2

Given that there are several chemicals that will be included in the risk assessment, data on each 

are required for conduct of a risk assessment. Data gaps for DCPA and TPA are summarized 

below. Additional details are provided in the problem formulation.

DCPA: No aquatic chronic studies have been submitted for DCPA. DCPA is relatively 

persistent in the environment and has a tendency to bioaccumulate in aquatic organisms. 

Therefore, availability of chronic studies using DCPA is important to an ecological risk 

assessment. In addition, a number of the aquatic studies that were formerly considered to be 

acceptable have been downgraded to unacceptable because of evidence that the test substance 

was not fully dissolved and no measurements were made to confirm test concentrations. 

Additional acute aquatic studies were downgraded from acceptable to supplemental, due to the 

failure to centrifuge the measured concentrations. The chemical properties of DCPA indicate 

that although the test concentrations were measured, without centrifugation the dissolved soluble 

test concentrations could not be estimated. 

TPA: No data have been submitted on the major degradate, TPA. TPA forms at high levels 

relative to parent chemical, it is expected to be more mobile than DCPA, and is expected to be 

somewhat persistent. Therefore, availability of a relatively comprehensive dataset on the toxicity 

and environmental fate of TPA is needed. However, a more limited testing strategy will be 

considered in lieu of a comprehensive data submission if one is proposed.

Manufacturing Contamination By-Products: No additional data are required on the 

contamination by-products because sufficient data are currently available to allow for a risk 

assessment on these by-products.
3

REGISTRATION REVIEW

Preliminary problem formulation for the environmental fate, 

ecological risk, endangered species and drinking water assessments

for:

DCPA

[dimethyl 2,3,5,6-tetrachloroterephthalate]

O O

CH 3

O O

CH 3

Cl

Cl

Cl

Cl

PREPARED BY:

Christina Wendel, Biologist

Wm. J. Shaughnessy, PhD, Environmental Scientist

Environmental Risk Branch II

Environmental Fate and Effects Division

Office of Pesticide Programs

REVIEWED BY:

Nelson Thurman, Senior Fate Scientist

Kristina Garber, Senior Effects Scientist

Environmental Risk Branch 2

Environmental Fate and Effects Division

Office of Pesticide Programs
4

TABLE OF CONTENTS

Description of Regulatory Action.............................................................................. 6

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

Pesticidal Mechanism of Action............................................................................... 10

Conclusions from Previous Assessments ................................................................ 10

Environmental Fate and Transport Characteristics............................................. 12

Physico-chemical Properties.................................................................................... 12

Environmental Fate .................................................................................................. 16

Environmental Transport Assessment.................................................................... 23

Monitoring Data........................................................................................................ 23

Clean Water Act........................................................................................................ 24

Ecological Effects...................................................................................................... 25

Effects to Aquatic Organisms.................................................................................. 31

Effects to Terrestrial Organisms............................................................................. 32

Degradate toxicity ..................................................................................................... 34

Contaminant toxicity (dioxins and HCB)............................................................... 35

Ecological Incidents.................................................................................................. 37

Characteristics of Ecosystems Potentially at Risk ................................................. 38

Assessment Endpoints .............................................................................................. 38

Conceptual Model ..................................................................................................... 39

Risk Hypothesis......................................................................................................... 41

Analysis Plan ............................................................................................................. 41

Stressors of Concern................................................................................................. 42

Measures of Exposure............................................................................................... 42

Measures of Toxicity................................................................................................. 45

Measures of Risk....................................................................................................... 46

Integration of Exposure and Effects ....................................................................... 46

Deterministic and Probabilistic Assessment Methods.............................................. 47

Drinking Water Assessment..................................................................................... 47

Endangered Species Assessments............................................................................ 47

Endocrine Disruptor Screening Program............................................................... 48

Preliminary Identification of Data Gaps ................................................................ 49

Environmental Fate .................................................................................................. 49

Effects ................................................................................................................... 50

Other Information Needs......................................................................................... 56

References.................................................................................................................. 57
5

List of Appendices

Appendix A. Maximum DCPA use rates and management practices by crop based on current 

labels. .......................................................................................................................... 70

Appendix B. Output generated by SIP v.1.0................................................................................ 79

Appendix C: Additional Information for DCI Rationale.............................................................. 80
6

Description of Regulatory Action

The Food Quality Protection Act of 1996 mandated the EPA to implement a new program for 

assessing the risks of pesticides, i.e., registration review1. All pesticides distributed or sold in the 

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

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

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

product labeling. The registration review program is intended to ensure that, as the ability to 

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

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

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

Through the new registration review program, the Agency periodically reevaluates pesticides to 

ensure that as 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 to determine whether dimethyl 2,3,5,6-tetrachloroterephthalate (DCPA)

uses continue to meet the FIFRA standard for registration. This problem formulation for the 

environmental fate and ecological risk assessment chapter in support of the registration review is 

intended for the initial docket opening, which starts the public phase of the review process. This 

problem formulation considers all current and active registrations for DCPA.

Problem formulations provide a strategic framework for the risk assessment. By identifying 

the important components of the problem, it focuses the assessment on the most relevant life 

history stages, habitat components, chemical properties, exposure routes, and endpoints. The 

structure of this risk assessment is based on guidance contained in U.S. EPA’s Guidance for 

Ecological Risk Assessment (U.S. EPA 1998a), the Services’ Endangered Species Consultation 

Handbook (U.S. FWS/NMFS 1998) and is consistent with procedures and methodology outlined 

in the Overview Document (U.S. EPA, 2004) and reviewed by the U.S. Fish and Wildlife 

Service and National Marine Fisheries Service (U.S. FWS/NMFS 2004).

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

fate and ecological risk assessment being conducted for DCPA. It sets the objectives for the risk 

assessment, evaluates the nature of the problem, and provides a plan for analyzing the data and 

characterizing the risk.

Stressor Source and Distribution

DCPA (also called dacthal), a pre-emergence herbicide first registered under FIFRA in 1958,

is used widely to control annual grass and certain broadleaf weeds. It is registered for a variety 

of food (vegetables, cole crops, herbs, melons, and others) and a variety of non-food uses (turf, 

residential lawns, ornamentals, nurseries, and sod farms). The formulations currently registered 

include granular, wettable powders, and flowable concentrates. DCPA may be applied via 

ground, chemigation, and aerial applications. Application methods include broadcast spray, soil 

 

1

(http://www.epa.gov/oppsrrd1/registration_review/)
7

incorporation, soil band treatments, layby treatments, spreader, sprinkler irrigation, and soil 

broadcast treatment and, in general, it is applied at seeding or transplanting or after cultivation to 

prevent germination of weeds. Depending on the crop, it may be applied to the crop pre-plant, 

preemergence, post emergence, or post transplant (OMAFRA, 2008).

Two major degradates were observed in laboratory studies, tetrachloroterephthalic acid 

(TPA) and monomethyl tetrachloroterephthalic acid (MTP). TPA reached maximums of 100% 

applied radioactivity and MTP maximums of 16% applied radioactivity in aerobic soil 

metabolism studies. TPA was also a major degradate in an anaerobic soil metabolism study, and

is stable to aerobic and anaerobic soil metabolism. MTP is an intermediate between DCPA and 

TPA. MTP is short lived and degraded to TPA. Exposure to DCPA and TPA is expected to be 

much greater than to MTP. In addition, TPA is a known groundwater contaminant. Therefore, 

the risk assessment of degradates focuses on exposure to TPA. 

The manufacturing processes of DCPA results in the formation of several known 

contaminants. Of toxicological concern are hexachlorobenzene (HCB), congeners (structurally 

related chemicals) of polyhalogenated dibenzo-p-dioxins/dibenzofurans (dioxins/furans), and 

other possible organochlorine contaminants. Dibenzofurans and dibenzodioxins other than 

2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) are a possible manufacturing by-products 

and were reported as a contaminant in the RED. The risk assessment will examine potential 

exposures to HCB and the dioxin 2,3,7,8-TCDD.

 The following uses are considered part of the federal action that will be evaluated in this 

assessment and reflect the current labeled uses of DCPA.

Terrestrial food crops

Terrestrial food crop uses include: arrowroot, dried-type succulent (snap) beans, brassica

(head and stem vegetables), broccoli, broccoli raab, brussels sprouts, cabbage, chinese cabbage, 

canola/rape, cauliflower, chayote, collards, cucumber, eggplant, garlic, gherkin, medicinal 

ginseng, gourd, Chinese (wax) gourd, groundcherry (strawberry tomato/tomatillo), hanover 

salad, horseradish, kale, head and leaf lettuce (black seeded simpson, salad bowl, etc.), manioc 

(cassava), melons, watermelons, cantaloupe, honeydew, musk melons, momordica spp., mustard, 

onion (including green and scallions), onion, southern peas, pepino (melon pear), pepper, 

white/Irish potato, radish, shallot, all or unspecified squash, summer squash, winter squash, 

hubbard squash, sweet potato, strawberry, taro, tomatillo, tomato, tumeric, turnip, and yam.

Terrestrial non-food crops

Terrestrial non-food crop uses include: golf course turf, nursery stock, ornamental and/or 

shade trees, ornamental ground cover, ornamental herbaceous plants, ornamental lawns and turf 

ornamental sod farm (turf), ornamental lawns and turf, ornamental nonflowering plants, 

ornamental woody shrubs and vines, and residential lawns.
8

USGS National Use Map

A national map showing the estimated poundage of DCPA applied in 2002 is presented in 

Figure 1. The map was downloaded from the U.S. Geological Survey (USGS), National Water 

Quality Assessment Program (NAWQA) website:

http://water.usgs.gov/nawqa/pnsp/usage/maps/show_map.php?year=02&map=m1872. It does 

not reflect any new registrations, label changes, changing use patterns, or mitigation measures 

that may have occurred between that time and the time of this problem formulation. The map is 

an illustration of the current extent of DCPA use for agricultural purposes and does not reflect 

non-agricultural uses. The risk assessment will be based on the labeled uses at the time the 

assessment is conducted.

Figure 1. DCPA National Use Map 

Label Application Rates and Intervals

DCPA labels may be categorized into two types: labels for manufacturing uses (including 

technical grade DCPA and its formulated products) and end-use products. While technical 

products are not used directly in the environment, they are used to make formulated products, 

which can be applied in specific areas to control annual grasses and broadleaf weeds. The 

formulated product labels legally limit DCPA’s potential use to only those sites that are specified 

on the labels. A complete list of all uses that will be assessed is presented in Table 1. The 
9

maximum application rate on the labels will be used to estimate exposure. When some labels 

had a lower maximum application rate relative to other labels, both rates are included in Table 1.

 

Table 1. DCPA Uses and Application Information 

Use Sites Type of 

Application

Maximum Single 

Application Rate 

(lbs a.i./A)

(Formulation)

Application 

Interval 

(days)

Crops 

Cycles per 

Year1

Brassica (head and stem

vegetables), Broccoli, 

Broccoli raab, Cabbage, 

Chinese Cabbage, 

Canola\rape, Cauliflower, 

Collards, Horseradish, Kale, 

Mustard

Aerial 

(G only)

Ground

10.5

(WP, FlC, G) 7, 30, NA 1 to 3

Canola/rape

Aerial 

(G only)

Ground

10.5

(WP, FlC, G) 7

1 

(assumed)

Garlic, Leek

Aerial 

(G only)

Ground 

10.4 (G) 7 1-2

Head and Leaf Lettuce, 

Brussels Sprouts, Hanover 

Salad

Aerial 

(G only)

Ground

10.5

(WP, FlC, G) 183 1-2

Ground 10.2 (WP) 183 1-2

Chayote, Cucumber, Gherkin, 

Gourd, Chinese Gourd, Bitter 

Melon, Cantaloupe, 

Honeydew, Watermelon, 

Musk Melon, Mormordica

spp.3, Pepino, Pear Melon, 

Summer Squash, Melon, 

Winter Squash, Hubbard 

Squash

Aerial 

(G only)

Ground

10.5 (WP, FlC, 

G) NA 1

Aerial

Ground 10.4 (G) NA 1

Onion, Green Onion, 

Scallions, Radish, Shallot, 

Taro, Ginseng, Arrowroot, 

Manioc, Tumeric

Aerial 

(restrictions)

Ground

10.5

(WP, FlC, G) 7

Often 

rotated 

with lettuce

Irish Potato, Sweet Potato, 

Turnip, Yam, Taro, Ginseng, 

Arrowroot, Manioc, Tumeric

Aerial

(G only)

Ground

10.5

(WP, FlC, G) 7 1

Ground 10.4 (G) 7 1

Dried type beans, succulent 

beans, snap beans, southern 

peas, pepper

Ground 10.4 (G) NA 1

Strawberry Ground 10.5 (G) NA 1

Eggplant, Groundcherry, 

strawberry tomato, Tomatillo, 

Tomato

Aerial 

(G only)

Ground

10.5 (FlC)

9.1 (G) 1 1

Nursery Stock and 

ornamentals

Aerial

Ground

11.4 (G)

12 (FlC, WP) 7

1 

(assumed)
10

Use Sites Type of 

Application

Maximum Single 

Application Rate 

(lbs a.i./A)

(Formulation)

Application 

Interval 

(days)

Crops 

Cycles per 

Year1

15.2 (G)

15 (FlC)

Ornamentals lawns, 

residential lawns, turf, 

ornamental sod farm, shade 

trees, ground cover 

herbaceous plants, 

nonflowering plants, woody 

shrubs and vines, golf course 

turf, residential lawns

Aerial

Ground

11.4 (G)

15 (FlC)

15.2 (G)

7, 30, 60 1 

(assumed)

Abbreviations: App. = application; Form. = formulation; WP = wettable powder; FlC = flowable concentrate; G = 

granular; a.i./A = active ingredient/acre

1- Seasons per year were obtained from Memorandum from Monisha Kaul in BEAD to Melissa Panger in EFED 

dated 2/28/2007, unless stated otherwise.

DCPA may be applied at planting, transplant, post-emergence, or post-transplant and as a 

broadcast, foliar, layby, banded, or soil incorporated application. For example, it is 

recommended for use after cultivation to prevent germination of weeds. 

The maximum amount of DCPA applied per season was not specified on the labels for most 

uses. Some labels specified one application of DCPA per crop cycle for lettuce but no other 

labels specified a maximum number of applications for any of the crops. In addition, minimum 

application intervals were not specified on any of the labels. In its absence, a varied application 

interval based on crop use scenarios used in the risk assessment will be assumed by EFED. 

Estimates of agricultural uses of DCPA as of June 17, 2008 are presented in Appendix A.

Changes in label allowed uses that occur between now and the time the risk assessment is 

conducted will be reflected in the risk assessment. 

Pesticidal Mechanism of Action

DCPA is a selective phthalic acid herbicide (Wood, 2007) and chlorinated benzoic acid 

herbicide (Cox, 1991). DCPA inhibits both root and shoot growth of emerging seedlings of 

annual grasses and certain annual broadleaf weeds (Holmesen and Hess, 1984). It is nonsystemic and is absorbed by the roots but not foliage and does not translocate in the plant 

(OMAFRA, 2008). DCPA disrupts mitosis resulting in abnormal cell division in the root tip 

meristem areas. It causes significant disruption of cell wall formation and disrupts microtubule 

formation and function (Monaco et al., 2002). The direction of cell wall formation during 

mitosis is random within the cell, rather than the usual straight walls formed between two 

daughter nuclei (Holmesen and Hess, 1984). 

Conclusions from Previous Assessments

DCPA was first registered under FIFRA in 1958 for use on turf grasses as an herbicide for 

the selective preemergence control of crabgrass and other assorted weeds (U.S. EPA, 1998b). 
11

Since that time more than 60 products were registered with the Agency. Given the long 

regulatory history with DCPA, a number of ecological risk assessments have been conducted. 

Results from two recent assessments are described in more detail below.

In 1998 an ecological risk assessment was completed in support of the RED (U.S. EPA, 

1998b). In the RED assessment for DCPA (U.S. EPA, 1998b), the Agency was unable to make 

an eligibility decision for the use of DCPA on turf. The Agency identified several risks of 

regulatory concern, and planned to undertake a full benefits assessment before determining 

whether such use would be eligible for re-registration. The risks of concern included chronic 

risks to wild mammalian species and acute risks to freshwater and estuarine mollusks. The 

Agency determined that all remaining uses of DCPA did not pose an unreasonable risk to 

humans or the environment and were eligible for re-registration.

To mitigate potential risks, the RED required:

The registrants to establish a certified upper limit for each impurity of toxicological 

significance (e.g., 15 dioxin/furan congeners) associated with the active ingredient and 

found to be present in any sample of the product. 

The registrant to produce no more than an agreed upon limit every three calendar years, 

beginning in January, 1997.

All fall turf uses to be dropped from the label and the maximum application rate to be 

reduced to 12 lbs a.i./A. 

All labels to contain surface water, ground water, and spray drift label advisories.

However, not all of these requirements are reflected on current labels. For instance, some fall 

uses on turf are still allowed on some labels, and some labels still allow for use at 15 lbs a.i./A.

The following ecological toxicity studies were required in the RED.

Dietary study with mallard ducks

Avian reproduction study using the mallard duck and bobwhite quail.

Vegetative vigor and seedling emergence studies for sensitive terrestrial plants

These studies have been submitted and are described in this problem formulation, however, 

the vegetative vigor and seedling emergence studies do not fulfill guideline requirements, and are 

considered data gaps. Therefore, additional terrestrial plant studies are needed to meet this 

requirement. 

In 2005, the Agency ordered that several uses be terminated, effective July 31, 2005, in 

response to concerns of contamination of ground water with TPA.2 The uses that were to be 

terminated included: alfalfa, arracacha, artichokes (Chinese and Jerusalem), beans, bean yam 

(yam bean), beets, chestnuts (soil treatment and nursery stock), chufa, citron melon, cotton, 

crabapples (soil treatment and nursery stock), cucumber, edible canna, garlic, ginger, leren, peas, 

pepper, potatoes, residential uses (turf and ornamentals), squash (including pumpkin), tanier, 

 

2 U.S. EPA. 2005a. DCPA: Order to amend to terminate uses. Fed Reg 70 (143): 43408-43410. Available at 

http://www.epa.gov/EPA-PEST/2005/July/Day-27/p14737.htm
12

walnuts (non-bearing and nursery stock), and yam. Some labels still list uses on beans, nursery 

stock, garlic, peas, peppers, potatoes, residential uses on turf and ornamentals, squash, and yam.

In February 2009, the Agency completed an assessment of the potential direct and indirect 

effects to the California red-legged frog (CRLF) and potential modification to designated critical 

habitat from uses of DCPA.

3

 Based on the information available at that time the Agency made a

May Affect and Likely to Adversely Affect determination for the CRLF from the use of 

DCPA. Additionally, the Agency determined that there is the potential for modification of 

CRLF designated critical habitat from the use of the chemical. The effects determinations were

based on the following predicted risks:

1) Risk of acute effects to freshwater fish exposed to TPA, for all uses;

2) Risk of acute effects to freshwater invertebrates exposed to TPA, for all uses;

3) Risk of chronic effects to freshwater fish and invertebrates exposed to DCPA and 

TPA, for all uses;

4) Risk of effects to freshwater plants exposed to DCPA and TPA, for all uses;

5) Risk of acute effects to small birds exposed to hexachlorobenzene (HCB) for uses 

with multiple applications;

6) Risk of chronic effects to small birds and small mammals exposed to DCPA and 

HCB, for all uses; and 

7) Risk of effects to terrestrial plants exposed to DCPA, for all uses

Environmental Fate and Transport Characteristics

Physico-chemical Properties

DCPA has a vapor pressure of 12.5x10-6and estimated Henry’s law constants ranging from 

1.0x10-3to 2.2x10-6atm-m

3

/mole, indicating that it is somewhat volatile. It is slightly soluble in 

water with a solubility limit of 0.5 mg/L and has a log KOW ranging from 4.3-4.4 (based on FAO 

classification system), indicating that it has a higher affinity for organics than for water and has 

the potential to accumulate in organisms. The air-water partition coefficient (KAW) was reported 

to be 10-4(Daly et al., 2007a). 

Two major degradates were observed in laboratory studies, tetrachloroterephthalic acid 

(TPA) and monomethyl tetrachloroterephthalic acid (MTP). TPA reached maximums of 100% 

applied radioactivity and MTP maximums of 16% applied radioactivity in aerobic soil 

metabolism studies. TPA was also a major degradate in an anaerobic soil metabolism study. 

MTP is an intermediate between DCPA and TPA. TPA is much more soluble than DCPA with a 

water solubility of 5780 mg/L and is stable to aerobic and anaerobic soil metabolism (Table 4). 

MTP is short lived and degraded to TPA. Therefore, the risk assessment of degradates will focus 

on exposure to TPA. The chemical identity information for these compounds is shown in Table 

2 and the structures are shown in Figure 2.

