2 fate, endangered species, and drinking water assessments to be conducted as part of the registration review for metam sodium, metam pot assium, and MITC. The problem formulation draws on information from both open literature an d studies submitted by the technical registrants in response to data requirements. This document is intended to provide an overview of what is currently known and the uncertainties regarding the environmental fate and ecological effects associated with metam sodium, metam potassium, and MITC. It describes the conceptual model and the processes that will be used during the completion of drinking water exposure and ecological risk assessments in support of registration review. This document also recommends studies that may be included in a data call-in (DCI) to address uncer tainties surrounding the environmental fate and potential ecol ogical effects of the three compounds.Page 3 of 79 

# Problem Formulation for the Environmental Fate, Ecological Risk, Endangered Species, and Drinking Water Exposure Assessments in Support of the Registration Review of Metam Sodium, Metam Potassium, and MITC

Metam Sodium Metam Potassium MITC CAS No. 137-42-8 CAS No. 137-41-7 CAS No. 556-61-6

PC Code 039003 PC Code 039002 PC Code 068103

P

repared by: Justin Housenger, M.S., Biologist Gabe Rothman, M.S., Environmental Scientist U.S. Environmental Protection Agency Office of Pesticide Programs E nvironmental Fate and Effects Division E nvironmental Risk Branch I V 1200 Pennsylvania Ave., NW M

ail Code 7507P Washington, DC 20460 R eviewed by: Mah Shamim, Ph.D., Chief ERB5

June 18, 2013Page 4 of 79 

### Table of Contents

1. Executive summary ........................................................................................... 5 2. Introducti on ....................................................................................................... 8 3. Use Characterization ........................................................................................ 9 4. Conclusions from Previous Risk Assessments ............................................. 13 4.1 Ecological Risk Assessments ............................................................................. 14 4.2 Drinking Water Exposure Assessments ............................................................. 15 4.3 Clean Water Act Programs ................................................................................. 15 

### 5. Environmental Fate and Transpo rt .............................................................. 16 6. Receptors .......................................................................................................... 24 6.1 Effects to Aquatic Organisms ............................................................................ 25 6.2 Effects to Terrestrial Organisms ........................................................................ 28 6.3 Ecological Incidents ........................................................................................... 28 

### 7. Exposure Pathways of Con cern ..................................................................... 32 8.

. Analysis Plan ................................................................................................. 35 8.1 Stressors of Concern........................................................................................... 35 8.2 Measures of Exposure ........................................................................................ 35 8.3 Measures of Effect ............................................................................................. 38 8.4 Endangered Species Assessments ...................................................................... 39 8.5 Endocrine Disruptor Screening Program ........................................................... 39 8.6 Drinking Water Assessment ............................................................................... 39 

### 9 Preliminary Identificati on of Data Gaps ...................................................... 39 9.1 Environmental Fate ............................................................................................ 39 9.2 Effects ................................................................................................................. 43 

### 9. Reference s ........................................................................................................ 47 Appendix A - California Department of Pesticide Regulation Report on Train Derailment and Metam Sodium Release to Sacramento River and MITC Dissipation Analysis....................................................................................................................... .. 49 Appendix B – Evaluation of Toxic Degradates of Concern ......................................... 53 Appendix C – STIR Model Run to Establ ish Drinking Water and Dietary Exposure Conceptual Model for Birds and Mammals .................................................................. 66 Appendix D – SIP Model Run to Establish Drinking Water Exposure Conceptual Model for Birds and Mammals ..................................................................................... 67 Appendix E – Earthworm Fugacity Model Results to Establish Dietary Exposure Conceptual Model for Birds and Mammals .................................................................. 68 Appendix F – Detailed Environmental Fate Summary and Degradate Tables for Metam Sodium, Metam Potassium, and MITC......................................................................... 69Page 5 of 79 

## 1. Executive summary

The Environmental Fate and Effects Divisi on (EFED) and Antimicrobials Division (AD) have completed the preliminary problem formulation for the ecological risk, environmental fate, endangered species, and drinking water assessments to be conducted as part of the registration review of metam sodium, metam potassium, and methyl isothiocyanate (hereafter referred to as MI TC). The problem formulation describes the methods planned to be used during the comp letion of drinking water and ecological risk assessments in support of registration re view and provides an overview of the environmental fate, ecological effects, and poten tial risks associated with the uses of the above mentioned chemicals and related uncertain ties unique to the risk assessment. This document also identifies additional studi es that would recommend conducting an ecological risk assessment.

MITC is considered the main stressor in this risk assessment. Metam sodium and metam potassium are similar salts and therefore, they are both expected to behave similarly in the environment. Metam sodium and metam potassium, as conventional pesticides , are incorporated to bare soil in pre-plant applications to control fungi, weeds, insects, nematodes, microbes and diseases. It is also applied in sewer lines for root control. Amongst the major antimicrobial uses are: oil drilling muds, packers fluids, cooling water systems, pulp/paper, and remedial wood treatment including poles /pilings, and large timber. The only registered use for dire ct MITC applications are for remedial wood treatment as well.

Once applied, metam sodium and metam potassium degrade to MITC with a half-life of 23 minutes in aerobic soil. In soil, an 83 percent conversion of metam sodium and metam potassium to MITC occurs. As a result, it is not expected th at metam sodium and metam potassium will be bioavailable to terrestrial or aquatic organisms in any environmentally relevant concentration.

MITC is volatile and resides mainly in the vapor phase once converted from metam sodium or metam potassium in the environm ent. For soil uses, post-application soil sealing methods ( e.g. , tarps, water, or soil) will be the largest factor determining off-site movement of dissolved MITC vapors via runoff to water bodies or MITC vapors to air. Given its high water solubility, leaching of dissolved MITC to ground water is also possible in well-draining sandy soils in areas where the water table is shallow, under all application scenarios. Once in water, MI TC aquatic dissipation will be mediated by hydrolysis and volatilization.

Exposure to aquatic organisms is predicated by runoff of MITC from treated fields. The PRZM/EXAMS model Georgia Farm Pond scen ario will be used to quantify EECs in surface water. The aquatic exposure modeli ng will account for MITC loss from soil through the use of the PRZM vol atilization algorithm. For MI TC and terrestrial animals, the main route of exposure is expected to be via inhalation. For terrestrial plants, exposure to vapor phase MITC is also expected. To estimate exposures for MITC vapor,Page 6 of 79 a tiered approach will be used. Both AERSCREEN and PERFUM can predict the upper bound air EEC at a point nearby the edge of th e treated field directly downwind from the application site. In additi on, both models can predict fumigant air concentrations at specified points downwind from the treated field. AERSCREEN, which considers worstcase meteorological conditions coupled with a peak flux rate, will be used as a screen. If LOCs are exceeded using AERSCREEN, PERFUM, which has the capability of producing a distribution of air EECs from a range of different meteorological conditions, will be used to refine the potential exposur e values for animals and plants (vegetative vigor). For exposure to plant seedlings, TerrPlant will be used. Although TerrPlant EECs are based on runoff, TerrPlant will captu re the overall exposure of plant seedlings whether it occurs from diffusion in the ga s phase or runoff of dissolved MITC. Additional background information on the models is provided in Section 8.2

.

The assessment for antimicrobial uses will also focus on MITC as the main stressor. The EFAST (PDM module) will be used to esti mate the EECs in surface water from the releases from uses in recirculating cooli ng towers and paper and pulp systems. Metam sodium, metam potassium, and their degrad ation product MITC are also used for remedial treatment of wooden poles, timbers by inserting metam sodium into the holes and use the product from 1⁄4 pint to 2 pints, depending upon the severity of wood decay. The holes are plugged with treated wooden plugs. Therefore, no exposure from metam sodium, metam potassium, or MITC is likely with this treatment. Metam sodium and metam potassium are also used to treat an imal waste products in storage that are eventually used outdoors. Aquatic and terrestr ial exposure associated with this use will be addressed consistent with the soil fumi gant uses. Surface water exposure estimates will rely on the PRZM/EXAMS model calculations . Air exposure estimates will rely on AERSCREEN and PERFUM if necessary. Othe r uses are indoor uses, and exposure from these uses will likely be addressed by way of Down-the-Drain (DtD, and PDM modules) of E-FAST model.

There are several sources of uncertainty fo r the aquatic exposure assessment for MITC. These include the following points:

1. The largest uncertainty in quantifying exposure in this assessment will be considering the impact of tarps, especi ally bedded tarps, on MITC’s ability to runoff. MITC may become available to runoff by possibly moving into the soil space between the bedded strips. It is intended that the estimated exposure concentrations (EECs) of MITC in surf ace water for untarped applications would result in an upper-bound estimate of e xposure for the overall usage of metam sodium and metam potassium.

2. The EECs for MITC are highly sensitive to rainfall events that occur close to applications, given high application rate s of metam sodium and metam potassium and that MITC volatilization in runoff water is not accounted for. However, there is also little experimental data on MITC’s overall reten tion time in water in the environment. In order to account for th is source of uncertainty, aquatic EECs will be corroborated using monitoring data, asso ciated with various incidents due toPage 7 of 79 pesticide applications, as well as a trai n derailment leading to a metam sodium spill into the Sacramento River in Calif ornia (CALDPR, 1991). While many of these lines of evidence such as the train incident may not be tied to registered pesticide uses, they provide evidence for th e ability of MITC to be transported to water bodies nearby releases which may occur over exposed treated fields not covered by a tarp. Furthermore, an aerobic aquatic metabolism study will be requested to address uncertainties related to MITC’s retention time in water.

There is also limited information on the role of how biodegradation mediates levels of MITC in the soil. Terrestrial field stud ies conducted in California and Mississippi indicate that MITC is not detected in soil 7 days after the application at both sites. A robust database of field volatility studies in dicate that large but variable amounts of MITC escape to the atmosphere. However, the mediation of biodegradation on MITC is unknown. Nonetheless, EECs in aquatic environm ents will incorporate all available data regarding the loss of MITC from treated soil.

Furthermore, there are several sources of uncertainty for the terrestrial exposure assessment for MITC. These include the following points:

1. For terrestrial exposure, EECs in air w ill conservatively assume that birds and mammals are not transient and are always being exposed to emissions of MITC downwind from the treated field. Such an assumption is perhaps more representative for plants since they are not transient. However, EECs will still assume that plants are always being e xposed to MITC downwind from the treated field.

2. One uncertainty for air EECs is the prope nsity for large exposures to occur on timescales less than one hour. Such c onditions are often associated with temperature inversions when light and variable wind speeds and highly stagnant air with limited mixing can occur. Theref ore, peak air concentrations may be underestimated. However, it is not e xpected that these conditions would significantly impact the expected fre quency of exposure events since these conditions may only occur within a few hours of certain days after fumigant applications. In addition, current labe ls contain specific language restricting applications during temperat ure inversions citing a numbe r of criteria indicating the presence or forecasted temperature inversion.

3. Another uncertainty includes the considera tion of field size for the quantification of air EECs. Air EECs will be based on emissions occurring from a maximum field size of 80 acres. 80 acres is cons idered to be the upper-bound field size for the maximum area that is typically treat ed in one day. However, in some applications such as in center pivot ch emigation, applications occur over much larger fields over multiple days. Therefore, a separate scenario addressing center pivot applications will be evaluated to quantify air EECs. Please refer to Section 8.2.2 . for further details.Page 8 of 79 The major data needs for envir onmental fate are listed below:

 Aerobic Aquatic Metabolism: MITC (835.4300)

 Environmental Chemistry Methods (EC Ms)/Independent Laboratory Validation (ILVs) in Air and Water: MITC (850.6100)

The major data needs for ecological effects are listed below:

 Acute vapor exposure study for the hone y bee (non-guideline study): MITC

 Tier I/II Seedling Emer gence Study (850.4100): MITC

The environmental fate requirements menti oned above are outstand ing data needs to address the conventional and antimicrobial us es of metam sodium and metam potassium. The ecological effects data needs are request ed to address the c onventional uses of metam sodium and metam potassium. Please refer to Section 9 on the rationale for the data requests.


## 2. Introduction

For this Problem Formulation (PF), EFED a nd AD evaluated the most recent ecological risk assessments for metam sodium, metam pot assium, and MITC in association with any updated toxicity, exposure, and use and usage information to determine if sufficient data are available and if further updates are needed to support registration re view. Recent risk assessments include a 2004 ecological risk assessment conducted for the Re-registration Eligibility Decision (RED) (DP Barcode 2016938, dated August 18, 2004). In addition, EFED considered the latest Agency science policies and risk asse ssment methodologies. The structures of metam sodium, metam pota ssium, and MITC as well as the chemical names and other identifiers can be found in Table 2 of this document.

Metam sodium, metam potassium, and MITC pr oducts are all available as emulsifiable concentrates. Metam sodium and metam potassium degrade rapidly to MITC via hydrolysis and biodegradation. Once MITC is formed, it readily changes phase to a gas due to its high volatility. Acting as a fumiga nt, MITC controls a wide spectrum of pests such as fungi, weeds, insects, nematodes, mi crobes and diseases, and used as root control as well. MITC exhibits nematicidal, bacteric idal, algaecidal, herbic idal, fungicidal, and insecticidal activity. MITC accounts for most of the fumi gant activity by diffusing, either as a gas or volatile liquid, upward through the interstitial spaces and killing living organisms with which it comes in contact. MITC is highly toxic and results in the disruption of biological functi ons of both target and non-target organisms. For example, MITC is highly reactive with the nucleophilic centers such as thiol groups in vital enzymes of nematodes (Cremlyn, 1991).Page 9 of 79 

## 3. Use Characterization

Conventional Uses

There are currently 14 active registered metam sodium e nd-use products and 3 active registered metam potassium end-use products .. Two metam sodium products are coformulated with dichlobenil. The major ity of metam sodium and metam potassium products are applied to bare soil in pre-plant applications fo r a wide variety of crops as well as turf greens 1 . Up to 320 lbs. metam sodium/A and 360 lbs. metam potassium/A are allowed on the labels. This translates to MITC equivalent maximum application rates of 150.31 lbs./A and 150.38 lbs./A from metam sodium and metam potassium applications, respectively 2 . In general, metam sodium and metam potassium are applied as frequently as once per year for soil uses.

There are also eleven Section 24c Special Lo cal Needs registrations for conventional uses of metam sodium. Two of th e registrations in Georgia a nd South Carolina are for preplant applications for peanuts at a maximum application rate of 63.9 lbs. a.i./A. Two other Section 24c Special Local Needs regist rations in North Carolina and Virginia are also for pre-plant applications for peanuts at a maximum applica tion rate of 63.6 lbs. a.i./A. Six other Special Local Needs regist rations were recently registered in North Carolina and Virginia. These labels will further be evaluated at a later date and incorporated into the registra tion review risk assessment Th ese labels are equivalent to the labels with the fore mentioned Special Lo cal Needs registered in Virginia and North Carolina except they contain buffer zones fo r application rates lo wer than those found on the section 3 labels.

Metam sodium and metam potassium soil uses may be applied by su rface applications such as chemigation (e.g., drip, solid set sp rinkler, or center pi vot chemigation), and flooded applications. Soil incor porated applications include shank injection, spray blade, and rotary tiller. Labels require metam sodi um and metam potassium to be injected to a minimum depth of 4 inches. For all met hods, metam sodium and metam potassium is required to be applied 14 days before planti ng (plant back interval). No maximum field size for metam sodium and metam potassium applications is specified on labels. However, worker and bystander buffer zone s address applications occurring up to 160

11 Listed crops on labels include apples, artichoke s, asparagus, beans (all types), berries (all types), broccoli, brussel sprouts, cabbage, carrots, cauliflower, celery, cherries, cover crops, guava, okra, corn, cilantro, corn (all types), cotton, cucumber, currant (all types), dandelion, dill, eggplant, endive, fennel, garlic, grapefruit, grapes, honeysuckle, kale, kiwi, kohlrabi, kumquat, leeks, lemon, lime, lettuce, oranges, mangoes, melons (all types), squash (all types), gourds (all types), mint, nectarines, pears, peaches, plums, nuts (all types), peanuts, nursery plants, onions, radicchio, radish, rhubarb, soybeans, rye, spinach, sugar beets, potatoes, sweet potatoes, peppers, tobacco, toma toes, turnips, wheat, and yams.
2 MITC Application Rate from Metam Sodium (lbs./A) = 320 lbs./A x 0.83 transformation factor x (73.12 g-mol -1 /129.2 g-mol -1 ) MITC Application Rate from Metam Potassium (lbs./A) = 360 lbs./A x 0.83 transformation factor x (73.12 g-mol -1 /129.2 g-mol -1 )Page 10 of 79 acre fields for center pivot applications; 120 acre fields for overhead chemigation, spray blade, rotary tiller, and sh ank injection applications; and 80 acre fields for drip chemigation applications.

For all methods, minimum Good Agricultural Practices (GAPs) include using an adequate sealing method includ ing the incorporation of so il or water over the applied metam sodium or metam potassium solution. GAPs are specified to optimize the efficacy of the fumigant by maximizing retention of the fu migant in the top soil that is treated. The sealing of the fumigant may be reinforced using tarps, but tarp s are not required on labels. Therefore, it is important to note that while GAPs are required for metam sodium and metam potassium soil applications, and th e application of tarp s is one of the nonmandatory GAPs specified, untarped applica tions using other GAPs are allowed. In addition, surface and incorporated metam sodi um and metam potassium applications are allowed to occur under a variety of field cul tivation settings. For example, broadcast applications (e.g., flat fume) or applications within bedded strips are allowed. The photos showing the variations on incorporated application methods for metam sodium and metam potassium soil uses are shown in Figure 1 and Figure 2 below. Surface chemigation applications ( e.g. , solid set sprinkler) are not s hown below. Moreover, all of the application methods shown in the figures below may also be used with water and soil sealing methods without th e application of tarps.

Credit: http://www.goodfruit.com Figure 1. Photograph showing flat fume or broadcast shank injection application followed by tarp covering.Page 11 of 79 Credit: EPA, 2005 Figure 2. Photograph showing shank injectio n application to raised beds followed by tarp covering.

There is also one metam sodium product that ca n be used for root control uses in sewage pipes. The maximum application rate for th ese uses is 0.212 lbs. of metam sodium per gallon of solution. No maximum number of a pplications are specified on the label for

sewer uses.
National pesticide usage data from the United States Geological Survey indicate that an average of 42 million pounds of meta m sodium and 12 million pounds of metam potassium was applied per year to agricultu ral crops in the United States from 2006 to 2011. It is expected that metam sodium and metam potassium usage will increase in the future in response to the phase-out of methyl bromide given the use of metam sodium and metam potassium products as an alternative to methyl bromide (; USEPA, 2012). The average fraction treated of crops was reporte d to be between 5 to 15 percent for most registered crops, with a maximum of up to 30% for potatoes and cantaloupes and 60% for carrots (USEPA, 2012).

Antimicrobial Uses

There are an additional 16 registered antimicrobial products. Metam sodium antimicrobial uses include remedial treat ment of wooden poles and timbers, and treatment of sewer sludge and animal waste. For metam potassium the uses include tanning drum leather, pulp and paper, recircul ating cooling water systems, and industrial water purification systems. For MITC, the only antimicrobial is for remedial treatment of wooden poles and timbers. Table 1 below lists the antimicro bial products, application type, and application rates of th e products. There is also a Section 24c registration exists in California for industrial waste stream uses.Page 12 of 79 Table 1. Anitmicrobial uses of metam sodium, metam potassium, and MITC.

