### UNITED STATES ENVIRONMENTAL PROTECTION AGENCY



### WASHINGTON D. C., 20460

O FFI C E O F C H EMICA L SAFE T Y

A N D POL L U T I O N PREV E N TI ON



### MEMORANDUM 

### September 17, 2015

Subject:

To:



### From:

Through: 

### R eg i s tration Re v i ew

- Pr e lim i n ary E c o lo g i cal Ri s k Assess m e n t for Dim e th o at e (P C Co de 0 35 001 ; DP Bar code D4 2 1ll 7)

K e ll y Ballard

, Ri sk Mana g er R ev i ew er N e il Anderso n
, B ranc h C hi e f

R isk M anagem e nt an d Impl e m e nt a t i on Br anc h I



### P es t ici de Re-e va lu a tion Di v i s ion (75 08P )

M a h Shamim

, Ph

. D

., Branch C hi ef

E n v ironment a l Ri sk Branch 5 

# ' qi 18/ l b

# ~ E n v i ro nment a l Fate and Eff ects Di vis ion (7507 P )

Th e E n v i ro nm e n tal Fa t e and Effec t s Di v i s i o n (E FED ) h as co mple t ed t he pr e limin ary ecol o g ical

ri s k assess m e nt of th e or g anop hos ph a

t e in sectic i de / ac ar ic i de

, d i met h oate ( P C Co d e 0 35001)

. Thi s

assessm en t, c o ndu cted as pru t of th e R eg i st r a

tion Re view, build s o n th e pr e limi nary probl e m for m u l ati o n fo r dim et h oat e th a t was c o mpl e t ed in 2 008 ( D 3 55609 ) an d av ailabl e in th e dock e t (E P A- HQ-OPP- 2 00 9 -0059 in http: // www.regulations.gov /#!home) . I n a d d i ti o n
, b o th op e n l ite r a t ure and st udi es s ubmitt e d b y th e te c hni ca l reg i s t ra

nt s in 

### r es pon se t o dat a r e quir e m e n ts furth e r i n fo rm t hi s ri sk assess m e nt

. This d ocu m e nt t herefo r e p rov id es a sy nth es i s of t h e env i ro nmen ta l

fate an d e c ot o x i c i ty inform a t io n t o ev alu ate p ote n t ia l ri sk to no n- targe t te rr estr i al an d aq u at i c pla n t s and anima ls.

P age 1 

### o f 1 44

### Page 2 of 144 

# Preliminary Ecological Risk Assessment in Support of the R egistration Review of Dimethoate

Dimethoate (CAS 60

- 51

- 5 )

Prepared by:

Hannah Yingling , Biologist

José M e l é ndez

, Chemist U. S. Environmental Protection Agency Office of Pesticide Programs Environmental Fate and Effects Division

Environmental Risk Branch V 1200 Pennsylvania Ave., NW

Mail Code 7507P Washington, DC 20460 Reviewed by: Keith Sappington, Senior Science Advisor Mah Shamim, Ph.D. , Branch Chief 

## Office of Chemical Safety

and Pollution Prevention

### Page 3 of 144 

# T

able of Contents

Executive Summary

................................ ................................ ................................ ... 4

1.0 Problem Formulation

................................ ................................ ................................ 6

1.1 Nature of Regulatory Action

................................ ................................ ........................ 6

1.2 Stressor Source and Distribution

................................ ................................ ................. 6

1.3 Stressors of Concern

................................ ................................ ................................ .... 8

1.4 Risk Hypothesis

................................ ................................ ................................ ........... 9

2.0 Exposure Characterization

................................ ................................ ..................... 10

2.1 Use and Usage Information

................................ ................................ ....................... 10

2.2 Environmental Fate and Transport

................................ ................................ ............. 16

2.3 Aquatic Exposure Modeling Approach

................................ ................................ ..... 23

2.4 Monitoring

................................ ................................ ................................ ................. 31

2.5 Terrestrial Exposure Modeling

................................ ................................ .................. 33

3.0 Ecological Toxicity

................................ ................................ ................................ ... 41

3.1 Aquatic Organisms

................................ ................................ ................................ ..... 41

3.2 Terrestrial Organisms

................................ ................................ ................................ . 43

3.3 Degradate toxicity

................................ ................................ ................................ ...... 46

3.4 Incident data

................................ ................................ ................................ ............... 50

4.0 Risk Characterization

................................ ................................ .............................. 52

4.1 Risk Estimation for Aquatic Organisms

................................ ................................ .... 54

4.2 Terrestrial Organisms

................................ ................................ ................................ . 60

4.3 Risk Description

................................ ................................ ................................ ......... 75

4.4 Characterization of Omethoate

................................ ................................ .................. 84

4.5 Endangered species

................................ ................................ ................................ .... 85

4.6 Uncertainties, Limitations, and Identification of Data Gaps

................................ ..... 86

5.0 References

................................ ................................ ................................ ................. 93 Appendix A. Fate Bibliography.

................................ ................................ .......................... 96 Appendix B. Eco Bibliography

................................ ................................ .......................... 101 Appendix C. Dimethoate and its transformation products

................................ ................. 118 Appendix D. Sample SWCC Output File

................................ ................................ ........... 120 Appendix E. T

- REX example output

................................ ................................ ................. 123 Appendix F. Example STIR Output

................................ ................................ ................. 126 Appendix G. Example SIP Output

................................ ................................ ..................... 127 Appendix H. Terrplant example output

................................ ................................ .............. 128 Appendix I. Classifications of Environmental Fate Studies

................................ ............... 129 Appendix J. Reviewed studies submitted in support of PRA

................................ ............. 131 Appendix K. Incident Summaries

................................ ................................ ...................... 133 Appendix L. ECOTOX Selected Articles of Interest

................................ ......................... 143

### Page 4 of 144 

# E xecutive Summary

Dimethoate is an insecticide/acaricide belonging to the organophosphate (OP) class of pesticides

which act through inhibition of acetylcholinesterase leading to neurological effects in sensitive taxa. The compound is used on a variety of agricultural crops including alfalfa, broccoli, corn, cotton, dry beans/peas, oranges, potatoes, soybeans, tomatoes, and wheat

. While primarily applied as a foliar s pray, soil and bark drenches are registered as well

. Dimethoate is

characterized as a highly mobile, generally non

- persistent organophosphate insecticide. The primary route of dissipation is microbially

- mediated degradation in aerobic soil. Consistent w ith laboratory

- based degradation studies, terrestrial d issipation studies indicate that dimethoate rapidly dissipates from soil and foliar surfaces

. Although not observed in environmental fate laboratory studies

, the degradate omethoate was detected in soi ls of terrestrial field dissipation studies as well as monitoring studies in multiple environmental compartments. Given that omethoate acts through the same mode of action as the parent compound and depending on the species tested, can be as toxic if not more toxic than the parent compound, it is considered a

residue of concern. Neither the parent nor its omethoate transformation product are expected to

bioaccumulate.

Dimethoate is moderately toxic to fish (and to aquatic

- phase amphibians for which fish s erve as surrogates) and is highly toxic to aquatic invertebrates on an acute exposure basis. The compound is moderately to very highly toxic to birds (and to terrestrial

- phase amphibians and reptiles for which birds serve as surrogates) and moderately tox ic to mammals on an acute exposure basis. The compound is highly toxic to beneficial insects such as bees on an acute oral and contact exposure basis.

Table 1 provides a summary of the environmental risk conclusions for aquatic and terrestrial organisms based on risk quotient (RQ) values and whether they exceed levels of concern (LOCs) for Federally

- listed threatened and endangered species (hereafter refers to as listed species) and

non

- listed species.

Table 1. Summary of Ecological Risk Conclusions for the Proposed Dimethoate Uses

Taxonomic Group Summarized Risk Characterization and Major Uncertainties Fish and Aquatic Invertebrates (freshwater and estuarine/marine) (plus aquatic

- phase amphibians for which fish serve as surrogates) The potential for acute or chronic risk to freshwater and estuarine/marine fish is considered low, as acute or chronic RQ values do no exceed the risk to listed species LOC of 0.05.

A potential for acute and chronic risk to freshwater and

estuarine/marine invertebrates is identified. Specifically, there are LOC exceedances across all dimethoate application scenarios for the listed species LOC of 0.05 for acute risk and 1.0 for chronic risk

. The chronic risk findings are uncertain because the y are based on

chronic values der ived using acute

- to

- chronic ratio s in the absence of

dimethoate

- specific chronic toxicity data for invertebrates. Aquatic and Terrestrial

Plants The potential for risk to aquatic and terrestrial plants is considered low, as RQ values do not exceed the LOC values for risk to listed

and non

- listed aquatic or terrestrial plants.

### Page 5 of 144 Table 1. Summary of Ecological Risk Conclusions for the Proposed Dimethoate Uses

Taxonomic Group Summarized Risk Characterization and Major Uncertainties

Birds (plus terrestrial

- phase amphibians and reptiles for

which birds serve as surrogates) There is a potential for acute and chronic risk to birds , reptiles and

terrestrial

- phas e amphibians . Specifically, acute dose

- based RQ values exceed the risk to listed species LOC of 0. 1 for at least one avian dietary forage category and size class across all uses. Acute

and chronic diet

- based RQs also exceed the risk to listed species

LOC of 0.1 for at least one avian dietary class across all uses.

Mammals There is a potential for acute and chronic risk to mammals. RQ

values exceed the chronic risk LOC by several orders of magnitude

. Bees Tier 1 Risk Assessment. B ased on Tier 1 acute contact and acute oral risk assessment of adult honey bees, RQ values exceed the acute

risk LOC

. Based on information on dimethoate toxicity to individual bee larvae, Tier 1 risks to larval bees are also indicated, primarily for

the non

- food uses. It is noted, h owever, that label requirements preclude application of dimethoate when bees are actively foraging (an assumption of Tier 1 risk assessment) , thus mitigating acute contact risks for bees foraging in the treated site. Because dimethoate undergoes sy stemic transport in plants, applications prior to bloom could result in exposure of bees via oral routes.

Tier 2 Risk Assessment. No tier 2 (semi

- field) studies were submitted for dimethoate. However, its use as a reference toxicant at 0.53 lb a.i./A sug gest that at least short term risks to bees are possible as a result of foliar spray applications (even residues are allowed to dry prior to bees foraging). Information reviewed on the potential for long

- term effects of dimethoate on brood development

was considered inconclusive.

Tier 3 Risk Assessment. A tier 3 full

- field study with free foraging

bees indicates high mortality and reduced foraging of adult bees shortly after exposure to dried residues on blooming foliage

. Mortality rates and foraging activity appeared to recover to levels similar to controls within 3 to 4 days. However, effects on developing brood were only qualitatively assessed in this study. Therefore, t he potential for long

- term exposure and effects could not

be asse ssed due to limitations in available data.

### Page 6 of 144 

# 1.0 Problem Formulation

As part of the Registration Review process, a detailed Problem Formulation ( DP Barcode

D355609 ) for this risk assessment was published to the docket [Docket ID: EPA

- HQ

- OPP

- 2009

- 0059 ] in December 3, 2008 . The following section summarizes some of the key points of that document and discusses any differences between the analysis outlined previously and the analysis conducted in this risk assessment.



## 1.1 **Nature of Regulatory Action**

Th is risk as sessment is con ducted as part of the Agency’s Registration R eview process for pesticide active ingredients. The Registration Review process was established under the Fo od Quality Protection Act (FQPA 1996 ).



## 1.2 **Stressor Source and Distribution**

1.2.1 Mechanism of A ction

Dimethoate [ O,O

- dimethyl S

- ( N

- methylcarbamoyl methyl)phosphorodithioate; CAS No. 60

- 51

- 5; PC Code 035001 ] , is an insecticide/acaricide belonging to the organophosphate (OP) class of pesticides. The pesticide acts through inhibition of acetylcholinesterase (AChE ) a choline hydrolase. According to Fukuto 1990 AChE is responsible for the rapid hydrolytic degradation

of the neurotransmitter acetylcholine into the inactive products choline and acetic acid

. Acetylcholine is one of a number of physiologically important neurotransmit ers and is involved in the transmission of nerve impulses to effector cells at cholinergic, synaptic, and neuromuscular junctions

. When AChE is inactivated, the enzyme is no longer able to hydrolyze

ac etylcholine and concentration s of neurotransmitter in the junction remains high resulting in

continuous s timulation of the muscle or nerve fiber, resulting eventually in exhaustion and
tetany.

As indicated in the Problem Formulation document, as a phosphorodithioate organophosphate, the chemical is subject to bioactivation into its oxon form (omethoate) similar to other members

of this class. Omethoate was not observed in any of the environmental fate laboratory studies, with the exception of a special study to evaluate the effects of chlorination treatment of water; however, omethoate was observed in the soils of the terrestrial field dissipation studies.

Omethoate has the same mode of action as the parent compound. The rate at which a phosphorodithioate pesticide is transformed to its oxon and the rate at which the oxon is subsequently detoxified can influence toxicity. According to labels for dimethoate, the compound “ has systemic and contact activity against a broad spectrum of piercing, sucking and chewing insects .”



## 1.2.2 Use Characterization

Currently, dimethoate is used for control of a variety of insect pests on a number of fruit, vegetable, grain, and field crops, as well as ornamentals and non

- cropland adjacent to

### Page 7 of 144 

### agricultural fields.

The pesticide is primarily applied as a foliar spray ( using aerial or ground application methods); however, soil and b ark drench uses are registered. Dimethoate is applied in liquid formulations (emulsifiable concentrate, wettable powder or soluble concentrate (liquid)) aerially or by ground methods of appli cations. Dimethoate also has uses on certain trees ( e.g ., Douglas fir, cottonwood, etc. ). Methods of application include ground, aerial and chemigation. Air blast applications are allowed on Douglas fir (seed orchard).

According to the labels, dimetho ate is a IRAC 1 

### Mode of Action Classification G roup 1 (AChE inhibitors, subgroup B (organophosphates) of the insecticide / miticide, to which target pests can develop cross

- resistance when applied with other chemicals within the subgroup consecutively

or repe atedly in the same field and/or in consecutive years. For that reason, it is recommended to

avoid its consecutive use and /or the consecutive use of other group 1B insecticides and to base its use on a comprehensive Integrated Pest Management ( IPM ) program (for example, refer to the label for Dimethoate 4EC).



## 1.2.3 Exposure

Terrestrial wildlife exposure estimates are typically calculated for birds and mammals by emphasizing the dietary exposure route of uptake of pesticide active ingredients. These

exposures are considered to be surrogates for exposures to terrestrial

- phase amphibians and reptiles. For exposures to terrestrial organisms, such as birds and mammals, pesticide residues on food items are estimated based on the assumption that organisms are exposed to pesticide residues as a function of the pesticide use pattern. However, other pathways of exposure may also be important to consider, including the inhalation and drinking water pathways.

Subsequent to the publication of the dimethoate preliminary P roblem Formulation and issuance

of generic data call

- in ( DCI 2 

### ) , EFED developed exposure pathway screening models for inhalation and drinking water which address the potential relevance of these exposure pathways

to birds. The Screening Tool for Inhalation Risk (STIR ; version 1.0 ) and Screening Imbibition Program (SIP 3 

### ; version 1.0 ) evaluate these two pathways of exposure 4



### .

The STIR model was used to calculate an upper

- bound estimate of exposure using dimethoate ’s vapor pressure and molecular weight for v apor phase exposure as well as the maximum application rate and method of application for spray drift. STIR incorporates results from several

1 IRAC. 2014. Insect Resistance Action Committee (IRAC) MoA Classification Scheme. Prepared by IRAC International MoA Working Group. Version 7.3. Issued February 2103. Available on line at: http://www.irac

online.org/documents/moa

- classification/?ext=pdf

2 USEPA. 2010. Dimethoate Generic Data Call In (GDCI

- 035001

- 874). http://w ww.regulations.gov/#!documentDetail;D=EPA

- HQ

- OPP

- 2009

- 0059

- 0022

3 USEPA. 2014. Pesticides: Science and Policy. Terrestrial Models. STIR Version 1.0 (Screening Tool for Inhalation Risk). http://www.epa.gov/oppefed1/models/terrestrial/#stir

4 USEPA. 2014. Pesticides: Science and Policy. Terrestrial Models. SIP Version 1.0 (Screening Imbibition Program). http://www.epa.gov/oppefed1/models/terrestrial/#sip

### Page 8 of 144 

### toxicity studies including acute oral and inhalation rat toxicity endpoints obtained from the “six

pack” of core s tudies, which are a series of six guideline studies of mammals (including acute oral, acute inhalation, acute dermal contact, and others) that are submitted to the Registration Division of the Office of Pesticide Programs for technical and formulated produ cts o f a pesticide (rat oral LD 50 

### = 358 mg/kg bw, MRID 00164219 ; and rat inhalation LC 50 

### > 2 mg/L, MRID

00060719 , respectively) as well as the most sensitive acute oral avian toxicity endpoint

, i.e

., red wing blackbird ( Agelaius phoeniceus ) 5 

### with a median lethal dose for 50% of the birds tested ( LD 50 

### )of 5.4 mg/kg bw ( MRID 00020560 ). Based on the results of the STIR model ( Appendix

4 ), exposure through inhalation of spray drift of the vapor phase of dimethoate was determined to be a potential pathway of concern for all application rates above 0.19 lb a.i./A for avian species on an acute exposure basis for ground sprays

.

Another run of STIR was used to evaluate the potential exposure via volatilization of the transformation product omethoat e, which is also considered by EFED to be of toxicological

relevance to birds and mammals. Toxicit y for omethoate to mammals are available (rat oral

LD 50 

### = 22 mg/kg bw, MRID 46099809; and rat inhalation LC 50 

### = 0.267 mg/L, MRID 46099813

, respectively) as well as the most sensitive acute oral avian toxicity endpoint

, i.e ., b obwhite quail

, ( Colinus virginianus of LD 50 

### = 9.6 mg/kg bw ( MRID 47769703 )

. Based on the results from the

STIR model for vapor

- phase exposure ( Appendix 4) , inhalation of the vapor phase of omethoate is not a potential pathway of concern for avian species on an acute exposure basis.

The inhalation pathway via spray drift of the pesticide is of potential significance to avian taxa for parent dimethoate al one. It is noted however, that this result was indicated for all uses except for succulent peas and other unspecified peas

.

Drinking water was also screened as an exposure route using SIP ; the screening tool was used to calculate an upper

- bound estimate of exposure based on dimethoate’s solubility (39,800 mg/L), the most sensitive acute and chronic avian toxicity endpoints

, i.e ., blackbirds acute oral LD50 of 5.4 mg/kg bw and a bobwhite quail chronic no observed effect concentration (NOAEC) of 4.0 mg/kg die t, respectively

, and the most sensitive acute oral ( LD 50 

### = 358 mg/kg bw ) and chronic oral equivalent mammalian no observed adverse effect level (NOAEL= 0.1 mg/kg diet. Drinking water alone was determined to be a potential pathway of concern for both avian and mammalian species on an acute and chronic exposure basis

.



## 1.3 **Stressors of Concern**

In addition to parent dimethoate , the primary toxic degradate of co ncern for dimethoate is omethoate. Available data indicate that omethoate is as toxic to amphibians as the parent compound (Sparling and Fellars 2007) while data on aquatic invertebrates indicate that they can be considerably more sensitive to omethoate co mpared to the parent compound on an acute exposure basis (Song et al . 1997). Also, omethoate as a major degradate is at least as toxic as the parent to birds. Submitted environmental fate studies for dimethoate do not identify omethoate,

as it does not f orm >10% of residues, indicating that it is not expected to be a major degradate of dimethoate in aquatic and terrestrial environments. However, omethoate has been detected in

5 Body weight of the red wing blackbird obtained from: http://birds.audubon.org/species /redbla3

### Page 9 of 144 

### air, precipitation and surface water samples, demonstrating that it is present in the environment. Furthermore, it has been detected in terrestrial field dissipation studies, as described later in this

assessment. Since laboratory data are not available to estimate the formation and decline of

omethoate from dimethoate

, and omethoate was not detected in any of the laboratory based environmental fate studies, results from the terrestrial field dissipation studies were used to make rough estimate s of aquatic exposures using the Surface Water Concentration Calculator ( SWCC ) (for addition al details, refer to section on Aquatic Modeling Approach below ; see also the

Uncertainties section )

.

The stressors of concern for this assessment include dimethoate and omethoate. Another major degradate observed in some of the fate studies, desmethyldi methoate was found to be much less toxic than the parent compound. Exposures in aquatic habitats will be quantified considering

dimethoate first ( since omethoate was not formed in any of the laboratory degradation studies ) ; however additionally , available data on the formation of omethoate ( from terrestrial field dissipation studies ) is used to bracket potential exposure of aquatic organisms to the oxon degradate. Exposures in terrestrial habitats will consider dimethoate only, since available data indicate similar acute toxicity of omethoate and dimethoate to birds and mammals.

Although previous analyses have indicated that formulated products of dimethoate are less toxic than the technical grade active ingredient (TGAI) , t he assessment will continue to analyze the toxicity of formulated products (including formulations involving more than one active ingredient) and will determine whether any additional formulated products are more toxic than

the TGAI data used for assessing both direct and in direct risks.



## 1.4 **Risk Hypothesis**

For a pesticide to pose an ecological risk, it must reach ecological receptors in biologically significant concentrations. An exposure pathway is the means by which a pesticide moves in the environment from a source to an ecological receptor. For an ecological pathway to be complete, it must have a source, a release mechanism, an environmental transport medium, a point of exposure for ecological receptors, and a feasible route of exposu re.

The risk hypothesis for dimethoate provides a written description of the predicted relati onships

between dimethoate , potential routes of exposure, and the predicted effects for the assessment endpoint. These previous assessments highlighted in the preliminary problem formulation and more recent data serve as a basis for the risk hypothesis and conceptual model developed for current registered uses of dimethoate

.

A r isk hypothes i s descri bes the predicted relationship among the stressor, exposure, and assessment endpoint response along with the rationale for their selection. For dimethoate , th e following ecological risk hypothesis is being employed for this national

- level ecological risk

ass essment:

Dimethoate , when used in accordance with current label s , can result in off

site movement of the compound and its oxon transformation product

### Page 10 of 144 

### (omethoate) via runoff, spray

- drift, and atmospheric transport leading to exposure of non

- target plants a nd animals. M onitoring data indicate frequent detections of dimethoate and its degradate omethoate in surface waters and at sites distant from use area s . Applications to foliar surfaces may serve as a major sou rce of dimethoate exposure to terrestrial and aquatic organi s ms

. This potential exposure pathway may result in adverse effects upon the survival, growth, and reproduction of non

- target organisms. These non

target organisms may include Federally

- listed threatened and endangered species.

The eco systems potentially at risk are often extensive in scope; therefore, it may not be possible to identify specific ecosystems during the development of a nationwide 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 downstream from, the treated field and might include impounded bodies such as ponds, lakes and reservoirs, or flowing waterways such as s treams or rivers. For uses in coastal areas, aquatic habitat also includes marine ecosystems, including estuaries.



# 2.0 Exposure Characterization

**2.1 Use and Usage Information** 

Currently , dimethoate is used for control of a variety of insect pests on a number of fruit, vegetable, grain, and field crops, as well as ornamentals and non

- cropland adjacent to agricultural fields. The pesticide is primarily applied as a foliar spray (using aerial or ground application methods); however, soil and b ark drench uses are registered. Dimethoate is applied in liquid formulations (emulsifiable concentrate, wettable powder or soluble concentrate (liquid)) aerially or by ground methods of applications. Table 2 shows the maximum application rates and maximum number of applica tions for the different crops for dimethoate. It also shows the application methods, pre

- harvest intervals, and for certain crops, the timing of application. As indicated earlier, dimethoate is used on several food crops and ornamentals; however, it also has uses on certain trees ( e.g ., Douglas fir, cottonwood, etc. ). Methods of application include ground, aerial and chemigation. Airblast applications are allowed on Douglas fir (seed orchard)..

### Page 11 of 144 Table 2. Summary of use information for d imethoate, formulated as emulsifiable concentrate (EC) , wettable powder (WP) or soluble concentrate (SC), i.e. , liquid formulations . Assumptions made regarding the use pattern are shaded

Use Maximum Single App.

Rate (lb. a.i./A) Number of Apps. at

Max Rate Maximum

Seasonal App. Rate (lb. a.i./A) Minimum

Interval Between Apps. (days) 1 Application Method

/ T iming of Application Pre

Harvest

Interval (days) Agricultural uncultivated areas (CA) (Noncropland adjacent to vineyards) 1.9 2 3.8 * 180 Groundboom/ Handgun app N/A

Alfalfa , Sainfoin 0.5 1/CC 3/year 1.5 * 30 A or G: B, C, S 10

Asparagus (not allowed in CA and AZ) 0.5 2 * 1 14 A or G: B, C, S/

Postharvest 180

Beans (includes dry beans, excludes cowpeas), Garbanzos (includes chick peas), Lupine 0.5 2 * 1 14 A or G: B, C, S 0

Lentils (some labels allow use in WA) 0.5 2 1 7 A or G: B, C, S 14

Dried peas (ID, OR, WA) 0.5 1* 0.5 N/A A or G: B, S 0 Succulent peas 0.15 6 1 * 0.156 N /A A or G: B, C, S 0 Succulent peas (CA only) 0.16 3* 0.5 14 A or G: B, C, S 0

Succulent peas (ID, OR, WA) 0.5 1* 0.5 N/A A or G: B, C, S 0

Unspecified peas 0.167 1 0.167 N/A A or G: B, C, S 0

Unspecified peas (ID) 0.321;

0.25x2 2 0.5 (ID) 14 A or G: B, S 0

Unspecified peas (WA) 0.323 2 0.67 (WA) 14 A or G: B, S 0
Broccoli, Cauliflower 0.5 3 1.5 7 A or G: B, C, S 7 Brussels sprouts (some labels allow use only in CA) 0.5 3* 1.5 7 A or G: B, C, S 10

Brussels sprouts (some labels allow use only in CA) 1;

0.75x2 2* 1.5 7 G: B, C, S 10

Celery (some labels allow use in FL) 0.5 3 1.5 7 A or G: B, C, S 7

Lettuce (leaf) , Endive

, Swiss chard 0.255 3 0.752 7 A or G: B, C, S 14

Kale 0.5 1 * 0.5 N/A A or G: B, C, S 14

Turnip (greens) 0.255 ; 0.251x7 7 * 1.755 3 A or G: B, C, S 14

Turnip (roots) 0.255 ; 0.251x7 7 * 1.755 3 A or G: B, C, S 14

Mustard greens 0.25 2 * 0.5 9 A or G: B, C, S 14

Cherry (only in ID, MT, OR, UT and WA) 1.35 1 1.35 N/A A or G: B, C, S/

Preharvest and

Postharvest 21

Christmas tree plantation 1 3 * 3 14 A or G: B, C, S N/A

Seed orchard trees 1 1 * 1 N /A A or G: B, C, S, FT N/A Conifers (seed orchard) 1 1 * 1 N/A A or G: B, C, S N/A Douglas fir (seed orchard) 1 1 * 1 (A) N/A A or G: B, C, S N/A Douglas fir (seed orchards) (only in OR and WA) 4.5 (AB) 1 * 4. 5 (AB) N/A G (AB) N/A

Cottonwood (forest/ shelterbelt) 2 3 6 14 A or G: B, C, S N/A

Hybrid cottonwood/poplar plantations (some labels allow use in ID, OR and WA) 2 3 6 10 A or G: B, C, S, SI N/A

### Page 12 of 144 Table 2. Summary of use information for d imethoate, formulated as emulsifiable concentrate (EC) , wettable powder (WP) or soluble concentrate (SC), i.e. , liquid formulations . Assumptions made regarding the use pattern are shaded

Use Maximum Single App.

Rate (lb. a.i./A) Number of Apps. at

Max Rate Maximum

Seasonal App. Rate (lb. a.i./A) Minimum

Interval Between Apps. (days) 1 Application Method

/ T iming of Application Pre

Harvest

Interval (days) Grapefruit, Kumquat, Lemon, Lime, Orange, Pummelo (shaddock), Tangelo, Tangerine (some

labels allow uses in AZ and CA, some disallow some uses in FL, some have no restrictions) 1 1 * 1 N/A A or G: B, C, S, SD,

FT 10

- 15

Citrus, non

- bearing and nursery stock ( o nly in CA and AZ) 0.5 (A) 1 (G)

1 & 1.9+ SD 2 (A)

1 * (G ) 1* ( SD) 1 10 *

N/A

N/A A or G: B, C, S, SD N/A

Grass grown for seed 0.33 3* 1 90 A or G: B, C, S N/A Grass grown for seed (allow use in WA, OR and ID) 0.5 2 * 1 90 A or G: B, C, S N/A

Melon, Watermelon 0.5 2 1 7 A or G: B, C, S 3 Ornamental woody shrubs

and vines 1 3 * 3 14 A or G: B, C, S, SD, drench, soil injection N/A

Ornamental and/or shade trees (some labels disallow uses in CA) 1 3 * 3 14 A or G: B, C, S, drench, drip line app, bark treatment, soil injection N/A

Ornamental herbaceous plants 0.25 6.5+ (SD) 1 0.25 N/A A or G: B, C, S, SD,

drench N/A

Pear (some labels disallow use in CA) 1 1 * 1 N /A A or G: B, C, S 28

Pecans 0.336 1 0.336 N/A A or G: B, C, S 21 Peppers 0.336 5 * 1.67 7 A or G: B, C, S 0

Tomato es 0.5 2 * 1 6 A or G: B, C, S 7

Potatoes 0.5 2 1 7 A or G: B, C, S 0

Field corn or pop corn 0.5 1 * 0.5 NS A or G: B, C, S 28 (grain) 14 (forage)

Cotton 0.5 2 1 14 * A or G: B, C, S 14

Safflower 0.5 1 CC 0.5/cutting 14 A or G: B, C, S 14 Safflower (CA and AZ only) 0.5 1 CC 0.5/cutting 14 A or G: B, C, S 14

Sorghum 0.5 2 1 7 A or G: B, C, S 28 Soybeans 0.5 2 1 7 A or G: B, C, S 21

Wheat , Triticale 0.5 1 0.5 N/A A or G: B, C, S 35 Metfile=meteorological file; NS=Not specified; N/A=does not apply; G=ground; A=aerial, B=broadcast, C=chemigation, S=spray (low or high volume), AB=airblast; SD=soil drench; FT=foliar treatment; SI=soil injection treatment; CC=crop cycle. Assumptions in the table are bolded *Calculated value, based on the number of applications, or the seasonal application rate. +For citrus, the label indicated 1.9 lb a.i./A and for ornamental herbaceous plant (soil drench applications) it said 6.5 lb a.i./A, both appear to be label errors.



### Additionally, data about typical (or average) application rates and average number of

ap plications were provided by BEAD for a number of crops. Table 3 summarizes the average number of applications and application rates for several of the dimethoate agricultural uses. The data is proprietary and it is averaged over the five year period of 2 008

- 2012. Average number of applications and application rates are not available for the non

- agricultural uses of dimethoate.

### Page 13 of 144 Table 3. Average number of applications and application rates for several dimethoate agricultural

crops 1



### Agricultural Crop Average

AI rate 2 

### Average # apps

Alfalfa 0.365 1.1

Almonds 0.625 2.0 Asparagus 0.500 1.5 Beans (Snap, Bush, Pole, String) 0.422 2.2

Broccoli 0.477 1.3 Cabbage 0.412 1.5 Cantaloupes 0.414 1.0

Carrots 0.502 1.0

Cauliflower 0.470 1.7 Celery 0.457 2.2

Cherries 1.202 1.0

Corn 0.302 1.1

Cotton 0.274 1.2

Cucumbers 0.470 1.0 Dry Beans/Peas 0.361 1.1

Garlic 0.500 1.3 Grapefruit 0.499 1.0 Grapes, Raisin 2.001 1.0 Grapes, Table 0.579 1.2

Lemons 1.749 1.1

Lettuce 0.250 1.2

Lima Beans 0.487 1.6

Onions 0.464 1.5 Oranges 0.680 1.1

Peanuts 0.301 1.3 Peas (Fresh/Green/Sweet) 0.293 1.2

Pecans 0.306 1.5 Peppers 0.267 2.6

Potatoes 0.329 1.6 Pumpkins 0.455 1.0 Sorghum (Milo) 0.266 1.0 Soybeans 0.432 1.0 Squash 0.499 4.0

Strawberries 0.408 3.7 Sugar Beets 0.250 2.0

Sunflowers 0.326 1.7

Sweet Corn 0.234 4.0

Tomatoes 0.444 1.3

Watermelons 0.469 2.7 Wheat, Spring 0.244 1.0
Wheat, Winter 0.303 1.0

1 

### Proprietary data averaged 2008

- 2012, provided by BEAD.

2 

### Application rate in units of lb a.i./A.

### Page 14 of 144 

### For dimethoate, there are no spray buffer zone restrictions. One of the label restrictions for dimethoate products is the wind speed limitation. Applications must be done when the wind speed is less than or eq ual to 10 mph. Additionally, for groundboom or aerial applications, the droplet must be medium or coarser according to ASABE 6 

### 572 definition for standard nozzles, or droplet size with volume median diameter (VMD) of 300 μm or greater for spinning atomizer nozzles. The maximum recommended release height is 4 ft above ground or crop canopy for groundboom applications and 10 ft for aerial applications.

According to the labels, dimethoate is a IRAC 7 

### Mode of Action Classification Group 1 (AChE inhibitors, sub group B (organophosphates) of the insecticides / miticides, to which target pests can develop cross

- resistance when applied with other chemicals within the subgroup consecutively or repeatedly in the same field and/or in consecutive years. For that reason, it is recommended to avoid its consecutive use and/or the consecutive use of other group 1B insecticides and to base its use on a comprehensive Integrated Pest Management (IPM) program.

The following environmental hazard statements appear in dimethoate products:

“ 

### ENVIRONMENTAL HAZARDS Do not apply directly to water, or to areas where surface water is present or to intertidal areas below the mean high water mark. Do not contaminate water when disposing of equipment washwater or rinsate.

Dimethoate is known to leach through soil into ground water under certain conditions as a result of label use.

Use of this chemical in areas where soils are permeable, particularly where the water table is shallow, may result in groundwater contamination.

This product may contaminate water through drift of spray in wind.

This product has a high potential for runoff for several days after application.

Poorly draining soils and soils with shallow water tables are more prone to produce runoff that contains this product. A level well

- maintained vegetative buffer strip between areas to which this product is applied and surface water features such as ponds, streams, and springs will reduce the potential for contamination of water from rainfall

- runoff.

Runoff of th is product will be reduced by avoiding applications when rainfall is forecasted to occur within 48 hours.

6 ASABE stands for American Society of Agricultural and Biological Engineers.

7 IRAC. 2014. Insect Resistance Action Committee (IRAC) MoA Classification Scheme. Prepared by IRAC International MoA Working Group. Version 7.3. Issued February 21 03. Available on line at: http://www.irac

online.org/documents/moa

- classification/?ext=pdf

### Page 15 of 144 

### A vegetative filter strip constructed and maintained in accordance with the 2000 Natural Resources Conservation Service publication "Conservation Buf fers to Reduce Pesticide Losses" ( http://www.nrcs.usda.gov/feature/buffers/ ) will significantly reduce the potential for contamination of water from rainfall

- runoff.

This pesticide is highly toxic to bees exposed to direct treatment or residues on blooming crops or weeds. Do not apply this product or allow it to drift to blooming crops or weeds if bees are visiting the treatment area. ”

According to the Screening

- Level Usage Analysis (SLUA), dated September 27, 2013 (Reporting Timeframe: 2004

- 2011) , major agricultural uses for dimethoate (at or above an average of 30,000 lb a.i./year), were: alfalfa, broccoli, corn, cotton, dry beans/peas, oranges, potatoes, soybeans, tomatoes, and wheat. Sources o f the SLUA include d the following :

• USDA

- NASS (United States Department of Agriculture’s National Agricultural Statistics Service)

– pesticide usage data from 2004 to 2011.

• Private pesticide market research

– pesticide usage data from 2004 to 2011.

• Califor nia Department of Pesticide Regulation (DPR) Pesticide Use Reporting (PUR) data for 2004 to 2010.

For most of the crops, the maximum percent crop treated (PCT) is relatively low. From the crops listed above, exceptions include: broccoli (maximum PCT = 55 %), oranges (25%), and tomatoes (40%). For the other crops listed above (with high usage), the maximum PCT is 15%.

### Page 16 of 144 

### Figure 1. Dimethoate Use Intensity by 

### Crop Reporting District (2007

- 2011)

BEAD provided a use intensity map (USEPA 2013b), covering the years 2007

- 2011 ( Figure 1 ). Based on the map in Figure 1 dimethoate has been used all across the continental U.S.



## 2.2 **Environmental Fate and Transport**

Registrant

- submitted data defining the physical, chemical, fate and transport characteristics

associated with dimethoate are summarized in Table 4 . Dimethoate is a highly mobile to mobile (FAO 2000) , generally non

- persistent organophosphate insecticide. M icrobially

- mediated degradation in aerobic soil s appears to be on e of the important fate processes for the dissipation

of dimethoate

. Consistent with laboratory

- based degradation studies, t errestrial d issipation studies indicate that dimethoate rapidly dissipates from soil and foliar surfaces

. It should be

stressed th at in the field, processes other than degradation may also occur ( e.g. , leaching and runoff). Results of fate and transport studies associated with dimethoate are also briefly

described below.

### Page 17 of 144 Table 4 . Summary of physicochemical and environmental fate and transport properties for
parent Dimethoate **

Parameter Value (s) (units) Source Comments

Selected Chemical/Physical Parameters

CAS Chemical Name O,O

- dimethyl S

- [2

- (methylamino)

- 2

- oxoethyl] phosphorodithioate -- --
Molecular Weight 229.25 g mol

-- --
Solubility (2 5 °C) 3 9800 mg/L 43461402

, 48696601 Soluble

Vapor Pressure (2 5 °C) 8.5 x 10

- 6 torr;
1.85 x 10

- 6 torr
Dimethoate lies between ‘non

- volatile’

and ‘intermediate to high volatility’ under

field conditions. 00245601/ 00245604;

48696601 Volatility classified

per USEPA 2010

Henry’s Law constant (2 5 °C) 1.40 x 10

- 11 atm

- m 3 /mol Calculated 2 Estimated from vapor pressure and

water solubility.

Octanol

- Water Partition

C oefficient (K OW ) K OW = 5.06 ( Log K OW = 0.704) 43274001 Hydrophilic

UV/Vis absorption The mean molar absorption coefficient and mean bandwidth for pH 7.10 (at 203.0 ± 0.0 nm) were determined to be

7661 L/mol

- cm and 16.5 nm. 4762 2901

--

No significant absorption was observed above 260 nm, in the UV/Vis spectrum provided in the study. 43276401

--

pH 3.39 in 1% freshly boiled & cooled water 48696601

--
Persistence

Hydrolysis Half

- life [pH 5, 7, 9; ( 23

- 25 °C )] pH 5: 156 d ays pH 7: 68 days pH 9: 4.4 d ays 00159761 Moderately low route of degradation.

Aqueous Photolysis Half

- life (pH 7) 353 days 00159762 Not an important degradation

pathway.

Soil Photolysis Half

- life No significant degradation 43276401 Considered relatively stable

Aerobic Soil Metabolism

Half

- life (25 0 C) Somersham sandy loam 1: 2. 4 d ays Riverside clay loam : 1.68 d ays 3

Middelfield silty clay loam : 1.65 d ays 3 Somersham sandy loam 2: 3.01 d ays 3 42843201

, 46719202 Significant degradation

pathway.

Anaerobic Soil Metabolism

Half

- life Somersham sandy loam: 22 days 42884402 Moderate degradation

pathway.

Aerobic Aquatic Metabolism

Half

- life (25 0 C) 2 North Carolina clay loam: 20.2 days 3 Maryland loamy sand: 16.5 days 3 48945601 Moderate degradation

pathway.

Anaerobic Aquatic

Metabolism Half

- life (25 0 C) 2 North Carolina clay loam: 17.1 days 3 North Dakota loamy sand: 6.78 days 3 48945501 Moderate ly rapid degradation

pathway.

Mobility

Soil Partition Coefficient S and 0.06 mL/ g

- soil 00164959 Based on a column

### Page 18 of 144 Table 4 . Summary of physicochemical and environmental fate and transport properties for
parent Dimethoate **

Parameter Value (s) (units) Source Comments

( K d ) S andy loam: 0.30 mL/ g

- soil

S ilt loam: 0.57 m L / g

- soil

C lay loam: 0.66 mL/g

- soil leaching study.

