Page 2 of 39 

levels to aquatic invertebrates resulting from propoxur’s expected use as a spot treatment. 

However, this risk is limited to spot treatments which occur nearby streams or water bodies. Please 

note that risk quotients (RQs) are not calculated considering that the application rate is not 

specified on the labels. Therefore, the risk conclusions are supported based upon the threshold 

amount of propoxur used to induce adverse impacts. The potential exposure is then characterized 

by considering this threshold amount determined in context with its low overall usage. Although 

risks to aquatic organisms are possible to aquatic organisms within water bodies which are close 

to propoxur spot treatments, risks to terrestrial taxa are not indicated for the outdoor uses for 

propoxur. 

Given these conclusions, EFED has identified the following uncertainties: 

1.) The header language for two labels1

 includes terminology including perimeter treatments, 

and there is some ambiguity as to the scope of these perimeter treatments as indicated on 

the labels. For this preliminary ecological risk assessment, as explained in Section 2.2,

EFED assumed that such applications to building perimeters are spot treatments and not 

full perimeter applications. Clarification of this label language is important since full 

perimeter treatments can result in substantially greater application of pesticide and 

subsequent runoff to aquatic ecosystems. 

2.) Protective language on the label to prevent propoxur outdoor spot treatment applications 

close to the vicinity of streams and other water bodies is not explicit on eight labels2

. As 

mentioned above, propoxur is very toxic to aquatic organisms and it has the potential for 

exposure via runoff to water bodies located nearby spot treatments. Otherwise, minimal 

exposure is expected with propoxur application away from water bodies given the low 

amounts of propoxur historically used given the nature of spot treatment applications. 

Please refer to Sections 3.1 and 3.2 which provide a description of the potential exposure 

based upon propoxur’s expected use as an outdoor spot treatment. 

 

1

 Including product Reg. nos. 84396-12 and 499-501. 

2

 Including product Reg. nos. 84396-12, 499-501, 655-546, 6218-24, 655-796, 82644-1 
Page 3 of 39 

 

Environmental Fate and Ecological Risk Assessment 

for the Registration Review of Propoxur 

2 – (1 – Methylethoxy) phenol methylcarbamate 

(Propoxur, CAS 000114-26-1) 

Prepared by:

Hannah Yingling, Biologist 

Gabe Rothman., Environmental Scientist 

U. S. Environmental Protection Agency 

Office of Pesticide Programs 

Environmental Fate and Effects Division

Environmental Risk Branch IV 

1200 Pennsylvania Ave., NW 

Mail Code 7507P 

Washington, DC 20460

Reviewed by: 

Al Vaughan, RAPL 

Keith Sappington,., Senior Biologist 

José Meléndez, Chemist 

Mah Shamim, Branch Chief
Page 4 of 39 

Table of Contents 

1. Executive Summary ................................................................................................................ 5

1.1 Nature of Chemical Stressor ............................................................................................ 5

1.2 Potential Risks to Non-target Organisms ......................................................................... 5

1.3 Conclusions - Exposure Characterization ........................................................................ 6

1.4 Conclusions - Effects Characterization ............................................................................ 7

2. Problem Formulation .............................................................................................................. 8

2.1 Nature of the Chemical Stressor ....................................................................................... 8

2.2 Overview of Pesticide Usage ........................................................................................... 8

2.3. Environmental Fate and Transport Characterization ..................................................... 10

2.4. Ecological Toxicity Characterization ............................................................................. 13

2.5. Conclusions from Previous Risk Assessments............................................................... 17

2.6. Conceptual Model .......................................................................................................... 17

2.7. Analysis Plan .................................................................................................................. 19

3. Risk Characterization ............................................................................................................ 21

3.1 Risk Estimation .............................................................................................................. 21

3.2 Risk Description ............................................................................................................. 26

3.3 Uncertainties, Limitations, and Data Gaps ..................................................................... 28

4. Federally Threatened and Endangered (Listed) Species Concerns ....................................... 30

5. Endocrine Disruptor Screening Program .............................................................................. 31

6. References ............................................................................................................................. 33

Appendix A Qualitative Aquatic Exposure Modeling Summary ................................................ 36

Appendix B Endangered Species Assessment Information ......................................................... 38

 
Page 5 of 39 

1. Executive Summary 

1.1 Nature of Chemical Stressor 

This document contains the environmental fate, ecological risk, and endangered species 

assessments for the registered uses of propoxur (2 – (1 – Methylethoxy) phenol methylcarbamate). 

This risk assessment is intended to address the potential ecological risks associated with the 

registered uses of propoxur. 

Propoxur was originally introduced in the United States in 1959. It has 23 active Section 3 

registrations. Propoxur is an N-methyl carbamate insecticide registered for indoor institutional, 

industrial, and commercial applications with very limited outdoor applications. Propoxur is used 

to control a variety of pests including, cockroaches, ants, wasps, crickets, silverfish, and other pest 

insects. There are 10 propoxur products registered with outdoor uses which include bait stations 

and liquid spray spot treatments to ant nests, cracks and crevices, and partial foundation treatments. 

Other propoxur outdoor uses include insecticide tape strips and patches, and formulations deployed 

in bait stations. The registered use sites include food processing facilities, hotels, apartments, 

homes, and commercial/office buildings. There are no registered agricultural uses for propoxur. 

In addition, broadcast treatments to lawns are not allowed. 

Currently, propoxur is formulated as a pressurized spray for perimeter and liquid spot treatments, 

granules in bait stations, and impregnated residues within insecticide tape strip or patch products. 

Propoxur is mixed within a peanut butter-base in the granular formulations contained within bait 

stations. Propoxur concentrations in end-use products range from 0.25 to 10 % a.i. 

1.2 Potential Risks to Non-target Organisms

The conceptual model for exposure only identifies the potential for exposure to aquatic organisms 

to propoxur resulting from outdoor spot treatments and subsequent runoff to nearby water bodies. 

(Section 2.6). EECs and RQs were not calculated in this assessment because standard exposure 

scenarios have not been developed in EFED for outdoor spot treatments, and the maximum 

application rate is not specified on labels for this use. However, the potential for risk is evaluated 

by determining the threshold amount of propoxur necessary to induce adverse impacts. This 

threshold analysis accounts for runoff which may occur after propoxur spot treatments utilizing 

PRZM/EXAMS. Minimum amounts of propoxur applied which results in adverse impacts are 

back-calculated from known toxicological information which exists for propoxur (Section 3.1). 

The propensity for risks occurring for the amounts of propoxur applied which are determined to 

result in adverse impacts are discussed in Section 3.2. The potential for exposure resulting in 

adverse impacts only exists for direct effects to listed aquatic species on an acute basis 

occurring due to propoxur hand-held sprayer spot treatments around foundations. 

However, this risk is anticipated to be confined to areas where spot treatments occur close to 

streams or water bodies considering their discontinuous nature of application. For remaining 

aquatic organisms, such as freshwater fish and estuarine/marine fish and invertebrates, all nonlisted aquatic species, and all listed and non-listed terrestrial organisms, no risks of concern are 

identified from current propoxur uses including outdoor spot treatments. 
Page 6 of 39 

Risk determinations by taxa for listed species are summarized in Table 1.1 below. A,“No Effect” 

risk determination for all listed species can be concluded for direct and indirect effects of propoxur 

use except for aquatic invertebrates either as there is no complete exposure pathway or adverse 

impacts are not expected. A “May Affect” determination is stipulated at this time for direct effects 

to aquatic invertebrates resulting from propoxur spot treatment use close to streams since adverse 

impacts are possible. This determination may be clarified further in the future depending on 

clarification of uncertainties which currently exist regarding propoxur spot treatments on product 

labels. 

Table 1.1. Potential Risks to Listed Taxa Associated with Direct or Indirect Effects from 

the Currently Registered Uses of Propoxur. 

Listed Taxon Direct Effects Indirect Effects 

Terrestrial and semi-aquatic plants – monocots No Effect 

Terrestrial and semi-aquatic plants – dicots No Effect 

Birds No Effect 

Terrestrial-phase amphibians and reptiles No Effect 

Mammals No Effect 

Terrestrial invertebrates No Effect 

Aquatic nonvascular plants No Effect 

Aquatic vascular plants No Effect 

Freshwater fish No Effect 

Aquatic-phase amphibians No Effect 

Freshwater invertebrates May Affect* No Effect 

Marine/estuarine fish No Effect 

Marine/estuarine invertebrates No Effect 

*Determination based on direct effects to listed species on an acute basis, only possible resulting from propoxur 

outdoor spot treatments using hand held sprayers applied to foundations which occur close to streams and water 

bodies. This determination may be clarified further in the future depending on clarification of uncertainties which 

currently exist regarding propoxur spot treatments which currently exist on product labels.

1.3 Conclusions - Exposure Characterization 

There is the potential for runoff of propoxur to aquatic environments mainly associated with its 

topical application in outdoor spot treatments occurring around the foundations of buildings, 

cracks and crevices, and ant nests (Section 2.6). Propoxur’s high mobility and high persistence 

suggest this route of exposure is possible (Section 2.3). However, aquatic exposure is likely to be 

reduced by the discontinuous, non-broadcast nature of spot treatment applications. Furthermore, 

the current use volume of propoxur is relatively limited based on nationwide data (Section 2.2). 

Any exposure in the aquatic environment is most likely limited to outdoor spot treatments that 

occur close to streams and other water bodies. Propoxur spot treatments occurring away from 

water bodies is expected to result in negligible exposure (i.e., well below toxicologically-relevant 

levels) based on its small application rate coupled with its dispersion within runoff during transport 

to water bodies. 
Page 7 of 39 

Exposure in terrestrial habitats is not expected since propoxur is not expected to be bioavailable to 

birds, mammals, or non-target terrestrial invertebrates in bait stations, nor are the insecticide tape 

strips or impregnated tag products of propoxur expected to serve as attractive food sources birds 

and mammals. Furthermore, non-target terrestrial invertebrates are not expected to be attracted to 

these propoxur products. Crack and crevice and spot treatments are not expected to overlap with 

potential food sources of birds and mammals. The only possible exception is the case for birds 

and mammals eating dead ants that are treated with propoxur. However, only limited exposure is 

expected given propoxur’s low use. Therefore, no risk for terrestrial organisms and plants are 

identified based on the lack of a complete exposure pathway or limited exposure due to low use. 

Please refer to Section 2.6 for further discussions on the rationale behind these findings for each 

propoxur outdoor use. 

 

1.4 Conclusions - Effects Characterization 

Acceptable toxicity studies for propoxur include an acute freshwater fish, acute freshwater 

daphnid, avian acute oral and an acute contact honeybee study. Supplemental studies include 

acute estuarine/marine fish, acute estuarine/marine invertebrate, avian subacute dietary, and 

avian reproduction. 

Aquatic Organisms 

Technical grade propoxur is classified as moderately toxic to fish (which serve as surrogates for 

aquatic-phase amphibians in the absence of amphibian toxicity data). The 96-hr LC50 for Rainbow 

trout (Oncorhynchus mykiss) was determined to be 3.7 mg/L (MRID 00149171). Propoxur is very 

highly toxic to aquatic invertebrates based on a 48-hr EC50 of 0.011 mg/L for the water flea, 

Daphnia magna (MRID 00149172). 

