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Problem Formulation for the Environmental Fate, 

Ecological Risk, Endangered Species, and 

Drinking Water Exposure Assessments in Support 

of the Registration Review of Oryzalin 

CAS Registry Number: 19044-88-3 

PC Code: 104201 

Prepared by:

Anita Ullagaddi, Biologist 

Christopher M. Koper, Chemist 

Reviewed by: 

James Lin, Environmental Engineer 

Sujatha Sankula, Risk Assessment Process Leader 

Nancy Andrews, Branch Chief

U. S. Environmental Protection Agency 

Office of Pesticide Programs 

Environmental Fate and Effects Division

Environmental Risk Branch I 

1200 Pennsylvania Ave., NW 

Mail Code 7507P 

Washington, DC 20460

December 9, 2010 
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Table of Contents 

1. Purpose........................................................................................................................... 4 

2. Problem Formulation ..................................................................................................... 4 

2.1. Nature of Regulatory Action................................................................................... 4 

2.2. Previous Assessments ............................................................................................. 4 

2.2.1. Ecological Risk Assessments........................................................................... 4 

2.2.2. Drinking Water Exposure Assessments........................................................... 5 

3. Stressor Source and Distribution ................................................................................... 6 

3.1. Mode of Action....................................................................................................... 6 

3.2. Overview of Pesticide Use and Usage.................................................................... 6 

3.3. Environmental Fate and Transport........................................................................ 12 

4. Receptors...................................................................................................................... 17 

4.1. Effects to Aquatic Organisms ............................................................................... 18 

4.2. Effects to Terrestrial Organisms ........................................................................... 19 

4.3. Incident Databases Review................................................................................... 20 

4.4. Ecosystems Potentially at Risk ............................................................................. 22 

5. Assessment Endpoints ................................................................................................. 22 

6. Conceptual Model........................................................................................................ 22 

6.1. Risk Hypothesis .................................................................................................... 23 

6.2. Conceptual Diagram ............................................................................................. 23 

7. Analysis Plan ............................................................................................................... 25 

7.1. Stressors of Concern ............................................................................................. 25 

7.2. Measures of Exposure........................................................................................... 26 

7.3. Measures of Effect ................................................................................................ 27 

7.4. Integration of Exposure and Effects ..................................................................... 28 

7.5. Deterministic and Probabilistic Assessment Methods.......................................... 29 

7.6. Endangered Species Assessment .......................................................................... 29 

7.7. Drinking Water Assessment ................................................................................. 30 

7.8. Preliminary Identification of Data Gaps............................................................... 30 

7.8.1. Fate Data Gaps............................................................................................... 30 

7.8.2. Effects Data Gaps .......................................................................................... 32 

8. References.................................................................................................................... 36 

Appendix A. Toxicity Data for Oryzalin ......................................................................... 48 

Appendix B. Data Call-In Tables..................................................................................... 53 

Appendix C. Oryzalin Formulations Containing Multiple Active Ingredients................. 61 

Appendix D. Oryzalin Incidents ....................................................................................... 63 

Appendix E. ECOSAR Analysis for the UN-2 Degradate ............................................... 66 
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1. Purpose 

The purpose of this problem formulation is to provide the status of the environmental fate 

and ecological effects of oryzalin, considering its currently registered uses. Oryzalin is a 

dinitroaniline herbicide that is registered nationally for the control of annual grasses and 

certain broadleaf weeds in fruit and nut crops, vineyards, Christmas tree plantations, 

ornamentals, turf, and several other non-crop sites. This document will provide a plan for 

analyzing data relevant to oryzalin and for conducting environmental fate, ecological 

risk, endangered species, and drinking water exposure assessments for its registered uses. 

Additionally, this problem formulation is intended to identify data gaps, uncertainties, 

and potential assumptions used to address those uncertainties relative to characterizing 

the ecological risk associated with the registered uses of oryzalin. 

2. Problem Formulation 

2.1. Nature of Regulatory Action 

Under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), all pesticides 

distributed or sold in the United States generally must be registered by the Environmental 

Protection Agency (EPA). In determining whether a pesticide can be registered in the 

United States, EPA evaluates its safety to non-target species based on a wide range of 

environmental and health effects studies. In 1996, FIFRA was amended by the Food 

Quality Protection Act, and the Agency was mandated to implement a new program for 

the periodic review of pesticides, i.e., registration review 

(http://www.epa.gov/oppsrrd1/registration_review/). 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 new 

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 new Registration Review program pursuant to 

Section 3(g) of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA), the 

Agency is beginning its evaluation of oryzalin to determine whether it continues to meet 

the FIFRA standard for registration. This problem formulation for the environmental 

fate, ecological risk, endangered species, and drinking water assessment chapter in 

support of the registration review will be posted in the initial docket which will open the 

public phase of the review process. 

2.2. Previous Assessments 

2.2.1. Ecological Risk Assessments 

Oryzalin was first registered in the United States in 1974 as a pre-emergence herbicide 

for use on weeds growing in fruit and nut orchards, vineyards, forestry, ornamentals, turf, 
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rights-of-ways, and other non-agricultural sites. A Registration Standard was issued in 

1987 (NTIS# PB89-102396) that evaluated the studies submitted on oryzalin to that date. 

Prior to the issuance of the Registration Standard, several agricultural crops were deleted. 

The only agricultural crop groups remaining on oryzalin labels are berries, vine and 

orchard crops (i.e., citrus fruits, pome fruits, stone fruits, tree nuts, and a few tropical 

fruits). In addition, oryzalin has many non-agricultural uses including ornamentals, 

Christmas trees, and established warm season turf and rights-of-ways. A Data Call-In 

was issued in 1991 requiring additional phytotoxicity data, plant and animal analytical 

methods, and non-dietary exposure data. EPA issued the Registration Eligibility Decision 

(RED) for oryzalin in September of 1994 by determining that all of the then registered 

oryzalin products were eligible for re-registration except for products labeled for use on 

residential lawns and turf. The results of the Agency’s 1994 ecological risk assessment 

for oryzalin, which was conducted as part of the RED, suggest the potential for adverse 

acute effects to non-target aquatic animals in shallow waters (6 inches deep) and 

terrestrial and aquatic plants. No acute or sub-lethal chronic effects to birds were reported 

due to exposure to oryzalin. 

The Agency also completed an effects determination for the threatened and endangered 

Pacific anadromous salmon and steelhead in 2003 based on oryzalin uses in grapes and 

almonds in the Pacific Northwest as part of the settlement for the petition filed against 

EPA by Washington Toxics Coalition (filed November 26, 2002). The results of this 

endangered species risk assessment showed that oryzalin may affect but is not likely to 

adversely affect 17 ESUs (Evolutionarily Significant Units) and will have no effect on 

nine ESUs. These determinations were based on possible indirect effects to listed 

salmonids from loss of aquatic plant cover in spawning and rearing habitats. 

In 2008, the potential for oryzalin to adversely affect the California Red Legged Frog 

(CRLF) was evaluated. An assessment was completed in September 2010 that 

determined the potential for oryzalin to adversely affect the California Tiger Salamander 

(CTS). The 2008 CRLF assessment and the 2010 CTS assessment concluded that 

oryzalin is Likely to Adversely Affect the CRLF and the CTS, respectively, from direct 

effects and indirect effects via impacts to aquatic and terrestrial plants and may modify 

the critical habitat of both species. 

2.2.2. Drinking Water Exposure Assessments 

The most recent comprehensive drinking water assessment was conducted in 2003 in 

support of the oryzalin Tolerance Reassessment Progress and Risk Management Decision 

(TRED; D209537). The TRED, dated May 26, 2004, determined that the lawn and turf 

uses for oryzalin are eligible for re-registration based on the submitted new studies on 

exposure monitoring on residential lawns and turf. However, the estimates were derived 

using older versions of the PRZM 3.12/EXAMS 2.975 models. 
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3. Stressor Source and Distribution

Oryzalin, applied to the soil surface prior to the emergence of weeds, is a herbicide used 

to control seedling grasses and some annual broadleaf weeds in a variety of agricultural 

crops such as avocado, fig, olives, berries, citrus fruits, pome fruits, tree nuts, tropical 

fruits, stone fruits, and vineyards. Other labeled non-agricultural uses for oryzalin 

include ornamentals, Christmas tree plantations, warm season turf grass, residential and 

non-croplands such as rights-of-ways, forest trees, industrial areas, and non-agricultural 

areas. Several degradates have been identified for oryzalin. However, only one 

degradate has been identified as a major (>10%) degradate (UN-2; 2-ethyl-7-nitro-1-

propyl-5-sulfonylaminobenzimidazole 3-oxide), which has been shown to form at 14% in 

an aquatic photodegradation study. The degradates of oryzalin were not found to be of 

concern for human health (US EPA, 2003). The toxicity of UN-2 is uncertain due to lack 

of submitted data; however, estimates of aquatic toxicity were conducted using structure 

activity relationships (ECOSAR, v. 1.0.0). This analysis suggests that UN-2 is estimated 

to be considerably less toxic to aquatic organisms than the parent chemical (Appendix 

E). 

3.1. Mode of Action 

Oryzalin is a broad spectrum herbicide that is used to control seedling grasses and some 

annual broadleaf weeds in both agricultural and non-agricultural settings. Depending on 

the formulation, the registered products of oryzalin are applied to the soil surface prior to 

the emergence of weeds as broadcast spray or band treatment for liquid formulations 

(using low pressure ground equipment) or soil broadcast for granular formulations (using 

spreaders). To facilitate activation and movement of the chemical to the weed seed 

germination zone, a single 1⁄2 to 1 inch of rainfall or sprinkler irrigation is required. 

Depending on the rate of application, the soil residual activity of oryzalin ranges between 

4 and 10 months. 

Oryzalin is mainly absorbed by roots, has little or no foliar activity, and is not 

translocated to the stem and leafy parts of the plant. Thus the primary effect of oryzalin is 

on root development. Roots of affected plants are relatively few in number, short, thick, 

and club shaped. The inhibited root growth causes the stem and leafy parts of plants to be 

stunted and become dark green. 

Oryzalin, similar to the other members of the dinitroaniline chemical family, acts by 

disrupting the assembly of microtubules. As a result, mitosis or cell division of plants,

ranging from single-celled algae to higher plants, is inhibited. Oryzalin, however, is 

ineffective against vertebrate and fungal microtubules. 

3.2. Overview of Pesticide Use and Usage 

Oryzalin is a dinitroaniline herbicide that is registered nationally for control of annual 

grasses and certain broadleaf weeds in fruit and nut crops, vineyards, Christmas tree 

plantations, ornamentals, turf, and several other non-crop sites. Oryzalin is formulated as 
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granules (0.4 to 1% a.i.), wettable powder (75% a.i.), water dispersible granules (60 - 

85% a.i.), emulsifiable concentrate (2.84 to 40.4% a.i.), flowable concentrate (40.4% 

a.i.), and formulation intermediate/liquid (40.4% a.i.). Depending on the formulation, 

oryzalin is typically applied using low pressure ground equipment or spreaders. The 

labels for oryzalin caution not to apply this herbicide to Douglas fir, slender deutzia, 

Techny arborvitae, eastern hemlock, begonia, and coleus due to phytotoxicity on the 

above species. 

All current labeled uses for oryzalin will be re-evaluated under registration review; these 

uses are agricultural uncultivated areas, almond, apple, apricot, avocado, blackberry, 

blueberry, boysenberry, caneberries, cashew, chestnut, cherry, chinquapin, citron, citrus, 

citrus hybrids, crabapple, currant, dewberry, elderberry, fig, filbert (hazelnut), forest 

trees, golf course turf, gooseberry, grapefruit, grapes, guava, hickory nut, 

household/domestic dwellings outdoor premises, industrial areas (outdoor), kiwi fruit, 

kumquat, lemon, lime, loganberry, loquat, macadamia nut (bushnut), mayhaw 

(hawthorn), nectarine, non-agricultural outdoor buildings/structures, non-agricultural 

rights-of-way/fencerows/hedgerows, non-agricultural uncultivated areas/soils, nursery 

stock, olive, orange, ornamental and/or shade trees, ornamental ground cover, ornamental 

herbaceous plants, ornamental lawns and turf, ornamental nonflowering plants, 

ornamental woody shrubs and vines, papaya, peach, pear, pecan, pistachio, plum, pome 

fruits, pomegranate, prune, pummelo (shaddock), quince, raspberry (black, red), 

recreation area lawns, residential lawns, small fruits, stone fruits, tangerines, tree nuts, 

and walnut (English/black). There are no new pending uses for oryzalin that are active at 

this time. Table 3.1 summarizes the oryzalin products that are currently registered in the 

United States. Table 3.2 presents the uses and corresponding application rates (single and 

maximum), application interval, and methods of application that will be considered in the 

registration review assessment. 

Table 3.1. Summary of Oryzalin Products Registered in the United States 

Product Name EPA Reg. No. Percent Active 

Ingredient Formulation 

Double O E-Pro Herbicide 000228-00632 1 G 

ET-029 000228-00698 40.4 L 

F8426 HERBICIDE FL05000400 40.4 EC 

Harrier WDG 081943-00008 85 DF 

HELENA XL2G 005905-00556 1 G 

LEBANON FERTILIZER WITH 

SURFLAN 000961-00352 1 G 

LILLY/MILLER HOSE 'N GO WEED 

& GRASS PREVENTER 000802-00565 2.84 L 

NATIONS AG II ORYZALIN 4 066222-00138 41 EC 

NATIONS AG II ORYZALIN 4 PRO 066222-00207 41 EC 

ORYZA AG 070506-00096 40.4 EC 

ORYZA T&O 070506-00097 40.4 EC 

Oryzalin 2G 053883-00220 1 G 
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Table 3.1. Summary of Oryzalin Products Registered in the United States 

Product Name EPA Reg. No. Percent Active 

Ingredient Formulation 

ORYZALIN COATED GRANULES 034704-00823 1.67 G 

ORYZALIN LIQUID 034704-00865 40.4 EC 

ORYZALIN PRO 4 053883-00168 41 EC 

ORYZALIN T&O 034704-00882 40.4 EC 

ROUT ORNAMENTAL HERBICIDE 058185-00027 1 G 

SNAPSHOT 80 DF 070506-00053 60 DF 

SURFLAN 0.25 A.S. 070506-00047 3 EC 

SURFLAN 75W 070506-00040 75 WP 

SURFLAN 75W WATER SOLUBLE 

PACKAGES 070506-00042 75 WP 

SURFLAN 85DF 070506-00050 85 DF 

SURFLAN A. S. 070506-00044 40.4 EC 

SURFLAN A.S. 070506-00043 40.4 EC 

SURFLAN DRY FLOWABLE 

HERBICIDE 070506-00046 85 DF 

TURF FERTILIZER CONTAINS 

GALLEY PLUS SURFLAN 070506-00055 0.86 G 

TURF FERTILIZER CONTAINS 

SURFLAN 0.75% 070506-00052 0.75 G 

TURF FERTILIZER CONTAINS 

SURFLAN 1% 070506-00051 1 G 

VERTAGREEN FERTILIZER FOR 

PROFESSIONAL TURF WITH 

SURFLAN 

008660-00150 1 G 

WEED STOPPER 054705-00005 40.4 EC 

WEED STOPPER HOSE'EM 054705-00011 3 L 

XL 2G 070506-00045 1 G 

XL 2GR 070506-00056 1 G 

XL2G 038167-00030 1 G 

070506-00095 98 TGAI 

083558-00024 41 MP 

070506-00041 98.3 TGAI 

070506-00054 75 MP 

083558-00022 95.6 TGAI 

Technical and Manufacturing Product 

Labels 

070506-00048 40.4 MP 

G=granular; L=liquid; EC=emulsifiable concentrate; DF=dry flowable; WP=wettable powder; TGAI=technical grade 

active ingredient; MP=manufacturing product 
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Table 3.2. Maximum Labeled Application Rates for Oryzalin

Use Formulation 

Code1

Application 

Method 

Maximum 

Single 

Application 

Rate 

(lb a.i./A) 

Maximum 

Number of 

Applications 

per Year 

(#) 

Maximum 

Seasonal 

Application 

Rate 

(lb a.i./A) 

Application 

Interval 

(days) 

EC/DF 

Low pressure 

ground 

sprayer/ 

Sprinkler 

irrigation 

/Broadcast/ 

Chemigation/ 

Soil broadcast 

treatment 

6 2 12 75 

Berries 

Blackberry, blueberries, 

boysenberry, caneberries, 

currant, dewberry, elderberry, 

gooseberry, loganberry and 

raspberry 

Citrus Fruits 

Grapefruit, kumquat, kiwi, 

lime, lemon, mandarin, 

tangerine, orange, pummelo, 

nectarine, orange 

Pome Fruits 

Apple, apricot, crabapple, fig, 

loquat, mayhaw, 

pomegranate, and quince 

Tree Nuts 

Almonds, cashew, chestnut 

chinquapin, filbert, hickory 

nut, macadamia nut, pecan, 

pistachio walnut 

Stone Fruits 

Avocado, cherry, nectarine, 

olive, peach, pear, plum, 

prune 

Vineyards 

Wine and table grapes 

Tropical Fruits 

Guava, papaya

G 

Granules by 

Spreader/ 

Broadcast 4 4 15 60 

EC/DF/WP/L 

Low pressure 

ground 

sprayer/ 

Sprinkler 

irrigation 

/Broadcast/ 

Chemigation/ 

Soil broadcast 

treatment 

4 3 12 90 

Non-bearing 

Trees/Vineyards

Granular 

Granule 

applicator 

Spreader, 

/Broadcast 

4 4 15 60 
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Table 3.2. Maximum Labeled Application Rates for Oryzalin

Use Formulation 

Code1

Application 

Method 

Maximum 

Single 

Application 

Rate 

(lb a.i./A) 

Maximum 

Number of 

Applications 

per Year 

(#) 

Maximum 

Seasonal 

Application 

Rate 

(lb a.i./A) 

Application 

Interval 

(days) 

EC/DF/WP/L 

Low pressure 

ground 

sprayer/ 

Sprinkler 

irrigation 

/Broadcast/ 

Chemigation/ 

Soil broadcast 

treatment 

4 3 12 90 

Ornamentals2

G 

Granule 

applicator 

Spreader, 

/Broadcast 

4 4 15 60 

EC/DF/L/WP 

Low pressure 

ground 

sprayer/ 

Sprayer/ 

Spreader 

/Broadcast/ 

Directed 

spray/ 

Soil broadcast 

treatment 

4 2 8 60 

G 

Granule 

applicator 

Spreader, 

/Broadcast 

4 2 8 60 

Christmas Tree Plantation

G 

Granule 

applicator 

Spreader, 

/Broadcast 

3.34 5 15 90 

EC/L 

Low pressure 

ground 

sprayer/ 

Sprayer 

1.5 2 2.25 90 

Ornamental Bulbs

G 

Granule 

applicator 

Spreader, 

/Broadcast 

1.5 2 2.25 90 

EC/L 

Low pressure 

ground 

sprayer/ 

Sprayer 

2 3 6 90 

Turf

G 

Granule 

applicator 

Spreader, 

/Broadcast 

1.5 4 6 90 
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Table 3.2. Maximum Labeled Application Rates for Oryzalin

