### Page 2 of 78 submitted to the Agency in response to the fumigant 2009 amended fumigant Reregistration Eligibility Decisions (REDs). It also builds on the issues raised in the two previous analyses of factors which impact fumigant emissions (S mith and Dawson; D306857; 06/09/08 and Smith and Dawson; D362369; 05/14/09).

Introduction

Predicting emissions from treated fields after fumigant applications can be highly complex because many factors can influence the rate of emissions. Available data demonstrate that

reductions in emissions can be achieved with measur es that are within, as well as outside of, the control of growers/applicators. While it is difficult to assign quan titative factors to account for these measures, it is appropriate to recognize the impact that they have on emissions and to offer relief to growers/applicators who employ them . However, care must be taken, given the uncertainties in the available data, that the pred icted reductions in emi ssions are not overstated. This memo analyzes the following factors and te chniques to determine if new available data requires revisions of the buffer zone credits pr esented in the 2009 credits memo (Smith and Dawson; D362369; 05/14/09):

• Soil moisture

• Soil temperature

• Organic content

• Soil type

• Injection Depth

• Water Seals

• Reactive Boundary Layers

• Field Preparation and Compaction

• Tarps

In addition, a discussion of the utility of real-time VOC (volatile organic compound) meters to

track emissions in real time in tr eated fields is also provided.

This revised factors analysis is based on two main data sources. The first main data source is a

number of field scale emission st udies which have been submitted by a variety of stakeholders, including:

• The Methyl Bromide Industry Panel (MBIP)

o EPA MRID 48006001: Monitoring of Methyl Brom ide and Chloropicrin Field Emissions From Shank Applications at Shallow and Deep Injection Depths

o EPA MRID 48107601: Monitoring of Methyl Brom ide and Chloropicrin Field Emissions From Shank Applications (Bedded and Broadcast) and a Methyl Bromide Hot-Gas Application U nder Totally Impermeable Film

• The Chloropicrin Manufacturer’s Task Force (CMTF)

o EPA MRID 48033801: Direct Flux Determination of Chloropicrin Emissions from Shank, Bedded, Non-Tarped Applications

o EPA MRID 48087401: Chloropicrin Flux Rates for Drip Fumigation with PE and TIF Tarps, Water Seal and KTS at Sa linas, California in September 2007

### Page 3 of 78 • The Metam Sodium A lliance (Alliance)

o EPA MRID 47956901: A Trial to Evaluate Concentrations and Emission Rates from the Application of Metam Sodium by Shank Injection/Compaction on a Daytime and Nighttime Basis

o MRID 47956701: Flux Evaluation of a Metam Potassium Application (KAPAMHL) Applied by the Drench Method (Study SEC- 2008D)

• The United States Department of Agriculture, Agricultural Research Service Area-Wide Pest Management Program for Methyl Br omide Alternatives (USDA ARS Areawide)

o EPA MRID 47820001: Monitoring Chloropicrin, Dime thyldisulfide, and Methyl Isothiocyanate Emissions from Shank Applications at Three Sites near Tifton, Georgia

o EPA MRID 47813901: Monitoring 1,3-Dichloropropene, Chloropicrin, and Methyl Isothiocyanate Emissions from Shank Applications at Three Sites Near Duette, Florida

o EPA MRID 47813901: Monitoring 1,3-Dichloropropene and Chloropicrin Emissions from Solid-Tarp Shank Injectio ns at Two Sites Near Fort Pierce,

Florida

• The Wisconsin Potato & Vegetable Growers Association, Inc. (WI Potato Growers)

o EPA MRID 48011601: Monitoring of Metam Sodium Airborne Flux for Shank Injection for Cultural Practice Applicable to Wisconsin

• The Michigan Potato Industry Commission (MI Potato Growers)

o EPA MRID 48005901: Monitoring of Metam Sodium Airborne Flux from Shank Injection/Compaction Based on Cultura l Practice Applicable to Michigan

• The Washington State Potato Co mmission (WA Potato Growers)

o EPA MRID 48115101: WA Potato Growers Study - Monitoring of Metam Sodium Airborne Flux from Shank In jection/Compaction Based on Cultural Practice Applicable to Washington State

• Washington State University (WSU)

o EPA MRID 47770001: Estimating Methyl Isothiocyanate Emission Rates Following Soil Incorporated Shank and M odified Center Pivot Chemigation Metam Sodium Applications

Basic summary information regarding the conditions of the fields, the use of varied cultural practices, and resulting peak emissions coll ected from the various studies submitted is summarized by individual chemical in Appendi x A (Tables A1-A3). Other more detailed information concerning the conditions specific to each field study can be found in the respective study review memos for methyl bromide (Daws on; D375752; 01/06/11), chloropicrin (Smith; D348650; 01/11/11), and metam sodium (Shelat and Smith; D385289; 01/06/11). These studies provided the basis for much of the discussion on a variety of the credits in this document.

The second main data source consists of two anal yses examining mass transfer coefficients of a number of agricultural tarps for various fumigant s. One of these analyses was performed by the United States Department of Agriculture, Ag ricultural Research Service (USDA ARS) (S. Papiernik, et al.; 2010). This analysis is publicly available on the internet. The other was performed by the Analytical Chemistry Branch (A CB) of the Office of Pesticide Programs (OPP) (Qian and Kamel; 6/17/10) and is provided in Appendix B of this document. These analyses mainly provided the basis for discussion of the tarp credits in this document.

### Page 4 of 78 Other data, although not necessarily specified in th is document, was also considered as part of

this credits memo. Much of this research was reported at the 2009 MBAO conference (see www.MBAO.org ) and generally, provides support for the conclusions presented in this document. The Agency plans to continue the process of developing more refined approaches and analyses for defining GAPs and emission credits which will include a la rger revision of the emission factors document. At that time, this other data will be incorporated in more detail as appropriate.

Buffer Credit Recommendations

The previous recommendations on emission reduction buffer credits have been outlined in D306857 and D362369 as noted above. The key factors which were addressed include:

• Soil moisture

• Soil temperature

• Organic content

• Soil type

• Injection Depth

• Water Seals

• Reactive Boundary Layers

• Field Preparation and Compaction

• Tarps

In addition, a discussion of the utility of real-time VOC (volatile organic compound) meters to

track emissions real time in treat ed fields is also provided.

The recommendations for buffer credits or criteri a for good agricultural practices related to many of these factors remain unchanged at this time. Generally the studies upon which this document is based were compliant with the requirements for good agricultural practices. In other cases,

studies met or exceeded the criteria for baseli ne values and were actually completed under

conditions which would otherwise elicit a buffer cr edit. Each of these conditions adds to the complexity of developing buffer credit recomm endations. The current recommendations related to each of the key factors are provided below.

Soil Moisture: The field capacity specified in the GAPs as part of the 2009 amended fumigant REDs is 50-80 percent (i.e., methyl bromide and chloropicrin) and 60 – 80 percent for the MITC generators. Almost all of the recently submitte d field study data was performed using the soil moisture GAPs (see Tables X-X for specific soil mo isture values for individual studies). In fact, some of the submitted studies were performed at soil moisture levels that far exceed 100 percent field capacity. Most of these st udies were bedded applications at sites with sand based soils where field capacities over 100% are required in order to form proper beds. No credit is being given for soil moisture since it is a critical requ ired part of the GAPs that have been developed. Where data is available and appropriate, buffer z ones should only be selected from studies that utilized the field capacity levels specified in the GAPs.

### Page 5 of 78 Soil Temperature: Available field scale and laboratory- based data typically show that increased soil temperature corresponds to increas ed fumigant emissions with all other factors being equal. However, the soil temperature in a fi eld is not a factor that growers can manipulate. If conditions warrant for a particular field wher e soil temperatures may be lower than the soil

conditions in the flux studies used to define the baseline buffer condition, it would be reasonable

to account for that in the asso ciated regulatory requirements. There is currently no minimum soil temperature specified in the GAPs presented as part of the 2009 amended fumigant REDs. The GAPs do prohibit fumigant applications when soil temperature is above 90 o 

### F for all application methods except for drip irrigati on applications (which is allowed due to evaporative cooling effects). Based on all of the available data, the Agency recommends the following credits for soil temperature:

• Methyl Bromide: In the 2009 credits memo (Smith and Dawson; D362369; 05/14/09), a credit for soil temperature was not re commended for methyl bromide based on its extremely high vapor pressure. The soil temp erature credit/GAP decisions for methyl bromide may be revisited if the MBIP studies discussed above provide more information around the effect of soil temper ature on methyl bromide emissions. No new information has been provided to the Agency at this tim e to suggest that a soil temperature credit should be provided for methyl bromide.

• Chloropicrin: In the 2009 credits memo (Smith and Dawson; D362369; 05/14/09), a 10% emission credit was provided for chloropicrin to reduce the buffers for applications in soils with temperatures of 50°F or less when me asured at a soil depth of 3 inches. All of the emissions studies, including those recently submitted, currently used to develop buffer distances for chloropicr in occurred at reasonable temperatures, with the average soil temperature around 70°F. No new inform ation has been provided to the Agency at this time to suggest this credit should be changed.

• Metam Sodium/Metam Potassium - MITC: In the 2009 credits memo (Smith and Dawson; D362369; 05/14/09), a 10% emi ssion credit was provided for metam sodium/potassium to reduce the buffers for a pplications in soils with temperatures of

50°F or less when measured at a soil depth of 3 inches. No new information has been provided to the Agency at this time to sugge st this credit should be changed. The 2009 credits memo also provided an additional 10% credit for metam sodium/potassium in soils with temperatures between 50-70°F b ecause the metam sodium/potassium buffer

tables were based on studies where the aver age day/night air temperature ranged from 80- 90°F (soil temperature was not measured in most of these studies). As discussed above, many new metam sodium emission studies have been submitted to the Agency that provide detailed soil temperature measurements . As a result, many of the studies that were performed at relatively high air temper atures (and assumed high soil temperatures) have now been replaced with studies that we re performed with average soil temperatures around 70°F and therefore, this additional 10% credit is no longer applicable for metam sodium/potassium.

• Dazomet - MITC: In the 2009 credits memo (Smith and Dawson; D362369; 05/14/09), a 10% emission credit was provided for dazomet to reduce the buffers for applications in soils with temperatures of 50°F or less when me asured at a soil depth of 3 inches. All of

### Page 6 of 78 the emissions studies currently used to deve lop buffer distances for dazomet occurred at reasonable temperatures, with the average soil temperature rangi ng from 55-65°F (soil temperature was not measured). No new info rmation has been provided to the Agency at this time to suggest this credit should be changed.

Organic Content: Available field scale and laboratory-based data typically show that increased organic matter corresponds to decreased fumigant emissions with all other factors being equal. However, the level of organic matter in a field is not a factor that grower s can easily manipulate. If conditions warrant for a particular field, or even region, where organic matter levels may be higher than the soil conditions in the flux studies used to define the baseline buffer condition it

would be reasonable to account for that in the associated regulato ry requirements. Based on all of the available data, the Agency recommends the following credits for organic matter:

• Methyl bromide and Dazomet/MITC: The cred it scheme described in the 2009 credits memo (Smith and Dawson; D362369; 05/14/09) for these chemicals is as follows. No credit shall be given for all soils with less th an 1% organic matter. A 10% credit shall be given for soils with an organic matter range of >1% - 2%; a 20% cred it shall be given for soils with an organic matter range of >2% - 3%; and a 30% credit sha ll be given for soils with an organic matter range of >3%. No new information has been provided to the Agency at this time to suggest th is credit scheme should be changed.

• Chloropicrin and Metam Sodium/Metam Potassi um - MITC: The credit scheme described in the 2009 credits memo (Smith and Dawson; D362369; 05/14/09) for these chemicals is as follows. No credit shall be given for all soils with less than 1% organic matter. A 10% credit shall be given for soils with an organic matter range of >1% - 2%; a 20% credit shall be given for soils with an organic matter range of >2% - 3%; and a 30% credit shall be given for soils with an organic matter range of >3%. A few exceptions are described in the chemical specific REDs where the soils utilized in the field flux studies already had organic matter levels >1%. In these few specific cases, a negative credit was applied to the buffer table. For instance, if a field flux study has an organic matter of 1.5% and the corresponding buffer was estimated to be 100 feet then a 10% negative credit would apply and the baseline buffer w ould actually be 110 feet. Most of the recent field scale emission studies were performed at field sites that have soil organic matter levels in the 1-2% range (see Tables A1-A 3 in Appendix A for specific organic content percentages for individual stud ies). Since many of these studies will be used as the baseline for selecting new chloropicrin and metam sodium buffers, this same process of applying a negative credit should be used. No other new information has been provided to the Agency at this time to suggest this credit scheme should be changed.

Soil Type: Available field scale and laboratory-based data typically show that increased levels of clay in the soil corresponds to decreased fumigant emissions with all other factors being equal. However, the level of clay in a field is not a fa ctor that growers can ma nipulate. If conditions warrant for a particular field where the soil ha s high clay content it would be reasonable to account for that in the associated regulatory re quirements since buffers are based on research with more typical soil types. Almost all of th e recently and previously submitted field study data was performed on fields with sand, loam, or sa ndy loam based soils (see Tables A1-A3 in Appendix A for specific soil types for individua l studies). In the 2009 credits memo, a 10%

### Page 7 of 78 credit was given for soils with a clay conten t >27%. A few exceptions are described in the chemical specific REDs where the soils utilized in the field flux studies already had soils with clay contents ≥ 27%. In these few specific cases, a negative credit was applied to the buffer table. For instance, if a field flux study has soil with a clay content of 31% and the corresponding
buffer was estimated to be 100 feet then a 10% negative credit would apply and the baseline buffer would actually be 110 feet. No new informa tion has been provided to the Agency at this time to suggest this credit scheme should be ch anged as all of the recently submitted flux studies were performed in fields that have a clay content <27%.

Injection Depth: Available field scale and laboratory-based data typically shows that increased injection depths can correspond to decreased emissions with all other factors being equal. However, injection depth is restricted for so me fumigants due to physical/chemical properties dictate the impact of this conditi on of application. No credit st ructure has been instituted for injection depth rather, where ava ilable, distinct studies were us ed to establish baseline buffer

table recommendations for indivi dual fumigants as follows:

• Methyl Bromide: In the 2009 amended methyl bromide RED, available flux data allowed for having different buffer tables for shallow a nd deep injection levels. Since that time, the MBIP produced a methyl bromide/chlo ropicrin emission study that examined differences in methyl bromide emissions from shallow and deep injection applications (12” vs. 18”). This study furt her supported the need for sepa rate buffer tables for shallow and deep injection applications for methyl bromide. However, since this study was performed using a totally impermeable film (TIF), no changes to the methyl bromide

buffer tables will be made at this time.

• Chloropicrin: In the 2009 ame nded chloropicrin RED, available flux data allowed for having different buffer tables for shallow and de ep injection levels. Since that time, the MBIP produced a methyl bromide/chloropicrin emission study that examined differences in chloropicrin emissions from shallow and d eep injection applicati ons (12” vs. 18”). This study further supported the need for se parate buffer tables for shallow and deep injection applications for chloropicrin. However, sin ce this study was performed using a totally impermeable film (TIF), no changes to the chloropicrin buffer tables will be made

at this time.

• Metam Sodium/Metam Potassium - MITC: Along with the drip irri gation study discussed in the 2009 credits memo, the Agency has re cently received multiple shank injection emission studies where applications occurred at various depths (9”, 12”, and multiple injection points at 5.5”/9.5”). When examined together, these studies do not show that increased injection depth has a significan t impact on reducing emissions for metam sodium/MITC. As a result, neither a credit nor a separate buffer table should be provided for depth of injection for metam sodium appli cations at this time. The Agency is willing to discuss any data that coul d be produced to better charact erize the effect of injection depth on metam sodium/metam potassium applications.

• Dazomet - MITC: There are currently no data th at specifically focuses on the impact of incorporation depth for dazomet on MITC emis sions. The Agency believes there is a

### Page 8 of 78 practical limit to the depth that dazomet can be incorporated into the soil. As a result, a credit for depth of incorporation for dazomet app lications has not been given at this time.