Supplemental data for qualitative use only is available for freshwater invertebrate life cycle, acute 

estuarine/marine fish, and acute estuarine/marine invertebrates showing propoxur to be slightly 

toxic, moderately toxic to estuarine/marine fish and invertebrates. No toxicity data are on the 

chronic toxicity of propoxur to freshwater fish, freshwater invertebrates, estuarine/marine fish, 

estuarine/marine invertebrates. 

Terrestrial Organisms 

Propoxur is highly toxic to bird on an acute basis. The 96-hr LD50 for the bait formulation is 23 

mg/kg a.i. (MRID 41625101). Technical grade propoxur is classified as highly toxic to 

terrestrial invertebrates. In an acute contact oral study for the honeybee (Apis mellifera) the 

endpoint was determined to be 1.35 μg/bee (MRID 00036935). An acute oral study conducted 

using a rat shows propoxur to be moderately toxic to mammals with an endpoint of 68 mg/kg 

(MRID00152443). 

Supplemental data for qualitative use only are available for avian dietary, avian reproduction, and 
Page 8 of 39 

mammalian reproduction showing propoxur to be highly toxic to avian species and moderately 

toxic to mammals. No data are available for terrestrial plants. 

2. Problem Formulation 

2.1 Nature of the Chemical Stressor 

Propoxur is an N-methyl carbamate non-systemic insecticide that is used to control a variety of 

pests including cockroaches, ants, wasps, crickets, silverfish, and other pest insects. Propoxur 

interferes with acetylcholinesterase, an essential enzyme in the transmission of signals in nerve 

cells. Exposure to propoxur results in the over-excitation of the nervous system and eventually 

death in fleas, ticks and other insects (American Conference of Governmental Industrial 

Hygienists, 2010). There are no longer any agricultural uses registered for propoxur, and the 

majority of current uses are limited to indoor applications. 

2.2 Overview of Pesticide Usage 

There are a total of 23 active registrations with propoxur with 10 active registered products 

containing outdoor uses. Outdoor uses of propoxur are applied as a spray or placed within bait 

stations, insecticide tags, or tape strips anywhere an infestation of target insects are observed. 

Propoxur spray products and bait stations are used outside of homes, apartments, office complexes, 

food processing facilities, and hotels. Propoxur insecticide tags or tape strips are used primarily 

on or around telecommunications utility lines, transformers, and circuit boxes. Previous broadcast 

granular bait application uses have been discontinued. 

Some of the registered spray products for outdoor use contain propoxur as the single active 

ingredient (1 percent a.i.) with petroleum distillates composing the remainder of the solutions. The 

remainder of the spray propoxur products are co-formulated with MGK 264, pyrethrins, and 

piperonyl butoxide, all composing of 1 percent propoxur. Propoxur is the single active ingredient 

in the bait (within bait stations, 0.25 percent a.i.) and impregnated formulations (within insecticide 

tags and tape strips, 9.4 and 10 percent a.i., respectively). The products types and formulations of 

propoxur used outdoors are listed in Table 2.1 below. It should be noted that maximum application 

rates, maximum retreatment intervals, or time between treatments are not specified on the labels. 

Table 2.1. Description of propoxur products used outdoors.

Use Description Product Photo 

Formulation 

Description % a.i. 

Propoxur 

Product 

Densitya

Spot Treatment – 

Ant Nests 

 

Pressurized 

spray 

(397 grams of 

product) 1 0.065 

lbs./gallon 

Crack and Crevice 

Treatment 

Foundation 

Treatment 

Ready-to-Use 

Solution 
Page 9 of 39 

Table 2.1. Description of propoxur products used outdoors.

Use Description Product Photo 

Formulation 

Description % a.i. 

Propoxur 

Product 

Densitya

(55 gallons of 

product) 

Insecticide Tag Impregnated 

Material 

9.4 1.65 x 10-3

lbs./tag 

Insecticide Tape 

Strip 10 1.96 x 10-3lbs./strip 

Bait Station Granules 0.25 2.59 x 10-5

lbs./bait station 

a

Derived from information on labels, and calculated according to following for each product type: 

Insecticide tag (From Reg. No. 13283-26 product label): Product net weight (8.0 g) x Conversion Factor (lb ) 

 453.6 g 

 x Percent a.i. (9.4%) 

Insecticide tape (From Reg. No. 8730-49 product label): Product net weight (8.9 g) x Conversion Factor (lb ) 

 453.6 g 

 x Percent a.i. (10%) 

Bait Station (From Reg. No. 9688-305 product label): Product net weight (4.7 g) x Conversion Factor (lb ) 

 453.6 g 

 x Percent a.i. (0.25%) 

Sprays (From Reg. Number 279-3995 Product Label): [Product net weight (397 g)/Volume of product solution (0.134 

gallons, calculated below)] x Percent a.i. (1 %). 

Where volume of product solution = Product net weight (397 g) x Reciprocal of the Product Solution 

Density ( mL, MRID No. 45233701) x Conversion Factor ( L ) x Conversion Factor (gal) 

0.787g 1,000 mL 3.79 L 

The scope of outdoor uses for propoxur is very limited. First, propoxur is used outdoors within 

bait stations in two products (Reg. Nos. 9688-305 and 1663-32). Second, it is also used as an 

impregnated material on insecticide tags (Reg. No. 13283-26) and insecticide tape (Reg. No. 

8730-49). Third, propoxur is used as liquid spray spot treatments to ant nests, cracks and 

crevices (Reg Nos. 655-546, 6218-24, 655-796, 82644-1, 84396-12, 499-501) from spray cans or 

hand-held sprayers. Propoxur is also used for foundation treatments. The headers on two labels 

(Reg. Nos. 84396-12 and 499-501) indicate that propoxur can be used around perimeters on 

buildings. Although this labeled use is ambiguous, it does not appear that the intended use of 

propoxur is for traditional perimeter treatments which completely surround the building. The 

reasons are stated below: 

1.) The label instructions on one label (Reg. No. 84396-12) suggests that propoxur use is 
Page 10 of 39 

limited to small areas where insects are observed (e.g., Spray thoroughly those areas 

where pests have been seen or found including outside surfaces of screens, doors, 

window frames, foundations, patios, or other places where insects may enter. For ants, 

spray runways. Repeat as necessary. Do not spray vegetation. Do not apply as a 

landscape treatment (to lawns, shrubs or trees, or plants). 

2.) The propoxur uses are either available as ready-to use solutions contained in pressurized 

sprays or a hand-held sprayers. Both types of products are manually applied to small 

areas. 

3.) The label instructions do not mention any continuous treatment such as banded 

treatments along foundations. 

There are several indications that the overall propoxur use is very limited. First, usage data 

provided to the Biological and Economic Analysis Division (BEAD) of the Office of Pesticide 

Programs for propoxur indicates that it is a minor use chemical in the professional pest 

management sector, accounting for <1% of the total chemicals applied each year (8,000 and 

9,000 lbs applied in 2001 and 2003, respectively). In more recent years, usage data suggests that 

limited use of propoxur continues. Commercial databases show that there is only 200 – 300 lbs. 

of propoxur bait station products available nationwide in the consumer market (Proprietary Data, 

2012). In addition, CALPUR reports that less than 1 pound of propoxur has been applied for 

outdoor spot treatments in 2012 throughout California where spot treatments and residential uses 

of insecticides are known to be prevalent3

. This limited use of propoxur further suggests that 

continuous perimeter treatments do not exist and that organized community use of propoxur is 

not prevalent. 

2.3. Environmental Fate and Transport Characterization 

In its natural form, propoxur is a colorless crystalline solid with a melting point of 81°C (Berg, 

G.L. 1986). It is relatively soluble in water (Berg, G.L. 1986) and stable in acidic environments, 

but highly unstable in alkaline environments. Propoxur is moderately volatile from dry surfaces. 

However its vapor pressure of 6.5 x 10-6 torr suggests that large amounts of propoxur are not 

expected to volatilize at a fast rate (Worthing C.R., 1983). The physicochemical characteristics 

associated with propoxur are summarized in Table 2.2. 

 

3

 Accessible on-line at: http://www.cdpr.ca.gov/docs/pur/pur12rep/chmrpt12.pdf 
Page 11 of 39 

Table 2.2. Physicochemical properties of propoxur.

Parameter Value Citation 

Structure PubChem Sketcher4

Molecular formula C11 H15 NO3 MRID 151791 

Molecular weight 209.25 g/mol MRID 151791 

CAS Number: 114-26-1 EpiSuite 

CAS Name: Phenol, 2-(1-methylethoxy)-, 

methylcarbamate EpiSuite 

Water solubility 1,750 mg/L at 20°C 

1,974 mg/L at 25°C 

Berg, S.L., 1983 

EpiSuite, WSKOW v.1.42 

Vapor pressure 6.5 x 10-6 torr @ 25°C Worthing C.R., 1983 

Henry’s law constant 3.35 x 10-9 atm-m3/mol @ 25°C EpiSuite, HENRYWIN v. 3.20 

Octanol-water partition coefficient 

(log Kow) 1.90 EpiSuite, KOWWIN v.1.68 

Bioconcentration factor (BCF) in 

fish 4.68 L/kg EpiSuite, BCFBAF v.3.01 

In soil where propoxur spot treatments can occur, propoxur appears to be relatively persistent with 

half-lives generally ranging between 80 – 210 days in aerobic and anaerobic soils (MRID No. 

085768). Propoxur mainly degrades to carbon dioxide under aerobic conditions. Under anaerobic 

conditions, propoxur degradation most likely occurred due to hydrolysis as degradation in sterile 

samples were equivalent to non-sterile samples. 

In water, propoxur is stable under neutral to acidic conditions, but degradation appears to occur 

mainly under alkaline conditions. Propoxur hydrolyzes with a half-life of 16 days at pH 8 to as 

rapidly as approximately 4 hours at pH 10. Hydrolysis results in breaking the carbamate linkage 

(MRID No. 085762). Propoxur demonstrates some photodegradation under exposure to weak 

irradiation relative to natural light with a photolysis half-life of 13 days. Propoxur was found to 

mainly degrade to carbon dioxide in the hydrolysis and aqueous photolysis studies. However, 

some levels of the isopropoxy phenol degradate was detected up to 24.3 percent of the applied 

radioactivity in the aqueous photolysis study. 

Propoxur appears to be mobile to highly mobile (per FAO classification) with Koc values ranging 

between 3.4 – 11.2 mL/g-oc in sandy loam and silt loam soils, respectively. Propoxur is 

moderately mobile in silty clay soil with a Koc value of 102.6 mL/g-oc determined in the study 

(MRID No. 085770). Propoxur’s overall relative high mobility is evident in a column leaching 

study in which propoxur was applied to 12-inch soil columns. Leachate material accounted for 

between 69 to 74 percent of the applied radioactivity after 45 days (MRID No. 085769). Ten 

supplemental terrestrial field dissipation studies with propoxur applied to soil plots further provide 

evidence of propoxur’s highly mobile characteristics. These field dissipation studies roughly show 

 

4

 Accessible on-line at: http://pubchem.ncbi.nlm.nih.gov/edit2/index.html
Page 12 of 39 

that propoxur moves rapidly through the soil below a 12 inch sampling depth (MRID No. 085772). 

