UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

OFFICE OF

PREVENTION, PESTICIDES AND

TOXIC SUBSTANCES

May 19,2010

MEMORANDUM

Subject:

To:

From:

Reviewers:

Through:

Registration Review - Preliminary Problem Formulation for the Ecological Risk

and Drinking Water Exposure Assessments for Fosamine Ammonium

(PC Code: 106701; DP Barcode: 372059)

Russell Wasem, Chemical Review Manager

Risk Management & Implementation Branch 1

Pesticide Re-evaluation Division

Office ofPesticide Programs . d,~~

Rochelle F. H. ~ohaty Ph.I?, c~emlsm~' .

Donna R. Judkins, Ph.D., Biologist ;j / "l J -

Environmental Risk Branch 3 I I

Environmental Fate and Effects Division

Office of Pesticide Programs t,

James Hetrick, Ph.D., Senior SCientist i\'t' .' ; ,0-. Pamela Hurley, Ph.D., Toxicologist ~~

Dana Spatz, Branch Chie~~~ Environmental Risk Branch

Environmental Fate and Effects ivision

Office of Pesticide Programs

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

formulation (attached) for the ecological risk, environmental fate, endangered species, and

drinking water assessments to be conducted as part ofthe Registration Review ofthe

organophosphonate herbicide, fosamine ammonium. This document is intended to provide an

overview ofwhat is currently known regarding the environmental fate and ecological effects

associated with fosamine ammonium and its degradation products, as well as outline

uncertainties regarding attributes ofthe parent compound and its transformation products. It

describes the preliminary ecological risk hypothesis and the processes that will be used during

the completion of drinking water and ecological risk assessments in support ofRegistration

Review.
ii

 

Problem Formulation for the 

Ecological Risk and 

Drinking Water Exposure Assessments 

in Support of the Registration Review of 

Fosamine Ammonium 

O P

O NH2

O O

NH4

Fosamine Ammonium (CAS 25954-13-6) 

ammonium ethyl carbamoylphosphonate 

Prepared by:

Rochelle F. H. Bohaty, Ph.D., Chemist 

Donna R. Judkins, Ph.D., Biologist 

Reviewed by:

James Hetrick, Ph.D., Senior Scientist 

Pamela Hurley, Ph.D., Toxicologist 

Dana Spatz, Branch Chief 

Date

May 19, 2010

U. S. Environmental Protection Agency

Office of Pesticide Programs

Environmental Fate and Effects Division

Environmental Risk Branch 3

1200 Pennsylvania Ave., NW

Mail Code 7507P

Washington, DC 20460
iii

Table of Contents

I. Purpose ....................................................................................................................................... 4 

II. Nature of Regulatory Action...................................................................................................... 4 

A. Regulatory History............................................................................................................... 4 

B. Previous Risk Assessment................................................................................................... 5 

III. Stressor Source and Distribution .............................................................................................. 5 

A. Mechanism of Action.......................................................................................................... 5 

B. Overview of Pesticide Usage .............................................................................................. 6 

C. Environmental Fate and Transport...................................................................................... 6 

Physical and Chemical Properties of Fosamine Ammonium ................................................. 6 

Environmental Fate Properties of Fosamine Ammonium ...................................................... 7 

Environmental Transport Mechanisms of Fosamine Ammonium........................................... 7 

Monitoring Data ................................................................................................................... 10 

IV. Receptors ............................................................................................................................... 10 

A. Effects on Aquatic Organisms .......................................................................................... 11 

B. Effects on Terrestrial Organisms....................................................................................... 13 

C. Adverse Ecological Incidents............................................................................................ 15 

D. Ecosystems at Risk .......................................................................................................... 15 

V. Assessment Endpoints............................................................................................................. 15 

VI. Conceptual Model................................................................................................................... 16 

A. Risk Hypotheses................................................................................................................ 16 

B. Diagram............................................................................................................................. 16 

Direct Terrestrial Uses......................................................................................................... 16 

VII. Analysis Plan Options ........................................................................................................... 17 

A. Ecological Risk Assessment ............................................................................................. 17 

B. Endangered Species........................................................................................................... 18 

C. Drinking Water Assessment.............................................................................................. 18 

D. Clean Water Act................................................................................................................ 19 

E. Anticipated Data Needs .................................................................................................... 20 

Other Information Needs ...................................................................................................... 23 

APPENDIX A............................................................................................................................... 24 

APPENDIX B ............................................................................................................................... 25 
4 

I. Purpose 

The purpose of this problem formulation is to provide a better understanding of the 

environmental fate and ecological effects of the registered uses of fosamine ammonium. 

Fosamine ammonium is a non-selective herbicide used to control undesirable brush/herbaceous 

plant species. This problem formulation uses a previous risk assessment as its basis. This 

document provides a plan for analyzing data relevant to fosamine ammonium and for conducting 

an updated ecological risk assessment for its registered uses. Additionally, this problem 

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

used to address those uncertainties relative to characterizing the ecological risk associated with 

the registered uses of fosamine ammonium. 

II. Nature of Regulatory Action 

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

program for assessing the risks of pesticides, i.e., registration review.1

 All pesticides distributed 

or sold in the United States generally must be registered by EPA. The decision to register a 

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

cause unreasonable risks to human health or the environment when used as directed on product 

labeling. 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 ensure that 

as such changes occur; 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 to determine whether fosamine ammonium continues to meet the FIFRA standard for 

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

chapter supporting the registration review is intended for the initial docket opening the public 

phase of the review process. 

A. Regulatory History 

Fosamine ammonium was first registered on August 12, 1975 under EPA Registration No. 352-

376 (Du Pont Krenite® Brush Control Agent). It was registered for non-cropland (non-food) use 

areas such as railroads, pipeline, utility and highway right-of-ways, reforestation areas, drainage 

ditch banks, storage areas, industrial plants sites, and other similar sites. 

