# Sodium Tetrathiocarbonate

Summary Document:

Registration Review

December 2007Docket Number: EPA-HQ-OPP-2007-1084 www.regulations.gov



### TABLE OF CONTENTS

Page #

I. Preliminary Work Plan (PWP) 4

II. Fact Sheet 9

III. Ecological Risk Assessme nt Problem Formulation 13

IV. Human Health Effects Scoping Document 36

V. Glossary of Terms and Abbreviations 46

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I. PRELIMINARY WORK PLAN

Introduction: The Food Quality Protection Act of 1996 ma ndated a new program: registration review. All pesticides distribut ed or sold in the United States generally must be registered by EPA, based on scientific data showing that they will not cause unreasonable risks to human health, workers, or the environment wh en used as directed on product labeling. The new registration review progr am is intended to make sure that, as the ability to assess risk evolves and as policies and practices cha nge, all registered pesticides continue to meet the statutory standard of no unreasonabl e adverse effects. Changes in science, public policy, and pesticide use practices will occur over time. Through the new registration review program, the Agency periodically reevaluate s pesticides to make sure that as change occurs, products in the market place can be used safely. Information on this program is provided at: http://www. epa.gov/oppsrrd1/registration_review/.

The Agency has begun to implement the new registration review program and will review each registered pesticide every 15 year s to determine whether it continues to meet the FIFRA standard for registration. The public phase of registration review begins when the initial docket is opened for each case. The docket is the Agency’s opportunity to state clearly what it knows about the pesticide and wh at additional risk analyses and data or

information it believes are needed to make a registration review decision. After reviewing and responding to comments and data received in the docke t during this initial comment period, the Agency will develop and commit to a Final Work Plan and schedule for the registration review of sodium tetrathiocarbonate.

Sodium tetrathiocarbonate (Na 2 Cs 4 ) is a soil fumigant which acts as a fungicide, insecticide, and nematicide. Sodium tetr athiocarbonate degrades to carbon disulfide (CS 2 ), hydrogen sulfide (H 2 S), sodium hydrazide, and elemen tal sulfur upon contact with

water. CS 2 (PC code 016401) is the major biologically active degradate. Tolerances are

established for CS 2 from the application of s odium tetrathiocarbonate. CS 2 from the application of sodium tetrathiocarbonate is the residue of concern for risk assessment.

Sodium tetrathiocarbonate is registered for pr e-plant and post-plant soil applications on almonds, grapes, lemons, oranges, peaches, prunes, and plums. It provides control of soil nematodes (e.g., ring, root-knot), diseases (e.g., phytophthora, armillaria) and insects (e.g., grape phylloxera). It ca nnot be used in greenhouses an d other enclosed areas. There are no registered residential uses. S odium tetrathiocarbonate is currently labeled for use only in Arizona, Califor nia, Oregon, and Washington.

Anticipated Risk Assessment and Data Needs: The Agency will conduct a comprehensive ec ological risk assessment, including an endangered species assessment, for the register ed uses of sodium tetrathiocarbonate. Human health occupational and residential bystander risk assessments will also be

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needed for the registered uses of sodium tetrathiocarbonate. The Agency also anticipates conducting a drinking water risk assessment for groundwater.

Ecological Risk:

• The environmental fate database for sodium tetrathiocarbonate is largely complete. Fate data requirements have been satisfied with data from sodium, calcium, or potassium tetrat hiocarbonate. Physical a nd chemical properties are available from open literature sources.

• There are gaps and uncertainties in the ecological effects database for sodium tetrathiocarbonate. The following data on freshwater fish and invertebrates, terrestrial plants, and honeybees will be required to complete the ecological

assessment and will be issued in a data call-in (DCI) during the registration review process:

o Early life stage freshwater-fish (850.1400)

o Freshwater invertebrate li fecycle toxicity (850.1300)

o Tier I vegetative vigor (850.4150)

o Tier I seedling emergence (850.4100)

o Acute oral or contact honeybees (850.3020)

• The planned ecological risk assessment w ill allow the Agency to determine if

sodium tetrathiocarbonate’s use has "no e ffect" on federally list ed threatened or endangered species (listed species) or thei r designated critical habitat. If the screening level assessment in dicates that sodium tetrathiocarbonate "may affect" a listed species or its designated critical ha bitat, the assessment will be refined. The refined assessment will allow the Agency to determine whether use of sodium tetrathiocarbonate is “likely to adversely affect” the species or critical habitat or "not likely to advers ely affect" the species or critical habitat. When an assessment concludes that a pes ticide's use "may affect" a list ed species or its designated critical habitat, the Agency will consult with the U.S. Fish and Wildlife Service

and/or National Marine Fisheries Service (Ser vices), as appropriate.

Human Health Risk:

• Human health risk assessments for agricultural workers and handlers and residential bystanders potentially exposed to CS 2 as a result of ag ricultural uses of

sodium tetrathiocarbonate will need to be updated to reflect current policy and practice for soil fumigants.

• The Agency anticipates needing the fo llowing study to complete the bystander

assessment for CS 2 as a result of agricultural uses of sodium tetrathiocarbonate:

o Special study to determine the fl ux rate of the compound off-site

• The Agency will also review and consider the available literature on toxicity and exposure, air monitoring databases de veloped by the California Air Resources Board (CARB), and other information available on CS 2 prior to issuing the Final

Work Plan.

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• Dietary assessments were not conducte d in the past because in food CS 2 residues from application of sodium tetrathioc arbonate were considered “de minimus” meaning that residues were not detected at levels above natural background.

• Although dietary risk from food is no t a concern, tolerances for CS 2 from application of sodium tetrathiocarbonate will need to be re-evaluated since the existing tolerances were established ba sed on exaggerated ap plication rates.

• The Agency anticipates conducting a drin king water assessment for groundwater.

• If a drinking water assessment i ndicates potential exposures to CS 2 as a result of agricultural uses of sodium tetrathio carbonate, an aggregate risk assessment combining potential residential bystande r exposures with dietary and drinking water exposures will be needed.

Timeline: EPA has created the following estimated timeline for the completion of the sodium

tetrathiocarbonate re gistration review.

Sodium Tetrathiocarbonate – Projected Registration Review Timeline

Activities Estimated

Year/Month Phase 1: Opening the docket
Open Public Comment Period 2007 – Dec.

Close Public Comment Period 2008 – Mar.
Phase 2: Case Development

Develop Final Work Plan (FWP) 2008 – Apr.-Jun.

Issue DCI 2009 – Jan.-Mar

Data Submission 2011 – Jan.-Mar.
Preliminary Risk Assessment and Public Comment 2012 – Jul.-Sep.

Close Public Comment Period 2012 – Oct.-Dec.

Phase 3: Registration Review Decision
Proposed Registration Review Decision 2013 – Jan.-Mar.

Public Comment Period 2013 – Apr.-Jun. Final Registration Re view Decision and Begin Post-Decision Follow-up 2013 – Jul.-Sep.

Total (years) 6

Guidance for Commenters: The public is invited to comme nt on EPA’s preliminary regi stration review work plan and rationale. The Agency will carefully consider all comments as well as any additional

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information or data provided prior to i ssuing a Final Work Plan for the sodium

tetrathiocarbonate case.

• Through the registration review process, th e Agency intends to solicit information on trade irritants and, to the extent feasible , take steps toward facilitating irritant

resolution. Growers and othe r stakeholders are asked to comment on any trade irritant issues resulting from lack of Maximum Residue Limits (MRLs) or disparities between U.S. tolerances and MRLs in key export markets, providing as much specificity as possible regarding the nature of the concern. See page 43 of Section IV, Human Health Effects Sc oping Document, for a listing of U.S.

tolerances.

• Sodium tetrathiocarbonate is not identif ied as a cause of impairment for any waterbodies listed as impaired under sect ion 303(d) of the Clean Water Act, based on information provided at http://oaspub.epa.gov/tmdl/waters_list.impairments?p_impid=3 . The Agency invites submission of water quality data for this pesticide. To the extent possible, data should conform to the quality sta ndards in Appendix A of the “OPP Standard Operating Procedure: Inclusion of Impa ired Water Body and Other Water Quality Data in OPP’s Registration Review Risk Assessment and Management Process” (see: http://www.epa.gov/oppfead1/cb/ ppdc/2006/november06/session1-sop.pdf ), to ensure they can be used quantitativ ely or qualitatively in pesticide risk

assessments.

• EPA seeks to achieve environmental justi ce, the fair treatment and meaningful involvement of all people, regardless of r ace, color, national origin, or income, in the development, implementation, and enforcement of environmental laws, regulations, and policies. To help address potential e nvironmental justice issues, the Agency seeks information on any groups or segments of the population who, as a result of their location, cultural practi ces, or other factors, may have atypical, unusually high exposure to sodium tetrathi ocarbonate, compared to the general population. Please comment if you are aw are of any such sub-populations.

Stakeholders are also specifically asked to pr ovide information and da ta that will assist the Agency in refining the ecological risk assessment, including any species-specific

effects determinations.

The Agency is interested in the following information regarding the use of sodium

tetrathiocarbonate:

1. confirmation on the following label information a. sites of application

b. formulations c. application methods and equipment d. maximum application rates

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e. frequency of application, application interv als, and maximum number of applications per season f. geographic limitations on use

2. use or potential use distri bution (e.g., acreage and geogr aphical distribution of relevant crops)

3. use history

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

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

6. sub-county crop location data

7. usage/use information for non-agricultura l uses (e.g., forestr y, residential) 8. directly acquired county-level us age data (not derived from state level data) a. maximum reported use rate (lbs ai/acre) from usage data – county b. percent crop treated – county

c. median and 90 th percentile number of a pplications – county d. total pounds per year – county e. the year the pesticide was last used in the county/sub-county area f. the years in which the pesticide wa s applied in the county/sub-county area

9. typical interval (days)

10. state or local use restrictions

11. ecological incidents (non-target plant dama ge and avian, fish, reptilian, amphibian and mammalian mortalities) not already reported to the Agency

12. monitoring data

Next Steps: After the comment period closes, the Agency will prepare a Final Work Plan for this pesticide.

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II. FACT SHEET

Background Information :

• Sodium tetrathiocarbonate [Carbono(dithiopero xo)dithioic acid, disodium salt] registration review case number: 7009.

• Sodium tetrathiocarbonate: PC Code: 128904; CAS#: 7345-69-9.

• The major biologically active de gradate, carbon disulfide (CS 2 ), is also considered

in the sodium tetrathiocarbona te registration review case.

• Carbon disulfide (CS 2 ): PC Code: 016401; CAS# 75-15-0.

• Technical registrant: Arysta Li fesSciences North America Corp.

• Not subject to reregistration; thus, no Re registration Eligibility Decision (RED) is

available.