Use Formulation 

Code1

Application 

Method 

Maximum 

Single 

Application 

Rate 

(lb a.i./A) 

Maximum 

Number of 

Applications 

per Year 

(#) 

Maximum 

Seasonal 

Application 

Rate 

(lb a.i./A) 

Application 

Interval 

(days) 

EC/L/WP 

Low pressure 

ground 

sprayer/ 

Sprayer 

6 2 12 180 

Non-agricultural Areas 

Rights-of-way, fencerows, 

hedgerows, 

buildings/structures, outdoor 

industrial areas

G 

Granule 

applicator 

Spreader, 

/Broadcast 

6 2 12 240 

Residential Areas 

G 

Granule 

applicator 

Spreader 

2 3 6 56 

Agricultural Uncultivated 

Areas DF Low pressure 

ground sprayer 3 3 9 120 

1

Formulation codes: DF- Water Dispersible Granules (Dry Flowable); EC-Emulsifiable Concentrate; G-Granular; L-Liquid; WPWettable Powder 

2

Use in landscape gardens, container and field grown ornamentals, drainage areas under shadehouse benches, ground 

covers/perennials

According to the United States Geological Survey’s (USGS) national pesticide usage data 

(based on information from 1999 to 2004), an average of 358,151 lb per year of oryzalin 

are applied nationally to agriculture in the United States (see Figure 3.1). As of 2002, 

over 93% of total agricultural uses for oryzalin are in the crops listed in Figure 3.1. The 

highest poundage (142,601 lbs) of oryzalin was applied to citrus fruits. Grapes (74,753 

lbs) and apples (39,855 lbs) represented the second and third highest total pounds of 

oryzalin applied, respectively. Based on a Screening Level Usage Analysis (SLUA) 

conducted by EPA (January 21, 2010), using data from 2001 to 2007, there is an 

estimated ~1,212,000 lb of oryzalin used per year [most of which is used on almonds 

(400,000 lb), grapes (400,000 lb), and pistachios (100,000 lb)]. Estimates of nonagricultural usage of oryzalin are not available. Reasons for the difference in the amount 

of oryzalin reportedly applied between the USGS data and the SLUA is unknown; 

however, the 2002 data may not be representative of the 2001 to 2007, which is covered 

by the SLUA. 
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Figure 3.1. Estimated, Annual, National, Agricultural Oryzalin Usage. (from 

http://water.usgs.gov/nawqa/pnsp/usage/maps/show_map.php?year=02&map=m1873) 

[The pesticide use maps available from this site show the average annual pesticide use intensity expressed 

as average weight (in pounds) of a pesticide applied to each square mile of agricultural land in a county. 

The area of each map is based on state-level estimates of pesticide use rates for individual crops that were 

compiled by the CropLife Foundation, Crop Protection Research Institute based on information collected 

during 1999 through 2004 and on 2002 Census of Agriculture county crop acreage. The maps do not 

represent a specific year, but rather show typical use patterns over the five year period 1999 through 2004.].

3.3. Environmental Fate and Transport 

Best-available data defining the physical, chemical, fate and transport characteristics 

associated with oryzalin are summarized in Table 3.3. It should be noted that several 

studies are currently under review, as noted in Table 3.3, and the values presented for 

these studies are based solely on a cursory review of the data; upon completion of review, 

it is possible that the fate profile for oryzalin may change. The major routes of oryzalin 

dissipation are aqueous photolysis, photodegradation on soil surface, and degradation 

under anaerobic conditions. Oryzalin appears to degrade slowly under aerobic soil 

conditions and is stable to hydrolysis. Under field conditions oryzalin appeared to be 
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moderately persistent, with a half-life of about two months. Based on its low vapor 

pressure (1.0 x 10-7 mm Hg at 25°C) and Henry's Law Constant 

(1.8 x 10-8 atm⋅m3/mol), volatilization loss of oryzalin from soil and water systems is 

expected to be insignificant compared to dissipation by abiotic and biotic degradation.

Table 3.3. Summary of Oryzalin Environmental Physicochemical and Fate Properties 

Parameter Value Major Degradates 

Minor Degradates

Source/ 

MRID # 

Study Status 

Common name Oryzalin --- USEPA, 1994 --- 

Chemical name 3,5-dinitro-N4,N4-

dipropylsulfanilamide --- USEPA, 1994 --- 

Chemical family Dinitroaniline --- USEPA, 1994 --- 

CAS Number 19044-88-3 --- USEPA, 1994 --- 

Empirical formula C12H18N4O6S --- USEPA, 1994 --- 

Structure --- USEPA, 1994 --- 

Molecular mass 346.35 --- USEPA, 1994 

Water solubility 

(20°C) 2.5 mg/L --- USEPA, 1994 -- 

Vapor pressure 

(25°C) 1.0 x 10-7 mm Hg at 25°C --- MRID 40454801 Acceptable

Henry’s Law 

Constant 1.82 x 10-8 atm m3

/mol --- Calculated 1 --- 

Octanol/water 

partition coefficient 

(Log Kow) 

3.73 at pH 7 --- USEPA, 1994 --- 

Hydrolysis Stable (pH 5, 7, 9) --- MRID 41378401 Under review*

Direct Aqueous 

Photolysis 0.06 days 

UN-2, 14.0% 

OR-3, 5.7%, 

OR-5, 4.0% 

OR-X, 2.9% 

MRID 41278701 Supplemental2

Soil Photolysis 3.8 days 

OR-3, 2.6%, 

OR-15, 3.2% 

OR-21, 4.6%. 

MRID 41050001 Under review*

Aerobic Soil 

Metabolism 63 days 

OR-20 4.7 %, 

UN-1, UN-2,OR-2, 

OR-4, OR-9, OR-13, 

OR-15 and OR-41, 

< 2.4% 

MRID 41322801 Under review*

Anaerobic Soil 

Metabolism 10 Days 

OR-20, <0.2% 

OR-15, <0.2% 

UN-1, <0.2% 

OR-2, <0.2% 

MRID 41322802 Under review*

Aerobic Aquatic data gap --- --- Call in data 
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Table 3.3. Summary of Oryzalin Environmental Physicochemical and Fate Properties 

Parameter Value Major Degradates 

Minor Degradates

Source/ 

MRID # 

Study Status 

Metabolism 

Anaerobic Aquatic 

Metabolism data gap --- --- Call in data 

Soil Partition 

Coefficient 

(Koc: L kg o.c.-1) 3

722, 602, 803 and 1109 

(average = 809) --- MRID 41479802 Under review*

Terrestrial Field 

Dissipation 

FL: 68 days 

MI: 77-138 days 

CA: 58-146 days 

--- MRID 42138001 Supplemental4

Fish 

Bioconcentration 

Factor (BCF) 

32x (edible) 

105x (non-edible) 

66x (whole fish) 

--- MRID 40787501 Acceptable

*Values presented for studies that are currently under review are based on a cursory review of the data and are subject to 

change. 

1

Henry’s Law (atm-m3/mole) = (VAPR/760)/(SOL/MWT), where VAPR is vapor pressure in torr, MWT is molecular 

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

2

The supplemental information submitted in addition to the study (MRID 41278701) completely satisfies the data 

 requirement (EFED Search Document 2002465). The OR-X degradate is identified as 3-nitro-5-aminosulfanilamide. 3

Koc was calculated from Kd and % o.m. from raw data using the formulas % o.c. = % o.m./1.72 and 

 Koc = (Kd/% o.c.) x 100 

4

Study is upgradeable pending submission and review of analytical method and independent laboratory validation. 

Laboratory studies indicate that oryzalin is stable to hydrolysis at pHs 5, 7 and 9. (MRID 

41378401) but exhibits susceptibility to rapid direct aqueous photolysis; the aqueous 

photolytic half-life is 1.4 hours (MRID 41278701). The degradates of aqueous photolysis 

are OR-5 (2.9%), OR-3 (5.7%), and UN-2 (14%). The chemical also readily 

photodegrades on the soil surface with an estimated half-life of 3.8 days, and the 

degradates are OR-3 (2.6%), OR-15 (3.2%) and OR-21 (4.6%) (MRID 41050001). 

Oryzalin degrades aerobically with a half-life of 63 days in sandy loam soil (MRID 

41322801). Nine degradates were identified, each accounting for < 2.4% of the applied 

radioactivity (Table 3.3) except for 4-hydroxy-3,5-dinitrobenzenesulfonamide (OR-20), 

which accounted for a maximum of 4.7% of radioactivity at 1 month post treatment in the 

soil aerobic metabolism study. The benzenesulfonamide ring remained intact in all of the 

identified metabolites. By the end of the experiment at 6.1 months, 63.1% of the applied 

radioactivity was nonextractable and 5.7% had been mineralized to CO2. Under anaerobic 

conditions oryzalin nitro groups undergo reduction to amines, dealkylation, and ring 

formation to produce benzimidazoles, with a half-life of 10 days (MRID 41322802). 

Anaerobic metabolites that accounted for < 0.2% are UN-1, OR-2, OR-15, and OR-20. 

Table 3.4 provides names, structures and the occurrence of various degradates detected 

in environmental fate studies. 
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In the field, oryzalin appears to dissipate slowly with a half-life of 68 days in Florida 

sand soil and a first phase half-life of 58 days in California loam soil and 77 days in 

Michigan silty clay loam soil. The second phase half-lives were 146 days in California 

loam soil and 138 days in Michigan silty clay loam soil. Parent oryzalin did not appear to 

be mobile under field conditions. The parent was undetectable and always less than 

detection limits (i.e., 0.01 ppm; MRID 42138001) below 12 inches of soil depth. Oryzalin 

degradates were not monitored in the field dissipation studies submitted. Although 

oryzalin does not appear to be mobile under field conditions, the soil partition 

coefficients (Koc = 602 to 1109 L Kg-1; MRID 41479802 ) indicate that chemical mobility 

will vary from moderately mobile to slightly mobile according to FAO Classification 

Scheme (FAO, 2000) depending on soil type and organic matter content. 

Oryzalin has potential to contaminate surface water via spray drift and runoff. Substantial 

quantities of oryzalin could be available for runoff for a few days to months postapplication depending on the degree of exposure to sunlight (photodegradation on soil 

half-life of 3.8 days; aerobic soil half-life of 63 days; terrestrial field dissipation half-lives 

of 77-138 and 58-146 days). The soil partitioning coefficients of oryzalin indicates that 

fractions of oryzalin could be transported via both dissolution in runoff water and 

adsorption to eroding soil in the event of significant rainfall occurring after application 

prior to soil incorporation. Based upon its Koc, significant fractions of the oryzalin in 

receiving surface waters should exist both dissolved in the water column and adsorbed to 

suspended sediment. The susceptibility of oryzalin to direct photolysis in water (half-life 

= 1.4 hours) should limit its persistence in clear shallow waters with low light 

attenuation. However, its resistance to abiotic hydrolysis coupled with only a moderate 

susceptibility to aerobic biodegradation indicate that it will be somewhat more persistent 

in receiving surface waters that are deeper, have high light attenuation, low 

microbiological activities and long hydrological resident times. 

Oryzalin is less likely to contaminate ground water resources due to reduction in the 

anaerobic soil layer. However, in sandy soils under some environmental conditions, such 

as excess precipitation, or where soil preferential flow conditions exist and exposure to 

sunlight is minimal, oryzalin residues may leach into ground water and undergo reduction 

to more polar compounds. 

Based on a laboratory bioaccumulation study (MRID 40787501), oryzalin did not 

significantly bioconcentrate in bluegill sunfish. The BCFs were 32X in edible tissue, 

105X in nonedible tissue, and 66X in whole fish. Depuration ranged from 79.2 to 80.8% 

after 24 hours and 88.7 to 95.1% after 14 days. 

Nine degradates have been identified for oryzalin in the soil aerobic metabolism study. 

Three other degradates were also identified in various fate studies (Table 3.4). 4-

Hydroxy-3,5-dinitrobenzenesulfonamide (OR-20) accounted for a maximum of 4.7% of 

radioactivity at 1 month post-treatment in the soil aerobic metabolism study. Eight other 

degradates were isolated, but each comprised < 2.4% of the applied radioactivity. The 

available data on degradates of oryzalin are insufficient to assess their runoff 

characteristics or persistence in surface waters. The registrant conducted a 
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mobility/adsorption/desorption study to determine the mobility of nine oryzalin 

degradates and whether or not degradate leaching is a major route of dissipation. Out of 

nine metabolites formed, three (OR-20, UN-2, and the unidentified compound UN-3; 

MRID 43433202) appeared to be very mobile. 

Table 3.4 Oryzalin Degradates Identified in Environmental Fate Studies 

Code Structure IUPAC Name Percent Formation 

/Reference 

OR-2 3,5-dinitro-4-(propylamino) benzenesulfonamide 

(<2.4%) MRID 413228011

(<0.2 %) MRID 413228022

OR-3 3,5-dinitro-4-aminobenzenesulfonamide 

(5.7%) MRID 412787013

(2.6%) MRID 410500014

OR-4 3-amino-4-(dipropylamino)- 

5-nitrobenzenesulfonamide 

(<2.4%) MRID 413228011

 

 MRID 413228022

OR-5 3-amino-4-propylamino)- 5-

nitrobenzenesulfonamide 

(4.0%) MRID 412787013

OR-9 3,4,5-triaminobenzenesulfonamide 

(<2.4%) MRID 413228011

OR-13 2-ethyl-7-nitro-1-propyl1H-benzimidazole-5-

sulfonamide 

(<2.4%) MRID 413228011

 MRID 413228022

OR-15 2-ethyl-7-nitro-1Hbenzimidazole-5-

sulfonamide 

(<2.4%) MRID 413228011

(< 0.2%) MRID 413228022

(3.2%) MRID 410500014

OR-20 4-hydroxy-3,5-dinitrobenzenesulfonamide 

(4.7%) MRID 413228011

(< 0.2%) MRID 413228022
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Table 3.4 Oryzalin Degradates Identified in Environmental Fate Studies 

Code Structure IUPAC Name Percent Formation 

/Reference 

OR-21 3,4-dinitro-4-

dipropylamineo-sulfanalic 

acid 

(4.6%) MRID 410500014

OR-41 4-[(2-hydroxypropyamino)]-3,5-dinitrobenzenesulfonamide 

(<2.4%) MRID 413228011

UN-1 3,3’-azoxybis[(4-

propylamino]-5-nitro]-

benzenesulfonamide 

(<2.4%) MRID 413228011

(< 0.2%) MRID 413228022

UN-2 2-ethyl-7-nitro-1-propyl1H-benzimidazole-5-

sulfonamide-3-oxide 

(<2.4%) MRID 413228011

 MRID 413228022

(14%) MRID 412787013

1

Aerobic soil metabolism; 2Anaerobic soil metabolism; 3Aquatic photolysis; 4Soil photolysis 

4. Receptors 

Consistent with the process described in the Overview Document (USEPA, 2004), the 

risk assessment for oryzalin will rely on a surrogate species approach. Toxicological data 

generated from surrogate test species, which are intended to be representative of broad 

taxonomic groups, are used to extrapolate the potential effects on a variety of species 

(receptors) included under these taxonomic groupings. Only one degradate may 

potentially form at amounts greater than 10% of the applied parent compound (UN-2, 

14%); however, none of the degradates of oryzalin were found to be of toxicological 

concern for mammalian species (MARC memo D289755 dated 5 June 2003). Toxicity 

estimates based on structure activity relationships suggest that UN-2 is less toxic than the 

parent compound to terrestrial and aquatic species. Therefore, only the toxicity and 

potential exposure to non-target organisms to the parent oryzalin will be quantified. The 

most sensitive endpoints from the available toxicity data for oryzalin will be used to 

quantify risk. 

Acute and chronic toxicity data from studies submitted by pesticide registrants along with 

the available open literature are used to evaluate the potential direct and indirect effects 

of oryzalin to aquatic and terrestrial receptors. This includes toxicity on the technical 

grade active ingredient, degradates, and when available, formulated products (e.g., “SixPack” studies). The open literature studies are identified through EPA’s 

ECOTOXicology (ECOTOX) database, which employs a literature search engine for 
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locating chemical toxicity data for aquatic life, terrestrial plants, and wildlife. The 

evaluation of both sources of data may also provide insight into the direct and indirect 

effects of oryzalin 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. A preliminary review of open literature data from ECOTOX (collected 

March 2010) on oryzalin was conducted as part of this Problem Formulation to help 

identify data gaps. A more complete review of the data from ECOTOX will be 

conducted for evaluation for possible quantitative and/or qualitative inclusion in this risk 

assessment. 

A summary of the most sensitive data representing non-target organisms exposed to 

oryzalin in aquatic and terrestrial habitats is provided in Sections 4.1 and 4.2, 

respectively. A summary of ecological incidents associated with oryzalin and a 

description of ecosystems potentially at risk are provided in Sections 4.3 and 4.4, 

respectively. 

4.1. Effects to Aquatic Organisms 

A summary of the most sensitive aquatic toxicity data for oryzalin from registrantsubmitted studies is provided in Table 4.1. A summary of all submitted ecotoxicity data 

for oryzalin is provided in Appendix A. Oryzalin is classified as moderately toxic to 

freshwater fish, moderately toxic to estuarine/marine fish, moderately toxic to freshwater 

invertebrates, and highly toxic to estuarine/marine invertebrates on an acute exposure 

basis. The EC50 for the most sensitive non-vascular aquatic plants (Green algae, 

Selenastrum capricornutum) is 52 μg a.i./L, with a NOAEC of 13.8 μg a.i./L based on 

cell density (MRID 431369-01). However, two non-vascular aquatic plant studies were 

classified as invalid; these species could yield potentially more sensitive endpoints. The 

EC50 for vascular aquatic plants (Duckweed, Lemna gibba) is 13 μg a.i./L, with a 

NOAEC of 3.28 μg a.i./L based on frond count (MRID 431369-05). 

Regarding chronic effects, the only data currently available for oryzalin and aquatic 

organisms are for freshwater fish and freshwater invertebrates (i.e., there are currently no 

chronic data available for estuarine/marine fish or invertebrates). For freshwater fish, the 

most sensitive NOAEC is 0.22 mg a.i./L for the fathead minnow (Pimephales promelas) 

based on a reduction in mean larval weights (MRID 00126841). The only chronic toxicity 

data available for freshwater invertebrates is for daphnids (Daphnia magna) (MRID 

439869-01). This study resulted in a NOAEC of 0.358 mg a.i./L based on reduction in 

dry weight of the first generation daphnids (LOAEC = 0.608 mg a.i./L). 

