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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C., 20460

March 3, 2009

PC Code: 057901

DP Barcode: D356654

MEMORANDUM

Subject: Registration Review: Problem Formulation for Ecological Risk, 

Environmental Fate, Endangered Species, and Drinking Water 

Assessments for Trichlorfon

To: Kylie Rothwell, Chemical Review Manager

Tracy Perry, Team Leader

Reregistration Branch

Special Review and Reregistration Division

Office of Pesticide Programs

From: Melissa Panger, Ph.D., Biologist

Kristina Garber, Biologist

Environmental Risk Branch 4

Environmental Fate and Effects Division

Office of Pesticide Programs

Through: Elizabeth Behl, Chief

Environmental Risk Branch 4

Environmental Fate and Effects Division

Office of Pesticide Programs

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

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

and drinking water assessments to be conducted as part of the Registration Review of the 

organophosphate insecticide, trichlorfon (PC Code 057901). Functioning as the first 

stage of the risk assessment process for registration review, this problem formulation 

provides an overview of what is currently known about the environmental fate and

ecological effects associated with trichlorfon and its degradates. It also describes the 

preliminary ecological risk hypothesis and analysis plan for evaluating and characterizing 

risk to non-target species and the environment in support of the registration of trichlorfon. 
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Problem Formulation for the 

Environmental Fate, Ecological Risk, Endangered 

Species, and Drinking Water Assessments

in Support of the Registration Review of 

Trichlorfon

dimethyl2,2,2-trichloro-1-hydroxyethyl-phosphonate (CAS 52-68-6)

Prepared by:

Melissa Panger, Ph.D., Biologist

Kristina Garber, Biologist

Reviewed by:

R. David Jones, Senior Agronomist

Anita Pease, Senior Biologist

Elizabeth Behl, Branch Chief

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

March 3, 2009
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Table of Contents

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

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

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

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

3. Stressor Source and Distribution .................................................................................... 5

3.1. Mechanism of Action............................................................................................... 6

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

3.3. Environmental Fate and Transport........................................................................... 8

3.3.1. Degradation..................................................................................................... 10

3.3.2. Transport......................................................................................................... 10

3.3.3. Terrestrial Field Dissipation ........................................................................... 10

3.3.4. Bioaccumulation ............................................................................................. 11

4. Receptors...................................................................................................................... 11

4.1. Effects to Aquatic Organisms................................................................................ 12

4.2. Effects to Terrestrial Organisms............................................................................ 15

4.3. Incident Database Review...................................................................................... 17

4.4. Ecosystems Potentially at Risk .............................................................................. 20

5. Assessment Endpoints .................................................................................................. 20

6. Conceptual Model........................................................................................................ 20

6.1. Risk Hypothesis.................................................................................................... 21

6.2. Conceptual Diagram ............................................................................................. 21

7. Analysis Plan ............................................................................................................... 23

7.1. Stressors of Concern ............................................................................................. 24

7.2. Measures of Exposure........................................................................................... 24

7.3. Measures of Effect ................................................................................................ 26

7.4. Integration of Exposure and Effects ...................................................................... 27

7.5. Deterministic and Probabilistic Assessment Methods........................................... 27

7.6. Endangered Species Assessments.......................................................................... 27

7.7. Drinking Water Assessment .................................................................................. 28

7.8. Preliminary Identification of Data Gaps................................................................ 28

7.8.1. Fate.................................................................................................................. 28

7.8.2. Effects data for Trichlorfon ............................................................................ 32

7.8.3. Effects data for DDVP.................................................................................... 36

8. References.................................................................................................................... 39

Appendix A. Submitted Toxicity Data for Trichlorfon and DDVP................................. 46

Appendix B. The Risk Quotient Method and Levels of Concern..................................... 63

Appendix C. Data Call-In Tables..................................................................................... 65
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1. Purpose

The purpose of this problem formulation is to provide an understanding of what is known 

about the environmental fate and ecological effects of the registered uses of trichlorfon. 

Trichlorfon is an organophosphate used as an insecticide on golf course turf, home lawns, 

ornamentals (flowers, trees and shrubs), and ponds (ornamental and bait fish and nonfood aquatic plants). This document will provide a plan for analyzing data relevant to 

trichlorfon, and for conducting environmental fate, ecological risk, endangered species 

and drinking water assessments for registered trichlorfon uses. Additionally, this 

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

assumptions used to address those uncertainties relative to characterizing the ecological 

risk associated with the registered uses of trichlorfon. 

2. Problem Formulation

2.1. Nature of Regulatory Action

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

distributed or sold in the United States generally must be registered by EPA. In 

determining whether a pesticide can be registered in the U.S., EPA evaluates its safety to 

non-target species based on a wide range of environmental and health effects studies. In

1996, FIFRA was amended by the Food Quality Protection Act, and EPA was mandated 

to implement a new program for the periodic review of pesticides, i.e., registration review 

(http://www.epa.gov/oppsrrd1/registration_review/). The registration review program is 

intended to ensure that, as the ability to assess risk evolves and as policies and practices 

change, all registered pesticides continue to meet the statutory standard of no 

unreasonable adverse effects to human health and the environment. Changes in science, 

public policy, and pesticide use practices will occur over time. Through the new 

registration review program, the Agency periodically reevaluates pesticides to make sure 

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

As part of the implementation of the new Registration Review program pursuant to 

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

Agency is beginning its evaluation of trichlorfon to determine whether it continues to 

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

environmental fate, ecological risk, endangered species, and drinking water assessment 

chapter in support of the registration review will be posted in the initial docket opening 

the public phase of the review process.

2.2. Previous Risk Assessments

A national-level ecological risk assessment was completed as part of the reregistration 

eligibility decision (RED) for trichlorfon in January 1997 (USEPA 1997). The 

Environmental Fate and Effects Division’s (EFED) science chapter for the RED, which 

incorporated new data, was revised in 2000 (USEPA 2000). An interim Tolerance 

Reassessment and Risk Management Decision (TRED) for trichlorfon was conducted in 
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2001 (USEPA 2001). The TRED was finalized in July 2006 after the cumulative human 

health risk assessment of the organophosphate (OP) class of pesticides was completed 

(USEPA 2006b). 

A drinking water assessment was conducted for the TRED. In this assessment, it was 

concluded that drinking water risk estimates for surface and ground waters did not exceed 

levels of concern, except for children aged 1-6 obtaining drinking water from surface 

water sources (USEPA 2006b).

The ecological risk assessment included in the trichlorfon RED was based on laboratory

fate and ecotoxicological data submitted by the registrant in support of reregistration and 

from data in publicly available literature, and incident reports of adverse effects on nontarget organisms associated with the use of trichlorfon. The previous ecological risk 

assessments considered the parent chemical only (i.e., the degradates of toxicological 

concern were not considered). The primary environmental concerns identified in the 

1997 and 2000 environmental fate and ecological risk assessments were acute and 

chronic risks to birds, mammals, fish, and aquatic invertebrates (USEPA 1997, 2000).

Based on the results of the TRED, a number of mitigation measures were recommended

to address risks to handlers and workers. These risk mitigation measures included the 

following: prohibit broadcast treatment to golf course fairways (permit spot treatment to 

fairways); require a 7-day application interval for application to turf and limit 

applications to no more than 3 per calendar year; require applicators to use a truck-drawn 

spray rig for application to fish ponds over 1 acre; and prohibit foliar applications to 

ornamentals (allow only direct soil spray to base of the plant). These mitigation 

measures appear on some, but not all, of the current trichlorfon labels (see Section 3.2).

An emergency exemption petition (Section 18) ecological risk assessment for use of 

trichlorfon on ornamentals (in Kansas) was also completed by EFED (1996). The results 

of the Section 18 assessment indicated that the proposed use of trichlorfon on 

ornamentals in Kansas would not result in risks to non-target organisms. 

EPA reinitiated a formal consultation with the U. S. Fish and Wildlife Service (USFWS)

in 1989 regarding trichlorfon impacts on endangered species. This consultation was on 

selected portions of five previous “cluster” biological opinions evaluating pesticides for 

certain crops (corn, cotton, soybeans, sorghum, wheat, barley, oats and rye), forestry use 

pesticides, mosquito larvicides, and rangeland and pastureland pesticides. As a result, the 

USFWS issued a formal Biological Opinion (USFWS 1989). The opinion identified 79

aquatic species (6 amphibians, 41 fish, 6 aquatic invertebrates, and 25 mussels) and one 

terrestrial species (a bird) that were classified as “in jeopardy” from trichlorfon use.

3. Stressor Source and Distribution

Trichlorfon degrades to dichlorvos (DDVP), which is also a pesticide active ingredient 

(PC Code: 084001). DDVP is a registered pesticide used as an insecticide applied to 

greenhouses, mushroom houses, residential areas, and premise treatments in agricultural 
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areas (e.g. barns and sheds) (USEPA 2006a). Unlike in previous ecological assessments 

conducted by the Agency for trichlorfon, the major degradate DDVP will be considered 

in the ecological risk assessment conducted as part of the Registration Review process.

The assessment for registration review will estimate risk from exposure to trichlorfon, 

and its degradate DDVP by evaluating “total trichlorfon residues of concern” (trichlorfon 

plus DDVP).

Although DDVP is a major degradate of trichlorfon, ecological and endangered species 

assessments for the trichlorfon registration review will not evaluate the usage or impact 

of DDVP as a primary active ingredient or as a degradate of other pesticide products. 

While DDVP may potentially be used simultaneously (for different purposes) within the 

same areas as trichlorfon, the use of DDVP will not be addressed in the ecological and 

endangered species risk assessments for the trichlorfon registration review. However, the 

upcoming drinking water assessment for the trichlorfon registration review will consider 

all sources of DDVP, including direct applications of DDVP as a pesticide active 

ingredient, as well as uses of trichlorfon and naled (PC code: 034401), which both 

degrade to DDVP.

3.1. Mechanism of Action

Trichlorfon, dimethyl 2,2,2-trichloro-1-hydroxyethyl-phosphonate, is an insecticide 

belonging to the organophosphate class of pesticides. Organophosphate toxicity is based 

on the inhibition of the enzyme acetylcholinesterase, which cleaves the neurotransmitter 

acetylcholine. Inhibition of acetylcholinesterase by organophosphate insecticides 

interferes with proper neurotransmission in cholinergic neurosynapses and neuromuscular 

junctions. The trichlorfon degradate DDVP has a similar mode of action.

3.2. Overview of Pesticide Use and Usage

Trichlorfon was originally registered for use in the United States in 1955. Currently, 

labeled uses of trichlorfon include turfgrass (golf courses, recreational turf and residential 

turf), flowers, shrubs, trees, and ponds (those that contain bait and/or ornamental fish

and/or non-food aquatic plants). There are both commercial and residential uses. There 

are currently nine active Section 3 and three Special Local Needs labels for products

containing trichlorfon (

Table 1). There are both granular and flowable uses. According to the product labels, 

trichlorfon can be applied by aerial or ground equipment. Currently there is only one 

label that allows for aerial applications (Dylox 80 SP, EPA reg. no.: 432-1326); all other 

labels limit applications to ground equipment. The maximum single application rate for 

trichlorfon is 8.15 lb a.i./acre. None of the current labels specify a maximum number of 

applications allowed per year. Some labels specify a minimum 7-day application interval

and a maximum yearly application rate of 24.5 lb a.i./acre (

Table 1). The remaining labels do not specify a minimum application interval or a 

maximum yearly application rate. 
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At this time, no national level use data have been identified for trichlorfon. Pesticide use 

information from the California Department of Pesticide Regulation (CDPR 2007), 

include county-level data for various trichlorfon uses from 2001-2003. Past uses of 

trichlorfon in California include: landscape maintenance, greenhouse, and water areas. 

Table 1. Summary of Current Trichlorfon Labels.

PRODUCT

(% a.i.)/ EPA 

REG. NO.

USES APPL. 

METHOD(S)

MAX. SINGLE 

APPL. RATE

MAX 

YEARLY 

APPL. 

RATE/NO. 

OF APPL.

APPL. 

INTERVAL

RESTRICTIONS

Dylox 80 

Concentrate 

(80%)/432-1289

For formulation 

into end use 

products

N/A N/A N/A N/A Only for formulations 

into end-use products 

on lawns, turf and 

recreation areas

Dylox 80 SP 

(80%)/432-1326 

Flowers, shrubs, 

and trees and 

recreational 

lawns and turf 

Ground

Aerial 

8.15 lb a.i./acre 

Narcissus - 16 

oz a.i./1,000 feet 

of row 

For Narcissus

– 1/year

All other use -

Not specified

Not specified - Do not apply directly 

to water.

Dylox 80 Turf and 

Ornamental 

(80%)/432-1289 

Landscape 

flowers, shrubs, 

trees, and 

landscape and 

recreational turf 

Ground 8.15 lb a.i./acre 

Narcissus - 16 

oz a.i./1,000 feet 

of row (repeat 

treatments 

annually)

24.5 lb 

a.i./acre

No. of 

Applications

Not Specified

7 days

Dylox 420 SL 

(37.3%)/432-1464 

Landscape 

flowers, shrubs, 

trees, and 

landscape and 

recreational turf; 

golf course and 

residential turf

Ground 7 lb a.i./acre 

Narcissus – 13.8 

oz a.i./1,000 feet 

of row 

24.5 lb 

a.i./acre 

For Narcissus

– 1 

application/ 

year

All other use 

– No. of 

applications 

not specified

7 days

- Do not apply directly 

to water.

- Do not apply when 

average wind speeds are 

greater than 15 mph

- Apply product using 

spray nozzles which 

produce a coarse 

droplet size 

- Do not apply within 

25 ft of lakes, 

reservoirs, rivers, 

permanent streams, 

marshes, natural ponds, 

or estuaries.

- Do not apply through 

any type of chemigation 

system

- Golf courses: 

broadcast use is limited 

to tees and greens; use 

on fairways is limited to 

spot treatments

Dylox 80 (80%)/ 

FL03001200

(432-1289)

Commerciallyoperated 

aquaculture 

production 

systems 

containing

ornamental fish 

or non-food 

aquatic plants

Hand-held 

sprayer 

(systems less 

than 1 acre)

Truck-drawn 

sprayer 

(systems 

greater than 1 

acre)

0.25 mg a.i./L Not specified 14-days None

Dylox 80 (80%)/ 

AR98000300

(432-1289)

Dylox 80 (80%)/ 

MO99000500

(432-1289)

Commerciallyoperated ponds 

used for bait fish 

and ornamental 

fish production

aquatic plants

Not specified 

(limited to 

ground 

equipment on 

Federal label)

0.25 mg a.i./L Not specified Not specified 

(7-day 

interval on 

Federal label)

None

Dylox 6.2 Turfgrass Ground 8.10 lb a.i./acre 24.5 lb 7 days - Do not apply directly 
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PRODUCT

(% a.i.)/ EPA 

REG. NO.

USES APPL. 

METHOD(S)

MAX. SINGLE 

APPL. RATE

MAX 

YEARLY 

APPL. 

RATE/NO. 

OF APPL.

APPL. 

INTERVAL

RESTRICTIONS

Granular (6.2% 

trichlorfon)/432-

1308 (Bayer 

Environmental 

Science)

Granular

The Andersons 

Tee Time 

Insecticide with 

6.2% Dylox (6.2% 

trichlorfon)/9198-

110 (the 

Andersons Lawn 

Fertilizer Division)

Granular

a.i./acre 

Max. no. of 

applications 

not secified

to water

- Golf courses: do not 

apply within 25 ft of 

lakes, reservoirs, rivers, 

permanent streams, 

marshes, natural ponds, 

or estuaries

- Not for use on turf 

being grown for sale

- Must be watered in 

after application to 

move product into root 

zone

- Golf courses: 

broadcast use is limited 

to tees and greens; use 

on fairways is limited to 

spot treatments

Dylox Grub 

Control 

(6.2%)/432-1394 

Granular

Lawns

Dylox 9.3% Insect 

Granules 

(9.3%)/72155-83 

Granular

Dylox Insect 

Granules 

(6.2%)/72155-33 

Granular

Lawns 

(residential use 

only)

Ground 8.10 lb a.i./acre Not specified Not specified - Do not apply directly 

to water

- Do not apply near fish 

pools, ponds, streams or 

lakes

- Water thoroughly 

within 24 hrs after 

applying

3.3. Environmental Fate and Transport

The chemical structures of trichlorfon and DDVP are depicted in Figure 1. Registrantsubmitted data defining the physical, chemical, fate and transport characteristics 

associated with trichlorfon are summarized in Table 2. As part of registration review, 

available fate studies for trichlorfon have been reevaluated by EPA. The fate and 

transport of trichlorfon in the environment is briefly discussed below.

Cl

Cl

Cl

OH

P O

CH3

O O

CH3 O

CH3

O

P O

CH3

O

Cl

Cl

Trichlorfon DDVP
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Figure 1. Structures of trichlorfon and DDVP.

Table 2. General Chemical and Environmental Fate Properties of Trichlorfon and DDVP.

Chemical/Fate Property Trichlorfon

Value (source)

DDVP 

Value (source)

Molecular Weight (MW; g/mol) 257.4

(MRID 00152133)

221.0

(USEPA 2006a)

Water Solubility (Sol; mg/L; at 25 °C) 1.36x105

(MRID 00152133)

0.15 x105

(USEPA 2006a)

Vapor Pressure (VP; torr; at 25oC) 3.75-4.5x10-6

(MRID 41535301, 41535302)

1.2x10-2(@20oC)

(USEPA 2006a)

Henry's Law Constant (H;atm-m

3

/mol) 8.20-9.84 x10-11

(*)

2.75 x10-6

(*)

Octanol-water Partition Coefficient (Log KOW) 0.30

(MRID 00162307)

1.58

(MRID 40798103)

Octanol-air Partition Coefficient (Log KOA) 9.7

(**)

6.1

(**)

Organic carbon normalized partition coefficient 

(L/kg; KOC)

58.8*

(EPISUITE v. 3.20)

37

(MRID 41354105)

Hydrolysis half lives (days) No data available pH 5: 11.6

pH 7: 5.2

pH 9: 0.88

(MRID 41723101)

Aqueous photolysis half-life (days) Stable

(MRID 00148975)

10 

(MRID 43326601)

Soil Photolysis half-life (days with 12 h light/12 h 

dark)

No data available 0.65

(MRID 43642501)

Aerobic Soil Metabolism half-life (days) 6.4

(MRID 42243601)

0.42

(MRID 41723102)

Anaerobic Soil Metabolism half-life (days) 1.8

(MRID 42243601)

6.2

(MRID 43835701)

Aerobic Aquatic Metabolism half-life (days) No data available No data available

Anaerobic Aquatic Metabolism half-life (days) No data available 4.5

(MRIDs 40618201, 41354102, 

42445101)

*Estimated according to: ( 2002)

*

*760 USEPA

Sol MW

VP H =

**Estimated using Episuite v. 3.20.
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3.3.1. Degradation

No scientifically valid studies are available to describe the degradation of trichlorfon by

hydrolysis. Degradation of DDVP by hydrolysis is pH dependant. In a hydrolysis study, 

DDVP half-lives decreased with increasing pH, with observed half-lives of 11.6 days, 5.2 

days, and 0.88 days, at pH 5, 7 and 9, respectively (MRID 41723101).

In a supplemental aqueous photolysis study, trichlorfon was stable to photolysis (MRID 

00148975). Available aqueous and soil photolysis studies indicate that DDVP is more 

susceptible to photodegradation than trichlorfon, with half-lives of 10 and 0.65 days, 

respectively (MRIDs 43326601 and 43642501).

In an acceptable aerobic soil metabolism study, trichlorfon had a half-life of 6.4 days on a 

sandy loam soil. During this study, 3 major degradates were observed: dichloroacetic acid 

(DCA) and 1-hydroxy-2,2-dichlorovinyl phosphate (HDCP) and carbon dioxide. DDVP 

was not detected as a degradate in this study (MRID 42243601). In an aerobic soil 

metabolism study, DDVP had a half-life of 0.42 days (MRID 41723102). 

