1 

### Appendix A. Environmental Fate and Transport Data

835-2120 Hydrolysis (MRID# 46903532)

Dimethyl disulfide remained stable to hydolysis at a test concentration of approximately 15 ppm. [ 14 C] Dimethyl disulfide was test ed at aqueous buffered pH 4 (0.01M phthalate), pH 7 (0.01M phosphate) and pH 9 (0.01M borate) solutions. The study was conducted in darkness at 50°C. Samples of dimethyl disulfide were taken at Days 0, 1, 2, 3, 4, and 5 posttreatment and conentrations ranged from 16.55 ppm to 15.39 in the pH 4 phthalate buffer solution, from 14.22 to 14.76 ppm in the pH 7 phosphate buffer solu tion, and from 14.78 ppm to 13.70 ppm in the pH 9 borate buffer solution. The pH of the buffe r solutions remained steady throughout the study, ranging from 4.039 - 4.069, 7.056 - 7.090, and 9.044 - 9.088. Based on the results reported by the registrant, a typical study environment of 25°C is not necessary in this case since dimethyl disulfide did not degrade substantially in this experimental environment. However, the study was only conducted for five days; a study duration of at least 30 da ys or one half-life should be conducted for hydrolysis studies per OPPTS Guid elines 835-2120. Therefore, this study is

classified Supplemental.

835-2240 Phototdegradation in Water (MRID# 47052818)

Approximately 0.2 ppm of [ 14 C] dimethyl disulfide in ster ile ultrapure water solution was exposed to 4 days of continuous artificial irradiation from a xenon arclamp with a wavelength spectrum of 295 – 800 nm. The study author indicated that the level of ir radiation in the study was the equivalent exposure of natural irradiation for a 30, 12-hour day and 12-hour night cycle.

The half-life was determined to be 28.125 hours ba sed on the experimental half-life, subtracted from the half-life observed in the dark control, and adjusted to the 12- hour day-night cycle. Samples were collected at 0, 1, 2, 5, and 24 hours posttreatment.

The registrant proposed a degradation pathway from aqueous photolysis of parent dimethyl disulfide (see figure below). DMDS can initially degrade to the methyl thiyl radical (CH 3 S·). A

series of oxidation and recombination reactions ca n result in the formation of the methyl thiyl peroxy radical (CH 3 SOO·) and the methyl thiyl oxy radical (CH 3 SO·). The methyl thiyl oxy radical can then decompose to the methyl radical (CH 3 ·) and sulfur dioxide and subsequent recombination with the methyl thiyl radi cal can form methane sulfonic acid (CH 3 SCH 3 ). In a more oxygen rich environment, the methyl radica l can further oxidize to form the the methyl peroxy radical (CH 3 OO·) and recombine with a second methyl peroxy radical and a methyl thiyl radical to form formic acid (CH 2 O 2 ) with hydride ion react ion, formaldehyde (CH 2 O) with hydroxide ion reaction, and methyl peroxide (CH 3 OOH) with hydrogen radical reaction.

The registrant identified but di d not quantify three possible major degradates. The registrant attributed one peak on the HPLC plot, designated Deg-1, to thr ee polar transformation products accounting for 59.3 percent of the applied residue peaking on Day 1 posttreatment, in one replicate. Two of the three products accounted fo r major components of the material balance (> 10 percent of the applied). The registrant iden tified that methanesulfonic acid, methanesulfinic acid, and sulfuric acid could have corresponded to the two major degradates detected in the Deg-1 region. Two additional peaks on the HPLC plot, designated as Reg-1 and Reg-2 accounting for 26.3 and 24.5 percent of the applied residue, were comprised of multiple unidentified minor transformation products. Residues in association w ith these regions on the HPLC plot peaked on Day 1 posttreatment.

This study is classified Supplemental due to high retrieved material balances up to 121 percent by 24-hours posttreatment, indicating the potential for possible contamination. In addition, the sampling intervals were too infrequent between hours 5 and 24 hours posttreatment. This gap in sampling leads to uncertainty in the form ation and decline of degradation products.

835-2240 Photodegradation in Water (MRID# 47052802)

23 This study followed the Tier I procedure proposed OECD Guideline, “Phototransformation of

Chemicals in Water – Direct and Indirect Photolysis”. A solution of 275 mg/L of [ 14 C] dimethyl disulfide in ultrapure water was irradiated po lychromatically in the UV and Visible spectra. However, it is unclear from the study the type of irradiation that dimethyl disulfide was exposed to. Regardless, an aquatic photolysis half-lif e was obtained through the cumulative calculated molar absorption coefficient over the 295 to 800 nm spectrum window and the average daily solar photon flux irradiance assuming a quantum yi eld of one. Molar absorption coefficients were calculated using the Beer-Lambert Law ba sed on the polychromatic absorbances measured by a dual-beam Varian 100-Bio UV-VIS Spectro photometer, the measured concentration of DMDS residues, and the photon path length of 1 cm. The average daily solar photon flux irradiance was set to the equiva lent seasonal value at 50oN lat itude with clear sky conditions. The minimum aqueous photolysis half lives calculated were 1.7, 1.3, 3.3, and 7.5 hours for spring, summer, fall, and winter, respectively. The theoretical maximum percent aqueous photolysis over a 30-day period was 100 percent over all seasons. According to the proposed OECD guideline, aqueous photolysis is signif icant enough of a process for which a refined aqueous photolysis study is need ed since the theoretical percen tages photolysis of dimethyl disulfide residues are greater than 50 percen t. Therefore, this study is classified Supplemental. The registrant submitted a refined study in MR ID No. 47052818, “Dimethyl diulfide photolysis

in the environment”.

835.2370 Photodegradation in Air (MRID# 47052803)

The registrant provided the value of the photoys is in air half-life of 0.047 days (1.1. hours)

calculated from the AOPWIN v1.91 software. This submittal will be classified as Supplemental for the purposes of satisfying the data requirement at this time. Howeve r, a photolysis in air study utilizing field or laboratory methods may be requested in the future pending revision of the OPPTS guidelines.