No Application type Reg. No %AI Application. Rate 1 Oil drilling muds, packer fluids 1448-52 Metam-K: 32.5 0.05 to 0.2% 500 ppm-2000ppm 2 Leather manufacture 100-750 ppm 3 Animal Glue solution 75-150 ppm 4 Clay slurries, phosphate dispersed 50-100 ppm

5 Coating formulation, protein binders, starch binders, starch slurries and solutions 150-400 ppm

6 Cooling Water systems 1448-115 Metam Na: 3.69 Metam-K: 5.07 6.9-13.9 fl oz/1000 gallons of system 7 Industrial Water purification 24.5-49.0 fl.oz/1000 gallons of water

8 Cooling water system 1448-128 Metam Na: 14.7 Metam K:20.3 1.5-3 fl.oz/1000 gallons of system
water 9 Industrial water purification system 5.0-10 floz/1000 gallons water 10 Industrial and commercial Cooling towers 1448-180 Metam-Na: 7.35 Metam-K: 10.15 3.3-6.6 fl.oz/1000 gallons of water system 11 Industrial Water purification 11.5-23.0 fl.oz/1000 gallons of water 12 Pulp/Paper mills 1448-53 Metam-Na: 14.7 Metam-K: 20.3 0.4 lbs-2.0 lbs/ton of pulp (dry basis) 13 Petroleum secondary recovery operations 1-1.5 fl.oz/1000 gallons of water 14 Cooling water systems 1.5-3.0 fl.oz/1000 gallons of water 15 Wood and wood products 1448-107 Metam-Na: 42.5 No application rate provided 16 Brine cured hides/skins Preservation of salt-cured hides/skins 1448-371 Metam-Na: 33 4000-10,000 ppm 100-250 ppm

17 Leather 125-500 ppm 18 Wood treatment: poles/pilings, large timbers 1448-437 Metam-Na: 33 Bore 4-5 holes of 3⁄4 inch in diameter; apply 1 pint of/pole. Plug holes with treated wood plugsPage 13 of 79 No Application type Reg. No %AI Application. Rate 19 Douglas fir poles, western red cedar poles, southern pine poles; Wood chips can also be treated by dipping 0.3%/100 gallons of water, and 0.8 % in 100 gallons of water 10182-196 Metam-Na: 32.7 Drill 9/16 inch holes and apply 1 pint to all holes; If severe conditions, apply 2 pints. Plug the holes with treated wood plugs; In 500 gallons of water and increase these amounts accordingly 20 Sewage sludge (biosolids) and animal waste 5481-477 Metam-Na: 42.0 1-3 gallons /ton of sludge or animal waste; store in a protected area for 14- 21 days until the tests show it is safe to use in agricultural and horticulture purposes

21 Remedial treatment of wooden poles/timbers 75341-2 Metam-Na: 33.0 Drill 7/8 inch holes, and apply 1⁄4 pint of the product (36 inch diameter size poles; for larger size poles, 1.5-2.0 pints for all holes. Plug the holes with plugs that are treated with the product. Also can use plastic plugs. 22 Remedial treatment of wooden poles/timbers 69850-1 MITC Drill 9 holes, 30 g per hole



## 4. Conclusions from Previous Risk Assessments

The following serves as the basis for this scoping document covering metam sodium, metam potassium, and MITC:Page 14 of 79  The Reregistration Eligibility Decisi on (RED) science chapter (DP Barcode 2016938, dated August 18, 2004)

 AD Memo from Heather Garvie to Mark Hartman May 11, 2008

Two other risk assessments were conducted for metam sodium after 2004 addressing local endangered species litigation for th e Red Legged Frog (dated July 19, 2007) and California Tiger Salamander (dated Decembe r 29, 2010). The RED document for metam sodium, metam potassium, and MITC was or iginally signed in 2008, but was amended and the revision was signed in 2009 (USEPA, 2009). The RED was amended to incorporate public comments; however, the Agen cy’s risk conclusions did not change. The major ecological risk conclusions pres ented in the RED are described below.



### 4.1 Ecological Risk Assessments

The reregistration eligibility decision (R ED) outlined the potential ecological risks associated with the soil fumigant pesticid e uses and the antimicrobial uses of metam sodium, metam potassium, and MITC, which were assessed separately.

Conventional Uses

The environmental fate and effects risk assessment conducted for the soil fumigant pesticidal uses of metam sodium and metam potassium (USEPA, 2009), was based completely on the risk from MITC as the stressor of concern 3 . For MITC, no risks to mammals were identified as it was determin ed that downwind air estimated exposure concentrations (EECs) from a single 80-acre field 4 did not exceed acute levels of concern (LOCs) for inhalation. Inhalation toxicity da ta were not available for MITC and other taxa (including birds and terrestrial plants) at the time of the RED, and therefore these taxa were not assessed. Acute aquatic LOCs are exceeded for both aquatic invertebrates and freshwater fish, based on MITC surface water EECs in the modeled pond. The effect of tarps were not included quantitatively in estimating aquatic concen trations, so aquatic EECs would especially represen t upper-bound events for those s cenarios. However, tarps are not exclusively requriedon labels. No LOCs were exceeded for aquatic plant exposure to MITC, based on a partially comple te data set for rela ted toxicity data. Table 2 below summarizes the previous risk conclusions from the RED.

Table 2. Summary of risk concerns identifi ed in previous assessments of metam sodium and metam potassium, and MITC

Birds Mammals Terr. Plants Terr. Inverts Fish Aq. Inverts BCF Aq. Plants Groundwater Contamination Persistence Degradates of Concern

--* None --* --* √ √ None √ √ None MITC *Toxicity data were not available at the ti me of the risk assessment to estimate risk.

3 The risk assessment for the RED was not conducted for sewer uses.
4 Air EECs from field sizes between 80 ac res and 120 acres were not calculated.Page 15 of 79 In 2007, risk to the federally thre atened California Red Legged Frog ( Rana aurora draytonii - CRLF), was assessed from the use of metam sodium. In that assessment, inhalation exposure was cited as the primary r oute of exposure for terrestrial organisms. Birds normally serve as a surrogate for terr estrial phase amphibians like the CRLF but there were no avian inhalation data available and so mammals served as a surrogate to the CRLF. This assessment considered MITC to be the stressor of concern in both the terrestrial and aquatic phases. Direct effects to the aquatic phase CRLF on survival were predicted as a likely to advers ely affect determination for most uses of metam sodium as a sprinkler irrigation method. Indirect effects caused by direct effects on prey for the CRLF were similar for those scenarios that predicted direct effects. No effect determinations were made for direct effects to survival for the CRLF for certain uses, for effects on reproduction and growth, and for i ndirect effects to the CRLF mediated by direct effects on prey for certain uses. No effects determinations were indicated to the terrestrial phase CRLF for a ny use of metam sodium.

In 2010, risk to the federally threat ened California Tiger Salamander ( Ambystoma californiense - CTS), was assessed from the use of metam sodium. As in the previous assessment to the CRLF, MITC was consider ed the stressor of concern for both the aquatic and terrestrial phase CTS. For the pote ntial for direct and i ndirect effects to the aquatic phase CTS was determined as likely to ad versely effect. For direct effects to the terrestrial phase CTS, a determination of no effect was made, again using the mammalian rat inhalation data as a surrogate for the CTS.

Antimicrobial Uses

In the RED document, AD determined that metam sodium, metam potasium and MITC antimicrobial uses do not pose an unreasonable risks or adverse effects to humans or environment, provided that the risk mitigati on measures and label changes outlined in the RED (July 2009) are implemented and therefore products containing metamsodium,metam-potassium and MITC for thes e uses are eligible for reregistration. 

### 4.2 Drinking Water Exposure Assessments

A drinking water exposure assessment was co nducted and the estimated drinking water concentrations (EDWCs) were calculat ed and submitted (DP Barcode D293341, dated September 16, 2003) to support HED’s human health risk assessment for the RED. Exposure estimates of MITC from metam s odium labeled uses maximum exposure (FL Tomato) were 73.22 μg/L (acute: 1-in-10-year peak), and 2.99  g/L for both chronic and cancer EDWCs (1-in-10-year annual mean and 30-year mean, respectively). A concentration of 0.72 μg/L was calculated fo r ground water using the SCIGROW model. It is important to note that SCIGROW does not account for volatility. In addition, there are uncertainties with using the SCIGROW mode l for mobile compounds such as MITC.



### 4.3 Clean Water Act ProgramsPage 16 of 79 MITC is not identified as a cause of impair ment for any water bodies listed as impaired under section 303(d) of the Clean Water Act, based on information provided at http://iaspub.epa.gov/tmdl_waters10/attain s_nation_cy.cause_detail_303d?p_cause_grou p_id=885 . No Total Maximum Daily Load (TMDL) criteria have been developed for MITC, based on information provided at http://iaspub.epa.gov/tmdl_waters10/attain s_nation.tmdl_pollutant _detail?p_pollutant_gr oup_id=885&p_pollutant_group_name=PESTICIDES . More information on impaired water bodies and TMDLs can be found at http://www.epa.gov/owow/tmdl/ . The Agency invites submission of water quality data for this pesticide. To the extent possible, data should conform to the quality standards in Appendix A of the OPP Standard Operating Procedure: Inclusion of Im paired Water Body and Other Water Quality Data in OPP’s Registration Review Risk A ssessment and Management Process (see: http://www.epa.gov/oppsrrd1/regist ration_review/water_quality_sop.htm ), in order to ensure they can be used quantitatively or qualitatively in pesticide risk assessments. 

## 5. Environmental Fate and Transport

Metam sodium and metam potassium are non- volatile and readily soluble (722 g/L @ 20 0 C for both compounds) in water and degrad e very rapidly to MITC in soil (soil photolysis and aerobic degradation half lives range from 23 to 63 minutes) and in water (hydrolysis half-life = 2 days at pH 7). Unlike the pare nt compounds metam sodium and metam potassium, MITC has a high va por pressure (19 mm Hg at 20 0 C) and Henry’s Law Constant of 1.79 x 10 -4 atm·m 3 /mol, which suggests that it will be volatilized from fields treated with metam sodium or metam potassium in a dry environment. However, its Henry’s Law Constant suggests that the retention time of MITC will probably be longer in moist soils. Table 3 lists the physical-chemi cal properties of metam sodium/metam potassium and MITC. Meta m sodium and metam potassium possess the same physical chemical properties since th ey are salt analogues of each other.Page 17 of 79 Table 3. Physical and chemical properties of metam sodium/metam potassium and MITC

.
Property Metam Sodium and Metam Potassium MITC

Value and units MRID or Source Value and units MRID or Source

Structure, Molecular Formula, and

Molecular

Weight Metam Sodium

C 2 H 4 NNaS 2 129.2 g/mol

Metam Potassium

C 2 H 4 NKS 2 145.3 g/mol EPISUITE MITC

C 2 H 3 NS 73.12 g/mol EPISUITE

Vapor Pressure (25°C) 4.53 x 10 -9 torr EPISuite (MPBPVP) 16 torr CDPR, 2002

Henry’s Law

Constant 7.7 x 10 -16 atm·m 3 /mol Calculated from Vapor Pressure/Solubility 1.79 x10 -4 atm·m 3 /mol CDPR, 2002

Water Solubility 722,000 mg/L Tomlin, 1997 (ed.) (20°C) 8,610 mg/L (25°C) CDPR, 2002

Octanol – water partition

coefficient (log K O W ) 0.46 EPISUITE 0.98 MRID 43540903

Aerobic soil metabolism, photodegradation in wa ter, and hydrolysis studies suggest that parent metam sodium and metam potassium are very unstable in the environment and degrade rapidly to MITC and other minor degradates. Metam sodium and metam potassium both degrade to MITC wi th a half-life of 23 minutes in aerobic soil. In soil, an 83 percent conversion of metam sodium and metam potassium to MITC occurs. For MITC, degradation in soil and water app ears to be dependent on hydrolysis and microbially-mediated degradation, and MITC appears to persist longer than metam sodium in the environment. The dissipa tion of MITC in aquatic and terrestrial environments appears to be predominantly dependent on volatiliza tion and to a lesser extent on leaching and degradation. Photolytic degradation is the major loss pathway of MITC in atmosphere (half-life of 1.21 – 1.60 days). Table 4 and Table 5 list the environmental fate properties and degradate formation of metam sodium/metam potassium and MITC, respectively. Table 6 shows the amount of MITC escaping to the atmosphere from field volatility studies with metam sodium and metam potassium applications. The open literature has been used to fulfill many outstanding data gapsPage 18 of 79 related to the environmental fate, especia lly for MITC. Detailed information on the environmental fate of metam sodium, me tam potassium, and MITC may be found in Appendix F . Furthermore, degradate structures can be found in Tables F-1 and Table F-2 of Appendix F for metam sodium/metam potassium and MITC, respectively.

Table 4. Summary of metam sodium/m etam potassium environmental fate properties.

Study 3 Value and unit Major Degradates MRID #

or Citation Study Classification,

Comment

Abiotic Hydrolysis t 1⁄2 = 2.0 days (pH 5)
t 1⁄2 = 2.0 days (pH 7)
t 1⁄2 = 4.5 days (pH 9) MITC (pH 5 and 7) Methylamine (pH 5, 7, and 9) MCDT (pH 9) DMTU (pH 5, 7, and 9) DMU (pH 5, 7, and 9) 41631101 Acceptable

Aqueous Photolysis t 1⁄2 = 28 minutes MITC Methylamine MCDTNMethylthioformamide 41517701 Acceptable

Soil Photolysis t 1⁄2 = 63 minutes - 42978701 Supplemental Degradation t 1/2 in air No Data - NA NA Aerobic Soil Metabolism t 1⁄2 = 23 minutes MITC 40198502 Acceptable Anaerobic Soil Metabolism No Data - NA NA
Aerobic Aquatic Metabolism No Data - NA NA
Anaerobic Aquatic Metabolism No Data - NA NA
Mobility, unaged leaching, adsorption/desorption and aged leaching soil column K oc = 4.04 ml/g - EPISUITE NA

Volatility from Soil (Laboratory) No Data 1 - NA NA
Volatility from Soil (Field) No Data 1 - NA NA

Terrestrial Field Dissipation Metam Sodium residues were not detected after application in Mississippi Silt Loam and California Sandy Loam Soils MITC DMU 41514402 41514401 Supplemental SupplementalPage 19 of 79 Table 4. Summary of metam sodium/m etam potassium environmental fate properties.

Study 3 Value and unit Major Degradates MRID #

or Citation Study Classification,

Comment Bioconcentration Factor (BCF)- Species Name No Data 2 - NA NA

1 Metam sodium/metam potassium possess a low vapor pressure of 4.53 x 10 -9 torr, therefore no data are
necessary. 2 Metam sodium/metam potassium Log Kow < 3. therefore no data are necessary.
3 All studies used metam sodium as the test substance.
4 Dashes mean no constituents found or measured.
5 NA means not applicable.

Table 5. Summary of MITC environmental fate properties.

Study 2 Value and unit Major Degradates MRID #

or Citation Study Classification,

Comment 6

Abiotic Hydrolysis t 1⁄2 = 3.5 days (pH 5)
t 1⁄2 = 20.4 days (pH 7)
t 1⁄2 = 4.6 days (pH 9) Methylamine (pH 5, 7, and 9)

DMTU (pH 9) 00158162 Acceptable

Aqueous Photolysis t 1⁄2 = 51.6 days - CALDPR, 2002 NA
Soil Photolysis - - - NA

Degradation t 1/2 in air 1.21 – 1.60 days MIC 5 Methyl Isocyanide 5 Sulfur Dioxide 5 Hydrogen Sulfide 5 Carbonyl Sulfur 5
Nmethylthioformamide 5 Methylamine 5 Geddes et al., 1995 NA

Aerobic Soil Metabolism 3.3 – 9.9 days - Gerstl et al., 1997 NA

Anaerobic Soil Metabolism No Data - NA NA
Aerobic Aquatic Metabolism No Data - NA NA
Anaerobic Aquatic Metabolism 21 Days - 43596501 Supplemental
Mobility, unaged leaching, adsorption/desorption and aged leaching soil column K d = 0.26 ml/g (mean value) - Gerstl et al., 1977 NA

Volatility from Soil (Laboratory) No Data - NA NAPage 20 of 79 Table 5. Summary of MITC environmental fate properties.

Study 2 Value and unit Major Degradates MRID #

or Citation Study Classification,

Comment 6

Volatility from Soil (Field) See Table 6 for field volatility study descriptions and volatile flux
measurements - 45703702 45703704 47131601 47314301 47732801 46379201 47820001 47813901 48011601 48005901 48115101 47956701 48467601 Acceptable Acceptable Acceptable Acceptable Supplemental Pending Pending Pending Pending Pending Pending Pending Pending

Terrestrial Field Dissipation Leland, MD Silt Loam Soil

t 1⁄2 < 24 hours MITC residues were not detected after 7 days

Visalia, CA Sandy Loam Soil

t 1⁄2 < 24 hours MITC residues were not detected after 7 days - 41514402

41514401 Supplemental

Supplemental

Bioconcentration Factor (BCF)- Species Name No data 1 - NA NA

1 MITC’s Log Kow < 3, therefore no data are needed.
2 All studies used MITC as the test substance except for the field dissipation and field volatility studies, where metam sodium was used.
3 Dashes means no constituents found or measured.
4 NA means not applicable.
5 Degradates detected in field volatility from Geddes et al., 1995. Limited information regarding material balance. 6 For studies with finalized classification pending, cursory review found studies adequate for risk

assessments. Finalized review with formal DER pending.Page 21 of 79 Table 6. Description of MITC field volatility studies and volatile flux measurements.

Parent Chemical Applied Field Volatility Study (Application Rate) Time Applied MRID Study Classification
1 Peak Flux Rate 2,3 (  mass

loss) Cumulative Mass Loss 2 (% mass loss)

Metam Sodium Bakersfield, CA Sandy Loam

Sprinkler Chemigation with water seal (320 lbs. a.i./A) August 21 5:00 am 45703702 Acceptable 4.22 15.86 percent through 96hours postapplication

Metam Sodium Lost Hills, CA Clay Loam Shank Injection to Raised Beds to

>16 inch depth with water seal (320 lbs. a.i./A) June 13 6:50 am 45703704 Acceptable 2.39 7.45 percent through 96hours postapplication

Metam Sodium Helm, CA Sandy Loam Shank Injection to Raised Beds to 4 inch depth with soil seal (297 lbs. a.i./A) February 3 9:30 am 47131601 Acceptable 1.11 6.38 percent through 72hours postapplication

Metam Sodium Brawley, CA Flooded Application (320 lbs. a.i./A) September 15 12:05 pm 47314301 Acceptable 4.53 14.64 percent through 68hours postapplication

Metam Sodium Franklin County, WA Broadcast Shank

Injection to 9 inch depth with water seal (219.44 lbs. a.i./A) October 9 12:10 pm 47732801 Supplemental 1.39 9.68 percent through 94hours postapplication

Metam Sodium Mount Vernon, WA Clay Loam Broadcast Shank Injection (depth unspecified) with Soil Compaction (285.76 lbs. a.i./A) July 21 8:27 am 46379201 Finalized Classification Pending TBD TBDPage 22 of 79 Parent Chemical Applied Field Volatility Study (Application Rate) Time Applied MRID Study Classification
1 Peak Flux Rate 2,3 (  mass

loss) Cumulative Mass Loss 2 (% mass loss)

Metam Sodium Tifton, GA Loamy Sand

Virtually Impermeable Film Tarped Shank Injection to Raised Beds to 4 inch depth (712.6 lbs. a.i./A) February 7 4:30 pm 47820001 (Field 1) Finalized Classification Pending TBD TBD

Metam Sodium Tifton, GA Loamy Sand Polytarp Film Shank Injection to Raised Beds to 4 inch depth (728.9 lbs. a.i./A) February 7 4:30pm 47820001 (Field 2) Finalized Classification Pending TBD TBD

Metam Sodium Tifton, GA Sand Polytarp Film Shank Injection to Raised Beds to 4 inch depth (709.1 lbs. a.i./A) February 7 4:30pm 47820001 (Field 3) Finalized Classification Pending TBD TBD

Metam Potassium Duette, FL Sand Metalized Tarped

Shank Injection to Raised Beds to 4 inch depth (311 lbs. a.i./A) January 14 10:43 am 47813901 (Field 1) Finalized Classification Pending TBD TBD

Metam Potassium Duette, FL Sand Virtually Impermeable Film Shank Injection to Raised Beds to 4 inch depth (300.1 lbs. a.i./A) January 14 1:22 pm 47813901 (Field 2) Finalized Classification Pending TBD TBD

Metam Potassium Duette, FL Sand Metalized Tarped

Shank Injection to Raised Beds to 4 inch depth (305.8 lbs. a.i./A) January 14 4:03 pm 47813901 (Field 3) Finalized Classification Pending TBD TBD

Metam Sodium Coloma, WI Loamy Sand Broadcast Shank

Injection with water seal to 5.5 inch and 9.5 inch depths (287 lbs. a.i./A) September 25 10:27 am 48011601 (Field 1) Finalized Classification Pending TBD TBDPage 23 of 79 Parent Chemical Applied Field Volatility Study (Application Rate) Time Applied MRID Study Classification
1 Peak Flux Rate 2,3 (  mass

loss) Cumulative Mass Loss 2 (% mass loss)

Metam Sodium Coloma, WI Loamy Sand Broadcast Shank

Injection with water seal to 5.5 inch and 9.5 inch depths (270.1 lbs. a.i./A) September 25 8:15 am 48011601 (Field 3) Finalized Classification Pending TBD TBD

Metam Sodium Howard City, MI Loamy Sand Broadcast Shank

Injection to 12 inch depth with Soil Compaction (318.2 lbs. a.i./A) October 28 4:10 pm 48005901 (Field 1) Finalized Classification Pending TBD TBD

Metam Sodium Howard City, MI Sand Broadcast Shank

Injection to 12 inch depth with Soil Compaction and Water Seal (321.1 lbs. a.i./A) October 28 2:34 pm 48005901 (Field 2) Finalized Classification Pending TBD TBD

Metam Sodium Pasco, WA Sandy Loam Broadcast Shank

Injection to 9 inch depth with Soil Compaction (823.3 lbs. a.i./A) March 24 9:40 am 48115101 (Field 1) Finalized Classification Pending TBD TBD

Metam Sodium Pasco, WA Sandy Loam Broadcast Shank

Injection to 9 inch depth with Soil Compaction and Water Seal

(880.46 lbs. a.i./A) October 28 8:30 am 48115101 (Field 2) Finalized Classification Pending TBD TBD

Metam Potassium Modesto, CA Sandy Loam Drench Application with Water Seal (49.15 lbs.

a.i./A) August 20 7:30 am 47956701 Finalized Classification Pending TBD TBDPage 24 of 79 Parent Chemical Applied Field Volatility Study (Application Rate) Time Applied MRID Study Classification
1 Peak Flux Rate 2,3 (  mass

loss) Cumulative Mass Loss 2 (% mass loss)

Metam Sodium Prosser, WA Sandy Loam Center Pivot Chemigation with Water Seal (422 lbs. a.i./A) October 13 9:40 am – 2:05 pm 48467601 (Field 1) Finalized Classification Pending TBD TBD

Metam Sodium Prosser, WA Sandy Loam Center Pivot Chemigation with Water Seal

(633.33 lbs. a.i./A) October 13 3:10 pm – 6:23 pm 48467601 (Field 2) Finalized Classification Pending TBD TBD

Metam Sodium Prosser, WA Sandy Loam Center Pivot Chemigation with Water Seal

(623.53 lbs. a.i./A) October 13 9:55 pm – October 14

3:40 am 48467601 (Field 3) Finalized Classification Pending TBD TBD

Metam Sodium Prosser, WA Sandy Loam Center Pivot Chemigation with Water Seal (520 lbs. a.i./A) October 14 2:25 am – 5:35 am 48467601 (Field 4) Finalized Classification Pending TBD TBD

1. For studies with finalized classification pending, cursory review found studies adequate for risk

assessments. Finalized review with formal DER pending.
2 TBD means peak flux rates to be determined pending finalization of study reviews.
3 Peak flux rate refers to the average over ~ 4 hours as per the sampling periods in the field volatility studies. 