In an acceptable anaerobic soil metabolism study conducted with the same sandy loam 

soil, trichlorfon had a half-life of 1.8 days. Major degradates observed during this study

included: DCA, HDCP, carbon dioxide and glyoxylic acid (GA). DDVP was observed as 

a minor degradate (MRID 42243601). In an anaerobic soil metabolism study, DDVP had 

a half-life of 6.2 days (MRID 43835701).

3.3.2. Transport 

No scientifically valid studies are available to define the mobility of trichlorfon in soil. 

The estimated organic carbon partition coefficient (Koc) of 58.8 (EPIsuite, v.3.20) 

suggests that trichlorfon may be mobile in soil. Based on the results of an acceptable soil 

TLC study, DDVP is also mobile, with a Koc of 37 L/kg (MRID 41354105).

Consideration of the vapor pressure (3.75-4.5x10-6 torr; MRIDs 41535301, 41535302) 

and Henry’s Law constant (8.20-9.84x10-11 atm-m

3

/mol) of trichlorfon indicates that it is 

unlikely to be transported significantly into the air through volatilization from the 

treatment site. In contrast, the vapor pressure (1.58x10-2torr; EPIsuite v.3.20) and 

Henry’s Law constant (3.62x10-7atm-m

3

/mol) of DDVP are several orders of magnitude 

higher than those of trichlorfon, suggesting that DDVP may volatilize when it has been 

formed from trichlorfon. 

In a laboratory volatility study, 84% of trichlorfon residues remained on the soil to which 

it was applied 14 days previously. Volatilized residues comprised 14% of the total 

applied, and were identified as carbon dioxide. Trichlorfon and DDVP were not 

identified as volatilized residues (MRID 40279302). 
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3.3.3. Terrestrial Field Dissipation

Two supplemental terrestrial field dissipation studies are available where trichlorfon was 

applied to sandy loam soil and to turf in field lysimeters contained in Ontario and 

Missouri (MRIDs 47519201 and 45895501, respectively). In the bare soil treatments of 

both studies, the majority of the applied residues were detected in the upper 0-6 inches of 

the test soil, with a half life of 3.1 days in the Ontario test and 1.9 days in the Missouri 

test. Carbon dioxide was detected as a major degradate in the Ontario test and a minor 

degradate in the Missouri studies. In both studies, DCA was detected as a major 

degradate. DDVP was detected as a minor degradate in the Ontario study, but undetected 

in the Missouri study. The maximum residues detected in the leachate comprised <0.2% 

of the applied. 

3.3.4. Bioaccumulation

The octanol-water partition coefficients of trichlorfon (Log KOW = 0.30; MRID 

00162307) and DDVP (Estimated Log KOW = 0.60; EPIsuite, v.3.20) indicate that 

trichlorfon and DDVP are not expected to bioaccumulate in aquatic ecosystems. 

The estimated Log octanol-air partition coefficients (Log KOA) for trichlorfon and DDVP 

(9.7 and 6.1, respectively; EPIsuite, v.3.20) in combination with their Log KOW suggest

that biomagnification of trichlorfon and DDVP in terrestrial food chains is unlikely

(Kelly et al. 2007). In addition, biomagnification in terrestrial food chains may be 

limited by transformation of trichlorfon and DDVP to less toxic degradates.

4. Receptors

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

assessment for trichlorfon relies on a surrogate species approach. Toxicological data 

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

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

(receptors) included under these taxonomic groupings. 

Because the trichlorfon degradate DDVP is also a registered pesticide (PC Code: 

084001), data are available to define the toxicity of this degradate of concern to nontarget organisms. To adequately capture the risk from trichlorfon use, the toxicity and 

potential exposure to non-target animals to trichlorfon and its degradate DDVP will be 

considered. The most sensitive endpoints from the available toxicity data for trichlorfon 

and DDVP will be used to quantify risk.

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

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

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

grade active ingredient, degradates, and when available, formulated products (e.g., “SixPack” studies). The open literature studies are identified through EPA’s 
12 of 74

ECOTOXicology (ECOTOX) database (USEPA 2007a), which employs a literature 

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

wildlife. The evaluation of both sources of data may also provide insight into the direct 

and indirect effects of trichlorfon and its degradate DDVP on biotic communities from 

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

functional characteristics of the affected communities. Open literature data from 

ECOTOX on trichlorfon are not currently available; however, once received, they will be 

evaluated for possible quantitative and/or qualitative inclusion in this risk assessment.

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

trichlorfon and DDVP in aquatic and terrestrial habitats is provided in Sections 4.1 and 

4.2, respectively. A summary of ecological incidents associated with trichlorfon and 

DDVP and a description of ecosystems potentially at risk are provided in Sections 4.3

and 4.4, respectively.

4.1. Effects to Aquatic Organisms

Trichlorfon is classified as very highly toxic to freshwater invertebrates, highly toxic to 

freshwater fish, and practically nontoxic to estuarine/marine invertebrates (Eastern 

oysters) on an acute exposure basis. No acceptable acute data for trichlorfon are 

available for estuarine/marine fish. DDVP is classified as very highly toxic to freshwater

and estuarine/marine invertebrates, highly toxic to freshwater fish, and moderately toxic 

to estuarine/marine fish on an acute exposure basis (Table 3). No acceptable aquatic 

plant toxicity data are currently available for trichlorfon or DDVP. Summaries of the 

most sensitive acute aquatic toxicity data available from registrant-submitted studies for 

trichlorfon and DDVP are provided in Table 4 and in Table 5, respectively. Additional 

information on the ecotoxicity data currently available for trichlorfon and DDVP are 

provided in APPENDIX A.

Table 3. Classifications of acute toxicities of trichlorfon and DDVP to aquatic animals.

TAXON Trichlorfon DDVP

Freshwater Invertebrate Very highly toxic1 Very highly toxic1

Freshwater Fish Highly toxic2 Highly toxic2

Marine/Estuarine Invertebrate Practically non-toxic4 Very highly toxic1

Marine/Estuarine Fish No data Moderately toxic3

1LC50<0.1 mg/L

2LC50 0.1 - 1.0 mg/L

3LC50 >1.0 - 10 mg/L

4LC50>100 mg/L

For trichlorfon, chronic effects in aquatic animals include diminished survival 

(freshwater and estuarine/marine invertebrates), reproduction (freshwater fish and 

estuarine/marine invertebrates), and growth (estuarine/marine invertebrate). No acute or 

chronic data are available for estuarine/marine fish for trichlorfon. For DDVP, chronic 

effects in aquatic animals include diminished survival (freshwater and estuarine/marine 

fish), reproduction (freshwater invertebrates), and growth (freshwater and 

estuarine/marine invertebrates and estuarine/marine fish). Summaries of the most 
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sensitive chronic aquatic toxicity data available from registrant-submitted studies for 

trichlorfon and DDVP are provided in Table 4 and in Table 5, respectively. 

Based on currently available data, DDVP appears to be more or equally as toxic to 

aquatic animals when compared to trichlorfon on both an acute and chronic exposure 

basis. 

Table 4. Summary of Submitted Studies for Aquatic Organisms Exposed to Technical Trichlorfon 

(Most Sensitive Endpoints for Each Taxon).

TAXON & SPECIES ENDPOINT MRID STUDY 

CLASSIFICATION

COMMENTS

Freshwater 

Invertebrate (Acute)

Pteronarcella badia

EC50 (96-hr) = 

5.3 μg a.i./L

40098001 Supplemental Adequate for RQ calculation; 

based on analysis of raw data, the 

slope is 5.2 (C.I.: 2.6 – 7.9)

Freshwater 

Invertebrate 

(Chronic)

Daphnia magna

NOAEC = 

0.0057 μg a.i./L

40452601 Acceptable LOAEC (0.0086 μg a.i./L)

based on survival (all endpoints 

were affected in the study, the 

most sensitive was survival)

Freshwater Fish

(Acute)

Rainbow trout

(Oncorhynchus mykiss)

LC50 (96-hr) = 

158 μg a.i./L

40098001 Supplemental Adequate for RQ calculation 

(reported as 156 in the M&E 

volume); no slope could be 

calculated

Freshwater Fish 

(Chronic) 

Rainbow trout

(Oncorhynchus mykiss)

NOAEC = 110 

μg a.i./L

425717-01 Acceptable Early life-stage study; LOAEC 

(234 μg a.i./L) based on increased 

time to swim up 

Estuarine/ Marine 

Invertebrate (Acute)

Eastern oyster 

(Crassostrea virginica)

EC50 >114 mg 

a.i./L

444992-01 Acceptable 96-hr shell-deposition study; 

NOAEC = 83 mg a.i./L (based on 

16% decrease in shell deposition)

Estuarine/ Marine 

Invertebrate 

(Chronic)

Mysid (Mysidopsis 

bahia)

NOAEC = 3.1 

μg a.i./L

444992-02 Acceptable Flow-through, life-cycle study; 

LOAEC (234 μg a.i./L)

based on decreased number of 

neonates produced, decreased 

survival, decreased weight, and 

decreased length

Estuarine/

Marine Fish 

No acute or chronic exposure data available

Aquatic Non-Vascular

and Vascular Plants

No data available
14 of 74

Table 5. Summary of Submitted Studies for Aquatic Organisms Exposed to Technical DDVP (Most 

Sensitive Endpoints for Each Taxon).

TAXON & 

SPECIES

ENDPOINT MRID STUDY 

CLASSIFICATION

COMMENTS

Freshwater 

Invertebrates 

(Acute)

Water flea (Daphnia 

pulex)

EC50 = 0.066 μg 

a.i./L

40098001 Acceptable None

Freshwater 

Invertebrates 

(Chronic)

Water flea (Daphnia 

magna)

NOAEC = 0.0058 

μg a.i./L

43890301 Acceptable LOAEC (0.0122 μg a.i./L) 

based on reduced egg 

production and growth 

(length and weight)

Freshwater Fish 

(Acute)

Cutthroat trout 

(Oncorhynchus 

clarki)

LC50 = 170 μg 

a.i./L

40098001 Acceptable None

Freshwater Fish 

(Chronic)

Rainbow trout 

(Oncorhynchus 

mykiss)

NOAEC = 5.2 μg 

a.i./L

43788001 Acceptable LOAEC (10.1 μg a.i./L)

based on decreased posthatch larval survival

Estuarine/ Marine 

Invertebrates 

(Acute)

Mysid (Americamysis 

bahia)

EC50 = 19.1 μg 

a.i./L

43571408 Acceptable None

Estuarine/ Marine 

Invertebrates

(Chronic)

Mysid (Americamysis 

bahia)

NOAEC = 1.48 μg 

a.i./L

43854301 Acceptable LOAEC (3.25 μg a.i./L)

based on reduced growth 

(weight and length)

Estuarine/ Marine 

Fish (Acute)

Sheepshead minnow

(Cyprinodon 

variegates)

LC50 = 7,350 μg 

a.i./L

43571403 Acceptable None

Estuarine/ Marine 

Fish (Chronic)

Sheepshead minnow

(Cyprinodon 

variegates)

NOAEC = 960 μg 

a.i./L

43790401 Acceptable LOAEC (1840 μg a.i./L)

based on reduced survival 

and length

Aquatic NonVascular and 

Vascular Plants 

No acceptable data available
15 of 74

4.2. Effects to Terrestrial Organisms

Trichlorfon is classified as moderately toxic to mammals on an acute oral basis. There 

are currently no acceptable trichlorfon acute oral or sub-acute dietary toxicity data for 

birds. DDVP is classified as very highly toxic and moderately toxic to birds on an acute 

oral and sub-acute dietary exposure basis, respectively, and is classified as moderately 

toxic to mammals on an acute oral exposure basis. Trichlorfon is practically nontoxic 

and DDVP is highly toxic to honey bees on an acute contact exposure basis (Table 6). 

Available data on the toxicity of trichlorfon and DDVP to terrestrial organisms are 

summarized in Table 7 and Table 8, respectively.

Table 6. Classifications of Acute Toxicities of Trichlorfon and DDVP to Terrestrial Animals.

TAXON Trichlorfon DDVP

Mammals Moderately toxic1 Moderately toxic1

Birds No data Very highly toxic2

Honey bees Practically non-toxic3 Highly toxic4

1LD50 51 -500 mg/kg

2LD50 <10 mg/kg

3LD50 >11 μg/bee

4LD50 <2 μg/bee

For trichlorfon, chronic effects in terrestrial animals include diminished reproduction 

(birds) and growth (mammals). For DDVP, chronic effects in terrestrial animals include 

diminished reproduction (birds and mammals) and growth (mammals).

As with aquatic animals, DDVP appears to be more or equally as toxic to terrestrial 

animals when compared to trichlorfon on both an acute and chronic exposure basis. 

No terrestrial plant data are available for trichlorfon or DDVP.
16 of 74

Table 7. Summary of Submitted Studies for Terrestrial Animals Exposed to Technical Trichlorfon 

(Most Sensitive Endpoints for Each Taxon).

TAXON & 

SPECIES

ENDPOINT MRID STUDY 

CLASSIFICATION

COMMENTS

Birds (Acute) No acceptable acute data available

Birds (Subacute)

No acceptable acute data available

Birds (Chronic)

Bobwhite quail 

(Colinus 

virginianus)

NOAEC = 9 

mg/kg-diet

43119501 Acceptable LOAEC (30 mg/kg-diet) based on 

a decrease in hatchling survival 

(no eggshell thickness effects at 

any level – highest = 85 ppm); 

there were 10 mortalties (1 

control, 1 at the 8 ppm conc., and 

8 at the 85 ppm conc.)

Mammals

(Acute)

Laboratory rat 

(Rattus 

norvegicus)

LD50 = 136 mg 

a.i./kg-bw

00256446 Acceptable None

Mammals 

(Chronic)

Laboratory rat 

(SpragueDawley)

NOAEC = 500 

mg a.i./kg-diet

42228301 Acceptable LOAEC (1,750 mg a.i./kg-diet)

based on reduced body weight and 

dilated renal pelvis in F1 males 

and females

Terrestrial 

Invertebrates

Honey bee (Apis 

mellifera)

LD50 = 59.83 μg 

a.i./bee (acute 

contact)

ACC 

00036935 

(Atkins et 

al., 1975)

Acceptable This study involved exposures of 

honey bees to trichlorfon in a 

formulated product. The slope for 

this study was 2.81.
17 of 74

Table 8. Summary of Submitted Studies for Terrestrial Animals Exposed to Technical DDVP (Most 

Sensitive Endpoints for Each Taxon).

TAXON & 

SPECIES

ENDPOINT MRID STUDY 

CLASSIFICATION

COMMENTS

Birds (Acute)

Bobwhite quail 

(Colinus 

virginianus)

LD50 = 8.8 mg a.i./kg 

bw

40818301 Acceptable None

Birds (Sub-acute)

Ring-necked 

pheasant 

(Phasianus 

colchicus)

LC50 = 568 mg a.i./kgdiet0022923 Acceptable None

Birds (Chronic) 

Mallard duck 

(Anas 

platyrhynchos)

NOAEC = 5 mg a.i./kgdiet44233401 Acceptable LOAEC (15 mg a.i./kgdiet)

based on reduced eggshell 

thickness, eggs laid, and 

number of viable embryos

Mammals (Acute) 

Laboratory rat 

(Rattus norvegicus)

LD50 = 56 mg a.i./kgbw0005467 Acceptable None

Mammals 

(Chronic) 

Laboratory rat 

(Rattus norvegicus)

NOAEC = 20 mg 

a.i./kg-diet

LOAEC = 80 mg 

a.i./kg-diet

42483901 Acceptable Based on reduced fertility 

and pup weight

Terrestrial 

Invertebrates 

Honey bee (Apis 

mellifera)

LD50 = 0.5 μg a.i./bee 

(contact)

00036935 Acceptable None

4.3. Incident Database Review

A preliminary review on October 20, 2008, of the Ecological Incident Information 

System (EIIS, version 2.0) maintained by the Agency’s Office of Pesticide Programs 

(OPP) indicates a total of 4 reported ecological incidents associated with the use of 

trichlorfon and 5 associated with the use of DDVP (Table 9). All of the trichlorfon 

incidents occurred between 1973 and 2003. Three of the trichlorfon incidents involved 

aquatic animals (i.e., fish) and one involved terrestrial animals (i.e., birds) and all were 

associated with mortality of the affected animals. The certainty categories for the four 

incidents ranged from possible (two incidents) to probable (two incidents), and two of the 

incidents involved registered uses while the remaining two involved misuses. Three of 

the incidents involved additional chemicals besides trichlorfon. Trichlorfon residues 

were reported in only one of the incident reports (see Table 9). The reported incidents for 

trichlorfon involved two uses that are no longer registered (alfalfa and agricultural area) 

and two uses that are currently registered (lawn and golf course). The two currently 

registered uses had certainty categories of probable and possible.
18 of 74

All of the DDVP incidents occurred between 1973 and 1997. One of the DDVP incidents 

involved aquatic animals (i.e., fish) and four involved terrestrial animals (i.e., birds and 

mammals). All of the aquatic incidents involved mortality while the terrestrial incidents 

involved mortality and/or incapacitation with recovery. The certainty categories for the 

five incidents ranged from possible (two incidents) to highly probable [probable (two 

incidents); highly probable (one incident)], and two of the incidents involved registered 

uses while the legality of use was undetermined for the remaining three. Only one of the 

incidents involved additional chemicals besides DDVP. DDVP residues were reported in 

one of the incident reports and ChE inhibition (brain) was reported in another (see Table 

9). The use site for one of the reported DDVP incidents was unknown. The remaining 

four incidents involved the following use sites: industrial operation, agricultural area, 

building (inside), and apple.

Although incident reports for trichlorfon and DDVP have not been received by the 

Agency since 2003 and 1997, respectively, the absence of reported incidents should not 

be construed as the absence of incidents. Incident reports for non-target organisms 

typically provide information on mortality events only. Reports for other adverse effects, 

such as reduced growth or impaired reproduction, are rarely received. EPA’s changes in 

the registrant reporting requirements for incidents in 1998 may also account for the 

reduced number of reported incidents. Registrants are now only required to submit 

detailed information on ‘major’ incidents. Minor incidents are generally reported 

aggregately and are not included in EIIS. In addition, there have been changes in state 

monitoring efforts due to lack of resources. However, the incident data that are available 

suggest that exposure pathways are complete and that exposure levels are sufficient to 

result in field-observable effects. 
19 of 74

Table 9. Wildlife Incidents from the EIIS Associated with Trichlorfon or DDVP.

CHEM. 

NAME

INCIDENT 

NO.

TAXA 

INVOLVED MAGNITUDE YEAR LOCATION USE LEGALITY OF USE

CERTAINTY 

CATEGORY RESIDUES

OTHER 

CHEMICALS 

INVOLVED

Endosulfan 

(0.3-0.59 ppb in 

affected water)

B0000-224 Aquatic 

animal

~1,000 fish 

(carp, sunfish, 

and catfish)

1973 California Alfalfa Misuse Possible 8.3 – 12 ppb 

in affected 

water

Toxaphene 

(3.5 ppb in 

affected water)

I000223-001 Aquatic 

animal

~100 dead 

bluegill sunfish

1992 Indiana Lawn Registered 

use

Probable No Isazofos

(5.5 ppb in pond 

water)

I008255-010 Terrestrial 

animal

2 dead geese 1998 USA Agricultural 

area Registered 

use

Possible No None

Chlorithalonil

Trichlorfon

I014538-013 Aquatic 

animal

~1,500 dead fish 2003 Indiana Golf course Misuse 

(rinsate 

released into 

pond)

Possible No

Propiconazole

B0000-500-31 Aquatic 

animal

379 dead fish 1973 Tennessee Industrial 

operation

Undetermined Probable No None

B0000-500-21 Terrestrial 

animal

8 dead mallard 

ducks

1975 USA Agricultural 

area

Registered 

use

Highly probable No but there 

was brain 

ChE 

inhibition

None

I002298-001 Terrestrial 

animal

5 dead fox pups 

(captive); 2 

incapacitated 

fox pups 

(captive)

1995 USA Building 

(inside)

Registered 

use

Possible No None

I003908-011 Terrestrial 

animal

2 bluebird 

chicks

1994 New York Apple Undetermined Probable No None

Naled

(73 ppm in crop 

contents)

DDVP

I019411-016 Terrestrial 

Animal

1 debilitated 

red-tailed hawk

1997 British 

Columbia, 

Canada

Unknown Undetermined Possible 28 ppm in 

crop contents

Fonofos

(14 ppm in crop 

contents)
20 of 74

4.4. Ecosystems Potentially at Risk

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

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

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

include the treated field and immediately adjacent areas that may receive drift or runoff. 