 

3 Memorandum from Jean Holmes, ERB 2, Environmental Fate and Effects Division, to Arthur-Jean Williams, 

Associate Director, Environmental Fate and Effects Division, Subj: Effects Determinations for DCPA Relative to 

the California Red-Legged Frog and Designated Critical Habitat, dated 2/18/2009.
13

Table 2. Identification Information for DCPA and its Degradates, TPA, and MTP1

Parameter DCPA MTP TPA

Common Name Chlorthal dimethyl

Tetrachloroterephthalic acid, 

monomethyl; chlorthal 

monomethyl, monomethyl 

2,3,5,6tetrachloroterephthalate

Tetrachloroterephthalic 

acid; chlorthal; 

perchloroterephthalic 

acid

Chemical Abstract 

Service (CAS) 

Number

1861-32-1 887-54-7 2136-79-0

International Union 

of Pure and Applied 

Chemistry (IUPAC) 

Name

Dimethyl 2,3,5,6-

tetrachloroterephthalate

CAS Name

Dimethyl

2,3,5,6-tetrachloro-1,4-

benzenedicarboxylate

2,3,5,6-Tetrachloro-1,4-

benzenedicarboxylic 

acid

Synonyms

Dacthal, Dacthalor,

chlorothal, chlorothal 

dimethyl; Chlorothal 

dimethyl ester

Chlorthal monomethyl Chlorthal

Empirical Formula C10H6Cl4O4 C9H4Cl4O4 C8H2Cl4O4

SMILES Notation c1(c(c(c(C(OC)=O)c(c1Cl

)Cl)Cl)Cl)C(OC)=O

c1(c(c(c(C(O)=O)c(c1Cl)Cl)Cl

)Cl)C(OC)=O

c1(c(c(c(C(O)=O)c(c1C

l)Cl)Cl)Cl)C(O)=O

1 Data from U.S. EPA, 1998b, U.S. EPA, 2008a, and the U.S. National Library of Medicine CHEMIDplus Lite 

Online Database available at http://toxnet.nlm.nih.gov/cgi-bin/sis/search.

O O

CH 3

O O

CH 3

Cl

Cl

Cl

Cl

HO O

O O

CH 3

Cl

Cl

Cl

Cl

HO O

HO O

Cl

Cl

Cl

Cl

(a) DCPA (b) MTP (c) TPA

Figure 2. Chemical structure of (a) chlorthal dimethyl (DCPA), (b) monomethyl 

tetrachloroterephthalic acid (MTP), and (c) tetrachloroterephthalic acid (TPA)(US EPA, 

1998a)

The manufacturing process of DCPA produces several known contaminants. Of 

toxicological concern are hexachlorobenzene (HCB), congeners (structurally related chemicals) 
14

of polyhalogenated dibenzo-p-dioxins/dibenzofurans (dioxins/furans), and other possible 

organochlorine contaminants. Dibenzofurans and dibenzodioxins, other than 2,3,7,8-TCDD, are 

possible manufacturing by-products and were reported as a contaminant in the re-registration 

eligibility decision (RED) (U.S. EPA, 1998b). The risk assessment will consider all impurities

of toxicological concern. The maximum level of HCB that is allowed in formulations of DCPA 

is 0.3 percent. Dioxin/furans do not have a maximum allowable level in formulations. The RED

reported that dioxin/furans in submitted samples were below 0.1 parts per billion (U.S. EPA, 

1998b).

The structure of hexachlorobenzene, 2,3,7,8-TCDD, and base structures of dibenzodioxins 

are shown in Figure 3. Polychlorinated dioxins have a triple ring structure that consists of two 

benzene rings connected by a ring with two oxygens. One to four chlorine atoms may be present 

on each benzene ring.

Cl

Cl

Cl

Cl

Cl

Cl

(a) Hexachlorobenzene

(b) Base structure for dibenzodioxin

O

Cl O Cl

Cl Cl

(c) 2,3,7,8-TCDD

Figure 3. Structure of (a) Hexachlorobenzene, (b) Dibenzodioxins, and (c) 2,3,7,8-

tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD)

Table 3 provides a summary of the physico-chemical properties of DCPA, the degradates 

MTP and TPA, and the impurities, HCB and 2,3,7,8-TCDD.
15

Table 3. Summary of Physico-Chemical Properties of DCPA, Its Degradates, and Impurities 

Property DCPA MTP TPA HCB 2,3,7.8-TCDD

Molecular Weight 331.97 g/mol (2) 317.94 g/mol (2) 303.91 g/mol (2) 284.79 (14) 321.9709 g/mol

Melting Point 155oC (1,2) 158.62oC (5) 178.10oC (5) 230 oC (14) 305-306 oC (13)

Boiling Point Not determinable 393.09 oC (5) 426.15 oC (5) 322 oC (14) NA

Bulk Density 0.75 g/cm3 (1) NA NA NA NA

Vapor Pressure at 25oC

0.33 mPa or 2.5 x 10-6torr 

(1,2)

0.21 mPa or 1.6x 10-7torr 

(4)

5.23 x 10-7 mm Hg 

(5)

4.89 x 10-8 mm Hg 

(5)

1089 x 10-5 mm Hg at 

20 °C (14) 1.5 x 10-9 mm Hg (12)

Henry’s Law Constant

2.2 x 10-6atm-m

3

/mol, 

measured (1, 7)

0.001042 atm-m

3

/mol (4)

2.11 x 10-10 atmm

3

/mole (5)

6.58 x 10-13 atmm

3

/mole (5)

6.84 x 10-4 atmm3/mol (14)

1.30 x 10-3 atmm3/mol (14)

1.62 x 10-5at-m

3

/mol (13)

Water Solubility 0.5 mg/L (1,2) 18.26 mg/L (5) 175.4 mg/L (5)

5780 mg/L (6) 3.5-20 μg/L (14) 19.3 ng/L (12)

Log Octanol – water partition 

coefficient (KOW)

4.28 (1, 4)

4.40 (2) 3.19 (5) 2.13 (5) 6.18 (14) 6.80 (12)

pKa No dissociation constant at 

pH 2-12 (11) NA NA NA NA

Air-water partition coefficient 

(KAW)

10-4at 25oC (8) NA NA NA NA

Log Octanol-air Partition 

Coefficient (KOA)

8.28 at 25oC (9)

8.45 at 25oC (10)

8.51 at 20oC (10)

NA NA NA NA

Log Particle-gas Partitioning

Coefficient (Kp) -4.1 (10) NA NA NA NA

Abbreviations: NA = not available

(1) Data from U.S. EPA, 1998b; (2) Data from U.S. EPA, 2008a; (3) Data from ChemBioFinder.com; (4) Data from Health Canada, 2008; (5) Data estimated 

from EPI Suite version 3.20 using the SMILES string from Table 2 as input; (6) Data from Wettasinghe and Tinsley, 1993 as reported by U.S. EPA, 1994; (7) 

Data from U.S. EPA, 1994 (8) Data from Muir et al., 2004 as reported by Daly et al., 2007a; (9) Data from Muir et al., 2004 (10) Data from Yao et al., 2007; 

(11) Data from U.S. EPA, 2001; (12) Data from U.S. EPA, 2003; The most reliable or definitive value reported by the review is reported; (13) Data from U.S. 

EPA, 2006b; (14) Data from U.S. EPA, 1998c
16

Environmental Fate

The primary route of degradation for the parent is aerobic metabolism. It is stable to 

hydrolysis and photolysis and biotic half-lives range from 27 - 66 days. Organic-carbon water 

partition coefficients (KOCs) ranging from 1863-3503 L/kg, indicate it is slightly mobile. 

Potential transport mechanisms include spray drift, runoff, volatilization, and atmospheric 

transport. The moderate KOC, indicates that DCPA may be present in runoff as a solute and/or 

bound to organic carbon in soil or sediment. Table 4 presents a summary of the environmental 

fate properties of DCPA. EFED will access existing data to obtain environmental fate data for 

HCB and dioxins. 

Table 4. Summary of DCPA Environmental Fate Properties

Study Value (units) Major Deg. (maximum %)

Minor Deg.1

MRID # Study Status or Comments

Hydrolysis Stable at pH 5, 7, and 9 None 00114648 Acceptable

Direct Aqueous 

Photolysis

No data available 00143063 

41508607

Unacceptable

Soil Photolysis Stable

TPA was Stable

MTP (5.2%) 41508608 Acceptable 

Aerobic Soil 

Metabolism

Single First Order (LN/Linear Fit)

Half-life (days)

TPA (100%)2

MTP (6.9%)

00114649

Supplemented 

by 41648801 

Supplemental due to 

insufficient mass balance (70-

114% on day 0), moisture 

95% of 1/3 bar, and 

temperatures were 30oC. 

Half-lives may be longer than 

predicted at 75% 1/3 bar and 

at 25oC. Additionally, soils 

were not completely 

characterized. See DER 

Addendum (02/10/2009)

Soil With 

Unextract.

Without 

Unextract.

Sand 

Loam 55 29

Sandy 

Clay 

Loam

66 48

Clay 57 31

TPA stable in all soils

Single First Order (LN/Linear Fit)

Half-life (days)

TPA (100%)3

MTP (16%)

00114652 Supplemental due to 

insufficient mass balance (70-

84% on day 0), moisture 95% 

of 1/3 bar, and temperatures 

were 30oC

Half-lives may be longer than

predicted at 75% 1/3 bar and 

at 25oC. Additionally, soils 

were not completely 

characterized. See DER 

Addendum (02/10/2009)

Soil With 

Unextract

Without 

Unextract

Sandy 

Loam 38 27

Sandy 

Clay 

Loam

61 47

Clay 41 29

TPA stable in all soils

Half life (days) = 

92 days at 10oC

18 days at 25oC and 30oC

Choi et al., 

1988

Not applicable
17

Study Value (units) Major Deg. (maximum %)

Minor Deg.1

MRID # Study Status or Comments

Half life (days)=

16.6 days at 25oC

Wettasinghe 

and Tinsley, 

1993

Not applicable

Anaerobic Soil 

Metabolism

Half-life (days) at 30oC = 

28 clay

38 sandy clay loam

23 sandy loam

TPA (26%)4

MTP (<10%)

00114651 

Supplemented 

by 41648802 

Supplemental, only 3 points 

sampled, conducted at 30oC, 

and at moisture levels with 

95% of 1/3 bar. Dissolved 

oxygen and redox potential 

were not reported. This study 

is not upgradeable. See DER 

update (1/17/1991)

Anaerobic Aquatic 

Metabolism

No data available

-- -- --

Aerobic Aquatic 

Metabolism No data available -- -- --

Kd-ads / Kd-des 

(mL/g)

Koc- ads / Koc-des 

(mL/g)

DCPA, not used in modeling 

--

41648803 Supplemental due to 

supernatant incompletely 

removed and finely sieved. 

See DER Addendum 

(02/10/2009)

MTP and TPA see Table 6 and 

Table 7

--

41648804 

41648805 

Acceptable. Supernatant was 

incompletely removed but due 

to low values, it was assumed 

to have little influence on the 

data. Finely sieved.

DCPA see Table 5 --

43661101 Acceptable

Terrestrial Field 

Dissipation

No half-life could be determined Not determined 41508609 Supplemental due to 

variability in data and low 

recoveries of analytical 

method. See DER Addendum 

(02/10/2009)

No half-life could be determined Not determined 41508610 Supplemental due to data too 

erratic to allow assessment of 

dissipation. See DER 

Addendum (02/10/2009)

Log-linear dissipation half-life = 

54 days (silt loam soil)

TPA Ross et al., 

1989

Circular plot planted with 

onion and then parsley. 

Aquatic Field 

Dissipation

No data available

-- -- --

Bioconcentration 

Factor (BCF)

Bluegill Sunfish

1894 (whole fish)

777 (fillet)

2574 (viscera)

Depuration complete in 14d

--

41155716

and 

41197602

Acceptable, aquarium water 

DCPA concentration 

increased over time. Little 

metabolism or degradation of 

DCPA in fish tissues. A 

detectable amount of 

demethylation was present. 

Metabolite was a monomethyl 

analog (2,3,56-
18

Study Value (units) Major Deg. (maximum %)

Minor Deg.1

MRID # Study Status or Comments

tetrachloroterephthalate). 

Study detected small trace 

quantities in organic extract 

concentratates of fish whole 

and viscera (0.62-1.06%).

Clam, lipid and organic carbon 

normalized

126 (whole clam)

--

Pereira et al, 

1996

Based on concentrations 

measured in field.

Biota-SedimentAccumulationFactor (BSAF) –

lipid normalized

Fish median = 0.1 

Bivalve median = 4.5 --

Wong et al, 

2001

Based on concentrations 

measured in field

Abbreviations: Unextract.= unextractables; Deg.= degradate

1. A major degradate made up more than 10% of applied radioactivity equivalents or is toxicologically significant. 

The maximum reported percent of applied equivalents is reported in parenthesis.

2. Approximately 80% of applied radioactivity was detected at time zero and 77% as TPA at later time points. 

Based on this, TPA may be assumed to reach a maximum of 100% applied radioactivity (DER 5/27/1987).

3. Approximately, 83.6% of applied radioactivity was detected at time zero and 85.0% as TPA at 96 days. Based 

on this, TPA may be assumed to reach a maximum of 100% applied radioactivity (DER 5/27/1987).

Abiotic Degradation

DCPA is stable to hydrolysis and photolysis. No significant hydrolysis occurred at pH 5, 7, 

and 9 over 36 days (MRID 00114648). No acceptable studies examining photolysis in water 

have been submitted. When DCPA was exposed to a black light and fluorescent lamps with 

wavelengths of 255-360 nm on soil, little degradation occurred (MRID 41508608). Based on the 

soil photolysis data, it may be assumed that DCPA is also stable to aqueous photolysis.

Biotic Degradation

Aerobic soil metabolism. The primary mechanism of degradation of DCPA is via aerobic 

metabolism, with rates dependent on temperature and level of moisture. Aerobic soil 

metabolism half-lives measured at 30oC and at a moisture level of 95% of 1/3 bar ranged from 

27-66 days (single first order, LN/linear fit; MRID 00114649, 00114652, 41648801). After 197 

days, virtually all of the parent DCPA had been converted into TPA. Small amounts of 

monomethyl tetrachloroterephthalic acid (MTP) were also identified. DCPA did not degrade in 

steam-sterilized soil. Open literature degradation rates are slightly faster than those reported in 

submitted studies and ranged from 17-18 days for 25oC (Choi et al., 1988; Wettasinghe and 

Tinsley, 1993).4 Walker (1978) reported that the DCPA half-life decreased by a factor of 17.9 

with a soil temperature increase from 10oC to 30oC (as reported by Choi et al. 1988). Choi et 

al.'s (1988) research indicated that degradation rates for DCPA reached maximums between 25-

30oC and then declined at higher temperatures and lower temperatures (e.g., an optimum 

temperature existed for maximum degradation rates). This suggests that for DCPA, the high 

 

4 The average half-life in Choi et al.'s (1988) work was 18 days at both 25oC and 30oC, indicating that the difference 

in measured degradation rates between submitted and open literature studies is not due to the differences in 

temperature.
19

temperature of the submitted studies did not significantly change the rate of degradation from 

that expected at a temperature of 25oC, the temperature of most degradation studies. 

Degradation rates of DCPA at low soil moisture levels were much lower than the medium and 

high moisture levels while medium and high moisture levels had similar degradation rates. This 

suggests that once a sufficient level of moisture is reached to support aerobic metabolism, more 

moisture would have little effect on the rate of degradation (Choi et al., 1988). TPA was stable 

to aerobic soil metabolism. The observed half-life for MTP was between 1 to 14 days in the 

sandy loam soil (MRID 00114649, 41648801). No data are available on aerobic aquatic 

metabolism for the parent and TPA. The aerobic soil metabolism data submitted by the 

registrant is considered supplemental and therefore is a data gap. Since aerobic metabolism is a 

primary degradation pathway the lack of aerobic aquatic metabolism data is also considered a 

data gap.

Anaerobic soil metabolism: The reported anaerobic soil conditions had little effect on 

degradation rates with estimated half-lives of 28-38 days at 30oC and a moisture level of 95% of 

1/3 bar. The high temperature and moisture level may have resulted in higher rates of 

degradation and reasonable anaerobic half-lives assuming 50% slower degradation rates at 25oC 

were estimated to range from 37-59 days (DER 2, 1/17/1991). Additionally, redox potential and 

dissolved oxygen levels were not measured/reported in the study and it cannot be confirmed 

whether anaerobic conditions were obtained. The similarity of the anaerobic degradation rates to 

the aerobic degradation rates, suggest that anaerobic conditions were not achieved. TPA was the 

final degradate under the reported anaerobic conditions (MRID 00114651, 41648802). No data 

are available on anaerobic aquatic metabolism. While this technically constitutes a data gap 

EFED believes that anaerobic aquatic conditions will also have little effect on degradation rates 

of the parent compound. 

Volatility

Based on a relatively low Henry's constant (2.2 x 10-6atm-m

3

/mol) and moderately to 

relatively high soil/water partitioning, DCPA does not appear to have a high volatilization 

potential from soil (Corbin et al., 2006). However, several published studies have shown that 

parent DCPA is volatile, especially from moist or wet soil (Glotfelty et al., 1984; Ross et al., 

1989; Majewski et al. 1991; Nash and Gish 1989). In the vapor phase, it may react slowly with 

hydroxyl radicals (Meylan and Howard, 1993). It may be deposited in nearby fields, areas with 

lower temperatures, or with wet and dry deposition. The measured log octanol-air partitioning 

coefficient (KOA) is 8.51 at 20oC and the estimated log particle-gas partitioning coefficient was 

-4.1, indicating that DCPA is likely to remain in the gas phase in air (Yao et al., 2007).

In a study by Ross et al. (1989), air samples showed that 10% of DCPA applied moved off 

site as a vapor and on particles for up to 21 days after application. The volatilization flux 

reached a maximum rate of 5.6 g/ha/hour (measured using the aerodynamic method). Based on 

flux data, 29% of DCPA was lost due to volatilization. Parsley planted on the plot 126 days after 

legal application of DCPA did not contain DCPA.

Majewski et al. (1991) measured air and soil concentrations of DCPA after it was applied at 

a rate of 7 kg/ha to a circular plot planted with white Lisbon onion. Fluxes were greatest 

after/during irrigation. A loss of between 1.27 and 1.59 kg per hectare out of 7 kg per hectare 

applied DCPA was reported. They also found that DCPA volatilization flux was very dependent 
20

upon the soil surface moisture content. High fluxes occurred immediately following irrigation. 

Approximately 36 to 52 percent of the total measured DCPA loss from soil was accounted for by 

volatilization and 26 percent by breakdown in soil during the 21 days of air sampling.

Nash and Gish (1989) measured pesticide decline in the atmosphere and the dissipation rate 

of DCPA from moist soil at different temperatures after application at 2.5 kg/ha. Volatilization

increased 1.8 times for each 10oC increase in temperature and dissipation increased 1.4 times. At 

temperature of 35oC (95oF), volatility accounted for the loss of most of the DCPA applied. 

Seiber et al. (1991) measured air residues of DCPA after it was applied at 11.2 kg/ha to a 

circular plot planted with white Lisbon onion in California. Downwind concentrations in air 

ranged from 910 ng/m3on day one to 22 ng/m3on day three based on XAD resin samples. Glass 

fiber filters contained 420 ng/m3on day one and were at a minimum of 5.8 ng/m3on day 11. 

Small amounts of DCPA were measured up-wind.

Mobility

Based on McCall's classification and FAO classifications of KOC values, DCPA is slightly 

mobile (Corbin et al., 2006; FAO 2000). Sorption of DCPA was measured in one acceptable 

study in four different soils at 25oC (see Table 5). Freundlich sorption coefficients (KF) ranged 

from 7-57 L/kg and the Freundlich exponent ranged from 0.94-0.99. Organic-carbon-water 

partition coefficients (KOCs) ranged from 1863 - 3503 L/Kg. Solid-water distribution 

coefficients (Kd) calculated by the study author ranged from 8 – 60 L/kg and are near the KF

values as the Freundlich exponents were all near one and the isotherms were almost linear. The 

variability in KOC values was much lower than KF values and the linear relationship between KF

and organic matter had an r2value of 0.86.5 This suggests that sorption of DCPA is strongly 

influenced by organic carbon.

Table 5. Summary of Sorption Coefficients measured for DCPA (MRID 43661101)

Soil %OC KF 

(L/kg) 1/N Kd (L/kg)

KOC 

(L/kg)

Ce range (mg/L) 1

Silt Loam 2.2 57 0.99 60 2577 0.001 – 0.01

Loamy Sand 0.86 30 0.94 38 3503 0.001 – 0.02

Sandy Loam 0.26 7 0.96 8 2563 0.005 – 0.05

Silt Clay Loam 1.77 33 0.96 39 1863 0.002 – 0.02

Average 32 0.96 36 2627

Standard Deviation 20 0.02 21 673

Coefficient of Variation 65% 2% 59% 26%

Lowest Value 7 0.94 8 1863

1 Ce range is the range of DCPA concentrations in water at equilibrium. This is the range of DCPA concentrations 

in water that the sorption coefficients may be confidently used to predict sorption.

Pereira et al. (1996) measured log KOCs in sediments of the San Joaquin River and 

Tributaries. Field KOC values ranged from 316 L/kg in bed sediment (102.5 L/kg) to 851 L/kg in 

suspended sediment (102.93 L/kg). Sorption was measured for the parent and degradates, MTP 

 

5 The coefficient of variation (standard deviation/mean) for KOC values was 26% versus 65% for KF values.
21

and TPA, in one other study. The study was determined to be supplemental for DCPA (see 

Table 6) by EFED. However, these are the only data available for the degradates. The KOC

values measured for DCPA have a wider range than those measured in the acceptable study but 

the values are similar, indicating that the values are a good preliminary estimate of sorption 

coefficients for the degradates.

6

 Based on the results of measured KOC values in finely sieved 

soils ranging from 4 - 90 L/kg, TPA and MTP are both highly mobile and will leach into ground

water (Table 77 and Table 8 8; FAO, 2000; U.S. EPA, 2001). Organic-carbon water partition 

coefficients (KOC) values are the values that are used in the classification system. MTP and TPA 

Kd values ranged from 0.1 – 0.3 L/kg. Coefficients of variation (standard deviation/mean x 100) 

for MTP were approximately the same for Kd and KOC values (49% versus 50%) and there was a 

linear relationship between the percent organic carbon and Kd values (r2= 0.9537). This 

indicates that organic carbon played a role in the sorption of MTP in these soils. Coefficients of 

variation for TPA were lower for Kd values than for KOC values (41% versus 102%) and there 

was not a linear relationship between the percent organic carbon and Kd values. This indicates 

that sorption of TPA was not greatly influenced by the percent of organic carbon in these soils. 