Mean K d = 0.398 mL/g

- soil

RSD = 68%

Organic Carbon Partition Coefficient ( K OC ) S and 6.7 mL/g OC Sandy loam: 20 mL/g OC Silt loam: 16 mL/g OC Clay loam: 16 mL/g OC 00164959 Based on a column leaching study

. Mean K
oc = 14.7 mL/g OC RSD = 38%

Laboratory Volatility Volatile organics: 2% AR. Mea n

. da ily air

concentratio n : . 1. 29 μ g/ m 3

. V

ol ati lization rate of organic volatiles : 1.0 8x 10

- 4 μg/ c m 2 /h ou r (e xpressed as d imethoate equivalents)

. 43276402 Slightly volatile

Field Dissipation

Terrestrial Field Dissipation

Half

- life CA loamy sand: 11 days CA sandy loam ~ 9 d ays CA sandy loam: ~16 d ays

TX silt loam : ~ 9 d ays NY sandy loam: ~5 days 42884403

, 43388001

, 43388002 --

F ish Bioconcentration

Bioconcentration in Fish (Maximum BCF) Data requirement was waived based on

its low K OW

. -- Not expected to

bioaccumulate

O ther Studies

Effects of chlorination on the degradation of dimethoate Maximum level of omethoate was 23% of the applied at 24 and 48 hours post

treatment. 48041103 Based on the results,

EFED assume s 100% conversion. Foliar Dissipation Half

- life 2.82 d ays ( from 24 values) D291565 Refer to Table 4

RSD=relative standard deviation (coefficient of variation) **This table includes half

- lives for the parent compound only ( i.e.

, it does not

include the parent plus unextracted residues n or omethoate).

1 Note that all chemicals may volatilize to some extent; this classification simply indicates that the volatility potential is intermediate. For classification scheme, see the “ Guidance for Reporting on the Environmental Fate and Transport of the Stressors of Concern in Problem Formulations,” available at : http://www.epa.gov/pesticides/science/efed/ policy_guidance/team_authors/endangered_species_reregistration_workgroup/esa_reporting_fate.

htm#I (USEPA 2010a), accessed July 18, 2014.

2 Calculated using the equation H enry’s L aw C onstant = (V apor P ressure x M olecular W eight ) / (760 x solubility).

3 Half

- lives were adjusted to a standard temperature of 25 ° C from an experimental temperature of 20 ° C using a Q 10 of 2 (USEPA 2010b).



### Omethoate was not reported in laboratory fate studies involving degradation of dimethoate. It was, however, observed in terrestrial field dissipation and foliar dissipation studies. Additionally, it was observed in a chlorination treatment study. Table 5 provides available physicochemical

and environmenta l fate properties available for omethoate

.

### Page 19 of 144 Table 5 . Summary of physicochemical and environmental fate and transport properties of Dimethoate’s ecologically significant transformation product, Omethoate

Parameter Value (s) (units) S ource Comments

Selected Chemical/Physical Parameters

CAS Chemical Name O,O

- dimethyl S

- [2

- (methylamino)

- 2

- oxoethyl] phosphorothioate -- --
Molecular Weight 213.19 g mol EPISUITE v.4.1

-- Solubility 1 x 10 6 mg/L EPISUITE v.4.1 Unspecified temp.

Vapor Pressure (20°C) 2.48 x 10

- 5 torr
Omethoate lies between ‘non

- volatile’ to

‘intermediate to high volatility’ under

field conditions. EPISUITE v.4.1 Volatility classified per USEPA 2010

Henry’s Law constant 4.56 x 10

- 14 atm

- m 3 /mol EPISUITE v.4.1

-- Octanol

- Water Partition

C oefficient (K OW ) K OW = 0.18 (Log K OW =

- 0.74 at 20oC ) EPISUITE v.4.1 Hydrophilic

Persistence

Aerobic Aquatic Metabolism

Half

- life (25 0 C) 1 Netherlands sandy clay loam: 2.7 days 1

Netherlands sand: 1.69 days 1 (Water pH 8.1

- 8.5 could have promoted hydrolysis of omethoate.) 47477303 Significant degradation

pathway.

M obility

Organic Carbon Partition Coefficient ( K OC ) Standard Soil 2.1 low humus sand:

110 mL/g
oc Standard Soil 2.2 high humus loamy

sand: 52.1mL/g
oc Standard Soil 2.3 high humus sandy clay: 174 mL/g
oc 4 7477304 Testing was conducted at a single

concentration.

Soil Partition Coefficient ( K d ) Standard Soil 2.1 low humus sand : 1.05 mL/g

- soil Standard Soil 2.2 high humus loamy sand: 1.26 mL/g

- soil Standard Soil 2.3 high humus sandy clay: 1.98 mL/g

- soil 4 7477304 Testing was conducted at a single

concentration.

1 Half

- lives were adjusted to a standard temperature of 25 ° C from an experimental temperature of 22 ° C using a Q 10 of 2 (USEPA 2010).



### Dimethoate underwent biotic degrad ation relatively rapidly under aerobic conditions, and at

moderate rates in an anaerobic soil, and under aerobic and anaerobic aquatic conditions. Laboratory studies of abiotic degra da tions indicate tha t dimethoate hydrolyses s lower at pH 7 than pH 9 , and it photolyzes slowly in water and on soils. Dimethoate residues o n foliage

showed half

- lives of a few days (for further details, see below)

. Upon chemical appli cation , it can be transported offsite by spray drift and/or surface (dissolved) runoff occurring within a few days to weeks after applications. T he chemical is considered highly mobile . D imethoate shows relatively low persistence in soil. According to the lab els, d imethoate is systemic (it also has contact activity), so in this assessment it is assumed to be taken up by plants and distributed through vegetation and/or root system s . Even though omethoate was not observed in the laboratory soil and sediment met abolism studies, the transformation product was observed in terrestrial field dissipation studies and also form ed upon chlorination during water treatment

. N ote that water chlorination is a pathway that is only relevant to human health risk

, for

additiona l details about th e chlorination study

, see below

.

### Page 20 of 144 

## 2.2.1 Degradation and Metabolism

The primary route of dissipation for dimethoate is degradation in aerobic soil, particularly under

moist conditions. In one aerobic soil metabolism study, dimethoate degraded r apidly, with a

half

- life of 2.4 days. The majority of dimethoate residues in this study were composed of carbon dioxide, accounting for >50% of total residues by D ay 7 of the test and approximately 75% by

D ay 181. Two non

- volatile degradates, O

- desmethyl dimethoate and dimethylthiophosphoric

acid (these two degradates are not oxons) , were identified, but were present at less than 2% of the applied radioactivity during the aerobic soil metabolism study. In three additional aerobic

soils conducted at 20 ° C in which degradates were not looked for ( since the study used cold material) , dimethoate degraded with temperature

- adjusted (25 ° C , using a Q 10 

### of 2 ) half

- lives of

1.65

- 3.01 days. Although not as rapidly as under aerobic conditions, dimethoate degrade s und er anaerobic soil conditions (half

- life of ca. 22 days), generating the major no n

- volatile degradate,

O

- desmethyl dimethoate.

Dimethoate hydrolyzes very slowly at pH’s 5 and 7 (half

- lives of 156 and 68 days, respectively), but degrades rapidly under alka line conditions to O

- desmethyldimethoate and dimethylthio

phosphoric acid (half

- life of 4.4 days at pH 9). O

- desmethyldimethoate was detected at all pH levels (maxim a 12%, 22% and 62% of the applied, respectively), while dimethylthiophosphoric

acid was a major degradate only at pH 9, with a maximum of 36%.

Under aerobic aquatic conditions, dimethoate degraded in two sediment systems with

temperature

- corrected ( from 20 to 25oC , using a Q 10 

### of 2 ) half

- lives of 16.5

- 20.2 days. The major degradate was O

- desm ethyldimethoate. Under anaerobic aquatic metabolism conditions, it degraded with slightly lower temperature

- corrected ( from 20 to 25oC , using a Q 10 

### of 2 ) half

lives of 6.78

- 17.1 days. The major degradate was also O

- desmethyldimethoate.

Data available ab out the aerobic aquatic metabolism of omethoate indicate that it degraded with

temperature

- adjusted ( from 22 to 25oC , using a Q 10 

### of 2 ) half

- lives of 1.69

- 2.7 days. The major degradate observed was O

- methyl

- S

- (2

- methylamino

- 2

- oxoethyl) thiophosphate.

Dimethoate photodegrades slowly in water (half

- life of 353 days), and is relatively stable to photodegradation on the soil surface

.



## 2.2.2 Transport

Dimethoate is mobile to highly mobile in soil s (FAO 2000)

. For this chemical, sorption appeared to be correla ted with organic carbon , making K OC 

### is a better model of sorption than K d 

### (the coefficient of variation for K OC 

### was smaller than for K d 

### ). In a soil column leaching study,

72

- 100% of applied radioactivity was eluted from the columns (loam, silt loam, sandy loam, and sand). Calculated soil dissociation constant ( K d 

### ) values based on these column studies ranged from 0.06 L/kg for sand to 0.66 L/kg for clay loam. Organic carbon partition coefficients ( K oc 

### )

value s were in the range of 6.7 mL/g
oc 

### for a sand to 20 mL/g oc 

### for a sandy loam. Degradate mobility has not been well defined, except for omethoate, for which analysis was performed at a single concentration. In three soils, the K d 

### values were 1.05

- 1.98 L/kg and K
oc 

### ’s were 52.1

- 174

### Page 21 of 144 

### L/k g oc 

### .

Volatilization of dimethoate from the soil surface is not expected to be a significant route of dissipation , compared to metabolism . In a study measuring the volatility of dimethoate from the soil surface, 2.7% of the applied radioactivity had volatilized by 30 days, 0.7% of which was

CO 2 

### . The majority of the radioactivity (83%) was extracted from the soil and most of this (93.2%) was dimethoate. Based on the Henry’s Law Constant ( 1.40 x 10

- 11 

### atm

- m 3 

### /mol)

, volatilization from moist soil or water will not be a signific ant route of dissipation for the parent compound. However, the degradate omethoate has been detected in both air and precipitation in

California (refer to section on monitoring

, reference: Majewski et al . 2006 ) , indicating that

omethoate may be transporte d in the atmosphere. Based on a vapor pressure of 2.48 x 10

- 5 

### torr, it is not expected to volatilize from dry soil, but omethoate should exist in both the vapor and particulate phases in the atmosphere.



## 2.2.3 Terrestrial Field Dissipation

The results of five terrestrial field studies indicate that dimethoate dissipates with half

- lives ranging from <5 to 16 days when applied post

- emergence to green beans, grapes, and bare ground in California, grain sorghum in Texas, and bare ground in New York

. These results a re reasonably consistent with those that might be expected from the laboratory studies, although the persistence is somewhat longer in the field studies. Generally, factors that could influence the

half

- lives in the field could include the temperature, rai nfall, viability of the soils, sunlight intensity, soil moisture, pH, and others. When detected, dimethoate was mostly in the top layer of soil (0

- 6”), with some detections below 6”. Omethoate was found under field conditions, although it was not detected in the laboratory studies.

Omethoate was detected in the top layer (0

- 6”) of soil in all five field dissipation studies, at amounts ranging from <1 to 24% of the total residues detected in that layer (note: the 24% level was observed only in one repli cate of only one of the field studies) . In the California bare ground study, omethoate was found through D ay 159 of the study. Omethoate is also formed

du ring drinking water treatment using oxidizing agents such as chlorine , although this formation pathway is only important for human health exposure

.



## 2.2.4 Bioaccumulation

The data requirement for a bioaccumulation in fish study was waived because dimethoate has a octanol/water partition coefficient (K ow 

### ) lower than 1000

. Therefo re, bioaccumulation of dimethoate by aquatic organisms is not considered an exposure pathway of concern.



## 2.2.5 Drinking Water Treatment Study

To determine the extent to which the parent and its omethoate transformation product may be present in treated drinkin g water, c hlorinated deionized laboratory water (free chlorine [Cl 2 

### ]

concentration 1.0 ± 0.4 mg/L), at a pH of 6.7, was treated with dimethoate at a nominal concentration of 30.0 μg/L and the solution was maintained at 20 0 C for up to 72 h ou rs (3 days).

Th e pH of the solutions ranged from 6.36 to 6.75. Samples were routinely taken in duplicates

### Page 22 of 144 

### quenched with sodium thiosulfate to prevent further residue degradation, and monitored for contents of dimethoate and omethoate. Immediately after treatment, dimet hoate concentrations ranged from 6.58 to 10.6 μg/L (22

- 34% of the applied) ; afterwards,

. d imethoate was not detected throughout the remainder of the sampling period. Omethoate however, was detected in all the samples at concentrations ranging from 11

- 12% of the applied immediately after treatment, to

13

- 23% of the applied in all subsequent intervals. Concentration appeared to be maintained at close to 20% of the applied at and after 2 h ou rs post

- treatment. Formation of omethoate upon chlorination is not considered a relevant exposure pathway for ecological risk assessments; however, it is important for human health exposure and risk assessment.



## 2.2.6 Foliar Dissipation

Multiple foliar dissipation studies are ava ilable for dimethoate and were evaluated previously (DP Barcode D291 607 ; note that these are not dislodgeable foliar residue studies ). A summary of results is provided in Table 6

. The upper 90 percent confidence boun d on the mean foliar dissipation half

- life value (over the 29 values available) is 2.82 days. This value was used in models to estimate terrestrial ( i.e., T

- REX ) and aquatic exposure ( i.e.

, SWCC )

.

A study (MRID 46486401) provided information on the degradation of dimethoate, and the formation and decline of omethoate on ground

- level vegetation and canopy arthropods in a mandarin orchard in Spain. The half

- life of dimethoate was found to be 1.7 days on the vegetation and 0.86 days on the canopy arthropods. Using a kinetics model that assumed that 100% of the dimethoate formed omethoate, the degradation half

- life of omethoate was determined to be 0.33 days on the foliage and 0.30 days on the arthropod s. For plant materials, these data are within the range of half

- lives seen below for the parent. No other measurements

exist for omethoat e on plant material or either omethoate or dimethoate in arthropods ( source: DP Barcode D323951+).

Table 6

. Foliar dissipation data for dimethoate ( Source of table: DP Barcode D323951+)

Crop Reference Comment T 1⁄2 

### (days)

A pple Pree et al . 1976 5.4

A lfalfa Shaw and Ziener, 1964 1.4

A pple Pree et al ., 1976 7.2

A pple Pree et al ., 1976 80 mm rain 2.6

A pple Pree et al ., 1976 11 mm rain 4.1

B irdsfoot trefoil Shaw and Ziener, 1966 2.1

S orghum Dorough et al . 1966 4

L adino clover Shaw and Ziener, 1966 1.8

L emon Bellows et al ., 1985 2.2

C oastal bermuda

G rass Beck et al ., 1966 22.6 mm rain 3.1

C orn Beck et al

., 1966 90.2 mm rain 2.7

S oybeans Beck et al ., 1966 0 mm rain 0.9

B eet Vail et al ., 1967 0 mm rain 2.5

B roccoli Nelson et al ., 1966 3

C abbage Nelson et al ., 1966 1.7

C hard Vail et al ., 1967 5.1 mm rain 2.6

### Page 23 of 144 C ollards Nelson et al ., 1966 2.5

L eaf lettuce Vail et al ., 1967 5.1 mm rain 2.8

L ima beans Nelson et al ., 1966 2.2

S nap beans Nelson et al ., 1966 2.6

S oybeans Nelson et al ., 1966 1.2

T urnip Vail et al ., 1967 83.8 mm rain 3.1

T urnip Nelson et al ., 1966 3.2

W heat Lee and Westcott, 1981 2.5

W heat MRID 466780

- 01 8.0

W heat MRID 466780

- 01 16.3

W heat MRID 466780

- 05 3.6

W heat MRID 466780

- 05 6.6

W heat MRID 466780

- 10 15.6



## 2.3 **Aquatic Exposure**  **Modeling Approach**

A brief description of the aquatic models used in this risk assessment follows. Additional information about these models is provided in the Agency’s website at http://www.epa.gov/pesticides/science/models_pg.htm#aquatic

. For agricultural and certain non

agricultural uses, exposure concentrations for surface drinking waters assessments are estimated based on EFED’s Tier II aquatic model Pesticide Root Zone Model coupled with the Variable Volume Water body Model ( PRZM/VVWM ) . A graphical user interface Surface Water Concentration Calculator (SWCC v.1.10 6; May 6, 2014), developed by the EPA, was used to facilitate inputting chemical and use specific parameters into the appropriate input files and chemical files, which used PRZM3 and the Exposure Analysis Model System ( EXAMS ); the SWCC replaced the older PRZM/EXAM ( PE5 ) shell (November 2006),. The SWCC estimates pesticide concentrations in water bodies that result fr om pesticide applications to land. The calculator was designed for regulatory applications as applied in the Office of Pesticide Programs, USEPA, as well as Health Canada’ Pest Management Regulatory Agency ( PMRA )

. The calculator uses the PRZM ( v5.0+, Ma y 6, 2014) and the VVWM ( May 6, 2014 ; a replacement for the older EXAMS model). The PRZM field or orchard crop scenario is the basic file which describes the local or regional climatological information, soil hydrology, soil characteristics, crop characte ristics, and the pesticide properties necessary to determine pesticide loadings to surface water. This basic file constitutes the first part of the “exposure scenario.” It simulates the processes in the agricultural field, such as runoff and erosion, on a daily time step. The runoff and erosion flux output data from PRZM are used as chemical loadings to the VVWM, which simulates surface water, in order to generate estimated environmental

concentrations ( E EC s )

.

The VVWM is conceptually similar to the c urrent EXAMS

- based model in that both are 2

- compartment models driven by first

- order processes. It simulates theEPA standard water bodies ( i.e ., farm pond and/or index reservoir) but with greater efficiency and flexibility for incorporation into a user in terface. The VVWM can also allow for variations in water body volume on a daily basis due to runoff, precipitation, and evaporation (note that for the standard pond, this feature is not used and the volume is held constant) . Temperature, wind speeds, and pesticide degradatio, sediment sorption and mass trasnsfer between water column and benthic

### Page 24 of 144 

### compartments are also simulated on a daily basis . E E Cs were determined using the standard pond which is expected to represent vulnerable surface water scenario for the VVWM component of the modeling exercise.

Table 7 provides a summary of chemical input parameters for dimethoate in the SWCC, to estimate surface waters EECs. Input values were based on the EFED Guidance on Input Parameters v.2.1, dated October 22, 2009 and approved November 10, 2009 (USEPA 2009 8 

### ) Application information is summarized in Tables 2 and 3 while the dates of first application are given in Tables 9 and 1 0 . For each crop, the meteorological file u sed is the standard one suggested for the modeled scenario. Even though dimethoate shows high mobility, it was found that there was better correlation of binding with organic carbon (OC); thus, the average K OC 

### was employed in the model ( i.e. , the coeffici ent of variation was higher for the K d 

### ’s than for the

K OC 

### ’s). For the aerobic soil metabolism, there were four available half

- lives from two studies. The model input value was the 90 percent upper confidence limit on the mean half

- life. Similarly, for a erobic and anaerobic aquatic metabolism, two values were available (for each of these parameter), and the 90 percent upper confidence limit on the mean half

- life served as input. The hydrolysis half

- life for the parent at pH 7 was entered (68 days). Fina lly, a foliar dissipation

half

- life (2.82 days) was derived in a previous review and used in the model (see Table 6 ).

Table 7 . Input parameters utilized in the surface water concentration calculator (SWCC) for

dimethoate

Parameter (units) Value(s) 1 Sources Comments

Output File Name Dimethoate

--- --- Chemical Name Dimethoate Label

---

Application Rate Kg a.i./ha

Refer to Table 9 ( lb a.i./A )
( Refer to Table 9 ) Maximum allowed by the

label and/or supplemental

labels ; focus was placed on crops with the highest

seasonal rates. Number of Applications

Allowed Refer to Table 9 Maximum allowed by

the labels. ---

Interval between Applications (days) Refer to Table 9 Minimum allowed by

the labels. ---
Crop Names and Days of Application (day

- month) Refer to Table 9 Labels

---

PRZM Scenario and

Metfile As suggested by the shell for

the SWCC. SWCC

---

K OC (ml/g oc ) 14.7 00164959 Represents the mean K OC value among four values ranging from 6.7 to 20 ml/g oc ; the K OC model was utilized because it represents the mobility of dimethoate better

than K d . Binding appears to

be correlated with OC.

8 USEPA. 2009. Revision on Input Parameter Guidance. Memorandum from Donald Bra dy, Division Director. Dated November 10, 2009. Available on line at: http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.pdf

### Page 25 of 144 Table 7 . Input parameters utilized in the surface water concentration calculator (SWCC) for

dimethoate

Parameter (units) Value(s) 1 Sources Comments

Aerobic Soil Metabolism (days)

= 2.71 42843201, 46719202 90 percen t upper confidence

limit on the mean half

- life

value: four values are available: 2.4, 1.68, 1.65, 3.01 days at 25°C; mean = 2.185 days, std. dev. = 0.6501 days, n = 4, t 90,n

- 1 = 1.638.

Method of Application Ground

, aerial or airblast (R efer to Table 9 ) Labels

---

Buffer Zone (ft.) 0 Labels

--- Application Efficiency (fraction) 0.99 ground

, 0.95 aerial --- ---

Spray Drift (fraction) 0.062 ground apps; 0.125 for aerial apps; 0.042 for airblast apps. AgDRIFT v. 2.1.1;

USEPA 2013 ---

Solubility in Water (ppm) 39

, 800 mg/L 43461402 Solubility at 25oC

.

Aerobic Aquatic Metabolism (days)

= 24.0 48945601 90 percent upper confidence

limit on the mean half

- life

value: two values are available: 20.2, 16.5 days at 25°C; mean = 18.35 days, std. dev. = 2.616 days, n = 2, t 90,n

- 1 = 3.078.

Anaerobic Aquatic Metabolism (days)

= 27.8 48945501 90 percent upper confidence

limit on the mean half

- life

value: two values are available: 17.1, 6.78 days at 25°C; mean = 11.94 days, std. dev. = 7.297 days, n = 2, t 90,n

- 1 = 3.078. Hydrolysi s (days) 0 00159761 At pH 7. Aqueous Photolysis (days) 353 00159762

--- Aqueous Photolysis Reference Latitude (o) 34 00159762 Envelope reference latitudes

include 34o for Arizona Molecular Weight (g/mole) 229.25 EPISUITE v.4.1 2

--- Vapor Pressure (torr) 1.85 x 10

- 6 48696601 VP at 25oC

Field Size EPA pond (eco. effects)

--- -- Incorporation Depth (cm) 0.0 Labels

---

CAM (Chemical Application Method) Foliar, except for soil drench applications, which are ground. Labels

---

IPSCND (Condition for disposition of pesticide remaining on foliage after harvest) 1 (default value) Labels 1 = pesticide remaining on foliage is converted to surface application to the top soil layer

PLDKRT, Foliar half

- life (days) 2.82 Refer to Table 6 90 percent upper confidence

limit on the mean half

- life

value out of 29 values

1 Data were selected according to EFED Guidance on Input Parameters v.2.1, dated October 22, 2009 and approved November 10, 200 9 (USEPA 2009).

2 USEPA. 2014. Estimation Program Interface (EPI) Suite. http://www.epa.gov/opptintr/exposure/pubs/episuite.htm



### After further consideration, additional refinements were included and are summarized in Table

8 . For the refinements, typical (average) application information was utilized, and a refined value for spray drift was used, based on the droplet size stated in the labels (medium or coarse). t t t s

n input n



### = + −
1 2 90 1

/ , 

### ( )



### t t t s

n input n



### = + −
1 2 90 1

/ , 

### ( )

t t t s

n input n



### = + −
1 2 90 1

/ , 

### ( )

### Page 26 of 144 

### Typical (average) use information is provided in Table 3 . No typical rate information was

available for the non

- agricultural uses of dimethoate.

Table 8 . Additional refinements to the input parameters utilized in the the surface water concentration calculator (SWCC) for dimethoate, for use with typical application rates and numbers of application

Parameter (units) Value(s) 1 Sources Comments

Application Rate Kg a.i./ha

Refer to Table 16 ( lb a.i./A )

Refer to Table 16 ---

Number of Applications

Allowed Refer to Table 16 Average number of

apps

. ---

Interval between Applications (days) Refer to Table 16 Minimum allowed by

the labels. ---
Crop Names and Days of Application (day

- month) Refer to Table 16 Labels Whenever possible, the same date of application used from

Table 15 was used with the typical rate (see Table 1 6 ). Spray Drift (fraction) 0.089 for aerial apps AgDRIFT v. 2.1.1;

USEPA 2013 Value for medium/coarse droplets 1

1 Guidance on Modeling Offsite Deposition of Pesticides via Spray Drift for Ecological and Drinking Water Assessments, dated December 19, 2013 and approved December 20, 2013 (USEPA 2013a)



### A set of runs was performed for a subgroup of scenarios, using the half

- lives that included the

u nextracted residues (UERs). These runs would provide upper

- bound estimates of the EECs, assuming that all the UERs are potentially residues of toxicological concern. Table 9 shows the input parameters for such runs.

Table 9 . Input parameters utilized in the surface water concentration calculator (SWCC) for dimethoate plus the unextracted residues

Parameter (units) Value(s) 1 Sources Comments

Aerobic Soil Metabolism (days)

= 147 42843201, 46719202 Only a single study tracked the radioactivity associated

with dimethoate and residues. For the study, the half

- life associated to dimethoate plus UERs was 49 days at 25°C. The input value is three times

as much to account for variability associated to lack

of additional studies.

Aerobic Aquatic

Met abolism (days)

= 47.6 48945601 90 percent upper confidence

limit on the mean half

- life

value: two values are

available: 39.3 days (SFO),

53.1 days (IORE) at 20°C ; temperature corrected half

lives are 27.8 and 37.5 days at 25°C, respectively; mean = 32.65 days, std. dev. = 6.86 days, n = 2, t 90,n

- 1 = 3.078. 

### t t t s

n input n



### = + −
1 2 90 1

/ , 

### ( )

t t t s

n input n



### = + −
1 2 90 1

/ , 

### ( )

### Page 27 of 144 Table 9 . Input parameters utilized in the surface water concentration calculator (SWCC) for dimethoate plus the unextracted residues

Parameter (units) Value(s) 1 Sources Comments

Anaerobic Aquatic Metabolism (days)

= 37.8 48945501 90 percent upper confidence

limit on the mean half

- life

value: two values are

available: 29.5 days (SFO),

21.5 days (IORE) at 20°C ; temperature corrected half

lives are 20.9 and 15.2 days at 25°C, respectively; mean = 25.50 days, std. dev. = 5.66 days, n = 2, t 90,n

- 1 = 3.078.

1 Data were selected according to EFED Guidance on Input Parameters v.2.1, dated October 22, 2009 and approved November 10, 2009 (USEPA 2009).



### None of the environmental fate laboratory studies shows omethoate in significant amounts (≥10% AR); however, it was previously estimated that a maximum of 24% of the total residues in replicate 2 of the terrestrial field dissipation study conducted in California bareground was omethoate. In order to obtain a rough estimate of the likely residues of omethoate, this percentage was used to calculate the application rate. The crops that yielded the highest EECs ( i.e ., FL cit rus and CA cole crops) were modeled under the assumptions for omethoate presented

in Table 1 0 . Since omethoate was not observed in the aquatic metabolism studies in significant amounts, omethoate drift was assumed to be negligible and the chemical was ass umed to be soil applied.

Table 1 0 . Input parameters utilized in the surface water concentration calculator (SWCC)

for omethoate

Parameter (units) Value(s) 1 Sources Comments

Output File Name O methoate

--- --- Chemical Name O methoate Label

---

Application Rate Kg a.i./ha
CA cole crops 0.202

FL citrus 0.269 ( lb a.i./A )

0.75 x 24/100 = 0.18

1.0 x 24/100 = 0.24 Maximum allowed by the

label. Residues of omethoate were a rough estimate from

the maximum observed in the terrestrial field dissipation study. Number of Applications

Allowed CA cole crops 2

FL citrus 1 Maximum allowed by

the labels. ---

Interval between Applications (days) CA cole crops 7

FL citrus N/A Minimum allowed by

the labels. ---
Crop Names and Days of Application (day

- month) CA cole crops 18

- 01

FL citrus 01

- 06 Labels Crops that yielded the highest

EECs for dimethoate

PRZM Scenario and

Metfile As suggested by the shell for

the SWCC. SWCC

---

K d (ml/g) 1.43 47477304 Represents the mean K d value

among three values ranging

from 1.05 to 1.98 ml/g; the K d model was utilized because it represents the mobility of

omethoate better than K OC

. Binding does not appear to be

correlated with OC. 

### t t t s

n input n



### = + −
1 2 90 1

/ , 

### ( )

### Page 28 of 144 Table 1 0 . Input parameters utilized in the surface water concentration calculator (SWCC)

for omethoate

Parameter (units) Value(s) 1 Sources Comments

Aerobic Soil Metabolism (days) 3.75 No data available, use

47477303 In the absence of data,

assumed to be similar to the aerobic aquatic metabolism input value (see below).

Method of Application A erial (but soil applied) Labels Omethoate was observed only

in the terrestrial field

dissi pation.
Buffer Zone (ft.) 0 Labels

--- Application Efficiency (fraction) 1.00 soil applied

--- ---

Spray Drift (fraction) 0.00 (no drift)

--- It is assumed to be formed in soils, not in water. Solubility in Water (ppm) 1 x 10 6 EPISUITE v.4.1

---

Aerobic Aquatic Metabolism (days)

= 3.75 47477303 90 percent upper confidence

limit on the mean half

- life

value: two values are

available: 1.69

, 2.7 days at 25°C; mean = 2.195 days, std.

dev. = 0.714 days, n = 2, t 90,n

- 1 = 3.078. Anaerobic Aquatic Metabolism (days) 0 No data available Assume stable.

Hydrolysis (days) 0 No data available Assume stable. Aqueous Photolysis (days) 0 No data available Assume stable. Aqueous Photolysis Reference Latitude (o) 40 No data available Assumed reference latitude.

Molecular Weight (g/mole) 213.19 EPISUITE v.4.1

--- Vapor Pressure (torr) 2.48 x 10

- 5 EPISUITE v.4.1

--- Field Size EPA pond (eco. effects)

--- Incorporation Depth (cm) 0.0 Labels

--- CAM (Chemical Application Method) Ground Labels

---

IPSCND (Condition for disposition of pesticide remaining on foliage after harvest) Surface applied Labels

---

PLDKRT, Foliar half

- life (days) 2.82 Refer to Table 4 90 percent upper confidence

limit on the mean of the 29

available half

- life value s

. Assume d to be similar to

dimethoate.

1 Data were selected according to EFED Guidance on Input Parameters v.2.1, dated October 22, 2009 and approved November 10, 200 9 (USEPA 2009).



### A summary of dimethoate modeled results related to the maximum application rate is presented

in Table 1 1

. Table 1 2 shows a summary of modeled dimethoate EECs for the typical (average) application rates provided by BEAD. Table 1 3 summarizes EECs based on the maximum application rate and those crops that yielded the highest EECs among the agricultural and non

agricultural crops using half

- lives that included dimethoate plus the unextracted residues (UERs). Using the typical application rate, the crop that yielded the highest EECs was run using the half

lives for the total toxic residues, dimethoate plus the UERs ( Table 1 4 ). t t t s

n input n



### = + −
1 2 90 1

/ , 

### ( )

### Page 29 of 144 Table 1 1 . Water column estimated environmental concentrations (EECs) in μg/L for dimethoate uses in the US, using the maximum application rate 1

Scenario (bold font)/ Crops/Uses Represented App

Method Date of

First Application (dd

- mm) App

Rate kg a.i./A (lb a.i./A) Number

of Apps App
Interval

(days) Water Column

Peak

EEC (μg/L) 21

- day

average

EEC (μg/L) 60

- day

average

EEC (μg/L)

03_ MN alfalfa/ Alfalfa, Sai n foin Aerial 20

- 05 0.560 ( 0.5 ) 1/CC 3/year 30 8.57 6.41 4.99

05_ CA cole crops/ Brussels
sprouts (ground) Ground 18

- 01 0.841 (0.75) 2 7 23.2 20.9 15.4

10_ WA orchards/ Cherry (only in ID, MT, OR, UT and WA) Aerial 15

- 11 (post

harvest) 1.51 ( 1.35 ) 1 N/A 9.44 7.97 6.08

12_ OR Xmas trees/ Douglas fir (seed orchards) (only in OR and WA) Airblast 01

- 06 5.04 (4.5) 1 N/A 10.6 8.65 5.74

14_ OR Xmas trees/ Hybrid cottonwood/poplar plantations (some labels allow certain use s in ID, OR and WA) Aerial 01

- 06 2.24 ( 2 ) 3 10 34.1 26.7 20.2

15_ CA nursery/ Citrus, non

bearing and nursery stock ( o nly in CA and AZ) Soil drench 01

- 06 2.13 ( 1.9 ) 1 N/A 6.60 5.07 3.28

17_ OR nursery/ Ornamental woody shrubs and vines ; Ornamental and/or shade trees Aerial 01

- 06 1.12 ( 1 ) 3 14 21.2 17.6 14.1

20_ FL peppers/ Peppers Aerial 20

- 10 0.377 ( 0.336 ) 5 7 22.2 17.6 13.1

23_MS Cotton / Cotton Aerial 20

- 07 0.5 60 (0.5) 2 14 9.71 6.74 4.48

2 6

_ FL citrus / Grapefruit, Kumquat, Lemon, Lime, Orange, Pummelo (shaddock), Tangelo, Tangerine Aerial 01

- 06 1 .121 (1) 1 N/A 22.1 14.7 8.21

`1 All EECs were rounded to three significant figures.



### Table 1 2 . Water column estimated environmental concentrations (EECs) in μg/L for dimethoate uses in the U.S. using typical application rates 1

Scenario (bold font)/ Crops/Uses Represented App

Method Date of

First Application (dd

- mm) Aver. App Rate kg a.i./A (lb a.i./A) 1 No. of Apps (aver. no. of apps) 1 App

Interval (days) Water Column

Peak

EEC (μg/L) 21

- day

average

EEC (μg/L) 60

- day

average

EEC (μg/L)

03c_ MN alfalfa/ Alfalfa Aerial 20

- 05 0.409 (0.365) 1 (1.1) N/A 2.76 2.23 1.49

04b_CA cole crops/ Broccoli Aerial 25

- 01 0.535 (0.477) 1 (1.3) N/A 7.69 6.33 4.45

10c_WA orchards/ Cherry (only in ID, MT, OR, UT and WA) Aerial 15

- 11 (post

harvest) 1.35 (1.202) 1 (1.0) N/A 6.01 5.08 3.88

20b_FL peppers/ Peppers Aerial 20

- 10 0.299 (0.267) 3 (2.6) 7 16.4 11.5 8.46

23c_MS Cotton / Cotton Aerial 20

- 07 0.307 (0.274) 1 (1.2) N/A 3.69 2.58 1.44

2 6b

_ FL citrus / Grapefruit, Kumquat, Lemon, Lime, Orange, Pummelo (shaddock), Tangelo, Tangerine Aerial 01

- 06 0.546 (0.487) 1 (1.1) N/A 9.89 6.59 3.64

1 All EECs were rounded to three significant figures. Average numbers of applications & application rates for the agricultural crops were provided by BEAD and represent data from 2008

- 2012.

### Page 30 of 144 Table 1 3 . Water column estimated environmental concentrations (EECs) in μg/L for dimethoate uses in the U.S. Special runs including dimethoate and the unextracted residues. 1

Scenario (bold font)/ Crops/Uses Represented App

Method Date of

First Application (dd

- mm) App

Rate kg a.i./A (lb a.i./A) Number

of Apps App
Interval

(days) Water Column

Peak

EEC (μg/L) 21

- day

average

EEC (μg/L) 60

- day

average

EEC (μg/L)

05b_ CA cole crops/ Brussels
sprouts (ground) Ground 18

- 01 0.841 (0.75) 2 7 31.7 27.2 20.7

14b_ OR Xmas trees/ Hybrid cottonwood/poplar plantations (some labels allow certain use s in ID, OR and WA) Aerial 01

- 06 2.24 ( 2 ) 3 10 36.0 30.2 23.8

1 All EECs were rounded to three significant figures. These runs represent the crops with the highest EECs among the agricultu ral and non

- agricultural crops.



### Table 1 4 . Water column estimated environmental concentrations (EECs) in μg/L for dimethoate uses in the U.S. using typical application rates. Special run including dimethoate and the unextracted residues

. 1

Scenario (bold font)/ Crops/Uses Represented App

Method Date of

First Application (dd

- mm) Aver. App Rate kg a.i./A (lb a.i./A) 1 No. of Apps

Modeled (aver. no. of apps) 1 App

Interval (days) Water Column

Peak

EEC (μg/L) 21

- day

average

EEC (μg/L) 60

- day

average

EEC (μg/L)

2 6c

_ FL citrus / Grapefruit, Kumquat, Lemon, Lime, Orange, Pummelo (shaddock), Tangelo, Tangerine Aerial 01

- 06 0.546 (0.487) 1 (1.1) N/A 12.1 9.47 6.15

1 All EECs were rounded to three significant figures. Average numbers of applications & application rates for the agricultural crop were provided by BEAD and
represent data from 2008

- 2012

.



### Special runs were performed for omethoate, using the assumptions outlined in Table 1 0 (the most critical assumption is the 24% formation of omethoate, based on one terrestrial field dissipation study). EECs are provided in Table 1 5

.

Table 1 5 . Water co lumn estimated environmental concentrations (EECs) in μg/L for omethoate due to

dimethoate uses in the U.S. 1

Scenario (bold font)/ Crops/Uses Represented App

Method Date of

First Application (dd

- mm) App

Rate kg a.i./A (lb a.i./A) Number

of Apps App
Interval

(days) Water Column

Peak

EEC (μg/L) 21

- day

average

EEC (μg/L) 60

- day

average

EEC (μg/L)

05_ CA cole crops/ Brussels
sprouts (ground) Ground 18

- 01 0.202 (0.18) 2 7 3.70 2.33 1.19

2 6

_ FL citrus / Grapefruit, Kumquat, Lemon, Lime, Orange, Pummelo (shaddock), Tangelo, Tangerine Aerial 01

- 06 0.269 (0.24) 1 N/A 3.40 0.856 0.305

1 All EECs were rounded to three significant figures.

### Page 31 of 144 

## 2.4 **Monitoring**

The technical registrant (Cheminova, Inc.) submitted a summary of available monitoring data (MRID 49178403). It provides data from 2001 from two sources: the USDA's Agricultural Marketing Service (AMS) Pesticide Data Program (PDP) (note that this monitori ng pertains only to drinking water sources), and U.S. Geological Survey’s (USGS) National Water

- Quality Assessment Program (NAWQA) (see additional details below). A previous review provides a summary of monitoring data from early years (Jones 2005, DP Bar code D291603).



## 2.4.1 Agricultural Marketing Service (AMS) Pesticide Data Program (PDP) Monitoring (2001

- 2011)

The U .S. Department of Agriculture’s (U SDA ) Agricultural Marketing Service (AMS) Pesticide Data Program ( PDP) has conducted monitoring of a total of 9209 samples tested for dimethoate since 2001 to 2011 (surface, ground and bottled water). EFED added to the summary 253 samples taken in 2012 (the last year available online) (USDA, 2014). Except for the groundwater samples, sites selected must be i n community water systems where surface water is the primary source of drinking water, and located in heavy agriculture sites (not further characterized), where the target pesticides have been applied (USDA, 2014, p. 13). The 2012 PDP results (USDA, 2014) indicated that EFED had recommended to focus monitoring on sites where carbamates and organophosphate pesticides have been applied. It should be noted that the focus of the PDP monitoring is on human drinking water sources; whereas, this risk assessment

focuses on surface water which serves as habitat for non

- target aquatic organisms.

During the years 2001 to 2012, analysis for dimethoate was conducted in 4,066 finished and 2,351 untreated drinking water samples. Dimethoate was detected in three of the se 6,417 drinking water samples. Additionally, analysis for omethoate has been incorporated more recently. Out of 2,076 samples tested (1,029 finished and 1,047 untreated drinking water samples), omethoate was detected in one sample in 2008, and three sa mples in 2009 (all four samples were of finished water). It should also be noted that while for omethoate the limit of detection (LOD) ranged between 0.3

- 7.5 ng/L (parts per trillion or ppt) (0.3 ppt for all years, except 2012), for dimethoate it has vari ed over time, and has been as high as 63 ppt. Dimethoate may have been present and reported as undetected in certain samples with concentrations below 60 ppt.

It is important to realize that the above mentioned monitoring is related to drinking waters an d is less relevant to ecological exposure.



## 2.4.2 National Water

- Quality Assessment (NAWQA) Groundwater Monitoring (2001

- 2012)

The U.S. Geological Survey’s National Water

- Quality Assessment Program (NAWQA) groundwater monitoring was summarized per year and by ty pe of land use (agricultural, urban,

### Page 32 of 144 

### mixed or other; MRID 49178403). Out of 5,236 samples tested for dimethoate throughout the period (2001

- 2012), there were no detects reported (0%). The LODs were reported to be

between 0.0021 and 0.0 6 μg/L (parts per b illion or ppb )

. According to the submission, NAWQA does not analyze for omethoate.



