sap/index.htm) and have been deemed as appropriate means of 

refining assessments where deterministic approaches have identified risks.

7.6 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 pendimethalin. This assessment will be conducted in accordance with the 

Overview Document (USEPA 2004), provisions of the ESA, and the Services’ Endangered 

Species Consultation Handbook (USFWS/NMFS, 1998).

The assessment of effects associated with the registration of pendimethalin is based on an action 

area. The action area is considered to be the area directly or indirectly affected by the federal 

action, as indicated by the exceedance of Agency LOCs used to evaluate direct or indirect 
37

effects. The Agency’s approach to defining the action area under the provisions of the Overview 

Document (USEPA 2004) considers the results of the risk assessment process to establish 

boundaries for that action area with the understanding that exposures below the Agency’s

defined LOCs constitute a no-effect threshold. For the purposes of this assessment, attention 

will be focused on the footprint of the action (i.e., the area where pendimethalin application 

occurs), plus all areas where offsite transport may result in potential exposure that exceeds the 

Agency’s LOCs. Specific measures of ecological effect that define the action area for listed 

species include any direct and indirect effects and/ or potential modification of its critical habitat, 

including reduction in survival, growth, and reproduction as well as the full suite of sub-lethal 

effects available in the effects literature. Therefore, the action area extends to a point where 

environmental exposures are below any measured lethal or sub-lethal effect threshold for any 

biological entity at the whole organism, organ, tissue, and/ or cellular level of organization. In 

situations where it is not possible to determine the threshold for an observed effect, the action 

area is not spatially limited and is assumed to be the entire United States.

7.7 Drinking Water Assessment

Drinking water assessments have been conducted to support human health risk assessments of 

pendimethalin, based on all the available environmental fate information. Any further drinking 

water assessments will incorporate model estimates of pendimethalin in surface and ground 

waters. Concentrations in surface waters will be estimated using FQPA Index Reservoir 

Screening Tool (FIRST, v.1.1.1, 12/18/07) (or subsequently using PRZM/ EXAMS, with the 

Index Reservoir if refinements are required). Ground water estimates of concentrations will be 

obtained using the Screening Concentration In GROund Water (SCI-GROW) model (v.2.3, July 

2003) or PRZM-GW (in development). Further drinking water assessments will also include a 

summary of available surface and ground water monitoring data. 

7.8 Endocrine Disruptor Screening Program

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

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

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

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

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

effects on endocrine target organ histopathology, organ weights, estrous cyclicity, sexual 

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

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

developmental and reproductive effects in different taxonomic groups. As part of its 

reregistration decision, EPA reviewed these data and selected the most sensitive endpoints for 

relevant risk assessment scenarios from the existing hazard database. However, as required by 

FFDCA section 408(p), pendimethalin is subject to the endocrine screening part of the Endocrine 

Disruptor Screening Program (EDSP). 

EPA has developed the EDSP to determine whether certain substances (including pesticide 

active and other ingredients) may have an effect in humans or wildlife similar to an effect 

produced by a “naturally occurring estrogen, or other such endocrine effects as the Administrator 

may designate.” The EDSP employs a two-tiered approach to making the statutorily required 

determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a 
38

chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal 

systems. Chemicals that go through Tier 1 screening and are found to have the potential to 

interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP where EPA 

will determine which, if any, of the Tier 2 tests are necessary based on the available data. Tier 2 

testing is designed to identify any adverse endocrine-related effects caused by the substance, and 

establish a dose-response relationship between the dose and the E, A, or T effect. 

Under FFDCA section 408(p), the Agency must screen all pesticide chemicals. Accordingly, as 

part of registration review, EPA will issue future EDSP orders/data call-ins, requiring the 

submission of EDSP screening assays for pendimethalin. For further information on the status of 

the EDSP, the policies and procedures, the current and future chemical lists, the test guidelines 

and the Tier 1 screening battery, please visit our website: http://www.epa.gov/endo/.

7.9 Preliminary Identification of Data Gaps

7.9.1 Environmental Fate Data Gaps

Currently the Agency has received one supplemental study on one soil type (MRID 40185104). 

Aerobic soil metabolism studies facilitate an understanding of a compound’s degradation in soil 

resulting from pesticide interaction with soil microorganisms in aerobic (oxygen-rich) conditions 

in the laboratory. The fate of pendimethalin formed in or deposited on soil cannot be 

characterized without the requested data. The Agency is asking for a minimum environmental 

fate data set for the pendimethalin in order to estimate aquatic and terrestrial exposure. Without 

these data, exposure estimates will be based on conservative assumptions. 

In addition, independently validated analytical methods for residues in water, sediment, and soil 

(environmental chemistry methods) submitted by the registrant are used to evaluate analyses 

described in submitted environmental fate and ecological effects studies. Submitted analytical 

methods are also used by various Federal, State, Tribal, and local agencies to detect and monitor 

residues that are or are suspected to be in environmental compartments due to outdoor uses and 

accidental releases. Independent laboratory validations for submitted analytical methods are 

necessary to confirm that the methods are functional and to confirm the levels of detection and 

quantitation reported in registrant-prepared validations.

Table 8.1 lists the status of the environmental fate data requirements for pendimethalin.

Guideline Study Title MRID / 

ACC No. Classification Data Gap?

835.2120 Hydrolysis 00106777 acceptable No

835.2240 Direct Aqueous 

Photolysis 

00153763 

43808201 

acceptable No

835.2410 Soil Photolysis 00153764 acceptable No

835.4100

Aerobic Soil 

Metabolism 

40185104 Supplemental Yes
39

7.9.2 Effects

For registration review, the following studies are requested to resolve uncertanties in the risk 

assessment:

Guideline Number: 850.2100

Study Title: Avian acute oral toxicity test (passerine species) with TGAI

Acute avian oral toxicity data are needed for either one waterfowl or one upland game species 

and one passerine species under the Part 158 data requirements (CFR 40 2008) for conventional 

pesticides. Based on previous risk assessments agricultural use patterns of pendimethalin result 

in acute LOC exceedances for listed and non-listed birds. Because passerine species have higher 

835.4200

Anaerobic Soil 

Metabolism 

40185105 acceptable No

835.4300

Anaerobic 

Aquatic 

Metabolism 

40813501 

43154702 

acceptable No

835.4400 Aerobic Aquatic 

Metabolism 

47385201 acceptable No

835.1240,

835.1230

Mobility –

Adsorption / 

Desorption ) 

00153765 

43041901 

acceptable No

835.1410 Laboratory 

Volatility 

00153766 

acceptable No

835.6100 Terrestrial Field 

Dissipation 

45364705,

45364706,

45 163802, 

45136801

acceptable No

850.1730

Fish 

Bioaccumulation 

00156726 

00158235 

acceptable No

850.6100

Environmental

Chemistry 

Methods

and Associated

Independent

Laboratory 

Validation (soil 

and water):

For the MRID#

45364705,

45364706,

45 163802, 

45136801

No Data 

Submitted

N/A Yes
40

metabolic rates due to their smaller sizes than either waterfowl or upland game bird species, and 

because they may utilize different metabolic pathways, they may be more or less sensitive to 

pendimethalin. An additional line of evidence from the reported bird incident (I007495-001, 

Appendix B), shows that the birds affected were passerines (although the causes were 

uncertain). In order to properly characterize risk to passerines, an avian oral toxicity test is 

requested. A passerine study protocol should be submitted for review by the Agency prior to 

initiation of the study.

Guideline Number: OCSPP 850.1760 (in prep), OCSPP 850.1770 (in prep.) and OCSPP 

850.1780 (in prep.) with TGAI

Study Title: Whole sediment: acute invertebrates freshwater and marine

One chronic sediment toxicity test for a freshwater invertebrate has been submitted for 

pendimethalin; however, this is not sufficient to satisfy the Agency’s updated data requirements 

for outdoor uses in 40 CFR Part 158 (October 26, 2007). For pendimethalin, available 

information indicates that benthic organisms may be exposed to pendimethalin which may be 

transported into aquatic environments via spray drift or runoff. Based on calculations in the most 

recent EFED assessment, the 21-day sediment porewater EECs predicted for pendimethalin

ranged from 0.4 to 8.00 μg a.i./L (DP Barcodes 39116 and 394467). The upper end of this range 

exceeds 0.1 of the most sensitive acute LC/EC50 (210 μg a.i./L for eastern oyster), which satisfies 

one of the criteria for requiring chronic whole sediment toxicity testing under 40 CFR Part 158. 

Furthermore, chronic reproductive effects were seen in water column studies with aquatic 

invertebrates (daphnid), with a NOAEC = 14.5 μg a.i./L and LOAEC = 17.2 μg a.i./L.

Pendimethalin is expected to persist in sediments, based on half-lives in submitted soil 

metabolism and aquatic metabolism studies (aerobic soil, 172 days; aerobic aquatic metabolism, 

27 days) (MRIDs 4018501 and 47385201). These half-life values exceed the 40 CFR Part 158 

criterion of 10 days. 

The third set of trigger criteria for needing chronic testing (Kd > 50 or log KOW >3 or KOC > 

1000) is also met for pendimethalin (log KOW is 5.18, and the mean KOC value is ~17,000). The 

physicochemical property triggers (Kd, KOW and KOC) reflect the propensity of the chemical to 

partition onto the particulate or organic matter phases of sediments. Exceeding any one of the 

physicochemical property triggers listed above is sufficient for indicating the pesticide has 

reasonable potential for partitioning to the sediment compartment. 

Although a registrant submitted study is available for a chronic whole sediment test on 

Chironomus riparius, significant uncertainties associated with the study design (e.g., total 

organic carbon was not measured) make the results unsuitable for use in risk assessment. 

Therefore, chronic whole sediment tests on Hyalella azteca, Chironomus riparius and 

Leptocheirus plumulosus are requested. Although both are freshwater species, Hyalella and 

Chironomus differ substantially in their morphology (crustacean vs. insect), ecological niche 

(epibenthic v. infaunal species), and physiology. Evidence also suggests that Hyalella is among 

the more sensitive invertebrates based on water column tests (Maund et al., 2002; Weston and 

Jackson, 2009). Pendimethalin has the potential to enter estuarine/marine water bodies based on 

current usage patterns that include coastal areas. Therefore, testing is also needed for an 

estuarine/marine sediment-dwelling invertebrate species (e.g., Leptocheirus plumulosus). 
41

Until the final OCSPP guidelines for chronic sediment toxicity tests are published, the registrant 

should submit a protocol to EFED for approval prior to test initiation, considering the following 

methods:

• Test Method 100.4: Hyalella azteca 42-d Test for Measuring the Effects of Sediment 

Associated Contaminants on Survival, Growth, and Reproduction in USEPA 2000 

Methods for Measuring the Toxicity and Bioaccumulation of Sediment-associated 

Contaminants with Freshwater Invertebrates EPA 600/R-99/064 (OCSPP 850.1770, in 

prep.);

• Test Method 100.5: Life-cycle Test for Measuring the Effects of Sediment-associated 

Contaminants on Chironomus dilutus (formerly known as C. tentans) in USEPA 2000 

Methods for Measuring the Toxicity and Bioaccumulation of Sediment-associated 

Contaminants with Freshwater Invertebrates EPA 600/R-99/064 (OCSPP 850.1760, in 

prep.); and 

• Leptocheirus plumulosus in USEPA 2001 Method for Assessing the Chronic Toxicity of 

Marine and Estuarine Sediment-associated Contaminants with the Amphipod 

Leptocheirus plumulosus EPA 600/R-01/020 (OCSPP 850.1780, in prep.).

As an alternative to recommending the conduct of 2 chronic (life cycle) sediment toxicity tests, 

EFED would also consider a tiered testing approach for sediment toxicity testing. In this 

approach, sediment toxicity testing would first be conducted with the aforementioned species 

using the 10-d (subchronic) sediment toxicity test guidelines (OSCPP 850.1735 and 850.1740). 

Then, pending a comparison of estimated environmental concentrations (EEC) in sediment and 

porewater with toxicity results from the 10-d sediment toxicity studies, the need for one or more 

chronic sediment toxicity studies would be determined. This tiered testing approach has the 

potential advantage of reducing the number of chronic (life cycle) studies that would be needed 

when results of the 10-d (subchronic) tests in conjunction with sediment EECs indicate chronic 

testing is not likely to alter risk assessment conclusions. In some cases, however, this tiered 

testing approach may result in the conduct of both a 10-d (subchronic) and a chronic (life cycle) 

study.

Guideline Number: 850.1350

Study Title: Saltwater Aquatic Invertebrate Life Cycle 

Previously submitted studies indicate that estuarine/marine invertebrates are among the most 

sensitive taxa to pendimethalin on an acute basis, with effects expected below 210 μg a.i./L. 

The need for a life cycle chronic toxicity of pendimethalin to estuarine/marine invertebrates is 

indicated based on its aquatic toxicity and environmental fate properties according to 40 CFR 

Part 158 data requirements (October 26, 2007). Specifically:

1. Pendimethalin is intended for use such that its presence in estuarine/marine 

environment in significant concentrations is expected; 

2. The acute LC/EC50 for pendimethalin is substantially lower than the 40 Part 158 

trigger value of 1 mg/L (210 μg a.i./L for pendimethalin; Crassostrea virginica); 

and

3. Previous risk assessments have indicated that the aquatic EECs are > 0.01 of the 

acute LC/EC50 values for the higher use patterns of pendimethalin, which is 

another condition for triggering an estuarine/marine invertebrate life cycle study. 
42

In the most recent assessment for pyrethrins, the 21-day aquatic estimated 

exposure concentrations modeled for all 8 scenarios modeled crop scenarios range 

from 0.51 – 14.3 μg/L (DP barcodes 391166 and 391167). 