If spot treatments are applied close enough to water bodies, propoxur’s environmental fate and 

behavior parameters indicate that propoxur residues may easily move to those water bodies 

through soil and runoff given its high mobility and persistence in soil. Table 2.3 shows the details 

of each fate and transport study for propoxur. Many of the environmental fate and transport studies 

available for propoxur have been submitted to the EPA as guideline studies. The study 

classifications and notes on study quality are provided in Table 2.3 below. 

Table 2.3 Summary of environmental fate and transport studies and parameter values 

for propoxur. 

Study 

(Guideline 

Nos.) 

Value and unit Major 

Degradates 

MRID 

# or 

Citation 

Study 

Classification, 

Comment 

Abiotic 

Hydrolysis 

(835.2120) 

t 1⁄2 = Stable (pH <7) 

t 1⁄2 = 16 days (pH 8) 

t 1⁄2 = 1.6 days (pH 9) 

t 1⁄2 = 0.17 days (pH 10) 

None determined 085762 

Supplemental 

-Degradates not 

analyzed 

Aqueous 

Photolysis 

(835.2240) 

t 1⁄2 = 13 days 

- Carbon Dioxide 

(30.9%, 21 

days) 

- Isopropoxy 

phenol 

(24.3 % AR, 21 

days) 

085763 

Acceptable 

- Half-life 

adjusted for 

hydrolysis 

- Irradiation 

approximately 

18% of natural 

sunlight during 

summertime in 

Kansas City, 

MO 

Soil Photolysis 

(835.2410) 

Sandy loam soil (pH 8.2) 

t1/2 = 77 days 

- Unextracted 

Residues 

(12 % AR, 28 

days) 

- Volatiles 

(10% AR, 28 

days) 

085765 

Acceptable 

- Irradiation 

approximately 

18% of natural 

sunlight during 

summertime in 

Kansas City, 

MO 

Aerobic Soil 

Metabolism 

(835.4100) 

Silt loam soil (pH 6.4) 

t1/2 = 80 days 

Sandy loam soil (pH 5.7) 

t1/2 =210 days 

- Carbon Dioxide 

(35%, 336 days) 

- Unextracted 

Residues 

085768 

Supplemental 

- Complete 

formation and 

decline of 
Page 13 of 39 

Table 2.3 Summary of environmental fate and transport studies and parameter values 

for propoxur. 

Study 

(Guideline 

Nos.) 

Value and unit Major 

Degradates 

MRID 

# or 

Citation 

Study 

Classification, 

Comment 

 (40%, 336 days) degradates 

could not be 

resolved in 336-

day study 

Anaerobic Soil 

Metabolism 

(835.4200) 

Silt loam soil (pH 6.4) 

t1/2 = 80 days 

Sandy loam soil (pH 5.7) 

t1/2 =108 days 

- 085768 

Supplemental 

- Degradation 

rate identical 

in sterile 

versus nonsterile 

samples; 

hydrolysis 

most likely 

observed. 

- Complete 

formation and 

decline of 

degradates 

could not be 

resolved in 

336-day study 

Mobility, unaged 

leaching, 

adsorption/ 

desorption and 

aged leaching soil 

column 

(835.1230) 

Sandy Loam Soil 

Koc = 3.4 mL/g 

OM = 2.8% 

Silt Loam Soil 

Koc = 11.2 mL/g 

OM = 5.1% 

Silty Clay Soil 

Koc = 102.6 mL/g 

OM = 0.5% 

N/A 085770 Acceptable 

AR = Applied radioactivity. 

N/A means not applicable. 

Bioaccumulation of propoxur is not expected in fish or aquatic organisms due to its low Log Kow

value of 1.90 (Kow= 79).

2.4. Ecological Toxicity Characterization 

In screening-level ecological risk assessments, effects characterization describes the types of 

effects a pesticide can have on aquatic and terrestrial organisms. In absence of toxicity data, birds 

are used as surrogates for reptiles and terrestrial-phase amphibians and freshwater fish are used as 
Page 14 of 39 

surrogates for aquatic-phase amphibians. This characterization is based on the registrantsubmitted toxicity data for birds, mammals, freshwater fish, aquatic invertebrates and aquatic 

plants. 

The assessment also evaluates the potential for propoxur to directly or indirectly affect listed 

species or modify designated critical habitat. Assessment endpoints may include direct toxic 

effects on the survival, reproduction, and growth of listed entities, as well as indirect effects, such 

as reduction of the prey base or modification of habitat. 

The most sensitive endpoint for each taxon is used for risk estimation, which in the case of 

propoxur is from a single study for each taxon. Toxicity data were available for 5 taxonomic 

groups including freshwater fish, estuarine/marine fish, estuarine/marine invertebrates, birds and 

mammals. Tables 2.4 and 2.5 provides a summary of the taxonomic groups, surrogate species 

tested, and results of studies to characterize the potential acute ecological effects of propoxur (no 

chronic toxicity studies are available). 

The ecological effects characterization for propoxur is based upon registrant-submitted toxicity 

data. Tables 2.4 and 2.5 lists these studies and their review classifications. Ecotoxicity data for 

propoxur was reviewed in a Preliminary Problem Formulation for Registration Review (USEPA 

2009, DP365168). These data are summarized briefly in the following sections. 

Aquatic Organisms

Technical grade propoxur is classified as moderately toxic to fish (which serve as surrogates for 

aquatic-phase amphibians) and very highly toxic to freshwater invertebrates. No chronic toxicity 

data were available for freshwater and estuarine/marine fish, freshwater and estuarine/marine 

invertebrates. No data was available for vascular and one supplemental study was available for 

non-vascular aquatic plants. A summary of the most sensitive aquatic toxicity data for propoxur, 

based on a current Agency review of all submitted data is provided in Table 2.4. 

The freshwater invertebrate 21-d life cycle toxicity test (MRID 41425301) was classified as 

supplemental due to a lack of reporting on a number of factors including health and history of 

organisms at start of testing, volume of test solution and loading factor, total organic carbon, 

length, bodyweight, and number of offspring per female. Given that a quantitative assessment 

was not conducted, the value of quantitative use of the reported endpoints in the study were not 

evaluated at this time. 

The estuarine/marine invertebrate acute toxicity test (MRID 40228401), estuarine/marine acute 

fish study (MRID 40228401), and algal growth inhibition test (MRID 00158414) were considered 

scientifically sound but were classified as supplemental because the test duration and other study 

features deviated from EPA guidelines and thus did not satisfy the requirement for data. 
Page 15 of 39 

Table 2.4. Most sensitive aquatic species evaluated for assessing potential ecological 

effects of propoxur. 

Study Type Tested Species 

Purity of 

Test 

Substance 

Toxicity Endpoint Study MRID and 

Toxicity Classification 

96-Hour Acute 

Freshwater Fish 

Rainbow trout 

(Oncorhynchus 

mykiss)

98.8 LC50 = 3.7 mg/L 

00149171 

Moderately Toxic 

Acceptable 

Freshwater Fish 

Early Life Stage No data 

48-hr Acute 

Freshwater 

Invertebrate 

Waterflea

(Daphnia magna) 98.8 EC50 = 0.011 mg/L 

00149172 

Very Highly Toxic 

Acceptable 

Freshwater 

Invertebrate 21-d 

Life Cycle 

Waterflea 

(Daphnia magna) 98.5 N/A 41425301 

Supplemental 

48-hour Acute 

Estuarine/Marine 

Fish 

Sheepshead 

Minnow 

(Cyprinodon 

variegatus) 

100 LC50 >1 mg/L 

40228401 

Moderately Toxic 

Supplemental 

Estuarine Marine 

Fish Early Life 

Stage 

No Data 

96-hour Acute 

Estuarine/Marine 

Invertebrate 

Pink Shrimp 

(Penaeus 

duorarum) 

100 LC50 = 0.041 mg/L 

40228401 

Moderately Toxic 

Supplemental 

Estuarine/Marine 

Invertebrate Life 

Cycle 

No data 

Aquatic Plants Green Algae 99.6 EC50 = 5.3 mg/L 00158414 

Supplemental 

Vascular and 

Nonvascular Plants No data 

1

 Freshwater fish are considered surrogates for aquatic-phase amphibians. 

Terrestrial Organisms

Propoxur is highly toxic to the Bobwhite quail on an acute basis when exposed to the formulated 

product. Table 4 in the 2009 Problem Formulation (DP365168) cites The Handbook of Toxicity 

of Pesticides to Wildlife, published in 1984, as a source of a number of avian endpoints more 

sensitive than the bobwhite quail (00160000, Hudson et al.). The most sensitive endpoint listed 

within the Handbook is LD50=3.55 mg ai/kg for the House Finch; while there are more sensitive 

endpoints available within the document, and the studies are considered to be scientifically 

sound, they are classified as supplemental because the methods, duration and standards of the 

study differ than those listed in our current guidelines. For this reason, the most sensitive 

endpoint considered in this assessment is that associated with the registrant submitted avian 

acute oral study (MRID 41625101). 

The avian 5-day dietary study is classified as supplemental because methods, duration and 

standards of the study differ than those listed in our current guidelines but are still considered to 

be scientifically sound. There are a number of additional avian subacute endpoints available 
Page 16 of 39 

conducted using different species; these can be found under MRID 00022923 within Table 4 of 

the 2009 Problem Formulation. 

In addition to the avian reproduction study conducted using the bobwhite listed below, there is a 

study available conducted using a mallard (MRID 00149016). The study showed reduced egg 

reproduction and embryo viability at 80 ppm; however the study was classified as supplemental 

because raw data was not provided to allowed statistical verification of the results. Therefore, 

the study conducted using the bobwhite was cited as the most sensitive endpoint, despite the 

inability to establish a NOEC for reproductive effects. The NOEC for brain cholinesterase 

inhibition was found to be 80 ppm. 

Data are available for acute toxicity to mammals, showing propoxur is moderately toxic to the 

laboratory rat. No chronic data are available for mammals. An acceptable study shows that 

propoxur is highly toxic to honeybees on an acute contact basis. Toxicity data on the effects of 

propoxur on terrestrial plants are not available. A summary of the most sensitive terrestrial 

toxicity data for propoxur, based on a current Agency review of all submitted data is provided in 

Table 2.5 

Table 2.5. Most sensitive terrestrial species evaluated for assessing potential ecological 

effects of propoxur.

Study Type Tested Species Percent a.i. Toxicity Endpoint Study MRID and 

Toxicity Classification 

Acute Avian Oral 

Bobwhite quail 

(Colinus 

virginianus) 

2 

(Formulated 

product—bait) 

LD50 = 23 mg a.i./kgbw 

41625101 

Highly toxic 

Acceptable 

Avian 5-d Dietary 

Bobwhite quail 

(Colinus 

virginianus)

Technical % 

unknown LC50 = 206 mg/L 00022923 Supplemental* 

Avian Reproduction 

Bobwhite quail 

(Colinus 

virginianus) 

98 

NOAEC =320 mg/L 

(highest dose; NOEC for 

reproductive effects not 

established) 

00149017 

Supplemental 

Acute Mammalian 

Oral 

Laboratory rat 

(Rattus 

norvegicus) 

Technical 

LD50 = 

68 mg/kg -bw (F) 

94 mg/kg-bw (M) 

00152443 

Moderately toxic 

Mammalian 

Chronic—2 

generation 

reproduction 

Laboratory rat 

(Rattus 

norvegicus) 

99.8 NOAEC = 80 ppm 

42615403 

No reproductive toxicity 

observed at levels up to 

80 ppm in diet 

Terrestrial 

Invertebrates acute 

contact 

Honeybee 

(Apis mellifera) Technical LD50 = 1.35 μg/bee 

00036935 

Highly Toxic 

Acceptable 

Terrestrial Plants No Data *

Although classified as supplemental, the USDI data are derived from scientifically sound studies. Although the actual 

% ai was not reported, it is assumed to be greater than 95% 

Degradate toxicity 
Page 17 of 39 

The existing collection of environmental biodegradation laboratory studies indicate that propoxur 

degrades mainly to carbon dioxide in soil and water under environmentally relevant conditions. 