## 2.4.3 National Water

- Quality Assessment Program (NAWQA) Surface Water Monitoring (2001

- 2012)

The NAWQA surface water monitoring data were summarized per year and by type of land use ( i.e. , agricultural, urban, mixed, or other; MRID 49178403). Out of 8,726 samples tested throughout the period (2001

- 2012), there were 138 detects reported for dimethoate (1.6%), ranging from 0.0036

- 0.494 ppb. The LODs were reported to be between 0. 0021 and 0.10 ppb

.

When ‘agricultural’ or ‘mixed land’ categories were taken individually, the percent of dimethoate detects was higher (2.8% for ‘agricultural land’, and 2.8% for ‘mixed land’). Meanwhile, for ‘urban’ and ‘other’ categories, the percent of dimethoate detects was smaller (0.3% and 0.2%, respectively). The highest concentration detected, i.e ., 0.494 ppb (or 494 ppt), was reported for a sample from agricultural land in 2010. Even though there were detections at up this level in surface wat ers in 2010, it appears that this value does not necessarily reflect the peak concentration in the field. Although monitoring showed a maximum concentration of 0.494 ppb, modeling yielded peak EECs ranging from 5.07 ppb to 44.3 ppb; therefore, the monit oring was around one order of magnitude lower than the modeling. New restrictions were imposed in the dimethoate labels as per the Revised Interim Reregistration Eligibility Decision (RED) document issued in 2008 (USEPA 2008). It was noted that the highe st detected dimethoate concentration was reported in 2010; however, a specific trend (increasing or decreasing concentrations) was not observed in the NAWQA monitoring results. In general, the NAWQA results appear to support a low frequency of detections. Despite what appears to be a low level of detections, EFED believes that modeling reflects concentrations in surface waters which are realistically conservative for each site represented.

The monitoring programs analyzed for this risk assessment do not specifically target dimethoate. Consequently, detections cannot be directly associated with a particular use pattern or site, nor are the detections expected to represent the potential peak dimethoate or omethoate exposures.

The reported concentrations f rom monitoring data are lower than estimated concentrations

derive d from modeling. This result may be attributed to the fact that water monitoring sampling programs do not specifically target dimethoate use areas, may not represent high dimethoate use

are as
, and may not correspond with applications of dimethoate; therefore, peak concentrations of dimethoate and omethoate may not be detected. For most monitoring locations, sampling frequencies are not designed to capture peak concentrations , and are unlike ly to do so by chance

. Because currently available monitoring data likely underestimate maximum dimethoate and omethoate concentrations, monitoring results are not an appropriate predictor of the potential peak exposure resulting from dimethoate use. For these reasons, EFED does not recommend that dimethoate and omethoate water monitoring data be used to generate risk quotient values

.

### Page 33 of 144 

## 2.4.4 Precipitation Samples (Majewski **et al** . 2006)

Dimethoate has been detected in precipitation samples in California. Accordi ng to Majewski et
al . 2006 , dimethoate was detected in 5% of rainfall samples (n=136) at a maximum concentration of 0.102 μg/L. Based on these data, it is possible that dimethoate can be deposited on land in precipitation. At this time, the Agency does not have an approved model for estimating atmospheric transport of pesticides and resulting exposure to organisms in areas receiving pesticide deposition from the atmosphere.



## 2.5 **Terrestrial Exposure Modeling**

2.5.1 Exposure to Birds and Mammals

Terrestrial wi ldlife a re exposed to dimethoate via consumption of residues on food items generated by spray applications. For spray applications, the T

- REX model (Terrestrial Residue

EX posure model; v. 1.5.2; June 6, 20132) is used to predict dietary exposure to dimethoate

resi dues on foliar surfaces and insects using the Kenaga nomogram as modified by Fletcher (Hoerger and Kenaga 1972, Fletcher et al. 1994). A default 35

- day foliar dissipation half

- life is typically used for terrestrial exposure modeling in this as sessment; how ever, suitable foliar dissipation data specific to dimethoate are available (Willis and McDowell 1987 ; MRID

46486401 ) and a mean value of 2.82 days was used in T

- REX . Estimated exposures of terrestrial

insects to dimethoate are evaluated in terms of the in sects’ potential relevance as dietary items

for terrestrial vertebrates and for use in risk characterization for listed terrestrial invertebrates. T

REX is unable to simulate label specifications f or certain uses of dimethoate such as soil drench

and soil injection use s.

.

T

- REX is used to calculate dietary and dose

- based EECs of dimethoate residues on food items

for mammals and birds as a result of spray applications at the labeled maximum use rates . Input

values for the use scenarios used to derive EECs using T

- REX and terrestrial plant ( TerrPlant )

tool are located in Table 16 for foliar spray uses that represent a range of single as well as seasonal application rates. Upper

- bound Kenaga nomogram values are used to derive EECs for dimethoate exposures to terrestrial mammals and birds based on a 1

- year time period.

Consideration is given to different types of feeding strategies for mammals, including herbivores, insectivores and granivores. Dose

- based exposures are estimated for three weight classes of birds (20 g, 100 g, and 1000 g) and three weight classes of mammals (15 g, 35 g, and 1000 g).

Table 16 . Input parameters for deriving screening

- level terrestrial estimated environmental

concentrations (EECs) for labeled spray uses of dimethoate related to terrestrial plants and animals. A foliar dissipation half

- life of 2.82 days was used

Use Maximum Single App.

Rate (lb.

a.i./A) Number of Apps.

a Max Rate Maximum Seasonal App. Rate (lb. a.i./A) Minimum

Interval

Between Apps. (days) 1 Application

Method Used in Modeling Pre

Harvest

Interval (days)

Non

- Food Uses

Douglas fir (seed orchards) (only in OR and WA) 4.5 (AB) 1 * 4. 5 (AB) N/A G (AB) N/A

Hybrid cottonwood/poplar plantations (some labels 2 3 6 10 A or G : spray N/A

### Page 34 of 144 Table 16 . Input parameters for deriving screening

- level terrestrial estimated environmental

concentrations (EECs) for labeled spray uses of dimethoate related to terrestrial plants and animals. A foliar dissipation half

- life of 2.82 days was used

Use Maximum Single App.

Rate (lb.

a.i./A) Number of Apps.

a Max Rate Maximum Seasonal App. Rate (lb. a.i./A) Minimum

Interval

Between Apps. (days) 1 Application

Method Used in Modeling Pre

Harvest

Interval (days)
allow use in ID, OR and WA) Ornamental woody

shrubs and vines 1 3 * 3 14 A or G: spray N/A

Ornamental Herbaceous plants 0.25 1 0.25 N/A A or G: spray N/A

Food Uses

Cherry 1.35 1 1.35 N/A A or G: spray 21 Soybeans 0.5 2 1 7 A or G: spray 21 Peppers 0.336 5 * 1.67 7 A or G: spray 0 Succulent peas 0.156 1 * 0.156 N /A A or G: spray 0 N/A=does not apply; G=ground; A=aerial, S=spray (low or high volume), AB=airblast *Calculated value, based on the number of applications, or the seasonal application rate.



### Differences in exposures between ground and aerial applications cannot be assessed with the

current T

- REX model; exposure and risk estimates from the T

- REX model are considered relevant to both application scenarios. A further uncertainty with the model is the inability to model systemic chemicals like dimethoate as T

- REX only simulates residues directl y on food

items.

Some use patterns of dimethoate employ a soil drench method. T

- REX is not able to simulate a soil drench scenario as the resultant EECs and RQs would assume that the entire application rate would be sprayed on terrestrial food items as th ey are for conventional aerial and ground applications. For soil drench, even though the label does not specifically preclude application on foliage, it is expected to take place on the root ball of the crop. Since dimethoate is systemic chemical in plants , food items are likely to contain dimethoate residues even if it is not directly applied, when it is translocated across plant tissue. However, the levels or concentrations of dimethoate in food items are uncertain for the soil drench applications

.

### Page 35 of 144 Table 17 . Screening

- level dose

- based estimated environmental concentrations (EECs) in mg/kg bw as food residues for birds from labeled uses of dimethoate (T

- Rex v. 1.5.2). toxicity to birds is based on acute oral toxicity data for dimethoate
Primary Feeding Strategy
 Herbivores and Omnivores Insectivores Granivores

Animal Size*  Small Med Large Small Med Large Small Med Large

Dietary Items Short GrassTall GrassBroad-leafPlantsFruits, pods,seeds,etc.Short GrassTall GrassBroadleafPlantsFruits, pods,seeds,etc.Short GrassTall GrassBroadleafPlantsFruits, pods,seeds,etc.

Arthropods Seeds, grains, etc

.

Use(s) 1 

N on

- Food Uses

Douglas fir (seed orchards) (only in OR and WA) 1230 563 691 76.8 701 321 394 43.8 314 143 176 19.6 481 274 123 17.0 9.74 4.36

Hybrid cottonwood/poplar plantations (some labels allow use in ID, OR and WA) 600 275 337 37.5 342 156 192 21.4 153 70.2 86.2 9.58 235 134.1 60.03 8.34 4.75 2.13

Ornamental woody shrubs and

vines 283 129 159 17.6 161 73.9 90.8 10.0 72.2 33.1 40.6 4.52 110 63.2 28.3 3.93 2.24 1.00

Ornamental Herbaceous plants 68.3 31.3 38.4 4.27 38.9 17.8 21.9 2.44 17.4 8.00 9.81 1.09 26.7 15.2 6.83 0.95 0.54 0.24

Food Uses

Cherry 369 169 207 23.1 210 96.4 118 13.1 94.2 43.1 52.9 5.89 144 82.4 36.9 5.13 2.92 1.31

Soybeans 162 74.2 91.1 10.1 92.3 42.3 51.9 5.77 41.3 18.9 23.2 2.59 63.4 36.1 16.2 2.25 1.28 0.57

Peppers 112 51.6 63.4 7.05 64.2 29.4 36.1 4.02 28.7 13.1 16.1 1.80 44.1 25.1 11.2 1.57 0.89 0.40

Succulent peas 42.6 19.5 23.9 2.67 24.3 11.1 13.6 1.52 10.8 4.99 6.12 0.68 16.7 9.52 4.26 0.59 0.34 0.15

### Page 36 of 144 Table 18 . Screening

- level dose

- based estimated environmental concentrations (EECs) in mg/kg bw as food residues for mammals from labeled uses of dimethoate (T

- Rex v. 1.5.2)

Primary Feeding Strategy  Herbivores and Omnivores Insectivores Granivores

Animal Size*  Small Med Large Small Med Large Small Med Large

Dietary Items Short GrassTall GrassBroad-leafPlantsFruits, pods,seeds,etc.Short GrassTall GrassBroadleafPlantsFruits, pods,seeds,etc.Short GrassTall GrassBroadleafPlantsFruits, pods,seeds,etc.

Arthropods Seeds, grains, etc

.

Use(s) 1 

Non

- Food Uses

Douglas fir (seed orchards) (only in OR and WA) 1030 471 579 64.3 711 326 400 44.4 165 75.6 92.8 10.3 403 278 64.6 14.3 9.88 2.29

Hybrid cottonwood/poplar plantations (some labels allow use in ID, OR and WA) 502 230 282 31.4 347 159 195 21.7 80.5 36.9 45.3 5.03 196 136 31.5 6.98 4.32 1.12

Ornamental woody shrubs and vines 237 108 133 14.8 163 75.0 92.1 10.2 37.9 17.4 21.3 2.37 92.8 64.1 14.8 3.29 2.27 0.53

Ornamental Herbaceous plants 57.2 26.2 32.1 3.58 39.5 18.1 22.2 2.47 9.17 4.20 5.16 0.57 22.4 15.4 3.59 0.79 0.55 0.13

Food Uses

Cherry 308 141 173 19.3 213 97.8 120 13.3 49.5 22.6 27.8 3.09 121 83.6 19.3 4.29 2.97 0.69

Soybeans 135 62.1 76.2 8.48 93.7 42.9 52.7 5.86 21.7 9.96 12.2 1.36 53.1 36.7 8.51 1.88 1.30 0.30

Peppers 94.3 43.2 53.0 5.90 65.2 2 9.8 36.6 4.08 15.1 6.93 8.51 0.95 36.9 25.5 5.92 1.31 0.91 0.21

Succulent peas 35.7 16.3 20.0 2.23 24.6 11.3 13.8 1.54 5.72 2.62 3.22 0.36 13.9 9.66 2.24 0.50 0.34 0.08

### Page 37 of 144 Table 19 . Screening

- level dietary

- based estimated environmental concentrations (EECs) in mg/kg bw as food residues for mammals, and birds from labeled uses of dimethoate (T

- Rex v. 1.5.2)

Primary Feeding Strategy  Herbivores, Omnivores, and Granivores Insectivores

Dietary Items Short GrassTall GrassBroad-leafPlantsFruits, pods,seeds,etc.Arthropods

Use(s) 

Non

- Food Uses

Douglas fir (seed orchards) (only in OR and WA) 1080 495 607 67.5 423

Hybrid cottonwood/poplar plantations (some labels allow use in ID, OR and WA) 527 241 296 32.9 206

Ornamental woody shrubs and vines 248 113 139 15.5 97.3

Ornamental Herbaceous plants 60.0 27.5 33.7 3.75 23.5

Food Uses

Cherry 324 148 182 20.2 126

Soybeans 142 65.2 80.0 8.89 55.7

Peppers 98.9 45.3 55.6 6.19 38.7

Succulent peas 37.4 17.1 21.0 2.34 14.6

### Page 38 of 144 

## 2.5.2 Bees

In addition to the terrestrial exposure modeling for birds and mammals, Tier 1 (screening level) exposure estimates were also derived for pollinating bees, using the honey bee as a surrogate. These exposure estimates include contact and dietary exposure pathways for both foliar and soil applications based on the EFED guidance document for assessing pesticide risk to bees ( USEPA

2014 9 

### ). Tier 1 estimates of daily exposure values in μg a.i./bee w ere derived for adult as well as for larval life stages of honey bees for both non

- food and food uses that represent a range in dimethoate application rates. For contact exposure of adult foragers to foliar sprays, EECs were based on the application rate ( lb a.i./A) and the unit dose estimate of 2.7 ug ai/bee per lb a.i./A as

described in USEPA ( 2013 10 

### ; 2014). For oral (dietary) exposure via pollen and nectar with foliar sprays, EECs were based on the application rate, T

- REX estimated unit residue (110 ug a i/g per lb ai/A), and the caste

- specific consumption rate of nectar and pollen (292 mg/d for adult foragers, 124 mg/d for larvae). These honey bee castes represent those with the highest expected exposures via oral ingestion ( e.g., adult foragers, 5

- d old larvae). Table 24 lists input parameters used for deriving exposure values for bees; Table 

### 25 presents the Tier 1 EECs for foliar spray applicatio ns, with additional details provided in Appendix 11

.

9 http://www.epa.gov/pesticides/science/efed/policy_guidance/team_authors/terrestrial_biology_tech_team/GuidanceAssessingPes ticideRisk2Bees. pdf

10 http://www.cdpr.ca.gov/docs/emon/surfwtr/presentations/epa_whitepaper.pdf



### Table 2 0 . Input parameters for deriving screening

- level terrestrial estimated environmental

concentrations (EECs) in pollen and nectar from systemic residues for soil drench uses of

dimethoate

Use Maximum Single App.

Rate (lb.

a.i./A) Number of Apps. a

Max Rate Maximum

Seasonal App. Rate (lb. a.i./A) Minimum

Interval Between Apps. (days) 1 Application Method Used in Modeling Pre

Harvest

Interval (days) Hybrid cottonwood/poplar plantations 2 3 6 10 SI N/A

Ornamental woody shrubs

and vines 1 3 * 3 14 SI N/A

Melon, Watermelon 0.5 2 1 7 C 3 Succulent peas 0.15 6 1 * 0.156 N /A C 0 N/A=does not apply; C=chemigation, SD=soil drench; SI=soil injection treatment Assumptions in the table are shaded grey

. *Calculated value, based on the number of applications, or the seasonal application rate.

### 39 Table 2 1 . Tier I Screening

- level 

### e stimated e nvironmental c oncentrations ( EECs ) for h oney b ees b ased on f oliar a pplications of d imethoate

.

Use Pattern Assessed Application

Rate (lb ai/A) Adult Larvae

Acute

Contact (μg a.i./bee/ day) Acute

Oral (μg a.i./bee/ day) Chronic (μg a.i./bee/ day)

Non

- Food Uses

Douglas fir (seed orchards) (only in OR and WA) 4.5 12.2 144.5 61.4

Hybrid cottonwood/poplar plantations (some labels allow use in ID, OR and WA) 2 5.4 64.2 27.3

Ornamental woody shrubs and vines 1 2.7 32.1 13.6

Ornamental Herbaceous plants 0.25 0.68 8.0 3.4

Food Uses

Cherry 1.35 3.65 43.4 18.4

Soybeans 0.5 1.35 16.1 6.8

Peppers 0.336 0.91 10.8 4.6

Succulent peas 0.156 0.42 5.0 2.1



### For applications of dimethoate to soil, bees are expected to be exposed primarily through the oral (ingestion) route due to systemic uptake of dimethoate by plants. As described in USEPA (2014), Tier 1 estimates of pesticide residues in pollen and nectar are derived using the Briggs model (a component of PRZM) and the pesticide application rate. The oral EECs are then determined using the same pollen and nectar consumption rates described previously for foliar applications. Table 22 presents the exposure values for soil applications with additional details provided i n Appendix 11.

Table 2 2 . Tier I Screening

- level e stimated e nvironmental c oncentrations ( EECs ) for h oney b ees b ased on s oil drench a pplications of d imethoate

Use Pattern Assessed Application Rate (lb ai/A) Adult Larvae

Oral (μg a.i./bee/day)

Hybrid cottonwood/poplar plantations 6 1.897 0.806

Ornamental woody shrubs and vines 3 0.949 0.403

Melon, Watermelon 1 0.316 0.134

Succulent peas 0.156 0.049 0.021



## 2.5.3 Runoff and Spray Drift to Terrestrial and Semi

- Aquatic Plants

The TerrPlant (v. 1.2.2; December 26, 2006) model is used to derive EECs relevant to terrestrial and wetland plants for dimethoate . The model employs the assumption that default fractions of the intended application are transported to an adjacent field thr ough runoff and spray drift.

### 40 Measures of exposure to terrestrial plants are expressed as a fraction of the mass of the

dimethoate applied to the treated field.

Loading via spray drift to dry, non

- target, adjacent areas is assumed to occur from one acre o f treated land to one acre of an adjacent non

- target area. Runoff is also expected to be a source of pesticide loading to non

- target areas. TerrPlant calculates EECs as a function of application rate, solubility, and default assumptions regarding spray dri ft. The default spray drift assumptions are 1% of the application rate for ground spray applications and 5% for aerial spray applications (USEPA 2006b).

The EECs for terrestrial and semi

- aquatic plants for a single application of dimethoate at the

maximum labeled rates for representative uses are presented in 

### Table 23 (see example output in Appendix 6 ).

Table 2 3

. Estimated environmental concentrations (EECs) for terrestrial plants based on various application rates and either ground or aerial spray application methods (TerrPlant v.1.2.2)

Crop Single

Max. Application

Rate ( lbs

a.i./A) EECs (lbs a.i./A)

Runoff to dry areas Runoff to

semi

aquatic

area s Spray drift Total for dry areas Total for

semi

- aquatic

areas

Non

- food uses

Douglas Fir Aerial: 4.5 0.225 2.25 0.225 0.45 2.47

Ground: 4.5 0.225 2.25 0.045 0.27 2.29 Hybrid

cottonwood Aerial: 2 0.1 1 0.1 0.2 1.1

Ground: 2 0.1 1 0.02 0.12 1.02

Ornamental woody shrubs

and vines Aerial: 1 0.05 0.5 0.05 0.1 0.55

Ground: 1 0.05 0.5 0.01 0.06 0.51

Ornamental

Herbaceous plants Aerial: 0.25 0.0125 0.125 0.0125 0.025 0.137

Ground:

0.25 0.0125 0.125 0.0025 0.015 0.127

Food Uses

Cherry Aerial: 1.35 0.0675 0.675 0.0675 0.135 0.742

Ground:

1.35 0.0675 0.675 0.0135 0.081 0.688

Soybeans Aerial: 0.5 0.025 0.25 0.025 0.05 0.275

Ground: 0.5 0.025 0.25 0.005 0.03 0.255

Peppers Aerial:

0.336 0.0168 0.168 0.0168 0.0336 0.184

Ground:

0.336 0.0168 0.168 0.00336 0.0201 0.171

Succulent peas Aerial:

0.156 0.0078 0.078 0.0078 0.0156 0.0858

Ground:

0.156 0.0078 0.078 0.00156 0.00936 0.0795

### 41 

## 2.5.4 Bioaccumulation

Bioaccumulation will not be assessed in this PRA because both dimethoate and its

transformation product omethoate have very low K OW 

### values ( i.e ., dimethoate K OW 

### = 5.06;

omethoate estimated K OW 

### = 0.18) and neither compound is expected to bioaccumulate extensively in aquatic organisms. As a result, the BCF study was previously waived for dimethoate, and EFED does not anticipate these two compounds bioaccumulating in the food chain sufficiently t o lead to exposure of concern in birds, reptiles, terrestrial

- phase amphibians, or mammals that feed on aquatic food items.



# 3.0 Ecological Toxicity

Assessment endpoints represent the actual environmental value that is to be protected, defined by an ecological entity (species, community, or other entity) and its attribute or characteristics (EPA 1998). For dimethoate, the ecological entities include t he following: birds, reptiles, terrestrial

phase amphibians, mammals, freshwater fish, freshwater aquatic

- phase amphibians and invertebrates, estuarine/marine fish and invertebrates, terrestrial plants, insects, aquatic plants, and algae. The attributes f or each of these entities include growth, reproduction, and survival.

The ecological effects characterization for dimethoate is based up on registrant

- submitted toxicity

data for the TGAI ( parent compound) and for specified formulations. The ecotoxicity data for dimethoate and its associated products have been reviewed previously in the Problem Formulation for Registration Review assessment (USEPA 2008). Various studies with terrestrial and aquatic plants, birds, and aquatic anima ls exposed to either th e TGAI, formulated

dimethoate , omethoate and other degradates have been received since the preliminary Problem

Formulation was issued. Those data that were reviewed and pr ovided a more sensitive endpoint

tha n those in the Problem Formulation have been inc luded in Tables 7 and 8 along with those data identified previously where more sensitive data have not been iden ti fied . A comprehensive

list of data submitted since the preliminary Problem Formulation can be found in Appendix 8

with their classification and a brief summary; some data are still in review.

A search of the ECOTOXicology database in 201 3 , yielded additional data to complement those data submitted by the registrant

. The d atabase was reviewed for studies , which meet data quali ty standards, with relevant endpoints considered to be more sensitive than those considered in the assessment. A cursory review of these studies was conducted to evaluate their potential utility in characterizing the potential risk associated with the us e of dimethoate . Additionally, the bibliography of acceptable studies considered in this assessment can be found in Appendix 10

.



## 3.1 **Aquatic Organisms**

Technical grade dimethoate is classified as moderately toxic to freshwater fish and aquatic

- phase amphibi ans and very highly toxic to freshwater and estuarine/marine aquatic invertebrates on an acute exposure basis. The 2008 Problem Formulation provides a summary of the methods used in estimating the a cute

- to

- c hronic r atio (ACR) for extrapolating the value used for c hronic

### 42 f reshwater i nver t ebrates in Table 24 below for wh ich dimethoate

- specific empirical data were

not available

. Additionally, the salt water mosquito ( Aedes taeniorhynchus ) 

### and the freshwater stonefly ( Pteronarcys californica ) 

### were found to be more acutely sensitive to dimethoate tha n the

freshwater daphnid ( Daphnia magna ) and estuarine/marine mysid shrimp ( Americamysis bahia )

. Dimethoate is practically nontoxic to estuarine/marine fish on an acute exposure basis. Chronic

exposure to dimethoate resulted in decreased growth in freshwater fish.

Aquatic vascular aquatic plants ( Table 24 ) were relatively insensitive to dimethoate ( Lemna gibba EC 50 

### >92.6 mg/L ) 

### compared to nonvascular aquatic plants ( Anabaena flos

- aquae IC 50 

### =20 mg/L)

.

The available information reported in the Interim Reregistration Eligibility Decision ( IRED )

document (USEPA 2000) indicates that aquatic organisms are more sensitive to the TGAI than to the formulated products of dimethoate; therefore, the focus of this assessment is on the TGAI of

dimethoate and its transformation product omethoate. Toxicity data for omethoate are discussed

later in the document

.

An acute non

- guideline toxicity study of dimethoate conducted using tadpoles of the African Clawed Frog ( Xenopus laevis) was submitted in support of this assessment (MRID 48634201) . A review of the study shows the endpoint to be greater than that of the LC 50 

### of 6.2 mg/L for

rainbow trout ( Oncorhynchus mykiss ) , thus freshwater fish will be continue to be used a surrogate for aquatic

- phase amphibians.

Table 24 . Most sensitive aquatic species evaluated for assessing potential ecological effects of

d imethoate

Study Type Tested Species Toxicity Endpoint Study MRID and Toxicity

Classification

850.1075 Acute Freshwater Fish Rainbow trout ( Oncorhynchus mykiss ) LC 50 1 = 6.2 mg/L 40094602 Moderately toxic

850.1400 Chronic Freshwater

Fish Rainbow Trout (Oncorrhynchus mykiss) NOAEC = 0.43 mg/L 43106303

850.1010 Acute Freshwater

Invertebrate Stonefly (Pteronarcys californica) EC 50 = 0.043 mg/L 00003503 Very highly toxic

850.1300 Chronic Freshwater

Invertebrate Stonefly (Pteronarcys californica NOAEC 2 = 0.0005 mg/L Estimated using ACR

850.1075 Acute Estuarine/marine

Fish Sheepshead Minnow ( Cyprinodon variegatus ) LC 50 > 11 1 mg/L 42760001 Practically non

- toxic

850.1400 Chronic

Estuarine/marine fish Sheepshead Minnow ( Cyprinodon variegatus ) NOAEC 3 =1.2 mg/L 48772901

48

- hour Acute

Estuarine/m arine

Invertebrate Salt Marsh Mosquito (aedes taeniorhynchus) LC 50 = 0.031 mg/L Song et al . 1997 Very highly toxic

850.1350 Chronic

Estuarine/marine

Invertebrate Salt Marsh Mosquito ( A edes taeniorhynchus) NOAEC 4 = 0. 0002 mg/L NA

850.4400 Vascular Plant Duckweed ( Lemna gibba ) EC 50 >92.6 mg/L NOAEC = 92.6 mg/L 47709703

850.4550 Nonvascular Plant Cyanobacteria Anabaena flos

- aquae EC 50 = 20 .0 mg/L NOAEC = 9.0 mg/L 48572804

1 Freshwater fish are considered surrogates for aquatic

- phase amphibians.

### 43 There are two studies available on the toxicity of the dimethoate formulation. Available data on the 4.0 emulsifiable (EC) dimethoate formulation indicate the formulation is less acutely toxic to rainbow trout when compared to the TGAI by about an order of magnitude; the acute LC 50 

### for rainbow trout was found to 59.8 mg/L (48298302) as compared to the parent toxicity of 6.2 mg/L (40094602). Another study conducted using the bluegill found an LC 50 

### of 44.5 mg/L (48298303) as compared to the parental toxicity of 31.5 mg/L (48821401).



## 3.2 **Terrestrial Organisms**

The most sensitive toxicity endpoints for dimethoate with terrestrial organisms are shown in

Table 25

. Dimethoate is moderately to very highly toxic to birds (and to terrestrial

- phase amphibians and reptiles for which birds serve as surrogates) and is mod erately toxic to mammals on an acute oral exposure basis, and ranges from slightly to highly toxic to birds on a subacute dietary exposure basis. Chronic exposure to dimethoate resulted in decreased reproduction and

survival in birds and decreased survival in mammals.

Terrestrial plant toxicity studies (seedling emergence and vegetative vigor) resulted in non

definitive endpoint for the monocotyledenous (monocot) onion ( Allium cepa ) . For dicotyledenous (dicot) plants, the seedling emergence study yielde d a definitive EC 25 

### of 0.84 lbs ai/A for sugar beets ( Beta vulgaris ) while the vegetative vigor study yielded a non

- definitive

EC 25 

### of greater than 1.51 lbs ai/A.

2 Estimated using acute

- to

- chronic ratio (ACR) with Daphnia magna data ( ACR= EC 50 /NOAEC = 83); acute daphnid effects based on immobility while chronic effects included impaired reproduction, growth, and survival

. 3 NOAEC based on growth; study classified as supplemental because time to hatch was not assessed

4 Estimated using ACR with Americamysis bahia data ( ACR= EC 50 /NOAEC = 107); acute mysid effects based on immobility while chronic effects included impaired reproduction, growth and survival

.



### Table 25 . Most sensitive terrestrial species evaluated for assessing potential ecological effects of

d imethoate.

Study Type Tested Species Toxicity Endpoint Study MRID and Toxicity

Classification

850.2100 Avian Acute Oral Red

- winged Blackbird (Agelaius phoneniceus) LD 50 = 5.4 mg/kg bw 00020560 Very highly

toxic

850.2200 Avian Dietary Northern Bobwhite Quail (Colinus virginianus) LC 50 = 150 mg/kg diet 47769705 Highly toxic

850.2300 Avian Reproduction Northern Bobwhite Quail (Colinus virginianus) NOAEC = 4.0 mg/kg diet 44049001

- Mammalian Acute

Oral Norway Rat (Rattus novegicus) LD 50 = 358 mg/kg bw 00164200 Moderately toxic

- Mammalian Reproduction Norway Rat (Rattus novegicus) NOAEL = 0.1 mg/kg bw 45529703

Non

- Gdln Honeybee Acute Oral Adult Toxicity Honeybee (Apis mellifera) Oral LD 50 = 0.056 μg/bee 00026489 Highly toxic

850.3020 Honeybee Acute

Contact Adult Toxicity Honeybee (Apis mellifera) Contact LD 50 = 0.16 μg/bee 00026489 Highly toxic

### 44 

## 3.2.1 Terrestrial Invertebrates

Bees (Tier 1 Individual Organism Effects) : Dimethoate is classified as highly toxic to adult honeybees ( Apis mellifera ) on both an acute oral and contact exposure basis ( Table 24 )

. No data are available for determining acute or c hronic

LD 50 

### values for larval honey bees. However, in a recent chronic toxicity test of sulfoxaflor submitted to the Agency, a daily dose of 1 μg dimethoate/bee/d for 5 days resulted in 98% mortality of larval honey bees by day 7 (MRID 48755603).

Bees ( Tiers 2 Colony Level Effects): Similarly, no Tier 2 (semi

- field, tunnel) studies have been submitted to the Agency for dimethoate. However, dimethoate is commonly used as a reference toxicity in Tier 2 tunnel studies. In a recent pesticide ecological risk assessment with sulfoxaflor 11 

### , EPA summarized

results from several Tier 2 tunnel studies in which dimethoate was used as the reference toxicant. Generally, foliar spray application of dimethoate at 600 g a.i./ha (0.53 lb a.i./A) to bees foraging

on Phacel ia during bloom resulted in sustained increases in worker bee mortality

, reduced flight activity and behavioral abnormalities ( MRID 48445807 ). Impacts on brood development were

not clear due to limitations in the submitted Tier 2 studies. It is noted tha t this application rate (0.53 lb a.i./A) is well within the range of registered application rates of dimethoate (see Table

2 ).

Bees (Tiers 3 Colony Level Effects): Study Design/Methods: A Tier 3 (full field) study was conducted in July

- August 2004 to

inve stigate the effects of dimethoate EC formulation 400 g/L on honey bee colony health (MRID

481013

- 02). Dimethoate was applied to flowering Phacelia tanacetifolia which were sown at a seeding rate of 11 kg/ha ca . 10 weeks before the start of the experiment. The study evaluated the impact of a single application of dimethoate (0.67 lb ai/A) in the evening after bee flight, and thus was designed to estimate the effects from presumably dried residues on foliage. Control and

dimethoate

- treated plots (~2,500 m 2 

### ) were separated by 2 km and applications were made during

full bloom although the percent bloom was not quantified. A total of 4 colonies each containing 9 and 11 frames in the lower and upper boxes (including 5 brood frames with brood in all stages)

wer e distributed in each plot 4 days prior to pesticide application. The Phacelia bloomed for 17 days post application, after which colonies were moved to an untreated meadow approximately 10 km away for continued monitoring. Colonies were queen right and r eportedly had a low

incidence of mite ( Varroa destructor) infestation (< 1 mite/colony/day), although the method of

11 http://www.regulations.gov/#!documentDetail;D=EPA

- HQ

- OPP

- 2010

- 0889

- 0022

850. 4100 Seedling Emergence Monocot: Onion ( Allium cepa ) EC 25 >1.48 lb a.i./A

NOAEC = 0.745 lb a.i./A 48628101 Dicot: Sugar beet

( Beta vulgaris ) EC 25 = 0.84 lb a.i./A

NOAEC <0.23 lb a.i./A

850.4150 Vegetative Vigor Monocot: Onion ( Allium cepa ) EC 25 > 1.46 lb a.i./A

NOAEC = 0.48 lb a.i./A 48572802 Dicot: Sugar beet ( Beta vulgaris ) EC 25 >1.51 lb a.i./A

NOAEC = 0.5 lb a.i./A

### 45 Varroa monitoring may have underestimate d actual mite loads. No evaluation of pathogen load ( e.g., fungal Nosema ceranae; N. apis ) was indicated. Mortality, foraging activity, hive weight, brood development, food stores, and behavioral abnormalities of the bees were assessed periodically before and after application. Samples of flowers, pollen, and nectar were not

collected for ana lysis of residues nor were samples from inside the hives collected for the determination of residues and confirmation of exposure. However, the presence of Phacelia pollen relative to other pollen sources was estimated visually by color through D ay 7 fo llowing application.

Mortality, Flight Activity, Behavior: Mean daily bee mortality in hives at the control plot ranged from 1 to 70 dead bees/day from D ays 1 through 7 after application. Following application of dimethoate, statistically significant ( p<0.05) increases in mean daily mortality of bees occurred from hives at the treated site relative to controls (1,100 vs 41 dead bees, respectively). Daily bee mortality decreased to 212 and 116 bees on D ays 2 and 3 post application, but these were not st atistically significant from controls. From D ay 4 through D ay 7 post application, bee mortality rates from dimethoate

- treated site were comparable to controls. Similar to the pattern observed for mortality, the incidence of abnormal behavior (uncoordinat ed movement, lethargy, aggressiveness) increased on D ays 1 and 2 relative to controls. From D ays 3

- 7, no further behavioral impairments, aside from aggressiveness, were observed through the duration of the study. Flight activity of bees was comparable amo ng the control and treated hives prior to pesticide application, but was consistently reduced to approximately 1⁄3 of controls through post application Day 7

.

Hive Weight, Pollen Collection): All colonies lost weight over the 29 day course of the experime nt, with treated colonies losing 3.5 kg on average compared to 3.0 kg for controls.

From D ays 0

- 7, hives at the treated site lost more weight than controls (

- 2.4 kg vs

- 0.1 in controls). By D ay 14 through D ay 29, changes in hive weights were comparable among control and treated hives. The greatest period of weight loss corresponded to reductions in foraging activity and high bee mortality in the dimethoate

- treated colonies . Observation of pollen from bees returning to the hives indicated that bees from the treated site did not return with Phacelia pollen (purple in color) from 1

- 3 D ays after application, unlike controls in which 50% of bees

were observed with Phacelia pollen. After 3 days, bees from the treated site intermittently

returned with Phaceli a pollen. After colonies were moved from the sites to the meadow on D ay 17, pollen from multiple sources (colors) was observed from both controls and treated hives. Overall, the pollen observations suggest that bees forage d on Phacelia pollen during the exposure period, although it is possible that bees foraging on treated plants died soon after application and did not return to the hive.

Brood and Colony Condition . At the beginning of the study, colonies in the two treatment

groups s howed all brood ( i.e ., egg, larvae, and pupae) stages, and sufficient amounts of nectar and pollen storage. Eight days following the application, all brood stages were still seen in colonies from controls and treated plots. The study authors report a decr ease in the number of

brood rearing areas of colony frames (not quantified) in the colonies of the dimethoate

- treated plot relative to controls. At 29 days following the application, the study deemed a “sufficient”

amount of nectar was found in all treatm ent groups and the amount of brood were comparable in both treatment groups with to indication of test

- related effect in the dimethoate

- treated colonies.

### 46 Either the queens or her eggs were found in all eight colonies during the brood checks indicating

the queens were alive and reproducing. The study authors report that less detailed observations

were made on D ay 14 and D ay 21 . However, they noted that all brood stages were present on
combs and that different sources of pollen were also present based on d ifferences in pollen color.

Conclusions/Interpretation. It can be concluded from this study that exposure to dried

dimethoate residues on Phacelia foliage resulting from a single 0.67 lb ai/A spray application at
full bloom leads to elevated forage bee m ortality, reduced foraging activity, increased behav i oral abnormalities and reduced pollen collection from 3 to 7 days after application. The study authors

report ed a temporary reduction in brood area in hives from the treated site, but did not conduct a quantitative analysis of the comb to support this conclusion. No colonies were lost 29 days after application and colonies appeared healthy according to the study authors. In this specific study, the treated colonies were able to recover 29 days after app lication. However, the study contains a number of limitations for risk assessment, including:

• Use of an application rate (0.67 lb ai/A) well below the maximum application rate for some uses ( e.g ., 4.5 lbs ai/A for forestry uses).

• The test plots were sma ll (50m x 50m) compared to typical agricultural fields

.

• Use of 4 colonies at a single site represents pseudo replication since the treatment unit is the field and not the colony, which brings the statistical comparisons into question (multiple sites/treatm ent should have been used for true replication).

• Conclusions regarding brood development were not supported by a quantitative analysis of comb area measurements; no estimates of numbers of bees was made

.



## 3.3 **Degradate toxicity**

3.3.1 Aquatic Organisms

There were a number of toxicity studies conducted using dimethoate degradates in support of th is PRA. Comparison of acute toxicity studies conducted using the rainbow trout, bluegill sunfish ( Lepomis macrochirus ) and, D

. magna have been tabulated in Table 26

. The available acute toxicity data for rainbow trout indicate that dimethoate and omethoate are of similar toxicity with

LC 50 

### values of 6.2 mg/L and 5.0 mg/L

, respectively

. T he other degradates

, i.e

., d imethylthiophosphoric acid ( sodium [ Na ]

- salt ) , O

- desmethyl dimethoate ( Na

- salt ) , and

d imethylphosphoric acid, ( N a

- salt ) are less toxic to rainbow trout than the parent dimethoate,

with non

- definitive LC 50 

### values (ranging from >80.8 mg/L to >1000 mg/L)

. Examination of

the acute toxicity data for the bluegill indicate that omethoate is more toxic by about a factor of

four when compared to dimethoate TGAI

. There are no chronic toxicity data available with

which to compare dimethoate to omethoate for freshwater fish. With D. magna , availab le data

indicate that omethoate is more toxic than dimethoate by a factor of four ; whereas omethoate is less toxic by about a factor of three on a chronic exposure basis

.

### 47 Table 26 . Comparison of Acute toxicities (96

- hr LC 50 

### ) of d imethoate and degradates to f reshwater f ish and

i nvertebrates

Species Endpoint Dimethoate Omethoate Dimethyl

thiophosphoric

acid, Na

- salt O

- Desmethyl Dimethoate,

Na

- salt Dimethyl phosphoric Acid, Na

- salt Dimethoate

Formulation

Rainbow

Trout LC 50 (95% CI) 6.2 mg/L ( 40094602 ) 5.0 mg/L (4.4

– 5.8) (48821404) >961 mg/L (48298308) >80.8 mg/L (48298305) >1000 mg/L (48298311) 59.8 mg/L (48298302)

NOAEC 1.5 mg/L (49083401) -- -- -- -- --

Bluegill LC 50 (95% CI) 31.5 mg/L (19.0

– 60.3) (48821401) 7.7 mg/L (5.7

– 9.5 ) (48821402) -- -- -- 44.5 mg/L (48298303)

Daphnid EC 50 1.6 mg/L ( 48298306 0.0325 mg/L (48821405) 66.7 mg/L (48298307) >82.9 mg/L (48298304) -- --

NOAEC 0.04 mg/L (42864701) 0.119 μg/L (48821413) -- -- -- --

### 48 

## 3.3.2 T errestrial organisms

Acute and chronic toxicity data are available to compare the toxicities of dimethoate to

omethoate to birds ( Table 27 )

. Omethoate appears to be of similar acute oral toxicity to the

red

- neck pheasant ( Phasianus colchicus ) wh en compared to dimethoate ( i.e., LC 50 

### values are

within a factor of 2X and confidence intervals overlap )

. The acute oral toxicity of dimethoate and omethoate are virtually identical with bobwhite quail as well . The sub acute dietary LC 50 

### values of dimethoate and omethoate for bobwhite quail are also within a factor of two with overlapping 9 5 % confidence intervals

.