An acute-to-chronic ratio is not appropriate because the freshwater acute and chronic data are 

based on the daphnid, which does not have a similar life history to the eastern oyster, the most 

senstitive salt water invertebrate species studied in the acute test. In addition, pendimethalin is 

very highly toxic to saltwater invertebrates on an acute basis. Therefore this study is necessary to 

reduce the uncertainty. Without this data chronic risk to saltwater species will be presumed. 

Guideline Number: 850.1400

Study Title: Saltwater Fish Early-Life Cycle 

Previously submitted studies indicate that estuarine/marine fish are among the most sensitive 

taxa to pendimethalin on an acute basis, with effects expected below 710 μg a.i./L. 

The need for a life cycle chronic toxicity study of pendimethalin to estuarine/marine fish is 

indicated based on its aquatic toxicity and environmental fate properties according to 40 CFR 

Part 158 data requirements (October 26, 2007). Specifically:

1. Pendimethalin is intended for use such that its presence in estuarine/marine 

environment in significant concentrations is expected; 

2. The acute LC/EC50 for pendimethalin is substantially lower than the 40 Part 158 

trigger value of 1 mg/L (710 μg a.i./L for pendimethalin; Crassostrea virginica); 

and

3. Previous risk assessments have indicated that the aquatic EECs are > 0.01 of the 

acute LC/EC50 values for the highest use patterns of pendimethalin, which is 

another condition for triggering an estuarine/marine invertebrate life cycle study. 

In the most recent assessment for pyrethrins, the 21-day aquatic estimated 

exposure concentrations modeled for all 8 scenarios modeled crop scenarios range 

from 0.51 – 14.3 μg/L (DP barcodes 391166 and 391167). 

An acute-to-chronic ration from the freshwater species is not appropriate because the acute and 

chronic studies used different freshwater species. In addition, pendimethalin is very highly toxic 

to saltwater fish on an acute basis. Therefore this study is necessary to reduce the uncertainty. 

Without this data chronic risk to saltwater species will be presumed. 

Guideline Numbers: 850.4150 and 850.4250

Study Title: Vegetative vigor and Seedling emergence, TierII8 with TEP

Terrestrial plant testing was conducted with TGAI and did not include solvent controls. The use 

of TEP instead of TGAI is recommended for all terrestrial non-plant target studies. Testing with 

only the TGAI may underestimate toxicity to plants because the TEP may include a solvent or 

adjuvant which results in additive or synergistic toxicity. 

The Agency is aware that additional data on pendimethalin are available for the European Food 

Safety Authority reports (EFSA, 2006). It is recommended that any applicable data generated for 

the European review process be submitted to EPA.

 8 A Tier II study is required. The DCI will provide that a Tier I plant study may be conducted in 

lieu of a Tier II study with the understanding that any adverse effects observed by the Tier I 

study would necessitate conduct and submission of a Tier II study as well.
43

Table 8.2 lists the status of the ecological effects data requirements for pendimethalin.

Table 8.2. Ecological Effects Data Requirements for Pendimethalin.

Data Requirement

Does EPA 

Have

Data To 

Satisfy

This 

Requirement?

Bibliographic

Citation (MRID)

Must Additional

Data Be 

Submitted

Under FIFRA 

3(c)(2)(B)?

§158.630 TERRESTRIAL ORGANISM TESTING

850.2100 Acute Avian Oral, 

Quail/Duck/Passerine 

Partially 00059739 Yes1

850.2200 Acute Avian Diet, Quail Yes 00026675 No

850.2200 Acute Avian Diet, Duck Yes 00026674 No

850.2300 Avian Reproduction Quail Yes 44907602 No

850.2300 Avian Reproduction Duck Yes 44907601 No

§158.630 AQUATIC ORGANISM TESTING

850.1075 Acute Fish Toxicity 

Bluegill 

Yes 00046291 No

850.1075 Acute Fish Toxicity 

Rainbow Trout 

Yes 00046291 No

Non-Guideline Acute Fish Toxicity 

(TEP)

Yes 00046292 No

850.1010 Acute Aquatic 

Invertebrate 

Yes 00153772 No

Non-Guideline Acute Aquatic 

Invertebrate (TEP) 

Yes 00059738 No

850.1075 Acute Est/Mar Toxicity 

Fish 

Yes 00131774 No

850.1075 Acute Est/Mar Toxicity 

Fish (TEP)

Yes 00131774 No

850.1035 Acute Est/Mar Toxicity 

Shrimp 

Yes 00131775 No

850.1035 Acute Est/Mar Toxicity 

Shrimp (TEP) 

Yes 00131775 No

850.1025 Acute Est/Mar Toxicity 

Mollusk 

Yes 00131772 No
44

Table 8.2. Ecological Effects Data Requirements for Pendimethalin.

Data Requirement

Does EPA 

Have

Data To 

Satisfy

This 

Requirement?

Bibliographic

Citation (MRID)

Must Additional

Data Be 

Submitted

Under FIFRA 

3(c)(2)(B)?

850.1025 Acute Est/Mar Toxicity 

Mollusk (TEP) 

Yes 00131772 No

850.1400 Early Life Stage Fish

(freshwater) 

Yes 00029791 No

850.1400 Early Life Stage Fish 

(salwater) 

No N/A Yes2

850.1300 Life Cycle Aquatic 

Invertebrate (freshwater) Yes 00100504 No

850.1350 Life Cycle Aquatic 

Invertebrate (saltwater) No N/A Yes3

850.1500 Life Cycle Freshwater 

Fish 

Yes 00037940 No

850.1730 Bioaccumulation in Fish Yes 00156726, 

00158235 No

OCSPP 850.1760 (in prep.), 

850.1770 (in prep.) and 850.1780 

(in prep.) Whole sediment: 

chronic invertebrates freshwater & 

marine

Partially 47891601 Yes4,5

850.1020 Aquatic Invertebrate Acute 

Toxicity (Hyalella) No N/A No

§158.660 PLANT PROTECTION TESTING

850.4100 Seed Germ, Seedling 

Emergence

Yes 42372201, 

42372202

Yes6

850.4150 Vegetative Vigor Yes 42372203 Yes7

850.4400, 850.5400 Aquatic Plant 

Growth

Yes 42137101, 

42372205,

42372204,

42372206

42372207

No

§158.490 INSECT POLLINATOR TESTING

850.3020 Honey Bee Acute Contact Yes 0009980 No
45

850.3030 Honey Bee Residue on 

Foliage 

No N/A No

850.3040 Field Test for Pollinators No N/A No

N/A = Not applicable because no citation is available.

1 Data are needed for a passerine species. The registrant should submit a protocol prior to conducting 

this study.

2 Data are needed for a saltwater fish species. Without this data EFED will use an acute-to-chronic ratio 

that may represent a more conservative value.

3

Data are needed for a saltwater invertebrate species. Without this data EFED will use an acute-tochronic ratio that may represent a more conservative value.

4 Until the final OCSPP guidelines for chronic sediment toxicity tests are published, the registrant 

should submit a protocol to EFED for approval prior to test initiation.

5 A chronic test is required. The DCI will provide that an acute sediment toxicity study may be 

conducted in lieu of a chronic study with the understanding that any adverse effects observed by the 

acute study would necessitate conduct and submission of a chronic study as well.

6 Tier II tests needed if a tested terrestrial species exhibits a statistically significant detrimental effect in 

the Tier I study.

7

Tier II tests needed if a tested aquatic species exhibits a statistically significant detrimental effect in a 

Tier I study.

8 Literature Cited 

Arnot, J.A. and F.A.P.C. Gobas. 2004. A food web bioaccumulation model for organic 

chemicals in aquatic ecosystems. Environmental Toxicology and Chemistry, 23 (10):

2343-2355.

Fletcher, J.S., J.E. Nellessen, and T.G. Pfleeger. 1994. Literature review and evaluation of the 

EPA food-chain (Kenaga) nomogram, an instrument for estimating pesticide residues on 

plants. Environ. Tox. Chem. 13:1383-1391.

Hoerger, F. and E. E. Kenaga. 1972. Pesticide Residues on Plants: Correlation of 

Representative Data as a Basis for Estimation of their Magnitude in the Environment. In

F. Coulston and F. Korte, eds., Environmental Quality and Safety: Chemistry, 

Toxicology, and Technology, Georg Thieme Publ., Stuttgart, West Germany, pp. 9-28.

Majewski, M.S. and P.D. Capel, 1995. Pesticides in the Atmosphere. Distribution, Trends, and 

Governing Factors. Ann Arbor Press, Chelsea, Mich., p. 160.

UCDAVIS. COOPERATIVE EXTENSION. UNIVERSITY OF CALIFORNIA. Kiwifruit 

Production in California. Accessed on March 7, 2012 @ 

http://sfp.ucdavis.edu/pubs/brochures/kiwi.html.
46

USEPA. 2002. Technical Basis for the derivation of Equilibrium Partitioning Sediment 

Guidelines (ESGs) for the Protection of Benthic Organisms: Nonionic Organics [Draft]. 

EPA Document No. 822R02041. October 2002.

U.S. EPA. 2007. Ecological Risk Assessment for the Proposed Use of Pendimethalin on 

Artichoke, Asparagus, Brassica 5a, and Grapes. Environmental Fate and Effects 

Division. Office of Pesticide Programs. October 31, 2007. DP334069. 

USEPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide 

Programs. U.S. Environmental Protection Agency, Office of Prevention, Pesticides and 

Toxic Substances, Office of Pesticide Programs, Washington DC. January 23, 2004

U.S. EPA. 2009. Risks of Pendimethalin Use to Federally Threatened California Red-Legged 

Frog (Rana aurora draytonii). Pesticide Effects Determination. Environmental Fate and 

Effects Division. Office of Pesticide Programs. October 31, 2007. 

http://www.epa.gov/espp/litstatus/effects/redleg-frog/index.html#pendimethalin

U.S. EPA. 2010. Ecological Risk Assessment for the Pendimethalin Section 3 New Use on 

Edamame and Cool- and Warm-Season Forage Grass.

USEPA. 1998. Guidelines for Ecological Risk Assessment. Risk Assessment Forum, Office of 

Research and Development, Washington, D.C. EPA/630/R-95/002F. April 1998. 

http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=30759.

Di Toro, D. M., Zarba, C. S., Hansen, D. J., Berry,W. J., Swartz, R. C., Cowan, C. E., Pavlou, S. 

P., Allen, H. E., Thomas, N. A. and Paquin, P. R. 1991. Technical basis for establishing 

sediment quality criteria for nonionic organic chemicals using equilibrium partitioning. 

Environmental Toxicology and Chemistry. 10:1541-1583.

9 Fate and Ecotoxicity Bibliography
47

Pendimethalin Fate Bibliography

Note to Reviewer

There are many 5 Year soil dissipation and residue studies in our folders that are not captured by OPPIN. 

Authors are Roman, Tondreau and others about 1979 all under one MRID 00046795. Most are invalid

See 2037406, 2037408, 2037409, 2037422, 2037423, 2037424, 2037425, 2037426, 2037427, 2037428, 2037429, 

2037430, 2037431, 2037432, 2037433

161-1 Hydrolysis

MRID Citation Reference

46287 See 106777 

below

Zulalian, J.; Eisner, S.K. (1974) Prowl Herbicide: A Study on the Behavior of 14?CLabeled CL 92,553 in an Hydrolytic Environ- ment: Project No. 2-463. (Unpublished 

study received Sep 27, 1974 under 5F1556; submitted by American Cyanamid Co., 

Prince- ton, N.J.; CDL:094674-A) 

46296 2037434 Zulalian, J.; Fasinski, R.; Eisner, S.K. (1973) CL 92,553: Metabo- lism VII. Fate of 

Carbon-14 Labeled CL 92,553 (Prowl Herbicide) on Exposure to Sunlight in Water 

and on Glass and Soil Surfaces: Report No. 2-463. (Unpublished study received Sep 

27, 1974 under 5F1556; prepared by American Cyanamid Co., Princeton, N.J.; 

CDL:094673-R) 

109914 See above Zulalian, J.; Fasinski, R.; Eisner, S. (1973) CL 92,553: Metabo- lism VII. Fate of 

Carbon-14 Labeled CL 92,553 (Prowl Herbicide) on Exposure to Sunlight in Water 

and on Glass and Soil Surfaces: PD-M 10:912-958. (Unpublished study received on 

unknown date under 4G1451; submitted by American Cyanamid Co., Princeton, NJ; 

CDL:094672-D) 

106777 2037438

Study in Hydrolytic environment

161-2 Photodegradation-water

MRID Citation Reference

153763 2037455 Sanders, P. (1985) Prowl Herbicide, Pendimethalin (AC 92,553): Photodegradation 

in Water: Project No. 0166: Report No. PD-M Volume 22-36. Unpublished study 

prepared by American Cyanamid Co. 32 p. 

43808201 Mentioned in 

RED chapter

Ta, C. (1995) Aqueous Photolysis of AC 92,553: Lab Project Number: ENV 95-

028: E-95-04. Unpublished study prepared by American Cyanamid Co. 99 p. 