Table 6. Summary of Sorption Coefficients measured for DCPA in a finely sieved soil 

(MRID 41648803)

Soil %OC KF

(L/kg) 1/N Kd(L/kg)

KOC

(L/kg) Ce range (mg/L)1

Silt Clay 1.6 70.31 0.95 90.2 5640 0.002 - 0.02

Silt Loam 0.4 9.4 0.91 12.8 3200 0.01-0.095

Sandy Loam 1.8 32.14 0.94 41.6 2310 0.004-0.04

Sand 0.2 5.56 0.94 6.8 3400 not in DER

Average 29.35 0.93 37.9 29.35

Standard Deviation 29.72 0.02 38.1 29.72

Lowest Value 5.56 0.91 6.8 5.56

1

Ce range is the range of DCPA concentrations in water at equilibrium. This is the range of DCPA concentrations 

in water that the sorption coefficients may be confidently used to predict sorption.

Table 7. Summary of Sorption Coefficients measured for MTP in a finely sieved soil 

(MRID 41648804)

Soil %OC KF

(L/kg) 1/N Kd(L/kg)

KOC

(L/kg) Ce range (mg/L)

Silt Clay 1.6 0.29 1.103 0.289 18 0.09 - 2.9

Silt Loam 0.4 0.17 0.9552 0.162 41 0.09 - 3.0

Sandy Loam 1.8 0.23 0.8226 0.296 16 0.09 - 2.9

Sand 0.2 0.11 0.9907 0.087 44 0.09 - 3.0

Average 0.20 0.9679 0.209 30

Standard Deviation 0.08 0.1155 0.102 15

Lowest Value 0.11 0.8226 0.087 16

1 Ce range is the range of MTP concentrations in water at equilibrium. This is the range of MTP concentrations in 

water that the sorption coefficients may be confidently used to predict sorption.

 

6 These supplemental DCPA sorption values were not used in modeling.
22

Table 8. Summary of Sorption Coefficients measured for TPA in a finely sieved soil 

(MRID 41648805)

Soil %OC KF

(L/kg) 1/N Kd(L/kg)

KOC

(L/kg) Ce range (mg/L)

Silt Clay 1.6 0.08 0.6842 0.07 4 0.1 - 9.89

Silt Loam 0.4 0.16 0.5869 0.18 45 not in DER

Sandy Loam 1.8 0.19 0.8545 0.23 13 0.1 - 9.74

Sand 0.2 0.16 0.707 0.18 90 0.1 - 9.92

Average 0.15 0.7082 0.17 38

Standard Deviation 0.05 0.1106 0.07 39

Lowest Value 0.08 0.5869 0.07 4

1 Ce range is the range of TPA concentrations in water at equilibrium. This is the range of TPA concentrations in 

water that the sorption coefficients may be confidently used to predict sorption.

Sorption of acidic compounds is influenced by pH and the dissociation state of the 

compound. Generally speaking, mobility is expected to decrease with pH for weak acids as 

more of the compound will be present in its neutral form at lower pH. Additionally, the pHdependent anion exchange capacity increases as pH decreases. TPA has two COOH groups and 

MTP has one COOH group, indicating that TPA’s sorption will be more influenced by pH than 

sorption of MTP. Several leaching studies performed for pesticide registration or re-registration 

of DCPA illustrated that TPA is very mobile and more mobile in higher pH soils (U.S. EPA, 

1994, MRID 00114650). The pKa values of MTP and TPA are not known.

Accumulation

DCPA has been detected in fish at several locations in the United States (DeVault, 1985; 

DeVault et al., 1988; Jaffé et al., 1985; Leiker et al., 1991; Miller and Gomes, 1974; Pereira et al., 

1994; Saiki and Schmitt, 1986; Schmitt et al., 1985, 1990). DCPA bioconcentration factors (BCFs) 

in bluegill sunfish were 1894, 777, and 2574 in whole fish, edible tissue, and viscera, 

respectively. Little metabolism or degradation of DCPA occurred in fish tissues, although there 

was a detectable amount of demethylation (MRID 41155716, 41197602). 

Pereira et al. (1996) estimated organic-carbon and lipid normalized bioconcentration factors 

for clams based on concentrations measured in field samples. The observed bioconcentration 

factor was 125.9 and was lower than that predicted based on the KOW (predicted BCF = 103.02).

Wong et al. (2001) measured biota-sediment accumulation factors (BSAF) for DCPA in fish 

and bivalves based on samples collected in the NAWQA program. Median BSAF values were 

0.1 in fish and 4.5 in bivalves.

Terrestrial Field Dissipation

Gilroy, CA: Bare ground plots of loam soil were treated up to three times with DCPA at 7.0-

10.5 lbs. a.i. per acre (lbs a.i./A). DCPA was detected down to the maximum sampling depth of 

18-inches in all of the plots, while the mono-acid was not detected below 6 inches in any plot. 

TPA was detected as deep as 60 inches 552 days after the first treatment and up to 96 inches 552 

days after the second treatment. TPA was found at 0.03 ppm at the 72 inch depth 552 days after 

the third treatment (MRID 41508609). The study was considered supplemental.
23

Greenfield, CA: Bare ground plots of sandy loam soil were treated up to three times with DCPA 

at 7.0-10.5 lbs. a.i./A. DCPA was detected at the maximum sampling depth of 18-inches in all of 

the plots, while the mono-acid was not detected below six inches in any plot. TPA was detected 

at 48 inches. In the plot treated three times, parent DCPA was again detected in the 15-18 inch 

layer. The mono-acid was not found below 6 inches and TPA was found at 18 inches (the lowest 

layer sampled). The study was considered supplemental. The data requirement is not satisfied 

(MRID 41508610).

Carry Over of Residues: Studies show that residues of DCPA can carry over from year to year. 

DCPA and its two major degradates were detected on land that had five years of application 

(cumulative total of 94 lb/acre) and was then untreated for three years (Gershon and McClure, 

1966; as reported by U.S. EPA, 2008a). This is also supported by the results observed in 

terrestrial field dissipation studies (MRID 41508609, 4158610).

Environmental Transport Assessment

Potential transport mechanisms include pesticide surface water runoff, spray drift, and 

secondary drift of volatilized or soil-bound residues leading to deposition onto nearby or more 

distant ecosystems. All of these transport mechanisms are important for DCPA.

Review of the environmental fate data and physico-chemical properties of DCPA indicate 

that spray drift, runoff, and volatilization are likely to be the dominant routes of exposure. 

Additionally, given the physico-chemical profile for DCPA and observed detections of DCPA in 

air, rainfall, and snow samples, the potential for offsite migration through the air exists in 

addition to runoff. DCPA and especially the degradate TPA have the potential to reach ground 

water. In addition, from the available data, bioaccumulation is also a potential route of concern, 

as observed in both fish and invertebrate samples. 

The magnitude of transport via secondary drift depends on DCPA’s ability to be mobilized 

into air and its eventual removal through wet and dry deposition of gases/particles and 

photochemical reactions in the atmosphere. Therefore, physicochemical properties of DCPA 

that describe its potential to enter the air from water or soil (e.g., Henry’s Law constant and 

vapor pressure), pesticide use data, modeled estimated concentrations in water and air, and 

available air monitoring data will be considered in evaluating the potential for atmospheric 

transport of DCPA.

Monitoring Data

There are a large number of studies and data available on DCPA and degradate residues in 

air, surface water, drinking water, ground water, tissue, rain, and snow. The most recent review 

of monitoring data was completed in May 2008, and reported in detail in the 2009 California 

Red-legged Frog risk assessment of DCPA. That assessment examined monitoring data relevant 

to drinking water, food, fish, shellfish, air, and soil. The major conclusions included:

Monitoring data indicate widespread occurrence of DCPA in surface water, ground 

water, drinking water, and air. DCPA and TPA are one of the most commonly found 
24

pesticides/degradates found in water samples (U.S. EPA, 2008a). DCPA is typically 

detected at low concentrations in remote areas where it is not used and at higher 

concentrations near where it is used. DCPA concentrations in water are typically well 

below the lifetime Health Advisory of 4000 μg/L for DCPA (U.S. EPA, 2008a). 

Additionally, the solubility of DCPA (0.5 mg/L) is well below the advisory level.

Non-agricultural uses of DCPA, e.g. use in urban areas, can be a significant source of 

DCPA in water. Higher frequencies of DCPA detections occurred in urban areas in the 

midwest and higher frequencies of detection were reported in some urban areas in 

NAWQA surface water samples (Kolpin et al., 1996; U.S. EPA, 2008a)

DCPA's degradates, TPA and MTP are more commonly detected in ground water 

samples than DCPA. TPA is typically found at higher concentrations. 

TPA was the most commonly detected pesticide in the National Survey of Pesticides in 

Drinking Water Wells Survey (U.S. EPA, 1998b).

Degradation rates are slower at lower temperatures and DCPA residues are commonly 

detected in cooler states. The re-registration eligibility decision for DCPA stated, 

"Seventeen states with DCPA residue detections could be classified as states with cooler 

temperatures (AK, CT, IA, IL, IN, MA, MI, MN, NH, NJ, NY, OH, OR, PA , RI, SD, 

and WI). States considered "warm" states with detections were California, Colorado, 

and New Mexico." (U.S. EPA, 1998b)

Food was the major source of exposure to DCPA for humans (U.S. EPA, 2008a).

No prospective surface water monitoring studies which specifically targeted DCPA use 

(application period and/or sites) were available. Two prospective ground water monitoring 

studies were conducted in support of the reregistration of DCPA, including one in California. 

Generally, targeted monitoring data are collected with a sampling program designed to capture, 

both spatially and temporally, the maximum use of a particular pesticide. Typically, sampling 

frequencies employed in monitoring studies are insufficient to document peak exposure values. 

The lack of targeted data coupled with the fact that these data are not temporally or spatially 

correlated with pesticide application times and/or areas limit the utility of these data in 

estimating exposure concentrations for risk assessment purposes. Therefore, model-generated 

values will be used for estimating acute and chronic exposure values, and the non-targeted 

monitoring data are typically used for qualitative characterizations. All open literature and water 

quality monitoring databases will be searched for updates since the May 2008 data retrieval.

Clean Water Act

DCPA is identified as a cause of impairment for one water body listed as impaired under 

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

http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=88

5. The water body affected is Calleguas Creek Reach 5 (was Beardsley Channel On 1998 303d 

List). A waterbody report was completed in 2006. In addition, a Total Maximum Daily Loads 

(TMDL) has been developed for the herbicide, based on information provided at 

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

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

TMDLs can be found at http://www.epa.gov/owow/tmdl/.
25

The Agency invites submission of water quality data for this pesticide. To the extent 

possible, data should conform to the quality standards in Appendix A of the OPP Standard 

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

Registration Review Risk Assessment and Management Process (see: 

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

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

Ecological Effects

The Agency evaluates the potential for adverse affects as a result of DCPA usage. As 

described in the Agency’s Overview Document (U.S. USEPA, 2004), the most sensitive 

endpoint for each taxon is evaluated. Assessment endpoints include direct toxic effects on the 

survival, reproduction, and growth of terrestrial and aquatic life, as well as indirect effects, such 

as reduction in prey base and/or modification of habitat. The evaluated taxa include freshwater 

fish, freshwater aquatic invertebrates, birds, small mammals, terrestrial invertebrates, algae, and 

terrestrial plants. 

The major degradates of DCPA are tetrachloroterephthalic acid (TPA) and monomethyl 

tetrachloroterephthalic acid (MTP). The toxicity data for these chemicals are limited to

mammals. The available data indicate that the adverse effects associated with TPA are much 

milder than those for the parent and tend to occur at doses that are lower by approximately an 

order of magnitude (U.S. EPA, 2008a). However, DCPA and TPA are among the most 

commonly found pesticides/degradates in water samples (U.S. EPA, 2008a), DCPA is slightly 

mobile and TPA is very mobile, respectively, and both are persistent. There is no aquatic 

toxicity data available for the degradate TPA. In past risk assessments for DCPA (i.e., the CRLF 

ESA, U.S. EPA 2009), EFED bridged the data gap using structurally similar benzoic acid 

herbicides (i.e., dicamba). However, for future assessments, in the absence of toxicity data for 

the degradate TPA, EFED will make highly conservative assumptions when evaluating the 

toxicity of TPA. 

Another possible source of toxicity from the use of DCPA products is the presence of the 

known impurities that result from the manufacturing process. Hexachlorobenzene (HCB),

dioxin/furan congeners (i.e., 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD)), and other 

possible organochlorine contaminants have been found in the DCPA herbicide formulation

products.

The term “dioxins” is used to represent polychlorinated dibenzo-p-dioxins (PCDDs) and 

polychlorinated dibenzofurans (PCDFs). There are 210 different congeners of dioxins (75 

PCDDs and 135 PCDFs); however, only 17 congeners are considered to be of toxicological 

concern (listed in Table 9). For these 17 congeners, evidence is sufficient to conclude that a 

common mechanism of action, involving binding of the chemicals to the aryl hydrocarbon 

receptor (AHR) as the initial step, underlies 2,3,7,8-TCDD-like toxicity elicited by these PCDDs,

PCDFs, and Polychlorinated biphenyls (PCBs) (Van den Berg et al., 1998, 2006; Hahn, 2002). 
26

Table 9. Dioxin congeners that are of toxicological concern. Toxicity equivalency factors for 

mammals, birds and fish associated with each isomer are from U.S. EPA 2008b.

Congener* Mammal TEF Bird TEF Fish TEF

2378-TCDF 0.1 1 0.05

12378-PeCDF 0.03 0.1 0.05

23478-PeCDF 0.3 1 0.5

123478-HxCDF 0.1 0.1 0.1

123678-HxCDF 0.1 0.1 0.1

234678-HxCDF 0.1 0.1 0.1

123789-HxCDF 0.1 0.1 0.1

1234678-HpCDF 0.01 0.01 0.01

1234789-HpCDF 0.01 0.01 0.01

OCDF 0.0003 0.0001 <0.0001

2378-TCDD 1 1 1

12378-PeCDD 1 1 1

123478-HxCDD 0.1 0.05 0.5

123678-HxCDD 0.1 0.01 0.01

123789-HxCDD 0.1 0.1 0.01

1234678-HpCDD 0.01 <0.001 0.001

OCDD 0.0003 0.001 <0.001

*Abbreviations are as follows: TCDD = tetrachlorodibenzodioxin; PeCDD = pentachlorodibenzodioxin; HxCDD = 

hexachlorodibenzodioxin; HpCDD = Heptachlorodibenzodioxin; OCDD = Octachlorodibenzodioxin; TCDF = 

Tetrachlorodibenzofuran; PeCDF = Pentachlorodibenzofuran; HxCDF = Hexachlorodibenzofuran; HpCDF = 

Heptachlorodibenzofuran; OCDF = octachlorodibenzofuran

Research has been conducted to characterize the toxicities of PCDDs and PCDFs especially 

relative to each other, since these compounds are often present together in the environment. 

Demonstrated toxic effects of 2,3,7,8-TCDD and other similar-acting PCDD, PCDF and PCB 

congeners in fish, birds, and mammals include adverse effects on reproduction, development, 

and endocrine functions; wasting syndrome; immunotoxicity; and mortality in both laboratory 

and field settings (U.S. EPA 2008b). The EPA (U.S. EPA 2008b) and the World Health 

Organization (Van Den Berg et al. 1998 and 2006) have established toxicity equivalency factors 

(TEFs) for dioxins as they relate to mammals, to birds and to fish (Table 9). In the TEF 

approach, the toxicities of individual congeners are related to 2,3,7,8-TCDD, which is the most 

toxic congener of dioxins to animals (U.S. EPA 2008b; Table 9). For each PCDD and PCDF, 

the concentration (or mass) of the chemical is multiplied by its TEF. The sum of the product for 

each PCDD and PCDF represents the toxicity equivalent (TEQ) concentration relative to 2,3,7,8-

TCDD (Equation 1; U.S. EPA 2008b). 

Equation 1. 

n

n TEFn TEQ Concentration *

Dioxins, and HCB are both listed under the Stockholm Convention as Persistent Organic 

Pollutants (POPs). These chemicals are persistent, bioaccumulative and subject to long range 

transport. In general, chronic toxicity endpoints for mammals and birds exposed to pesticides are 

expressed in terms of mg pesticide/kg-bw. The toxicity of 2,3,7,8-TCDD is expressed in units of 

ng/kg-bw, which indicates that this chemical is orders of magnitude more toxic than pesticides 
27

which are typically assessed by OPP. To characterize the risk associated with HCB, the toxicity 

of HCB will be summarized from the scientific literature. The Agency for Toxic Substances and 

Disease Registry (ATSDR), associated with the Center for Disease Control (CDC), 

Toxicological Profile for HCB (ATSDR, 2002) will be used as one source of information in the 

characterization of the toxicity of HCB.

Acute (short-term) and chronic (long-term) toxicity information is characterized based on 

registrant-submitted studies and a comprehensive review of the open literature on DCPA. Other 

sources of information, including use of the acute probit dose response relationship to establish 

the probability of an individual effect and reviews of the Ecological Incident Information System 

(EIIS), are conducted to further refine the characterization of potential ecological effects 

associated with exposure to DCPA. A summary of the available ecotoxicity information and the 

incident information for DCPA are provided below. 
28

Table 10 and Table 911 summarize the most sensitive ecological toxicity endpoints based on 

currently available data. A preliminary evaluation of open literature, suggests that there may be 

more sensitive toxicity endpoints for both aquatic and terrestrial organisms. These will be 

reviewed and evaluated to determine potential use in the ecological risk assessment. A brief 

summary of submitted data considered relevant to this ecological risk assessment is presented 

below.
29

Table 10. Applicable DCPA endpoints for terrestrial organisms

Assessment 

Endpoint 

Measures of 

Effect 

Species Toxicity Value Study 

classification

(Selection basis)

Reference 

(MRID)

Abundance 

(i.e., survival, 

reproduction, and 

growth) of 

individuals and 

populations of 

birds 

Avian (single 

dose) acute 

oral 21-day 

LD50

Northern 

bobwhite quail

(Colinus 

virginianus)

LD50 >2,250 mg a.i./kgbw (1) Acceptable 41155705 

Avian 

subacute 

5-day dietary 

LC50

Northern 

bobwhite quail

(Colinus 

virginianus) and 

Mallard duck 

(Anas 

platyrhynchos)

LC50 >5620 mg a.i./kgdiet (ppm) (1)

Acceptable

&

Acceptable

41155706 

&

41155707

Avian 

reproduction 

NOAEC

Northern 

bobwhite quail

(Colinus 

virginianus)

and Mallard duck

(Anas 

platyrhynchos)

NOAEC = 1280 mg 

a.i./kg-diet (2)

LOAEC = 3170 mg 

a.i./kg-diet

Supplemental

& 

Supplemental

47550001

&

47550002

Abundance

(i.e., survival, 

reproduction, and 

growth) of 

individuals and 

populations of 

mammals 

Mammalian 

acute oral 

(single dose) 

LD50

Rat 

(Rattus 

norvegicus)

Acute oral LD50 >5000 

mg a.i./kg-bw (3) Acceptable 41054808

Mammalian 2-

generation rat 

reproduction

NOAEL

Rat 

(Rattus 

norvegicus)

NOAEL=50 mg/kg/day 

(1000 ppm)

LOAEL= 250 mg/kg/day

(5000 ppm) (4)

Acceptable 41750103

Survival of 

beneficial insect 

populations 

Honey bee 

acute contact 

LD50

Honey bee 

(Apis mellifera)

Acute contact 

LD50>230 g/bee (5) Supplemental 00018842

Survival and 

growth of 

terrestrial plants

Seedling 

Emergence

Tomato 

(Solanum 

lycopersicum) 

EC25 = 5.36 lbs a.i./A (6) Supplemental 41564901

Vegetative 

Vigor Soybean

(Glycine max)

EC25 > 7.5 lbs a.i./A (7) Supplemental 41440101

1 Product tested contains 100% active ingredient (Technical Grade).

2 Based on mortality, signs of toxicity, and effects on reproduction and offspring (reduction in eggs laid, eggs set, live 3-week 

embryos, number hatched, the ratios of number hatched to eggs laid and to eggs set, and hatchling survival); Product tested 

contains 98.0% active ingredient (Technical Grade).

3 Product tested contains 98.0% active ingredient (Technical Grade).

4 Based on pup weight decrements. Product tested contained 96-98% active ingredient (Technical Grade).

5 Formulation was not identified although was described as technical; however only 3.2% mortality at 229.63 g/bee was 

observed.

6 Most sensitive parameter is fresh weight. Product tested contained 97.8% active ingredient (Technical Grade) dissolved in 90% 

acetone, 10% deionized water, and 0.05% Triton X-100 (as a surfactant) solution. NOAEC for tomato was 0.47 lb ai/A based on 

fresh weight. EC25’s could not be determined for all other species tested and tolerant plant species were used. 

7 EC25’s could not be determined for nearly all species and tolerant plant species were used. Product tested contained 97.8% 

active ingredient (Technical Grade) dissolved in 90% acetone, 10% deionized water, and 0.05% Triton X-100 (as a surfactant). 