Water Seals: Available field scale and laboratory-based data typica lly show that applying a water seal after application of certain fumigants results in decr eased fumigant emissions. The available data on the emissions reduction potential of water seals was used in a variety of ways, depending on the particular fumigant, in the 2009 credits memo (Smith and Dawson; D362369; 05/14/09). Since that time, the Agency has rece ived some new field scale emissions data and based on all of the data available, the Agency recommends the following regarding water seals:

• Methyl Bromide: In the 2009 credits memo (Smith and Dawson; D362369; 05/14/09), there was no data available to provide a cred it for water seals for methyl bromide. No new information has been provided to the Agen cy at this time to suggest that a credit should be given for using water seals with methyl bromide applications.

• Chloropicrin: In the 2009 credits memo (Smith and Dawson; D362369; 05/14/09), the Agency provided a 15% water seal credit (1⁄4 to 1⁄2 inch water seal) for all chloropicrin applications. This credit was based on limite d field scale data (t arped, drip irrigation fields) produced by Hussein Ajwa and th e California Strawberry Commission that

showed that water seals reduce chloropicrin emissions. At that time, this study had not been formally submitted to the Agency, however, the CMTF has since formally submitted this study. This study showed that applying a water seal over the bedded tarped drip irrigation field resulted in an approximate 30% reduction in the peak chloropicrin emissions. No other new data on using water seals with chloropicrin applications has been submitted to the Agency at this time. Given the limited available data and the uncertainty that water seals would work in the sa me way for untarped broadcast or untarped bedded chloropicrin a pplications; the Agency is not providing a larger water seal credit for chloropicrin at th is time. The Agency is willing to discuss any data that could be produced to better characte rize the effect of water seals on chloropicrin applications.

• Metam Sodium/Metam Potassium – MITC: In the 2009 credits memo (Smith and Dawson; D362369; 05/14/09), the Agency did not provide any credits for the use of

water seals with metam sodium because wate r seals are a typical emission control for many types of applications of metam sodium (i.e., sprinkler irrigation, broadcast shank injection, and drench applica tions). The Agency’s metam sodium assessment relies on a

number of emission studies that utilize a num ber of water sealing techniques, including standard water seals, double water seals, and intermittent water seals.

Since that time, a number of emission studies have been submitted by a variety of stakeholders (e.g., the Alliance, the WI Potato Growers, the MI Potato Gowers, the 

### WA Potato Growers) that examined the impacts of water seals on me tam sodium broadcast untarped shank injection applic ations. These studies clearl y show that water seals can significantly reduce MITC emissi ons during this type of a pplication. However, given that waters seals are already required to be used with other meta m sodium application methods, the Agency does not believe providi ng a credit for use of water seals with metam sodium is appropriate at this time. The Agency is recommending that the newly

### Page 9 of 78 submitted data be used to produce two new buffer tables for broadcast untarped shank injection applications; one table for applicatio ns using a water seal (1⁄4 to 1⁄2 inch water seal) and one without. The Agency is willing to discuss any data that could be produced

to better characterize the effect of wa ter seals on other types of metam sodium applications.

• Dazomet - MITC: Water seals are the typical emission control for all applications of dazomet and are required on current labels. The Agency’s dazomet risk assessment relies

on a number of flux studies that utilize the labe l required water seal regime. As a result, the Agency is not currently recommending spec ific credits for water seals because all of

the flux data utilized in the dazomet PE RFUM modeling already incorporated these techniques.

Reactive Boundary Layers: Available field scale and laborat ory-based data typically shows that the use of potassium thiosu lfate (KTS) after a fu migant application results in decreased fumigant emissions with all othe r factors being equal. Howeve r, use of thes e reactive boundary layers is restricted to the ha logenated fumigants only (e.g., methyl bromide, chloropicrin, methyl iodide, and 1,3-dichloropropene). KTS is not su itable for reducing MITC emissions resulting from metam sodium,metam potassium, or dazome t applications. The limited available data on the emissions reduction potential of KTS was used to provide a buffer credit for methyl bromide and chloropicrin in the 2009 credits memo. Sin ce that time, the Agency has received some new

field scale emissions data and based on all of th e data available, the Agency recommends the following regarding use of KTS:

• Methyl Bromide and Chloropicrin: In th e 2009 credits memo (Smith and Dawson; D362369; 05/14/09), the Agency provided a 15% cr edit for use of KTS as long as it was applied with 1⁄4 to 1⁄2 inch of water for all me thyl bromide and chloropicrin applications.

This credit was based on two fi eld scale studies (bot h using tarped, drip irrigation fields) produced by Hussein Ajwa and the California Strawberry Commission that showed that KTS reduced chloropicrin emissions. Neither of these studies was formally submitted to the Agency at the time of the 2009 credits memo . The Agency also utilized a laboratory study that looked at use of KTS with all halogenated fumigants as the basis for this credit (Wang et. al., 2000). Since that time, the MBIP has produced a methyl bromide/chloropicrin emission study that examined the impacts of KTS on methyl bromide/chloropicrin emissions and one of the Ajwa studies has been formally submitted to the Agency.

In both of the Ajwa studies, KTS was applie d with water over the top of a bedded, drip irrigation field via solid set sp rinklers after the application occurred. In the MBIP study, KTS was applied under the tarp to a broadcast, shank injection tarped field. All of these studies showed that KTS reduced methyl br omide (MBIP study) and chloropicrin (two Ajwa studies and MBIP study) to varying degrees. In the Ajwa studies, peak chloropicrin emissions were reduced by approximately 32 % and 36% while in the MBIP study, peak chloropicrin emissions were reduced by approximately 60%. In the MBIP study, peak methyl bromide emissions were reduced by ap proximately 55%. Based on the available information, the Agency does not believe the credit scheme for use of KTS should be changed at this time.

### Page 10 of 78 • Metam Sodium/Metam Potassium and Dazomet – MITC: There is currently no available

data that shows that use of KTS after an MI TC generator application results in decreased MITC emissions. The Agency is aware of one laboratory study (W ang et. al., 2000) that was performed that looked at KTS use with all halogenated fumigants, including methyl bromide, methyl iodide, chloropicrin, and 1,3-dichloropropene. Based on this study, the Agency believes that this credit should not apply to MITC gene rators, however, the Agency is willing to discuss any data that could be produced to better characterize the effect of potassium thiosulfates on MITC emissions.

Field Preparation and Compaction: It is clear based on the prev iously existing and the most current research that proper field preparati on and managing application systems to achieve proper compaction during applicatio n are critical to an applicati on that is compliant with the GAPs established for fumigants. There has b een substantive discussions around a means to categorize and quantify the proper levels of field preparation a nd compaction during applications

to both reduce emissions and achieve conditions appropriate to crop production (e.g., develop raised beds which will persist over a growing se ason). Assigning a credit structure for field preparation or compaction is inappropriate at th is time because available empirical data does not warrant it. Also, as noted, these practices should be accounted for in all applications.

Tarps: The Agency has a number of field scale emi ssion studies as well as laboratory studies that examine the ability of high-barrier tarps to reduce emissions of a variety of fumigants. Since the 2009 credits memo (Smith and Da wson; D362369; 05/14/09) was completed, a number

of new emission studies have been submitted to the Agency that examine the emission reduction potential of high barrier tarps in real-world conditions. However, due to the cost of these studies, it is not feasible to perform these types of st udies for every fumigant/tarp combination. As a result, in the last few years, Scott Yates of the USDA, ARS has developed a two chamber laboratory method that can test a tarp’s permeab ility to a particular fumigant. A recently published paper details the results of USDA’s tarp analysis (S. Papiernik, et al.; 2010). Utilizing a similar methodology, the ACB has also perfor med a thorough examination of MTCs for a number of fumigant/tarp combinations whic h is provided in Appe ndix B (Qian and Kamel; 6/17/10). This analysis including examination of MTCs for methyl bromide, chloropicrin, MITC, methyl iodide, 1,3-dichlo ropropene, sulfuryl fluoride, di methyl disulfide, and propylene oxide for 25 agricultural tarps. Table 1 presents a list of tarps that were analyzed. The Agency has analyzed both the USDA and ACB MTC data and determined that both studies produced similar MTC measurements for the fumigant/tarp combinations.

### Page 11 of 78 Table 1: List Of Agricultural Films Subm itted By Various Manufacturers And Vendors

Film Name Description Manufacturer

Sun Film High Barrier 1.0 mil, Clear Polyethylene AEP Industries

AEP-One EVOH barrier, 1.0 m il, clear AEP Industries

EVOH-High Barrier EVOH, Black Berry Plastics

High Barrier w/improved toughness EVOH, Black Berry Plastics

EVOH-Supreme Barrier EVOH , Black Berry Plastics

Cadillac VIF 1.25 mil Cadillac Products Packaging Company

Cadillac HDPE Cadillac Pr oducts Packaging Company

Canslit Metalized 1.25 mil Black/silver Canslit Inc. /Imaflex Inc.

Canslit Metalized 1.25 mil White/silver Canslit Inc. /Imaflex Inc.

Embossed HDPE 0.6 mil, Black Canslit Inc. /Imaflex Inc.

Embossed LDPE 1.25 mil, Black Canslit Inc. /Imaflex Inc.

SARANEX A Black Dow Chemical Co.

SARANEX B Black Dow Chemical Co.

FilmTec VIF 1.25 mi l, Black ARI, CA

Ginegar Ozgard 1.25 mil, Black Ginegar Plastic Products, Ltd.

Ginegar VIF 1.25 mil, embossed black Ginegar Plastic Products, Ltd.

Guardian AgroPlastics VIF 1.2 mil, Embossed black Guardian Agroplastics Olefinas USA

Mid South VIF 1.25 mil, embossed black Mid South Extrusion

Embossed Polyethylene Film 1.25 mil, Embossed LDPE Pliant Corp

Pliant Blockade 1.25 mil, Black Pliant Corp

Pliant Blockade White 1.25 mil, White Pliant Corp

Pliant Metalized 1.25 mil, black/silver Pliant Corp

Raven TIF “VaporSafeTM” 1.0 mil includes EVOH resin barrier, clear Raven Industries Inc.

Raven TIF “VaporSafeTM” 1.4 mil LDPE with EVOH core, black Raven Industries Inc.

Klerk Hytibar VIF Clear Klerk's Plastic/HyPlast



### In reviewing the ACB data, the Agency attempte d to define tarp groupings based on MTC values for individual fumigants as well as across a ll of the fumigants combined via a number of statistical methods. The Agency determined that a hierarchical clustering analysis provided the most pertinent results for both types of tarp groupings. The Agency’s analysis (Sarkar; D381403; 8/27/10) is included as Ap pendix C of this document. The results of the Agency’s analysis indicate that the tested tarps essentially can be divided into 4 distinct groups. Table 2 presents the individual fumigant tarp groupi ng for each tarp and the MTCs for individual fumigant/tarp combinations.

### Page 12 of 78 Table 2: Individual Fumigant Tarp Groupings and MTCs for Tested Agricultural Tarps

Film Name Methyl Bromide Chloropicrin MITC Average

MTC MeBr Tarp Grouping Average

MTC Chloropicrin Tarp Grouping Average

MTC MITC Tarp Grouping

AEP Sun Film High Barrier 0.8238 1 1.5404 1 8.5298 1

Cadillac HDPE 0.4800 1 0.7104 1 7.3816 1

Canslit Embossed HDPE 1.3611 1 2.2558 1 13.4456 1

Canslit Embossed LDPE 0.6269 1 1.2124 1 8.1979 1

Pliant Embossed Polyethylene Film 1.1078 1 2.2710 1 11.7678 1

Canslit Metalized (Black) 0.0217 2 0.0362 2 0.3596 2

Canslit Metalized (White) 0.0185 2 0.0342 2 0.3030 2

Pliant Metalized 0.0570 2 0.0828 2 1.1435 2

Guardian AgroPlastics VIF 0.0151 2 0.0016 3 0.2928 2

Cadillac VIF 0.0085 3 0.0011 3 0.1093 2

Ginegar VIF 0.0053 3 0.0005 3 0.0592 2

Pliant Blockade (Black) 0.0045 3 0.0010 3 0.0527 2

Pliant Blockade (White) 0.0057 3 0.0001 4 0.0823 2

FilmTec VIF 0.0029 3 0.0001 4 0.0512 2

Mid South VIF 0.0017 3 0.0000 4 0.0097 3

Dow SARANEX A 0.0006 3 0.0007 3 0.0051 3

Ginegar Ozgard 0.0019 3 0.0001 4 0.0180 3

Klerk Hytibar VIF 0.0010 3 0.0000 4 0.0097 3

Berry EVOH-Supreme Barrier 0.0009 3 0.0002 4 0.0002 4

Dow SARANEX B 0.0002 4 0.0002 4 0.0021 3

AEP-One 0.0001 4 0.0002 4 0.0003 4

Berry EVOH-High Barrier 0.0000 4 0.0001 4 0.0002 4

Berry High Barrier w/improved toughness 0.0000 4 0.0000 4 0.0004 4

Raven TIF “VaporSafeTM” (1.0 mil) 0.0000 4 0.0000 4 0.0000 4

Raven TIF “VaporSafeTM” (1.4 mil) 0.0001 4 0.0002 4 0.0008 4



### Two major factors; temperature and relative humidity, must be considered when using these

MTC data. Temperature: USDA, ARS and ACB have each performed tests examining the impacts of both of these factors. USDA’s tests focusing on how temperature impacts agricultural tarps have shown that a tarp’s permeability typically increases as temperature increases (Papiernik et al.; 2010). However, the magnitude of this increase appears to be very dependent on the specific properties of a tarp. ACB’s tests have also shown that a tarp’s permeability typically increases as temperature increases but their re sults have been less dramatic (see Figure 1 below).

### Page 13 of 78 Figure 1: Impact of Temperature on MTCs Using ACB Data

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### Relative Humidity: USDA’s tests focusing on how relati ve humidity impacts agricultural tarps have shown that a tarp’s permeability typi cally increases as relative humidity increases (Papiernik et al.; 2010). This was especially true of so-cal led virtually impermeable films (VIF) and the magnitude of this increase wa s very significant in some instances. ACB completed some similar tests and have s hown similar results to USDA’s results.

The Agency acknowledges these limitations; however , additional research is needed to more fully characterize the effects of temperature and relative humidity on the permeability of agricultural tarps to fumigant va pors. The Agency does not believe that these limitations impact the tarp credits scheme discussed below. The MT C data is currently being used solely to group the tarps. The quantitative credits have been developed using the field scale emissions studies which represent varying temperature and relative humidity in the ambient air within the particular studies.

In the 2009 credits memo (Smith and Dawson; D362369; 05/14/09), the Agency provided credits for a limited number of tarps. These credits were based mainly on the available field scale emission studies and limited preliminary MTC data produced by USDA, ARS. With the

submission of numerous field scal e emissions studies that utilize high barrier tarps as well as the new MTC data, the Agency is now providing cred its for many more tarps. Based on all the available information, the Agency recommends the following regarding use of high barrier tarps:

• Methyl Bromide: No buffer credit is bei ng given for tarps in group 1. A 20% buffer credit is appropriate for tarps in group 2, a 40% buffer credit is appropriate for tarps in group 3, and a 60% buffer credit is appropriate for tarps in group 4.

### Page 14 of 78 • Chloropicrin: No buffer credit is being given for tarps in group 1. A 20% buffer credit is appropriate for tarps in group 2, a 40% buffer credit is appropriate for tarps in group 3, and a 60% buffer credit is appr opriate for tarps in group 4.

• All MITC Generators: No buffer credit is be ing given for tarps in group 1. A 10% buffer credit is appropriate for tarps in group 2, a 20% buffer credit is appropriate for tarps in group 3, and a 30% buffer credit is appropriate for tarps in group 4. The tarp buffer

credits for MITC are lower than those for methyl bromide and chloropicrin because

available field scale emissions data shows MITC passes through all tarps much easier than methyl bromide or chloropicrin (e .g., tarps are more permeable to MITC).