05001076 2037439

Open lit on photodecomposition – 11 herbibcides

46296 Zulalian, J.; Fasinski, R.; Eisner, S.K. (1973) CL 92,553: Metabo- lism VII. Fate of 

Carbon-14 Labeled CL 92,553 (Prowl Herbicide) on Exposure to Sunlight in 

Water and on Glass and Soil Surfaces: Report No. 2-463. (Unpublished study 

received Sep 27, 1974 under 5F1556; prepared by American Cyanamid Co., 

Princeton, N.J.; CDL:094673-R) 

161-3 Photodegradation-soil
48

MRID Citation Reference

46296 2037434 Zulalian, J.; Fasinski, R.; Eisner, S.K. (1973) CL 92,553: Metabo- lism VII. Fate of 

Carbon-14 Labeled CL 92,553 (Prowl Herbicide) on Exposure to Sunlight in Water and 

on Glass and Soil Surfaces: Report No. 2-463. (Unpublished study received Sep 27, 

1974 under 5F1556; prepared by American Cyanamid Co., Princeton, N.J.; 

CDL:094673-R) 

109914 See above Zulalian, J.; Fasinski, R.; Eisner, S. (1973) CL 92,553: Metabo- lism VII. Fate of 

Carbon-14 Labeled CL 92,553 (Prowl Herbicide) on Exposure to Sunlight in Water and 

on Glass and Soil Surfaces: PD-M 10:912-958. (Unpublished study received on 

unknown date under 4G1451; submitted by American Cyanamid Co., Princeton, NJ; 

CDL:094672-D) 

153764 2037456 Mangels, G. (1985) Prowl Herbicide, Pendimethalin (AC 92,553): Photodegradation on 

Soil: Project No. 0166: Report No. PD-M Volume 22-35. Unpublished study prepared 

by American Cyanamid Co. 27 p. 

162-1 Aerobic soil metabolism

MRID Citation Reference

46282 2037414

Summary 

2037315

Barringer, D.F., Jr.; Haugwitz, M.I.; Eisner, S.K. (1974) CL 92,553: Metabolism XIII. 

The Behavior of CL 92,553 (Prowl Herbicide) in Soil, Part III. Anaerobic Studies: 

Project No. 2- 463. (Unpublished study received Sep 27, 1974 under 5F1556; 

submitted by American Cyanamid Co., Princeton, N.J.; CDL: 094475-I) 

40185104 2037461 Lavin, M.; Cranor, W. (1987) Aerobic Soil Metabolism of [Carbon 14]-

Pendimethalin: Lab. Rept. No. 33731. Unpublished study pre- pared by Analytical 

Bio-Chemistry Laboratories, Inc. 677 p. 

162-2 Anaerobic soil metabolism

MRID Citation Reference

151795 or 

137706

2037518 pg 

2

Mangels, G. (1984) Prowl Herbicide, Pendimethalin (CL 92,553): Anaerobic 

Metabolilsm in Soil from a Rice Field: Project NO. 0470: Rept. No. PD-M Vol. 21-

2.1. Unpublished study prepared by American Cyanamid Co. 29 p. 

40185105 2037462 Lavin, M.; Cranor, W. (1987) Anaerobic Soil Metabolism of [Carbon 14]-

Pendimethalin: Lab. Rept. No. 33732. Unpublished study pre- pared by Analytical 

Bio-Chemistry Laboratories, Inc. 

162-3 Anaerobic aquatic metab.

MRID Citation Reference

40813501 2037483 Sanders, P. (1988) Pendimethalin (AC 92,553): Anaerobic Aquatic De- gradation in 

Soil from a Rice Field: Laboratory Project ID PD-M- 25-25. Unpublished study 

prepared by American Cyanamid Co. 53 p. 

43154701 Response Mangels, G.; Ahmed, Z. (1994) Pendimethalin Registration Standard--Response to 
49

EFGWB Review. Unpublished study prepared by American Cyanamid Co. 88 p. 

43154702 No DER but 

summarized in 

REDs 

2038941

Mangels, G. (1991) Pendimethalin (AC 92, 553): Anaerobic Aquatic Degradation 

in Static Canadian Pond Water: Lab Project Number: PD-M 28-5: E-89-30: 0466. 

Unpublished study prepared by American Cyanamid Co. 117 p. 

162-4 or 835.4300 Aerobic aquatic metab.

MRID Citation Reference

47385201 2081628 Ebert, D. (2008) Degradation of Pendimethalin (BAS 455 H) in Water/Sediment 

Systems Under Aerobic Conditions: Final Repost. Project Number: 169996, 

2004/1022517. Unpublished study prepared by BASF Aktiengesellschaft. 75 p.

163-1 Leach/adsorp/desorption

MRID Citation Reference

46288 2037416

Summary 

2037315

Barringer, D.F., Jr.; Haugwitz, M.I.; Jakowlew, S.B.; et al. (1974) CL 92,553: A 

Study of the Leaching of CL 92,553 (Prowl Herbi- cide) from Four Different Soil 

Types: Project No. 2-463. (Un- published study received Sep 27, 1974 under 5F1556; 

submitted by American Cyanamid Co., Princeton, N.J.; CDL:094674-B) 

46289 2037417

Summary 

2037315

O'Grodnick, J.S.; Dupre, G.D. (1974) Leaching Characteristics of ^14IC-Prowl^(R)I 

and Its Degradation Products following Aging in Princeton Sandy Loam Soil under 

Greenhouse Conditions: Report No. 74003-1. (Unpublished study received Sep 27, 

1974 under 5F1556; prepared by Bio/dynamics, Inc., submitted by American 

Cyanamid Co., Princeton, N.J.; CDL:094674-C) 

46290 2037418

Summary 

2037315

Dupre, G.D. (1974) Runoff Characteristics of ^14IC-Prowl^(R)I Ap- plied to Silt 

Loam Soil under Greenhouse Conditions: Report No. 74004. (Unpublished study 

received Sep 27, 1974 under 5F1556; prepared by Bio/dynamics, Inc., submitted by 

American Cyanamid Co., Princeton, N.J.; CDL:094674-D) 

46296 Zulalian, J.; Fasinski, R.; Eisner, S.K. (1973) CL 92,553: Metabo- lism VII. Fate of 

Carbon-14 Labeled CL 92,553 (Prowl Herbicide) on Exposure to Sunlight in Water 

and on Glass and Soil Surfaces: Report No. 2-463. (Unpublished study received Sep 

27, 1974 under 5F1556; prepared by American Cyanamid Co., Princeton, N.J.; 

CDL:094673-R) 

106777 Summary 

2037315

American Cyanamid Co. (1974) Introduction to Environmental Chem- istry Studies 

with Prowl (AC 92,553). (Compilation; unpublished study received on unknown date 

under 5G1567; CDL:094279-A; 094280; 094281; 094282) 

106782 2037310 Zulalian, J.; Godney, R.; Fasinski, R. (1973) CL 92,553--Metabo- lism V: Fate of 

Carbon-14 Labeled CL 92,553 (Prowl Herbicide) in Soil: PD-M 10:837-911. 

(Unpublished study received on un- known date under 4G1451; submitted by 

American Cyanamid Co., Princeton, NJ; CDL:094672-B) 

153765 2037457 Mangels, G. (1985) Prowl Herbicide, Pendimethalin (AC 92,553): 

Adsorption/Desorption Studies: Project No. 0166: Report No. PD-M Volume 22-37. 

Unpublished study prepared by American Cyanamid Co. 76 p. 

43041901 Mangels, G. (1993) Pendimethalin (AC 92,553): Adsorption/Desorption on Japanese 

Soils: Lab Project Number: PD/M/28/11: PD/M: E/90/3. Unpublished study prepared 

by American Cyanamid Co. 37 p. 
50

163-2 Volatility - lab

MRID Citation Reference

153766 2037458 Sanders, P. (1985) Prowl Herbicide, Pendimethalin (AC 92,553): Volatilization 

from Soil: Project No. 0166: Report No. PD-M Volume 22-38. Unpublished study 

prepared by American Cyanamid Co. 28 p. 

164-1 Terrestrial field dissipation

MRID Citation Reference

24857 Kennedy, J.M.; Talbert, R.E.; Fischer, B. (1974) ?Dinitroaniline Herbicides: Their 

Persistence on the Soil Surface, Residual Ac- tivity, and Relative Crop Tolerance|. 

(Unpublished study re- ceived 1975 under 2G1285; prepared by Univ. of Arkansas, 

Agri- cultural Experiment Station, submitted by Union Carbide Agricul- tural 

Products Co., Ambler, Pa.; CDL:095154-E) 

26872 Moyer, M.; Potts, C.; Devine, J.M.; et al. (1975) Prowl^(R)I(CL 92,553): 

Determination of CL 92,553 ?N-(1-Ethylpropyl)-3,4-di- methyl-2,6-

dinitrobenzenamine| and Sencor ?4-Amino-6-t-butyl-3- (methylthio)-1,2,4-triazin5-one| in Soil: Report No. C-859. (Unpublished study received Nov 20, 1975 under 

6F1704; submitted by American Cyanamid Co., Princeton, N.J.; CDL:094647-H) 

26873 Potts, C.R.; Laporta, M.M.; Devine, J.; et al. (1975) Prowl^(R)I (CL 92,553): 

Determination of CL 92,553 ?N-(1-Ethylpropyl)-3,4- dimethyl-2,6-

dinitrobenzenamine| and Sencor ?4-Amino-6-t-butyl- 3-(methylthio)-1,2,4-triazin5(4H)-one| in Soil: Report No. C- 801. (Unpublished study received Nov 20, 1975 

under 6F1704; submitted by American Cyanamid Co., Princeton, N.J.; CDL: 

094647-I) 

46281 2037413

Summary 

2037315

Barringer, D.F., Jr.; Zulalian, J.; Fisner, S.K. (1974) CL 92,553: Metabolism XI. 

The Behavior of CL 92,553 (Prowl Herbicide) in Soil, Part II. A 16-Month FieldExposure Study: Project No. 2- 463. (Unpublished study received Sep 27, 1974 

under 5F1556; submitted by American Cyanamid Co., Princeton, N.J.; CDL: 

094475-H) 

46294 Wyckoff, J.C.; Nzewi, G.I.; Roberts, W.W.; et al. (1974) ?Residue Study of Prowl, 

Atrazine, Bladex and Banvel in Soil|: Report No. C-518. (Reports by various 

sources; unpublished study in- cluding report no. C-517, received Sep 27, 1974 

under 5F1556; submitted by American Cyanamid Co., Princeton, N.J.; CDL: 

094674-N) 

46295 2037420

Summary 

2037315

Nzewi, G.I.; Tondreau, R.E.; Jakowlew, S.; et al. (1974) ?Residue Study of Prowl 

in Soil|: Report No. C-473. (Reports by various sources; unpublished study 

including report nos. C-476, C-477, C-475..., received Sep 27, 1974 under 5F1556; 

submitted by Amer- ican Cyanamid Co., Princeton, N.J.; CDL:094673-C) 

106782 Summary 

2037315

2037413

Zulalian, J.; Godney, R.; Fasinski, R. (1973) CL 92,553--Metabo- lism V: Fate of 

Carbon-14 Labeled CL 92,553 (Prowl Herbicide) in Soil: PD-M 10:837-911. 

(Unpublished study received on un- known date under 4G1451; submitted by 

American Cyanamid Co., Princeton, NJ; CDL:094672-B) 

106798 Summary 

2037315

American Cyanamid Co. (1978) Amounts of Residues of Prowl, Its Metabolite (CL 

202,347), Metribuzin (Sencor or Lexone) and Eptam in Soil. (Compilation; 

unpublished study received Oct 5, 1978 under 241-243; CDL:097435-A) 

106805 Devine, J.; Kust, C.; Moyer, M.; et al. (1975) Prowl (CL 92,553): Determination of 
51

CL 92,553 ... and Sencor ... in Soil. Indi- ana.: Report No. C-859. (Unpublished 

study received Nov 14, 1975 under 6F1704; submitted by American Cyanamid Co., 

Prince- ton, NJ; CDL:097956-E) 

106806 2037454 Devine, J.; Kust, C.; Potts, C.; et al. (1975) Prowl (CL 92,553): Determination of 

CL 92,553 ... and Sencor ... in Soil. Kan- sas. 1974: Report No. C-801. 

(Unpublished study received Nov 14, 1975 under 6F1704; submitted by American 

Cyanamid Co., Princeton, NJ; CDL:097956-F) 

129090 American Cyanamid Co. (1979) ?Residue of Prowl Herbicide in Soil|. 

(Compilation; unpublished study received May 17, 1979 under 241- 243; 

CDL:238510-D) 

5001077 Summary 

2037315

Parochetti, J.V.; Dec, G.W., Jr.; Burt, G.W. (1976) Volatility of eleven 

dinitroaniline herbicides. Weed Science 24(6):529-532. 

41725204 2037464 Steller, W.; Smyth, M. (1990) Pendimethalin (AC 92,553): Residues of AC 92,553 

in Soil (Postemergence, Sandy Loam) Kerman, Cali- fornia--1988: Lab Project 

Number: C-3280. Unpublished study prepared by American Cyanamid Co. 90 p. 