Regarding chronic dietary toxicity to birds, a n avian reproducti on study (MRID 4816201) was conducted to compare the effects of die tary exposure of omethoate and dimethoate in separate groups of 27

- week old bobwhite quail. The study evaluated effects on adult health, body weight, and f oo d consumption as well as the number of eggs laid, normal development of eggs, embryo viability, ha tchability, number of offspring and egg shell thickness. A number

of sublethal effects were reported in both the omethoate and dimethoate treatment group s including reduced reaction to external stimuli, lethargy, loss of coordination, wing droop, and

low er limb weakness. The most sensitive endpoints evaluated for dimethoate were number of eggs laid per pen, mean food consumption and adult female body weight gain; these resulted in a NOAEC of 10.7 mg ai/kg diet. The m ost sensitive endpoint evaluated for omethoate was

female adult body weight gain resulting in a NOAEC of 4.44 mg ai/kg diet. O methoate appears to be of similar toxicity as dimethoate when considering normal variability in toxicity

test data.

Table 27 . Comparison of t oxicity of t echnical grade d imethoate to o methoate for

birds

Species Dimethoate (MRID) Omethoate (MRID)

Acute Oral LD 50


### Red

- winged Black

bird ( Agelaius phoeniceus ) 5.4 mg/kg

- bw (00020560) --

Canary ( Serinus canaria ) 145 mg/kg

- bw (49096101) --

Ring

- necked pheasant ( Phasianus colchicus ) 14.1 mg/kg

- bw

95% CI = 10

- 20 mg/kg

- bw (47769702) 28 mg/kg

- bw

95% CI = 15

- NC mg/kg

- bw (47769704) Starling 

### ( Sturnus vulgaris ) 32 mg/kg

- bw (00020560) --

Mallard ( Anas platyrhynchos ) 41 .6 mg/kg

- bw (115198) --

Northern Bobwhite ( Colinus virginianus ) 10.9 mg/kg

- bw

95% CI = 5

- 20 mg/kg

- bw (47769701) 9.6 mg/kg

- bw

95% CI = 6.1

- 15 mg/kg

- bw (47769703) Japanese Quail ( Coturnix japonica ) -- --

### 49 Table 27 . Comparison of t oxicity of t echnical grade d imethoate to o methoate for

birds

Species Dimethoate (MRID) Omethoate (MRID)
Dietary LC 50 

### Ring

- necked pheasant ( Phasianus colchicus ) 353 mg/kg

- diet (47769706)

Northern Bobwhite ( Colinus virginianus ) 150 mg/kg

- diet

95% CI = 68.7

- 210 mg/kg bw (47769705) 81.7 mg/kg

- diet (47709501)

Mallard ( Anas platyrhynchos ) 1077 mg/kg

- diet (47744401) --

Chronic NOAEC

Northern Bobwhite ( Colinus virginianus ) 10.7 mg/kg

- diet (4816201) 4.44 mg/kg

- diet (4816201 )

*These studies were mention ed in the Evaluation of Fully Approved or Provisionally Approved Products, Evaluation on Omethoate, 1994 . The specific studies from which these endpoints were derived were not cited within the

document.



### In addition, mammalian data on omethoate and dimethoate are available for comparison as

well. O methoate is a more potent AChE inhibitor. To account for the increased potency of omethoate in risk estimates, benchmark dose modeling was used to e valuate relative potency for dimethoate and omethoate and to estimate the toxicity adjustment factors (TAFs) for acute and steady state exposure durations. As described in the Office of Pesticide Programs’ Health Effects Division guidance document for cum ulative risk assessment (USEPA, 2002), to the extent possible comparisons of toxic potency should be made using a uniform basis of comparison, by deriving a common response from a comparable measurement methodology, species, and sex for all the exposure routes of interest. TAFs have been estimated previously

for dimethoate and omethoate by the Human Effect Division within the EPA (A. Lowit; 11

- APR

- 2005; TXR# 0052940). The originally calculated steady

- state TAF of 3 (A. Lowit; 24

- APR

- 2002) was verified by HED with additional subchronic and chronic studies ; therefore no changes were made to the steady state TAF.

It is noted here that the TAF of 3 used by the Health Effects Division to assess potential risks

to human health is based on AChE inhibition. For ecological risk assessment, the relationship between AChE inhibition and apical endpoints of interest ( i.e ., impaired growth, survival, reproduction) has not been quantitatively established. However, for the purposes of this assessment, omethoate will be assumed to have toxicity 3X greater than that of dimethoate; comparable acute mammalian data for omethoate is not available at this time.

Acute toxicity data for honeybees indicates a similar toxicity for the parent dimethoate and its omethoate degrad ate. In an acute contact study, the reported LD 50 

### was 0.048 μg/bee for honeybees exposed to technical omethoate (DEFRA 1993). As discussed above, the most conservative acute contact honey bee LD 50 

### for dimethoate is 0.05 μg/bee.

### 50 

## 3.4 **Incident data**

3.4.1 EIIS

A review of the Ecological Incident Information System (EIIS) database for ecological incidents involving dimethoate was completed on November 2014. This database consists of incident report s submitted to the EPA from 1972 to present. A summary of these in cidents can

be found in Appendix K ; this table is divided into incidents involving aquatic organisms only, terrestrial organisms only, and both aquatic and terrestrial organisms. Within each of these sections of the table, incidents are ordered by date be ginning with the earliest incident.

Incidents listed in EIIS are categorized by certainty index, i.e

., the likelihood that a particular pesticide is associated with that particular incident. These classifications include highly probable, probable, possible, unlikely or unrelated. “Highly probable” incidents usually require measured residues of the suspected compound in the affected organism or clear circumstances regarding the exposure. “Probable” incidents include those where residue information was not available or circumstances were less clear than those for “highly probable.” Incidents categorized as “ p o ssible” occur when multiple chemicals may have been

involved and the contribution of an individual chemical is not obvious. An incident categorized as “unlikely” when a given chemical is considered nontoxic to the type of organism involved or the chemical analysis indicated no residues in the samples. Incidents categorized as “unrelated” are those where an investigation demonstrated that the loss did not involve pesticides. No incidents categorized as “unrelated” were listed for dimethoate.

The number of incidents listed in the EIIS database is believed to be only a small fraction of the total incidents involving organismal mortality and damage caused by pesticides. Therefore, the absence of incident reports or a limited number of incident reports cannot b e construed as the absence of incidents or that there were in fact a limited number of incidents.

The EIIS database contained 27 incident reports associated with dimethoate. The majority of the incident reports involve d terrestrial ecosystems (23 or 85% of the total incidents) while 4 (15%) of incident reports involve aquatic ecosystems. Washington state with 10 reports was the most represented among the 50 states followed by California (6), Idaho (3), North Carolina (2) and Illinois, South Dakota, New Y ork, Colorado and Minnesota with 1 each. There was an additional report from China. Additional characterization of these incidents is provided below.

Of the 27 incidents, 5 (19%) are categorized as ‘highly probable’ and 10 (27%) have been

classified as ‘probable’. Collectively, the ‘highly probable’ and ‘probable’ categories represent 5 6 % of the reported incidents. Regarding the legal status ( i.e ., whether the incident resulted from a misuse/label violation) , the ‘unknown’ and ‘misuse’ represent the l argest legality categories with 41% and 26% of the incident reports, respectively. Approximately 33% of the reports were the result of registered uses.

Of the incident reports categorized as ‘highly probable’ and ‘probable’ and that involved

### 51 registered uses, most described runoff to an aquatic habitat following periods of rainfall or

drift to an off

- site field where bees were actively foraging. Of the 27 incidents, 21 of them involved application of other chemicals as well , where dimethoate was classif ied as ‘possible’ for 10, ‘probable’ for 8, and ‘highly probable for 3 of the incidents

.

Aquatic Incidents :

All four aquatic incident reports involved mortality to fish. None of the aquatic incidents

involved aquatic invertebrates, but the likelihood o f observing impacts to aquatic

invertebrates is likely low compared to fish. Of the 4 aquatic incidents, 3 (75%) are classified as ‘probable’ and one is classified as ‘possible’ in the context of dimethoate use.

Terrestrial Incidents : Of the 21 terrestrial incident reports, 7 of them involved avian species and 14 of them involved pollinators. O f the 7 incidents involving avian species , 4 were classified as ‘highly probable; and 2 were classified as ‘probable.’ Within the seven, two o f the se incidents were

classified as an ‘accidental misuse’ and one was an ‘intentional misuse.’ A ffected a vian species included cedar wax w ing ( Bombycilla cedrorum ) , Canadian geese ( Branta canadensis )

and rock dove ( Columba livia )

.

Fourteen of the 21 t errestrial incident reports involved bee s

. Ten of the incidents were classified as ‘possible’ and 4 were classified as ‘probable.’ A majority of the se incidents indicate that bees were exposed to the chemical because the bees were actively foraging on

th e use site during application, or were actively foraging on an adjacent site and came into contact via spray drift.

Plant Incidents : There were 2 incidents reported involving pla nts; one was classified as ‘highly probable’ and one was classified as ‘probable’. Both incidents were due to equipment malfunction and were

classified as an ‘accidental misuse.’

### Page 52 of 144 

## 3.4.2 Other Incident Databases

The American Bird Conservancy (ABC) Avian Incident Monitoring System (AIMS 12 

### ) was

searched in May 201 4 and returned nine records of incidents associated with dimethoate (ABC, 2007). All of these incidents are recorded in the EIIS and discussed in the preceding section

.

A search in May 2014 of t he Incident Database System (IDS) maintained by OPP’s Information Technology and Resource Management Division (ITRMD) yielded no incidents for dimethoate in the main database nor in the aggregate incident module. Measures of Exposure



# 4.0 Risk Characterizati on

As discussed in the problem formulation, risk characterization integrates EECs and toxicity

estimates and evaluate s the likelihood of adverse ecological effects to non

- target species. For dimethoate, a deterministic approach is used to evaluate the li kelihood of adverse ecological

effects to non

- target species. In this approach, RQs are calculated by dividing EECs by acute and chronic ecotoxicity values for non

- target species.

Risk Quotient (RQ) = Exposure Estimate/Toxicity Estimate

The RQ value i s a unitless number and for this reason, the magnitude of the RQ value cannot be used to quantitatively gauge the likelihood or magnitude of an adverse effect resulting from exposure to dimethoate. Rather, t he resulting RQ value s are compared to LOCs ( Tab le 2 8 )

which serve as thresholds above which exposure from the labeled use (or proposed use) of the pesticide is considered to have the potential to cause adverse effects for the non

- target organisms /taxa for which the value is intended to represent

. The LOCs currently address the following risk presumption categories:

Animals:

• Acute risk

— potential for acute risk to non

- target organisms which may warrant regulatory

action in addition to restricted classification

• Acute risk, restricted use

— potential for acute risk to non

- target organisms, but may be mitigated through restricted use classification

• Acute risk, listed species

— listed species may be potentially affected by use

• Chronic risk

— potential for chronic risk may warrant regulatory action, listed specie s may potentially be affected through chronic exposure

Plants:

• Non

- listed plant risk

— potential for effects in non

- target (non

- endangered) plants

• Listed plant risk

— potential for effects in endangered plants

12 American Bird Conservancy. 2014. Avian Incident Monitoring System. http://www.abcbirds.org/abcprograms/policy/toxins/aims/aims/login.cfm

### Page 53 of 144 

### In the following sections, RQ values are calculat ed for aquatic and terrestrial organisms ( Table

29

– 41 ). In this assessment, RQs that exceed the risk to non

- listed species LOC also exceed the risk to listed species LOC. Note that with plants, unlike with animals, RQ values are not presented for acu te risk separately from chronic risk; instead, RQ values are presented for risk to

listed and non

- listed species based on a comparison of a given EEC to NOAEL and EC 25 

### /EC 50 

### values, respectively. A discussion of the RQ values for dimethoate and of other in formation that provides context for the interpretation of potential risk to various taxa is presented in the Risk Description

.

Table 28 . Agency Risk Quotient (RQ) Metrics and Levels of Concern (LOC) Per Risk Class.

Risk Class Risk Description RQ LOC

Aquatic Animals (fish and invertebrates)

Acute Risk to

non

- listed

Species Potential for effects to non

- listed animals from acute

exposures Peak EEC/LC 50 1 0.5

Acute

Restricted Use Potential for effects to animals from acute exposures Risks may be mitigated through restricted use classification Peak EEC/LC 50 1 0.1

Acute Risk to Listed Species Listed species may be potentially affected by acute

exposures Peak EEC/LC 50 1 0.05

Chronic Potential for effects to non

- listed and listed animals from

chronic exposures 60

- day EEC/NOAEC (fish) 1 21

- day EEC/NOAEC (invertebrates)

Aquatic Plants

Non

- Listed Potential for effects to non

- listed plants from exposures Peak EEC/LC 50 1 1

Listed Potential for effects to listed plants from exposures Peak EEC/NOAEC 1

Terrestrial Animals (mammals and birds) 2

Acute Risk to

non

- listed

Species Potential for effects to non

- listed animals from acute

exposures EEC/LC 50 (Dietary)

0.5 EEC/LD 50 (Dose)

Acute

Restricted Use Potential for effects to animals from acute exposures Risks may be mitigated through restricted use classification EEC/LC 50 (Dietary) 0.2 EEC/LD 50 (Dose)

Acute Risk to Listed Species Listed species may be potentially affected by acute

exposures EEC/LC 50 (Dietary) 0.1 EEC/LD 50 (Dose)

Chronic Risk Potential for effects to non

- listed and listed animals from chronic exposures EEC/NOAEC 1

Terrestrial and Semi

- Aquatic Plants

Non

- Listed Potential for effects to non

- target, non

- listed plants from

exposures EEC/ EC 25 1

Listed Plant Potential for effects to non

- target, listed plants from

exposures EEC/ NOAEC 1 EEC/ EC 05

### Page 54 of 144 

## 4.1 **Risk Estimation for Aquatic Organisms** 

4.1.1 Freshwater and Estuarine/Marine fish

Maximum acute RQ values from fr eshwater and estuarine/marine fish are one to two orders of magnitude below the acute risk to listed species LOC ( Table 29 ) . The RQs for freshwater fish ranged from 0.001 to 0.006 while the RQs for estuarine marine fish were all <0.001. None of the RQ values exceed the chronic risk LOC for freshwater and estuarine/marine fish wit h RQ value s ranging from 0.009 to 0.047 and 0.005 and 0.017

, respectively.

### Page 55 of 144 Table 29. Acute and c hronic risk quotients ( RQs ) for d irect e ffects to f reshwater an d e stuarine/ m arine f ish from d imethoate technical grade active ingredient ( TGAI ) 1

Use(s) Scenario App.

Method Peak

EECs

(μg ai/L) Freshwater

EC 50 = 6

, 2 00

μ g/L Estuarine/

Marine

EC 50 = >111 ,000

μ g/L 60

- day

EECs

(μg ai/L) Freshwater

NOAEC = 43 0

μ g/L Estuarine/

marine

NOAEC =

1

, 2 00 μ g/L

Acute RQ Chronic RQ

03_MN_alfalfa Alfalfa, sainfoin Aerial 8.5 0.001 <0.001 4.9 0.012 0.004

05_CA_Cole crops Brussels Sprouts (ground) Ground 23 0.004 <0.001 15 0.036 0.013

10_WA_Orchards Cherry (only in ID, MT, OR, UT or WA) Aerial 9.4 0.002 <0.001 6.0 0. 0 14 0.005

12_OR_Xmas trees Douglas fir (seed orchards) (only in OR and WA) Airblast 10 0.002 <0.001 5.7 0.013 0.005

14_OR_Xmas trees Hybrid cottonwood/poplar plantations (some labels

allow certain uses in ID, OR and WA) Aerial 34 0.006 <0.001 20 0.047 0.017

15_CA_Nursery Citrus, non

- bearing and nursery stock (only in CA and AZ) Soil

drench 6.6 0.001 <0.001 3.2 0.009 0.003

17_OR_Nursery Ornamental woody shrubs and vines;

Ornamental and/or shade

trees Aerial 21 0.003 <0.001 14 0.033 0.012

20_FL_Peppers Peppers Aerial 22 0.004 <0.001 13 0.030 0.011

23_MS_Cotton Cotton Aerial 9.7 0.002 <0.001 4.4 0.010 0.004

26_FL_Citrus Grapefruit, kumquat, lemon, lime, orange, pumello (shaddock),

tangelo, tangerine Aerial 22 0.004 <0.001 8.2 0.019 0.007

App. = Application

1 Acute risk listed species LOC = 0.05; acute restricted use LOC = 0.1, acute risk to non

- listed species LOC = 0.5; chronic risk to listed and non

- listed species LOC = 1

### Page 56 of 144 

## 4.1.2 Freshwater and Estuarine/Marine Invertebrates

There a re a number of acute and chronic risk LOC exceedances for invertebrates ( Table 30 )

. For freshwater and estuarine/marine invertebrates

, acute RQ values exceed the acute risk to listed species LOC of 0.05 for all uses assessed ; whereas

, the risk to non

- listed species LOC of 0.5 was exceeded in four of the 10 crop scenarios assessed . Chronic RQs for freshwater invertebrates

exceed the LOC for all u ses and ranged from roughly 10 to 53. The RQs for estuarine/marine

invertebrates also exceed the chronic risk LOC across all uses and ranged from roughly 25 to

13 3

.

### Page 57 of 144 Table 30. Acute and c hronic risk quotients ( RQs ) for d irect e ffects to f reshwat er and e stuarine/ m arine i nvertebrates from

d imethoate technical grade active ingredient ( TGAI ) 1

Use(s) Scenario App.

Method Peak

EECs

(μg ai/L) Freshwater

EC 50 = 4.3 x

10

- 5 μg/L Estuarine/

Marine

EC 50 = 3.1 x 10

- 5 μg/L 21

- day

EECs

(μg ai/L) Freshwater

NOAEC = 5

x 10

- 7 μg/L Estuarine/

marine

NOAEC = 2

x 10

- 7 μg/L

Acute RQ Chronic RQ

03_MN_alfalfa Alfalfa, sainfoin Aerial 8.5 0.199 * 0.276 * 6.4 12 32

05_CA_Cole

crops Brussels Sprouts (ground) Ground 23 0.54 0.74 20 4 0 100

10_WA_Orchards Cherry (only in ID, MT, OR, UT or WA) Aerial 9.4 0.22 * 0.30 * 7.9 15 3 9

12_OR_Xmas

trees Douglas fir (seed orchards) (only in OR and WA) Airblast 10 0.24 * 0.34 * 8.6 17 42

14_OR_Xmas

trees Hybrid cottonwood/poplar plantations (some labels

allow certain uses in ID, OR and WA) Aerial 34 0.79 1.1 26 53 133

15_CA_Nursery Citrus, non

- bearing and nursery stock (only in CA and AZ) Soil drench 6.6 0.15 * 0.23 * 5.0 10 25

17_OR_Nursery Ornamental woody shrubs and vines; Ornamental

and/or shade trees Aerial 21 0.4 4* 0.68 17 35 88

20_FL_Peppers Peppers Aerial 22 0.51 0.71 17 35 88

23_MS_Cotton Cotton Aerial 9.7 0.22 * 0.31 * 6.7 13 33

26_FL_Citrus Grapefruit, kumquat, lemon, lime, orange, pumello (shaddock), tangelo, tangerine Aerial 22 0.51 0.71 14 29 73

App. = Application

1 Acute risk to listed species LOC = 0.05; acute restricted use LOC = 0.1, acute risk to non

- listed species LOC = 0.5; chronic risk to listed and non

- listed species LOC = 1

Bolded values indicate exceedance of LOC for risk to non

- listed species.
* indicates LOC exceedance for risk to listed species

.

### Page 58 of 144 

## 4.1.3 Aquatic Plants

The RQ values for aquatic nonvascular plants and aquatic vascular plants d o not exceed the LOC

for risk to listed or non

- listed species ( Table 31 ) . The RQs for l isted aquatic nonvascular plants range from 0.001 to 0.004; the RQs for non

- listed aquatic nonvascular plants range from <0.001 to 0.002. The RQs for listed and non

- listed vascular plants a re <0.001 across all scenarios.

### Page 59 of 144 Table 31. Risk quotient ( RQ ) v alues for d irect e ffects to a quatic n onvascular and vascular p lants from d imethoate technical grade active ingredient ( TGAI ) 1

Use (s) Scenario Applica

tion

Method Peak

EECs (μg ai /L) Aquatic Nonvascular Plants

E C 50 = 20 ,000 μ g/L

NOAEL = 9 ,000 μ g/L Aquatic Vascular Plants

E C 50 >92

, 6 00 μ g/L

NOAEL = 92

, 6 00 μ g/L

Listed RQs 2 Non

- listed RQs 3 Listed RQs 2 Non

- listed RQs 3

03_MN_alfalfa Alfalfa, sainfoin Aerial 8.5 0.001 <0.001 <0.001 <0.001

05_CA_Cole crops Brussels Sprouts (ground) Ground 23 0.003 0.001 <0.001 <0.001

10_WA_Orchards Cherry (only in ID, MT, OR, UT or WA) Aerial 9.4 0.001 <0.001 <0.001 <0.001

12_OR_Xmas trees Douglas fir (seed orchards) (only in OR and WA) Airblast 10 0.001 0.001 <0.001 <0.001

14_OR_Xmas trees Hybrid cottonwood/poplar plantations (some labels allow certain uses in ID, OR and WA) Aerial 34 0.004 0.002 <0.001 <0.001

15_CA_Nursery Citrus, non

- bearing and nursery stock (only in CA and AZ) Soil

drench 6.6 0.001 <0.001 <0.001 <0.001

17_OR_Nursery Ornamental woody shrubs and vines; Ornamental

and/or shade trees Aerial 21 0.002 0.001 <0.001 <0.001

20_FL_Peppers Peppers Aerial 22 0.002 0.001 <0.001 <0.001

23_MS_Cotton Cotton Aerial 9.7 0.001 <0.001 <0.001 <0.001

26_FL_Citrus Grapefruit, kumquat, lemon, lime, orange, pumello (shaddock),

tangelo, tangerine Aerial 2 0.002 0.001 <0.001 <0.001

1 Risk to l isted aquatic plant LOC = 1; Risk to n on

- listed aquatic plant LOC = 1

2 Estimated by dividing the peak EEC by the most sensitive NOAEC

3 Estimated by dividing the peak EEC by the most sensitive EC 50

### Page 60 of 144 

## 4.2 **Terrestrial Organisms**

4.2.1 Acute Dose

- Based Risk to Birds

Acute dose

- based RQs for birds exceed the acute risk to listed and non

- listed LOCs for nearly all

scenarios and all bird sizes ( Table 32 )

. RQs excee d the LOC for risk to listed and non

- listed species for all uses for a small bird consuming short grass, tall grass, broadleaf plants, fruits and arthropods. Acute RQ value s that exceed the LOC s for acute risk to non

- listed and listed species ranged from roughly 9 to 262 for short grass, 4 to 120 for tall grass, 5 to 147 for broadleaf plants,

0.57 to 16 for fruits and 3.5 to 10 3 for arthropods. For a small bird consuming grains, RQs exceeding the LOC for listed s pecies ranged from 0.13 to 0.48 and RQs exceeding the LOC for

risk to non

- listed species range from roughly 1. 1 to 3.6.

For medium

- size d birds, acute, dose

- based RQ values exceed the LOC for risk to listed and non

listed species for all uses with short gr ass, tall grass, broadleaf plants and arthropods . F or a medium

- sized bird s consuming fruits, the dose

- based RQ value s exceed the acute risk LOC for

non

- listed species for all but two scenarios. The dose

- based RQ value s that exceed the acute risk

LOC for n on

- listed species range from roughly 4 to 117 for short grass, 1. 9 to 5 4 for tall grass,

2. 3 to 66 for broadleaf plants, 1. 6 to 4 6 for arthropods and 0.67 to 7.3 for fruits; RQ value s that only exceed the LOC for acute risk to listed species range from 0.2 5 to 0.41 for medium

- sized birds consuming fruit. For a medium

- sized bird consuming grains, RQ value s range from roughly 0.06 to 1.6; RQs that exceed the LOC for risk to listed species range from 0.15 to 0.49 and RQ value s that exceed the LOC for acute ri sk to non

- listed species ranged from roughly 0 .80

to 1.6 3

.

For large

- sized birds, dose

- based RQ value s exceed the acute risk LOC for listed and non

- listed species for all scenarios with short grass, tall grass, broadleaf plants and arthropods. D ose

- based RQ value s that exceed the acute risk LOC for non

- listed species range from roughly 1 .3 to 37 for short grass, 0.59 to 17 for tall grass, 0.7 to 2 1 for broadleaf plants and 0.5 to 1 5 for arthropods.

The dose

- based RQ value s for large

- sized bird s consuming fruits exceed the acute risk LOC for listed species and rang e from 0.13 to 0.21 ; RQ values that exceed the acute risk LOC for non

listed species range from roughly 0.5 to 2.3. For a large

- sized bird s consuming grains, dose

based RQ value s r ange from 0.02 to 0.52 and for those that exceed the acute risk LOC for listed species ranged from 0.12 to 0.25 ; o nly one RQ value exceed s the acute risk LOC for non

- listed large birds consuming grains at 0.52.

### Page 61 of 144 Table 32 . Acute d ose

- based risk quotient ( RQ ) values for b irds e xposed to technical grade d imethoate (T

- REX v. 1.5.2) 1,2
Primary Feeding Strategy  Herbivores and Omnivores Insectivores Granivores

Animal Size
 Sm Med Lg Sm Med Lg Sm Med Lg

Dietary Items Short GrassTall GrassBroad-leafPlantsFruits, pods,seeds,etc.Short GrassTall GrassBroadleafPlantsFruits, pods,seeds,etc.Short GrassTall GrassBroadleafPlantsFruits, pods,seeds,etc.

Arthropods Seeds, grains, etc

.

Use(s) 

Non

- Food Uses

Douglas fir (seed orchards) (only in OR and WA) 262 120 147 16 117 53 66 7.3 37 17 20 2.3 102 45 14 3.6 1.63 0.52

Hybrid cottonwood/poplar plantations (some

labels allow use in ID, OR and WA) 127 58 71 8.0 57 26 32 3.5 18 8.3 10 1.1 50 22 7 1. 7 0.80 0.25*

Ornamental woody shrubs and

vines 60 27 33 3.7 27 12 15 1.6 8.5 3.9 4.8 0.54 23 10 3.3 0.84 0.38* 0.12*

Ornamental Herbaceous plants 14 6 8 0.9 1 6.5 2.9 3.6 0.41* 2.0 0.95 1.1 0.13* 5.7 2.5 0.81 0.20* 0.09 0.03

Food Uses

Cherry 78 36 44 4.9 35 16 19 2.2 11 5 6 0.7 0 30 13 4.3 1. 1 0.49* 0.16*

Soybeans 34 15 19 2. 2 15 7. 1 8.7 0.97 4.9 2. 3 2.7 0.31* 13 6. 1 1.9 0.48* 0.21* 0.07

Peppers 24 11 13.5 1.50 10 4.9 6.0 0.67 3.4 1.5 1.9 0.21* 9.4 4.2 1.3 0.33* 0.15* 0.05

Succulent peas 9. 1 4.1 5.1 0.57 4. 1 1.8 2.2 0.25* 1.2 0.59 0.73 0.08 3.5 1.5 0.51 0.13* 0.06 0.02

1 RQ values in bold exceed the acute risk to non

- listed species LOC of 0.5. Values with an asterisk i ndicate that the RQ exceeds the LOC for acute risk to listed birds.

2 Acute risk to listed species LOC = 0.1; acute restricted use LOC = 0.2; acute risk to non

- listed species LOC = 0.5

### Page 62 of 144 

## 4.2.2 Acute D ietary Risk to Birds

D ietary

- based RQ value s c an be found in Table 3 3

. RQ value s exceed the acute risk LOC for all

but two uses for those birds wh ich consume short grass, tall grass, broad leaf plants and arthropods. The uses of dimethoate on ornamental herbaceous plants and succulent peas are the only uses that d o not result in exceedance of the acute risk to non

- listed species LOC o f 0.5.

### Page 63 of 144 Table 3 3 . Acute d ietary

- b ased risk quotients ( RQs ) for b irds of Different Feeding Classes (T

- REX v. 1.5.2) 1,2

Primary Feeding Strategy  Herbivores, Omnivores, and Granivores Insectivores

Dietary Items 

Short Grass Tall Grass Broad

- leaf Plants Fruits, pods, seeds, etc

. Arthropods

Use(s) 

Non

- Food Uses

Douglas fir (seed orchards) (only in OR and WA) 7.2 3.3 4.0 0.45 * 2.8

Hybrid cottonwood/poplar plantations (some labels allow use in ID, OR and WA) 3.5 1.6 1.9 0.22 * 1.3

Ornamental woody shrubs and vines 1.6 0.7 0.93 0.10 * 0.65

Ornamental Herbaceous plants 0.40 * 0.18 * 0.23 * 0.03 0.16 *

Food Uses

Cherry 2.1 0.9 0 1.2 0.14 * 0.85

Soybeans 0.95 0.43 * 0.53 0.06 0.37 *

Peppers 0.66 0.30 * 0.37 * 0.04 0.26 *

Succulent peas 0.25 * 0.11 * 0.14 * 0.02 0.10 *

1 RQ values in bold exceed the non

- listed species LOC of 0.5. *Indicate RQ value exceeding the listed species LOC of 0.05

2 Acute risk to listed species LOC = 0.1; acute restricted use LOC = 0.2; acute risk to non

- listed species LOC = 0.5

### Page 64 of 144 

## 4.2.3 Chronic Risk to Birds

D ietary based RQ value s for birds exceed the chronic risk LOC for birds foraging on short grass, tall grass, broad

- leaf plants and arthropod s ( Table 3 4 ) . For birds consuming short grass, RQ

value s exceed the chronic risk LOC across all uses and ranged from roughly 9.3 to 270. For

birds consuming tall grass, RQs exceed the chronic risk LOC across all uses and ranged from roughly 4. 3 to 12 3 . For birds consuming broad

- leaf plants, RQs exceed the chro nic risk LOC across all uses and ranged from roughly 5. 2 to 151. For birds consuming fruits, pods, seeds etc

., RQs ranged from 0.59 to roughly 16. For birds consuming arthropods, RQs exceed the chronic

risk LOC across all uses and ranged from 3.6 to 105.

### Page 65 of 144 Table 34 . Chronic d ietary

- b ased risk quotients ( RQs ) for Birds of d ifferent f eeding c lasses (T

- REX v. 1.5.2)
Primary Feeding Strategy  Herbivores, Omnivores, and Granivores Insectivores

Dietary Items 

Short Grass Tall Grass Broad

- leaf

Plants Fruits, pods, seeds, etc. Arthropods

Use(s) 

Non

- Food Use s

Douglas fir (seed orchards) (only in OR and WA) 270 123 151 16 105

Hybrid cottonwood/poplar plantations (some labels allow use in ID, OR and WA) 131 60 74 8.2 51

Ornamental woody shrubs and vines 62 28 34 3.8 24

Ornamental Herbaceous plants 15 6.8 8. 4 0.94 5.8

Food Uses

Cherry 81 37 45 5.0 31

Soybeans 35 16 20 2.2 13

Peppers 24 11 13 1.5 9.6

Succulent peas 9.3 4. 3 5.2 0.59 3.6

RQ values in bold exceed the LOC of 1 for chronic risk to both listed and non

- listed species.

### Page 66 of 144 

## 4.2.4 Acute Risk to Mammals

D ose

- based RQs for mammals exposed to dimethoate exceed LOCs for acute risk to listed and

non

- listed species for multiple uses ; the majority of the exceedances a re for small

- sized

herbivorous and omnivorous mammals. These results are tabulated in Table 3 5.

For small

- sized mammals consuming short grass, RQs range from 0.05 to 1.3; four of the scenarios result in RQs that exceed the LOC for acute risk to listed species and range fr om 0.12 to 0.39; two scenarios resulted in RQs that exceed the LOC for acute risk non

- listed species at 0.64 and 1.3. For small mammals consuming tall grass, RQs ranged from 0.02 to 0.60; three of the scenarios resulted in RQs that exceed the LOC for acut e risk to listed species and range from 0.14 to 0.29; one RQ exceed s the LOC for acute risk to non

- listed species at 0.60. For small mammals consuming broad

- leaf plants, RQs range from 0.03 to 0.74; four of the scenarios result in RQs that exceed the LOC for acute risk to listed species and range from 0.1 to 0.36; only one

scenario has an RQ that exceed s the LOC for acute non

- listed species at 0.74. For small mammals consuming arthropods, RQs ranged from 0.02 to 0.51; three of the scenarios have RQs

that e xceed the LOC for acute risk to listed species and range from 0.12 to 0.25; one scenario has

an RQ that exceed s the LOC for acute risk to non

- listed species at 0.51. For small mammals consuming fruits, the RQs range from < 0.0 1 to 0.08; within this foraging category there is only one RQ that exceed s the LOC for acute risk to listed species. N o ne of the RQ values for

medium

- sized mammals consuming grains exceed the acute risk LOCs as RQs range from <0.01

to 0.02.

For medium

- sized mamma ls consuming short grass, RQs range from 0.04 to 1.1 ; four of the scenarios result in RQs that exceed the LOC for acute risk to listed species and range from 0.10 to 0.34; two of the scenarios result in RQs that exceed the LOC for acute risk to non

- listed species at 0.55 and 1.1. For medium

- sized mammals consuming tall grass, the RQs range from 0.02 to 0.51; four of the scenarios result in RQs that exceed the LOC for risk to listed species and range from 0.12 to 0.25; one of the scenarios exceed s the LOC f or risk to non

- listed species at

0.51. For medium

- sized mammals consuming broadleaf plants, RQs range from 0.02 to 0.63; three of the scenarios result in RQ s that exceed the LOC for risk to listed species and range from 0.14 to 0.31; only one scenario wit h an RQ of 0.63 exceed s the LOC for risk to non

- listed species. For medium

- sized mammals consuming arthropods, overall RQs range from 0.02 to

0.44 with four scenarios that exceed the LOC for risk to listed species and ranged from 0.10 to 0.44; there were no RQs that exceed the LOC for risk to non

- listed species. For medium

- sized mammals consuming fruits, RQs range from 0.00 to 0.07 with only one RQ of 0.07 that exceed s the LOC for risk to listed species. There a re no RQ exceedances for medium

- sized mamm als consuming grains.

For large

- sized mammals consuming short grass, overall the RQs range from 0.02 to 0.06; three

of the scenarios result in RQs that exceed the LOC for acute risk to listed species and range from 0.14 to 0.29; there i s one RQ that exc eed s the LOC for acute risk to non

- listed species at 0.60. For large

- sized mammals consuming tall grass, overall RQs range from 0.01 to 0.27; there a re two scenarios where the RQs exceed the LOC for acute risk to listed species at 0.13 and 0.27;

there a re no LOC exceedances for acute risk to non

- listed species. For large

- sized mammals consuming broadleaf plants, overall RQs range from 0.01 to 0.34; there a re three scenarios that

### Page 67 of 144 

### exceed the LOC for acute risk to listed species and range from 0.10 to 0.34; no ne of the RQs for large mammals foraging on broadleaf plants exceed the LOC for risk to non

- listed species. For large mammals consuming fruits, overall RQs range from 0.01 to 0.23; there a re two scenarios

where RQs exceed the LOC for risk to listed sp ecies at 0.11 and 0.23; there a re no exceedances

for acute risk to non

- listed species. There a re no RQs that exceed the LOC for risk to listed or

non

- listed speci es for large mammals consuming fruits or grains as RQ value s range from 0.0 to

0.04 and <0.01 to 0.01

, respectively.

### Page 68 of 144 Table 35. Acute d ose

- based risk quotient ( RQ ) values for m ammals e xposed to d imethoate (T

- REX v. 1.5.2) 1

Primary Feeding Strategy  Herbivores and Omnivores Insectivores Granivores

Animal Size  Sm Med Lg Sm Med Lg Sm Med Lg

Dietary Items Short GrassTall GrassBroad-leafPlantsFruits, pods,seeds,etc.Short GrassTall GrassBroadleafPlantsFruits, pods,seeds,etc.Short GrassTall GrassBroadleafPlantsFruits, pods,seeds,etc.

Arthropods Seeds, grains, etc

.

Use(s) 

Non

- Food Uses

Douglas fir (seed orchards) (only in OR and WA) 1.3 0.60 0.74 0.08 * 1.1 0.51 0.63 0.07 * 0.60 0.27 * 0.34 * 0.04 0.51 0.44 * 0.23 * 0.02 0.02 0.01

Hybrid cottonwood/poplar plantations (some labels allow use in ID, OR and WA) 0.64 0.29 * 0.36 * 0.04 0.55 0.25 * 0.31 * 0.03 0.29 * 0.13 * 0.16 * 0.02 0.25 * 0.21 * 0.11 * 0.01 0.01 <0.01

Ornamental woody shrubs and

vines 0.30 * 0.14 * 0.17 * 0.02 0.26 * 0.12 * 0.14 * 0.02 0.14 * 0.06 0.08 0.01 0.12 * 0.10 * 0.05 <0.01 <0.01 <0.01

Ornamental Herbaceous plants 0.07 0.03 0.04 0.00 0.06 0.03 0.03 0.00 0.03 0.02 0.02 0.00 0.03 0.02 0.01 <0.01 <0.01 <0.01

Food Uses

Cherry 0.39 * 0.18 * 0.22 * 0.02 0.34 * 0.15 * 0.19 * 0.02 0.18 * 0.08 0.10 * 0.01 0.15 * 0.13 * 0.07 0.01 <0.01 <0.01

Soybeans 0.17 * 0.08 0.10 * 0.01 0.15 * 0.07 0.08 0.01 0.08 0.04 0.04 0.00 0.07 0.06 0.03 <0.01 <0.01 <0.01

Peppers 0.12 * 0.05 0.07 0.01 0.10 * 0.05 0.06 0.01 0.05 0.03 0.03 0.00 0.05 0.04 0.02 <0.01 <0.01 < 0.01

Succulent peas 0.05 0.02 0.03 0.00 0.04 0.02 0.02 0.00 0.02 0.01 0.01 0.00 0.02 0.02 0.01 <0.01 <0.01 <0.01

1 RQ values in bold exceed the acute risk to non

- listed species LOC of 0.5. Values with an asterisk indicate that the RQ exceeds the LOC for acute risk to listed species

.

### Page 69 of 144 

## 4.2.5 Chronic Dose

- Based Risk to Mammals

D ose

- based RQ values for mammals result in LOC exceedances for chronic risk to listed and

non

- listed species across all scenarios ( Table 36 )

.

For s mall

- sized mammals chronic RQs exceed the chronic risk LOC by up to three orders of magnitude; the ranges of the RQs across scenarios for small mammals consuming the following

food items are : 162 to 4685 for short grass, 74 to 2147 for tall gras s, 91 to 2635 for broadleaf plants, 10 to 292 for fruits, 63 to 183 4 f or arthropods and 1.9 to 55 for grain. For medium

- sized mammals RQs also exceed the chronic risk LOC by up to three orders of magnitude; ranges RQs

across scenarios and food items are : 138 to 4001 for short grass, 63to 1834 for tall grass, 78 to

225 1 for broadleaf plants, 8.6 to 250 for fruits, 54 to 1567 for arthropods, and 1.9 to 55 for grains. For large

- sized mammals

, chronic RQs ranges across all scenarios and forag e categories are: 74 to 2145 for short grass, 34 to 983 for tall grass, 41to 1206 for broadleaf plants, 4.6 to 134 for fruits, 29 to 840 for arthropods, and 1.0 to 29 for grains.

### Page 70 of 144 Table 36. Chronic d ose

- based risk quotient ( RQ ) v alues for m ammal s e xposed to d imethoate (T

- REX v.1.5.2). 1,2

Primary Feeding Strategy  Herbivores and Omnivores Insectivores Granivores

Animal Size  Sm Med Lg Sm Med Lg Sm Med Lg

Dietary Items Short GrassTall GrassBroad-leafPlantsFruits, pods,seeds,etc.ShortGrassTall GrassBroadleafPlantsFruits, pods,seeds,etc.Short GrassTall GrassBroadleafPlantsFruits, pods,seeds,etc.