NOAEC was 7.5 lb ai/A based on fresh weight (only one parameter was measured and recorded).
30

Table 9. Applicable DCPA endpoints for aquatic organisms

Assessment 

Endpoint 

Measures of 

Effect 

Species Toxicity Value Study 

classification

(Selection basis)

Reference 

(MRID)

Survival and 

reproduction of 

individuals and 

communities of 

freshwater fish

Freshwater fish 

acute 96-hr LC50

Bluegill sunfish 

(Lepomis 

macrochirus) 

& 

Rainbow trout 

(Oncorhynchus 

mykiss)

BG LC50> 6.7 mg/L (TWA) 

(> 5.4 mg/L; meanmeasured) &

RT LC50> 6.6 mg/L (TWA) 

(> 4.7 mg/L; meanmeasured) (1)

Supplemental 

&

Supplemental

41054827

&

40154826

Freshwater fish 

early life-stage 

NOAEC

No Data – submission of studies are needed

Survival and 

reproduction of 

individuals and 

communities of 

freshwater 

invertebrates 

Freshwater 

invertebrate 

acute 48-hr LC50

Water flea 

(Daphnia magna)

EC50 >100 mg/L nominal 

(2a)

Supplemental 40098001

EC50 =18.02 mg/L nominal 

(2b)

Supplemental 40098001

Freshwater 

invertebrate 

reproductive 

NOAEC

No Data – submission of studies are needed

Survival and 

reproduction of 

individuals and 

communities of 

estuarine and 

marine fish 

Estuarine and 

marine acute 

fish 96-h LC50

Sheepshead 

minnow 

(Cyprinodon 

variegatus)

LC50 >1.0 mg/L (3) Supplemental 40228401

Estuarine and 

marine fish 

reproductive 

NOAEC

No Data – submission of studies are needed

Survival and 

reproduction of 

individuals and 

communities of 

estuarine and 

marine 

invertebrates 

Estuarine and 

marine 

invertebrate 

acute 96-hr LC50

Eastern oyster 

(Crassostrea 

virginica)

EC50 = 0.62 mg/L (4) Supplemental 40228401

Brown shrimp 

(Penaeus 

aztecus)

EC50 >1.0 mg/L (5) Supplemental 40228401

Estuarine and 

marine 

invertebrate 

reproductive 

NOAEC

No Data – submission of studies are needed

Standing crop or 

biomass and 

growth of aquatic 

plants 

Freshwater 

green algae, 

cyanobacteria or 

diatom 96-h 

IC50 for 

biomass.

Freshwater 

diatom (Navicula 

pelliculosa) 

and/or Green 

algae 

(Selenastrum 

capricornutum)

No Acceptable Data Available (6)

42882401 

&

42836103

Vascular aquatic 

plants

Duckweed

(Lemna gibba) No Acceptable Data Available (6) 42836101

1 Product tested contains 96.7% active ingredient (Technical Grade), greater than solubility limit (0.5 mg/L), and although 

concentrations were measured, they were not centrifuged, and therefore do not represent total dissolved soluble concentrations.

2a Product tested contains Technical Grade material, could not determine actual exposure concentration, concentrations were not 

measured.

2b Product tested contains 75% active ingredient (Dacthal W-75), could not determine actual exposure concentration, 
31

concentrations were not measured.

3 Product tested contains Technical Grade material, could not determine actual exposure concentration, concentrations were not 

measured, and therefore, the concentrations are likely at least the solubility limit (0.5 mg/L).

4 Product tested contains Technical Grade material, could not determine actual exposure concentration, concentrations were not 

measured, therefore the concentrations are likely at least the solubility limit (0.5 mg/L).

5 Product tested contains Technical Grade material, could not determine actual exposure concentration, concentrations were not 

measured, therefore the concentrations are likely at least the solubility limit (0.5 mg/L).

6 Test substance was not completely in solution; throughout the test the treatment solution appeared cloudy with white 

particulates; test material was neither centrifuged nor measured, therefore the studies are considered invalid, and not for use in 

risk assessments.

Effects to Aquatic Organisms

Fish

Available freshwater and estuarine/marine acute fish toxicity studies (MRID 41054827, 

40154826, and 40228401) indicated issues with the solubility of the TGAI in water, and are not 

usable for quantitative assessment. Although there were issues with the solubility of the 

compound, no mortality was observed in the treatment concentration for the rainbow trout, and 

3.3% mortality was observed in treatment concentration for the bluegill sunfish. No information 

is available to determine if there was or was not any mortality observed for the sheepshead 

minnow. Given that one can assume the exposure was at least at the level of solubility and fish 

may have consumed or had contact with the precipitate. The available data suggest that DCPA 

does not result in mortality to freshwater and/or estuarine/marine fish (based on TGAI exposure)

at the limit of solubility (0.5 ppm).

Estimated chronic effects of DCPA exposure for freshwater and estuarine/marine fish are 

uncertain because no chronic data were submitted by the registrant for freshwater or 

estuarine/marine fish, and as a result these studies are considered to be data gaps. In the absence 

of data chronic risk to freshwater and estuarine/marine fish will be assumed. Chronic toxicity 

data are important to this ecological risk assessment given the high Kow, persistence, and 

bioconcentration potential of DCPA. 

Aquatic Invertebrates

Available acute toxicity data for freshwater and estuarine/marine invertebrates (MRID 

40098001, and 40228401) using the TGAI also indicated issues with solubility in water, and are 

not usable for quantitative assessment. Although there were issues with the solubility of the 

compound, 20% of freshwater invertebrates (daphnids, scuds, and midges) were affected in the 

highest treatment concentration, and no information is available to determine if there was or was 

not any mortality/affects observed for the estuarine/marine invertebrates (mysid, or oyster). 

There is toxicity data available for the formulated product (Dacthal W-75) for freshwater 

invertebrates only that can be used for quantitative assessment; however, there are still 

limitations with the data. Given that one can assume the exposure was at least at the level of 

solubility and invertebrates may have consumed or had contact with the precipitate, the available 

data suggest that DCPA may result in effects to freshwater invertebrates (based on TGAI 

exposure) at the limit of solubility (0.5 ppm). For estuarine/marine invertebrates, from available 

data, DCPA is highly toxic on an acute exposure basis. For freshwater invertebrates, available 

data for the end use formulated product data DCPA is slightly toxic on an acute exposure basis. 
32

Estimated chronic effects of DCPA exposure for freshwater and estuarine/marine 

invertebrates are uncertain because no chronic data were submitted by the registrant for 

freshwater or estuarine/marine invertebrates, and as a result these studies are considered to be 

data gaps. In the absence of data chronic risk to freshwater and estuarine/marine invertebrates

will be assumed. Chronic toxicity data are important to this ecological risk assessment given the 

high Kow, persistence, and bioconcentration potential of DCPA. 

Aquatic Plants

As with the other aquatic taxa, DCPA toxicity data for aquatic plants are limited by 

solubility. Tier I testing was conducted with Lemna gibba, Skeletonema costatum, Navicula 

pelliculosa, and Anabaena flos-aquae (MRID 42882401, 42836103, and 42836101), and in all 

tests a white precipitate was observed. In addition, there was large variability within the data 

that prevented the statistical analysis from detecting a significant difference even if one was 

present, and are considered not usable for quantifying risk to non-target aquatic plants. Based on 

the number of target species and the adverse effects observed in the submitted aquatic plant 

toxicity studies, effects to aquatic plants can be expected at or below solubility. Without a Tier 

II study, it is not possible to determine the level at which no effects will occur.

Effects to Terrestrial Organisms

Birds

One avian acute oral toxicity study is available for DCPA exposure to Northern bobwhite 

quail (MRID 41155705). No treatment related effects were observed during the study and the 

LD50 value was determined to be greater than 2250 mg/kg-body weight (bw). DCPA is 

therefore classified as practically non-toxic to birds on an acute oral basis. 

An avian subacute dietary toxicity study was submitted for Northern bobwhite quail (MRID 

41155706), and mallard duck (MRID 41155707). Both bobwhite chicks and mallard ducklings 

were exposed to 560, 1000, 1780, 3160, and 5620 ppm in their diet for five days. There were no 

treatment related mortalities at any exposure level for either the bobwhite quail or the mallard 

duck, and therefore the LC50 was greater than 5620 ppm for both species. DCPA is therefore 

classified as practically non-toxic to birds on a subacute dietary basis. 

Avian reproductive toxicity studies were submitted for two species: mallard duck (MRID 

47550002) and Northern bobwhite quail (MRID 47550001). Both studies followed the same 

DCPA exposure scheme, which was 0 (control), 1280, 3170, and 8020 mg a.i./kg-diet. There are 

concerns with the overall health of the test birds (both mallard duck and bobwhite quail) and the 

results are not reliable for use in a quantitative risk assessment. Bobwhite quail were more 

sensitive and thirteen treatment related mortalities were observed during the study. A NOAEC 

of 1280 mg a.i./kg-diet and a LOAEC of 3170 mg a.i./kg-diet were found, based on mortality, 

signs of toxicity, and effects on reproduction and offspring. Treatment related reductions in 

multiple reproductive parameters were detected at the top two treatment levels. More 

specifically, reproductive and offspring effects included the ratios of live 3-week embryos to 

viable embryos, number hatched to live 3-week embryos, hatchling survivors to eggs set and to 

number hatched, as well as survivor weights. Some animals at the higher treatment levels were 
33

so debilitated that they were sacrificed after week 18, three weeks prior to the end of the 21-week 

observation period. However, the results are not reliable for use in a quantitative risk 

assessment. Therefore, avian reproductive toxicity is considered a data gap, and new studies are 

needed.

Mammals

Acute mammalian toxicity studies resulted in no observable effects to rats exposed to DCPA. 

In an acute oral toxicity study with Sprague-Dawley rats, no effects were observed at 5000 

mg/kg-bw throughout the 14-day observation period and therefore, the acute LC50 was greater 

than 5000 mg/kg-bw for mammals (MRID 41054810).

In a 2-generation reproduction study in rats (MRID 41750103), DCPA was administered in 

the feed to Sprague-Dawley rats. The F0 parental generation produced two litters, F1a and F1b. 

The F1b generation was mated to produce two litters, F2a and F2b. There were 35 rats/sex/dose 

group in the F0 and F1 generations with a ten week growth phase for the F0 generation before 

the first mating and a ten week growth phase for the F1b generation before the first mating. 

There were 20 rats/sex/dose group in the F2b generation which were observed for a six week 

growth period. 

Dietary concentrations were 0, 1000, 5000, or 20000 ppm (equivalent to 0, 50, 250, or 1000 

mg/kg/day using a 0.05 mg/kg/day per ppm conversion factor). Doses were changed to 0, 200, 

500, or 20000 ppm on day 0 of lactation for the F2b litters (equivalent to 10, 25, or 1000 

mg/kg/day using a 0.05 conversion factor) in order to ensure a NOAEL for F2 pup body weight 

decrements. 

The parental NOAEL is 50 mg/kg/day and the parental LOAEL is 250 mg/kg/day based upon 

body weight decreases, gross and microscopic changes in kidneys and lungs, and microscopic 

changes in liver and thyroids (MRID 41750103). There were no treatment-related effects upon 

reproductive indices. Mating index, fertility index, pregnancy rates, and litter size were not 

affected by treatment. Pup body weights in the 500 ppm F2b litters were not affected by 

treatment. Body weight decrements in weaned pups were accompanied by decreased food 

consumption in F1 animals but not in F2 animals. There were no treatment-related effects seen at 

pup necropsy. The offspring NOAEL is 50 mg/kg/day and the offspring LOAEL is 250 

mg/kg/day based upon pup body weight decrements. 

Terrestrial Invertebrates

A honey bee acute contact study (formulation was not identified) resulted in honey bee 

LD50>230 g a.i./bee, 3.2% mortality was observed at this concentration (MRID 00018842). 

DCPA is therefore classified as practically non-toxic to bees. 

Terrestrial Plants

For Tier II seedling emergence test with DCPA, tomato was the most sensitive test species of 

all (soybean, lettuce, carrot, tomato, cucumber, cabbage, oat, ryegrass, corn, and onion) that were 

tested based on fresh weight. The tomato EC25 and NOAEC values were 5.36 lbs a.i./A and 0.47 

lbs a.i./A, respectively, based on fresh weight. The seedling emergence study was classified as 

supplemental because the test material was not applied to the maximum labeled rate, DCPA was 
34

not applied at low enough concentrations to determine the NOAEC for corn, lettuce, and oat 

radicle length, and tolerant plant species were used. 

For the Tier II vegetative vigor test with DCPA, of the ten species (ryegrass, corn, oat, onion, 

soybean, lettuce, carrot, tomato, cucumber, and cabbage) tested; soybean, tomato, and cucumber 

were visually affected (phytotoxicity) by DCPA. Phytotoxicity (crinkled leaves, and mottled 

chlorosis) was observed in soybean plants at all rates of DCPA, and slight necrosis was observed 

at 1.88 lbs a.i./A on both soybean and cucumber plants. Tomato plants were affected at 3.75 and 

7.5 lbs a.i./A. Although phytotoxicity was observed, no treatment effects were observed with the 

single measurement of fresh weight. Therefore, the soybean EC25 and NOAEC values based on 

fresh weight were >7.5 lbs a.i./A, and 7.5 lbs a.i./A, respectively. The vegetative vigor study 

was classified as supplemental because the percent active ingredient was not specified, the 

material was not applied to the maximum labeled rate, only one parameter (fresh weight) was 

recorded and measured, and tolerant plant species were used. 

Degradate toxicity

The Health Effects Support Document for Dacthal Degradates: Tetrachloroterephthalic 

Acid (TPA) and Monomethyl Tetrachloroterephthalic Acid (MTP) summarized the data for the 

degradates for TPA and MTP in the following excerpts (U.S. EPA, 2008a). 

“Both DCPA and TPA do cause adverse health effects in laboratory animals. Currently, no 

toxicological studies are available to assess the toxicological effects of MTP (the mono-acid 

degradate). Three studies in rats (30- and 90-day feeding studies and a developmental study) 

are available for TPA. The effects of exposure were mild (weight loss and diarrhea) and 

occurred at doses greater than or equal to 2000 mg/kg/day. No reproductive effects were 

observed. The critical effects for DCPA, the parent compound, include effects on the lung, 

liver, kidney, and thyroid in male and female rats in a 2-year chronic bioassay (ISK Biotech, 

1993). The available data indicate that the adverse effects associated with TPA are much 

milder than those for the parent and tend to occur at doses that are lower by approximately an 

order of magnitude.” Page 1-2

“The only noncancer health effects noted with TPA were soft stools and occult blood in urine 

at doses of greater than 2000 mg/kg/day (Major, 1985). Doses of 2500 mg/kg/day 

administered during gd 6-15 also caused soft stools, increased salivation, decreased body 

weight gain, and decreased food consumption (Mizen, 1985). No effects were observed in the 

single study of MTP (Hazelton, 1961).” Page 7-7

“The results from the short-term TPA study differed from those for DCPA in a 28-day 

dietary study in groups of five male and female Sprague-Dawley rats given doses of 0, 250, 

1000, or 2000 mg/kg/day (ISK Biotech Corp., 1990b). In the DCPA study, there was a doserelated increase in liver weight and centrilobular hypertrophy of hepatocytes. The lowest 

dose tested (250 mg/kg/day) was the LOAEL for these effects (U.S. EPA, 1994c). The 

difference in the effect levels suggests that the parent DCPA is more acutely toxic than the 

TPA degradate. The results of a 28-day study of MTP by Hazleton Laboratory (1961), 

comparable to Hazleton’s TPA study described above, did not identify any signs of toxicity 

at the 1% (860 mg/kg/day) dietary dose tested.” Page 7-2
35

Based on this analysis, we concluded that TPA was less toxic than DCPA and therefore, 

terrestrial risk from exposure to DCPA is considered to encompass potential sources of risk from 

degradates.

No aquatic toxicity (acute or chronic, animal or plant) data are currently available for TPA, 

and are required for registration review. TPA is structurally similar to the parent DCPA, and 

other benzoic acid herbicides, and thus may retain the herbicidal mechanism of action. Since the 

terrestrial animal data indicate this chemical is generally toxic on a chronic exposure basis but 

not an acute exposure basis, these data are critical to the future ecological risk assessments. In 

the absence of toxicity data for TPA, EFED will assume equal toxicity to the parent compound, 

DCPA.

Contaminant toxicity (dioxins and HCB)

As indicated above, when using the TEQ approach, the exposure concentration of each 

dioxin congener is adjusted relative to the toxicity of 2,3,7,8-TCDD. 

In 1993, EPA developed a report (interim) on the available data and methods for assessing 

ecological risks associated with 2,3,7,8-TCDD (USEPA 1993). This section summarizes the 

ecological effects data for aquatic organisms that are described in that report. Because of the low 

solubility and high Koc and Kow values of dioxins, a more appropriate method for 

characterizing toxicity is based on the concentration of dioxin in the organism (tissue-based 

residues), rather than freely dissolved in the water. Therefore, this section will report toxicity 

data in terms of organism concentrations. 

Currently, the toxicity and risk associated with the presence of the contaminant HCB has not 

been fully characterized. However, information from available scientific literature, including the

Toxicological Profile for HCB (ATSDR, 2002) will be used characterize the toxicity and 

estimate the risk associated with the presence of HCB as a contaminant of DCPA.

Fish

Toxicity data are available for several species of freshwater and saltwater fish exposed to 

2,3,7,8-TCDD. A review of the data indicates that the most sensitive life stage is fish fry. 

According to the 1993 EPA report, “[T]here is no definitive evidence of adverse effects in any of 

the fish species tested if accumulation in eggs is less than 34 pg TCDD/g [ng TCDD/kg], the 

highest no observed effect level for trout fry. This likely corresponds to an accumulation in

parent fish, with lipid content similar to the eggs, of less than 50 pg TCDD/g.” Based on this 

information, the NOAEC for effects of 2,3,7,8-TCDD on fish fry is 34 ng/kg, which corresponds 

to an accumulation in parent fish (who transfer dioxins to eggs) of <50 ng/kg. Effects to fish fry 

survival are expected when concentrations of 2,3,7,8-TCDD in eggs are 50-500 ng/kg, which 

corresponds to concentrations of 75-705 ng/kg in parent fish. Mortality in adult fish is expected 

with body concentrations of 2,3,7,8-TCDD are 1000-15000 ng/kg (USEPA 1993).

Aquatic Invertebrates

Data are available from toxicity studies where a species of freshwater invertebrates, i.e., the 

cladoceran Daphnia magna, and a snail (Physa sp.) were exposed to 2,3,7,8-TCDD. After 33-d 

exposures, no adverse effects were observed in either species. Concentrations of 2,3,7,8-TCDD 
36

in the cladoceran and snail were 1,570,000 and 502,000 ng/kg, respectively (Inensee and Jones 

1975; Inensee 1978). These concentrations are based on measured levels of 2,3,7,8-TCDD in 

tissues.

Aquatic Plants

Data are available from toxicity studies where non-vascular, i.e., algae (Oedogonium 

cardiacum) and vascular, i.e., duckweed (Lemna minor), aquatic plants were exposed to 2,3,7,8-

TCDD. After 33-d exposures, no toxic effects were observed in either species. Concentrations of 

2,3,7,8-TCDD in duckweed and algae were 30,700 and 2,295,000 ng/kg, respectively, without 

any apparent adverse effects on the aquatic plants (Inensee and Jones 1975; Inensee 1978). 

These concentrations are based on measured levels of 2,3,7,8-TCDD in aquatic plants.

Birds

In 2003, EPA finalized a document summarizing available laboratory and field studies 

involving reproductive toxicity in birds that are exposed to dioxins. A review of available studies 

indicates that exposures of birds to dioxins leads to mortality, deformity and inhibited 

development in offspring (USEPA 2003b). 

In the Great Lakes Water Quality Initiative Criteria for the Protection of Wildlife for 2,3,7,8-

TCDD, OW also identified several studies reporting toxicity data involving chronic exposures of 

birds to 2,3,7,8-TCDD. From these studies, OW selected a reproduction study with the ringnecked pheasant (Phasianus colchicus) exposed to 2,3,7,8-TCDD (Nosek et al. 1992a, 1992b, 

1993) to derive the avian wildlife value used for the 2,3,7,8-TCDD criteria. In this study, female 

birds were dosed intraperitonieally with 2,3,7,8-TCDD for 10 weeks at 1.4, 14 and 140 ng/kgday. Relative to control birds, no effects were observed in the lowest two treatments, resulting in 

a NOAEL of 14 ng/kg-day. At the highest test concentration which represents the study LOAEL 

(i.e., 140 ng/kg-day), egg production was significantly reduced and mortality of embryos was 

significantly increased. 

The NOAEL from Nosek et al. (1992a, 1992b, 1993) will be used as the chronic effect 

endpoint for birds exposed to dioxins. Although studies involving intraperitoneal injections are 

not typically used by EFED to determine measures of effects for avian reproduction, no feeding 

studies have been identified where birds were exposed to dioxins. 

Mammals

Chronic toxicity endpoints for mammals exposed to 2,3,7,8-TCDD have been identified by 

the USEPA Office of Water (OW) for the Great Lakes Water Quality Initiative Criteria for the 

Protection of Wildlife (USEPA 1995). OW defined a no observed adverse effect level (NOAEL) 

of 1 ng/kg-bw/day (i.e., 0.001 μg/kg-bw/day or 1x10-6 mg/kg-bw/day) for reproductive effects 

to mammals exposed to 2,3,7,8-TCDD in food. This NOAEL was based on reduced fertility in 

first (f1) and second generation (f2) rats at the lowest observed adverse effect level (LOAEL) of 

10 ng/kg-bw/day (Murray et al. 1979). 
37

Ecological Incidents

A preliminary review was made on December 1, 2010, of the Ecological Incident 

Information System (EIIS, version 2.1.1), which is maintained by the Agency’s Office of 

Pesticide Programs, and the Avian Monitoring Information System (AIMS), which is maintained 

by the American Bird Conservancy. One incident was found in AIMS, however this incident is 

also found in the EIIS database as well. EIIS indicates a total of 2 reported ecological incidents 

associated with the use of DCPA (chlorthal dimethyl), the incidents involve both fish and birds. 