835.2370 Photodegradation in Soil

All proposed labels require imme diate tarping after applicatio n. Therefore, this study is waived since the tarping material is expected to mi nimize direct solar radi ation reaching the soil.

835.4300 Aerobic Soil Metabolism (MRID#47052819)

Aerobic soil metabolism was tested under darkness with 390 mg/kg of [ 14 C] dimethyl disulfide on two domestic soils, California loamy sand and Florida sand as well as on two foreign soils, Swiss Clay and France clay loam. FAO soil classi fications were also provided to discern the chemical and mineralogical representativeness of these foreign soils to domestic soils. The

France and Switzerland soils were classified as Dystric Cambisol and Calcaric Cambisol, respectively. Cambisols fall unde r the category of the Inceptisol U.S. Taxonomic Classification, which are found domestically in th e Southwest. Therefore, the mineral and chemical properties of these soils can be considered represen tative of that which is found domestically.

The California loamy sand test was sampled on days 0, 1, 7, 14, 21, 62; and 120 days4 posttreatment; the Florida sand test was sampled on days 0, 1, 4, 7, 14, 21, 60, and 120 days posttreatment; the France clay loam test was sampled on 0, 1, 4, 7, 11, 14, 21, and 59 days posttreatment; and the Switzer land clay soil test was sampled on days 0, 1, 4, 7, 11, 14, 21, 59, and 120 days posttreatment.

In each of the four test soils, most of the total residue of DMDS in the soil diffused rapidly to the solid-phase carbon trap within 5 minutes postapplic ation. However, over tim e, residues of the major degradate, Methanesulfonic Acid, accumulate d in the acetonitrile and aqueous soil extracts over time to levels of 3.26 percent for Califor nia sandy loam soil by Day 120 posttreatment, 4.95 percent for Florida sandy soil by Day 120 posttr eatment, 33.17 percent France clay loam soil by Day 14 posttreatment, and 32.86 percent in the Sw itzerland clay soil by Day 21 posttreatment. In addition, residues of volatile organic compoun ds and carbon dioxide accumulated in the KOH trapping solution to 27.24 percent of the appl ied parent. Although unclear, the reviewer postulates that the build up of th e degradate over time in the soil is due to gaseous deposition of dimethyl disulfide in the equilibrium process of the experimental system and subsequent formation of degradation products. This is unc lear since only trace amounts of dimethyl

disulfide in the soil were detected.

The aerobic soil metabolism half-life of DM DS was estimated from soil degradate (methanesulfonic acid, unidentified extracta ble residue, non-extractable residue, and CO 2 )

formation rates in soil because of the high volatility of DMDS; DMDS was only detected in the head space of the biometer flask. Additionally, the aerobic soil metabolism studies for DMDS were designed as closed-head space test system s. The combination of the high volatility of DMDS and the closed-head space of the test system s led to no detection of DMDS in the soil as well as possible sterilization of the soil in th e test system from a fumigation effect.

The DMDS concentration in soil was approximated in aerobic soil metabolism data (MRID 47052819) using the following equation:

DMDS estimate = 1.00 – ∑ (soil degradation products) time

Soil degradation product = methanesulfonic acid + unident ified extractable residue +

unextractable residue + CO 2 (% of applied radioactivity) at each time interval.

The table below shows the estimated concentra tion of DMDS from the aerobic soil metabolism studies using a total system mass balance.5 DMDS Concentration Estimate in Soil in the Aerobic Soil Metabolism Study (MRID 47052819) Using a Total System Mass Balance Switzerland clay France clay loam Time (Days) Soil Degradation

Products Estimate DMDS Soil Degradation

Products Estimate DMDS

0 2.46 97.54 2.18 97.82

1 21.79 78.21 8.86 91.14

4 23.17 76.83 37.83 62.17

7 34.65 65.35 47.8 52.2

11 41.25 58.75 49.7 50.3

14 44.64 55.36 50.97 49.03

21 47.14 52.86 47.68 52.32

59 47.35 52.65 75.18 24.82

120 42.7 57.3

For modeling purposes, the 90 th percentile of the mean half-life was calculated using the total

mass balance estimated DMDS half-lives in soil. The 90 th percentile of the mean half-life for total mass balance DMDS is 4.07 days (mean=3.607151, Standard deviation=0.214651 days, t 90,

n-1 = 3.078).

Fitted Parameters for Exponential Decay Mo del for DMDS in Aerobic Soil Metabolism Study (MRID 47052819) Using a Total System Mass Balance.

Soil Model Y

o (% applied) a (% applied) b (days -1 ) Estimated

Half-life

(days) Adjusted

R2

France Clay

Loam 48.0940 47.6464 0.2006 3.45 0.8022

Switzerland Clay 3-parameter exponential decay 53.9264 38.9367 0.1844 3.75 0.9325

Another approach was to assume the degradati on of DMDS can be indirectly modeled from the

formation of methanesulfonic acid. Methanesulfonic acid forms through the breaking of the

disulfide bond in DMDS. The DMDS concentra tion in soil was approximated in aerobic soil metabolism data (MRID 47052819) us ing the following equation:

[DMDS] estimate = 1.00 – [methanesulfonic acid] time

The table below shows the estimated concentra tion of DMDS from the aerobic soil metabolism studies using the residue soil data for methanesulfonic acid.

DMDS Concentration Estimate in Soil in the Aerobic Soil Metabolism Study (MRID6 47052819) Using Methanesulfonic acid formation Switzerland clay France clay loam Time (Days) Methanesulfonic

acid Estimate DMDS Methanesulfonic

acid Estimate DMDS

0 1.42 98.58 1.45 98.55

1 8.09 91.91 6.17 93.83

4 17.47 82.53 21.68 78.32

7 25.67 74.33 29.1 70.9

11 30.34 69.66 32.5 67.5

14 32.16 67.84 33.17 66.83

21 32.86 67.14 32.97 67.03

59 26.8 73.2 35.3 64.7

120 5.76 94.24

Bolded values were not included in the degr adation kinetic analysis because they indicat e DMDS formation. This situation is li kely an artifact of from the degradation of me thanesulfonic acid in soil.