In the future, the Agency would like to adopt a tarp credit scheme that does not name specific tarps. Instead, the tarp credit scheme would likely be based on the combined fumigant tarp groupings with MTC cut points for the individual fumigants. This would simplify labeling and grower use of tarps as an indivi dual tarp would be placed into a group regardless of the fumigant being used. It would also allow tarp manufacturers to test their own tarps to determine the MTCs for a particular fumigant using the method desc ribed in ACB’s memo. ACB’s protocol for the MTC test is available upon request . At some point in the future, the Agency may seek to make this protocol a more formal standard for testi ng agricultural tarps, such as an ASTM (American Society for Testing and Material s) standard. Based on the currently available MTC data, the recommended cut points for each fumigant at this time are as follows:

• Methyl Bromide

o Group 1 MTCs > 0.27

o Group 2 MTCs of 0.27 to 0.012

o Group 3 MTCs of 0.012 to 0.0004

o Group 4 MTCs < 0.0004

• Chloropicrin

o Group 1 MTCs > 0.40

o Group 2 MTCs of 0.40 to 0.018

o Group 3 MTCs of 0.018 to 0.00035

o Group 4 MTCs < 0.00035

• All MITC Generators

o Group 1 MTCs > 4.26

o Group 2 MTCs of 4.26 to 0.035

o Group 3 MTCs of 0.035 to 0.0015

o Group 4 MTCs < 0.0015

Credit Cap: In the 2009 credits memo, an 80 percent cred it cap was put in place because of the inherent uncertainty and variability in the data on which the credits are based. The Agency also stated at that time that a higher credit cap was not likely plausible. No new information has been provided to the Agency at this time to support changing the 80 percent credit cap.

### Page 15 of 78 Future Considerations

Use of VOC Meters: In many of the recently submitted fi eld scale emission studies, a volatile organic compound (VOC) meter was used to take re al time measurements of the fumigants being emitted from the treated field (Chellemi et al.; 2010). VOC meters have also been used in a number of research projects that have been pr esented at MBAO over the last few years (Noling et al.; 2008 and Fennimore; 2009). These devices are hand-held and utilize a photoionization detector (PID) typically equipped with a 10.6 eV lamp. They permit immediate on-site collection of air samples which could potentially provide a grower with information regarding real-time fumigant emissions in a particular field. For example, a VOC meter could be used as an early detection device to identif y an issue with a particular fumi gant application. If detected soon enough, mitigation could be put in place to reduce or prevent future emissions. These meters might also be used to reduce the durati on the buffer zone must be kept in place for a particular field if no VOCs are detected for a certain time after an application.

VOC meters are not without thei r drawbacks. First and foremost, fumigants with ionization potentials higher than the UV lamp are not de tected by photoionization. The ionization energy of chloropicrin is greater than that of the typi cal 10.6 eV lamp used in the detectors. This presents a significant challenge to using these me ters since chloropicrin is being applied in combination with a number of the methyl bromide alternatives. Another issue with these meters is that the gasses used to calibrate the meters ar e not agricultural fumiga nts. Correction factors

must be used to convert the measured read ings to VOCs of agricultural fumigants. Unfortunately these are difficult to use when mi xtures of fumigants ar e applied and ambient temperatures are variable. As a result, typi cally measurements are not fumigant specific.

The Agency believes these meters could potentially be a valuable tool for growers to monitor the fumigant emissions in a treated field. However, given the curren t limitations of the meters, the Agency feels that additional research is needed with regards to how these could be specifically implemented in the field by a grower.

### Page 16 of 78 References

Chellemi, D.O; H.A. Ajwa; D.A. Sullivan. 09/15/2010

. Atmospheric Flux of Agricultural Fumigants in Raised-Bed, Plastic-Mulch Crop Production Systems. Atmospheric Environment (online).

Dawson, J. and Smith, C. 06/09/2008. Factors Which Impact Soil Fumigant Emissions - Evaluation For Use In Soil Fumigant Buffer Zo ne Credit Factor Approach. DP Barcode

D306857.

Dawson, J. and Smith, C. 05/14/2009. Updated Health Effects Division Recommendations for Good Agricultural Practices and Associated Buffer Credits. DP Barcode D362369.

Dawson, J. 01/06/2011. Methyl Bromide, PC Code 053201, DP Barcode 375752; Health Effects Division (HED), Human Health Risk As sessment For Methyl Bromide Soil Uses Based On Methyl Bromide Industry Panel (MBI P) Studies In California and Florida.

Fennimore, S. 2009. Pic-Clor 60 Retention Under Totally Impermeable Film In Strawberry. http://www.mbao.org/2009/052Fennimore.pdf

Qian, Y. and Kamel, A. 06/17/10. Agricultural Tarp Permeability to Fumigants. U.S. EPA, Analytical Chemistry Branch.

Noling, J.W.; J.P. Gilreath; and R. Kreger. 2008. Measuring Fumigant Concentrations and

Persistence in Soil With PID – VOC Detectors. http://www.mbao.org/2008/024Noling.pdf

Papiernik, S. K.; S.R. Yates; and D.O. Chelle mi. 06/22/2010. A Standardized Approach for Estimating the Permeability of Plastic Films to Soil Fumigants Under Various Field and

Environmental Conditions. Jour nal of Environmental Quality.

Sarkar, B. 8/27/10. Analysis of Mass Transfer Coefficient Data Cont ained In Analytical Chemistry Branch Laboratory Report Entitely Agricultural Tarp Permeability to Fumigants

, D381403.

Shelat, S. and Smith, C. 01/06/2011. Metam Sodi um: Addendum to the Third Revision of the

HED Human Health Risk Assessment. DP Barcode D385289.

Smith, C. 01/11/2011. Chloropicrin: Addendum to the Third Revision of the HED Human

Health Risk Assessment. DP Barcode D348650.

Wang, Q., J. Gan, S.K. Papiernik, and S.R. Ya tes. 2000. Transformation and detoxification of halogenated fumigants by ammonium thio sulfate. Environ. Sci. Technol. 34:3717–3721.

EPA MRID 48006001: Monitoring of Methyl Bromide and Ch loropicrin Field Emissions From Shank Applications at Shallo w and Deep Injection Depths ; Authors: Ajwa, H. and Sullivan, D,; Sponsor: Methyl Bromide Industry Panel, LLC c/o David McAllister Chemtura Corporation 1801 Highway 52, West Lafayette IN 93905

### Page 17 of 78 EPA MRID 48107601: Monitoring of Methyl Bromide and Ch loropicrin Field Emissions From Shank Applications (Bedded and Broadcast) and a Methyl Bromide Hot-Gas Application Under Totally Impermeable Film ; Authors: Ajwa, H. and Sulliva n, D,; Sponsor: Methyl Bromide Industry Panel and Hendrix and Dail, Inc.

EPA MRID 47770001: Estimating Methyl Isothi ocyanate Emission Rates Following Soil Incorporated Shank and Modified Center Pi vot Chemigation Metam Sodium Applications; Authors: ;4/10/2009; Washington State Un iversity Food and Environmental Quality Laboratory, 2710 Univertiy Drive, Richla nd, WA 99354-1671; Sponsor: Washington State University, 2710 Univertiy Drive, Richland, WA 99354-1671.

EPA MRID 47820001: Monitoring Chloropicrin, Dimet hyldisulfide, and Methyl Isothiocyanate Emissions from Shank Applications at Three Sites near Tifton, Geor gia; Authors: Ajwa, Sullivan, and Chellemi; 7/27/2009; Sponsor: USDA, ARS Area-Wide Pest Management Program for Methyl Bromide Alternatives, 2001 South Rock Road, Fort Pierce, Florida, 34945 and Florida Specialty Crop Foundation, P.O. Box 941853, Maitland, Florida 32794-8153.

EPA MRID 47813901: Monitoring 1,3-Dichlor opropene, Chloropicrin, and Methyl Isothiocyanate Emissions from Shank Applications at Three Sites Near Due tte, Florida; Authors: Ajwa, Sullivan, and Chellemi; 6/30/2009; Spons or: USDA, ARS Area-Wide Pest Management Program for Methyl Bromide Alternatives, 2001 South Rock Road, Fort Pierce, Florida, 34945 and Florida Specialty Crop Foundation, P.O. Box 941853, Maitland, Florida 32794-8153.

EPA MRID 48011601: Monitoring of Metam Sodium Airborne Flux for Shank Injection for Cultural Practice Applicable to Wisconsin; Authors: Sullivan, Holdworth, and Sullivan; 12/31/2009; Sponsor: Wisconsin Potato & Vegetabl e Growers Association, Inc, P.O. Box 327, Antigo, Wisconsin 54409-0327.

EPA MRID 48005901: Monitoring of Metam Sodium Airborne Flux from Shank Injection/Compaction Based on Cultural Practice A pplicable to Michigan; Authors: Sullivan, Holdsworth, Sullivan; 1/31/2010; Sponsor: Michigan Potato Industry Commission, Michigan Carrot Industry Development Program, 13109 Schavey Road, Suite 7, Dewitt, MI 48820.

EPA MRID 48115101: WA Potato Growers Study - Monitoring of Metam Sodium Airborne Flux from Shank Injection/Compaction Based on Cultural Practice Applicable to Washington State; Authors: Sullivan, Ajwa, Holdswort h, and Sullivan; 4/30/2010; Sponsor: Washington State Potato Commission, 108 Interl ake Road, Moses Lake, WA 98837

EPA MRID 47956901: A Trial to Evaluate Concen trations and Emission Rates from the Application of Metam Sodium by Shank Inje ction/Compaction on a Daytime and Nighttime Basis; Author: Sullivan; 5/11/2009; 1900 El kin Street, Suite 200, Alexandria, VA 22308; Sponsor: Amvac Chemical Corporation, 4695 M acArthur Court, Suite 1250, Newport Beach, CA 92660-1868, Taminco, Inc., 3350 Riverwood Parkway, Ste 1900, Atlanta, GA 30339, and Tessenderlo Kerley, Inco rporated, 2255 N. 44 th 

### Street, Suite 300, Phoenix, AZ 85008.

### Page 18 of 78 EPA MRID 47956701: Flux Evaluation of a Me tam Potassium Application (KAPAM-HL) Applied by the Drench Method (Study SEC- 2008D); Author: Sulliv an; 3/2009; 1900 Elkin Street, Suite 200, Alexandria, VA 22308; S ponsor: Amvac Chemical Corporation, 4695 MacArthur Court, Suite 1250, Newport B each, CA 92660-1868 and Ratto Bros., Inc, 6312 Beckwith Road, Modesto, CA 95358.

EPA MRID 47813901 - Monitoring 1,3-Dichloropropene and Chloropicrin Emissions from Solid-Tarp Shank Injections at Two Sites Near Fort Pierce, Florida ; Authors: Ajwa, Sullivan, and Chellemi; 4/28/2010; Sponsor: USDA, ARS Area-Wide Pest Management Program for Methyl Bromide Alternatives, 2001 South Rock Road, Fort Pierce, Florida, 34945 and Florida Specialty Crop Foundation, P.O. Box 941853, Maitland, Florida 32794-8153.

EPA MRID 48033801 - Direct Flux Determina tion of Chloropicrin Emissions from Shank, Bedded, Non-Tarped Applications ; Authors: Rotondaro and Ro tondaro; 3/16/2010; Sponsor: The Chloropicrin Manufacturers Task Force, c/o Ni klor Chemical Company, Inc, 1667 Purdy Ave, Mojave, CA 93501

EPA MRID 48087401- Chloropicrin Flux Rates for Drip Fumigation with PE and TIF Tarps, Water Seal and KTS at Salinas, California in September 2007 ; Authors: Ajwa; 3/7/2010; Sponsor: The Chloropicrin Manufacturers Task Fo rce, c/o Niklor Chemical Company, Inc, 1667 Purdy Ave, Mojave, CA 93501