A second product, EPA Registration No. 352-395, was registered on May 2, 1980. This product 

was registered under two trade names, DuPont Krenite® S Brush 5 Control Agent and DuPont 

Krenite® UT Brush Control Agent. In addition to the uses registered in 1975, forestry 

applications are included for this product. 

 

1 http://www.epa.gov/oppsrrd1/registration_review/
5 

The registrant’s request to cancel EPA Registration No. 352-376 (DuPont Krenite® Brush 

Control Agent) was approved and went into effect on June 22, 1994. 

On August 23, 1994, DuPont filed an Application for Amended Registration, requesting 

voluntary cancellation of direct applications to water, ditchbanks, and to other sites adjacent to 

and surrounding domestic water such as supply reservoirs, supply streams, lakes, and ponds. 

In 1995, fosamine ammonium was the subject of a Reregistration Eligibility Decision (RED) 

(EPA 738-R-95-004). All previous uses sites were eligible for reregistration except aquatic sites. 

The Agency approved a new label for DuPont Krenite® S Brush 5 Control Agent on June 5, 

2006 (EPA Registration No. 352-395) which does not include aquatic use sites. 

B. Previous Risk Assessment 

The only risk assessment completed for fosamine ammonium since 1975 was completed in 

conjunction with the 1995 RED. Although fosamine ammonium is highly soluble in water and 

mobile in various soils, the probability of it impacting groundwater quality is low because 

fosamine ammonium degrades rapidly in the environment. Due to lack of definitive fate data, 

the environmental fate and transport of fosamine ammonium transformation products were not 

evaluated at the time of reregistration. The Agency concluded in this assessment that fosamine 

ammonium products, labeled and used on sites as specified in the RED, do not pose 

unreasonable risks of adverse effects to humans or the environment. For avian, mammalian, 

invertebrate, and aquatic studies the estimated risk quotients (RQs) did not exceed the Agency’s 

levels of concern (LOCs). Acute risk to terrestrial plants could not be assessed at the time 

because data were still outstanding for corn, sugarbeet, pea, and cucumber. Chronic exposure 

RQs for small mammals did not exceed Agency LOCs. Chronic data were unavailable for 

terrestrial plants and aquatic fish, invertebrates, and plants. The only level of concern exceeded 

(RQ = 23) was from a mallard reproduction study; however, there is some uncertainly associated 

with the experimental results (D214645). EPA suggested modifying the label to account for the 

potential adverse effects on avian reproduction including threatened and endangered species 

exposed to fosamine ammonium. This change is no longer an issue since EPA later (1997; per 

memo D231023) accepted a mallard reproduction study (MRID 44143501) showing the 

registered uses of fosamine ammonium do not result in RQs that exceed the Agency’s LOCs. 

III. Stressor Source and Distribution 

A. Mechanism of Action 

Fosamine ammonium is the ammonium salt of fosamine (CAS Number 25954-13-6; ammonium 

ethyl carbamoylphosphonate). It is an herbicide belonging to the organophosphonate class of 

pesticides. Fosamine is a non-selective herbicide used to control undesirable brush/herbaceous 

plant species. Mainly fosamine is used for brush control of nonagricultural rights-of-way (e.g., 

highways, railroads, and utilities), industrial sites, and fencerows. Fosamine ammonium controls 

brush growth by inhibiting bud growth the year following application. The exact mechanism of 

action is unknown. 
6 

B. Overview of Pesticide Usage 

Fosamine ammonium is used on a wide variety of terrestrial non-food and forestry applications. 

Target species include american elder, basswood, bigleaf maple, birch, blackberry, black cherry, 

blackgum, black locust, bracken, chinese tallow, chokecherry, eastern cottonwood, eastern pine, 

elm, field bindweed, hawthorn, hickory, leafy spurge, loblolly pine, multiflora rose, persimmon, 

pin cherry, quaking aspen, red alder, red maple, red oak, salmonberry, slippery elm, sassafras, 

sourwood, sumac, sweetgum, sycamore, thimbleberry, tree-of-heaven, tuliptree, vine maple, 

virginia pine, water oak, white ash, white oak, wild grape, wild plum, winged elm, and willow. 

Currently, fosamine ammonium is marketed under the trade name DuPont Krenite S Brush 

Control Agent. Krenite S is an end-use product formulated as a 41.5% soluble fosamine 

ammonium liquid concentrate. The label calls for the concentrate to be diluted in water. Based 

on the product label, application equipment includes helicopter and high or low volume ground 

sprayers. Uses include foliar, broadcast, high volume spray (dilute ≥ 1.5% by volume), low 

volume spray (concentrate, ≤ 30% by volume), and stump treatments. The maximum use rate for 

fosamine ammonium is 24 lbs a.i./A per year. For some uses, the single application rates are 

equal to the maximum annual treatment. Application use rates and methods for fosamine 

ammonium are summarized in Appendix A. Application of fosamine ammonium directly to 

water is not permitted nor is application through an irrigation system. Currently, fosamine 

ammonium is not registered for sale or use in California or Arizona. 

Pesticides with high water solubility, such as fosamine ammonium, do not “wet” (cover) 

properly the waxy (hydrophobic) surfaces of plants. To attain proper coverage and distribution 

of the herbicide on plant surfaces, the label recommends adding a surfactant or crop oil to the 

spray solution. The label also suggests adding an anti-foam agent if foaming is a problem during 

mixing. 

No usage data were reported to the Environmental Fate and Effects Division (EFED). 

C. Environmental Fate and Transport 

Physical and Chemical Properties of Fosamine Ammonium 

The physical and chemical properties of fosamine ammonium are shown in Table 1. Based on 

these physical and chemical properties alone, fosamine ammonium has low potential to volatilize 

from soils (vapor pressure) or from water (Henry’s Law Constant). It is also unlikely to 

bioaccumulate in fish given the low value of the Log n-octanol/water partition coefficient. 