41725205 Sreller, W.; Smyth, M. (1990) Pendimethalin (AC 92,553): Residues of AC92, 553 

in Soil (Post-emergence, Sandy) Brawley, California 1988: Lab Project Number: C3281. Unpublished study prepared by American Cyanamid Co. 65 p. 

41725206 Smyth, M; Koch, D.; Smith, J. (1990) Pendimethalin (AC 92, 553): Freezer 

Stability in Soil: Lab Project Number: C-3467. Unpub- lished study prepared by 

American Cyanamid Co. and Analytical Biochemistry Labs, Inc. 281 p. 

43154701 Mangels, G.; Ahmed, Z. (1994) Pendimethalin Registration Standard--Response to 

EFGWB Review. Unpublished study prepared by American Cyanamid Co. 88 p. 

45136801 2002727 Kukel, C. (2000) CL 92553 (Pendimethalin): Rate of Dissipation of CL 92553 

Residues in Air and Soil After Treatment with Prowl 3.3 EC Herbicide Applied 

Pre-Plant Incorporated (PPI) to Soybeans in Indiana, U.S: Lab Project Number: 

PR98IN01: A011.294: A011.310. Unpublished study prepared by American 

Cyanamid Company, Heartland Technologies, H.E.R.A.C., Inc. and Maxim 

Technologies. 207 p. 

45136802 2002728 Kukel, C. (2000) CL 92553 (Pendimethalin): Rate of Dissipation of CL 92553 

Residues in Air and Soil After Treatment with Prowl 3.3 EC Herbicide Applied 

Pre-Emergence (PE) to Cotton in Louisiana, U.S: Lab Project Number: PR98LA02: 

A011.295: A011.311. Unpublished study prepared by American Cyanamid 

Company, H.E.R.A.C., Inc. and Maxim Technologies. 214 p. 

45364705 2002730 or 

2002732

Horton, W. (2001) CL 92553 (Pendimethalin): Comparison of the Rate of 

Dissipation of CL 92553 Residues in Soil Following a Single Preemergent 

Application of Either Prowl 3.3 EC Herbicide or Prowl 3.8 CS Herbicide to Cotton 

in Mississippi: Lab Project Number: RES 00-040: PR98MS01: M 820.04. 

Unpublished study prepared by BASF Agro Research Corporation and Maxim 

Technologies, Inc. 199 p. 

45364706 2002729 Horton, W. (2001) CL 92553 (Pendimethalin): Comparison of the Rate of 

Dissipation of CL 92553 Residues in Soil Following a Single Pre-Plant 

Incorporation of Either Prowl 3.3 EC Herbicide or Prowl 3.8 CS Herbicide to 

Soybeans in Indiana: Lab Project Number: RES 00-039: PR9907: PR9907IN01. 

Unpublished study prepared by BASF Agro Research Corporation. 198 p. 

164-2 Aquatic field dissipation

MRID Citation Reference
52

29031 Tondreau, R.E. (1973) CL 92,553: N-(1-Ethylpropyl)-2,6-dinitro-3,4- xylidine 

Residues in Soil: Report No. C-355. Includes method M-388 dated Oct 25, 1973. 

(Unpublished study received on un- known date under 4G1451; submitted by 

American Cyanamid Co., Princeton, N.J.; CDL:093869-Q) 

29032 2037407 Bodnarchuk, D.; Moyer, M.; Tondreau, R.E.; et al. (1973) Prowl: Determination of 

CL 92,553...Residues in Soil (Waseca, Minneso- ta) Treated by Pre-emergence 

Spray: Report No. C-400. Includes method M-437 dated Oct 25, 1973. 

(Unpublished study received on unknown date under 4G1451; submitted by 

American Cyanamid Co., Princeton, N.J.; CDL:093869-R) 

31976 Boughton, P.J.; Benson, G.L.; Moyer, M.; et al. (1975) Residue Sum- maries--PayOff Tobacco Sucker Control Agent. (Unpublished study received Mar 18, 1975 

under 241-247; prepared in coopera- tion with U.S. Agricultural Research Service 

and others, submit- ted by American Cyanamid Co., Princeton, N.J.; CDL:050910-

D) 

67293 Summary 

2037315

Marei, A.H.; Haugwitz, M.I.; Eisner, S.K. (1974) CL 92,553: Metabo- lism: XII. 

Residual Radioactivity in Rice Grain and Plants Grown in Soil Treated with 

Carbon-14 CL 92,553: PD-M 11:376-416. Fi- nal rept. (Unpublished study received 

Aug 25, 1980 under 241- 243; submitted by American Cyanamid Co., Princeton, 

N.J.; CDL: 099565-K) 

41245601 2037465 Manual, A. (1980) Analysis for Residues of Prowl in Soil and in Water from Prowl 

Treated Rice Fields: Report No. CY 17. Unpub- lished study prepared by American 

Cyanamid Co. 114 p. 

44527601 

and 602

2002731 Leonard, R.; Xu, B.; Cenni, M. et al. (1997) Dissipation of CL 92,553 Residues in 

Water, Soil and Sediment from a PROWL 3.3 EC Herbicide Treated Rice Field: 

Lab Project Number: RES 95-195: RES 96-057: RES 96-112. Unpublished study 

prepared by Centre Analytical Labs., Inc., American Cyanamid Co., and Maxim 

Technologies, Inc. 302 p. {OPPTS 840.1200} 

165-0 Accumulation Studies -- General

MRID Citation Reference

46293 2037419 Kapoor, I.P.; Barringer, D.F., Jr.; Haugwitz, M.I.; et al. (1974) Prowl Herbicide: 

Metabolism X. Isolation, Identification, and Characterization of CL 92, 553 and Its 

Metabolites in Fish and Its Aquatic Environment: Project No. 2-463. (Unpublished 

study received Sep 27, 1974 under 5F1556; prepared in cooperation with 

Bionomics EG&G, Inc., submitted by American Cyanamid Co., Princeton, N.J.; 

CDL:094674-G) 

165-1 Confined rotational crop

MRID Citation Reference

41806801 2037466 Lee, T. (1989) Pendimethalin (CL 92,553): Confined Accumulation studies of 

Carbon-14 Labeled Cl 92,553 in Lettuce, Wheat, Carrot Radishes, and Snap Beans 

as Representative Rotational Crops (Princeton New Jersey): Lab Project Number: 

CY 38: PD-M 26-4: PD-M 24-33. Unpublished study prepared by American 

Cyanamid Co. 210 p. 
53

43918601 Afzal, J. (1996) Pendimethalin (CL 92,553): Confined Accumulation Study of 

Carbon-14 Labeled CL 92,553 in Lettuce, Radishes, and Wheat as Rotational 

Crops: Lab Project Number: MET 96-002: M94P553NC1: 95AASIFRF001. 

Unpublished study prepared by American Cyanamid Co. and American 

Agricultural Services, Inc. 342 p. 

165-4 Bioaccumulation in fish

MRID Citation Reference

158235 and 

156726

2037459 Forbis, A.; Burgess, D.; Burnett, J. (1986) Uptake, Depuration and 

Bioconcentration of [Carbon-14]-AC 92,553 by Bluegill Sunfish (Lepomis 

macrochirus): PD-M Volume 23-17; ABC Final Report # 33408. Unpublished 

study prepared by Analytical Bio-Chemistry Laboratories, Inc. 276 p. 

71124 McAllister, W.A.; Thompson, C.M.; Forbis, A.D.; et al. (1980) Resi- due Accumulation Study in Crayfish 

(~Procambarus simulans~) with ^14IC-CL 92,553 (Pendimethalin) under Static Conditions: Final Residue 

Accumulation Report # 25687. (Unpublished study received Jan 22, 1981 under 241-243; prepared by 

Analytical Bio Chemistry Laboratories, Inc., submitted by American Cyanamid Co., Princeton, N.J.; 

CDL:099889-C) 

Drift study – 00029344= 2037410

Residues in Water 00071126, 00058834, and 00071129 = 2037437

Pendimethalin Ecotoxicity Bibliography

71-1 Avian Single Dose Oral Toxicity

MRID Citation Reference

59739 2037321 Fink, R. (1976) Final Report: Acute Oral LD50--Mallard Duck: Proj- ect No. 

130-110. (Unpublished study received 1976 under 241- 243; prepared by 

Truslow Farms, Inc., submitted by American Cyanamid Co., Princeton, N.J.; 

CDL:228391-B) 

71-2 Avian Dietary Toxicity

MRID Citation Reference

26674 or 52577 or 

72900

2037317 Fink, R. (1973) Final Report: Eight-Day Dietary LCI50^--Mallard Ducks: 

Project No. 362-138. (Unpublished study received on un- known date under 

4G1451; prepared by Hazleton Laboratories, Inc., submitted by American 

Cyanamid Co., Princeton, N.J.; CDL:093868-X) 

26675 or 52578 or DER not Fink, R. (1973) Final Report: Eight-Day Dietary LCI50^--Bobwhite Quail: 
54

72899 located Project No. 362-137. (Unpublished study received on un- known date under 

4G1451; prepared by Hazleton Laboratories, sub- mitted by American 

Cyanamid Co., Princeton, N.J.; CDL:093868-Y) 

29791 DER not 

located

Shaffer, C.B. (1974) ?Toxicology Studies of Prowl Herbicide|. (Un- published 

study received Dec 21, 1974 under 5G1580; submitted by American Cyanamid 

Co., Princeton, N.J.; CDL:094331-A) 

52577 2007317 Fink, R. (1973) Final Report: Eight-Day Dietary LCI50^--Mallard Ducks: 

Project No. 362-138. (Unpublished study received Sep 27, 1974 under 

5F1556; prepared by Environmental Sciences Corp., submitted by American 

Cyanamid Co., Princeton, N.J.; CDL: 094232-H) 

52578 See 26675 

above

Fink, R. (1973) Final Report: Eight-Day Dietary LC50--Bobwhite Quail: 

Project No. 362-137. (Unpublished study received Sep 27, 1974 under 

5F1556; prepared by Environmental Sciences Corp., submitted by American 

Cyanamid Co., Princeton, N.J.; CDL: 094232-I) 

71-4 Avian Reproduction

MRID Citation Reference

44907601 2037344 Beavers, J.; Foster, J.; Jaber, M. et al. (1996) Reproduction Study with AC 

92553 Technical in Mallard (Anas platyrhynchos): Lab Project Number: 954-

93-195: 130-171: TAN 95-004. Unpublished study prepared by Wildlife 

International, Ltd. 270 p. {OPPTS 850.2300} 

44907602 2037345 Beavers, J.; Foster, J.; Jaber, M. et al. (1996) Reproduction Study with AC 

92553 Technical in the Northern Bobwhite (Colinus virginianus): Lab Project 

Number: 954-93-197: 130-170: TAN 95-004. Unpublished study prepared by 

Wildlife International, Ltd. 274 p. 

72-1 Acute Toxicity to Freshwater Fish

MRID Citation Reference

106764 or 37778 

or 

46291

2037331

2037320

Sleight, B. (1973) Acute Toxicity of AC-92553 to Bluegill (Lepomis 

macrochirus), Rainbow Trout (Salmo gairdneri) and Channel Cat- Fish 

(Ictaluras punctatus). (Unpublished study received on unknown date under 

5G1567; prepared by Bionomics, Inc., sub- mitted by American Cyanamid 

Co., Princeton, NJ; CDL:094287-E) 

131773 2037330 LeBlanc, G.; Sousa, J. (1983) Acute Toxicity of AC 92,553 to Chan- nel 

Catfish ...: Report #BW-83-2-1361. (Unpublished study re- ceived Oct 28, 

1983 under 241-243; prepared by EG & G Bionomics, submitted by American 

Cyanamid Co., Princeton, NJ; CDL:251601-C) 

37778 See 106764 

above

Sleight, B.H., III (1972) Bioassay Report: Acute Toxicity of AC- 92553 to 

Bluegill (?~Lepomis macrochirus~?), Rainbow Trout (?~Salmo gairdneri~?) 
55

and Channel Catfish (?~Ictaluras puncta~?- ?~tus~?). (Unpublished study 

received on unknown date under 4G1451; prepared by Bionomics, Inc., 

submitted by American Cyanamid Co., Princeton, N.J.; CDL:093868-W) 

46291 2037320 Sleight, B.H., III (1972) Acute Toxicity of AC-92553 to Bluegill (~Lepomis 

macrochirus~), Rainbow Trout (~Salmo gairdneri~) and Channel Catfish 

(~Ictaluras punctatus~). (Unpublished study received Sep 27, 1974 under 

5F1556; prepared by Bionomics, Inc., submitted by American Cyanamid Co., 

Princeton, N.J.; CDL: 094674-E) 

46292 or 37927? 2037318 Bentley, R.E. (1974) Acute Toxicity of Prowl^(TM)I 3E, Prowl^(TM)I 4E, and 

Avenge 2A-S to Bluegill (~Lepomis macrochirus~) and Rainbow Trout 

(~Salmo gairdneri~). (Unpublished study re- ceived Sep 27, 1974 under 

5F1556; prepared by Bionomics EG&G, Inc., submitted by American 

Cyanamid Co., Princeton, N.J.; CDL: 094674-F) 

37927 2037318 Bentley, R.E. (1974) Acute Toxicity of Prowl^(TM)I 3E, Prowl^(TMI) 4E, and 

Avenge 2A-S to Bluegill (?~Lepomis macrochirus?~) and Rainbow Trout 

(?~Salmo gairdneri?~). (Unpublished study re- ceived Nov 14, 1975 under 

6F1703; prepared by Bionomics, EG&G, Inc., submitted by American 

Cyanamid Co., Princeton, N.J.; CDL: 094732-H) 

72-2 Acute Toxicity to Freshwater Invertebrates

MRID Citation Reference

59738 2037322 LeBlanc, G.A. (1976) Acute Toxicity of Prowl to~Daphnia magna~. 