These incidents are summarized in Table 10.

The reported DCPA (named “chlorthal dimethyl” in the EIIS database) incidents occurred in 

1984 and 1988. The certainty categories on the likelihood that the use of DCPA caused 2

incidents are both listed as possible. Both incidents also involved other chemicals besides 

DCPA. Residues of both DCPA and the other chemicals involved are available for one of the 

incidents (B0000-501-87). 

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

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

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

incidents reported in aggregate reports include those categorized as “minor fish and wildlife” 

(W-B), “minor plant” (P-B), and “other nontarget” (ONT) incidents. “Other non-target” 

incidents include reports of adverse effects to insects and other terrestrial invertebrates. For 

DCPA there were no aggregate incidents reported by the registrant(s). 

In the risk assessment, the incidents will be further evaluated to determine if the reported 

incidents represent current patterns of use for DCPA (chlorthal dimethyl). Examples of 

additional considerations are mitigation (e.g., reduced application rates), product cancellations, 

and changes in use patterns that have occurred since the date of the reported incident(s).

Table 10. Ecological Incidents Associated with DCPA.

Incident No.

(EIIS, AIMS)

Year State Magnitude Other Chemicals 

Associated with 

the Incident

Certainty 

index

Comments

I000636-014 1984 MO UN Chlorothalonil

Cyclohexamide

Benomyl

possible A fish kill (of an unknown 

magnitude) occurred in a pond on the 

grounds of the St. Joe Minerals Corp 

(a golf course). Two days before the 

fish kill; the golf course was sprayed 

with dacthal (DCPA), Daconil, 

Tersan, and Acti-Dione. No analyses 

of fish or water were included in the 

report.

B0000-501-87

AIMS Event #396

CA: P-1140/1161

1988 CA 112 Diazinon

Endosulfan

possible Approximately 100 fish (50 catfish & 

50 shad) and 12 birds (egrets) died at a 

pond at a duck club in Imperial 

County, CA, after an accidental 

misuse (a spill) that resulted in runoff 

to a nearby pond. The dead fish were 

analyzed and found to contain dacthal 
38

Incident No.

(EIIS, AIMS)

Year State Magnitude Other Chemicals 

Associated with 

the Incident

Certainty 

index

Comments

(DCPA) (26.3 ppm), DDE (0.11 ppm), 

diazinon (0.1 ppm), and endosulfan 

(0.92 ppm) based on whole body and 

fresh weight. An analysis of the water 

showed no pesticides present, but no 

mention was made of the time lag 

between the event and the sampling of 

the water. Analyses of the livers of 

several egrets showed dacthal to be 

present but at less than 1 ppm. Two 

weeks later, on May 24, several 

catfish were seined from the pond and 

high concentrations of dacthal were 

found in their livers (1.77 to 9.2 ppm). 

The source of the incident at the pond 

seemed to be a nearby crop dusting 

loading facility.

Characteristics of Ecosystems Potentially at Risk

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

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

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

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

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

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

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

from, the treated site and might include impounded bodies such as ponds, lakes and reservoirs, or 

flowing waterways such as streams or rivers including all adjacent off-channel habitats that are 

permanently or intermittently connected to flowing waters. For uses in coastal areas, aquatic 

habitat also includes marine ecosystems, including estuaries, embayment’s, and near shore 

environments.

Assessment Endpoints

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

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

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

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

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

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

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

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

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

assessment for addressing risk management issues of concern. Changes to assessment endpoints 
39

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

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

DCPA. For a summary of the terrestrial and aquatic toxicological endpoints for DCPA see 

Tables 11 and 12 in the Ecological Effects section, respectively. 

Conceptual Model

The conceptual model is a graphic representation of the structure of the risk assessment. It 

specifies the DCPA release mechanisms, biological receptor types, and effects endpoints of 

potential concern. The conceptual models for aquatic and terrestrial exposures are shown in 

Figure 4 and Figure 5, respectively. Dashed lines denote minor exposure routes.

Based on available fate and transport data for DCPA, potential transport mechanisms include 

surface water runoff, movement into ground water and subsequent recharge into surface water, 

spray drift, and volatilization and deposition to nearby fields, and long range transport in air. 

Significant amounts of DCPA have been shown to volatize off the field and be deposited to 

nearby fields. This could lead to exposure via inhalation or deposition of DCPA on nearby areas. 

Volatilization and deposition on nearby fields is expected to result in lower exposure than that 

estimated for runoff and spray drift for the field that DCPA is applied to and therefore, was not 

assessed separately. Exposure to DCPA due to long range transport of DCPA in ground water is

also discussed qualitatively. In addition to DCPA terrestrial and aquatic organisms may be 

exposed to the degradate TPA, and the impurities hexachlorobenzene (HCB) and dioxins/furans, 

thereby increasing the bioaccumulation risk.
40

Stressor

Source

Receptors

Attribute

Change

DCPA applied to use site and associated degradate and impurities

Spray drift

Fish/aquaticphase 

amphibians

**Piscivorous 

mammals and 

birds 

Individual organisms

Reduced survival

Reduced growth

Reduced reproduction

Food chain

Reduction in algae

Reduction in prey

Modification of 

PCEs

related to prey 

availability

Habitat integrity

Reduction in primary 

productivity

Reduced cover

Community change

Modification of PCEs related to 

habitat

Surface water/

Sediment

Runoff

Aquatic Animals

Invertebrates

Vertebrates

Exposure

Media

Uptake/gills 

or integument

Ingestion Ingestion

Long range 

atmospheric 

transport

Wet/dry deposition

Soil Groundwater

Uptake/gills 

or integument

Aquatic Plants

Non-vascular

Vascular

Uptake/cell, 

roots, leaves Riparian plant

terrestrial 

exposure 

pathways

Figure 4. Conceptual Model for Pesticide Effects on Aquatic Systems
41

Figure 5. Conceptual Model for Pesticide Effects on Terrestrial Systems

Risk Hypothesis

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

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

following ecological risk hypothesis is being employed for this national-level ecological risk 

assessment:

DCPA, when used in accordance with current labels, can result in off-site 

movement of the compound via runoff, leaching to ground water, spray drift and 

atmospheric transport leading to exposure of non-target plants and animals. 

Direct applications to and atmospheric deposition to foliar surfaces may serve as 

a major source of DCPA exposure to wildlife. Exposure in these environmental 

compartments will result in adverse effects upon the survival, growth, and 

reproduction of non-target terrestrial and aquatic organisms. These non-target 

organisms include federally-listed threatened and endangered species. 

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 DCPA are 

Stressor

Source

Receptors

Attribute

Change

DCPA applied to use site and associated degradate and impurities

Direct

application

Spray drift

Birds/terrestrial

-

phase 

amphibians/

reptiles/mammals

Terrestrial 

insects

Individual organisms

Reduced survival

Reduced growth

Reduced reproduction

Food chain

Reduction in prey

Modification of 

PCEs related to 

prey availability

Habitat integrity

Reduction in primary productivity

Reduced cover

Community change

Modification of PCEs related to

habitat

Terrestrial/riparian 

plants grasses/forbs, 

fruit, seeds (trees, 

shrubs)

Runoff

Mammals/ 

birds

Exposure

Media

Soil

Ingestion/

inhalation

Ingestion/

inhalation

Ingestion/

inhalation

Ingestion

Dermal uptake/Ingestion/

inhalation

Long range 

atmospheric 

transport

Root uptake

Wet/dry deposition

Terrestrial 

phase 

amphibians

-

Ingestion/

inhalation
42

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

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

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

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

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

individual organisms from particular uses of DCPA is estimated using the probit dose-response 

slope and either the level of concern (discussed below) or actual calculated risk quotient value.

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

submitted by the public in response to the opening of the Registration Review docket for DCPA.

Stressors of Concern

DCPA or dacthal, a pre-emergence herbicide is used widely to control annual grass and 

certain broadleaf weeds. Two major degradates were observed in laboratory studies, 

tetrachloroterephthalic acid (TPA) and monomethyl tetrachloroterephthalic acid (MTP). In 

addition, the manufacturing processes of DCPA results in the formation of several known 

contaminants. Of toxicological concern are hexachlorobenzene (HCB), congeners (structurally 

related chemicals) of polyhalogenated dibenzo-p-dioxins/dibenzofurans (dioxins/furans), and 

other possible organochlorine contaminants. 

Measures of Exposure 

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

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

and methods cited in Table 1 and will be estimated for each use of DCPA. The environmental 

fate properties of DCPA along with available monitoring data indicate that runoff and spray drift 

may be the principle potential transport mechanisms of DCPA to the aquatic and terrestrial 

organisms. DCPA is also volatile and may travel to nearby fields in the air or to remote areas via 

long range transport. In this assessment, transport of DCPA through runoff and spray drift will 

be considered in deriving quantitative estimates of DCPA. Additionally, exposure due to 

deposition of DCPA in precipitation and movement of DCPA and TPA into ground water will be

qualitatively assessed. Bioaccumulation may occur; however, rapid depuration was observed in 

fish and residues measured in organisms are very low (MRID 41155716, 41197602). Therefore, 

we do not expect bioaccumulation of DCPA to be a major exposure pathway. However, this 

measure of exposure will be looked at more closely during the risk assessment.

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

environmental concentrations (EECs) of DCPA using maximum labeled application rates and 

methods of application. The models used to predict aquatic EECs are the Tier I model GENeric 

Estimated Environmental Concentration (GENEEC) and the Tier II Pesticide Root Zone Model 

coupled with the Exposure Analysis Model System (PRZM/EXAMS). PRZM (currently version 

3.12.2; 5/15/05) and EXAMS (currently version 2.98.04.06; 4/25/05) are simulation models 

coupled with the linkage program shell: PE5 (PRZM EXAMS Model Shell; v5.0; 11/15/06), 

which incorporates the standard scenarios developed by EFED. The models generate daily 

exposures and calculated 1-in-10 year EECs of DCPA and separate EECs for its two major 

degradates, TPA and MTP, which may occur in surface water bodies adjacent to application 
43

sites. The major degradates of DCPA (TPA and MTP) are not naturally-occurring compounds 

and are formed in significant quantities. Degradates will likely be modeled using the total toxic 

residue approach unless data are submitted that suggest the degradates are not a toxicological 

concern.

PRZM simulates pesticide fate and transport as a result of leaching, direct spray drift, runoff 

and erosion from an agricultural field, and EXAMS estimates environmental fate and transport of 

pesticides in a surface water body for a 30-year period. The combined model is designed to 

estimate pesticide concentrations found in water (standard pond) at the edge of the treated field. 

As such, it provides high-end values of the pesticide concentrations that might be found in 

ecologically sensitive environments following pesticide application. The location of the field is 

specific to the crop being simulated using site-specific information on the soils, weather, 

cropping, and management factors associated with the scenario. The crop/location scenario is 

intended to represent a high-end exposure site on which the crop is normally grown. Based on 

historical rainfall patterns, the receiving water body receives multiple runoff events during the 

years simulated. Weather and agricultural practices are simulated for 30 years so that the 10-

year exceedance probability at the site can be estimated. The simulation is generated using 30 

years of meteorological data, encompassing the years from 1961 to 1990. Additional information 

on these models can be found at: http://www.epa.gov/oppefed1/models/water/index.htm. 

The standard scenarios used for ecological pesticide assessments assume application to a 10-

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

(20,000 m3volume) with no outlet. PRZM/EXAMS is used to estimate screening-level exposure 

of aquatic organisms to DCPA. The measure of exposure for aquatic species is the 1-in-10 year 

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

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

assessing chronic exposure to fish and aquatic-phase amphibians. The 1-in-10-year 21-day mean 

is used for assessing chronic exposure to aquatic invertebrates.

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

exposed to spray drift are derived using the T-REX model (version 1.4.1, 10/09/2008). This 

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

on a large set of field residue data. The upper limit values from the nomograph represent the 

upper bound 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. 

In general, deposition of drifting or volatilized pesticides is expected to be greatest close to 

the site of application. Two spray drift models, AgDisp and AgDRIFT are used to assess 

exposures of terrestrial plants to DCPA deposited in terrestrial habitats by spray drift. AgDisp 
44

(version 8.13; dated 12/14/2004) (Teske and Curbishley 2003) is used to simulate aerial and 

ground applications. AgDrift (version 2.01; dated 5/24/2001) is used to simulate spray blast 

applications to orchard crops. The distance of potential impact away from the use sites is 

determined by the distance required to fall below the LOC for chronic effects to small mammals 

consuming short grass.

Aquatic exposure to the impurities, HCB and dioxins, will be characterized. PRZM/EXAMS 

will be used to estimate screening-level exposure of aquatic organisms to these compounds.

Terrestrial exposure to HCB and 2,3,7,8-tetrachlorodebenzo-p-dioxin (TCDD) will be estimated 

using TREX, and KABAM, as bioaccumulation is a major transport pathway for these 

chemicals. The application rate input value will be either the maximum allowed amount of the 

impurity in the final formulation or an upper estimate of the amount in the final formulation, 

respectively.

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

an upper bound estimate of exposure using DCPA’s solubility (0.5 ppm), the most sensitive 

acute and chronic (not available) avian toxicity endpoints (Bobwhite Quail with LD50 >2250

mg/kg-bw), and the most sensitive acute and chronic mammalian toxicity endpoints (Rat LD50

>5000 mg/kg-bw and NOAEL = 1000 mg/kg-bw, respectively). Drinking water exposure alone 

was determined not to be a potential pathway of concern for avian and mammalian species on an 

acute basis, and mammalian species on a chronic basis. Risk cannot be precluded for avian 

species on a chronic basis, as there is no acceptable avian reproduction data available for DCPA. 

Results for mammalian and avian species are presented in Table 11 and Table 12 respectively.

Table 11. Mammalian SIP Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 0.0860 0.0860

Adjusted toxicity value (mg/kg-bw) 3845.8028 769.1606

Ratio of exposure to toxicity 0.0000 0.0001

Conclusion*

Drinking water exposure alone 

is NOT a potential concern for 

mammals

Drinking water exposure alone 

is NOT a potential concern for 

mammals

Table 12. Avian SIP Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 0.4050 0.4050

Adjusted toxicity value (mg/kg-bw) 1620.9664 0.0000

Ratio of exposure to acute toxicity 0.0002 0.0000

Conclusion*

Drinking water exposure alone 

is NOT a potential concern for 

birds

Due to insufficient data, risk 

cannot be precluded

*Conclusion is for drinking water exposure alone. This does not combine all routes of exposure. Therefore, when 

aggregated with other routes (i.e., diet, inhalation, dermal), pesticide exposure through drinking water may contribute to 

a total exposure that has potential for effects to non-target animals.
45

This pathway will be explored further with the development of SIP v.2.0 in the Ecological 

Risk Assessment for DCPA. For a sample of the output generated by SIP v.1.0, please see 

Appendix B. Detailed information about the SIP v.1.0, as well as the tool, can be found on the 

EPA’s website at http://www.epa.gov/pesticides/science/models_pg.htm#terrestrial.

The Screening Tool for Inhalation Risk (STIR v.1.0, November 19, 2010) could not be used to 

calculate an upper bound estimate of exposure as no valid mammalian inhalation data was 

available. The inhalation pathway via spray drift of the pesticide may be of potential 

significance for avian and mammalian species given DCPA’s vapor pressure and method of 

application. In addition, without a valid mammalian inhalation study available the potential 

differences in toxicity via the inhalation route as compared to the oral cannot be estimated. 

Therefore, an acute avian inhalation toxicity test is being requested for the bobwhite quail. This

study will aid in evaluating this pathway of concern for avian taxa. If inhalation acute toxicity 

data are not submitted for birds, then risk to birds from acute inhalation exposure to DCPA will 

be presumed. 

Measures of Toxicity

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

receptors. Data were obtained from registrant-submitted studies. Also, prior to completion of the 

risk assessment, literature studies identified by ECOTOX will also be incorporated as 

appropriate. The ECOTOXicology database (ECOTOX) will be searched in order to provide 

more ecological effects data 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 (USEPA 2007d).

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

Ecological Incident Information System (EIIS; USEPA 2007c). The EIIS is a database 

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

effects have been associated with the use of pesticides. 

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

studies will be evaluated qualitatively. Such effects have included behavioral changes (e.g., 

lethargy, changes in coloration and effects olfaction). 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 DCPA 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 screening-level 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% 
46

of the test organisms. EC stands for “Effective Concentration” and the EC50 is the concentration 

of a chemical that is estimated to produce a specific effect in 50% of the test organisms. 

Endpoints for chronic measures of exposure for listed and non-listed animals are the 

NOAEL/NOAEC and NOEC. NOAEL stands for “No Observed-Adverse-Effect-Level” and 

refers to the highest tested dose of a substance that has been reported to have no harmful 

(adverse) effects on test organisms. The NOAEC (i.e., “No-Observed-Adverse-EffectConcentration”) is the highest test concentration at which none of the observed effects were 

statistically different from the control. The NOEC is the No-Observed-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. 

The Agency will conduct a search of the open literature to ensure that all best available 

science is utilized. The Agency uses the ECOTOX database as its mechanism for searching the 

open literature for ecological effects information. ECOTOX integrates three previously 

independent databases - AQUIRE, PHYTOTOX, and TERRETOX - into a system which 

includes toxicity data derived predominately from the peer-reviewed literature, for aquatic life, 

terrestrial plants, and terrestrial wildlife, respectively.

Measures of Risk

Previously completed screening level risk assessments and exceedances of Agency levels of 

concern indicate a need to further examine and refine phytotoxic risk to aquatic and terrestrial 

plant species. Analysis of potential indirect effects on listed species (both aquatic and terrestrial) 

is also required. 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.

Use information will be retrieved from registration labels and used as inputs for estimating 

exposure concentrations from the various use scenarios. DCPA’s use patterns (aerial 

application) suggest potential risk concerns to non-target aquatic and terrestrial plants. The 

range of potential exposure to DCPA to non-target plants can vary on application method (aerial 

or ground), application rate, and use pattern. 

Integration of Exposure and Effects

Risk characterization is the integration of exposure and ecological effects characterization to 

determine the potential ecological risk from the use of DCPA on crops listed in Table 1 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 DCPA 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 LOCs 

(USEPA 2004). These criteria are used to indicate when DCPA’s uses, as directed on the label, 

have the potential to cause adverse direct or indirect effects to non-target organisms. As noted 

previously, where data are lacking on the toxicity of DCPA, risk will be presumed.

 
47

Deterministic and Probabilistic Assessment Methods

The quantitative assessment of risk will primarily depend on the deterministic point-estimate 

based approach described in the risk assessment. An effort 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 and have been deemed as appropriate means of 

refining assessments where deterministic approaches have identified risks.

Drinking Water Assessment

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

assessments of DCPA. The drinking water assessment will incorporate model estimates of 

DCPA in surface water and ground water. Concentrations of DCPA residues in surface waters 

will be estimated using PRZM/EXAMS. The major degradates, TPA and MTP, are not 

naturally-occurring compounds and may be formed in significant quantities. These degradates 

have not been considered in previous drinking water assessments, however, this will be revisited 

during the risk assessment process. 

An Estimated Drinking Water Concentration (EDWC) of DCPA residues in ground water 

will be developed. Since DCPA/TCP are among the most frequently detected pesticides in 

groundwater, in all likelihood, SCI-GROW will not be used. EFED will likely use available 

monitoring and a refined/Tier 2 groundwater model that is currently being finalized. Output from 

that model represents the concentrations that might be expected in shallow unconfined aquifers 

under sandy soils, which is representative of the ground water most vulnerable to pesticide 

contamination likely to serve as a drinking water source.

The drinking water assessment will also include available surface and ground water 

monitoring data with consideration of changes in use patterns that may have occurred. States are 

encouraged to submit monitoring data for review. 

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 DCPA. 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 action area is used to identify all listed (threatened and endangered) species and 

designated critical habitat that could be affected by the Federal action. The Federal action is the 

authorization or registration of pesticide use or uses as described on the label(s) of pesticide 

products containing a particular active ingredient. The action area is defined by the Endangered 

Species Act as, “all areas to be affected directly or indirectly by the Federal action and not 

merely the immediate are involved in the action” (50 CFR §402.2). Based on an analysis of the 

Federal action, the action area is defined by the actual and potential use of the pesticide.
48

In the case of nationwide ecological risk assessment conducted for DCPA under Registration 

Review, the action area will encompass the entire United States and its territories. The purpose 

of defining the action area as the entire United States and its territories is to ensure that the initial 

area of consideration encompasses all areas where DCPA may be used now and in the future, 

including the potential for off-site transport via spray drift and downstream dilution. 

Additionally, the concept of a nationwide action area takes into account the potential for direct 

and indirect effects and any potential modification to critical habitat based on ecological effect 

measures associated with reduction in survival, growth, and reproduction, as well as the full suite 

of sublethal effects available in the effects literature. It is important to note that the nationwide 

action area does not imply that direct and/or indirect effects and critical habitat modification are 

expected to or are likely to occur over the full extent of the action area, but rather to identify all 

listed species and critical habitat that may potentially be affected by the action. The Agency will 

use more rigorous analysis including consideration of available land cover data, toxicity data, 

and exposure information to determine areas where individual listed species and designated 

critical habitat may be affected or modified via endpoints associated with reduced survival, 

growth, or reproduction.

Endocrine Disruptor Screening Program

As required under FFDCA section 408(p), EPA has developed the Endocrine Disruptor 

Screening Program (EDSP) to determine whether certain substances (including pesticide active 

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

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

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

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

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

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

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

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

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

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

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

group of 67 chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. 