Arthropods Seeds, grains,

etc

. Use(s) 

Non

- Food Uses

Douglas fir (seed orchards) (only in OR and WA) 4685 2147 2635 292 4001 183 4 2251 250 2145 983 1206 134 1835 1567 840 65 55 29

Hybrid cot tonwood/poplar plantations (some labels allow use in ID, OR and WA) 2286 1048 1286 142 1953 895 1098 122 1047 479 588 65 895 765 410 31 27 14

Ornamental woody shrubs and vines 1078 494 606 67 920 422 518 57 493 226 277 30 422 360 193 1 5 12 6

Ornamental Herbaceous plants 260 119 146 16 222 101 125 13 119 54 67 7.4 101 87 46 3.6 3.0 1. 7

Food Us es

Cherry 140 5 644 790 87 1200 550 675 75 643 29 5 362 40 550 470 252 19 16 8.9

Soybean s 617 282 347 38 527 241 296 32 282 129 158 17 241 206 110 8.5 7.3 3.9

Peppers 429 196 241 26 366 168 206 22 196 90 110 12 168 143 77 5.9 5.0 2.7

Succule nt peas 162 74 91 10 138 63 78 8.6 74 34 41 4.6 63 54 29 2.2 1.9 1.0

1 RQ val ues in bold exceed the chronic risk LOC of 1 for both listed and non

- listed species. 2 Using adjusted NOAEL values of 23.30, 18.85, and 8.15 for small, medium, and large mammals, respectively.

2 Chronic risk to listed and non

- listed species LOC = 1.

### Page 71 of 144 

## 4.2.6 Chronic Dietary

- Based Risk to Mammals

D ietary

- based RQs for mammals exceed the chronic risk LOC across all forage items and for all

scenarios ( Table 37 )

. The range of RQs across forage items is 18 to 540 for mammals consuming short gr ass, 8.5 to 247 for mammal s consuming tall gra ss, 10 to 303 for mammal s consuming broadleaf plants , 1.1 to 33 for mammals consuming fruits and 7.3 to 211 for

mammals consuming arthropods.

Table 37. Chronic d ietary

- b ased risk quotient ( RQ ) values for m ammals e xposed to d imethoate (T

- REX v.1.5.2) 1,2
Primary Feeding Strategy  Herbivores, Omnivores, and Granivores Insectivores

Dietary Items 

Short Grass Tall Grass Broad

- leaf

Plants Fruits, pods, seeds,

etc

. Arthropods

Use(s) 

Non

- Food Uses

Douglas fir (seed orchards) (only in OR and WA) 540 247 303 33 211

Hybrid cottonwood/poplar plantations (some labels allow use in ID, OR and WA) 263 120 148 16 103

Ornamental woody shrubs and vines 124 56 69 7.7 48

Ornamental Herbaceous plants 30 13 16 1.8 11

Food Uses

Cherry 162 74. 91 10 63

Soybeans 73 32 40 4. 4 27

Peppers 49 22 27 3.0 19

Succulent peas 18 8.5 10 1 .1 7. 3

1 Bolded cells indicate that the dietary

- based RQ exceeds the LOC for chronic risk to listed and non

- listed mammals.

2 Chronic risk LOC = 1, NOAEL used for RQ estimation i s 0.1 mg/kg bw

.



## 4.2.7 Risk to Honey B ees

Tier 1 Risk Assessment Tier 1 (screening

- level) RQ values for bees are derived below by dividing the contact or oral

EEC b y the acute contact or oral LD 50 

### value s ( Table 25 ) , r espectively. These Tier 1 RQ values are then compared to the acute risk LOC of 0.4, which corresponds to a 10% probability of mortality based on the median probit mortality slope across multiple pesticides. Tier 1 RQ

values for selected folia r and soil applications of dimethoate are provided in Table 38 and Table

39 , respectively. Since data on the acute toxicity of dimethoate to honey bee larvae were not available, RQ values could not be determined for larval bees. Although dimethoate is comm only

used as a reference toxic

### Page 72 of 144 

### As indicated in Tables 38 and 39 , the Tier 1 acute RQ values for adult honey bees exceed the

acute risk LOC of 0.4 for all use categories and exposure routes assessed. Specifically, acute contact RQ values derived for folia r applications range from 4.2 to 76 while acute oral RQ values range from 89 to 2580. For soil applications, Tier 1 acute RQ values for adult honey bees range from 0.88 to 34. These findings of potential risk of dimethoate to honey bees are not

unexpecte d given its high acute toxicity to honey bees and also because it is commonly used as a

reference toxicant in laboratory

- based studies as well as in semi

- field (tunnel) studies conducted at similar application rates ( e.g. , 600 g a.i./ha or 0.54 lb a.i./A).

Table 38. Tier I risk quotient ( RQ ) values for honey bees exposed to dimethoate through foliar spray applications

Use Pattern Adult Larvae

Contact * Dietary * Dietary*

Non

- Food Uses

Douglas fir (seed orchards) (only in OR and WA) 7 6 2580 N/A

Hybrid cottonwood/poplar plantations (some labels allow use in ID, OR and WA) 3 4 1150 N/A

Ornamental woody shrubs and vines 1 7 574 N/A

Ornamental Herbaceous plants 4.2 143 N/A

Food Uses

Cherry 2 3 774 N/A

Soybeans 8.4 287 N/A

Peppers 5. 7 193 N/A

Succulent peas 2.6 89 N/A

* Adult contact LD 50 = 0.16 μ g a.i./bee; a dult oral LD 50 = 0.056 μ g a.i./bee. Data on the toxicity of dimethoate to honey bee larvae are not

available . EECs for foliar applications are provided in Table 14.

**Values in bold exceed the acute risk LOC of 0.4

.



### Table 39

. Tier I risk quotient ( RQ ) values for honey bees exposed to dimethoate through soil applications

Use Pattern Adult * Larvae *

Dietary

Hybrid cottonwood/poplar plantations 3 4 N/A

Ornamental woody shrubs and vines 1 7 N/A

Melon, Watermelon 5.6 N/A

Succulent peas 0.88 N/A

* Adult contact LD 50 = 0.16 μ g a.i./bee; a dult oral LD 50 = 0.056 μ g a.i./bee. Data on the acute toxicity of dimethoate to honey bee larvae are

not available . EECs for soil applications are provided in Table 15.

**Values in bold exceed the acute risk LOC of 0.4

.



### Although RQ values could not be calculated for larval bees due to the lack of a larval LD 50 

### value with dimethoate, dimethoate is routinely used as a reference toxicity in larval bee toxicity studies. In these tests, a single dose of dimethoate is used to demonstrate exposure and toxicity to bees. Although an LD 50 

### for dimethoate cannot be calcu lated from these studies, the toxicity

### Page 73 of 144 

### associated with the administered dose to larval bees can be used to provide context to the calculated Tier 1 EECs for honeybee larvae. For example, in a recent study with sulfoxaflor and honeybee larvae (MRID 4875560 3), dimethoate was administered at 1 ug a.i./larval bee/day for 5 days. By day 7, 98% mortality was observed with larval honeybees. Data from later portions of this study could not be used due to high mortality of control bees during pupation. Nonetheles s, it is evident that Tier 1 screening EECs honeybee larvae determined with foliar applications of dimethoate (2.1

– 61 ug a.i./bee/d; Table 2 1 ) are 2X to 60X greater than the dose causing near complete mortality in larval bees (1 ug a.i./bee/d). This sug gests risk to larval bees based on Tier 1 exposure modeling. The Tier 1 EECs determined for soil drench applications (0.021

– 0.81 ug a.i./bee/d; Table 2 2 ) are lower than dose associated with 98% mor t ality of larval bees (1 ug a.i./bee/d). Since a dose

- r esponse relationship is not available for dimethoate and larval honeybees, it cannot be determined to what extent soil drench applications may result in risk to

larval bees.

Higher Tier Risk Assessment : Although risks to adult honey bees are indicated bas ed on Tier 1 risk assessment, it is desirable to evaluate risks at higher tiers of refinement, particularly since higher tier studies evaluate the

effects on whole colonies whereas Tier 1 studies evaluate effects on individual bees. As noted previously in the characterization of effects of dimethoate on bees, no Tier 2 (semi

- field) studies were submitted to the Agency in order to evaluate the potential for colony

- level effects under

semi

- controlled conditions. However, relevant information can be gleaned from the use of

dimethoate as a reference toxicant in semi

- field (tunnel) studies 13 

### . Available data indicate that a foliar application of 0.53 lb a.i./A to blooming Phacelia with bees actively foraging in tunnels,

sustained increases in worker bee mortalit y, decreases in flight activity and behavioral

abnormalities occurred (MRID 48755603). Effects on brood development was inconclusive due to limitations in the design and execution of the tunnel studies considered in that assessment.

The results from th e Tier 3 full field study with dimethoate indicates that acute mortality was observed, which is consistent with what dose

- and dietary

- based RQs would suggest. However, at the whole colony level, the bees appeared to recover. Although the Tier 1 and Tier 2 risk assessment identifies the uncertainty related to risk to larvae, the Tier 3 field study suggests that under the conditions tested, larvae appeared to be less sensitive than adults; however, the extent of exposure experienced by bees in the Tier 3 f ield study is uncertain. There is also uncertainty given that the application rate in the study is lower than the maximum allowed and it is unclear as to the extent to which bees foraged on the treated site.



## 4.2.8 Risk to Terrestrial Plants

N one of th RQs ex ceed the LOC for risk to non

- target monocots adjacent to dimethoate use areas for spray drift only as a route of exposure, and runoff and spray drift in dry areas as a route of exposure. For runoff and spray drift in semi

- aquatic areas, there a re RQs that exceed the LOC

for risk to both listed and non

- listed terrestrial plant species. For non

- listed species in a semi

-

13 http://www.regulations.gov/#!documentDetail;D=EPA

- HQ

- OPP

- 2010

- 0889

- 0022

### Page 74 of 144 

### aquatic area exposed via runoff and spray drift, overall RQs range from <0.1 to 1.67, with two RQ scenarios exceeding the LOC at 1.55 and 1. 67; for listed species, RQs range from 0.17 to 3.32 with five scenarios exceeding the LOC with values ranging from 1.00 to 3.32. Results have

been tabulated in Table 40

.

Table 40. Risk quotient ( RQ ) values for n on

- target m onocots plants a djacent to d imethoate Use

Areas 1

Crop Single Max. Application

Rate (lbs ai /A) Monocot RQ Values

Spray Drift Only Runoff and Spray Drift ( Dry Areas ) Runoff and Spray Drift ( Semi

- Aquatic

Areas )

Non

listed Species Listed Species Non

listed Species Listed Species Non

- listed Species Listed Species

Douglas Fir Aerial: 4.5 0.15 0.47 0.30 0.60 1.67 3.32

Ground: 4.5 <0.1 <0.1 0.18 0.36 1.55 3.08

Hybrid cottonwood Aerial: 2 <0.1 0.21 0.14 0.27 0.74 1.48

Ground: 2 <0.1 <0.1 <0.1 0.1 6 0. 69 1.37

Ornamental woody

shrubs and vines Aerial: 1 <0.1 0.10 <0.1 0.13 0.37 0.74

Ground: 1 <0.1 <0.1 <0.1 <0.1 0.34 0.68

Ornamental Herbaceous Aerial: 0.25 <0.1 <0.1 <0.1 <0.1 <0.1 0.18

Ground: 0.25 <0.1 <0.1 <0.1 <0.1 <0.1 0.17

Cherry Aerial: 1.35 <0.1 0.14 <0.1 0.18 0.50 1.00

Ground: 1.35 <0.1 <0.1 <0.1 0.11 0.47 0.92

Soybeans Aerial: 0.5 <0.1 <0.1 <0.1 <0.1 0.19 0.37

Ground: 0.5 <0.1 <0.1 <0.1 <0.1 0.17 0.34

Peppers Aerial: 0.336 <0.1 <0.1 <0.1 <0.1 0.12 0.25

Ground: 0.336 <0.1 <0.1 <0.1 <0.1 0.12 0.23

Succulent peas Aerial: 0.156 <0.1 <0.1 <0.1 <0.1 <0.1 0.12

Ground: 0.156 <0.1 <0.1 <0.1 <0.1 <0.1 0.11

1 LOCfor listed and non

- listed species = 1 ; values in bold exceed the LOC



### None of the RQs exceed the LOC for risk to non

- list ed dicots adjacent to dimethoate use area for crops exposed via spray drift only. For listed non

- target dicots, RQs range from <0.1 to 1.96 with two scenarios resulting in RQ values with LOC exceedances at 1.17 and 1.96. There a re LOC exceedances for risks to both non

- listed and listed dicot species exposed via runoff and spray drift in a semi aquatic area; overall, RQs range from <0.1 to 2.95 for non

- listed species and 0.35 to 10.76 for listed species. There were four scenarios that result in LOC exceedan ces for

risk to non

- listed species with RQs rang ing from 1.21 to 2.95; there a re 10 scenarios that result in

LOC exceedances for risk to listed species with RQ values rang ing from 1.11 to 10.76. Results

have been tabulated in Table 41

.

### Page 75 of 144 Table 41. Risk quotient ( RQ ) value s for n on

- target d icot plants a djacent to d imethoate u se a reas 1

Crop Single Max. Application

Rate (lbs ai /A) Dicot RQ Values

Spray Drift Only Runoff and Spray Drift ( Dry Areas ) Runoff and Spray Drift ( Semi

- Aquatic Areas )

Non

listed Species Listed Species Non

listed Species Listed Species Non

- listed Species Listed Species

Food crops

Douglas Fir Aerial: 4.5 0.27 0.98 0.54 1.96 2.95 10.76

Ground: 4.5 <0.1 0.20 0.32 1.17 2.73 9.98

Hybrid cottonwood Aerial: 2 0.12 0.43 0.24 0.87 1.31 4.78

Ground: 2 <0.1 <0.1 0.14 0.52 1.21 4.43 Ornamental woody

shrubs and vines Aerial: 1 <0.1 0.22 0.12 0.43 0.65 2.39

Ground: 1 <0.1 <0.1 <0.1 0.26 0.61 2.22

Ornamental Herbaceous Aerial: 0.25 <0.1 <0.1 <0.1 0.11 0.16 0.60

Ground: 0.25 < 0.1 <0.1 <0.1 <0.1 0.15 0.55

Cherry Aerial: 1.35 <0.1 0.29 0.16 0.59 0.88 3.23

Ground: 1.35 <0.1 <0.1 <0.1 0.35 0.82 2.99

Soybeans Aerial: 0.5 <0.1 0.11 <0.1 0.22 0.33 1.20

Ground: 0.5 <0.1 <0.1 <0.1 0.13 0.30 1.11

Peppers Aerial: 0.336 <0.1 <0.1 < 0.1 0.15 0.22 0.80

Ground: 0.336 <0.1 <0.1 <0.1 <0.1 0.20 0.75

Succulent peas Aerial: 0.156 <0.1 <0.1 <0.1 <0.1 0.10 0.37

Ground: 0.156 <0.1 <0.1 <0.1 <0.1 <0.1 0.35

1 LOC for listed and non

- listed species = 1 ; values in bold exceed the LOC



## 4.3 **Risk Description** 

In risk description, the results from the risk estimation are interpreted and synthesized into overall risk conclusions. This description considers other lines of evidence ( e.g ., monitoring data, field data, refined exposure and effects modeling) for characterizing ecological risk. In addition, the risk description also contains a discussion of relevant sources of uncertainty in the risk assessment and sensitivity of the risk assessment findings to important methodological assumptions. The risk descripti on also addresses other concerns including risks to threatened and endangered species, a discussion of uncertainty, and the sensitivity of risk conclusions to assumptions made in the assessment.

Based on the preliminary problem formulat ion written in support of the Registration Review of dimethoate, the risk hypothesis indicated that when used in accordance with current labels, o ff

site movement of dimethoate and its omethoate transformation product can occur via runoff,

spray

- drift, and atmospheric transport leading to exposure of non

- target plants and animals. Monitoring data indicate detections of dimethoate and omethoate in surface waters and at sites

distant from use areas. Therefore, a pplications to foliar surfaces may serve as a major source of dimethoate exposure to terrestrial and aquatic organi s ms. These potential exposure pathway s may result in adverse effects upon the survival, growth, and reproduction of non

- target organisms. Based on exposure and effects data presented in the preceding section, potential risks to multiple taxa are identified. Other lines of evidence are considered in this section in order to put risk estimates into context and to highlight uncertainties and underlying assumptions that can

### Page 76 of 144 

### affect the asses sment.



## 4.3.1 Risk to Aquatic Organisms

A summary of the maximum dimethoate acute and chronic RQ values derived for aquatic

animals is shown in Table 42 . None of the RQ values for freshwater fish and estuarine/marine fish exceed the applicable acute or chronic risk LOC s ; specifically, the acute RQ values are two

orders of magnitude below the acute risk to non

- listed species LOC of 0.5. The RQ values are also two orders of magnitude below the chronic risk LOC of 1.0. Both acute and chronic

freshwater an d estuarine/marine invertebrate RQs exceed the respective LOC s of 0.5 and 1.0. For estuarine/marine invertebrates, the RQ s exceed the chronic risk LOC of 1.0 by 2 orders of magnitude.

Table 42. Summary of aquatic animal risk profile for Dimethoate

Exposure FW Fish RQ SW Fish RQ FW Invert. RQ SW Invert. RQ

Acute 0.006 <0.001 0.793 1.110

Chronic 0.047 0.013 53.40 133.5

RQ values based on the maximum aquatic EECs derived from the 14 OR Christ mas t rees exposure scenario; see Risk Estimation Section 5.1 for derivation of these RQ values



### Monitoring data found dimethoate to be present in surface water. Based on NA W QA data , there were 8,726 samples taken from 2001 to 2012; dimethoate was detected in 128 of the samples and ranged from 0.0036 to 0.494 ppb while the LODs were reported to be between 0.0021 and 0.10 ppb. The highest concentration of 0.494 ppb was taken in 2010

, modeling yielded peak EECs ranging from 5.07 ppb to 44.3 ppb; therefore, the monitoring was around one order of magnitud e lower than the modeling, which is expected for non

- targeted monitoring ; however, the monitoring results appear to support a low frequency of detection. Despite the low level of detection seen in the monitoring data, EFED believes the concentrations used for modeling surface waters are realistically conservative such that the low risk to fish and potential risk to aquatic invertebrates are considered reasonable

.



## 4.3.2 Risk to Freshwater and Estuarine/Marine Fish

None of the RQ values for freshwater fish and e stuarine/marine fish exceed the applicable acute

or chronic risk LOC.

There were four incidents reported in EIIS involving fish kills from 1972 to 1995. Two of the

incidents were considered to be the result of misuse of the registered products and outsi de of the registered used of dimethoate and thus will not be considered here. Two of the incidents were a result of a ‘registered use’ of dimethoate; one was classified as ‘probable’ and the other classified as ‘possible.’ There were few details provided in the incidents regarding application scenarios or events leading up to the fish kill; additionally in both incidents, dimethoate was found in addition to other chemicals. While the incidents demonstrate the potential for a

### Page 77 of 144 

### complete exposure pathway for dimethoate to harm aquatic organisms, there is uncertainty regarding the role of other chemicals ; furthermore, RQ values for are well below the acute risk

LOC s (maximum RQ = 0.006) and chronic risk LOC (maximum RQ= 0.036).



## 4.3.3 Risk to Aquatic Invertebrates

Based on the results of risk estimation, there is potential risk to both freshwater and

estuarine/marine invertebrates on an acute and chronic exposure basis using maximum labeled

use rates

.

To evaluate potential risks, EECs were also calculated using typ ical use rates found in Table 12

. The RQs calculated using the typical use rates can be found in Table 4 3

. Typical use rates were only available for certain agricultural crops; however, 14_OR_Xmas trees (a non

- agricultural crop) which had the maximum EEC and use rate was not included in this analysis since there is no average application rate for this crop . Uses that were modeled using both labeled rates and typical rates will be compared here.

On an acute exposure basis, t he R Qs for freshwater invertebrates when modeled using maximum labeled rates range from 0.199 to 0.540 and exceed LOC s for acute risk to listed and non

- listed species , with 3 of the scenarios exceeding the listed species LOC and 3 exceeding the non

- listed

spec ies LOC. When freshw ater invertebrates a re modeled using typical rates, the RQs range

from 0.089 to 0.381 and exceed the LOC for acute risk to listed species across all scenarios

while none of the RQ values exceed the LOC for acute risk to non

- listed spe cies.

For estuarine/marine invertebrates, the RQs based on maximum rates range from 0.276 to 0.748 and with 3 of the scenarios exceeding the acute risk to listed species LOC and 3 exceeding the

acute risk to non

- listed species LOC. When estuarine/marin e invertebrates a re modeled using typical use rates, the RQs range from 0.119 to 0.529 and exceed the LOC for acute risk to listed species in 5 of the scenarios and one scenario exceed ing the LOC for acute risk to non

- listed species at 0.529.

On a chro nic exposure basis, the RQs for freshwater invertebrates and estuarine/marine

invertebrates exceed the chronic risk LOC across all scenarios when modeled using the

maximum labeled rates as well as the typical use rates.

There is some uncertainty surroundi ng the chronic value for freshwater invertebrates as it was calculated through the use of an acute

- to

- chronic ratio. The most sensitive value for acute freshwater invertebrates was 0.043 mg/L for the s tone fly (MRID 00003503). An ACR was calculated using D

. magna data ( ACR =83); the acute daphnid effects were based on immobility while the chronic effects included impaired reproduction, growth and survival. However, an RQ based on the empirical d aphnid NOAEC of 0.041 mg/L and 21

- d EECs did not exceed the LOC

for chronic risk.

### Page 78 of 144 

### There is additional uncertainty surrounding the chronic toxicity value for estuarine/marine

invertebrates as it too was calculated using an ACR . The most sensitive value for acute estuarine/marine invertebrates was 0.031 mg/L for t he salt marsh mosquito. An ACR was calculated using data from mysids ( ACR =107); the acute mysid effects were based on immobility while the chronic effects included impaired reduction, growth and survival.

### Page 79 of 144 Table 43

. Risk quotient ( RQ ) value s for i nvertebrates using estimated environmental concentrations ( EECs ) calculated using t ypical u se r ates

Use (s) Scenarios App.

Method Peak

EECs Acute RQ s 21

- d

EECs Chronic RQs

Freshwater Estuarine/

Marine Freshwater Estuarine/Marine

03_MN_alfalfa Alfalfa Aerial 2.76 0.064 * 0.089 * 2.23 4.4 11

05_CA_Cole

crops Broccoli Ground 7.69 0.17 * 0.24 * 6.33 12 31

10_WA_Orchards Cherry (only in ID, MT, OR, UT and WA) Aerial 6.01 0.14 * 0.19 * 5.08 10 25

20_FL_Peppers Peppers Aerial 16.4 0.38 * 0.52 11.5 23 57
23_MS_Cotton Cotton Aerial 3.69 0.086 * 0.11 * 2.58 5.1 12

26_FL_Citrus Grapefruit, Kumquat, Lemon,

Lime, Orange,

Pummelo (shaddock),

Tangelo, Tangerine Aerial 9.89 0.23 * 0.31 * 6.59 13 32

*Indicates the RQ exceeds the listed species LOC of 0.05

Bolded text indicated the RQ exceeds the risk to non

- listed species LOC of 0.5 Shaded cell indicates RQ exceeded risk to non

- listed species LOC with labeled use rates, but only exceeds risk to listed species LOC when modeled with typical use rates

### Page 80 of 144 

### Invertebrate RQs were also calculated for d imethoate including u nextracted r esidues. The EEC

values for unextracted residues can be found in Table 13

. The resulting RQ value s exceed LOCs

for acute and chronic risk to listed and non

- listed species.

Table 44

. Risk quotient ( RQ ) value s using estimated environmental concentrations ( EECs ) for

d imethoate plus u nextracted r esidues

Use Peak

EEC Acute RQs 21

- day

EEC Chronic RQs

Freshwater Estuarine/Marine Freshwater Estuarine/Marine

CA _cole 31.7 0.7 6 1.02 27.2 54 136
FL_Citrus 36 0.83 1.16 30.2 60 151

Bolded values exceed LOC for risk



## 4.3.4 Risk to Aquatic Plants

RQ values calculated using the maximum peak aquatic EEC and the lowest toxicity endpoint for aquatic vascular and non

- vascular plats are two to three orders of magnitude below the LOC. This finding, combined with the knowledge of the mode of action of dimethoate as an AChE agonist support s a conclusion of low potential risk to aquatic plants.



## 4.3.5 Risk to Terrestrial Organ isms

A summary of the overall acute and chronic risk profile for dimethoate based on the exposure scenario producing the highest terrestrial EECs and the most sensitive species within each taxonomic group is shown in T able 44

. Results indicate a potential for acute and chronic risk to birds, reptiles and terrestrial

- phase amphibians (using birds as a surrogate), and mammals. In

addition to LOC exceedan ces, there were incidents that involv ed avian species and pollinators.

Table 44. Summary of the avian and mammalian risk profile for dimethoate with uses that produced the greatest terrestrial estimated environmental concentrations ( EECs )

Exposure Avian Dose RQ Avian Dietary RQ Mammalian Dose RQ Mammalian Dietary RQ

Acute 262 7.2 1.3 n/a

Chronic n/a 270 4685 540

RQ values based on the terrestrial EECs derived from Douglas Fir 1 x 4.5 lb ai/A; see Risk Estimation for derivation of these RQ values

* Refined RQ estimate using a foli ar dissipation half

- life of 2.82 days

Bolded value s exceed LOC for 

### risk



## 4.3.6 Risk Characterization Birds

For birds (also used as a surrogate for terrestrial

- p hase amphibians and reptiles) , a potential for

acute and chronic risks w as identified using the dose

- based and dietary

- based RQ values

. For

acute dose

- based and acute dietary

- based risk estimates, there was a general trend of exceedances for herbivorous and insectivorous birds as well as birds consuming fruits, pods an d

### Page 81 of 144 

### seeds, with fewer exceedances as the body size increased. Comparatively, there were fewer scenarios which resulted in LOC exceedances for birds consuming seeds and grains. Dietary

acute

- based risk exhibited a similar trend.

For chronic dietary

- based ri sk estimates, the LOC was exceeded for all scenarios for birds consuming short grass, tall grass, broadleaf plants, and arthropods. For birds consuming fruits, pods and seeds, a majority of the scenarios exceeded the chronic risk RQ.

For further examinat ion the Upper Bound Kenaga values, as part of the T

- REX output, for the

maximum food use and non

- food use were analyzed. For the Douglas Fir scenario, the avian

chro nic LOC is exceeded for 24 day s

. For the cherry scenario, the maximum rate for food uses,

the avian chronic LOC is exceeded for 1 9 days.

There a re seven incidents involving birds that were reported in EIIS. The incidents occurred

from 1972 to 2000. Three of the incidents a re classified as a misuse of the product and thus will

not be conside red here. Of the remaining four incidents, three of them a re classified as ‘highly probable.’ Two of them involved t he Cedar Wax w ing species and two involved Can adian Gee se. Significant mortality of 60

- 80 Cedar Wax w ing birds were found in one incident, with 40 and 25 Canadian Geese mortality in the other two incidents. The findings reported in EIIS demonstrate that there is a complete exposure pathway for avian species.

The SIP and STIR tools flagged contaminated water and inhalation of spray drift a s a potential

route s of exposure for avian species. These pathways are of concern but are currently unaccounted for as EFED does not currently have stand ard models for addressing these specific routes of exposure



## 4.3.7 Risk Characterization Mammals

For mammals, the acute dose base risk estimates varied with concentrated LOC exceedances with smaller mammals and highest application rates. For mammals consuming fruits, seeds and pods, or arthropods or seeds and grains there were significantly fewer scenarios that exceeded

the LOC.

Chronic risk concerns a re identified for mammals across all feed items and scenarios. For

chronic

- dose based risk to mammals

. The RQ values calculated across all mammal sizes, foraging categories and scenarios exceed the chronic risk LO C for listed and non

- listed

mammals . For chronic

- dietary based risk to mammals, the maximum RQ is 540 for small mammals consuming short grass. There is significant uncertainty associated with chronic

- dose based RQ values pertaining to the duration over w hich chronic effects to mammals are likely to manifest. These RQ values are derived using the maximum peak concentration of dimethoate that is predicted to occur on the dietary forage items.

For further examination the Upper Bound Kenaga values, as part of the T

- REX output, for the

maximum food use and non

- food use were analyzed. For the Douglas Fir scenario, the mammalian chronic LOC is exceeded for 36 days. For the cherry scenario, the maximum rate for food uses, the mammalian chronic LOC is exce eded for 31 days.

### Page 82 of 144 

### There were no incidents reported in EIIS related to mammals.

SIP (Screening Imbibition Tool) was used to evaluate an upper

- bound estimate of exposure to ingestion of contaminated water using dimethoate’s solubility and a suite of toxici ty studies. Drinking water alone i s identified as potential pathway of concern for mammalian species on an

acute and chronic exposure basis. Although this exposure pathway is of concern , it is currently unaccounted for as EFED does not currently have a s tand ard mode l for addressing th i s specific route of exposure.



## 4.3.8 Risk Characterization for Bee s

There are multiple lines of evidence to suggest risk to bees from registered uses of dimethoate

for foliar an d soil applications . First, screening

- level (Tier 1) analysis suggest s potential risk of

acute l ethality to adult bees resulting from acute oral and contact exposure routes ( Tables 38 and

39 ). Although the Tier 1 exposure estimates represent “high end” exposure values for screening

purp oses , the acute risk LOC of 0.4 is exceeded by up to four orders of magnitude . This
suggests that the risk estimate s are not likely to be sensitive to the conservatism of the Tier 1 exposure estimates. Second, available data from ecological incident reports is suggestive,

t hough not conclusive, that dimethoate use may be associated with a number of bee kill incidents

in the U.S. For two reported incidents ( I024335

- 001 and I013884

- 033), dimethoate was the only pesticide reportedly applied at the time of the incident with “pr obable” and “possible” certainty designations assigned, respectively. However, the legality of these dimethoate applications is undetermined. Two other bee kill incidents indicate dimethoate applications with

“ p robable” c ertainty , although other pesticid es were also applied near the vicinity and time of these incidents. Third, available information from a full field study indicates increased bee mortality, reduced foraging activity, and increased behavior abnormalities is associated soon after foliar app lications of 0.67 lb ai/A dimethoate to P hacelia at bloom just prior to bee s foraging. Long

- term effects on brood development and overall colony performance were not
indicated and may suggest possible recovery; however, there are substantial limitations with the field study. Lastly, the mode of action and use of dimethoate as a reference toxicant in semi

field (tunnel) studies at application rates comparable to those registered in the U

. S

. also supports
at least short

- t erm risk to bees from applications near or during foraging.

At the time of this assessment, available data were inadequate to address a number of uncertainties, including lack of chronic toxicity data to larvae and adult bees, lack of exposure data on dimethoate residues in pollen and nectar, and lack of robust, higher

- tier studies to quantify long

- term impacts of dimethoate to developing brood and colony survival. Since most of these studies have only recently been required by EPA for pesticide regist ration decisions, these data gaps will be addressed in the future with a DCI once they are identified as critical data

gaps

.



## 4.3.9 Risk Characterization Terrestrial Plants

### Page 83 of 144 

### Risks to terrestrial plants from the currently labeled uses of dimethoate are not expect ed based on the available toxicity data and model

- generated exposure estimates . This risk conclusion is supported by the mode of action of dimethoate, which would not be expected to affect pla n ts at
the levels applied to address target insects. Despite t he lack of predicted risk to plants, there were two incidents reported in the EIIS database. Both incidents were due to a malfunction of machinery and were classified as a misuse.

### Page 84 of 144 

## 4.4 **Characterization of Omethoate**

4.4.1 Aquatic Species

A comparison of aquatic toxicity data of dimethoate and omethoate can be f ound in Table 26

. Omethoate data are only available for freshwater fish and freshwater invertebrates; there are no estuarine/marine data available for omethoate

. C omparison of available data indicate that the sensitivity to each chemical is species and taxa specific.

For the r ainbow t rout, dimethoate has an LC 50 

### of 6.2 m g/L ( MRID 40094602) and omethoate has a roughly equivalent LC 50 

### of 5.0 mg/L ( MRID 48821404). However, for the b luegill su nfish

, dimethoate has an LC 50 

### of 31.5 mg/L ( MRID 48821401) while omethoate exhibited increased toxicity with an LC 50 

### of 7.7 mg/L. For dimethoate, acute RQs are below the risk to listed species LOC of 0.05 by a factor of 10 or greater for both r ainbow t rou t and b luegill. Given that the LC 50 

### values of both parent and omethoate are roughly equivalent for r ainbow t rout and the LC 50 

### of

omethoate is about 1⁄4 that o f the parent for b luegill, consideration of omethoate in the EEC

would not affect the final risk co nclusion for this taxa.

For aquatic invertebrates, dimethoate has an EC 50 

### of 1.6 mg/L while omethoate has increased toxicity to daphnids at an EC 50 

### of 0.0325 mg/L. The inclusion of omethoate in the EEC

calculation will alter the risk conclusions based on just the parent alone . EECs for omethoate

were calculated in ( Aquatic Modeling Approach ) Table 15

. Using the peak EEC for omethoate

and the invertebrate E C 50 

### values for dimethoate and omethoate, a dimethoate Toxic Equivalent

EEC was calculated 14 

### ; this value was then added to the dimethoate EEC to get a total EEC reflecting toxic equivalency of dimethoate. This Total EEC was then used to calculate a n RQ that would incorporate both dimethoate and omethoate exposure and toxicity. The calculation

has been summarized below in Table 45

. According t o this calculation, inclusion of omethoate increased the RQ by greater than 8 fold , and indicates the potential for acute risk to listed aquatic

invertebrate species.

Table 45

. Acute r isk Quotient (RQ) values ba sed on o methoate for f reshwater a quatic

i nvertebrates

Omethoate

EEC (peak) μg/L Dimethoate

Toxic Equivalent

EEC Dimethoate

EEC (peak) μg/L Total

EEC Total RQ (Dimethoate

LC 50 = 1600 μg/L) Dimethoate RQ



### 05_CA_Cole_Crops 3.70 182 23.2 205 0.128 0.0145

26_FL_CITRUS 3.40 167 22.1 189 0.118 0.013

14 Dimethoate toxi c equivalent EEC = (Dimethoate LC50 / Omethate LC50) * Dimethoate EEC

### Page 85 of 144 

### Omethoate also displayed increased toxicity to freshwater invertebrates on a chronic exposure basis with a daphnid NOAEC of 0

. 119 μ g/L as compared to the dimethoate NOAEC of 41 μ g/L. According to the calculation of a combined d imethoate and o methoate outlined in Table 46

, where RQ estimations previously did not exceed the chronic risk LOC, the inclusion of

omethoate results in an exceedance for the chronic LOC by a factor of 20. However, there is a degree of uncertainty associated with these equations because they assumed that acute and chronic exposure are occurring at the same time; since omethoate was not observed in the aquatic metabolism studies, here it was assumed to be ap plied via the soil instead of via foliar application with drift. The acute and chronic exposure may not occur simultaneously. Therefore there is uncertainty concerning the toxic equivalent conversion concurrent to the acute and chronic exposure uncertain ty.

Table 46 . Estimation of c hronic risk quotient (RQ) values based on o methoate for

freshwater invertebrates

Omethoate

EEC (21

- day)

μg/L Dimethoate

Toxic Equivalent

EEC Dimethoate

EEC (21

- day)

μg/L Total

EEC Total RQ (Dimethoate

LC 50 = 1600 μg/L) Dimethoate RQ



### 05_CA_Cole_Crops 2.33 783 20 803 20 0.5

26_FL_CITRUS 0.856 287 14.7 301 7.5 0.36



### Risk conclusions from Table s 29 and 30 have been made using risk quotients calculated using toxicity values for the Stonefly because it present s a more sensitive species than the daphnid; however, omethoate toxicity estimation i n this section has used data available for daphnid. There is some uncertainty assuming that the differential acute toxicity observed with the daphnid applies to the stonef ly as well

.



## 4.4.2 Terrestrial Species

A comparison of avian toxicity data for dimethoate and omethoate can be found in Table 27

. Omethoate data are available for acute oral toxicity, sub

- acute dietary toxicity and chronic toxicity. The comparison show s the sensitivity to each chemical is species specific. Based on these data, omethoate and dimethoate exhibit similarly toxic for birds on an acute , sub

- acute and

chronic exposure basis. With available data, we are uncertain as to whether or not inclusion of omethoate would substantially increase the risk estimates for terrestrial animals.

There is some uncertainty concerning the toxicity of omethoate to mammals. HED had previously con cluded a 3

- fold increase in the toxicity of omethoate in terms of AChE inhibition

in mammal s ; however

, there is uncertainty in applying this factor to the apical endpoints of survival, growth and reproduction

.



## 4.5 **Endangered species**

In November 2013, the EPA, along with the U.S. Fish & Wildlife Service (USFWS), the

### Page 86 of 144 

### National Marine Fisheries Service (NMFS) (collectively, the Services) , and the U.S. D epartment of Agriculture (USDA) released a summary of their joint Interim Approaches for assessing risks

to l isted species from pesticides. The Interim Approaches were developed jointly by the

a g encies in response to the N ational A cademy of S ciences’ (NAS) recommendations and reflect a common approach to risk assessment shared by the a gencies as a way of address ing scientific

differences between the EPA and the Services. The NAS report outlines recommendations on specific scientific and technical issues related to the development of pesticide risk as sessments
that EPA and the Services must conduct in connection with their obligations under the Endangered Species Act (ESA) and FIFRA

.

The joint Interim Approaches were released prior to a stakeholder workshop held on November 15, 2013. In addition, the EPA presented the joint Interim Approaches at the December 2013

P esticide P rogram D ialogue C ommittee (PPDC) and S tate

- FIFRA Issues Research and Evaluation Group ( SFIREG ) meetings, and held a stakeholder workshop in April 2014, allowing

ad ditional opportunities for stakeholders to comment on the Interim Approaches. As part of a phased, iterative process for developing the Interim Approaches, the agencies will also consider public comments on the Interim Approaches in connection with the de velopment of upcoming Registration Review decisions. The details of the joint Interim Approaches are contained in the white paper “Interim Approaches for National

- Level Pesticide Endangered Species A ct Assessments Based on the Recommendations of the National Academy of Sciences April 2013 Report,” dated November 1, 2013.

Given that the agencies are continuing to develop and work toward implementation of the Interim Approaches to assess the potenti al risks of pesticides to listed species and their designated critical habitat, this preliminary risk assessment for dimethoate does not contain a complete ESA analysis that includes effects determinations for specific listed species or designated critical habitat. Although EPA has not yet completed effects determinations for specific species or habitats, for this preliminary assessment EPA conducted a screening

- level

assessment for all taxa of non

- target wildlife and plants that assumes for the sake of the assessment that listed species and designated critical habitats may be present in the vicinity of the application of dimethoate. This screening level assessment will allow EPA to focus its future evaluations on the types of species where the potential f or effects exists once the scientific methods being developed by the agencies have been fully vetted. This screening

- level risk

assessment for dimethoate indicates potential risks of direct effects to listed freshwater and estuarine/marine invertebrates, a vian species and mammals on some of its registered use sites. Once the agencies have fully developed and implemented the scientific methods necessary to complete risk assessments for endangered and threatened (listed) species and their designated

critical habitats, these methods will be applied to subsequent analyses for dimethoate as part of completing this registration review.



## 4.6 **Uncertainties, Limitations, and Identification of Data Gaps**

4.6.1 Environmental Fate Database

Regarding the input values used in this risk assessment, the environmental fate database for

### Page 87 of 144 

### dimethoate was considered to be complete and no estimated values, or uncertainty factors were

used. Three of the aerobic soil metabolism values were derived from non

- labeled studies. Usually, studies conducted with non

- labeled compounds show recoveries within a range of 70

- 120% of the applied, while the ones conducted with labeled compounds range from 90

- 110% of the applied radioactivity. The one study conducted with radiolabeled compound had a half

- life which was very similar than the studies conducted with non

- radiolabeled compounds (2.4 days for the labeled compound compared to 1.65

- 3.01 days for the non

- radiolabeled compounds).



## 4.6.2 Modeling Omethoate in the SWCC

Although omethoate was not observed in any of the laboratory environmental fate studies, some fate data was available for the chemical ( e.g. , mobility and aerobic aquatic metabolism). In this assessment, the rate of formation of omethoate was based on the maximum observed in terrestrial field dissipation studies. This brings uncertainty to the analysis since in field dissipation studies several processes may be occurring simultaneously, like for example leaching and runoff, besides degradation. The expos ure may have been underestimated. With respect to the aquatic modeling, since there was no aerobic soil metabolism half

- life, it was assumed to be similar to the aerobic aquatic metabolism half

- life.