Table 4.1. Summary of the Most Sensitive Endpoints from Submitted Aquatic Toxicity Studies 

for Oryzalin 

Study Type Species Toxicity Value Toxicity Classification MRID & Status 

Acute – 

Freshwater Fish 

Bluegill sunfish 

(Lepomis 

macrochirus)

96-hr LC50: 2.88 mg/L 

NOAEC: 1 mg/L 

Slope: 9.3

Moderately toxic 00072595 

Acceptable 
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Table 4.1. Summary of the Most Sensitive Endpoints from Submitted Aquatic Toxicity Studies 

for Oryzalin 

Study Type Species Toxicity Value Toxicity Classification MRID & Status 

Chronic – 

Freshwater Fish 

Fathead minnow 

(Pimephales 

promelas) 

NOAEC: 0.22 mg/L 

LOAEC: 0.43 mg/L 

(based on mean larval 

weights)

NA 00126841 

Acceptable 

Acute – 

Estuarine/Marine 

Fish 

Sheepshead minnow 

(Cyprinodon 

variegatus) 

96-hr LC50: >3.04 mg/L 

NOAEC: 3.04 mg/L Moderately toxic 438877-01 Acceptable 

Acute – 

Freshwater 

Invertebrate Water flea 

(Daphnia magna) 

48-hr EC50: 1.5 mg/L 

NOAEC: 0.62 mg/L 

(based on hypoactivity, 

prostration, and immobility) 

Slope: 9.5

Moderately toxic 00072596 

Acceptable 

Chronic – 

Freshwater 

Invertebrate 

Water flea 

(Daphnia magna) 

NOAEC: 0.358 mg/L 

LOAEC: 0.608 mg/L 

(based on dry weight of first 

generation daphnids) 

NA 439869-01 

Acceptable 

Acute – 

Estuarine/Marine 

Invertebrate 

Eastern oyster 

(Crassostrea 

virginica) 

96-hr EC50: 0.285 mg/L 

NOAEC: 0.0994 mg/L 

(based on shell deposition) 

Highly toxic 438877-02 

Acceptable 

Aquatic – Nonvascular Plants Green algae 

(Selenastrum 

capricornutum) 

5-day EC50: 52 μg a.i./L 

NOAEC: 13.8 μg a.i./L 

 (based on cell density) 

NA 431369-01 

Supplemental 

Aquatic – 

Vascular Plants Duckweed 

(Lemna gibba) 

14-day EC50: 13 μg/L 

NOAEC: 3.28 μg/L 

(based on frond count) 

NA 431369-05 

Supplemental 

4.2. Effects to Terrestrial Organisms 

Table 4.2 summarizes the most sensitive terrestrial toxicity endpoints for oryzalin based 

on an evaluation of submitted studies. Oryzalin is classified as slightly toxic to birds on 

an acute oral basis and practically non-toxic to birds on an acute dietary basis. Oryzalin 

is classified as practically non-toxic to mammals and honey bees on an acute basis. The 

Tier II terrestrial plant studies were classified as supplemental because the studies utilize 

a technical grade active ingredient (TGAI) instead of the required typical end-use product 

(TEP). The lack of Tier II terrestrial plant studies conducted with a TEP is considered a 

data gap (see Section 7.8.2). 

For chronic effects, the NOAEC for birds is 132 mg/kg-diet based on a reduction of 

female body weight in bobwhite quail (Colinus virginianus) (MRID 441622-01). For 

mammals, the chronic toxicity value is a NOAEL of 13.82 mg/kg-bw/day based on 

numerous endpoints in the laboratory rat (Rattus norvegicus) (MRID 00026779, 

00044332, 00070569). 
-20 of 69-

Table 4.2. Summary of the Most Sensitive Endpoints from Submitted Terrestrial Toxicity 

Studies for Oryzalin 

Study Type Species Toxicity Value Toxicity Classification MRID & Status 

Acute – Avian 

Oral 

Bobwhite quail 

(Colinus virginianus)

LD50: 506.7 mg/kg-bw/day 

Slope: 4.5 Slightly toxic 00098462 Acceptable 

Acute – Avian 

Dietary 

Bobwhite quail 

(Colinus virginianus) 

LC50: >5,000 mg/kg-diet 

NOAEC: <625 mg/kg-diet 

(based on reduced food 

consumption and body 

weight gain) 

Practically non-toxic 00072593 

Acceptable 

Chronic – Avian 

Reproduction Bobwhite quail 

(Colinus virginianus) 

NOAEC: 132 mg/kg-diet 

LOAEC: 311 mg/kg-diet 

(based on female body 

weight) 

NA 441622-01 

Acceptable 

Acute – 

Mammalian Oral 

Rat (Rattus 

norvegicus) LD50: 10,000 mg/kg-bw Practically non-toxic 00026592 

Acceptable 

Chronic – 

Mammalian 

Reproduction Rat (Rattus 

norvegicus) 

NOAEL: 13.82 mg/kgbw/day 

LOAEL: 42.9 mg/kgbw/day 

(based on numerous 

endpoints) 

NA 

00026779 

00044332 

00070569 

Acceptable 

Acute – Contact 

Toxicity 

Honey bee 

(Apis mellifera) LC50: >11 μg/bee Practically non-toxic 00066220 

Acceptable 

Terrestrial Plant 

– Tier II 

Seedling 

Emergence 

Oat, Corn, Ryegrass, 

Onion, Cabbage, 

Cucumber, Lettuce, 

Tomato, Soybean, 

Radish 

EC25: 0.014 lb a.i./acre 

(monocot: ryegrass shoot 

length) 

EC25: 0.050 lb a.i./acre 

(dicot: tomato shoot length) 

NA 

426024-01 

Supplemental 

(used TGAI) 

Terrestrial Plant 

– Tier II 

Vegetative Vigor 

Corn, Oat, Ryegrass, 

Onion, Lettuce, 

Tomato, Cabbage, 

Cucumber, Radish, 

Soybean 

EC25: 0.080 lb a.i./acre 

(monocot: corn dry weight) 

EC25: 0.030 lb a.i./acre 

(dicot: tomato dry weight) 

NA 

426024-01 

Supplemental 

(used TGAI) 

4.3. Incident Databases Review 

Preliminary reviews of the Ecological Incident Information System (EIIS, version 2.1) 

and the Avian Incident Monitoring System (AIMS)1

 were conducted on August 2, 2010. 

There were no avian incidents reported in the AIMS database. There were five plant 

incidents and one fish incident involving oryzalin reported in the EIIS database. The 

reported incidents occurred between 1989 and 2002. The certainty in which these 

incidents were a result of oryzalin use was described as unlikely in one incident, possible 

in four incidents, and probable in one incident. Two of the incidents were the results of 

registered uses, one was an accidental misuse, one was an intentional misuse, and the 

causes of two incidents were unknown. Specific details of the incidents are described 

below (more detailed information can be found in Appendix C). 

 

1

 http://www.abcbirds.org/abcprograms/policy/pesticides/aims/aims/index.cfm 
-21 of 69-

Terrestrial Incidents 

Five incidents were reported in the EIIS database that involved ornamental or crop plants. 

In 1989 in Washington state, Douglas fir trees, which were treated directly, experienced 

damage (I001734-001). The magnitude of the injury is unknown, and the incident was 

classified as an intentional misuse. It was probable that oryzalin caused this injury. 

Another incident involving Douglas fir trees (I001485-027) occurred when the trees were 

treated directly, causing death. It is possible that oryzalin caused this mortality. In 1992 

in Benton, Washington, an unspecified type of tree experienced damage (I014409-062). 

It is possible that oryzalin caused this damage. In 1998, thirteen acres of grapes in Grant, 

Washington were damaged when they were treated directly with oryzalin (I013884-027). 

The incident was classified as a registered use and it was unlikely that oryzalin caused the 

damage. In 2002 in Washington, Oregon six acres of tulips were damaged when they 

were treated directly with oryzalin (I013636-027). The incident was classified as a 

registered use, and it was possible that oryzalin caused this damage. 

Aquatic Incidents 

In 2001, about 450 to 500 bluegill sunfish and largemouth bass were found dead in a 

three-acre pond in Georgia (I011444-011). Small numbers began dying around April 6 -

7, 2001, and heavier numbers began dying around April 12 and 13. SURFLAN had been 

sprayed on March 31 at a time when 35-40 mph winds were blowing, and the application 

site was within 50-60 feet of the pond in an uphill direction. It is possible that the pond 

was contaminated by either spray drift or runoff because rain fell on April 4. The 

fisheries biologist, who reported the incident to the chemical company, believed that the 

fish most likely died of a bacterial infection. The report contained no mention of 

analytical data in this case. The incident was classified as an intentional misuse, and it is 

possible that oryzalin contributed to this fish kill. 

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

reported to the Agency in an aggregated format. Pesticide registrants report certain types 

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

quarter. Ecological incidents reported in aggregate reports include those categorized as 

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

incidents. ‘Other non-target’ incidents include reports of adverse effects to insects and 

other terrestrial invertebrates. Two minor aggregate incident reports involving plants 

have been submitted to the Agency for oryzalin. 

Due to limitations with data in the EIIS, a low number or lack of reported incidents in the 

database cannot be used as evidence that additional incidents have not occurred. Incident 

reports for non-target plants and animals typically provide information on mortality 

events only. Reports for other adverse effects, such as reduced growth or impaired 

reproduction, are rarely received. EPA’s changes in the registrant reporting requirements 

of incidents may also account for the reduced number of reported incidents. Registrants 

are now only required to submit detailed information on ‘major’ incidents. Minor 
-22 of 69-

incidents are generally reported aggregately and are not included in EIIS. In addition, 

there have been changes in state monitoring efforts due to lack of resources. 

4.4. Ecosystems Potentially at Risk 

The ecosystems at risk are often extensive in scope; therefore, it may not be possible to 

identify specific ecosystems during the development of a nation-wide ecological risk 

assessment. However, in general terms, terrestrial ecosystems potentially at risk could 

include the treated field and immediately adjacent areas 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. 

Aquatic ecosystems potentially at risk include water bodies adjacent to or down stream 

from the treated field and could 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, including estuaries. 

5. Assessment Endpoints 

Assessment endpoints represent the actual environmental value that is to be protected, 

defined by an ecological entity (species, community, or other entity) and its attribute or 

characteristics (USEPA, 1998). For oryzalin, the ecological entities may include the 

following: birds, mammals, terrestrial-phase amphibians, reptiles, freshwater fish and 

invertebrates, aquatic-phase amphibians, estuarine/marine fish and invertebrates, 

terrestrial plants, terrestrial invertebrates, and aquatic plants. The attributes for each of 

these entities include survival, growth, and reproduction. 

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. 

The conceptual model for oryzalin provides a written description and visual 

representation of the predicted relationships between oryzalin, 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). 
-23 of 69-

6.1. Risk Hypothesis 

A risk hypothesis describes the predicted relationship among the stressor, exposure, and 

assessment endpoint response along with the rationale for their selection. For oryzalin, 

the following ecological risk hypothesis is being employed for this ecological risk 

assessment: 

Based on the application methods, mode of action, fate and transport, and the 

sensitivity of non-target aquatic and terrestrial species, oryzalin has the potential 

to reduce survival, reproduction, and/or growth in non-target terrestrial and 

aquatic organisms when used in accordance with the current labels. These nontarget organisms include Federally-listed threatened and endangered species as 

well as non-listed species. 

6.2. Conceptual Diagram 

The environmental fate properties of oryzalin indicate that runoff, spray drift and direct 

spray represent potential transport mechanisms of oryzalin to aquatic and terrestrial 

habitats where non-target organisms may be exposed. These transport mechanisms (i.e., 

sources) are depicted in the conceptual models below (Figures 6.1 and 6.2) along with 

the receptors of concern and the potential attribute changes in the receptors due to 

exposure to oryzalin. 
-24 of 69-

Figure 6.1. Conceptual Model for Oryzalin Exposure and Effects to Aquatic 

Organisms. Dotted Lines Indicate Exposure Pathways that Have a Low Likelihood 

of Contributing to Ecological Risk. 

Stressor 

Source

Receptors 

Attribute 

Change 

Oryzalin applied to use site 

Spray drift 

Fish/aquatic-phase 

amphibians 

Eggs 

Larvae 

Juveniles / Adults 

Individual organisms 

Reduced survival 

Reduced growth 

Reduced reproduction 

Food chain 

Reduction in algae 

Reduction in prey 

Habitat integrity 

Reduction in primary productivity

Reduced cover 

Community change 

Surface water/ 

Sediment 

Runoff 

Aquatic Animals 

Invertebrates 

Vertebrates 

Exposure 

Media 

Uptake/gills 

or integument 

Ingestion Ingestion

Soil Groundwater 

Uptake/gills 

or integument 

Aquatic Plants 

Non-vascular 

Vascular 

Uptake/cell, 

roots, leaves Riparian plant

terrestrial 

exposure 

pathways see 

Figure 6.2 
-25 of 69-

Figure 6.2. Conceptual Model for Oryzalin Exposure and Effects to Terrestrial 

Organisms. 

7. Analysis Plan 

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

environment will be estimated. The use, environmental fate, and ecological effects of 

oryzalin will be characterized and integrated to assess the risks. Risk quotients (RQs) 

will be derived for oryzalin by dividing estimated environmental concentrations (EEC) 

by the most sensitive endpoint from the relevant, available toxicity data for oryzalin. 

This analysis plan will be revisited and may be revised depending upon a full review of 

the data available in the open literature and the information submitted by the public in 

response to the opening of the Registration Review docket. 

7.1. Stressors of Concern 

One degradate has been identified as a major (>10%) degradate (UN-2, 2-ethyl-7-nitro-1-

propyl-5-sulfonylaminobenzimidazole 3-oxide), which has been shown to form at 14% in 

Stressor 

Source

Receptors 

Attribute 

Change 

Oryzalin applied to use site 

Direct 

application Spray drift 

Birds / Terrestrialphase amphibians 

/ reptiles / 

mammals 

Terrestrial 

insects 

Individual organisms 

Reduced survival 

Reduced growth 

Reduced reproduction 

Food chain 

Reduction in prey 

Habitat integrity 

Reduction in primary productivity

Reduced cover 

Community change 

Terrestrial/riparian plants 

grasses/forbs, fruit, seeds 

(trees, shrubs) 

Runoff 

Mammals 

Exposure 

Media 

Soil 

Ingestion 

Ingestion

Ingestion

Ingestion

Dermal uptake/Ingestion 

Root uptake 

Birds / 

Amphibians 

Ingestion 
-26 of 69-

an aquatic photodegradation study. The degradates of oryzalin were not found to be of 

concern for human health (US EPA, 2003). The toxicity of UN-2 is uncertain due to lack 

of submitted data; however, estimates of aquatic toxicity were conducted using structure 

activity relationships (ECOSAR, v. 1.0.0). This analysis suggests that UN-2 is estimated 

to be considerably less toxic to aquatic organisms than the parent chemical (Appendix 

E). 

The Agency does not routinely include, in its risk assessments, an evaluation of mixtures 

of active ingredients, either those mixtures of multiple active ingredients in product 

formulations or those in the applicator’s tank. In the case of the product formulations of 

multiple active ingredients (that is, a registered product containing more than one active 

ingredient), each active ingredient is subject to an individual risk assessment for 

regulatory decision regarding the active ingredient on a particular use site. If effects data 

are available for a formulated product containing more than one active ingredient, they 

may be used qualitatively or quantitatively in accordance with the Agency’s Overview 

Document and the Services’ Evaluation Memorandum (U.S., EPA 2004; USFWS/NMFS 

2004). 

There are ten registered products that contain oryzalin and one or more additional active 

ingredients (Appendix D). Based on a review of the available studies on oryzalin 

mixtures, it appears that the information presented in the papers pertain to efficacy and 

phytotoxicity of the mixtures for weed control. No information is available on the 

toxicity of individual components of oryzalin mixtures (Appendix D).

7.2. Measures of Exposure 

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

exposure modeling and resulting risk conclusions will be based on registered labels 

including maximum application rates and methods cited in Table 3.2 for each use of 

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

estimated environmental concentrations (EECs) of oryzalin. The models used to predict 

aquatic EECs are the Pesticide Root Zone Model coupled with the Exposure Analysis 

Model System (PRZM/EXAMS). The model used to predict terrestrial EECs on food 

items is T-REX. The model used to derive EECs relevant to terrestrial and wetland 

plants is TerrPlant. These models are parameterized using relevant reviewed 

environmental fate data from registrant submissions and the literature; model input values 

will be consistent with the most recent version of the input parameter guidance (Version 

2.1; EFED 2009). 

PRZM (v3.12.2, May 2005) and EXAMS (v2.98.4.6, April 2005) are simulation models 

coupled with the input shell pe5.pl (November 2006). The models generate daily 

exposures and calculate 1-in-10 year EECs of oryzalin that may occur in surface water 

bodies adjacent to application sites receiving oryzalin through runoff and spray drift. 

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. EXAMS simulates the fate of the pesticide in the water body and estimates 
-27 of 69-

resulting concentrations. The standard scenarios used for ecological pesticide 

assessments assume application to a 10-hectare agricultural field that drains into an 

adjacent 1-hectare water body that is 2 meters deep (20,000 m3 volume) with no outlet. 

PRZM/EXAMS is used to estimate screening-level exposure of aquatic organisms to 

oryzalin. 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 chronic exposure to aquatic invertebrates. 

In addition to modeling estimates, available monitoring data will be evaluated. 

Monitoring data will include those collected/reported by states as well as other federal 

departments/agencies (e.g., USGS National Water Quality Assessment (NAQWA; 

http://water.usgs.gov/nawqa)). 

Exposure estimates for terrestrial animals assumed to be in the target area or in an area 

exposed to spray drift are derived using the T-REX model (version 1.4.1, October 2008). 

This model incorporates the Kenaga nomograph, as modified by Fletcher et al. (1994), 

which is based on a large set of field residue data. The upper limit values from the 

nomograph represent the 95th percentile of residue values from actual field measurements 

(Hoerger and Kenega 1972). The Fletcher et al. (1994) modifications to the Kenaga 

nomograph are based on measured field residues from 249 published research papers, 

including information on 118 species of plants, 121 pesticides, and 17 chemical classes. 

EECs for terrestrial plants inhabiting dry and wetland areas are derived using TerrPlant 

(version 1.2.2, December 2006). This model uses estimates of pesticides in runoff and in 

spray drift to calculate EECs. EECs are based upon solubility, application rate and 

minimum incorporation depth in addition to type of formulation and method of 

application. 

Two spray drift models, AGDisp and AgDRIFT are used to assess exposures of terrestrial 

plants to oryzalin deposited in terrestrial habitats by spray drift. AGDisp (version 8.13; 

December 2004) is used to simulate aerial and ground applications. AgDrift (version 

2.01; May 2001) is used to simulate spray blast applications to orchard crops. 