• Tolerances were reassessed under FQPA to include a new use May 16, 1997 (62 FR 26946) (FRL – 5716-8).

• Currently, there are two ac tive Section 3 registrations : 66330-63 (ETK-1101) and 66330-69 (ENZONE).

• Labeled for use only in Arizona, California, Oregon, and Washington.

• Currently, there are no active Section 24c registrations.

• Special Review and Reregistration Divi sion Chemical Review Manager (CRM): Katherine St. Clair ( stclair.katherine@epa.gov ).

• Registration Division Product Contacts: Tawanda Spears ( spears.tawanda@epa.gov ) and/or Cynthia Giles-Parker ( gilesparker.cynthia@epa.gov ).

Use & Usage Information:

For additional details on label rates and allowed uses, please refer to the BEAD Appendix A document in the Sodium tetrathiocarbonate docket.

• Sodium tetrathiocarbonate is fumigant pesticide which acts as a fungicide, nematicide, and insecticide.

• It is registered for pre-plant and post-pl ant soil applications on almonds, grapes, lemons, oranges, peaches, prunes, and plums.

• It is used to control soil nemat odes (e.g., ring, root-knot), diseases (e.g., phytophthora, armillaria) and inse cts (e.g., grape phylloxera).

• The pesticidal mode of action of sodium tetrathiocarbonate and carbon disulfide is

unknown.

• Sodium tetrathiocarbonate is formulated as an aqueous solution that breaks down

in the soil to CS 2 gas, the major biologi cally active degradate.

• Sodium tetrathiocarbonate may be applie d through ground inject ion equipment or may be metered into irrigation water used for low-volume irrigation (chemigation) or flood and furrow irrigation.

• Sodium tetrathiocarbonate cannot be us ed in greenhouses and other enclosed

areas.

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• There are no residential uses.

• Approximately 700,000 pounds of sodium tetr athiocarbonate are used annually (lbs a.i./yr.).

• Nearly 90% (600,000 lbs a.i./yr.) of sodium tetrathiocarbonate usage is on grapes; almonds is the crop with the next highes t usage at approximately 6% (40,000 lbs a.i./yr.).

Recent Actions:

• A request to expand use dire ctions, add restri ctions, and add Florida to EPA reg# 66330-63 was denied in February 2003 due to data and label deficiencies.

Ecological Risk Assessment Status:

Please refer to Section III of this document, Ecological Risk Assessment Problem Formulation, for a detailed discussion of the an ticipated ecological risk assessment needs. The following is a summary of these anticipated needs:

• The most recent ecological risk assessment for sodium tetrathiocarbonate was conducted in 1995 for proposed new uses on almonds, peaches, and prunes. The 1995 ecological risk assessment concl uded that labeled use of sodium tetrathiocarbonate was not expected to pose acute or chronic risk to non-target avian, mammalian, fish, aquatic invertebrate, or plant species. However, some of the risks were assessed qualitativel y (i.e., aquatic exposures were not quantitatively estimated), and the potential risks to some receptors (terrestrial plants and terrestrial invert ebrates) were not assessed.

• An additional uncertainty is the potential for exposure to aquatic organisms through release of treated tail water. Labels state that “tailwater must not be allowed to leave the treated field,” but no details, such as trapping methods or holding times, are included. The possibi lity remains, then, that different interpretations of this requirement by us ers could lead to surface water exposure.

• The environmental fate database for sodium tetrathiocarbonate is largely complete. Fate data requirements have been satisfied with data from sodium, calcium, or potassium tetrat hiocarbonate. Physical a nd chemical properties are available from open literature sources.

• There are gaps and uncertainties in the ecological effects database for sodium

tetrathiocarbonate. Data on freshwater fish and invertebrates, terrestrial plants, and honeybees will be required to complete the ecological assessment and will be issued in a data call-in (DCI) durin g the registration review process.

• The Agency plans to conduct a comprehensive ecological risk assessment, including an endangered species assessment, for the registered uses of sodium

tetrathiocarbonate.

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Human Health Risk Assessment Status : Please refer to Section IV of this documen t, Human Health Effects Scoping Document, for a detailed discussion of the anticipated risk assessment needs for human health. The following is a summary of these anticipated needs:

Dietary (Food and Water):

• Dietary assessments were not conducte d in the past because in food CS 2 residues from application of sodium tetrathioc arbonate were considered “de minimus” meaning that residues were not detected at levels above natural background.

• Although dietary risk from food is no t a concern, tolerances for CS 2 from application of sodium tetrathiocarbonate will need to be re-evaluated since the existing tolerances were established ba sed on exaggerated ap plication rates.

• The Agency anticipates conducting a drin king water assessment for groundwater.

Residential:

• There are no residential us es for sodium tetrathiocarbonate. However, there is potential for residentia l bystander exposure to CS 2 as a result of agricultural uses

of sodium tetrathiocarbonate.

• Human health risk assessments for reside ntial bystanders potentially exposed to

CS 2 as a result of agricultural uses of sodi um tetrathiocarbonate will need to be updated to reflect current policy and practice for soil fumigants.

Occupational :

• Human health risk assessments for agri cultural workers and handlers potentially exposed to CS 2 as a result of agricultural uses of sodium tetrathiocarbonate will need to be updated to reflect current policy and practice for soil fumigants.

Aggregate:

• If a drinking water assessment i ndicates potential exposures to CS 2 as a result of agricultural uses of sodium tetrathio carbonate, an aggregate risk assessment combining potential residential bystande r exposures with dietary and drinking water exposures will be needed.

Overall:

• The Agency anticipates needing a “flux” study in order to complete a risk assessment of occupational and residential bystander exposure to CS 2 as a result of agricultural uses of sodium tetrathio carbonate and for use in setting appropriate buffer zones to mitigate off-site exposure.

• The Agency will review and consider the available literature on toxicity and exposure, air monitoring databases de veloped by the California Air Resources Board (CARB), and other information available on CS 2 prior to issuing the Final

Work Plan.

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Incident Reports :

• Three data bases were searched for incidents reports on sodium

tetrathiocarbonate: Poison Control Cent er (PCC) Data, NIOSH SENSOR, and the Incidents Data System. No incidents for sodium tetrathiocarbonate were reported in the PCC during the period 1993 through 2005 or the Incident Data System from 1999 to the present. NIOSH SENSOR reported 2 cases of sodium tetrathiocarbonate poisonings. Both incide nts occurred in California with one in

1999 and one in 2001. A more detailed su mmary is provided in the scoping document for registration revi ew located in the docket.

Tolerances:

U.S. tolerances are listed under 40 CFR 180.46 7. Tolerances are established for the nematicide, insecticide, and fungicide CS 2 from the application of sodium

tetrathiocarbonate. No MRLs for sodium te trathiocarbonate have been established or proposed by Codex for any agricultural commodities. There are no Canadian or Mexican

tolerances for carbon disulfide.

Data Call-In Status:

A DCI has not been issued for sodium tetrathiocarbonate.

Labels : A list of registration numbers is included belo w and the labels can then be obtained from the Pesticide Product Label System (PPLS) website: http://oaspub.epa.gov/pestlabl/ppls.home

. These labels were transferred from Entek Corp. to Arysta LifeScience North America Corp. and the labels are avai lable under their previous EPA registration numbers, 68891-

9 for 66330-63 and 68891-2 for 66330-69.

Registration

Number Product Name Company % Active Ingredient

66330-63 ETK-1101 Arysta LifeScience North America Corporation 53

66330-69 ENZONE Arysta LifeScience North America Corporation 31.8

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III. ECOLOGICAL RISK ASSESS MENT PROBLEM FORMULATION

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An additional uncertainty is the potential for exposure to aquatic organisms through

release of treated tailwater. Labels state that “tailwater must not be allowed to leave the treated field,” but no details, such as trap ping methods or holding times, are included. The possibility remains, then, that different interpretations of this requirement by users could lead to surface water exposure.

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1. PRELIMINARY PROBLEM FORMULATION

The purpose of problem formulation is to pr ovide the foundation for the ecological risk

assessment to be conducted for sodium tetrathi ocarbonate. It sets the objectives for the risk assessment, evaluates the nature of th e problem, and provides a plan for analyzing the data and characterizing the risk (US EPA, 1998).

1.1 Nature of Regulatory Action

The registration for sodium te trathiocarbonate is being re viewed under the Registration Review program mandated by the Federal Insect icide, Fungicide, and Rodenticide Act in

order to determine whether it continues to meet the statutory sta ndard for registration.

The current analysis is based on the original new chemical assessment, the most recent new use and drinking water assessments, and an early fate review which includes the most complete discussion of available field studies:

• Review of lysimeter and groundwater m onitoring studies (7/27/1988, P. Holden)

• Section 3 New Chemical Risk Assessment of proposed uses on grapes, citrus, orchards, and potatoes (Eco: 9/20/88, J. Ackerman; Fate: 5/16/89, E. Regelman)

• Section 3 New Use Risk Assessment of proposed uses on almonds, peaches, and prunes (Eco: 5/4/1995, DP Barcode D 213559; Fate: 7/9/1996, DP Barcodes D220367, D223296)

• Drinking Water Assessment for proposed new use on citrus in Florida (3/19/02, A. Clem)

Additional ecological toxici ty studies (MRIDs 46423901, -02, -03, -04) have been submitted and will be formally reviewed during the risk assessment process.

1.2 Stressor Source and Distribution

1.2.1 Nature of the Chemical Stressor

Sodium tetrathiocarbonate (Na 2 CS 4 ) is a fumigant which acts as a fungicide and

nematicide. Sodium tetrathiocarbonate ha s two soluble concentrate formulations,

EnZone ® (3.4 lb a.i./gal, 31.8% a.i ., Reg No. 68891-2) and ETK-1101 ® (6.8 lb a.i./gal, 53% a.i., Reg. No. 68891-9). Upon mixing with water, Na 2 CS 4 converts readily to carbon disulfide (CS 2 ), the compound that is actually res ponsible for pesticidal activity.

The pesticidal mode of action of carbon di sulfide is unknown. Chemical identification information and physical and chemical prope rties of these compounds are presented in

Table 1.

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Table 1. Nature of the Chemical Stressor

Common name Sodium tetrathiocarbonate ( parent chemical ) Carbon disulfide ( major degradate )

Chemical name Carbono(dithioperoxo)dithioic acid, disodium salt Carbon disulfide

Pesticide type fungicide, nematicide fungicide, nematicide

CAS number 7345-69-9 75-15-0

PC Code 128904 016401

Empirical formula Na 2 CS 4 CS 2

Chemical Structure S = C = S

Molecular Mass (g/mol) 186.2 76.1

Vapor pressure (mm Hg) 4E-10 a,b 359 a

Henry’s Law Constant (atm-m 3 /mol) -- 0.014 a

Solubility in water (g/L) 1E6 a,b 1180 a

Log K

ow -4.68 a,b 1.94 a

a From the SRC Physical Propertie s database (http://www.syrres.com/esc/physdemo.htm, accessed 9/07).

b Estimated rather than experimental value.