## 6. Receptors

Since metam sodium and metam potassium rapidly hydrolyze to MITC, and degrade by microbial degradation and by soil photolysis qui ckly, the toxicity data for MITC will be used to assess risk to fish, a quatic invertebrates, and aquati c plants. Terr estrial exposure to birds, mammals, invertebrates can occur by inhalation of MITC. Additionally, exposure to terrestrial plants can occur vi a MITC vapors or runoff exposure of MITC. Therefore, for aquatic and terrestrial organisms, toxicity data for only MITC will be considered. Table 7 and Table 8 provide a summary of the MI TC aquatic toxicity data and terrestrial toxicity data, respectively. Th e most sensitive species tested in each taxon is reported and will be used to characteri ze the potential acute and chronic ecological effects of MITC to terrestria l and aquatic organisms.Page 25 of 79 

### 6.1 Effects to Aquatic Organisms

Table 7. Summary of the most sensitive e ndpoints from aquatic toxicity studies for MITC (degradate of metam sodium and metam potassium)

Taxonomic

Group Study Type Surrogate Species Toxicity Value MRID and Classification Acute Toxicity Classification

Freshwater fish 1 Acute Rainbow Trout ( Oncorhynchus mykiss ) LC 50 = 94 μg a.i./L (slope = N/A) 42058002 Acceptable Very highly toxic

LC 50 = 53 μg a.i./L (slope = N/A) 45919420 Supplemental (due to (hydrolytic instability and insufficient sampling of the test chemical) Very highly toxic

Chronic (EarlyLifeStage) No data available

Freshwater invertebrates Acute Water Flea ( Daphnia magna ) EC 50 = 55 μg a.i/L (slope not available) 41819302 Acceptable Very highly toxic

Chronic Water Flea NOAEC = 25 μg a.i./L

LOAEC = >25 μg a.i./L (based on parental mortality and reproduction) 45634001 Supplemental (based on mean measured concentrations not determined, stability of chemical not assessed, terminal growth
measurements not obtained, two highest treatment concentrations excluded from analysis to reproduction endpoint due to 100% mortality) N/A

Estuarine/marine fish Acute Sheepshead Minnow ( Cyprinodon variegatus ) Study in review 48731101 Study in reviewPage 26 of 79 Taxonomic

Group Study Type Surrogate Species Toxicity Value MRID and Classification Acute Toxicity Classification

Estuarine/marine invertebrates Acute Eastern Oyster ( Crassostrea virginica ) Study in review 48985201 Study in review Saltwater mysid ( Americamysis bahia ) Study in review 48649301 Study in review

Aquatic plants and algae Vascular Duckweed ( Lemna gibba ) 7-day EC 50 (frond number) = 0.59 mg a.i/L

NOAEC (frond number and growth rate) = 0.09 mg a.i/L 45919421 Acceptable

Nonvascular 2 Freshwater Algae ( Scenedesmus subspicatus ) 96-hour EC 50
( cell density) = 0.2 mg a.i/L

NOAEC = 0.13 mg a.i/L 44588903 Supplemental

(non-guideline species used)

Freshwater algae Pseudokirchnerella subcapita (99 % a.i) 72-hour EC 50 (area under the curve)= 0.3 mg a.i/L (95% C.I = 0.26 – 0.34) NOAEC(cell density, growth rate, area under the curve) = 0.21 mg a.i/L 45919416 Supplemental

(72-hour
exposure instead of guideline recommended 96-hour
exposure conducted)

CyanobacteriaAnabaena flosaquae ( 99.6 % a.i.) 72 hour-EC 50 (cell density) = 1.5 mg a.i/L (95% C.I = 1.1 – 2.0) NOAEC (cell density, growth rate, area under the curve) = 5.0 mg a.i/L 45919422 Supplemental

(72-hour
exposure instead of guideline recommended 96-hour
exposure conducted)

Freshwater diatom Navicula pelliculosa (99.7% a.i) N/A 48733401 Study in reviewPage 27 of 79 Taxonomic

Group Study Type Surrogate Species Toxicity Value MRID and Classification Acute Toxicity Classification Marine diatom Skeletonema
costatum (99.7% a.i) N/A 48733501 Study in review

CyanobacteriaAnabaena flosaquae (99.7 % a.i.) N/A 48733601 Study in review Freshwater algae Pseudokirchnerella subcapita (99.7 % a.i) N/A 48733701 Study in review

1 Freshwater fish may be surrogates for aquatic-phase amphibians.
2 Several additional aquatic non-vascular plants studies have been submitted for MITC and are currently under review (MRIDs: 48733401, 48733501, 48733601, and 48733701).Page 28 of 79 

### 6.2 Effects to Terrestrial Organisms

Table 8. Summary of the most sensitive e ndpoints from terrestria l toxicity studies for MITC

Taxonomic

Group Study Type Surrogate Species Toxicity Value (all units in

terms of measured active ingredient) MRID and Classification Acute Toxicity Classification

Birds 1 Acute (Inhalation) Bobwhite quail ( Colinus virginianus ) Study in review 48788401 Study in review

Mammals Acute (Inhalation) Laboratory rat ( Rattus norvegicus ) 4 hour LC 50 = <0.0296 mg a.i/L 42365605 Acceptable

Acute (oral) Laboratory rat ( Rattus norvegicus ) 14-d LD 50 = 55 mg ai/kg bw 00162331 Acceptable

Insects Acute
contact Honey bee ( Apis mellifera L. ) No data available N/A --

Terrestrial plants Vegetative Vigor (Tier II) Various species Study in review 49058001 Study in review

Seedling Emergence Various species No data available N/A This study was previously waived (see USEPA, 2012)

1 Birds represent surrogates for terrest rial-phase amphibians and reptiles.



### 6.3 Ecological Incidents

A review of the Ecological Incident Information System (EIIS, version 2.1), the Aggregate Summary Module (ASM) (v.1.0) of Office of Pesticide Program’s Incident database maintained by the Information T echnology and Resource Management Division, and the Avian Monitoring Information System (AIMS) for ecologica l incidents involving MITC from metam sodium applications was completed. The results of this review for terrestrial, plant, and aquatic in cidents are discussed below.

Incidents from the EIIS Database:

Incidents are reported separately for MITC in the EIIS database. Metam sodium use has been linked to six reported adverse ecological incidents in aquatic systems from the EIIS system, which included mortality ( Table 9 ). Amphibians are not among the reported mortalities; however, this doe s not necessarily mean that they have not occurred. No aquatic or terrestrial incidents for MITC were reported in the EIIS database.Page 29 of 79 Table 9. Reported aquatic ecological incidents for metam sodium.

EIIS Incident No. (Date) Location Species
Affected Magnitude of Effect (number of organisms) Incident Summary Certainty Index

I006515- 001 (01 June 1991) Sacramento River, CA Fish 1,000 A railroad tank car spill in which thousands of fish (as well as most insects and some plants) were killed in a 42-mile stretch of the Sacramento River in California in 1991. While not representative of agricultural applications, this incident shows clearly that metam-sodium has the ability to kill large numbers of aquatic organisms if the chemical gets into water in large quantities. (3) Probable

I005525- 016 (July 17 1991 ) Sacramento River, CA Trout, suckers, squawfish and sculpin

and other fish 1,000 This incident report is a summary report only, but cites the death of over 1000 fish, including trout, suckers, squawfish, and sculpin in Siskiyou and Shasta counties in California in 1991. It very likely refers to the same railroad tank car spill cited above. It provides the additional information of fish species involved.
I012648- 001 (Nov 1 1994) St Johns, FL Fish Unknown This incident report involved a phone call in which a Florida fish farm representative claimed that the use of metam-sodium nearby resulted in several fish kills from 1994 - 2001. (2) Possible

I008259- 001 (December

23 1998) Hastings, FL Bass 2,700 This incident report under 6(a)(2) (from a registrant) cites a claim from a Florida fish farm owner that 2700 hybrid bass were killed after metam-sodium was applied within 300 feet of the fish tanks. The owner suspected that drift occurred (i.e., of MITC, the toxic degradate of metam-sodium that off-gasses) and that his aerationsystem picked it up and redissolved it into the fish tanks. Also cited in the report is a pump malfunction that apparently interrupted water and oxygen circulation. (2) PossiblePage 30 of 79 EIIS Incident No. (Date) Location Species
Affected Magnitude of Effect (number of organisms) Incident Summary Certainty Index

I008275- 003 (Nov 30 1998) NR Fish NR This incident report under 6(a)(2) (from a registrant) cites a reported pond contamination anda fish kill following metamsodium application. There was no report of application method or if there was a misapplication. Very few details were provided, although it states that USFWS was notified when the incident occurred. (2)
Possible

I011162- 001 (Jan 6

2001) Hastings, FL Bass >400 This incident report under 6(a)(2) (from a registrant) cites a claim from a Florida fish farm owner that approximately 400 stripedbass were killed after metamsodium was applied within about 600 feet of the fish tank. Although reportedly most of the tanks receive air from a common source, mortality was reported in only one of 94 tanks (1)
Not probable

The aquatic incidents reported in this assessm ent include agriculture applications based on the conceptual model. The incidents I 012648-001 and I008259-001 report applications to adjacent areas with drift impacting fish. Th e distances reported vary from 300 feet to 1⁄4 mile. These reports were assigned an uncertainty index of possible (2 out of 4). Both of these reports fail to provide sufficient inform ation to exclude other causes for the fish mortality and therefore are not used in the asse ssment. However, since fish tanks at fish farms were impacted, it is unlikely that the in cidents occurred as a result of runoff of MITC residues. In addition, a recent newspape r article in the Tribune Weekly Chronicle (October 5, 2010) reported that small levels of MITC were detected in a canal in the Sonoran Desert town of Holtville, CA. A dditional details were provided by Nelson Perez of the County of Imperial Office of the Agriculture Commissioner (Personal Communication).The levels of MITC were attributed to cases of human exposure and a fish kill in the area possibly associated w ith metam sodium applications in the region which occurred throughout late September and early October 2010. MITC was detected at a level of 1.62 μg/L (Nelson Perez, Count y of Imperial Office of the Agriculture Commissioner, Personal Comm unication). The resulting RQ=0.03 for both fish and Daphnia would indicate a “No Effect” determ ination. There is uncertainty regarding when measurements were taken relative to th e suspected application and in the distance from the source of release to the measurement si te. This incident report is not available in the EIIS database at this time.

There are several other incidents which are no t tied to the agricultural use of metamPage 31 of 79 sodium, metam potassium, or MITC. I005525- 016, the tank car spi ll incident, does not reflect an agricultural labele d use or method of applicati on. Incident I008275-003 did not include extensive information in the report. The county or state was not identified, and the number of dead fish and the application method or if this was a misapplication was not reported. Incident I011162-001 was assi gned certainty inde x assigned, of 1, indicating a classificat ion of not probable.

Table 10 shows five terrestrial incidents report s involving metam sodium included in the agency’s Ecological Incident Information Syst em (EIIS) database. They have certainty indices ranging from 1 (unlik ely) to 4 (hi ghly probable).

Table 10. Adverse terrestrial ecol ogical incidents for metam sodium. EIIS Incident No. (Date) Location Species Affected Magnitude of Effect Incident Summary Certainty Index
I011510- 001 (12 November 1999) Bullard, TX Pine 30 acres This incident report under 6(a)(2) (from a registrant) cites an incident in which 30 acres of pine seedlings in Texas were alleged to be damaged by drift (presumably of MITC) from a metam-sodium application in which no water seal was used. (3) Probable

I011838- 056 (22 May 2001) Robersonville River, NC Peanuts 80 acres This incident report under 6(a)2 cites an incident in which 80 acres of peanuts were damaged in North Carolina. Metam sodium was one of five products applied (2) Possible

I012457- 005 (22 May 2001) Robersonville River, NC Peanuts 120 acres This incident report under 6(a)(2) (from a registrant) cites an incident in which 120 acres of peanuts were damaged in North Carolina. Metam-sodium was apparently one of two pesticides applied. (2) Possible

I014405- 002 (23 May 1996) Grant County, WA Potato NR This incident reported in the Washington State Department of Health 1997 Annual Report. Misapplication of metam sodium damaged potato crop. Complaint was withdrawn. (2) Possible

I016107- 001 (23 September 2004) Broad Brook,CT Spruce and Cherry
trees Several A complaint was received by the State of Connecticut Department of Environmental Protection citing damage to spruce trees as well as a cherry tree. (2) Possible

Incident I016107-001 reported application on ac cording to label instructions with a certainty index of 2 (possible) . This demonstrates the possi ble adverse effect of MITC exposure from metam sodium applications to ve getation or crops off-site treated fields. No distance off the treated field was reported, the application rate of metam sodium usedPage 32 of 79 and the concentration of MITC was not repor ted, and no other pesticide use was reported. Incidents I011510-001 and I014405-002 were not used in this assessment due to misapplication of metam sodium. Both I011838-056 and I012457-005 reported use of multiple pesticides. No percentages of the mixture were reported.

Incidents from the AIMS Database:

Bird incidents for metam sodium and MITC were reviewed in the Avian Incident Monitoring System (AIMS). No avian inci dents for metam sodium or MITC were reported in the AIMS database.



## 7. Exposure Pathways of Concern

Conventional Uses

Given MITC’s volatile and soluble physical ch emical properties, broad spectrum mode of action as a fumigant, application methods, and application to soil at most once per year, the following lists the pathways of exposure anticipated for MITC associated with metam sodium and metam potassium applications:

 Inhalation exposure for mammals, birds, and terrestrial invertebrates (honey bee) (acute)

 Air exposure for plants (full-grown)

MITC has been shown to escape to the atmos phere from soil in larg e quantities over short time frames close to the time of application from the collection of field volatility studies from metam sodium and metam potassium applications submitted to the Agency. Despite previous risk assessments not showi ng risk due to MITC exposure, more recent field volatility studies will be utilized to evaluate MITC ai r exposure to mammals, birds, plants, and terrestrial inverteb rates. For mammals, bird s and terrestrial organisms, chronic exposure may occur due to repeat exposure of applied fumigants from multiple applications across an airshed. Since meta m sodium and metam potassium are expected to rapidly convert to MITC in the environment, spray drift is not expected to be of concern for terrestrial organisms. In addi tion, MITC vapor-phase exposure to plants will only be evaluated as it is e xpected to be the dominate e xposure route compared exposure of MITC dissolved in runoff water.

 Soil exposure for plant seedlings (acute)

MITC exposure to plant seedlings is expect ed from metam sodium and metam potassium applications off the treated field. MITC’s broad spectrum mode of action as a fumigant, metam sodium and metam potassium large appl ication rates to soil, and the mobile and diffuse nature of MITC as a vapor in so il all justify this e xposure pathway.Page 33 of 79  Aquatic exposure for freshwater fish, estuarine marine organisms, aquatic invertebrates, and aquatic plants (acute and chronic)

Although not the dominant route of exposure, MITC aquatic exposure can occur from metam sodium and metam potassium soil applica tions. When rain events occur close to the time of metam sodium and metam potassi um applications, the large amounts of MITC that is present on the field can dissolve and runoff to neighboring water bodies. Infiltration and runoff of MITC may occur particularly with un tarped applications. It is important to note that only runoff will predicate exposure to aquatic organisms for soil uses. Since MITC is the primary stressor of concern and conversion from metam sodium and metam potassium occurs rapidly beneath the soil, the spray drift contribution to aquatic exposure is not of c oncern. MITC discharges to wa ter bodies from sewer uses for root control will also be evaluated.

A train derailment resulted in a metam sodium spill over the Sacramento River in 1991. Up to 27,000 kg of metam sodium was released into the river. MITC was detected transporting downstream about 40 miles from th e derailment site to the inlet of Lake Shasta where monitored concentrations of up to 5,800 ppb were detected two days after the spill (CALDPR, 1991). This demonstrat es that 1.) though not resulting from a pesticide application, there is a potential for MITC from pe sticide applications to be transported into a nearby watershed from a re lease site and 2.) that significant quantities of MITC may remain in water long enough for acute exposure to occur. Based on a time series of monitoring data at the inlet to Lake Shasta, a DT50 value of 3.75 hours was calculated. It is important to note that this short DT50 may be due to volatilization of MITC as well as due to flow through the in let into Lake Shasta . The CALDPR report concerning the train derailment leading to the metam sodium spill to the Sacramento River and resulting dissipation analysis usi ng the monitoring data at Lake Shasta is provided in Appendix A

. MITC is shown to dissipate significantly over time in the water column. An inspection of previous PRZM/EXAMS modeling indicates that MITC in the receiving water body from runoff volatilizes to very low levels (< 0.1 ppb) between 15 – 30 days as controlled by Henry’s Law Constant. However, laboratory st udies show that volatilization from water for other fumigants with similar physical chem ical properties indica te that volatilization may occur at an even more rapid rate th an what Henry’s Law Constant shows.