7.3. Measures of Effect 

 

Ecological effects data are used as measures of direct and indirect effects to biological 

receptors. Data are 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 EPA, Office 

of Research and Development, and the National Health and Environmental Effects 

Research Laboratory's Mid-Continent Ecology Division. 
-28 of 69-

Information on the potential effects of oryzalin on non-target animals is also collected 

from the Ecological Incident Information System (EIIS; USEPA, 2007c). The EIIS is a 

database containing adverse effect (typically mortality) reports on non-target organisms 

where such effects have been associated with the use of pesticides. Incidents reported in 

the aggregate incident reports and the Avian Incident Monitoring System (AIMS) will 

also be searched. AIMS is a database administered by the American Bird Conservancy 

(partially funded by EPA). It contains publicly available data on reported avian incidents 

involving pesticides 

(http://www.abcbirds.org/abcprograms/policy/pesticides/aims/aims/index.cfm). 

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 toxicity of oryzalin to birds is similar to terrestrial-phase amphibians and reptiles. 

The same assumption is made for fish and aquatic-phase amphibians. 

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 ObservedAdverse-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., “NoObserved-Adverse-Effect-Concentration”) is the highest test concentration at which none 

of the observed effects were statistically different from the control. The NOEC is the NoObserved-Effects-Concentration. 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. 

7.4. Integration of Exposure and Effects 

Risk characterization is the integration of exposure and ecological effects characterization 

to determine the potential ecological risk from the use of oryzalin 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 non-target species. For the assessment of oryzalin 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 (LOC) (USEPA, 2004). These criteria are used to 
-29 of 69-

indicate when oryzalin’s use, as directed on the labels, has the potential to cause adverse 

direct or indirect effects to non-target organisms. In addition, incident data from EIIS, 

aggregate incident reports, and AIMS 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 pointestimate based approach described in the risk assessment. Depending on the risk 

manager’s need for additional information regarding risk, an effort will be made to 

further 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 Assessment 

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 oryzalin. 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 oryzalin 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 Levels of Concern (LOCs) 

used to evaluate direct or indirect 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 oryzalin application occurs), plus all areas where offsite 

transport (i.e., spray drift, runoff, etc.) 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 sublethal effect threshold for any biological entity at the whole organism, organ, tissue, and 

cellular level of organization. In situations where it is not possible to determine the 

threshold for an observed effect, the action area will be assumed to encompass the entire 

United States. 
-30 of 69-

7.7. Drinking Water Assessment 

The most recent comprehensive drinking water assessment was conducted in 2003 in 

support of the oryzalin TRED. However, the estimates were derived using older versions 

of the PRZM/EXAMS models. As such, a drinking water assessment will be conducted 

to support future human health risk assessments of oryzalin. The drinking water 

assessment will incorporate model estimates of the parent oryzalin in surface and ground 

waters. Concentrations of the residue in surface waters will be estimated using 

PRZM/EXAMS (see description above). The PRZM model simulates pesticide 

movement and transformation on and across the agricultural field resulting from crop 

applications. The EXAMS model simulates pesticide loading via runoff, erosion, and 

spray drift assuming a standard watershed of 172.8 ha that drains into an adjacent 

standard drinking water index reservoir of 5.26 ha and an average depth of 2.74 m. 

Percent Cropped Areas (PCA) that account for the maximum area within a watershed that 

may be planted with the modeled crop will be applied to adjust predicted concentrations 

by PRZM/EXAMS. Ground water estimates of oryzalin concentrations will be 

established using SCI-GROW. The SCI-GROW model was developed by fitting a linear 

model to ground water concentrations with the Relative Index of Leaching Potential 

(RILP) as the independent variable. Ground water concentrations were taken from 90-

day average high concentrations from Prospective Ground Water studies. The RILP is a 

function of aerobic soil metabolism and the soil-water partition coefficient. The drinking 

water assessment will also include available surface and ground water monitoring data. 

7.8. Preliminary Identification of Data Gaps 

Oryzalin use is defined as having terrestrial agricultural and non-agricultural uses. 

According to the Code of Federal Regulations 40 (CFR40 2007) Part 158 Subpart D (data 

requirements for pesticides) environmental fate and non-target organism effects data are 

required for oryzalin based on its terrestrial use. Available studies submitted to fulfill 

environmental fate and ecological effects guideline requirements, as well as outstanding 

data gaps for oryzalin, are defined in Sections 7.8.1 and 7.8.2. 

Further information on data required to fulfill the Agency’s guideline requirements for 

oryzalin and its formulated products is presented as the Data Call-in (DCI) table in

Appendix B. In addition to providing the guideline number and study title for required 

data, the DCI table provides a rationale for requiring the data, an explanation of how the 

data will be used, and a brief description of the how the data could impact the Agency’s 

future decision-making. 

7.8.1. Fate Data Gaps 

The environmental fate data requirements for oryzalin are partially fulfilled, and some 

data gaps still remain (Table 7.1). 
-31 of 69-

Table 7.1. Status of Available Environmental Fate Data and Remaining Data Gaps 

Guideline Description MRID Classification Data Gap? Additional MRIDs a Comments 

835.2120 

161-1 

Hydrolysis 41378401 Currently Under 

Review 

See 

Comment 

66193, 106697, 131990 The study is currently 

under review, and it 

has not yet been 

determined whether 

guideline 

requirements will be 

satisfied. 

835.2240 

161-2 

Photodegradation in Water 41278701 Acceptable b No 155491 -- 

835.2410 

161-3 

Photodegradation in Soil 41050001 Currently Under 

Review 

See 

Comment 

38892, 41576, 106695, 

106697, 106698, 

45716303 

The study is currently 

under review, and it 

has not yet been 

determined whether 

guideline 

requirements will be 

satisfied. 

835.4100 

162-1 

Aerobic Soil Metabolism 41322801 Currently Under 

Review 

See 

Comment 

131992 The study is currently 

under review, and it 

has not yet been 

determined whether 

guideline 

requirements will be 

satisfied. 

835.4200 

162-2 

Anaerobic Soil Metabolism 41322802 Currently Under 

Review 

See 

Comment 

-- The study is currently 

under review, and it 

has not yet been 

determined whether 

guideline 

requirements will be 

satisfied. 

835.4300 

162-3 

Aerobic Aquatic Metabolism -- -- Yes -- Call-In Data 

835.4400 

162-4 

Anaerobic Aquatic Metabolism -- -- Yes -- Call-In Data 

835.1230 

835.1240 

163-1 

Leaching 

Adsorption/Desorption 

41479801 

41479802 

Currently Under 

Review 

See 

Comment 

2803, 2804, 38888, 

38889, 106699, 106700, 

106732, 160842, 

5001264, 43433201, 

43433202 

These studies are 

currently under 

review, and it has not 

yet been determined 

whether guideline 

requirements will be 

satisfied. 

835.6100 

164-1 

Terrestrial Field Dissipation 42138001 Supplementalc Yes 24857, 38890, 38891, 

106687, 106696, 

106701, 106704, 

106705, 106709, 

106710, 106717, 

106724, 106725, 

106732, 131991, 

5001077, 5001264, 

41859701 

Mobility on 

degradates received. 

See MRIDs 

43433201 and 

43433202. 

Call-In Data for 

analytical method 

and independent 

laboratory 

validation. 
-32 of 69-

Table 7.1. Status of Available Environmental Fate Data and Remaining Data Gaps 

Guideline Description MRID Classification Data Gap? Additional MRIDs a Comments 

835.6200 

164-2 

Aquatic Field Dissipation -- -- Yes -- Call-In Data for 

analytical method 

and independent 

laboratory 

validation.

850.1730 

165-4 

Bioaccumulation in Fish (BCF) 40787501 Acceptable d No -- -- 

a

Additional studies submitted to the Agency to support the data requirement. See reference section for the bibliographies of submitted fate studies. b

The supplemental information submitted in addition to the study (MRID 41278701) completely satisfies the data requirement. c

The study is upgradeable pending submission and review of the analytical method and independent laboratory validation. d

The supplemental information submitted in addition to the study (MRID 40787501) completely satisfies the data requirement. 

7.8.2. Effects Data Gaps 

Although many submissions have been made to provide data on the effects of oryzalin to 

aquatic and terrestrial organisms, data gaps still exist and are included in Tables 7.2 to 

7.4, below. 

Table 7.2. Available Ecological Effects Data for Terrestrial Animals Exposed to Oryzalin 

and Remaining Data Gaps 

Guideline Description MRID/ 

Accession Classification Data Gap? Comments 

850.2100 Avian oral toxicity 00098462 Acceptable Yes1

850.2200 Avian dietary toxicity 00072593 Acceptable 

00072594 Acceptable 

No 

850.2300 Avian reproduction 441622-01 Acceptable No 

441622-02 Supplemental Yes2

850.3020 Honeybee acute 

contact toxicity 

00066220 Acceptable No 

1

Acceptable avian data was 

submitted for the bobwhite 

quail. However, avian acute 

oral toxicity data are not 

available for passerines, which 

are required under 40 CFR 

Part 158. 

2

Acceptable avian data are 

required for mallard duck. 
-33 of 69-

Table 7.3. Available Ecological Effects Data for Aquatic Animals Exposed to Oryzalin 

and Remaining Data Gaps 

Guideline Description MRID/ 

Accession Classification Data Gap? Comments 

TN 1078 Acceptable 

850.1075 00072595 Acceptable 

Freshwater fish – 

Acute toxicity 

00072595 Acceptable 

No 

850.1075 Estuarine/marine fish – 

Acute toxicity 438877-01 Acceptable No 

850.1010 

Freshwater 

invertebrates – 

Acute toxicity 

00072596 Acceptable No 

438877-01 Acceptable 850.1025 

850.1035 

Estuarine/marine 

invertebrates – 

Acute toxicity 438877-02 Acceptable 

No 

00126842 Acceptable 850.1400 Freshwater fish – 

early life stage test 00126841 Acceptable 

No

850.1400 Estuarine/marine fish – 

early life stage test 

Not 

submitted - Yes1

850.1300 

Freshwater 

invertebrate – 

 life cycle test 

439869-01 Acceptable No 

850.1350 

Estuarine/marine 

invertebrates – 

life cycle test 

Not 

submitted - Yes2

850.1735 

Freshwater 

invertebrate – Acute 

whole sediment 

Not 

submitted - Yes3

850.1740 

Estuarine/marine 

invertebrate – Acute 

whole sediment 

Not 

submitted - Yes3

OtherA

Freshwater and 

estuarine/marine 

invertebrate – Chronic 

whole sediment 

Not 

submitted - Yes3

1

An estuarine/marine fish 

early life stage test is required 

because oryzalin may enter 

this environment due to its use 

and mobility patterns. It is 

also expected to be persistent 

in water under some 

conditions. 

2

An estuarine/marine 

invertebrate life cycle test is 

required because oryzalin may 

enter this environment due to 

its use and mobility patterns. 

It is also expected to be 

persistent in water under some 

conditions. 

3

This data is required. 

However, it is currently 

uncertain if an acute or a 

chronic study is required. 

Oryzalin’s chemical properties 

trigger the requirement for 

sediment toxicity studies (the 

Kd >50, the log Kow is >3, 

and a Koc is >1000). Acute 

studies are required if the 

persistence in sediment is ≤ 10 

days, and chronic studies are 

required if the persistence in 

sediment is expected to be >10 

days. The requested aquatic 

metabolism study will allow 

EFED to determine if an acute 

or a chronic study is required. 
-34 of 69-

Table 7.3. Available Ecological Effects Data for Aquatic Animals Exposed to Oryzalin 

and Remaining Data Gaps 

Guideline Description MRID/ 

Accession Classification Data Gap? Comments 

AThree species required using the following study guidance: 1) EPA 600/R-99/064 Test Method 100.4: Hyalella 

azteca 42-d Test for Measuring the Effects of Sediment Associated Contaminants on Survival, Growth, and 

Reproduction; 2) EPA 600/R-99/064 Test Method 100.5: Life-cycle Test for Measuring the Effects of Sedimentassociated Contaminants on Chironomus dilutus or C. tentans in USEPA 2000 Methods for Measuring the 

Toxicity and Bioaccumulation of Sediment-associated Contaminants with Freshwater Invertebrates; 3) 

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. 

Protocols should be submitted for approval prior to testing for chronic studies. The preferred sediment is 

formulated; guidance for the formulated sediment can be found in OECD 218 Sediment-Water Chironomid 

Toxicity Test using Spiked Sediment. Based on test variability for the endpoints of concern and the need to 

establish a NOAEC/LOAEC, the following number of replicates and test animals are recommended: for the 

midge test with C. dilutus: 16 replicates containing 12 test organisms each (12 replicates at test initiation; 4 added 

at 10 days for auxiliary males); for the freshwater amphipod test with H. azteca: 12 replicates per treatment (4 for 

28-d survival and growth and 8 for the remainder of the test) with 10 neonates per replicate; and for the L. 

plumulosus: 10 replicates per treatment with 20 neonates per replicate. For alternative test designs, the protocol 

should discuss the power of the test. 

Table 7.4. Available Ecological Effects Data for Plants Exposed to Oryzalin and 

Remaining Data Gaps 

Guideline Description MRID Classification Data Gap? Comments 

850.4225 

Terrestrial Plant 

toxicity: Tier II 

seedling emergence 

426024-01 Supplemental Yes1

850.4250 

Terrestrial Plant 

toxicity: Tier II 

vegetative vigor 

426024-01 Supplemental Yes1

431369-01 Supplemental 

431369-02 Invalid 

431369-03 Invalid 

850.5400 Aquatic Plant Growth: 

algae 

431369-04 Supplemental 

Yes2

850.4400 Aquatic Plant Growth: 

vascular plants 431369-05 Supplemental Yes2

1

The submitted study 

utilizes the technical 

grade active ingredient 

(TGAI). The data 

requirements specify the 

use of a typical end-use 

product (TEP). 

2

Acceptable data are 

required for non-vascular 

and vascular plants. 

Avian Acute Oral Toxicity 

Acceptable acute avian oral toxicity data were submitted for exposures of bobwhite quail 

to oryzalin; however, data are not available for passerines, which are required under 40 

CFR Part 158 (October 26, 2007) data requirements for conventional pesticides (72 FR 

60934; USEPA, 2007d). The Part 158 data requirements specify that acute avian oral 

toxicity data be submitted for either a mallard duck or bobwhite quail and a passerine 

species. Therefore, an avian oral toxicity test (OCSPP Guideline 850.2100) is required 
-35 of 69-

for passerine birds. A passerine study protocol should be submitted for review by EPA 

prior to initiation of this study. If oral acute toxicity data are not submitted for 

passerines, EFED will assume acute risk for passerine species. 

Avian Chronic Reproduction Toxicity

Acceptable chronic avian reproduction toxicity data were submitted for exposures of 

bobwhite quail for oryzalin. However, the 40 CFR Part 158 data requirements for 

conventional pesticides require acceptable to be submitted for the mallard duck as well. 

A mallard duck study was submitted but was classified as supplemental because the prelaying exposure period was not of sufficient length. 

Chronic Toxicity Studies with Estuarine/Marine Fish and Invertebrates 

Chronic toxicity data for oryzalin are not available for estuarine/marine fish or 

invertebrates. Because the registered use patterns permit oryzalin to enter 

estuarine/marine environments, these data are required. Therefore, an estuarine/marine 

invertebrate life cycle toxicity test (OCSPP Guideline 850.1350) and an estuarine/marine 

fish early life stage toxicity test (OCSPP Guideline 850.1400) are required. Chronic 

studies are important for oryzalin because it is stable to hydrolysis and may, therefore, be 

persistent in water under some conditions. In the absence of chronic oryzalin toxicity 

data for estuarine/marine invertebrates and fish, the Agency will assume risks to 

estuarine/marine animals from the uses of oryzalin. 

Acute and Chronic Toxicity Studies with Freshwater and Estuarine/Marine Sedimentdwelling Invertebrates 

Oryzalin’s chemical properties trigger the requirement for sediment toxicity studies (the 

Kd >50, the log Kow is >3, and a Koc is >1000). Acute studies (OCSPP 850.1735, 

850.1740) are required if the persistence in sediment is ≤ 10 days, and chronic studies2

are required if the persistence in sediment is expected to be >10 days. The requested 

aquatic metabolism study will allow EFED to determine if acute or chronic studies are 

required. If chronic studies are required, protocols should be submitted prior to test 

initiation. 

Terrestrial and Aquatic Plant Studies 

Aquatic (both vascular and non-vascular species) and terrestrial plant toxicity studies and 

associated risk analysis of plants are required for registration of pesticides with outdoor 

 

2

 Three species required using the following study guidance: 1) EPA 600/R-99/064 Test Method 100.4: 

Hyalella azteca 42-d Test for Measuring the Effects of Sediment Associated Contaminants on Survival, 

Growth, and Reproduction; 2) EPA 600/R-99/064 Test Method 100.5: Life-cycle Test for Measuring the 

Effects of Sediment-associated Contaminants on Chironomus dilutus or C. tentans in USEPA 2000 

Methods for Measuring the Toxicity and Bioaccumulation of Sediment-associated Contaminants with 

Freshwater Invertebrates; 3) 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. 
-36 of 69-

uses (CFR Part 158). For terrestrial plants, Tier II studies (OCSPP Guidelines 850.4225 

and 850.4250) are required when potential concerns are triggered (i.e., when there is 

some indication that there may be significant toxicity to plants). For oryzalin, these 

indicators include the herbicidal mode of action and statements on the label indicating 

toxicity to plants. 

The submitted terrestrial plant toxicity studies utilized the technical grade active 

ingredient (TGAI) and were classified as supplemental. The data requirements specify the 

use of a typical end-use product (TEP). The submitted aquatic (vascular and nonvascular) plant studies were classified as supplemental or invalid due to numerous 

problems with the study designs. The scientific soundness of the studies is in question, as 

the conducting laboratory may not have had appropriate QA/QC methods in place. The 

two studies that were classified as invalid showed statistically significant differences, 

which were also biologically relevant, between the solvent control and the negative 

control. 

Degradate Toxicity 

No toxicity data were submitted for the degradate UN-2. UN-2 is a major degradate of 

oryzalin that forms primarily via aqueous photolysis. However, ECOSAR analysis 

(Appendix E) predicted the UN-2 would be less toxic than the parent, and considering 

the amount at which UN-2 forms (14%), submission of degradate toxicity data is unlikely 

to add value or change the outcome of the risk assessment. Therefore, no degradate 

studies are recommended for request at this time. 

8. References 

Food and Agriculture Organization of the United Nations (FAO). 2000. Appendix 2. Parameters of 

pesticides that influence processes in the soil. In FAO Information Division Editorial Group (Ed.), 

Pesticide Disposal Series 8. Assessing Soil Contamination: A Reference Manual. Rome: Food & 

Agriculture Organization of the United Nations. 

http://www.fao.org/DOCREP/003/X2570E/X2570E06.htm

Fletcher, J.S., J.E. Nellessen, and T.G. Pfleeger. 1994. Literature review and evaluation of the EPA foodchain (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. 