# Appendix A: Summary of Field Study Monitoring

ConditionsPage 20 of 78Appendix A/Table A1: Methyl Bromide Flux Data OverviewMRID Location Application TypeApplicationRate(lbsai/treatedacre)MaxPeriod fluxrate(ug/m2-s)MaxApplicationRate (lbsai/treatedacre)MaxAdjustedPeriod FluxRate(ug/m2-s)% FieldCapacityAir Temp -AverageDay/Night(oC)Avg. SoilTemp(oC)% OM(6-9")Soil Type(6-9")Start Time ofApplicationCompletionTime ofApplicationTime ofhighestpeak% MassLossShallow UntarpedSE1.1 Monterey CABed (no tarp - rearfacing chisel - 12"depth)186NA430282.6NA NA NA NA NA NA NANAAvg 0.43Max 0.56DPR 0.40SE1.2 Monterey CABed (no tarp - rearfacing chisel - 12"depth)180 430 NA NA NA NA NA NA NASE1.3 Monterey CABed (no tarp - rearfacing chisel - 12"depth)180 430 NA NA NA NA Clay NA NADeep UntarpedSE2.2 Kern Cty CABroadcast (no tarp,forward chisel, 20'depth)396NA430222.4NA NA NA NA NA NA NANAAvg 0.34Max 0.62DPR 0.40S104.2-1 Fresno CABroadcast (no tarp,forward chisel, 24'depth)396 430 NA NA NA NA NA NA NAS100B1.1 Madera CABroadcast (no tarp,forward chisel, 24'depth)400 430 NA NA NA NA NA NA NAS110.1San JoaquinCABroadcast (no tarp,forward chisel, 24'depth)450 430 NA NA NA NA NA NA NABedded Tarp StudiesEH164-11San LuisObispoBed (tarp, rear chisel,1.5 mil black plastic)206NA430889.6NA NA NA NA NA NA NANAAvg 0.81Max 1.0DPR 0.80BR787.1B OrangeBed (tarp, rear chisel inbed shaper, 1.5 milblack plastic)177 430 17.5% M NA NA NALoam/siltloamNA NABR787.1C OrangeBed (tarp, forwardchisel, 1.5 mil blackplastic)176 430 17.5% M NA NA NALoam/siltloamNA NABR787.2B Santa BarbaraBed (tarp, rear chisel inbed shaper, 1.5 milblack plastic)245 430 7% M NA NA NALoamysandNA NABR787.2C Santa BarbaraBed (tarp, forwardchisel, 1.5 mil blackplastic)174 430 7% M NA NA NALoamysandNA NAPage 21 of 78Appendix A/Table A1: Methyl Bromide Flux Data OverviewMRID Location Application TypeApplicationRate(lbsai/treatedacre)MaxPeriod fluxrate(ug/m2-s)MaxApplicationRate (lbsai/treatedacre)MaxAdjustedPeriod FluxRate(ug/m2-s)% FieldCapacityAir Temp -AverageDay/Night(oC)Avg. SoilTemp(oC)% OM(6-9")Soil Type(6-9")Start Time ofApplicationCompletionTime ofApplicationTime ofhighestpeak% MassLoss481076-01 Fort Pierce FLBed (tarp, rear chisel inbed shaper, Vapor SafeTIF tarped))235 19.8 430 36 138% ~25/12 ~181.4(surface~3.1)Sand 9:45 AM 12:52 PM 5-10 15.348006001 Wasco CAStrip, VaporSafe TIFtarped202.0 22.01 430 47 72 ~32/12 ~29 0.28loamysand1:18 PM 1:47 PM 24-30 17.9Tarped Broadcast StudiesTC199 Kern Cty CABroadcast ("highbarrier" tarp, Nobelplow)396NA430183.7NA NA NA NA NA NA NANAAvg 0.24Max 0.25DPR 0.25EH127-1 Monterey CABroadcast ("highbarrier" tarp, Nobelplow)235 430 NA NA NA NA Clay loam NA NA48006001 Wasco CABroadcast, LDPEtarped189.1 291 430 662 75~32/12~29 0.63loamysand8:26 AM 9:29 AM 6-12 18.348006001 Wasco CABroadcast, VaporSafeTIF tarped180.3 92.41 430 220 73 ~27 0.86loamysand8:28 AM 9:41 AM 0-6 12.848006001 Wasco CABroadcast, VaporSafeTIF tarped, KTS undertarp177.9 55.74 430 135 74 ~28 0.35loamysand10:35 AM 11:27 AM 0-6 9.848006001 Wasco CADeep 18"Broadcast,VaporSafe TIF tarped181.0 81.17 430 193 71 ~28 0.042loamysand1:13 PM 2:46 PM 30-36 9.4Drip Hot Gas StudiesEH150-1 Riverside CADrip ("high barrier"tarp, hot gas)200NA4301481NA NA NA NA NA NA NANAAvg 0.88Max 1.0DPR 1.0EH150-3 Kern CADrip (1.25 mil clearplastic, hot gas)200 430 NA NA NA NALoamysandNA NAEH150-4 Imperial CADrip (1.5 mil blackplastic, hot gas)200 430 NA NA NA NALoamysandNA NA481076-01 Fort Pierce FLHot Gas (Vapor SafeTIF tarped))426 150.3 430 152 109% ~25/12 ~21 1.50 Sand 9:50 AM ~12:30:00 PM 11-16 33.4Page 22 of 78Appendix A/Table A2: Chloropicrin Flux Data OverviewMRID Location Application TypeApplicationRate(lbsai/treatedacre)Max 1-hrflux rate(ug/m2-s)MaxApplicationRate (lbsai/treatedacre)MaxAdjusted1-hr fluxrate(ug/m2-s)% FieldCapacitySoilTemp(oC)% OM Soil TypeStart Time ofApplicationCompletionTime ofApplicationTime ofhighestpeak% MassLossBedded Untarped Shank Injection Studies44149201 Phoenix, AZ Bedded, untarped 149114.1 175 134.0 34 (0-6") N/A 0.23 (0-6") Loamy sand 10:43 14:12 14-18 6148033801 Elkton, FL Bedded, untarped 258.5 5.9 350 8.0 75 (6-12")11-23(6")1.3 (6-12") Sand 1:21 2:11 0-5 2.148033801 Elkton, FL Bedded, untarped 281.4 5.6 350 7.0 77 (6-12")11-23(6")1.2 (6-12") Sand 3:41 4:40 0-5 1.448011601 Coloma, WIBedded, untarped, water seal (0.1 in)(Field 2)350 65 350 65 ~50-55~7-25(3")0.7 Loamy sand 11:28 11:50 30-34 33.5Bedded Tarped Shank Injection Studies44149201 Phoenix, AZ Bedded, LDPE tarped377 142.1 350 131.8 35 (0-6") N/A 0.29 (0-6")Sandyloam/Loam6:25 18:56 24-30 6947295203Bainbridge,GABedded, Hytiblock Tarped 77 0.9 350 4.3 N/A N/A 0.45Sandy clayloamNA NA NA NA47295202 Dover, FL Bedded, MetallizedTarped 72 13.6 350 65.6 N/A N/A 1.3Sand/LoamysandNA NA NA NA47295204 Hart MI Bedded, Blockade Tarped 80 1.0 350 4.2 N/A N/A 0.8Sand/LoamysandNA NA NA NAWasco CA Strip, LDPE tarped (Field 2) 165 38.1 350 80.8 79 (6-12")~24-35(6")0.53 (6-12") Sandy loam 9:41 9:55 24-36 47.547820001 Tifton, GA Bedded, Blockade Tarped(Field 1) 143.2 9.6 350 23.5 70 (6-9")~8-21 (6-9")0.7 (0-12")Sandy clayloam3:19 4:47 33-39 1047820001 Tifton, GABedded, LDPE tarped (Field 2) - BadSoil Prep151.2 13.3 350 30.8 69 (6-9")~7-21 (6-9")0.6 (0-12") Loamy sand 5:42 7:58 36-42 9.547820001 Tifton, GA Bedded, LDPE tarped (Field 3) 145.3 2.1 350 5.1 82 (6-9")~9-22 (6-9")0.6 (0-12") Sandy loam 12:47 2:20 56-68 347813801 Duette, FLBedded, Metallized tarped, with 1,3-D(Field 1)171.7 17.1 350 34.9 245 (0-6")~7-24 (6-9")0.94 (0-6") NA 10:43 11:51 0-6 1.5347813801 Duette, FL Bedded, Guardian VIF tarped (Field 2) 176.5 1.8 350 3.5 207 (0-6")~7-24 (6-9")1.38 (0-6") NA 1:22 2:38 0-6 0.2847813801 Duette, FLBedded, Metallized tarped, without1,3-D (Field 3)164.7 9.6 350 20.3 228 (0-6")~7-24 (6-9")1.26 (0-6") NA 4:03 4:52 0-6 0.0848006001 Wasco CA Strip, VaporSafe TIF tarped (Field 4) 202.0 6.3 350 11 77 (6-9")~24-36(6-9")0.28 (6-9") NA NA NA 24-30 17.948107601 Ft. Pierce, FLBed (tarp, rear chisel in bed shaper,Vapor Safe TIF tarped)244 15.8 350 22.6 138 (6-9")~16-24(6-9")1.4 (6-9")) Sand 9:45 12:52 NA NABroadcast Untarped Shank Injection StudiesPage 23 of 78Appendix A/Table A2: Chloropicrin Flux Data OverviewMRID Location Application TypeApplicationRate(lbsai/treatedacre)Max 1-hrflux rate(ug/m2-s)MaxApplicationRate (lbsai/treatedacre)MaxAdjusted1-hr fluxrate(ug/m2-s)% FieldCapacitySoilTemp(oC)% OM Soil TypeStart Time ofApplicationCompletionTime ofApplicationTime ofhighestpeak% MassLoss44149201 Phoenix, AZ Broadcast, untarped 171 180 175 184.638 (0-6") N/A 0.61 (0-6") Loam 7:18 12:45 18-24 62Wasco CA Broadcast, untarped (Field 3) 197 60.5 175 54 72 (6-12")~20-33(6")0.56 (6-12") Sandy loam 11:10 11:35 30-36 46.6Wasco CA Deep 18" Broadcast, untarped (Field 4) 321 74.8 350 82 75 (6-12")~18-34(6")0.59 (6-12") Sandy loam 12:18 13:00 30-36 46.3Broadcast Tarped Shank Injection Studies44149201 Phoenix, AZ Broadcast, LDPE tarped 332 211 350222.4 32 (0-6") N/A 0.38 (0-6") Loam 7:13 11:55 18-24 6344149201 Yakima, WA Broadcast, LDPE tarped 343 70350 71.4 71 (0-6") N/A 1.59 (0-6") Loam 7:55 15:22168 (tarpsplitting)3444149201 Bradenton, FL Broadcast, LDPE tarped 346 58 35058.7 95 (0-6") N/A 1.88 (0-6") Sand 7:52 13:22 24-30 37Wasco CA Broadcast, LDPE tarped (Field 1) 358 75.1 350 73 69 (6-12")~21-35(6")0.52 (6-12") Sandy loam 7:40 8:23 24-30 47.848006001 Wasco CA Broadcast, LDPE tarped (Field 1) 189.1 31 350 57 80 (6-9")~24-35(6-9")0.63 (6-9") loamy sand NA NA 6-12 18.348006001 Wasco CABroadcast, VaporSafe TIF tarped(Field 2)180.3 25.8 350 50 77 (6-9")~24-35(6-9")0.86 (6-9") loamy sand NA NA 0-6 12.848006001 Wasco CABroadcast, VaporSafe TIF tarped, KTSunder tarp (Field 3)177.9 31 350 61 77 (6-9")~25-33(6-9")0.35 (6-9") loamy sand NA NA 0-6 9.848006001 Wasco CADeep 18"Broadcast, VaporSafe TIFtarped (Field 5)181.0 6.3 350 12 77 (6-9")~24-35(6-9")0.42 (6-9") loamy sand NA NA 30-36 9.447813901 Ft. Pierce, FLBroadcast (Low Disturbance Rig),HDPE tarped233.8 46.8 350 70.1 155 (6-12")~21-28(6-9")2.3 (0-6") Sand NA NA 28-34 35.2647813901 Ft. Pierce, FLBroadcast (Backswept Shanks), HDPEtarped222.8 46.5 350 73.0 99 (6-12")~22-29(6-9")1.8 (0-6") Sand NA NA 31-37 44.67Drip Irrigation Studies45112901 CA Drip irrigation, bedded, VIF tarped 88 15 300 51.1 NA NA NA NA NA NA NA 945112902 GA Drip irrigation, bedded, poly tarped 90 7 300 23.3 NA NA NA NA NA NA NA 1247456001 Yuma, AZBuried (10") drip irrigation, bedded,poly tarped403 2.85 3002 100 ~30-34 NA Siltloam NA NA 13-24 347456001 Yuma, AZBuried (10") drip irrigation, bedded,untarped403 16 300 12100 ~30-35 NA Silt loam NA NA 21-27 1645112901 Salinas, CA Drip irrigation, bedded, poly tarped 300 70 300 70 37 NA 1.36Sandyloam/LoamysandNA NA NA NA47679301 Yuma, AZBuried (6") drip irrigation, bedded,untarped298 47 300 47100 1.3 Silt loam 36.648087401 Salinas, CA Drip irrigation, bedded, LDPE tarped 345 300 N/A~16-27(6-12")0.7 Sandy loamPage 24 of 78Appendix A/Table A2: Chloropicrin Flux Data OverviewMRID Location Application TypeApplicationRate(lbsai/treatedacre)Max 1-hrflux rate(ug/m2-s)MaxApplicationRate (lbsai/treatedacre)MaxAdjusted1-hr fluxrate(ug/m2-s)% FieldCapacitySoilTemp(oC)% OM Soil TypeStart Time ofApplicationCompletionTime ofApplicationTime ofhighestpeak% MassLoss48087401 Salinas, CA Drip irrigation, bedded, TIF tarped 345 300 N/A~16-27(6-12")0.7 Sandy loam48087401 Salinas, CADrip irrigation, bedded, LDPE tarped,water seal (0.33") with KTS345 300 N/A~16-27(6-12")0.7 Sandy loam48087401 Salinas, CADrip irrigation, bedded, LDPE tarped,water seal (0.33")345 300 N/A~16-27(6-12")0.7 Sandy loamPage 25 of 78Appendix A/Table A3: MetamSodium/Metam Potassium Flux Data OverviewMRID Location Application TypeApplication Rate(lbs ai/treatedacre)Max 1-hrflux rate(ug/m2-s)Max ApplicationRate (lbsai/treated acre)Max Adjusted1-hr flux rate(ug/m2-s)% FieldCapacitySoilTemp(oC)% OM Soil TypeStart TimeofApplicationCompletionTime ofApplicationTime ofhighestpeak% MassLossSprinkler Irrigation Studies45703701 Bakersfield, CASolid set sprinkler, standard water seal(2 water seals for a 1" total-0.5" afterapp and 24 hours after app)320 358.1 320 358.1 NA NA NA NA NA NA 20-24 NACSREES#74Bakersfield, CASolid set sprinkler, Intermittent waterseal (6 water seals for a 1.5" total0.25" after app, 4, 11, 24, 30, and 35hours after app)320 54.8 320 54.8 NA ~25 NASandyloamNA NA 12-16 NA45703702San Joaquin,CASolid set sprinkler, Intermittent waterseal (5 water seals for a 1.5" total-0.5"after app; 0.25" at 8, 24, 30, and 48hours after app)320 48.0 320 48.0 ~60-80 NA NA NA 5:00 11:30 12-16 NA46969601 Mettler, CASolid set sprinkler, double water seal(2 water seals for a 0.69" total-0.23"after app and 0.46" 8 hours after app)320 80.7 320 80.7 ~50-75 ~20-25 0.5-0.8LoamySand16:00 22:00 0-4 NABroadcast Shank Injection Studies45703701 Bakersfield, CABroadcast, standard water seal (0.5"after app)320 118.3 320 118.3 NA NA NA NA NA NA 36-40 NACSREES#74Bakersfield, CABroadcast, Intermittent water seal (6water seals for a 1.5" total-0.25" afterapp, 6, 11, 24, 30, and 35 hours afterapp)320 52.4 320 52.4 NA ~25 NASandyloamNA NA 8-12 NA45703704 Lost Hills, CABroadcast, Intermittent water seal (5water seals for a 1.5" total-0.5" afterapp; 0.25" at 8, 12, 30, and 34 hoursafter app)320 36.3 320 36.3 NA ~27 NAClayLoam6:50 14:00 4-8 NA46379201Mt. Vernon,WABroadcast "Roozen Rig" 320 159 320 159.1 NA NA NA NA NA NA 8-1247770001 Pasco, WA Broadcast 219 12 320 18.2 NA 7 to 16 NA NA 12:10 12:50 4-8 12.648011601 Coloma, WIBroadcast (Dual Injection at 5.5 and9.5"), water seal (0.1" of rain afterapp)287 9.8 320 10.9 ~75-80 ~13 to 16 0.7LoamySand10:27 10:38 29-33 6.9848011601 Coloma, WIBroadcast (Dual Injection at 5.5 and9.5"), water seal (0.1" of rain afterapp)270 10.7 320 12.7 ~75-80 ~13 to 16 1.3LoamySand8:15 8:35 37-41 10.3748005901 Howard City, Broadcast (Injection at 12") 318 2.8 3202.8 ~60-80 ~7 to 12 1.1-1.6 Loamy 16:10 16:22 28-32 0.55Page 26 of 78Appendix A/Table A3: MetamSodium/Metam Potassium Flux Data OverviewMRID Location Application TypeApplication Rate(lbs ai/treatedacre)Max 1-hrflux rate(ug/m2-s)Max ApplicationRate (lbsai/treated acre)Max Adjusted1-hr flux rate(ug/m2-s)% FieldCapacitySoilTemp(oC)% OM Soil TypeStart TimeofApplicationCompletionTime ofApplicationTime ofhighestpeak% MassLossMISand/Sand48005901Howard City,MIBroadcast (Injection at 12"), waterseal (0.33" after app)321 0.3 320 0.2 ~60-80 ~7 to 12 0.5-1.3 Sand 14:34 14:45 28-32 0.0747956901Bakersfield,CABroadcast (daytime), double waterseal (0.4" after app, 0.4" at sunset)317 4.4 320 4.4 ~72 ~27 NA NA 6:00 7:45 0-4 1.247956901 Bakersfield, CABroadcast (nightime), double waterseal (0.4" after app, 0.4" at sunset)320 34.3 320 34.3 ~54 ~27 NA NA 0:20 1:35 4-8 12.87Pasco, WA Broadcast (Injection at 9") 317 7.1320 7.1 72.4 ~8 1.6-1.9 NA 9:40 9:55 47-59 6.78Pasco, WABroadcast (Injection at 9"), water seal(0.25" after app)368 1.7 320 1.5 70.9 ~8 1.1-1.4 NA 8:30 8:45 0-4 0.45Bedded Shank Injection Studies47131601 Helms, CA Bedded, untarped 294 18.77 320 20.4 NA ~13 8Sandyloam9:03 10:54 4-8 NACSREES#74Citra, FL Bedded, LDPE tarped 320 174.95 320 175.0 NA ~18 NA Sand 9:30 12:30 4-8 NA47820001 Tifton, GA Bedded, Blockade Tarped (Field 1) 299.5 16.5 320 17.6 70 ~10 to 21 0.7Sandyloam12:47 14:20 41-47 547820001 Tifton, GABedded, LDPE tarped (Field 2) - BadSoil Prep306.3 55.2 320 57.7 65 ~10 to 21 0.6Sandyclay loam15:19 16:47 17-23 1347820001 Tifton, GA Bedded, LDPE tarped (Field 3) 295.2 32.9 320 35.7 74 ~10 to 21 0.6Loamysand17:42 19:58 17-23 647813901 Duette, FL Bedded, Metallized tarped (Field 1) 313.62.2 320 2.3 142 ~10 to 21 0.94NA 10:43 11:51 124-136 2.647813901 Duette, FLBedded, Guardian VIF tarped (Field2)302.6 10.4 320 11.0 189 ~10 to 21 1.38 NA 13:22 14:38 6-12 5.547813901 Duette, FL Bedded, Metallized tarped (Field 3) 308.415.1 320 15.7 171 ~10 to 21 1.26NA 16:03 16:52 0-6 2.31Drench Studies47956701 Modesto, CADrench, triple water seal (0.2" afterapp, 0.2" at sunset of Day 1 and 2)164.7 128.3 320 267.8 ~67 ~24 to 27 ~1.3Sandyloam7:30 9:45 0-4 37.56Drip Irrigation StudiesCSREES#74Citra, FL Bedded, LDPE tarped 383 46.94 320 39.3 NA ~18 NA Sand 9:30 16:00 32-36 NA45703708 Irvine, CA Bedded, LDPE tarped 320 15 320 14.9 NA NA NA NA 18:20 20:45 0-4 NAPage 27 of 78Appendix A/Table A3: MetamSodium/Metam Potassium Flux Data OverviewMRID Location Application TypeApplication Rate(lbs ai/treatedacre)Max 1-hrflux rate(ug/m2-s)Max ApplicationRate (lbsai/treated acre)Max Adjusted1-hr flux rate(ug/m2-s)% FieldCapacitySoilTemp(oC)% OM Soil TypeStart TimeofApplicationCompletionTime ofApplicationTime ofhighestpeak% MassLoss45703708 Irvine, CABedded, untarped (drip lines on soilsurface)320 9 320 9.4 NA NA NA NA 18:00 22:00 8-12 NACenter Pivot Irrigation Studies47770001 Pasco, WA Center Pviot Irrigation-Drizzle Boom 300172.1 320 183.8 NA 7 to 16 NA NA 11:35 13:30 0-4 47Flood Irrigation Studies47314301Brawley, CA Flood Irrigation 318 68.34 320 68.8 NA NA NA NA NA NA5-9NARotary Tiller and Spray Blade47572201Smith River,CABroadcast Spray/Rototill/Roller 320 49320 49.4 ~30-35 ~19 to 21 ~4Clayloam/ClayNA NA 4-8 14.1Page 28 of 78 

# Appendix B: Agricultural Tarp Permeability to Fumigants

, Qian and Kamel 2010Page 29 of 78 OFFICE OF CHEMICAL SAFETY
AND POLLUTION PREVENTION UNITED STATES ENVIRONMENTAL PROTECTION AGENC Y
WASHINGTON, D.C. 20460



### Analytical Chemistry Branch 701 Mapes Road Fort Meade, Maryland 20755-5350

June 17, 2010

MEMORANDUM

SUBJECT: Agricultural Ta rp Permeability to Fumigants

FROM: Yaorong Qian, Chemist Analytical Chemistry Branch

Alaa Kamel, Chemist Analytical Chemistry Branch

THRU: Thuy Nguyen, Chief Analytical Chemistry Branch (7503P)

TO: Jeffrey Dawson, Health Effects Division (7509P)

John E. Leahy, Senior Advisor Speci al Review and Reregist ration Division (7508P)

Introduction

The Analytical Chemistry Branch (ACB) was asked by the Office of Pesticide Programs’

Health Effects Division and Pesticide Re-evalu ation Division to eval uate existing testing methodology and then conduct tests on commonly-us ed agricultural films to determine their permeability to various fumigants. The objec tive of the testing program is to produce a comprehensive database comparing permeability of various films under standard conditions. This permeability data will be used to help dete rmine the risk associated with fumigant use and guide product label directions for safety buffer zones.