1.2.2 Overview of Pesticide Usage

1.2.2.1 Labeled Uses and Application Rates

Sodium tetrathiocarbonate is a fumigant used on grapes, some citrus crops (oranges, grapefruit, lemons) and some orchard crops (a lmonds, peaches, prunes, and plums). It is currently only labeled for use in Ariz ona, California, Oregon, and Washington.

In crops established for one year or more and in preplant sites, s odium tetrathiocarbonate

is used to control nematodes in all labeled crops and to control phytophthera root rot in all crops except grapes. It is also used to control oak r oot fungus in all crops, although for grapes and citrus crops, it can only be us ed in preplant sites. In grapes, sodium

tetrathiocarbonate is also used to control phylloxera. Sodium tetr athiocarbonate cannot be used in greenhouses a nd other enclosed areas.

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Sodium tetrathiocarbonate is applied thr ough ground injection or through chemigation, where the active ingredient is metered into water used for low-volume irrigation or flood and furrow irrigation. Low-volume irrigation systems allowed by the label include drip, drip-tape, strip tubing, foggers, jets, misters, and mini-sprinkl ers, with limits specified for pressure and flow rates of the equipment. Gr ound injection is to a depth of six to nine inches and is only used for established crops. Applications to esta blished orchard crops, citrus crops, and grapes can generally be made through the entire growing season. Preplant applications can be made one to four weeks before planting.

The label directs application by specific pr ocedures designed for rapid penetration and uniform coverage: 1) prior to application, the soil is to be brought to near, but less than, field moisture capacity; 2) chemigation is continuously metered for up to 12 hours to attain the necessary application rate; 3) fi nally, the soil is “seale d” by slowly flushing lines and emitters for up to 4 hours with suffici ent clean water to attain field moisture capacity. Chemigation water concentrations are required to be maintained at minimum levels of 250 to 2400 ppm, depending on the use. The labels direct that “tailwater must

not be allowed to leave the treated fiel d” but no holding times or other specific

instructions are included.

The maximum annual application rate for sodium tetrathiocarbonate is 340 lb a.i./A (139

lb CS 2 /A). For ground injection, it is applied in one to three applications with maximum single application rates of up to 170 lb a.i./A (69 lb CS 2 /A) and minimum application intervals of 30 days. For most low-volume or flood and furrow applications, sodium tetrathiocarbonate is applied in one to six applications w ith maximum single application rates of 102 to 204 lbs a.i./A (42 to 84 lb CS 2 /A), depending on the use. For preplant use in citrus and orchard crops, though, it can be applied as a single application at 340 lbs a.i./A. For flood and furrow irrigation, the minimum application interval is 30 days, while for low-volume irrigation, the application interval can be up to 21 days with no minimum specified.

1.2.2.2 Use Characterization

The Screening Level Usage Analysis (SLUA) report prepared by the Biological and Economics Analysis Division (5/29/07) indicates a national use of sodium tetrathiocarbonate of approximately 674,000 lbs a.i./yr. Nearly 90% of this use (600,000 lbs) is on grapes, with almonds being the next highest use at 6% ( 40,000 lbs). Other uses of sodium tetrathiocarbonate include peach es, prunes and plums, lemons, oranges, nectarines, pecans, and cherries. These estimates are based on data from USDA-NASS, private market research from 2000 to 2006, the 2000 National Pesticide Use Database, and California Department of Pe sticide Regulation (CDPR) data.

Annual data specific to California are availa ble from the Pesticide Use Reports compiled by CDPR. In 2005, approximately 330,000 lbs of sodium tetrathiocarbonate were applied to 8,000 acres in California. The pr imary use that year was on grapes (table, raisin, and wine), which accounted for 227,000 lbs. Also in 2005, about 90,000 lbs of

sodium tetrathiocarbonate were used on almonds; this is a dramatic increase in usage on

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this crop since less than 5,000 lbs were us ed annually on almonds between 2000 and

2004. Total sodium tetrathiocarbonate use in California has been dropping since 2000, when approximately 600,000 lbs were used (Source: http://calpip.cdpr.ca.gov/c fdocs/calpip/prod/main.cfm , accessed 9/07).

1.2.3 Environmental Fate and Transport Summary

The environmental fate database for sodium tetrathiocarbonate (Na 2 CS 4 ) is largely complete. Fate studies show that Na 2 CS 4 degrades rapidly in water (half-lives on the

order of several hours to one day) through hydrolysis and photolysis. Carbon disulfide (CS 2 ) is the active agent released through hydrolysis in water. CS 2 has a high vapor pressure and a high Henry’s Law consta nt, physical properties favorable for

volatilization. CS 2 diffuses rapidly thr ough soil air, initially moving downward through the soil profile, followed by diffusion upwards and volatilization to the atmosphere. In aerobic soil environments, CS 2 is oxidized to sulfates th rough biological degradation (half-lives ranging from 3-27 days). Field studies show that contamination of CS 2 in ground water may occur under normal uses of sodium tetrathiocarbonate. The observed contamination was short-lived, but these studie s did not represent worst case conditions. Air monitoring shows half-lives of hours to several days for dissipation of CS 2 in air from ground level to five feet about the surface.

1.2.3.1 Environmental Fate Assessment

Some of the available fate studies test ed the calcium or potassium salts of

tetrathiocarbonate rather than the sodium salt. Data from sodium, calcium, and potassium tetrathiocarbonate are considered to be equivalent for the purposes of this discussion. Aqueous solutions of the salts are essentially tota lly ionized and the character of the solution is dominated by the common anion, CS 4 2- , so the nature of the cation has little direct effect on the properties of the product (11/20/86, E. Regelman).

When Na 2 CS 4 is mixed with water, it hydrolyzes rapidly to the volatile degradate CS 2 at rates dependant on concentration and pH. Below pH 7, hydrolysis is essentially immediate, with rates limited only by the rate of mass transfer of CS 2 out of solution. At a higher pH, hydrolysis is slower, with half-lives from 3 hours to 1 day (MRID 40375114). Aquatic photolysis of Na 2 CS 4 can also contribute to the formation of CS 2 , with thiosulfate (S 2 O 3 - ) as another major degradate. Th e photolysis half-life at pH 9 was 3.8 hours; at lower pHs, hydrolysis is too rapid for measurement of photolysis rates (MRIDs 43817201, 40437401).

Other products of these reactions include sodium hydroxide (NaOH), sulfur (S), and hydrogen sulfide (H 2 S). The environmental chemistry of these sulfur species is complex and highly dependent on local conditions. In aerobic conditions, sulfate (SO 4 2- ) and carbon dioxide (CO 2 ) tend to be the ultimate products and in anaerobic conditions, degradates can remain as generated or be redu ced to lower oxidation states. All of these species can be present naturally and are also generated from common agricultural

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fertilizers. CS 2 is the only substance produced in disproportionate environmental concentrations that also may be of t oxicological concern (3/19/02, A. Clem).

The major degradate CS 2 , the active pesticide agent, is a gas with a high vapor pressure (359 mm Hg) and a high Henry’ s Law constant (0.014 atm-m 3 /mol), so rapid volatilization is likely 1 . CS 2 is subject to aerobic soil metabolism with half-lives of 3 to 25 days, leading to sulfate and carbon dioxide as end pr oducts (MRID 00152990).

Aerobic soil metabolism studies were conducted in closed systems and so do not include dissipation by volatilization. CS 2 is not metabolized in anaerobic soil environments (MRID 40375115). Because of the rapid volatilization of CS 2 , its adsorption to soil cannot be measured and is not expected to affect its environmental fate (MRID 00152991). No laboratory studies of th e air or soil photolysis of CS 2 are available, although based on its known chemistry, carbon disulfide is expected to undergo photochemical reactions to yield carbonyl sulfide (COS), sulfur dioxide (SO 2 ) and carbon monoxide (CO) (5/16/89, E. Regelman).

1.2.3.2 Environmental Transport Assessment

The labeled application methods are designed to distribute Na 2 CS 4 below the soil surface, either through ground injection to a depth of 6 to 9 inches or by application in irrigation water to soils near field capacity, followed by “sealing” with additiona l irrigation water. The irrigation methods us ed for application of Na 2 CS 4 are not expected to result in spray drift. Ground injection and chemigation thr ough drip, drip-tape or st rip tubing systems or through flood and furrow irrigation do not have an opportunity for drift. Other lowvolume irrigation systems including foggers, jets, misters, and mini-sprinklers are permitted but labels include equipment specifications for pressure and flow rates designed to prevent drift. Drift is therefor e not considered here as a likely route for aquatic or terrestrial exposure.

The labeled application methods also ha ve relatively low runoff potential. Na 2 CS 4 labels specify that following application, fields shoul d not be irrigated to the point of runoff (Reg Nos. 68891-2 and 68891-9), although runoff c ould still be possible in a situation where rainfall occurs right after applicati on. The pathway leading to the greatest potential concentrations of carbon disulfid e in surface water would be release of tailwater from flood and furrow application methods. Labels require that treated tailwater be trapped and not allowed to leave the field, but no specifications for implementation of this requirement, such as holding times or trapping methods, are included. Different interpretations of this requirement by users coul d therefore lead to surface water exposure.

The high vapor pressure and Henry’s Law constant of CS 2 suggest that it will volatilize rapidly from surface water, but available aqua tic studies show contradictory results and rates cannot be quantified based on the availa ble information. Measurements taken in concurrence with hydrolysis studies found th at, at concentrations from 65 to 1300 ppm

1 Lyman, W.J., W.F. Reehl, and D.H. Rosenblatt, 1990. Handbook of Chemical Property Estimation Methods: Environmental Behavior of Organic Compounds. ACS, Washington D.C.

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CS 2 , mass transfer of CS 2 out of water took place with a mean half-life of 90 minutes (MRID 40375114). A bluegill sunfish acute toxi city study, however, showed rates of dissipation that were substantially lower (MRID 40375113). This static 96-hour test, conducted in five gallon tanks with nominal concentrations from 4.1 to 41 ppm as CS 2 , showed that after 2 hours, 80% to 95% of th e initial concentration remained. After 96 hours, tests at lower concentrations ( ≤ 7.4 ppm CS 2 ) showed complete dissipation, but at higher doses (13 to 41 ppm), up to 46% of the initial concentration remained.

Concentrations in these studies are on the sa me scale as those in irrigation water at the time of application but they are much highe r than the concentrations likely to reach surface water through runoff. At lower concen trations, it is probable that more rapid

volatilization will occur.