U.S. Department of Agriculture (USDA). 2007. National Agricultural Statistics Service. United States 

Department of Agriculture. http://www.nass.usda.gov/

U.S. EPA. 1994. Oryzalin: Reregistration Eligibility Decision (RED). Office of Prevention, Pesticides, 

and Toxic Substances. Office of Pesticide Programs. Washington, D.C. September 1994. 

http://www.epa.gov/oppsrrd1/REDs/0186.pdf
-37 of 69-

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 

USEPA. 2002. Guidance for Selecting Input Parameters in Modeling the Environmental Fate and 

Transport of Pesticides, Version II. US Environmental Protection Agency, Washington DC. 

Online at: http://www.epa.gov/oppefed1/models water/input_guidance2_28_02.htm. 

USEPA. 2003. Oryzalin; Health Effects Division (HED) Metabolism Assessment Review Committee 

(MARC) Decision Document. U.S. Environmental Protection Agency, Office of Prevention, 

Pesticides and Toxic Substances, Office of Pesticide Programs, Health Effects Division, 

Memorandum. June 5, 2003. 

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. 

USEPA. 2006a. Standardized Soil Mobility Classification Guidance. U.S. Environmental Protection 

Agency, Office of Prevention, Pesticides and Toxic Substances, Office of Pesticide Programs, 

Environmental Fate and Effects Division, Memorandum. April 21, 2006. 

USEPA. 2007c. Ecological Incident Information System. http://www.epa.gov/espp/consultation/ecoriskoverview.pdf

USEPA. 2007d. 40 CFR Part 158. Pesticides; Data Requirements for Conventional Chemicals: Final Rule. 

72 FR 60934. October 26, 2007. 

USEPA. 2007e. ECOTOXicology Database. Office of Research and Development National Health and 

Environmental Effects Research Laboratory’s (NHEERL’s) Mid-Continent Ecology Division 

(MED). http://cfpub.epa.gov/ecotox/. 

U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries Service (NMFS). 1998. 

Endangered Species Consultation Handbook: Procedures for Conducting Consultation and 

Conference Activities Under Section 7 of the Endangered Species Act. Final Draft. March 1998. 

Worthing, C. R and R. J. Hance, editors. 1991. The Pesticide Manual: A World Compendium (9th 

edition). British Crop Protection Council, Surrey, UK. June, 1991. 

SUBMITTED ENVIRONMENTAL FATE STUDIES:

Guideline 161-1 Hydrolysis:

MRID 38892 

Day, E.W.; Mosier, J.W.; Saunders, D.G. (1972) Studies on the Rate of Degradation of EL-119 by 

Sunlight. (Unpublished study received Dec 29, 1972 under 3F1347; submitted by Elanco Products Co., 

Div. of Eli Lilly and Co., Indianapolis, Ind.; CDL 093605-J) 

 

MRID 66193 

Day, E.W.; Sullivan, W.L.; Decker, O.D. (1976) A Hydrolysis Study of the Herbicides Oryzalin and 

Metribuzin. (Unpublished study received Sep 16, 1977 under 1471-96; submitted by Elanco Products Co., 

Div. of Eli Lilly and Co., Indianapolis, Inc.; CDL 231825-D) 

 

MRID 106697 
-38 of 69-

Day, E.; Mosier, J.; Saunders, D. (1972) Studies on the Rate of Degradation of EL-119 by Sunlight. 

(Unpublished study received Dec 22, 1972 under 3F1347; submitted by Elanco Products Co., Div. of Eli 

Lilly and Co., Indianapolis, IN; CDL 092131-B) 

MRID 131990 

Elanco Products Co. (1983) Oryzalin Technical, Surflan 75W/AS Product Chemistry. (Compilation; 

unpublished study received Oct 6, 1983 under 1471-96; CDL 251445-A) 

MRID 41378401 

Saxena, A. (1990) Hydrolysis of Oryzalin in Buffered Aqueous Solutions Final Report Lab Project 

Number HLA 6313-100. Unpublished study prepared by Hazleton Laboratories America, Inc. 52 p. 

Guideline 161-2 Photodegradation in Water:

MRID 155491 

Gray, J.; Moiser, J.; Saunders, D. (1980) Photolysis of Oryzalin in Aqueous Solution. Unpublished study 

prepared by Lilly Research Laboratories. 30 p. 

MRID 41278701 

Gohdes, M. (1989) Artificial Sunlight Photodegradation of ?Carbon 14|-Oryzalin in a Buffered Aqueous 

Solution Lab Project Number HLA/6237/103. Unpublished study prepared by Hazleton Laboratories 

America, Inc. 115 p. 

Guideline 161-3 Photodegradation in Soil:

 

MRID 38892 

Day, E.W.; Mosier, J.W.; Saunders, D.G. (1972) Studies on the Rate of Degradation of EL-119 by 

Sunlight. (Unpublished study received Dec 29, 1972 under 3F1347; submitted by Elanco Products Co., 

Div. of Eli Lilly and Co., Indianapolis, Ind.; CDL 093605-J) 

MRID 41576 

Elanco Products Company (1968?) Photodecomposition. (Unpublished study received Apr 30, 1970 under 

0F0968; CDL 091661-AB, 091660) 

MRID 106695 

Elanco Products Co. (1972) Radiochemical Procedure for the Determination of the Photochemical 

Degradation of Oryzalin. (Unpublished study received on unknown date under 1471-96; CDL 101596-C) 

MRID 106697 

Day, E.; Mosier, J.; Saunders, D. (1972) Studies on the Rate of Degradation of EL-119 by Sunlight. 

(Unpublished study received Dec 22, 1972 under 3F1347; submitted by Elanco Products Co., Div. of Eli 

Lilly and Co., Indianapolis, IN; CDL 092131-B) 

 

MRID 106698 

Elanco Products Co. Photodecomposition of 14C Oryzalin. (Unpublished study received Dec 22, 1972 

under 3F1347; CDL 092131-C) 

MRID 41050001 

Gohdes, M. (1989) Artificial Sunlight Photodegradation of ?carbon 14|-Oryzalin on Soil Amendment No. 

1 to the Final Report Project ID HLA 6237-102. Unpublished study prepared by Hazleton Laboratories 

America, Inc. 111 p. 

MRID 45716303 
-39 of 69-

Saunders, D.; Emery, K.; Powers, F. (1989) Photolysis of Fenarimol, Tebuthiuron, and Oryzalin on Soil at 

pH 5.7 and 7.7 Lab Project Number AAC8922 33160. Unpublished study prepared by Lilly Research 

Laboratories. 135 p. 

Guideline 162-1 Aerobic Soil Metabolism: 

MRID 131992 

Sassic, K.; Golab, T.; Wooten, H.; et al. (1982) 14C Oryzalin Anaerobic Soil Degradation Study 

Experiment No. ABC-0110. (Un- published study received Oct 6, 1983 under 1471-96; submitted by 

Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL 251446-C) 

MRID 41322801 

Graper, L.; Rainey, D. (1989) Aerobic Metabolism of Carbon 14| Oryzalin in Sandy Loam Soil Lab 

Project Number ABC/0434. Unpublished study prepared by DowElanco 33 p. 

Guideline 162-2 Anaerobic Soil Metabolism: 

MRID 41322802 

Graper, L.; Rainey, D. (1989) Anaerobic Metabolism of Carbon 14| Oryzalin in Sandy Loam Soil Lab 

Project Number ABC/0435. Unpublished study prepared by DowElanco 26 p. 

Guideline 163-1 Leaching and Adsorption/Desorption:

MRID 2803 Barrentine, J.L. (1969) Experiment No. JLB9-1 Soil Leaching Data|. (Unpublished 

study received Apr 30, 1970 under 0F0968; submitted by Elanco Products Co., Div. of Eli Lilly and Co., 

Indianapolis, Ind.; CDL 091661-O) 

MRID 2804 Barrentine, J.L. (1969) Experiment No. JLB9-2 Soil leaching Data|. (Unpublished study 

received Apr 30, 1970 under 0F0968; submitted by Elanco Products Co., Div. of Eli Lilly and Co., 

Indianapolis, Ind.; CDL 091661-P) 

MRID 38888 Holzer, F.J. (1972) EL-119--Leaching study. (Unpublished study received Dec 29, 1972 

under 3F1347; prepared in cooperation with Purdue Univ., Agronomy Dept., Soil Testing Laboratory, 

submitted by Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, Ind.; CDL 093605-F) 

MRID 38889 

Elanco Products Company (1972) EL-119 Leaching Study on Degradation Products. (Unpublished study 

received Dec 29, 1972 under 3F1347; prepared in cooperation with Purdue Univ., Dept. of Agronomy, 

Plant and Soil Analysis Laboratory; CDL 093605-G) 

MRID 106699 

Holzer, F. (1972) EL-119 Leaching Study Reference 450-AD-64-111. (Unpublished study received Dec 

22, 1972 under 3F1347; prepared in cooperation with Purdue Univ., Agronomy Dept., Soil Testing 

Laboratory, submitted by Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL 092131-E) 

MRID 106700 

Elanco Products Co. (1972) EL-119 Leaching Study on Degradation Products Reference 450-AD-64-71. 

(Compilation; unpublished study received Dec 22, 1971 under 3F1347; CDL 092131-F) 

MRID 106732 
-40 of 69-

Golab, T.; Ward, N.; Donoho, A.; et al. (1971) Oryzalin As a Pre- emergence Surface-applied Herbicide for 

Soybeans. (Unpublished study received Sep 27, 1971 under 1471-EX-36; submitted by Elanco Products 

Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL 210006-B) 

MRID 160842 

Jacques, G.; Harvey, R. (1979) Adsorption and diffusion of dinitroaniline herbicides in soils. Weed 

Science 27(4) 450-455. 

MRID 5001264 

Harvey, R.G. (1974) Soil adsorption and volatility of dinitroaniline herbicides. Weed Science 22(2) 120-

124. 

MRID 41479801 

Saunders, D. (1990) Oryzalin Aged Soil Leaching Study Lab Project Number AAC8923. Unpublished 

study prepared by DowElanco, Plant Science Chemical Development. 57 p. 

MRID 41479802 

Saunders, D.; Powers, F. (1987) Adsorption and Desorption of Oryzalin on Soil Lab Project I.D. 

EWD8726. Unpublished study prepared by Lilly Research Laboratories. 66 p. 

MRID 43433201 

Cook, W. (1994) Adsorption and Desorption of OR-20 on Soil Lab Project Number ENV93117. 

Unpublished study prepared by DowElanco. 76 p. 

MRID 43433202 

Merritt, D.; Patterson, V. (1994) Aged Desorption of Oryzalin and Metabolites on Four Soils Lab Project 

Number ENV93102. Unpublished study prepared by DowElanco. 156 p. 

Guideline 164-1 Terrestrial Field Dissipation:

MRID 24857 

Kennedy, J.M.; Talbert, R.E.; Fischer, B. (1974) Dinitroaniline Herbicides Their Persistence on the Soil 

Surface, Residual Activity, and Relative Crop Tolerance|. (Unpublished study received 1975 under 

2G1285; prepared by Univ. of Arkansas, Agricultural Experiment Station, submitted by Union Carbide 

Agricultural Products Co., Ambler, Pa.; CDL 095154-E) 

MRID 38890 

Elanco Products Company (1971) Introduction. (Unpublished study received Dec 29, 1972 under 3F1347; 

CDL 093605-H) 

MRID 38891 

Massey, G.D.; Webster, H.L.; Watson, J.H.; et al. (1972) Degradation Study--Oryzalin|. (Unpublished 

study including experiment nos. GDM1-26, HLW1-8, JHW1-14..., received Dec 29, 1972 under 3F1347; 

submitted by Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, Ind.; CDL 093605-I) 

MRID 106687 

Elanco Products Co. (1976) Summary Environmental Chemistry Surflan|. (Compilation; unpublished study 

received Sep 1, 1976 under 1471-96; CDL 095261-A) 

MRID 106696 

Elanco Products Co. (1972) Analyses for Residues of Surflan 75W in Beans and Other Crops|. 

(Compilation; unpublished study received Dec 22, 1972 under 3F1347; CDL 092131-A) 
-41 of 69-

MRID 106701 

Elanco Products Co. (1971) Determination of Residues of EL-119 and Dieldrin in Water and Soil|. 

(Unpublished study received Dec 22, 1972 under 3F1347; CDL 092131-G) 

MRID 106704 

Massey, G. (1971) EL-119 Environmental Study Experiment No. GDMO-18. (Unpublished study 

received Dec 22, 1972 under 3F1347; submitted by Elanco Products Co., Div. of Eli Lilly and Co., 

Indianapolis, IN 

MRID 106705 

Shoop, G. (1971) EL-119 Environmental Study Experiment No. GJSO- 21. (Unpublished study received 

Dec 22, 1972 under 3F1347; submitted by Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; 

CDL 092131-L) 

MRID 106709 

Webster, H. (1972) General Summary EL-119 Experiment No. HLWO- 7. (Unpublished study received 

Dec 22, 1972 under 3F1347; sub- mitted by Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, 

IN; CDL 092131-P) 

MRID 106710 

Webster, H. (1972) EL-119 Environmental Study| Experiment No. HLW1-8. (Unpublished study received 

Dec 22, 1972 under 3F1347; submitted by Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; 

CDL 092131-Q) 

MRID 106717 

Keaton, J. (1972) General Summary EL-119| Experiment No. JAKO- 37. (Unpublished study received 

Dec 22, 1972 under 3F1347; submitted by Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; 

CDL 092131-X) 

MRID 106724 

Warner, L. (1971) EL-119 Environmental Study Experiment No. LCWO-17. (Unpublished study received 

Dec 22, 1972 under 3F1347; submitted by Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; 

CDL 092131-AE) 

MRID 106725 

Ascheman, R. (1971) EL-119 Environmental Study Experiment No. REAO-13. (Unpublished study 

received Dec 22, 1972 under 3F1347; submitted by Elanco Products Co., Div. of Eli Lilly and Co., 

Indianapolis, IN; CDL 092131-AF) 

MRID 106732 

Golab, T.; Ward, N.; Donoho, A.; et al. (1971) Oryzalin As a Pre- emergence Surface-applied Herbicide for 

Soybeans. (Unpublished study received Sep 27, 1971 under 1471-EX-36; submitted by Elanco Products 

Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL 210006-B) 

MRID 131991 

Golab, T.; Sherman, W.; Wooten, H.; et al. (1980) Radiochemical Studies with 14C Oryzalin in Soil, 

Soybean (Primary Crop) and Various Rotational Crop Plants. (Unpublished study received Oct 6, 1983 

under 1471-96; submitted by Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL 

251446-A) 

MRID 5001077 

Parochetti, J.V.; Dec, G.W., Jr.; Burt, G.W. (1976) Volatility of eleven dinitroaniline herbicides. Weed 

Science 24(6) 529-532. 
-42 of 69-

MRID 5001264 

Harvey, R.G. (1974) Soil adsorption and volatility of dinitroaniline herbicides. Weed Science 22(2) 120-

124. 

MRID 41859701 

Day, E.; Griggs, R.; Decker, O. (1990) Oryzalin Terrestrial Field Dissipation Study-An Interim Report Lab 

Project No AAC8914. Unpublished study prepared by DowElanco, Formulation and Chemistry Lab. 48 p. 

MRID 42138001 

Decker, O. (1991) Oryzalin Terrestrial Field Dissipation Study Lab Project Number AAC8914. 

Unpublished study prepared by DowElanco, North American Environ. Chem. Lab. 349 p. 

Guideline 164-2 Aquatic Field Dissipation:

MRID 22059 

Day, E.W.; Decker, O.D.; Rodewald, K.J.; et al. (1977) A Laboratory Hydrolysis Study on the Herbicide 

Oryzalin. (Unpublished study received Mar 9, 1978 under 1471-96; submitted by Elanco Products Co., 

Div. of Eli Lilly and Co., Indianapolis, Ind.; CDL 233020-B) 

MRID 38890 

Elanco Products Company (1971) Introduction. (Unpublished study received Dec 29, 1972 under 3F1347; 

CDL 093605-H) 

Guideline 165-4 Bioaccumulation in Fish: 

MRID 40787501 

Magnussen, J. (1988) Laboratory Studies of Carbon 14| Oryzalin Accumulation in Fish Laboratory Project 

ID's ABC-0393 ABC-0394. Unpublished study prepared by Lilly Research Laboratories, Inc. 59 p. 

SUBMITTED EFFECTS STUDIES:

71-1 Avian Single Dose Oral Toxicity 

MRID 

SAN 

Document 

Number 

Citation Reference 

26763 See 106728 West, H.C.; Kehr, C.C.; Hoffman, D.G.; et al. (1972) The Acute Oral 

Toxicity of Technical EL-119 in Bobwhite Quail and Mallard Ducks. 

(Unpublished study received Dec 12, 1979 under 1471-96; submitted by 

Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, Ind., 

CDL:241537-I) 

38670 See 106728 West, H.C.; Kehr, C.C.; Hoffman, D.G.; et al. (1972) The Acute Oral 

Toxicity of Technical EL-119 in Bobwhite Quail and Mallard Ducks. 

(Unpublished study received on unknown date under 1471- 96; 

submitted by Elanco Products Co., Div. of Eli Lilly and Co., 

Indianapolis, Ind.; CDL:242443-H) 

98462 2002391 Cochrane, R.L.; Kehr, C.C.; Jordan, W.H.; et al. (1982) The Toxicity of 

Oryzalin (EL-119, Compound 67019) to Bobwhite in a 14- day Acute 
-43 of 69-

Oral Study: Study A02980. (Unpublished study received Apr 8, 1982 

under 1471-96; submitted by Elanco Products Co., Div. of Eli Lilly and 

Co., Indianapolis, Ind.; CDL:247229-B) 

98464 2002392 Cochrane, R.L.; Kehr, C.C.; Jordan, W.H.; et al. (1982) The Toxicity of 

Oryzalin (EL-119, Compound 67019) to Bobwhite in a 14-day Acute 

Oral Study: Study A03580. (Unpublished study received Apr 8, 1982 

under 1471-96; submitted by Elanco Products Co., Div. of Eli Lilly and 

Co., Indianapolis, Ind.; CDL:247229-D) 

106728 2002393 

2045653 

West, H.; Kehr, C.; Hoffman, D.; et al. (1972) The Acute Oral Toxicity 

of Technical EL-119 in Bobwhite Quail and Mallard Ducks. 

(Unpublished study received Dec 22, 1972 under 3F1347; submitted by 

Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, IN; 

CDL:092131-AL) 

71-2 Avian Dietary Toxicity 

MRID 

SAN 

Document 

Number 

Citation Reference 

72593 2002386 Carter, J.L.; Negilski, D.S.; Kehr, C.C.; et al. (1980) The Toxicity of 

Compound 67019 (Oryzalin) to Bobwhite Quail in a Five- day Dietary 

Study: Study No. A010-79. Includes undated method ATY. 