(Unpublished study received 1976 under 241-243; prepared by Bio- nomics, 

EG&G, submitted by American Cyanamid Co., Princeton, N.J.; CDL:228391-

A) 

71123 2037326 Thompson, C.M.; Griffen, J.; McAllister, W.A. (1980) Acute Toxicity of AC 

92,553 to the Freshwater Crayfish (Procambarus simulans): Static Acute 

Bioassay Final Report # 25725. (Unpublished study received Jan 22, 1981 

under 241-243; prepared by Analytical Bio Chemistry Laboratories, Inc., 

submitted by American Cyanamid Co., Princeton, N.J.; CDL:099889-B) 

153772 2037525 Forbis, A.; Georgie, L.; Burgess, D. (1985) Acute Toxicity of AC 92,553 4E to 

Daphnia magna: Static Acute Toxicity Report #33409. Unpublished study 

prepared by Analytical Bio-Chemistry Laboratories, Inc. 39 p. 

72-3 Acute Toxicity to Estuarine/Marine Organisms

MRID Citation Reference

131772 2037333 Ward, G. (1983) Acute Toxicity of AC 92,553 Technical and Formulat- ed to 

Embryos-larvae of Eastern Oysters ...: Report No. BP-83- 6-65; Project No. 

R95. (Unpublished study received Oct 28, 1983 under 241-1243; prepared by 

EG & G Bionomics, submitted by American Cyanamid Co., Princeton, NJ; 

CDL:251601-A) 

131774 2037334 Ward, G.; Shuba, P. (1983) Acute Toxicity of AC 92,553 Technical and 

Formulation to Sheepshead Minnows ...: Report No. BP-83-3- 39; Project No. 

R95. (Unpublished study received Oct 28, 1983 under 241-243; prepared by 

EG & G Bionomics, submitted by American Cyanamid Co., Princeton, NJ; 

CDL:251601-E) 
56

131775 2037335 Ward, G.; Shuba, P. (1983) Acute Toxicity of AC 92,553 Technical and 

Formulation to Pink Shrimp ...: Report No. BP-83-1-5; Pro- ject No. R95. 

(Unpublished study received Oct 28, 1983 under 241-243; prepared by EG & 

G Bionomics, submitted by American Cy- anamid Co., Princeton, NJ; 

CDL:251601-G) 

72-4 Fish Early Life Stage/Aquatic Invertebrate Life Cycle Study

MRID Citation Reference

29791 Shaffer, C.B. (1974) ?Toxicology Studies of Prowl Herbicide|. (Un- published 

study received Dec 21, 1974 under 5G1580; submitted by American Cyanamid 

Co., Princeton, N.J.; CDL:094331-A) 

37940 2037319 EG&G, Bionomics (1975?) Chronic Toxicity of CL-92,553 to the Fat- head 

Minnow (Pimephales promelas). (Unpublished study received Sep 8, 1977 

under 241-243; submitted by American Cyanamid Co., Princeton, N.J.; 

CDL:096342-A) 

100504 2037323

2037329

Graney, R.L. (1981) The Chronic (21 Day) Toxicity of AC 92,553 to 

?~Daphnia magna~Straus: Project No. 5179. (Unpublished study received Apr 

20, 1982 under 241-243; prepared by Biospherics, Inc., submitted by American 

Cyanamid Co., Princeton, N.J.; CDL: 247299-A) 

158305 Letter Sauter, S. (1976) Letter sent to J. Wyckoff dated Aug 3, 1976: Chronic 

exposure of fathead minnows to Prowl. 6 p. 

106819 Letter Sauter, S. (1978) Letter sent to R. Barron dated Feb 20, 1978 ?Chronic 

toxicity test with fathead minnows and CL-92,553|. (Unpublished study 

received Mar 22, 1978 under 241-243; prepared by EG & G Bionomics, 

submitted by American Cyanamid Co., Prince- ton, NJ; CDL:233264-A) 

72-5 Life cycle fish

MRID Citation Reference

37940 2037319 EG&G, Bionomics (1975?) Chronic Toxicity of CL-92,553 to the Fat- head 

Minnow (Pimephales promelas). (Unpublished study received Sep 8, 1977 

under 241-243; submitted by American Cyanamid Co., Princeton, N.J.; 

CDL:096342-A) 

58831 2037324 Sleight, B.H., III (1976) Letter sent to John Wyckoff dated Apr 20, 1976 

(Progress report on chronic exposure of fathead minnows to CL-92,553). 

(Unpublished study received Jun 1, 1976 under 241- 243; prepared by EG&G, 

Bionomics, submitted by American Cyanamid Co., Princeton, N.J.; 

CDL:224592-A) 

58833 2037325 Sleight, B.H., III (1976) Letter sent to John Wyckoff dated May 21, 1976 

?Raw data for water samples from fathead minnow chronic ex- posure study 

with Prowl|. (Unpublished study received Jun 1, 1976 under 241-243; prepared 

by EG&G, Bionomics, submitted by American Cyanamid Co., Princeton, N.J.; 

CDL:224592-C) 

72-6 Aquatic org. accumulation
57

MRID Citation Reference

156726 2037526 Forbis, A.; Burgess, D.; Burnett, J. (1986) Uptake, Depuration and 

Bioconcentration of [Carbon-14]-AC 92,553 by Bluegill Sunfish (Lepomis 

macrochirus): Final Report #33408. Unpublished study prepared by Analytical 

Bio-Chemistry Laboratories, Inc. 277 p. 

123-1 Seed germination/seedling emergence and vegitative vigor

MRID Citation Reference

42372201 2037337 Chetram, R.; Gagne, J. (1992) A Tier 2 Plant Phytotoxicity Study for Seedling 

Emergence Using AC 92,553: Pendimethalin: Lab Project Number: BL91-453. 

Unpublished study prepared by American Cyanamid Comp. and PanAgricultural Laboratories, Inc. 243 p. 

42372202 2037338 White, T.; Gagne, J. (1992) A Tier 2 Plant Phytoxicity Study for Seed 

Germination Using AC 92,553: Pendimethalin: Lab Project Number: BL91-

471. Unpublished study prepared by American Cyanamid Comp. and PanAgricultural Laboratories, Inc. 131 p. 

42372203 2037339 Canez, V; Gagne, J. (1992) A Tier 2 Plant Phytoxicity Study for Vegetative 

Vigor Using AC 92,553: Pendimethalin: Lab Project Number: BL91-454. 

Unpublished study prepared by American Cyanamid Comp. and PanAgricultural Laboratories, Inc. 212 p. 

123-2 Aquatic plant growth

MRID Citation Reference

42137101 No DER

See 2037379 or 

2037381

Hughes, J.; Alexander, M.; Wisk, J. (1991) Effect of AC 92,553 on Growth of 

Duckweed, Lemna gibba: Lab Project Number: B400-31-1. Unpublished study 

prepared by Malcolm Pirnie, Inc. 60 p. 

42372204 2037340 Hughes, J.; Alexander, M.; Wisk, J. (1992) Effect of AC 92,553 on Growth of 

the Green Alga, Selenastrum Capricornutum: Pendimethalin: Lab Project 

Number: B400-32-1. Unpublished study prepared by American Cyanamid 

Comp. and Malcolm Pirnie, Inc. 58 p. 

42372205 2037341 Hughes, J.; Alexander, M.; Wisk, J. (1992) Effect of AC 92,553 on Growth of 

the Marine Diatom, Skeletonema Costatum: Pendimethalin: Lab Project 

Number: B400-32-4. Unpublished study prepared by American Cyanamid 

Comp. and Malcolm Pirnie, Inc. 53 p. 

42372206 2037342 Hughes, J.; Alexander, M.; Wisk, J. (1992) Effect of AC 92,553 on Growth of 

the Freshwater Diatom, Navicula Pelliculosa: Pendimethalin: Lab Project 

Number: B400-32-3. Unpublished study prepared by American Cyanamid 

Comp. and Malcolm Pirnie, Inc. 53 p. 

42372207 2037343 Hughes, J.; Alexander, M.; Wisk, J. (1992) Effect of AC 92,553 on Growth of 

the Blue-Green Alga, Anabaena Flos-Aquae: Pendimethalin: Lab Project 

Number: B400-32-2. Unpublished study prepared by American Cyanamid 

Comp. and Malcolm Pirnie, Inc. 60 p. 
58

47954502 Open lit Ma, J.; Liang, W.; Xu, L.; et al. (2000) Acute Toxicity of 33 Herbicides to the 

Green Alga Chlorella pyrenoidosa. Bulletin of Environmental Contamination 

and Toxicology 66:536-541.

47954503 Open lit Ma, J. (2001) Differential Sensitivity to 30 Herbicides Among Populations of 

Two Green Algae Scenedesmus obliquus and Chlorella pyrenoidosa. Bulletin 

of Environmental Contamination and Toxicology 68:275-281.

47954504 Open lit Ma, J.; Xu, L.; Wang, S.; et al. (2001) Toxicity of 40 Herbicides to the Green 

Alga Chlorella vulgaris. Exotoxicology and Environmental Safety 51:128-132.

47954505 Open lit Ma, J.; Lin, F.; Wang, S.; et al. (2004) Acute Toxicity Assessment of 20 

Herbicides to the Green Alga Scenedesmus quadricauda (Turp.) Breb. Bulletin 

of Environmental Contamination and Toxicology 72: 1164-1171. 

141-1 Honeybee Toxicity

51271 or 

108773

2037332 Atkins, E.L. (1974) Letter sent to A.J. Tafuro dated May 20, 1974 ?Toxicity of 

Prowl to honeybees|. (Unpublished study received Sep 27, 1974 under 5F1556; 

prepared by Univ. of California-- Riverside, Citrus Research Center and 

Agricultural Experiment Station, Dept. of Entomology, submitted by American 

Cyanamid Co., Princeton, N.J.; CDL:094674-M) 

99890 2037327

2037328 Atkins et al at UCR Honeybee acute

850-1790 Chironomid Sediment Toxicity Test

47891601 scanning Backfisch, K. (2009) Chronic Toxicity of Pendimethalin (BAS 455 H) to the NonBiting Midge Chironomus riparius: A Spiked Sediment Study. Project Number: 

326800, 2008/1010543. Unpublished study prepared by BASF SE. 35 p.

Non Guideline

48298805 Open lit Mullin, C.; Frazier, M.; Frazier, J.; et al. (2010) High Levels of Miticides and 

Agrochemicals in North American Apiaries: Implications for Honey Bee Health. 

PLoS ONE: 5(3): 1-19.

48261117 Open lit Gustavson, K.; Mohlenberg, F.; Schluter, L. (2003) Effects of Exposure Duration of 

Herbicides on Natural Stream Periphyton Communities and Recovery. Archives of 

Environmental Contamination and Toxicology 45(1): 48-58.

48033008 Open lit Kojima, H.; Katsura, E.; Takeuchi, S.; et al. (2004) Screening for Estrogen and 

Androgen Receptor Activities in 200 Pesticides by In Vitro Reporter Gene Assays 

Using Chinese Hamster Ovary Cells. Environmental Health Perspectives 112(5): 

524-531.

48033010 Open lit Nishihara, T.; Nishikawa, J.; Kanayama, T.; et al. (2000) Estrogenic Activities of 

517 Chemicals by Yeast Two-Hybrid Assay. Journal of Health Science 46(4): 282-

298.

47164601 Moore, D.; Breton, R.; Rodney, S.; et al. (2007) Generic Problem Formulation for California RedLegged Frog. Project Number: 89320, 05232007. Unpublished study prepared by Cantox 

Environmental Inc. 87 p.

47164602 Holmes, C.; Vamshi, R. (2007) Data and Methodology Used for Spatial Analysis of California Red 

Legged Frog Observations and Proximate Land Cover Characteristics. Project Number: 3152007, 

WEI/252/03. Unpublished study prepared by Waterborne Environmental, Inc. (WEI). 19 p.
59

Appendix A. PRD Data Request Justification Tables 

The following proposed Data Call-in tables include rationales for requiring the data requested in 

this problem formulation, explanations of the utility of the data, and explanations for how the 

data might impact risk assessment, following the format provided by PRD.

Guideline Number: 835.4100

Study Title: Aerobic Soil Metabolism

Rationale for Requiring the Data

Currently the Agency has received one supplemental study on one soil type (MRID 40185104). 

Aerobic soil metabolism studies facilitate an understanding of a compound’s degradation in soil 

resulting from pesticide interaction with soil microorganisms in aerobic (oxygen-rich) conditions 

in the laboratory. The fate of pendimethalin formed in or deposited on soil cannot be 

characterized without the requested data. 

The Agency is asking for a minimum environmental fate data set for the pendimethalin in order 

to estimate aquatic and terrestrial exposure. Without these data, exposure estimates will be based 

on conservative assumptions. 