Since carbon dioxide is considered benign in comparison to propoxur, this risk assessment will 

focus on propoxur as the main stressor of concern.5

ECOTOX Open Literature

Literature identified in search of the publically available ECOTOX database did not result in 

identification of listed endpoints that were toxicologically relevant or more sensitive than those 

found in registrant submitted studies. There are endpoints available for estuarine/marine 

invertebrates that are considered to be virtually identical to those found in registrant submitted 

studies. 

2.5. Conclusions from Previous Risk Assessments 

The ecological risk assessment included in the propoxur RED was based on laboratory fate and 

ecotoxicological data submitted by the registrant in support of reregistration, data in publicly 

available literature, and incident reports of adverse effects on non-target organisms associated with 

the use of propoxur. The previous ecological risk assessments considered the parent chemical only 

as the stressor of concern. The primary environmental concerns identified in the 1996 RED were 

acute risks to birds and mammals based on broadcast granular bait applications. EFED did not 

have the tools with which to assess chronic risk to birds or mammals based on the granular bait 

application. Therefore, chronic risk to either birds or mammals was not assessed. Regardless, 

broadcast granular bait applications of propoxur have been cancelled. 

Based on the RED risk assessment, a number of mitigation measures were suggested for 

consideration to address risks. The only measure relevant to current uses of propoxur proposed 

included to limit outdoor uses to crack and crevice treatment considering registrants have 

previously indicated in the Phase 3 Response that this is the main way the product is applied 

outdoors. However, labels allowing for broader spot treatment uses such as those around structure 

foundations and to ant nests still exit today. 

2.6. Conceptual Model 

Outdoor uses of propoxur include spot treatments, bait station uses, insecticide tags, and 

insecticide tape strips. Descriptions of the relevance of potential risk to terrestrial and aquatic 

organisms are discussed below for each use: 

 Bait Stations: Target pests for propoxur bait station uses include ants and roaches. Bait 

stations contain granular forms of propoxur enclosed within them. The bait stations have 

opening indentations on its side where these target insects can enter to access the 

 

5

 Isoproxy phenol was detected in aqueous photolysis study. The formation of this degradate is not expected to be 

prevalent in the environment since aqueous photolysis is not expected to be an important degradation pathway in 

water bodies which may exist nearby propoxur treated areas. 
Page 18 of 39 

propoxur bait. There are dimensions of 0.5 inch by 0.25 inch openings in the design for 

each bait station. Please refer to Table 2.1 for a side-view photograph of the bait station. 

Given the containment of propoxur within bait stations, exposure is not expected for 

aquatic or terrestrial organisms. Propoxur in bait stations is not expected to be 

translocated to water bodies. Therefore risk for bait station uses to aquatic organisms 

is not expected. 

For non-target terrestrial organisms, exposure to propoxur in bait stations is not expected. 

Non-target terrestrial invertebrates are not expected to be impacted from propoxur bait 

stations since the small dimensions of the openings prohibit these insects from entering, 

restricting the bioavailability of propoxur to these organisms. The same reasoning would 

apply to mammals and birds. Therefore, risk associated with bait station uses to 

terrestrial organisms is not expected. 

 Insecticide Tags and Insecticide Tape Strips: These products compose of padded 

material impregnated with propoxur. Use of these products are restricted to placement on 

or around telecommunications utility lines, transformers, and circuit boxes. 

Since electrical equipment is located in dry places to prevent electrocution problems 

associated with water interaction, propoxur from these products is not expected to wash 

off into water, preventing exposure to aquatic environments from occurring. Therefore, 

risk for these uses to aquatic organisms is not expected. 

In addition, use of these products are not expected to attract non-target terrestrial 

invertebrates, birds, or mammals. Furthermore, these products are not likely to result in 

any habitat modification for terrestrial organisms as propoxur use is restricted only to 

around electrical facilities. Therefore, risk for these uses to terrestrial organisms is 

not expected. 

 Spot Treatments: Propoxur is applied around crack and crevices, to ant nests, and 

around foundations in spot treatments. Propoxur is not applied in broadcast applications 

and is not allowed to be applied to lawns. 

Propoxur spot treatments to cracks and crevices, around foundations, and ant nests are 

not expected to be applied to surfaces would serve as food sources for birds or mammals. 

In addition, propoxur is not directly applied to flowering plants nor is substantial spray 

drift expected to occur to off-target plants from spot treatment applications. Also, it is 

not expected to be expected to be uptaken by these plants since it is a non-systemic 

insecticide6

. However, exposure is plausible as mammals and birds can eat dead ants 

which are covered with propoxur residues during spot treatment. However, considering 

propoxur’s very low use, large amounts of dead ants covered with propoxur are not 

expected to be present over wide areas for birds and mammals to consume. Therefore, 

risk is not anticipated for terrestrial organisms from propoxur spot treatments. 

 

6

 Citation: http://pmep.cce.cornell.edu/profiles/extoxnet/metiram-propoxur/propoxur-ext.html
Page 19 of 39 

Since spot treatments of propoxur are applied directly to ant nests or around foundations 

outdoors, aquatic exposure may result from translocation of propoxur residues to water 

bodies via runoff. However, only a small fraction of propoxur applied is expected to 

runoff since it is not used in high quantities, nor is it used in broadcast applications. In 

addition, propoxur is most likely to runoff to water particularly where applications occur 

close to water bodies. Therefore, considering the potential for a small amount of 

exposure and high toxicity for propoxur to aquatic organisms (see Section 4.1), there 

is a potential for risk to aquatic organisms, which this risk assessment will address.

Table 2.6 below summarizes the findings addressing the conceptual model for this propoxur 

ecological risk assessment. In summary, exposure to terrestrial organisms is not expected for all 

outdoor propoxur applications. Exposure to aquatic organisms is not expected for propoxur bait 

station, insecticide tag, and insecticide tape uses. However, there is potential risk to aquatic 

organisms associated with propoxur outdoor spot treatments. 

Table 2.6. Conceptual model findings for identification of potential risk for ecological 

risk assessment associated with propoxur outdoor uses. 

Outdoor Uses Terrestrial Risk? Aquatic Risk? 

Bait Stations No – no exposure 

Insecticide Tags and Tape No – no exposure 

Spot Treatments 

(Cracks and Crevices, 

Foundations, Ant Nests) 

No – dietary exposure 

scenario from dead ants 

negligible 

Possible – small exposure 

possible 

Consistent with the findings presented in Table 5.1, the following ecological risk hypothesis is 

being employed for this ecological risk assessment: 

Based on the application methods and available toxicity data for non-target aquatic 

species, propoxur has the potential to reduce survival, reproduction, and/or growth in nontarget freshwater fish, estuarine/marine fish, aquatic invertebrates, and aquatic plants 

when used for outdoor spot treatments in accordance with the current labels. These nontarget organisms include federally listed threatened and endangered species as well as 

non-listed species.

2.7. Analysis Plan 
Page 20 of 39 

In order to address the risk hypothesis, the potential for adverse effects from propoxur outdoor 

spot treatments on the environment is evaluated. However, since there is no standard scenario 

established to evaluate outdoor spot treatment applications and very limited information on 

maximum application rates on the labels, this risk assessment will not rely on risk quotients (RQs) 

for the determination of risk as in traditional risk assessments. Rather, a threshold analysis relating 

the exposure necessary to induce adverse impacts will be used to describe the potential exposure 

that exists for aquatic organisms based on its expected use as a spot treatment. The use of 

environmental fate, and ecological effects will be integrated together in order to characterize the 

potential exposure. The parent compound, propoxur, is the toxicant that will be assessed. Besides 

propoxur, carbon dioxide is the only other compound that has been detected in environmentallyrelevant laboratory environmental fate studies. 

First, the risk hypothesis, provided at the end of Section 2.6, will be tested in a Preliminary 

Adverse Impacts Analysis by calculating the critical amount of propoxur (by mass and volume) 

which is necessary to induce potential adverse impacts to listed and non-listed aquatic organisms. 

This information is directly determined from the most sensitive aquatic species endpoint. Please 

refer to Section 3.1 for further details. This critical amount will then be compared to the amount 

of parcels for propoxur products (e.g., number of spray cans) in order to relate the critical mass 

causing adverse impacts to aquatic taxa in water bodies to an amount of propoxur that is inside a 

spray can. In this way, the critical mass of propoxur causing adverse impacts is placed into 

perspective with the amount of propoxur potentially applied from a parcel, and therefore, the 

likelihood for the critical mass ever entering a water body can be described. 

The propensity of the critical amount of propoxur causing adverse impacts via direct entry into a 

water body, as determined from the Preliminary Adverse Impacts Analysis above, will be further 

evaluated in a Refined Adverse Impacts Analysis. In this analysis, the threshold application 

amount of propoxur causing adverse impacts to listed and non-listed aquatic species will be further 

examined by considering propoxur’s overall potential to reach water bodies via runoff at 

toxicologically-relevant concentrations. The fate and transport properties of propoxur, soil 

properties, and variability in rainfall will be factors accounted for in this analysis. The most 

sensitive endpoint for aquatic species along with propoxur density within products (0.065 

lbs./gallon), volume of the water body (20,000 m3

 farm pond), and estimated exposure 

concentration (EECs) which are based on a first-guess application rate (1 kg a.i./ha) will all be 

used determine this critical application amount for propoxur . Please refer to Section 3.1 for 

further details on the back-calculation approach to determine the amount of gallons necessary for 

propoxur to induce adverse impacts. EECs normalized to the first-guess application rate will be 

calculated using the Pesticide Root Zone Model coupled with the Exposure Analysis Modeling 

System model (PRZM/EXAMS). Finally, the critical amount of propoxur to induce adverse 

effects to listed and non-listed species determined in the Refined Adverse Impacts Analysis will 

be put into context considering the likely use patterns of propoxur considering its limited use 

outdoors as a spot treatment. This discussion is included in Section 3.2. 

Considering the lack of expected bioavailability and limited scope of use sites for propoxur spot 

treatments, exposure to non-target terrestrial organisms and plants is presumed negligible (Section 

2.6) and will not be estimated. 
Page 21 of 39 

3. Risk Characterization 

3.1 Risk Estimation 

Since maximum application rates are not specified on the labels for propoxur outdoor spot 

treatments, threshold levels of exposure and product application (by mass and volume) that 

induce adverse impacts are determined. First, a Preliminary Adverse Impacts analysis

evaluating the amount of propoxur necessary to trigger adverse impacts to aquatic organisms 

based upon its direct entry into a water body is first considered. Then, a Refined Adverse 

Impacts Analysis will be conducted to show how runoff occurring after propoxur spot treatments 

can impact the adverse impacts application threshold level of propoxur impacting water bodies. 