For modeling purposes, the 90 th percentile of the mean half-life was calculated using the estimated methanesulfonic acid (MS) -DMDS half-lives in soil. The 90 th percentile of the mean

half-life for total mass balance MS-DMDS is 4.66 days (mean= 3.3032, Standard deviation=0.6242 days, t 90, n-1 = 3.078).

Fitted Parameters for Exponential Decay Mo del for DMDS in Aerobic Soil Metabolism Study (MRID 47052819).

Soil Model Y

o (% applied) a (% applied) b (days -1 ) Estimated

Half-life

(days) Adjusted

R 2

France Clay

Loam 65.4818 34.1053 0.2422 2.86 0.80

Switzerland Clay 3-parameter exponential decay 65.8673 32.38 0.1851 3.74 0.9948

The registrant proposed a degradation pathway fo r aerobic soil metabolism below. The enzyme

methanethiol oxidase as well as protein disulfide isomerases and oxido reductases may act as catalysts to degrade dime thyl disulfide to methane thiol, methane sulfenic acid, methane sulfinic acid, and methanesulfonic acid. Further degr adation to formaldehyde can occur due to

methanesulfonic activation with a mono-oxygenase enzyme. Multi-step CO 2 mineralization can cause further degradation to formic acid and the hydrocarboxyl radical.This study is classified as Supplemental. Since dimethyl disulfide re sidues were detected in the headspace immediately upon the beginning of the st udy, the route of degradation, as observed with the accumulation of degradate products in the soil over time, is unclear. Furthermore, in the European soil tests, material balances were incomplete with up to 18-23% of the applied unaccounted for at study termination.

835.4200 Anaerobic Soil Metabolism (MRID# 43759301)

Dimethyl disulfide was applied in California sandy loam soil under anaerobic conditions as the the system was flushed with Nitrogen gas in the headspace and then flooded with a layer of 2 - 3 cm of Nitrogen-sparged deionized water. [ 14 C] Dimethyl disulfide was applied at a concentration of 280 mg/L. Samples were extracted on Days 0, 3, 7, 14, 21, and 71 days posstreatment, and the experiment was conducted under darkness. The majority of dimethyl disulfide residues diffused from the test system a nd was detected in solid-phase carbon traps and the KOH solution traps (including the pre-cart ridge KOH trapping solution) within 4 hours posttreatment. Since there is evidence that volat ilization is the major route of dissipation for dimethyl disulfide in the anaer obic environment, a total syst em half-life of 19.6 days was determined considering the formation of metabolite s. However, this is an undefinitive value as

there was an undetermined detec tion of diemthyl disulfide resi dues in the water layer and KOH solution traps as well throughout mo st of the study period. A DT 50 of 14.3 days was determined by the registrant using kinetic modeling KinGui Software.

The major degradates detected included methanet hiol detected at a maximum level of 16 percent of the applied parent residue extracted 14 days posstreatment from the KOH trapping solutions, and methanesulfonic acid which was definitively detected at a maximum level of 16.2 percent 21 days postreatment. However, methanesulfonic acid may have accounted for as much as 38.5 percent of the material balance on 21 days postt reatment extracted from one other replicate KOH trapping solution samples and from the water co lumn sample with undefinitive levels of

methanesulfonic acid residues detected.

7The registrant proposed a degradation pathway shown below. In the mircrobial metabolism process, dimethyl disulfide can interact with with enzyme methionine- γ -lyase to form

methanethiol which can reoxidize to dimethyl disulfide. Methanethi ol can also interact with the methyl-transferase enzyme to form dimethyl sulf ide in saline marine waters. Further microbial

metabolism can result in the breakdown to methane from dimethyl sulfide or from methanethiol.

Methanethiol can also further be metabolized through through cynergisti c interaction between the oxidase and dehyrogenase enzymes to form formaldehyde. Subsequent CO 2 mineralization can occur due to activation with the formaldehyde hyrdrogenase enzyme and intermediate hydrolysis processes can cause the formation formic acid. Further CO 2 mineralization can occur due to activation with the dehydrogenase enzyme resulting in oxidation for the formation of formic acid and the hydrocarobxyl radi cal. Methanesulfonic acid can also form directly from the degradation of dimethyl disulf ide in an oxic environment.

This study is classified as Supplemental. First, the cause of degrad ation is unclear given the study was conducted in darkness and degradates we re definitively detected in the KOH trap solutions. Second, parent and metabolite residues, detected in the water layer, were not quantified. Third, the material balance was inco mplete with up to 29.8 percent of the applied material unaccounted for in one replicate of the Day 3 sample with an additional 19.4 percent of

residues unidentified or undefi nitively determined (e.g., DMDS in KOH traps or DMDS and

89 Methanesulfonic acid in initial water layer). Fourth, verification of the anaerobic environment throughout the duration of the experiment by the determination of dissolved oxygen concentrations or redox potential was not co mpleted. Fifth, multiple samples of widely distributed soil types should be tested to obtain a sufficient database of anaerobic soil

metabolism rates.

835.1230 Leaching and Adsoprtion/Desorptio n – Batch Equilibrium (MRID Nos. 46917014 and 46917015)

The adsorption and desorption of dimethyl disulfid e was determined in four foreign soils: and one domestic soil was determined (Speyer, Germany sandy loam soil, pH 5.6, organic carbon 2.3 %; Mechtildshausen, Germany loam soil, pH 7.4, organic carbon 1.3 %; Mussig, France clay loam soil, pH 7.6, organic carbon 3.0%; Br etagne 1b, France silt loam soil, pH 5.4, organic carbon 2.0%; and California sandy loam soil, pH 7.8, organic carbon 0.6%). These studies are Acceptable and were conducted in accordance with USEPA 835.1230 guidelines. FAO soil classifications were provided by the registra nt. The Speyer, Germany, Mussig, France, and Bretagne, France soils are all classified as cambi sols which are equivalent to Inceptisols in the U.S. Taxonomic Classification sy stem. The Mechtildshausen, Germany soil is classified as Luvic Phaeozem which is equivalent to the Chernozemic soils in the U.S. Taxonomic Classification system. Therefore, the mineral and chemical properties of these soils can be considered representative of th at which is found domestically.