A previously submitted chronic life cycle toxi city study to the freshwater invertebrate Daphnia magna MRID 45634001) shows that the NOEAC (for mortality and reproductive endpoints) was determined to be 25 μg a.i/L, based on initial nominal concentrations. However, given the high peak MITC aquatic exposure concentration possible and the short exposure duration for s ub-lethal adverse effects to occur, the lethality resulting from acute MITC peak e xposure concentrations will be the primary endpoint of concern. Therefore, a chronic early life stage test for freshwater fish is not being requested at this time.Page 34 of 79  Drinking water exposure for mammals and birds

While dietary and drinking water exposures are possible for mammals and birds, acute risk from inhalation is determined to be prim ary route of exposure for several reasons. For birds, based on MITC’s vapor pressure and calculations using STIR, the maximum 1- hour vapor inhalation dose for birds is 7914 mg/kg. By contrast, based on MITCs solubility limit and calculations using SIP, the upper bound daily drinking water intake dose for a bird is 6974 mg/kg bw. Multiplyi ng the STIR estimate of one hour by 12 (to match the daily exposure duration of the SI P estimate) yields 94968 mg/kg which is 2 orders of magnitude more than the SIP drinki ng water dose. For MITC, this suggests that the potential daily inhalation expos ure of a bird is substantiall y greater than the potential daily drinking water exposure of a bird indi cating that inhalation exposure may be of

more concern.
Additionally, acute oral and acute inhalation toxicity data are available for the laboratory rat (MRIDs 00162331 and 42365605, respectively). The acute inhalation study did not achieve a definitive toxicity endpoint with an inhalation LC 50 of <0.0296 mg/L. Using the STIR model, which es timates an inhalation LD 50 from an oral LD 50 endpoint, the rat inhalation LD 50 value would be 0.80 mg/L. Th is indicates that MITC is at least 2 orders of magnitude more toxic on an acute inhalati on basis than for an acute oral one (although this estimate is non-definitive as the rat inhalation study did not achieve a definitive endpoint).

Therefore, while the potentia l for drinking water exposure ex ists to birds and mammals, inhalation exposure is determined to be the one of primary concern for the terrestrial risk assessment. By being protective of bird s and mammals via the inhalation route of exposure, EFED believes that the dietary and drinking water routes of exposure will be protected as well.

 Dietary exposure for mammals and birds

Like drinking water exposure described above , inhalation exposure is expected to be the dominate exposure route for mammals and birds. First, residues are not expected to be present on crops due to pre-planting applic ation methods for metam sodium and metam potassium and plant back interval specified on the label. Second, once applied, birds and mammals are expected to be much more sensit ive to inhalation than to any ingested soil borne food material exposed to MITC. The dominance of the inha lation exposure over dietary exposure is confirmed by analys is comparing upper bound inhalation exposure dose to dietary exposure doses using STIR and the Earthworm Fugacity Model, respectively. This analysis is shown in Appendix E.

Antimicrobial Uses

The antimicrobial metam sodium uses for reme dial treatment of wooden poles may be of a concern, but the pesticide is inserted into a hole in the pole and th en is sealed off. Therefore, the environmental risk is minimal for this use.Page 35 of 79 The antimicrobial metam potassium use in pu lp and paper, and cooling water systems may trigger risk to aquatic ecosystems. In addition, there may be risks associated with aquatic exposure and air expos ure with animal waste product s treated with metam sodium and metam potassium. Other antimicrobial us es are considered as indoor uses, but may be discharged through storm drains. Therefore, these uses may also trigger aquatic risks.



## 8.

. Analysis Plan

The ecological risk assessment will focus on MI TC as the main stressor of concern for air, soil, and aquatic exposure. This determination is discussed further in Section 8.1 below. EECs will be calculated for air, soil , and water using various environmental fate and transport models discussed in Section 8.2 below. The EECs will be compared with toxicological endpoints from various aquati c and terrestrial taxa to quantitatively compute a risk quotient (RQ). The RQ will be compared to the Agency’s levels of concern (LOC) to determine th e risk to organisms resulti ng from MITC exposure from metam sodium and metam potassium applications.



### 8.1 Stressors of Concern

Table 5 and Table F-1 in Appendix F shows degradates which form in soil, water, and air resulting from the application of metam sodium and metam potassium and subsequent conversion to MITC in soil. Structural activ ity relationships (SARs) of the degradates and the resulting estimated toxicity endpoint values for various a quatic and terrestrial taxa were compared to MITC’s measured to xicity values to the same organisms to identify the toxic residues of concern. This analysis was conducted using ECOSAR version 1 (February 2, 2009) and is shown in Appendix B . Among the major degradates found in environmental fate studies, none have been identified as being potentially of toxicological concern compared to MITC. Therefore, MITC is considered the primary stressor of concern in the ecological risk assessment.



### 8.2 Measures of Exposure

Measures of exposure of MITC to the aquati c and terrestrial organisms are derived from the utilization of environmental fate and transport models. Section 8.2.1 and Section 8.2.2 describe the exposure estimation met hodology in the aquatic and terrestrial environments, respectively. Exposures to aquatic and terrestrial organisms will be estimated based on maximum application rate s and all application methods cited in Section 3 . MITC equivalent application rates will be calcul ated considering appropriate transformation scaling factors from environmen tal fate studies and the ratio of molecular weights from MITC to parent metam s odium or metam potassium. Please see Section 3 on the determination of appropriate MITC application rates by use.Page 36 of 79 

### 8.2.1 Estimating Exposure in the Aquatic Environment

The models used to predict aquatic EECs are the Pesticide Root Zone Model coupled with the Exposure Analysis Modeling System (PRZM/EXAMS) publically available at: http://www.epa.gov/oppefed1/models/water/pe5_user_manual.htm . The PRZM/EXAMS Georgia Farm Pond scenario will be used to estimate the aquatic EECs in surface water resulting from both soil fumigant and animal waste product uses. Since both surface chemigation and incorporated chemigation a nd injection application methods for metam sodium and metam potassium application exis t, two separate runs will be conducted for each crop scenario addressing the surface and incorporated applications. The PRZM volatilization algorithm will be us ed to address both MITC’s upward movement in soil to the runoff extraction zone and escape to the atmosphere.

The PDM module of EFAST model to estimat e the concentrations of metam sodium, metam potassium in water for use in paper and pulp and recalculating cooling water systems. Sewer root control uses and i ndoor uses requiring disc harges down drainage pipes will be addressed through the EFAS T using the DtD, and PDM modules for exposure determination.



### 8.2.2 Estimating Exposure in the Terrestrial Environment

MITC acute exposures of the birds, mammals, te rrestrial invertebrates, and plants through inhalation exposure for metam sodium and me tam potassium soil fumigant applications and treatment for animal waste products are determined using the EECs from atmospheric dispersion models. Consistent with the aquatic exposure assessment, the ecological risk assessment w ill assess two separate scenarios addressing surface and incorporated application of metam sodium and metam potassium. The Agency’s recommended screening dispersion mode l for the near field, the American Meteorological Society/EPA Regulatory Scre ening Model (AERSCREEN), will be used to generate Tier I EECs. The Tier I anal ysis will consider the maximum flux rate for each application method from the collecti on of MITC flux studies and worst-case meteorological conditions (light winds and st agnant conditions) to calculate peak air EECs, representing one-hour average c oncentrations. Documentation on the AERSCREEN model is available at http://www.epa.gov/scram 001/dispersion_screening.htm . The exposure scenario evaluated in the Tier 1 analys is will assume that the terres trial receptors are directly downwind from the emissions source. This is illustrated in Figure 3 below.Page 37 of 79 Figure 3. Schematic showing soil fumigant air exposure scenario due to volatilization and subsequent release from soil evaluated in Tier 1 analysis.

If the Tier 1 EECs for either surface or incorporated applications result in an exceedance with the LOC, EECs will be further examined using the Tier 2 model, the Probabilistic Exposure and Risk Model for Fumigants (PERFUM). PERFUM is parameterized by a time series of flux data obtained from field volatility studies. PE RFUM considers these flux values with a robust sta tistical sampling of meteorologi cal data from points within rings surrounding a treated field (usually 5 years of hourly meteorological data). The current version of PERFUM processes es timated air concentrations from EPA’s previously recommended atmospheric dispersi on model in the near field, the Industrial Source Complex Short-Range Model, Version 3 (ISCST3). The framework for PERFUM is illustrated in Figure 4 below. Estimated air conc entrations are calculated and binned by percentile distribu tions within each ring and aver aging time period. First, a peak one-hour averaging peri od will be used to calculat e air EECs. If necessary, a higher averaging period equivale nt to the exposure duration in toxicity studies will be used to characterize the RQs resulting from utilizing the one-hour peak EECs. The highest 90 th percentile estimated air concentration from all averaging periods from the receptor ring closest to the edge of the fi eld will be considered as the upper-bound EEC to determine the RQ. The PERFUM model is publically availabl e on the web from the follow link: http://www.exponent.com/projectdetail.aspx?project=450 . For this soil fumigant assessment, maximum air exposure will occur at the edge of the field corresponding to the where MITC mass emissions from the tr eated field will accumulate to maximum levels along the fetch of wind bl owing over the treated field. Wind, Dispersion, and Accumulation of Va p ors or Gas

Volatilization of residues in soil Soil incorporated and chemigation fumigant applicationPage 38 of 79 Figure 4. Illustration of the spatial and tempor al aspects of the source to receptor configuration in PERFUM. The wind rose (lef t) illustrates the frequency distribution of variations in wind speed and wind direction that PERFUM accounts for in the transport of the vapor plume from the treat ed source to receptors (right).

All modeling scenarios will be parameteri zed based on field volatility flux data normalized to an 80 acre field for drip chem igation applications and 120 acre field for overhead chemigation, shank injection, rotary t iller, and spray blade applications. Other applications such as center pivot chemigation, can be applied to larger areas over multiple days. Therefore, a separate scenario will account for MITC emissions occurring within a circular field over areas which increa se over time as treatment occurs.

For exposure to plant seedlings , TerrPlant will be used. Although TerrPlant EECs are based on runoff, TerrPlant will capture the ov erall exposure of plant seedlings whether it occurs from diffusion in the gas phase or r unoff of dissolved MITC. Terrplant EECs can only be calculated at th e edge of the field.



### 8.3 Measures of Effect

Toxicity data presented in Sections 6.1 and 6.2 of this problem formulation will be used with EECs to calculate risk quotients. Any additional information submitted by the registrant or found in the open literature prior to conducting th e risk assessment will also be considered. The open literature studies are identified using EPA’s ECOTOXicology database (ECOTOX) (USEPA, 2007 c ), which employs a literature search engine for locating chemical toxicity data for aquatic life, terrestrial plants, and wildlife. The evaluation of both sources of data can also pr ovide insight into the direct and indirect efects of pesticides on biotic communities fr om loss of species that are sensitive to the chemicals and from changes in structure and functional characteristics of the affected communities. Treated Field Receptor RingsPage 39 of 79 

### 8.4 Endangered Species Assessments

Consistent with the Agency’s responsibility under the Endangered Species Act (ESA), the Agency will evaluate risks to federally th reatened and/or endangered (listed) species from registered uses of pesticides in registration review. These assessments will be conducted in accordance with standard EPA procedures.. 

### 8.5 Endocrine Disruptor Screening Program

Metam sodium, metam potassium and MITC we re not included in the first group of 67 chemicals issued an order to conduct Tier 1 EDSP testing. For additional information the EDSP program, visit http://www.epa.gov/endo/

. 

### 8.6 Drinking Water Assessment

For soil fumigation, runoff of MITC to reserv oirs after rain even ts may occur shortly after soil treatments given the option for unt arped application methods of metam sodium and metam potassium,. In addition, leaching of MITC to ground water and wells nearby treated fields are possible due to MITC’s hi gh water solubility. The relative importance of MITC drinking water dosing concentrati ons with MITC inhalation doses resulting from metam sodium and metam potassium applic ation will be determined. As a result of this determination, drinking water assessm ents addressing metam sodium and metam potassium applications will be conducted on an as needed basis. In case that a drinking water assessment is conducted, the PRZM-GW model accounting for volatility from soil will be used to calculate the EDWCs.

For sewer root control uses, there is reportedly (Martyn, P., 2004) a contaminant (NDMA, nnitrosodimethylamine) in the Vapor ooter product for which there is a National Recommended Water Quality Criteria of 0.00069 

### : g/L (current/potentia l drinking water) and 3.0 

### : g/L (no potential for drinking water). Any water quality data for NDMA and MITC submitted at the discha rge point in sewage treatmen t plants where MITC use in sewers occurs will also be considered in any drinking water assessment.

Drinking water exposure of parent compounds metam sodium and metam potassium are not expected due to the large transf ormation of these compounds to MITC (transformation fraction = 83 percent) and tr ansformation of the parent compounds in the environment to MITC (half life = 23 minutes). 

## 9 Preliminary Identification of Data Gaps

9.1 Environmental Fate

Table 11 and Table 12 identify environmental fate studies for metam sodium and MITC, respectively, by MRID that offer data for each guideline requirement, as well asPage 40 of 79 study classifications and whether or not furthe r data are needed in order to support risk
assessment.

Table 11. Submitted and requested environm ental fate data for metam sodium.

OCSPP Guideline Data Requirement Submitted Studies (MRID) Study Classifications Are data needed to conduct

risk assessment? Current Additional Data Need

835.2120 Hydrolysis 4163 1101 Acceptable No -- 835.2240 Aqueous photolysis 41517701 Acceptable No --

835.2410 Soil photolysis 42978701 Supplemental No --
835.4100 Aerobic soil metabolism 40198502 Acceptable No --

835.4200 Anaerobic soil metabolism (None) (Not applicable) No --

835.4300 Aerobic aquatic metabolism (None) (Not applicable) No --

835.4400 Anaerobic aquatic metabolism (None) (Not applicable) No --

835.1230 835.1240 Adsorption/ desorption and leaching (None) (Not applicable) No --

835.1410 Volatility – laboratory (None) (Not applicable) No --

835.6100

850.6100 Terrestrial field dissipation 41514401 Supplemental No -- 41514402 Supplemental Analytical method in soil (None) (Not applicable)

835.8100

850.6100 Volatility - Field (None) (Not applicable) No --

Analytical method in air (None) (Not applicable)

835.6200

850.6100 Aquatic field dissipation (None) (Not applicable) No --

Analytical method in water (None) (Not applicable)

850.1730 Fish bioconcentration (None) (Not applicable) No --

A Metam potassium is expected to possess similar envi ronmental fate properties since it is an analogue salt

of metam sodium.
B All studies were conducted with metam sodium as the test substance and provided information on

environmental degradation of metam sodium.Page 41 of 79 Table 12. Submitted and requested environm ental fate data for MITC from metam sodium/potassium pre-plant soil products..

OCSPP Guideline Data Requirement Submitted Studies (MRID) Study Classifications Are data needed to conduct risk assessment? Current Additional Data Need

835.2120 Hydrolysis 0015 8162 Acceptable No -- 835.2240 Aqueous photolysis (None) (Not applicable) No --

835.2410 Soil photolysis (None) (Not applicable) No --

835.4100 Aerobic soil metabolism (None) (Not applicable) No

-- 835.4200 Anaerobic soil metabolism (None) (Not applicable) No --

835.4300 Aerobic aquatic metabolism 4 (None) (Not applicable) Yes A laboratory aquatic study is needed to determine MITC’s residence time in
water. 835.4400 Anaerobic aquatic metabolism 43596501 Supplemental No --

835.1230 835.1240 Adsorption/ desorption and leaching (None) (Not applicable) No --

835.1410 Volatility – laboratory (None) (Not applicable) No --

835.6100 Terrestrial field dissipation (None) (Not applicable) No --

Analytical method in soil (None) (Not applicable)

835.8100 Volatility - Field 45703702 45703704 47131601 47314301 47732801 48552102 48552101 47956901 45703708 45703701 46969601 46379201 47820001 47813901 48011601 48005901 48115101 47956701 48467601 Acceptable Acceptable Acceptable Acceptable Supplemental Supplemental Supplemental Supplemental Supplemental Supplemental Supplemental Supplemental Supplemental Pending Pending Pending Pending Pending Pending No --Page 42 of 79 OCSPP Guideline Data Requirement Submitted Studies (MRID) Study Classifications Are data needed to conduct risk assessment? Current Additional Data Need

860.6100 Analytical method in air (None) (Not applicable) Yes Environmental chemistry methods (ECMs) and independent laboratory validation (ILVs) are needed to support all methods used in each MITC field volatility study. 835.6200

850.6100 Aquatic field dissipation (None) (Not applicable) No -

Analytical method in water (None) (Not applicable) Yes Although MITC is volatile in water, an ILV/ECM in water is needed because of MITC’s high acute aquatic toxicity and its potential to reach surface water.

850.1730 Fish bioconcentration (None) (Not applicable) No --

1. For studies with finalized classification pending, cursory review found studies adequate for risk

assessments. Finalized review with formal DER pending.
2. With the exception of field volatility studies, all stud ies were conducted with MITC as the test substance

and provided information on the environmental degradation of MITC in the environment.
3. Field volatility studies were conducted with either metam sodium or metam potassium as the test

substance (see Table 5 for further details). MITC flux is measured in all field volatility studies.
4 The aerobic aquatic laboratory study for MITC is being requested to address both conventional and

antimicrobial uses of metam sodium and metam potassium.

835.4300: Aerobic Aquatic Metabolism: MITC

An aerobic aquatic metabolism study with MITC as the test substan ce is being requested at this time. This study will enable the de termination of MITCs residence time in water to address the potential of MITC to reach water sheds and water bodies adjacent to fields treated with metam sodium and metam potassium. The DT 50 and residence time from this study will be used quantitatively in PRZM/EXAMS surface water acute EEC calculations. Since volatilization is expected to be the dominate loss route and that sorption to sediment is expected to be mi nimal, this study should only address measuring MITC concentrations in water and in the headspace. Howe ver, known degradates should be quantified to recover and track the comple te material balance over the course of the study.

850.6100: Environmental Chemistry Methods (ECMs)/Independent Laboratory Validation (ILVs) in Air and Water: MITC

There are no ECMs or ILVs available for a ny of the MITC field volatility studies. Therefore, ECMs and ILVs for air should be submitted to support the field volatility studies. In addition, although MI TC is volatile, an ECM and ILV is being requested for water since it is highly toxic on an acute basis and it may reach water bodies at a veryPage 43 of 79 large initial level. The ECM and ILV in wa ter will help validate the aerobic aquatic study that is also bei ng requested for MITC.



### 9.2 Effects

Table 13 and Table 14 identify ecological effects studies by MRID that offer data for each guideline requirement, as well as study classifications and wh ether or not further data are needed in order to support risk a ssessment. Rationale for the additional data requested is presented below the tables.

The adequacy of the current toxicity data submitted to assess MITC will largely depend on the review of recently submitted data that were submitted in response to a RED data call-in (DCI). These studies are listed as ‘in review’ in the follo wing tables. If these studies are found to be adequate for use in risk assessment, EFED recommends requesting the following studies to assess the environmental ri sks associated with the use of MITC: a honey bee vapor exposure study with MITC and a terrestrial plant seedling emergence study with MITC. The justificati ons for recommending the request of these studies are provided below.

Table 13. Submitted and requested aquati c ecological effect s data for MITC.

OCSPP Guideline Data Requirement Submitted Studies (MRID) Study Classifications Are data needed to conduct

risk assessment? Current Additional Data Need

850.1010 Freshwater invertebrate acute toxicity 41819302 Acceptable No -- 45919419 Supplemental

850.1025 850.1035 850.1045 850.1055 Saltwater invertebrate acute toxicity 48985201 In review

Yes Depending on the results of the review of the recently submitted study. 48649301 In review

850.1075 Freshwater fish acute

toxicity 44523412 Acceptable

No -- 44523413 Acceptable 45919420 Supplemental

850.1075 Saltwater fish acute toxicity 48731101 In review Yes Depending on the results of the review of the recently submitted study.

850.1300 Freshwater invertebrate

life cycle 45634001 Supplemental No --Page 44 of 79 OCSPP Guideline Data Requirement Submitted Studies (MRID) Study Classifications Are data needed to conduct

risk assessment? Current Additional Data Need

850.1350 Saltwater invertebrates

life cycle (None) (N/A) No

850.1400 Freshwater fish early-life

stage (None) (N/A) No MITC shown to dissipate rapidly from the water column. See Section 7

.

850.1400 Saltwater fish early-life

stage (None) (N/A) No --

850.1500 Fish life cycle (None) (N/A) No --

850.4400 Aquatic plant growth: Tier II vascular

plants 45919421 Acceptable No --

850.5400 Aquatic Plant Growth: Tier II algae 44588903 Supplemental

Yes Depending on the results of the review of the recently submitted study. 45919416 Supplemental 45919422 Supplemental

48733401 In review

48733501 In review

48733601 In review

48733701 In review N/A = Not applicable

Table 14. Submitted and requested terrestr ial ecological effect s data for MITC.

OCSPP Guideline Data Requirement Submitted Studies (MRID) Study Classifications Are data needed for risk assessment? Current Additi onal Data Need

850.2100 Avian oral toxicity (None) (N/A) No

Nonguideline Avian inhalation

toxicity 48788401 In review Yes Depending on the results of the review of the recently submitted study.