The preliminary and refined threshold analyses for acute listed aquatic species are described 

below. The results for threshold propoxur amounts resulting in adverse impacts for acute listed 

aquatic species and acute non-listed aquatic species are shown in Tables 3.1 and 3.2 for the 

preliminary and refined analyses, respectively. Due to a lack of scientifically-sound 

toxicological data, chronic exposure is not considered. Please refer to Section 3.3 for further 

characterization for chronic exposure. 

Preliminary Adverse Impacts Analysis

As mentioned in Section 2.6, the first test of the risk hypothesis for aquatic exposure associated 

with propoxur spot treatments will involve calculating the critical mass of propoxur necessary to 

induce adverse impacts to aquatic organisms. This calculation will be solely based on the most 

sensitive acute endpoint resulting from effects to aquatic invertebrates. The endpoint used is for 

the daphnid EC50 = 0.011 mg/L (MRID No. 0149172). Based on this endpoint, 11 grams of 

propoxur or 0.373 gallons of product will result in adverse impacts to listed species assuming 

it enters a water body. This critical mass of propoxur is determined from the following 

calculations: 

Acute Concentration of Concern (COC) in Water Body = Endpoint (0.011 mg/L) x 0.05 (Acute 

Level of Concern or LOC) = 5.5 x 10-4 mg/L = 5.5 x 10-4 mg/L 

Water Body Propoxur Mass Influx Triggering LOC = Acute COC (5.5 x 10-4 mg/L) x 

Conversion Factor (1,000 L/m3) x Conversion Factor (grams/1,000 mg) x Volume of Standard 

Pond (20,000 m3) = 11 grams of propoxur 

Equivalent Product Amount Triggering LOC = Mass of propoxur causing adverse impacts 

(11 grams) x Reciprocal of Propoxur Product Density (gallon/0.065 lbs from Table 2.1) x 

Conversion Factor (lbs./453.6 grams) = 0.373 gallons of product

This 11 gram critical mass of propoxur triggering the LOC for aquatic taxa can be placed into 

context with a spray can containing propoxur that is currently used. Based on spray cans of 
Page 22 of 39 

propoxur containing 397 grams of solution (from Reg. No. 279-3995 product label), the amount 

of solution that would trigger the LOC for listed aquatic invertebrates is an equivalent of 2.77 

spray cans. The calculation showing the determination of this quantity is provided below. It 

should be noted that there is one other product which is a much larger parcel of propoxur, 

containing 55 gallons of product at 1 percent a.i. (Reg. No. 84396-12). This product is also used 

for spot treatments by professional applicators using hand-held sprayers. However, the reference 

to spray cans shown below provides an clear perspective for the equivalent quantity of propoxur 

that would cause a concern for aquatic organisms associated with propoxur spot treatment use 

assuming that all of this quantity entered a water body. 

Equivalent	number	of	spray	cans ൌ 	 11	g	propoxur

൬

397	g	product

can ൰ ൈ 0.01fraction	of	propoxur

 = 2.77 spray cans

The results above show the application of propoxur required to induce adverse impacts to 

propoxur for listed species on an acute basis based upon the adverse impact LOC of 0.05. Table 

3.1 below summarizes these results for listed species and also includes the equivalent results for 

non-listed species based upon the acute adverse impact LOC of 0.5. . Due to a lack of 

scientifically-sound toxicological data, chronic exposure is not considered. 

a

 Acute impacts based on the following calculation: Daphnid acute endpoint (EC50 = 0.011 mg/L) x 0.05 

or 0.5 (LOCs for listed and non-listed species). Daphnid acute endpoint from MRID No. 00149172. 

b

 Based on the following calculation: Concentration of concern (mg/L) x Conversion factor (1,000 L/m3) 

x Conversion factor (grams/1,000 mg) x Volume of standard pond (20,000 m3

) 

c

 Based on the following calculation: Propoxur mass of concern (grams) x Reciprocal of propoxur 

product density (gallon/0.065 lbs from Table 2.1) x conversion factor (lbs./453.6 grams) 

d Based on the following calculation: Propoxur mass of concern (grams)/[Mass of product in spray can 

(grams) x % a.i.]. 

Refined Adverse Impacts Analysis 

Table 3.1. Summary of propoxur application thresholds to trigger adverse impacts for 

listed and non-listed species on an acute basis based on preliminary analysis. 

Adverse Impacts 

Thresholds 

Propoxur 

Water Body 

Concentration 

of Concern 

(mg/L) 

Propoxur 

Mass of 

Concern 

(grams)b

Equivalent 

Product 

Amount 

(gallons)c

Equivalent 

Number of 

Spray Cans 

(quantity)d

Acute Listed Species 

(LOC = 0.05) 

5.5 x 10-4 a 11 0.373 2.77 

Acute Non-Listed 

Species (LOC = 0.5) 

5.5 x 10-3 a 110 3.73 27.70 
Page 23 of 39 

The potential for the entire contents of 2.77 spray cans or 11 grams of propoxur entering a water 

body from a property spot treated with propoxur can be further qualified by evaluating the 

amount of propoxur that can enter a water body via runoff at toxicologically relevant 

concentrations. Since runoff of propoxur is being evaluated, PRZM/EXAMS can be used to 

evaluate the amount of propoxur applied that would be required to runoff in sufficient quantities 

to trigger adverse impacts to listed and non-listed aquatic species. Like the preliminary analysis 

above, this threshold will be based on the most sensitive endpoint for aquatic species 

(daphnid.EC50 = 0.011 mg/L) and LOCs for listed and non-listed species (LOC = 0.05 and LOC 

= 0.5, respectively). Therefore, the COCs determined from the preliminary analysis and shown 

in Table 3.1 are still used in this analysis to define the concern for adverse impacts associated 

with propoxur spot treatments. However, in this analysis, the equivalent amount of propoxur 

applied that can cause adverse impacts can be determined from the equivalent application rate 

input into PRZM/EXAMS from a propoxur spot treatment application scenario which produce 

EECs equivalent to the COCs. However, due to information lacking on the label regarding 

propoxur spot treatment applications, the following assumptions were developed to define the 

application scenario for propoxur spot treatments: 

The first assumption defining this application scenario will stipulate that only one propoxur 

application is made per year per site over time. The standard thirty-year simulation will be 

conducted in PRZM/EXAMS. Such an assumption with infrequent applications (one per year) is 

plausible for propoxur considering its very small overall usage. 

The second assumption defining this application scenario will apportion aquatic exposure 

according to treatment source area characteristics composing of 50 percent impervious surfaces 

and 50 percent residential ground surfaces. This apportionment to the source area is 

representative of many insecticide spot treatments for foundations encompassing the foundation 

itself and the surrounding grounds. This is further described in insecticide treatment surveys for 

pyrethroids provided by the Pyrethroid Working Group (MRID No. 49292101). 

The third assumption is that the use of modeling scenarios in the evaluation represent 

environmental conditions which result in upper-bound modeling concentrations. The CA 

Impervious Modeling Scenario was used to represent the impervious surface apportionment and 

the CA Residential Modeling Scenario was used to represent the residential grounds surface 

apportionment. It was verified that this was a vulnerable scenario since the weather station used 

for San Francisco Airport (WBAN No. 23234) was found to result in modeling concentrations 

similar to that resulting from climatologically wetter parts of the country such as Florida.7

The fourth assumption is regarding the determination of the amount of propoxur resulting in 

the adverse impacts. It will be assumed that the amount of mass of propoxur will be evenly 

distributed to a 10-hectare watershed. However, given its limited use and therefore propensity 

for it not to be used in community treatments, the calculation of the final determination of the 

amount of propoxur leading to adverse impacts will only assume that one property is treated per 

10-hectare watershed. Other ecological risk assessments have assumed treatments to multiple 

properties over a 10-hectare watershed. 

 

7

 The verification involved PRZM/EXAMS modeling using the CA Impervious and CA Residential scenarios 

simulated with 30-years of weather data from Tallahassee, FL. 
Page 24 of 39 

The remaining parameterization for PRZM/EXAMS is composed of the physical chemical and 

fate properties of propoxur utilizing EFED Model Input Parameter Guidance. The Surface Water 

Concentration Calculator interface (SWCC version 1.092, dated March 6, 2014) for 

PRZM/EXAMS is used in this supplemental evaluation. 

The application rate resulting in the acute COCs with the runoff scenarios may be determined by 

scaling the first-guess application rate of 1 kg a.i./ha used in the PRZM/EXAMS simulation to 

the application rate where PRZM/EXAMS EECs are equivalent to the acute COCs. The 

computation below shows that an application rate of 0.008 kg/ha of propoxur would correspond 

to an amount available for runoff to a water body which would result in adverse impacts for 

listed species on an acute basis: 

Equivalent App. Rate Causing Adverse Impacts = Acute COC (0.55 g a.i./L) ÷ 

PRZM/EXAMS Peak EEC Normalized to First-Guess Application Rate (69.25 g a.i./L per kg 

a.i./ha) = 0.008 kg a.i./ha 

Information on the PRZM/EXAMS simulations (e.g., input and processing to arrive at the 

results) is shown in Appendix A. Following the results calculated by PRZM/EXAMS, an 

equivalent minimum mass of 0.08 kg (80 grams) propoxur would have to be applied in order for 

enough of it to be available in runoff to cause adverse impacts to listed species. This is shown by 

assuming that this mass is applied uniformally throughout a 10-ha watershed, and that only one 

site is treated within this watershed. The calculation is shown below: 

Equivalent Mass Amount of Propoxur Causing Adverse Impacts = Equivalent App. Rate for 

Adverse Impacts (0.008 kg a.i./ha per site treated) x 10 ha = 0.08 kg a.i. = 80 grams of 

propoxur per site treated

A minimum of 80 grams of propoxur applied for adverse acute impacts for listed aquatic species 

is equivalent to 20.15 spray cans or 2.75 gallons or of product. These calculations are shown 

below: 

Equivalent	number	of	spray	cans ൌ 	 80	g	propoxur

൬

397	g	product

can ൰ ൈ 0.01fraction	of	propoxur

 = 20.15 spray cans 

Equivalent Product Amount Causing Adverse Impacts = Mass of propoxur causing adverse 

impacts = (80 grams) x Reciprocal of Propoxur Product Density (gallon/0.065 lbs from Table 

2.1) x Conversion Factor (lbs./453.6 grams) = 2.75 gallons of product

The results above show the application of propoxur required to induce adverse impacts to 

propoxur for listed species on an acute basis based upon the adverse impact LOC of 0.05. Table 

3.2 below summarizes these results for acute listed species and also includes the equivalent 
Page 25 of 39 

results for non-listed species based upon the adverse impact LOC of 0.5. . Due to a lack of 

scientifically-sound toxicological data, chronic exposure is not considered. 

a

 Acute impact based on the following calculation: Daphnid acute endpoint (EC50 = 0.011 mg/L) x 0.05 

or 0.5 (LOCs for listed and non-listed species). Daphnid acute endpoint from MRID No. 00149172. 

b

 Acute impact based on the following calculation: [COC (0.55 g a.i./L) ÷ PRZM/EXAMS peak EEC 

normalized to first-guess application rate (69.25 g a.i./L per kg a.i./ha)] x 10 ha watershed x Conversion 

Factor (1,000 grams/kg). Please refer to Appendix A for information regarding PRZM/EXAMS 

modeling. 

c

 Based on the following calculation: Propoxur mass of concern (grams) x Reciprocal of propoxur 

product density (gallon/0.065 lbs from Table 2.1) x conversion factor (lbs./453.6 grams) 

d Based on the following calculation: Propoxur mass of concern (grams)/[Mass of product in spray can 

(grams) x % a.i.]. 