During the initial project pla nning it was agreed that the perm eability of a film would be best expressed as the “mass tran sfer coefficient (MTC)”, which is believed to be dependent upon the properties of the film , the fumigant type, and environmental conditions such as temperature.

Samples of agricultura l films tested during this study we re obtained from manufacturers

and their vendors. The name of manufacturer, film brand, material type, film thickness and other pertinent information supplied by the film submitters were recorded.Page 30 of 78 

### Methodology

The method used for the determination of permeability was adapted from the technique previously developed by Dr. Scott Yates of th e U.S. Department of Agriculture (USDA), Agricultural Research Service (ARS), at Ri verside, CA (Papiernik et al., 2001, 2002). The testing apparatus consists of an airtight cylinder constructe d from two stainless steel caps (chambers) separated by the te st film. Test compounds are introduced into the chamber on one side of the film (source chamber) and the concentr ations of the test compounds from both sides of the film (source and receiving chambers) are monitored over ti me by analyzing the vapor in each chamber. The rate of change in the concentr ations over time is used to calculate the MTC.

Attachment 1 describes the method used at ACB in detail. The mathematical reasoning relating to the change of concentrations over time and calculation of the MTC can be found in Papiernik et al. (2001, 2002). The MTCs in this report were measured at the standard temperature of 25 o 

### C. In general, triplicate tests of each film were c onducted for each fumigant at ambient humidity. Several films were selected randomly and the test s were repeated to verify the obtained MTCs.

All the test results are included.

Experiments

Several tests were performed to test different factors that might affect the MTCs or the performance of the method. There tests were con ducted at the beginning of this project. There

tests include:

1. Tests to evaluate whether mixing different fumigants together in the test apparatus affects the permeability of individual fumigant when compared to testing each fumigant individually using a single component te st system. Although it has been reported previously that no effect was observed for so me fumigants, the pot ential interactions among fumigants may affect film permeability.

2. Tests to evaluate whether different concentr ation gradients across the film would affect the film MTCs. Fumigants were placed in the permeability cells at different concentrations for one high density polyethylene film. Theo retically, the MTC is independent of the fumigant concentration. The calculated MTCs at these different fumigant concentrations were compared to assess the imp act of fumigant concentration.

3. Tests to evaluate other factors which c ould affect film permeability, including humidity and temperature. Experiments were conducted to verify the effect of humidity (moisture content inside the testing cells) and temperatur e on the permeability of films. The possible influence of humidity was evaluated at two humidity levels, ambient humidity and saturated humidity, at the testing temperature of 25 o 

### C.

4. In order to demonstrate comparability with the results generated by ARS, several films which had been previously tested by ARS were also tested at ACB at the same temperature (25 o 

### C).

5. Several films were tested after they had b een used in the field for soil fumigation. The used films were provided by Dan Ch ellemi of ARS, USDA in FL.Page 31 of 78 

### Fumigants and Films

Table 1 lists the fumigants tested in this study. 1,3-Dichloropropene has two structural isomers ( cis - and trans -1,3-D) and the film permeability to both isomers were determined individually. Table 2 is the films submitted by the manufacturers and their vendors. More

detailed information for the film s is provided in Attachment 2.

Table 1. List of fumigants tested

.

Fumigants

Methyl bromide (MeBr) 1,3-dichloropropene (1,3-D)

Iodomethane (IOM) Sulfuryl fluoride (SF)

Chloropicrin (PIC) Dimethyl disulfide (DMDS)

Methyl isothiocyanate (MITC) Propylene oxide (PPO)



### Table 2. List of agricultural films submi tted by various manufacturers and vendors.

Film Name Description Manufacturer

Sun Film High Barrier 1.0 mil, Clear Polyethylene AEP Industries

AEP-One EVOH barrier, 1.0 mil, clear AEP Industries

EVOH-High Barrier EVOH, Black Berry Plastics

High Barrier w/improved toughness EVOH, Black Berry Plastics

EVOH-Supreme Barrier EVOH, Black Berry Plastics

Cadillac VIF 1.25 mil Cadillac Products Packaging Company

Cadillac HDPE Cadillac Products Packaging Company

Canslit Metalized 1.25 mil Black/silver Canslit Inc. /Imaflex Inc.

Canslit Metalized 1.25 mil White/silver Canslit Inc. /Imaflex Inc.

Embossed HDPE 0.6 mil, Black Canslit Inc. /Imaflex Inc.

Embossed LDPE 1.25 mil, Black Canslit Inc. /Imaflex Inc.

SARANEX A Black Dow Chemical Co.

SARANEX B Black Dow Chemical Co.

FilmTec VIF 1.25 mil, Black ARI, CA

Ginegar Ozgard 1.25 mil, Black Ginegar Plastic Products, Ltd.

Ginegar VIF 1.25 mil, embossed black Ginegar Plastic Products, Ltd.

Guardian AgroPlastics VIF 1.2 mil, Embo ssed black Guardian Agroplastics Olefinas

USA

Mid South VIF 1.25 mil, embossed black Mid South ExtrusionPage 32 of 78 Embossed Polyethylene Film 1.25 mil, Embossed LDPE Pliant Corp

Pliant Blockade 1.25 mil, Black Pliant Corp

Pliant Blockade White 1.25 mil, White Pliant Corp

Pliant Metalized 1.25 mil, black/silver Pliant Corp

Raven TIF “VaporSafeTM” 1.0 mil includes EVOH resin barrier,

clear Raven Industries Inc.

Raven TIF “VaporSafeTM” 1.4 mil LDPE with EVOH core, black Raven Industries Inc.

Klerk Hytibar VIF Clear Klerk's Plastic/HyPlast



### Experimental Results

1. Comparison of the MTC results of indivi dually tested fumigant s and mixed fumigants suggests that the mixing of different fumigants does not affect the calculated MTC. Table 3 lists

the MTC results from both mixed and individu ally tested fumigants for one high density polyethylene (HDPE) film. The variation in the obtained MTC va lues is within the expected analytical uncertainty of the method.

Table 3. Comparison of calculated MTCs obtain ed from individually tested fumigants vs. mixed fumigants.

MeBr IOM DMDS 1,3-D-cis 1,3-D trans PIC MITC

Mixed (avg. of 6 replicates) 0.53 0.91 2.84 3.12 4.55 0.91 9.35

Individually tested Rep 1 0.50 0.84 3.02 2.87 4.89 0.89 11.6

Rep 2 0.48 0.88 3.24 2.67 4.30 0.94 9.96



### 2. In the test of possible effects of fumiga nt concentrations on the calculated MTCs, mixed fumigants were loaded into the permeability cells at different concentrations. This test

was to determine whether the film MTC woul d be different under different concentration gradients. Because the MTC is a parameter expressing the properties of the film and the chemicals, the MTC is theoretically independent of the concentration gr adient. Our laboratory

test results indicate that the MTC is independent of the initial fu migant concentration within the test cell (Table 4). This conclusion is in agreement with Scott Yates’s results.Page 33 of 78 Table 4. Comparison of the MTCs obtained from different concentrations of fumigants for a HDPE

film

. Concentration MeBr IOM DMDS 1,3-D-cis 1,3-D trans PIC MITC

Instrument Response,
Low Conc. 4480 33784 9622 8235 8218 n.a. 20641

Instrument Response,
Intermediate Conc. 169034 (* 38 X ) 58383 (* 2 X ) 27290 (* 3 X ) 24745 (* 3 X ) 19138 (* 2 X ) 11230 38097 (* 2 X )
Instrument Response, High Conc. 1515656 (* 338 X ) 658969 (* 20 X ) 46609 (* 5 X ) 98645 (* 12 X ) 97405 (* 12 X ) 953969 (* 76 X ) 105996 (* 5 X )

Calculated MTC

, Low Conc. 0.59 0.87 3.31 2.75 4.95 n.a. 9.13 Calculated MTC,

Intermediate Conc. 0.50 0.91 3.34 2.72 4.35 1.06 8.30

Calculated MTC, High Conc. 0.48 0.84 3.36 2.67 4.30 0.79 9.96



### *Multiples of increased instrument response compared to the low concentration test.

n.a. – not added in the initial test.

3. During soil fumigation, moisture condensatio n often occurs under th e film. Humidity is therefore one factor that might impact the pe rmeability of films. B ecause of the limitation of ACB testing equipment, the relative humidity inside the permeability cells could not be controlled easily. The relative humidity in the ACB laboratory is generally low (about 30-40%). Therefore, the ambient laboratory humidity at 25 o 

### C was considered to be “low humidity”. At the opposite extreme, a test was perf ormed by adding a small amount of water (about 2 mL) to the source side of a permeability cell. This test cell was considered to be at “high humidity”. After equilibrating for several hours, fumigants were added and the permeability was determined under these conditions. Results of these tests (Table 5) indicate that the relati ve humidity inside the permeability cell does not impact the film permeab ility. The variation in the calculated MTC is within the range of expect ed testing uncertainty.

Table 5. Comparison of the MTCs under different relative humidity at 25 o C

.

MeBr IOM DMDS 1,3-D-cis 1,3-D trans PIC MITC

Low humidity

(avg of 6 mixed replicates) 0.56 0.99 2.84 3.35 4.66 1.09 9.09

High Humidity

Rep 1 0.62 1.17 2.72 3.42 4.86 1.29 9.48

Rep 2 0.59 1.15 3.13 3.45 5.59 1.15 10.05



### 4. Comparison of the MTC values obtained fr om the same films tested at both ACB and Scott Yates’ lab at ARS, USDA suggests that th e MTCs determined at each lab are in general agreement (Fig. 1 and 2). Based on the testing of many different films, ACB has found that thePage 34 of 78 

### variation in the condition of the film samples being tested could be the largest contributor to the variation of the calculated MTCs. Depending upon how the film samples were handled (roughly or minimally, as indicated by the presence of fo lding marks and stretched segments) the obtained MTCs can vary significantly. Th e variations in the measured MT Cs of the same branded films as shown in Figs. 1 and 2 are likely the result of this variation in the condition of individual film samples. This observation is consistent with the MTC results of field- stretched films vs. new films. The field used films are usually stretche d to some degree during a pplication and removal. The handling of the films in the field appears to compromise the integrity of the films. The MTC results of used films are generally higher than fr esh films (Fig. 3), particularly for the metalized

films.

Fig.1. Comparison of the MTCs determined by USDA and EPA labs for MeBr, IOM, cis-1,3-D, and PIC for the Cadillac HDPE film. The same film (different samples) was tested several times by Scott Yates and

the individual MTC values are shown. A CB results are the last bar in each chart. cis 1,3 D

0.000 1.000 2.000 3.000 4.000 5.000 6.000

FM25 FM27 FM29 FM41 FM44 FM50 FM66 FM84 ACBMTC PIC

0.000 0.200 0.400 0.600 0.800 1.000 1.200 1.400 1.600

FM25 FM27 FM29 FM41 FM44 FM50 FM66 FM84 ACBMTC MeBr

0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800 0.900

FM25 FM27 FM29 FM41 FM44 FM50 FM66 FM84 ACBMTC IOM

0.000 0.200 0.400 0.600 0.800 1.000 1.200 1.400 1.600

FM25 FM27 FM29 FM41 FM44 FM50 FM66 FM84 ACBMTCPage 35 of 78 Fig. 2. Comparison of the MTC’s determined by USDA and EPA labs for MeBr, IOM, cis-1,3-D, and PIC for the Pliant Blockade VIF film. The same film (d ifferent samples) was test ed several times by Scott

Yates and the individual MTC values are shown. ACB results are the last bar in each chart.

Fig. 3. Comparison of the MTCs from fresh films (not stretched, blue color bar) vs. field used films (stretched, maroon color bar) for several fumigants. MeBr

0.00 0.01 0.01 0.02 0.02 0.03 0.03 0.04 IOM

0.00 0.01 0.01 0.02 0.02 0.03

cis 1,3-D

0.00 0.01 0.01 0.02 0.02 0.03 0.03 0.04 0.04 0.05 0.05 PIC

0.00 0.00 0.00 0.00 0.00 0.00 0.00

Canslit Metalized

0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00

Me Br

P ro p ylene Oxide IOM 1,3 D-cis DMDS MITC Chloropicr i n

1,3 - D tr

a n s

FumigantsMTC (cm/hr) Pliant LDPE

0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00

M eBr Propylene Ox i d e IOM

1 ,3 D -c i s DMDS MITC

Ch l o r op i crin

1 ,3 - D tr a n s

FumigantsMTC (cm/hr)

Guardian VIF

0.00 0.10 0.20 0.30 0.40 0.50 0.60

Me B r

P ro p ylen

e Oxide IOM 1,3 D-cis DMDS MI T C Chloropicrin

1,3 - D t

ra n s

FumigantsMTC (cm/hr) Pliant Blockade

0.00 0.01 0.01 0.02 0.02 0.03 0.03 0.04 0.04

M eBr

Pr o pylene Oxide IOM

1 , 3 D-

c is DM DS M I T C

Ch lo r o pi c r in

1 ,3 - D tra

n s

FumigantsMTC (cm/hr)Page 36 of 78 

### Mass Transfer Coefficient of all Films

All the analytical data used to generate the MTCs for all the films have been reviewed by a second chemist for the accuracy and logic in ca lculation and transcription. The quality control measurements and criteria established in the Quality Assurance Project Plan (QAPP) and the Addendum of the QAPP for this project are impl emented and verified. The criteria for the precision and accuracy of the analytical results defined in the QAPP are generally met.

Specifically, the relative standard deviation for the replicate analyses is, in general,
within 30% for the MTCs that are above 0.001 cm/h. The recovery of the stable fumigants, such as MeBr and IOM, from the permeability cells in the collected samples, compared to the amount added to the cells, is within the predefined ra nge of 60% to 120% for experiments lasting up to three days. For experiments that last more than three days, the recovery sometimes is lower. The recovery of the less table compounds, such as MITC and PIC, from the permeability cells is

variable. The relative standard deviation for the instrument response verification standards is within 25% for a period of up to 12 days.

Several films were randomly selected and th e tests were repeated. The obtained MTCs

are consistent with the initial tests. All the re sults are included. All the films were tested in triplicate, except for one film (Pliant Blockade, Bl ack). It was discovered after the test that one of the triplicate samples had a small hole in the fi lm. Consequently only duplicate test results are available for this film (Pliant Blockade, Black).

The MTC results of the twenty five films th at were submitted for testing from twelve

manufacturers are listed in Attach ment 3 and 4. Attachment 3 lists the individual MTC values of the triplicate tests for all the films. Attach ment 4 lists the average calculated MTC and the standard error of the replicate tests for each fumi gant and each film. All the values are reported to four decimal points.