For all soils tested in the studies, [ 14 C] dimethyl disulfide was app lied at concentrations of 0.001, 0.002, 0.011, 0.021, and 0.102 μ g a.i./ml in 14.5 ml CaCl 2 supernatant over a 14.5 g layer of air-dried and sieved (2 mm) soil. The samp les were shaken by a rotary shaker for a 24 hour period followed by an equilibration time of 24 hours. Residues were then extracted from the supernatant by centrifuge at 2800 rp m. The residues in the supe rnatant were quantified using LSC, and the mass that was left over in the soil we re indirectly determined considering the initial mass of dimethyl disulfide in the system. The temperature of the study environment was

maintained at 20 + 2°C.

A desorption phase experiment was also carried out. Following equilibrium from the adsorption phase, the supernatant was removed and repl aced with an equivalent volume of CaCl 2 solution. The desorption phase was then initiated as sample s were shaken by a rotary shaker for a 44 hour period followed by an equilibration time of 44 hours. Residues were then extracted from the supernatant by centrifuge at 2800 rp m. The residues in the supe rnatant were quantified using LSC, and the mass that was left over in the soil we re indirectly determined considering the initial mass of dimethyl disulfide in the system. The temperature of the study environment was

maintained at 20 + 2°C.

For the Speyer, Germany sandy loam soil

, mass balances were 100.6-102.1 percent of the applied residue in the preliminary study. Di methyl disulfide residues accounted for 27.4 - 30.3 percent adsorbed in the soil. The resulting adsorption partiti on coefficients ranged from 0.538 – 0.774 ml/g for all test concentra tions with an average of 0.678 ml/g. The Freundlich adsorption partition coefficient based on all fi ve concentrations was nearly equivalent at 0.719 ml/g with a10 1/n value of 1.011. In the desorp tion phase of the experiment, dimethyl disulfide residues accounted for 21.7 – 25.0 percent desorbed of adso rbed in the soil. The desorption partition coefficients ranged from 3.0 – 4.0 ml/g for all test concentrations with an average of 3.377 ml/g. The Freundlich desorption partition coefficient base d on all five test concentrations was nearly equivalent at 2.531 ml/g with a 1/n value of 0.9535.

For the Mechtildshausen, Germany loam soil

, mass balances were 100.3-101.1 percent of the applied residue in the preliminary study. Di methyl disulfide residues accounted for 25.6 – 38.8 percent adsorbed in the soil. The resulting adsorption partiti on coefficients ranged from 0.451 – 0.667 ml/g for all test concentra tions with an average of 0.597 ml/g. The Freundlich adsorption partition coefficient based on all fi ve concentrations was not near ly equivalent 0.297 ml/g with a 1/n value of 0.867. Desorption properties of the soil were not determined since all dimethyl disulfide residues degraded by 44 hours of equilib rium time during the desorption phase of the experiment.

For the Mussig, France clay loam soil

, mass balances were 102.0-102.1 percent of the applied residue in the preliminary study. Dimethyl di sulfide residues accounted for 24.7 – 39.6 percent adsorbed in the soil. The resulting adsorpti on partition coefficients ranged from 0.415 – 0.667 ml/g for all test concentrations with an average of 0.554 ml/g. The Freundlich adsorption partition coefficient based on all fi ve concentrations was not near ly equivalent 0.300 ml/g with a 1/n value of 0.883. Desorption properties of the soil were not determined since all dimethyl disulfide residues degraded by 44 hours of equilib rium time during the desorption phase of the experiment.

For the Bretagne 1b, France silt loam soil

, mass balances were 102.0-102.1 percent of the applied residue in the preliminary study. In th e desorption phase of the experiment, dimethyl disulfide residues accounted for 25.7 - 32.9 percen t adsorbed in the so il. The resulting adsorption partition coefficients ra nged from 0.670 – 1.00 ml/g for all test concentrations with an average of 0.860 ml/g. The Freundlich adsorp tion partition coefficient based on all five concentrations was nearly equivalent at 1.36 ml/g with a 1/n value of 1.087. Dimethyl disulfide residues accounted for 16.2 – 17.3 percent desorbed of adsorbed in the soil. The desorption partition coefficients ranged from 3.0 – 4.0 ml/g for all test concentrations with an average of 3.181 ml/g. The Freundlich desorption partition coefficient representative of all five concentrations was nearly equivalent at 1.891 ml/g with a 1/n value of 0.9535.

For the California sandy loam soil

, mass balances were 100.3-101.2 percent of the applied residue in the preliminary study. Dimethyl di sulfide residues accounted for 16.1 – 47.6 percent adsorbed in the soil. The resulting adsorpti on partition coefficients ranged from 0.270 – 1.00 ml/g for all test concentrations with an average of 0.537 ml/g. The Freundlich adsorption partition coefficient based on all fi ve concentrations was not nearly equivalent at 0.083 ml/g with

a 1/n value of 0.656. In the deso rption phase of the experiment , dimethyl disulfide residues accounted for 5.6 – 11.5 percent desorbed of adso rbed in the soil. The desorption partition coefficients ranged from 7.7 – 19.0 ml/g for all test concentrations with an average of 12.621 ml/g. The Freundlich desorption partition coe fficient based on all five initial sampled11 concentrations was not near ly equivalent at 1.272 ml/g with a 1/n value of 0.687.

The percent organic carbon of each so il, percent clay content of each soil, and pH of each soil do not show a clear relation to the average partit ion coefficients of each soil with correlation coefficients of 0.792, 0.329, and 0.010, respectively.