This list of chemicals was selected based on the potential for human exposure through pathways 

such as food and water, residential activity, and certain post-application agricultural scenarios. 

This list should not be construed as a list of known or likely endocrine disruptors.

DCPA is among the group of 58 pesticide active ingredients receiving EDSP test orders. For 

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

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

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

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

website.
49

Preliminary Identification of Data Gaps 

Environmental Fate

Several environmental fate studies have not been submitted, including: acceptable studies on 

the photolysis of DCPA in water, aerobic aquatic metabolism, anaerobic soil metabolism, and 

anaerobic aquatic metabolism. Additionally, anaerobic soil metabolism studies and terrestrial 

field dissipation studies were considered supplemental and therefore, the value of the 

information provided in the studies is limited. The photolysis data for soil indicate that DCPA is 

most likely stable to photolysis in water and an assumption that DCPA is stable was made. 

Metabolism in the aerobic aquatic environment was estimated using the aerobic soil study which 

was conducted under very moist conditions and at high temperatures (30oC). DCPA was 

assumed to be stable to anaerobic metabolism because it is not known if an anaerobic 

environment was present in the submitted study. While data from terrestrial field dissipation 

studies do not allow the calculation of dissipation rates, they do provide some information on the 

degradates of concern likely to be found in the environment and on the mobility of DCPA and 

TPA. Any future terrestrial field dissipation study should include measurement of the 

volatilization of DCPA

TPA, a major degradate of DCPA, did not undergo any degradation in the aerobic soil 

metabolism study. It is more stable and more water soluble than DCPA and thus, higher 

exposure concentrations are likely. Little data are available on the environmental fate or toxicity 

of TPA. 

The final environmental fate data gaps involve label information. The labels do not specify a 

maximum number of applications or a minimum application interval. Assumptions will be made 

using the best information available for each use scenario. However, conservative assumptions 

will be unless labels are clarified to specify maximum annual application rates.

The status of environmental fate studies for the parent compound is presented in Table 17. In 

addition to the data gaps noted for the parent, EFED notes the need for a full suite of studies, 

with the exception of soil photolysis, for the TPA degradate. EFED does not anticipate requiring 

any environmental fate-related data for HCB and dioxin. The following studies are required for 

the TPA degradate:

Guideline 835.2120 Hydrolysis

Guideline 835.2240 Aqueous Photolysis

Guideline 835 4100 Aerobic Soil Metabolism

Guideline 835 4200 Anaerobic Soil Metabolism

Guideline 835 4300 Aerobic Aquatic Metabolism

Guideline 835 4400 Anaerobic Aquatic Metabolism

Guideline 835 1230/40 Adsorption/ desorption and Leaching

Guideline 835 6100 Terrestrial Field Dissipation

Guideline 835 1730 Fish Bioconcentration
50

Table 13. Environmental fate data requirement table for parent DCPA

OPPTS 

Guideline

Data 

Requirement

Submitted Studies 

(MRID)

Classification Data 

Gap?

Comments

835.2120 Hydrolysis 00114648 Acceptable No

835.2240 Aqueous 

photolysis 143063; 41508607 Unacceptable No

Technically, this is a gap in guideline 

studies; however, there is not much 

evidence that photolysis is going to be a 

route. Therefore, we will continue to 

assume stability.

835.2410 Soil photolysis 41508608 Acceptable No

835.4100 Aerobic soil 

metabolism

00114649;

41648801; 00114652 Supplemental No Data from a new study would be of limited utility

835.4200 Anaerobic soil 

metabolism 00114651; 41648802 Supplemental No Data from a new study would be of limited utility 

835.4300 Aerobic aquatic 

metabolism No studies Yes Data are needed

835.4400 Anaerobic aquatic

metabolism No studies No Data from a new study would be of limited utility

835.1230

835.1240

Adsorption/ 

desorption and 

leaching

41648803 Supplemental

41648804 Acceptable No

43661101 Acceptable

835.6100 Terrestrial field 

dissipation

41508609 Supplemental

Yes

The field studies, though limited, suggest 

that DCPA/TPA may persist longer than 

what is predicted in the lab metabolism 

studies. A new study could be used to 

confirm persistence of both parent AND 

degradates. In the absence of such data, 

EFED assumes that DCPA moves off site 

because of the evidence from field 

measurements.

41508610 Supplemental

850.1730 Fish 

bioconcentration 41155716 Acceptable No

Effects

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

aquatic and terrestrial organisms, numerous data gaps exist (Tables 18, 19 and 20). Previously 

submitted acute toxicity data for DCPA has been found to be insufficient for use in quantitative 

assessment, and as a result new acute aquatic toxicity data for fish, aquatic invertebrates, and 

aquatic plants (vascular and non-vascular) are needed. Chronic aquatic toxicity data for fish or 

aquatic invertebrates for DCPA were never submitted by the registrant. Chronic toxicity data in 

particular are important to this ecological risk assessment given the high Kow, persistence, and 

bioconcentration potential of DCPA. In addition, submitted chronic avian reproductive toxicity 

data were found to be insufficient and not reliable for use in a quantitative risk assessment, there 

are questions regarding the health of the birds and as a result new chronic avian toxicity studies 

are needed.
51

Due to the potential for persistence and movement into water for both the parent, DCPA, and 

the degradate, TPA, a full suite of aquatic toxicity (both acute and chronic) data are needed to 

evaluate the potential risk to freshwater and estuarine/marine fish, aquatic invertebrates, and 

aquatic plants, resulting from use of DCPA, and subsequent degradation to TPA. 

The log Kow of DCPA is 4.28-4.40 and therefore, as the log Kow is greater than 3 for the 

parent DCPA, the data requirement of both freshwater and marine whole sediment acute toxicity 

data was triggered.

A major uncertainty is the amount of dioxins and HCB in technical DCPA, therefore more 

information is needed to characterize risk to non-target organisms relative to the amount of the 

contaminant(s) they are exposed to.

Acute avian oral toxicity data need to be submitted for a passerine species exposed to DCPA. 

Although the available acute oral toxicity data for bobwhite quails, when compared to estimated 

environmental concentrations, indicate that levels of concern are not exceeded for birds on an 

acute basis, the high application rate of DCPA indicate that any small change in toxicity could 

result in a change to the risk conclusions. In addition, passerine species have higher metabolic 

rates due to their smaller sizes, than either waterfowl or upland game bird species and because 

they may utilize different metabolic pathways, they may be more sensitive to DCPA. In order to 

properly characterize risk to passerines, an avian oral toxicity test is required for passerine birds. 

DCPA is considered to be volatile, and is frequently found at great distances from applied 

field locations. As a result, more information is needed to evaluate other potential exposure 

pathways to non-target avian species. In addition, there is no valid mammalian inhalation study 

available to estimate potential differences in toxicity via the inhalation route as compared to the 

oral. Therefore, an acute avian inhalation toxicity test is being requested using the most sensitive 

avian species as shown by avian acute oral studies. The study being requested will aid in 

evaluating this pathway of concern for avian taxa. An avian inhalation study protocol must be 

submitted for review and approval by the Agency prior to initiation of this study. If inhalation 

acute toxicity data are not submitted for birds, then risk to birds from acute inhalation exposure 

to DCPA will be presumed. 

As an herbicide, it is important to identify the potential risk to non-target plants. A revised 

terrestrial plant study was requested by the Agency using different plant species at publication of 

the RED in 1998 for DCPA. At this date, these studies have not been submitted and therefore 

are considered data gaps. Without submission of these data, it is not possible to make an effects 

determination for plants or animals that depend on plants for food or shelter. 

More thorough rationale for the data is contained in Appendix C. There will be a revision of 

the risk assessment in the event that new or revised information becomes available that changes 

the outcome or determinations made in this document. The following data needs may result in 

reassessment of risks. Other changes may be made if current information is substantially reevaluated.
52

The terrestrial studies listed below are requested for the parent, DCPA, and the seedling 

emergence study is also requested for its major degradate, TPA, to increase certainty in the risk 

estimation.

Guideline Number: Non-guideline, Study Title: Avian Inhalation Toxicity, DCPA 

only.

Guideline Number: 850.2100, Study Title: Acute Avian Oral Toxicity Test using a 

Passerine species, DCPA only. 

Guideline Number: 850.2300, Study Title: Avian Reproduction, Two species, DCPA 

only.

Guideline Number: 850.4100, Study Title: Tier II Seedling Emergence Toxicity 

Testing – Terrestrial Plants, non-tolerant species, extended study time (28-days).

Guideline Number: 850.4150, Study Title: Tier II Vegetative Vigor Toxicity Testing–

Terrestrial Plants, non-tolerant species, extended study time (28-days).

The full suite of aquatic toxicity studies below are requested for the parent, DCPA, and its 

major degradate, TPA, to increase certainty in the risk estimation. 

Guideline Number: 850.1010, Study Title: Acute Toxicity to Freshwater 

Invertebrates, Daphnid (Daphnia magna) is the preferred species.

Guideline Number: 850.1025, Study Title: Oyster (Crassostrea virginica) Acute 

Toxicity Test (shell deposition) 

Guideline Number: 850.1035, Study Title: Mysid (Mysidopsis bahia) Acute Toxicity 

Test

Guideline Number: 850.1075, Study Title: Freshwater Fish Toxicity, Rainbow trout 

(Oncorhynchus mykiss) and Bluegill sunfish (Lepomis macrochirus) are the preferred 

species.

Guideline Number: 850.1075 , Study Title: Estuarine/Marine Fish Acute Toxicity, 

Sheepshead minnow (Cyprinodon variegates) is the preferred species

Guideline Number: 850.1300, Study Title: Aquatic Invertebrate Life Cycle Toxicity 

Daphnid (Daphnia magna) is the preferred species. 

Guideline Number: 850.1350, Study Title: Aquatic Invertebrate Life Cycle Toxicity 

(estuarine/marine) Mysid shrimp (Mysidopsis bahia) is the preferred species. 

Guideline Number: 850.1400, Study Title: Early Life-Stage Toxicity Test, Rainbow 

trout (Oncorhynchus mykiss) and Bluegill sunfish (Lepomis macrochirus) are the 

preferred species.

Guideline Number: 850.1400, Study Title: Early Life-Stage Toxicity Test, 

Sheepshead minnow (Cyprinodon variegates) is the preferred species.

Guideline Number: 850.1735, Study Title: Whole Sediment Acute Toxicity 

invertebrates, freshwater.

Guideline Number: 850.1740, Study Title: Whole Sediment Acute Toxicity 

invertebrates, marine.

Guideline Number: 850.4400, Study Title: Aquatic Plant Toxicity Test Using Lemna

spp., Tier II.

Guideline Number: 850.5400, Study Title: Algal Toxicity Test, Tier II – The four 

species typically submitted are Pseudokirchneriella subspicata (formerly 

Selanastrum capricornutum), a freshwater green algae; Anabaena flos-aquae, a 
53

freshwater cyanobacterium; Navicula pelliculosa, a freshwater pinnate diatom and 

Skeletonema costatum, an estuarine/marine centric diatom.

Table 18. Available Ecological Effects Data for Terrestrial Animals Exposed to DCPA and 

Remaining Data Gaps.

Guideline Description MRID Classification Data Gap? Comments

850.2100 Avian oral toxicity 41155705 Acceptable No *There are questions regarding 

the health of the birds, in both 

avian reproduction studies and 

as a result the studies are 

classified as Supplemental, 

and are considered data gaps. 

**The formulation was not 

clearly identified in the study;

therefore, the TGAI is 

considered a data gap. 

However, due to low mortality 

(3.2% at 220 g/bee), the 

study is not necessary to call in 

at this time. 

850.2200 Avian dietary 

toxicity 

41155706 Acceptable

No

41155707 Acceptable

850.2300 Avian reproduction 47550001 Supplemental

Yes* 

47550002 Supplemental

850.3020 Honeybee acute 

contact toxicity 00018842 Supplemental Yes**

Table 19. Available Ecological Effects Data for Aquatic Animals Exposed to DCPA and 

Remaining Data Gaps.

Guideline Description MRID Classification Data 

Gap? Comments

850.1075 Freshwater fish –

Acute toxicity 

41054827 Supplemental

Yes

Issues with solubility, 

precipitated out over 

time, measured 

samples were not 

centrifuged. Test 

system should be flowthrough. 

41054826 Supplemental

40227001, 

TN0908 Supplemental Form. product W-75, limited information

40227002, 

TN0878 Supplemental

Form. product W-75, 

10% mortality in 

highest treatment level.

00107142, 

TN0481 Supplemental

Solubility issues –

addition of acetone as 

solvent apparently 

increased toxicity of 

product to fish.

00114686, 

TN0711 Supplemental

2 active ingredient’s 

(chlordane & DCPA); 

no information 

provided on solubility 

problems

TN0437 Supplemental Concentrations were 

not measured
54

Guideline Description MRID Classification Data 

Gap? Comments

00045822 Supplemental

Study was only 48h, 

30% mortality in 

highest concentration, 

Used Dacthal W-75.

40098001 Invalid

Solubility issues with 

TGAI, nominal only, 

Solvent concentrations 

were not known.

850.1400 Freshwater fish –

early life stage test No data No data Yes The submission of studies is needed.

850.1010 Freshwater invertebrates –

Acute toxicity

40226901, 

TN0933 Supplemental

Yes

Issues with solubility of 

chemical (TGAI only), 

which is expected with 

such a low solubility 

limit in water (0.5 

ppm). Definitive EC50

and NOAEC values 

cannot be determined. 

Test concentrations

were not measured.

40098001 Supplemental

& Invalid

850.1300 Freshwater invertebrate –

life cycle test No data No data Yes The submission of studies is needed.

850.1075 Saltwater fish –

Acute toxicity 40228401 Supplemental Yes

Issues with solubility 

of chemical, which is 

expected with such a 

low solubility limit in 

water (0.5 ppm). Test 

concentrations were 

not measured, and the 

exchange rate as a 

flow-through study was 

not provided. 

Definitive EC50 and 

NOAEC values cannot 

be determined. 

850.1025

850.1035

850.1045

850.1055

Saltwater invertebrates –

Acute toxicity 40228401 Supplemental Yes

850.1400 Saltwater fish –

early life stage test No data No data Yes

The submission of 

studies is needed.

850.1350 Saltwater invertebrates –

life cycle test No data No data Yes
55

Table 14. Available Ecological Effects Data for Plants Exposed to DCPA and Remaining 

Data Gaps.

Guideline Description MRID Classification Data 

Gap? Comments

850.4100

Terrestrial Plant toxicity: 

seedling emergence 

(Tiers 1 and 2)

41564901 Supplemental Yes

Test material was not applied to the 

maximum labeled rate to determine 

possible EC values. DCPA was not 

applied at low enough rates to 

determine the NOAEC for corn, 

lettuce, and oat radicle length. An 

EC25 value was calculated for the 

Tomato data; however, due to the 

lack of raw data a NOAEC could 

not be definitively calculated. It 

was recommended that additional 

studies be conducted following 

specific guidelines as outlined 

below in Appendix D after the study 

review in 1992. Since that time, 

new data has not been submitted, 

and is still considered a data gap.

850.4150

Terrestrial Plant toxicity: 

vegetative vigor 

(Tiers 1 and 2)

41440101 Supplemental Yes

The percent active ingredient was 

not specified, the material was not 

applied to the maximum labeled 

rate, and only one parameter (fresh 

weight) was measured and 

recorded. It was recommended that 

additional studies be conducted 

following specific guidelines as 

outlined below in Appendix D after 

the study review in 1992. Since that 

time, new data has not been 

submitted, and is still considered a 

data gap.

850.5400

Aquatic Plant Growth: 

algae 

(Tier 1 & 2)

42836102 Invalid

Yes

Potential issues (interference) with 

the solvent. Test concentrations 

were not measured, above solubility 

limit without knowing the actual 

concentration that test species were 

exposed to. Test solutions were 

cloudy white with the presence of a 

precipitate, and were neither 

centrifuged nor measured. Tier II

studies are needed to establish 

definitive EC50 and NOAEC values.

The submission of new studies is 

needed.

42836103 Invalid

42882401 Invalid
56

Guideline Description MRID Classification Data 

Gap? Comments

850.4400

Aquatic Plant Growth: 

vascular plants 

(Tier 1 & 2)

42836101 Invalid Yes

Not a sufficient limit test. Potential 

issues (interference) with the 

solvent. Test concentration was not 

measured, above solubility limit 

without knowing the actual 

concentration that test species was 

exposed to. Test solutions were 

cloudy white with the presence of a 

precipitate, and were neither 

centrifuged nor measured. A Tier II

study is needed to establish 

definitive EC50 and NOAEC values.

The submission of new studies is 

needed.

Other Information Needs

There is specific information that will assist the Agency in refining the ecological risk 

assessment, including any species-specific effects determinations. The Agency is very much 

interested in obtaining the following information:

1. confirmation on the following label information

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

applications per season

b. geographic limitations on use

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

crops)

3. use history

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

state, and county

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

state, and county

6. sub-county crop location data

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

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

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

b. percent crop treated – county

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

d. total pounds per year – county

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

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

9. typical interval (days)

10. state or local use restrictions

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

mammalian mortalities) not already reported to the Agency

12. monitoring data 
57

13. the amount of dioxins/furans, and HCB present in technical DCPA.

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

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

Registration review docket.

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MRID Environmental Fate Bibliography

MRID 

Number

Study Citation

00114648 Szalkowski, M. (1975) The Effect of Light, Temperature, and pH on the Hydrolysis of 

Dacthal. (Unpublished study received Mar 23, 1976 under 3F1417; submitted by Diamond 

Shamrock Chemical Co., Cleveland, OH; CDL:095189-D)

00114649 Duane, W. (1976) Aerobic Soil Metabolism of Dacthal. (Unpublished study received Mar 23, 

1976 under 3F1417; submitted by Diamond Shamrock Chemical Co., Cleveland, OH; 

CDL:095189-F)

00114651 Duane, W. (1976) Anaerobic Soil Metabolism of Dacthal. (Unpublished study received Mar 

23, 1976 under 3F1417; submitted by Diamond Shamrock Chemical Co., Cleveland, OH; 

CDL:095189-H)

00114652 Duane, W. (1976) The Effect of Steam Sterilization on the Metabolism of Dacthal in Soils. 

(Unpublished study received Mar 23, 1976 under 3F1417; submitted by Diamond Shamrock 

Chemical Co., Cleveland, OH; CDL:095189-I)

00143063 Szalkowski, M. (1976) Photohydrolysis of Dacthal. Unpublished study prepared by Diamond 

Shamrock Corp. 10 p.

41155715 Szalkowski, M.; Marciniszyn, J.; Killeen, J. (1981) Accumulation, Distribution and 

Depuration of Carbon 14-Residues of Dacthal (DS-893) in Channel Catfish (Ictalurus 

punctatus) Under Static Aquatic Conditions: Document No. 139-4EI-81-0015-002. 

Unpublished study prepared by Analytical Bio Chemistry Laboratories, Inc. 76 p.

41155716 Szalkowski, M.; Stallard, D.; Killeen, J. (1980) Accumulation, Distribution and Depuration of 

Carbon 14-Dacthal (DS-893) in Bluegill Sunfish (Lepomis macrochirus) under Flow Through 

Aquatic Conditions: Document No. 141-3EI-79-0138-001. Unpublished study prepared by 

Analytical Bio Chemistry Laboratories, Inc. 40 p.
63

41197601 Szalkowski, M.; Marciniszyn, J.; Killen, J. (1981) Characterization and Quantitation of 

(Carbon-14) in Water, Soil and Fish Exposed to (Carbon-14)-Dimethyl 2,3,5,6-

Tetrachloroterephthalate (Dacthal, DS-893) in a Static Aquatic System: Document No. 140-

4EI-81 -0018-002. Unpublished study prepared by Analytical Bio Chemistry Laboratories, 

Inc. 102 p.

41197602 Szalkowski, M.; Marciniszyn, J.;Killeen, J. (1981) Characterization and Quantitation of 

(Carbon-14)-Residues in Water and Fish Exposed to (Carbon-14)-dimethyl 2,3,5,6-

Tetrachloroterephthalate (Dacthal, DS-893) in a Flow Through Aquatic System: Document 

No. 142-4EI-81-0017-002. Unpublished study prepared by Analytical Bio-Chemistry 

Laboratories, Inc. 80 p.

41508607 Korsch, B. (1990) A Photolysis Study of Carbon 14-Dimethyl Tetra- chloroterephthalate in 

Water: Lab Project Number: 89-0366: 3496- 89-0366-EF-001: SDS-893. Unpublished study 

prepared by Ricerca, Inc. 119 p.

41508608 Korsch, B. (1990) A Photolysis Study of Carbon 14-Dimethyl Tetra- chloroterephthalate on 

Soil: Lab Project Number: 89-0365: 3495- 89-0365-EF-001: SDS-893. Unpublished study 

prepared by Ricerca, Inc. 115 p.

41508609 Formanik, J. (1989) Determination of Residues of DCPA, Its Soil Metabolites and HCB from 

Soil Dissipation Studies near Gilroy, CA. 1987-1988: Lab Project Number: 1537-88-0066: 

1537-88-0066-CR- 001. Unpublished study prepared by Ricerca, Inc. 477 p.

41508610 Formanik, J. (1990) Determination of Residues of DCPA, its Soil Metabolites and HCB from 

Soil Dissipation Studies near Greenfield, CA: 1987-1988: Lab Project Number: 1537-88-

0066: 1537-88-0066- CR-002. Unpublished study prepared by Ricerca, Inc. 462 p.

41648801 Doran, T. (1990) Response to EPA Review: Aerobic Soil Metabolism of Dacthal: Lab Project 

Number: 000/3EF/76/2083/001. Unpublished Study prepared by Ricerca, Inc. 76 p.