Appendix B provides the chemical structures fosamine ammonium and its known degradates. 
7 

Table 1. Physical and Chemical Properties of Fosamine Ammonium 

Common name Fosamine Ammonium 

Chemical name ammonium ethyl carbamoylphosphonate 

Pesticide type herbicide 

Chemical class orthophosphonate 

CAS number 25954-13-6 

Empirical formula C3H11O4N2P 

Molecular mass (g/mol) 170.11 

Vapor pressure 4 x 10-6 mm Hg (25° C) 

5.3 x 10-3 Pa (25° C) 

Henry’s Law Constant 5.04 x 10-7 PA m3/mol (calculated) 

Solubility in water 1,795,000 mg L-1 (20°C) 

1,790,000 mg L-1 (25° C)1

Kow 0.0012 (0.00104-0.00139) 

Melting Point 173-175° C (tech.) 

1

http://www.invasive.org/gist/products/handbook/13.Fosamine.pdf 

Environmental Fate Properties of Fosamine Ammonium

Fosamine ammonium is highly solubility in water. However, it does not break down by abiotic 

processes, such as hydrolysis and photolysis (MRIDs 40133701, 40133702, and 40133703). In 

the environment, its major route of dissipation is through rapid microbial-mediated degradation. 

One aerobic soil metabolism study indicates the half-life of fosamine ammonium is 0.5 days 

(MRID 42060601). Supplemental soil metabolism data indicate the half-life of fosamine 

ammonium can extend to 12 days depending on the soil (MRID 141554). No aerobic aquatic 

metabolism data have been submitted to the EPA. No degradation is observed for fosamine 

ammonium under anaerobic conditions (MRIDs 42060602 and 42680701). Major degradates 

(>10% of the applied) of fosamine ammonium are carbamolyphosphonic acid (CPA) and 

carboxylphosphonic acid (ING-3003), and carbon dioxide (MRIDs 42020206 and 42724301). 

There is limited environmental fate data available for CPA and ING-3003. 

Table 2 summarizes the environmental fate behavior of fosamine ammonium and its degradates. 

These data are taken from studies submitted in support of the registration or reregistration of 

fosamine ammonium. 

Environmental Transport Mechanisms of Fosamine Ammonium 

Fosamine ammonium is not expected to dissipate through volatilization from soil or water 

(MRID 42492201). 

Fosamine ammonium has a low Koc indicating that it can leach to groundwater and that it can 

move to surface water at high levels through runoff. However, this scenario is unlikely due to 

rapid microbial-mediated degradation of fosamine ammonium in soil. 

For three of the four acceptable studies submitted to EPA, the calculated Kd for fosamine 

ammonium ranges from 0.11 to 0.14 and Koc rangesfrom 3 to 13 mL/g. Based on these 
8 

Table 2. Environmental Fate Data for Fosamine Ammonium 

Study/Current 

Guidelines Value Major Degradates1/ Comments MRID 

Hydrolysis 

835.2120 0, Stable None 40133701 

Photodegradation 

in Water 

835.2240 

0, Stable None 40133702 

Photodegradation 

on Soil 

835.2410 

0, Stable None 40133703 

Laboratory 

Volatility 

835.1410 

<0.00631 μg/cm2/hour 

<22μg/m3

Fosamine ammonium (2% AR in soil) CPA (max 89% AR in soil) IN-G3003 (max 15% in soil) 

42492201 

Aerobic Soil 

Metabolism 

835.4100 

t1/2 = 0.5 to 12 days 

CPA (max 94% AR immediately posttreatment) t1/2 = 144 days 

IN-G3003 (max 26% AR at 1 month posttreatment) t1/2 = 34 days Total residue t1/2 = 204 days; observed DT50 = 220 

CO2 (max at 33% at study termination) 

42060601 

141554 

Anaerobic 

Aquatic 

Metabolism 

835.4400 

t1/2 = 2 days 

CPA (max 59% AR at 14 days posttreatment) t1/2 = 12 days 

ING-3003 (max 43% AR at 9 months posttreatment) CO2 (max at 7.6% at 12 months--study termination) 

42060602 42680701 42724301 
9 

Study/Current 

Guidelines Value MRID 

Soil Kd (mL/g) Koc (mL/g) KF(ad) (μg 1-1/n (cm3)1/n g -1) 1/n KFoc (μg 1- 1/n (cm)1/n g -1) 

New Jersey 

sandy loam > 1 8.087 0.066 0.8603 

Woodstown 

sandy loam 0.14 13.249 0.14 0.98 13.249 

Cecil sandy 

loam 0.11 5.302 0.11 ~1 5.302 

Adsorption/ 

Desorption 

(Batch 

equilibrium) 

835.1230 

Flanagan silt 

loam 0.11 2.645 0.11 ~1 2.645 

42492401 40133704 42492301

Study/Current 

Guidelines Value Major Degradates1/ Comments MRID 

Terrestrial Field 

Dissipation 

835.6100 

1 d Lexington, TN 1 d Newark, DE 5 d Fayetteville, NC 

Fosamine ammonium found predominantly in the 0 to 15 cm soil samples. CPA (max at 26.7% at six weeks, DE silt loam; max at 40% at six weeks, IL silt loam; and 83% at two weeks, FL sandy loam) 

40955701 

Fish BCF 

850.1730 

No accumulation observed therefore no BCF could be calculated. A 9% observed mortality. 42587601 

1 Major degradates are defined as those that >10% of the applied. 
10 

Koc values, fosamine ammonium is classified as highly mobile according to the Food and 

Agriculture Organization (FAO) of the United Nations classification scheme. 

Terrestrial field data indicate that fosamine ammonium degrades rapidly. This is 

consistent with aerobic soil metabolism data. 