850.2200 Avian dietary toxicity (None) (N/A) No --

850.2300 Avian reproduction (None) (N/A) No --Page 45 of 79 OCSPP Guideline Data Requirement Submitted Studies (MRID) Study Classifications Are data needed for risk assessment? Current Additi onal Data Need

850.3020 Honey bee
acute contact toxicity 00018842 Acceptable No --

850.3030 Honey bee residue on

foliage (None) (N/A) No --

Nonguideline Acute honey bee vapor exposure study (None) (N/A) Yes This study is needed to quantitatively determine risk to terrestrial

invertebrates.

850.3040 Field testing for pollinators (None) (N/A) No --

850.4100 Terrestrial plant toxicity: Tier II seedling

emergence 41280801 (N/A) Yes The requirement was previously waived (see USEPA 2012, D395875);

however, upon further

evaluation, it was determined that exposure to MITC via runoff is a potential risk concern.

850.4150 Terrestrial plant toxicity: Tier II vegetative

vigor 49058001 In Review Yes Depending on the results of the review of the recently submitted study.

N/A = Not applicable

Non-Guideline Study: Acute honey b ee vapor exposure study with MITC

As discussed further in this assessment, i nhalation exposure is determined to be the primary route of exposure for the terrestria l risk assessment. Inhalation studies are available for mammals (MRID 41277004) a nd birds (MRID 48788401) and given the volatile nature of MITC, inha lation risk would also be applicable to terrestrial invertebrates using the honey bee as a surroga te. A protocol should be submitted to the Agency for review prior to conducting the st udy. See the justificat ion table below for more information.

850.4100: Tier I/II Seedling Emergence Study: MITC

Section 7 of this assessment details the exposur e pathways for MITC. Included in these pathways is one of soil exposure to plant seed lings on and off the treated field. The broad spectrum mode of action of MITC, the large application rates of metam sodium and metam potassium, and mobile and diffuse nature of the MITC as a vapor in soil justifyPage 46 of 79 this exposure pathway. The guideline study method will adequately capture the effects occurring from MITC movement off-site result ing either from runoff in the dissolved phase or diffusion in the gas phase. Guideline Number: N/A (Non

‐ Guideline Study) Study Title: Acute Honey Bee Vapor Exposure Study Rationale for Requiring the Data Due to the fate properties of fumigants, in particular their high volatility, it is expected that honey bees and other insect pollinators will be exposed to fumigants in the vapor phase. Neither of the standard Tier I toxicity studies with honey bees ( i.e., acute contact

or acute oral toxicity study for honey bees) account for exposure to vapor phase pesticides. Therefore, to assess risks of MITC to bees, EFED recommends that the Agency require a non

‐ guideline acute honey bee vapor exposure study for MITC, to be conducted in lieu of the normally required acute honey bee contact study that would fulfill guideline 850.3020 and the newly proposed requirements for oral toxicity tests including adult and larval honey bees. Practical Utility of the Data How will the data be used? Data from an acute honey bee vapor exposure study will be used to determine the potential for MITC to affect non

‐ target terrestrial invertebrates in the terrestrial environment. Of particular interest is quantification of a toxicity endpoint, i.e., a 4

‐ hour LC50, that can be used to derive risk quotients. In the absence of vapor exposure data specific for honey bees, risk to terrestrial invertebrates, including listed species, will be assumed.

How could the data impact the Agency’s future decision

‐ making? If future ecological risk assessments are performed without these data, the Agency would have to presume risk to non

‐ target terrestrial invertebrates, including honey bees, from use of MITC. Therefore, use of MITC and its formulated products may need
to be restricted in areas where terrestrial invertebrates, including honey bees, could be exposed. The lack of these data will limit the flexibility the Agency and registrants have in mitigating potential risks and could result in use restrictions for MITC that are unnecessarily severe.Page 47 of 79 

### 9. 

## References

Alvarez, R. and C.B. Moore. 1994. Quantu m yield for production of CH3NC in the photolysis of CH3NCS. Science263: 205-207.

ARB, 1997. Ambient air monitoring for MIC and MITC after a soil in jection application of metam sodium in Kern County duri ng August 1995. Test Report No. C94-046, May 20, 1997. Air Resources Board, Sacramento, CA.

ARB, 1999. Lompoc pesticide monitoring progra m-phase I; System evaluation report of Trace Analytical Laboratory, University of Ca lifornia, Davis; Center for Environmental Sciences and Engineering, Un iversity of Nevada, Reno; and Inorganics Laboratory Section, Air Resources Board. March 3, 1999. Monitoring and Laboratory Division, Quality Assurance Section, Air Resources Board, Sacramento, CA.

Ashley, M.G., B.L. Leigh, and L.S. Llyod. 1963. The action of metam sodium in soil. II. Factors affecting removal of methyl isothiocya nate residues. J. Sci. Food Agric. 14: 153- 161.

Boesten, J.J.T.I., L.J.T. Van Der Pas, J.H. Smelt, and M. Leistra. 1991. Transformation rate of methyl isothiocyanate and 1,3-dich loropropane in water-saturated sandy subsoils. Netherlands Jour. of Agric. Sci. 30: 170-190.

CDPR (California Dept. of Pesticide Regulation). 2002. Evaluation of Methyl Isothiocyanate as a Toxic Air Contaminan t, Part A-Environmental Fate. California Environmental Protection Agency, Sacramento, CA.

Cremlyn, R.J. 1991. Agrochemi cals: Preparation and Mode of Action. p. 283-307. John Wiley and Sons. New York, NY.

Dungan, R.S. and S.R. Yates. Degrad ation of fumigant Pesticides. 2003. 1,3- Dichloropropane, methyl isothiocyanate, a nd methyl bromide. Vodose Zone Jour. 2: 279- 286.

Geddes, J.D., G.C. Miller, and G. E. Tayl or Jr. 1995. Gas phase photolysis of methyl isothiocyanate. Environ. Sci. Technol. 29:2590-2594.

Gerstl, Z., U. Mingelgrin, B. Yaron. 1977. Beha vior of Vapam and Methylisothiocyanate in soils. Soil Sci. Soc. Am. J. 41: 545-548.

Martyn, P. 2004. 7/27/04 Letter to Metam-Sodi um Docket. County Sanitation Districts of Los Angeles County.Page 48 of 79 Segawa, R.T., S.J. Marade, N.K. Miller, and P.Y. Lee. 1991. Monitoring of the Cantara metam-sodium spill. Environmental Hazards Assessment Program, Report Number EH 91-09. Department of Pesticide Regulation. Sacramento, CA.

Seiber, J.N., J.E. Woodrow, R.I. Krieger, a nd T. Dinoff. 1999. Determination of ambient MITC residues in indoor and outdoor air in townships near fields treated with metam sodium. June 1999. Amvec Chemical Corporation, Newport Beach, CA.

Smelt, J.H., S.J.H. Crum, and W. Teini ssen. 1989. Accelerated transformation of the fumigant methyl isocyanate in soil after repeated application of metam sodium. J. Environ. Sci. Health B24: 437-455.

Tomlin, C.D.S. (ed.) 1997. The Pesticide Manual. Eleventh Ed. P 335-339. British Crop Protection Council, Surrey, GU9 7PH, UK

U.S. EPA, 2005. Overview of the use and us age of soil fumigants. Biological and Economic Analysis Division. Office of Pesticide Programs. Washington, D.C.

U.S. EPA. 2009. Amended Reregistration Eligibility Decision (RED) for the Methyldithiocarbamate Salts (Metam sodium, Metam-potassium) and Methyl Isothiocyanate (MITC). Office of Pesticide Programs. Washington, D.C.

USEPA, 2012. Screening Level Estimates of Agricultural Uses of Metam Sodium. Office of Pesticide Programs. Washington, D.C.

Warton, B. and J.N. Matthiessen. 2000. Enhan ced biodegradation of metham sodium soil fumigant in Australia. Proc. BCPC C onf.-Pest and Diseases 4C-4:377-380.

Wofford, P.L., K.P. Bennett, J. Hernandez, and P. Lee. 1994. Air monitoring for Methyl isothiocyanate driung a sprinkler applica tion of metam sodium. Report No. EH 94-02, Environmental Hazards Assessment Program, De pt. of Pesticide Regulation, Sacramento, CA.Page 49 of 79 

### Appendix A - California Depart ment of Pesticide Regulation

Report on Train Derailment and Metam Sodium Release to Sacramento River and MITC Dissipation AnalysisSlAlE OF CALIkORNIA

. ENVIRONMENTAL PHOTECTION AGENCY PETE WILSON, Governor 

### DEPARTMENT 

### OF PESTICIDE 

## REGULATION

EXECUTIVE SUMMARY 

### Of 

### Report EH-91-8 Entitled "Monitoring 

### of the Cantara Metam-Sodium Spill" 

### Environmental Monitoring and Pest 

### Management Branch Department 

### of Pesticide Regulation

On July 14, 

### 1991, a 

### railroad 

### car derailed 

### north of Dunsmuir, California, releasing 49,000 to 72,000 

### liters (13,000-19,000 gallons) 

### of metam-sodium into the 

### Sacramento River. Metam-sodium 

### is the active ingredient in 18 pesticide products registered in California. Metam-sodium 

### is 

### a soil fumigant effective against weeds, 

### soil diseases, 

### nematodes and insects. The product that 

### was spilled is 

### 32.7% metam-sodium in an inert ingredient that 

### is not of toxicological concern. The 

### principal breakdown product, methyl isothiocyanate (MITC), 

### causes 

### most of the pesticidal activity. Breakdown to MITC 

### in 

### normal use situations occurs very rapidly, within a 

### few hours.

Since the 

### release of metam-sodium into the Sacramento River 

### was caused by an accident during transport and not by 

### its use 

### as a pesticide, the 

### Department of Pesticide 

### Regulation of the 

### California Environmental Protection Agency does 

### not have regulatory oversight. However, because of the Department's experience in monitoring the environment for pesticide 

### residues, 

### Department personnel from the Environmental Monitoring :and Pest 

### Management Branch 

### were asked to assist other state 

### and federal agencies 

### in documenting the 

### changes in concentrations of MITC 

### in the waters of Shasta Lake 

### at 

### two sampling sites from July 16 

### through July 23, 1991.

Studv:



### Water samples 

### were collected 

### at two 

### sites in Shasta Lake 

### twice daily, 

### in the 

### morning and evening, for eight days. After 

### this, 

### other agencies continued monitoring 

### at these 

### sites. The 

### northernmost site 

### was a 

### boat launching 

### area at Antlers Campground located on the 

### Sacramento River inlet to Shasta Lake, 62 

### kilometers (39 miles) downstream of the 

### spill. 

### The other 

### was located 

### at the Centimudi Boat Ramp approximately 800 meters (875 yards) northeast of Shasta Dam, 87 kilometers (54 

### miles) downstream of the spill, and 24 

### kilometers (15 

### miles) south 

### of the sampling 

### site 

### at Antlers Campground.
Samples 

### were analyzed for MITC 

### by two laboratories: Chemistry Laboratory Services of the 

### California Department of Food and Agriculture, and a 

### private laboratory, the Agricultural and Priority Pollutants Laboratory (APPL), 

### Inc. 

### In normal use, metam-sodium would not be 

### expected to enter surface water: therefore, neither 

### laboratory 

### was experienced in analyzing for either 

### metam-sodium or 

### its 

### breakdown product, MITC. 

### This meant that 

### special care had 

### to be 

### taken in collecting samples and 

### in conducting the 

### analyses.

### Metam-Sodium Long 

### term 0.02 

### milligramdliter (mg/L) = 20 

### ppb 

### Short 

### term 0.35 mg/L 

### = 350 

### ppb

MITC 

### Long 

### term 0.05 

### mg/L 

### = 50 

### ppb Short 

### term 1.0 mg/L = 1000 

### ppb

Levels of MITC 

### in 

### the lake exceeded the 

### short-term action level for one day and the 

### long-term action level for 

### three days during the 

### eight-day sampling period. However, 

### water from the 

### Sacramento River from the 

### point 

### where the. spill 

### occurred to the 

### area above Centimudi Boat,Ramp in Shasta Lake 

### is not used for 

### drinking. In 

### addition, fishing (eating fish 

### would be 

### another source of exposure) 

### was not allowed 

### in Shasta 

### Lake from 

### July 22 

### to August 

### 5, 1991.



### Ronald 

### J, Oshima Branch Chief

-2- 

### October, 1991MONITORING 

### OF THE CANTARA METAM-SODIUM SPILL



### BY

R .T. Segawa' 

## , S. 

### J. Maradel, 

### N.K. Miller' and P 

### .Y. Lee2

September 

### 1991



# ' California Department of Pesticide Regulation, Environmental Hazards Assessment Program

California Department of Food and Agriculture, Chemistry Laboratory Services

### ABSTRACT

On July 14, 1991 

### a railroad car derailed at the Cantara Loop, north of Dunsmuir, California and spilled between 49,000 

### and 72,000 

### liters of 

### a product containing the pesticide metam-sodium (19,000 

## - 27,000 

### kg active ingredient) into the Sacramento River. This spill posed a threat to public health and the environment. Therefore, monitoring was conducted by several agencies including the California Department of Pesticide Regulation (CDPR). Most 

### of the pesticidal activity of metam-sodium is produced by its primary breakdown product methyl isothiocyanate (MITC).

In cooperation with the California Department of Fish and Game, the Environmental Hazards Assessment Program of CDPR collected surface water samples to help characterize the temporal distribution 

### of MITC residues in Shasta Lake, downstream of the spill. MITC water concentrations were monitored at Antlers Campground (62 km 

### downstream of 

### spill) and the Centimudi boat ramp 

### (87 km 

### downstream of spill) between July 16 

### and 23, 1991.



### MITC concentrations at the north end (closest to the spill) of 

### Shasta Lake at Antlers Campground reached 

### a maximum 

### of 5500 

### ppb three days after the spill. MITC levels decreased to 

### 8 ppb 

### six days later, 

### No MITC was detected at the Centimudi Boat Ramp located at the southern end of 

### Shasta Lake (detection limit 

### 5 ppb).

This monitoring alone 

### is not enough to assess the movement, dissipation and possible effects of the metam-sodium spill. When the data from all 

### monitoring groups are available, such an assessment will be possible.

i

### ACKNOWLEDGEMENTS

The authors wish to thank the hard-working members of the Environmental Hazards Assessment Program's field group and the the California Department of 

### Food and Agriculture Chemistry Lab's environmental monitoring section. Thanks 

### also to Linda Heath 

### for preparing the graphics and to the owners of 

### the Antlers Campground.

DISCLAIMER

The mention of 

### commercial products, their source or use in connection with material reported herein 

### is not to be construed 

### as an actual or 

### implied endorsement of 

### those products.

ii

### TABLE 

### OF CONTENTS

Page ABSTRACT



# .............................................................. i



### ACKNOWLEGEMENTS.



# ..................................................... ii



### DISCLAIMER


# ........................................................... ii



### TABLE 

### OF CONTENTS..



# ................................................. iii



### LIST 

### OF FIGURES



# ..................................................... iii



### LIST OF 

### TABLES



# ...................................................... iii



### INTRODUCTION



# .......................................................... 1



### MATERIALS AND METHODS .................................................3



### RESULTS AND DISCUSSION .................................,.,............5



### MONITORING 

### BY OTHER AGENCIES ......................................,,..g


### Appendix 1 

### - Environmental Fate 

### of Metam-Sodium

Appendix 2 

## - Chemical Analysis Methods

Appendix 

### 3 

## - Quality Control Data



### LIST OF FIGURES
Figure 1. 

### Location of 

### metam-sodium spill and downstream areas



## ........ 2


### Figure 2. 

### MITC at 

### Antlers Campground



# ................................. 8

LIST OF 

### TABLES

Table 1. 

### Results 

### of the Cantara metam-sodium spill water monitoring at Antlers Campground, Shasta Lake



# .......................... 6

Table 2. Results of 

### the Cantara metam-sodium spill water monitoring
at the Centimudi Boat Ramp, Shasta Lake



# ..................... 7

iii

### INTRODUCTION

On July 14, 1991 

### a Southern Pacific railroad car carrying Alco Metam
Sodium"' derailed at the Cantara Loop, north of Dunsmuir, California and spilled between 49,000 

### and 72,000 

### liters (13,000 

## - 19,000 

### gal) of the product into the Sacramento River. The spilled material degraded to several toxic and volatile chemicals which could pose a threat to public


### health and the environment. Of particular concern were the people living in small communities adjacent to this part of 

### the river, the aquaticor

### ganisms in the river, and Shasta Lake, downstream of the spill which is 

### a major recreation area and drinking water reservoir. For these and other reasons monitoring 

### was conducted by several agencies, including the California Department of 

### Pesticide Regulation (CDPR).

Alco Metam Sodium", formulated by the Amvac Chemical Corporation, contains
32.7% 

### metam-sodium (by weight) as the active ingredient. Assuming 

### 49,000



## - 72,000 

### L of 

### the product were released into the river, 19,000 

## - 27,000 kg
(42,000 

## - 60,000 

### lbs) 

### of active ingredient would have been spilled into
the river. This chemical is 

### used agriculturally as a 

### fungicide, herbicide, insecticide, nematicide and soil fumigant. Most of 

### its pesticidal
action is produced by its primary breakdown product, methyl isothiocyanate
(MITC). Breakdown to 

### MITC normally occurs very rapidly, within a few 

### hours. Other chemicals are also produced from the breakdown of rnetarn

### sodium, including hydrogen sulfide, carbon disulfide, and methylamine.

See Appendix 1 

### for references and more details about the environmental
fate of metam-sodium.

Monitoring by the CDPR was conducted by the Environmental Hazards Assessment Program (EHAP) in cooperation with the California Department of


### Fish and Game, Water was sampled over time 

### at two locations on Shasta Lake (Figure 1). 

### The purpose of the monitoring by the EHAP was to 

### characterize the temporal distribution of MITC in Shasta Lake.

1

### Figure 1. 

### Location of 

### metam-sodium spill 

### and downstream areas

2

### MATERIALS AND METHODS

Sample Collection

Water samples were collected from two sites in Shasta Lake (Figure 1) 

### twice daily. Site 1 

### was a boat launching area at Antlers Campground located on the Sacramento River inlet to Shasta Lake, 62 

### km (39 mi, by 

### river) downstream of the spill site. It is 

### a narrow channel at the north
end of the lake which expands into a wide bend to the south. Site 2 

### was located at the Centimudi boat ramp which is located approximately 800 

### m northeast of Shasta Dam, 

### 87 km 

### (54 mi, by river) downstream of the spill site. Sampling was initiated on July 16, 1991 

### at 9:05 

### in the morning. Samples continued to be collected twice a day, once in the morning and

once in the evening. The last set of samples was collected the morning 

### of
July 23.



### One-liter amber glass bottles and 

### 40 mL glass vials were submerged approximately two meters from the lake edge and 50 

### cm below the water
surface to collect the samples. The containers were filled to capacity and then capped under water with teflon-lined lids. This procedure reduced the possibility of trapping air inside the containers. Containers were checked to determine if air was trapped inside by inverting the 

### sample. Each sample 

### was accompanied by a chain of custody which documented its history. The pH 

### and water temperature of each sample were also
measured.

The samples were placed on 

### wet ice (4°C) immediately aftersample collection. Samples were kept under refrigeration during transport until delivery to the CDPR West Sacramento facility. Samples were checked in at the West Sacramento facility and then delivered to the laboratory for analysis.



### 3

### Chemical Analysis and Quality Control

Samples were analyzed for MITC by two laboratories, the California
Department of Food and Agriculture, Chemistry Laboratory Services Branch (CDFA) and the Agricultural and Priority Pollutants Laboratory, Inc.
(APPL). The primary method, by CDFA, consisted of direct sample injection
into 

### a high pressure liquid chromatograph with 

### a post-column reactor and a fluorescence detector. Samples that were positive using this method were
confirmed by the CDFA laboratory by extracting the water samples with a minimum amount of 

### carbon disulfide and injecting the extract into a 

### gas chromatograph equipped with a nitrogen-phosphorous detector. APPL confirmed all samples using a purge and trap apparatus equipped with photoionization and flame ionization detectors. Details 

### of the MITC analytical methods are given in Appendix 2.



### Analysis for other chemicals was attempted. The CDFA laboratory analyzed
for 

### a combination of metam-sodium and carbon disulfide. Their method incorporated 

### a step to convert metam-sodium to carbon disulfide and analyzing for 

### total carbon disulfide. No 

### distinction was 

### made between true carbon disulfide present in the sample and carbon disulfide that was present as the result of metam-sodium conversion.