Omethoate was modeled separately from dimethoate ( i.e. , an approach similar to the residue summation was used). The EECs for omethoate are rough estimates which, as indicated above, are based on the maximum amount observed in the terrestrial field dissipation studies. However, there is a degree of uncertain ty associated with these equations because they assumed that acute and chronic exposure are occurring at the same time; since omethoate was not observed in the aquatic metabolism studies, here it was assumed to be applied via the soil instead of via foliar application with drift. The acute and chronic exposure may not occur simultaneously. Therefore there is uncertainty concerning the toxic equivalent conversion concurrent to the acute and chronic exposure uncertainty.



## 4.6.3 Application Information

Meteorolog ical data and crop profiles, as well as best professional judgment, were used to establish an application date for modeling; however, the selected date may not represent the intended or actual application dates. The application date used for model runs can significantly

alter the E EC s; thus, E E Cs reported could over or under predict actual exposure. The dates of application used in this risk assessment were generally selected based on the crop cycle to make sure that the applications were to folia ge (unles s otherwise specified o n the label). It is unclear how much the application dates differ from the typical timing of application, which is based on

pest pressure.



## 4.6.4 Number of Seasons per Year

Many dimethoate labels include application restrictions on a per season basis; however, for some crops there can be multiple growing seasons per year. For modeling purposes one season was considered to be equal to one year. If multiple crop seasons are possible per year it is

conceivable the n E E Cs reported in this do cument are more likely to underestimate actual

### Page 88 of 144 

### exposure. In general, this assessment makes conservative assumptions regarding re

- cropping and rotations ( i.e. , applications on the same crop every year for a period of 30 consecutive years).

EFED evaluated a number of labels for specific information regarding application methods and timing, and noted some application rates provided on the label are on a per season basis. The yearly /seasonal application rates used in this assessment are primarily based on da ta from BEAD’s label data report and supplemented by the review of a number of labels

.

Some of the labels do not provide maximum single or annual application rates for dimethoate or number of applications or application retreatment intervals. When this information is not specified on the label, a conservative application scenario was modeled , based on assumptions

. These assumptions are shaded grey in Table 2

.



## 4.6.5 Use of Maximum Labeled Rates

According to the labels, dimethoate is a IRAC MoA sub group 1B i nsecticide/miticide, to which
target pests can develop resistance if the chemical is applied consecutively or repeatedly in the same field and/or in consecutive years with other chemicals belong to subgroup 1B . For that reason, it is recommended to avoid its consecutive use of the compound

, as well as the consecutive use of other group 1B insecticides and to base dimethoate’s use on a comprehensive

I ntegrated P est M anagement program. Thus, even though the initial E E Cs were based on maximum application rat es and minimum intervals between applications, it appears unlikely that users will apply this chemical under these circumstances, and on a yearly basis for 30 consecutive years, as assumed in the modeling performed in this ecological risk assessment

. In

t his risk assessment , results from typical (or average) application rates and number of applications were presented in addition to the maximum application rates , although applications during 30 consecutive years were also assumed

. The frequency at which actual uses approach this maximum use scenario may be dependent on pest resistance, timing of applications, cultural practices, and market forces.



## 4.6.6 Volatility of Dimethoate

In a laboratory volatility study, dimethoate showed some potential for volatilizati on. At the end of the study 2% of AR was volatile organics. The SWCC accounts for this route of dissipation partially when the solubility and vapor pressure are entered; however, it is uncertain as to what degree the chemical would be lost in the environ ment to volatilization under field conditions. Compared to other routes of dissipation for dimethoate, it appears that volatilization is not a significant dissipation pathway for the chemical. At the present time, the volatility routine of

PRZM has not b een incorporated in the SWCC.



## 4.6.7 Unextracted R esidues

Issues with un

- extracted radioactivity were identified in the laboratory

- based aquatic metabolism

studies. Regarding the aerobic and anaerobic aquatic metabolism studies, there were observed

levels of un extracted radioactiv e residues . Nonetheless, these levels only reached up to 12.9% AR (with the exception of the last test interval) under aerobic aquatic condition, and 13.3% AR under anaerobic aquatic conditions. Although these levels were considered o nly marginally

### Page 89 of 144 

### high, and, t o help clear this uncertainty, m odeling of total toxic residues comprising parent plus unextracted radioactivity was performed.



## 4.6.8 Aquatic Modeling with the SWCC

The standard ecological water body scenario ( VVWM standard pond) used to calculate potential aquatic exposure to pesticides such as dimethoate is intended to represent conservative water
concentration estimates, and to avoid underestimating most actual exposure s . The standard

scenario assumes pesticide application to a 10

- hectare field bordering a 1

- hectare, 2

- meter deep (20,000 m 3 

### ) pond with no outlet. Exposure estimates generated using the VVWM pond are intended to represent a wide variety of vulnerable water bodies that occur at the top of watersheds including prairi e pot holes, playa lakes, wetlands, vernal pools, man

- made and natural ponds, and intermittent and lower order streams. As a group, there are factors that may make such water bodies either more or less vulnerable than the VVWM pond. Static water

bodies t hat have larger ratios of pesticide

- treated drainage area to water body volume would be expected to have higher potential peak EECs than the VVWM pond. These water bodies may be either smaller in size or have larger drainage areas. Smaller water bodies h ave l ess dilution volume, may have less ability to store excess inflow

, and thus may periodically overflow and

export pesticide in the discharge ; whereas

, the VVWM pond has no discharge. As watershed size increases beyond 10

- hectares, it presumably become s increasingly less likely that the entire watershed is planted with a single crop that is all treated simultaneously with the pesticide.

Headwater streams can also exhibit peak concentrations higher than th ose in the VVWM pond,

but that persist for short er periods of time as they are then carried and dissipated (advected)

downstream.

In general, the linked PRZM/ VVWM model (through the SWCC GUI) produces EECs that are expected to be exceeded once within a ten

- year period. PRZM is a process or “simulation”

model that calculates runoff of a pesticide from an agricultural field on a daily temporal resolution, over a period of decades . It considers factors such as rainfall and plant transpiration of water, as well as how and when the pesticide is applied. It has two major components: hydrology and chemical transport. Water movement is simulated by the use of generalized soil parameters, including field capacity, wilting point, and saturation water content. The chemical

transpor t component can simulate pesticide application on the soil or on the plant foliage. Dissolved, adsorbed, and vapor

- phase concentrations in the soil are estimated by simultaneously considering the processes of pesticide uptake by plants, surface runoff, er osion, decay, volatilization, foliar wash

- off , sorption and leaching

.

Uncertainties associated with each of these individual components add to the overall uncertainty of the modeled concentrations. Additionally, model inputs from the environmental fate

d egradation studies are chosen to re flect the upper 90 percent upper confidence limits on mean half

- lives . Mobility input values (soil sorption coefficients) are chosen to represent average sorption in the environment. The natural variation in soils adds to the uncertainty of modeled values. Factors such as application date, crop emergence date, and canopy cover can also affect estimated concentrations, adding to the uncertainty of modeled values. Factors within the ambient environment such as soil tempe ratures, sunlight intensity, antecedent soil moisture, and surface water temperatures can cause actual aquatic concentrations to differ for the modeled

### Page 90 of 144 

### values.



## 4.6.9 Uncertainties Regarding Dilution and Chemical
Transformations in Estuaries

The SWCC

- modeled EEC s are intended to represent exposure of aquatic organisms in relatively small ponds

, low

- order streams , and other vulnerable water bodies

. I t is likely that EECs generated from the SWCC model over

- estimate (especially on an acute basis) potential concentrations in larger receiving water bodies including estuaries, embayments, and coastal marine areas because chemicals in runoff water (or spray drift, etc. ) is diluted by larger volume s of water. In addition , as chemical constituents in water draining from freshwater streams

encounter brackish or other near

- marine

- associated conditions, there is potential for new chemical transformations to occur. Many chemical compounds can undergo changes in mobility, toxicity, or persistence when chan ges in pH, E h 

### (redox potential), salinity, dissolved oxygen (DO) content, or temperature are encountered. For example, desorption and re

- mobilization of some chemicals from sediments can occur with changes in salinity ( Jordan et al. , 2008; Means, 1995; Sw arzenski et al. , 2003 ) , changes in pH ( e.g ., Wood and Baptista 1993 ), E h 

### changes ( Velde and Church, 1999; Wood and Baptista, 1993 ) , and other factors. Thus, although chemicals in discharging rivers may be diluted by large volumes of water within receiving estuaries and embayments, the hydrochemistry of the marine

- influenced water may negate some of the attenuating impact of the grea ter water volume; for example, the effect of dilution may be confounded by changes in chemical mobility (and/or bioavailability) in brackish water. In addition, freshwater contributions from discharging streams and rivers do not instantaneously

mix with m ore saline water bodies. In estuarine settings, water is often vertically stratified, with fresh water lying atop denser, h igher salin ity water

– meaning that exposure to concentrations

found all in discharging stream water may propagate some distance bey ond the point of the confluence with higher salinity water (especially near the water surface) without substantial dilution occurring . Therefore, it is not assumed that discharging water will be rapidly diluted by

the entire water volume within an estuar y, embayment, or other coastal aquatic environment.

SWCC model results should be considered consistent with concentrations that might be found near the head of an estuary unless there is specific information

– such as monitoring data

– to
indicate otherwi se. Conditions nearer to the mouth of a bay or estuary, however, may be closer

to a marine

- type system, and thus more subject to the notable buffering, mixing, and diluting capacities of an open marine environment. Conversely, tidal effects (pressure wav es) can propagate much further upstream than the actual estuarine water, so discharging river water may become temporarily partially impounded near the mouth (discharge point) of a channel, and resistant to mixing until tidal forces are reversed.

The Agency does not currently have sufficient information regarding the hydrology and hydrochemistry of estuarine aquatic habitats to develop alternate scenarios for assessed species that inhabit these types of ecosystems. The Agency acknowledges that there a re unique brackish and estuarine habitats that may not be accurately captured by SWCC modeling results, and may, therefore, under

- or over

- estimate exposure, depending on the aforementioned variables.

### Page 91 of 144 

## 4.6.10 Uncertainties regarding Acute to Chronic Ratio

The c hronic values for e stuarine/marine invertebrates and freshwater invertebrates were estimated using an acute to chronic ratio (Se e Table 24 ) . F or freshwater invertebrates, a study conducted using the stonefly ( Pteronarcys californica) was found to have a more sensitive EC 50 

### than Daphnia magna; thus this endpoint was used as the regulatory endpoint in risk estimation. In using an Acute to Chronic Ratio, it is assumed that the increased sensitivity the stonefly

exhibited on an acute bas is, will be exhibited on a chronic basis and may result in an overestimation of toxicity to the organism, thus there is some uncertainty surrounding the use of ACR risk estimation of the stonefly and Salt Marsh Water Mosquito.



## 4.7 **Endocrine Disruption S creening Program** 

As required by FIFRA and the Federal Food, Drug, and Cosmetic Act (FFDCA), EPA reviews numerous studies to assess potential adverse outcomes from exposure to chemicals. Collectively, these studies include acute, subchronic and chronic tox icity, including assessments of carcinogenicity, neurotoxicity, developmental, reproductive, and general or systemic toxicity. These studies include endpoints which may be susceptible to endocrine influence, including effects on endocrine target organ hist opathology, organ weights, estrus cyclicity, sexual maturation, fertility, pregnancy rates, reproductive loss, and sex ratios in offspring. For ecological hazard assessments, EPA evaluates acute tests and chronic studies that assess growth, developmental and reproductive effects in different taxonomic groups. As part of the Preliminary Problem Formulation for Registration Review D355609, EPA reviewed these data and selected the most sensitive endpoints for relevant risk assessment scenarios from the exist ing hazard

database. However, as required by FFDCA section 408(p ), Dimethoate is su bject to the endocrine screening part of the Endocrine Disruptor Screening Program (EDSP).

EPA has developed the EDSP to determine whether certain substances (including p esticide 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 t o making the statutorily required determinations. Tier 1 consists of a battery of 11 screening assays to identify the potential of a chemical substance to interact with the estrogen, androgen, or thyroid (E, A, or T) hormonal
systems. Chemicals that go th rough Tier 1 screening and are found to have the potential to interact with E, A, or T hormonal systems will proceed to the next stage of the EDSP where EPA will determine which, if any, of the Tier 2 tests are necessary based on the available data. Tier 2 testing is designed to identify any adverse endocrine

- related effects caused by the substance, and establish

a dose

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

Under FFDCA section 408(p), the Agency must screen all pesticide chemic als. Between October 2009 and February 2010, EPA issued test orders/data call

- ins for the first group of 67 chemicals, which contains 58 pesticide active ingredients and 9 inert ingredients. A second list of chemicals identified for EDSP screening was publ ished on June 14, 2013 [1] 

### and includes some pesticides

[1] See http://www.regulations.gov/#!documentDetail;D=EPA

- HQ

- OPPT

- 2009

- 0477

- 0074 for the fin al second list of

chemicals.

### Page 92 of 144 

### scheduled for registration review and chemicals found in water

. Neither of these lists should be construed as a list of known or likely endocrine disruptors. Dimethoate is on List 1 for which

EPA has received all of the required Tier 1 assay data

. The Agency has reviewed all of the assay data received for the appropriate List 1 chemicals and the conclusions of those reviews are

available in the chemical

- specific public dockets. For further informati on on the status of the EDSP, the policies and procedures, the lists of chemicals, future lists, the test guidelines and Tier 1 screening battery, please visit our website [2]



### .

[2] Available: http://www.epa.gov/endo/

### Page 93 of 144 

# 5.0 References

Beck, E. W., L. H. Dawsey, D. W. Woodham, and D. B. Lueck. 1966. Dimethoate residues on soybean, corn , and grass forage. Journal of Economic Entomology 59: 78

- 82. in Willis, G.

H. and L. L. McDowell. 1987. Bellows, jr., T. S., J. G. Morse, D. G. Hadjidemetr iou. and Y. Iwata. 1985. Resicual toxicity of four insecticides used for control of citrus thrips ( Thysanoptera: Thripidae ) on three beneficial species in the citrus ecosystem. Journal of Economic Entomology 78: 681

- 686.

in Willis, G. H. and L. L. McDowell . 1987. Dorough H.. W., N. M. Randolph, and G. H. Wimbish. 1966. Residual nature of certain organophosphorus insecticides in grain sorghum and coastal bermudagrass. Bulletin of Environmental Contamination and Toxicology 1: 46

- 58. in Willis, G. H. and L. L.

McDowell. 1987.

Food and Agriculture Organization of the United Nations. FAO PESTICIDE DISPOSAL SERIES

8. Assessing Soil Contamination: A Reference Manual. Appendix 2. Parameters of pesticides that influence processes in the soi l. Editorial Group, FAO Information Division:
Rome, 2000. http://www.fao.org/DOCREP/003/X2570E/X2570E00.htm (accessed July 18, 2014 )

. Fukuto, T.R. 1990. Mechanism of Action of Organophosp horus and Carbamate Insecticides. Environmental Health Perspectives 87, pp. 245

- 254. Jordan, T. E., Cornwell, J. C., Walter, R. B., & Anderson, J. T. 2008. Changes in phosphorus biogeochemistry along an estuarine salinity gradient. Limnology and Oceanograp hy 53 (1),

172

- 184

. Lee, Y. W., and N. D. Westcott, 1981. Gas chromatographic quantitative analysis and persistence of dimethoate and dimethoxon residues on and in wheat plants. Journal of Agricultural and Food Chemistry 29: 860

- 862. in Willis, G. H. and L. L. McDowell. 1987. Majewski, M.S., Zamora, C., Foreman, W.T., and C.R. Kratzer. 2006. Contribution of atmospheric deposition to pesticide loads in surface water runoff. United States Geological Survey. Open

file Report 2005

- 1307. Available online at: http://pubs.usgs.gov/of/2005/1307/

. 

### Means, J. C. 1995. Influence of salinity upon sediment

- water partitioning of aromatic hydrocarbons. Marine Chemistry, 51 (1), 3

- 16

. Nelson, K. A., R. E. Menzer, and L. P. Dittman. 1966. Dimethoate residues on leafy crops. Journal of Economic Entomology 59: 404

- 406. Pree, D. J., K. P. Butler, E. R. Kimball, and D. K. R. Stewart. 1976. Persistance of foliar residues of dimethoate and azinphos methyl and toxicity to apple maggot. Journal of Economic Entomology 69: 473

- 478 as r eferenced in Willis, G. H. , W. F. Spencer, and L. L. McDowell. 1985. The Interception of Applied Pesticides by Foliage and Their Persistence and Washoff Potential. Chapter 18 in CREAM: A Field Scale Model for Chemical, Runoff, and Erosion from Agricultura l Management Systems. USDA Conservation Research Report Number 26. United States Department of Agriculture, Washington, DC. pp. 595

- 606. Shaw, F. R., and W. H. Ziener. 1964. The disappearance of dimethoate and SD

- 7438 from alfalfa. Journal of Economic Ento mology 57: 997

- 998. in Willis, G. H. and L. L. McDowell. 1987. Swarzenski, P. W., Porcelli, D., Andersson, P. S., & Smoak, J. M. 2003. The behavior of U

- and

### Page 94 of 144 

### Th

- series nuclides in the estuarine environment. Reviews in Mineralogy and Geochemistry

REviews in M ineralogy and Geochemistry, 52 (1), 577

- 606. U.S. Department of Agriculture. 2012. Pesticide Data Program 2012 Annual Summary, Calendar Year 2012. Agricultural Marketing Service, Science and Technology Program, February

2014. Available online at the follow ing site accessed June 10, 2014: http://www.ams.usda.gov/AMSv1.0/getfile?dDocName=stelprdc5106521

. USEPA. 1998. Guidelines for Ecological Risk Assessment. EPA/630/R

- 95/002F. Published in 63 FR 26846; May 14, 1998. U.S. Environmental Protection Agency, Washington, DC. April, 1998.

USEPA

. 2004. Overview of the Ecological Risk Assessment Process in the Office of Pesticide Programs, U.S. Environmental Protection Agency. Endan gered and Threatened Species Effects Determinations. Office of Prevention, Pesticides and Toxic Substances, Office of Pesticide Programs, Washington, D.C. Available online at http://www.epa.gov/oppfead1/endanger/consultation/ecorisk

- overview.pdf (accessed July 18, 2014)

. USEPA. 2008. Revised Interim Reregistration Eligibility Decisions for Dimethoate. Office of Pesticide Programs. Available online at: http://www.epa.gov/pesticides/reregistration/REDs/dimethoate_ired_revised.pdf (accessed February 6, 2015).

USEPA

. 2009. Guidance for Selecting Input Parameters in Modeling the Env ironmental Fate and Transport of Pesticides, Version 2.1. Office of Chemical Safety and Pollution Prevention

, Office of Pesticide Programs, Environmental Fate and Effects Division, dated October 22, 2009 and issued November 10, 2009. Available online at: http://www.epa.gov/oppefed1/models/water/input_parameter_guidance.htm (accessed July 18, 2014 )

. USEPA. 2010 a

. Guidance for Reporting on the Environmental Fate and Transp ort of the Stressors of Concern in Problem Formulations for Registration Review, Registration Review Risk Assessments, Listed Species Litigation Assessments, New Chemical Risk Assessments,

and Other Relevant Risk Assessments . Memorandum from Donald Brady d ated January 25, 2010

. Office of Pesticide Programs. Environmental Fate and Effects Division. ( http ://www.epa.gov/pesticides/science/efed/policy_guidance/team_authors/endangered_ species_reregistration_workgroup/esa_reporting_fate.htm ).

USEPA

. 2010 b . Guidance for Making Temperature Adjustments to Metabolism Inputs to EXAMS

and PE5 and WQTT Advisory Note Number 9: Temperature Adjustments for Aquatic Metabolism Inputs to EXAMS and PE5. OCSPP/OPP/Environmental Fate and Effects Division. Dated 09/21/2010 and approved 10/18/2010

. USEPA. 2013 a

. Guidance on Modeling Offsite Deposition of Pest icides via Spray Drift for Ecological and Drinking Water Assessments, dated December 19, 2013

. Memorandum from Donald Brady dated and approved December 20, 2013. Office of Pesticide Programs.

Environmental Fate and Effects Division.

USEPA 2013b. Use Int ensity Maps by Crop Reporting District for Dimethoate, Esfenvalerate, Ethoprop, Fenpropathrin, Fipronil, and Oxyfluorfen (PC codes: 097805, 109303, 041101, 127901, 129121, and 111601). Memorandum from Monisha Kaul to Rochelle Richardson, dated March 13, 20 13. Office of Pesticide Programs. Environmental Fate and Effects

Division

.

### Page 95 of 144 

### Vail, P. V., M. W. Stone, J. C. Maitlen, D. A. George, and L. I. Butler. 1967. Performance of insecticides against cabbage and green peach aphids on leafy vegetables and persisten ce of residues during cool weather. Journal of Economic Entomology 60: 537

- 541 in Willis, G.

H. and L. L. McDowell. 1987. Velde, B., & Church, T. 1999. Rapid clay transformations in Delaware salt marshes. Applied Geochemistry, 14 (5), 559

- 568. Wood, T. M., & Baptista, A. M. 1993. A model for diagnostic analysis of estuarine geochemistry.

Water Resources Research 29 (1), 51

- 71

.

### Page 96 of 144 

# Appendix A.

035001 Dimethoate Fate Chemistry Bibliography

161

- 1 Hydrolysis

MRID Citation Reference

159761 Hawkins, D.; Kirkpatrick, D.; Till, C.; et al. (1986) The Hydrolysis of [Carbon

- 14]

- Dimethoate: Report No. HRC/DTF 6A/86268. Un

- published study prepared by Huntingdon Research Centre, Ltd. 40 p.



## 161

- 2 Photodegradation

- water

MRID Citation Reference

159762 Hawkins, D.; Kirkpatrick, D.; Till, C. et al. (1986) The Photodegradation of [Carbon

14]

- Dimethoate in Water. Report No. HRC/ DTF 6b/86231. Unpublished study prepared by Huntingdon Research Centre Ltd. 29 p.



## 161

- 3 Photodegradation

- soil

MRID Citation Reference

77535 Dauterman, W.C.; Viado, G.B.; Casida, J.E. et al. (1959) Persistence of Dimethoate and Metabolites following Foliar Application to Plants: Contract No. AT(11

- 1); Project No. 14. (Univ. of Wisconsin, Dept. of Entomology for U.S. Atomic Energy Commission; unpublished study; CDL:109340

- AG)

135671 Melnikoff, N. (1974) Pesticides and the environment: Decomposition of organophosphorus pesticides. Khimiia Sel'skom Khoziaistve 12(4):289

- 297. (Also In unpublished submission received Dec 4, 1974 under 5F1531; submitted by American Cyanamid Co., Princeton , NJ; CDL:094151

- U)

159763 Hawkins, D.; Kirkpatrick, D.; Till, C. et al. (1986) The Photolysis of Dimethoate on Soil: Report No. HRC/DTF 6C/86318. Unpublished study prepared by Huntingdon Research Centre Ltd. 35 p.

159791 Duff, W.; Menzer, R. (1973) Pe rsistence, mobility, and degradation of [carbon

- 14]

- dimethoate in soils. Environmental Entomology 2(3):309

- 318. Includes 9 pages of unpublished test data.

164958 Hawkins, D.; Kirkpatrick, D.; Till, C. et al. (1986) The Photo

- lysis of [Carbon 14]

- dimetho ate on Soil: HRC Rept. No. DTF 6C/ 86318. Unpublished study prepared by Huntingdon Research Centre Ltd. 49 p.

43276401 Skinner, W.; Shepler, K. (1994) Photodegradation of (carbon 14)Dimethoate in/on Soil by Natural Sunlight: Lab Project Number: 414W. Unp ublished study prepared by

### Page 97 of 144 PTRL West, Inc. 101 p.



## 162

- 1 Aerobic soil metabolism

MRID Citation Reference

52091 Getzin, L.W.; Rosefield, I. (1968) Organophosphorus insecticide deradation by heat

labile substances in soil. Journal of Agricultural and Food Chemistry 16(4):598

- 601. (Also In unpublished submission received Dec 4, 1974 under 5F1531; submitted by American Cyanamid Co., Princeton, N .J.; CDL:094151

- M)

52099 Montedison, S.p.A. (1972) Laboratory Tests on the Degradation of Dimethoate (Rogor) in Soil as a Function of the Pollution Hazards Possibly Deriving from This Active Substance: Report No. 88/1972. (Unpublished study received Dec 4, 1974 under 5F1531; submi tted by American Cyanamid Co., Princeton, N.J.; CDL:094151

- W)

42843201 Hawkins, D.; Kirkpatrick, D.; Shaw, D.; et al. (1988) The Metabolism of (carbon 14)

- Dimethoate in Soil Under Aerobic Conditions: Lab Project Number: HRC/DTF/7/881515. Unpublished stud y prepared by Huntingdon Research Centre Ltd. 60 p.

52086 Bro

- Rasmussen, F.; Noddegaard, E.; Voldum

- Clausen, K. (1970) Comparison of the disappearance of eight organophosphorus insecticides from soil in laboratory and in outdoor experiments. Pes

- ticide Science 1(?/Sep

- Oct):179

- 182. (Also In unpublished submission received Dec 4, 1974 under 5F1531; submitted by American Cyanamid Co., Princeton, N.J.; CDL:094151

- H)



## 162

- 2 Anaerobic soil metabolism

MRID Citation Reference

159764 Hawkins, D.; Kirkpatrick, D.; Till, C. et al. (1986) The Metabolism of [Carbon

- 14]

- Dimethoate in Soil under Anaerobic Conditions: Report No. HRC/DTF 6d/86368. Unpublished study prepared by Huntingdon Research Centre Ltd. 31 p.

160148 Hawkins, D.; Kirkpat rick, D.; Till, C. et al. (1986) The Metab lism of [Carbon 14]

- dimethoate in Soil under Anaerobic Conditions: HRC/DTF 6d/86368. Unpublished study prepared by Hunting

- don Research Centre Ltd. 35 p.

42884402 Hawkins, D.; Kirkpatrick, D.; Shaw, D. et al. (1990) The Metabolism of (Carbon 14)

- Dimethoate in Sandy Loam Soil Under Anaerobic Conditions: Final Report: Lab Project Number: HRC/DTF/ 13/901535. Unpublished study prepared by Huntingdon
Research Centre Ltd. 86 p.



## 163

- 1 Leach/adsorp tion /desorption

MRID Citation Reference

### Page 98 of 144 52092 Graham

- Bryce, L.J. (1969) Diffusion of organophosphorus insecticides in soils. Journal of Science and Food Agriculture 20 (?/Aug):489

- 494. (Also In unpublished submission received Dec 4, 1974 under 5F1531; submitted by American Cyanamid Co., Princeton, N.J.; CDL:094151

- N)

52094 Kawamori, I.; Saito, T.; Iyatomi, K. (1971) Fate of organophosphorus insecticides in soils. Part I. Botyu

- Kagaku 36(? ):7

- 1 2. (Also In unpublished submission received Dec 4, 1974 under 5F1531; submitted by American Cyanamid Co., Princeton, N.J.;
CDL:094151

- Q)

52095 Kawamori, I.; Saito, T.; Iyatomi, K. (1971) Fate of organophosphorus insecticides in

soils. Part II. Botyu

- Kagaku 36:12

- 17. (Also In unpublished submission received Dec 4, 1974 under 5F1531; submitted by American Cyanamid Co., Princeton, N.J.;
CDL:094151

- R)

52098 Mishra, R.C.; Gupta, D.S. (1972) Persistence of Dimethoate in soils. Pesticides (Nov):28

- 3 0. (Also In unpublished study received Dec 4, 1974 under 5F1531; submitted by American Cyanam

- id Co., Princeton, N.J.; CDL:094151

- V)

52099 Montedison, S.p.A. (1972) Laboratory Tests on the Degradation of Dimethoate (Rogor) in Soil as a Function of the P ollution Hazards Possibly Deriving from This Active Substance: Report No. 88/1972. (Unpublished study received Dec 4, 1974 under 5F1531; submitted by American Cyanamid Co., Princeton, N.J.; CDL:094151

- W)

52100 Parker, B.L.; Dewey, J.E. (1965) Decline of Phorate and Dimethoate residues in treated soils based on toxicity to Drosophila melanogaster . Journal of Economic Entomology 58(1):106

- 111. (Also i n i unpublished submission received Dec 4, 1974 under 5F1531; submitted by American Cyanamid Co., Princeton, N .J.; CDL:094151

- X)

157237 Sato, Y.; Miyamoto, J. (1967) [An aspect concerning the movement of dimethoate from its granular formulation in soil]. Unknown Japanese source 16:23

- 28.

164959 Hawkins, D.; Kirkpatrick, D.; Till, C.; et al. (1986) The Mobility of [Carbon 14]

- dimethoate in Soil: HRC Rept. No. HRC/DTF/6e/ 86806. Unpublished study prepared by Huntingdon Research Centre Ltd. 66 p.



## 163

- 2 Volatility

- lab

MRID Citation Reference

159765 Huntingdon Research Centre Ltd. (1986) [The Mobility of Dimethoate on Soil]: Summary: DTF6e. Unpublished study. 10 p.

162776 Sanders, P. (1986) Cygon Systemic Insecticide

- miticide, Dimethoate (AC 12,880): Volatilization from Soil: Report No. PD

- M Volume 23

- 24: Project No. 0423. Unpublished study prepared by American Cyanamid Co. 35 p.

43276402 Skinner, W. (1994) Laboratory Volatility of (carbon 14)Dimethoate: Lab Project Number: 415W. Unpublished study prepared by PTRL West, Inc. 76 p.



## 164

- 1 Terrestrial field dissipation

### Page 99 of 144 MRID Citation Reference

33896 Bohn, W.R. (1962?) The Disappearance of Dimethoate from Soil. (Unpublished study received May 6, 1965 under 241

- 94; submitted by American Cyanamid Co., Princeton, N.J.; CDL:001779

- C)

52085 Bohn, W.R. (1964) The disappearance of Dimethoate from soil. Jour nal of Economic Entomology 57(6):798

- 799. (Also In unpublished submission received Dec 4, 1974 under 5F1531; submitted by American Cyanamid Co., Princeton, N.J.; CDL:094151

- G)

52086 Bro

- Rasmussen, F.; Noddegaard, E.; Voldum

- Clausen, K. (1970) Comparison of the disappearance of eight organophosphorus insecticides from soil in laboratory and in outdoor experiments. Pes

- ticide Science 1(Sep

- Oct):179

- 182. (Also In unpublished

sub

- mission received Dec 4, 1974 under 5F1531; submitted by American Cyanamid Co., Princeton, N.J.; CDL:094151

- H)

52089 Duff, W.G.; Menzer, R.E. (1973) Persistence, mobility, and degradation of ^14IC

Dimethoate in soils. Environmental Entomology 2 (3):309

- 318. (Also In unpublished submission received Dec 4, 1974 under 5F1531; submitte d by American Cyanamid Co., Princeton, N.J.; CDL:094151

- K)

52097 Manuel, A.J. (1972) Cygon(R) 267 and 25 WP: Dimethoate and Dimethoxon Residues in Soil: Report No. C

- 334. Includes method M

- 220 dated Aug 3, 1971. (Unpublished study received Dec 4, 1974 u nder 5F1531; submitted by American Cyanamid Co., Princeton, N.J.; CDL:094151

- T)

52100 Parker, B.L.; Dewey, J.E. (1965) Decline of Phorate and Dimethoate residues in treated soils based on toxicity to Drosophila melanogaster . Journal of Economic Entomology 58(1):106

- 111. (Also~In~unpublished submission received Dec 4, 1974 under 5F1531; submitted by American Cyanamid Co., Princeton, N.J.; CDL:094151

- X)

52103 American Cyanamid Company (1964) Dimethoate

-- Soils

-- Gainesville (N ov. 1964). (Unpublished study received Dec 4, 1974 under 5F1531; CDL:094151

- AC)

75600 Bohn, W.R. (1962?) The Disappearance of Dimethoate from Soil. (Unpublished study, including letter dated Apr 6, 1964 from F.R. Barron, Jr. to J.A. Shaughnessy,

received Apr 28, 1964 under 241

- 78; submitted by American Cyanamid Co., Princeton, N.J.; CDL:120250

- A)

75602 Orloski, E.J. (1964) Letter sent to F. Ray Barron, Jr. dated Feb 20, 1964: Cygon soil residue study. (Unpublished study received Feb 25, 1964 under 241

- 7 8; submitted by American Cyanamid Co., Princeton, N.J.; CDL:120258

- A)

75663 Duff, W.G. (1972) Persistence, Mobility, and Degradation of Dimethoate in Soils. Master's thesis, Univ. of Maryland. (Unpublished study received Mar 4, 1975 under 5F1531; submitt ed by American Cyanamid Co., Princeton, N.J.; CDL:094152

- A)

42884403 Becker, S. (1991) Dissipation of Dimethoate from Soil following Application to Bean, Grape, and Bareground Plots Located in Fresno County, CA, USA: Amended Final Report: Lab Project Num ber: 135

- 005. Unpublished study prepared by EPL Bio

Analytical Services, Inc. 633 p.

43388001 Jacobson, B.; Williams, B. (1994) Dissipation of Dimethoate in Soil Under Field Conditions with Grain Sorghum in Texas: Lab Project Number: 40972. Unpublished study prepared by ABC Labs, Inc. 160 p.

### Page 100 of 144 43388002 Jacobson, B.; Williams, B. (1994) Dissipation of Dimethoate in Soil Under Field Conditions when Applied to Bare Ground in New York : Lab Project Number: 40971. Unpublished study prepared by ABC Labs, Inc. 152 p.



# Non Guideline Selections

85344 Mendoza, C.E.; Wales, P.J.; Grant, D.L.; et al. (1969) Effect of bromine and ultraviolet light on eight pesticides detected with liver ester ases of five species. Journal of Agricultural and Food Chemistry 17(6):1196

- 1198. (Also In unpublished submission received Aug 28, 1972 under 279

- 2280; submitted by FMC Corp., Philadelphia, Pa.; CDL:120619

- G)

### Page 101 of 144 

# Appendix B

035001 Dimethoate Eco Effects Bibliography R evised 18 July 2014



## 71

- 1 Avian Single Dose Oral Toxicity

MRID Citation Reference

95520 Bunyan, P.J.; Jennings, D.M.; Taylor , A. (1968) Diagnosis of poisoning in pheasants owing to a number of common pesticides. Journal of Agricultural and Food Chemistry 16(2):332

- 229. (Sub

- mitter 22721; also~In~unpublished submission received Aug 10, 1970 under 3125

- 111; submitted by Mobay Ch emical Corp., Kansas City, Mo.; CDL:006922

- L)

116057 Bunyun, P.; Jennings , D.; Taylor, A. (1968) Organophosphorus poisoning: Diagnosis of poisoning in pheasants owing to a num

- ber of common pesticides. J. Agr. Food Chem. 16(2):332

- 339. (Also In unpublished submission received 1970 under 1E1082; submitted by Shell International Chemical Co., Ltd., London, Eng.; CDL:090840

- AI)

47769701 Zok, S. (3001) Dimethoate

- Acute Toxicity in the Northern Bobwhite Quail (Colinus virginianus) after Single Oral Administration (LD50). Project Number: 11W0466/99128, 441/008, 470/DMT. Unpublis hed study prepared by BASF Aktiengesellschaft, Labor fuer Oekotoxicologie. 71 p.

47769702 Zok, S. (2001) Dimethoate

- Acute Toxicity in the Ring

- Necked Pheasant (Phasianus colchicus) after Single Oral Administration (LD50). Project Number: 12W0466/99126, 441/007, 471/DMT. Unpublished study prepared by BASF Aktiengesellschaft, Labor fuer Oekotoxicologie. 67 p.

47769703 Gallagher, S.; Grimes, J.; Beavers, J. (2003) Omethoate: An Acute Oral Toxicity Study with the Northern Bobwhite. Project Number: 542/101

, 0/811/002, 581/DMT. Unpublished study prepared by Wildlife International, Ltd. 67 p. Omethoate degradate

47769704 Gallagher, S.; Grimes, J.; Beavers, J. (2003) Omethoate: An Acute Oral Toxicity Study with the Ring

- Necked Pheasant. Project Number: 542/1 02, 0/811/001. Unpublished study prepared by Wildlife International, Ltd. 69

p. Omethoate degradate



## 850.2100 Avian acute oral toxicity test

MRID Citation Reference

48964901 Hubbard, P.; Beavers, J. (2012) Dimethoate Technical: An Acute Oral Toxicity Study with the Mallard. Project Number: 232/159. Unpublished study prepared by Wildlife International, Ltd. 68p.

49096101 Hubbard, P.; Martin, K.; Beavers, J. (2013) Dimethoate: An Acute Oral Toxicity Study with the Canary. Project Number: 232/165. Unpublished study prepared by Wildlife International, Ltd. 95p.

### Page 102 of 144 

## 71

- 2 Avian Dietary Toxicity

MRID DOC NUM Citation Reference

51679 Edson, E.F.; Lade, B.I.; Barron, J.R. (1958) The Toxicology of N.C.262 (Rogor): Recovery from Acute Poisoning in the Rat and Hen: Report No. 22. (Unpublished study received Jul 18, 1963 under PP0385; prepared by Fisons Pest Control, Ltd., submitted by Amer ican Cyanamid Co., Princeton, N.J.; CDL:090415

- T)

159767 Munk, R. (1984) Preliminary Study with Dimethoate on the Bobwhite Quail (Colinus virginianus) by Administration in the Diet for a Period of 4 Weeks: Test Report: Project No. 71W326/82. Unpub

- lish ed study prepared by BASF Toxikologie. 52 p.

47744401 Hubbard, P.; Martin, K.; Beavers, J. (2009) Dimethoate: A Dietary LC50 Study with the Mallard. Project Number: 232/148, 232/021809/MLCB/100P. Unpublished study prepared by Wildlife

International Ltd. 113 p.

47769705 Zok, S. (2001) Dimethoate

- Avian Dietary LC50 Test in Chicks of the Bobwhite Quail (Colinus virginianus). Project Number: 31W0466/99127, 445/010, 469/DMT. Unpublished study prepared by BASF Aktiengesellschaft, Labor fuer Oekotoxicologie . 59 p.

47769706 Zok, S. (2001) Dimethoate

- Avian Dietary LC50 Test in Chicks of the Ring

- Necked Pheasant (Phasianus colchicus). Project Number: 36W0466/99130, 445/009. Unpublished study prepared by BASF Aktiengesellschaft. 57 p.

48680201 

### Hubbard, P.M., J.B. Beavers, and K.H. Martin. 2010. Dimethoate

Technical: A One

- Day Acute Dietary Exposure Study With The Northern Bobwhite Including An Assessment Of Avoidance Behavior. Unpublished study performed by Wildlife Interna tional, Ltd., Easton, Maryland. Project

No. 542

- 107. Study sponsored and submitted by Cheminova A/S, EU Regulatory Office, Harrogate, HG3 1RY, United Kingdom. Study initiated July 9, 2010 and completed December 16, 2010

.



## 71

- 4 Avian Reproduction

MRID Citation Reference

159768 Munk, R. (1986) 1

- Generation Reproduction Study with Dimethoate on the Mallard Duck (Anas platyrhynchos L.) by Administration in the Diet: Test Report: Project No. 72W326/82. Unpublished study prepared by BASF Toxikologie. 190 p.

162777 Munk, R. (1986) 1

- Generation Reproduction Study with Dimethoate... on the Bobwhite Quail (Colinus virginianus) after Administration in the Diet: Project No. 71W326/8256. Unpublished study pre

- pared by BASF AG. 314 p.

### Page 103 of 144 43661501 Cheminova Agro A/S. (1995) Six

- Week Dimethoate Avian Pilot Reproduction Study With Mallard Ducks: Preliminary Data. Unpublished study prepared by Wildlife Int'l. 4 p.

43967101 Gallagher, S.; Foster, J.; Beavers, J. et al. (1996) Dimethoate: A Reproduction Study with the Mallard (Anas platyrhynchos): (Final Report): Lab Project Number: 232

- 116: 232/050995/MR.WC/CHP82. Unpublished study prepared by Wildlife International Ltd. 205 p.

44049001 Gallagher, S.; Foster, J.; Beavers, J.; et al. (1996) Dimethoate: A Reproduction Study w ith the Northern Bobwhite (Colinus virginianus): Amended Report: Lab Project Number: 232

- 115: 232/050995/QR.WC/CHP: 2/050995/QR.WC/CHP82. Unpublished study prepared by Wildlife International Ltd. 208 p.

48033005 Albers, P.; Hoffman, D. (1984) Evaluation of Potential Embryotoxicity and Teratogenicity of 42 Herbicides, Insecticides, and Petroleum Contaminants to Mallard Eggs. Archives of Environmental Contamination and Toxicology 13: 15

- 27.



## 850.2300 Avian reproduction test

MRID Citation Reference

48216201 Temple, D.; Martin, K.; Beavers, J.; et al. (2010) Omethoate and Dimethoate: A Comparative Reproduction Study with the Northern Bobwhite: Final Report. Project Number: 232/149. Unpublished study prepared by Wildlife International, Ltd. 300 p.