(Unpublished study received May 7, 1981 under 1471-96; submitted by 

Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, Ind.; 

CDL:245053-A) 

72594 2002387 

2045657 

Carter, J.L.; Negilski, D.S.; Kehr, C.C.; et al. (1980) The Toxicity of 

Compound 67019 (Oryzalin) to Mallard Ducks in a Five- day Dietary 

Study: Study No. 7005-79. Includes undated method ATY. 

(Unpublished study received May 7, 1981 under 1471-96; submitted by 

Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, Ind.; 

CDL:245054-A) 

71-4 Avian Reproduction 

MRID 

SAN 

Document 

Number 

Citation Reference 

126843 

LE00RY01 on 

the DER 

2002382 Cochrane, R.; Jordan, W.; Brannon, D.; et al. (1982) The Toxicity of 

Oryzalin (EL-119, Compound 67019) in a One-generation Study with 

Mallards: Study A00482. (Unpublished study received Apr 14, 1983 

under 1471-96; submitted by Elanco Products Co., Div. of Eli Lilly and 

Co., Indianapolis, IN; CDL:071521-C) 

129050 2002383 Cochrane, R.; Jordan, W.; Brannon, D.; et al. (1983) The Toxicity of 

Oryzalin (EL-119, Compound 67019) in a One-generation Reproduction 

Study with Bobwhite: Study A01282. (Unpublished study received Jun 

3, 1983; Jun 8, 1983 under 1471-96; submitted by Elanco Products Co., 

Div. of Eli Lilly and Co., Indianapolis, IN; CDL:250589-A) 

44162201 2023890 Gallagher, S.; Beavers, J.; Jaber, M. (1996) Oryzalin: A Reproduction 
-44 of 69-

Study with the Northern Bobwhite (Colinus virginianus): Lab Project 

Number: 103-415: ES-3084. Unpublished study prepared by Wildlife 

International Ltd. 177 p. 

44162202 2023891 Gallagher, S.; Beavers, J.; Jaber, M. (1996) Oryzalin: A Reproduction 

Study with the Mallard (Anas platyrhynchos): Lab Project Number: 103-

416: ES-3085. Unpublished study prepared by Wildlife International 

Ltd. 174 p. 

 72-1 Acute Toxicity to Freshwater Fish 

MRID 

SAN 

Document 

Number 

Citation Reference 

72595 2002388 = 

BG 

2002389 = 

RBT 

Sleight, B.H., III (1971) Acute Toxicity of EL-119 to Bluegill (Lepomis 

macrochirus) and Rainbow Trout (Salmo gairdneri). (Unpublished study 

received May 7, 1981 under 1471- 96; prepared by Bionomics, Inc., 

submitted by Elanco Products Co., Div. of Eli Lilly & Co., Indianapolis, 

Ind.; CDL:245055-A) 

TN1078 2002431 USEPA Beltsville Animal Biology Lab with Rainbow trout and 95% 

active ingredient 

106663 2002395 

2045652 

Elanco Products Co. (1968) Environmental Bioassay, Fish: Oryzalin. 

(Unpublished study received Jun 18, 1972 under 2G1201; CDL:091019-

F) 

106729 2002394 

2045654 

Elanco Products Co. (1968) Environmental Exposure of Oryzalin to 

Goldfish: Acute Toxicity. (Unpublished study received Dec 22, 1972 

under 3F1347; CDL:092131-AO) 

26758 See 106729 Elanco Products Company. Acute Toxicity: Environmental Expo- sure 

of Goldfish to Oryzalin. (Unpublished study received Dec 12, 1979 

under 1471-96; CDL:241537-B) 

 72-2 Acute Toxicity to Freshwater Invertebrates 

MRID 

SAN 

Document 

Number 

Citation Reference 

72596 2002390 

2045656 

Carter, J.L.; Karnak, R.E.; Kehr, C.C.; et al. (1980) The Toxicity of 

Compound 67019 (Oryzalin) to Daphnia magna in a 48-hour Static 

Test: Study Nos. 5005-79 and 5012-79. (Unpublished study received 

May 7, 1981 under 1471-96; submitted by Elanco Products Co., Div. of 

Eli Lilly & Co., Indianapolis, Ind.; CDL:245056-A) 

72-3 Acute Toxicity to Estuarine/Marine Organisms 

MRID 

SAN 

Document 

Number 

Citation Reference 
-45 of 69-

43887701 2002375 Ward, T.; Kowalski, P.; Boeri, R. (1995) Oryzalin: Acute Toxicity to 

the Sheepshead Minnow, Cyprinodon variegatus: Lab Project Number: 

654-DO: ES-2956. Unpublished study prepared by T.R. Wilbury Labs, 

Inc. 24 p. 

43887702 2002376 Boeri, R.; Kowalski, P.; Ward, T. (1995) Oryzalin: Acute FlowThrough Mollusc Shell Deposition Test: (Crassostrea virginica): Lab 

Project Number: 653-DO: DECO-ES-2955. Unpublished study prepared 

by T.R. Wilbury Labs, Inc. 25 p. 

43887703 2002377 Boeri, R.; Kowalski, P.; Ward, T. (1995) Oryzalin: Acute Toxicity to 

the Grass Shrimp, Palaemonetes pugio: Lab Project Number: 652-DO: 

DECO-ES-2954. Unpublished study prepared by T.R. Wilbury Labs, 

Inc. 24 p. 

72-4 Fish Early Life Stage/Aquatic Invertebrate Life Cycle Study 

MRID 

SAN 

Document 

Number 

Citation Reference 

106665 2002396 

2045655 

Worth, H. (1971) Effect of a Season-long Exposure to Oryzalin on 

Fathead Minnow Production. (Unpublished study received Jun 18, 1972 

under 2G1201; submitted by Elanco Products Co., Div. of Eli Lilly and 

Co., Indianapolis, IN; CDL:091019-H) 

126841 

LE00RY03 on 

DER 

2042384 Sauter, S.; Meyerhoff, R.; Jordan, W.; et al. (1983) The Toxicity of 

Oryzalin (EL-119, Compound 67019) in Water to Fathead Minnows ... 

in a 34-day Early Life-stage Study: Study F11482. (Unpublished study 

received Apr 14, 1983 under 1471-96; submitted by Elanco Products 

Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:071521-A) 

126842 

LE00RY04 on 

DER 

2002385 Meyerhoff, R.; Sauter, S.; Jordan, W.; et al. (1983) The Toxicity of 

Oryzalin (EL-119, Compound 67019) in Water to Rainbow Trout ... in a 

66-day Early Life-stage Study: Study F11382. (Unpublished study 

received Apr 14, 1983 under 1471-96; submitted by Elanco Products 

Co., Div. of Eli Lilly and Co., Indianapolis, IN; CDL:071521-B) 

43986901 2002374 Kirk, H.; Hugo, J.; Miller, K.; et al. (1996) Evaluation of the Chronic 

Toxicity of Oryzalin Herbicide (3,5-Dinitro-N4,N4-di(Npropyl)sulfanilamide) to the Daphnia magna Straus: Lab Project 

Number: DECO-ES-2995. Unpublished study prepared by The Dow 

Chemical Co. 84 p. 

122-1 Seed Germination/Seedling Emergence and Vegetative Vigor 

MRID 

SAN 

Document 

Number 

Citation Reference 

42602401 Feutz, E. (1992) Evaluating the Effects of Oryzalin on the Germination, 

Emergence, and Vegetative Vigor of Non-target Terrestrial Plants: Lab 

Project Number: 40292. Unpublished study prepared by ABC Labs, Inc. 

155 p. 
-46 of 69-

123-1 Seed Germination/Seedling Emergence and Vegetative Vigor 

MRID 

SAN 

Document 

Number 

Citation Reference 

42602401 Feutz, E. (1992) Evaluating the Effects of Oryzalin on the Germination, 

Emergence, and Vegetative Vigor of Non-target Terrestrial Plants: Lab 

Project Number: 40292. Unpublished study prepared by ABC Labs, Inc. 

155 p. 

123-2 Aquatic Plant Growth 

MRID 

SAN 

Document 

Number 

Citation Reference 

43136901 2082507 Hughes, J.; Williams, T. (1994) The Toxicity of Oryzalin to 

Selanastrum capricornutum: Lab Project Number: B460-155-1: DR0320-8068: ES-2693. Unpublished study prepared by Malcolm Pirnie, 

Inc. 37 p. 

43136902 2082508 Hughes, J.; Williams, T. (1994) The Toxicity of Oryzalin to Anabaena 

flos-aquae: Lab Project Number: B460-155-2: DR-0320-8068: ES2691. Unpublished study prepared by Malcolm Pirnie, Inc. 37 p. 

43136903 2082509 Hughes, J.; Williams, T. (1994) The Toxicity of Oryzalin to Navicula 

pelliculosa: Lab Project Number: B460-155-3: DR-0320-8068: ES2694. Unpublished study prepared by Malcolm Pirnie, Inc. 34 p. 

43136904 2082510 Hughes, J.; Williams, T. (1994) The Toxicity of Oryzalin to 

Skeletonema costatum: Lab Project Number: B460-155-4: DR-0320-

8068: ES-2695. Unpublished study prepared by Malcolm Pirnie, Inc. 37 

p. 

43136905 2082511 Hughes, J.; Williams, T. (1994) The Toxicity of Oryzalin to Lemna 

gibba G3: Lab Project Number: B460-155-5: DR-0320-8068: ES-2692. 

Unpublished study prepared by Malcolm Pirnie, Inc. 35 p. 

141-1 Honeybee Acute Toxicity 

MRID 

SAN 

Document 

Number 

Citation Reference 

00066220 2002379 ATKINS, E.L., L.D. ANDERSON, D. KELLUM, and K. W. NEUMA. 

(1976) PROTECTING HONEY BEES FROM PESTICIDES. University 

of California, Division of Agricultural Science, Leaflet 2883. 

Non Guideline 

MRID Type of 

Document Citation Reference 

47164601 Registrant Moore, D.; Breton, R.; Rodney, S.; et al. (2007) Generic Problem 
-47 of 69-

assessment Formulation for California Red-Legged Frog. Project Number: 89320, 

05232007. Unpublished study prepared by Cantox Environmental Inc. 87 

p. 

47164602 Registrant 

assessment 

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. 

38668 Summary Worth, H.M.; Anderson, R.C., eds. (1971) The Safety Evaluation of 

Oryzalin, EL 119. (Unpublished study received on unknown date under 

1471-96; submitted by Elanco Products Co., Div. of Eli Lilly and Co., 

Indianapolis, Ind.; CDL:242443-A) 

38671 Summary Elanco Products Company (1971) Toxicology Studies with Oryzalin 

75WP. (Unpublished study received on unknown date under 1471- 96; 

CDL:242443-I) 

106658 Summary Elanco Products Co. Toxicology Studies with Oryzalin 75WP.

Summary of studies 091019-B through 091019-H. (Unpublished study 

received Jun 18, 1972 under 2G1201; CDL:091019-A) 

38671 Summary Elanco Products Company (1971) Toxicology Studies with Oryzalin 

75WP. (Unpublished study received on unknown date under 1471- 96; 

CDL:242443-I) 

106658 Summary Elanco Products Co. Toxicology Studies with Oryzalin 75WP.

Summary of studies 091019-B through 091019-H. (Unpublished study 

received Jun 18, 1972 under 2G1201; CDL:091019-A) 

106666 Summary Elanco Products Co. The Safety Evaluation of Oryzalin, EL119. 

(Unpublished study received Jun 18, 1972 under 2G1201; CDL:091019-

I) 

106667 Summary Elanco Products Co. (1968) Single Exposure Effects: ?Oryzalin|. 

(Unpublished study received Jun 18, 1972 under 2G1201; CDL: 091019-

J) 

2002432 Summary of Mammalian laboratory toxicity data 

27401 DER not 

located -

Efficacy study 

Christensen, C.; Rogers, W.; Colbert, F.; et al. (1976) Sward 50W for 

Preemergence Control of Annual Grasses and Some Broad- leaf Weeds 

in Mature Turfgrasses. (Unpublished study received Aug 12, 1976 under 

1471-106; prepared in cooperation with Univ. of Florida, submitted by 

Elanco Products Co., Div. of Eli Lilly and Co., Indianapolis, Ind.; 

CDL:224918-A) 
-48 of 69-

Appendix A. Toxicity Data for Oryzalin 

Table A-1. Summary of Guideline Aquatic Organisms’ Acute Toxicity Data 

Species 

LC50/EC5

0 

(mg/L) 

Slope 95% C.I. 

(mg/L) MRID Toxicity Category 

Study 

Classification Notes 

Freshwater Fish 

3.45 - 3.0 – 3.9 TN 1078 Moderately 

toxic 

Rainbow trout Acceptable - 

(Onchorhynchus 

mykiss) 3.26 - 2.9 – 3.7 00072595 Moderately 

toxic 

Acceptable 96 hr test with 

cold water fish; 

reported NOAEC 

= 3.2 ppm

Bluegill sunfish 

(Lepomis 

macrochirus)

2.88 9.3 2.23 – 3.7 00072595 Moderately 

toxic 

Acceptable 96 hr study with 

warm water fish; 

reported NOAEC 

= 1 ppm 

Marine/Estuarine Fish 

Sheepshead 

minnow 

(Cyprinodon 

variegatus) 

> 3.04 - - 43887701 Moderately 

toxic 

Acceptable 96 hr test; 

NOAEC = 

highest 

concentration 

tested (3.04 ppm) 

Freshwater Invertebrates 

Water flea 

(Daphnia magna)

1.5 9.5 1.4 – 1.6 00072596 Moderately 

toxic 

Acceptable 48-hour test; 

hypoactivity, 

prostration, and 

immobility were 

the effects noted 

at concentrations 

greater than 1.6 

ppm; NOAEC = 

0.62 ppm 

Marine/Estuarine Invertebrates 

Grass shrimp 

(Palaemonetes 

pugio) 

>3.11 - - 43887701 Moderately 

toxic to 

practically 

non-toxic 

Acceptable 96 hr test; only 

20% mortality at 

the highest dose 

tested (3.1 ppm); 

NOAEC = 1.95 

ppm

Eastern oyster 

(Crassostrea 

virginica) 

0.285 - 0.2 – 0.5 43887702 Highly toxic Acceptable 96 hour oyster 

shell deposition 

study; NOAEC = 

0.0994 ppm 
-49 of 69-

Table A-2. Summary of Guideline Aquatic Organisms’ Chronic Toxicity Data

Species LOAEC 

(mg/L) 

NOAEC 

(mg/L) MRID Study Classification Notes 

Freshwater Fish 

Rainbow trout 

(Onchorhynchus 

mykiss) 

>0. 46 >0.46 00126842 Acceptable 66 day early life-stage study; no 

adverse effects at any 

concentration tested; based on 

MRID 00072595, NOAEC 

could range between 0.46 to 3.2 

ppm 

Fathead minnow 

(Pimephales 

promelas) 

0.43 0.22 00126841 Acceptable 34 day early life-stage study; no 

adverse effects at all 

concentrations tested; however, 

mean larval weights were 

significantly lower than solvent 

control with the highest dose 

tested 

Freshwater Invertebrates 

Water flea 

(Daphnia magna) 

0.608 0.358 43986901 Acceptable Life cycle test; dry weight of 

first generation daphnids is the 

most sensitive endpoint 

Table A-3. Summary of Aquatic Plant Data 

Species EC50 Slope 95% C.I. 

(ppb) 

MRID & 

Classification Notes 

Aquatic non-vascular plants 

Green algae 

(Selenastrum 

capricornutum) 

52 ppb - 17.1 – 98.7 43136901 

Supplemental 

Endpoint affected = cell density; 

5-day study duration; NOAEC = 

13.8 ppb 

Blue-green algae 

(Anabaena flos-aquae) 

NA - NA 43136902 

Invalid 

NA 

Freshwater diatom 

(Navicula pelliculosa) 

NA - NA 43136903 

Invalid 

NA 

Marine diatom 

(Skeletonema costatum) 

Not 

Determined 

- NA 43136904 

Supplemental 

Endpoint affected = cell density; 

5-day study duration; NOAEC = 

30.6 ppb 

Aquatic vascular plants 

Duckweed 

(Lemna gibba)

13 ppb - 9.7 – 19 43136905 

Supplemental 

Endpoint affected = frond count; 

14-day study duration; NOAEC = 

3.28 ppb 
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Table A-4. Summary of Guideline Acute Avian Data

Species LD50/LC50 

(mg/kg ai) Slope 95% C.I. MRID Toxicity Category 

Study 

Classification Notes 

Avian Acute Oral 

Bobwhite quail 

(Colinus 

virginianus) 

506.7 

(combined 

male and 

female) 

4.5 391 - 

656 

00098462 Slightly 

toxic 

Acceptable Effects noted include 

lethargy, ataxia, ruffled 

appearance, 

emaciation, and yellow 

colored loose feces 

within 5 hours 

following treatment; 

dose-related decline in 

food consumption (3 to 

7 days after treatment) 

and body weight loss 

were also noted 

Avian Sub-acute Dietary 

Bobwhite quail 

(Colinus 

virginianus) 

>5000 - - 00072593 Acceptable The 10% mortality 

noted in the highest 

dose is not treatmentrelated 

Mallard duck 

(Anas 

platyrhynchos) 

>5000 - - 00072594 

Practically 

non-toxic 

Acceptable No mortality at highest 

doses; food 

consumption is greater 

in the treatments 

compared to controls 

Table A-5. Summary of Guideline Chronic Avian (Reproductive Effects) Data 

Species LOAEC 

mg/kg ai 

NOAEC 

mg/kg ai MRID Endpoints Affected 

Study 

Classification Notes 

Bobwhite quail 

(Colinus virginianus) 

> 1000 1000 00129050 No effects at 

highest dose on 

any endpoints 

tested 

Supplemental High bird 

mortality in 

controls due to 

head injuries led 

to supplemental 

classification of 

the study 

Mallard duck 

(Anas platyrhynchos) 

> 1000 1000 00126843 No effects at 

highest dose on 

any endpoints 

tested 

Supplemental The initial Core 

classification of 

the study was 

changed to 

Supplemental in 

oryzalin RED due 

to a 4-fold 

increase in 

oryzalin use rates 

since the study 

was first 

classified in 1982 

Bobwhite quail 

(Colinus virginianus) 

311 132 44162201 Female body 

weight 

Acceptable - 

Mallard duck >311 311 44162202 No effects at Supplemental Reduction in 
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Table A-5. Summary of Guideline Chronic Avian (Reproductive Effects) Data 

Species LOAEC 

mg/kg ai 

NOAEC 

mg/kg ai MRID Endpoints Affected 

Study 

Classification Notes 

(Anas platyrhynchos) highest dose on 

any endpoints 

tested 

hatchling body 

weight at the 

lowest dose tested 

was not 

treatment-related 

Table A-6. Summary of Mammalian Data

Species Endpoint MRID Toxicity 

Category 

Study 

Classification Notes 

Rat 

(Rattus norvegicus) 

LD50 

= 10,0000 

mg/kg ai 

00026592 Practically 

non-toxic 

Acceptable No mortality at highest dose 

tested 

Mammalian Chronic Dietary 

Rat 

(Rattus norvegicus) 

NOAEL = 

13.82 

mg/kg/day; 

LOAEL = 

42.9 

mg/kg/day 

00026779 

00044332 

00070569 

- Acceptable Females were more sensitive 

than males; LOAEL values are 

based on decreased body weight 

gain, decreased hematology 

parameters, increased 

microscopic findings in the 

thyroid in females and decreased 

survival; increased thyroid 

weight, increased incidence of 

skin lesions; follicular cell 

thyroid tumors in both sexes, 

skin tumors in both sexes, and 

mammary gland tumors in 

females 

Table A-7. Summary of Terrestrial Non-Target Insect Toxicity Data 

Species LC50 

μg/bee 

Toxicity 

Category MRID # Notes 

Honey bee 

(Apis mellifera) 

> 11 Practically 

non-toxic 

00066220 Acute contact toxicity at 48 hours 
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Table A-8. Summary of Terrestrial Plant Data 

Crop Type of Study Species NOAEC 

(lb ai/A) 

EC25

(lb ai/A) 

Seedling Emergence 

Oats 0.0740 0.16 

Corn 0.667 ND 

Ryegrass 0.008 0.014 

Monocots 

Onion 0.222 0.12 

Cabbage 0.222 0.52 

Cucumber 0.667 0.78 

Lettuce 0.222 0.088 

Tomato <0.0056* 0.050 

Soybean 6.00 >6.00 

Dicots 

Radish 2.00 >6.00 

Vegetative Vigor 

Corn 0.0740 0.080 

Oats 0.222 0.22 

Ryegrass 0.0253 0.097 

Monocots 

Onion 2.00 >6.00 

Lettuce 0.0253 0.040 

Tomato 0.0253 0.030 

Cabbage 0.222 3.0 

Cucumber 0.222 1.5 

Radish 0.222 >6.00 

Dicots 

Soybean 2.00 3.1 

ND = not determined 

MRID 426024-01 classified as supplemental 

*NOAEC could not be determined. EC05 was determined to be 0.0056 lb a.i./acre, but this value is outside 

the tested concentration range. 
-53 of 69-

Appendix B. Data Call-In Tables. 