Most of the films that have been tested we re labeled as “virtually impermeable film (VIF)” and “totally impermeable film (TIF)”. Th e testing for each of these films lasted for up to 12 days. At the end of the testing period for some films, some fumigants were still not detected in the receiving chamber of the pe rmeability cells, or the detectab le amount was so low that the MTC could not be confidently calcul ated. The calculated MTCs in th ese cases are listed as zero.

Most of the calculated MTCs for the VIF and TIF films are very low. Because the analytical uncertainties associated with determin ing very low levels of fumigants are relatively large, the variance relative to the calculated MTCs in these films appears high, although the actual values of the variance are very low.

The MTC differs for different fumigants, w ith MITC being the compound that permeates through all the films much faster than the othe r fumigants. DMDS a nd both isomers of 1,3-D migrate through all the films at a slower rate than MITC, but at a relatively faster rate than other

tested fumigants. Sulfuryl fl uoride is the slowest compound to pe rmeate all the tested films. MeBr, IOM, PIC and PPO are generally slow to permeate through a film. The distribution of the MTCs of different fumigants for various films is shown in Fig. 4a and 4b.Page 37 of 78 MTC of Different Tarps

0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00

Sulfury l Flu

o r i de M e B r PPO IO M 1,3 D

-c is

D M D S M ITC

C hl oropicrin 1,3- D trans

FumigantMTC (cm/hr)

MTC of Different Tarps

0.000 0.020 0.040 0.060 0.080 0.100 0.120

Sul

f u r y l Fluoride MeB r P PO IOM 1,3 D -cis

D MDS MI T C

C hloropicri n 1,3-D tra

n s

FumigantMTC (cm/hr)

Fig. 4. MTCs of different fumigants for various films. (a). High permeability films. (b). Low permeability films.



### cc: William Chism, BEAD Jack E. Housenger, BEAD Charles W. Smith, HED Steven Weiss, PRD Gabe Rothman, EFED Tony Kish, RD Betsy Grim, OPP Betty Kolbe, ACB Charles J. Stafford, ACBPage 38 of 78 

# Appendix C: Analysis of Mass Transfer Coefficient Data Contained In Analytical Chemistry Branch

Laboratory Report Entitled - Agricultural Tarp Permeability to Fumigants

, Sarkar 2010Page 39 of 78 

### UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D.C. 20460

OFFICE OF CHEMICAL SAFETY AND
POLLUTION PREVENTION 

### MEMORANDUM

Date: August 27, 2010

SUBJECT: A Classification of Tarps by Cluster Analysis Based On Mass Transfer Coefficient Data Contained In Analytical Chemis try Branch Laboratory Report Entitled Agricultural Tarp Permeability to Fumigants

PC Code: 053201; 081501; 035602; 039003; 039002;

068103 DP Barcode: 381403

Decision No.: 345514 Registration No.: NA

Petition No.: NA Regulatory Action: RED FOLLOW UP Risk Assessment Type: Special Project Case No.: 0335

TXR No.: NA CAS No.: 74-83-9; 76-06-2; 533-74-4; 137-42-8; 137-41-7; 556-61-6

MRID No.: NA 40 CFR.: NA



### FROM: Bayazid Sarkar, Mathematical Statistician Chemistry and Exposure Branch Health Effects Division (7509P)

THROUGH: David J. Miller, Chief Chemistry and Exposure Branch Health Effects Division (7509P)

TO: Jeffrey L Dawson, Chemist Registration Action Branch 7 Health Effects Division (7509P)

Jack Housenger, Director Biological and Economic An alysis Division (7503P)

John Leahy

Pesticide Reevaluati on Division (7508P)

Chemistry and Exposure Branch (CEB) was requ ested to evaluate da ta contained in the Biological and Economic Analysis Division (B EAD) Analytical Chemistry Branch (ACB) Laboratory Report entitled Agricultural Tarp Permeability to Fumigants (Qian and Kamel, June 17, 2010) with the goal of developing a “grouping scheme” through which agricultural films or tarps could be classified based on measures of permeability against several fumigants. Permeability is measured in terms of mass transfer coefficients (MTCs) and expressed cm/hr.

MTCs were determined under standard conditions a nd the impact of varied temperature, relative humidity, and challenge concentrations was al so evaluated to a limited degree for a small number of film/fumigant combinations. A statis tical analysis was completed to ascertain if clusters could be identified with respect to MTC measurements. Such information could bePage 40 of 78 

### relevant to risk management decisions related to agricultural film use and granting relief from fumigant buffer zones (e.g., in the form of credits ) if users opt to use less permeable films.

This memorandum is divided into five sections. Section 1 introduces specific objectives of this analysis; Section 2 describes th e statistical methods which were used; Section 3 presents the results of global clustering using range plot a nd multidimensional clustering; Section 4 discusses the results; and Section 5 summarizes conclusions.

1 INTRODUCTION

Mass transfer coefficients (MTCs) are widely re cognized in the literatu re as an appropriate means for describing the permeability of agricultural films to fumi gants. As indicated above, the BEAD ACB generated a series of MTCs which serv e as the basis for this analysis. These are available in the following report: 1



### Agricultural Tarp Permeability to Fumigants ; Authors: Qian, Y. and Kamel, A.; Sponsor: U.S. EPA, Analytical Chemistry Bran ch, 701 Mapes Road, Fort Meade MD 20755-5350 (6/17/10).

Additional data developed by the United States Department of Agriculture (USDA) was also used as a basis for a qualitative comparison to the results from the ACB report. These data were reported in the following document:

A Standardized Approach for Estimating the Pe rmeability of Plastic Films to Soil Fumigants Under Various Field and Environmental Conditions ; Papiernik, S. K.; Yates, S.R.; and Chellemi, D.O. (2010)

- in press

Specifically, CEB was asked to classify 25 tarps according to the results from the permeability tests for nine different fumigants with the goal of developing a “grouping scheme” through which agricultural films or tarps could be classified based on measures of permeability against several fumigants. In addition, the following issu es important to the risk management approach for fumigants were also evaluated:

1) Is a tarp consistent among fumigants in terms of its permeability? In other words, are the relative rankings based on aggregate permeabilities to the nine fumigants reasonably concordant with the individua l rankings based on fumigant-specific permeabilities?

2) In what ways do factors such as temperatur e, humidity, fumigant concentration affect the MTC value of a tarp and do these c onditions affect estimated MTC values consistently?

3) Is the measurement process adequate and re liable as defined by the similarity among
replicate MTC measurements in the availabl e data? Also, are there similarities in MTC measurements for any given tarp/fumigant combination between the ACB

1 ACB also produced a supplemental report entitled Addendum to the Report of Agricultural Tarp Permeability to Fumigants, Permeability at 40°C (Qian & Kamel, 8/16/2010). The results of this report have been addressed in the HED memo on emission factors (Dawson and Smith, 8/2010).Page 41 of 78 

### laboratory and USDA laboratories which is important for evaluating the MTC testing
protocol?

2 STATISTICAL BACKGROUND AND METHODOLOGY

In order to perform the anal ysis, data were obtained fr om ACB in MS Excel format and imported into Stata and R for analysis. Stata and R are st atistical software packages available to CEB.

CEB determined that a “Cluster Analysis” approa ch would be an appropriate primary statistical technique to address the issues associated with the interpretati on of these data and generating overall conclusions with respect to appropriate grouping or classi fication of tarps per their MTC values for the nine fumigants. This would be supplemented by the use of both range plots and lognormal probability plots in order to better char acterize observed differences and to evaluate outlying or “irregular” tarp/fumigant combinations . Each of these three techniques is described

in additional detail below:

HIERARCHICAL CLUSTERING ANALYSIS (HCA) 2 

### : Cluster analysis is a descriptive term used generically to desc ribe univariate and multivariate exploratory statistical methods which attempt to dis cern natural groupings (or clusterings) of

observations. A cluster is a collection of objects which are similar to other objects within

the cluster but are dissimilar to the objects belonging to ot her clusters. Clustering is one of the most important unsupervised learning processes that organize objects into groups whose members are similar in some way. C lusters, like classes, shoul d partition the data: every object in the given set of objects should belong to one, a nd only one, cluster

. 

### Nearly all clustering approaches use a c oncept of distance and operate not on the

observed raw data per se but rather on an observed inte r-individual distance matrix generated from the raw data. In this way, data points can be conceptualized in a multidimensional space where we can compute a distance measure between each pair of points. Points that are closer together get placed in same group or “cluster”.

A “hierarchical” clustering is a sequence of pa rtitions in which each partition is nested into the next (subsequent) part ition in the sequence. Hierar chical clustering has been a standard component of the st atistician’s toolbox si nce the 1960s and has recently become a common method for pattern recognition, machine learning, data mining, and bioinformatics. It is one of several genera l types of cluster analysis methods and, like many, uses the concept of “distance” for determining the similarity and dissimilarity

between observations and uses this “distan ce” to group or classify those observations. Advantages of hierarchical cluste ring techniques are th at the data analyst does not need to specify number of clusters in advance and it permits analyst to view the data at any number of levels of hierarchy or granular ity. The detailed algorithm is provided in Appendix 1.

There are two typical approaches us ed in hierarchi cal clustering:

2 Other clustering methods include K -means, Bayesian model based clustering, Fuzzy clustering, Self Organizing Maps, and a variety of other unsupervised learning methods. Due to time constraints and lack of availability of appropriate software, these alternative methods were not applied. The clustering method used is considered reasonably robust and results would not be expected to su bstantively change if these other approaches were used.Page 42 of 78 

### • agglomerative or “the bottom up approach": grouping small clusters into larger

ones, or

• divisive or “the top down approach": splitting large clusters into small ones.

Regardless of which HCA analysis is used (agglomerative or divi sive), the standard output of hierarchical cluste ring is a dendrogram. A dendrogr am is a visualization of hierarchical clustering and is a cluster tree diagram where the distance of a split or merge is recorded. Using a dendrogram, the analyst can easily specify the cut point to determine the number of clusters. The height of a node is proportional to the distance between groups to which it links and the sh ape of a dendrogram gives information on the number of clusters. Thus, cutting a dendr ogram horizontally at a specific height

constructs clusters in whic h similar tarps are grouped.

RANGE PLOT : A range plot is a plot which illustrates a gi ven percentile range of values for each of a number of categorical variables and creates a visual impression of the order (from high to low), mid-point, and spread (or range) of those values. In this case, the log (MTC) for each of the tarps and its 90% range of values were used.

LOG-NORMAL PROBABILITY PLOT : In addition to the above two methods and to
confirm and/or further visual ize the grouping and highlight ex ceptions or special cases, a log-normal probability plot tec hnique has also been used for an exploratory qualitative cluster analysis of the film s based on a single fumigant. 3 

### A log-normal probability plot provides a powerful technique for determ ining whether the data fit a lognormal distribution. Data points falling on a straight line on a log-normal probability plot imply that a log-normal distribution will fit the data. With a log-normal probability plot, we can see the nature and the quality of the fit ove r the whole distribution, and can detect any systematic departures from a fit. More im portantly for the task at hand, we can also evaluate and define clusters by looking for and defining natural breaks of the points. By investigating the fumigant-specific exceptions or outliers that become readily apparent on log-normal probability plots, both the magnit ude and nature of the exceptions can be more easily seen and evaluated. The global classification on the fumigant-by-fumigant graphs of permeability on log-normal probability plots permit the exceptions to be more easily seen and identified such that a more refined clas sification or grouping can be developed which accounts for fumigant-specifi c disparities among films.

Together, the above three technique s – range plots, hierarchical cl ustering techniques with their resulting dendrograms, and log-normal probabil ity plots – provide a reasonable method for grouping of tarps as ranked or evaluated by the measured MTC. A comparison of the advantages and disadvantages of range plots vs. HCA is presented in Table 1.

3 MTCs for a number of fumigant/film combinations were sometimes reported as zero in the ACB report indicating that no permeation of the tarp was observed. In these cases, 0.0001 was added to MTC scores so that logarithm

of MTC is not undefined when MTC is zero.Page 43 of 78 Table 1. Comparison between Range Plot and Hierarchical Clustering Analysis Methods Range Plot Hierarchical Clustering

Not a standard tool for clustering One of the most common methods for cluster analysis. Its theory is well developed and widely used. Distance between two films is defined by the distance of their midpoints of the ranges. Distance between two films within the same cluster is calculated using Euclidian method Because it is not a standard clustering technique,

distance between two clusters has not been defined Distance between two clusters is determined by complete linkage. Midpoint may not be a sufficient statistic for all the samples of a given film. So distance calculation method is questionable. Euclidean method uses all points of two films, instead of a single value, sampled under different fumigants to

calculate distance

The above method converts a multidimensional problem to a one dimensional problem resulting loss of

information Hierarchical method of clustering preserves multidimensionality and it can pool information from different fumigants.

Cluster is created by visual inspection which can be

erroneous Cluster is created by cutting the dendrogram at different height which is more precise than just visual inspection. The above method is simple and easy to implement, visualize, and interpret, but lacks any formal justification The above method is mathematically rigorous and requires intensive computation



### 3 RESULTS

As discussed and explained above, the Range Plot was used as a preliminary grouping technique. This technique is considered semi-quantitative in that it is not an objective and rigorous mathematical approach in terms of ranking tarp s according to (log) permeability. As described in Table 1 it is quick and easy but necessarily imprecise and is somewhat imperfect in determining overall ranking with clusters or groups; however, th e plot does create a visual ranking which can be complemented by other, mo re quantitative (and some what more objective)

methods such as hierarchi cal clustering techniques.

Figure 1 displays the 90 percentile range of the MTCs by tarp name (i.e., tarp identifier). The plots are ordered by midpoint (from high permeability to low permeability) with the tarps ranked (from high to low) by midpoint MTC value 4 

### and the arrows extend from the 5 th 

### to the 95 th


### percentile MTC values for any given tarp. For example log 10 

### (MTC) of Pliant Regular Black ranges roughly from

- 1.8 to 1.1.

To complement the above range plot and provi de a more objective ranking, log-transformed MTC values were also used for cluster analysis. 5 

### R version 2.10.1 was used for this cluster analysis. For multivariate clustering 6 

### , there are n lists of k tarps for a given cluster where n is the number of fumigants tested (here, n =9). The goal of this approach is to find an aggregate ranking

of the set of k tarps that is closest to the given set of input rankings of the tarps

. 

### CEB has used

4 Let “a” be the minimum and “b” be the maximum of lo g (MTC) of a given film sampled under different fumigants. For any given tarp: Range = 95 th percentile logMTC value – 5 th percentile value; midpoint = 50 th
percentile of MTC value.

5 A value of 0.0001 was added to each column of the 25 (films) by 9 (fumigants) data matrix before log transformation to prevent log (MTC) from being undefined when MTC score is zero.

6 For more information on multivariate analysis and cluster techniques, see Everitt,B.S and Dunn ,G (1997).Applied Multivariate Data Analysis: Arnold ; and Johnson, D.E (1998). Applied Multivariate Methods For Data Analysis: Duxbury Press

.Page 44 of 78 

### the Cross-Entropy Monte Carlo algorithm (CE) (P ihur et al., 2009) available in R package RankAggreg to find aggregate ranking of tarps. Fi gure 2 displays the dendrogram of the hierarchical multivariate clustering of 25 tarps. Figure 2 is based on samples from all fumigants and groups the tarps – based on all fumigants cons idered as a whole – in to four clusters as outlined by the red borders

. Each red rectangular box indicates a separate cluster, or “grouping”, as determined by the mathematical distance algor ithm which was used (described above). As can be seen the algorithm determined that ther e are 4 “groupings”, which are separated by the

indicated red lines.Page 45 of 78 Figure 1: Range Plot for Tarps Raven, 1.0 mil, Clear Berry EVOH High Barrier Berry EVOH High Barrier w/Improved toughness Hyplast/Klerk, clear Raven, 1.4 mil, Black Dow Saranex B AEP-one Berry EVOH Supreme Barrier Dow Saranex A Ginegar Ozgard FilmTec VIF Mid South Extrusion VIF Pliant Blockade, Black Pliant Blockade, White Ginegar Embossed VIF Cadillac VIF Guardian Black VIF Canslit Metalized White

Canslit Metalized Black Pliant Metalized Cadillac HDPE Canslit LDPE A EP Sun Film High Barrie r Canslit HDPE Pliant, Regular Black



### -6 -4 -2 0 2

Tarp data from BEAD/ACB (tarpdata.dta and tarp5.do)) No permeability recorded here as 10^-5 cm/hr 

# 90 Percentile Range of log10 Permeabilities, by TarpPliant MetalizedCanslit Metalized BlackCanslit Metalized WhiteCanslit HDPEPliant, Regular BlackCadillac HDPEAEP Sun Film High BarrierCanslit LDPECadillac VIFGuardian Black VIFMid South Extrusion VIFFilmTec VIFPliant Blockade, WhiteGinegar Embossed VIFPliant Blockade, BlackHyplast/Klerk, clearDow Saranex AGinegar OzgardBerry EVOH Supreme BarrierDow Saranex BRaven, 1.4 mil, BlackRaven, 1.0 mil, ClearAEP-oneBerry EVOH High BarrierBerry EVOH High Barrier w/Improved toughness0 10 20 30 Cluster Dendrogram

hclust ( *

, "com p lete" ) dist(tg)Height

Figure 2: Dendrogram of Hiararchial Clustering of Tarps Combining MTCs from 9 Fumigants



### Note that the dendrogram does not show the a ggregate ranking (orderin g) of the tarps. Aggregate ranking based on nine fu migants is shown in Table 2.