48216202 Allemang, D. (2010) Second Waiver Request : Omethoate One

Generation Avian Reproduction Studies. Unpublished study prepared by Cheminova, Inc. 13 p.



## 71

- 5 Simulated or Actual Field Testing

MRID Citation Reference

75575 Wang, G.T. (1971) Letter sent to R.J. Little dated Dec 21, 1971: Necropsy of linnets and starlings. (Unpublished study received Jun 11, 1973 under 3F1301; submitted by American Cyanamid Co., Princeton, N.J.; CDL:092203

- F)

75585 Boudreau, G.W. (1971) Rep ort of Cygon Systemic 25W Test in Grapes. (Unpublished study received Oct 29, 1971 under 0F0928; prepared by Almaden Vineyards, submitted by American Cyanamid Co., Princeton, N.J.; CDL:093234

- B)

77485 Boudreau, G.W. (1972) Effects on Birds of Cygon 2E A pplied in Feed

lots To Control Houseflies. (Unpublished study, including let

- ter dated May 11, 1972 from G.T. Wang to R.J. Little and Jul 18, 1972 from F.R. Barron, Jr. to Pat C. Williams, received Jul 27, 1972 under 241

- 82; submitted by American Cyanami d Co., Prince

- ton, N.J.; CDL:100007

-

### Page 104 of 144 A)

97399 Barron, F.R., Jr. (1971) Letter sent to Pat C. Williams dated Oct 27, 1971: Cygon 267 systemic insecticide. (Unpublished study received Oct 29, 1971 under 241

- 94; submitted by American Cyanamid Co.,

Princeto n, N.J.; CDL:001977

- A)

107310 American Cyanamid Co. (1973) Summary of Report Submitted to EPA on May 3, 1973, in Connection with PP No. 3F1301. (Unpublished study received Apr 21, 1976 under 241

- 233; CDL:224122

- C)

139969 American Cyanamid Company (19 73) Summary of Report Submitted to EPA on May 3, 1973, in Connection with PP No. 3F1301. (Unpub

lished study received May 14, 1976 under 241

- 175; CDL:224705

- B)

40919001 Barrett, G.; Darnell, R. (1967) Effects of dimethoate on small mammal populations. American Midland Naturalist 77(1):164

- 175.

93912 Westlake, G.E.; Bunyan, P.J.; Martin, A.D.; et al. (1981) Organo

phosphate poisoning. Effects of selected organophosphat e pesti

- cides on plasma enzymes and brain esterases of Japanese quail (?~Coturnix coturnix japonica~?). Journal of Agricultural and Food Chemistry 29(4):772

- 778. (Also~In~unpublished submission received Jan 26,

1982 under 239

- 2471; submitted by Chevron Ch em

- ical Co., Richmond, Calif.; CDL:246657

- I)

46486401 Knabe, S. (2004) Residues of Dimethoate and Omethoate in Different Feed Sources for Wild Birds After Application of an EC Formulation Containing 400 g/L Dimethoate, (Spain 2003): (Final Report). Pro ject Number: 20031130/S1/FNTO, SCI/100/033067, 030317SB. Unpublished study prepared by GAB Biotechnologie Gmbh, Dr. U.

Noack

- Laboratorium fuer and Huntingdon Life Sciences, Ltd. 238 p.

46486403 Rodgers, M. (2004) EC Formulation of Dimethaote Containing 4 00 G/L. Assessment to Determine the Effect on Palatability via Drinking Water in the Bobwhite Quail. Project Number: SCI/085/030117, SCI/085. Unpublished study prepared by Huntingdon Life Sciences, Ltd. 42 p.

35180 Fowle, C.D. (1966) Effects of Forest

- Spray Pesticides on New Brunswick Birds: Effects of Phosphamidon and Experimental Insecticides on Birds. (Unpublished study received Jan 28, 1970 under

241

- 216; prepared by York Univ., Dept. of Biology, submitted by American Cyanamid Co., Princeton, N.J.; CDL:002057

- Z)



## 72

- 1 Acute Toxicity to Freshwater Fish

MRID Citation Reference

6043 Walker, C.P. (1963) Results of Preliminary Screening of Compounds Submitted by American Cyanamid Co. in a 24 Hour Bioassay Conduc

-

### Page 105 of 144 ted at Selected Concentrations of Commodity under Standard Con

ditions at 12^oIC. in Reconstituted Water. (Unpublished study received Dec 2, 1965 under 595

- 265; prepared by U.S. Fish and Wildlife Service, Fish Control Laboratory, submitted by Haviland Agr icultural Chemical Co., Grand Rapids, Mich.; CDL:128248

- A)

70341 Walker, C.R. (1963) Letter sent to Elton L. Clark dated Oct 22, 1963: Fish toxicity test with~n~

- dodecylguanidine acetate (Cy

- prex 5,223 tech.). (U.S. Fish and Wildlife Service, Fish Con

- trol Laboratory;
CDL:109804

- F)

75541 Chambers, H.; Fabacher, D.L. (1974) Acute toxicity of pesticides to channel catfish fingerlings. MAFES Research Highlights 37(2):1. (Also~In~unpublished submission received on unknown date under

538

- 135; submitted b y O.M. Scott & Sons Co., Marysville, Ohio;
CDL:221963

- A)

77504 McCann, J. (1970) ?Cygon 267: Goldfish (~Carassius auratus~)|: Test No. 292. (U.S. Agricultural Research Service, Pesticides Regulation Div.; unpublished study; CDL:129659

- A)

102572 Cope, O. (19??) Sport fishery investigations. Pages 29

- 30,38, In Fish and Wildlife Service Circular 199. By U.S. Fish and Wild

- life Service, Div. of Fishery Research. ?S.l.|: USFWS. (In

- complete; published study; CDL:003596

- D)

115880 Baywood Chemicals , Ltd. (1965) Placement of Disyston for Carrot Fly Control; Fish Toxicity Tests

-- 5006. London, Eng.: BCL. (Sub

- mitter 16569; technical bulletin 21/65; also In unpublished sub

- mission received Sep 23, 1968 under 3125

- 73; submitted by Mobay Chemical Corp., Kansas City, MO; CDL:007009

- Q)

119954 Watkins, J. (1966) Letter sent to K. Jackson dated Oct 26, 1966: Bio

assays: ?Methyl

- trithion 4E and other pesticides' toxicity to coho fry|:

File No. 34

- 5

- 2

- 4. (Unpublished study received Dec 1, 1970 under 1F1129; prepared by Government of Canada, sub

- mitted by Stauffer Chemical Co., Richmond, CA; CDL:090905

- J)

45202909 Grande, M.; Andersen, S.; Berge, D. (1994) Effects of pesticides on fish: experimental and field studies. Norwegian Journal of Agricultural
Sci ences Suppl. 13: 195

- 209.



## 850.1075 Fish acute toxicity test, freshwater and marine

MRID Citation Reference

48821401 Brougher, D.; Kendall, T.; Gallagher, S.; et al. (2012) Dimethoate: A 96

- Hour Static

- Renewal Acute Toxicity Test with Bluegill (Lepomis macrochirus): Final Report. Project Number: 232A/135. Unpublished study prepared by Wildlife International, Ltd. 61p.

48821402 Brougher, D.S., Kendall, T.Z., Gallagher, S.P., Krueger, H.O. 2012. Omethoate: A

96

- Hour Static

- Renewal Acute Toxicity Test with the Bluegill ( Lepomis

macrochirus ). Study performed by Wildlife International, Ltd., Easton, Maryland. Study number 232A

- 137A. Study sponsored by Cheminova A/S/

### Page 106 of 144 and submitted to Cheminova, Inc. Study initiated 02 January 2012 and comple ted 18 April 2012.

48821403 Brougher, D.; Kendall, T.; Gallagher, S.; et al. (2012) Dimethoate: A 96

- Hour Static

- Renewal Acute Toxicity Test with the Rainbow Trout (Oncorhynchus mykiss): Final Report. Project Number: 232A/136A. Unpublished study prepared by Wildlife International, Ltd. 61p.

48821404 

### Brougher, D.S., Kendall, T.Z., Gallagher, S.P., Krueger, H.O. 2012.

Omethoate: A 96

- Hour Static

- Renewal Acute Toxicity Test with the Rainbow Trout ( Oncorhynchus mykiss ). Study performed by Wildlife International, Ltd., Easton, Maryland. Study number 232A

- 138. Study sponsored by Cheminova A/S and submitted to Cheminova, Inc. Study initiated 16 December 2011 and completed 28 February 2012.

48298301 Armstrong, K.; Ca ley, C.; Cameron, B.; et al. (1984) Prolonged Toxicity Test (LC50) of EC Formulation of Dimethoate Containing 400 g.1^

- 1 to Rainbow Trout (21 Day, Semi

- Static). Project Number: 380500, 6914, 119/DMT. Unpublished study prepared by Inveresk Research Internat ional. 92 p.

48298302 Caley, C.; Cameron, B.; Knight, B.; et al. (1984) EC Formulation of Dimethoate Containing 400 g.1^

- 1: Determination of Acute Toxicity (LC50) to Rainbow Trout (96 h, Semi

- Static). Project Number: 380474, 6912, 120/DMT. Unpublished study prepared by Inveresk Research International. 91 p.

48298303 Caley, C.; Cameron, B.; Knight, B.; et al. (1984) Determination of Acute Toxicity (LC50) of EC Formulation of Dimethoate Containing 400 g.1^

- 1 to Bluegill Sunfish (96 h, Semi

- Static). Proj ect Number: 380495, 6944, 121/DMT. Unpublished study prepared by Inveresk Research International. 92 p.



## 850. Amphibian acute toxicity test, freshwater

MRID Citation Reference

48634201 Schneider, S.; Kendall, T.; Gallagher, S.; et al. (2011) Dimethoate

Technical: A 96

- Hour Flow

- Through Acute Toxicity Test with Tadpoles of the African Clawed Frog (Xenopus laevis): Final Report. Project Number: 232A/133. Unpublished study prepared by Wildlife International, Ltd. 66p.



## 72

- 2 Toxicity To Freshwater Invertebrates

37343 Muncy, R.J.; Oliver, A.D., Jr. (19??) Toxicity of ten insecticides to the red crawfish,~Procambarus clarki~(Girard). Pages 428

- 431,~In~?Without Title|. N.P. (Published study; CDL:091902

- C)

57053 Sanders, H.O. (1969) Toxicity of Pesticides to the Crustacean ?~Gammarus lacustris~. By U.S. Fish and Wildlife Service, Fish

- Pesticide

### Page 107 of 144 Research Laboratory. Washington, D.C.: USFWS. (Incomplete; technical paper # 25, published study; CDL: 228727

- AG)



## 850.1 010 Aquatic invertebrate acute toxicity, test, freshwater daphnids

MRID Citation Reference

48298306 Hertl, J. (2002) Acute Toxicity of Dimethoate to Daphnia magna in a 48

- Hour Immobilization Test. Project Number: 10591220, 482/DMT. Unpublished study prepared by Institut fuer Biologische Analytik und Consulting IBACON. 68 p.

48298309 Heintze, A. (2002) Assessment of Side Effects of Dimethoate on Larvae of the Midge, Chironomus riparius with the Laboratory Test Method: Final Report. Project Number: 20011123/01/ASCR, 446/003, 521/DMT. Unpublished study prepared by GAB Biotechnologie Gmbh. 131 p.

48821405 

### Simon, M. 2012. Daphnia magna , Acute Immobilization Test (OECD 202) Static Exposure. Unpublished study performed by Fraunhofer

- Institute for Molecular Biology and Applied Ecology (IME), 57377 Schmallenberg, Germany. CHA Doc. No. 1364 DMT. S tudy sponsored by the Dimethoate Task Force and submitted by Cheminova A/S, Lemvig, Denmark. Study initiated July 27, 2010 and (amended final report) submitted April 26, 2012.



## 72

- 3 Acute Toxicity to Estuarine/Marine Organisms

MRID Citation Reference

42760001 Graves, W.; Swigert, J. (1993) Dimethoate: A 96

- Hour Static Acute Toxicity Test with the Sheepshead Minnow (Cyprinodon variegatus): Final Report: Lab Project Number: 242A

- 101. Unpublished study prepared by Wildlife International Ltd. 79 p.

42760002 Grav es, W.; Swigert, J. (1993) Dimethoate: A 96

- Hour Shell Deposition Test with the Eastern Oyster (Crassostrea virginica): Final Report: Lab Project Number: 242A

- 104. Unpublished study prepared by Wildlife International Ltd. 70 p.

42760003 Graves, W.; Swig ert, J. (1993) Dimethoate: A 96

- Hour Static Acute Toxicity Test with the Saltwater Mysid (Mysidopsis bahia): Final Report: Lab Project Number: 242A

- 102. Unpublished study prepared by Wildlife International Ltd. 81 p.

### Page 108 of 144 

## 850.1350 Mysid chronic toxicity test

MRID Citation Reference

48804201 Claude, M.; Kendall, T.; Gallagher, S.; et al. (2012) Dimethoate Technical:

A Flow

- Through Life

- Cycle Toxicity Test with the Saltwater Myseid (Americamysis bahia): Final Report. Project Number: 232A/139, 232/101311/MYS/LC/SUB232. Unpublished study prepared by Wildlife International, Ltd. 121p.



## 72

- 4 Fish Early Life Stage/Aquatic Invertebrate Life Cycle Study

MRID Citation Reference

45273 Fabacher, D.L.; Chambers, H. (1973) Acute Toxicity of Three Pes

- ticides to Channel Catfish Fingerlings: Report No. 40426. (Un

- published study received Mar 7, 1975 under 5F1559; prepared by Mississippi State Univ., Agricultural and Forestry Experiment Sta tion, Dept. of Entomology, submitted by Mobay Chemical Corp., Kansas City, Mo.; CDL:094870

- A)

55391 Alabaster, J.S.; Edson, E.F. (1959) The Toxicology of Rogor (N.C.262): Toxicity to Rainbow Trout: Report No. 28. (Unpub

- lished study received Mar 1, 1960 under PP0255; prepared by Fi

- sons Pest Control, Ltd., England, submitted by Fisons (Canada), Ltd., A gricultural Chemicals Div., Toronto, Ontario; CDL: 090281

- Y)

42864701 Wuthrich, V. (1990) Influence of Dimethoate on the Reproduction of Daphnia Magna: Final Report: Lab Project Number: 264464. Unpublished study prepared by RCC Umweltchemie AG 462 p.

43106301 Strawn, T.; Muckerman, M. (1994) Early Life

- stage Toxicity of Dimethoate to the Rainbow Trout (Oncorhynchus mykiss) Under Flow

- through Conditions: Final Report: Lab Project Number: 40864. Unpublished study prepared by ABC Labs, Inc. 436 p.

4310 6302 Strawn, T.; Muckerman, M. (1994) Raw Data Report for: Early Life

- stage Toxicity of Dimethoate to the Rainbow Trout (Oncorhynchus mykiss) Under

Flow

- Through Conditions: Final Report: Lab Project Number: 40864R. Unpublished study prepared by ABC Labs, Inc. 1359 p.



## 850.1400 Fish early

- life stage toxicity test

MRID Citation Reference

48772901 Hurd, K.; Sharpe, A. (2011) Dimethoate Technical: Determination of the Effects on the Early

- life Stage of the Sheepshead minnow (Cyprinodon variegatus). Project Number: BR0555/B. Unpublished study prepared by AstraZeneca UK, Ltd. 53p.

### Page 109 of 144 49083401 Hicks, S. (2013) Dimethoate: Early Life

- Stage Toxicity Test with the Rainbow Trout, Oncorhychus mykiss, Under Flow Through Conditions. Project Number: 68796. Unpublished study prepared by ABC Laboratories, Inc. 175p.



## 123

- 1 ( 850.4100 or 850.4150 

## )Terrestrial Plant Toxicity

47709701 Porch, J.; Krueger, H.; kendall, T. (2009) Dimethoate: A Toxicity Test to
Determine the Effects of the Test Substance on Vegetative Vigor of Ten Species of Plants: Final Report. Project Number: 232/140, 232/110408/VEGVIG10/SUB232. Unpublished study prepared by Wildlife International, Ltd. 295 p.

47709702 Porch, J.; Kendall, T.; Krueger,H. (2009) Dimethoate: A Toxicity Test to Determine the Effects of the Test Substance on Seedling Emergence of Ten Species of Plants: Final Report . Project Number: 232/139, 232/100708/SEEDEM/10/SUB232. Unpublished study prepared by Wildlife Internationa,l Ltd. 283 p.



## 850.4225 Seedl ing emergence, Tier II

MRID Citation Reference

48572801 Porch, J.; Krueger, H.; Martin, K. (2011) Dimethoate TEP and TGAI: A Tier II Toxicity Test to Determine the Effects of the Test Substances on Seedling Emergence of Ten Species of Plants: Final Report. Project Number: 232/151. Unpublished study prepared by Wildlife International, Ltd. 246p.

48628101 Porch, J.; Krueger, H.; Martin, K. (2011) Dimethoate TEP and TGAI: A Tier II Toxicity Teest to Determine the Effects of the Test Substances on Seedling Emergence of Ten Species of Plants: Final Report. Project Number: 232/151. Unpublished study prepared by Wildlife International, Ltd. 248p.



## 850.4250 Vegetative vigor, Tier II

MRID Citation Reference

48572802 Porch, J.; Krueger, H.; Martin, K. (2011) Dimethoate TEP and TGAI: A Tier II Toxicity Test to Determine the Effects of the Test Substances on Vegetative Vigor of Ten Species of Plants: Final Report. Project Number: 232/152. Unpublished study prepared by Wildlife Internationa l, Ltd. 290p.



## 123

- 2 Aquatic plant growth

### Page 110 of 144 MRID Citation Reference

43679309 Ibrahim, E. (1983) Effects of some common pesticides on growth and metabolism of the unicellular algae Skeletonema costatum, Amphiprora paludosa, and Phaeodactylum tricornutum. Aquatic Toxicology (3):1

- 14.

43679310 Ibrahim, A. (1984) Effect of growth ra te of the microscopic algae Ankistrodesmus falcatus (Corda) ralfs, Scenedesmus quadricauda (Turp.) breb. and Phaeodactylum tricornutum (bohlin). Aqua 5:303

- 306.

47784001 Cally, C.; Cameron, B.; Knight, B.; et al. (1992) Alga, Growth Inhibition (72h, EC 50) with Technical Dimethoate: IRI Project No. 381038. Project Number: 381038, 8077, 123/DMT. Unpublished study prepared by Inveresk Research International. 85 p.



## 850.4400 Aquatic plant toxicity test using Lemna spp. Tiers I and II

MRID Citation Reference

47709703 Porch, J.; Kendall, T.; Krueger, H. (2009) Dimethoate: A 7

- Day Static

Renewal Toxicity Test with Duckweed (Lemna gibba G3): Final Report. Project Number: 232A/118, 232/120508/LEM7D/SR/OECD/OPPTS/SUB232. Unpublished study prepared by Wildlife International, Ltd. 157 p.



## 850.5400 Algal toxicity, Tiers 1 and II

MRID Citation Reference

48572803 Porch, J.; Kendall, T.; Krueger, H. (2011) Dimethoate TGAI: A 96

- Hour Toxicity Test with the Marine Diatom (Skeletonema costatum): Final Report. Project Number: 232A/130. Unpublished study prepared by Wildlife International, Ltd. 68p.

48572804 Porch, J.; Kendall, T.; Krueger, H. (2011) Dimethoate TGAI: A 96

- Hour Toxicity Test with the Freshwater Alga (Anabaena flos

- aquae): Final Report. Project Number: 232A/125B. Unpublished study prepared by Wildlife International, Ltd. 67p.

48572805 Porch, J.; Kendall, T.; Krueger, H. (2011) Dimethoate TGAI: A 96

- Hour Toxicity Test with the Freshwater Alga (Pseudokirchneriel la subcapitata): Final Report. Project Number: 232A/129. Unpublished study prepared by Wildlife International, Ltd. 68p.

48572806 Porch, J.; Kendall, T.; Krueger, H. (2011) Dimethoate TGAI: A 96

- Hour Toxicity Test with the Freshwater Diatom (Navicula pel liculosa): Final Report. Project Number: 232A/128. Unpublished study prepared by Wildlife International, Ltd. 68p.

### Page 111 of 144 

## 141

- 1 Honey bee acute contact

MRID Citation Reference

45024201 Thompson, H. (1999) Flusilazole 40EC (400 G/L): Acute Oral and Contact Toxicity to the Honey Bee, Apis mellifera L: Final Report: Lab Project Number: GQ8400: DUPONT

- 3296: 3296. Unpublished study prepared by Central Science Lab. 46 p. {OPPTS 850.320}

45024202 Thompson, H. (2000) Flusilazole 40EC (400 G/L): Acute Oral and Contact Toxicity to the Honey Bee, Apis mellifera L: Report Amendment No. 1: Lab Project Number: DUPONT

- 3296: GQ8400: 3296. Unpublished study prepared by Central Science Lab. 5 p. {OPPTS

850.30 20}

30454 Kerry, J.C.; Weighton, D.M. (1977) ?Toxicity Studies on Bees|. (Unpublished study including French text, received Apr 9, 1980 under

43142

- EX

- 1; prepared in cooperation with France, Ministry of Agriculture, Dept. of Zoology, Research Station fo r Bees and Social Insects, submitted by Boots Hercules Agrochemicals Co., Wilmington, Del.; CDL:099369

- M)

45044 Clark, A.M. (1976) Permethrin: Oral and Contact Toxicity to Honey

bees of Technical Material and an Encapsulated Emulsion: TMJ 1273 A. (Unpublished study received Dec 20, 1976 under 100

- EX

- 53; prepared by Plant Protection, Ltd., submitted by Ciba

- Geigy Corp., Greensboro, N.C.; CDL:0 95990

- B)

45046 Johansen, C.; Mayer, D.; Madsen, R.; et al. (1975) Bee Research Investigations, 1975. (Unpublished study received Dec 20, 1976 under

100

- EX

- 53; prepared by Washington State Univ., submitted by Ciba

Geigy Corp., Greensboro, N.C.; CDL:09599 0

- E)

59971 Cole, J.H. (1974) The Acute Contact and Oral Toxicity to Worker Honey Bees of Technical Dowco 290: DWC246/74726. (Unpublished study received Nov 12, 1980 under 464

- 563; prepared by Hunting

- don Research Centre, England, submitted by Dow Chemi cal U.S.A., Midland, Mich.; CDL:099724

- F)

108108 Fraser, W.; Jenkins, G. (1971) The Acute Contact and Oral Tox

- icities of CP67573 and MON2139 to Worker Honey Bees: 5369/72/ 765. (Unpublished study received Jul 12, 1974 under 5F1536; prepared by Huntingdon Research Centre, Eng., submitted by Monsanto Co.

, Washington, DC; CDL:094171

- J)

81595 Cole, J.H. (1974) The Acute Contact and Oral Toxicity to Worker Honey Bees of Technical Dowco 290: DWC246/74726. (Unpublished study received Jul 30, 1979 under 464

- EX

- 55; prepared by Hunt

- ingdon Research Centre, En gland, submitted by Dow Chemical U.S.A., Midland, Mich.; CDL:098875

- I)

49178402 Zenker, K. (2011) Acute Toxicity of Dimethoate 400 g/L EC to the Honeybee Apis mellifera L. Under Laboratory Conditions: Final Report. Project Number: DE/81265162, 1171/DMT, 11/10/48/003/D. Unpublished study prepared by Biochem Agrar, Labor fuer Biologische und Chemische. 49p.

### Page 112 of 144 49178404 Gough, H.; Mcindoe, E.; Lewis, G. (1994) The Use of Dimethoate as a Reference Compound in Laboratory Acute Toxicity Tests on Honey Bees (Api s mellifera L.) 1981

- 1992. Journal of Apicultural Research 33(2): 119

- 125.

26489 or

67044 Fraser, W.D.; Jenkins, G. (1972) The Acute Contact and Oral Toxicities
of CP67573 and Mon2139 to Worker Honey Bees. (Unpublished study

received on unknown date unde r 4G1444; prepared by Huntingdon Research Centre, submitted by Monsanto Co., Washington, D.C.;
CDL:093848

- R)

42805203 Pietrzik, J. (1991) Assessment of Side Effects of Dimethoate EC 400 g/l (SAG 103 20) on the Ground Beetle, Poecilus cupreus L. in the Laboratory: Translation of Final Report to Study 120/01

- Pc: Lab Project
Number: 120/01

- PC: 946

- 005: Dimethoate EC 400 G/L (SAG 103 20). Unpublished study prepared by GAB Biotechnologie GmbH. 17 p.

42805204 Petto, R. (1993) Effects of an EC Formulation of Dimethoate Containing 400 g/l on Aphidius matricariae HAL (Hymenoptera, Aphidiidae) in the Laboratory: Lab Project Numbe r: 946

- 007: 322806. Unpublished study prepared by RCC Umweltchemie GmbH & Co. KG. 28 p.

42805205 Decker, U. (1993) The Effects of Larval and Pupal Exposure to the EC Formulation of Dimethoate Containing 400 g/l on the Hover

- Fly, Syrphus corollae Fabr. ( syn.: Eupeodes Corollae) (Diptera: Syrphidae) in the Laboratory: Lab Project Number: 325078: 946

- 008. Unpublished study prepared by RCC, Research & Consulting Co., Ltd. and BRL, Biological Research Labs, Ltd. 59 p.

42805206 Pietrzik, J. (1992) Assessmen t of Side Effects of Dimethoate EC 400 g/l (SAG 103 20) on the Predatory Mite, Typhlodromus pyri Scheuten in the Laboratory: Translation of Final Report to Study 120/01

- Tp: Lab Project
Number: 120/01

- TP: 946

- 006: Dimethoate EC 400 G/L (SAG 103 20). Unpubli shed study prepared by GAB Biotechnologie GmbH. 23 p.

42805207 Kuhner, C. (1993) Assessment of Side

- Effects of SAG 10320 on the Lady

- Bird Beetle, Coccinella septempunctata L. in the Laboratory: Translation of Final Report to the Study: Lab Project Numbe r: 120/02

- CS: 946

- 001: SAG 10320. Unpublished study prepared by Institut fur Umweltanalytik und Biotechnologie GmbH. 26 p.

42805208 Kuhner, C. (1993) Assessment of Side

- Effects of an EC

- Formulation Containing 400 g/l of Dimethoate (SAG 10320) on the Green Lacewing, Chrysoperla carnea Steph. in the Laboratory: Translation of Final Report to the Study: Lab Project Number: 120/01

- CC: 946

- 002: SAG 10320. Unpublished study prepared by GAB Biotechnologie GmbH. 22 p.

47841001 Barber, I.; Ebeling, M.; Edwards, P.; et al. (2005) Review on Initial Residue Levels of Pesticides in Arthropods Samples in Field Studies. Project Number: RC05/029, 31 51957. Unpublished study prepared by RIFCon GmbH. 59 p.



## 142

- 3 Simulated or Actual Field Testing Pollinators

MRID Citation Reference

### Page 113 of 144 82973 Duval, C.T. (1969) Pesticides and the honey bee. Pest Articles and News Summaries 15(3):321

- 324. (Also~In~unpublished sub

- mission received Apr 26, 1977 under 464

- 402; submitted by Dow Chemical U.S.A., Midland, Mich.; CDL:230691

- N)

88398 Johansen, C.; Eves, J. (1970) Bee Research Investigations, 1970. (Unpublished study received Feb 1, 1973 under unknown admin. no.; prepared by Washington State Univ., submitted by Shell Chemical Co., Washington, D.C.; CDL:222266

- D)

105372 Alexandrescu, S.; Serban, M. (1966) Toxicitatea unor insecticide fata de albine, determinata in laborator si camp. ?Toxicity to bees of some insecticides, as determined by laboratory and field tests|. An. Inst. Cercet. Prol. Plant, Inst. Cent. Cercet. Agr. IV:411

- 417. ( Rumanian text;

al so In unpublished submission re ceived Nov 1, 1970 under unknown admin. no.; submitted by Hercules, Inc., Agricultural Chemicals, Wilmington, DE; CDL: 005103

- AN)

5000837 Johansen, C.A. (1972) Toxicity of field

- weathered insecticide resid ues to four kinds of bees. Environmental Entomology 1(3):393

- 394.

5008360 Hoy, M.A.; Flaherty, D.; Peacock, W.; Culver, D. (1979) Vineyard and laboratory evaluations of methomyl, dimethoate, and permethrin for a grape pest management program in the San Joaquin Valley of California. Journal of Economic Entomology 72(2):250

- 255.

115038 Lemon, R. (1973) Bee Toxicity Tests

-- NC 8458: Biosc/73/1/35. (Un

published study received Apr 12, 1974 under 10065

- EX

- 4; prepared by Fisons Ltd., Eng., submitted by Fiso ns Corp., Agricultural Chemicals Div., Bedford, MA; CDL:127694

- D)

125900 Sarrazin, R., ed. (1976) The Ecological Impact of Forest Insect Control Operations in Quebec during 1976: ?Submitter| 50217. (Unpublished study received Jun 26, 1978 under 3125

- EX

- 150; prepared by Canada, Dept. of Tourism, Fish and Game, submitted by Mobay Chemical Corp., Kansas City, MO; CDL:234509

- K)

138669 Waller, G.; Barker, R. (1979) Effe cts of dimethoate on honey bee colonies. Journal of Economic Entomology 72(4): 549

- 551. (Also In unpublished submission received Jan 11, 1984 under 4581

- 292; submitted by Agchem Div., Pennwalt Corp., Philadelphia, PA;
CDL:252448

- I)

47800504 Decourtye, A .; Devillers, J.; Genecque, E.; et al. (2005) Comparative Sublethal Toxicity of Nine Pesticides on Olfactory Learning Performances of the Honeybee Apis mellifera. Archives of Environmental Contamination and Toxicology 48:242

- 250.

47800506 Porrini, C.; S abatini, A.; Girotti, S.; et al. (2003) The Death of Honey Bees and Environmental Pollution by Pesticides: The Honey Bees as Biological Indicators. Bulletin of Insectology 56(1):147

- 152.

47800519 Incerti, F.; Bortolotti, L.; Porrini, C.; et al. (2003) A n Extended Laboratory Test to Evaluate the Effects of Pesticides on Bumblebees: Preliminary Results. Bulletin of Insectology 56(1):159

- 164.

48101301 Habig, C. (2010) Summary of a Dimethoate Field Pollinator Study Entitled: Toxicity Testing of an EC Formulation Containing 400g/L Dimethoate (BAS 152 11 I) on Honeybees (Apis mellifera L.) in the Field.

### Page 114 of 144 Unpublished study prepared by Exponent, Inc., and Ins titut fuer Biologische Analytik und Consulting IBACON GmbH. 21 p.

48101302 Schmitzer, S. (2005) Toxicity Testing of an EC Formulation Containing 400 g/L Dimethoate (BAS 152 11 I) on Honey Bees (Apis mellifera L.) in the Field. Project Number: 21551039, 4 48/014, 695/DMT. Unpublished study prepared by Institut fuer Biologische Analytik und Consulting IBACON GmbH. 76 p.



## Non Target Beneficial Insect Studies

42805201 Pietrzik, J. (1991) Assessment of Side Effects of Dimethoate EC 400 g/l (SAG 103 20) on t he Rove Beetle, Aleochara bilineata Gyll, In the Laboratory: Translation of Final Report to Study 120/01

- Ab: Lab Project
Number: 120/01

- AB: 946

- 003: Dimethoate EC 400 G/L (SAG 103 20). Unpublished study prepared by GAB Biotechnologie GmbH. 19 p.

42805202 Kuhner, C. (1991) Effect of Dimethoate EC 400 g/l (SAG 103 20) on Trichogramma cacoeciae Marchal (Hym., Trichogrammatidae) as a Representative of Microhymenoptera in the Laboratory: Translation of Final Report to the Study: Lab Project Number: 120/01

- TC: Dimethoate EC 400 G/L (SAG 10320): 946

- 004. Unpublished study prepared by GAB Biotechnologie GmbH. 24 p.

49187601 Halsall, N. (2001) A Field Study to Evaluate the Effects of Drift Rates of the Insecticide Dimethoate on Parasitic Wasps. Project Number: BASF/00/8, 532/DMT, 449/012. Unpublished study prepared by Mambo

Tox, Ltd. 53p.

49187602 Muther, J. (2001) A Field Study to Evaluate the Effects of BAS 152 11 I on Predatory Mites and Other Beneficial Arthropods in an Apple Orchard in Germany: Final Repo rt. Project Number: 99023/G3/NFTP, G00N046E, 535/DMT. Unpublished study prepared by Arbeitsgemeinschaft GAB Biotechnologie. 81p.

49187603 Muther, J. (2001) A Field Study to Evaluate the Effects of BAS 152 11 I on Predatory Mites and Other Beneficial Arthropods in an Apple Orchard in Germany: Final Report. Project Number: 99023/G1/NFTP, G00N037E, 536/DMT. Unpublished study prepared by Arbeitsgemeinschaft GAB Biotechnologie. 81p.

49187604 Muther, J. (2001) A Field Study to Evaluate the Effects of BAS 152 11 I on Predatory Mites and Other Beneficial Arthropods in an Apple Orchard in Germany: Final Report. Project Number: 99023/G2/NFTP, 449/015, 537/DMT. Unpublished study prepared by Arbeitsgemeinschaft GAB Biotechnologie. 82p.

49187605 Knabe, S. (2009 ) A Field Trial Assessing the Impact of Two Applications of Dimethoate 400 g/L EC on the Non

- Target Arthropod Fauna of Alfalfa (Medicago sativa) Crop (Germany). Project Number: S08/01268, 816/DMT. Unpublished study prepared by Eurofins

- GAB GmbH. 460p.



## 890.1100 Amphibian Metamorphosis (Frog)

### Page 115 of 144 MRID Citation Reference

48670601 Schneider, S.; Kendall, T.; Krueger, H. (2012) Dimethoate: Amphibian Metamorphosis Assay: Final Report. Project Number: 232A/132A. Unpublished study prepared by Wildlife International, Ltd. 139p.

48670602 Schneider, S.; Kendall, T.; Krueger, H. (2012) Dimethoate Technical: Amphibian Metamorphosis Range Finding Assay: Final Report. Project Number: 232A/134. Unpublished study prepared by Wildlife International,

Lt d. 76p.



## 890.1350 Fish Short

- Term Reproduction

MRID Citation Reference

48670603 Schneider, S.; Martin, K.; Kendall, T.; et al. (2012) Dimethoate: Fish
Short

- Term Reproduction Assay with the Fathead Minnow (Pimephales promelas): Final Report. Project Number: 232A/131. Unpublished study prepared by Wildlife International, Ltd. 163p.



## Non

- Guideline Study

MRID Citation Reference

51681 Sutherland, G.L. (1960?) Cholinesterase Inhibitory Activity of Dimethoate and Its Metabolites. (Unpublished study received Jul 18, 1963 under PP0385; submitted by American Cyanamid Co., Princeton, N.J.;
CDL:090415

- V)

52093 Graham

- Bryce, I.J.; Etheridge, P. (1967) Effect of soil moisture conditions on uptake of systemic insecticides from soil by plants. Proceedings, 4th British Insecticide Fungicide Confer

- ence 1:336

- 343. (Also~In~unpublished submission received Dec 4, 1974 under 5F1531; submitted by Ame rican Cyanamid Co., Princeton, N.J.; CDL:094151

- O)

52104 Zaki, M.; Reynolds, H.T. (1961) Effects of various soil types and methods

upon uptake of three systemic insecticides by cotton plants in the greenhouse. Journal of Economic Entomology 54(3): 568

- 572. (Also~In~unpublished submission received Dec 4, 1974 under 5F1531; submitted by American Cyanamid Co., Princeton, N.J.; CDL:094151

- AD)

56466 Kenaga, E.E. (1973) Factors to be considered i n the evaluation of the toxicity of pesticides to birds in their environment. Pages 166

- 181,~In~Environmental Quality and Safety: Global Aspects of Chemistry, Toxicology and Technology As Applied to the Environ

- ment: Vol. II. Edited by F. Coulston and F. Korte. Stuttgart, W. Germany: Georg Thieme

### Page 116 of 144 Publishers; New York, N.Y.: Academic Press, Inc. (Also~In~unpublished submission received Jun 21, 1976 under 464

- 512; submitted by Dow Chemical U.S.A., Midland, Mich.; CDL:224700

- G)

57054 Coppage, D.L. (1972) O rganophosphate pesticides: Specific level of brain ACHE inhibition related to death in sheepshead minnows. Transactions of the American Fisheries Society 101(3):534

- 536. (Also In unpublished submission received Mar 21, 1977 under 352

- 338; submitted by E.I . du Pont de Nemours & Co., Wilmington, Del.; CDL:228727

- AJ)

126904 Menzie, C. (19??) Acute Toxicity of Some Organophosphorus Pesti

- cides against Fish & Aquatics: ?Sumithion|. (Unpublished study received Mar 15,

1973 under 10308

- 2; prepared by U.S. Dep t. of Interior, submitted by Sumitomo Chemical Co., Ltd., Baltimore, MD; CDL:004892

- F)

47164602 Holmes, C.; Vamshi, R. (2007) Data and Methodology Used for Spatial Analysis of California Red Legged Frog Observations and Proximate Land Cover Characteristics. Project Number: 3152007, WEI/252/03. Unpublished study prepared by Waterborne Environmental, Inc. (WEI). 19

p.

48033001 Andersen, H.; Vinggaard, A.; Rasmussen, T.; et al. (2002) Effe cts of Currently Used Pesticides in Assays for Estrogenicity, Androgenicity, and Aromatase Activity in vitro. Toxicology and Applied Pharmacology 179: 1

- 12.

77534 Sutherland, G.L. (1959) Mammalian Toxicity of the Oxy

- carboxy Metabolite of Dimethoate. (Un published study received Mar 21, 1960 under unknown admin. no.; submitted by American Cyanamid Co., Princeton, N.J.;
CDL:109340

- AF)

48065601 Allemang, D. (2010) Evaluation of the Cholinesterase Inhibiting Potential of the Plant Metabolites of Dimethoate, O

- Desmethyl Omethoate Carboxylic Acid (Metabolite XX) and Des

- O

- Methyl Isodimethoate (Metabolite XII) in Comparison with the Parent Compound. Unpublished study prepared by Cheminova A/S. 32 p.

48065602 Barnett, J. (2009) Oral (Gavage) Acute Dose Range

- F inding Cholinesterase Depression Study of Dimethoate, O

- Desmethyl

Omethoate

- Carboxylic Acid, di

- Na

- Salt and Des

- O

- Methyl Isodimethoate,

Na

- Salt in Rats: Final Report. Project Number: TQC00034. Unpublished study prepared by Charles River Laboratories. 183 p

.

48065603 Barnett, J. (2009) Oral (Gavage) Acute Dose Range

- Finding Study of O

Desmethyl

- Omethoate

- Carboxylic Acid, di

- Na

- Salt and Des

- O

- Methyl Isodimethoate, Na

- Salt in Rats: Final Report. Project Number: TQC00047. Unpublished study prepared by Charles River Laboratories. 183 p.

48160705 Chen, H.; Xiao, J.; Hu, G.; et al. (2002) Estrogenicity of Organophosphorus and Pyrethroid Pesticides. Journal of Toxicology and Environmental Health

65:1419

- 1435.

48298310 Stabler, D. (2002) Dimethoate: Assessment of Effects on Reproduction and Growth on Eisenia foetida in Artificial Soil: Final Report. Project Number: 20011123/01/NREF, 449/018, 522/DMT. Unpublished study prepared by GAB Biotechnologie Gmbh. 53 p.

48298314 Stabler, D. (2001) Acute Toxicity of Dimethoate on Earthworms, Eisenia foetida Using an Artificial Soil Test. Project Number: 20011123/01/NLEF,

### Page 117 of 144 721/DMT. Unpublished study prepared by GAB Biotechnologie Gmbh. 61

p.