Field dissipation studie s suggest that the CS 2 formed by breakdown of CS 4 2- initially moves downward through the soil prof ile, followed by diffusion upwards and

volatilization to the atmos phere (7/9/1996, DP Barcode s D220367, D223296). Initial downward diffusion is rapid, with one study detecting CS 2 at 20 ft below the surface after

8 hours. All studies found maximum soil air concentrati ons, up to 37,500 ppmv, at one foot below the surface on the first day afte r application. Half-lives measured for dissipation of CS 2 in soil air were one to six days . The relative contributions of

metabolism and diffusion to CS 2 dissipation have not been quantified and may vary depending on environmental conditions.

Under normal uses of sodi um tetrathiocarbonate, CS 2 may reach groundwater. Prospective groundwater (PGW) studies in Florida found CS 2 concentrations of up to 215 ppb with observed dissipation half-lives on th e order of several days to one week (7/27/1988, P. Holden). The one PGW conduc ted in California did not detect carbon disulfide in groundwater after sodium tetrathiocarbonate ap plication, although terrestrial field dissipation studies in California found carbon disulfide reaching the water table in soil air. Volatilization, rather than movement off-site, was determined to be the primary mechanism for dissipation. Maximum potential concentrations have not been predicted

because these studies indicate that CS 2 occurrence in groundwater is highly dependent on recharge conditions, and none of these studies had significan t recharge during the times

when CS 2 levels in soil air were at a maximum.

Volatilization is the primary pathway for transport of CS 2 . A ground level air monitoring study using several application methods at half of the current labeled application rate found maximum air concentrations ranging from 2 ppm (furrow) to 24 ppm (minisprinkler) (MRID 42569101). At one hour after a pplication, these le vels had dropped to 1.1 to 5.7 ppm. Higher application rates may result in higher concentrations, but the observed dissipation suggests that any e xposure will not be long-lived. A second air monitoring study measuring CS 2 levels at one foot and five feet above the ground surface found mean dissipation half-lives of 1.8 days (MRID 42304401). Maximum concentrations at one foot off the ground were 4.50 ppmv on the field and 0.252 ppmv

100 ft off site. The amounts of CS 2 and its degradates that may be released to the atmosphere as a result of the pesticidal use of sodium tetrathiocarbonate are not expected

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to be high enough to have any impact on globa l sulfur cycles (5/4 /89, S. Termes; 7/7/89, G. Hume). 1.3 Receptors

1.3.1 Aquatic and Terrestrial Effects

For sodium tetrathiocarbonate and carbon di sulfide, the major degradate and active pesticide agent, ecological measures of eff ect are based on a suite of registrant-submitted toxicity studies as well as other lines of evidence, in cluding studies from the open literature. A scan of the on-line ECOTOX database ( http://www.epa.gov/ecotox ) shows

that there are several studies available for carbon disulfide, which will be considered during the risk assessment process. Below is a brief summary of currently available ecotoxicity information for sodium tetrat hiocarbonate and car bon disulfide. Where toxicity data gaps exist, the associated un certainties and the “value added” for new data are briefly discussed (see S ection 1.6.2 for more details).

Aquatic Effects

Several of the available freshwater toxici ty studies were conducted with calcium tetrathiocarbonate (CaCS 4 ) as the test substance, rather than sodium tetrathiocarbonate (Na 2 CS 4 ). Due to the rapid hydrolysis of the parent compound, though, test organisms were actually exposed to carbon disulfide (CS 2 ), and it is CS 2 concentrations which were analytically verified. The na ture of the cation, then, is not expected to affect the properties of the product. Two bluegill sunfish acute toxicity studies confirmed that the aquatic toxicity of sodium tetrathiocarbonate and calcium tetrathiocarbonate are equivalent in aquatic toxicity, and th e data can be bridged (Acc. # 072331, MRID 40375113). Available data for the most sensitive species indicate that CS 2 is highly toxic to freshwater fish based on acute toxicity information for the rainbow trout (96-hr LC 50 = 0.87 mg CS 2 /L or 6.7 mg CaCS 4 /L; Acc. # 072331). An acute toxicity test with the freshwater invertebrate, Daphnia magna , also indicates that CS 2 is highly toxic (48-hr

EC 50 = 0.87 mg CS 2 /L or 6.6 mg CaCS 4 /L; Acc. # 072331).

There are no chronic toxicity data available to assess the potential effects of CS 2 on freshwater animal growth and/or reproduction. A fish early life stag e toxicity test (§72- 4(a)) with rainbow trout, the most acutely sensitive species of those tested, and a freshwater invertebrate lifecycle toxicity test (§72-4(b)) with Daphnia magna would reduce the uncertainty in the risk assessment. These data gaps have been identified as important uncertainties in risk assessme nts for other fumigant pesticides.

Acute toxicity data for estuarine and ma rine organisms are re quired to support the registration of an end use product intended fo r direct application to the estuarine or marine environment or if the product is expect ed to enter this environment in significant concentrations because of its expected use or mobility pattern. Use on citrus represents a potential for estuarine exposure. However, since Enzone ® labeling prohibits use “in areas adjacent to or draining to marine or estuarine waters,” estuarine/marine toxicity testing is not required at this time.

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No aquatic plant toxicity information was available for previous assessments, but an additional 72-hour study with Selenastrum capricornutum with the ENZONE formulation as the test substance has recently be en submitted (MRID 46423901). A preliminary review of these data suggests that biomass is the most sensitive endpoint with a NOAEC

and EC 50 of 9.98 and 17 mg ENZONE/L, respec tively. Based on the time-weightedaverages of measured concentrations, this is equivalent to a NOAEC and EC 50 of 80.1 and 150 μg CS 2 /L. 2 The open literature ecotoxicity database indicates that additional carbon disulfide toxicity data exist for non-vascular aquatic plants, and this information will be considered during the risk assessment process.

Terrestrial Effects

Given the nature of sodium tetrathiocar bonate and its expected behavior in the environment, there is a potential risk to terrestrial animals via drinking contaminated water at the application site. A mallard duc k drinking water toxicity study revealed no mortality among ducklings that drank wa ter contaminated with 2400 ppm sodium

tetrathiocarbonate 3 , the maximum concentration of e xpected to be the environment (MRID 422308501). The study also shows that the birds found the Enzone ® treated water to be less palatable. These findings ar e consistent with a drinking water toxicity study with rats; no mortality occurred in male or female rats following exposure to drinking water with 2000 ppm sodium te trathiocarbonate (MRID 43185201). This study

also shows that the rats found the Enzone ® treated water to be less palatable.

Another potential exposure route fo r terrestrial animals is via inhalation of the degradate, carbon disulfide (CS 2 ). A bobwhite quail inhalation toxi city study revealed no mortality, clinical signs of toxicity, or effects on food consump tion or body-weight following 4 hours of inhalation exposure to 1060 ppm CS 2 (MRID 42531001). For mammals, based on the 1995 ecological risk assessment for new uses on almonds, peaches, and prunes, the

rat acute inhalation LC 50 is 1513 ppm CS 2 (males) and 1014 ppm CS 2 (females) (guideline grade) and 736 ppm CS 2 (minimum grade) for both male and female rats. Potential reproductive and/or developmental t oxicity effects in te rrestrial animals via

inhalation of CS 2 will be explored, and relevant study reviews from the Health Effects Division (HED) will be considered during the risk assessment process.

Given the method of application of sodium tetrathiocarbonate and its predicted behavior in the environment, dietary exposures are unlik ely for terrestrial animals. Nevertheless, acute oral and dietary toxicity data are available for birds and mammals. A bobwhite quail acute oral toxicity test (with calcium tetrathiocar bonate) suggests that sodium tetrathiocarbonate (a.i.) is moderately toxic to birds on an acute oral basis (LD 50 = 1180 mg product/kg or 363 mg a.i./kg; Acc. # 260638). Based on information from the HED,

the rat acute oral LD 50 is > 587 mg a.i./kg, which classifi es sodium tetrathiocarbonate as no more than slightly toxic to mammals on an acute basis. (However, it is unclear if this endpoint has been adjusted for the purity of the test substance; th is will be explored

2 Conclusions may change pending formal review of the study.

3 Drinking water toxicity is considered in terms of nominal concentrations of parent Na 2 CS 4 , rather than

measured concentrations of CS 2 . This differs from aquatic toxicity studies in which CS 2 was the species analytically verified. Due to rapid hydrolysis, actual exposure is likely to a mix of Na 2 CS 4 and CS 2

.

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during the risk assessment process). An acute dietary toxicity test is available for the bobwhite quail and the mallard duck; both test s suggest that sodium tetrathiocarbonate (a.i.) is no more than slightly toxic to birds on an acute dietary basis (LC 50 > 5620 ppm product or >1731 ppm a.i.; Acc. # 260638).

Terrestrial invertebrate toxicity informati on has recently been submitted for earthworms and two beneficial insects, the pred atory mite and the parasitic wasp. 4 A 14-day earthworm ( Eisenia foetida ) acute toxicity test with th e formulation ENZONE suggests

that the NOAEC and LC 50 are 607 and 1300 mg a.i./kg dw soil, respectively (MRID 46423902). A 7-day acute toxicity testwith the predatory mite ( Typhlodromus pyri Scheuten) revealed almost complete mortal ity (92%) at the lowe st level tested, 3.125 L ENZONE/ha (MRID 46423903). A 48-hour acute toxi city test with th e parasitic wasp ( Aphidius rhopalosiphi ) suggests the NOAEC and LC 50 are <0.1 and 0.41 L ENZONE/ha, respectively (MRID 46423904). There are no acute oral or contact toxicity data available for honey bees (§141-1). These da ta would be useful for characterizing the potential risk of carbon disulfide to non-target beneficial insects.

There are no terrestrial plant to xicity data available with which to assess the potential risk of sodium tetrathiocarbonate. Due to the appl ication methods and fate properties of this pesticide, exposure to terrestrial plants th rough drift and runoff is unlikely. However, there is a possibility of vapor phase exposure to terrestrial plants, and adverse ecological incidents in which non-target terrestrial plants have been impacted by off-gassing have been reported for other fumigants. In addi tion, the label suggests that phytotoxic effects are possible (e.g., ENZONE Reg. No. 68891-2 says that the “cr op must be established in the field for at least one year prior to treatm ent or injury may occur”). Tier I seedling emergence and vegetative vigor studies (§122-1) using the maximum application rate of formulated product would reduce the amount of un certainty in this risk assessment. Tier II phytotoxicity tests would be re quired if a 25% or greater de trimental effect is found in one or more plant species in the Tier I tests.