The Environmental Fate and Effects Division (EFED) has completed a Data Call-In 

(DCI) table for the oryzalin environmental fate and effects data gaps identified in 

registration review. The attached DCI table, which includes the guideline number and 

study title for required data, also provides a rationale for requiring the data, an 

explanation of how the data will be used, and a brief description of how the data could 

impact the Agency’s future decision-making. 

Environmental Fate Data:

Pending completion of review of fate studies (MRID 41050001, 41378401, 41322801, 

41322802, 41479801, 41479802; see Table 7.1 for details), additional data gaps may be 

identified. 

Guideline Number: 835.4300 

Study Title: Aerobic Aquatic Metabolism Study 

Rationale for Requiring the Data 

An aerobic aquatic metabolism study has not been submitted to support the registration 

review of oryzalin. Per 40 CFR 158, Subpart N, this study is part of the required 

environmental fate data. 

Practical Utility of the Data 

How will the data be used? 

The aerobic aquatic metabolism study would facilitate a better understanding of oryzalin’s 

degradation in the water column or sediment under oxygen-rich conditions in the 

laboratory. 

In order to reliably estimate aquatic exposure, aerobic aquatic metabolism data are 

necessary inputs to the EXAMS model. The data will identify any transformation products 

that may occur. In addition, this study will also help determine if sediment toxicology 

studies are required for oryzalin. 

How could the data change the Agency’s decision or impact the Agency’s future 

decision-making? 

If data indicate that oryzalin persists in aerobic aquatic environments, additional use 

precautions and/or restrictions may be necessary. In addition, 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 oryzalin which are 

unnecessarily severe. 

Guideline Number: 835.4400 

Study Title: Anaerobic Aquatic Metabolism Study 

Rationale for Requiring the Data 

An anaerobic aquatic metabolism study has not been submitted to support the registration 

review of oryzalin. Per 40 CFR 158, Subpart N, this study is part of the required 

environmental fate data. 
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Practical Utility of the Data 

How will the data be used? 

The anaerobic aquatic metabolism study would facilitate a better understanding of 

oryzalin’s degradation in the water column or sediment under oxygen-poor conditions in 

the laboratory. 

In order to reliably estimate aquatic exposure, anaerobic aquatic metabolism data are 

necessary inputs to the EXAMS model. The data will identify any transformation products 

that may occur. In addition, this study will also help determine if sediment toxicology 

studies are required for oryzalin. 

How could the data change the Agency’s decision or impact the Agency’s future 

decision-making? 

If data indicate that oryzalin persists in anaerobic aquatic environments, additional use 

precautions and/or restrictions may be necessary. In addition, 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 oryzalin which are 

unnecessarily severe. 

Guideline Number: 835.6100 and 835.6200 

Study Title: Environmental Chemistry Methods 

Rationale for Requiring the Data 

Independently validated analytical methods for residues in soil and in water 

(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. The availability of these 

analytical methods is necessary to ensure the safety of those in proximity to releases of 

oryzalin residues in the environment. Independent laboratory validations for submitted 

analytical methods are necessary to confirm the levels of detection and quantitation 

reported in registrant-prepared validations. 

Use of oryzalin may contaminate surface water due to spray drift and runoff of residues. 

There is also the potential for ground water contamination in sandy soils or where soil 

preferential flow conditions exist and exposure to sunlight is minimal. Additionally, based 

upon its Koc, significant fractions of the oryzalin in receiving surface waters may adsorb to 

suspended sediment. Given its resistance to abiotic hydrolysis coupled with only a 

moderate susceptibility to aerobic biodegradation, oryzalin will be more persistent in 

receiving deeper surface waters, resulting in potential sediment contamination. Therefore, 

outside agencies may request analytical methods with which to monitor for oryzalin 

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 
-55 of 69-

the Agency may lack chemical-specific methods for analyses in environmental 

compartments. Independently validated environmental chemistry methods will be used to 

evaluate the submitted environmental fate and ecological effects data and will be made 

available to the public to support monitoring for oryzalin residues. 

How could the data change the Agency’s decision, or impact the Agency’s future 

decision-making? 

Risk assessment conclusions could be altered if they are not supported by either study data 

or environmental monitoring detections that are based on independently validated 

environmental chemistry methods. Furthermore, while not directly related to Agency 

decision-making, independently validated environmental chemistry methods are necessary 

to ensure the safety of those in proximity to releases of oryzalin residues in the 

environment. 

Environmental Effects Data:

Guideline Number: 850.2100 

Study Title: Avian Acute Oral Toxicity Test 

Rationale for Requiring the Data 

Acceptable acute avian oral toxicity data were submitted for exposures of bobwhite quail 

to oryzalin; however, data are not available for a passerine species, which is now required 

under the 40 CFR Part 158 (Oct. 26, 2007) data requirements for conventional pesticides. 

The Part 158 data requirements specify that acute avian oral toxicity data be submitted for 

either mallard duck or bobwhite quail and a passerine species. Therefore, an avian oral 

toxicity test is required for passerine birds, as specified in 40 CFR Part 158 (OCSPP 

Guideline 850.2100). A passerine study protocol must be submitted for review by the 

Agency prior to initiation of this study. 

Practical Utility of the Data 

How will the data be used? 

Acute avian oral toxicity data for passerine species will be used to refine the screeninglevel assessment by determining whether there are differences in avian species sensitivity 

to oryzalin between passerines and upland game species. If oral acute toxicity data are not 

submitted for passerines, risk will be assumed for all passerine species. 

How could the data impact the Agency’s future decision-making? 

If future endangered species risk assessments are performed without these data, the 

Agency would have to assume that oryzalin “may affect” listed passerine birds directly 

(and listed species from other taxa indirectly), and use of oryzalin and its formulated 

products may need to be restricted in areas where listed 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 

oryzalin use that are unnecessarily severe. 
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Guideline Number: 850.2300 

Study Title: Avian Chronic Reproduction Toxicity Test 

Rationale for Requiring the Data 

Acceptable reproduction toxicity data were submitted for exposures of bobwhite quail to 

oryzalin; however, the submitted mallard duck study was classified as supplemental due to 

the pre-laying exposure period being of insufficient length. The Part 158 data 

requirements specify that acceptable reproduction toxicity data be submitted for both the 

mallard duck and the bobwhite quail. 

Practical Utility of the Data 

How will the data be used? 

Chronic avian reproduction toxicity data for the mallard duck will be used to refine the 

screening-level assessment by determining whether there are differences in avian species 

sensitivity to oryzalin between waterfowl and upland game species. If acceptable data are 

not submitted for mallard ducks, risk will be assumed for all waterfowl species. 

How could the data impact the Agency’s future decision-making? 

If future endangered species risk assessments are performed without these data, the 

Agency would have to assume that oryzalin “may affect” listed waterfowl birds directly 

(and listed species from other taxa indirectly), and use of oryzalin and its formulated 

products may need to be restricted in areas where listed 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 

oryzalin use that are unnecessarily severe. 

Guideline Number: 850.1350 

Study Title: Estuarine/Marine Invertebrate Life Cycle Toxicity Test 

Rationale for Requiring the Data 

Chronic toxicity data for oryzalin are not available for estuarine/marine invertebrates. 

Since the current use patterns permit oryzalin to enter estuarine/marine environments, these 

data are required under the 40 CFR Part 158 (Oct. 26, 2007). In addition, under some 

conditions, oryzalin may be persistent in water. Therefore, an estuarine/marine 

invertebrate life cycle toxicity test (OCSPP Guideline 850.1350) is required. 

Practical Utility of the Data 

How will the data be used? 

Chronic toxicity data for estuarine/marine invertebrate species will be used to refine the 

screening-level assessment by determining whether there are potential risks to 

invertebrates inhabiting estuarine/marine environments from the use of oryzalin. If chronic 

toxicity data are not submitted for estuarine/marine invertebrates, risk will be assumed for 

all invertebrates in estuarine/marine environments potentially exposed to oryzalin. 

How could the data impact the Agency’s future decision-making? 

If future endangered species risk assessments are performed without these data, the 

Agency would have to assume that oryzalin “may affect” listed estuarine/marine 

invertebrate species directly (and listed species from other taxa indirectly), and use of 

oryzalin and its formulated products may need to be restricted in areas where listed species 
-57 of 69-

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 oryzalin use that are unnecessarily severe. 

Guideline Number: 850.1400 

Study Title: Estuarine/Marine Fish Early Life Stage Toxicity Test 

Rationale for Requiring the Data 

Chronic toxicity data for oryzalin are not available for estuarine/marine fish. Since the 

current use patterns permit oryzalin to enter estuarine/marine environments, these data are 

required under the 40 CFR Part 158 (Oct. 26, 2007). In addition, under some conditions, 

oryzalin may be persistent in water. Therefore, an estuarine/marine fish early life stage 

toxicity test (OCSPP Guideline 850.1400) is required. 

Practical Utility of the Data 

How will the data be used? 

Chronic toxicity data for estuarine/marine fish species will be used to refine the screeninglevel assessment by determining whether there are potential risks to fish inhabiting 

estuarine/marine environments from the use of oryzalin. If chronic toxicity data are not 

submitted for estuarine/marine fish, risk will be assumed for all fish potentially exposed to 

oryzalin in estuarine/marine environments. 

How could the data impact the Agency’s future decision-making? 

If future endangered species risk assessments are performed without these data, the 

Agency would have to assume that oryzalin “may affect” listed estuarine/marine fish 

species directly (and listed species from other taxa indirectly), and use of oryzalin and its 

formulated products may need to be restricted in areas where listed 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 oryzalin use that are unnecessarily severe. 

Guideline Number: 850.1735, 850.1740, Other1

Study Title: Freshwater and Estuarine/Marine Invertebrate Acute and Chronic 

Whole Sediment Toxicity Tests 

Rationale for Requiring the Data 

Acute and chronic toxicity data for oryzalin are not available for freshwater and 

estuarine/marine invertebrates. Since the current use patterns permit oryzalin to enter 

aquatic environments, these data are required under the 40 CFR Part 158 (Oct. 26, 2007). 

In addition, under some conditions, oryzalin may be persistent in water. Oryzalin’s 

chemical properties trigger the requirement for sediment toxicity studies (the Kd >50, the 

log Kow is >3, and a Koc is >1000). Acute studies are required if the persistence in 

sediment is ≤ 10 days, and chronic studies are required if the persistence in sediment is 

expected to be >10 days. The requested aquatic metabolism study will allow EFED to 

determine if an acute or a chronic study is required. 

Practical Utility of the Data 

How will the data be used? 

Sediment toxicity data for freshwater and estuarine/marine invertebrate species will be 
-58 of 69-

used to refine the screening-level assessment by determining whether there are potential 

risks to sediment-dwelling invertebrates inhabiting freshwater and estuarine/marine 

environments from the use of oryzalin. If sediment toxicity data are not submitted for 

freshwater and estuarine/marine invertebrates, risk will be assumed for all sedimentdwelling invertebrates in freshwater and estuarine/marine environments potentially 

exposed to oryzalin. 

How could the data impact the Agency’s future decision-making? 

If future endangered species risk assessments are performed without these data, the 

Agency would have to assume that oryzalin “may affect” listed freshwater and 

estuarine/marine invertebrate species directly (and listed species from other taxa 

indirectly), and use of oryzalin and its formulated products may need to be restricted in 

areas where listed 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 oryzalin use that are unnecessarily severe. 1

Three species required for chronic test using the following study guidance: 1) EPA 600/R-99/064 Test 

Method 100.4: Hyalella azteca 42-d Test for Measuring the Effects of Sediment Associated Contaminants on 

Survival, Growth, and Reproduction; 2) EPA 600/R-99/064 Test Method 100.5: Life-cycle Test for 

Measuring the Effects of Sediment-associated Contaminants on Chironomus dilutus or C. tentans in USEPA 

2000 Methods for Measuring the Toxicity and Bioaccumulation of Sediment-associated Contaminants with 

Freshwater Invertebrates; 3) 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. 

Protocols should be submitted for approval prior to testing for chronic studies. The preferred sediment is 

formulated; guidance for the formulated sediment can be found in OECD 218 Sediment-Water Chironomid 

Toxicity Test using Spiked Sediment. Based on test variability for the endpoints of concern and the need to 

establish a NOAEC/LOAEC, the following number of replicates and test animals are recommended: for the 

midge test with C. dilutus: 16 replicates containing 12 test organisms each (12 replicates at test initiation; 4 

added at 10 days for auxiliary males); for the freshwater amphipod test with H. azteca: 12 replicates per 

treatment (4 for 28-d survival and growth and 8 for the remainder of the test) with 10 neonates per replicate; 

and for the L. plumulosus: 10 replicates per treatment with 20 neonates per replicate. For alternative test 

designs, the protocol should discuss the power of the test.

Guideline Numbers: 850.4225 and 850.4250 

Study Title: Terrestrial Plant Toxicity Tests (Tier II) 

Rationale for Requiring the Data 

Terrestrial plant toxicity studies and associated risk analysis of plants are required for 

registration of pesticides with outdoor uses (CFR Part 158). For terrestrial plants, Tier II 

studies are required when potential concerns are triggered (i.e., when there is some 

indication that there may be significant toxicity to plants). These indicators may be an 

herbicidal mode of action or statements on the label indicating toxicity to plants. 

The submitted studies utilize the technical grade active ingredient (TGAI) rather than a 

typical end-use product (TEP). A formulated product may contain adjuvants or other inert 

ingredients that may increase risks to non-target terrestrial plants. Therefore, Tier II 

seedling emergence and vegetative vigor studies (OCSPP Guidelines 850.4225 and 

850.4250) that utilize a TEP are required. In the absence of such data, risks to terrestrial 
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plants from the use of oryzalin will be assumed in the risk assessment. 

Practical Utility of the Data 

How will the data be used? 

Tier II vegetative vigor and seedling emergence data for terrestrial plants will be used to 

determine the potential for oryzalin to affect non-target plant species in the terrestrial 

environment. In the absence of data specific for these plants, risk to terrestrial plants will 

be assumed. 

How could the data impact the Agency’s future decision-making? 

If future endangered species risk assessments are performed without these data, the 

Agency would have to presume risk to non-target terrestrial plants from use of oryzalin. 

Therefore, use of oryzalin and its formulated products may need to be restricted in areas 

where listed 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 oryzalin that are unnecessarily severe. 

Guideline Number: 850.4400 

Aquatic Plant Growth Tier II Study (Vascular Aquatic Plant) 

Rationale for Requiring the Data 

Aquatic (both vascular and non-vascular species) toxicity studies and associated risk 

analysis of plants are required for registration of pesticides with outdoor uses (CFR Part 

158). The data submitted for oryzalin are classified as supplemental because of problems 

with the study design; in addition, the reliability of the study is in question. Therefore, an 

acceptable aquatic vascular plant study is required as specified in 40 CFR Part 158 

(OCSPP Guideline 850.4400). 

Practical Utility of the Data 

How will the data be used? 

Data from Tier II aquatic plant toxicity studies will be used to estimate potential risks to 

aquatic plants associated with uses of oryzalin. The data will reduce uncertainties 

associated with the current risk assessment for plants and will improve understanding of 

the potential risks of oryzalin on aquatic plants. Because plants form the basis of most 

habitats and significantly contribute to overall environmental quality, a solid understanding 

of the potential risks to aquatic plants is essential for sound environmental management. 

The data will also be used in determining whether a “may affect” to Federally-listed 

threatened and endangered species is likely under the Endangered Species Act. 

Additionally, the need for labeling language to mitigate effects on non-target aquatic plant 

species is unknown. Results of this study would be used to determine if surface water 

exposure concentrations, due to run-off, are below levels of concern at the current label 

rates and to identify what, if any, label language is needed to mitigate identified risks. 

How could the data impact the Agency’s future decision-making? 

Without acceptable aquatic plant growth data for oryzalin, the Agency cannot determine 

the levels of oryzalin that result in effects to vascular aquatic plants. 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 oryzalin which may 
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otherwise be avoided, or which are unnecessarily severe. 

Guideline Number: 850.5400 

Aquatic Plant Growth Tier II Study (Non-vascular Aquatic Plant) 

Rationale for Requiring the Data 

Aquatic (both vascular and non-vascular species) toxicity studies and associated risk 

analysis of plants are required for registration of pesticides with outdoor uses (CFR Part 

158). The data submitted for oryzalin are classified as supplemental because of problems 

with the study design or invalid due to significant differences between the solvent and 

negative controls. Therefore, acceptable aquatic non-vascular plant studies are required as 

specified in 40 CFR Part 158 (OCSPP Guideline 850.4400). 

Practical Utility of the Data 

How will the data be used? 