835.8100 Field Volatility (MRID Nos. 47052821, 47052822, 47052823, 47052824, and 47377801)

All above field volatilit y studies studies are Acceptable , and no significant deviations from good scientific practices were noted.

Yuma, AZ Loamy Sand – Shank Injection to Raised Beds with Polyethylene Tarp

784 lbs. of 99.5 percent dimethyl disulfide per acr e was applied by shank in jection to depth of 8 inches to raised beds followed by immediate ta rping with 1.5 mm plastic material. The treated field had dimensions of 330 feet by 330 feet with ra ised beds 67 inches wide, 4-6 inches tall. A total of 16 air samplers were symmetrically di stributed about radial distances of 10, 50, and 200 feet completely surrounding the center of the tr eated field at 5-feet above ground-level. Wind and air temperature observations at 1.5 meters and 10 meters above groun d level were collected and were sampled every minute at for the duration of the field study.

The field air samples were fortified with 1.0, 100, 500, and 1,000 μ g of dimethyl disulfide. On the day of treatment, sample periods includ ed Hours 0-7, Hours 7-11, Hours 11-17, and hours 17-23. On Days 1 – 8, samples were collected ev ery six hours. On Days 8 – 14, samples were collected every 12 hours. The Day 0 – 2 averag e field spike recoveries were 85 percent, 93 percent, 91 percent, and 104 percent for the 1.0, 100, 500, and 1,000 μ g fortifications, respectively. The Day 3 – 14 average field spik e recoveries were 86 percent, 96 percent, 84 percent, and 92 percent for the 1.0, 100, 500, and 1,000 μ g fortifications, respectively.

Flux of dimethyl disulfide was b ack-calculated using monitored o ff-field concentrations and the meteorological data using the ISCST3 model. Flux profiles were developed from the comparison of monitored concentrations to mode led concentrations from a unit flux rate of 0.001 g/m 2 s. The relationship between monitored vers us modeled concentrations used in the determination of the flux was statistically significant for the first 12 sampling periods.

The total calculated cumulative flux was 3,811 μ g/m 2 s over the 71 hour period posttreatment. Since 784 lbs. a.i./acre was applied, the calculated flux accounts for approximately 81.43 percent of the applied residue while tarpe d. Temporal peak flux rates of 1,660 μ g/m 2 s (Day 0, Hours 7 – 11) and 37 μ g/m 2 s (Day 1, Hours 11 – 17) were calculated.

Nipomo Lake, CA Sandy Loam – Drip Irrigati on to Raised Beds with Polyethylene Tarp

573 lbs. of 95 percent dimethyl disulfide per ac re was applied to raised beds via two drip12 irrigation tapes, separated by 12 inches at a de pth of two inches below the surface followed by immediate tarping with 1.5 mm plas tic material. The treated fiel d had dimensions of 330 feet by 330 feet with raised beds 51 inches wide, 14 inches tall. The tarp was cut and removed five days post-application.

A total of 20 air samplers were symmetrically distributed about radial distances of 100, 150, and 250 feet completely surrounding the center of the treated field at 5-feet above ground-level. In addition, there were measurements taken from a ma st located at the cente r of the treated field with concentration at the 1, 3, 6, and 10 feet levels above ground level, as well as wind and temperature measurements at th e 1, 3, and 10 feet levels above ground level. Wind speed and

direction data were also collected at th e 20-feet level above ground level as well.

The field air samples were fortified with 0.2, 1.0, 5.0, 100, and 5,000 μ g of dimethyl disulfide. On Days 0 - 8 posttreatment, samples were collect ed every four hours. On Days 9 – 15, samples were collected every 12 hours. The average field spike recoveries were 298 percent, 128 percent, 96 percent, 104 percent, and 91 percent for the 0.2, 1.0, 5.0, 100, and 5,000 μ g fortification samples, respectively.

Flux of dimethyl disulfide was b ack-calculated using monitored o ff-field concentrations and the meteorological data using the ISCST3 model. Flux profiles were developed from the comparison of monitored concentrations to mode led concentrations from a unit flux rate of 0.001 g/m 2 s. The relationship between monitored vers us modeled concentrations used in the determination of the flux was statistically significant for the first 18 sampling periods.

The total calculated cumulative flux de termined by the indirect method was 1,295 μ g/m 2 s over the 72 hour period posttreatment. Temporal peak flux rates of 515 μ g/m 2 s (Day 0, Hours 4 – 8),

119 μ g/m 2 s (Day 1, Hours 4 – 8), and 48 μ g/m 2 s (Day 2, Hours 8 – 12) were calculated.

Flux of dimethyl disulfide wa s also calculated using the aer odynamic method. This method incorporates atmospheric stability along with vertical gradients of temperature, concentration, and wind speed using monitored profile d data at four or fi ve height levels at the center of the

treated field.

In general, the aerodynamic method calculation of dimethyl disulfid e flux showed a similar trend in values to the indirect method, although the indi rect method generally showed higher flux rates. However, the data necessary to complete the flux calculation was limited to Hours 4 – 8 of Day 1 to Hours 1 – 4 of Day 2 posttreatment as temperat ure data was not available at any time outside of this period.

Since 602 lbs. a.i./acre was applied and based on the indirect and aerodynamic flux calculations, dimethyl disulfide flux accounts for at least 27.6 4 percent of the applied residue while tarped.

Cantua Creek, CA Clay Loam – Broadcast Sha nk Injection with Polyethylene Tarp

580 lbs. of 95 percent dimethyl disulfide per acre was broadcast applied by shank injection at13 depth of 12 inches followed by immediate tarpin g with 1.0 mm plastic material. The tarp was cut and removed five days post-application.

The treated field had dimensions of 660 feet by 660 feet. A total of 24 air samplers were symmetrically distributed about radial distances of 100, 150, and 250 feet completely surrounding the center of the treated field at 5-feet above ground-level. In addition, there were

measurements taken from four ma sts located at the center of the treated field with concentration at the 1, 3, 6, and 10 feet levels above gr ound level, as well as wind and temperature measurements at the 1, 3, and 10 feet levels above ground level. Wind speed and direction data

were also collected at the 20-feet level above ground level as well.