1.3.2 Ecosystems Potentially at Risk

The ecosystems at risk are often extensive in sc ope, and as a result, it may not be possible to identify specific ecosystems during the deve lopment of a baseline risk assessment. However, in general terms, terrestrial ecosy stems potentially at ri sk could include the treated field and areas immediately adjacent to the treated field that may be impacted by drift, runoff, or volatilization of the applied pesticide. This could include the field itself as well as other cultivated fields, fencerow s and hedgerows, meadows, fallow fields or grasslands, woodlands, riparian habitats and other uncultivated areas. For Tier 1 assessment purposes, risk will be assessed to te rrestrial animals that are assumed to feed on and otherwise occupy the treated area. Expos ure to animals off the treated site is also possible, but exposure and risk estimates are not likely to be higher than on the treated

site.

4 Conclusions may change pending formal review of these studies.

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Aquatic ecosystems potentially at risk include water bodies adjacent to, or down stream from, the treated field and might include impounded bodies such as ponds, lakes and reservoirs, or flowing waterways such as str eams or rivers. For uses in coastal areas, aquatic habitat also includes marine ecosy stems, including estuaries. For Tier 1 assessment purposes, risk will be assessed to aquatic animals assumed to occur in small, static ponds receiving runoff and drift from treated areas. These ponds are used as surrogates for a number of small vulnerable wa ter bodies that occur near the headwaters of watersheds including swamps, bogs, prairie potholes, vernal pools, playa lakes, and

first-order streams.

1.4 Assessment Endpoints

A summary of the assessment endpoints and m easures of ecological effect selected to characterize potential ecological risks associated with exposure to sodium tetrathiocarbonate is provided in Table 2.

Table 2. Summary of Ecological Risk Assessment Endpoints for Sodium Tetrathiocarbonate and Carbon Disulfide

Assessment Endpoint Effects Measurement Endpoint

1. Survival, reproduction and growth of birds(Birds are surrogates for reptiles and terrestrialphase amphibians) Acute oral LD 50 (bobwhite quail) Acute dietary LC 50 (bobwhite quail, mallard duck)

Acute inhalation LC 50 (bobwhite quail) Acute drinking water exposure NOAEC (mallard duck)

* No chronic bird toxicity data available

2. Survival, reproduction and growth of

mammals Acute oral LD 50 (rat)

Acute inhalation LC 50 (rat) Acute drinking water exposure NOAEC (rat)

* No chronic rat toxicity data available

3. Survival, reproduction, and growth of

freshwater fish and invertebrates

(Fish are surrogates for aquatic-phase amphibians) Acute fish LC 50 (rainbow trout, bluegill sunfish)

Acute invertebrate EC 50 ( Daphnia magna ) * No chronic fish or invertebrate toxicity data available

4. Survival, reproduction, and growth of

saltwater fish and invertebrates * No acute or chronic toxicity data available.

5. Survival of beneficial insect s Parasitic wasp NOAEC and LC50 * No honey bee toxicity data available

6. Perpetuation of individuals and populations of

non-target terrestrial plant species (crops and non-crop plant species) * No seedling emergence or vegetative vigor data available

7. Maintenance and growth of individuals and populations of aquatic plants from standing crop Selenastrum capricornutum NOAEC and EC50

LC 50 = Lethal concentration to 50% of the test population.

LD 50 = Lethal dose to 50% of the test population.

NOAEC = No observed adverse effect level.

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1.5 Conceptual Model

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

A conceptual model provides a written desc ription and visual re presentation of the predicted relationships between the applied pe sticide, potential routes of exposure, and the predicted effects for the assessment endpoint. A conceptual model consists of two major components: risk hypotheses and a conceptual diagram (US EPA, 1998).

For sodium tetrathiocarbonate , the conceptual model has be en developed in terms of carbon disulfide. In water, sodium tetrat hiocarbonate is rapidly converted to carbon disulfide, which is likely to be the stressor in any aquatic exposure route. All aquatic toxicity has been measured in terms of carbon disulfide. Carbon disu lfide is volatile and off-gasses from treated fields and so will also be the stressor in any exposure through air.

1.5.1 Risk Hypotheses

For carbon disulfide, the following ecological risk hypothesis is being employed for this

baseline risk assessment:

Carbon disulfide, when produced by degradation of sodium tetrathiocarbonate

used in accordance with th e label, results in potentia l adverse effects upon the survival, growth, and reproduction of non-target terrestrial and aquatic organisms.

1.5.2 Conceptual Diagram

The conceptual diagram depicts the potent ial ecological risk associated with carbon disulfide by identifying possible exposure ro utes and receptors and providing a visual representation of their relationships.

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*Dotted lines indicate that although this exposure rout e was considered, it was not thought to contribute significantly to the fate and transport of carbon disulfide. St r es so r

Rece p tors

Attribute Changes Source/ Transport

Path w a y s Runoff Leaching (Infiltration/ Percolation) Volatilization/ Off-gassing

from soil

Source/ Exposure

Media

Exposure

Route

Terrestrial Vertebrates: Birds, Mammals, Reptiles, Terrestrial Phase Amphibians Aquatic Invertebrates,

Vertebrates Aquatic

Plants Terrestrial

Upland

Plants Wetland/ Riparian

Plants

Individual Animals

Reduced survival or reproduction Individual Plants Reduced survival, growth, or reproduction Individual

Vertebrates and

Invertebrates

Reduced survival or reproduction Plant Population

Reduced population

growth Ground Water Irrigation

Water Upland Foliage/Soil Riparian/

Wetland Foliage/Soil Receiving Water Body/

Sediment Air

Gill / Integument Uptake Ingestion Uptake/ Adsorption Inhalation Direct Contact/ Root Uptake Direct Contact/ Root Uptake CARBON DISULFIDE, formed through rapid

hydrolysis of sodium tetrathiocarbonate

Sodium Tetrathiocarbonate, applied through chemigation or ground injection

Figure 1. Conceptual model of the enviro nmental transport and effects of carbon

disulfide.

Carbon disulfide is released from sodium tetrathio carbonate applied through ground injection or in irrigation water. Spray drif t does not occur with th ese application methods and so is not considered in this conceptual model. The major exposure routes of carbon disulfide for terrestrial animals are likely vi a ingestion of irrigati on (drinking) water on the treated field or via inhalation resulting from off-gassing from the soil. Volatile carbon disulfide released by off- gassing may also impact nearby terrestrial plants. Due to its physical properties, off-ga ssing carbon disulfide is not exp ected to settle on adjacent soils, water bodies, or food items so these e xposure routes are not considered. Carbon disulfide can move off-site through runoff to adjacent upland or ri parian/wetland areas, where it may affect plants through direct contact or root uptake. Carbon disulfide in runoff also may reach adjacent water bodies wher e it could affect aquatic plants through uptake or adsorption and aquatic animals vi a uptake through the respiratory surface (gills) or the integument. Leaching to groundwater may occur but carbon disulfide is expected

to be too transient to reach surface water through this route.

1.6 Analysis Plan

In Registration Review, pesticide ecological risk assessments will follow the Agency’s Guidelines for Ecological Risk Assessment, will be in compliance with the paper titled “Overview of the Ecological Risk Assessm ent Process in the Office of Pesticide

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Programs, U.S. Environmental Protection Agency” (“Overview Document”; Janu 2004), and will be done in accordance with S ection 7 of the Endangered Species Act. ary

1.6.1 Conclusions from Previous Risk Assessments

he original new chemical registration for sodium tetrathiocarbonate was completed in

he most recent ecological risk assessment for sodium tetrathiocarbonate conducted by

otential

he only available drinking water asse ssment found estimated drinking water f 120 ppb

.2 Preliminary Identification of Data Gaps and Analysis Plan

1.6.2.1 Environmental Fate

The fate database for sodium tetrathiocarbon ate is largely complete. All fate data

s are

sed by

S 2

• Due to the complexity of environmental sulfur chemistry, the relative

/HS - /H 2-

.

Studies of CS 2 photolysis behavior in soil and air have not been submitted, so

ir T 1988 (Eco: 9/20/88, J. Ackerman; Fate: 5/16/89, E. Regelman). Since then, additional

data for sodium tetrathiocarbonate and its ma jor degradate, carbon disulfide, have been received and considered during the risk a ssessment process for several new uses.

T the EFED is the 1995 assessment for the proposed new uses on almonds, peaches, and prunes (Eco: 5/4/1995, DP Barcode D213559; Fate: 8/21/1995, DP Barcodes D213560, D199125, D196916). The application scheme (max imum rates, use areas, general use instructions) considered in that assessment is the same as that on the current labels. The 1995 ecological risk assessment concluded that labeled use of sodium tetrathiocarbonate was not expected to pose acute or chronic risk to non-target av ian, mammalian, fish, aquatic invertebrate or plant species. However, some of the risks were assessed qualitatively ( i.e., aquatic exposures were not quantita tively estimated), and the p risks to some receptors (terrestrial plants, te rrestrial invertebrates) were not assessed.

T concentrations (EDWCs) in groundwater of 1 to 100 ppb and in surface water o (acute), 1 ppb (chronic, n on-cancer) and 0.35 ppb (chronic, cancer), based on modeling using PRZM/VADOFT and PRZM/EXAMS (3/19/02, A. Clem). These were estimated based on use in Florida at application rates that are half of maximum labeled rates.

1.6

requirements are satisfied or partially satisfi ed and physical and ch emical propertie available from open literature sources. Past assessments have identified some uncertainties about the fate and transport of carbon disulfide that are not addres required studies; additional in formation would help to furthe r characterize the fate of C but would not be expected to change risk conclusions:

concentrations of individual degradation products of CS 2 have not been determined, particularly for “H 2 S,” which really repr esents a mix of H 2 S

• rates and degradation products are uncerta in. Studies of photodegradation in a may be useful in understanding the fate of CS 2 in the atmosphere, important

because air is the ultimate sink for CS 2

.

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The relative contributions of degradati on and diffusion to dissipation of CS 2 from

1.6.2.2 Aquatic Exposure

previously completed screening level risk assessments for sodium tetrathiocarbonate,

w:

• All available ecological aquatic t oxicity data are reported as Na 2 CS 4 rather than

o

In the most recent (1995) ecological risk a ssessment, all levels of concern (LOCs)

For other routes of aquatic exposure, it is likely that subs tantial dilution and

and

ased on available data, the most sens itive aquatic animal endpoint is the

ould

e

tial

Previous assessments have concl uded that applica tion of sodium

lfide that

and • soil have not been determined.

In there has been some uncertainty in risk conclusions for aquatic organisms and for drinking water. These uncertainties and pot ential paths forward are described belo

CS 2 , which is likely to be the actual stressor. CS 2 is formed rapidly in water through hydrolysis of Na 2 CS 4 , though, and test solutions were aged at least tw hours. It is likely that these studies are effectively testing CS 2 exposure, and in

fact it was CS 2 that was analytically verified. No additional data are therefore required.