Several measures were taken to insure valid results were obtained. To 

### protect against sample tampering, each bottle 

### was accompanied with a chain


### of custody form which was signed by every individual who handled the sample. Laboratory results and field notes were also written on the chain


### of custody forms. To check for sample contamination, blank samples were
created in the field and in the laboratory. Field blanks were created by pouring distilled water into sample bottles at the same time and place as the actual samples. Additional blanks were created in the laboratory.
For 

### a qualitative check, all positive samples were confirmed using the
solvent extraction method described above; this method was not used to quantitate. To check for 

### quantitation, spiked samples (known amount 

### of

MITC added to a sample) were submitted to the laboratory disguised as 

### real

4

### samples. In addition, the purge and trap method described above was used

to quantitate concentrations. 

### To check for possible dissipation during
storage, 

### a storage stability test was conducted. This test consisted of storing a set of 

### spiked samples under the same conditions 

### as real samples and analyzing them over a period of 

### six days.

RESULTS AND DISCUSSION

Results of 

### the water monitoring are shown in Tables 1 

### and 2 

### and Figure 2.


### The highest MITC concentration, 5500 

### ppb, 

### was detected at the Antlers Campground site on July 17. 

### Concentrations declined from the peak, to 

### 8 ppb six 

### days later. No MITC was detected in any sample collected from the Centimudi site (detection limit 

### 5 ppb). These results agree with preliminary results obtained by other agencies.

Results of the quality control analyses were good. None of 

### the blank 

### samples were positive and there was good agreement between laboratories.
Recoveries of the two blind spike samples were both 100%. 

### The storage stability test indicated that no dissipation occurred during the time between sampling and analysis. The quality control raw data are shown in Appendix 

### 3.

Thirteen samplesthat were positive for MITC were also analyzed for metamsodium/carbon disulfide, 

### as described earlier. Only one which corresponded to the sample that contained 5500 

### ppb of MITC was able to be quantified at 1240 

### ppb of 

### carbon disulfide. 

## If all of 

### the carbon disulfide detected 

### was converted metam-sodium, then the original metam-sodium
concentration would have been 2100 

### ppb (adjusted for stoichiometric change in molecular weight). The CDFA laboratory also attempted to analyze for hydrogen sulfide, but could not develop an adequate method.

This monitoring alone is not enough to assess the movement, dissipation and possible effects of 

### the metam-sodium spill. 

### When the data from 

### all monitoring groups are available, such an assessment will be possible.Table 1. Results of the Cantara metam-sodium spill water monitoring at Antlers Campground, Shasta Lake.

Methyl Isothiocyanate (ppb) Temperature Date T ime CDFA APPL pH ("C)

7/16/91 0905 None Detecteda 7.2 21.1 1830 None Detected 7.6 21.8

7/17/91 0825 5500 5800 

### 7.8 19.8 1805 1580 1600 7.9 25.4

7/18/91 0850 454 474 7.2 20.3 1815 242 170 7.4 25.4

7/ 1919 1 0645 134 broken 7.4 21.2 1830 85 70 7.4 25.6

7/20/9 1 0700 61 54 7.4 21.6 1800 44 36 7.9 25.4

7/21/91 0645 35 27 7.5 21.7 1740 22 20 7.6 26.4

7/22/51 1 0700 20 1830 12 16 7.5 22.3 12 7.6 26.1

7/23/9 1 0730 8.0 

### 8.3 7.4 22.1

a 

## - CDFA detection limit = 5.0 ppb, 

### APPL detection limit = 2.0 ppb

6

### Table 2. 

### Results of the Cantara metam-sodium spill water monitoring at the Centimudi Boat Ramp, 

### Shasta Lake.

Methyl Isothiocyanate (ppb) 

### Temperature Date Time CDFA APPL pH ("C)

7/16/91 1010 

### None Detecteda 7.6 25.7 1925 

### None Detected 7.8 25.8

71 1719 1 0945 

### None Detectedb 8.0 25.6 1920 

### None Detected 8.2 28.0

7/ 18/9 1 1010 

### None Detected 7.9 26.3 1945 

### None Detected 7.8 27.7



### 71 1919 1 0830 

### None Detected 7.6 26.4 1945 

### None Detected 7.8 26.5 

### b

7/20/9 1 0815 

### None Detected 7.8 25.8 1915 

### None Detected 7.6 25.9

7/21/91 0800 

### None Detected 7.4 25.3 1840 

### None Detected 7.8 28.9

7/22/9 1 0800 

### None Detected 7.9 26.9



### a 

## - CDFA detection limit = 5.0 

### ppb, APPL detection limit = 2.0 ppb



### b 

## - APPL sample broken, no analysis

70 d 0 0 0 Iu 0 0 0 8

0 0 0 0 P 0 0 0 01 0 0 0 Q) 0 0 0
I I I I I 

# z
-i 

### 0 

# -

TI TI 

## u n

Y

### MONITORING BY OTHER AGENCIES

The CDPR monitoring program was very minimal, Extensive monitoring has
been and continues to be conducted by other agencies, particularly by the Regional Water Quality Control Board. In addition, the Cal EPA Office of Environmental Health Hazard Assessment is acting as a central repository for all monitoring data. Listed below are the agencies conducting monitoring; the list may not be complete.



### U.S. Bureau of 

### Reclamation: water monitoring

Cal EPA 

## - Regional Water Quality Control Board, Central Valley Region: water, soil, 

### and sediment monitoring

Cal EPA 

### - Air Resources Board: air monitoring

Cal EPA 

## - State Water Resources Control Board: air monitoring

Cal EPA 

### - Department of Toxic 

### Substances Control: water, soil, and sedi

### ment monitoring

California Department of Fish and Game: water, sediment, and biota monitoring

California Occupational Safety and Health: air monitoring

California Department of Health Services: water monitoring

Shasta County Department of Environmental Health: groundwater monitoring (public and private drinking water wells)

Southern Pacific 

## - Terra and OHM (under contract): water, air, soil, and sediment monitoring

In addition, the California Department of Fish and Game 

### is conducting biological surveys for 

### impacts to fish, wildlife and vegetation.

9Appendix 1 

## - Environmental Fate 

### of Metam-Sodium

# Degradation Pathways for 

# Metam-Sodium

n 

# CH,NHC Na+ 43

\n 

## 3- 

# Metam-Sodium

(MW 129.1 7) 

# s=c=s Carbon 

# Disulfide (MW 76.1 3)



# +

_I____, 

# CH,NH2 Methylamine (MW 31.06)



# + 

# - CH,N=C=S Methyl Isothiocyanate 

# (MW 73.11)



# + 

# - H2S Hydrogen Sulfide (MW 34.08)

Molecular weight is shown in parentheses

1-1State of California


## Memorandum

TO : 

### Don Weaver : 

### November 20, 

### 1990 Sr. 

### Environmental Research Scientist Environmental Hazards Assessment Program I 

### Sacramento

From : Department of Food and Agriculture 

### Chris Collison, Assoc. Env. Research Scientist Environmental Hazards Assessment Program

Subject: 

### LITERATURE REVIEW OF THE 

### ENVIRONMENTAL FATE OF METAM-SODIUM (VAPAMm)



### This review was based on data from the CDFA 

### pesticide registration packages cited as Stauffer Chemical Company and 

### IC1 Americas, Inc., and from open literature articles.
Metam-sodium (sodium methyldithiocarbamate) 

### is the active ingredient 

### in Vapamo, a broad-spectrum soil fumigant produced by Stauffer Chemical Company. It 

### is commonly applied as a preplant fumigant incorporated into the irrigation system.

Metam-sodium degrades rapidly to methyl isothiocyanate 

### (MITC) when ---, 

### in contact with moist soil. Smelt and Lcistra 

### (1974) found that the conversion of 

### metarn-sodium to MITC (>go%) 

### took only a few 

### hours. In experiments using spiked moist soil 

### in glass septum flasks incubated at 1Z0C, 

### conversion was 

### complete ino 3 

### hours in 

### loamy soils and in G 

### hours in a humic sandy soil. At 

### 21 C 

### in the sandy soil, 

### a period of 3-4 

### hours was sufficient for conversion to MITC.
The decomposition rate 

### of MITC 

### in moist soil was 

### also investigated

(Smelt and Leistra, 1974). 

### Depending on the soil type, half-lives for 

### MITC were in the range of 8-14 

### days. The most rapid decomposition occurred in heavy, loamy 

### soils at higher temperatures. Smelt et al. (1989) 

### also 

### investigated decomposition rates of MITC in 

### "problem" soils (those demonstrating inadequate pest 

### control by 

### fumigation with metam-sodium). MITC in amounts ranging from 1.5 to 2.0 mg 

### (equivalent to'150 kg/ha) was 

### added to 

### glass flasks 

### partially filled with moist soil and incubated in the dark at 15OC. 

### A comparison of the decomposition patterns 

### of MITC 

### in previously treated and untreated soils showed that, 

### in general, MITC degraded much faster in the previously treated soils. This suggested that repeated applications of metam-sodium induced microbial adaptation resulting 

### in enhanced biotransformation of MITC. In 

### this study, MITC half-lives ranged from 0.5 

### to 50 

### days. The study results also indicated that the decomposition rate of 

### MITC greatly depends 

### on the initial content of the fumigant.

1-2

### Don 

### Weaver November 20, 

### 1990 

### Page 2



### In two field studies conducted "under normal agricultural conditions" in Mississippi and California by IC1 Americas, 

### Inc. (1989), 

### MITC was found no deeper than 9 

### inches in soil and undetected at any depth 13 days after application. Vapam was 

### applied to 

### bare fallow soil at 

### a rate 

### of 100 

### gallons 

### of formulated material 

### (32.7% AI) per acre by chemigation with an 

### overhead sprinkler. The respective zero-time MITC residues were 18 and 42 

### ppm in the upper 6 

### inches of soil in Mississippi and California. Half-lives were 13 and 26 

### hours 

### in loam soil near Visalia, California and loam/silt-loam soil near Leland, Mississippi respectively. Four days post application, maximum residues of the degradation product 1,3-dimethylurea were from 0.13 

### to 

### 0.51 ppm. ' 

### Leaching experiments were performed 

### by Stauffer Chemical Company (1985a) 

### using 32-37 cm Aong 

### glass 

### and steel columns hand packed with soil. A 

### radiolabeled 

### C metam-sodium solution was used to spike 

### the columns at 

### concentrations equivalent to 

### 1 quart/100 

### sq ft and, 

### at the highest application rate recommended, 2 

### quarts/100 

### sq 

### ft. Four 

### soil types ranging from sand to loamy sand to sandy clay were tested. 

### In each case, 

### about 60% 

### of 

### the applied 14C leached from the columns after 48 

### mL of water were poured on the soil (equivalent to 20 

### inches X 

### thlT cross sectional area of the columns). About 90% 

### of 

### the leached C 

### was iqtntified 

### as MITC. Results indicated that the bulk of the soluble C leached out 

### of the soil soon after the volume of water necessarX for soil saturation was added. Between 11 and 14% 

### of 

### the applied C 

### remained bound to the soil and 23 

### to 30%


### was assumed to 

### have been lost as volatile degradation products, mainly MITC.

Emissions 

### of MITC 

### from greenhouse soil were studied by Leistra and Crum, (199Oj. Concentrations 

### of MITC 

### in treated soil were measured and the data was used in.a computer model 

### to simulate emissions from the soil. The experimental fumigation was conducted in 

### a greenhouse with wetted, sandy soil cultivated to 

### a depth of 0.25 

### m. 

### Two hundred and forty liters of 

### the trade product (510 

### g metam-sodium per liter), which corresponds to 1950 L/ha of the trade product, was applied with a 

### small self-propelled shank injector to 

### a depth of 0.05-0.10 m. A 

### 30 vm 

### thick low density polyethene .film was used to 

### completely cover the soil after application and was left on the soil surface for 

### 7 days. Refore removal of the cover, the cumulative emission of MITC 

### from the greenhouse soil 

### was computed to 

### be about 45% of 

### the applied dosage. At 

### day 14, seven days after removal. of 

### the cover, the total cumulative emission was 50% 

### of the applied dosage.

1-3

### Don Weaver November 20, 

### 1990 Page 3

The highest rate 

### of emission from the film-covered soil ocurred 

### on the first day after application. Concentrations 

### in greenhouse 

### air

were computed to be 

### around 50 

### mg/m on the first day and exceeded 10 

### mg/m during the first 

### 4 days after injection. When the 

### model was modified to exclude the factor 

### of a film cover, the computed 

### MITC emission rate one day after application was 2.5 

### times greater than the rate with a film cover. The cumulative emission after 14 days 

### without a film cover 

### was computed to be 648 

### sf the applied dosage. The vapor pressure of MITC 

### is 2.7 

### kPa at 20 

### C (Hartly and Kidd, 

### 1983) 

# .
The emission model was further 

### modified to simulate the homogeneous incorporation of metam-sodium into the soil to a depth 

### of 0.24 m after a 

### surface application. The results indicated a somewhat lower emission rate in the first 3-4 days. After about 4 

### days, the emission rate was similar to that for injection. At the end of 

### the 14 

### day period, the computed cumulative emission corresponded 

### to 38% 

### of 

### the applied dosage. Without a film cover, the emission was 49% of the equivalent dosage.

Half-lives for 

### metam-sodium at 2OoC 

### in dilute solutions at pH 5, 

### 7, 

### and 9 

### were 23, 180, and 46 

### hours respectively. The major products of hydrolytic degradation at pH 5 

### were methylamine, MITC, and carbon disulfide. Minor hydrolytic degradation products included elemental sulfur and 1,3-dimethylthiourea (Stauffer Chemical Company, 198513).

The major products arising from pohotolysis of metam-sodium in aqueous solution (120 ppm) at 25 

### C and pH 7 

### were MITC, N

### methylthioformamide, methylamine, and elemental 

### sulfur. 

### Minor photolytic degradation products included N-methylformamide, carbon disulfide, carbon oxide sulfide, and hydrogen sulfide. Under these conditions, the half-life for metam-sodium was 

### 1.6 hours (Stauffer Chemical Company, 1985b)

References Cited
Hartley, 0. 

### and H. 

### Kidd. 1983. The agrochemicals handbook. Royal Society of Chemistry.

IC1 Americas Inc. 1989. RR2021: Two field dissipation studies for terrestrial USCS. 

### CDFA Doc. 5015-025.
Leistra, M. 

## , and S.J.1-l. 

### Crum. 1990. 

### Emission of 

### MITC to the 

### air after application of 

### metam-sodium to 

### greenhouse soil. Water, Air and Soil 

### Pollution 50:109-121.

1-4

### Don 

### Weaver November 20, 

### 1990 Page 4

Smelt, J.HOI S.J.H. 

### Crum and W. 

### Teunissen. 1989. Accelerated transformation of the fumigant MITC 

### in soil after repeated application 

### of metham-sodium. 

### J. Environ. Sci. Health 

### B24(5) 437-455 

# . Smelt, J.H. 

### and M. 

### Leistra. 1974. Conversion 

### of metham-sodium 

### to MITC and basic data on the behavior 

### of MITC 

### in soil. Pestic. Sci. 5:401-407.

Stauffer Chemical Company. 1985a. 

### Vapam 

### soil mobility. CDFA 

### Doc. 

### 50150-006.
Stauffer Chemical Company. 1985b. Hydrolysis 

### and photolysis 

### of metam-sodium. CDFA Doc. 50150-006.

cc: Ronald J. 

### Oshima

.. , , 

### John Sanders Randy Segawa Kean Goh

1-5Appendix 2 

# - Chemical Analysis MethodsCALIFORNIA DEPT. OF FOOD & ACRIC. ENVIRONMENTAL MONITORING SECTION CHEMISTRY LABORATORY SERVICES 3292 Meadowview Road Sacramento, CA 95832 (916)+427-4408 Original Date: July 17, 1991 Supersedes: .New Current Date: August 14, 1991 Method #: 17

METHYL ISOTHIOCYMATE 

### IN RIVER WATER 

### BY HPIX: AND GC

SCOPE:

This method is for the determination of methyl isothiocyanate (MITC) in river water. Its sensitivity is 5 ppb.

PRINCIPLE:

HPLC method : The water samples are directly injected to HPLC, separated on A reverse phase octadecyl bonded column. The eluant: is derivatizod with OPA by post column reaction and detected with a fluorescence detector (Excltatlon-340 nm, Emission-450 nm).

GC method: MITC in water is extracted with a minimum amount of carbon disulfide. The extracts are analyzed by GC with a nitrogen specific detector.

REAGENTS AND EQUIPMENT:

Distilled water, HPLC grade Acetonitrile, HPLC grade Carbon disulfide, residue grade Disposable filters 0.2 micron (Nylon Acrodisc). HPLC 

# - Hewlett Packard HP 1090 Liquid Chromatoghaph controlled by HP 79994A

Fluorescence Detector 

# - Hewlett Packard HP 1046A Post Column derivatization system 

## - Pickering Laboratory CRX 390 high HPLC ChemStationTH

temperature reaction control device,
two Milton Roy miniPumpsTH with pressure readout devices and an ambient temperature reaction coil. Reagent A, 0.2% NaOH/H 0 Reagent B; Dissolve 0.5 gram of o-Phthalaldehyde in 10 mL of methanol, add 1 mL 2-mercaptoethanol, then add 50 mL of pH 10.4 buffer (1 M of -Potassium borate), and dilute to 1 L with distilled water.



### ANALYSIS :



### PRIHARY ANALYSIS (HPLC)

Sample Preparati.on: 1. Filter the water sample, using a 10 mL hypodermic syringe, through a 0.2 micron nylon Acrodisc filter into an autosampler vial. Seal the top with a crimp top cap.

2- 1

\

### MITC in river water by 

### HPLC and GC Page 

### 2

PRIWY ANALYSIS (HPLC)

Sample Preparation: continued. 2. The content of the autosampler vials is ready for 

### HPLC analysis.

.

Instrument Conditions:

Column: Beckman Ultrasphere ODS C-18, 5 micron 4.6 mm X 25 cm.

Sample Loop: 250 microliter

Sample injection: 250 microliter (same volume of standard and sample injected)

Mobile Phase: Gradient

Time (minutes) % Water % Acetonitrile 0.0 YO 

### 10 1.0 90 10 6.0 30 70 10.0 30 70 13.0 90 10

Retention time of 

### MITC: 9.624 min (SD=O.O18min, n-20) Flow: 1.0 ml/min

Post Column System:

Flow: Reagent A 0.2 ml/mfn Reagent B 0.2 ml/min

Detector: Fluorescence Excitation 

# - 340 nm Emission 

# - 450 nm

METHOD VALIDATION:

This method for water analysis 

### does not require solvent extraction. Samples

are directly injected to the HPLC system. Thus, the method recovery is at about 100% level. The varfation in recoveries is mainly due to the performance 

### of the instrument.

Spike

Level MITC 

### SD Percent 

### n PPb % Recovery Variation

5 20 100 500 1000 92.6 0.32 6.5 5 105.2 0 .*74 3.7 5 102.2 1.5 1.5 5 97.5 4.0 0.8 

### 5 102.2 5.0 0.5 5

\ 2-2MITC in river water by HPLC and GC Page 3

CONFIRMATION ANALYSIS (CC)

Sample preparation: 1. Remove sample from refrigerated storage.

.2. Shake sample and weigh out 500 g by difference and transfer this aliquot to a 1 L separatory funnel.

3. Extract sample by adding 10 mL of carbon disulfide and shake vigorously for 1 minute.

4. Allow the layers to separate and drain the lower layer into a 25 mL test tube.

5. Repeat the extraction one more time using 10 mL carbon disulfide. Combine the extracts.

6. Add approximately 1 g sodium sulfate and shake to remove water.

7. The extract is ready for CC analysis.

Instrument conditionr:

Varian 3700 GC with NPD Column: HP-FFAP (cross-linked polyethylene glycol-TPA modified) 10 m x 0.53 mm 

### x 1.0 um Column temperature: 5O0C/1 minute, program at lO'C/mInute to 110°C Retention time: 2.60 min Injector temperature: 200'C Detector base temperature: 220°C



### DISCUSSION: MITC is very volatile, Rotary vacuum evaporation and open beaker evaporation yields no' recovery. Kuderna-Danish solvent evaporation which is very tedious can produce approximately 60% recovery. Thus, to avoid these problems we chose
to use a minimum amount of solvent for extraction and not to concentrate the
extract. The average recovery of this solvent extraction method is 60-70%.