As expected, the result in this refined analysis demonstrate that more propoxur has to be applied 

to exist at toxicologically relevant concentrations when its availability to runoff is considered 

versus when its availability to runoff is not considered as in the preliminary analysis. 

Water Quality Monitoring Data 

An extensive database of surface water and ground water monitoring exists for propoxur. 

However, there are no recent monitoring data available for propoxur beyond the year 20008

. 

Therefore, the existing monitoring data would not reflect the any representation of the current 

usage of propoxur considering that overall scope of uses has dramatically decreased. 

Incident Database Review 

A review on April 28, 2014, of the Ecological Incident Information System (EIIS version 2.1, 

USEPA, 2008), which is maintained by the Agency’s Office of Pesticide Programs and the 

 

8

 Citation: National Water Quality Monitoring Council Water Quality Portal: http://www.waterqualitydata.us/

Table 3.2. Summary of propoxur application thresholds to trigger adverse impacts for 

listed and non-listed species on an acute basis based on the refined analysis. 

Adverse Impacts 

Thresholds 

Propoxur 

Water Body 

Concentration 

of Concern 

(mg/L) 

Propoxur 

Mass of 

Concern 

(grams per 

site treated) 

Equivalent 

Product 

Amount 

(gallons)c

Equivalent 

Number of 

Spray Cans 

(quantity)d

Acute Listed Species 

(LOC = 0.05) 

5.5 x 10-4 a 80b 2.75 20.15 

Acute Non-Listed 

Species (LOC = 0.5) 

5.5 x 10-3 a 800b 27.50 201.50 
Page 26 of 39 

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

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

propoxur. 

All of the propoxur incidents were classified as highly probable and a result of misuse occurring 

between 1992 and 2000. All of the propoxur incidents involved birds and involved additional 

chemicals used in conjunction with propoxur. 

 Incident 004169-075 was reported by the Virginia Department of Game and Inland 

Fisheries in November 1992. After a group of thirty geese landed on a small pond, three 

dead geese were found floating in the water. Two of the dead geese were submitted for 

necropsy for pesticide analysis; residues of propoxur and famphur were found. It is 

suspected that the chemicals were misused to intentionally poison the geese. 

 Incident 004169-079 was reported by the Virginia Department of Game and Inland 

Fisheries in January 1993. A number sick or dead starlings (18) fell from a tree at a 

residence in Wythe county in late January. Analysis of the stomach contents of birds 

were analyzed and found to contain high concentrations of famphur and propoxur. In 

addition to the incident, there were reports of a neighbor purposefully poisoning the 

starlings. 

 Incident I011301-002 was reported by the New York Department of Environmental 

Conservation in November 2000. A pigeon was found dead on a rooftop in Queens, New 

York adjacent to a pile of mush food made up of peanuts and green pellets; analysis of 

the food showed the feed contained 424.2 mg/L of propoxur and 0.50 mg/L of 

brodifacoum. 

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

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

Agency as aggregate counts of incidents occurring per product per quarter. Ecological incidents 

reported in aggregate reports include those categorized as “minor fish and wildlife” (W-B), 

“minor plant” (P-B), and “other nontarget” (ONT) incidents. “Other nontarget” incident include 

reports of adverse effects to insects and other terrestrial invertebrates. For propoxur, registrants 

have reported 13 minor plant incidents, no minor fish and wildlife incidents, and no other 

nontarget incidents. The 13 plant incidents occurred between 1995 and 1998. One additional 

report of a wildlife incident was reported in 2011. No other details of the incidents are avialble. 

Although incident reports for propoxur have not been received by the Agency since 2011 and only 

three major incidents have been reported to the Agency, the absence of reported incidents should 

not be construed as the absence of incidents. Incident reports for non-target organisms typically 

provide information only on mortality events and plant damage incidents. Except for phytotoxic 

effects in terrestrial plants, sublethal effects, such as reduced growth or impaired reproduction, are 

rarely reported. However, the incident data that are available suggest that exposure pathways for 

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

3.2 Risk Description 
Page 27 of 39 

3.2.1 Exposure and Risk to Aquatic Organisms 

The discussion for this risk description will be based on the refined analysis in Section 3.1 since 

these results encompass a feasible exposure potential of propoxur spot treatments to aquatic water 

bodies since this analysis accounts for propxur’s availability in runoff. The underlying conclusions 

that can be developed from this analysis based upon the known use of propoxur outdoor spot 

treatments are described below: 

1. Propoxur risks to listed aquatic invertebrates associated with spot treatments are only 

possible to listed species on an acute basis. This finding is based on the effects observed 

to aquatic invertebrates most sensitive species (daphid), which may occur when greater 

than or equal to 2.75 gallons of product are applied (see Table 3.2). High-end propoxur 

spot treatment applications may potentially approach 2.75 gallons of product when hand 

held sprayers are used, mainly by professional applicators, most likely occurring only when 

relatively large treatments to foundations occur. However, it is important to note that while 

this potential exposure exists, the potential is low. Furthermore, the equivalent threshold 

application of 20.15 spray cans of propoxur products that need to be used in order for 

propoxur to exist in high enough quantities to pose a concern is very large (see Table 3.2). 

Therefore, this suggests that spot treatments with propoxur using spray cans would not 

pose a concern as risks would occur due to exorbitant and implausible uses of propoxur. 

2. Propoxur acute risks to non-listed aquatic species to aquatic species are not likely since the 

results of the refined analysis in Section 3.1 indicate that propoxur would need to be used 

in quantities in the range of 27.5 – 114.1 gallons of product or 201.5 – 849.2 spray cans 

(see Table 3.2). These are very large amounts of propoxur for any type of spot treatments. 

Therefore, none of the propoxur spot treatment uses are anticipated to result in any concern 

to non-listed aquatic species on an acute basis. 

As mentioned in the first point above, the potential for exposure leading to adverse impacts to 

listed aquatic species associated with hand-held spray applications to foundations are small. This 

is qualified further below: 

1. It appears that small applications and non-frequent applications are typical consistent with 

usage data associated with propoxur spot treatments. Please refer to Section 2.2 for details 

on the nationwide usage of propoxur. There is the propensity for small applications and 

non-frequent applications to be the prevailing trend for propoxur uses as suggested by small 

use volume for spot treatments. Therefore, propoxur product usage at 2.75 gallons would 

represent a very high application than what would be expected given the usage data 

available. 

2. The limited use of propoxur also suggests that it is not used widely in an organized fashion 

within communities. Therefore, the amount of material used in outdoor spot treatments 

will not be used in copious amounts and distributed widespread among different regions. 
Page 28 of 39 

3. Third, low use over specific areas are likely for propoxur since labels do not allow 

broadcast or continuous banded type of applications outdoors in many cases. 

It should be noted that further reductions in exposure would result if spot treatments occur at 

distances that are far enough away from streams and water bodies for propoxur to allow it become 

highly dispersed in runoff water upon entry to any downstream aquatic habitat. However, given 

propoxur’s high mobility and persistence in soil and water, especially in acidic and neutral 

environments, and high toxicity especially for aquatic invertebrates, even small exposures to 

propoxur occurring from spot treatments close to streams and water bodies may result and cause 

adverse impacts in aquatic habitats. Therefore, any possibility for exposure identified in this 

assessment is limited to instances where spot treatments occur close to aquatic habitats. 

Some of the current labels do not include hazard statements related to aquatic organisms. 

Therefore, EFED recommends that protective measures for addressing aquatic organisms 

associated with outdoor propoxur spot treatments be considered on future labels. 

There are no reported incidents of propoxur exposure to aquatic organisms resulting from spot 

treatment uses. However, the lack of incidences do not pre-empt any potential for risk identified 

for aquatic organisms. 

3.2.2 Risks to Terrestrial Organisms 

Exposure in terrestrial habitats would be contained within the bait stations, and propoxur residues 

would not be bioavailable to terrestrial organisms to other uses included spot treatments, tape strips 

and insecticide tags. As there is no complete exposure pathway to result in substantive exposure 

of non-target terrestrial organisms under the currently registered uses, EFED has presumed risk is 

discountable to terrestrial organisms. Refer to Section 2.6 for the full discussion on this rationale. 

3.3 Uncertainties, Limitations, and Data Gaps 

There are many uncertainties related to propoxur, mainly related to the instruction for its use on as 

a spot treatment on labels. However, there is some information submitted to the Agency that is 

valuable for use in the risk assessment and to use for the basis of default assumption for missing 

parameters. 

For example, for environmental fate data, there is some information lacking on facets of 

propoxur’s degradation in water. The hydrolysis study for propoxur indicates that it degrades 

mainly in alkaline environments (MRID No. 085762). However, the formation of degradates were 

not quantitatively determined in the study submitted to the Agency. In addition, there are no 

aquatic metabolism studies available for propoxur to confirm the alkaline-mediated mode of 

degradation found in the hydrolysis study. However, slow rates of degradation in weakly acidic 

conditions, consistent with the hydrolysis study, were also found in flooded conditions within the 

existing anaerobic soil metabolism study (MRID No. 085768). Therefore, following these lines 

of evidence, the supplemental non-deterministic aquatic exposure calculations for propoxur 

assumed that propoxur’s half-lives in the aquatic environment were parameterized as highly 

persistent following EFED’s modeling input parameter guidance. Propoxur’s persistent properties 
Page 29 of 39 

as the only stressor of concern is expected to be a conservative depiction of the exposure and risk 

profile from propoxur’s outdoor spot treatments considering propoxur’s high toxicity especially 

for aquatic invertebrates. 

Additionally, data gaps exist in the ecotoxicological profile for propoxur. For aquatic organisms, 

which are only expected to be potentially adversely impacted from outdoor propoxur spot 

treatment applications close to water bodies, there are only three acceptable studies available (two 

acute studies for freshwater fish and one acute study for freshwater invertebrates). One chronic 

study for aquatic invertebrates (MRID 41425301) is available but is classified as supplemental; 

classification was due to a lack of reporting on a number of factors including health and history of 

organisms at start of testing, volume of test solution and loading factor, total organic carbon, 

length, bodyweight, and number of offspring per female. These deviations resulted in invalidation 

of the endpoints for quantitative use. Therefore, no scientifically sound data are available to assess 

the potential application threshold of propoxur leading to adverse impacts to aquatic species on a 

chronic basis. However, the underlying conclusion that adverse impacts resulting from propoxur 

use are only possible where applications occur close to streams and water bodies would not be 

different due to chronic exposure considerations; adverse impacts would not anticipated to occur 

with spot treatments which occur over large distance from aquatic habitats. Furthermore, any 

protective measures placed on the label addressing potential exposure to aquatic invertebrates 

restricting outdoor spot treatments to areas far away from streams and water bodies would reduce 

any concerns for exposure. 