Per 40 CFR part 158, promulgated July 1, 2009, requires aerobic soil metabolism data for 

pesticide food and nonfood terrestrial uses. An acceptable soil is required per OCSPP guideline 

835.4100. For transformation rate studies at least three additional soils should be used 

representing a range of relevant soils. 

Aerobic soil metabolism studies facilitate an understanding of a compound’s degradation in the 

soil under aerobic conditions in the laboratory. Depending on how quickly, to what extent, and to 

which transformation products the compound degrades, pendimethalin may or may not pose 

potential exposure concern.

Practical Utility of the Data

How will the data be used?

Aerobic soil metabolism data will facilitate a better understanding of pendimethalin in soil. 

Aerobic soil metabolism data on pendimethalin along with adsorption/desorption data, will allow 

for direct estimation of expected exposures resulting from use of this pesticide. In addition, these 

data will allow the Agency to assess the expected persistence of the pendimethalin in surface 

waters for both human health drinking water assessments and ecological risk assessments. 

How could the data change the Agency’s decision or impact the Agency’s future decisionmaking? 

If the rate of pendimethalin degradation increases in aerobic soil conditions, then antibiotic 

resistance may be a public health risk of concern and additional use precautions and/or 

restrictions may be necessary.
60

Study Title: Analytical Methods (and Associated Independent Laboratory Validations) for Residues in Water, 

Sediment, and Soil

Guideline Number: 835.6100 

Study Substance: Pendimethalin

Rationale for Requiring the Data

Independently validated analytical methods for residues in water, sediment, and soil (environmental chemistry 

methods) submitted by the registrant are used to evaluate analyses described in submitted environmental fate and 

ecological effects studies. Submitted analytical methods are also used by various Federal, State, Tribal, and local 

agencies to detect and monitor residues that are or are suspected to be in environmental compartments due to outdoor 

uses and accidental releases. Independent laboratory validations for submitted analytical methods are necessary to 

confirm that the methods are functional and to confirm the levels of detection and quantitation reported in registrantprepared validations.

Use of pendimethalin may impact surface water quality due to runoff of rain water and drift of residues. This is 

especially true for poorly draining soils, erodible soils, and soils with shallow ground water. Pendimethalin has a 

potential for reaching both surface water and aquatic sediment via runoff. Therefore, outside agencies may request 

analytical methods with which to monitor for pendimethalin residues in water and in soil or sediment.

Practical Utility of the Data

How will the data be used?

In the absence of independently validated environmental chemistry methods, submitted environmental fate and 

ecological effects data may not be reviewable and entities outside the Agency may lack chemical-specific methods for 

analyses in environmental compartments. Independently validated environmental chemistry methods will be used to 

evaluate any newly submitted environmental fate and ecological effects data and will be made available for 

enforcement and monitoring purposes at the federal, state, and local levels.

How could the data impact the Agency’s future decision-making?

Without these required data, the fate of pendimethalin cannot be fully characterized and exposure to potentially toxic 

degradates cannot be quantified. The persistence of pendimethalin and potential degradates to which terrestrial and 

aquatic organisms will be exposed to is uncertain. In the absence of acceptable data, conservative assumptions will be 

made regarding the potential for formation of pendimethalin degradates. Therefore, potential for risk to aquatic 

organisms may be overestimated and the use of pendimethalin might need to be restricted in areas where endangered 

species could be exposed. The lack of these data will limit the flexibility the Agency and registrants have in coming 

into compliance with the Endangered Species Act and could result in use restrictions for pendimethalin which are 

unnecessarily severe.

Guideline Numbers and Study Titles: 

• Test Method 100.4 (OCSPP 850.1770, in prep.); Whole sediment: chronic invertebrates 

freshwater (Hyalella azteca) 

• Test Method 100.5 (OCSPP 850.1760, in prep.); Whole sediment: chronic invertebrates 

freshwater (Chironomus dilutus) US EPA 2001, 
61

• EPA 600/R-01/020 (OCSPP 850.1780, in prep.); Whole sediment: chronic invertebrates 

marine (Leptocheirus plumulosus)

Rationale for Requiring the Data

One chronic sediment toxicity test for a freshwater invertebrate has been submitted for 

pendimethalin; however, this is not sufficient to satisfy the Agency’s updated data 

requirements for outdoor uses in 40 CFR Part 158 (October 26, 2007). For

pendimethalin, available information indicates that benthic organisms may be exposed 

via run-off or spray drift applications used in agricultural, forest, and residential settings. 

Based on calculations in the most recent EFED assessment, the 21-day sediment 

porewater EECs predicted for pendiemthalin ranged from 0.4 to 8.00 μg a.i./L (DP 

Barcodes 39116 and 394467). The upper end of this range exceeds 0.1 of the most 

sensitive acute LC/EC50 (210 μg a.i./L for eastern oyster), which satisfies one of the 

criteria for requiring chronic whole sediment toxicity testing under 40 CFR Part 158. 

Furthermore, chronic reproductive effects were seen in water column studies with aquatic 

invertebrates (daphnid), with a NOAEC = 14.5 μg a.i./L and LOAEC = 17.2 μg a.i./L.

Pendimethalin is expected to persist in sediments, based on half-lives in submitted soil 

metabolism and aquatic metabolism studies (aerobic soil, 172 days; aerobic aquatic 

metabolism, 27 days) (MRIDs 4018501 and 47385201). These half-life values exceed the 

40 CFR Part 158 criterion of 10 days. 

The third set of trigger criteria for needing chronic testing (Kd > 50 or log KOW >3 or KOC

> 1000) is also met for pendimethalin (log KOW is 5.18, and the mean KOC value is 

~17,000). The physicochemical property triggers (Kd, KOW and KOC) reflect the 

propensity of the chemical to partition onto the particulate or organic matter phases of 

sediments. Exceeding any one of the physicochemical property triggers listed above is 

sufficient for indicating the pesticide has reasonable potential for partitioning to the 

sediment compartment. 

A registrant submitted study is available for a chronic whole sediment test on 

Chironomus riparius, therefore, chronic whole sediment tests on Hyalella azteca and 

Leptocheirus plumulosus are requested. Although both are freshwater species, Hyalella

and Chironomus differ substantially in their morphology (crustacean vs. insect), 

ecological niche (epibenthic v. infaunal species), and physiology. Evidence also suggests 

that Hyalella is among the more sensitive invertebrates based on water column tests 

(Maund et al., 2002; Weston and Jackson, 2009). Pendimethalin the potential to enter 

estuarine/marine water bodies based on current usage patterns that include coastal areas. 

Therefore, testing is also needed for an estuarine/marine sediment-dwelling invertebrate 

species. 

Until the final OCSPP guidelines for chronic sediment toxicity tests are published, the 

registrant should submit a protocol to EFED for approval prior to test initiation, 

considering the following methods:

• Test Method 100.4: Hyalella azteca 42-d Test for Measuring the Effects of 

Sediment Associated Contaminants on Survival, Growth, and Reproduction in 

USEPA 2000 Methods for Measuring the Toxicity and Bioaccumulation of 

Sediment-associated Contaminants with Freshwater Invertebrates EPA 600/R-
62

99/064 (OCSPP 850.1770, in prep.);

• Test Method 100.5: Life-cycle Test for Measuring the Effects of Sedimentassociated Contaminants on Chironomus dilutus (formerly known as C. tentans) 

in USEPA 2000 Methods for Measuring the Toxicity and Bioaccumulation of 

Sediment-associated Contaminants with Freshwater Invertebrates EPA 600/R99/064 (OCSPP 850.1760, in prep.); and 

• Leptocheirus plumulosus in USEPA 2001 Method for Assessing the Chronic 

Toxicity of Marine and Estuarine Sediment-associated Contaminants with the 

Amphipod Leptocheirus plumulosus EPA 600/R-01/020 (OCSPP 850.1780, in 

prep.).

As an alternative to recommending the conduct of 2 chronic (life cycle) sediment toxicity 

tests, EFED would also consider a tiered testing approach for sediment toxicity testing. 

In this approach, sediment toxicity testing would first be conducted with the 

aforementioned species using the 10-d (subchronic) sediment toxicity test guidelines 

(OSCPP 850.1735 and 850.1740). Then, pending a comparison of estimated 

environmental concentrations (EEC) in sediment and porewater with toxicity results from 

the 10-d sediment toxicity studies, the need for one or more chronic sediment toxicity 

studies would be determined. This tiered testing approach has the potential advantage of 

reducing the number of chronic (life cycle) studies that would be needed when results of 

the 10-d (subchronic) tests in conjunction with sediment EECs indicate chronic testing is 

not likely to alter risk assessment conclusions. In some cases, however, this tiered testing 

approach may result in the conduct of both a 10-d (subchronic) and a chronic (life cycle) 

study.

Practical Utility of the Data

How will the data be used? 

Data from sediment toxicity studies will be used to estimate potential risks to benthic 

organisms associated with uses of pendimethalin. The data will reduce uncertainties 

associated with the current risk assessment for benthic species and will improve our 

understanding of the potential effects of pendimethalin.

How could the data impact the Agency’s future decision-making?

Although there was uncertainty in estimating the effect of pendimethalin on benthic 

organisms in previous assessments, there was a potential risk associated with adverse 

effects identified for other aquatic organisms. Acceptable data for benthic organisms will 

reduce the uncertainty from the previous assessment If the data indicates that registered 

pendimethalin usage may pose a risk of adverse effects to non-target benthic organisms 

above the Agency Level of Concern, the Agency may explore decision options to 

mitigate this risk. The lack of these data will limit the flexibility the Agency and 

registrants have in coming into compliance with the Endangered Species Act, and could 

result in use restrictions which may otherwise be avoided, or which are unnecessarily 

severe.
63

Appendix B. Reported Pendimethalin Ecological Incident Summaries in the 

EIIS Database

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

I007677-

001

Bass, bluegill Possible Registered 

use

A tank mix of pesticide was 

applied to a 4-acre corn field 

next to a 2-3 acre pond with a 

depth of 4-6 feet. The distance 

from the treatment site was a 

grass bottom of 14-70 feet 

between the pond and the 

treated field. Water and fish 

samples were taken but findings 

were not submitted. The soil 

had a high moisture level and 

an inch of rain fell causing 

drainage into the farm pond. 

(Site location: Chippewa, OH).

I002685-

005

Minnow Possible Unknown According to the report, 996 (?) 

minnows died in Schwerin 

Creek. Their deaths were 

attributed to the weed killer 

Prowl.

I005880-

019

Raspberry, unknown 

tree

Probable Accidental 

Misuse

This is one of the incidents 

regarding clomazone that was 

reported by the Wisconsin 

Dept. of Agriculture, Trade, and 

Consumer Protection in 1997. 

In Waupaca County trees and 

raspberries were discolored on 

two sides following an 

application of Command 3ME, 

Pursuit, and Prowl 3.3 EC at a 

distance of less than 300 feet. 

Also an illegal tank mix was 

used.

I000689-

001

Corn Highly Probable Registered 

use

A soybean crop was planted in 

1991 and pesticide was applied 

according to the label.

A corn crop was planted in the 

same area in 1992 with 

impunity because the label 

stated that there was no 

"carryover" of pesticide from 

soybean crop to corn crop..."9 

and one-half months after 

application", BUT the corn crop 

failed. The farmers sued the 
64

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

pesticide Company for 

mislabelling the product. 

Judgment in June, 1993 was in 

favor of the plaintiffs and 

against "Cyanamid",the 

defendant Company, which had 

to pay court costs and interest 

on decreed amounts.

I014702-

053

Soybean Possible Registered 

use

To comply with 6(a)2 

requirements, Dow reported an 

incident in Auburn, IL, in 

which Pendimax damaged 1100 

acres because of a carryover 

problem.

B000621-

001

Grass, unknown fruit 

tree, vegetable

Possible Registered 

use

Included in the report from the 

IL Dept. of Agriculture to 

Region 5 was an incident that 

took place in Woodstock, IL. A 

farmer there applied Command 

(1 1/3 pts/acre) and Prowl (amt. 

not stated) to a field of beans 

that was adjacent to the 

properties of three homeowners. 

Some of their plants that were 

not affected by the spraying 

were tomatoes, strawberries, 

and evergreens. But the grass, 

other vegetables, and fruit trees 

ended up with bleached and 

whitened leaves

I010927-

005

Corn Possible Registered 

use

To comply with 6(a)2 

regulations, Dow reported a 

complaint from Montfort, WI, 

that Pendimethalin 3.3LBS 

DAS damaged an entire 422 

acre crop of corn. Dow's 

explanation was that "Field 

observations of treated areas 

versus incidental check strips 

included stand losses of up to 

65%, leaf burn, and stunted 

plants. It is strongly suspected 

that cyanazine and cool, wet 

conditions following 

application greatly contributed 
65

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

to the observed symptoms."

I012366-

015

Corn field Possible Unknown To comply with 6(a)2 

requirements, Dow reported a 

complaint from Alumbank, PA, 

that PYTHON damaged 93 

acres of corn. Here is the 

Problem Description according 

to the Dow report: "Yield lag 

in PYTHON field split with 

PROWL within the same 

variety. PYTHON corn stunted 

early in season."

I013636-

051

Corn field Probable Registered 

use

The farmer alleges that crop 

injury followed hornet 

herbicide application. Field 

observations included uneven 

corn plants, chlorotic new tissue 

growth in the whorl, and lack of 

secondary root hair

development. Corn in an 

unintentional check strip was 6" 

taller, uniform in height and 

much darker green in color. 