The field air samples were fortified with 0.2, 1.0, 5.0, 100, and 5,000 μ g of dimethyl disulfide. On Days 0 - 8 posttreatment, samples were collect ed every four hours. On Days 9 – 15, samples were collected every 12 hours. The average field spike recoveries were 219 percent, 99 percent, 91 percent, 88 percent, and 77 pe rcent for the 0.2, 1.0, 5.0, 100, and 5,000 μ g fortification samples, respectively.

Flux of dimethyl disulfide was b ack-calculated using monitored o ff-field concentrations and the meteorological data using the ISCST3 model. Flux profiles were developed from the comparison of monitored concentrations to mode led concentrations from a unit flux rate of 0.001 g/m 2 s. The relationship between monitored vers us modeled concentrations used in the determination of the flux was statistically significant for the first 18 sampling periods.

The total calculated cumulative flux de termined by the indirect method was 2,451 μ g/m 2 s over the 72 hour period posttreatment. Temporal peak flux rates of 312 μ g/m 2 s (Day 0, Hours 12 – 16), 296 μ g/m 2 s (Day 1, Hours 0 – 4), 268 μ g/m 2 s (Day 1, Hours 8 – 12), 83.0 μ g/m 2 s (Day 1, Hours 20 – 24), and 112 μ g/m 2 s (Day 2, Hours 8 – 12) were calculated.

Flux of dimethyl disulfide wa s also calculated using the aer odynamic method. This method incorporates atmospheric stability along with vertical gradients of temperature, concentration, and wind speed using monitored profile d data at four or fi ve height levels at the center of the

treated field.

In general, flux rates determined using the aerodynamic method show ed a similar general temporal trend compared to the indirect method except for the maximum peak of ca. 502 μ g/m 2 s occurred much later between Hours 1 – 4 of Day 2. . The data necessary to complete the flux calculation was limited to Hours 8 – 12 of Day 0 to Hours 18 – 24 of Day 2 posttreatment as temperature, concentration, and wind data was not available at any time outside of this period.

Since 580 lbs. a.i./acre was applied and based on the indirect and aerodynamic flux calculations, the calculated flux accounts for at least 54.29 percent of the applied residue while tarped.

Bradenton, FL Sand - Shank Injection to Raised Beds with Polyethylene Tarp

633 lbs. of 99 percent dimethyl disu lfide per acre was applied to 82 raised beds, with height of 614 - 8 inches and width of 28 inches, by shallow sha nk injection at depth of 8 to 10 inches followed by immediate tarping with 1.5 – 2.0 mm plastic mate rial. The treated field had dimensions of 333 feet by 530 feet. The tarp was cut a nd removed five days post-application.

A total of 14 air samplers were symmetrically distributed about radial distances of 100, 250, and 500 ft completely surrounding the center of the tr eated field at 5-feet above ground-level. In addition, there were measurements taken from thr ee masts located at the center of the treated

field with concentration at the 0.5, 1, 3, 6, and 10 feet levels above ground level, as well as wind and temperature measurements at the 1, 3, and 10 feet levels above ground level.

The field air samples were fortified with 0.2, 1.0, 5.0, 100, and 5,000 μ g of dimethyl disulfide. On Days 0 - 8 posttreatment, samples were collect ed every four hours. On Days 9 – 15, samples were collected every 12 hours. The average field spike recoveries for al l fortifications ranged between 78.7 - 92 percent with an overal l average recovery of 81.4 percent.

Flux of dimethyl disulfide was b ack-calculated using monitored o ff-field concentrations and the meteorological data using the ISCST3 model. Flux profiles were developed from the comparison of monitored concentrations to mode led concentrations from a unit flux rate of 0.001 g/m 2 s. The relationship between monitored vers us modeled concentrations used in the determination of the flux was statistically significant for the first 18 sampling periods.

The total calculated cumulative flux de termined by the indirect method was 2,849 μ g/m 2 s over the 48 hour period posttreatment. Temporal peak flux rates of 1,189 μ g/m 2 s (Day 0, Hours 20 – 24), and 117 μ g/m 2 s (Day 1, Hours 20 – 24) were calculated.

Flux of dimethyl disulfide wa s also calculated using the aer odynamic method. This method incorporates atmospheric stability along with vertical gradients of temperature, concentration, and wind speed using monitored profile d data at four or fi ve height levels at the center of the

treated field.

In general, flux rates determined using the aero dynamic method showed a similar temporal trend compared to the indirect method. . The data necessary to complete th e flux calculation was limited to Hours 0 – 4 of Day 1 to Hours 20 - 24 of Day 1 posttreatment as temperature and

concentration data was not available at any time outside of this period.

Since 633 lbs. a.i./acre was applied and based on the indirect and aerodynamic flux calculations, the calculated flux accounts for 57.82 percent of the applied residue while tarped.

Dover, FL Loamy Sand - Shank Injection to Raised Beds with Metalized Tarp

608.2 lbs. of 99 percent dimethyl disulfide per acre was applied to 82 raised beds, with height of 6 - 8 inches and width of 28 inches, by shallo w shank injection at depth of 8 to 10 inches followed by immediate tarping with 1.5 – 2.0 mm plastic material. The treated field had dimensions of 333 feet by 530 feet. The tarp wa s cut and removed five days post-application.15 A total of 14 air samplers were symmetrically distributed about radial distances of 100, 250, and 500 ft completely surrounding the center of the tr eated field at 5-feet above ground-level. In addition, there were measurements taken from thr ee masts located at the center of the treated

field with concentration at the 0.5, 1, 3, 6, and 10 feet levels above ground level, as well as wind and temperature measurements at the 1, 3, a nd 10 feet levels above ground level.