Besides data gaps, there is a substantial lack of information related to propoxur outdoor spot 

treatments on labels. First, there are not maximum application rates specified. In addition, there 

is no information or restriction on propoxur retreatments included on any label’s instructions. As 

a result of this lack of information and lack of a standard approach existent to evaluate outdoor 

spot treatments for risk assessments, a qualitative evaluation which back-calculated the amount of 

propoxur which would be required to be applied to induce adverse impacts based upon available 

toxicological data was conducted. Considering that propoxur spot treatments are expected to cover 

small discontinuous areas based on its limited use, any potential exposure causing adverse impacts 

for listed aquatic species resulting from hand-held spot treatment applications of propoxur is only 

defined to exist for treatments occurring close to streams or water bodies. Assumptions regarding 

the application scenario for the refined assessment conducted to evaluate the potential exposure 

causing adverse impacts is described in Section 3.1. The assumptions considered the scope of 

outdoor spot treatment uses of propoxur coupled with existing information on its overall low use 

volume nationwide. It should be noted that the assumption related to the 50 percent apportionment 

of the treated area to impervious surfaces and the remaining 50 percent to residential nonimpervious surfaces was based on the survey data for pyrethroid residential uses (MRID No. . 

49292101). While there may be uncertainty of the nature of the related surfaces for propoxur, it 

is expected that the proportion of propoxur impacted by impervious and non-impervious surfaces 

to be similar to pyrethroids even given propoxur’s small applications as compared to pyrethroid. 

The apportionment mentioned above used to evaluate the potential aquatic exposure related to 

propoxur spot treatments is consistent with previous aquatic exposure assessments for pyrethroids 

conducted to support ecological risk assessments. For details on the assumptions, please refer to 

Section 3.1 or Appendix A for information on the PRZM/EXAMS input parameters that were 

used to address spot treatments which may occur around foundations. 
Page 30 of 39 

4. Federally Threatened and Endangered (Listed) Species 

Concerns 

Section 7 of the Endangered Species Act, 16 U.S.C. Section 1536(a)(2), requires all federal 

agencies to consult with the National Marine Fisheries Service (NMFS) for marine and 

anadromous listed species, and/or the United States Fish and Wildlife Service (USFWS) for listed 

wildlife and freshwater organisms, if they are proposing an "action" that may affect listed species 

or their designated critical habitat. The federal action addressed herein is the proposed registration 

renewal of propoxur outdoor uses and it is expected that the use could occur nationwide. For a 

more detailed general description of the Endangered Species assessment process and the various 

components and assumptions of this process see Appendix B at the end of this document. 

For the outdoor uses of propoxur, risk only to listed species from acute exposure is possible 

for aquatic invertebrates associated with hand-held sprayer spot treatment uses for 

propoxur occurring close to streams or water bodies. However, the Agency has determined 

that there will be no habitat modification of any designated critical habitat for listed species from 

the current registered uses of propoxur. No other acute risks of concern were identified for 

non-listed aquatic invertebrates other listed or non-listed aquatic organisms including 

freshwater fish, estuarine/marine fish, and estuarine/marine invertebrates. 

Conclusions regarding terrestrial organisms and plants are based on the lack of a complete 

exposure pathway (Section 2.6). Exposure in terrestrial habitats would be limited, and therefore, 

listed species are not expected to be impacted from outdoor propoxur uses. 

Risk determinations by taxa for listed species are summarized in Table 4.1 below. A,“No Effect” 

risk determination for all listed species can be concluded for direct and indirect effects of propoxur 

use except for aquatic invertebrates either as there is no complete exposure pathway or adverse 

impacts are not expected. A “May Affect” determination is stipulated at this time for direct effects 

to aquatic invertebrates resulting from propoxur spot treatment use close to streams since adverse 

impacts are possible. This determination may be clarified further in the future depending on 

clarification of uncertainties which currently exist on product labels regarding propoxur spot 

treatments. 

Table 4.1. Potential Risks to Listed Taxa Associated with Direct or Indirect Effects from 

the Currently Registered Uses of Propoxur. 

Listed Taxon Direct Effects Indirect Effects 

Terrestrial and semi-aquatic plants – monocots No Effect 

Terrestrial and semi-aquatic plants – dicots No Effect 

Birds No Effect 
Page 31 of 39 

Table 4.1. Potential Risks to Listed Taxa Associated with Direct or Indirect Effects from 

the Currently Registered Uses of Propoxur. 

Listed Taxon Direct Effects Indirect Effects 

Terrestrial-phase amphibians and reptiles No Effect 

Mammals No Effect 

Terrestrial invertebrates No Effect 

Aquatic nonvascular plants No Effect 

Aquatic vascular plants No Effect 

Freshwater fish No Effect 

Aquatic-phase amphibians No Effect 

Freshwater invertebrates May Affect* No Effect 

Marine/estuarine fish No Effect 

Marine/estuarine invertebrates No Effect 

*Determination based on direct effects to listed species on an acute basis, only possible resulting from propoxur 

outdoor spot treatments using hand held sprayers applied to foundations which occur close to streams and water 

bodies. This determination may be clarified further in the future depending on clarification of uncertainties which 

currently exist on product labels regarding propoxur spot treatments.

5. Endocrine Disruptor Screening Program 

As required by FIFRA and FFDCA, EPA reviews numerous studies to assess potential adverse 

outcomes from exposure to chemicals. Collectively, these studies include acute, subchronic and 

chronic toxicity, including assessments of carcinogenicity, neurotoxicity, developmental, 

reproductive, and general or systemic toxicity. These studies include endpoints which may be 

susceptible to endocrine influence, including effects on endocrine target organ histopathology, 

organ weights, estrus cyclicity, sexual maturation, fertility, pregnancy rates, reproductive loss, 

and sex ratios in offspring. For ecological hazard assessments, EPA evaluates acute tests and 

chronic studies that assess growth, developmental and reproductive effects in different 

taxonomic groups. 

EPA has developed the EDSP to determine whether certain substances (including pesticide 

active and other ingredients) may have an effect in humans or wildlife similar to an effect 

produced by a “naturally occurring estrogen, or other such endocrine effects as the Administrator 

may designate.” The EDSP employs a two-tiered approach to making the statutorily required 

determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a 

chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal 

systems. Chemicals that go through Tier 1 screening and are found to have the potential to 

interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP where EPA 

will determine which, if any, of the Tier 2 tests are necessary based on the available data. Tier 2 

testing is designed to identify any adverse endocrine-related effects caused by the substance, and 

establish a dose-response relationship between the dose and the E, A, or T effect. 

Under FFDCA section 408(p), the Agency must screen all pesticide chemicals. Between 

October 2009 and February 2010, EPA issued test orders/data call-ins for the first group of 67 

chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. A second list 
Page 32 of 39 

of chemicals identified for EDSP screening was published on June 14, 20139 and includes some 

pesticides scheduled for registration review and chemicals found in water. Neither of these lists 

should be construed as a list of known or likely endocrine disruptors. 

Propoxur is not among the group of 58 pesticide active ingredients receiving EDSP test orders. 

For information on the status of the orders issued under the EDSP for each chemical, please visit 

our website at http://www.epa.gov/endo/ and click on the "Status of EDSP Orders/DCIs" in the 

Highlights Box. Additional information on the EDSP, including the policies and procedures, the 

list of 67 chemicals, the test guidelines and the Tier 1 screening battery, can also be found at this 

website. 

 

9

 See http://www.regulations.gov/#!documentDetail;D=EPA-HQ-OPPT-2009-0477-0074 for the final second list of 

chemicals. 
Page 33 of 39 

6. References 

American Conference of Governmental Industrial Hygienists, Inc. 1986. Documentation of the 

threshold limit values and biological exposure indices. Fifth edition. Cincinnati, OH: 

Publications Office, ACGIH. 

American Housing Survey for the United States, 2011. Department of Housing and Urban 

Development and U.S. Census Bureau. 

Berg, G. L., ed. 1986. Farm Chemicals Handbook. Willoughby, Ohio: Meister Publishing Co. 

Fletcher, J.S., J.E. Nellessen, and T.G. Pfleeger. 1994. Literature review and evaluation 

of the EPA food-chain (Kenaga) nomogram, an instrument for estimating pesticide 

residues on plants. Environ. Tox. Chem. 13:1383-1391. 

California DPR Pesticide Use Reporting. 2012. Chemical data. Available at: 

http://www.cdpr.ca.gov/docs/pur/pur12rep/chmrpt12.pdf 

Hayes, W. J. 1982. Pesticides studied in man. Baltimore, MD: Williams and Wilkins 

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. 

TOXNET. 1986. National library of medicine's toxicology data network. Hazardous Substances 

Databank. Public Health Service. National Institute of Health. U.S. Department of Health 

and Human Services. Bethesda, MD: NLM. 

USEPA. 1975. Ney, Ronald E Jr. Registration – Baygon MOS Insecticide. File No. 2075270 

U.S. Environmental Protection Agency, Office of Pesticide Programs, Environmental Fate 

and Effects Division. August 13, 1975. 

USEPA. 1976. Ney, Ronald E Jr. For use on mole cricket bait on lawn, golf courses, ornamental 

turfs, and pastures. U.S. Environmental Protection Agency, Office of Pesticide Programs, 

Environmental Fate and Effects Division. August 4, 1976. 

USEPA. 1977a. Cook, N. Registration for Use around the house. File No. 5719-AA. U.S. 

Environmental Protection Agency, Office of Pesticide Programs, Environmental Fate and 

Effects Division. January 18, 1977. 

USEPA. 1977b. Windberg, L.A. Amendment to Registration. File No. 3125-214, 3125-122, 

3125-146. U.S. Environmental Protection Agency, Office of Pesticide Programs, 

Environmental Fate and Effects Division. November 23, 1977. 

USEPA. 1977c. Windberg, L.A. and R.W. Holst. Amendment to Registration to Alfalfa and 

Pasture grass and Registration. File No. 3125-146 and 3125-GNA. U.S. Environmental 
Page 34 of 39 

Protection Agency, Office of Pesticide Programs, Environmental Fate and Effects 

Division. November 22, 1977. 

USEPA. 1977d. Sanders, F. Registration of SMCP Baygon 2% Mole Cricket Bait Insecticide. 

File No. 6720-EAU. U.S. Environmental Protection Agency, Office of Pesticide Programs, 

Environmental Fate and Effects Division. January 13, 1977. 

USEPA. 1977e. Windberg, Lamar A. Amendment to Registration – Barns. File No. 2075281. 

U.S. Environmental Protection Agency, Office of Pesticide Programs, Environmental Fate 

and Effects Division. November 23, 1977. 

USEPA. 1977f. O’Brien, Thomas F. Registration-Best Earwig and Sowbog Bait. File No. 

2075278. U.S. Environmental Protection Agency, Office of Pesticide Programs, 

Environmental Fate and Effects Division. August 5, 1977. 

USEPA. 1977g. Ney, Ronald E Jr. Registration for control of ants, including fire ants + carpenter 

ants. File No. 2075277. U.S. Environmental Protection Agency, Office of Pesticide 

Programs, Environmental Fate and Effects Division. February 17, 1977. 