• for aquatic organisms were exceeded base d on the assumption of direct exposure to treated irrigation water, the maximum possible exposure. This assumption is appropriately conservative to estimate the risk if treated tailw ater were to reach

surface water bodies. Labels direct that “t ailwater must not be allowed to leave the treated field,” but no details such as trapping methods or holding times are included, so there is still some possibility for exposure through this route.

volatilization will occur before irrigation water reaches aquatic environments so this assumption may be ove rprotective. For this case, past assessments have qualitatively concluded that use of sodium tetrathio carbonate is unlikely to pose significant risk to aquatic organisms, but there has been no quantitative

assessment of risk.

B Daphnia magna EC 50 of 0.86 mg CS 2 /L. An aquatic EEC ≥ 43 μg CS 2 /L w be required to exceed the endangered speci es LOC. Based on the aquatic plant NOAEC of 80.1 μg CS 2 /L, an aquatic EEC ≥ 80.1 μg CS 2 /L would yield a risk quotient that would exceed the acute endangered species LOC for plants. Surfac water exposure is expected to be low, but at these LOCs, the possibility of risk cannot be precluded at this time. For the current risk assessment, aquatic exposures will be quantitatively estimate d using models to determine poten risk to aquatic organisms. No additional data are required to complete this modeling.

• tetrathiocarbonate may result in groundw ater levels of carbon disu exceed background levels, based on prosp ective groundwater (PGW) studies

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modeling. These sources do not represent worst-case scenarios because of the recharge conditions of the PGW studies and the application rate used in modeli However, both sources are based on envir onmental conditions in Florida, which has higher vulnerability to leaching th an would be expected in Arizona, California, Oregon, and Washington, the areas where use of sodium tetrathiocarbonate is currently supported. ng.

For this assessment, we w ill characterize the potential for groundwater exposure

d

er

ese

ng water

1.6.2.3 Ecological Effects

able 3 presents an evaluation of the uncertainty resulting from each ecotoxicity data

s.

his from current uses based on the Florida PGW studies and modeling, as well as several PGW and terrestrial field dissip ation studies conducted in California an Arizona. Additional PGW studies or monitoring data could reduce the uncertainty in this characterization by investigating potential groundwat exposure in worst-case recharge conditions in the areas labeled for use. Th studies would be rated as being of low va lue. In the absen ce of additional data, any conclusions of potential exposure fo r the current uses may lead to a recommendation of label language requiring a 100 ft setback from drinki wells, as has been recommended in past assessments.

T gap. There is inherent uncertainty associated with not receiving data to fulfill data gap However, the submission of some studies to address specific data gaps is unlikely to affect conclusions in the risk assessment, wher eas some data gaps are more critical. T determination is made on a case-by-case basis.

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Table 3. Summary of ecotoxicity data gaps for sodium tetrathiocarbonate

Assessment endpoint with data

gap Value of

Additional

Data* Rationale

Early life-stage freshwater fish toxicity study (72-4a) High Persistence of carbon di sulfide in surface water bodies may be unlikely; however, given the high annual application rate of sodium tetrathiocarbonate and the potential for multiple applications per year, chronic risk to freshwater fish cannot be precluded at this time. This data gap has been identified as an important uncertainty in risk assessments for other fumigants.

The value of this chronic study would be in quantifying and potentially refining the risks to fish (surrogate for aquatic-phase amphibians). Defining an action area for endangered species and exploring risk mitigation strategies cannot be evaluated without these data.

Freshwater invertebrate lifecycle toxicity study (72-4b) High See above. Chronic risk of to freshwater invertebrates cannot be precluded at this time.

The value of this chronic study would be in quantifying and potentially refining the risks to aquatic invertebrates. Defining an action area for endangered species and exploring risk mitigation cannot be

evaluated without these data.

Acute toxicity to estuarine/marine fish and invertebrates (72-3) Low Enzone ® labeling prohibits use “in areas adjacent to or draining to marine or estuarine waters.”

Survivorship, reproduction, and growth (chronic toxicity) of

estuarine/marine fish and invertebrates (72-4) Low Enzone ® labeling prohibits use “in areas adjacent to or draining to marine or estuarine waters.”

Perpetuation of non-target terrestrial plants, crops and non-crop species (122-1, vegetative vigor and seedling emergence)* High Risk to terrestrial plants has not been considered in previous assessments, and no terrestrial plant toxicity data are currently available for sodium tetrathiocarbonate. Potential exposure routes for terrestrial plants include r unoff and via off-gassing and volatilization. Adverse ecological incidents have been reported for other fumigants in which non-target terrestrial plants have been impacted by off-gassing. At one foot above ground level, the mean dissipation

half-life for CS 2 is 1.8 days, long enough for potential

exposure.

The value of these seedling emergence and vegetative vigor studies would be in quantifying and potentially refining risks to non-target terrestrial plants. Defining an action area for endangered species and exploring risk mitigation strategies cannot be evaluated without

these data.

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Table 3. Summary of ecotoxicity data gaps for sodium tetrathiocarbonate

Maintenance and growth of aquatic plants from standing crop or biomass (122-2, aquatic plant growth) High Risk to vascular aquatic plants (e.g., duckweed) has not been considered in previous assessments, and no vascular aquatic plant toxicity data are currently

available for sodium tetrathiocarbonate.

The value of a vascular aquatic plant toxicity study would be in quantifying and potentially refining risks to non-target terrestrial plan ts. Defining an action area for endangered species and exploring risk mitigation strategies cannot be evaluated without these data.

Acute oral or contact toxicity to honeybees (141-1) High Non-target terrestrial inve rtebrates have the potential to be exposed to sodium tetrathiocarbonate by direct contact and via off-gassing. There are no honey bee toxicity data available for sodium tetrathiocarbonate.

The value of these honey bee studies would be in quantifying and potentially refining risks to non-target terrestrial invertebrates. Defining an action area for endangered species and exploring risk mitigation strategies cannot be evaluated without these data.

Reproduction and growth of birds (71-4) Moderate Given the method of application of sodium tetrathiocarbonate and its predicted behavior in the environment, dietary exposu res are unlikely. Thus, a dietary exposure chronic avian reproduction study

would be of limited use in this risk assessment. Since inhalation is a more likely exposure route for carbon disulfide, a non-guideline chronic avian toxicity test (with inhalation exposure) would address this uncertainty.
* Tier II phytotoxicity tests would be required if a 25% or greater detrimental effect is found in one or more plant species in the Tier I tests.

1.6.3 Measures of Effect and Exposure

1.6.3.1 Exposure

Exposure estimates will be determined for carbo n disulfide, the rapidly formed degradate that is the actual active ingr edient, rather than for pare nt sodium tetrathiocarbonate.

For ecological aquatic exposures, previ ous assessments have based EECs on the

minimum concentration of sodium tetrathioc arbonate in irrigati on water required by the label, a very conservative a pproach. For drinking water exposure in surface water, EDWCs have been estimated for applicati on rates lower than the current labeled maximum. Additionally, thes e estimates have used out of date models which don’t account for irrigation. New modeling will theref ore be required to quantitatively estimate aquatic exposures to assess ecologi cal and human health risk.

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Tier I aquatic exposure models are not suffi cient to estimate exposure from fumigants because they do not account for volatilization. New estimates of surface water exposure in aquatic environments and in drinking water will be determined using the linked Tier II aquatic exposure models, PRZM (v. 3.12.2; May 12, 2005) and EXAMS (v. 2.98.04; April 25, 2005), run with the PE5 (v. 5.0; Nov. 15, 2006). Modeling will assume the maximum application rate, a single app lication of 340 lb a.i./A (139 lb CS 2 /A).

Potential groundwater exposure will be charac terized based on previous model results and based on available prospective groundwater studies and terrestri al field dissipation

studies.

Drift is not a potential route of exposure from these appli cation methods, so the highest exposure to terrestrial species would be from drinking treat ed irrigation water or from exposure to off-gassing carbon disulfide, either through inhalation or direct contact. Ecological exposure in drinking water is based on the irrigation concentrationsrecommended by the labels and additional estimates are not needed. For exposure to offgassing CS 2 , there are acceptable data from field st udies which measure concentrations of

CS 2 in air from one inch to five feet above ground level. Further refinement of these

values will not be needed.

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1.6.3.2 Effects

Ecotoxicity data are available fo r several assessment endpoints. Table 4 summarizes the specific toxicity values that will be used to assess acu te and chronic risk of carbon disulfide to receptors.

Table 4. Summary of Measure of Effects for Sodium Tetrathiocarbonate (a.i.) and Carbon Disulfide (CS 2 )

Assessment Endpoint Effects Measurement Endpoint

1. Survival, reproduction and growth of birds (Birds are surrogates for reptiles and terrestrial-phase amphibians) Bobwhite quail acute oral 14-day LD 50 = 1180 mg/kg = 363 mg a.i./kg Bobwhite quail dietary 8-day LC 50 >5620 ppm or >1731 ppm a.i. Bobwhite quail acute inhalation 4-hr NOAEC = 1060 ppm CS 2 Mallard duck acute drinking water exposure 8-hr NOAEC = 2400 ppm a.i.

* No chronic bird toxicity data available

2. Survival, reproduction and growth of mammals Rat acute oral LD 50 >587 mg a.i./kg

Rat acute inhalation LC 50 = 736 ppm CS 2 Rat acute drinking water exposure 24-hour NOAEC = 2000 ppm a.i.

* No chronic rat toxicity data available

3. Survival, reproduction, and growth of freshwater fish and

invertebrates (Fish are surrogates for aquatic-phase amphibians) Rainbow trout acute 96-hr LC 50 = 6.7 mg a.i./L = 0.87 mg CS 2 /L Daphnia magna 48-hr EC 50 = 6.6 mg a.i./L = 0.86 mg CS 2 /L * No chronic fish or invertebrate toxicity data available

4. Survival, reproduction, and growth of saltwater fish and

invertebrates * No acute or chronic toxicity data available.