Areas adjacent to the treated field could include cultivated fields, fencerows and

hedgerows, meadows, fallow fields or grasslands, woodlands, riparian habitats and other 

uncultivated areas. 

Aquatic ecosystems potentially at risk (beyond the aquatic use sites) include water bodies 

adjacent to, or down stream from, the treated field and could include impounded bodies 

such as ponds, lakes and reservoirs, or flowing waterways such as streams or rivers. For 

uses in coastal areas, aquatic habitat also includes marine ecosystems, including estuaries. 

5. Assessment Endpoints

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

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

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

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

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

terrestrial plants, insects, and aquatic plants and algae. The attributes for each of these 

entities may include growth, reproduction, and survival. 

6. Conceptual Model

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

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

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

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

environmental transport medium, a point of exposure for ecological receptors, and a 

feasible route of exposure.

The conceptual model for trichlorfon provides a written description and visual 

representation of the predicted relationships among trichlorfon (and its degradate DDVP), 

potential routes of exposure, and the predicted effects for the assessment endpoint. A 

conceptual model consists of two major components: risk hypothesis and a conceptual 

diagram (USEPA 1998).

The primary environmental concerns identified in the 1997 and 2000 environmental fate 

and ecological risk assessments for trichlorfon were acute and chronic risks to birds, 

mammals, fish, and aquatic invertebrates (USEPA 1997, 2000). However, these risks did 
21 of 74

not include a consideration of the trichlorfon degradate DDVP. Based on available data, 

DDVP is more or equally as toxic to aquatic and terrestrial animals when compared to 

trichlorfon. Therefore, risks to non-target species may be greater than previously 

assumed once DDVP is considered in the risk assessment process. Due to the number of 

data gaps that currently exist for trichlorfon and DDVP (see Section 7.8), preliminary

RQs for trichlorfon will not be calculated in this problem formulation. The Agency 

believes that calculating RQs for trichlorfon use at this time would not be informative due 

to the uncertainties associated with the current data gaps. 

6.1. Risk Hypothesis

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

assessment endpoint response. For trichlorfon, the following ecological risk hypothesis 

is being employed for this ecological risk assessment:

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

sensitivity of non-target aquatic and terrestrial species, trichlorfon residues of 

concern (including trichlorfon and its degradate DDVP) have the potential to 

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

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

well as non-listed species.

6.2. Conceptual Diagram

The environmental fate properties of trichlorfon and DDVP indicate that runoff, spray

drift, volatilization and direct spray represent potential transport mechanisms of 

trichlorfon and DDVP to aquatic and terrestrial habitats where non-target organisms may

be exposed. These transport mechanisms (i.e., sources) are depicted in the conceptual 

models below (Figure 2 and Figure 3) along with the receptors of concern and the 

potential attribute changes in the receptors due to exposures of trichlorfon and DDVP. 
22 of 74

Figure 2. Conceptual model for trichlorfon and DDVP effects on aquatic organisms.

Stressor

Source

Receptors

Attribute

Change

Trichlorfon applied to use site

Trichlorfon degrading to DDVP

Spray drift

Fish/aquatic-phase 

amphibians

Eggs 

Larvae 

Juveniles / Adults

Individual organisms

Reduced survival

Reduced growth

Reduced reproduction

Food chain

Reduction in algae

Reduction in prey

Habitat integrity

Reduction in primary productivity

Reduced cover

Community change

Surface water/

Sediment

Runoff

Aquatic Animals

Invertebrates

Vertebrates

Exposure

Media

Uptake/gills 

or integument

Ingestion Ingestion

Long range 

atmospheric 

transport

Wet/dry deposition

Soil Ground water

Uptake/gills 

or integument

Aquatic Plants

Non-vascular

Vascular

Uptake/cell, 

roots, leaves Riparian plant

terrestrial 

exposure 

pathways see 

Figure 3
23 of 74

Figure 3. Conceptual model for trichlorfon and DDVP effects on terrestrial organisms.

7. Analysis Plan

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

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

trichlorfon (and DDVP) are characterized and integrated to assess the risks using a ‘total 

trichlorfon residues of concern’ approach. In this approach, estimated environmental 

concentrations (EECs) will be derived for combined trichlorfon and DDVP. Risk 

quotients (RQs) will be derived for the total residues of concern by dividing EECs by the 

most sensitive endpoint from the available toxicity data for trichlorfon and DDVP. 

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

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

opening of the Registration Review docket.

Stressor

Source

Receptors

Attribute

Change

Trichlorfon applied to use site

Trichlorfon degrading to DDVP

Direct

application Spray drift

Birds / Terrestrialphase amphibians 

/ reptiles / 

mammals

Terrestrial 

insects

Individual organisms

Reduced survival

Reduced growth

Reduced reproduction

Food chain

Reduction in prey

Habitat integrity

Reduction in primary productivity

Reduced cover

Community change

Terrestrial/riparian plants

grasses/forbs, fruit, seeds 

(trees, shrubs)

Runoff

Mammals

Exposure

Media

Soil

Ingestion

Ingestion

Ingestion

Ingestion

Dermal uptake/Ingestion

Long range 

atmospheric 

transport

Root uptake

Wet/dry deposition

Birds / 

Amphibians

Ingestion
24 of 74

7.1. Stressors of Concern

The primary degradate of concern, DDVP, is considered to have attributes and effects 

similar to parent trichlorfon. Thus, DDVP degradate residue levels will be considered 

along with trichlorfon residue levels as ‘total trichlorfon residues of concern’ in this 

assessment, and model results (exposure estimates) will reflect the predicted fate of both 

trichlorfon and DDVP resulting from trichlorfon usage. 

In its ecological risk assessments, the Agency does not routinely include an evaluation of 

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

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

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

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

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

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

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

Overview Document and the Services’ Evaluation Memorandum (USEPA 2004; 

USFWS/NMFS 2004). 

Available toxicity data for environmental mixtures of trichlorfon with other pesticides 

will be presented as part of the ecological risk assessment. It is expected that the toxic 

effect of trichlorfon, in combination with other pesticides used in the environment, is 

likely to be a function of many factors including but not necessarily limited to: (1) the 

exposed species, (2) the co-contaminants in the mixture, (3) the ratio of trichlorfon and 

co-contaminant concentrations, (4) differences in the pattern and duration of exposure 

among contaminants, and (5) the differential effects of other physical/chemical 

characteristics of the receiving waters (e.g. organic matter present in sediment and 

suspended water). Quantitatively predicting the combined effects of all these variables 

on mixture toxicity to any given taxa with confidence is beyond the capabilities of the 

available data and methodologies. However, a qualitative discussion of implications of 

the available pesticide mixture effects data on the confidence of risk assessment 

conclusions will be addressed as part of the uncertainty analysis.

7.2. Measures of Exposure

In order to estimate risks of trichlorfon and DDVP exposures in aquatic and terrestrial 

environments, all exposure modeling and resulting risk conclusions will be made based 

on the maximum application rates for turfgrass, flowers, shrubs, trees, and ponds 

discussed in Section 3.2. Measures of exposure are based on aquatic and terrestrial 

models that predict estimated environmental concentrations of trichlorfon residues of 

concern using maximum labeled application rates and methods, as well as any mitigation 

measures specifically indicated on the label (e.g. spray drift buffers). The models used to 

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

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

on food items is T-REX. These models are parameterized using relevant reviewed 

registrant-submitted environmental fate data.
25 of 74

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

simulation models coupled with the input shell pe5.pl (Aug 2007) to generate daily 

exposures and 1-in-10 year EECs of trichlorfon residues of concern that may occur in 

surface water bodies adjacent to application sites receiving trichlorfon through runoff and 

spray drift. PRZM simulates pesticide application, movement and transformation on an 

agricultural field and the resultant pesticide loadings to a receiving water body via runoff, 

erosion and spray drift. EXAMS simulates the fate of the pesticide and resulting 

concentrations in the water body. The standard scenario used for ecological pesticide 

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

adjacent 1-hectare water body that is 2 meters deep (20,000 m3volume) with no outlet. 

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

trichlorfon residues of concern. The measure of exposure for aquatic species is the 1-in10 year return peak or rolling mean concentration. The 1-in-10 year peak is used for 

estimating acute exposures of direct effects to aquatic organisms. The 1-in-10-year 60-

day mean is used for assessing chronic exposure to fish and aquatic-phase amphibians. 

The 1-in-10-year 21-day mean is used for assessing aquatic invertebrate chronic 

exposure.

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

exposed to spray drift are derived using the T-REX model (version 1.3.1, 12/07/2006). 

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

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

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

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

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

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

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

(version 1.2.2, 12/26/2006). This model uses estimates of pesticides in runoff and in 

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

minimum incorporation depth.

Exposure estimates for birds (and, thus, terrestrial-phase amphibians and reptiles), 

terrestrial invertebrates, and mammals assumed to be in the target area or in an area 

exposed to trichlorfon granules are derived using the T-REX model (version 1.3.1, 

12/07/2006). T-REX includes the capability to calculate the LD50 ft-2risk index values. 

Conceptually, an LD50 ft-2is the amount of a pesticide estimated to kill 50% of exposed 

animals in each square foot of applied area. Although a square foot does not have 

defined ecological relevance and any unit area could be used, risk presumably increases 

as the number of LD50s/ft2 increases. The LD50/ft2is used to estimate risk for granular 

formulations and row, banded, and in-furrow applications. For additional information on 

the LD50 ft-2risk index, please reference U.S. EPA (1992). The LD50 ft-2is calculated 

using a toxicity value (adjusted LD50) and the EEC (mg a.i. ft-2) and is directly compared 

with the Agency's levels of concern (LOCs).
26 of 74

The AgDRIFT spray drift model (version 2.01; dated 5/24/2001) is used to assess 

exposures of terrestrial organisms to trichlorfon deposited on terrestrial habitats by spray

drift. AgDRIFT will also be used to determine the appropriate PRZM/EXAMS parameter 

values for modeling the percent drift corresponding to the buffers indicated on the label

and to model areas of effect for aquatic and terrestrial taxa. 

Any available monitoring data obtained from the scientific literature or submitted studies 

will be used to characterize exposures of trichlorfon and DDVP to non-target organisms.

7.3. Measures of Effect

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

receptors. Data are obtained from registrant-submitted studies or from literature studies 

identified by ECOTOX. The ECOTOX database (USEPA 2007a) provides more 

ecological effects data in an attempt to bridge existing data gaps. ECOTOX is a source 

for locating single chemical toxicity data and potential chemical mixture toxicity data for 

aquatic life, terrestrial plants, and wildlife. ECOTOX was created and is maintained by

the USEPA, Office of Research and Development, and the National Health and 

Environmental Effects Research Laboratory's Mid-Continent Ecology Division.

Information on the potential effects of trichlorfon (and DDVP) on non-target animals is 

also collected from the Ecological Incident Information System (EIIS; USEPA 2007b). 

The EIIS is a database containing adverse effect (typically mortality) reports on nontarget organisms where such effects have been associated with the use of pesticides.

Where available, sublethal effects observed in both registrant-submitted and open 

literature studies will be evaluated qualitatively. Such effects may include behavioral 

changes (e.g., lethargy and changes in coloration). Quantitative assessments of risks, 

though, are limited to those endpoints that can be directly linked to the Agency’s 

assessment endpoints of impaired survival, growth and reproduction.

The assessment of risk for direct effects to non-target organisms makes the assumption 

that toxicity of trichlorfon and DDVP to birds is similar to terrestrial-phase amphibians 

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

The acute measures of effect used for animals in this assessment are the LD50, LC50 and 

EC50. LD stands for "Lethal Dose", and LD50 is the amount of a material, given all at 

once, that is estimated to cause the death of 50% of the test organisms. LC stands for 

“Lethal Concentration” and LC50 is the concentration of a chemical that is estimated to 

kill 50% of the test organisms. EC stands for “Effective Concentration” and the EC50 is 

the concentration of a chemical that is estimated to produce a specific effect in 50% of 

the test organisms. Endpoints for chronic measures of exposure for listed and non-listed 

animals are the NOAEL/NOAEC and NOEC. NOAEL stands for “No ObservedAdverse-Effect-Level” and refers to the highest tested dose of a substance that has been 

reported to have no harmful (adverse) effects on test organisms. The NOAEC (i.e., “NoObserved-Adverse-Effect-Concentration”) is the highest test concentration at which none 
27 of 74

of the observed effects were statistically different from the control. The NOEC is the NoObserved-Effects-Concentration. For non-listed plants, only acute exposures are 

assessed (i.e., EC25 for terrestrial plants and EC50 for aquatic plants); for listed plants 

either the NOAEC or EC05 is used. 

7.4. Integration of Exposure and Effects

Risk characterization is the integration of exposure and ecological effects characterization 

to determine the potential ecological risk from the registered uses of trichlorfon and the 

likelihood of direct and indirect effects to non-target organisms in aquatic and terrestrial 

habitats. The exposure and toxicity effects data are integrated in order to evaluate the 

risks of adverse ecological effects on non-target species. For the assessment of 

trichlorfon risks, the risk quotient (RQ) method is used to compare exposure and 

measured toxicity values. EECs are divided by acute and chronic toxicity values. The 

resulting RQs are then compared to the Agency’s Levels of Concern (LOCs) (USEPA

2004) (See Appendix B). These criteria are used to indicate when trichlorfon’s uses, as 

directed on the labels, have the potential to cause adverse direct or indirect effects to nontarget organisms. In addition, incident data from the EIIS will be considered as part of 

the risk characterization.

7.5. Deterministic and Probabilistic Assessment Methods

The quantitative assessment of risk will primarily depend on the deterministic pointestimate based approach described in the risk assessment. An effort will be made to 

further qualitatively describe risk using probabilistic tools that the Agency has developed. 

These tools have been reviewed by FIFRA Scientific Advisory Panels 

(http://www.epa.gov/scipoly/sap/index.htm) and have been deemed as appropriate means 

of refining assessments where deterministic approaches have identified risks.

7.6. Endangered Species Assessments

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

the Agency will evaluate risks to Federally-listed threatened and/or endangered (listed) 

species from registered uses of trichlorfon. This assessment will be conducted in 

accordance with the Overview Document (USEPA 2004), provisions of the ESA, and the 

Services’ Endangered Species Consultation Handbook (USFWS/NMFS, 1998).

The assessment of effects associated with the registration of trichlorfon (and its degradate 

DDVP) is based on an action area. The action area is considered to be the area directly or 

indirectly affected by the federal action, as indicated by the exceedance of Agency Levels 

of Concern (LOCs) used to evaluate direct or indirect effects. The Agency’s approach to 

defining the action area under the provisions of the Overview Document (USEPA 2004) 

considers the results of the risk assessment process to establish boundaries for that action 

area with the understanding that exposures below the Agency’s defined LOCs constitute 

a no-effect threshold. For the purposes of this assessment, attention will be focused on 

the footprint of the action (i.e., the area where trichlorfon application occurs), plus all 
28 of 74

areas where offsite transport (i.e., spray drift, runoff, etc.) may result in potential 

exposure that exceeds the Agency’s LOCs. Specific measures of ecological effect that 

define the action area for listed species include any direct and indirect effects and/or 

potential modification of its critical habitat, including reduction in survival, growth, and 

reproduction as well as the full suite of sublethal effects available in the effects literature. 

Therefore, the action area extends to a point where environmental exposures are below 

any measured lethal or sublethal effect threshold for any biological entity at the whole 

organism, organ, tissue, and cellular level of organization. In situations where it is not 

possible to determine the threshold for an observed effect, the action area is not spatially

limited and is assumed to be the entire United States.

7.7. Drinking Water Assessment

A drinking water assessment will be conducted to support the human health risk 

assessment of trichlorfon in registration review. The drinking water assessment will 

incorporate model estimates of trichlorfon residues of concern (including DDVP and 

parent) in surface and ground waters. Concentrations of trichlorfon residues of concern 

in surface waters will be estimated using PRZM/EXAMS (see description above). 

Ground water estimates of concentrations of trichlorfon residues of concern will be 

estimated using the Screening Concentration in Ground Water (SCI-GROW) model 

(v.2.3, July 2003). The drinking water assessment will also include a summary of 

available surface and ground water monitoring data. 

This drinking water assessment will consider all sources of DDVP, including direct 

applications of DDVP as a pesticide active ingredient, as well as uses of trichlorfon and 

naled (PC code: 034401), which both degrade to DDVP.

7.8. Preliminary Identification of Data Gaps

7.8.1. Fate

The environmental fate data requirements for trichlorfon are partially fulfilled with some 

data gaps still remaining (
29 of 74

Table 10). The data gaps are discussed below. Data Call-In (DCI) tables for these data 

gaps are provided in Appendix C.
30 of 74

Table 10. Available environmental fate data for trichlorfon and remaining data gaps.

Guideline Description MRID Classification Data 

Gap?

comments

835.2120 Hydrolysis 00148974 Invalid Yes

835.2240 Photodegradation in 

water

00148975 Supplemental Yes

835.2410 Photodegradation in 00148976 Invalid

soil 402614011

Invalid

Yes

835.2370 Photodegradation in air none Not applicable No2

835.4100 Aerobic soil 00098625 Invalid

metabolism 42243601 Acceptable

No

00161359 Invalid

40279301 Invalid

835.4200 Anaerobic soil 

metabolism

42243601 Acceptable

No

835.4300 Aerobic Aquatic 

Metabolism

none Not applicable Yes

835.4400 Anaerobic Aquatic 

Metabolism

none Not applicable Yes

835.1230 00148977 Invalid

835.1240

Leaching and 

adsorption/

desorption 402614023

Invalid

Yes

835.1410 Laboratory Volatility 40279302 Acceptable No

40279303 Invalid

42322501 Invalid

45303501 Under review

45895501 Supplemental

835.6100 Terrestrial Field 

Dissipation

47519201 Supplemental

Yes

835.6200 Aquatic Field 

Dissipation

none Not applicable Yes

850.1730 Accumulation in Fish none Not applicable No4

1

It appears that this study reports 

the same results as MRID 

00157859.

2Because trichlorfon is not 

expected to be volatile, data 

describing the photodegradation

of trichlorfon in air are not 

necessary.

3

It appears that this study reports 

the same results as MRID 

00157860.

4 Code of Federal Regulations 40 

(CFR40 2007) Part 158 Subpart 

D state that these data are not 

required when the Log Kow of a 

chemical and its major 

degradates are <3. Based on a 

Log octanol-water partition 

coefficient of 0.30 (MRID 

00162307) for trichlorfon and 

0.60 for DDVP, these data are 

not required for trichlorfon or 

DDVP.

Hydrolysis

Acceptable data have not been provided to quantify the hydrolysis of trichlorfon.

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

requirements for pesticides), hydrolysis data are required for pesticides with terrestrial or 

aquatic uses. Since trichlorfon uses are classified as terrestrial and aquatic, acceptable

hydrolysis data for trichlorfon should be submitted to fulfill OPPTS Guideline

835.2120. These data are used to estimate the degradation of trichlorfon in aquatic 

systems and ultimately to derive aquatic EECs using PRZM/EXAMS. 
31 of 74

In the case that these data are unavailable at the time risk assessments are conducted, it 

will be assumed that trichlorfon is stable to hydrolysis.