Average concentrations of fosamine ammonium in bluegill sunfish is 0.337 mg/kg (whole fish), 

while 0.334 mg/kg is observed in fillet tissues and 0.348 mg/kg in viscera tissues. The Kow of 

fosamine ammonium is low (less than 0.0012). These data indicate fosamine ammonium 

residues should not accumulate in fish tissues. 

Monitoring Data 

No surface or ground water monitoring data are available for fosamine ammonium. 

IV. Receptors 

Consistent with the process described in the Overview Document,2 the risk assessment for 

fosamine ammonium will rely on a surrogate species approach. Toxicological data generated 

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

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

taxonomic groupings. 

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 fosamine 

ammonium on aquatic and terrestrial receptors. Toxicity studies for the technical grade active 

ingredient (TGAI) and the typical end-use product will all be considered in the ecological risk 

assessment. Open literature studies are identified using EPA’s ECOTOX database3

 that employs 

a literature search engine for locating chemical toxicity data for aquatic life, terrestrial plants, 

and wildlife. Research papers accepted into the ECOTOX database are screened using standard 

procedures to ensure consistent, high quality information; these studies will be considered during 

the ‘Analysis’ phase of risk assessment process. The Ecological Incident Information System 

(EIIS, version 2.1) and the Avian Monitoring Information System (AIMS) will be used to 

identify supportive, line of evidence information on exposure of aquatic and terrestrial receptors. 

Data from all of these sources can also provide insight into the direct and indirect effects of 

fosamine ammonium 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. 

 

2Overview of the Ecological Risk Assessment Process in the Office of Pesticide Programs. Office of Prevention, 

Pesticides, and Toxic Substances. Office of Pesticide Programs. Washington, D.C. January 23, 2004. 

3

 http://www.epa.gov/ecotox
11 

A. Effects on Aquatic Organisms 

Acute aquatic toxicity data are available for consideration in this ecological risk assessment for 

fosamine ammonium; however, chronic toxicity data are unavailable. Table 3 provides a 

summary of the taxonomic groups and the surrogate species tested to characterize the potential 

acute and chronic aquatic effects of fosamine ammonium. 

Data from fish acute toxicity studies reviewed for the RED indicate that fosamine ammonium is 

practically nontoxic to coldwater and warm water fish (MRIDs 41607103, 41607102, and 

00129075). The most sensitive LC50s for freshwater and saltwater fish, respectively, are 377 

ppm a.i. for rainbow trout and >128 ppm a.i. for sheepshead minnows (MRID 42715101), 

using technical grade fosamine ammonium. No data are available from freshwater or 

estuarine/marine fish early life-stage or life-cycle studies. 

Fosamine ammonium is practically nontoxic to freshwater and estuarine/marine 

invertebrates on an acute basis. The most sensitive acute endpoint for freshwater 

invertebrates is the Daphnia magna LC50 of 1524 ppm a.i. using technical grade fosamine 

ammonium (MRIDs 00143492 and 92086005). The eastern oyster LC50 is >122 ppm a.i. 

This study was also conducted using technical grade fosamine ammonium (MRID 

42715102). 

There are no chronic toxicity data available to assess the potential risk of fosamine ammonium 

and its major degradates to fish or aquatic invertebrates; this is a major source of uncertainty in 

the ecological risk assessment. 

Tier I aquatic plant studies with both non-vascular and vascular plants (MRIDs 42902904 

and 42587602, respectively) resulted in EC50s that are above the EEC in the most recent 

RED. The duckweed study, however, had an EC40 at EEC. 
12 

Table 3. Aquatic Toxicity Profile for Fosamine Ammonium 

Study/Current Guidelines Taxon Exposure Duration Most Sensitive Species Tested 

Toxicity 

Value 

mg a.i./L 

Acute Toxicity 

Category1 

Fish Acute Toxicity Test, 

Freshwater and Marine 

850.1075 

Freshwater Fish Acute Rainbow trout, Oncorhynchus mykiss LC50= 377 Practically nontoxic 4

Fish Acute Toxicity Test, 

Freshwater and Marine 

850.1075 

Estuarine/ Marine Fish Acute Sheepshead minnow, Cyprinodon variegatus LC50= >128 Practically nontoxic 4

Aquatic Invertebrate Acute Toxicity Test, 

Freshwater Daphnids 

850.1010 

Freshwater 

Invertebrates 

Acute Water Flea, 

Daphnia magna 

LC50= 1524 Practically 

nontoxic 

00

9

Oyster Acute Toxicity Test 

(Shell Deposition) 

850.1025 

Estuarine/ Marine 

Invertebrates Acute Eastern oyster LC50 = >122 Practically nontoxic 4

Algal Toxicity, 

Tiers I and II 

850.5400 

Non-vascular plant Tier I Alga, Skeletonema costatum EC25 = >15 NOAEC = 15 Slightly toxic to practically nontoxic 4

Aquatic Plant Toxicity 

Test Using Lemna spp., 

Tiers I and II 

850.4400 

Vascular plant Tier I Duckweed, Lemna gibba 

EC50 = >21 

(EC40 = 21) 

NOAEC = 

<21 

Slightly toxic to 

practically 

nontoxic 

4

1Categories of acute toxicity for aquatic organisms (U.S. EPA, 2004) based on LC50 (mg/L): < 0.1 very highly toxic; 0.1-1 highly toxic; >1-10 mode

toxic; >100 practically nontoxic. Toxicity categories for aquatic plants have not been defined. 
13 

B. Effects on Terrestrial Organisms 

Laboratory and field toxicity studies are available for characterization of the effects from acute 

exposures of fosamine ammonium to birds (also surrogate for terrestrial-phase amphibians and 

reptiles), mammals, and terrestrial invertebrates. Table 4 provides a summary of the most 

sensitive species tested for each terrestrial taxonomic group. 