Both the Range Plot and Hierarchical Clustering techniques were used jointly to provide a global ranking of the fumigants and to separate them in to broad classes or cate gories with respect to MTC values. Both the Range plot shown in Fi gure 1 and the hierarchi cal clustering dendogram shown as Figure 2 are in basic agreement with re spect to the relative grouping for the tarps. Specifically, these suggest that the tarps can be grouped into “high permeability”, “moderate permeability”, “low permeability” and “very low pe rmeability” groupings, as detailed in Table 2.

Table 2. Overall (Global) Tarp Groupings Based on Range Plot a nd Hierarchical Cluster Analyses (samples from nine fumigants) Cluster 1 (high permeability):

Cansilt HDPE Pliant, Regular Black AEP Sun Tarp High Barrier

Canslit LDPE

Cadillac HDPE Cluster 2 (moderate permeability):

Pliant Metalized

Canslit Metalized Black

Canslit Metalized White Cluster 3 (low permeability):

Guardian Black VIF

Cadillac VIF Ginegar Embossed VIF Pliant Blockade, White Pliant Blockade, Black TarpTec VIF
Mid South Extrusion VIF Cluster 4 (lowest permeability):Page 47 of 78 Table 2. Overall (Global) Tarp Groupings Based on Range Plot a nd Hierarchical Cluster Analyses (samples from nine fumigants) Ginegar Ozgard

Dow Saranex A Berry EVOH Supreme Barrier

Dow Saranex B Raven, 1.4 mil, Black

AEP-One Berry EVOH High Barrier with Improved Toughness Hyplast/klerk, clear Berry EVOH High Barrier Raven, 1.0 mil, Clear



### From Table 2, we observe that polyethylen e tarps are all ranked in Group 1 (highest permeability). Metalized tarps appear to form th eir own separate cluster (Group 2). Clusters 3 and 4 consist of the least permeable tarps described as Virtually Impermeable Films (VIFs) or

those described as Totally Impermeable Films (TIFs). These tarps have an alternative layer of other material included typically between layers of polyethylene which dramatically decreases their permeability. For example, the tarps specifica lly referred to by their manufacturers as TIFs

contain ethylene vinyl-alcohol ( EVOH) copolymer resins as this central layer, but any film based on performance, regardless of the materials used to produce it, would be ch aracterized as such.

4 DISCUSSION

The above results and rankings reflect a global mu ltidimensional score for each of the tarps. In reality, these represent for each tarp an aver age or ‘composite’ permeability score across the 9 fumigants tested; as such, it is possible that certa in tarps are outliers with respect to any given specific fumigant and the above multidimension al methodology will not necessarily reflect or otherwise incorporate these aberrant permeability va lues as part of its clustering scheme. The well-recognized limitations of the multi-dimensi onal cluster analysis done above include:

1. It is difficult to determine ranking of ta rps within a cluster. Sophisticated Rank aggregation techniques are required for co mbining individual ordered lists for each
fumigant into a single list reflec tive of the overall preference.

2. The MTC value of the tarps of a cluster is a vector of nine co mponents instead of a
single scalar which can be diffi cult to understand and communicate.

3. A tarp can potentially have widely disparate permeability to different fumigants
(Papiernik et al. 2010) a nd/or a specific tarp/fumigant combination can be an

‘outlier’ with an MTC value that differs dr amatically from the other MTCs in that
grouping; since these issues can be hidden or otherwise not readily obvious when a single ranking system is used, it is important to be aware of and determine the ranking
of tarps based on MTC values for each fumi gant separately, and evaluate the degree to which the overall or global ranking co mports with the fumigant-by-fumigant
rankings for each tarp.

In order to address the above issues, CEB conducted a similar hi erarchical cluster analysis (univariate HCA) on each fu migant separately (i.e., one fumigant at a time) in order to highlightPage 48 of 78 

### any differences from the results of the composite analysis (or “irregularities”) that a specific tarp/fumigant combination may disp lay. As an example, an analysis of MeBr is presented below in Figure 3 which illustrates the dendrogram-d etermined “groupings” that results when only

MeBr is considered

.Cadillac HDPECanslit LDPEAEP Sun Film High BarrierCanslit HDPEPliant, Regular BlackRaven, 1.0 mil, ClearBerry EVOH High BarrierBerry EVOH High Barrier w/Improved toughnessDow Saranex BAEP-oneRaven, 1.4 mil, BlackPliant MetalizedGuardian Black VIFCanslit Metalized BlackCanslit Metalized WhiteCadillac VIFPliant Blockade, BlackGinegar Embossed VIFPliant Blockade, WhiteDow Saranex ABerry EVOH Supreme BarrierHyplast/Klerk, clearFilmTec VIFGinegar OzgardMid South Extrusion VIF0 2 4 6 8 10 Cluster Dendrogram

hclust ( *

, "com p lete" ) dist(tg2)Height

Figure 3. Dendrogram for Hierarchical Clustering (considering MeBr only)



### The groupings or classifications will necessarily differ to some degree when comparisons of permeabilities are done for each tarp on an indivi dual fumigant-by-fumigant basis as opposed to the global or ‘composite’ basis described earlier. For this reason (and as discussed in the “Statistical Background and Me thodology” section of this memorandum), a log-normal probability plot was developed for each fumigant in order to confirm the grouping and highlight exceptions or special cases. By use of a log-normal probability plot for each fumigant on a fumigant-by-fumigant basis, we can evaluate and define clus ters by looking for and defining natural “breaks” (i.e., distinct separations) of the poi nts. Log-normal probability plots permit analyst to determine if fumigant–specific exceptio ns or outliers exist, and allow the magnitude and nature of the exceptions to be more easily se en and evaluated. In this way, a more refined classification or grouping can be developed whic h accounts for fumigant-specific disparities or exceptions among films. A comparison between the global cluster rankings (indicated by the colored symbols) and the MeBr-s pecific rankings (represented by the oval shapes) is presented below in Figure 4.Page 49 of 78 Figure 4. Log-Normal Probability plot displaying both global and MeBr specific clustering



### The Methyl Bromide (MeBr) groupings presented in Figure 4 are in most cases similar to the global ‘composite’ groupings. For example the fi ve tarps that are grouped in MeBr Cluster 1 (for highest permeability) and symbolized by red squa res are also classified that same way with respect to the global groupings . Similarly, MeBr Cluster 2 Grouping generally corresponds well with the Global Cluster 2 Grouping. Some exceptions can be seen with respect to MeBr Cluster 3 Grouping in that roughly half of these 7 

### are classified as Global Cluster 4. This means that while these tarps are globally classified as “ver y low permeability – Group 4”, they would have a somewhat different grouping -- “low permeab ility – Group 3” -- for any MeBr-specific permeability rankings. This information may be useful since it details exceptions to the general classification scheme which may be of interest with respect to informing risk mitigation activities. A summary of these findings for MeBr is presented in Table 3.

7 Ginegar Ozgard, (Hyplast/Klerk, Clear), Berry EVOH Supreme Barrier, Dow Saranex A 99.9 99 98 95 90 80 70 50 30 20 10 5 2 1 0.1 2.0000

1.0000

0.5000

0.2500

0.1250

0.0625

0.0313

0.0156

0.0078

0.0039

0.0020

0.0010

0.0005

0.0002

0.0001 y = 3.0224x - 5.1128

R2 = 0.9293

**M TC** 

**P ercentiles**  **Lognormal Probability Plot**

**EPA MeBr Global Cluster 1**  **Global Cluster 2 Global Cluster 3**  **Global Cluster 4**

Cluster 1

MeBr

Cluster 2

MeBr

Cluster 3

Me Br

Cluster 4 MeBrPage 50 of 78 Table 3: Classification of tarps for MeBr Only Fumigant: MeBr Tarps Ranked By MTC Score Range of

MTC (cm hr -1 ) Tarp MTC (cm hr -1 ) MeBrspecific

Cluster Grouping Cluster mean

10 -1 to 10 1 Canslit HDPE 1.3611 1

0.8799 Pliant, Regular Black 1.1078 1

AEP Sun Film High Barrier 0.8238 1

Canslit LDPE 0.6269 1

Cadillac HDPE 0.4800 1

10 -2 to 10 -1 Pliant Metalized 0.0570 2

0.0281 Canslit Metalized Black 0.0217 2

Canslit Metalized White 0.0185 2

Guardian Black VIF 0.0151 2

10 -3 to 10 -2 Cadillac VIF 0.0085 3

0.0033 Pliant Blockade, White 0.0057 3

Ginegar Embossed VIF 0.0053 3

Pliant Blockade, Black 0.0045 3

FilmTec VIF 0.0029 3

Ginegar Ozgard 0.0019 3

Mid South Extrusion VIF 0.0017 3

Hyplast/Klerk, clear 0.0010 3

< 10 -3 Berry EVOH Supreme Barrier 0.0009 3

Dow Saranex A 0.0006 3

Dow Saranex B 0.0002 4

0.0001 AEP-one 0.0001 4

Raven, 1.4 mil, Black 0.0001 4

Berry EVOH High Barrier w/Improved toughness 0.0000 4

Raven, 1.0 mil, Clear 0.0000 4

Berry EVOH High Barrier 0.0000 4



### Similar fumigant-by-fumigant analyses to th e one presented above for MeBr are found in Appendix 2 of this document. Specifically, the fu migant-specific MTCs associated with each of the nine fumigants are investig ated and the results -- includin g the fumigant-specific cluster dendogram and the log-normal probability plot -- are presented in Appendix 2 of this document,

as described below in Table 4.Page 51 of 78 Table 4. Location of Fumiga nt-specific Statistical Analyses a Location in Appendix 2 Description Table A2-1 Classification of tarps for MeBr Table A2-2 Classification of tarps for PPO Table A2-3 Classification of tarps for IOM Table A2-4 Classification of tarps for cis-1,3-D

Table A2-5 Classificati on of tarps for DMDS

Table A2-6 Classificati on of tarps for MITC Table A2-7 Classification of tarps for Chloropicrin Table A2-8 Classification of tarps for trans-1,3-D Table A2-9 Classification of tarps for SF

a Each fumigant-specific table is followe d in the Appendix by the fumigant-speci fic cluster dendogram and the fumigantspecific log-normal probability plot. These are done in a manner similar to the MeBr example presented in the text (which duplicates the material in Table A2-1)



### Based on the above analysis, the final tarp gr oupings – with their fumigant-specific exceptions as determined by the fumigant-specific analyses pr esented in Appendix 2 -- are listed in Table 5.

Specific Questions:

As part of CEB’s review of the data, the fo llowing three specific questions were addressed:

Question 1: Is a tarp consistent among fumigants in te rms of its permeability? In other words, are the relative rankings based on aggregate pe rmeabilities to nine fumigants reasonably concordant with the individual rankings based on fumigant-specific permeabilities?

Answer: Tarps do appear to be fairly consistent in term s of permeability across the nine fumigants that were tested. However, there are exceptions to this statement and these are presented in Table 5

and described in further detail below.

• Mid South Extrusion VIF is grouped in cl uster-3 according to the global clustering method but it is grouped in cluster-4 for IOM and chloropicrin usi ng fumigant specific clustering.

• Dow Saranex A is grouped in cluster-4 accord ing to the global clustering method but it is grouped in cluster-3 for MITC, chloropicri n, trans-1,3-D and SF using fumigant specific clustering.

All the tarps which are grouped in cluster-4 by gl obal clustering are grouped in cluster-3 for SF using a fumigant specific clustering scheme. SF has only three clusters in stead of four because distances between the tarps with in cluster 3 are very small which implies the tarps are very similar in terms of MTC score (see Ta ble A2-9 and corresponding dendrogram).Page 52 of 78 Table 5. Global clustering of individual tarps using nine fumigants along with exceptions with fumigant specific clustering Tarps Exceptions with fumigant specific cluster

Global Cluster 1

Cansilt HDPE

No exceptions Pliant, Regular Black AEP Sun Tarp High Barrier

Canslit LDPE

Cadillac HDPE

Global Cluster 2

Pliant Metalized No exceptions Canslit Metalized Black

Canslit Metalized White

Global Cluster 3 Guardian Black VIF For MITC, trans-1, 3-D, & MeBr : Cluster 2 Cadillac VIF For PPO, MITC, trans-1,3-D, & SF : Cluster 2 Ginegar Embossed VIF For MITC & SF : Cluster 2 Pliant Blockade, White For MITC: Cluster 2; For Chloropicrin: Cluster 4 Pliant Blockade, Black For MITC: Cluster 2 TarpTec VIF For Chloropicrin: Cluster 4 Mid South Extrusion VIF For IOM & Chloropicrin : Cluster 4

Global Cluster 4 Ginegar Ozgard For trans-1,3-D, MITC, SF, & MeBr : Cluster 3 Dow Saranex A For MITC, SF, Chloropicrin, & trans-1,3-D : Cluster 3 Berry EVOH Supreme Barrier For MeBr & SF: Cluster 3

Dow Saranex B For MITC: Cluster 3 Raven, 1.4 mil, Black For SF: Cluster 3

AEP-One For SF: Cluster 3 Berry EVOH High Barrier with Improved toughness For SF: Cl uster 3 Hyplast/klerk, clear For MeBr & SF: Cluster 3 Berry EVOH High Barrier For SF: Cluster 3 Raven, 1.0 mil, Clear For SF: Cluster 3



### In an effort to address tarp consistency in a more intuitive and visual way, Figure 5 shows the distribution of twenty five tarp s based on log (MTC) score across the nine tested fumigants and serves to highlight the degree of consistency in ranking of tarps for different fumigants. Overall, it can be seen that MITC has the highest MTC scores for all tarps among all the fumigants. DMDS and both isomers of 1,3-D migr ate through all the tarps at a sl ower rate than MITC but at a relatively faster rate than ot her tested fumigants. SF is the slowest compound to permeate all the tested tarps. In addition—and im portantly -- SF is the least cons istent in terms of cross-tarp rankings (as evidenced by the cros sed lines): specifically, there are a number of tarps which are ranked highly (i.e., low permeability) for other fu migants, but which are ranked poorly (i.e., high permeability) for SF. That is, while a tarp with low relative permeability for one fumigant generally also has low relative permeability fo r other fumigants (and vi ce versa), this is NOT true for SF in which rankings can reverse themselves.Page 53 of 78 Figure 5

. Distribution of tarps across different fumigants based on log (MTC) score



### Question 2: How do potentially differen t field conditions such as temperature, humidity, and application rate/fumigant concentration affect the MTC value of a tarp?