Aqueous Photolysis

Acceptable data have not been provided to quantify the aqueous photolysis of trichlorfon.

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

requirements for pesticides), aqueous photolysis data are required for pesticides with 

terrestrial or aquatic uses. Although this represents a data gap, EFED does not 

recommend that the Agency request these data at this time because the available 

supplemental data are sufficient to characterize the photolysis of trichlorfon in the aquatic 

environment.

Photolysis on soil

Acceptable data have not been provided to quantify the photolysis of trichlorfon on soil. 

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

requirements for pesticides), soil photolysis data are required for pesticides with 

terrestrial or aquatic uses. Since trichlorfon uses are classified as terrestrial and aquatic, 

acceptable soil photolysis data for trichlorfon should be submitted to fulfill OPPTS 

Guideline 835.2410. These data are used to characterize the degradation of trichlorfon in 

soil. In the case that these data are not submitted, it will be assumed that trichlorfon is 

stable to photolysis on soil. 

Aerobic and Anaerobic Aquatic Metabolism

Acceptable data have not been provided to quantify the metabolism of trichlorfon under 

aerobic and anaerobic aquatic conditions. According to Code of Federal Regulations 40 

(CFR40 2007) Part 158 Subpart D (data requirements for pesticides), aerobic and 

anaerobic aquatic metabolism data are required for pesticides with terrestrial or aquatic 

uses. Since trichlorfon uses are classified as terrestrial and aquatic, acceptable aerobic 

and anaerobic aquatic metabolism data for trichlorfon should be submitted to fulfill 

OPPTS Guidelines 835.4300 and 835.4400. These data are used to estimate the 

degradation of trichlorfon in aquatic systems and ultimately to derive aquatic EECs using 

PRZM/EXAMS. In the case that these data are unavailable at the time risk assessments 

are conducted, PRZM/EXAMS input parameter guidance default values will be 

employed to account for aerobic and anaerobic aquatic metabolism.

Leaching and Adsorption/Desorption

At this time, there are no acceptable studies to quantify the adsorption and desorption 

characteristics of trichlorfon in U.S. soils. EFED recommends that the Agency request 

the submission of an acceptable study under OPPTS Guideline 835.1230 to define Kd and 

KOC values of trichlorfon in U.S. soils. In the absence of these data, EFED will assume 

that there is no sorption of trichlorfon to soils or organic matter on the treatment site. In 

order to implement this in derivation of aquatic EECs, a KOC value of 0 will be used to 
32 of 74

parameterize PRZM/EXAMS. Input of a KOC value >0 is expected to result in lower 

aquatic EECs. If acceptable data are provided, the uncertainties associated with this 

assumption will be reduced.

Terrestrial Field Dissipation

At this time, two supplemental studies are available to describe the dissipation of 

trichlorfon under terrestrial field conditions (MRIDs 45895501 and 47519201). An 

additional study has been submitted and is currently under review by EFED (MRID 

45303501). At this time, no acceptable studies have been identified to fulfill the OPPTS 

Guideline 835.6100. Although this represents a data gap, EFED does not recommend 

that the Agency request these data at this time because the available supplemental data 

are sufficient to characterize the terrestrial field dissipation of trichlorfon.

Aquatic Field Dissipation

At this time, no acceptable studies are available to describe the dissipation of trichlorfon 

under aquatic field conditions. According to Code of Federal Regulations 40 (CFR40 

2007) Part 158 Subpart D (data requirements for pesticides), aquatic field dissipation data 

are required for pesticides with aquatic uses. Since trichlorfon uses are classified as 

aquatic, aquatic field dissipation data for trichlorfon should be submitted to fulfill 

OPPTS Guideline 835.6200.

Environmental Chemistry Methods

Independently validated analytical methods for residues in soil and water (environmental 

chemistry methods) submitted by the registrant are used to evaluate analyses described in 

submitted environmental fate and ecological effects studies. Submitted analytical 

methods are also used by various Federal, State, Tribal, and local agencies to detect and 

monitor residues that are or are suspected to be in environmental compartments due to 

outdoor uses and accidental releases. Therefore, availability of these analytical methods 

is necessary in order to protect human health and the environment from trichlorfon 

residues in the environment. Independent laboratory validations for submitted analytical 

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

registrant-prepared validations.

Use of trichlorfon may impact surface water quality due to runoff of rain water and drift 

of residues. Therefore, analytical methods for are necessary for detecting trichlorfon 

residues in water and in soil or sediment.

In the absence of independently validated environmental chemistry methods, submitted 

environmental fate and ecological effects data may not be reviewable and entities outside 

the Agency may lack chemical-specific methods for analyses in environmental 

compartments. Independently validated environmental chemistry methods will be used 

to evaluate the submitted environmental fate and ecological effects data and will be made 

available to the public to support monitoring for trichlorfon residues.
33 of 74

7.8.2. Effects data for Trichlorfon

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

to aquatic and terrestrial organisms, several data gaps still exist (

Table 11 - Table 13). Data gaps include the following: avian acute oral toxicity, avian 

sub-acute dietary toxicity, estuarine/marine fish acute toxicity, estuarine/marine 

invertebrate acute toxicity, estuarine/marine fish early-life stage toxicity, and terrestrial 

and aquatic plant toxicity studies. The data gaps are discussed below. 

Table 11. Available Ecological Effects Data for Terrestrial Animals Exposed to Trichlorfon and 

Remaining Data Gaps (Studies Classified as ‘Invalid’ are Not Included).

Guideline Description MRID/

Accession

Classification Data 

Gap?

Comments

850.2100 Avian oral toxicity None Not applicable Yes1

850.2200 Avian dietary 

toxicity 

None Not applicable Yes2

850.2300 Avian reproduction 43019501 Acceptable

43019601 Acceptable

No

850.3020 Honeybee acute 

contact toxicity

00036935 Acceptable No

1 An acute oral toxicity study 

using either a mallard duck or 

bobwhite quail AND 

passerines must be submitted 

to fulfill this data requirement.

2 Dietary toxicity studies using 

a waterfowl and an upland 

game species must be 

submitted to fulfill this data 

requirement.
34 of 74

Table 12. Available Ecological Effects Data for Aquatic Animals Exposed to Trichlorfon and 

Remaining Data Gaps (Studies Classified as ‘Invalid’ are Not Included).

Guideline Description MRID/ 

Accession

Classification Data 

Gap?

comments

40098001 Supplemental

65495 Supplemental

850.1075 Freshwater fish –

Acute toxicity 

91766 Acceptable

No

850.1075 Saltwater fish –

Acute toxicity 

None Not applicable Yes1

850.1010 Freshwater 

invertebrates –

Acute toxicity

40098001 Supplemental No

850.1025

850.1035

850.1045

850.1055

Saltwater invertebrates 

–

Acute toxicity 

444992 Acceptable Yes1

850.1300 Freshwater 

invertebrate –

life cycle test

40452601 Acceptable No

850.1350 Saltwater invertebrates 

–

life cycle test

44499202 Acceptable No

850.1400 Freshwater fish –

early life stage test

42571701 Acceptable No

850.1400 Saltwater fish –

early life stage test

None Not applicable Yes2

850.1500 Fish –

life cycle test

None Not applicable No

1 The new Part 158 data 

requirements specify that 

acute toxicity data are required 

on one estuarine/marine 

mollusk (guideline fulfilled), 

one estuarine/marine 

invertebrate (guideline not 

fulfilled), and one 

estuarine/marine fish 

(guideline not fulfilled).

2 A saltwater fish early-life 

stage test (850.1400) is 

required for trichlorfon 

because the acute toxicity

value for saltwater fish is < 1 

mg/L (using freshwater fish as 

a surrogate).
35 of 74

Table 13. Available Ecological Effects Data for Plants Exposed to Trichlorfon and Remaining Data 

Gaps (Studies Classified as ‘Unacceptable’ are Not Included).

Guideline Description MRID Classification Data 

Gap?

comments

850.4100 Terrestrial Plant toxicity: 

Tier I seedling 

emergence

None Not applicable Yes1

850.4225 Terrestrial Plant toxicity: 

Tier 2 seedling 

emergence

None Not applicable No2

850.4150 Terrestrial Plant toxicity: 

Tier I vegetative vigor

None Not applicable Yes1

850.4150 Terrestrial Plant toxicity: 

Tier 2 vegetative vigor

None Not applicable No2

850.4400 Aquatic Plant Growth: 

algae

None Not applicable Yes1

850.4400 Aquatic Plant Growth: 

vascular plants

None Not applicable Yes1

1 The new Part 158 data 

requirements specify that 

toxicity data are required for 

terrestrial and aquatic plants.

2 Tier II studies will be 

required if tested terrestrial 

species exhibit a 25% or 

greater detrimental effect in 

the Tier I study.

Avian Acute Oral Toxicity

No acceptable avian acute oral toxicity data are currently available for trichlorfon. The 

new Part 158 data requirements [40 CFR Part 158 (CFR 40 2007) data requirements for 

conventional pesticides (72 FR 60934; USEPA 2007c)] specify that acute avian oral 

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

species. Additionally, there is one possible ecological incident involving birds (geese) 

and the use of trichlorfon (I008255-010). There is also evidence to indicate that 

passerines are more sensitive to at least some OPs when compared to data from upland 

and game species. For example, dimethoate (an OP) is an order of magnitude more toxic 

to passerines than to upland/game species (USEPA 2008). Therefore, an avian oral 

toxicity test (OPPTS Guideline 850.2100; 

http://www.epa.gov/opptsfrs/publications/OPPTS_Harmonized/850_Ecological_Effects_Test_Guidelines/

Drafts/850-2100.pdf) is required for either a mallard duck or bobwhite quail AND a 

passerine species, as specified in 40 CFR Part 158 (CFR40 2007). Trichlorfon registrants 

will need to submit a passerine study protocol for review by the Agency prior to initiation 

of the passerine study. If oral acute toxicity data are not submitted for either mallard 

duck or bobwhite quail AND passerines, EFED will assume acute risk to birds in its 

assessment of trichlorfon.

Avian Sub-Acute Dietary Toxicity

No acceptable avian sub-acute dietary toxicity data are currently available for trichlorfon. 

The new Part 158 data requirements [40 CFR Part 158 (CFR 40 2007) data requirements 

for conventional pesticides (72 FR 60934; USEPA 2007c)] specify that avian dietary
36 of 74

toxicity data be submitted for both a waterfowl and an upland game species. There are 

currently no acceptable acute oral or sub-acute dietary toxicity data available for 

trichlorfon. However, there is one possible ecological incident involving birds (geese) 

and the use of trichlorfon (I008255-010), indicating a potential risk to birds. Therefore, 

an avian dietary toxicity test (OPPTS Guideline 850.2200; 

http://www.epa.gov/opptsfrs/publications/OPPTS_Harmonized/850_Ecological_Effects_Test_Guidelines/

Drafts/850-2200.pdf) is required for both a waterfowl and an upland game species, as 

specified in 40 CFR Part 158 (CFR40 2007). If dietary toxicity data are not submitted for

birds, EFED will assume acute risk to birds in its assessment of trichlorfon.

Estuarine/Marine Fish Acute Toxicity

Acute toxicity data are not available for estuarine and marine fish. In the absence of 

these data, an acute-to-chronic ratio (ACR) would normally be derived and the acute

toxicity to estuarine and marine fish would be estimated based on the ACR for freshwater 

fish. However, there are currently no toxicity data (acute or chronic) for estuarine/marine 

fish, therefore, an ACR cannot be derived. In addition, three of the four reported 

ecological incidents associated with the use of trichlorfon have involved fish kills. 

Therefore, an estuarine/marine fish acute toxicity test (OPPTS Guideline 850.1075; 

http://www.epa.gov/opptsfrs/publications/OPPTS_Harmonized/850_Ecological_Effects_Test_Guidelines/

Drafts/850-1075.pdf) is required in order to fulfill the data requirement. In the absence of 

acute toxicity data for estuarine and marine fish, EFED will assume acute risk to nonlisted and listed species of estuarine and marine fish.

Estuarine/Marine Invertebrate Acute Toxicity

Although, acute toxicity data are available for an estuarine/marine mollusk, no acute data 

are currently available for a non-mollusk estuarine/marine invertebrate. The new Part 

158 data requirements specify that acute toxicity data are required on one 

estuarine/marine mollusk (guideline fulfilled) and one estuarine/marine invertebrate 

(guideline not fulfilled). In the absence of these data, an acute-to-chronic ratio (ACR) 

would normally be derived and the acute toxicity to estuarine/marine invertebrates would 

be estimated based on the ACR for freshwater invertebrates. However, the freshwater 

invertebrate data necessary for calculating the ACR are not available. Chronic data are 

not available for the most acutely sensitive freshwater species (Pteronarcella badia).

Therefore, an estuarine/marine acute toxicity test (OPPTS Guideline 850.1035; 

http://www.epa.gov/opptsfrs/publications/OPPTS_Harmonized/850_Ecological_Effects_Test_Guidelines/

Drafts/850-1035.pdf) is required in order to fulfill the data requirement. In the absence of 

acute toxicity data for estuarine and marine invertebrates, EFED will assume acute risk to 

non-listed and listed species of estuarine and marine invertebrates.

Chronic Toxicity Studies with Estuarine and Marine Fish

Chronic toxicity data are not available for estuarine and marine fish. In the absence of 

these data, an acute-to-chronic ratio (ACR) would normally be derived and the chronic 

toxicity to estuarine and marine fish would be estimated based on the ACR for freshwater 

fish. However, there are currently no toxicity data (acute or chronic) for estuarine/marine 
37 of 74

fish, therefore, an ACR cannot be derived. Some of the reported ecological incidents

associated with the use of trichlorfon have involved fish kills. Therefore, an

estuarine/marine fish early life-stage toxicity test (OPPTS Guideline 850.1400; 

http://www.epa.gov/opptsfrs/publications/OPPTS_Harmonized/850_Ecological_Effects_Test_Guidelines/

Drafts/850-1400.pdf) is required in order to fulfill the data requirement. In the absence of 

chronic toxicity data for estuarine and marine fish, EFED will assume chronic risk to 

non-listed and listed species of estuarine and marine fish.

Terrestrial Plant Toxicity Studies

Toxicity data for terrestrial plants are not available for trichlorfon. Based on the 40 CFR 

Part 158 data requirements, Tier I level seedling emergence and vegetative vigor 

terrestrial plant data are required for all insecticides. Therefore, this data gap must be 

filled, and seedling emergence terrestrial plant data (OPPTS Guideline 850.4100; 

http://www.epa.gov/opptsfrs/publications/OPPTS_Harmonized/850_Ecological_Effects_Test_Guidelines/

Drafts/850-4100.pdf) and vegetative vigor terrestrial plant data (OPPTS Guideline 850.4150; 

http://www.epa.gov/opptsfrs/publications/OPPTS_Harmonized/850_Ecological_Effects_Test_Guidelines/

Drafts/850-4150.pdf) are required for trichlorfon at the Tier 1 level. In the absence of Tier I 

data, EFED will assume risk to non-listed and listed terrestrial plants.

Aquatic Plant Studies

Toxicity data for vascular and non-vascular aquatic plants are not available. Based on the 

40 CFR Part 158 data requirements, Tier I level non-target aquatic plant data are required 

for all insecticides. Therefore, this data gap must be filled, and non-target aquatic plant 

data for algae and vascular plants (OPPTS Guideline 850.4400; 

http://www.epa.gov/opptsfrs/publications/OPPTS_Harmonized/850_Ecological_Effects_Test_Guidelines/

Drafts/850-4400.pdf) are required for trichlorfon at the Tier 1 level. In the absence of Tier I 

data, EFED will assume risk to non-listed and listed species of vascular and non-vascular 

aquatic plants.

7.8.3. Effects data for DDVP

Although much data has been provided on the effects of DDVP to aquatic and terrestrial 

organisms, several data gaps still exist (Tables 14-16). Data gaps include the following: 

avian acute oral toxicity, life-cycle freshwater fish toxicity, and terrestrial and aquatic

plant toxicity studies. The data gaps are discussed below. 
38 of 74

Table 14. Available Ecological Effects Data for Terrestrial Animals Exposed to DDVP and 

Remaining Data Gaps (Only Studies with the most Sensitive Toxicity Endpoints are Reported).

Guideline Description MRID/

Accession

Classification Data 

Gap?

Comments

850.2100 Avian oral toxicity 40818301 Acceptable Yes1

850.2200 Avian dietary 

toxicity 

0022923 Acceptable No

850.2300 Avian reproduction 44233401 Acceptable No

850.3020 Honeybee acute 

contact toxicity

00036935 Acceptable No

1 The new Part 158 data 

requirements specify that 

acute avian oral toxicity data 

be submitted for either a 

mallard duck or bobwhite 

quail AND a passerine 

species. An acute oral toxicity 

study using passerines must be 

submitted to fulfill this data 

requirement.

Table 15. Available Ecological Effects Data for Aquatic Animals Exposed to DDVP and Remaining 

Data Gaps (Only Studies with the most Sensitive Toxicity Endpoints are Reported).

Guideline Description MRID/ 

Accession

Classification Data 

Gap?

comments

850.1075 Freshwater fish –

Acute toxicity 

40098001 Acceptable No

850.1075 Saltwater fish –

Acute toxicity 

43571403 Acceptable No

850.1010 Freshwater 

invertebrates –

Acute toxicity

40098001 Acceptable No

850.1025 43571408 Acceptable No

850.1035

850.1045

850.1055

Saltwater invertebrates 

–

Acute toxicity 

43571404 Acceptable No

850.1300 Freshwater 

invertebrate –

life cycle test

43890301 Acceptable No

850.1350 Saltwater invertebrates 

–

life cycle test

43854301 Acceptable No

850.1400 Freshwater fish –

early life stage test

43788001 Acceptable No

850.1400 Saltwater fish –

early life stage test

43790401 Acceptable No

850.1500 Fish –

life cycle test

None Not applicable No

None
39 of 74

Table 16. Available Ecological Effects Data for Plants Exposed to DDVP and Remaining Data Gaps 

(Only Studies with the most Sensitive Toxicity Endpoints are Reported).

Guideline Description MRID Classification Data 

Gap?

comments

850.4100 Terrestrial Plant toxicity: 

Tier I seedling 

emergence

None Not applicable Yes1

850.4225 Terrestrial Plant toxicity: 

Tier 2 seedling 

emergence

None Not applicable No2

850.4150 Terrestrial Plant toxicity: 

Tier I vegetative vigor

None Not applicable Yes1

850.4150 Terrestrial Plant toxicity: 

Tier 2 vegetative vigor

None Not applicable No2

850.4400 Aquatic Plant Growth: 

algae

None Not applicable Yes1

850.4400 Aquatic Plant Growth: 

vascular plants

None Not applicable Yes1

1 The new Part 158 data 

requirements specify that 

toxicity data are required for 

terrestrial and aquatic plants

2 Tier II studies will be

required if tested terrestrial 

species exhibit a 25% or 

greater detrimental effect in 

the Tier I study.

Avian Acute Oral Toxicity

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

to DDVP; however, data are not available for passerines, which are required under the 

new 40 CFR Part 158 (CFR 40 2007) data requirements for conventional pesticides (72 

FR 60934; USEPA 2007c). The new Part 158 data requirements specify that acute avian 

oral toxicity data be submitted for either a mallard duck or bobwhite quail AND a 

passerine species. Based on the results of previous ecological risk assessments for 

DDVP, risks are expected for non-listed and listed birds due to acute exposures to DDVP 

from the use of trichlorfon. Additionally, three of the five ecological incidents associated 

with DDVP involved birds, including one involving passerines (bluebirds; I003908-011). 