The HPLC method is superior to the GC iethod. It requires no solvent extraction, The recoveries are approximately 100%.

2-3NX'X in river water by 

### HPLC and GC Page 4

REFERENCE:

Lee, 

### P, RPLC determination of Aldicarb, Afdfcarb 

## sulfoxide, and Aldicarb sulfone in Groundwater, September 28, 1989, Environmental Monitoring Method, California Department of Food and Agriculture.

MIlTEN BY: PAUL LEE

REVIELED BY: Catherine Cooper

APPROVED BY: Terry Jackson

1

APPROVED 

### BY: Mark Lee

K T1TLE:Reseerch'Agricultural Chemist

2-4WTC 

### in water by Modified EPA 

### Method 602



### Equipment:

1) 

### Gas chromatograph: HP Model 5890 2) 

### Detector: 01 

### Tandem PID/FID 3) 

### Column: 30m 

### DB624 Temperature program: 50*C 

### for 3 

### minutes; 8'C/Min. to 200.C. 

### Hold 0.25 

## min. Run time 

# - 22 

### minutes RT MITC = 

### 7.1 

### min.

Trap: 1 

### cm 3kSP-2100, 23 

### cm Tenax. Supelco #2-0295M 

### Purge Time: 11 min. at <30'C Desorb Time: 3 

### min. at 180'C Brake Time: 6 

### min. at 225.C 4) 

### Purge 

### and Trap: 

### Tekmar Model 4000

5) 

### Autosampler: Dynatech Precision Sampling .FTA3O-WS



### Procedure:

Prepare a aalibration curve from a 1000 

### ppm MITC 

### stock solution in methanol. A 

### five point curve is run at 5, 10, 25, 50 

### and 100 

### pg/L. Prepare spikes at 10-25 pg/L.

Load autosampler with standards and samples in 40 

### ml VOA 

### vials in the following order: Blank, calibration curve, spikes, 10 

### samples, midpoint standard (25 pg/L), spikes, 10 

### samples, blank, midpoint standard, etc.

Set the autosampler to purge 10 

### ml aliquots in the water mode using internal standard addition. 

### The internal standard solution 

### is 100 

### ppm of 

### Volatiles Internal Standards Mix 502 

### (Supelco)
The Turbochrom 111 calculates spike and sample amounts off 

### the calibration curve. Peak area and internal standard calculation 

### is used. Linearity must be 2 0.997. 

### A new calibration curve is 

### run whenever the midpoint standard has a linearity 

### below 0.997. Samples containing MITC 

### > 100 

### pg/L are diluted and 

### rerun.
pg/L 

### MITC 

### in chromatography report times the dilution 

### is pg/L 

### MITC 

### in sample.

..

2-5Appendix 

### 3 

# - Quality Control Data

# Comparison 

# of CDFA 

# and APPL 

# Results MITC Water 

# Concentrations

1 10 

## 100 1000 

### CDFA (ppb) 10000

Line shows ideal 

### slope of 1Table 3-1. Method validation data (% recoveries) for the Metam Sodium Study.

Study: X56 Analyte: MlTC MDL 5ppb Date of Report: 8/1/91 Sample Type: Surface water Lab: CDFA Chemist: Paul Lee Method: GC/NPD

Lab Sample Results Spike Level Recovery 

### cv Y @pb) @p b) % X SD (%) 134 3.81 5.0 76 134 3.33 5.0 67 134 3.33 5.0 67 70 5.2 7.4 136 7.13 10.0 71 136 7.56 10.0 76 136 7.56 10.0 76 74 2.9 3.9 135 30.51 50.0 77 135 41.84 50.0 a3
135 43.95 50.0 87 82 5.0 6.1 

### -

OVERALL 76 6.7 8.8

Table 3-11. Method validation data (% recoveries) for the Metam Sodium Study.

Study: X56 Analyte: MlTC MDL 5ppb Date of Report: 8/1/91 Sample Type: Surface water Lab: CDFA Chemist: Paul Lee Method: HPLC/ post column/ fluorescence

Lab Sample Results Spike Level Recovery cv
# (ppb) @pb) % X SD (%) -

390 4.4 5.0 80
390 5.0 5.0 100 390 5.0 5.0 100 390 4.4 5.0 88
390 4.5 5.0 90 93 6.3 6.7
389 22 20 110 389 21 20 105
389 21 20 105 389 20 20 100 389 21 20 105 105 3.54 3.37 388 100 100 100 388 101 100 101 388 104 100 104 388 103 100 103 388 102 100 102 1 02 1.58 1.55
387 493.3 500 98.6 387 485.6 500 97.1 387 486.2 500 97.2 387 482.9 500 96.6 387 489.5 500 97.9 97 0.8 0.8 386 1028 lo00 102.8 386 1027 lo00 102.7 386 1023 lo00 102.3 386 1015 lo00 101.5 386 1020 lo00 102.0 102 0.53 0.52

OVERALL 100 5.22 5.22

3-2Table 3-111. Continuing quality control data for the Metam Sodium Study.

Study: X56 Analyte: MlTC MDL 5ppb Date of Report: 8/1/91 Sample Type: Surface water Lab: CDFA Chemist: Paul Lee Method: GC/NPD

Extraction Lab Results Spike Level Recovery - cv Set No:s x (ppb) (ppb) % X SD (%) 31,43,49,55 305
- 15 20 75
7 303

7.27 10 73

OVERALL: 74 1.4 1.9

Table 3-IV. Continuing quality control data for the Metam Sodium Study.

Study: X56 Analyte: MlTC MDL: 5ppb Date of Report: 0/1/91 Sample Type: Surface water Lab: CDFA Chemist: Paul Lee Method: HPLC/ post column/ fluorescence

Extraction Lab Results Spike Level Recovery 

### cv Set No.'s x (ppb) (PPb) % X SD (%) -

25 380 lo00 lo00 100 1, 13 378 1012 lo00 101 221,233,239,227,245,197, 377 98.3 100 98

137,167,140,142,209,250, 375 100 100 100 364,370,155,302,394,161, 127 251,376,413,407,501,455, 367 97.2 100 97 308,479,482,504,450,391, 381,256,410,412 417,425,431,437,424,507, 373 99.3 100 99 226,202,232,230

430,436,442 401,406,449,454,508 370 97.20 100 97

OVERALL 99 1.6 1.6

3-3Table 34. Storage dissipation data for the Metam Sodium Study (room temperature, pH 7.5).

Study: X56 Analyte: MlTC MDL: Sppb Date of Report: 0/1/91 Sample Type: Surface water Lab: CDFA Chemist: Jean Hsu Method: GC/NPD

Lab Sample Date Oat8 Results Spike Level Recovery 

### - cv
# Day Extracted Analyzed (ppb) (ppb) 96 X SD (%) 202 0 7/19/91 7/19/91 156 200 78 203 0 7/19/91 7/19/91 154 200 77 78 0.71 0.91
21 1 1 7/20/91 7/20/91 159 200 79 212 1 7/20/91 7/20/91 140 200 74 77 3.5 4.6
220 2 7/21/91 7/21/91 152 200 76 222 2 7/21/91 7/21/91 149 200 72 74 2.0 3.0 230 3 7/22/91 7/22/91 156 200 76 23 1 3 7/22/91 7/22/91 138* 200 69 73 4.9 6.8 267 4 7/23/91 7/23/91 145 200 73

276 5 7/24/91 7/24/91 131 200 66 277 5 7/24/91 7/24/91 131 200 66 66 0.0 0.0 260 4 7/23/91 7/23/91 152 200 76 75 2.1 2.0

303 6 7/25/91 7/25/91 134 200 67
304 6 7/25/91 7/25/91 120 200 64 66 2.1 3.2

OVERALL 72 5.0 7.0 Low recovery due to leak during extraction.

Table %VI. Storage dissipation data for the Metam Sodium Study (refrigerated, pH 7.5).

Study: X56 Analyte: MlTC MDL: 5 ppb Date of Report: 0/1/91 Sample Type: Surface water Lab: CDFA Chemist: Jean Hsu Method: GC/NPD

Lab Sample Date Date Results Spike Level Recovery cv
# Day Extracted Analyzed @pb) (ppb) % X SD (%) 204 0 7/19/91 7/19/91 151 200 76 205 0 7/19/91 7/19/91 156 200 70 77 1.41 1.04 

### -

213 1 7/20/91 7/20/91 145 200 72 214 1 7/20/91 7/20/91 146 200 73 73 0.7 1 0.96 223 2 7/21/91 7/21/91 124* 200 62 224 2 7/21/91 7/21/91 141 200 71 67 6.4 9.6

233 3 7/22/91 7/22/91 156 200 76 76 0.0 0.0 232 3 7/22/91 7/22/91 156 200 76

269 4 7/23/91 7/23/91 141 200 71 270 4 7/23/91 7/23/91 145 200 72 72 0.71 0.99

279 5 7/24/91 7/24/91 140 200 74 73 1.4 1.9 278 5 7/24/91 7/24/91 145 200 72

305 6 7/25/91 7/25/91 124. 200 62 306 6 7/25/91 7/25/91 152 200 76 69 9.9 14

* Low recovery due to leak during extraction. OVERALL 72 4.9 6.7

3-4Table 3-Vll. Storage dissipation data for the Metam Sodium Study (room temperature, pH 10).

Study: X56 Analyte: MlTC MDL: 5 ppb Date of Report: 8/1/91 Sample Type: Surface water Lab: CDFA Chemist: Jean Hsu Method: GC/NPD

Lab Sample Date Date Results Spike Level Recovery 

### cv
# Day Extracted Analyzed (ppb) (ppb) % X SD (%) 

### -

206 0 7/19/91 7/19/91 129 200 64 207 0 7/19/91 7/19/91 120 200 60 62 3 5
21 5 1 7/20/91 7/20/91 93 200 47 216 1 7/20/91 7/20/91 90 200 45 46 1.4 3.1 225 2 7/21/91 7/21/91 48 200 24 226 2 7/21/91 7/21/91 50 200 25 25 0.71 2.9 234 3 7/22/91 7/22/91 27.6 200 14 235 3 7/22/91 7/22/91 27.6 200 14 14 0.0 0.0 27 1 4 7/23/91 7/23/91 9.5 200 4.7 272 4 7/23/91 7/23/91 9.0 200 4.5 5 0.1 3.1

28 1 5 7/24/91 7/24/91 8 200 4.2 4 0.0 0.0 280 5 7/24/91 7/24/91 8 200 4.2

307 6 7/25/91 7/25/91 nd 200 0 308 6 7/25/91 7/25/91 nd 200 0 0 0.0 0.0

OVERALL 22 23 102

Table 3-Vlll. Storage dissipation data for the Metam Sodium Study (refrigerated, pH 10).

Study: X56 Analyte: MlTC MDL 5ppb Date of Report: 8/1/91 Sample Type: Surface water Lab: CDFA Chemist: Jean Hsu Method: GC/NPD

Lab Sample Date Date Results Spike Level Recovery cv
# Day Extracted Analyzed @p b) (ppb) % X SD (%) 208 0 7/19/91 7/19/91 133 200 67 209 0 7/19/91 7/19/91 116 200 58 63 6.4 10 

### -

217 1 7120191 7/20/91 110 200 55 218 1 7/20/91 7/20/91 114 200 57 56 1.4 2.5 227 2 7/21/91 7/21/91 106 200 53 228 2 7/21/91 7/21/91 106 200 53 53 0.0 0.0

237 3 7/22/91 7/22/91 103 200 52 50 2.8 5.7 273 4 7/23/91 7/23/91 89.7 200 45 274 4 7/23/91 7/23/91 89.7 200 45 45 0.00 0.00 282 5 7/24/91 7/24/91 90 200 45 236 3 7/22/91 7/22/91 97 200 48

283 5 7/24/91 7/24/91 93 200 47 46 1.4 3.1 309 6 7/25/91 7/25/91 83 200 41 310 6 7/25/91 7/25/91 79 200 40 41 0.71 1.7

OVERALL 50 7.4 15

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### s*n L‘n 9LZ ‘ELZ ‘082 ‘UZ ‘91 ‘P ZLZ ‘89z ‘V9Z ‘092 ‘26 ‘96 ‘b8 ‘88 ‘08 ‘9L ‘ZL ‘89 ‘69Z ‘‘31 ‘19Z ‘LPZ ‘68 ‘€6 ‘18 ‘98 ‘U ‘EL ‘69 ‘E9 ZLZ ‘W ‘HZ ‘092 ‘26 ‘95 ‘b9 ‘88 ‘08 ‘9L ‘ZL ‘89 ‘692 ‘Mz ‘192 ‘LSZ ‘68 ‘E6 ‘18 ‘G8 ‘K ‘EL ‘69 ‘E9Page 51 of 79 Figure A-1. Dissipation curve and analysis of MITC in Lake Shasta inlet (Antlers Campground) monitoring sitePage 52 of 79 Nonlinear Regression Friday, March 29, 2013, 12:36:49 PM

Data Source: Data 1 in Notebook2 Equation: Exponential Decay, Single, 2 Parameter f = a*exp(-b*x)

R Rsqr Adj Rsqr Standard Error of Estimate

0.9869 0.9739 0.9728 256.2562

Coefficient Std. Error t P

a 5642.2748 181.1738 31.1429 <0.0001 b 0.1848 0.0198 9.3232 <0.0001

Analysis of Variance:

DF SS MS Regression 2 65463774.2748 32731887.1374 Residual 23 1510346.6152 65667.2441 Total 25 66974120.8900 2678964.8356

Corrected for the mean of the observations: DF SS MS F P Regression 1 56410535.7752 56410535.7752 859.0361 <0.0001 Residual 23 1510346.6152 65667.2441 Total 24 57920882.3904 2413370.0996

Statistical Tests:

Normality Test (Shapiro-Wilk) Failed (P = <0.0001)

W Statistic= 0.7539 Significance Level = 0.0500

Constant Variance Test Failed (P = <0.0001)

Fit Equation Description: [Variables] x = col(1) y = col(2) reciprocal_y = 1/abs(y) reciprocal_ysquare = 1/y^2 reciprocal_pred = 1/abs(f) reciprocal_predsqr = 1/f^2 'Automatic Initial Parameter Estimate Functions F(q) = if(size(x)>1, if(total(abs(y))>0, ape(x,log(abs(y)),1,0,1), -306), 0) asign(q) = if(mean(q)>=0,1,-1) [Parameters] a = if(F(0)[1]< 307, if(F(0)[1]>-307, asign(y)*10^F(0)[1], asign(y)*10^(-307)), asign(y)*10^307) ''Auto {{previous: 5642.27}} { {MinRange: -3}} {{MaxRange: 9}} b = if(x50(x,y)-min(x)=0, 1, -ln(.5)/(x50(x,y)-min(x))) ''Auto {{previous: 0.184804}} {{MinRange: 0}} {{MaxRange: 1}} [Equation] f = a*exp(-b*x) fit f to y ''fit f to y with weight reciprocal_y ''fit f to y with weight reciprocal_ysquare

''fit f to y with weight reciprocal_pred ''fit f to y with weight reciprocal_predsqr [Constraints] b>0 [Options] tolerance=0.0000000001 stepsize=1 iterations=200Page 53 of 79 

### Appendix B – Evaluation of Toxic Degradates of ConcernPage 54 of 79 Structural activity relationship models su ch as ECOSAR are used to characterize major degradates and identif y toxic degradates of con cern by comparing degradate modeled toxicities to MITC, which is the stre ssor of concern in this risk assessment. ECOSAR, a utility under EPISuite 4, estimates the toxicity of chemicals discharged to water. ECOSAR predicts toxicity to fis h, aquatic invertebrates and algae using an extensive set of structure-activity relati onships (SARs). The program estimates a chemical's acute (short-term) toxicity and, when available, and chronic (long-term or delayed) toxicity (USEPA, 2010[2]). Table B-1 shows that ECOSAR estimated MITC toxicities are underpredicted with the exception of fres hwater, which is slightly overpredicted. However, Table B-2 shows that the margins of the underprediction are generally surpassed by the margin that ECOS AR predicts higher toxicity for parent MITC as compared to all of the major de gradates as shown in Table C-2. The only exception to this is DMU toxicity for green al gae, which ECOSAR predicts is lower than the measured toxicity for MITC. However, inclusion of DMU as a degradate of concern based on green algae toxicity is not expect ed to significantly impact the existing risk determinations. The ECOSAR RUNS for MITC, methylamine, DMTU, DMU, and synmethylthioformamide/anti-methylformamide are shown in Figures B-1, B-2, B-3, B-4, and B-5 , respectively.

Table B-1. MITC measured versus ECOSAR predicted toxicity.

Taxa Endpoint MITC Measured Toxicity

(ppm) MITC ECOSAR Toxicity

(ppm) ECOSAR Departure

Factor 2
Freshwater Fish 1 96-hr LC 50 (Acute) 0.0512 0.079 0.556 Daphnid 48-hr LC 50 (Acute) 0.055 1.207 21.945 Green Algae 96-hr EC 50 (Acute) 0.254 1.412 5.559

1. The lowest toxicity value between rai nbow trout and bluegill sunfish shown in the table.
2. ECOSAR Departure Factor = MITC ECOSAR Toxicity/MITC Measured Toxicity.

Table B-2. MITC versus ECOSAR predic ted toxicity for methylamine (deg. 1), DMTU (deg. 2), DMU (deg. 3), syn-N-meth ylthioformamide (deg. 4), and anti-Nmethylthioformamide (deg. 5) (dep arture factors in parenthesis).

Taxa Endpoint MITC ECOSAR Toxicity

(ppm) Deg. 1 ECOSAR Toxicity

(ppm) Deg. 2 ECOSAR Toxicity

(ppm) Deg. 3 ECOSAR Toxicity

(ppm) Deg. 4 ECOSAR Toxicity

(ppm) Deg. 5 ECOSAR Toxicity

(ppm) Freshwater Fish 1 96-hr LC 50 (Acute) 0.079 210.956 (2,670.3) 56,266.277 (712,231.2) 306.85 (3,884.2) 17,844.49 (225,879.6) 17,844.49 (225,879.6) Daphnid 48-hr LC 50 (Acute) 1.207 12.337 (10.2) 6.720 (5.6) 6,171.71 (5,113.3) 6,623.911 (5,487.9) 6,623.911 (5,487.9)

Green Algae 96-hr LC 50 1.412 2.247 (1.6) 4.617 (3.27) 0.075 (0.05) 920.575 (652.0) 920.575 (652.0)Page 55 of 79 Taxa Endpoint MITC ECOSAR Toxicity

(ppm) Deg. 1 ECOSAR Toxicity

(ppm) Deg. 2 ECOSAR Toxicity

(ppm) Deg. 3 ECOSAR Toxicity

(ppm) Deg. 4 ECOSAR Toxicity

(ppm) Deg. 5 ECOSAR Toxicity

(ppm) (Acute) 1. The lowest toxicity value between rai nbow trout and bluegill sunfish shown in the table.
2. ECOSAR Departure Factor = Degradate ECOSAR Toxic ity/MITC Measured Toxicity.Page 56 of 79 Figure B-1. MITC ECOSAR run.

SMILES : N(=C=S)CCHEM : Methane, isothiocyanatoCAS Num: ChemID1: ChemID2: ChemID3: MOL FOR: C2 H3 N1 S1 MOL WT : 73.11 Log Kow: 1.30 (KowWin estimate) Melt Pt: Wat Sol: 7600 mg/L (experimental database)

ECOSAR v1.00 Class(es) Found

------------------ ------------ Thiocyanates Predicted ECOSAR Class Organism Duration End Pt mg/L (ppm)

========================= == ================== ======== ======

========== Thiocyanates : Fish 96-hr LC50 0.079 Thiocyanates : Daphnid 48-hr LC50 1.207 Thiocyanates : Green Algae 96-hr EC50 1.412 Thiocyanates : Fish ChV 0.013 ! Thiocyanates : Daphnid ChV 0.180 ! Thiocyanates : Green Algae ChV 0.333

========================= == ================== ======== ======

========== Neutral Organic SAR : Fish 96-hr LC50 220.353 (Baseline Toxicity) : Daphnid 48-hr LC50 116.832 : Green Algae 96-hr EC50 37.792 : Fish ChV 21.244 : Daphnid ChV 9.534 : Green Algae ChV 12.036

Note: * = asterisk designates: Chemical may not be soluble enough to measure this predicted effect.