The field air samples were fortified with 0.2, 1.0, 5.0, 100, and 5,000 μ g of dimethyl disulfide. On Days 0 - 8 posttreatment, samples were collect ed every four hours. On Days 9 – 15, samples were collected every 12 hours. The average field spike recoveries for al l fortifications ranged between 78.0 – 94.6 percent w ith an overall average recovery of 84.1 percent.

Flux of dimethyl disulfide was b ack-calculated using monitored o ff-field concentrations and the meteorological data using the ISCST3 model. Flux profiles were developed from the comparison of monitored concentrations to mode led concentrations from a unit flux rate of 0.001 g/m 2 s. The relationship between monitored vers us modeled concentrations used in the determination of the flux was statistically signifi cant for the first 18 sampling periods with the exception of the Day 0, Hours 16 – 24 and Day 1, Hours 1 - 4 samples.

The total calculated cumulative flux de termined by the indirect method was 383.53 μ g/m 2 s over the 48 hour period posttreatment. Temporal peak flux rates of 128.62 μ g/m 2 s (Day 0, Hours 20 – 24), and 19.12 μ g/m 2 s (Day 1, Hours 16 – 20) were calculated.

Flux of dimethyl disulfide wa s also calculated using the aer odynamic method. This method incorporates atmospheric stability along with vertical gradients of temperature, concentration, and wind speed using monitored profile d data at four or fi ve height levels at the center of the

treated field.

In general, flux rates determined using the aero dynamic method showed a similar temporal trend compared to the indirect method. . The tre nds between the aerodynamic method and indirect method were similar except the absolute maxi mum occurred 8 hours later during Hours 4 - 8 in Day 1, reaching a level of 38.44 μ g/m 2 s.

Since 608 lbs. a.i./acre was applied and based on the indirect and aerodynamic flux calculations, the calculated flux accounts for 8.1 percen t of the applied residue while tarped.Tifton, GA Loamy Sand (Field 1), Loamy Sand (Field 2), and Sand – Pre-Bedded Shank Injection to Raised Beds with HDPE Tarp (Field 1) and LDPE Tarp (Field 2 and 3)

A three-way mixture of containing a co-formu lated product (containing 79 % DMDS and 21% chloropicrin) and the Vapam formulation of Meta m Sodium (containing 42% a.i.) was applied to three fields. An equivalent of 546.7 lbs. of DMDS was applied to field 1, 538.8 lbs. of DMDS was applied to field 2, and 568.9 lbs. DMDS was a pplied to field 3. The mixture was applied to around ~1 acre fields, with 32 - 35 raised beds, with height of 8 inches, followed by immediate tarping with Virtually Impermeable Film and on field 1, and Low Density Polyethylene (LDPE) tarp on fields 2 and 3. Application times were unknown, but were all expected to occur during the afternoon on February 7. The tarp was cut and removed 270 hour s post-application.

The field air samples were fortified with 1.0, 10.0, and 100 μ g of dimethyl disulfide. Posttreatment samples were collected were co llected every five hours through hours 0 – 5, every 6 hours from hours 5 – 47, every 9 hours from hours 47 – 56, every 12 hours from hours 56 – 272, every 6 hours from hour 272 – 284, and every 12 hours from hour 284 – 320 hours posttreatment for Field 1. Posttreatment samples were collected were co llected every five hours through hours 0 – 4, every 5 hours from hours 4 – 9, every 6 hours from hours 9 – 45, every 9 hours from hours 45 – 54, every 12 hours from hours 55 – 270, every 6 hours from hours 270 – 282, and every 12 hours from hour 282 – 318 hours pos ttreatment for Field 2. Posttreatment samples were collected were collected ever y two hours through hours 0 – 2, every 4 hours from hours 2 – 6, every 6 hours from hours 6 – 42, ev ery 9 hours from hours 42 – 51, every 12 hours from hours 51 – 267, every 6 hours from hour 26 7 – 279, and every 12 hours from hours 279 – 315 hours posttreatment for Field 3. The average fi eld spike recoveries fo r all fortifications ranged between 58.02 – 176.5 percent with an over all average recovery of 104.8 percent.

Flux of dimethyl disulfide was b ack-calculated using monitored o ff-field concentrations and the meteorological data using the IS CST3 model for the first sampli ng period for Fields 1 and 2 and the first two sampling period for Field 3. Flux profiles were developed from the comparison of

monitored concentrations to modeled concen trations from a unit flux rate of 0.001 g/m 2 s. The relationship between monitored versus modeled con centrations used in the determination of the flux was statistically significant for the first 18 sampling periods with the exception of the Day 0, Hours 16 – 24 and Day 1, Hours 1 - 4 samples.

Flux of dimethyl disulfide was al so calculated using the integrated horizontal flux method for the remaining sampling periods. This method in corporates measurem ents of wind speed, concentration, and fetch (dependent on wind direction) at four or five height levels. The wind speed and concentrations are fit to log-linear regression following the ex pected Log Law profile

over the treated field. The flux is solved usi ng the following equation, which integrates the components of flux from the surface roughness length height (z 0 ) to the top of the plume height (z p ):



# ∑ + + = P Z

Z i i dzDzLnCBzLnA

x P

0 ))(*(*))(*( 1

16where A is the slope of the wind speed regressi on line from monitoring data by ln(z), B is the intercept of the wind speed regres sion line from monitoring data by ln(z), C is the slope of the concentration regression from monitoring data by ln(z), D is the intercept of the concentration regression from monitoring data by ln(z), z is the height above ground level. Z p can be determined from the following equation:

Equation 3 

## ( ) ⎥ ⎦ ⎤ ⎢ ⎣ ⎡

−

= C D Z P 1.0 exp

In general, flux rates on Field 1 with VIF tarps applied varied between 3.16 – 54.37 μ g/m 2 s and accounted for 35.2 percent of the amount applied on the field of 546.7 lbs. a.i./A. For Field 2 with LDPE tarp applied, flux rates were higher and varied between 1.46 – 298.19 μ g/m 2 s and accounted for 68.27 percent of the amount applied. For Field 3 with LDPE tarp applied, flux rates were higher than Field 1 but lower th an Field 2 and varied between 0.72 – 153.34 μ g/m 2 s and accounted for 37.92 percent of the amount applied.