Settlement $1,251.63 

I014702-

049

Corn field Possible Registered 

use

To comply with 6(a)2 

requirements, Dow reported an 

incident that Keystone with 

Prowl as a tank mix damaged 

corn. Corn exhibited severe 

burning and some plants died.

I000663-

001

Corn, soybean Probable Unknown Alleged crop damage resulted 

from crop rotation over several 

years of corn and soybeans 

accompanied by pesticide 

application. The rotational crop 

pesticide application was as 

follows:

1989 - Trifluralin, as Treflan*, 

and imazethapyr, as Pursuit* 

applied; soybeans were planted.

1990 - Corn planted.

1991 - Treflan* and Pursuit* 

applied (soil incorporated); soy 

beans planted.

1992 - Metolachlor, as Dual*, 

and dicamba salt, as Banvel* 
66

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

applied; corn planted.

1993 - Planted corn was 

observed to be stunted; it turned 

brown and perished.

During these years several other 

herbicides were also applied to 

this crop area. There was 

pendimethalin, as Prowl*, and 

trifluralin, as Tri-4*. This 

rotational crop injury was 

deemed to be carryover effect 

and was quite marked by 1991. 

On 07/01/92 Inspector Paul 

Kassel, Iowa State Cooperative 

Extension Service, made his 

report, including planting 

schedule above. He observed 

typical Pursuit* carryover 

symptoms. Residue analysis 

revealed a sufficient amount in 

the soil to cause the observed 

damage. He also observed 

some typical dinitroanaline 

(DNA), (Treflan* is a DNA), 

carryover symptoms and felt 

that it probably contributed to 

the observed stunting damage. 

According to the report there is 

no record of a similar 

occurrence but the product 

labels caution regarding the 

use of both Prowl* and Pursuit* 

with corn and soybean 

rotation.

This event was updated with 

I000688-001. Soil analysis, 

09/01/93, revealed a sufficient 

amount of pendimethalin, as 

Prowl*, probably another 

carryover, to cause crop 

damage. The residue amount 

was not given.

I015748-

018

Cotton Probable Registered 

use

To comply with 6(a)2 

requirements, Dow reported an 

incident in Somerville, TN, in 

which Pendimax + 3.3 EC 
67

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

Herbicide damaged a field 

(acreage not stated) of cotton. 

The report from the Dow 

inspector was as follows: 

"Grower applied Pendimax 

behind a cotton planter while 

planting cotton. Cotton came 

up to 2-leaf stage and received a 

heavy rain causing dirt which 

contained Pendimax to be 

splashed onto the leaf surface 

causing damage to the cotton. 

Grower followed all label 

directions and amounts used per 

acre within the label."

I013884-

037

Unknown tree Probable Unknown This is from the 1999 Annual 

Report from the Washington 

State Department of Health 

Pesticide Incident Reporting 

and Tracking Review Panel, 

November 2000, from the 1998 

PIRT Data. A driveway was 

treated with a herbicide and a 

100 year old black walnut, plus 

several other plants showed 

symptoms of herbicide 

application. Analysis of foliage 

was found positive for 

Pendimethain. No analysis 

results was given.

I004869-

001

Azelea Probable Registered 

use

A greenhouse floor in Sylmar 

was treated with the pesticide 

Pendulum, causing tinting and 

wilting of azaleas in the 

greenhouse. The damage 

progressed, making 172,637 

azaleas unmarketable. Property 

loss was claimed to be 

$600,000.

I009262-

054

Grass Probable Registered 

use

As part of its reporting of 

August, 1999, incidents, Scotts 

Co. included a complaint from a 

homeowner in Edison, N.J.. 

She had used one 15M bag of 

Turf Builder with Halts and one 

bag of Turf Builder with Weed 
68

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

Control; the first application 

was in the spring and the 

second in the fall, and both 

times the lawn was completely 

burned out. The customer was 

to be given a refund.

I013587-

052

Corn Probable Unknown In the 2000-2001 Annual 

Report of the Pesticide Incident 

Reporting and Tracking (PIRT) 

Review Panel of Washington 

State there is an incident that 

took place in Benton County, 

July 23, 1999. The herbicide 

mentioned is Pendimethalin. It 

was, evidently, the cause of an 

earlier event related to a 

herbicide application made in 

1998. Large limbs in trees were 

dying, and there was damage to 

ornamentals. This is a notice of 

correction to CASE# 40Y-98

I010837-

069

Grass Possible Unknown To comply with 6(a)2 

regulations Novartis reported a 

complaint from Caledonia, NY, 

that BICEP LITE II Magnum 

damaged all of a corn crop. 

There is a discrepancy in the 

Novartis report; on the front 

page, the Treated Acres is said 

to be 130, but the "Plant A" 

Crop Damage report shows that 

65 acres were treated and 65 

acres were affected. In each 

case, the report says that 100% 

of the crop was affected. 

PROWL was said to be 

involved also but no details 

were given of its involvement. 

Here is the report of the 

Novartis inspector: "Corn 

showed severe stunting and 

twisting but thought it would 

grow out of these symptoms. It 

appeared that grower was 

satisfied until harvest of silage. 

A $4,000 settlement is required 
69

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

now before more yield is 

determined."

I012094-

001

Unknown tree Possible Registered 

use

To comply with 6(a)2 

requirements, Scotts Co. 

reported a complaint from a 

golf course in Fort Worth, TX, 

that Ronstar had damaged 30 

acres of Tifsport Bermuda 

fairways. Here is Scotts Co.'s 

report: "30 Acres of Tifsport 

Bermuda fairways, Ronstar 

Burn. Made first observation 

on Saturday 8/25 after being 

alerted to damage by DSR. 

Tifsport fairways had severe 

turf burn in the overlap areas. 

The common Bermuda rough 

areas were undamaged. The 

decision was made by Duane 

and myself to let the turf 

recover and take another look 

on Wednesday, 8/29. Damage 

still severe in some areas. Turf 

is alive, just recovering slowly."

 Evidently there was no 

damage settlement made on the 

claim.

I011838-

106

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Wakefield, VA, 

that VALOR damaged two sites 

of peanuts, one of 6 acres and 

the other 36. PROWL and 

DUAL were also applied at 0.5 

pt/acre. The damage symptoms 

were described as: 

"Phytotoxicity: Heavy damage 

to leaves & petioles."

I011838-

085

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Carnegie, OK, 

that VALOR damaged two sites 

of peanuts, one of 48 acres and 

one of 58. Other products used 

were PROWL and TEMIK but 

no details were given of their 
70

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

application rates. The symptom 

was described as 

"Phytotoxicity: Brown, dead 

peanuts."

I011838-

011

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Pelham, GA, 

that VALOR damaged 10 acres 

of a 224-acre crop of peanuts. 

The symptoms were "desication 

of stems, petioles, leaves." 

PROWL was in the tank mix 

but no details were gievn about 

its concentration.

I011838-

074

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Fort Cobb, OK, 

that VALOR damaged two sites 

of peanuts, one of 110 acres and 

one of 90. Also applied was 

PROWL at 2.4 pints/acre. The 

symptom of damage was noted 

as "Phytotoxicity: Slow 

growing, severe stunting."

I011838-

060

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Hydro, OK, 

that VALOR damaged 58 acres 

of peanuts. PROWL and 

ORTHENE IFS were also 

involved but no details of their 

use were given. The symptoms 

were described as "Leaves 

unfolded & matted to ground, 

terminals burnt out."

I011838-

062

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Lookeba, OK, 

that VALOR damaged 160 

acres of peanuts. PROWL PPI 

was another product applied but 

no details were given of its use. 

The symptoms were described 

as "Dry leaves @ cracking." 

(sic)

I011838- Peanut Possible Unknown To comply with 6(a)2 
71

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

061 requirements, Valent reported a 

complaint from Hydro, OK, 

that VALOR damaged two 

peanut sites, one of 124 acres 

and the other 93. PROWL and 

TEMIK were also applied but 

no details were given of their 

use. The symptoms were 

described as "Burnt terminals & 

foliage brown."

I011838-

065

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Hydro, OK, 

that VALOR damaged two sites 

of peanut crops, one of 109 

acres and one of 98. PROWL 

was also used at the time of 

application but no details were 

given. The symptoms of the 

damaged crop were "Burnt 

plants, not growing."

I011838-

064

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Hydro, OK, 

that VALOR damaged two sites 

of peanut crops, one of 190 

acres and the other 120. Other 

products used at the time of 

application were PROWL, 

DUAL, and SPREADER but no 

details were given of their use. 

The symptoms of the affected 

plants were described as "Burnt 

plants, not growing."

I011838-

088

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Ft. Cobb, OK, 

that VALOR damaged two 

peanut sites, one of 99 acres 

and one of 28. PROWL and 

THIMET were also applied but 

their application rates were not 

given. The symptom of damage 

was given as "Phytotoxicity: 

Burnt tops, stunting."

I011838- Peanut Possible Unknown To comply with 6(a)2 
72

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

079 requirements, Valent reported a 

complaint from Fort Cobb, OK, 

that VALOR damaged two sites 

of peanuts, one of 32 acres and 

the other 28. PROWL was also 

applied at 2.5 pts/acre. The 

damage symptom was 

described as "Phytotoxicity: 

Burned leaves, stunted."

I011838-

056

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Windsor, NC, 

that VALOR damaged 80 acres 

of peanuts. Other products used 

at application were OUTLOOK, 

PURSUIT, VAPAM, and 

PROWL but no details were 

given. The symptoms listed 

were "Burnt leafes, petioles" 

(sic).

I011838-

069

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Gracemont, 

OK, that VALOR damaged two 

sites of peanuts, one of243 

acres and the other 126. 

PROWL was also applied at 2.4 

pints/acre. The symptoms of 

the plants were described 

simply as "Phyotoxicity."

I011838-

058

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Fort Cobb, OK, 

that VALOR damaged to sites 

of peanuts, one of 37 acres and 

one of 34. PROWL and 

SUPER BIO were also involved 

but no details werer given of 

their use. The symptoms were 

described as "Burnt leaves, 

stunting, slow growing."

I011838-

089

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Sayre, OK, that 

VALOR damaged all 122 acres 

of one peanut site, and 40 acres 
73

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

of another 210 acre plot. 

PROWL was also applied but 

no details of its use were given. 

The symptom was described as 

"Phytotoxicity: Burnt leaves, 

plants look dead."

I011838-

098

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Milburn, OK, 

that VALOR damaged 255 

acres of peanuts at one site and 

40 acres at another. PROWL 

was also applied but no details 

of its use were given. The 

damage symptom was reported 

as: "Phytotoxicity: Burnt spots, 

reduced stand."

I011838-

090

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Erick, OK, that 

VALOR damaged 100 acres of 

a 125-acre peanut crop. 

PROWL was also applied but 

no details of its use were given. 

The damage symptom was 

described as "Phytotoxicity: 

Burnt leaves."

I011838-

091

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Holdenville, 

OK, that VALOR damaged two 

sites of peanuts, one of 60 acres 

and one of 20. Other products 

applied were PROWL and 

CYCLONE but no details of 

their use were given. The 

symptoms of damage were 

described as: "Phytotoxicity: 

Burnt peanuts, dead plants."

I011838-

109

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Windsor, VA, 

that VALOR damaged 55 acres 

of peanuts. Also applied were 

DUAL at 1.3 pt and PROWL at 

1.5 pt/acre. The damage 
74

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

symptoms were described as: 

"Phytotoxicity: Slow emerge 

w/burned leaves & petioles."

I011838-

071

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Lookeba, OK, 

that VALOR damaged 52 acres 

of peanuts. PROWL was also 

applied, at 1 quart/acre. The 

symptoms of damage were 

"Phytotoxicity: Initial leaves 

burned."

I011838-

111

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Girade, GA, 

that VALOR damaged 26 acres 

of peanuts. PROWL, BRAVO, 

and STRONGARM were also 

applied but the application rates 

were not given. The damage 

symptoms were reported as: 

"Phytotoxicity: Burnt lower 

leaves."

I011942-

002

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Girade, GA, 

that VALOR damaged an entire 

peanut crop. There were two 

sites, one of 26 acres and 

another of an unspecified area. 

Other products used at the time 

of application were Prowl,

Bravo, and Strongarm.

I011838-

107

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Yale, VA, that 

VALOR damaged 23 acres of 

peanuts at one site, and 3 acres 

at another. PROWL was also 

applied at 1.4 pt/acre. The 

damage symptoms were 

reported as: "Phytotoxicity: 

Burned and stunted."

I011838-

014

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Camilla, GA, 
75

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

that VALOR damaged all 48 

acres of a peanut crop. 

PROWL and THIMET were 

also applied but no information 

was given regarding their 

application rates. The 

symptoms of the damage were 

"stunting, reduction."

I011838-

035

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Tifton, GA, that 

VALOR damaged 209.8 acres 

of peanuts. Other products used 

at the time of application were 

PROWL and ROUNDUP but 

no details were given of their 

application rates.

I011838-

073

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Carnegie, OK, 

that VALOR damaged 45 acres 

of peanuts. PROWL was also 

applied but no details were 

given of its use. The symptom 

of the damage was described as 

"Phytotoxicity: Burn on low 

leaves."

I011838-

039

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Lenox, GA, that 

VALOR damaged 91.5 acres of 

peanuts. PROWL was also 

applied but no details of its use 

were given. The symptoms 

shown were "Burnt & stunted 

plants."