### Page 118 of 144 

# Appendix C. Dimethoate and its transformation products

C ode Name /

Synonym Nomenclature , formula, molecular weight, SMILES Code Structure

Dimethoate IUPAC: O,O

- dimethyl S

- methylcarbamoylmethyl phosphorodithioate

CAS: O,O

- dimethyl S

- [2

- (methylamino)

- 2

- oxoethyl] phosphorodithioate

CAS No.: 60

- 51

- 5

Formula: C 5 H 12 NO 3 PS 2 MW: 229.3 g/mol

SMILES: O=C(NC)CSP(OC)(OC)=S O

N C H 3

H O C H 3 P O C H 3 S

S C

H 2

Omethoate CAS: O,O

- Dimethyl S

- [2

- (methylamino)

- 2

- oxoethyl] phosphorothioate

CAS No.: 1113

- 02

- 6

Formula: C 5 H 12 NO 4 PS 2 MW: 213.2 g/mol

SMILES: CNC(=O)CSP(=O)(OC)OC N

H C H 3 O

C

H 2 S P O O C H 3

O C H 3

Desmethyl

dimethoate CAS: Phosphorodithioc acid, O

- methyl S

- [2

- (methylamino)

- 2

- oxoethyl ester

Formula: C 4 H 10 NO 3 PS 2 MW: 215.2 g/mol

SMILES: CNC(=O)CSP(=S)(O)OC N

H C H 3 O

C

H 2 S P S O C H 3

O H

Des

- O

- methyl

isodimethoate CAS: S

- (methyl)

- S

- [(N

- carbamoyt)methyl]

- phosphorodithioic acid

Formula: C 4 H 10 NO 3 PS 2 MW: 215.2 g/mol

SMILES: CNC(=O)CSP(=O)(O)SC N

H C H 3 O

C

H 2 S P O S C H 3

O

O

- desmethyl

dimethoate carboxylic acid IUPAC: 2

- [Hydroxy(methoxy)phosphinothioyl]sulfanylacetic

acid

Formula: C 3 H 7 O 4 PS 2 MW: 202.2 g/mol

SMILES: COP(=S)(O)SCC(=O)O O H O

C

H 2 S P S O C H 3

O H

O

- desmethyl

omethoate carboxylic acid IUPAC: 2

- [hydroxy(methoxy)phosphoryl]sulfanylacetic acid

Formula: C 3 H 7 O 5 PS

MW: 186.12 g/mol

SMILES: COP(=O)(O)SCC(=O)O O H O

C

H 2 S P O O C H 3

O H

### Page 119 of 144 Methyl phosphate IUPAC: Methyl dihydrogen phosphate

Formula: CH 5 O 4 P

MW: 112.0 g/mol

SMILES: COP(=O)(O)O O H P

O O C H 3

O H

O

- desmethyl

omethoate CAS: Phosphoric acid, O

- methyl S

- [2

- (methylamino)

- 2

- oxoethyl] ester

Formula: C 4 H 10 NO 4 PS

MW: 199.16 g/mol

SMILES: CNC(=O)CSP(=O)(O)OC P

O H O C H 3 O

S C

H 2 O

N C H 3

H

S

- methyl phosphorothioate IUPAC: Methoxy(methylsulfanyl)phosphinic acid

Formula: C 2 H 7 O 3 PS

MW: 142.1 g/mol

SMILES: COP(=O)(O)SC P

O H S C H 3 O

O C H 3
Oxithiaphosphiran Formula: C 4 H 12 NO 3 PS 2 MW: 217.25 g/mol

SMILES: CNC(=O)CSP(O)(OC)S P S O

O C H 3 S C

H 2

N

H C H 3 O

### Page 120 of 144 

# Appendix D

. Sample SWCC O utput File

Example for the MN alfalfa modeling scenario



# Summary of Water Modeling of Dimethoate and the USEPA Standard

Pond

Estimated Environmental Concentrations for Dimethoate are presented in Table 1 for the USEPA standard pond with the MNalfalfaOP field scenario. A graphical presentation of the year

to

- y ear peaks is presented in Figure 1. These values were generated with the Surface Water Concentration Calculator (SWCC Version 1.106). Critical input values for the model are

summarized in Tables 2 and 3.

This model estimates that about 1.4% of Dimethoate applied to the field eventually reaches the water body. The main mechanism of transport from the field to the water body is by spray drift (89.1% of the total transport) followed by runoff (10.9%).

In the water body, pesticide dissipates with an effective water column half

- life of 33.7 days. (This value does not include dissipation by transport to the benthic region; it includes only processes that result in removal of pesticide from the complete system.) The main source of
dissipation in the water column is metabolism (effective average half

- life = 66.9 days) followed by hydrolysis (68 days), photolysis (67604 days), and volatilization (1.76249E+07 days). In the benthic region, pesticide dissipates (53.8 days). The main source of dissipation in the

benthic region is metabolism (effective average half

- life = 77.5 days) followed by hydrolysis (176 days). Most of the pesticide in the benthic region (61%) is sorbed to sediment rather than
in the pore water.

Table 1. Estimated Environmental Concentrations (ppb) for Dimethoate.

Peak (1

- in

- 10 yr) 8.57

4

- day Avg (1

- in

- 10 yr) 8.10

21

- day Avg (1

- in

- 10 yr) 6.41

60

- day Avg (1

- in

- 10 yr) 4.99

365

- day Avg (1

- in

- 10 yr) 1.32

Entire Simulation Mean 1.12

Table 2. Summary of Model Inputs for Dimethoate.

Scenario MNalfalfaOP
Cropped Area Fraction 1 Koc (ml/g) 14.7

Water Half

- Life (days) @ 25 °C 24.0

Benthic Half

- Life (days) @ 25 °C 27.8

### Page 121 of 144 

### Photolysis Half

- Life (days) @ 34

°Lat 353

Hydrolysis Half

- Life (days) 68

Soil Half

- Life (days) @ 25 °C 2.71

Foliar Half

- Life (days) 2.82

Molecular Wt 229.25 Vapor Pressure (torr) 1.85e

- 6 Solubility (mg/l) 39800

Table 3. Application Schedule for Dimethoate.

Date (Mon/Day) Type Amount (kg/ha) Eff. Drift
05/20 Foliar 0.560 0.95 0.125 06/19 Foliar 0.560 0.95 0.125 07/19 Foliar 0.560 0.95 0.125

Figure 1. Yearly Peak Concentrations

### Page 122 of 144 

### Sample output screen shot from SWCC Pond



## 5.1

### Page 123 of 144 

# Appendix E. T

- REX example output

Summary of Risk Quotient Calculations Based on Upper

- Bound Kenaga Estimated

Environmental Concentrations ( EECs ) for Applications of Dimethoate to Douglas fir (seed orchards) (only in OR and WA)

.

Table 1.1 . Upper Bound Kenaga, Acute Avian Dose

- Based Risk Quotients

Size

Class (grams ) Adjuste

d

LD50 EECs and RQs

Short Grass Tall Grass Broadleaf Plants Fruits/Pods/Seeds Arthropods Granivore

EEC RQ EEC RQ EEC RQ EE

C RQ EEC RQ EE

C RQ

20 4.69 1230.0

1 262.1

2 563.7

6 120.1

4 691.8

8 147.44 76.8

8 16.38 481.7

5 102.6

6 17.0

8 3.6

4

100 5.97 701.40 117.4

1 321.4

8 53.81 394.5

4 66.04 43.8

4 7.34 274.7

2 45.99 9.74 1.6

3

1000 8.44 314.03 37.21 143.9

3 17.06 176.6

4 20.93 19.6

3 2.33 122.9

9 14.58 4.36 0.5

2

Table 1.2 . Upper Bound Kenaga, Subacute Avian Dietary Based Risk Quotients

LC50 EECs and RQs

Short Grass Tall Grass Broadleaf

Plants Fruits/Pods/Seeds Arthropods

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

150 1080.00 7.20 495.0

0 3.30 607.5

0 4.05 67.50 0.45 423.00 2.82

Size class not used for dietary risk quotients

Table 1.3 . Upper Bound Kenaga, Chronic Avian Dietary Based Risk Quotients

NOA

EC (ppm ) EECs and RQs

Short Grass Tall Grass Broadleaf

Plants Fruits/Pods/S

eeds Arthropods

EEC RQ EE

C RQ EE

C RQ EEC RQ EEC RQ

4 1080.0

0 270.0

0 495.

00 123.

75 607.

50 151.

88 67.50 16.88 423.

00 105.7

5

Size class not used for dietary risk quotients

### Page 124 of 144 Table 1.4 . Upper Bound Kenaga, Acute Mammalian Dose

- Based Risk Quotients

Size

Class (gra ms) Adjus

ted

LD50 EECs and RQs

Short Grass Tall Grass Broadleaf

Plants Fruits/Pods/

Seeds Arthropods Granivore

EEC RQ EE

C RQ EE

C RQ EEC RQ EEC RQ EE

C RQ

15 786.82 1029.

70 1.31 471.

94 0.60 579.

20 0.74 64.36 0.08 403.2

981 0.512

565 14.3

01 0.01

82

35 636.62 711.6

6 1.12 326.

18 0.51 400.

31 0.63 44.48 0.07 278.7

329 0.437

83 9.88

41 0.01

55

1000 275.36 165.0

0 0.60 75.6

3 0.27 92.8

1 0.34 10.31 0.04 64.62

521 0.234

694 2.29

17 0.00

83

### Page 125 of 144 Table 1.5 . Upper Bound Kenaga, Acute Mammalian Dietary Based Risk Quotients

LC50 (ppm) EECs and RQs

Short Grass Tall Grass Broadleaf

Plants Fruits/Pods/Seeds Arthropods

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

N/A 1080.0

0 N/A 495.0

0 N/A 607.5

0 N/A 67.50 N/A 423.0 N/A Size class not used for dietary risk quotients

N/A = Not available

Table 1.6 . Upper Bound Kenaga, Chronic Mammalian Dietary Based Risk Quotients

NOAE

C (ppm) EECs and RQs

Short Grass Tall Grass Broadleaf

Plants Fruits/Pods/Seeds/Larg

e Insects Arthropods

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

2 1080.0

0 540.0

0 495.0

0 247.5

0 607.5

0 303.7

5 67.50 33.75 423.0

0 211.5

0 Size class not used for dietary risk quotients

Table 1.7 . Upper Bound Kenaga, Chronic Mammalian Dose

- Based Risk Quotients

Size Class

(grams) Adjusted

NOAEL EECs and RQs

Short Grass Tall Grass Broadleaf Plants Fruits/Pods/Seeds Arthropods

EEC RQ EEC RQ EEC RQ EEC RQ EEC RQ

15 0.22 1029.70 4685.06 471.94 2147.32 579.20 2635.35 64.36 292.82 403.30 1834.98

35 0.18 711.66 4001.95 326.18 1834.23 400.31 2251.10 44.48 250.12 278.73 1567.43

1000 0.08 165.00 2145.20 75.63 983.22 92.81 1206.68 10.31 134.08 64.63 840.20

### Page 126 of 144 

# Appendix F. Example STIR Output

Input

Application and Chemical Information

Enter Chemical Name Dimethoate

Enter Chemical Use AirBlast - Doug Fir Is the Application a Spray? (enter y or n) y If Spray What Type (enter ground or air) ground Enter Chemical Molecular Weight (g/mole) 229.25 Enter Chemical Vapor Pressure (mmHg) 1.85E-06 Enter Application Rate (lb a.i./acre) 4.5

Toxicity Properties

**Bird**

Enter Lowest Bird Oral LD 50 (mg/kg bw) 5.4
Enter Mineau Scaling Factor 1.15 Enter Tested Bird Weight (kg) 0.051

**Mammal**

Enter Lowest Rat Oral LD 50 (mg/kg bw) 358

Enter Lowest Rat Inhalation LC 50 (mg/L) 2
Duration of Rat Inhalation Study (hrs) 4 Enter Rat Weight (kg) 0.35



## Output

Results Avian (0.020 kg )

Maximum Vapor Concentration in Air at Saturation (mg/m 3 ) 2.28E-02 Maximum 1-hour Vapor Inhalation Dose (mg/kg) 2.87E-03
Adjusted Inhalation LD 50 2.03E-01

Ratio of Vapor Dose to Adjusted Inhalation LD 50 1.41E-02 Exposure not Likely Significant
Maximum Post-treatment Spray Inhalation Dose (mg/kg) 4.76E-01
Ratio of Droplet Inhalation Dose to Adjusted Inhalation LD 50 2.34E+00 Proceed to Refinements



### Results Mammalian (0.015 kg )

Maximum Vapor Concentration in Air at Saturation (mg/m 3 ) 2.28E-02 Maximum 1-hour Vapor Inhalation Dose (mg/kg) 3.61E-03
Adjusted Inhalation LD 50 1.19E+02

Ratio of Vapor Dose to Adjusted Inhalation LD 50 3.03E-05 Exposure not Likely Significant
Maximum Post-treatment Spray Inhalation Dose (mg/kg) 5.98E-01
Ratio of Droplet Inhalation Dose to Adjusted Inhalation LD 50 5.02E-03 Exposure not Likely Significant **NOTE**: When entering values, pres in order to update linked cells.

### Page 127 of 144 

# Appendix G

. Example SIP Output

Table 1. Inputs

Parameter Value

Chemical name Dimethoate
Solubility (in water at 25 o C; mg/L) 39800

Mammalian LD 50 (mg/kg-bw) 358
Mammalian test species laboratory rat Body weight (g) of "other" mammalian species

Mammalian NOAEL (mg/kg-bw) 0.005 Mammalian test species laboratory rat Body weight (g) of "other" mammalian species

Avian LD 50 (mg/kg-bw) 5.4
Avian test species other Body weight (g) of "other" avian species 51 Mineau scaling factor 1.15

Mallard NOAEC (mg/kg-diet) Bobwhite quail NOAEC (mg/kg-diet) 4 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

Enter body weight of 'other' avian species for LD50.

Table 2. Mammalian Results

Parameter Acute Chronic Upper bound exposure (mg/kg-bw) 6845.6000 6845.6000 Adjusted toxicity value (mg/kg-bw) 275.3595 0.0038 Ratio of exposure to toxicity 24.8606 1780018.4489

Conclusion* Exposure through drinking water alone is a potential

concern for mammals Exposure through drinking water alone is a potential

concern for mammals

Table 3. Avian Results

Parameter Acute Chronic Upper bound exposure (mg/kg-bw) 32238.0000 32238.0000 Adjusted toxicity value (mg/kg-bw) 4.6926 0.4252 Ratio of exposure to acute toxicity 6869.9782 75819.6361

Conclusion* Exposure through drinking water alone is a potential

concern for birds Exposure through drinking water alone is a potential

concern for birds

*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.

### Page 128 of 144 

# Appendix H . Terrplant example output

TerrPlant v. 1.2.2 Green values signify user inputs (Tables 1, 2 and 4). Input and output guidance is in popups indicated by red arrows.

Chemical Name

PC code

Use Application Method

Application Form Solubility in Water (ppm)

Input Parameter Symbol Value Units

Application Rate A 4.5 lb. a.i/A

Incorporation I 1 none
Runoff Fraction R 0.05 none

Drift Fraction D 0.05 none

Equation EEC

(A/I)*R 0.225 (A/I)*R*10 2.25

A*D 0.225 ((A/I)*R)+(A*D) 0.45 ((A/I)*R*10)+(A*D) 2.475

Plant type EC 25 NOAEC EC 25 NOAEC

Monocot 1.48 0.745 1.46 0.48

Dicot 0.84 0.23 1.51 0.5

Plant Type Listed Status Dry Semi-Aquatic Spray Drift

Monocot non-listed 0.30 1.67 0.15

Monocot listed 0.60 3.32 0.47

Dicot non-listed 0.54 2.95 0.27

Dicot listed 1.96 10.76 0.98 Total for semi-aquatic areas Table 1. Chemical Identity.

Dimethoate

Douglas fir (seed orchards) (only in OR and WA)

Table 2. Input parameters used to derive EECs. Aerial

Airblast

39800 128975

Table 3. EECs for Dimethoate . Units in lb. a.i/A.

Runoff to dry areas Runoff to semi-aquatic areas Spray drift Total for dry areas Description

*If RQ > 1.0, the LOC is exceeded, resulting in potential for risk to that plant group. Vegetative Vigor Seedling Emergence

Table 5. RQ values for plants in dry and semi-aquatic areas exposed to Dimethoate through runoff and/or spray drift.* Table 4. Plant survival and growth data used for RQ derivation. Units are in lb. a.i/A.

### Page 129 of 144 

# Appendix I

. Classifications of Environmental Fate Studies

Table A7.1. Classification of Environmental Fate Studies Conducted on Dimethoate

Guideline

No

. Data Requirement Study ID Study

Classification Classification Justifications or Comments (for Supplemental and Unacceptable Studies)

835.2120 Hydrolysis 00159761 Acceptable

---

835.2240 Photolysis in

Water 00159762 Acceptable

---

835.2410 Photodegradation

on Soil 43276401 Acceptable

---

835.2370 Photodegradation

in Air No data

submitted N/A N/A

835.4100 Aerobic Soil

Metabolism 42843201 ; 46719202 Acceptable ; Supplemental --- Concurrent recoveries were outside the recommended ranges of 70

- 120% of the applied for the Riverside and Middlefield soils in some instances. The soils used in this study were of foreign origin and comparison with domestic soils should be provided ( i.e.

, USDA soil orders and WRB classifications are needed). The soil textures according to USDA

classification could not be confirmed. The soils were maintained at 40% of MWHC, but the moisture content could not be rela ted in pF units.

835.4200 Anaerobic Soil

Metabolism 42884402 Acceptable

---

835.4300 Aerobic Aquatic

Metabolism 48945601 Supplemental Material balances were incomplete in the latter test intervals (starting from day 14 for the Calwich, U.K. test system). Levels of unextracted residues were very high in the latter test intervals (starting from day 14 for the Calwich test system). Given the high level of uncertainty related to the

unextracted residue s and recoveries of the Calwich system, its results w ere not used quantitatively in risk assessment until these and other deficiencies are explained.

835.4400 Anaerobic Aquatic

Metabolism 489 45501 Supplemental The material balances were incomplete in the latter test intervals, particularly in the pond water:clay loam sediment system . The water and sediment pH increased throughout the study duration, which may have promoted hydrolysis. A pola r product detected at ≥10% of the applied was not adequately identified. The position of the radiolabel may have

limited potential for identification of products of dimethoate.

835.1230 Leaching

Adsorption/ Desorption 00164959 ; 47477301,

49300701 Acceptable; Supplemental --- Material balances were incomplete

.

835.1410 Laboratory Volatility 43276402 Acceptable

---

835.6100 Terrestrial Field Dissipation 42884403 ; 43388001 ; 43388002 Acceptable; Acceptable; Acceptable ---

835.6100 Long

- term Soil Dissipation No data

submitted N/A N/A

835.6200 Aquatic Dissipation No data

submitted N/A N/A

835.6300 Forestry No data

submitted N/A N/A

835.6400 Combination and

Tank Mixes No data

submitted N/A N/A

860.1400 Accumulation in Irrigated Crops No data

submitted N/A N/A

850.1730 Accumulation in

Fish No data

submitted Waived Waived on 3/1/93 (DP Barcode D176363)

.

### Page 130 of 144 Guideline

No

. Data Requirement Study ID Study

Classification Classification Justifications or Comments (for Supplemental and Unacceptable Studies)

850.1950 Aquatic Non

target Organism No data

submitted N/A N/A

835.7100 Ground Water Monitoring No data

submitted N/A N/A

835.8100 Field Volatility No data

submitted N/A N/A

Non

guideline Percolation

Behavior of

dimethoate in lysimeter trial 48298315 Supplemental I t could not be determined if the test substance was applied to the soil at the highest recommended label rate. Data supporting the stability of

dimethoate in soil and water w as not reported. T he material balance and

the amounts of [ 14 C ]

- C0 2 and of volatile compounds emitted to the atmosphere from the soil were not measured directly ; they were estimated by subtracting the radioact ivity found from that which was applied to the lysimeters and therefore could not be verified. The unextracted residues were unacceptably high and there were no attempts to further extract the additional radioactivity.

Non

guideline Effects of

chlorinati on on the degradation of

dimethoate 48041103 Supplemental Control samples, containing no chlorine were not tested at the same time

than the treated samples. These samples would have allowed confirming the presence of undegraded dimethoate in treated samples with no chlorination, or the possible hydrolysis of the chemical under the testing

conditions. No mass balance could be established

.

850.6100 ECM/ILV in Soil 42884403 Acceptable ILV report was generated by BEAD’s contractor.

ECM/ILV in

Water 46276301 Unacceptable Portions of this study submission may be used in the future to support a complete submission to satisfy the ECM/ILV data requirement for

dimethoate.
N/A = Not applicable ; ECM=Environmental Chemistry Method; ILV=Independent Laboratory Validation



### Table A7. 2 . Classification of Environmental Fate Studies Conducted on O methoate

Guideline

No

. Data Requirement Study ID Study

Classification Classification Justifications or Comments (for Supplemental and Unacceptable Studies)

835.4300 Aerobic Aquatic

Metabolism 47477303,

49300701 Supplemental No GLP standards were cited and/or Quality Assurance statements were provided. The first sampling interval occurred too late to confirm the application rate. The water:sediment ratio was atypical of aerobic aquatic

studies. All transformation products d etected at ≥10% of the applied may

not have been identified. No attempt was made to characterize the significant levels (>50%) of unextracted sediment residues.

835.1230 Leaching

Adsorption/ Desorption 47477304

, 49300701 Supplemental The study was conducted using a single test concentration. Material balances were not reported. It was not reported whether the study was

conducted in the dark. A total of three test soils were used. A desorption phase was not conducted.

### Page 131 of 144 

# Appendix J

. Reviewed studies submitted in support of PRA

Table 6.1

. S pecies evaluated for assessing potential ecological effe cts of Dimethoate

.

Guideline Test Substance Tested Species Toxicity Endpoint Study MRID

and Acceptability

850.1010 Dimethoate Daphnid ( Daphnia Magna) EC 50 = 1.6 mg/L 48298306 Acceptable

850.1010 Dimethylthiophosphoric acid, Na

- salt Daphnid ( Daphnia Magna) EC 50 = 66.7 mg/L 48298307 Acceptable

850.1010 O

- desmethyl Dimethoate,

Na

- salt Daphnid ( Daphnia Magna) EC 50 >82.9.7 mg/L 48298304 Acceptable

850.1010 Omethoate Daphnid ( Daphnia Magna) EC 50 = 32.5 ug/L 48821405 Acceptable

850.1075 Omethoate Bluegill ( Lepomis macrochirus ) LC 50 = 7.7 mg/L 48821402 Acceptable

850.1075 Dimethoate Bluegill ( Lepomis macrochirus ) LC 50 = 31.5 mg/L 48821401 Acceptable

850.1075 Dimethoate Formulation Bluegill ( Lepomis macrochirus ) LC 50 = 44.5 mg/L 48298303 Acceptable

850.1075 Omethoate Rainbow Trout ( Oncorhynchus mykiss ) LC 50 = 5 mg/L 48821404 Acceptable

850.1075 Dimethoate Rainbow Trout ( Oncorhynchus mykiss ) LC 50 = 23 mg/L 48821403 Acceptable

850.1075 Dimethoate Formulation Rainbow Trout ( Oncorhynchus mykiss ) LC 50 =59.8 mg/L 48298302 Acceptable

850.1075 O Desmethyl Dimethoate

Potassium Salt Rainbow Trout ( Oncorhynchus mykiss ) LC 50 > 80.8 mg/L 48298305 Acceptable

850.1075 Dimethylthiophosphoric acid, Na

- salt Rainbow Trout ( Oncorhynchus mykiss ) LC 50 >961 mg/L 48298308 Supplemental

850.1075 Dimethyl phosphoric acid,

Na

- salt Rainbow Trout ( Oncorhynchus mykiss ) LC 50 >1000 mg/L 48298311 Acceptable

850.1400 Dimethoate Rainbow Trout ( Oncorhynchus mykiss ) NOAEC = 1.25 mg/L 49083401 Acceptable

850.1400 Dimethoate Sheepshead minnow ( Cyprinodon variegatus ) NOAEC = 1.2 mg/L 48772901 Supplemental

850.4550 Dimethoate Cyanobacteria ( Anabaena flos

- aquae) EC 50 = 20 mg/L 48572804 Acceptable

850.4550 Dimethoate Marine Diatom (Navicula pelliculosa ) EC 50 >98 mg/L 48572806 Acceptable

850.4550 Dimethoate Green Algae (Pseudokirchneriella subcapitata) EC 50 = 23 mg/L 48572803 Acceptable

850.4550 Dimethoate Marine Diatom (Skeletonema costatum) EC 50 >96 mg/L 48572803 Acceptable

850.2100 Dimethoate Mallard (Anas platyrhynchos) LD 50 = 44.1 mg/kg

bw 48964901

Invalid

850.2200 Omethoate Northern Bobwhite (Colinus Virginianus) LC 50 = 81.7 mg/kg

bw 47709501 Acceptable

850.2200 Omethoate Mallard (Anas platyrhynchos) LC 50 >1500 mg/kg

bw 47709502 Supplemental

850.2300 Dimethoate Northern Bobwhite (Colinus Virginianus) -- 48216201 Supplemental

### Page 132 of 144 850.2300 Omethoate Northern Bobwhite (Colinus Virginianus) -- 48216201 Supplemental

850.4400 Dimethoate Duckweed Lemna gibba EC 50 >92.6 mg/L 47709703 Supplemental

850.4225 Dimethoate Most sensitive species NA

-- 48572801 Supplemental

850.4225 Dimethoate 400 Sugar beet EC 25 = 0.84 la / A 48572802 Supplemental

850.4150 Dimethoate Most sensitive species NA

-- 4857802 Acceptable

850.4150 Dimethoate 400 Most sensitive species NA

-- 4857802 Acceptable

NG

850.2200 Dimethoate Bobwhite (Colinus Virginianus) 36

- week bobwhite 48680201 Supplemental

NG

850.1075 Dimethoate Rainbow Trout ( Oncorhynchus mykiss ) 21

- day exposure 48153501 Supplemental

### Page 133 of 144 

# Appendix K. Incident Summaries

Incident ID Use Site Date State County Certainty Legal Code Species Magnitude Effect Summary Description

TERRESTRIAL AVIAN INCIDENTS

B0000

- 219

- 02 I005754

- 003 Ornamental /woody 3/22/1972 CA Tulare Highly probable Registered

Use Cedar waxing 60

- 80 MOR 60 dead and 20 sick cedar waxing birds

were found in a residential area within the vicinity of a treated area. Birds in the area were observed to be feeding on pyracantha

berries.

Gizzard contents were found to contain 1.1 ppm dimethoate.

10 days la ter additional birds were found outside the areas spray but contained over ripe pyrancantha berries. Investigators

were unable to determine whether these birds died from the ingestion of treated berries or intoxication resulting from the ingestion of ferm ented berries.

B0000

- 219

- 03 Garden 5/1/1971 CA Contra

Contra Highly probable Registered

Use Cedar Waxing N/R MOR Other chemicals involved: Dieldrin: Unlikely (0.15 ppm) Diazinon Possible (0.75 ppm)

Number of Cedar Waxing birds found dead in residential yard which contained

over

- ripe pyracantha berries. Garden had

been treated with dieldrin and diazinon on April 10 and dimethoate on April 18.

Sample of gizzard contents and berries were analyzed an d found to have 5.1 ppm

dimethoate.

### Page 134 of 144 I000920

- 001 Seed alfalfa 6/10/1993 ID Canyon Highly probable Registered

Use Canadian

Geese 40 MOR Other chemicals involved: Carbofuran: (0.52

- 2.9 ppm)

Bird kill occurred after the application of

dimethoate and carbofuran to seed alfalfa.

Tissue from the craw stomach and liver

contained 2.4

- 4.0 ppm dimethoate and foliage samples contained 0.45

- 0.076 ppm

dimethoate.

I005524

- 004 Alfalfa 2/10/1986 CA Imperial Possible Registered

Use Canadian

Geese 25 MOR Other chemicals involved: Carbofuran: highly probable (2

- 9.9 ppm)

No other details were provided.

I005572

- 003 Seed alfalfa 5/22/1988 ID N/R Probable Accidental

Misuse Canadian

Geese 150 MOR Other chemicals involved:

Disulfuton: Probable

Carbofuran: Probable

Bird kill was found the day after the application of disulfuton, dimethoate and

carbofuran to seed alfalfa.

I005751

- 001 Alfalfa 5/1/1988 ID N/R Probable Accidental

Misuse Canadian

Geese Hundreds MOR Other chemicals involved:

Dilsulfoton: Probable Carbofuuran: Highly probable

Farmer applied a mixture of disulfoton,

dimethoate and carbofuran to a 50 acre

field of alfalfa. The use was a violation of a Migratory Bird Act.

I010916

- 001 Bait 8/9/2000 NY Onondag

a Highly probable Intentional

Misuse Rock Dove 1 MOR Dead rock dove was found and sent in for study; it was found to have consumed bird

seed and corn at the time of death.

Pesticide screen revealed a concentration of 5.31 ppm dimethoate.

It is suspected that dimethoate was purposefully used as bait to purposefully poison the bird.

### Page 135 of 144 TERRESTRIAL HONEYBEE INCIDENTS

I003826

- 009 Orchard 4/28/1995 NC Henderson

ville Probable Undetermined Honeybee N/R MOR Other chemicals involved: Methyl parathion: highly probable (3.1 ppm) Carbaryl: Unlikely Endosulfan: Possible (0.20 ppm) Chlorpyrifos (0.10 ppm)

Combination of dimethoate, methy parathion, carbaryl, endosulfan and captan. Dead bee tissue contained

concentrations of a number of

different chemicals.

I013587

- 012 Alfalfa 7/14/1999 WA Grant Possible Undetermined Honeybee 150 Hives MOR Other chemicals involved: Carbaryl: Possible Chlorothalonil: possible Methamidophos: Possible

Be kill reported following the aerial application of dimethoate, carbaryl, chlorthalonil and methamisophos on alfalfa. The incident indicated that the carbaryl applications began after sunrise when the bees were atticely foraging; this is a violation of the labeling instructions.

Tissue samples found dimethoate concentrations ranging from 0.0222 to 0.041 ppm.

### Page 136 of 144 I013883

- 018 Potato 7/15/1997 WA Grant Possible Registered Use Leafcutter

Bee N/R MOR Other chemicals involved;

Carbofuran: Possible Methamidophos: Possible

Bee kill reported following the application of dimethoate, methamidphose and carofuran onto a potato field. The materials drifted to a nearby field of alfalfa

where the cutter bees had been actively foraging.

Tissue samples sho wed dimethoate

at a concentration of 0.087 to 0.12

I013884

- 020 Bean 8/12/1998 WA Adams Possible Registered Use Honeybee 20 colonies MOR Bee kill was reported after a bean field with blooming weeds was sprayed with dimethoate. Bees had been observed foraging on the beans but laboratory analysis did not detect the presence of the pesticide. The incident did state

that there was an off site detection

of dimethoate but no other details

were included.

I013884

- 024 Bean 8/21/1998 WA Adams Possible Undetermined Honeybee 20 colonies MOR Other chemicals involved:

Naled: Possible

Bee kill occurred after aerial application of dimethoate and

naled.

Incident was reported as part of a spreadsheet form the Washington State Dept. of Agriculture and

included minimal detail.

### Page 137 of 1 44 I013884

- 028 Orchard 4/15/1998 WA Yakima Possible Registered Use Honeybee N/R MOR Other chemicals involved: Chlorpyrifos: possible

Bee kill was reported 4 to 8 days following the application of dimethoate and chlorpyrifos.

Dimethoate was found in tissue samples at a concentration of 0.26

ppm.

Incident was reported as part of a spreadsheet form the Washington State Dept. of Agriculture and

included minimal detail.

I013884

- 033

I014341

- 026 Bean 7/8/1998 WA Yakima Possible Registered Use Leafcutter

bee N/R MOR Bee kill was reported after aerial application of dimethoate to a field

of beans. Material drifted to a nearby blooming field of alfalfa where the bees has been actively foraging.

Tissue samples found dimethoate at a concentration of 0.5 ppm.

Incident was reported as part of a spreadsheet form the Was hington State Dept. of Agriculture and

included minimal detail.

I014341

- 006 Orchard 1/1/1996 WA Benton Possible Undetermined Honeybee 1,256 bees MOR Other chemicals involved: Chlorpyrifos: possible

Bee kill was reported after aerial application of dimethoate and chlorpyrifos to an orchard.

Incident was reported as part of a spreadsheet form the Washington State Dept. of Agriculture and

included minimal detail.

### Page 138 of 144 I014341

- 015 Bean 1/1/1998 WA Grant Possible Undetermined Honeybee 20 hives MOR Other chemicals involved:

Naled: Possible

Bee kill was reported after aerial application of dimethoate and

naled to a field of beans.

Incident was reported as part of a spreadsheet form the Washington State Dept. of Agriculture and

included minimal detail.

I014341

- 016 N/R 1/1/1998 WA Grant Possible Undetermined Honeybee 20 hives MOR Other chemicals involved: Bentazon: possible

Tissue samples of bees found 0.55 ppm concentration of dimethoate.

Incident was reported as part of a spreadsheet form the Washingt on State Dept. of Agriculture and

included minimal detail.

I020741

- 001 Corn 7/19/2006 CO Larimer Probable Undetermined Honeybee Half worker

bees in 22

hives MOR Other chemicals involved: Spiromesifen: unlikely

Dimethoate and spromesifen were sprayed aerially on a cornfield.

Bee hives that were the most damaged were within 200 yards of

the treatment site. Corn field had blooming weed within the field an

it is believes that bees made direct contact with the pesticide in their active foraging or their hives were exposed through spray drift of the pesticide off site.

### Page 139 of 144 I023107

- 019 Cotton 7/26/2011 CA Kings Probable Undetermined Honeybee Effects in 92

hives Complete

loss 12 hives MOR Other chemicals involved:

Lambda

- cyhalothrin: possible Methoxyfenozide: unlikely

Dimethoate and lambda cyhalothrin were applied aerially to

a field of cotton. There was an additional ground application of lambda cyhalothrin and methoxyfenozide to a pistachio

orchard.

Bee swabs and samples show dimethoate present at 0.007 and 0.0024 ppm.

I024335

- 001 Soybean 7/31/2012 MI St. Clair Probable Undetermined Honeybee 60% foraging

bees

7

- 9 Hives MOR Bees had been actively foraging at the time of the application of dimethoate in the vicinity of a soybean field. It was stated that the grower was unware the bees were actively foraging when the dimethoate was applied.

I026191

- 001 Onion August 2013 Chi na Shijzhuang Possible Undetermined Honeybee 106 boxes MOR Other chemicals involved: Dichlorvos: possible

No other details on the incident were provided.

### Page 140 of 144 TERRESTRIAL PLANTS

I013587

- 025 Lentils 7/17/1999 WA Spoanoke Probable Misuse Grass N/R/ Plant Damag

e Plant damage was reported due to spray drift of dimethaote following an aerial application in unfavorabl conditions. Three foliage samples tested positive for dimethoate.

I016940

- 010 Corn 3/3/2005 Imperial CA Highly probable Misuse Corn 30 acres Plant Damag

e Other chemicals involved: Cyfluthrin: highly probable

Cornfields showed symptoms after a crop duster experienced mechanical problems and discharged dimethoate and cyfluthrin onto the field. Grower disposed of 2,500 pounds of corn

which had been shown to have 199.2 ppm of dimethoate.

### Page 141 of 144 AQUATIC FISH INCIDENTS

B0000

- 219

- 12

I005754

- 017 Loading

Area 1972

- 1973 CA Riverside Probable Misue

- Accident Fish

— unknown species 13,000 MOR Other chemicals involved: Methyl parathion: possible (2.96 ppm) Parathion: possible (1.04 ppm) Diazinon: (0.27 ppm) Malathion: (1.46 ppm) Thiodan: (0.17 ppm)

Fish kill reported after heavy rain

resulted in substantial runoff of pesticides from a crop dusting loading area.

Water analysis showed presence o dimethoate, diazinon, methyl parathion, parathion, malathion,

and thiodan. Dimethoate was

found at a concentration of 5.7

ppm.
I000403

- 001 Soybeans 8/13/1988 IL Tazewell Probable Registered Use Bass

Bullhead Carp

Channel

catfish

Drum

Minnow

Shad

Sucker

Sunfish

White

bass 9,242 MOR Other chemicals involved: Chlorpyrifos: probable

No residue analysis was conducted on the water, soil, sediment or

individual fish.

### Page 142 of 144 I000804

- 014 Lake 6/24/1991 SD Haakon Probable Intentional

Misuse Fish

— unknown species N/R MOR Other chemicals involved: 2,4

- D: possible

Unknown number of fish found dead after the operator of a spraying service used a barrel containing dimethoate and a barrel containing 2,4

- D. The sprayer admitted that disposal of the pesticide containers was not in accordance with regulations.

I003826

- 002 N/R 6/12/1995 NC Johnston Possible Undetermined Fish

— unknown species N/R MOR Other chemicals involved:

Dissulfton:Possible 2,4

- D: Unlikely

Aldicarb: Possible

Dead fish noticed in a pond and reported 4 days later.

Samples of water, soil, sediment

and vegetation showed the presence of disulfoton, 2,4

- D,

aldicarb and dimethoate.

Dimethoate was found at a concentration of 0.2 ppm.

### Page 143 of 144 

# Appendix L . ECOTOX Selected Articles of Interest

Species Effect Endpoint Duration Concentration Unit Mea s ured or Unmeasured

concentrations Test ID Reference

Midge MOR LC50 96 h 1.29 ug/L M 2053647 Single Versus Combined Lethal Effects of Three Agricultural Insecticides on Larvae of

the Freshwater Insect Chironomus dilutus

Mosquito MOR LC50 48 h 31 ug/L U 1203438 Comparative Toxicity of Four Insecticides, Including Imidacloprid and Tebufenozide, to Four Aquatic Arthropods

Common Carp MOR LC50 96 h 1.61 mg/L U 2084953 Acute Toxicity and Behavioral Responses of Common Carp Cyprinus carpio (Linn.) to an Organophosphate (Dimethoate)

Zebra Danio MOR LC50 96 h 21.64 ug/L U 2084967 Embryo and Fingerling Toxicity of Dimethoate and Effect on Fecundity, Viability, Hatchability and Survival of Zebrafish, Danio rerio (Cyprinidae)

Rainbow Trout MPH NOAEL 5 d 0.735 mg/L U 2084764 Endocrine Disruption and Altered Biochemical Indices in Male Oncorhynchus mykiss in Response to Dimethoate

Indian Catfish MOR LC50 96 h 2.98 mg/L U 2084734 Acute Toxicity Bioassay of Dimethoate on Freshwater Airbreathing Catfish, Heteropneustes fossilis (Bloch)

Skipping Frog MOR LC50 96 h 36 mg/L U 1226902 Toxic Effects of Dimethoate and Methyl Parathion on Glycogen Reserves of Male and Female Rana cyanophlyctis

Common Hourglass Tree Frog MOR LC50 48 h 8.4 ppm U 2049627 Toxicity of Agrochemicals to Common Hourglass Tree Frog (Polypedates cruciger) in Acute and Chronic Exposure

Common Bay Mussel,Blue

Mussel ENZ NOAEL 14 d 15.75 ug/L U 2084926 The Use of Selected Biomarkers, Phagocytic and Cholinesterase Activity to

Detect the Effects of Dimethoate on Marine Mussel (Mytilus edulis)

Mussel MOR LC50 96 h 36.34 mg/L U 2084829 Acute Toxicity and Behavioural Responses

of a Freshwater Mussel Lamellidens marginalis (Lamarck) to Dimethoate Exposure

### Page 144 of 144 Blue

- Green Algae POP EC50 15 d 0.2 ppm U 2084808 Differential Response of Cyanobacteria to an Organo

- Phosphate Pesticide, Rogor (Dimethoate 30 EC)

Green Algae BCM NOAEL 2 h 1 uM/L U 1264603 Comparative Toxicity of Two Organophosphorus Insecticides on Membrane Integrity of Chlorella vulgaris. I. Effect on Membrane Permeability

Honey Bee DVP NOAEL ma 0.156 ug/g U 451681 Laboratory Studies of Honeybee Larval Growth and Development as Affected by Systemic Insecticides at Adult

- Sublethal

Levels

Honey Bee MOR NOAEL 6 d 0.8 ug/org U 2084991 Honey Bee Risk Assessment: New Approaches for In Vitro Larvae Rearing and Data Analyses

Honey Bee MOR NOEC 7 d 2.5 mg/kg U 468461 Toxicity of Dimethoate and Fenoxycarb to Honey Bee Brood (Apis Mellifera), Using a new In Vitro Standardized Feeding Method

Norway Rat MOR LD50 72 h 152 mg/kg U 2084565 Acute Oral Toxicity of Dimethoate in

Albino Rats Fed a Protein

- Deficient Diet

Grass Family POP NOAEL 2 yr 0.336 AI kg/ha U 569739 Effects of Insecticide Application on Weed

and Pasture Plant Communities

Alfalfa POP NOAEL 1 gs 0.21 AI kg/ha U 447455 Field Evaluation of Insecticides for Control

of the Alfalfa Blotch Leafminer and Its

Effect on Alfalfa Yield in Prince Edward

Island

Pea POP NOAEL hv 0.167 AI lb/acre U 2080801 Control of Insects in Spring Peas, 1996 Shepherd's

Purse REP NOAEL 21 d 400 ai g/L U 413393 Insecticides and Arable Weeds: Effects on Germination and Seedling Growth