Therefore, an avian oral toxicity test (OPPTS Guideline 850.2100; 

http://www.epa.gov/opptsfrs/publications/OPPTS_Harmonized/850_Ecological_Effects_Test_Guidelines/

Drafts/850-2100.pdf) is required for passerine birds, as specified in 40 CFR Part 158 (CFR40 

2007). Trichlorfan registrants will need to submit a passerine study protocol for review 

by the Agency prior to initiation of this study. If oral acute toxicity data are not 

submitted for passerines, EFED will assume acute risk for passerine species.

Terrestrial Plant Toxicity Studies

Toxicity data for terrestrial plants are not available for DDVP. Based on the 40 CFR Part 

158 data requirements, Tier I level seedling emergence and vegetative vigor terrestrial

plant data are required for all insecticides. Therefore, this data gap must be filled, and 

seedling emergence terrestrial plant data (OPPTS Guideline 850.4100; 

http://www.epa.gov/opptsfrs/publications/OPPTS_Harmonized/850_Ecological_Effects_Test_Guidelines/
40 of 74

Drafts/850-4100.pdf) and vegetative vigor terrestrial plant data (OPPTS Guideline 850.4150; 

http://www.epa.gov/opptsfrs/publications/OPPTS_Harmonized/850_Ecological_Effects_Test_Guidelines/

Drafts/850-4150.pdf) are required for DDVP at the Tier 1 level. In the absence of Tier I 

data, EFED will assume risk to terrestrial plants.

Aquatic Plant Studies 

Toxicity data for vascular and non-vascular aquatic plants are not available. Based on the 

40 CFR Part 158 data requirements, Tier I level non-target aquatic plant data are required 

for all insecticides. Therefore, this data gap must be filled, and non-target aquatic plant 

data for algae and vascular plants (OPPTS Guideline 850.4400; 

http://www.epa.gov/opptsfrs/publications/OPPTS_Harmonized/850_Ecological_Effects_Test_Guidelines/

Drafts/850-4400.pdf) are required for trichlorfon at the Tier 1 level. In the absence of Tier I 

data, EFED will assume risk to both vascular and non-vascular aquatic plants.

8. References

CDPR. 2007. a. Pesticide Use Reporting. California Environmental Protection Agency, Department of 

Pesticide Regulation. Available online at: http://www.cdpr.ca.gov/docs/sw/surfcont.htm. 

(Accessed 5/31/2007).

CFR 40. 2007. Code of Federal Regulations 40 Parts 150 to 189. Protection of the Environment. U.S. 

Government Printing Office.

Fletcher, J.S., J.E. Nellessen, and T.G. Pfleeger. 1994. Literature review and evaluation of the EPA foodchain (Kenaga) nomogram, an instrument for estimating pesticide residues on plants. Environ. 

Tox. Chem. 13:1383-1391.

Hoerger, F. and E. E. Kenaga, 1972. Pesticide Residues on Plants: Correlation of Representative Data as a 

Basis for Estimation of their Magnitude in the Environment. In F. Coulston and F. Korte, eds., 

Environmental Quality and Safety: Chemistry, Toxicology, and Technology, Georg Thieme Publ., 

Stuttgart, West Germany, pp. 9-28.

U.S. Environmental Protection Agency (USEPA). 1996. Emergency Exemption for use of Trichlorfon on 

Ornamentals in Kansas (PC Code# 057901; DP Barcode D229695; ID# 96KS0006; Case# 287853; 

Sponsor: Kansas Dept. of Agriculture).

USEPA. 1997. Reregistration Eligibility Decision (RED): Trichlorfon. U.S. Environmental Protection 

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

Washington DC. January 1997.

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. 2000. Reregistration Eligibility Science Chapter for Trichlorfon: Fate and Environmental Risk 

Assessments. U.S. Environmental Protection Agency, Office of Prevention, Pesticides and Toxic 

Substances, Office of Pesticide Programs, Washington DC. April 2000.
41 of 74

USEPA. 2001. Report on FQPA Tolerance Reassessment Progress and Interim Risk Management 

Decision (TRED) for Trichlorfon. U.S. Environmental Protection Agency, Office of Prevention, 

Pesticides and Toxic Substances, Office of Pesticide Programs, Washington DC. September 2001.

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

of Pesticides, Version II. US Environmental Protection Agency, Washington DC. Online at: 

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

USEPA. 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide Programs. 

U.S. Environmental Protection Agency, Office of Prevention, Pesticides and Toxic Substances, 

Office of Pesticide Programs, Washington DC. January 23, 2004.

USEPA. 2006a. Interim reregistration Eligibility Decision for Dichlorvos (DDVP). U.S. Environmental 

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

Programs, Washington DC. June 2006.

USEPA. 2006b. Finalization of Interim Reregistration Eligibility Decisions (IREDs) and Interim 

Tolerance Reassessment and Risk Management Decisions (TREDs) for the Organophosphate 

Pesticides, and Completion of Tolerance Reassessment and Reregistration Eligibility Process for 

Organophosphate Pesticides. Office of Prevention, Pesticides and Toxic Substances, Office of 

Pesticide Programs, Washington DC. July 31, 2006.

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

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

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

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

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

72 FR 60934. October 26, 2007.

USEPA. 2008. Risks of dimethoate use to the federally-listed California red-legged frog (Rana aurora 

draytonii). U.S. Environmental Protection Agency, Office of Prevention, Pesticides and Toxic 

Substances, Office of Pesticide Programs, Environmental Fate and Effects Division. January 31, 

2008.

U.S. Fish and Wildlife Service (USFWS). 1989. U.S. Fish and Wildlife Service Biological Opinion on 

Selected Pesticides: Dated June 14, 1989; Revised September 14, 1989. 

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.

SUBMITTED FATE STUDIES:

MRID: 00098625 

Khasawinah, A.M. (1972) The Fate of ^(R)IDylox in Soil: Report No. 32365. (Unpublished study received 

May 20, 1977 under 3125-210; submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:230752-S)

MRID: 00148974 

Pither, K.; Johnson, T. (1985) Hydrolysis of Dylox in Sterile Aqueous Buffer Solutions: Report No. 90113.

Unpublished study prepared by Mobay Chemical Corporation. 16 p.
42 of 74

MRID: 00148975 

Pither, K.; Johnson, T. (1985) Photodecomposition of Dylox in Aqueous Solution: Report No. 90155. 

Unpublished study prepared by Mobay Chemical Corporation. 15 p.

MRID: 00148976 

Pither, K.; Johnson, T. (1985) Photodecomposition of Dylox on a Soil Surface: Report No.90153. 

Unpublished study prepared by Mobay Chemical Corporation. 17 p.

MRID: 00148977

Lee, S.; Hanna, L. (1985) Leaching Characteristics of Aged Dylox Soil Residues: Report No. 90154. 

Unpublished study prepared by Mobay Chemical Corporation. 13 p.

MRID: 00152133 

Mobay Chemical Corp. (1985) Product Chemistry of Trichlorfon Technical: Dylox Technical. Unpublished 

compilation. 22 p.

MRID: 00161359 

Minor, R.; Freeseman, P. (1986) [Carbon 14] Dylox Anaerobic Soil Metabolism: 93088.Unpublished study 

prepared by Mobay Corp. 29 p.

MRID: 00162307 

Technology Services Group (1986) [Product Chemistry Data for Technical Trichlorfon]. Unpublished 

compilation. 101 p.

MRID: 40261401 

Pither, K. (1987) Photodecomposition of Dylox on a Soil Surface: Report No. 91700. Unpublished study 

prepared by Mobay Corp. 35 p.

MRID: 40279301 

Minor, R.; Freeseman, P.; Pfankuche, L. (1987) The Fate of Dylox under Anaerobic Soil Conditions: 

Mobay Project ID: 94596. Un- published study prepared by Mobay Corp. 58 p.

MRID: 40279302 

Ridlen, R. (1987) Volatility of Dylox and Its Degradates from Soil: Report No. 94598.Unpublished study 

prepared by Mobay Corp. 40 p.

MRID: 40279303 Loeffler, W. (1987) Dissipation of Dylox in Field Soil: Laboratory Project ID: DL-8300-

86: Dylox Objective No. 8300. Unpublished study prepared by Chemonics Laboratories. 62 p.

MRID: 40618201

Pack, D.; Fry, C. (1988) Anaerobic Aquatic Metabolism of (Ethyl-1- ?Carbon 14|Naled): Revised Report: 

Laboratory Project ID MEF- 0012/8809272. Unpublished study prepared by Chevron Chemical Co. 52 p.

MRID: 41354102

Pack, D.; Fry, C. (1988) Supplement to "Anaerobic Aquatic Metabo- lism of (Ethyl-1-[Carbon - 14]) 

NALED": Lab Project Number: MEF/ 0012/8716931. Unpublished study prepared by Chevron Chemical 

Co. 3 p.

MRID: 41354105

Pack, D. (1987) Supplement to "Estimation of Soil Adsorption Coefficient of NALED from TLC Data": 

Lab Project Number: MEF0051/8716396A. Unpublished study prepared by Chevron Chemical Co. 4 p.

MRID: 41535301 Sewekow, ?. (1988) Vapor Pressure of Trichlorfon Pure Active Ingredient: Lab Project 

Number: 100 128: 87267. Unpublished study prepared by Mobay Corp. 11 p.
43 of 74

MRID: 41535302 Weber, ?. (1987) Vapor Pressure of Trichorfon Pure Active Ingredient: Lab Project 

Number: 681 538: 94641. Unpublished study prepared by Corp., and Bayer Ag. 7 p.

MRID: 41723101 

Vithala, R. (1990) DDVP--Hydrolysis of ?C 14| DDVP in Aqueous Solu- tions Buffered at pH 5, 7, and 9: 

Lab Project Number: 006/006/ 001/89. Unpublished study prepared by Univ. of Pittsburgh, Center for 

Hazardous Materials Research. 141 p.

MRID: 41723102 

Vithala, R. (1990) DDVP--Aerobic Soil Metabolism of ?C 14| DDVP: Lab Project Number: 

006/006/004/89. Unpublished study prepared by Univ. of Pittsburgh, Center for Hazardous Materials 

Research. 7 p.

MRID: 42243601 

Ridlen, R.; Pfankuche, L. (1989) Metabolism of ?1-carbon 14| Trichlorfon in Soil: LabProject Number: 

99640. Unpublished study prepared by Mobay Corp. 66 p.

MRID: 42322501 

Grace, T.; Cain, K. (1990) Dissipation of Trichlorfon in California Soils: Lab ProjectNumber: 

DL830089R01: 100160: ML022101. Unpublished study prepared by Plant Sciences, Inc.; NET Atlantic, 

Inc.; Pace Labs. 3801 p.

MRID: 42445101

Pack, D.; Fry, C. (1988) Naled--Anaerobic Aquatic Metabolism of ?Ethyl-1-carbon 14|Naled--Reivsed 

Report: Supplemental: Lab Project Number: MEF-0012/8809272. Unpublished study prepared by Chevron 

Chemical Co. 11 p.

MRID: 43326601 

Mobley, S. (1994) Aqueous Photolysis of (carbon 14) DDVP (Dichlorvos) in Artificial Light: Lab Project 

Number: 838: 1611. Unpublished study prepared by PTRL East, Inc. 95 p.

MRID: 43642501 

Misra, B. (1995) Photodegradation of (Carbon-14)-DDVP (Dichlorvos) on Sandy Loam Soil Under 

Artificial Sunlight Irradiation: Final Report: Lab Project Number: ME 9400184. Unpublished study 

prepared by Pittsburgh Environmental Research Lab, Inc. 79 p.

MRID: 43835701 

Mobley, S. (1995) Anaerobic Soil Metabolism of (carbon 14)DDVP (Dichlorvos): Lab Project Number: 

882: 1847. Unpublished study prepared by PTRL East, Inc. 82 p.

45303501 

Kasper, A.; Shadrick, B. (1993) Abbreviated Soil Dissipation of (carbon 14) Trichlorfon on California 

Soils: Lab Project Number: 92157-B: DL042102: 105157. Unpublished study prepared by Pan-Agricultural 

Laboratories, Inc. 102 p.

MRID: 45895501 

Damon, A.; Lenz, M. (2003) Terrestrial Field Dissipation of (Carbon 14)-TrichlorfonUsing Field 

Lysimeters--Missouri: Lab Project Number: 110960: 45525: DL022101.Unpublished study prepared by 

Analytical Bio-Chemistry and Bayer CropScience. 82 p.

MRID: 47519201 

Damon, A.; Lenz, M. (2002) Terrestrial Field Dissipation of 14 C-Trichlorfon Using Field Lysimeters -

Ontario. Project Number: 111049. Unpublished study prepared by ABC Laboratories, Inc. and Bayer 

Corporation. 123 p.
44 of 74

SUBMITTED EFFECTS STUDIES:

ECOTOX Reference Number: 000347-69

Hill, E.F., et al. 1975. Lethal Dietary Toxicities of Environmental Pollutants to Birds. U.S. Department of 

the Interior, Fish and Wildlife Service, Special Scientific Report – Wildlife No. 191. Washington, D.C.

MRID: 43019601

Pedersen, C.; Thompson, S.; Lesar, C. (1993) Effects of DYLOX Technical on Mallard Duck 

Reproduction: Lab Project Number: 101/006/08: DL740801: 106226. Unpublished study prepared by BioLife Associates, Ltd. and Miles Inc. Agricultural Division. 261 p.

MRID: 43119501

Pedersen, C.; Thompson, S. (1994) Effect of DYLOX Technical on Bobwhite Quail Reproduction: Lab 

Project Number: 101/005/07: DI741701: 106409. Unpublished study prepared by Bio-Life Associates, Ltd. 

and Miles Agricultural Division. 301 p. 

ACCESSTION NO.: AC0023

Clinch, P.G. (1967). The residual contact toxicity to honey bees of insecticides sprayed on to white clover 

(Trifolium repens) in the laboratory. New Zealand Journal of Agricultural Research, 10(2):289-300.

ACCESSTION NO.: AC0008

Clinch, P.G. (1969). Laboratory determination of the residual fumigant toxicity to honey bees of 

insecticide sprays on white clover (Trifolium repens). New Zealand Journal of Agricultural Research, 

12(1):162-170.

ACCESSTION NO.: AA0Q01

Bartlett, B.R. (1966). Toxicity and acceptance of some pesticides fed to parasitic Hymenoptera and 

predatory coccinellids. Journal of Economic Entomology, 59(5):1142-1149.

ACCESSTION NO.: 00001949

Johansen, C.; Eves, J. (1969). Bee research investigations, 1969: Small-scale bee poisoning tests with 

honey bees (HB) and alfalfa leafcutter bees (LB). Unpublished study received Sept. 15, 1971 under 

1F1032; prepared by Washington State Univ., submitted by Hercules, Inc., Wilmington, Del.; 

CDL:091917-H.

ACCESSTION NO.: 00060628

Johansen, C.; Eves, J. (1969). Bee poisoning investigations, 1965: Report No. G-1705; Report No. 17338. 

Unpublished study, including letter dated June 12, 1973 from C.A. Johansen to A.D. Cohick, received Mar 

27, 1974 under 4F1485; prepared by Washington State Univ., Dept. of Entomology, submitted by 

Chemagro Corp., Kansas City, MO.; CDL:092011-I.

ACCESSTION NO.: 00036935

Atkins, E.L.; E.A. Greywood; R.L. MacDonald (1975). Toxicity of pesticides and other agricultural 

chemicals to honey bees. Laboratory studies. Univ. of Californis, Division of Agricultural Science. 

Leaflet 2287. 38 pp.

ACCESSTION NO.: 05008149

Gholson, L.E.; C.C. Beegle; R.L. Best; J.C. Owens (1978). Effects of several commonly-used insecticides 

on cornfield carabids in Iowa. J. Econ. Entomol., 71(3):416-418.

MRID: 40098001

Mayer, F.; Ellersieck, M. (1986) Manual of Acute Toxicity: Interpretation and Data Base 410 Chemicals 

and 66 Species of Fresh-Water Animals. US Fish & Wildlife Service; Resource Publica tion (160): 579 p.
45 of 74

MRID: 404526-01

Forbis, A.D. (1987). Chronic Toxicity of 14C-DYLOX® to Daphnia magna Under Flow-Through Test 

Conditions. Unpublished study performed by Analytical Bio-Chemistry Laboratories, Inc., Columbia, MO. 

Laboratory Final Report No. 35738. Study sponsored by Mobay Corporation, Stilwell, KS. Study initiated 

June 15, 1987 and completed July 6, 1987. 

MRID: 65495

Pickering, Q.H., C. Henderson and A.E. Lemke. 1981. The Toxicity of Organic Phosphorous Insecticides 

to Different Species of Warm Water Fishes. U.S. Department of Health, Education and Welfare. Public 

Health Service. R.A. Taft Sanitary Engineering Center, Cincinnati, Ohio.

MRID: 42571701

Gagliano, G. (1992) Early Life Stage Toxicity of Dylox Technical to the Rainbow Trout (Oncorhynchus 

mykiss) under Flow-through Conditions: Lab Project Number: DL842201: 103928: Unpublished study 

prepared by Miles Incorporated. 192 p. 

MRID: 44499201

Drottar, K.; Krueger, H. (1998) Trichlorfon (Dylox): A 96-Hour Shell Deposition Test with the Eastern 

Oyster (Crassostrea virginica): Lab Project Number: 149A-105: 108069. Unpublished study prepared by 

Wildlife International Ltd. 43 p. 

MRID: 44499202

Drottar, K.; Krueger, H. (1998) Trichlorfon (Dylox): A Flow-Through Life-Cycle Toxicity Test with the 

Saltwater Mysid (Mysidopsis bahia): Lab Project Number: 149A-106: 108070. Unpublished study prepared 

by Wildlife International Ltd. 55 p. Relates to L0000302. 

MRID: 42228301

Eigenberg, D. (1991) A Two-Generation Dietary Reproduction Study in Rats Using Technical Grade 

Trichlorfon (Dylox): Lab Project Number: 89-672-EA. Unpublished study prepared by Mobay Corp. 1075 

p. 

MRID: 40818301

Grimes, J.; Jaber, M. (1988) DDVP: An Acute Oral Toxicity Study with the Bobwhite: Final Report: 

Project No. 246-102. Unpub- lished study prepared by Wildlife International Ltd. 21 p. 

MRID: 22923

Hill, E.F.; Heath, R.G.; Spann, J.W.; et al. (1975) Lethal Dietary Toxicities of Environmental Pollutants to 

Birds: Special Scientific Report--Wildlife No. 191. (U.S. Dept. of the Interior, Fish and Wildlife Service, 

Patuxent Wildlife Research Center; unpublished report)

MRID: 44233401

Redgrave, V. (1997) Mallard Duck Dietary Reproduction and Tolerance Studies: DDVP: Lab Project 

Number: AVC 7/961821: AVC 7. Unpublished study prepared by Huntingdon Life Sciences Ltd. 243 p. 

MRID: 5467

Gaines, T.B. (1960) The acute toxicity of pesticides to rats. Toxicology and Applied Pharmacology 

2(1):88-99. (Also in unpublished submission received Feb 14, 1961 under PP0299; submitted by Chemagro 

Corp., Kansas City, Mo.; CDL:090320-Q) 

MRID: 42483901

Tyl, R.; Myers, C.; Marr, M. (1992) Two-Generation Reproductive Toxicity Study of DDVP Administered 

in Drinking Water to CD (Sprague-Dawley) Rats: Final Report: Lab Project Number 60C-4629-170. 

Unpublished study prepared by Research Triangle Institute. 1225 p. 
46 of 74

MRID: 43890301

Ward, G.; Davis, J. (1995) DDVP Technical Grade: Chronic Life-Cycle Toxicity to the Water Flea, 

Daphnia magna, Under Flow-Through Test Conditions: Lab Project Number: J94030071: J9403007N. 

Unpublished study prepared by Toxikon Environmental Sciences. 74 p. 

MRID: 43788001

Davis, J. (1995) DDVP Technical Grade: Toxicity to Embryos and Larvae of the Rainbow Trout, 

Oncorhynchus mykiss, Under Flow-Through Conditions: Lab Project Number: J9403007M. Unpublished 

study prepared by Toxikon Environmental Sciences. 77 p. 