Data from the avian single-dose studies show fosamine ammonium to be practically nontoxic to 

avian species on an acute basis, with LD50s of greater than 5000 mg/kg (the highest dose tested) 

for 99.4% TGAI fosamine ammonium in both mallard and bobwhite quail (MRIDs 00093715 

and 00130225, respectively). Exposure calculations cited in the 1995 RED suggest that the 

right-of-way use may produce concentrations that are close to, and may exceed, 5000 ppm (5670 

maximum residue on short grass from 24 lb a.i./A application). This is an uncertainty, especially 

for passerine species which may be more sensitive, and for which we have no toxicity data. 

Avian subacute toxicity data show fosamine ammonium to be practically nontoxic via dietary 

exposure. The LC50 (>5620 ppm) is estimated to be greater than the highest dose tested for both 

mallards and quail (MRIDs 41891602 and 41891603, respectively). 

In the submitted avian reproduction study, the highest dose level tested, 11,600 ppm, did not 

produce effects. This is above the maximum EEC from the most recent risk assessment, 5760 

ppm on short-grass. 

The rat LD50 for formulated fosamine ammonium is 24,400 mg/kg. This value characterizes the 

acute toxicity to mammals as practically nontoxic (MRIDs 00075735 and 00026835). 

Technical fosamine ammonium (95% a.i.) was shown to be practically nontoxic to the honey 

bee. The estimated LD50 is >200 μg/bee (MRID 41215802). 

Applications of fosamine ammonium at the registered rates may pose a significant risk to 

endangered plant species inhabiting treated rights-of-way. The test data were not calculated at 

the time of the RED due to lack of acceptable data. Data accepted since the RED show, upon 

preliminary risk assessment, that terrestrial plants are under considerable risk especially from the 

right-of-way use (application rate 12 - 24 lb a.i./A). Comparing the maximum application rate to 

the most sensitive plant acute endpoints presented in Table 4, result in acute RQs of 4 and 57 for 

seedling emergence and vegetative vigor, respectively (MRIDs 42647601 and 43651101). This 

exceeds the Agency’s LOCs.1 A complete risk assessment will be done during registration 

review. 
14 

Table 4. Terrestrial Toxicity Profile for Fosamine Ammonium 

Guideline Taxon Exposure Duration Most Sensitive Species Tested Toxicity Value Acute Toxicity Category 

Acute 

Rat 

Rattus norvegicus

Waived; LD50 >1954 mg a.i./Kg bw 

(adjusted for 97.7% purity) from acute 

neurotoxicity study with no deaths up 

to HDT1 (2000 mg tech/kg bw)

Practically 

nontoxic 

Mammal Acute 

Toxicity 

850.2400 

Mammals 

Chronic Rat 

R. norvegicus

NOAEC = 200 mg/Kg/d 

LOAEC = 1000 mg/Kg/d

N/A 

Avian Acute Oral 

Toxicity Test 

850.2100 

Acute Oral 

Northern bobwhite 

quail 

(Colinus 

virginianus) 

Mallard 

(Anas 

platyrhynchos) 

Passerine 

LD50= >5000 mg/Kg bw LD50= >5000 mg/Kg bw 

Data Gap 

Practically 

nontoxic 

Practically 

nontoxic 

Avian Dietary 

Toxicity 

Test 

850.2200 

Sub-acute 

Dietary 

Quail and mallard 

(C. virginianu and

A. platyrhynchoss)

>5620 ppm diet Practically nontoxic 

Avian Reproduction 

Test 

850.2300 

Birds 

Chronic 

Reproduction 

Mallard 

A. platyrhynchoss

NOAEC = 11,600 ppm 

LOAEC = >11,600 ppm 

(mg/Kg/d) 

Practically 

nontoxic 

Honey Bee Acute 

Contact Toxicity 

850.3020 

Terrestrial 

Invertebrates Acute Honey Bee Apis mellifera LD50 = >200 ug a.i./bee Practically nontoxic 

Rape, shoot length 

inhibition 

EC25 = 2.3 

EC50 = 5.8 NOAEL = 1.5 lb a.i./acre 

Terrestrial Plant 

Toxicity, 

Tier II 

850.4100 850.4150 

Tier II – 

Seedling 

Emergence 

Vegetative Vigor Soybean, total weight inhibition EC25 = 0.099 EC50 = 0.42 NOAEL = <0.094 lb a.i./acre 

N/A 

1 HDT = highest dose tested. 
15 

C. Adverse Ecological Incidents 

A preliminary review of the Ecological Incident Information System (EIIS)4

 maintained by the 

Agency’s Office of Pesticide Programs (OPP) produced one incident (I015280-001; June 4, 

2004). According to the incident report spray drift from the registered uses of fosamine 

ammonium “possibly” caused plant damage to cantaloupe (1 acre), tomato (2 acres) and 

watermelon (1-2 acres) crops. A search of the American Bird Conservancy’s database revealed 

no incident data.5

 The reported incident suggests that exposure pathways for fosamine 

ammonium are complete and exposure levels sufficient to result in field-observable effects. 

 D. Ecosystems at Risk 

Fosamine ammonium may be applied as an aerial or ground spray herbicide to terrestrial habitats 

for agricultural uses, and as a spot treatment in non-agricultural areas. The ecosystems 

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

specific ecosystems at risk 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 spray drift or runoff. Areas adjacent to the 

treated field could include residential areas, cultivated fields, fencerows, hedgerows, meadows, 

fallow fields, grasslands, woodlands, riparian habitats, and other uncultivated areas. 

Fosamine ammonium has the potential to contaminate surface water through spray drift and 

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

from a treated field. Such water bodies may include ponds, lakes, reservoirs, streams, rivers, and 

estuaries. 

V. Assessment Endpoints 

The most sensitive toxicity endpoints are used from surrogate test species to estimate treatmentrelated direct effects on acute mortality and chronic reproductive, growth, and survival 

assessment endpoints. Surrogate aquatic organisms include freshwater and estuarine/marine fish 

and invertebrates. Surrogate terrestrial animal species include birds and mammals. The risk 

assessment also assumes that reptiles and terrestrial-phase amphibians are approximately as

sensitive to pesticide-induced effects as birds. These tests include short-term acute, subacute, 

and reproduction studies. They are also typically arranged in a hierarchical or tiered system that 

progresses from basic laboratory tests to applied field studies. Incidents of toxicity from field 

uses will also be considered as lines of evidence.