41648802 Doran, T. (1990) Response to EPA Review: Anaerobic Soil Metabolism of Dacthal: Lab 

Project Number: 000/3EF/76/2082/001. Unpublished study prepared by Ricerca, Inc. 40 p.

41648803 Korsch, B. (1988) Adsorption and Desorption of Dimethyl Tetra- chloroterephthalate to Soils: 

Lab Project Number: 1701/87/0099/ EF/001/001. Unpublished study prepared by Ricerca, 

Inc. 64 p.

41648804 Korsch, B.; Kapostasy, W. (1990) Adsorption and Desorption of Mono- methyl 

Tetrachloroterephthalate to Soils: Lab Project Number: 1736/88/0005/EF/001. Unpublished 

study prepared by Ricerca, Inc. 8 p.

41648805 Korsch, B.; Kapostasy, W. (1989) Adsorption and Desorption of Tetrachloroterephthalic Acid 

to Soils: Lab Project Number: 1735/ 88/0004/EF/001. Unpublished study prepared by 

Ricerca, Inc. 64 p.

42262602 Korsch, B.; Waller, R. (1992) Adsorption and Desorption of Dimethyl 

Tetrachloroterephthalate to Soils: Amendment II: Lab Project Number: 1701-87-0099-EF001. Unpublished study prepared by Ricerca, Inc. 192 p.

43661101 Shelby, D. (1995) Adsorption and Desorption of Dimethyl Tetrachloroterephthalate (DCPA) 

to Soil: Lab Project Number: 5971-94-0018-EF-001. Unpublished study prepared by Ricerca, 

Inc. 123 p.

078701 DCPA Eco Effects Bibliography

71-1 Avian Single Dose Oral Toxicity

MRID Citation Reference

83574 DeWitt, J.B. (1962) Toxicity of Pesticides to Upland Birds and 

Waterfowl. (U.S. Fish and Wildlife Service, Patuxent Wildlife Research 

Center, Section of Chemical and Physiological Studies; unpublished 

study; CDL:090443-J) 

114657 Dewitt, J. (1961) Toxicity of Pesticides to Upland Birds and Water fowl: 
64

Dacthal. (U.S. Fish and Wildlife Service, Branch of Wildlife Research; 

unpublished study; CDL:095363-E) 

41155705 Shults, S.; Roblin, M.; Killeen, J. (1989) Acute Oral Toxicity (LD 50) 

Study in Bobwhite Quail with Technical DCPA: Project ID 230- 112. 

Unpublished study prepared by Wildlife International Ltd. 61 p. 

71-2 Avian Dietary Toxicity

MRID Citation Reference

31877 DeWitt, J.B. (1963) Toxicity of Dacthal (Dimethyl ester of Tetrachloroterephthalic acid). (Unpublished study received Sep 27, 1974 

under 677-318; prepared by U.S. Fish and Wildlife Service, Patuxent 

Wildlife Research Center, submitted by Diamond Shamrock Agricultural 

Chemicals, Cleveland, Ohio; CDL:009849-M) 

69191 DeWitt, J.B.; Stickel, W.H.; Springer, P.F. (1963) Wildlife Studies, 

Patuxent Wildlife Research Center, 1961-1962. Pages 74-75, 90, In

Pesticide Wildlife Studies: A Review of Fish and Wildlife Service 

Investigations during 1961 and 1962. By U.S. Fish and Wildlife Service, 

Branch of Wildlife Research. Washington, D.C.: USFWS. (Circular 167; 

published study; CDL:230691-G) 

70082 DeWitt, J.B. (1961) Toxicity of Pesticides to Upland Birds and 

Waterfowl. Progress rept., period ending Dec 31, 1966. (U.S. Fish and 

Wildlife Service, Branch of Wildlife Research, Section of Chemical and 

Physiological Studies; unpublished study; CDL: 093786-D) 

70083 DeWitt, J.B. (1962) Toxicity of Pesticides to Upland Birds and 

Waterfowl. Progress rept., period ending Jun 30, 1962. (U.S. Fish and 

Wildlife Service, Patuxent Wildlife Research Center, Section of 

Chemical and Physiological Studies; unpublished study; CDL:093786-E) 

70084 DeWitt, J.B. (1963) Letter sent to L. Gordon Utter dated Nov 7, 1963?

Toxicity of Dacthal to upland birds and waterfowl|. (U.S. Fish and 

Wildlife Service, Patuxent Wildlife Research Center, Section of 

Chemical and Physiological Studies; CDL: 093786-F) 

103762 Uniroyal Chemical (1963) Toxicity Tests of Selected Chemicals at 

Patuxent, 1963. (Unpublished study received Aug 20, 1974 under 400-

41; CDL:130997-B) 

41155706 Shults, S.; Roblin, M.; Killeen, J. (1989) Dietary (LC50) Study in 

Bobwhite Quail with Technical DCPA: Project ID 230-110 and 89- 0018. 

Unpublished study prepared by Wildlife International Ltd. in association 

with Ricerca, Inc. 113 p. 

41155707 Shults, S.; Roblin, M.; Killeen, J. (1989) Dietary (LC50) Study in Mallard 

Ducks with Technical DCPA: Project IDs 230-111 and 89- 0017. 

Unpublished study prepared by Wildlife International, Ltd. in association 

with Ricerca, Inc. 114 p. 

31876 DeWitt, J.B. (1961) Toxicity of Dacthal. (Unpublished study received 

Sep 27, 1974 under 677-318; prepared by U.S. Fish and Wildlife 

Service, Patuxent Wildlife Research Center, submitted by Diamond 

Shamrock Agricultural Chemicals, Cleveland, Ohio; CDL:009849-L) 
65

71-4 Avian Reproduction

MRID Citation Reference

69191 DeWitt, J.B.; Stickel, W.H.; Springer, P.F. (1963) Wildlife Studies,

Patuxent Wildlife Research Center, 1961-1962. Pages 74-75, 90, In

Pesticide Wildlife Studies: A Review of Fish and Wildlife Service 

Investigations during 1961 and 1962. By U.S. Fish and Wildlife Service, 

Branch of Wildlife Research. Washington, D.C.: USFWS. (Circular 167; 

published study; CDL:230691-G) 

47550001 Frey, L.; Martin, K.; Beavers, J.; et al. (2003) Chlorthal-Dimethyl 

(DCPA): A Reproduction Study with the Northern Bobwhite: Final 

Report. Project Number: 246/115, 246/1/16, 246/020802/QR/SUB246. 

Unpublished study prepared by Wildlife International Ltd. 187 p.

47550002 Frey, L.; Martin, K.; Beavers, J.; et al. (2003) Chlorthal-Dimethyl 

(DCPA): A Reproduction Study with the Mallard: Final Report. Project 

Number: 246/116, 246/020802/MR/SUB246. Unpublished study 

prepared by Wildlife International, Ltd. 179 p.

72-1 Acute Toxicity to Freshwater Fish

MRID Citation Reference

68507 Hughes, J.S.; Davis, J.T. (1964?) Effects of Selected Herbicides on 

Bluegill Sunfish. (Louisiana, Wild Life and Fisheries Commission; 

unpublished study; CDL:231131-A) 

70085 Takematsu, T. (19??) Undated letter sent to L. Gordon Utter Toxicity of 

Dacthal to fish|. (Unpublished study received Jun 29, 1973 under 

3F1417; prepared by Utsunomiya Univ., Japan, submitted by Diamond 

Shamrock Agricultural Chemicals, Cleveland, Ohio; CDL:093786-H) 

70086 Diamond Shamrock Agricultural Chemicals (19??) Effects of Dacthal on 

Marine Organisms. (Unpublished study received Jun 29, 1973 under 

3F1417; CDL:093786-I) 

107142 McCann, J. (1972) Dacthal G-2.5 Herbicide: Rainbow Trout (Salmo 

gairdneri): Test No. 481. (U.S. Agricultural Research Service, Pesticides 

Regulation Div., Animal Biology Laboratory; unpublished study; 

CDL:130357-A) 

Static Jar Test # 437. Unpublished study prepared by Animal Biology 

Laboratory. 3 p.

114658 Takematsu (1963) Letter sent to L. Utter dated 1963 (Dacthal toxicity to 

carp). (Unpublished study received on unknown date under 6E1711; 

prepared by Utsunomiya Univ., Japan, submitted by Interregional 

Research Project No. 4, New Brunswick, NJ; CDL: 095363-H) 

114686 Pitcher, F. (1974) Corenco One Twenty Three: Rainbow Trout|: Test No. 

711. (U.S. Environmental Protection Agency, Pesticides Regulation Div., 

Animal Biology Laboratory; unpublished study; CDL:132390-A) 

40227001 McCann, J. (1975) Diamond Chemical Dacthal W-75 Herbicide: Toxicity 
66

to Rainbow Trout (Salmo gairdneri): Static Jar Test #908. Un- published 

study prepared by Animal Biology Laboratory. 3 p. 

40227002 McCann, J. (1975) Diamond Chemical Dacthal W-75 Herbicide: Toxicity 

to Bluegill (Lepomis macrochirus): Static Jar Test #878. Unpublished 

study prepared by Animal Biology Laboratory. 3 p. 

40098001 Mayer, F.; Ellersieck, M. (1986) Manual of Acute Toxicity: Interpretation 

and Data Base for 410 Chemicals and 66 Species of Freshwater 

Animals. US Fish & Wildlife Service, Resource Publication 160. 579 p.

41054826 Shults, S.; Wilson, N. (1989) Static, Acute Toxicity (LC50) Study in 

Rainbow Trout with Technical DCPA (Dimethyl 2,3,5,6-Tetrachloroterephthalate): Doc. No. 690-5TX-84-0046-002. Unpublished 

study prepared by SDS Biotech Corp. 64 p. 

41054827 Shults, S.; Wilson, N. (1985) Static, Acute Toxicity (LC50) Study in 

Bluegill with Technical DCPA (Dimethyl 2,3,5,6-Tetrachloroterephthalate): Doc. No. 690-5TX-84-0047-002. Unpublished study 

prepared by SDS Biotech Corp. 64 p. 

45822 McCann, J.A. (1969) Diamond Chemical Dacthal W-75 Herbicide: 

Toxicity to Bluegill, Lepomis macrochirus. (U.S. Agricultural Research 

Service, Pesticides Regulation Div., Animal Biology Laboratory, 

unpublished study; CDL:109530-A) 

18644 Toa Agricultural Chemical Company, Limited (1962) Test on Fish 

Toxicity of C-1936, C-1983, and C-2059. (Unpublished study received 

Oct 8, 1964 under 100-548; submitted by Ciba-Geigy Corp., 

Greensboro, N.C.; CDL:023178-K) 

19161 Toa Agricultural Chemical Company, Limited (1962) Test on Fish 

Toxicity of C-1936, C-1983, and C-2059. (Unpublished study received 

Oct 8, 1964 under 100-549; submitted by Ciba-Geigy Corp., 

Greensboro, N.C.; CDL:007070-Q) 

31878 Kodama, J.K. (1960) Subacute Fish Toxicity-Bluegills and Goldfish. 

(Unpublished study including letter dated Dec 10, 1963 from Takematsu to L. Gordon Utter, received Sep 27, 1974 under 677-318; 

prepared by Hazleton Laboratories, Inc., submitted by Diamond 

Shamrock Agricultural Chemicals, Cleveland, Ohio; CDL:009849-N) 

72-2 Acute Toxicity to Freshwater Invertebrates

MRID Citation Reference

40103302 Shults, S. (1985) Static, Acute Toxicity (EC50) Study in Daphnia with 

Technical DCPA: Laboratory ID: 690-5TX-84-0048-02. Unpublished 

study prepared by SDS Biotech Corp. 70 p. 

40226901 McCann, J. (1976) Diamond Chemical Dacthal W-75 Herbicide: Toxicity 

to Daphnia magna: Static Jar Test #933. Unpublished study pre- pared 

by Animal Biology Laboratory. 3 p. 

40098001 Mayer, F.; Ellersieck, M. (1986) Manual of Acute Toxicity: Interpretation and Data Base for 410 Chemicals and 66 Species of 

Freshwater Animals. US Fish & Wildlife Service, Resource Pub- lication 
67

160. 579 p.

41054828 Shults, S.; Wilson, N. (1985) Static, Acute Toxicity (EC50) Study in 

Daphnia with Technical DCPA (Dimethyl 2,3,5,6-Tetrachloroterephthalate): Doc. No. 690-5TX-84-0048-002. Unpublished study 

prepared by SDS Biotech Corp. 63 p. 

72-3 Acute Toxicity to Estuarine/Marine Organisms

MRID Citation Reference

114659 U.S. Fish and Wildlife Service (19??) Effects of Dacthal on Marine 

Organisms. (Bureau of Commercial Fisheries, Biological LaboratorySabine Island; unpublished study; CDL:095363-I) 

31879 Lowe, J.I. (1964) Effects of Dacthal on Marine Organisms. (Unpublished study received Sep 27, 1974 under 677-318; prepared by U.S. 

Fish and Wildlife Service, Bureau of Commercial Fisheries, Biological 

Laboratory, submitted by Diamond Shamrock Agricultur- al Chemicals, 

Cleveland, Ohio; CDL:009849-O) 

40228401 1986, USEPA Gulfbreeze Laboratory Acute testing summaries

Brown shrimp, Sheepshead minnow, Eastern oyster

38448 Butler, P.A. (1963) Commercial Fishery Investigations. U.S. Fish and 

Wildlife Service, Div. of Biological Research, Bureau of Commercial 

Fisheries. (Circular 199; published study; CDL: 091902-B) 

122-2 Aquatic plant growth

MRID Citation Reference

41054829 Shults, S.; Wilson, N. (1985) Algal Growth Inhibition Study in Scenedesmus subspicatus with Technical DCPA (Dimethyl 2,3,5,6-Tetrachloroterephthalate): Doc. No. 688-5TX-84-0049-002. Unpub- lished 

study prepared by SDS Biotech Corp. 54 p. 

42836101 Hughes, J.; Balcom, P. (1993) The Toxicity of DCPA Technical to 

Lemna gibba G3: Lab Project Number: B038-033-4. Unpublished study 

prepared by Malcolm Pirnie, Inc. 23 p. 

42836102 Hughes, J.; Balcom, P. (1993) The Toxicity of DCPA Technical to 

Anabaena flos-aquae: Lab Project Number: B038-033-1. Unpublished 

study prepared by Malcolm Pirnie, Inc. 24 p. 

42836103 Hughes, J.; Balcom, P. (1993) The Toxicity of DCPA Technical to 

Skeletonema costatum: Lab Project Number: B038-033-3. Unpublished 

study prepared by Malcolm Pirnie, Inc. 24 p. 

42882401 Hughes, J.; Balcom, P.; Alexander, M. (1993) The Toxicity of DCPA 

Technical to Navicula pelliculosa: Lab Project Number: B038-033-2. 

Unpublished study prepared by Malcolm Pirnie, Inc. 25 p. 
68

123-1 Seed germination/seedling emergence and vegetative vigor

MRID Citation Reference

41440101 Backus, P.; Crosby, K.; Schollenberger, (1990) Effect of DCPA on 

Vegetative Vigor of Plants (Tier 2): Lab Project No: 89-0128. 

Unpublished study prepared by Ricerca, Inc. 29 p. 

41564901 Backus, P.; Crosby, K. (1990) Effect of DCPA on Seed Germination/ 

Seedling Emergence (Tier 2): Lab Project Number: 89-0129: 3322- 89-

0129-BE-001. Unpublished study prepared by Ricerca, Inc. 193. 

123-2 Aquatic plant growth

MRID Citation Reference

41155714 Hughes, J. (1989) The Toxicity of DCPA (Dacthal/Dimethyl Tetrachloroterephthalate) to Selenastrum capricornutum: Project ID 1401- 01-

1100-1. Unpublished study prepared by Malcolm Pirnie, Inc. 26 p. 

141-1 Honeybee Acute Toxicity

75129 Anderson, L.D.; Atkins, E.L., Jr. (1960) Pesticides Hazardous to 

Honeybees. : Univ. of California, Agricultural Extension Service. (OSA # 

72; also In unpublished submission received Dec 5, 1960 under 271-14; 

submitted by International Minerals & Chemical Corp., Terre Haute, 

Ind.; CDL:231122-B) 

9181 or 

18842

Atkins, E.L., Jr.; Anderson, L.D.; Greywood, E.A. (1969) Effect of 

Pesticides on Apiculture: Project No. 1499. (Unpublished study received 

Jul 29, 1976 under 352-342; prepared by Univ. of California-Riverside, 

Dept. of Entomology, submitted by E.I. du Pont de Nemours & Co., 

Wilmington, Del.; CDL:224800-C)

NON Guideline Selections

29844 Klingman, G.C.; Freeman, J.F.; Ahrens, J.F.; et al. (1962) Toxicity of 

Herbicides to Various Crops and Residues of Diphenamid and Other 

Chemicals in Soils|: Experiment No. GLP2-62. (Unpublished study 

including experiment nos. M2-5, M2-6, C2-26...; received Nov 1, 1962 

under unknown admin. no.; prepared in cooperation with North Carolina 

State College and others, submitted by Elanco Products Co., Div. of Eli 

Lilly and Co., Indianapolis, Ind., CDL:120175-C) 

30128 Jensen, H.L.; Petersen, H.I. (1952) Detoxication of hormone herbicides by soil bacteria. Nature 170(4314):39-40. (Also In un-published 

study received Jan 2, 1980 under 2217-641; submitted by PBI-Gordon 

Corp., Kansas City, Kans.; CDL:241574-Z) 

47164601 Moore, D.; Breton, R.; Rodney, S.; et al. (2007) Generic Problem 

Formulation for California Red-Legged Frog. Project Number: 89320, 

05232007. Unpublished study prepared by Cantox Environmental Inc. 

87 p.

47164602 Holmes, C.; Vamshi, R. (2007) Data and Methodology Used for Spatial 
69

Analysis of California Red Legged Frog Observations and Proximate 

Land Cover Characteristics. Project Number: 3152007, WEI/252/03. 

Unpublished study prepared by Waterborne Environmental, Inc. (WEI). 

19 p.

27401 Christensen, C.; Rogers, W.; Colbert, F.; et al. (1976) Sward^(TM)I 50W 

for Preemergence Control of Annual Grasses and Some Broad- leaf 

Weeds in Mature Turfgrasses. (Unpublished study received Aug 12, 

1976 under 1471-106; prepared in cooperation with Univ. of Florida, 

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

Ind.; CDL:224918-A) 

114641 Diamond Alkali Co. (1963) Abstracts of Reports of Investigations Made 

with Respect to the Safety of the Pesticide Chemical, Dacthal. 

(Compilation; unpublished study received Jan 9, 1968 under 8F0640; 

CDL:091112-A) 
70

Appendix A. Maximum DCPA use rates and management practices by crop based on current 

labels. 