I011838-

047

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Tifton, GA, that 

VALOR damaged two peanut 

crops, one of 14 acres and the 

other 26.2 acres. Also involved 

were PROWL and DUAL 

although no details were given 

about them. The symptoms 

noted were "Burnt & wilted
76

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

plants."

I011838-

041

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Douglas, GA, 

that VALOR damaged 260 

acres of peanuts. there were 60 

acres at one site and 200 at 

another. PROWL was also 

involved but no details were 

given of its use. the symptoms 

noted were "Burnt & wilted 

plants."

I011838-

043

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Douglas, GA, 

that VALOR damaged all 25 

acres of a peanut crop. 

PROWL was also involved but 

no details were given of its use. 

The description fo the 

symptoms was "Not 

developing, root strong."

I011838-

050

Peanut Possible Unknown To comply with 6(a)2 

requirements, Valent reported a 

complaint from Wray, GA, that 

VALOR damaged 29.7 acres of 

a peanut crop. PROWL was 

also involved but no details of 

its use were given. The 

symptoms cited were "Burnt & 

wilted plants."

I015278-

001

Potato Probable Registered 

use

This 6(a)(2) reported by Griffin 

LLC is one of the most 

complete incident I have seen. 

Gives history of the field from 

April 1990 to June 2003 when 

the symptoms appeared. There 

were several applications of 

many different herbicides 

during this period. The first 

applications were on April 2, 

1990 to an asparagus crop. In 

2000, there was another 

application to asparagus. The 

field was left fallow for 2001 

and 2002 with out any 
77

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

herbicides being applied. The 

field was prepared for potatoes 

in the spring of 2003 and 

several more applications of 

herbicides, April 1, April 25 

and May 10. The report from 

the fieldsman was that the crop 

emerged normally, but began to 

show chlorosis before row 

closure. On June 20, 2003 it 

became evident that the plants 

were dying. The fieldsman 

took composite soil samples for 

analysis of diuron, linuron, 

terbacil and simazine. Only 

diuron was detected at 0.1 ppm. 

Additional testing show 

detections of pendimethalin, 

trifluralin, chlorpyrifos diuron, 

and DCPMU (primary 

metabolite of diuron). See 

report for full history.

I010927-

004

Soybean Probable Registered 

use

To comply with 6(a)2 

requirements, Dow reported a 

complaint from Greenville, MS, 

that Pendimethalin 3.3LB DAS 

damaged all 809 acres of a 

soybean crop. According to 

Dow's account of the incident, 

the effect known as Brittle Stem 

occurs when Pendimax is 

surface applied at planting, 

followed by heavy rainfall. As 

the soybeans emerge the 

Pendimax forms a "toxic layer" 

around the stem of the plant at 

ground level. This make it very 

brittle and causes it to fall over.

I010927-

006

Soybean Possible Registered 

use

To comply with 6(a)2 

regulations, Dow reported a 

complaint from Litchfield, MI, 

that Pendimethalin 3.3LBS 

DAS damaged 150 acres of 

soybeans (out of a total of 180 

acres). This pesticide was tank 

mixed with Python and 
78

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

FirstRate. Following is the 

account of the Dow inspector: 

"Two days after planting, 

excessive (5") of rainfall 

occurred. Within 7 days I 

walked these fields showing 

stunting and a swollen, brittle, 

and callused hypocotyl. My 

references indicated a higher 

than normal probability of 

DNA injury. We made the 

decision to replant into the 

remaining 55-60% stands. The 

fields were monitored all 

summer and taken to yield. I 

was present for harvest, all 

trucks were weighed and 

comparison made to other 

conventional soys planted on 

similar dates in nearby fields." 

 I called Dow to ask whether 

any data was available on the 

yield for this crop as well as 

others in the area, but they had 

no such data.

 To comply with 6(a)2 

regulations, Dow reported a 

complaint from Schoolcraft, 

MI, that Pendimethalin 3.3 LB 

DAS damaged 78 acres of 

soybeans. This pesticide was 

tank mixed with Python. The 

account of the Dow inspector is 

as follows: "Callus area formed 

at soil level on many of the 

plants. In a wind storm in 

August many plants were 

knocked down. Plants could be 

easily snapped off just by 

walking through them."

I010927-

008

Soybean Possible Registered 

use

To comply with 6(a)2 

regulations, Dow reported a 

complaint from Vicksburg, MI, 

that a tank mix of Python, 

Pendimax, and FirstRate 

damaged 65.8 acres of 
79

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

soybeans. The account of the 

Dow inspector is as follows: 

"Pendimax, Python, FirstRate 

tank mix. Beans emerged, 

receive a lot of rain and died 

back to the ground. Especially 

prevalent where spray boom 

overlapped. late in the season, 

beans were very brittle."

To comply with 6(a)2 

regulations, Dow reported a 

complaint from Cedar, KS, that 

Python damaged all 180 acres 

of a soybean crop. The Dow 

inspector's report is as follows: 

"Grower used too much active 

of Python on a high pH soil 

over 7.9. The grower was 

emulating the Broadstrik + 

Dual and the ratios were off 

contributing to high AE per 

acre."

I010927-

007

Soybean Possible Registered 

use

To comply with 6(a)2 

regulations, Dow reported a 

complaint from Schoolcraft, 

MI, that Pendimethalin 3.3 LB 

DAS damaged 78 acres of 

soybeans. This pesticide was 

tank mixed with Python. The 

account of the Dow inspector is 

as follows: "Callus area formed 

at soil level on many of the 

plants. In a wind storm in 

August many plants were 

knocked down. Plants could be 

easily snapped off just by 

walking through them."

 To comply with 6(a)2 

regulations, Dow reported a 

complaint from Vicksburg, MI, 

that a tank mix of Python, 

Pendimax, and FirstRate 

damaged 65.8 acres of 

soybeans. The account of the 

Dow inspector is as follows: 
80

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

"Pendimax, Python, FirstRate 

tank mix. Beans emerged, 

receive a lot of rain and died 

back to the ground. Especially 

prevalent where spray boom 

overlapped. late in the season, 

beans were very brittle."

 

To comply with 6(a)2 

regulations, Dow reported a 

complaint from Cedar, KS, that 

Python damaged all 180 acres 

of a soybean crop. The Dow 

inspector's report is as follows: 

"Grower used too much active 

of Python on a high pH soil 

over 7.9. The grower was 

emulating the Broadstrik + 

Dual and the ratios were off 

contributing to high AE per 

acre."

I014702-

057

Soybean Possible Registered 

use

To comply with 6(a)2 

requirements, Dow reported an 

incident in Fonda, IA, in which 

Pendimax and/or Authority, 

with wet conditions, damaged 

251 acres of soybeans. 

Soybean stems became brittle 

and broke off at ground level. 

Settlement for 1.36 bushels per 

acre at $7.76/bu, for a total of 

$2562.74.

I014702-

056

Soybean Possible Registered 

use

To comply with 6(a)2 

requirements, Dow reported an 

incident that Pendimax and/or 

Authority, along with extreme 

wet conditions, caused brittle 

stems allowing the plant to 

break off at the ground. 

Settlement was at $7.76/bushel 

for 1 bushel per acre, for a total 

of $2187.16. This occurred in 

Fonda, IA.

I014702-

058

Soybean Possible Registered 

use

To comply with 6(a)2

requirements, Dow reported an 

incident in Ayrshire, IA, in 
81

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

which extreme wet weather 

allowed the herbicides, 

Pendimax and Python, to stay 

in continuous contact with the 

soybeans in a 543 acre crop. 

This caused stem brittleness at 

the ground level and then the 

plants broke off causing a stand 

and yield reduction. Settled on 

4.5 bushels per acre at $7.66/bu, 

for a total of $18,717.21.

I014702-

055

Soybean Possible Registered 

use

To comply with 6(a)2 

requirements, Dow reported an 

incident in Ruthven, IA, in

which 56 acres of soybeans 

were damaged by Python and 

Pendimax 3.3. Wet weather 

contributed to the problem, 

causing brittle stems and the 

death of some plants. A total 

settlement of $1693.44 was 

made.

I014702-

059

Soybean Possible Registered 

use

To comply with 6(a)2 

requirements, Dow reported an 

incident that Pendimax and 

Python, along with extreme wet 

weather, caused damage to 

soybeans. Prolonged contact of 

the herbicides with the soybean 

stem caused callusing and 

brittleness.

I014702-

061

Soybean Possible Registered 

use

To comply with 6(a)2 

requirements, Dow reported an 

incident in which Pendimax 

and/or Python, along with 

extreme wet weather, caused 

soybean brittle stems and the 

death of some plants. A total 

settlement of $1639.44 was 

made, based on the reduction in 

yield.

I015748-

046

Soybean Possible Registered 

use

To comply with 6(a)2 

requirements, Dow reported an 

incident in Ashton, IA, in which 

Pendimax 3.3 EC Herbicide 

damaged an entire 460-acre 
82

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

crop of soybeans. The Dow 

inspector's report said: 

"Pendimax applied in midApril. 3 weeks later, disked in. 

Soybeans were showing 

injury/disease more noticeably 

in overlap areas, but all across 

field. Problems attributed to 

planting depth, Pendicamx 

slowing soybean growth 

allowing seed to sit in cold, we 

ground longer. Settled for cost 

of Pendimax To comply with

6(a)2 requirements, Dow 

reported an incident in Elm 

Creek, NE, in which Starane 

Herbicide damaged 46 acres of 

field corn. The Dow 

inspectpor's report said: "The 

corn field being settled on was a 

Mycogen conventional hybrid 

(2R773) which is sensitive to 

PGRs. The evening following 

chemical application, the wind 

picked up to 60 mph gusts 

which snapped off an estimated 

60% of the corn. The corn 

which was still standing 

showed very clear signs of PGR 

damage (pictures available). It 

was then decided to wait until 

harvest to see how much yield 

loss would occur. By using 

county data I calculated that the 

2004 yields were on average 

down 6% in the given area. 

Therefore, 6% was removed 

from the field's historical 

average (derived from the 

grower's insurance company) in 

order to create a more accurate 

estimation of yield loss for this 

growing season."

I016962-

001

Soybean Possible Registered 

use

Grower applied 3.3 of 

Pendimax with 3-inch soil 

incorporation. The soybean 
83

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

hypocotlys were swollen and 

brittle causing stand loss 

throughout the season and yield 

loss at harvest.

I015175-

001

Soybean Possible Registered 

use

To comply with 6(a)2 

requirements, DuPont reported 

a complaint from a soybean 

farmer in Arkansas, alleging 

that DuPont's Authority 

Herbicide, and Prowl, damaged 

his 5,000 acre crop. In the next 

week, DuPont representatives 

visited many sites having 

similar symptoms. In the case 

of the Arkansas man, the 

products were sprayed at 

planting with 2 different 

sprayers. The beans emerged 

prior to receiving the first rain, 

after which rainfall had been 

rather consistent and with 

occasional great intensity. 

Soon after the first rain, the 

beans started showing 

symptoms that appear to be 

consistent with those associated 

with sulfentrazone. There were 

variations in the soil in these 

fields, and the greater damage 

seemed to be related to the 

lighter soil; the affected plants 

have a yellowish look. 

DuPont's report admitted that 

the symptoms may be 

consistent with those of 

sulfentrazone.

I010581-

083

Grass Probable Accidental 

Misuse

To comply with 6(a)2 

requirements, Scotts reported a 

complaint from Chicago, IL, 

that Turf Builder with Halts 

damaged about 75% of a lawn. 

The approximate area of the 

lawn was 1200 sq ft and the 

customer applied about half of a 

15M bag (which would be an 

excessive amount). Scotts was 
84

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

to offer a refund.

I010581-

092

Grass Probable Registered 

use

To comply with 6(a)2 

requirements, Scotts reported a 

complaint from Woodbury, NJ, 

that Turf Builder with Halts 

damaged a lawn. The customer 

used the product which he 

claims to have been lumpy and 

which evidently did not spread 

evenly. There are brown 

patches throughout the lawn 

and it is estimated that 50% of 

the lawn was damaged. Scotts 

offered to provide a refund for 

the seed and fertilizer.

I010581-

082

Grass Probable Accidental 

Misuse

To comply with 6(a)2 

requirements, Scotts reported a 

complaint from New Albany, 

IN, that Crabgrass Preventer 

Plus Lawn Fertilizer damaged 

90% of a lawn. Three days 

after the complainant applied 

the product the grass was dead 

but the crabgrass was thriving. 

The Scotts inspector explained 

that applying the product at this 

time on existing crabgrass 

would not work. The 

complainant used a rotary 

spreader that had only one 

setting. The temperature was 

65 degrees and the product was 

watered in.

I007495-

001

American robin, rock 

dove

Possible Unknown The State of Kansas Deot. of 

Wildlife and Parks received a 

report of a bird kill in 

Hutchinson in April, 1998. Six 

American robins and 6 or 7 

rock doves were found dead 

after the application of 

pendimethalin. The biologist 

who investigated the incident 

thought that pendimethalin was 

responsible for the event but 

there was no report of a 

toxicological analysis to 
85

Table B-1. Pendimethalin Incident Report Summaries

Incident # Organism(s) 

Affected

Certainty of 

Involvement

Legality of 

Use Description

confirm this possibility.