MRID: 43571408

Jones, F.; Davis, J. (1994) DDVP 4-E Emulsifiable Concentrate: Acute Toxicity to the Mysid, Mysidopsis 

bahia, Under Flow-through Test Conditions: Lab Project Numbers: J9403007J: J9403007B. Unpublished 

study prepared by Toxikon Environmental Sciences. 60 p. 

MRID: 43854301

Ward, S.; Davis, J. (1995) DDVP Technical Grade: Chronic Toxicity to the Mysid (Mysidopsis bahia) 

Under Flow Through Conditions: Lab Project Number: J9407006A. Unpublished study prepared by 

Toxikon Environmental Sciences. 90 p. 

MRID: 43571403

Jones, F.; Davis, J. (1994) DDVP Technical Grade: Acute Toxicity to Sheepshead Minnow (Cyprinodon 

variegatus) Under Flow-through Test Conditions: Lab Project Numbers: J9403007F: J9403007B. 

Unpublished study prepared by Toxikon Environmental Sciences. 59 p. 

MRID: 43790401

Ward, G.; Davis, J. (1995) DDVP Technical Grade: Toxicity to Embryos and Larvae of the Sheepshead 

Minnow (Cyprinodon variegatus) Under Flow-Through Test Conditions: Lab Project Number: J9407006B. 

Unpublished study prepared by Toxikon Environmental Sciences. 81 p. 
47 of 74

Appendix A. Submitted Toxicity Data for Trichlorfon and DDVP.

Studies classified as ‘unacceptable’ are excluded.

TABLE A.1. Submitted Toxicity Data for Trichlorfon (The studies with the most 

sensitive endpoint for each taxon are highlighted).

TAXON ENDPOINT FORMULATION MRID STUDY 

CLASSIFICATION

COMMENTS

Birds (Chronic)

Mallard duck 

(Anas 

platyrhynchos)

NOAEC = 

27 mg/kgdiet

LOAEC = 

78 mg/kgdiet

Technical (99.8%) 43019601 Acceptable Based on decrease 

in eggshell 

thickness (16% 

reduction 

compared to 

control) and 

percent viable 

embryos (i.e., %of 

eggs set); 4 birds 

at the 235 

concentration died 

after exhibiting 

clinical signs of 

toxicity; 1 control 

bird died

Bobwhite quail 

(Colinus 

virginianus)

NOAEC = 9 

mg/kg-diet

LOAEC = 

30 mg/kgdiet

Technical (99.8%) 43119501 Acceptable Based on a 

decrease in 

hatchling survival 

(no eggshell 

thickness effects 

at any level –

highest = 85 

ppm); there were 

10 mortalties (1 

control, 1 at the 8 

ppm

concentration, and 

8 at the 85 ppm 

conc.)

Terrestrial Invertebrates

Honey bee 

(Apis mellifera)

LC50 > 1.20 

lb a.i./acre

Formulation (SP, 

80%)

AC0023 

(Clinch, 

1967)

Supplemental Non-guideline 

study; insecticide 

sprayed from 

tower – honey 

bees enclosed with 

contaminated 

flowers for 1 hr (3 

hrs after spray); 

no mortalities up 

to 24-hr after 

exposure; only 1 

conc. tested.
48 of 74

TAXON ENDPOINT FORMULATION MRID STUDY 

CLASSIFICATION

COMMENTS

Honey bee 

(Apis mellifera)

LC50 > 1.20 

lb a.i./acre

Formulation (SP, 

80%)

AC0008 

(Clinch, 

1969)

Supplemental Non-guideline 

study; test to 

mimic fumigant 

toxicity; bees 

exposed for 1 hr; 

no ‘fumigant 

toxicity’ noted for 

trichlorfon; only 1 

conc. tested.

Lady beetle 

(Lindorus 

lophanthae)

LC50 > 

0.477% a.i. 

in honey 

(w/w) = 

4,770 ppm 

(some 

mortality, 

specifics not 

provided 

except 

<50%)

Mealybug 

destroyer 

(Cryptolaemus 

montrouzieri)

LC50 > 

0.477% a.i. 

in honey 

(w/w) = 

4,770 ppm 

(some 

mortality, 

specifics not 

provided 

except 

<50%)

Scale predator 

(Aphytis 

melinus)

LC50 = 

0.477% a.i. 

in honey 

(w/w) = 

4,770 ppm 

(up to 4-days 

after 

exposure)

Parasitic wasp 

(Metaphycus 

luteolus)

LC50 = 

0.477% a.i. 

in honey 

(w/w) = 

4,770 ppm 

(up to 4-days 

after 

exposure)

Formulation (SP, 

50%)

AA0Q01 

(Bartlett, 

1966)

Supplemental Non-guideline; 

dietary study; 

pesticides mixed 

into honey bait; 

bees allowed to 

feed for 6 hrs, 

then held for 4 

days; only 2 conc. 

tested.

Alfalfa 

leafcutter bee 

(Megachile 

rotundata)

65% 

mortality (2 

lb a.i./acre 

application 

rate) – when 

exposed to 

Dylox SP (80%) ACC 

00001949 

(Johansen 

and Eves, 

1969)

Supplemental Non-guideline; 

alfalfa treated 

using hand 

sprayer, bees were 

caged on treated 

foliage; mortality 
49 of 74

TAXON ENDPOINT FORMULATION MRID STUDY 

CLASSIFICATION

COMMENTS

8-hr old 

residues

evaluated 24-hr 

post exposure; 

only 1 conc. tested

Honey bee 

(Apis mellifera)

44% 

mortality (2 

lb a.i./acre 

application 

rate) – when 

exposed to 

3-hr old 

residues

Dylox SP (80%) ACC 

00001949 

(Johansen 

and Eves, 

1969)

Supplemental Non-guideline; 

alfalfa treated 

using hand 

sprayer, bees were 

caged on treated 

foliage; mortality 

evaluated 24-hr 

post exposure; 

only 1 conc. tested

Honey bee 

(Apis mellifera)

17% 

mortality (1 

lb a.i./acre 

application 

rate) – when 

exposed to 

3-hr old 

residues; 0% 

with 2-day 

old residues

Dylox SP (50%) ACC 

00060628 

(Johansen 

and Eves, 

1965)

Supplemental Non-guideline; 

alfalfa treated 

using hand 

sprayer, bees were 

caged on treated 

foliage; mortality 

evaluated 48-hr 

post exposure; 

only 1 conc. tested

Alkali bee 

(Nomia 

melanderi)

31% 

mortality (1 

lb a.i./acre 

application 

rate) – when 

exposed to 

3-hr old 

residues; 

10% with 2-

day old 

residues

Dylox SP (50%) ACC 

00060628 

(Johansen 

and Eves, 

1965)

Supplemental Non-guideline; 

alfalfa treated 

using hand 

sprayer, bees were 

caged on treated 

foliage; mortality 

evaluated 48-hr 

post exposure; 

only 1 conc. tested

Leafcutter bee 

(Megachile 

rotundata)

5% mortality 

(1 lb a.i./acre 

application 

rate) – when 

exposed to 

3-hr old 

residues

Dylox SP (50%) ACC 

00060628 

(Johansen 

and Eves, 

1965)

Supplemental Non-guideline; 

alfalfa treated 

using hand 

sprayer, bees were 

caged on treated 

foliage; mortality 

evaluated 48-hr 

post exposure; 

only 1 conc. tested

Honey bee 

(Apis mellifera)

LD50 = 

59.83 μg 

a.i./bee 

(acute 

contact); 

slope – 2.81

Formulation ACC 

00036935 

(Atkins et 

al., 1975)

Acceptable A bell-jar vacuum 

duster was used to 

apply the 

pesticide, mixed 

with pyrolite dust 

diluent, to bees; 

observations up to 

96-hrs post 

treatment

Ground beetle 100% Formulation (80%) ACC Supplemental Non-guideline; 
50 of 74

TAXON ENDPOINT FORMULATION MRID STUDY 

CLASSIFICATION

COMMENTS

(Scarites 

substriatus)

mortality at 

1 lb a.i./acre

05008149 

(Gholson 

et al., 

1978)

soil surface 

sprayed with 

pesticide; beetles 

placed in soil and 

mortality 

evaluated after 5 

days; only 1 conc. 

tested

Ground beetle 

(Pterostichus 

chalcites)

100% 

mortality at 

1 lb a.i./acre

Formulation (80%) ACC 

05008149 

(Gholson 

et al., 

1978)

Supplemental Non-guideline; 

soil surface 

sprayed with 

pesticide; beetles 

placed in soil and 

mortality 

evaluated after 5 

days; only 1 conc. 

tested

Ground beetle 

(Bembidion 

rapidum)

97.5% 

mortality at 

1 lb a.i./acre

Formulation (80%) ACC 

05008149 

(Gholson 

et al., 

1978)

Supplemental Non-guideline; 

soil surface 

sprayed with 

pesticide; beetles 

placed in soil and 

mortality 

evaluated after 5 

days; only 1 conc. 

tested

Ground beetle 

(Harpalus 

pensylvanicus)

50% 

mortality at 

1 lb a.i./acre

Formulation (80%) ACC 

05008149 

(Gholson 

et al., 

1978)

Supplemental Non-guideline; 

soil surface 

sprayed with 

pesticide; beetles 

placed in soil and 

mortality 

evaluated after 5 

days; only 1 conc. 

tested

Freshwater Invertebrates (Acute)

Daphnia pulex EC50 (48-hr) 

= 0.18 μg/L

Technical 40098001 Supplemental (also reported in 

40094602); raw

data from M&E 

not legible

Simocephalus 

serrulatus

EC50 (48-hr) 

= 0.70 μg/L

Technical 40098001 Supplemental (also reported in 

40094602); no 

raw data available

Simocephalus 

serrulatus

EC50 (48-hr) 

= 0.32 μg/L

Technical 40098001 Supplemental No raw data 

available

Gammarus 

lacustris

EC50 (96-hr) 

= 40 μg/L

Technical 40098001 Supplemental

Gammarus

pseudolimnaeus

EC50 (96-hr) 

= 108 μg/L

Technical 40098001 Supplemental

Gammarus

pseudolimnaeus

EC50 (96-hr) 

= 275 μg/L

Technical 40098001 Supplemental

Gammarus EC50 (96-hr) Technical 40098001 Supplemental
51 of 74

TAXON ENDPOINT FORMULATION MRID STUDY 

CLASSIFICATION

COMMENTS

pseudolimnaeus = 90 μg/L

Gammarus

pseudolimnaeus

EC50 (96-hr) 

= 108 μg/L

Technical 40098001 Supplemental

Gammarus

pseudolimnaeus

EC50 (96-hr) 

= 119 μg/L

Technical 40098001 Supplemental

Gammarus

pseudolimnaeus

EC50 (96-hr) 

= >40 μg/L

Technical 40098001 Supplemental

Gammarus

pseudolimnaeus

EC50 (96-hr) 

= 43 μg/L

Technical 40098001 Supplemental

Gammarus

pseudolimnaeus

EC50 (96-hr) 

= 32 μg/L

Technical 40098001 Supplemental

Gammarus 

pseudolimnaeus

EC50 (96-hr) 

= 17 μg/L

80% wettable 

powder

40098001 Supplemental

Procambarus

sp.

EC50 (96-hr) 

= 7,800 μg/L

Technical 40098001 Supplemental

Procambarus

sp.

EC50 (96-hr) 

= 13,300 

μg/L

Technical 40098001 Supplemental

Claassenia 

sabulosa

EC50 (96-hr) 

= 22 μg/L

Technical 40098001 Supplemental

Isogenus sp. EC50 (96-hr) 

= 24 μg/L

Technical 40098001 Supplemental

Isogenus sp. EC50 (96-hr) 

= 12 μg/L

80% wettable 

powder 

40098001 Supplemental

Pteronarcella 

badia

EC50 (96-hr) 

= 11 μg/L

Technical 40098001 Supplemental Not enough 

information 

available in the 

raw data to 

confirm the results

Pteronarcella 

badia

EC50 (96-hr) 

= 100 μg/L

Technical 40098001 Supplemental

Pteronarcella 

badia

EC50 (96-hr) 

= 9.8 μg/L

Technical 40098001 Supplemental

Pteronarcella 

badia

EC50 (96-hr) 

= 5.3 μg/L

Technical 40098001 Supplemental Adequate for RQ 

calculation; based 

on analysis of raw 

data, the slope is 

5.2 (C.I.: 2.6 –

7.9)

Pteronarcys 

californica

EC50 (96-hr) 

= 35 μg/L

Technical 40098001 Supplemental

Freshwater Invertebrates (Chronic)

Daphnia magna NOAEC = 

0.0057 μg 

a.i./L

LOAEC = 

0.0086 μg 

a.i./L

Technical 40452601 Acceptable Based on survival 

(all endpoints 

were affected in 

the study, the most 

sensitive was 

survival)

Freshwater Fish (Acute)

Coho salmon LC50 (24-hr) 

= >4,110 

Technical 40098001 Supplemental Flow-through
52 of 74

TAXON ENDPOINT FORMULATION MRID STUDY 

CLASSIFICATION

COMMENTS

μg/L

Cutthroat trout LC50 (96-hr) 

= 2,700 μg/L

Technical 40098001 Supplemental

Cutthroat trout LC50 (96-hr) 

= 6,800 μg/L

Technical 40098001 Supplemental

Cutthroat trout LC50 (96-hr) 

= 5,750 μg/L

Technical 40098001 Supplemental

Cutthroat trout LC50 (96-hr) 

= 1,680 μg/L

Technical 40098001 Supplemental

Cutthroat trout LC50 (96-hr) 

= 4,750 μg/L

Technical 40098001 Supplemental

Cutthroat trout LC50 (96-hr) 

= 375 μg/L

Technical 40098001 Supplemental

Cutthroat trout LC50 (96-hr) 

= 5,70 μg/L

Technical 40098001 Supplemental

Cutthroat trout LC50 (96-hr) 

= 620 μg/L

Technical 40098001 Supplemental

Cutthroat trout LC50 (96-hr) 

= 1,730 μg/L

Technical 40098001 Supplemental “0 DAY DEGRA”

Cutthroat trout LC50 (96-hr) 

= 470 μg/L

Technical 40098001 Supplemental “7 DAY DEGRA”

Cutthroat trout LC50 (96-hr) 

= 170 μg/L

Technical 40098001 Supplemental “14 DAY 

DEGRA”

Cutthroat trout LC50 (96-hr) 

= 340 μg/L

Technical 40098001 Supplemental “21 DAY 

DEGRA”

Cutthroat trout LC50 (96-hr) 

= 3,250 μg/L

80% wettable 

powder

40098001 Supplemental

Cutthroat trout LC50 (96-hr) 

= 5,220 μg/L

Technical 40098001 Supplemental

Cutthroat trout LC50 (96-hr) 

= 4,400 μg/L

Technical 40098001 Supplemental

Cutthroat trout LC50 (96-hr) 

= 6,170 μg/L

Technical 40098001 Supplemental

Cutthroat trout LC50 (96-hr) 

= 1,080 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 1,750 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 1,410 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 11,400 

μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 1,775 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 2,000 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 970 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 8,800 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 1,120 μg/L

Technical 40098001 Supplemental
53 of 74

TAXON ENDPOINT FORMULATION MRID STUDY 

CLASSIFICATION

COMMENTS

Rainbow trout LC50 (96-hr) 

= 700 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 700 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 1,380 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 355 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 210 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 280 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 700 μg/L

80% wettable 

powder

40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 700 μg/L

40.5% EC 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 1,400 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 4,250 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 1,020 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 1,820 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 860 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 72 μg/L

Technical 40098001 Supplemental Not adequate for 

RQ calculation; 

legible raw data 

not available for 

review

Rainbow trout LC50 (96-hr) 

= 158 μg/L

Technical 40098001 Supplemental Adequate for RQ 

calculation 

(reported as 156 in 

the M&E 

volume); no slope 

could be 

calculated

Rainbow trout LC50 (96-hr) 

= 1,400 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 3,500 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 5,850 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 167 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 3,500 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 4,500 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 310 μg/L

Technical 40098001 Supplemental
54 of 74

TAXON ENDPOINT FORMULATION MRID STUDY 

CLASSIFICATION

COMMENTS

Rainbow trout LC50 (96-hr) 

= 2,600 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 2,500 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 780 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 820 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 430 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 370 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 580 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 780 μg/L

80% Wettable 

poweder

40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 2,400 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 1,100 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 430 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 960 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 860 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 9,000 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 6,410 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 1,750 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 2,460 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 390 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 580 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 560 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 700 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 360 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 860 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 1,000 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 1,100 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 570 μg/L

Technical 40098001 Supplemental
55 of 74

TAXON ENDPOINT FORMULATION MRID STUDY 

CLASSIFICATION

COMMENTS

Rainbow trout LC50 (96-hr) 

= 500 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 500 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 208 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 230 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 160 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 1,000 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 820 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 562 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 740 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 190 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 440 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 6,410 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 1,000 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 820 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 560 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 8,000 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 2,460 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 740 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 562 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 700 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 1,230 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 390 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 580 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 190 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 440 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 360 μg/L

Technical 40098001 Supplemental
56 of 74

TAXON ENDPOINT FORMULATION MRID STUDY 

CLASSIFICATION

COMMENTS

Rainbow trout LC50 (96-hr) 

= 780 μg/L

Technical 40098001 Supplemental

Rainbow trout LC50 (96-hr) 

= 1,060 μg/L

80% Wettable 

powder

40098001 Supplemental

Atlantic salmon LC50 (96-hr) 

= 1,400 μg/L

Technical 40098001 Supplemental

Atlantic salmon LC50 (96-hr) 

= 2,000 μg/L

Technical 40098001 Supplemental

Atlantic salmon LC50 (96-hr) 

= 4,100 μg/L

Technical 40098001 Supplemental

Atlantic salmon LC50 (96-hr) 

= 580 μg/L

Technical 40098001 Supplemental

Atlantic salmon LC50 (96-hr) 

= 540 μg/L

Technical 40098001 Supplemental

Atlantic salmon LC50 (96-hr) 

= 380 μg/L

Technical 40098001 Supplemental

Atlantic salmon LC50 (96-hr) 

= 4,400 μg/L

Technical 40098001 Supplemental

Atlantic salmon LC50 (96-hr) 

= 610 μg/L

Technical 40098001 Supplemental

Atlantic salmon LC50 (96-hr) 

= 300 μg/L

Technical 40098001 Supplemental

Atlantic salmon LC50 (96-hr) 

= 2,970 μg/L

Technical 40098001 Supplemental

Atlantic salmon LC50 (96-hr) 

= 10,400 

μg/L

Technical 40098001 Supplemental

Brook trout LC50 (96-hr) 

= 3,500 μg/L

Technical 40098001 Supplemental

Brook trout LC50 (96-hr) 

= 2,500 μg/L

Technical 40098001 Supplemental

Brook trout LC50 (96-hr) 

= 9,400 μg/L

Technical 40098001 Supplemental

Brook trout LC50 (96-hr) 

= 1,100 μg/L

Technical 40098001 Supplemental

Brook trout LC50 (96-hr) 

= 8,400 μg/L

Technical 40098001 Supplemental

Brook trout LC50 (96-hr) 

= 3,400 μg/L

Technical 40098001 Supplemental

Brook trout LC50 (96-hr) 

= 470 μg/L

Technical 40098001 Supplemental

Brook trout LC50 (96-hr) 

= 240 μg/L

Technical 40098001 Supplemental

Brook trout LC50 (96-hr) 

= 2,420 μg/L

Technical 40098001 Supplemental

Brook trout LC50 (96-hr) 

= 620 μg/L

Technical 40098001 Supplemental

Brook trout LC50 (96-hr) 

= 9,200 μg/L

80% Wettable 

powder

40098001 Supplemental

Brook trout LC50 (96-hr) 