Note: ! = exclamation designates: Th e toxicity value was determined from a predicted SAR using establis hed acute-to-chronic ratios and ECOSAR regression techniques which ar e documented in the supporting Technical Reference Manual. When possi ble, this toxicity value should be considered in a weight of evidence approach.Page 57 of 79 Thiocyanates:

------------ For All Acute and Chronic Toxicity Va lues: If the log Kow of the chemical is greater than the valu e listed below, or if th e compound is solid and the LC50, EC50 or ChV exceeds the water solubility by 10X, no effects at saturation are predicted for these endpoints.

ECOSAR v1.00 SAR Limitations:

--------------- ------------- Maximum LogKow: 6.0 (Fish 96-hr LC50) Maximum LogKow: 5.0 (Daphnid LC50) Maximum LogKow: 6.4 (Green Algae EC50 Maximum LogKow: 8.0 (ChV) Maximum Mol Wt: 1000

Baseline Toxicity SAR Limitations:

------------------ --------------- Maximum LogKow: 5.0 (Fish 96-hr LC50; Daphnid LC50) Maximum LogKow: 6.4 (Green Algae EC50) Maximum LogKow: 8.0 (ChV) Maximum Mol Wt: 1000

------------------ ------------------ --------------- --------------- ------------Page 58 of 79 Figure B-2. Methylamine ECOSAR run.

SMILES : NC CHEM : Methanamine CAS Num: ChemID1: ChemID2: ChemID3: MOL FOR: C1 H5 N1 MOL WT : 31.06 Log Kow: -0.64 (KowWin estimate) Melt Pt: Wat Sol: 1.08E+006 mg/L (experimental database)

ECOSAR v1.00 Class(es) Found

------------------ ------------ Aliphatic Amines Predicted ECOSAR Class Organism Duration End Pt mg/L (ppm)

========================= == ================== ======== ====== Aliphatic Amines : Fish 96-hr LC50 210.956 Aliphatic Amines : Daphnid 48-hr LC50 12.337 Aliphatic Amines : Green Algae 96-hr EC50 2.247 Aliphatic Amines : Fish ChV 2.907 Aliphatic Amines : Daphnid ChV 0.007 Aliphatic Amines : Green Algae ChV 1.794 Aliphatic Amines : Fish (SW) 96-hr LC50 219.921 Aliphatic Amines : Mysid Sh rimp (SW) 96-hr LC50 12.503 Aliphatic Amines : Green Algae (SW) 96-hr EC50 2.224 Aliphatic Amines : Fish (SW) ChV 2.907 Aliphatic Amines : Mysid Shrimp (SW) ChV 0.007 Aliphatic Amines : Green Algae (S W) ChV 1.575

========================= == ================== ======== ======

========== Neutral Organic SAR : Fish 96-hr LC50 4088.551 (Baseline Toxicity) : Daphnid 48-hr LC50 1714.937 : Green Algae 96-hr EC50 250.419 : Fish ChV 411.433 : Daphnid ChV 99.337 : Green Algae ChV 55.980

Note: * = asterisk designates: Chemical may not be soluble enough to measure this predicted effect.

Aliphatic Amines:Page 59 of 79 ---------------- For Fish 96-hr LC50: For aliphatic amines with log Kow greater than 7.0, a test duration of greater than 96 hrs may be required for proper expression of toxicity. Also, if th e toxicity value obtained by the use of this equation exceeds the water so lubility (measured or estimated), mortalities greater than 50% would not be expected in a saturated solution during an exposure period of 96 hrs.

For Daphnid 48-hr LC50: For aliphatic amines with log Kow greater than 5.0, a test duration of greater than 48 hrs may be required for proper expression of toxicity. Also, if th e toxicity value obtained by the use of this equation exceeds the water so lubility (measured or estimated), significant mortalities w ould not be expected in a saturated solution during an exposure period of 48 hrs.

For Green Algae Acute Toxicity Values : If the log Kow of the chemical is greater than 7, or if the compound is solid and the EC50 exceeds the water solubility by 10X, no effects at satura tion are predicted for these endpoints.

For Mysid Shrimp Acute Toxicity Valu es: If the log Kow of the chemical is greater than 6, or if the compound is solid and the EC50 exceeds the water solubility by 10X, no effects at satura tion are predicted for these endpoints.

For Fish and Daphnid Chronic Toxicity Values: If the log Kow of the chemical is greater than 8.0, or if the compound is solid and the ChV exceeds the water solubility by 10X, no effects at satura tion are predicted for these endpoints.

For Green Algae Chronic Toxicity Va lues: If the log Kow of the chemical is greater than 7.0, or if the compound is solid and the ChV exceeds the water solubility by 10X, no effects at satura tion are predicted for these endpoints.

ECOSAR v1.00 SAR Limitations:

--------------- ------------- Maximum LogKow: 6.0 (Fish, Mysid LC50) Maximum LogKow: 5.0 (Daphnid LC50) Maximum LogKow: 7.0 (Green Algae EC50) Maximum LogKow: 8.0 (Fish, Daphnid ChV) Maximum LogKow: 7.0 (Green Algae ChV) Maximum Mol Wt: 1000

Baseline Toxicity SAR Limitations:

------------------ --------------- Maximum LogKow: 5.0 (Fish 96-hr LC50; Daphnid LC50) Maximum LogKow: 6.4 (Green Algae EC50) Maximum LogKow: 8.0 (ChV) Maximum Mol Wt: 1000Page 60 of 79 Figure B-3. DMTU ECOSAR run.

SMILES : N(C(=S)NC)CCHEM : Thiourea, N,N'-dimethylCAS Num: 000534-13-4 ChemID1: ChemID2: ChemID3: MOL FOR: C3 H8 N2 S1 MOL WT : 104.17 Log Kow: -0.38 (KowWin estimate) Melt Pt: Wat Sol: 1E+006 mg/L (experimental database)

ECOSAR v1.00 Class(es) Found

------------------ ------------ Thioureas Predicted ECOSAR Class Organism Duration End Pt mg/L (ppm)

========================= == ================== ======== ======

========== Thioureas : Fish 96-hr LC50 56266.277 Thioureas : Daphnid 48-hr LC50 6.720 Thioureas : Green Alg ae 96-hr EC50 4.617 Thioureas : Fish ChV 4731.437 ! Thioureas : Daphnid ChV 0.523 ! Thioureas : Green Algae ChV 0.338

========================= == ================== ======== ======

========== Neutral Organic SAR : Fish 96-hr LC50 8259.677 (Baseline Toxicity) : Daphnid 48-hr LC50 3575.216 : Green Algae 96-hr EC50 580.884 : Fish ChV 826.408 : Daphnid ChV 216.845 : Green Algae ChV 136.173

Note: * = asterisk designates: Chemical may not be soluble enough to measure this predicted effect.

Note: ! = exclamation designates: Th e toxicity value was determined from a predicted SAR using establis hed acute-to-chronic ratios and ECOSAR regression techniques which ar e documented in the supporting Technical Reference Manual. When possi ble, this toxicity value should be considered in a weight of evidence approach.Page 61 of 79 Thioureas :

---------- For Fish and Daphnid Acute Toxicity Values: If the log Kow of the chemical is greater than 5.0, or if the com pound is solid and the LC50 exceeds the water solubility by 10X, no effects at saturation are predicted for these endpoints.

For Green Algae Acute Toxicity Values : If the log Kow of the chemical is greater than 6.4, or if the compound is solid and the EC50 exceeds the water solubility by 10X, no effects at satura tion are predicted for these endpoints.

For All Chronic Toxicity Values: If the log Kow of the chemical is greater than 8.0, or if the compound is solid a nd the ChV exceeds the water solubility by 10X, no effects at saturation ar e predicted for these endpoints.

ECOSAR v1.00 SAR Limitations:

--------------- ------------- Maximum LogKow: 5.0 (LC50) Maximum LogKow: 6.4 (EC50) Maximum LogKow: 8.0 (ChV) Maximum Mol Wt: 1000

Baseline Toxicity SAR Limitations:

------------------ --------------- Maximum LogKow: 5.0 (Fish 96-hr LC50; Daphnid LC50) Maximum LogKow: 6.4 (Green Algae EC50) Maximum LogKow: 8.0 (ChV) Maximum Mol Wt: 1000Page 62 of 79 Figure B-4. DMU ECOSAR run.

SMILES : O=C(NC)NCCHEM : Urea, N,N -dimethylCAS Num: 000096-31-1 ChemID1: ChemID2: ChemID3: MOL FOR: C3 H8 N2 O1 MOL WT : 88.11 Log Kow: -0.62 (KowWin estimate) Melt Pt: Wat Sol: 1.615E+004 mg/L (WskowWin estimate)

ECOSAR v1.00 Class(es) Found

------------------ ------------ Substituted Ureas Amides Predicted ECOSAR Class Organism Duration End Pt mg/L (ppm)

========================= == ================== ======== ======

========== Substituted Ureas : Fish 96-hr LC50 2055.694 Substituted Ureas : Daphnid 48-hr LC50 6171.706 Substituted Ureas : Green Algae 96-hr EC50 0.075 Substituted Ureas : Fish ChV 24.377 Substituted Ureas : Daphnid ChV 308.215 Substituted Ureas : Green Algae ChV 0.026 !

Amides : Fish 96-hr LC50 1348.192 Amides : Daphnid 48-hr LC50 306.850 Amides : Green Al gae 96-hr EC50 1.042 Amides : Fish ChV 7.970 Amides : Daphnid ChV 4.048 ! Amides : Green Algae ChV 0.147

========================= == ================== ======== ======

========== Neutral Organic SAR : Fish 96-hr LC50 11265.005 (Baseline Toxicity) : Daphnid 48-hr LC50 4733.666 : Green Algae 96-hr EC50 695.488 : Fish ChV 1133.227 : Daphnid ChV 274.924 : Green Algae ChV 155.900

Note: * = asterisk designates: Chemical may not be solublePage 63 of 79 enough to measure this predicted effect.

Note: ! = exclamation designates: Th e toxicity value was determined from a predicted SAR using establis hed acute-to-chronic ratios and ECOSAR regression techniques which ar e documented in the supporting Technical Reference Manual. When possi ble, this toxicity value should be considered in a weight of evidence approach.

Substituted Ureas:

----------- ------ For Fish and Daphnid Acute Toxicity Values: If the log Kow of the chemical is greater than 5.0, or if the com pound is solid and the LC50 exceeds the water solubility by 10X, no effects at saturation are predicted for these endpoints.

For Green Algae Acute Toxicity Values : If the log Kow of the chemical is greater than 6.4, or if the compound is solid and the EC50 exceeds the water solubility by 10X, no effects at satura tion are predicted for these endpoints.

For All Chronic Toxicity Values: If the log Kow of the chemical is greater than 8.0, or if the compound is solid a nd the ChV exceeds the water solubility by 10X, no effects at saturation ar e predicted for these endpoints.

ECOSAR v1.00 SAR Limitations:

--------------- ------------- Maximum LogKow: 5.0 (LC50) Maximum LogKow: 6.4 (EC50) Maximum LogKow: 8.0 (ChV) Maximum Mol Wt: 1000

Amides :

------- No limitations known at this time.

ECOSAR v1.00 SAR Limitations:

--------------- ------------- Maximum LogKow: >8.5 (LC50) Maximum LogKow: >8.0 (EC50,ChV) Maximum Mol Wt: 1000

Baseline Toxicity SAR Limitations:

------------------ --------------- Maximum LogKow: 5.0 (Fish 96-hr LC50; Daphnid LC50) Maximum LogKow: 6.4 (Green Algae EC50) Maximum LogKow: 8.0 (ChV) Maximum Mol Wt: 1000Page 64 of 79 Figure B-5. syn-N-methylthioformamide (d eg. 4), and anti-N-methylthioformamide ECOSAR run.

SMILES : NC(=S)C CHEM : Ethanethioamide CAS Num: 000062-55-5 ChemID1: ChemID2: ChemID3: MOL FOR: C2 H5 N1 S1 MOL WT : 75.13 Log Kow: -0.83 (KowWin estimate) Melt Pt: Wat Sol: 1.63E+005 mg/L (experimental database)

ECOSAR v1.00 Class(es) Found

------------------ ------------ Neutral Organics Predicted ECOSAR Class Organism Duration End Pt mg/L (ppm)

========================= == ================== ======== ======

========== Neutral Organics : Fish 96-hr LC50 17844.490 Neutral Organics : Fish 14-day LC50 17238.707 Neutral Organics : Daphnid 48-hr LC50 6623.911 Neutral Organics : Green Alga e 96-hr EC50 920.575 Neutral Organics : Fish 30-day ChV 1538.136 Neutral Organics : Daphnid ChV 490.584 Neutral Organics : Green Algae ChV 219.521 Neutral Organics : Fish (S W) 96-hr LC50 30757.049 Neutral Organics : Mysid Shr imp 96-hr LC50 1.34e+005 Neutral Organics : Fish (SW) ChV 511.459 Neutral Organics : Mysid Shr imp (SW) ChV 26748.623 Neutral Organics : Earthworm 14-day LC50 256.639

Note: * = asterisk designates: Chemical may not be soluble enough to measure this predicted effect.

Neutral Organics:

---------------- For Fish LC50 (96-h), Daphnid LC50, Mysid: If the log Kow is greater than 5.0, or if the compound is so lid and the LC50 exceeds the water solubility by 10X, no effects at saturation are predicted.

For Fish LC50 (14-day) and Earthw orm LC50: If the log Kow is greater than 6.0, or if the compound is so lid and the LC50 exceeds the waterPage 65 of 79 solubility by 10X, no effects at saturation are predicted.

For Green Algae Acute Toxicity Values : If the log Kow of the chemical is greater than 6.4, or if the compound is solid and the EC50 exceeds the water solubility by 10X, no effects at satura tion are predicted for these endpoints.

For All Chronic Toxicity Values: If the log Kow of the chemical is greater than 8.0, or if the compound is solid a nd the ChV exceeds the water solubility by 10X, no effects at saturation ar e predicted for these endpoints.

ECOSAR v1.00 SAR Limitations:

--------------- ------------- Maximum LogKow: 5.0 (Fish 96-hr LC50; Daphnid LC50, Mysid LC50) Maximum LogKow: 6.0 (Fish 14-day LC50; Earthworm LC50) Maximum LogKow: 6.4 (Green Algae EC50) Maximum LogKow: 8.0 (ChV) Maximum Mol Wt: 1000Page 66 of 79 

### Appendix C – STIR Model Run to Establish Drinking Water and Dietary Exposure Conceptual M odel for Birds and MammalsPage 67 of 79 

### Appendix D – SIP Model Run to Establish Drinking Water Exposure Conceptual Model for Birds and Mammals

Table 1. Inputs Parameter Value Chemical name Solubility (in water at 25 o C; mg/L) 8610

Mammalian LD 50 (mg/kg-bw) 55 Mammalian test species laboratory rat Body weight (g) of "other" mammalian species

Mammalian NOAEL (mg/kg-bw) Mammalian test species Body weight (g) of "other" mammalian species

Avian LD 50 (mg/kg-bw) 0 Avian test species northern bobwhite quail Body weight (g) of "other" avian species Mineau scaling factor

Mallard NOAEC (mg/kg-diet) Bobwhite quail NOAEC (mg/kg-diet) NOAEC (mg/kg-diet) for other bird species Body weight (g) of other avian species NOAEC (mg/kg-diet) for 2nd other bird species Body weight (g) of 2nd other avian species

Table 2. Mammalian Results Parameter Acute Chronic Upper bound exposure (mg/kg-bw) 1480.9200 1480.9200 Adjusted toxicity value (mg/kg-bw) 42.3038 0.0000 Ratio of exposure to toxicity 35.0068 0.0000

Conclusion* Exposure through drinking water alone is a potential concern for mammals Due to insufficient data, risk cannot be precluded

Table 3. Avian Results Parameter Acute Chronic Upper bound exposure (mg/kg-bw) 6974.1000 6974.1000 Adjusted toxicity value (mg/kg-bw) 0.0000 0.0000 Ratio of exposure to acute toxicity 0.0000 0.0000

Conclusion* Due to insufficient data, risk cannot be precluded Due to insufficient data, risk cannot be precludedPage 68 of 79 

### Appendix E – Earthworm Fugacity Model Results to Establish Dietary Exposure Conceptual M odel for Birds and Mammals

Parameter MITC Application Rate (lbs. a.i./A) 219.4 1

Molecular Weight (g/mol) 73.12

Vapor Pressure (torr) 16

Kd (L/kg) 0.260 Log Kow 1.30 Earthworn Conc g/kg 0.00014

Mammal Diet Dose mg/kg 0.14

Avian Diet Dose mg/kg 0.16

Air conc. 6.3EE4 Mammal Inhaled Dose mg/kg 9.95EE3

Avian Inhaled Dose mg/kg 7.91EE3

15 g mammal, 20g bird. Results based on STIR model and Earthworm Fugacity Model. Depth 10 cm for earthworm exposure zone.
1 Dazomet maximum application rate results in highest MITC equivalent application rate of MITC generators (from Metam Sodium = 150.31 lbs. a.i./A, from Metam Potassium = 150.38 lbs. a.i./A).Page 69 of 79 

### Appendix F – Detailed Environmental Fate Summary and Degradate Tables for Metam Sodium, Metam Potassium, and MITCPage 70 of 79 Hydrolysis

Metam sodium degrades rapidly due to hydr olysis, especially unde r acid and neutral conditions. The hydrolysis of metam sodium ha lf-lives were 2 days at pH 5 and 7, and 4.5 days at pH 9 (Table ). In the hydrolysis study, the degradates id entified in all test solutions were MITC, methylamine, 1,3-di methylthiourea (DMTU) and 1,3 dimethylurea (DMU). Methylcarbamo (dithioperoxo) thioate (MCDT) was identified in the pH 9 test solutions. The major degradate formed at pH 5 and 7 was MITC (16% to 65% respectively). At pH 9, two major degradat es formed, with 20 % of MITC and 16% of MCDT. The formation of methylamine was fa vored under acidic cond itions compared to neutral or alkaline conditions. MITC is modera tely persistent with hydrolysis half-lives of 3.5 days at pH 5, 20.4 days at pH 7, and 4.6 days at pH 9 (MRID 00158162). Methylamine was the main degradatee of MI TC identified in all pHs. One other degradate, 1,3-dimethylthi ourea was isolated in the pH 9 only, comprised a maximum 22.1% of the recovered at 13.04 days post-treatment.

Photolysis in Water

The photodegradation of metam sodium in aqueous solution is very rapid with a half-life of 28 minutes. Except for N-methylthioformam ide, the degradates identified in the photodegradation study were also iden tified in the hydrolysis study. Nmethylthioformamide were at a maximum c oncentration of 22.3% by the end of the study interval; methylamine increased to 17.5%, MITC increased to 16%, and MCDT increased to 14.1%. The placement of metam sodium below the soil surface (except surface applications), and rapid degr adation of metam sodium in soil to volatile MITC suggest that photolysis on soil would be a negligible route of dissipa tion in the environment.

Microbial Degradation

In an aerobic soil metabolism study (MRID 401985-02), metam sodium degrades very rapidly in soil with a half-life of 23 minutes . The majority of the residues had been volatilized: 83% of the applie d as MITC; 0.2% as other or ganic volatiles, and 0.9% as CO 2 . The major nonvolatile degrad ate was DMU at a maximum of 0.45 ppm at 3 and 7 days. The degradation rates of MITC in soils have been reported in number of studies (Ashley et al., 1963, Gerstl et al., 1977). These studies generally found that MITC degradation in soil was dominated by micr obial processes and followed first-order degradation kinetics. Gerstl et al. (1977) demonstrated th at metam sodium breakdown to MITC was rapid and generally less than 30 minutes at moisture contents below saturation. They also reported that MITC was found to persist longer than metam sodium, with half-lives ranging from 3.3 to 9.9 days depending on soil composition. Since MITC is a volatile compound, very little information is available on the metabolites of MITC degradation in soil. Smelt et al. (1989) investigated the accelerated decomposition rates of MITC in previously me tam sodium treated soil and suggested that repeated application of metam sodium induced microbial adaptation, resulting in enhanced biotransformation of MITC. D ungan and Yates (2003) reported that the microorganisms responsible for enhanced degr adation of MITC specifically target the