For plants in terrestrial and semi-aquatic environments, the screening assessment endpoint is the 

perpetuation of populations of non-target species (crops and non-crop plant species). When data 

are available, endpoints assessed include emergence of seedlings and vegetative vigor. For 

aquatic plants, the assessment endpoint is the maintenance and growth of standing crop or 

biomass. When data are available, measurement endpoints for this assessment endpoint focus on 

 

4 EIIS was accessed on January 12, 2010.

5

 American Bird Conservancy database was assessed on January 13, 2010.
16 

algal and vascular plant (i.e., duckweed) growth rates and biomass measurements. Incidents of 

phytotoxicity from field uses will also be considered as lines of evidence. 

VI. Conceptual Model 

A. Risk Hypotheses 

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

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

or probability models.2 For this assessment, the risk is stressor-initiated, where the stressor is the 

release of fosamine ammonium to the environment. The following risk hypothesis is presumed 

for this screening-level assessment: 

When used in accordance with current labels for terrestrial applications, fosamine 

ammonium and its degradates can move off-site via runoff (both dissolved phase and with 

eroded sediment) and spray drift to expose non-target organisms. Application to foliar 

surfaces and soil may also result in exposure to non-target organisms. These potential 

exposure pathways may result in adverse effects on the survival, growth, and/or 

reproduction of non-target terrestrial and aquatic organisms, including federally-listed 

threatened and endangered species. 

B. Diagram 

Direct Terrestrial Uses 

The environmental fate properties indicate that runoff of dissolved fosamine ammonium, erosion 

of fosamine ammonium bound sediment, and spray drift represent potential transport 

mechanisms for fosamine ammonium and its degradates to aquatic and terrestrial organisms. As 

depicted in Figure 1, these transport mechanisms (e.g. sources) for spray (ground, aerial) 

applications may result in the movement of fosamine ammonium into aquatic (water) and 

terrestrial (soil and foliage) habitats. The movement away from the site of application represents 

exposure pathways for a broad range of biological receptors of concern (non-target animals) and 

the potential attribute changes, i.e., effects such as reduced survivals, growth, and reproduction 

in the receptors. 
17 

Figure 1. Conceptual Model for Effects of Fosamine Ammonium on Non-target Aquatic 

and Terrestrial Organisms for Direct Terrestrial Use Patterns 

VII. Analysis Plan Options 

As part of Registration Review, pesticide ecological risk assessments will follow EPA’s 

Guidelines for Ecological Risk Assessment,6 will be consistent with the EPA’s overview 

document,2 and will be done in accordance with Section 7 of the Endangered Species Act. 

 A. Ecological Risk Assessment 

Previously completed risk assessments indicate that fosamine ammonium is practically nontoxic 

to aquatic and terrestrial animals and the registered uses do not produce RQs that exceed the 

Agency’s LOCs. Use of fosamine ammonium may, however, directly affect terrestrial plants, 

especially from the right-of-way use (RQs = 4 and 57 for seedling emergence and vegetative 

vigor, respectively, see above) and through loss of food source, indirectly affect animals 

depending on terrestrial plants for food or habitat. The registered uses of fosamine ammonium 

do not result in RQs that exceed Agency LOC for aquatic plants on an acute basis. Chronic risk 

 

6Guidelines for Ecological Risk Assessment, United States Environmental Protection Agency, Washington, D.C.: 

Government Printing Office. Available at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=12460 (Accessed 

June 19, 2009).

Stressor 

Source/ 

Transport 

Pathways 

Volatilization/ 

Wind Suspension

Direct 

Deposition

Spray 

Drift 

Runoff/ 

Erosion 

Leaching 

(infiltration/ 

percolation) 

Source/ 

Exposure 

Media 

Terrestrial Food 

Residues (foliage, 

fruit, insects) 

Upland 

Foliage/Soil

Riparian/ 

Wetland 

Foliage/Soil

Water 

Column/ 

Sediment 

Groundwater 

Exposure 

Point 

Ingestion Direct contact Direct contact Gill/ 

 Integument Uptake 

Receptors

Attribute 

Changes 

Terrestrial Vertebrates

Birds, Small Mammals, 

Reptiles, Terrestrial 

Insects 

Terrestrial

Upland 

Plants 

Individual Animals

 Reduced survival 

 Reduced growth 

 Reduced reproduction 

Aquatic Invertebrates 

Aquatic Vertebrates 

Amphibians 

Aquatic Plants 

Wetland/ 

Riparian 

Plants 

Individual Plants

 Seedling emergence 

 Vegetative vigor 

Individual 

Vertebrates and 

Invertebrates

 Reduced 

 survival 

 Reduced 

 growth 

 Reduced 

 reproduction 

Food Web Exposure 

(biconcentration) 

Piscivourous 

Vertebrates

Birds, 

Mammals 

Individual 

Animals

 Reduced 

 survival, 

 growth, and 

 reproduction 

Plant 

Population

 Reduced 

 population 

 growth 

Fosamine ammonium applied as ground/aerial spray in agricultural and residential 

settings. 
18 

to aquatic plants has not been assessed since none of the registered uses include direct 

application to water. If such uses are requested, chronic tests will be required. 

Preliminary identification of data gaps include: 

• Toxicity of fosamine ammonium to passerine bird species (OPPTS Guideline 850.2100). 

• Chronic toxicity and sublethal effects of fosamine ammonium to aquatic invertebrates and 

fish (OPPTS Guidelines 850.1300 and 850.1400). 