= 500 μg/L

Technical 40098001 Supplemental

Brook trout LC50 (96-hr) Technical 40098001 Supplemental
57 of 74

TAXON ENDPOINT FORMULATION MRID STUDY 

CLASSIFICATION

COMMENTS

= 9,200 μg/L

Brook trout LC50 (96-hr) 

= 6,000 μg/L

Technical 40098001 Supplemental

Brook trout LC50 (96-hr) 

= 960 μg/L

Technical 40098001 Supplemental

Brook trout LC50 (96-hr) 

= 840 μg/L

Technical 40098001 Supplemental

Brook trout LC50 (96-hr) 

= 650 μg/L

Technical 40098001 Supplemental

Brook trout LC50 (96-hr) 

= 290 μg/L

Technical 40098001 Supplemental

Brook trout LC50 (96-hr) 

= 5,500 μg/L

40% EC 40098001 Supplemental

Lake trout LC50 (96-hr) 

= 550 μg/L

Technical 40098001 Supplemental

Lake trout LC50 (96-hr) 

= 1,030 μg/L

Technical 40098001 Supplemental

Fathead 

minnow

LC50 (96-hr) 

= 7,900 μg/L

Technical 40098001 Supplemental

Black bullhead LC50 (96-hr) 

= 515 μg/L

Technical 40098001 Supplemental

Channel catfish LC50 (96-hr) 

= 2,200 μg/L

40.5% EC 40098001 Supplemental

Channel catfish LC50 (96-hr) 

= 7,600 μg/L

Technical 40098001 Supplemental

Channel catfish LC50 (96-hr) 

= 880 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 3,170 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= >50,000 

μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 50,000 

μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 10,300 

μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 10,300 

μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= >50,000 

μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 32,000 

μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 3,400 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 2,900 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) Technical 40098001 Supplemental
58 of 74

TAXON ENDPOINT FORMULATION MRID STUDY 

CLASSIFICATION

COMMENTS

= 14,500 

μg/L

Bluegill LC50 (96-hr) 

= 4,500 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 1,720 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 1,720 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 940 μg/L

80% Wettable 

powder

40098001 Supplemental

Bluegill LC50 (96-hr) 

= 5,200 μg/L

40.5% EC 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 2,500 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 600 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 1,300 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 1,500 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 1,000 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 2,500 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 2,700 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 1,650 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 2,200 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 1,050 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 1,050 μg/L

80% Wettable 

powder

40098001 Supplemental

Bluegill LC50 (96-hr) 

= 15,000 

μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 3,300 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 39,000 

μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 800 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 35,500 

μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 31,000 

μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 3,500 μg/L

Technical 40098001 Supplemental
59 of 74

TAXON ENDPOINT FORMULATION MRID STUDY 

CLASSIFICATION

COMMENTS

Bluegill LC50 (96-hr) 

= 7,200 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 2,820 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 9,200 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 12,300 

μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 7,200 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 5,000 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 1,730 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 3,150 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 2,250 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 410 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 8,700 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 14,000 

μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 5,800 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 5,000 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 2,800 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 2,000 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 234 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 5,200 μg/L

40.5% EC 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 3,360 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 13,000 

μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 15,000 

μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 45,000 

μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 40,000 

μg/L

Technical 40098001 Supplemental
60 of 74

TAXON ENDPOINT FORMULATION MRID STUDY 

CLASSIFICATION

COMMENTS

Bluegill LC50 (96-hr) 

= 6,800 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 9,600 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 8,100 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 2,350 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 2,250 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 2,250 μg/L

Technical 40098001 Supplemental

Bluegill LC50 (96-hr) 

= 1,050 μg/L

80% Wettable 

powder

40098001 Supplemental

Bluegill LC50 (96-hr) 

= 1,880 μg/L

Technical 40098001 Supplemental

Largemouth 

bass

LC50 (96-hr) 

= 3,450 μg/L

Technical 40098001 Supplemental

Yellow perch LC50 (96-hr) 

= 3,450 μg/L

Technical 40098001 Supplemental

Fathead 

minnow

LC50 (96-hr) 

= 110,000 

μg/L

Bluegill LC50 (96-hr) 

= 3,800 μg/L

Goldfish LC50 (96-hr) 

= 100,000 

μg/L

Guppy LC50 (96-hr) 

= 7,200 μg/L

Technical 65495 Supplemental Adequate for RQ 

calculation; No 

analytical 

verification was 

reported for any of 

the bioassays.

Bluegill LC50 (96-hr) 

= 2,200 μg/L

Technical 91766 Acceptable

Rainbow trout LC50 (96-hr) 

= 1,600 μg/L

Technical 91766 Acceptable

Freshwater Fish (Chronic)

Rainbow trout NOAEC = 

110 μg a.i./L

LOAEC = 

234 μg a.i./L

Technical 425717-

01

Acceptable Early life-stage 

study; endpoint 

based on increased 

time to swim up 

Estuarine/Marine Invertebrates (Acute)

Eastern oyster 

(Crassostrea 

virginica)

EC50 >114 

mg a.i./L

Technical 444992-

01

Acceptable 96-hr shelldeposition study; 

NOAEC = 83 mg 

a.i./L (based on 

16% decrease in 

shell deposition)

Estuarine/Marine Invertebrates (Chronic)

Mysid 

(Mysidopsis 

bahia)

NOAEC = 

3.1 μg a.i./L

LOAEC = 

Technical 444992-

02

Acceptable Flow-through, 

life-cycle study; 

endpoints based 

on decreased 
61 of 74

TAXON ENDPOINT FORMULATION MRID STUDY 

CLASSIFICATION

COMMENTS

6.7 μg a.i./L number of 

neonates 

produced, 

decreased 

survival, dreased 

weight, and 

decreased length

Thalassiosire 

pseudonana

LC50 = >50 

mg a.i./L
62 of 74

TABLE A.2. Summary of the Studies with the Most Sensitive Endpoints from 

Submitted Toxicity Data for DDVP.

TAXON ENDPOINT FORMULATION MRID STUDY 

CLASSIFICATION

COMMENTS

Birds (Acute)

Bobwhite quail 

(Colinus 

virginianus)

LD50 = 8.8 mg 

a.i./kg bw

Technical 40818301 Acceptable

Birds (Sub-Acute)

Ring-necked 

pheasant 

(Phasianus 

colchicus)

LC50 = 568 

mg a.i./kgdiet

Technical 0022923 Acceptable

Birds (Chronic)

Mallard duck 

(Anas 

platyrhynchos)

NOAEC = 5 

mg a.i./kgdiet

LOAEC = 15 

mg a.i./kgdiet

Technical 44233401 Acceptable Based on 

reduced 

eggshell 

thickness, eggs 

laid, and 

number of 

viable embryos

Mammals (Acute)

Laboratory rat 

(Rattus 

norvegicus)

LD50 = 56 mg 

a.i./kg-bw

Technical 0005467 Acceptable

Mammals (Chronic)

Laboratory rat 

(Rattus 

norvegicus)

NOAEC = 20 

mg a.i./kgdiet

LOAEC = 80 

mg a.i./kgdiet

Technical 42483901 Acceptable Based on 

reduced fertility 

and pup weight

Terrestrial Invertebrates

Honey bee 

(Apis mellifera)

LD50 = 0.5 μg 

a.i./bee 

(contact)

Technical 00036935 Acceptable

Freshwater Invertebrates (Acute)

Water flea 

(Daphnia 

pulex)

EC50 = 0.066 

μg a.i./L

Technical 40098001 Acceptable

Freshwater Invertebrates (Chronic)

Water flea 

(Daphnia 

magna)

NOAEC = 

0.0058 μg 

a.i./L

LOAEC = 

0.0122 μg 

a.i./L

Technical 43890301 Acceptable Based on 

reduced egg

production and 

growth (length 

and weight)

Freshwater Fish (Acute)

Cutthroat trout 

(Oncorhynchus 

clarki)

LC50 = 170 

μg a.i./L

Technical 40098001 Acceptable

Freshwater Fish (Chronic)
63 of 74

TAXON ENDPOINT FORMULATION MRID STUDY 

CLASSIFICATION

COMMENTS

Rainbow trout 

(Oncorhynchus 

mykiss)

NOAEC = 

5.2 μg a.i./L

LOAEC = 

10.1 μg a.i./L

Technical 43788001 Acceptable Based on 

decreased posthatch larval 

survival

Estuarine/Marine Invertebrates (Acute)

Mysid 

(Americamysis 

bahia)

EC50 = 19.1 

μg a.i./L

Technical 43571408 Acceptable

Estuarine/Marine Invertebrates (Chronic)

Mysid 

(Americamysis 

bahia)

NOAEC = 

1.48 μg a.i./L

LOAEC = 

3.25 μg a.i./L

Technical 43854301 Acceptable Based on 

reduced growth 

(weight and 

length)

Estuarine/Marine Fish (Acute)

Sheepshead 

minnow 

(Cyprinodon 

variegates)

LC50 = 7,350 

μg a.i./L

Technical 43571403 Acceptable

Estuarine/Marine Fish (Chronic)

Sheepshead 

minnow 

(Cyprinodon 

variegates)

NOAEC = 

960 μg a.i./L

LOAEC = 

1840 μg a.i./L

Technical 43790401 Acceptable Based on 

reduced survival 

and length
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Appendix B. The Risk Quotient Method and Levels of Concern 

The Risk Quotient Method is the means used by EFED to integrate the results of 

exposure and ecotoxicity data. For this method, Risk Quotients (RQs) are calculated by 

dividing exposure estimates by the acute and chronic ecotoxicity values (i.e., RQ = 

EXPOSURE/TOXICITY). These RQs are then compared to OPP's levels of concern 

(LOCs). These LOCs are criteria used by OPP to indicate potential risk to non-target 

organisms and the need to consider regulatory action. EFED has defined LOCs for acute 

risk, potential restricted use classification, and for endangered species. 

The criteria indicate that a pesticide used as directed has the potential to cause adverse 

effects on non-target organisms. LOCs currently address the following risk presumption 

categories: 

(1) acute - there is a potential for acute risk; regulatory action may be warranted in 

addition to restricted use classification; 

(2) acute restricted use - the potential for acute risk is high, but this may be mitigated 

through restricted use classification; 

(3) acute endangered species - the potential for acute risk to endangered species is high, 

regulatory action may be warranted; and 

(4) chronic risk - the potential for chronic risk is high, regulatory action may be 

warranted. 

Currently, EFED does not perform assessments for chronic risk to plants, acute or 

chronic risks to non-target insects, or chronic risk from granular/bait formulations to 

mammalian or avian species. 

The ecotoxicity test values (i.e., measurement endpoints) used in the acute and chronic 

RQs are derived from required studies. Examples of ecotoxicity values derived from 

short-term laboratory studies that assess acute effects are: (1) LC50 (fish and birds), (2) 

LD50 (birds and mammals), (3) EC50 (aquatic plants and aquatic invertebrates), and (4) 

EC25 (terrestrial plants). Examples of toxicity test effect levels derived from the results 

of long-term laboratory studies that assess chronic effects are: (1) the Lowest Observed 

Adverse Effect Concentration (LOAEC) (birds, fish, and aquatic invertebrates), and (2) 

the No Observed Adverse Effect Concentration (NOAEC) (birds, fish and aquatic 

invertebrates). The NOAEC is generally used as the ecotoxicity test value in assessing 

chronic effects. Risk presumptions, along with the corresponding RQs and LOCs are 

summarized in Table B1.
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Table B1. Agency risk quotient (RQ) metrics and levels of concern (LOC) per risk class.

Risk Class Risk Description RQ LOC

Aquatic Animals (fish and invertebrates)

Acute Potential for effects to non-listed animals from acute 

exposures

Peak EEC/LC50

1

0.5

Acute 

Restricted Use

Potential for effects to animals from acute exposures

Risks may be mitigated through restricted use classification

Peak EEC/LC50

1

0.1

Acute Listed 

Species

Listed species may be potentially affected by acute 

exposures

Peak EEC/LC50

1

0.05

Chronic Potential for effects to non-listed and listed animals from 60-day EEC/NOEC (fish)

chronic exposures 

21-day EEC/NOEC (invertebrates)

1

Terrestrial Animals (mammals and birds)

EEC2 Acute Potential for effects to non-listed animals from acute /LC50 (Dietary)

exposures

EEC/LD50 (Dose)

0.5

EEC2 Acute /LC50 (Dietary)

Restricted Use

Potential for effects to animals from acute exposures

Risks may be mitigated through restricted use classification

EEC/LD50 (Dose)

0.2

EEC 2 Acute Listed /LC50 (Dietary)

Species

Listed species may be potentially affected by acute 

exposures

EEC/LD50 (Dose)

0.1

Chronic Potential for effects to non-listed and listed animals from 

chronic exposures

EEC 2/NOAEC 1

Plants

Non-Listed Potential for effects to non-target, non-listed plants from 

exposures

EEC/ EC25 1

Listed Plant Potential for effects to non-target, listed plants from EEC/ NOEC

exposures

EEC/ EC05

1

1 LC50 or EC50. 2 Based on upper bound Kenaga values.
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Appendix C. Data Call-In Tables

The Environmental Fate and Effects Division (EFED) has completed a Data Call-In 

(DCI) table for the trichlorfon (and DDVP) environmental fate and effects data gaps 

identified in registration review. The effects data gaps may change if relevant toxicity

data are identified from the ECOTOX literature review. The attached DCI tables, which 

include the guideline number and study title for required data, also provides a rationale 

for requiring the data, an explanation of how the data will be used, and a brief description 

of how the data could impact the Agency’s future decision-making.

Trichlorfon:

Guideline Number: 835.2120 

Study Title: Hydrolysis

Rationale for Requiring the Data

Acceptable data have not been provided to quantify the hydrolysis of trichlorfon. According to 

Code of Federal Regulations 40 (CFR40 2007) Part 158 Subpart D (data requirements for 

pesticides) hydrolysis data are required for pesticides with terrestrial or aquatic uses. Since 

trichlorfon uses are classified as terrestrial and aquatic, hydrolysis data for trichlorfon should be 

submitted to fulfill OPPTS Guideline 835.2120. 

Practical Utility of the Data

How will the data be used?

These data are used to estimate the degradation of trichlorfon in aquatic systems and ultimately to 

derive aquatic EECs using PRZM/EXAMS. 

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

In the case that these data are unavailable at the time risk assessments are conducted, it will be 

assumed that trichlorfon is stable to hydrolysis. If trichlorfon does degrade due to hydrolysis, this 

assumption will result in overestimates of the concentrations of trichlorfon in the environment.

Guideline Number: 835.2410

Study Title: Photodegradation in soil

Rationale for Requiring the Data

Acceptable data have not been provided to quantify the photolysis of trichlorfon in water. 

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

requirements for pesticides) aqueous photolysis data are required for pesticides with terrestrial or 

aquatic uses. Since trichlorfon uses are classified as terrestrial and aquatic, aqueous photolysis 

data for trichlorfon should be submitted to fulfill OPPTS Guideline 835.2410. 

Practical Utility of the Data

How will the data be used?

These data are used to characterize the degradation of trichlorfon in soil. 

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

In the case that these data are not submitted, it will be assumed that trichlorfon is stable to 

photolysis on soil. 
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Guideline Number: 835.4300 

Study Title: Aerobic Aquatic Metabolism

Rationale for Requiring the Data

Acceptable data have not been provided to quantify the metabolism of trichlorfon under aerobic 

aquatic conditions. According to Code of Federal Regulations 40 (CFR40 2007) Part 158 Subpart 

D (data requirements for pesticides) aerobic aquatic metabolism are required for pesticides with 

terrestrial or aquatic uses. Since trichlorfon uses are classified as terrestrial and aquatic, aerobic 

aquatic metabolism data for trichlorfon should be submitted to fulfill OPPTS Guideline 

835.4300. 

Practical Utility of the Data

How will the data be used?

These data are used to estimate the degradation of trichlorfon in aquatic systems and ultimately to 

derive aquatic EECs using PRZM/EXAMS. 

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

In the case that these data are unavailable at the time risk assessments are conducted, 

PRZM/EXAMS input parameter guidance default values will be employed to account for aerobic 

aquatic metabolism. 

Guideline Number: 835.4400 

Study Title: Anaerobic Aquatic Metabolism

Rationale for Requiring the Data

Acceptable data have not been provided to quantify the metabolism of trichlorfon under 

anaerobic aquatic conditions. According to Code of Federal Regulations 40 (CFR40 2007) Part 

158 Subpart D (data requirements for pesticides) anaerobic aquatic metabolism data are required 

for pesticides with terrestrial or aquatic uses. Since trichlorfon uses are classified as terrestrial 

and aquatic, anaerobic aquatic metabolism data for trichlorfon should be submitted to fulfill 

OPPTS Guideline 835.4400. 

Practical Utility of the Data

How will the data be used?

These data are used to estimate the degradation of trichlorfon in aquatic systems and ultimately to 

derive aquatic EECs using PRZM/EXAMS. 

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

In the case that these data are unavailable at the time risk assessments are conducted, 

PRZM/EXAMS input parameter guidance default values will be employed to account for 

anaerobic aquatic metabolism. 

Guideline Number: 835.1240 

Study Title: adsorption/desorption

Rationale for Requiring the Data

Acceptable data have not been provided to quantify the adsorption/desorption characteristics of 

trichlorfon in U.S. soils. According to Code of Federal Regulations 40 (CFR40 2007) Part 158 

Subpart D (data requirements for pesticides) adsorption/desorption data are required for 

pesticides with terrestrial uses. Since trichlorfon uses are considered to be terrestrial, an 

acceptable study should be submitted to fulfill OPPTS Guideline 835.1240. This study should 

define Kd and KOC values of trichlorfon in U.S. soils. It is preferred that this study be conducted 

using a batch equilibrium method.

Practical Utility of the Data
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How will the data be used?

These data are used to estimate the transport of trichlorfon from treatment sites to aquatic systems 

and ultimately to derive aquatic EECs using PRZM/EXAMS. 

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

In the absence of these data, EFED will assume that there is no sorption of trichlorfon to soils or 

organic matter on the treatment site. In order to implement this in derivation of aquatic EECs, a 

KOC value of 0 will be used to parameterize PRZM/EXAMS. Input of a KOC value >0 is expected 

to result in lower aquatic EECs. If acceptable data are provided, the uncertainties associated with 

this assumption will be reduced.

Guideline Number: 835.6200 

Study Title: Aquatic Field Dissipation

Rationale for Requiring the Data

At this time, no acceptable studies are available to describe the dissipation of trichlorfon under 

aquatic field conditions. According to Code of Federal Regulations 40 (CFR40 2007) Part 158 

Subpart D (data requirements for pesticides), aquatic field dissipation data are required for 

pesticides with aquatic uses. Since trichlorfon uses are classified as aquatic, aquatic field 

dissipation data for trichlorfon should be submitted to fulfill OPPTS Guideline 835.6200.

Practical Utility of the Data

How will the data be used?

These data are used to characterize the fate of trichlorfon in the aquatic environment resulting 

from direct applications to water. 

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

These data are useful to validate laboratory fate data of trichlorfon with a field study that 

accounts for all of the fate processes studied under laboratory conditions (e.g., hydrolysis, 

photolysis).

Guideline Number: 835.6100 (7), 835.6200 (7)

Study Title: Environmental Chemistry Methods

Rationale for Requiring the Data

Independently validated analytical methods for residues in soil and water (environmental 

chemistry methods) submitted by the registrant are used to evaluate analyses described in 

submitted environmental fate and ecological effects studies. Submitted analytical methods are 

also used by various Federal, State, Tribal, and local agencies to detect and monitor residues that 

are or are suspected to be in environmental compartments due to outdoor uses and accidental 

releases. Therefore, availability of these analytical methods is necessary in order to protect 

human health and the environment from trichlorfon residues in the environment. Independent 

laboratory validations for submitted analytical methods are necessary to confirm the levels of 

detection and quantitation reported in registrant-prepared validations.