USEPA. 1977h. Ney, Ronald E Jr. For use on alfalfa and pasture grass to control mosquitoes. 

File No. 2075279. U.S. Environmental Protection Agency, Office of Pesticide Programs, 

Environmental Fate and Effects Division. September 21, 1977. 

USEPA. 1977i. Cook, Norman J. Registration for Use around the house. File No. 2075274. U.S. 

Environmental Protection Agency, Office of Pesticide Programs, Environmental Fate and 

Effects Division. January 18, 1977. 

USEPA. 1978a. Craven, Henry T. Registration – Ant Trap. Acc No. 094546. U.S. 

Environmental Protection Agency, Office of Pesticide Programs, Environmental Fate and 

Effects Division. October 6, 1978. 

USEPA. 1978b. Tice, John. Registration of New Product – Grant’s Ant Control-Jel. Acc No. 

232459. U.S. Environmental Protection Agency, Office of Pesticide Programs, 

Environmental Fate and Effects Division. October 27, 1978. 

USEPA. 1983. Balcomb, R. Proposed Section 18 for use over flowing water to control 

mosquitoes. File No. 83-CA-76. U.S. Environmental Protection Agency, Office of 

Pesticide Programs, Environmental Fate and Effects Division. July 8, 1983. 

USEPA. 1987. Noles, John. Propoxur Registration Standard. Record No. 2075291 U.S. 

Environmental Protection Agency, Office of Pesticide Programs, Environmental Fate and 

Effects Division. May 5, 1987. 

USEPA. 1990. Felthousen, R.W. Amendment-Label Revision-Data Required. DP Barcode 

154393. U.S. Environmental Protection Agency, Office of Pesticide Programs, 

Environmental Fate and Effects Division. August 15, 1990. 
Page 35 of 39 

USEPA. 1991. Rexrode, Miachel. Label Review for Registration. File No. 62451-R. U.S. 

Environmental Protection Agency, Office of Pesticide Programs, Environmental Fate and 

Effects Division. January 24, 1991. 

USEPA.1996a.Food Quality Protection Act. http://www.epa.gov/oppsrrd1/registration_review/ 

USEPA. 1996b. Reregistration Eligibility Document for Propoxur, Science Chapter. U.S. 

Environmental Protection Agency, Office of Pesticide Programs. July 10, 1996. 

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. 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. 2006. N-methyl Carbamate Revised Cumulative Risk Assessment. U.S. Environmental 

Protection Agency, Office of Prevention, Pesticides and Toxic Substances, Office of 

Pesticide Programs, Washington DC. September 24, 2007. 

USEPA. 2008a. ECOTOXicology Database. Office of Research and Development National 

Health and Environmental Effects Research Laboratory’s (NHEERL’s) Mid-Continent 

Ecology Division (MED). June 30, 2008. http://cfpub.epa.gov/ecotox/ 

USEPA. 2008b. Ecological Incident Information System. June 24, 2008. 

http://www.epa.gov/espp/consultation/ecorisk-overview.pdf

U.S. Environmental Protection Agency. 1986 (Jan). Estimating pesticide sorption coefficients for 

soils and sediments. Richard E. Green and Samuel W. Karickhoff. Environmental Research 

Laboratory. Office of Research and Development. Athens, GA. 

U.S. Environmental Protection Agency. 1984 (Dec.). User's manual for the pesticide root zone 

model (PRZM). Release 1. Athens, GA: Environmental Research Laboratory. 

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., ed. 1983. The pesticide manual: A world compendium. Croydon, England: The 

British Crop Protection Council. 
Page 36 of 39 

Appendix A Qualitative Aquatic Exposure Modeling 

Summary 

Table A.1. Summary of PRZM/EXAMS input parameter values for physical chemical and fate 

properties used for propoxur surface water aquatic EECs associated with outdoor spot 

treatments. 

PRZM/EXAMS Input Parameter Input Value and Unit Source 

Physical Chemical Property Parameters 

Molecular Weight 209.2 g/mol MRID No. 151791 

Solubility in Water 1,974 mg/L EpiSuite, WSKOW v.1.42 

Vapor Pressure 6.5 x 10-6 torr@ 25°C Worthing C.R., 1983 

Environmental Fate Property Parameters

Soil-Water Partition Coefficient (Kd) 0.23 mL/g MRID No. 085770 

Average of Kd values from 

sandy loam, silt loam, and 

silty clay soils 

Hydrolysis (t1/2) Stable MRID No. 085762 

Value for pH7 

Aqueous Photolysis (t1/2) 13 days MRID No. 085763 

Aerobic soil metabolism (t1/2) 267.59 days MRID No. 085768 

90th percentile upper 

confidence bound from silt 

loam and sandy loam soil 

Aerobic aquatic metabolism (t1/2) 535.18 days EFED Model Input 

Parameter Guidance for Data 

Gap 

t1/2= Aerobic soil metabolism 

half-life x 2 

Anaerobic aquatic metabolism (t1/2) Stable MRID No. 085768 

No metabolism evident in 

water layer as degradation 

was equivalent in sterile 

versus non-sterile samples. 
Page 37 of 39 

Table A.1. Summary of PRZM/EXAMS input parameter values for physical chemical and fate 

properties used for propoxur surface water aquatic EECs associated with outdoor spot 

treatments. 

PRZM/EXAMS Input Parameter Input Value and Unit Source 

Application Parameters

Modeling Scenarios, Meteorological 

Station, Application Rate, Number of 

Applications, and 

Application Date 

CA_RLF Impervious & 

CA_RLF Residential 

 Weather Station: 

W23234 (San 

Francsico) 

 Application Rate: 

1.0 kg a.i./ha 

 1 application per year 

 Application Date: 

Nov. 10 

 Application dates 

conservatively selected 

based on maximum 

rainfall climatological 

date at meteorological 

station defined in each 

modeling scenario site 

after crop emergence 

date specified in PRZM 

crop scenario. 

 Application rates 

calculated based on 

assumptions for 

propoxur spot 

treatments defined in 

Section 6.1

Chemical Application Method Ground Application Propoxur product labels for 

spot treatment applications 

Application Efficiency 0.99 EFED Model Input 

Parameter Guidance 

Spray Drift Fraction 0 Assumption for spot 

treatment applications* 

* Spray drift not anticipated exposure route for spot treatment applications. 

Table A.2. Determination of total exposures determined from aquatic EECs from modeling 

scenarios for propoxur spot treatments.

Scenario 

Percent 

Contribution 

(%) 

Peak EEC 

(ppb per kg/ha) 

21-day EEC 

(ppb per kg/ha) 

60-day EEC 

(ppb per kg/ha) 

Surface Type Scenario Source Apportionment EECs 

CA Impervious 50 133 131 125.75 

CA Residential 50 6.38 6.25 6.13 

Composite One-in-Ten Year EEC from Above Surface Source Apportionment Contributions 

Total Exposure* 69.25 68.25 66.63 *

 Total exposure determined by weighted average of contributions from apportionments of source surface type 

defined in modeling scenario. Post-processing with daily concentrations from PRZM/EXAMS 30-year simulation 

with each scenario was conducted to determine the one-in-ten year composite aquatic EEC. 

 
Page 38 of 39 

Appendix B Endangered Species Assessment Information 

At this current stage of the Registration Review process, it is premature to make effects 

determinations for listed species until further refinements are conducted. To make effects 

determinations for individual species, useful refinements may include analyses of 1) more 

detailed, species-specific ecological and biological data; 2) more detailed and accurate 

information on Propoxur use patterns; and 3) sub-county level spatial proximity data for the cooccurrence of potential effects areas and listed species and any designated critical habitat. 

Examples of such refinements are described below. 

EFED is currently developing tools that are expected to further refine the assessment and are 

designed to support effects determinations for individual federally listed species and their 

designated critical habitats (where applicable). Scientific information obtained from the U.S. 

Fish & Wildlife Service (USFWS), the National Marine Fisheries Service (NMFS), and other 

reliable sources is being collated by EFED to address all currently listed species. The 

information will be stored in an Office of Pesticide Programs Pesticide Registration Information 

SysteM (PRISM) knowledgebase. The listed species knowledgebase will consist of an 

information repository that houses biological and behavioral information relevant to individual 

species (e.g., habitat, diet, and life history, including specific temporal and spatial associations) 

and a document repository that contains supporting documents (e.g., USFWS recovery plans) 

and electronic information (e.g., GIS data files). 

Refinements may also include more detailed analyses of the registered uses and their use patterns 

that result in LOC exceedances for federally listed species in the screening-level assessment. 

The analyses may include more information on where, when, and how Propoxur is used. Actual 

usage data (when available) and national land-cover datasets that indicate potential use sites 

[e.g., national land cover dataset (NLCD), crop data layer (CDL)] may be used to support a more 

refined analysis of where Propoxur is reasonably expected to be used. Similarly, refinements for 

the timing of applications and how Propoxur is used may be based on the analysis of additional 

usage data, beyond what were available at the time of the screening-level assessment, and a more 

in-depth exploration of agronomic practices. 

The U.S. Environmental Protection Agency, along with the U.S. Department of Agriculture 

(USDA), the U.S. Fish and Wildlife Service (FWS), and the National Marine Fisheries Service 

(NMFS), have announced the availability of a report developed by the National Academy of 

Sciences’ National Research Council outlining recommendations on specific scientific and 

technical issues related to the development of endangered and threatened species risk 

assessments for pesticides that are compliant with the Endangered Species Act (ESA) and the 

Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). The EPA, USDA, FWS and 

NMFS asked the NRC to consider a range of scientific and technical issues including: 

• identifying best available scientific data and information; 

• considering sub-lethal, indirect and cumulative effects; 

• assessing the effects of chemical mixtures and inert ingredients; 

• analyzing the effects of pesticide use through the use of models; 
Page 39 of 39 

• incorporating uncertainties into the evaluations; and 

• using geospatial information and datasets that can be employed by the agencies in the 

course of these assessments. 

After reviewing the NRC’s recommendations on these scientific and technical issues, the EPA 

and its federal partners will determine how these recommendations can be implemented and 

incorporated into the scientific approaches for developing listed species risk assessments. It is 

anticipated that any draft guidance and/or science policies developed by EPA and its federal 

partners as a result of the NAS recommendations would be released for public comment prior to 

implementation. 

The refinements based on individual species data; additional, detailed usage information, when 

available; and further recommendations from the NRC report are expected to help to more 

accurately identify potential areas of effect and to better inform effects and habitat 

determinations for listed species and any designated critical habitats. For example, if quizalofopp-ethyl is used when a particular species of concern is not present (e.g., it is migratory) or is not 

co-located in space, then risk of potential direct effects to the species may often be precluded. If 

LOCs are still exceeded for monocots, mammals, freshwater invertebrates, estuarine/marine 

invertebrates, and freshwater fish after conducting the refined analyses, further analyses of the 

potential spatial and temporal co-occurrence of listed species of concern (and any designated 

critical habitat) may be conducted. The extent of possible refinement in the analyses of 

spatial/temporal co-occurrence will largely depend on the scale and quality of the available subcounty level use site (e.g., NLCD, CDL) and species location data.