Data from Tier II aquatic plant toxicity studies will be used to estimate potential risks to 

aquatic plants associated with uses of oryzalin. The data will reduce uncertainties 

associated with the current risk assessment for plants and will improve understanding of 

the potential risks of oryzalin on aquatic plants. Because plants form the basis of most 

habitats and significantly contribute to overall environmental quality, a solid understanding 

of the potential risks to aquatic plants is essential for sound environmental management. 

The data will also be used in determining whether a “may affect” to Federally-listed 

threatened and endangered species is likely under the Endangered Species Act. 

Additionally, the need for labeling language to mitigate effects on non-target aquatic plant 

species is unknown. Results of this study would be used to determine if surface water 

exposure concentrations, due to run-off, are below levels of concern at the current label 

rates and to identify what, if any, label language is needed to mitigate identified risks. 

How could the data impact the Agency’s future decision-making? 

Without acceptable aquatic plant growth data for oryzalin, the Agency cannot determine 

the levels of oryzalin that result in effects to non-vascular aquatic plants. 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 oryzalin which 

may otherwise be avoided, or which are unnecessarily severe. 
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Appendix C. Oryzalin Formulations Containing Multiple Active Ingredients 

The Agency does not routinely include, in its risk assessments, an evaluation of mixtures 

of active ingredients, either those mixtures of multiple active ingredients in product 

formulations or those in the applicator’s tank. In the case of the product formulations of 

active ingredients (that is, a registered product containing more than one active 

ingredient), each active ingredient is subject to an individual risk assessment for 

regulatory decision regarding the active ingredient on a particular use site. If effects data 

are available for a formulated product containing more than one active ingredient, they 

may be used qualitatively or quantitatively3,4

. 

There are no product LD50 values, with associated 95% Confidence Intervals (CIs) 

available for oryzalin. As discussed in USEPA (2000) a quantitative component-based 

evaluation of mixture toxicity requires data of appropriate quality for each component of 

a mixture. In this mixture evaluation, an LD50 with associated 95% CI is needed for the 

formulated product. The same quality of data is also required for each component of the 

mixture. Given that the formulated products for oryzalin do not have LD50 data available 

it is not possible to undertake a quantitative or qualitative analysis for potential 

interactive effects. However, because the active ingredients are not expected to have 

similar mechanisms of action, metabolites, or toxicokinetic behavior, it is reasonable to 

conclude that an assumption of dose-addition would be inappropriate. Consequently, an 

assessment based on the toxicity of oryzalin is the only reasonable approach that employs 

the available data to address the potential acute risks of the formulated products.

 

3

 Overview of the Ecological Risk Assessment Process in the Office of Pesticide Programs, Environmental 

Protection Agency (January 2004) (Overview Document). 

4

 Memorandum to Office of Prevention, Pesticides and Toxic Substance, US EPA conveying an evaluation 

by the U.S. Fish and Wildlife Service and National Marine Fisheries Service of an approach to assessing 

the ecological risks of pesticide products (January 2004). 
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Pesticide Products Formulated with Oryzalin and Other Active Ingredients5,6

PRODUCT ADJUSTED FO

PRODUCT/TRADE NAME EPA Reg.No. % Oryzalin INGREDI

LD50 (mg/kg) CI (mg/kg) LD50 (mg/kg) 

HELENA XL2G 00590500556 1 >5000 

NA 

Limit Dose 

NA 

Limit Dose 

XL2G 03816700030 1 >5000 

NA 

Limit Dose 

NA 

Limit Dose 

ORYZALIN 2G 05388300220 1 >5000 

NA 

Limit Dose 

NA 

Limit Dose 

ROUT ORNAMENTAL HERBICIDE 05818500027 1 >5000 

NA 

Limit Dose 

NA 

Limit Dose 

XL 2G 07050600045 1 >5000 

NA 

Limit Dose 

NA 

Limit Dose 

TURF AND ORNAMENTAL FERTILIZER CONTAINS BALAN 0.575% + SURFLAN 0.575% 07050600049 0.575 4444 No Data No CI Data UP-SHOT DF HERBICIDE 07050600053 60 >5000 

NA 

Limit Dose 

NA 

Limit Dose 

TURF FERTILIZER CONTAINS GALLEY PLUS SURFLAN 07050600055 0.86 >5000 

NA 

Limit Dose 

NA 

Limit Dose 

XL 2GR 07050600056 1 >5000 

NA 

Limit Dose 

NA 

Limit Dose 

DOUBLE O G-PRO HERBICIDE 07967600020 1 >5000 

NA 

Limit Dose 

NA 

Limit Dose 

5From registrant submitted data to support registration. Compiled by the Office of Pesticide Programs Registration Division. 6Oryzalin LD50= >10000 mg/kg 
-63 of 69-

Appendix D. Oryzalin Incidents 

A search for ecological incidents related to oryzalin use, conducted on August 2, 2010, yielded 

six incidents. Of these, one incident pertained to aquatic organisms where as five incidents were 

on terrestrial plants. The summary of the six incidents reported for oryzalin is provided below. 

 

Aquatic Incidents 

Approximately 450 bluegill sunfish and largemouth bass were killed between April 6 and 13, 

2001 in Georgia, following the application of a formulated product of oryzalin (Surflan) on 

March 31. Rain fell on 4 April and it is possible that the pond was contaminated by either spray 

drift or runoff. The legality of use for this incident was listed as “misuse”. Residues in fish tissue 

were not measured. The certainty index for this incident (I011444-011) is POSSIBLE. 

Terrestrial Incidents 

The Washington Department of Agriculture reported that 13 acres of merlot wine grapes in Grant 

County were damaged on April 3, 1998 due to direct application of oryzalin. The legality of use 

for this incident was listed as “registered use”. The certainty index for this incident (I013884-

027) is UNLIKELY as oryzalin is a registered pesticide in grape. The damage to grapes is 

possibly due to the application of norflurazon, the legality of which was listed as “misuse”. 

A plant incident (7/3/1992) that resulted in damage to trees and shrubs (specific plants not 

reported) was reported from Benton County, Washington in 1992. The incident resulted due to 

applicator error of mixing oryzalin with bromacil/diuron. The legality of this use was reported as 

“undetermined”. The certainty index for this incident (I014409-062) is POSSIBLE. 

A nursery in the Washington county of Oregon reported on February 2, 2002 that six acres of 

tulips were damaged by exhibiting twisting of leaves. The certainty index for this incident 

(I013636-027) is POSSIBLE. The legality of this use was reported as “registered use”. The 

report mentions that isoxaben was used along with glyphosate, diclofop-methyl, fenhexamid, 

iprodione, and oryzalin and that diclofop-methyl was used previously used in the sprayer. 

Dow Elanco reported an incident in 1994 that 676,000 Douglas fir seedlings treated with 

Snapshot herbicide (isoxaben + oryzalin) had to be discarded as they turned chlorotic and 

swollen. The certainty index for this incident (I001485-001) is “undetermined” and the legality 

was reported as POSSIBLE. The incident report noted that little information was provided to 

determine which herbicide in the mixture caused the damage. 

An acre of Idaho strain fir trees experienced loss of turgidity, necrosis, stem brittleness, fissures, 

and death in Washington state in 1989/90. Pesticide application history indicated use of 

oxyfluorfen at planting, napropamide one month after planting, oxyfluorfen five months after 

planting, and oryzalin eleven months after planting. The legality of use for this incident was 

listed as “intentional misuse” as the label for Surflan (oryzalin) clearly states “do not apply to 

Douglas fir”. The certainty index for this incident (I001734-001) is PROBABLE. 
-64 of 69-

Uncertainties Related to the Use of Incident Information from the Ecological Incident 

Information System 

Incident data are used in risk assessments to provide evidence that the risk predictions from the 

screening level assessment are supported by actual effects in the field. Incident reports 

submitted to EPA since approximately 1994 have been tracked by assignment of incident 

numbers in an Incident Data System (IDS), microfiched, and then entered to a second database, 

the Ecological Incident Information System (EIIS). Additionally, there is an on-going effort to 

enter information to EIIS on incident reports received prior to establishment of current databases. 

Incident reports are not received in a consistent format (e.g., states and various labs usually have 

their own formats), may involve multiple incidents involving multiple chemicals in one report, 

and may report on only part of a given incident investigation (e.g., residues). 

Incidents entered into EIIS are categorized into one of several certainty levels regarding the 

likelihood that a particular pesticide is associated with the incident: highly probable, probable, 

possible, unlikely, or unrelated. In brief, “highly probable” incidents usually require carcass 

residues and/or clear circumstances regarding the exposure. “Probable” incidents include those 

where residues were not available and/or circumstances were less clear than for “highly 

probable.” “Possible” incidents include those where multiple chemicals may have been involved 

and it is not clear what the contribution was of a given chemical. The “unlikely” category is 

used, for example, where a given chemical is practically nontoxic to the category of organism 

killed and/or the chemical was tested for but not detected in samples. “Unrelated” incidents are 

those that have been confirmed to be not pesticide-related. 

Incidents entered into the EIIS are also categorized as to use/misuse. Unless specifically 

confirmed by a state or federal agency to be misuse, or there was very clear misuse such as 

intentional baiting to kill wildlife, incidents are not typically considered misuse. 

The number of documented kills in EIIS is believed to be a small fraction of total mortality 

caused by pesticides. Mortality incidents must be seen, reported, investigated, and have 

investigation reports submitted to EPA to have the potential for entry into the database. 

Incidents often are not seen, due to scavenger removal of carcasses, decay in the field, or simply 

because carcasses may be hard to see on many sites and/or few people are systematically 

looking. Poisoned animals may also move off-site to less conspicuous areas before dying. 

Incidents may not get reported to appropriate authorities capable of investigating the incident for 

a variety of reasons including the finder may not know of the importance of reporting incidents, 

may not know who to call, may not feel they have the time or desire to call, or may hesitate to 

call because of their own involvement in the kill. Incidents reported may not get investigated if 

resources are limited or may not get investigated thoroughly, with residue analyses, for example. 

Also, if kills are not reported and investigated promptly, there will be little chance of 

documenting the cause, since tissues and residues may deteriorate quickly. Reports of 

investigated incidents often do not get submitted to EPA, since reporting by states is voluntary. 
-65 of 69-

Furthermore, the database relies heavily on registrant-submitted incident reports, and registrants 

are currently only required to submit detailed information on ‘major’ ecological incidents, while 

‘minor’ incidents are reported aggregately. 

Based on the 40 CFR (§159.184 Toxic or adverse effect incident reports), an ecological incident 

is considered ‘major’ if any of the following criteria are met: 

Fish or wildlife: 

(A) Involves any incident caused by a pesticide currently in Formal Review 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. 

All other ecological incidents are considered ‘minor’ and only need to be aggregately reported. 

‘Minor’ incidents reported by the registrants are not included in the EIIS database. Therefore, 

for example, an incident could affect 900 fish, 150 birds, 45 mammals, and 40% of an exposed 

crop and not be included in the EIIS database [unless is it reported by a non-registrant (e.g., an 

incident submitted by a state agency – which are not systematically collected)]. Therefore, 

because the number of documented kills in EIIS is believed to be a small fraction of total 

mortality caused by pesticides, absence of reports does not necessarily provide evidence of an 

absence of incidents. 
-66 of 69-

Appendix E. ECOSAR Analysis 

UN-2 Degradate 

SMILES : CCCN2c1c(N(=O)(=O))cc(S(N)(=O)=O)cc1N(=O)N2CC 

CHEM : 

CAS Num: 

ChemID1: 

ChemID2: 

ChemID3: 

MOL FOR: C11 H16 N5 O5 S1 

MOL WT : 330.34 

Log Kow: -2.33 (KowWin estimate) 

Melt Pt: 

Wat Sol: 3.257E+005 mg/L (WskowWin estimate) 

ECOSAR v1.00a Class(es) Found 

------------------------------ 

Hydrazines 

Amides 

 Predicted 

ECOSAR Class Organism Duration End Pt mg/L 

(ppm) 

=========================== ================== ======== ====== 

========== 

Hydrazines : Fish 96-hr LC50 125.736 

Hydrazines : Daphnid 48-hr LC50 39.927 

Hydrazines : Green Algae 72-hr EC50 6.19e-005 

Hydrazines : Fish ChV 15.102 ! 

Hydrazines : Daphnid ChV 21.599 ! 

Hydrazines : Green Algae ChV 1.55e-005 ! 

Amides : Fish 96-hr LC50 1.14e+005 

Amides : Daphnid 48-hr LC50 14346.239 

Amides : Green Algae 96-hr EC50 11.699 

Amides : Fish ChV 672.586 

Amides : Daphnid ChV 189.251 ! 

Amides : Green Algae ChV 0.552 

=========================== ================== ======== ====== 

========== 

Neutral Organic SAR : Fish 96-hr LC50 1.18e+006 * 

(Baseline Toxicity) : Daphnid 48-hr LC50 4.04e+005 * 

 : Green Algae 96-hr EC50 29421.822 

 : Fish ChV 1.23e+005 

 : Daphnid ChV 17337.098 

 : Green Algae ChV 4826.486 

 Note: * = asterisk designates: Chemical may not be soluble 

 enough to measure this predicted effect. 

 

 Note: ! = exclamation designates: The toxicity value was determined from 

 a predicted SAR using established acute-to-chronic ratios and ECOSAR 

 regression techniques which are documented in the supporting Technical 

 Reference Manual. When possible, this toxicity value should be 

 considered in a weight of evidence approach. 

 

Hydrazines: 

---------- 

 For Fish and Daphnid Acute Toxicity Values: If the log Kow of the chemical 

is greater than 5.0, or if the compound is solid and the LC50 exceeds the 

water solubility by 10X, no effects at saturation are predicted for these 

endpoints. 
-67 of 69-

 

 For Green Algae Acute Toxicity Values: If the log Kow of the chemical is 

greater than 6.4, or if the compound is solid and the EC50 exceeds the water 

solubility by 10X, no effects at saturation are predicted for these 

endpoints. 

 

 For All Chronic Toxicity Values: If the log Kow of the chemical is greater 

than 8.0, or if the compound is solid and the ChV exceeds the water 

solubility 

by 10X, no effects at saturation are predicted for these endpoints. 

 

ECOSAR v1.00 SAR Limitations: 

---------------------------- 

Maximum LogKow: 5.0 (LC50) 

Maximum LogKow: 6.4 (EC50) 

Maximum LogKow: 8.0 (ChV) 

Maximum Mol Wt: 1000 

 

Amides : 

------- 

No limitations known at this time. 

 

ECOSAR v1.00 SAR Limitations: 

---------------------------- 

Maximum LogKow: >8.5 (LC50) 

Maximum LogKow: >8.0 (EC50,ChV) 

Maximum Mol Wt: 1000 

 

Baseline Toxicity SAR Limitations: 

--------------------------------- 

Maximum LogKow: 5.0 (Fish 96-hr LC50; Daphnid LC50) 

Maximum LogKow: 6.4 (Green Algae EC50) 

Maximum LogKow: 8.0 (ChV) 

Maximum Mol Wt: 1000 

 

----------------------------------------------------------------------------- 

Parent Oryzalin 

SMILES : CCCN(CCC)c1c(cc(cc1N(=O)(=O))S(N)(=O)=O)N(=O)(=O) 

CHEM : Oryzalin 

CAS Num: 

ChemID1: 

ChemID2: 

ChemID3: 

MOL FOR: C12 H18 N4 O6 S1 

MOL WT : 346.36 

Log Kow: 2.73 (KowWin estimate) 

Melt Pt: 

Wat Sol: 2.5 mg/L (experimental database) 

ECOSAR v1.00a Class(es) Found 

------------------------------ 

Dinitrobenzenes 

Amides 

 Predicted 

ECOSAR Class Organism Duration End Pt mg/L 

(ppm) 

=========================== ================== ======== ====== 

========== 

Dinitrobenzenes : Fish 96-hr LC50 3.477 * 
-68 of 69-

Dinitrobenzenes : Daphnid 48-hr LC50 24.885 * 

Dinitrobenzenes : Green Algae 96-hr EC50 0.817 

Dinitrobenzenes : Fish ChV 0.040 

Dinitrobenzenes : Daphnid ChV 0.294 

Dinitrobenzenes : Green Algae ChV 0.103 

Dinitrobenzenes : Fish (SW) 96-hr LC50 3.075 * 

Dinitrobenzenes : Fish (SW) ChV 0.298 ! 

Amides : Fish 96-hr LC50 11.902 * 

Amides : Daphnid 48-hr LC50 8.612 * 

Amides : Green Algae 96-hr EC50 0.478 

Amides : Fish ChV 0.070 

Amides : Daphnid ChV 0.114 ! 

Amides : Green Algae ChV 0.579 

=========================== ================== ======== ====== 

========== 

Neutral Organic SAR : Fish 96-hr LC50 64.922 * 

(Baseline Toxicity) : Daphnid 48-hr LC50 40.896 * 

 : Green Algae 96-hr EC50 23.743 * 

 : Fish ChV 6.065 * 

 : Daphnid ChV 4.294 * 

 : Green Algae ChV 9.810 * 

 Note: * = asterisk designates: Chemical may not be soluble 

 enough to measure this predicted effect. 

 

 Note: ! = exclamation designates: The toxicity value was determined from 

 a predicted SAR using established acute-to-chronic ratios and ECOSAR 

 regression techniques which are documented in the supporting Technical 

 Reference Manual. When possible, this toxicity value should be 

 considered in a weight of evidence approach. 

 

Dinitrobenzenes: 

--------------- 

 For Fish and Daphnid Acute Toxicity Values: If the log Kow of the chemical 

is greater than 5.0, or if the compound is solid and the LC50 exceeds the 

water solubility by 10X, no effects at saturation are predicted for these 

endpoints. 

 

 For Green Algae Acute Toxicity Values: If the log Kow of the chemical is 

greater than 6.4, or if the compound is solid and the EC50 exceeds the water 

solubility by 10X, no effects at saturation are predicted for these 

endpoints. 

 

 For All Chronic Toxicity Values: If the log Kow of the chemical is greater 

than 8.0, or if the compound is solid and the ChV exceeds the water 

solubility 

by 10X, no effects at saturation are predicted for these endpoints. 

 

ECOSAR v1.00 SAR Limitations: 

---------------------------- 

Maximum LogKow: 5.0 (LC50) 

Maximum LogKow: 6.4 (EC50) 

Maximum LogKow: 8.0 (ChV) 

Maximum Mol Wt: 1000 

 

Amides : 

------- 

No limitations known at this time. 

 

ECOSAR v1.00 SAR Limitations: 

---------------------------- 

Maximum LogKow: >8.5 (LC50) 
-69 of 69-

Maximum LogKow: >8.0 (EC50,ChV) 

Maximum Mol Wt: 1000 

 

Baseline Toxicity SAR Limitations: 

--------------------------------- 

Maximum LogKow: 5.0 (Fish 96-hr LC50; Daphnid LC50) 

Maximum LogKow: 6.4 (Green Algae EC50) 

Maximum LogKow: 8.0 (ChV) 

Maximum Mol Wt: 1000 

 

-----------------------------------------------------------------------------