B. Endangered Species 

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

evaluate risks to federally-listed threatened and/or endangered (listed) species from registered 

uses of fosamine ammonium. This assessment will be conducted in accordance with the 

Overview Document2

, provisions of the ESA, and the Services’ Endangered Species 

Consultation Handbook7. 

The assessment of effects associated with registrations of fosamine ammonium is based on an 

action area. The action area is considered to be the area directly or indirectly affected by the 

federal action, as indicated by the exceedance of Agency LOCs used to evaluate direct or indirect 

effects. The Agency’s approach to defining the action area under the provisions of the Overview 

Document2

 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 fosamine ammonium application occurs), plus all 

areas where offsite transport (i.e., spray drift and runoff) 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 sublethal 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 is not spatially limited and is assumed to be the entire United States. 

C. Drinking Water Assessment 

A drinking water assessment has not been completed for fosamine ammonium. Prior to the 

enactment of FQPA, a drinking water assessment was not required for non-food use chemicals; 

therefore, a drinking water assessment will need to be completed as part of the human health 

 

7Endangered Species Consultation Handbook: Procedures for Conducting Consultation and Conference Activities 

Under Section 7 of the Endangered Species Act. Final Draft, United States Fish and Wildlife Service (USFWS) and 

National Marine Fisheries Service (NMFS). Washington, D.C.: Government Printing Office. Available at 

http://www.fws.gov/endangered/consultations/s7hndbk/s7hndbk.htm (Accessed June 19, 2009). 
19 

dietary risk assessment. Tier I Estimated Drinking Water Concentrations (EDWCs) for human 

health assessments will be estimated using EFED’s aquatic models FIRST (FQPA Index 

Reservoir Screening Tool, version 1.0, August 1, 2001) for surface water and SCI-GROW 

(Screening Concentration in Groundwater, version 2.3, August 8, 2003) for ground water.

8

 

If needed, Tier II EDWCs in surface water will be estimated using PRZM (Pesticide Root Zone 

Model, version 3.12.3, June 2006) and EXAMS (EXposure Analysis Modeling System, version 

2.98.04.06, April 2005) models in the PE5 shell. PRZM is used to simulate pesticide transport in 

soil within and immediately below the plant root zone. EXAMS estimates the fate, transport, 

and exposure concentration of pesticides in an index reservoir from surface water for an 

agricultural watershed.8

D. Clean Water Act 

Fosamine ammonium is not identified as a cause of impairment for any water bodies listed as 

impaired under section 303(d) of the Clean Water Act, based on information provided at 

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

In addition, no Total Maximum Daily Loads (TMDL) have been developed for fosamine 

ammonium, based on information provided at 

http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id

=885&p_pollutant_group_name=PESTICIDES. More information on impaired water bodies and 

TMDLs can be found at http://www.epa.gov/owow/tmdl/. 

EPA invites submission of water quality data for this pesticide. To the extent possible, data 

should conform to the quality standards in Appendix A of the OPP Standard Operating 

Procedure: Inclusion of Impaired Water Body and Other Water Quality Data in OPP’s 

Registration Review Risk Assessment and Management Process (see: 

http://www.epa.gov/oppfead1/cb/ppdc/2006/november06/session1-sop.pdf), in order to ensure 

they can be used quantitatively or qualitatively in pesticide risk assessments. 

 

8

 http://www.epa.gov/oppefed1/models/water/index.htm.
20 

E. Anticipated Data Needs 

Guideline Number: OPPTS 850.2100 

Study Title: Avian Acute Oral Toxicity

Test Species: Passerine Species

Rationale for Requiring the Data

Acute risk to passerines as a result of exposure to fosamine ammonium has not been considered in 

previous assessments since there are no acute oral toxicity data available. Current Part 158 data 

requirements (CFR 40 2007) specify that acute avian oral toxicity data be submitted for either mallard

duck or bobwhite quail AND a passerine species. (A protocol for the acute oral toxicity test with the 

house sparrow should be submitted to the Agency prior to test initiation.) Without this study, the Agency 

would have to presume risk to listed and non-listed passerines, and would not be able to quantify the risk. 

Practical Utility of the Data

How will the data be used?

Acute oral avian toxicity data will be used to quantitatively estimate the risk of fosamine ammonium to 

birds (and terrestrial-phase amphibians and reptiles) and to define an action area for endangered species 

and explore risk mitigation strategies. These toxicity data will reduce uncertainties associated with the 

risk assessment for passerines. In the absence of data on fosamine ammonium, quantitative risk 

estimation will not be possible. Therefore, determination of the distance from a treated field to which the 

risk to passerines may extend and application rate reductions resulting in no LOC exceedances cannot be 

quantified without these data. The current method of calculating a weight-adjusted LD50 using 

bobwhite quail or mallard duck data may over- or under-estimate risks to passerines because 

these birds may metabolize the chemical differently. 

How could the data change the Agency’s decision or impact the Agency’s future decision-making? 

The value of these acute oral toxicity studies would be in quantifying and potentially refining risks to 

passerine birds. Defining an action area for endangered species and exploring risk mitigation strategies 

for passerines cannot be accurately evaluated without these data. If future endangered species risk 

assessments are performed without these data, the Agency will assume that fosamine ammonium “may 

affect” passerines directly, and use of fosamine ammonium 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 fosamine ammonium which are unnecessarily severe. Because the 850.2100 guideline 

has not yet been finalized, protocols for the study of passerine species should be submitted to 

EPA for approval prior to study initiation. 
21 

Guideline Number: 850.1400

Test Substance: Fosamine Ammonium 

Study Title: Fish Early Life-Stage (freshwater) 

Test Species: Rainbow trout (Oncorhynchus mykiss) or Bluegill sunfish (Lepomis macrochirus)

Rationale for Requiring the Data 

The freshwater fish early life-stage test using TGAI is currently listed as “Required” in 40 CFR 

part 158 for all out-door uses, unless they are only residential (exclusion does not apply to turf). 