5. Survival of beneficial insect s Parasitic wasp 48-hr NOAEC <0.1 L ENZONE/ha

and LC 50 = 0.41 L ENZONE/ha * No honey bee toxicity data available

6. Perpetuation of individuals and populations of non-target terrestrial plant species (crops and non-crop plant species) * No seedling emergence or vegetative vigor data available

6. Maintenance and growth of individuals and populations of aquatic plants from standing

crop Selenastrum capricornutum biomass 72-hour NOAEC = 80.1 μg CS 2 /L and EC50 = 520 μg CS 2 /L

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1.6.3 Other Information Needs

There is specific information that will assist the Agency in refining the ecological risk assessment, including any species-specific eff ects determinations. The Agency is very much interested in obtaining the following information:

1. confirmation on the following label information

a. sites of application

b. formulations

c. application methods and equipment

d. maximum application rates

e. annual frequency of application, date of initial application per year, application intervals, and maximum number of applications per year

f. geographic limitations on use

2. use or potential use distribution ( e.g ., acreage and geographi cal distribution of relevant uses)

3. use history

4. median and 90 th percentile reported use rates (l bs. a.i./acre) from usage data – national, state, and county

5. application timing (date of first applica tion and application intervals) by use – national, state, and county

6. sub-county crop location data

7. usage/use information fo r non-agricultural uses ( e.g ., golf courses, athletic fields, ornamentals)

8. directly acquired coun ty-level usage data (not de rived from state level data)

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

b. percent crop treated – county

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

d. total pounds per year – county

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

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

9. typical application interval (days)

10. state or local use restrictions

11. ecological incidents (non-target plant dama ge and avian, fish, reptilian, amphibian and mammalian mortalities) not already reported to the Agency

12. monitoring data

The analysis plan will be revisited and may be revised depending upon the data available in the open literature and the information s ubmitted by the public in response to the opening of the Registration Review docket.

35Docket Number: EPA-HQ-OPP-2007-1084 www.regulations.gov

IV. HUMAN HEALTH EFFECTS SCOPING DOCUMENT

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reflect current policy and practice for soil fu migants. If an assessment indicates the potential for signifi cant exposures to CS 2 above naturally-occurring background levels in drinking water as a result of registered uses, a drinking wa ter risk assessment will be needed. In addition, tolerances for carbon disulf ide need to be reassessed and potentially lowered. Prior to requiring any new data, a thorough review of re levant and available papers, reports, and databases covering wo rker and bystander exposures, and mammalian toxicity should be conducted.

Introduction: Registration activity on sodium te trathiocarbonate occurred mainly between 1985 and 1995. Although tolerances for CS 2 have been reassessed under the Food Quality Protection Act (FQPA), neither a Registration Standard nor a Reregistration Eligibility Decision (RED) has been developed for it. HED’s databases contain individual decision memoranda regarding the history and disposition of data requirements and registration actions. Although these memoranda capture the registration process and decisions as practiced at the time, no risk assessments in accordance with FQPA have

been conducted for sodium tetrathiocarbonate or CS 2

.

Sodium tetrathiocarbonate is a soil fumigant used for the management of nematodes and phytophthora root rot, oak root fungus, and phylloxera. There are two end-use products registered for use: Enzone and Entek. It is registered for use on grapes, citrus, almonds, peaches, prunes, and plums in Arizona (AZ), California (CA), Oregon (OR), and Washington (WA), only. CDPR reports that during the five years from 2001 to 2005, between 200,000 and 400,000 pounds of sodium tetrat hiocarbonate were used annually in CA. There is also a registration for non-bear ing fruit and nut trees, considered a non-food use and exempt from tolerances. Ther e are no registered residential uses.

Sodium tetrathiocarbonate is applied thr ough dilution in irrigation water by means of low-volume irrigation (chemigation), flood a nd furrow irrigation, a nd ground injection equipment. The majority of sodium terathioca rbonate used in CA is applied to grapes (vineyards) via irrigation. A 14-day post harves t interval (PHI) has been established on all labels. Once in water, it rapidly dissolves and then hydrolyzes in moist soil to form

H 2 S, CS 2 , sodium hydroxide, and elemental sulfur. Soil particles rapidly bind and

immobilize the sulfur ion and H 2 S components, leaving only CS 2 to migrate and act as the biocide (nematicide). CS 2 ’s vapor pressure (294 mmHg @ 20C) suggests that it will exist as vapor in the air. The degradation half-life is approximately 3 to 25 days.

Literature searches on sodium tetrathicarbon ate revealed no new information. However,

literature searches on CS 2 revealed extensive sources of information on this soil fumigant. HED has identified multiple articles and papers published in the open literature within the last five years rele vant to worker exposure to CS 2 and mammalian toxicity of

CS 2 . HED has also contacted the California De partment of Pesticide Registration (CDPR) and will ensure that information and data are exchanged on sodium tetrathiocarbonate

and CS 2. CDPR is actively working on their asse ssments for sodium tetrathiocabonate

and CS 2

.

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Hazard: CS 2 is a neurotoxicant. Headache and nausea are commonly associated with exposures to CS 2 as well as a range of more severe effects. These effects include obvious clinical signs of neurotoxic ity, such as, convulsions and death, as well as changes in tissues and organs, such as lesions on and sw elling of nerves, and brain weight effects, respectively. Additional eff ects observed in developmen tal and reproduction studies include: abortions/resorptions and body weight changes.

The most recent documents (memoranda) indicate that the available toxicity data on

sodium tetrathiocarbonate include: acut e toxicity studies, oral rat and rabbit developmental studies, and several mutagenicity studies. These studies are considered to be of either acceptable or “minimum” qua lity. The developmental studies indicate endpoints based on neurotoxicity (including death) in the adults, and increased resorptions and post-implantation losses in fetu ses. The effects occur in adults at lower doses than in fetuses. The mutagenicity studies were negative. A data waiver for a 21-day dermal study was granted because of the severe corrosive nature of CS 2

.

Available toxicity studies on CS 2 include: three inhalation studies (one in mice and two in rats) and developmental studies in rats and rabbits using CS 2 . Inhalation effects included epithelial necrosis of the nasal trac t and death at the highest doses.

Requirements for all subchronic and long-term studies, including acu te, subchronic, and developmental neurotoxicity studies, have b een waived because dietary exposures to CS 2 were determined to be “de minimus” rele vant to background (n aturally-occurring)

concentrations of CS 2 . Endpoints for risk assessment ha ve not been selected previously.

Dietary Exposure: Field trial data were submitted in the late 1980s and early 1990s to support an Experimental Use Permit (EUP) on citrus and grapes. An extension allowed for the inclusion of many trials in 5 states (AZ, CA, OR, WA, and FL). A nature of the residue study in plants outlining the metabolism of sodium tetrathiocarbonate in plants was submitted, reviewed, and a determination made that the study was adequate. The

nature of the residue is understood and the primary degradate and re sidue of concern for regulation and risk assessment is CS 2 . Animal metabolism studies are not required because plant metabolism studies indicate that significant, reversibly bound CS 2 is only detected in root crops, but not in other cr ops. As there are no regi strations of sodium tetrathiocarbonate on root crops, HED does not expect any transfer of residues through livestock commodities. Consequently, animal feeding studies are not warranted either.

Issues related to th e analytical method used to detect CS 2 in plants were resolved; an adequate analytical met hod exists to analyze CS 2 in plants. No processing studies were required given the volatile nature of the residue of concern (CS 2 ); residues are not expected to withstand conditions normally encountered during processing. Storage stability data are adequate.

By 1996, HED determined that residue data were adequate to grant permanent tolerances of 0.1 ppm for peaches, plums (fresh plums), prunes, citrus, almonds, and grapes. All of the residue data on peaches, plums, and almonds were from field tria ls in CA. Field trial data were also submitted for lemons, tomatoes, and apricots. Residue data from the

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available field trials showed that levels of CS 2 were generally either non-detectable or in the low parts per billion (ppb), i.e., 1 to 3 ppb. Maximum residues were detected in one sample in tomatoes, in which residues were 6 ppb, one sample of peaches, in which residues were 18 .4 ppb, and one sample of almo nd nutmeats, in which residues were 6.8 ppb. HED concluded that residues of CS 2 were likely to be less than 10 ppb on the commodities treated, and a tolerance of 0.05 pp m would be appropriate, but retained the 0.1 ppm tolerance since availabl e residue data from field trials conducted at maximum and exaggerated rates were limited. Thes e tolerances should be reassessed and a determination made if they can be lowered.

HED chemists used information on the background levels of CS 2 in soils, decaying organic matter, plants, and air in making their determination that CS 2 is always present in the environment, is ubiquitous, and occurs at low levels in the environment. HED

concluded that CS 2 was probably present in the diet of humans at low levels (< 10 ppb). Higher levels have been detected in Shitake mushrooms and in the headspace above beer, but on average are not expected to exceed 10 ppb. HED concluded that because “ residues of CS 2 in crops do not exceed natural background levels and will be indistinguishable from those background levels, the standard approac h to dietary [sic] risk assessment is

not warranted ”.

Previously, OPP conclude d that residues of CS 2 generated from the use of sodium tetrathiocarbonate as a result of registered uses were not likely to impact potable water provided labels contain restri ctions prohibiting application within 100 feet of a potable well. OPP will revisit the pot ential for exposures to CS 2 in drinking water under registration review.

Occupational and Residential Exposures: HED previously determined that worker exposures to individuals ha ndling, mixing, and applying pr oducts containing sodium tetrathiocarbonate will be “de minimus” pr ovided appropriate PPE as per the labels are

used. The labels state that handlers must wear respirators (NIOSH TC-23C or TC-14G). Post-application worker exposures were also determined to be “de minimus” previously provided the 4-day REI on the labels was followed. Monitoring data from a field volatility/dissipation st udy representing worst-case condi tions for use of the products

indicated that residues of CS 2 are below detectable levels at 96 hours. The detection limit for that study was 0.019 ng/m 3 . Occupational exposure and risk assessments reflecting current policy and practice for soil fumigants are necessary to conf irm worker safety.

There are no residential uses of sodium tetrathiocarbonate. However, application techniques such as flood and furrow irriga tion provide the potential for bystander exposure. Current labels state “posting” requirements to address issues of drift that may affect bystanders. CA labels provide buffer z ones to protect bystanders. However, a risk assessment for residential bystand ers potentially exposed to CS 2 as a result of sodium tetrathiocarbonate applications in nearby fields reflecting current policy and practice for soil fumigants has not been conducted. A ri sk assessment for potential bystander exposures to CS 2 is necessary under registration review and new data may be required to support this risk assessment.

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Incident Reports: Three data bases were searched for incidents reports on sodium

tetrathiocarbonate: Poison Control Cent er (PCC) Data, NIOSH SENSOR, and the Incidents Data System. No exposures to sodi um tetrathiocarbonate were reported in the PCC during the period 1993 through 2005 or the Incident Data System from 1999 to the present. NIOSH SENSOR reported 2 cases of sodium tetrathiocar bonate poisonings. One case took place in CA in 1999. A 31 year-old man was a mechanic exposed to ENZONE; he reported headache, diarrhea, and malaise. The second incident also occurred in CA, but in 2001, when a 50-year old farm worker inhaled the pesticide and reported nausea, palpitations, upper respiratory pain and irritation, and musc le weakness. Both are likely

attributed to CS 2 poisoning.