Use Site Max. Rate

per App

Max. Rate

Unit/Area

*UG 

Form Max.#

Apps

cc & yr 

Max. App

Rate/

cc & yr 

Min. App

Interval

(days) 

Application Equipment

//Type

(Reg # Code)

NON-FOOD/NON-FEED USES

golf course turf 15 lb A FlC NS NS NS Sprayer 

//Broadcast (a)

nursery stock 12 lb A WP NS NS NS Aircraft/ Sprayer/ Sprinkler 

irrigation 

//Soil treatment (a)

ornamental and/or shade 

trees 

9 lb A G NS NS NS Spreader 

//Soil treatment (a)

.2410 lb 1K sq.ft

*C2 

G NS NS NS Not on label 

//Soil treatment (b)

2.609E-04 lb sq.ft

*C2 

G NS NS NS Spreader 

//Soil treatment (c)

ornamental ground cover 2.609E-04 lb sq.ft

*C2 

G NS NS NS Spreader 

//Soil treatment (a)

ornamental herbaceous 

plants 

9 lb A G NS NS NS Spreader 

//Soil treatment (a)

.2410 lb 1K sq.ft

*C2 

G NS NS NS Not on label 

//Soil treatment (b)

2.609E-04 lb sq.ft

*C2 

G NS NS NS Spreader 

//Soil treatment (c)

ornamental lawns and turf 15 lb A FlC

G 

NS NS NS Sprayer/ Spreader 

//Broadcast/ Soil broadcast

treatment (a)

.3500 lb 1K sq.ft

*C2 

G NS NS NS Spreader 

//Soil broadcast treatment (b)

ornamental nonflowering 

plants 

9 lb A G NS NS NS Spreader 

//Soil treatment (a)

.2410 lb 1K sq.ft

*C2 

G NS NS NS Not on label 

//Soil treatment (b)

2.609E-04 lb sq.ft

*C2 

G NS NS NS Spreader 

//Soil treatment (c)

ornamental sod farm (turf) 15 lb A FlC NS NS NS Sprayer 

//Broadcast (a)

ornamental woody shrubs 

and vines 

9 lb A G NS NS NS Spreader 

//Soil treatment (a)

.2410 lb 1K sq.ft

*C2 

G NS NS NS Not on label 

//Soil treatment (b)

2.609E-04 lb sq.ft

*C2 

G NS NS NS Spreader 

//Soil treatment (c)

recreation area lawns 15 lb A FlC NS NS NS Sprayer 

//Broadcast (a)

residential lawns .3500 lb 1K sq.ft

*K1 

G NS NS NS Spreader 

//Soil broadcast treatment (a)
71

Use Site Max. Rate

per App

Max. Rate

Unit/Area

*UG 

Form Max.#

Apps

cc & yr 

Max. App

Rate/

cc & yr 

Min. App

Interval

(days) 

Application Equipment

//Type

(Reg # Code)

FOOD/FEED USES

arrowroot 10.5 lb A G

WP 

NS NS NS Aircraft/ Ground/ Sprayer/ 

Spreader/ Sprinkler irrigation

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil treatment (a)

beans, dried-type 10.35 lb A G NS NS NS Spreader 

//Soil treatment (a)

2.410E-04 lb sq.ft

*A2 

G NS NS NS Not on label 

//Soil treatment (b)

beans, succulent (snap) 10.35 lb A G NS NS NS Spreader 

//Soil treatment (a)

2.410E-04 lb sq.ft

*A2 

G NS NS NS Not on label 

//Soil treatment (b)

2.078E-04 lb sq.ft

*A1 

G NS NS NS Spreader 

//Soil treatment (c)

brassica (head and stem) 

vegetables 

10.5 lb A FlC

G

WP 

NS NS NS Aircraft/ Ground/ Soil 

incorporation equipment/ 

Sprayer/ Spreader/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil 

incorporated treatment/ 

Soil treatment (a)

broccoli 10.5 lb A FlC

G

WP 

NS NS NS Aircraft/ Ground/ Soil 

incorporation equipment/ 

Sprayer/ Spreader/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil 

incorporated treatment/ 

Soil treatment (a)

2.410E-04 lb sq.ft

*A1 

G NS NS NS Not on label 

//Soil treatment (b)

2.078E-04 lb sq.ft

*A1 

G NS NS NS Spreader 

//Soil treatment (c)

broccoli raab 10.5 lb A FlC

G

WP 

NS NS NS Aircraft/ Ground/ Soil 

incorporation equipment/ 

Sprayer/ Spreader/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast treatment/ 

Soil 

incorporated treatment/ 

Soil treatment (a)

brussels sprouts 10.5 lb A FlC

G

WP 

NS NS NS Aircraft/ Ground/ Soil 

incorporation equipment/ 

Sprayer/ Spreader/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 
72

Use Site Max. Rate

per App

Max. Rate

Unit/Area

*UG 

Form Max.#

Apps

cc & yr 

Max. App

Rate/

cc & yr 

Min. App

Interval

(days) 

Application Equipment

//Type

(Reg # Code)

treatment/ Soil 

incorporated treatment/ 

Soil treatment (a)

2.410E-04 lb sq.ft

*A1 

G NS NS NS Not on label 

//Soil treatment (b)

cabbage 10.5 lb A FlC

G

WP 

NS NS NS Aircraft/ Ground/ Soil 

incorporation equipment/ 

Sprayer/ Spreader/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil 

incorporated treatment/ 

Soil treatment (a)

2.410E-04 lb sq.ft

*A1 

G NS NS NS Not on label 

//Soil treatment (b)

2.078E-04 lb sq.ft

*A1 

G NS NS NS Spreader 

//Soil treatment (c)

cabbage, chinese 10.5 lb A WP NS NS NS Aircraft/ Soil incorporation 

equipment/ Sprayer/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil 

incorporated treatment (a)

canola\rape 10.5 lb A WP NS NS NS Aircraft/ Soil incorporation 

equipment/ Sprayer/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil 

incorporated treatment (a)

cauliflower 10.5 lb A FlC

G

WP 

NS NS NS Aircraft/ Ground/ Soil 

incorporation equipment/ 

Sprayer/ Spreader/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil 

incorporated treatment/ 

Soil treatment (a)

2.410E-04 lb sq.ft

*A1 

G NS NS NS Not on label 

//Soil treatment (b)

2.078E-04 lb sq.ft

*A1 

G NS NS NS Spreader 

//Soil treatment (c)

chayote 10.5 lb A G

WP 

NS NS NS Aircraft/ Ground/ Shaker can/ 

Soil incorporation equipment/ 

Sprayer/ Spreader/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil treatment (a)

collards 10.5 lb A FlC

G

NS NS NS Aircraft/ Ground/ Soil 

incorporation equipment/ 
73

Use Site Max. Rate

per App

Max. Rate

Unit/Area

*UG 

Form Max.#

Apps

cc & yr 

Max. App

Rate/

cc & yr 

Min. App

Interval

(days) 

Application Equipment

//Type

(Reg # Code)

WP Sprayer/ Spreader/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil 

incorporated treatment/ 

Soil treatment (a)

2.410E-04 lb sq.ft

*A1 

G NS NS NS Not on label 

//Soil treatment (b)

cucumber 10.35 lb A G NS NS NS Spreader 

//Soil treatment (a)

2.410E-04 lb sq.ft

*A1 

G NS NS NS Not on label 

//Soil treatment (b)

eggplant 10.5 lb A FlC

G

WP 

NS NS NS Aircraft/ Ground/ Soil 

incorporation equipment/ 

Sprayer/ Spreader/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil treatment (a)

2.410E-04 lb sq.ft

*A1 

G NS NS NS Not on label 

//Soil treatment (b)

garlic 10.35 lb A G NS NS NS Spreader 

//Soil treatment (a)

2.410E-04 lb sq.ft

*A1 

G NS NS NS Not on label 

//Soil treatment (b)

gherkin 10.5 lb A G

WP 

NS NS NS Aircraft/ Soil incorporation 

equipment/ Sprayer/ Spreader/ 

Sprinkler irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil treatment (a)

ginseng (medicinal) 10.5~ lb A WP NS NS NS Sprayer 

//Soil broadcast treatment (a)

gourd (wax), chinese 10.5 lb A G

WP 

NS NS NS Aircraft/ Soil incorporation 

equipment/ Sprayer/ Spreader/ 

Sprinkler irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil treatment (a)

gourds 10.5 lb A G

WP 

NS NS NS Aircraft/ Soil incorporation 

equipment/ Sprayer/ Spreader/ 

Sprinkler irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil treatment (a)

groundcherry (strawberry 

tomato/tomatillo) 

10.5 lb A G

WP 

NS NS NS Aircraft/ Sprayer/ Spreader/ 

Sprinkler irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil treatment (a)

hanover salad 10.5 lb A FlC NS NS NS Aircraft/ Ground/ Soil 
74

Use Site Max. Rate

per App

Max. Rate

Unit/Area

*UG 

Form Max.#

Apps

cc & yr 

Max. App

Rate/

cc & yr 

Min. App

Interval

(days) 

Application Equipment

//Type

(Reg # Code)

G

WP 

incorporation equipment/ 

Sprayer/ Spreader/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil 

incorporated treatment/ 

Soil treatment (a)

horseradish 10.5 lb A FlC

G

WP 

NS NS NS Aircraft/ Ground/ Soil 

incorporation equipment/ 

Sprayer/ Spreader/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil treatment (a)

kale 10.5 lb A FlC

G

WP

NS NS NS Aircraft/ Ground/ Soil 

incorporation equipment/ 

Sprayer/ Spreader/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil 

incorporated treatment/ 

Soil treatment (a)

2.410E-04 lb sq.ft

*A1 

G NS NS NS Not on label 

//Soil treatment (b)

lettuce, head 10.21 lb A WP 1/cc NS NS Sprayer 

//Spray (a)

2.410E-04 lb sq.ft

*A1 

G NS NS NS Not on label 

//Soil treatment (b)

lettuce, leaf (black seeded 

simpson, salad bowl, etc.) 

10.21 lb A WP 1/cc NS NS Sprayer 

//Spray (a)

2.410E-04 lb sq.ft

*A1 

G NS NS NS Not on label 

//Soil treatment (b)

manioc (cassava) 10.5 lb A G

WP 

NS NS NS Aircraft/ Ground/ Sprayer/ 

Spreader/ Sprinkler irrigation

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil treatment (a)

melons 10.21 lb A WP NS NS NS Sprayer 

//Spray (a)

melons, bitter (balsam 

pear) 

10.5 lb A G NS NS NS Spreader 

//Soil treatment (a)

melons, cantaloupe 10.5 lb A FlC NS NS NS Aircraft/ Ground/ Soil 

incorporation equipment/ 

Sprinkler irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment (a)

2.410E-04 lb sq.ft

*A1 

G NS NS NS Not on label 

//Soil treatment (b)

melons, honeydew 10.5 lb A FlC NS NS NS Aircraft/ Ground/ Soil 
75

Use Site Max. Rate

per App

Max. Rate

Unit/Area

*UG 

Form Max.#

Apps

cc & yr 

Max. App

Rate/

cc & yr 

Min. App

Interval

(days) 

Application Equipment

//Type

(Reg # Code)

incorporation equipment/ 

Sprinkler irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment (a)

2.410E-04 lb sq.ft

*A1 

G NS NS NS Not on label 

//Soil treatment (b)

melons, musk 10.5 lb A G

WP 

NS NS NS Aircraft/ Soil incorporation 

equipment/ Sprayer/ Spreader/ 

Sprinkler irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil treatment (a)

melons, water 10.5 lb A FlCG

WP 

NS NS NS Aircraft/ Ground/ Soil 

incorporation equipment/ 

Sprayer/ Spreader/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil treatment (a)

2.410E-04 lb sq.ft

*A1 

G NS NS NS Not on label 

//Soil treatment (b)

momordica spp. 10.5 lb A G

WP 

NS NS NS Aircraft/ Soil incorporation 

equipment/ Sprayer/ Spreader/ 

Sprinkler irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil treatment (a)

.2406 lb 1K sq.ft

*A1 

G NS NS NS Shaker can 

//Soil treatment (b)

mustard 10.5 lb A FlC

G

WP 

NS NS NS Aircraft/ Ground/ Soil 

incorporation equipment/ 

Sprayer/ Spreader/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil 

incorporated treatment/ 

Soil treatment (a)

2.410E-04 lb sq.ft

*A2 

G NS NS NS Not on label 

//Soil treatment (b)

onion 10.5 lb A FlC

G

WP 

NS NS NS Aircraft/ Ground/ Soil 

incorporation equipment/ 

Sprayer/ Spreader/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil treatment (a)

2.410E-04 lb sq.ft

*A1 

G NS NS NS Not on label 

//Soil treatment (b)

2.078E-04 lb sq.ft

*A1 

G NS NS NS Spreader 

//Soil treatment (c)

onions (green) 10.5 lb A FlC NS NS NS Aircraft/ Ground/ Soil 
76

Use Site Max. Rate

per App

Max. Rate

Unit/Area

*UG 

Form Max.#

Apps

cc & yr 

Max. App

Rate/

cc & yr 

Min. App

Interval

(days) 

Application Equipment

//Type

(Reg # Code)

G

WP 

incorporation equipment/ 

Sprayer/ Spreader/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil treatment (a)

onions (scallions) 10.5 lb A FlC

G 

NS NS NS Aircraft/ Ground/ Soil 

incorporation equipment/ 

Spreader/ Sprinkler irrigation

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil treatment (a)

peas, southern 10.35 lb A G NS NS NS Spreader 

//Soil treatment (a)

2.410E-04 lb sq.ft

*A2 

G NS NS NS Not on label 

//Soil treatment (b)

pepino (melon pear) 10.5 lb A G

WP 

NS NS NS Aircraft/ Sprayer/ Spreader/ 

Sprinkler irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil treatment (a)

pepper 10.35 lb A G NS NS NS Spreader 

//Soil treatment (a)

2.410E-04 lb sq.ft

*A1 

G NS NS NS Not on label 

//Soil treatment (b)

potato, white/irish 10.35 lb A G NS NS NS Spreader 

//Soil treatment (a)

2.410E-04 lb sq.ft

*A2 

G NS NS NS Not on label 

//Soil treatment (b)

radish 10.5 lb A FlC

WP 

NS NS NS Soil incorporation equipment/ 

Sprayer/ Sprinkler irrigation 

//Chemigation/ Soil band 

treatment (a)

shallot 10.5 lb A G NS NS NS Spreader 

//Soil treatment (a)

squash (all or unspecified) 10.21 lb A WP NS NS NS Sprayer 

//Spray (a)

squash (summer) 10.35 lb A G NS NS NS Spreader 

//Soil treatment (a)

2.410E-04 lb sq.ft

*A1 

G NS NS NS Not on label 

//Soil treatment (b)

squash (winter) (hubbard) 10.35 lb A G NS NS NS Spreader 

//Soil treatment (a)

2.410E-04 lb sq.ft

*A1 

G NS NS NS Not on label 

//Soil treatment (b)

strawberry 10.5 lb A G NS NS NS Spreader 

//Soil treatment (a)

2.078E-04 lb sq.ft G NS NS NS Spreader 
77

Use Site Max. Rate

per App

Max. Rate

Unit/Area

*UG 

Form Max.#

Apps

cc & yr 

Max. App

Rate/

cc & yr 

Min. App

Interval

(days) 

Application Equipment

//Type

(Reg # Code)

*A1 //Soil treatment (b)

2.008E-04 lb sq.ft

*A1 

G NS NS NS Not on label 

//Soil treatment (c)

sweet potato 10.5 lb A FlC

G

WP 

NS NS NS Aircraft/ Ground/ Soil 

incorporation equipment/ 

Sprayer/ Spreader/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil treatment (a)

2.078E-04 lb sq.ft

*A1 

G NS NS NS Spreader 

//Soil treatment (b)

taro 10.5 lb A G

WP 

NS NS NS Aircraft/ Ground/ Sprayer/ 

Spreader/ Sprinkler irrigation

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil treatment (a)

tomatillo 10.5 lb A FlC

G

WP 

NS NS NS Aircraft/ Ground/ Soil 

incorporation equipment/ 

Sprayer/ Spreader/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil treatment (a)

tomato 10.5 lb A FlC

G

WP 

NS NS NS Aircraft/ Ground/ Soil 

incorporation equipment/ 

Sprayer/ Spreader/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil treatment (a)

2.410E-04 lb sq.ft

*A2 

G NS NS NS Not on label 

//Soil treatment (b)

2.078E-04 lb sq.ft

*A1 

G NS NS NS Spreader 

//Soil treatment (c)

turmeric 10.5 lb A G

WP 

NS NS NS Aircraft/ Ground/ Sprayer/ 

Spreader/ Sprinkler irrigation

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil treatment (a)

turnip (greens) 10.5 lb A FlC

G

WP 

NS NS NS Aircraft/ Ground/ Soil 

incorporation equipment/ 

Sprayer/ Spreader/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil 

incorporated treatment/ 

Soil treatment (a)

2.410E-04 lb sq.ft

*A2 

G NS NS NS Not on label 

//Soil treatment (b)

turnip (root) 10.5 lb A FlC

G

NS NS NS Aircraft/ Ground/ Soil 

incorporation equipment/ 
78

Use Site Max. Rate

per App

Max. Rate

Unit/Area

*UG 

Form Max.#

Apps

cc & yr 

Max. App

Rate/

cc & yr 

Min. App

Interval

(days) 

Application Equipment

//Type

(Reg # Code)

WP Sprayer/ Spreader/ Sprinkler 

irrigation 

//Chemigation/ Soil band 

treatment/ Soil broadcast 

treatment/ Soil 

incorporated treatment/ 

Soil treatment (a)

2.410E-04 lb sq.ft

*A2 

G NS NS NS Not on label 

//Soil treatment (b)

yam 10.35 lb A G NS NS NS Spreader 

//Soil treatment (a)
79

Appendix B. Output generated by SIP v.1.0

Table 1. Inputs

Parameter Value

Chemical name DCPA

Solubility (in water at 25oC; mg/L) 0.5

Mammalian LD50 (mg/kg-bw) 5000

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian species

Mammalian NOAEL (mg/kg-bw) 1000

Mammalian test species laboratory rat

Body weight (g) of "other" mammalian species

Avian LD50 (mg/kg-bw) 2250

Avian test species northern bobwhite quail

Body weight (g) of "other" avian species

Mineau scaling factor 1.15

Mallard NOAEC (mg/kg-diet) 0

Bobwhite quail NOAEC (mg/kg-diet) 0

NOAEC (mg/kg-diet) for other bird species

Body weight (g) of other avian species

NOAEC (mg/kg-diet) for 2nd other bird species

Body weight (g) of 2nd other avian species

Table 2. Mammalian Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 0.0860 0.0860

Adjusted toxicity value (mg/kg-bw) 3845.8028 769.1606

Ratio of exposure to toxicity 0.0000 0.0001

Conclusion*

Drinking water exposure 

alone is NOT a potential 

concern for mammals

Drinking water exposure 

alone is NOT a potential 

concern for mammals

Table 3. Avian Results

Parameter Acute Chronic

Upper bound exposure (mg/kg-bw) 0.4050 0.4050

Adjusted toxicity value (mg/kg-bw) 1620.9664 0.0000

Ratio of exposure to acute toxicity 0.0002 0.0000

Conclusion*

Drinking water exposure 

alone is NOT a potential 

concern for birds

Due to insufficient data, risk 

cannot be precluded

*Conclusion is for drinking water exposure alone. This does not combine all routes of exposure. Therefore, 

when aggregated with other routes (i.e., diet, inhalation, dermal), pesticide exposure through drinking water 

may contribute to a total exposure that has potential for effects to non-target animals.
80

Appendix C: Additional Information for DCI Rationale

Environmental Fate 

Ecological Effects

Fish, Aquatic Invertebrates and Aquatic Plants: Previously submitted DCPA TGAI toxicity 

data for freshwater and estuarine/marine fish, aquatic invertebrates and aquatic plants (vascular 

and non-vascular) are not acceptable, as there were issues with the solubility of the technical 

grade compound. The solubility of the DCPA is an issue that was not properly examined in the 

previously submitted studies for fish, aquatic invertebrates, and aquatic plants. Without 

measurement or centrifugation of the water samples, especially in the presence of precipitates, 

the actual dissolved soluble concentration the test organisms were exposed to is not known. The 

actual soluble, dissolved concentrations are likely lower than the nominal concentrations, 

resulting in a potential underestimation of risk to aquatic species. Therefore, new TGAI acute 

and chronic toxicity data are required for fish, aquatic invertebrates, and aquatic plants for 

DCPA. 

No toxicity data are currently available to assess the risk of the DCPA degradate TPA to 

freshwater and estuarine/marine fish, aquatic invertebrates, and aquatic plants (vascular and nonvascular). Given the structural similarity between the parent chemical and the major degradate, 

the degradate may retain the toxicological properties of the parent. In addition, TPA is mobile 

and persistent, and has been detected in ground/surface water. Therefore, both acute and chronic 

toxicity data is needed to evaluate the risk potential resulting from the degradation of DCPA to 

TPA in the aquatic environment. 

The log Kow of DCPA is 4.28-4.40 and therefore, as the log Kow is greater than 3 for the parent 

DCPA, the data requirement of both freshwater and marine whole sediment acute toxicity data 

was triggered. As acute sediment toxicity data for neither freshwater nor marine organisms were

ever submitted to the Agency, this data requirement is considered a data gap. In addition, both 

fish and oyster BCF studies indicate that DCPA bioaccumulates in both test organisms. Thus 

indicating that bioaccumulation may be a potentially important pathway in aquatic organisms. In

the fish BCF study a trace amount of the MTP degradate was observed in both fish viscera and 

whole fish tissue, with the greatest amount accumulating on day 14 of 30. 

Although there is limited information regarding the log Kow for the two the major degradates of 

DCPA, estimated values using data from EPI Suite version 3.20 (which used the SMILES string 

from Table 2 as input) determined values for TPA and MTP. For TPA the log Kow was 2.13 and

the log Kow for MTP was 3.19, respectively. From this information, it can be understood that 

there is the potential for bioaccumulation in both organisms and the environment. Due to the 

significant amount of TPA reported in the environment via monitoring data, both BCF and 

sediment toxicity studies are needed to better characterize the risk to non-target organisms 

resulting from use of DCPA. Therefore, whole sediment toxicity for the parent DCPA, and 

bioaccumulation (BCF) and whole sediment (both acute and chronic) toxicity studies for the two 

major degradates, are needed to better characterize risk to non-target aquatic organisms. 
81

Birds: An acute avian inhalation toxicity test is being requested using the bobwhite quail, the 

species that was tested in the acute oral studies. The study being requested will aid in evaluating 

this pathway of concern for avian taxa. An avian inhalation study protocol must be submitted for 

review and approval by the Agency prior to initiation of this study. If inhalation acute toxicity 

data are not submitted for birds, then risk to birds from acute inhalation exposure to DCPA will 

be presumed. 

It is likely that, for most pesticide use patterns, passerines are more likely to be exposed to 

pesticides than upland game species and waterfowl. Because passerine species have higher 

metabolic rates due to their smaller sizes than either waterfowl or upland game bird species and 

because they may utilize different metabolic pathways, they may be more or less sensitive to 

DCPA. In order to properly characterize risk to passerines, an avian oral toxicity test is required 

for passerine birds. A passerine study protocol must be submitted for review by the Agency prior 

to initiation of the study. 

Terrestrial Plants: The toxicity studies that were submitted did not provide enough information 

to definitively estimate the toxicity of DCPA to terrestrial plants. Both seedling emergence and 

vegetative vigor tests should be conducted for a minimum of 28 days to accommodate the 

delayed mode of action (mitotic disruption) of DCPA. In mitotic disruption, the chemical first 

will stop the growth of roots and shoots of seedlings. Then after a period of time it causes 

deterioration. This delay may be several weeks depending on environmental conditions and 

species tested, and the species that were tested originally were considered tolerant species, and 

others need to be used in subsequent studies. 

The following information should be required from each replicate of the seedling emergence 

tests:

Percentage of emergence and survival of seedlings every seven days;

Height of shoots every seven days; and 

Fresh weights and dry weights of shoots at study termination

The following information should be required from each replicate of the vegetative vigor tests:

Plant height every seven days

Phytotoxicity rating every seven days; and

Fresh weight of foliage, dried weight of foliage, fresh weight of roots, dried weight of 

roots at test termination.