835.8100 Field Volatility (MRID No. 47377801)

Nominally 98 percent dimethyl disulfide was app lied at rates of 378.4 kg a.i./ha, 400.8 kg a.i./ha, 377.6 kg a.i./ha, and 417.7 kg a.i./ha in Lagosanto, Italy loamy sand soil

, Agrofresas, Spain

sand soil

, San Giuseppe, Italy loamy sand soil , and Aldhams Farm sandy silt loam soil

, respectively over 1 – 1.557 ha fields. In the Lagosanto, Italy study, dimethyl disulfide was applied via broadcast shank injec tion to a depth of 25 to 30 cm. In the Spain study, dimethyl disulfide was applied via shank injection to a depth of 25 cm over raised beds. In the San Giuseppe, Italy study, dimethyl disulfide was app lied via broadcast shank in jection to a depth of 20 cm. In the United Kingdom study, dimethyl di sulfide was applied via shank injection to a depth of 15 to 20 cm over raised beds. In all fi elds, tarps classified as Virtually Impermeable Film (VIF) by the study author were a pplied immediately after treatment.

At all sites, a total of 20 air samplers were symm etrically distributed about radial distances of 25, 50, and 75 meters completely surrounding the cent er of the treated field at 1.5 meters above ground-level. Meteorological data consisted of air temperature, rainfall, wind speed, and wind direction (heights above ground leve l unspecified). All air and meteorological monitoring data was collected up to 10 days posttreatment. Tarp s were cut and removed 8 days posttreatment.

This study is classified as Supplemental. The necessary meteorological data of solar radiation was not provided. Given the study design using off-field air monitors, solar radiation is necessary to determine the Pasquill-Gifford Stability Class turbulence parameterization in order to back-calculate dimethyl disulfide emissions ove r time using the ISCST3 dispersion model. In addition, the application rates were lower than th e maximum labeled application rate in all of the

studies.

835.1710, 850.1730, 850.1850 Aquatic Organisms – Bioava ilability, Biomagnification, and

1718 Toxicity

WSKOW version 1.4 calculates log K

ow of dimethyl disulfide to be 1.77. Furthermore, Hansch, C. et al., 1995 experimentally determined that dimethyl disulfide possesses a log K

ow of 1.87. Partitioning of dimethyl disulfid e residues to tissue is not a c oncern with these properties. Therefore, this study is waived.

835.6100 Terrestrial Field Dissipation

This study is waived since the all proposed labels require immediate tarping after application. The traditional terrestrial field study guideline re quires residues of the test substance to be extracted immediately following its application. This study proce dure will not be representative

of real-world conditions as the ta rp will have to be punctured in order to collect and extract the samples.

Volatility of Dimethyl Disulf ide in Aqueous Media (MRID #47307501)

In this non-guideline study, 1, 000 ppm of diemthyl disulfide was applied in duplicate to samples of fresh water (tap water) and salt water, pr epared by dissolving 33 g of Crystal Sea Marinemix in 1 liter of MilliQ water. Dimethyl disulfide samples were then extracted directly and analyzed by HPLC at 0, 15, 30, 60, 120, 240, and 1,200 minutes posttapplication. In all samples, dimethyl disulfide was undetected by 20 hours posttapplication. The study author states accordingly that the residues of dimethyl disulf ide remained unstable overtime.

Several factors indicating the fate of dimethyl disu lfide in water are inconclusive from this study. The dissipation and degradation rout es of dimethyl disulfide in th is study are unclear. Due to the volatile nature of dimethyl di sulfide, volatile trapping soluti ons (not mentioned in the study report) may account for a portion of the material balance. In addi tion, it was not stated whether the study was conducted in darkness. As indica ted by, “Dimethyl disulf ide photolysis in the environment”, (MRID No. 47052818), aqueous photolys is along with volatilization can both be significant pathways contributing to the unstable trend in dimet hyl disulfide observed in this study. Furthermore, the lack of sterility by th e usage of tap water a nd possibly the sea water (sterility not verified) suggests that additives in the water samples may lead to chemical reactions and subsequent formation of degradates (detectio ns also not attempted in the determination of the overall material balance) which may not occur in the natural environment.

Exposure Assessment of Dimethyldisulfide Mo vement to Ground Water and Surface Water Associated with Shank Injection and Drip Irrigation on Agricultural Crops (MRID# 47307502)19 The registrant conducted an independent asse ssment on aquatic expos ure using the EXPRESS shell (version1.00.00.00 – January 2005) to execute PRZM and EXAMS. The study report shows estimates of dimethyl disulfide residue concentrations in surface water (Georgia Farm Pond). Dimethyl disulfide residue loadings are compartmentalized by erosion, runoff, leaching, degradation, soil storage, and volatilization elements. The ex posure modeling was conducted at application rates of 100, 200, 375, and 600 kg/ha for drip irrigation (soil in corporation depth of 5 cm) and shank injection (soil in corporation depth of 20 cm) ma nagement practices. The study author conducted the exposure assessment with the California onion, California tomato, Florida strawberry, Florida tomato, North Carolina sw eet potato, and North Ca rolina tobacco PRZM crop scenarios.

This study was not considered in this ri sk assessment for the following reasons:

• The current approved version of EXPRESS is 1.03.02 (July 2007). The earlier version of EXPRESS possessed known errors in the way data from the PRZM and EXAMS environment were imported. Therefore, the results from utilizing the version of EXPRESS presented in the study author’s assessment may not be consistent with actual PRZM/EXAMS modeling results.

• The versions of PRZM and EXAMS for whic h simulations are conducted are not stated by the study author. Revisions to numerous algorithms have been incorporated into the current approved version of PRZM (Versi on 3.12.3 – June 2006) and EXAMS (Version 2.98.04.06 – April 2005).

• Numerous additional crop scenarios are available to be considered in the current version of PRZM based on the proposed label uses.