An additional poisoning incident associated with sodium tetrathiocarbonate was reported under Section 6(a)2 of the Fede ral Insecticide, Fu ngicide, and Rodenticide Act (FIFRA).

Two workers at Unocal’s West Sacramento Pl ant in California were exposed to sodium tetrathiocarbonate in 1994 and reported headaches lasting two days. The company reported the effects to be due to CS 2 , a known degradation product of Enzone.

Exposures to sodium tetrathiocarbonate are not reported frequently in the available databases capturing poisoning incidents with pesticides.

Aggregate Risk: There are no dietary exposures anticipated to sodium

tetrathiocarbonate. Di etary exposures to CS 2 have been determined to be “de minimus”. As a result, no quantitative dietary risk a ssessments have been conducted for sodium tetrathiocarbonate, or CS 2 in food. A drinking water expos ure assessment has not been conducted. There are no register ed residential uses; however, as CS2 is a soil fumigant, the potential for residential bystander exposur es needs to be asse ssed under registration review. If a drinking water assessment indicates potential exposures to CS 2 in drinking water, an aggregate risk assessment combin ing potential residential bystander exposures with drinking water exposures may be warranted.

Cumulative Risk: Sodium tetrathiocarbonate has not been identified as a member of a common mechanism group. However, it breaks down to CS 2 , as do dithiocarbamates. A common mechanism of toxicity across th ese compounds has not been established.

Environmental Justice

The Office of Pesticide Programs (OPP) t ypically considers the highest potential exposures from the legal use of a pestic ide when conducting human health risk assessments, including, but not limited to, pe ople who obtain drinking water from sources near agricultural areas, the va riability of diets within the U.S. (including different ages, regions, and ethnicities), and people who may be exposed wh en harvesting crops. Should these highest exposures indicate potential risks of concern, OPP further refines the risk

assessments to ensure that the risk estimate s are based on the best available information.

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As part of the California Environmental Ju stice Action Plan, the CDPR is currently conducting an environmental mon itoring program in the town of Parlier, CA. Parlier is a small agricultural town in the San Joaquin Va lley of CA 20 miles southeast of Fresno. Fruit orchards and grape vineyards are th e dominant crops grown in the area. This program is a pilot project designed to measure air quality in the area. CS2 is included in the list of pesticides to be monitored under the pilot project. Findings from this project

related to CS 2 ’s impact on air quality and environmen tal justice issues will be considered in HED’s updated risk assessments for CS 2

.

Human Studies. No toxicity studies invol ving human subjects e xposed intentionally to sodium tetrathiocarbonate, or CS 2 have been used or mentioned in any of the HED

assessments or memoranda on sodium tetrathi ocarbonate to date. A field volatility study in which air monitoring was conducted after application of sodium tetrathiocarbonate may require an ethics review. Additional et hics reviews may be needed depending on the data used to update existing assessments a nd develop a new reside ntial bystander risk

assessment.

Data Requirements:

New data may be required on CS 2. Specifically, a “flux” st udy for use in setting appropriate off-site exposure mitigation buffer zones may be required. However, HED believes that available toxicity and exposure da ta (field volatility a nd flux studies and air monitoring) already identified in the open literature and throu gh the CDPR may be sufficient to update existing CS 2 assessments to today’s standards for the fumigants. HED

will wait until the available l iterature on toxicity and expos ure, air monitoring databases developed by the California Air Resources Board (CARB), and other information

available on CS 2 have been reviewed prior to determ ining what data requirements, if any,

are warranted.

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Tolerance Harmonization:

No MRLs for sodium tetrathiocabonate have been established or proposed by Codex for any agricultural commodities. There are no Canadian or Mexican tolerances for carbon disulfide. Consequently, at this time, there are no harmonization issues. The US

tolerances for CS 2 are listed under 40 CFR 180.467 and summarized in the attached

tolerance status table.



### US Canada Mexico Codex

Residue Definition:
Registrations include 66300-63 and 66330-

69.

Tolerances established for carbon disulfide from the use of sodium tetrathiocarbonate,

40CFR.180.467 None (including both

sodium

tetrathiocarbonate

and sodium disulfide) None (including both

sodium

tetrathiocarbonate

and sodium disulfide) None (including both

sodium

tetrathiocarbonate

and sodium disulfide) Commodity Tolerance (ppm) /Maximum Residue Limit (mg/kg)

Almond 0.1 N/A N/A N/A Almond, hulls 0.1 Grapefruit 0.1 Grape 0.1

Lemon 0.1 Orange, sweet 0.1

Peach 0.1 Plum, prune, fresh 0.1

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References

Blondell, J., “Review of incident reports – sodium tetrathiocarbonate”, August 15, 1994. California Air Resources Board, Annual Stat ewide Toxics Summary, Carbon Disulfide.

California Department of Pesticide Regulat ion, Environmental Justice Pilot Project, Pesticide Air Monitoring in Parlier, Second Progress Report, December 2006.

California Department of Pesticide Regulat ion, Environmental Justice Pilot Project, Pesticide Air Monitoring in Parlier, A ddendum, ARB Monitoring Results, September

2007.

“Carbon Disulfide; Pesticide Tolerances”, Fe deral Register Notice, Volume 62, Number 95, 26946-26949, May 16, 1997.

Dang, W., “Ground-Level Concentrations Study of Carbon Disulfide in Air During and After Application of GY-81”, December 31, 1992.

Hawkins, M., “Review of Sodium Tetrathiocarbonate Incident Reports, DP Barcode D343827, Chemical # 128904”, August 31, 2007.

Morales, J., “PP#5F4482; ID#000612-00005. Sodi um Tetrathiocarbonate(GY-81) in/on Almonds, Peaches, and Plums (Fresh Prunes), Ev aluation of Residue Data and Analytical Methodology, MRID# 435717-01, 435901-01 thr ough -05. DP Barcodes: D213554 and 213557. CBTS Nos. 15344 and 15345”, September 25, 1995.

Morales, J., “PP#5F4482; ID#000612-00005. Sodi um Tetrathiocarbonate(GY-81) in/on Almonds, Peaches, and Plums (Fresh Prunes). Amendment in Response to CBTS memo of 9/25/95”, April 8, 1996.

Olinger, C., “PP#9G3800; GY-81 (Sodium Te trathiocarbonate solution) on Almonds, Prunes, Tomatoes, Lemons, And Apricots; Te mporary Tolerances and Experimental Use Permit; MRID Nos. 412173 – 01 through -06; Record Nos. 250714 and 251358; 612- EUP-U; DEB nos. 5770 and 5771.”, December 11, 1989.

Olinger, C., “PP#9G3800; GY-81 (Sodium TEt rathiocarbonate solution) on Almonds, Prunes, Tomatoes, Lemons, And Apricots; Te mporary Tolerances and Experimental Use Permit; Record Nos. 258610 and 258611; EUP-U; DEB nos. 6281 and 6282. February 16, 1990.

Roush, T., “Use Information and Air Mon itoring Recommendations for the Pesticide Active Ingredients Sodium Tetrathiocarbona te”, Environmental Hazards Assessments Program, California Department of Pesticide Regulation, September 2006.

44Docket Number: EPA-HQ-OPP-2007-1084 www.regulations.gov

Segawa, R. “Literature Review of the Environmental Fate of Sodium Tetrathiocarbonate (Enzone)”, Environmental Hazards Assessmen ts Program, California Department of Pesticide Regulation, January 18, 1991.

Taylor, L., “GY-81 - Responses to DEB Review Dated August 6, 1990 and NDEB Reviews Dated August 2 and 27, 1990”, October 22, 1990.

Taylor, L., “Carbon Disulfide – 90-Day Inhalatio n Toxicity Studies in Rats and Mice”, December 4, 1990.

Taylor, L., “Two 90-Day CS2 Inhalation Studies in Rats”, December 23, 1991.

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V. GLOSSARY of TERMS and ABBREVIATIONS

ai Active Ingredient AR Anticipated Residue CFR Code of Federal Regulations cPAD Chronic Population Adjusted Dose

CSF Confidential Statement of Formula CSFII USDA Continuing Surveys for Food Intake by Individuals

DCI Data Call-In DEEM Dietary Exposure Evaluation Model DFR Dislodgeable Foliar Residue DNT Developmental Neurotoxicity DWLOC Drinking Water Level of Comparison

EC Emulsifiable Concentrate Formulation EDWC Estimated Drinking Water Concentration

EEC Estimated Environmental Concentration EPA Environmental Protection Agency

EUP End-Use Product FDA Food and Drug Administration FIFRA Federal Insecticide, Fungicide, and Rodenticide Act FFDCA Federal Food, Drug, and Cosmetic Act FQPA Food Quality Protection Act FOB Functional Observation Battery GENEEC Tier I Surface Water Computer Model

IR Index Reservoir

LC 50 Median Lethal Concentration. A statistically derived concentration of a substance that can be expected to cause death in 50% of test animals. It is usually expressed as the weight of substance per weight or volume of water, air or feed, e.g., mg/l, mg/kg or ppm.

LD 50 Median Lethal Dose. A statistically derived single dos e that can be expected to cause death in 50% of

the test animals when ad ministered by the route indicated (oral, dermal, inhalation). It is expressed as a weight of substance per unit weight of animal, e.g., mg/kg.

LOC Level of Concern

LOAEL Lowest Observed Adverse Effect Level

μ g/g Micrograms Per Gram

μ g/L Micrograms Per Liter mg/kg/day Milligram Per Kilogram Per Day mg/L Milligrams Per Liter MOE Margin of Exposure MRID Master Record Identification (number). EPA' s system of recording/tr acking submitted studies. MUP Manufacturing-Use Product NA Not Applicable NAWQA USGS National Ambient Water Quality Assessment NPDES National Pollutant Discharge Elimination System NR Not Required

NOAEL No Observed Adverse Effect Level OPP EPA Office of Pesticide Programs OPPTS EPA Office of Prevention, Pe sticides and Toxic Substances PAD Population Adjusted Dose PCA Percent Crop Area PDP USDA Pesticide Data Program PHED Pesticide Handler's Exposure Data

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PHI Preharvest Interval ppb Parts Per Billion PPE Personal Protective Equipment ppm Parts Per Million PRZM/ Tier II Surface Water Computer Model

EXAMS Q 1 * The Carcinogenic Potential of a Compound, Quantified by the EPA's Cancer Risk Model RAC Raw Agriculture Commodity RED Reregistration Eligibility Decision REI Restricted Entry Interval

RfD Reference Dose RQ Risk Quotient SCI-GROW Tier I Ground Water Computer Model SAP Science Advisory Panel SF Safety Factor SLN Special Local Need (Registrati ons Under Section 24©) of FIFRA) TGAI Technical Grade Active Ingredient USDA United States Department of Agriculture UF Uncertainty Factor

WPS Worker Protection Standard

47