Data are required on one freshwater fish species. If the test species is different from the two 

species used for the freshwater fish acute toxicity tests, a 96-h LC50 on that species must also be 

provided. 

Without this study, the Agency would have to presume chronic risk to listed and non-listed fish, 

but would not be able to quantify the risk. 

Practical Utility of the Data 

How will the data be used? 

The freshwater fish early life-stage test data would allow the Agency to refine the screening level 

risk assessment for Registration Review. The study would allow the Agency to analyze chronic 

effects, including effects on reproductive success and growth, to fish. The effects data would be 

used to determine the likelihood that the chronic risks can potentially impact aquatic 

communities, either by direct effects on fish or by indirect effects on fish and other organisms 

that feed on them. 

This data will, in turn, be used to calculate a fish ACR for fosamine ammonium, which will be 

applied to the saltwater fish acute data to calculate a more refined chronic saltwater fish toxicity 

endpoint. 

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 fosamine ammonium "may affect" fish directly and other taxa that 

feed on fish, indirectly. The use of fosamine ammonium might need to be restricted in areas 

where these species could be exposed. The lack of these data would limit the flexibility the 

Agency and registrants have and could result in unnecessarily severe use restrictions for fosamine 

ammonium.
22 

Guideline Number: 850.1300

Test Substance: Fosamine Ammonium 

Study Title: Aquatic Invertebrate Life-Cycle (freshwater) 

Test Species: Water Flea (Daphnia magna)

Rationale for Requiring the Data 

The freshwater invertebrate life cycle test using TGAI is currently listed as “Required” in 40 CFR 

part 158 for all out-door uses, unless they are only residential (exclusion does not apply to turf). 

Data are required on one freshwater invertebrate species. 

Without this study, the Agency would have to presume chronic risk to listed and non-listed 

aquatic invertebrates, but would not be able to quantify the risk. 

Practical Utility of the Data 

How will the data be used? 

The freshwater invertebrate life cycle test data would allow the Agency to refine the screening 

level risk assessment for Registration Review. The study would allow the Agency to analyze 

chronic effects, including effects on reproductive success and growth, to freshwater invertebrates. 

The effects data would be used to determine the likelihood that the chronic risks can potentially 

impact aquatic communities, either by direct effects on invertebrates or by indirect effects on fish 

and other organisms that feed on them. 

This data will, in turn, be used to calculate an aquatic invertebrate ACR for fosamine ammonium, 

which will be applied to the saltwater invertebrate acute data to calculate a more refined chronic 

saltwater invertebrate toxicity endpoint. 

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 fosamine ammonium "may affect" aquatic invertebrates directly and 

other taxa that feed on them, indirectly. The use of fosamine ammonium might need to be 

restricted in areas where these species could be exposed. The lack of these data would limit the 

flexibility the Agency and registrants have and could result in unnecessarily severe use 

restrictions for fosamine ammonium.
23 

Other Information Needs 

There is specific information that will assist EPA in refining the ecological risk assessment, 

including any species-specific effects determinations. EPA is interested in obtaining the 

following information: 

1. confirmation on the following label information 

a. sites of application 

b. formulations 

c. application methods and equipment 

d. maximum application rates 

e. frequency of application, application intervals, and maximum number of 

applications per season 

f. geographic limitations on use 

2. use or potential use distribution (e.g., acreage and geographical distribution of relevant 

crops) 

3. use history 

4. median and 90th percentile reported use rates (lbs ai/acre) from usage data – national, 

state, and county 

5. application timing (date of first application and application intervals) by crop – national, 

state, and county 

6. sub-county crop location data 

7. usage/use information for non-agricultural uses (e.g., forestry, residential, rights-of-way) 

8. directly acquired county-level usage data (not derived from state level data) 

a. maximum reported use rate (lbs ai/acre) from usage data – county 

b. percent crop treated – county 

c. median and 90th percentile number of applications – county 

d. total pounds per year – county 

e. the year the pesticide was last used in the county/sub-county area 

f. the years in which the pesticide was applied in the county/sub-county area 

9. typical interval (days) 

10. state or local use restrictions 

11. ecological incidents (non-target plant damage and avian, fish, reptilian, amphibian and 

mammalian mortalities) not already reported to the Agency 

12. monitoring data 

The analysis plan will be revisited and may be revised depending upon the data available in the 

open literature and the information submitted by the public in response to the opening of the 

Registration Review docket. 
24 

APPENDIX A 

Maximum Fosamine Ammonium Use Rate and Management Practices 

(Generalized Screening Level Portrayal of Current Label Uses. Source: current label; accepted June 5, 2006) 

Group name Uses represented Max. Rate 

per App. (lb 

a.i./A) 

Seasonal 

Max. 

Dose/Year 

(lb) 1 

Application 

Method 2

Terrestrial 

Non-Food 

Crop 

Agricultural and 

nonagricultural right-ofway/fencerows/hedgerows 

Agricultural uncultivated 

areas 

Airports/landing fields 

Industrial areas (outdoor) 

Nonagricultural 

uncultivated areas/soils 

Sewage disposal areas 

24 12 (aerial) 

24 (ground) 

Aerial and 

ground 

Forestry Pine (forest/shelterbelt) 6 12 Aerial and 

ground 

1

Application methods reported for any labeled application rates (maximum rate per application and/or seasonal 

maximum dose/year) for that crop/use. The term ground includes any of the ground methods previously defined as 

ground. In some cases when both aerial and ground application methods are reported for a crop/use, both methods 

may not be used at the maximum reported application rates (single application and/or seasonal application). 

2

 Aerial refers to helicopter application only. 
25 

APPENDIX B 

Chemical Structures 

Fosamine Ammonium; DXP-R1108 

O P

O NH2

O O

NH4

Carbamoylphosphonic Acid; CPA; INT-3691 

O P

O NH2

O O

Carboxylphosphonic Acid; ING-3003 

O P

O O

O O