Use of trichlorfon may impact surface water quality due to runoff of rain water and drift of 

residues. Therefore, analytical methods for are necessary for detecting trichlorfon residues 

in water and in soil or sediment.

Practical Utility of the Data
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How will the data be used?

In the absence of independently validated environmental chemistry methods, submitted 

environmental fate and ecological effects data may not be reviewable and entities outside the 

Agency may lack chemical-specific methods for analyses in environmental compartments. 

Independently validated environmental chemistry methods will be used to evaluate the submitted 

environmental fate and ecological effects data and will be made available to the public to support 

monitoring for trichlorfon residues.

How could the data change the Agency’s decision, or impact the Agency’s future decisionmaking? 

Risk assessment conclusions could be altered if they are not supported by either study data or 

environmental monitoring detections that are based on independently validated environmental 

chemistry methods. Furthermore, while not directly related to Agency decision-making, 

independently validated environmental chemistry methods are necessary in order to protect 

human health and the environment from use of trichlorfon.

Guideline Number: 850.2100 

Study Title: Avian Acute Oral Toxicity Test (mallard duck or bobwhite quail and a 

passerine species)

Rationale for Requiring the Data

No acceptable acute avian oral toxicity data were submitted for trichlorfon. The new Part 158 data 

requirements [40 CFR Part 158 (CFR 40 2007)] specify that acute avian oral toxicity data be 

submitted for either mallard duck or bobwhite quail and a passerine species. The available chronic 

toxicity data for mallard ducks and bobwhite quails demonstrate that trichlorfon can cause toxic 

effects in these birds. In addition, avian data for other organophosphate (OP) insecticides, including 

dimethoate, show that a passerine species, such as the red-winged blackbird, are one order of 

magnitude more sensitive than other tested bird species to acute OP insecticide exposure (USEPA 

2008). Therefore, an avian oral toxicity test is required for passerine birds and either the mallard 

duck or the bobwhite quail, as specified in 40 CFR Part 158. A passerine study protocol must be 

submitted for review by the Agency prior to initiation of this study.

Practical Utility of the Data

How will the data be used?

Acute avian oral toxicity data will be used to identify potential risks to birds from acute exposure to 

trichlorfon. The data will reduce uncertainties associated with the current risk assessment for birds

and will improve the Agency’s understanding of the potential effects of trichlorfon on terrestrial 

species. If oral acute toxicity data are not submitted for any bird, than risk to birds from acute 

exposure to trichlorfon will be assumed.

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

If future endangered species risk assessments are performed without these data, the Agency would 

have to assume that trichlorfon “may affect” listed birds directly (and listed species from other taxa 

indirectly), and use of trichlorfon and its formulated products may need to be restricted in areas 

where listed species could be exposed. The lack of these data will limit the flexibility the Agency 

and registrants have in coming into compliance with the Endangered Species Act and could result 

in use restrictions for trichlorfon use that are unnecessarily severe.

Guideline Number: 850.2200 

Study Title: Avian Dietary Toxicity Test (mallard duck and bobwhite quail)

Rationale for Requiring the Data

No acceptable sub-acute avian dietary toxicity data were submitted for trichlorfon. The new Part 
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158 data requirements [40 CFR Part 158 (CFR 40 2007)] specify that avian dietary toxicity data be 

submitted for both a waterfowl and upland game species. The available chronic toxicity data for 

mallard ducks and bobwhite quails demonstrate that trichlorfon can cause toxic effects in these 

birds. Therefore, an avian dietary toxicity test is required for mallard ducks and bobwhite quails as 

specified in 40 CFR Part 158. 

Practical Utility of the Data

How will the data be used?

Sub-acute avian dietary toxicity data will be used to identify potential risks to birds from acute 

exposure to trichlorfon. The data will reduce uncertainties associated with the current risk 

assessment for birds and will improve the Agency’s understanding of the potential effects of 

trichlorfon on terrestrial species. If dietary toxicity data are not submitted for any bird, than risk to 

birds from dietary exposure to trichlorfon will be assumed.

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

If future endangered species risk assessments are performed without these data, the Agency would 

have to assume that trichlorfon “may affect” listed birds directly (and listed species from other taxa 

indirectly), and use of trichlorfon and its formulated products may need to be restricted in areas 

where listed species could be exposed. The lack of these data will limit the flexibility the Agency 

and registrants have in coming into compliance with the Endangered Species Act and could result 

in use restrictions for trichlorfon use that are unnecessarily severe.

Guideline Number: 850.1075

Study Title: Fish Acute Toxicity Test, Estuarine/Marine

Rationale for Requiring the Data

Acute toxicity data are not available for estuarine and marine fish. The updated Part 158 data 

requirements, published in October 2007, specify that acute toxicity data are required on one 

estuarine/marine mollusk (guideline fulfilled), one estuarine/marine invertebrate (guideline not 

fulfilled), and one estuarine/marine fish (guideline not fulfilled) for terrestrial (food crop, feed 

crop, and nonfood), aquatic food crop, and nonfood (outdoor), forestry, and residential outdoor 

uses. Trichlorfon has terrestrial (turf), aquatic nonfood (ornamental/bait ponds) and residential 

outdoor uses registered, and therefore, the acute estuarine/marine organism toxicity studies are 

required.

In the absence of these data, an acute-to-chronic ratio (ACR) would normally be derived; and the 

acute toxicity to estuarine and marine fish would be estimated based on the ACR for freshwater 

fish. However, there are currently no toxicity data (acute or chronic) for estuarine/marine fish, 

therefore, an ACR cannot be derived. In addition, three of the four reported ecological incidents 

associated with the use of trichlorfon have involved fish kills. 

Practical Utility of the Data

How will the data be used?

Estuarine/marine fish acute toxicity data will be used to determine the potential for trichlorfon to 

affect fish species in estuarine/marine environments. The data will reduce uncertainties associated 

with the current risk assessment for estuarine/marine fish and will improve the Agency’s

understanding of the potential effects of trichlorfon on aquatic animals. In the absence of data 

specific for these fish, data from freshwater fish species will be used as a surrogate for 

estuarine/marine fish.

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

Using toxicity data from a freshwater species as a surrogate for estuarine/marine species increases 

the uncertainty for assessing risks to estuarine/marine species in screening-level assessments. 
71 of 74

Additionally, if future endangered species risk assessments are performed without these data, the 

Agency would have to presume risk to listed estuarine/marine fish species in the absence of such 

data for trichlorfon. Therefore, the use of trichlorfon and its formulated products may need to be 

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

flexibility the Agency and registrants have in coming into compliance with the Endangered Species 

Act and could result in use restrictions for trichlorfon that are unnecessarily severe.

Guideline Number: 850.1035

Study Title: Mysid Acute Toxicity Test

Rationale for Requiring the Data

Although, acute toxicity data are available for an estuarine/marine mollusk, no acute data are 

currently available for a non-mollusk estuarine/marine invertebrate. The updated Part 158 data 

requirements, published in October 2007, specify that acute toxicity data are required on one 

estuarine/marine mollusk (guideline fulfilled), one estuarine/marine invertebrate (guideline not 

fulfilled), and one estuarine/marine fish (guideline not fulfilled) for terrestrial (food crop, feed 

crop, and nonfood), aquatic food crop, and nonfood (outdoor), forestry, and residential outdoor 

uses. Trichlorfon has terrestrial (turf), aquatic nonfood (ornamental/bait ponds) and residential 

outdoor uses registered, and therefore, the acute estuarine/marine organism toxicity studies are 

required.

In the absence of these data, an acute-to-chronic ratio (ACR) would normally be derived; and the 

acute toxicity to estuarine/marine invertebrates would be estimated based on the ACR for 

freshwater invertebrates. However, the freshwater invertebrate data necessary for calculating the 

ACR are not available. Chronic data are not available for the most acutely sensitive freshwater 

species (Pteronarcella badia). 

Practical Utility of the Data

How will the data be used?

Estuarine/marine invertebrate acute toxicity data will be used to determine the potential for 

trichlorfon to affect non-mollusk invertebrate species in estuarine/marine environments. The data 

will reduce uncertainties associated with the current risk assessment for estuarine/marine 

invertebrates and will improve the Agency’s understanding of the potential effects of trichlorfon on 

aquatic animals. In the absence of data specific for these invertebrates, data from freshwater 

invertebrate species will be used as a surrogate for estuarine/marine invertebrates.

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

Using toxicity data from a freshwater species as a surrogate for estuarine/marine species increases 

the uncertainty for assessing risks to estuarine/marine species in screening-level assessments. 

Additionally, if future endangered species risk assessments are performed without these data, the 

Agency would have to presume risk to listed non-mollusk estuarine/marine invertebrate species in 

the absence of such data for trichlorfon. Therefore, the use of trichlorfon and its formulated 

products may need to be restricted in areas where listed species could be exposed. The lack of these 

data will limit the flexibility the Agency and registrants have in coming into compliance with the 

Endangered Species Act and could result in use restrictions for trichlorfon that are unnecessarily 

severe.

Guideline Number: 850.1400

Study Title: Fish Early Life-Stage Toxicity Test, Estuarine/Marine

Rationale for Requiring the Data

Chronic toxicity data are not available for estuarine and marine fish. In the absence of these data, 

an acute-to-chronic ratio (ACR) would normally be derived; and the chronic toxicity to estuarine 
72 of 74

and marine fish would be estimated based on the ACR for freshwater fish. However, there are 

currently no toxicity data (acute or chronic) for estuarine/marine fish, therefore, an ACR cannot be 

derived. Additionally, due to the potential use pattern of trichlorfon , exposure to estuarine/marine 

environments is possible. Therefore, an early life-stage toxicity study is required for 

estuarine/marine fish, as specified in 40 CFR Part 158. 

Practical Utility of the Data

How will the data be used?

Estuarine/marine fish chronic toxicity data will be used to determine the potential for trichlorfon to 

affect fish species in estuarine/marine environments. The data will reduce uncertainties associated 

with the current risk assessment for estuarine/marine fish and will improve the Agency’s

understanding of the potential effects of trichlorfon on aquatic animals. In the absence of data 

specific for these fish, data from freshwater fish species will be used as a surrogate for 

estuarine/marine fish.

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

Using toxicity data from a freshwater species as a surrogate for estuarine/marine species increases 

the uncertainty for assessing risks to estuarine/marine species in screening-level assessments. 

Additionally, if future endangered species risk assessments are performed without these data, the 

Agency would have to presume risk to listed estuarine/marine fish species in the absence of such 

data for trichlorfon. Therefore, the use of trichlorfon and its formulated products may need to be 

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

flexibility the Agency and registrants have in coming into compliance with the Endangered Species 

Act and could result in use restrictions for trichlorfon that are unnecessarily severe.

Guideline Number: 850.4100, 850.4150 

Study Title: Terrestrial Plant Toxicity Test, Tier I (Seedling Emergence and Vegetative 

Vigor)

Rationale for Requiring the Data

Toxicity data for terrestrial plants are not available for trichlorfon. The current 40 CFR Part 158 

data requirements, require Tier I level seedling emergence and vegetative vigor terrestrial plant 

data for all insecticides. Additionally, other OPs are known to be phytotoxic (e.g., tribufos, a plant 

defoliant). Therefore, Tier I plant toxicity studies (seedling emergence and vegetative vigor) are 

required for terrestrial plants, as specified in 40 CFR Part 158. 

Practical Utility of the Data

How will the data be used?

Vegetative vigor and seedling emergence data for terrestrial plants will be used to determine the 

potential for trichlorfon to affect non-target plant species in the terrestrial environment. The data 

will reduce uncertainties associated with the current risk assessment for terrestrial plants and will 

improve the Agency’s understanding of the potential effects of trichlorfon on terrestrial plants. In 

the absence of data specific for these plants, risk to terrestrial plants will be assumed.

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

Because terrestrial plants form the basis of the food chain in many terrestrial habitats, a solid 

understanding of the potential risks to terrestrial plants is essential for sound environmental risk 

management decision-making. Without terrestrial plant data for trichlorfon, the Agency cannot 

determine if the current application rates for trichlorfon may result in direct adverse effects to

terrestrial plants and/or indirect effects resulting from reduction in the prey base and/or loss of 

habitat/cover. If future endangered species risk assessments are performed without these data, the 

Agency would have to presume risk to non-target terrestrial plants from use of trichlorfon. 

Therefore, use of trichlorfon and its formulated products may need to be restricted in areas where 
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listed species could be exposed. The lack of these data will limit the flexibility the Agency and 

registrants have in coming into compliance with the Endangered Species Act and could result in 

use restrictions for trichlorfon that are unnecessarily severe.

Guideline Number: 850.4400 

Study Title: Aquatic plant toxicity (Tier I)

Rationale for Requiring the Data

Trichlorfon toxicity data for vascular and non-vascular aquatic plants are not available. Based on 

the 40 CFR Part 158 data requirements, Tier I level non-target aquatic plant data are required for 

all insecticides. Additionally, other OPs are known to be phyotoxic (e.g., tribufos, which is a 

defoliant). Therefore, non-target aquatic plant data for algae and vascular plants are required for 

trichlorfon at the Tier I level.

Practical Utility of the Data

How will the data be used?

Data from Tier I aquatic plant toxicity studies will be used to estimate potential risks to aquatic 

vascular and non-vascular plants associated with the use of trichlorfon. The data will reduce 

uncertainties associated with the current risk assessment for aquatic plants and will improve the 

Agency’s understanding of the potential effects of trichlorfon on aquatic plants. In the absence of 

Tier I data, risks for both vascular and non-vascular aquatic plants will be presumed.

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

Because aquatic vascular and non-vascular plants form the basis of the food chain for aquatic 

habitats and significantly contribute to overall water quality, a solid understanding of the potential 

risks to aquatic plants is essential for sound environmental risk management decision-making. 

Without aquatic plant data for trichlorfon, the Agency cannot determine if the current application 

rates for trichlorfon may result in direct adverse effects to aquatic plants and/or indirect effects 

resulting from reduction in the prey base and/or loss of habitat/cover. If future endangered species 

risk assessments are performed without these data, the Agency would have to assume that 

trichlorfon “may affect” aquatic plants directly (and listed species from other taxa indirectly via 

reduction in prey base and/or habitat), and use of trichlorfon may need to be restricted in areas 

where listed species could be exposed. The lack of these data will limit the flexibility the Agency 

and registrants have in coming into compliance with the Endangered Species Act and could result 

in use restrictions for trichlorfon which are unnecessarily severe.

DDVP:

Guideline Number: 850.2100 

Study Title: Avian Acute Oral Toxicity Test

Rationale for Requiring the Data

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

DDVP; however, data are not available for passerines, which are required under the new 40 CFR 

Part 158 (CFR 40 2007) data requirements for conventional pesticides (72 FR 60934; USEPA 

2007c). The available data for bobwhite quails show that DDVP is classified as very highly toxic 

to birds on an acute exposure. In addition, avian data for other organophosphate (OP) insecticides, 

including dimethoate, show that a passerine species, such as the red-winged blackbird, are one 

order of magnitude more sensitive than other tested bird species to acute OP insecticide exposure. 

Therefore, an avian oral toxicity test is required for passerine birds, as specified in 40 CFR Part 

158. A passerine study protocol must be submitted for review by the Agency prior to initiation of 

this study.

Practical Utility of the Data
74 of 74

How will the data be used?

Acute avian oral toxicity data will be used to identify potential risks to birds from acute exposure to 

DDVP from the use of trichlorfon. The data will reduce uncertainties associated with the current 

risk assessment for birds and will improve the Agency’s understanding of the potential effects of 

trichlorfon on terrestrial species. If oral acute toxicity data are not submitted for passerines, than 

risk to passerines from acute exposure to DDVP from the use of trichlorfon will be assumed.

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

If future endangered species risk assessments are performed without these data, the Agency would 

have to assume that trichlorfon “may affect” listed passerine species directly (and listed species 

from other taxa indirectly), and use of trichlorfon and its formulated products may need to be 

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

flexibility the Agency and registrants have in coming into compliance with the Endangered Species 

Act and could result in use restrictions for trichlorfon use that are unnecessarily severe.

Guideline Number: 850.4100, 850.4150 

Study Title: Terrestrial Plant Toxicity Test, Tier I (Seedling Emergence and Vegetative 

Vigor)

Rationale for Requiring the Data

Toxicity data for terrestrial plants are not available for DDVP. The current 40 CFR Part 158 data 

requirements, require Tier I level seedling emergence and vegetative vigor terrestrial plant data for 

all insecticides. Additionally, other OPs are known to be phytotoxic (e.g., tribufos, a plant 

defoliant). Therefore, Tier I plant toxicity studies (seedling emergence and vegetative vigor) are 

required for terrestrial plants, as specified in 40 CFR Part 158. 

Practical Utility of the Data

How will the data be used?

Vegetative vigor and seedling emergence data for terrestrial plants will be used to determine the 

potential for DDVP (from the use of trichlorfon) to affect non-target plant species in the terrestrial 

environment. The data will reduce uncertainties associated with the current risk assessment for 

terrestrial plants and will improve the Agency’s understanding of the potential effects of trichlorfon 

on terrestrial plants. In the absence of data specific for these plants, risk to terrestrial plants will be 

assumed.

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

Because terrestrial plants form the basis of the food chain in many terrestrial habitats, a solid 

understanding of the potential risks to terrestrial plants is essential for sound environmental risk 

management decision-making. Without terrestrial plant data for DDVP, the Agency cannot 

determine if the current application rates for trichlorfon may result in direct adverse effects to 

terrestrial plants and/or indirect effects resulting from reduction in the prey base and/or loss of 

habitat/cover. If future endangered species risk assessments are performed without these data, the 

Agency would have to presume risk to non-target terrestrial plants from use of trichlorfon. 

Therefore, use of trichlorfon and its formulated products may need to be restricted in areas where 

listed species could be exposed. The lack of these data will limit the flexibility the Agency and 

registrants have in coming into compliance with the Endangered Species Act and could result in 

use restrictions for trichlorfon that are unnecessarily severe.

Guideline Number: 850.4400 

Study Title: Aquatic plant toxicity (Tier I)

Rationale for Requiring the Data

DDVP toxicity data for vascular and non-vascular aquatic plants are not available. Based on the 40 
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CFR Part 158 data requirements, Tier I level non-target aquatic plant data are required for all 

insecticides. Additionally, other OPs are known to be phyotoxic (e.g., tribufos, which is a 

defoliant). Therefore, non-target aquatic plant data for algae and vascular plants are required for 

DDVP at the Tier I level.

Practical Utility of the Data

How will the data be used?

Data from Tier I aquatic plant toxicity studies will be used to estimate potential risks to aquatic 

vascular and non-vascular plants from DDVP exposure associated with the use of trichlorfon. The 

data will reduce uncertainties associated with the current risk assessment for aquatic plants and will 

improve the Agency’s understanding of the potential effects of trichlorfon on aquatic plants. In the 

absence of Tier I data, risks for both vascular and non-vascular aquatic plants will be presumed.

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

Because aquatic vascular and non-vascular plants form the basis of the food chain for aquatic 

habitats and significantly contribute to overall water quality, a solid understanding of the potential 

risks to aquatic plants is essential for sound environmental risk management decision-making. 

Without aquatic plant data for DDVP, the Agency cannot determine if the current application rates 

for trichlorfon may result in direct adverse effects to aquatic plants and/or indirect effects resulting 

from reduction in the prey base and/or loss of habitat/cover. If future endangered species risk 

assessments are performed without these data, the Agency would have to assume that trichlorfon

“may affect” aquatic plants directly (and listed species from other taxa indirectly via reduction in 

prey base and/or habitat), and use of trichlorfon may need to be restricted in areas where listed

species could be exposed. The lack of these data will limit the flexibility the Agency and 

registrants have in coming into compliance with the Endangered Species Act and could result in 

use restrictions for trichlorfon which are unnecessarily severe.