Answer:

a. Effect of temperature: MTC is believed to be dependent upon the temper ature, and this has been demonstrated in the literature for polyethylene tarps but less informati on is available for less permeable tarps such as VIFs and TIFs. USDA experiments showed R which is the reciprocal of MTC decreased with increasing temperature from 15 to 35 °C (Fig. 4, Table 1, Papiernik et al. 2010). The USDA experiment further showed that for the VIF, R values increased by a factor of 2 to 3 for each 10 °C decrease from 35 to 15 °C (potentially increas ing an order of magnitude over this range). For the HDPE and LDPE tarps tested, the R value increased by an average of 1.5 times for each 10 °C decrease. These changes in permeability of polyethylene were consistent with previous reports showing that that fumigant R values increased by 1.4 to 1.9 times for each 10 °C decrease in temperature from 20 to 40 °C (Papiernik a nd Yates, 2002). For all tarps, temperature had a stronger effect on R at lower temperatures (Papiernik et al. 2010). Therefore, temperature appears to affect both the cl ustering as well as the ranking of tarps and may do so in a substantive or meaningful way. More expe rimentation – and comp lex statistics involving interactions -- would need to be performed in or der for these results to be extended to different temperature ranges (and tarps) than those tested here by the ACB.Page 54 of 78 

### b. Effect of relative humidity. Humidity is another factor that may impact the permeability of tarps. During soil fumigation,

moisture condensation often occurs under the tar p. Because of the limitation of the testing protocol/equipment, the relative humidity inside the permeability cells could not be controlled easily. The relative humidity in the ACB lab was generally low (about 30- 40%). Therefore, the ambient laboratory humidity at 25 o 

### C was considered to be “l ow humidity”. At the opposite extreme, a test was performed by adding a small amount of water (about 2 mL) to the source side of a permeability cell. This test cell was consid ered to be at “high humidity”. After equilibrating for several hours, fumigants were added and the permeability was determined under these

conditions. The ACB memo concludes based the resu lts of these tests that the relative humidity does not impact the MTC score. However, CE B notes that the above lab experiment was conducted using only one tarp, and believes th e ACB conclusion cannot be extended beyond the single tarp tested or generalized to ot her tarps without additional data.

Previous research showed that condensed water, even a continuous layer, did not affect the mass transfer of fumigants through a HDPE tarp (Papiernik and Yates, 2002). The USDA Lab conducted experiments testing effect of relati ve humidity on permeability. Relative humidity had a large impact on the permeability of a VIF tarp (FM4) to five fumiga nts (Table 2, Papiernik et al. 2010). For this tarp, when the RH was 100% on either side of the tarp, the R was at least 100 times lower than when RH was very low (Table 2, Papiernik et al. 2010 ). At high humidity, the permeability of this VIF to fumigant vapors was of similar magnitude as the permeability of a polyethylene tarp (Papiernik et al. 2010). Therefore relative humi dity affects both the clustering as well as the ranking of some of the tarps and may do so in a substantive or meaningful way. More experimentation – and complex statistics involving interactions -- would need to be performed in order for these results to be extend ed to different humidity ranges (and tarps) than those tested here by the ACB.

c. Effect of concentration Because the MTC is a parameter expressing the pr operties of the tarp and the chemicals, the MTC is theoretically independent of the c oncentration gradient. Qian and Kamel 2010 concluded that the MTC is indepe ndent of initial concentration (s ee Table-4 of the ACB memo). However, as this experiment was conducted using only one tarp the result s cannot be generalized

to the classification scheme to other c oncentrations based on the data presented.

Question 3: Is the measurement process adequate and reliable (e.g., similarity among MTC measurements in replicates)? Are there sim ilarities in MTC measur ements for any given tarp/fumigant combination between the ACB results and those developed in the USDA laboratory?

Answer: In most of the cases, there is similarity between replicates. There are some instances that the measured permeability of the tarps differs among the replicates

. 

### As an example, the MTC values of three replicates of the Canslit HDPE for SF are 0.01917, 0.01807, and 0.16991. The third replicate has a value nearly 10 times higher than the first two replicates

. 

### The MTC values of Raven, 1.4 mil, Black also differ among th e replicates for most fumigants.Page 55 of 78 

### ACB’s memo compared the MTC values obtained from the same tarps tested at both ACB and USDA. Based on this comparison, the ACB memo c oncluded that the MTCs determined at each lab are in general agreement (Fig.1 and 2 of the ACB memo). However the ACB memo used only two tarps for this comparison: Cad illac HDPE, and Pliant Blockade VIF.

5 SUMMARY AND CONCLUSION

ACB used methods developed by USDA’s Agriculture Research Service (Papiernik et al. 2010) to determine the MTC of 25 different types of tarps under laboratory conditions that involved 9 fumigants and controlled for temperature (25 o 

### C) and relative humidity (30 to 40%). Because the tarps and fumigants used in ACB’s tests repr esent the most commonly used products for the fumigation of soil and subsequent control of chemical emissions, CEB performed a cluster analysis to determine if the tarps coul d be categorized based on their MTC.

CEB analyzed the MTC testing data collected by ACB using two statistica l clustering techniques to determine if the 25 different tarps could be categorized based on their composite MTC scores (i.e., a vector of nine MTC values) from nine fu migants. First, a qualitative-oriented approach called the Range Midpoint Method was used to vi sually compare the 25 tarps by rank-ordering their median MTC value and then examining each tarps’ 90 th 

### percentile range. Second, a quantitative-oriented multivariate hierarchical clustering analysis was performed, which is a

standard statistical method for ev aluating clusters. In addition, CEB also used the Cross-Entropy Monte Carlo algorithm (CE) (Pihur et al., 2009) to determine an appropriate “aggregate” or “composite” ranking of tarps. The results from the Range Midpoint Method and the Hierarchical Cluster Analysis were then join tly evaluated to group tarps on a global basis using a “weight-ofthe-evidence” approach. In addition to multivaria te analysis, univariate hierarchical clustering method was used to classify the tarps base d on MTC score for a single fumigant. To confirm and further visualize the groupi ng and highlight exceptions from composite clustering, a lognormal probability plot technique was used as an exploratory qualitative cluster analysis of the tarps based on a single fumigant

.

Based on CEB’s analysis, it was determined th at both the qualitative Range Midpoint Method and quantitative hierarchical clustering analysis identified similar clusters based on the MTC data on 25 different types of tarps. In particul ar, four categories of ta rps were identified using MTC scores of tarps from nine fumigants jointl y (composite groupings). Moreover, it was also observed that polyethylene tarps tended to clus ter in Group 1 (highest permeability), metalized tarps tended to cluster in Group 2 (moderate perm eability), and tarps clustered in Groups 3 and 4 (low and lowest permeability, respectively) consisted of Virtually Impermeable Films (VIFs) and Totally Impermeable Films (TIFs). These tarps have an al ternative layer of other material included typically between layers of polyeth ylene which dramatically decreases their permeability. For example, the tarps specifically referred to by their manufacturers as TIFs

contain ethylene vinyl-alcohol ( EVOH) copolymer resins as this central layer, but any film based on performance, regardless of the materials used to produce it, would be characterized as such. The composite groupings of tarps based on nine fu migants in general agr ee with the groupings of tarps based on a single fumiga nt with some exceptions.

In addition to cluster analysis, CEB also re viewed the ACB memo (6/17/2010) to determine consistency between ACB lab and USDA lab with re spect to MTC scores of different tarps.Page 56 of 78 

### ACB memo compared the MTC values obtained fr om the same tarps tested at both ACB and USDA. Based on the comparison, the ACB memo c oncluded that the MTCs determined at each lab were in general agreement.

The clustering methods applied by CEB in this memorandum are complex and require knowledge of multivariate analysis as well as data mining techniques. Hence it is recommended

that a statistician be consulted to determine the category of a new tarp if more information

becomes available.

6 REFERENCES

Agricultural Tarp Permeability to Fumigants ; Authors: Qian, Y. and Kamel, A,; Sponsor: U.S. EPA, Analytical Chemistry Bran ch, 701 Mapes Road, Fort Meade MD 20755-5350 (6/17/10).

A Standardized Approach for Estimating the Permeability of Plastic Tarps to Soil Fumigants Under Various Field and Environmental Conditions ; Papiernik, S. K.; Yates, S.R.; and Chellemi, D.O. (2010) – in press

Pattern Classification and Scene Analysis ; Duda, R. O. and Hart, P. E. (1973).Wiley.

Effect of environmental conditions on the permea bility of high density polyethylene tarp to fumigant vapors

. Papiernik, S. K., and S. R. Yate s. 2002. Environ. Sci. Technol. 36:1833-

1838.

RankAggreg, an R package for weighted rank aggregation. Pihur V, Datta S, Datta S. 2009.

BMC Bioinformatics

. 10 : 62Page 57 of 78 

# APPENDIX 1

Hierarchical cluster Algorithms 8 

### :

1. . Here m is the number of tarps. Each

is a vector of log (MTC) score which has n

components: . Here n denotes number of

fumigants.

2.

3.

;

Here C and D indicate different clusters.

4.

5.

•

• : , add

[Duda and Hart 1973]

For step 2, CEB used Euclidian distance:

Where g = (x 1 

### -y 1 

### ) 2 

### +..........+(x

n 

### -y n 

### ) 2



### For step 3, CEB used Complete Linkage:

The above algorithm is greedy and deterministic (no random initial conditions, unlike k-means). It returns a sequence of nested partitions, where each level up merges two cells of the lower partition.

8 http://www.datamodelling.group.shef .ac.uk/winterschool2008/talks/Hierarchical%20Clustering%20- %20Yee%20Whye%20Teh.pdfPage 58 of 78 

# APPENDIX 2

Table A2-1: Classification of tarps for MeBr Fumigant : MeBr Tarps Ranked By MTC Score Tarp MTC (cm hr-1) Cluster Cluster mean

Canslit HDPE 1.3611 1

Pliant, Regular Black 1.1078 1

AEP Sun Tarp High Barrier 0.8238 1 0.8799

Canslit LDPE 0.6269 1

Cadillac HDPE 0.4800 1

Pliant Metalized 0.0570 2

Canslit Metalized Black 0.0217 2 0.0281

Canslit Metalized White 0.0185 2

Guardian Black VIF 0.0151 2

Cadillac VIF 0.0085 3

Pliant Blockade, White 0.0057 3

Ginegar Embossed VIF 0.0053 3

Pliant Blockade, Black 0.0045 3 0.0033

TarpTec VIF 0.0029 3

Ginegar Ozgard 0.0019 3

Mid South Extrusion VIF 0.0017 3

Hyplast/Klerk, clear 0.0010 3

Berry EVOH Supreme Barrier 0.0009 3

Dow Saranex A 0.0006 3

Dow Saranex B 0.0002 4

AEP-one 0.0001 4

Raven, 1.4 mil, Black 0.0001 4 0.0001

Berry EVOH High Barrier w/Improved toughness 0.0000 4

Raven, 1.0 mil, Clear 0.0000 4

Berry EVOH High Barrier 0.0000 4Page 59 of 78Cadillac HDPECanslit LDPEAEP Sun Film High BarrierCanslit HDPEPliant, Regular BlackRaven, 1.0 mil, ClearBerry EVOH High BarrierBerry EVOH High Barrier w/Improved toughnessDow Saranex BAEP-oneRaven, 1.4 mil, BlackPliant MetalizedGuardian Black VIFCanslit Metalized BlackCanslit Metalized WhiteCadillac VIFPliant Blockade, BlackGinegar Embossed VIFPliant Blockade, WhiteDow Saranex ABerry EVOH Supreme BarrierHyplast/Klerk, clearFilmTec VIFGinegar OzgardMid South Extrusion VIF0 2 4 6 8 10 Cluster Dendrogram

hclust ( *

, "com p lete" ) dist(tg2)Height

99.9 99 98 95 90 80 70 50 30 20 10 5 2 1 0.1 2.0000

1.0000

0.5000

0.2500

0.1250

0.0625

0.0313

0.0156

0.0078

0.0039

0.0020

0.0010

0.0005

0.0002

0.0001 y = 3.0224x - 5.1128

R2 = 0.9293**MTC**

**Percentiles Lognormal Probability Plot** 

**EPA MeBr Global Cluster 1**  **G lobal Cluster 2**  **G lobal Cluster 3**  **Global Cluster 4**

Cluster 1

MeBr

Cluster 2

MeBr

Cluster 3

MeBr

Cluster 4 MeBrPage 60 of 78 Table A2-2: Classification of tarps for PPO Fumigant : PPO Tarps Ranked By MTC Score Tarp MTC (cm hr-1) Cluster Cluster mean

Canslit HDPE 0.8553 1

0.5673 Pliant, Regular Black 0.7473 1

AEP Sun Tarp High Barrier 0.5250 1

Canslit LDPE 0.4189 1

Cadillac HDPE 0.2896 1

Pliant Metalized 0.0359 2

0.0147 Canslit Metalized Black 0.0124 2

Canslit Metalized White 0.0111 2

Guardian Black VIF 0.0089 2

Cadillac VIF 0.0053 2

Ginegar Embossed VIF 0.0023 3

0.0016 Mid South Extrusion VIF 0.0019 3

Pliant Blockade, White 0.0015 3

Pliant Blockade, Black 0.0013 3

TarpTec VIF 0.0011 3

Ginegar Ozgard 0.0006 4

0.0002 Dow Saranex A 0.0003 4

Berry EVOH Supreme Barrier 0.0002 4

Hyplast/Klerk, clear 0.0002 4

Dow Saranex B 0.0001 4

Berry EVOH High Barrier w/Improved toughness 0.0001 4

Raven, 1.4 mil, Black 0.0001 4

AEP-one 0.0000 4

Berry EVOH High Barrier 0.0000 4

Raven, 1.0 mil, Clear 0.0000 4Page 61 of 78Ginegar Embossed VIFMid South Extrusion VIFFilmTec VIFPliant Blockade, BlackPliant Blockade, WhiteRaven, 1.0 mil, ClearAEP-oneBerry EVOH High BarrierRaven, 1.4 mil, BlackBerry EVOH High Barrier w/Improved toughnessDow Saranex BGinegar OzgardDow Saranex ABerry EVOH Supreme BarrierHyplast/Klerk, clearCanslit HDPEPliant, Regular BlackCadillac HDPEAEP Sun Film High BarrierCanslit LDPEPliant MetalizedCadillac VIFGuardian Black VIFCanslit Metalized BlackCanslit Metalized White0 2 4 6 8 10 Cluster Dendrogram

hclust ( *

, "com p lete" ) dist(tg3)Height

99.9 99 98 95 90 80 70 50 30 20 10 5 2 1 0.1 1.0000

0.5000

0.2500

0.1250

0.0625

0.0313

0.0156

0.0078

0.0039

0.0020

0.0010

0.0005

0.0002

0.0001

0.0001**MTC**

**Percentiles Lognormal Probability Plot** 

**EPA PPO Global Cluster 1**  **Global Cluster 2 G**  **lobal Cluster 3 G**  **lobal Cluster 4**

Cluster 1

PPO

Cluster 2 PPO

Cluster 3

PPO

Cluster 4 PPOPage 62 of 78 Table A2-3: Classification of tarps for IOM Fumigant IOM: Tarps Ranked By MTC Score Tarp MTC (cm hr-1) Cluster Cluster Mean

Canslit HDPE 2.1783 1 1.4733

Pliant, Regular Black 1.9215 1

AEP Sun Tarp High Barrier 1.4124 1

Canslit LDPE 1.0387 1

Cadillac HDPE 0.8157 1

Pliant Metalized 0.0876 2 0.0516

Canslit Metalized Black 0.0360 2

Canslit Metalized White 0.0313 2

Guardian Black VIF 0.0109 3 0.0043

Cadillac VIF 0.0061 3

Ginegar Embossed VIF 0.0030 3

Pliant Blockade, White 0.0027 3

Pliant Blockade, Black 0.0020 3

TarpTec VIF 0.0015 3

Mid South Extrusion VIF 0.0008 4 0.0002

Ginegar Ozgard 0.0007 4

Dow Saranex A 0.0003 4

Dow Saranex B 0.0002 4

Berry EVOH High Barrier w/Improved toughness 0.0001 4

Hyplast/Klerk, clear 0.0001 4

Berry EVOH Supreme Barrier 0.0001 4

Raven, 1.4 mil, Black 0.0001 4

AEP-one 0.0000 4

Raven, 1.0 mil, Clear 0.0000 4

Berry EVOH High Barrier 0.0000 4Page 63 of 78Cadillac HDPECanslit LDPEAEP Sun Film High BarrierCanslit HDPEPliant, Regular BlackRaven, 1.0 mil, ClearAEP-oneBerry EVOH High BarrierRaven, 1.4 mil, BlackHyplast/Klerk, clearBerry EVOH High Barrier w/Improved toughnessBerry EVOH Supreme BarrierGinegar OzgardMid South Extrusion VIFDow Saranex ADow Saranex BPliant MetalizedCanslit Metalized BlackCanslit Metalized WhiteCadillac VIFGuardian Black VIFGinegar Embossed VIFPliant Blockade, WhiteFilmTec VIFPliant Blockade, Black02468 Cluster Dendrogram

hclust ( *

, "com p lete" ) dist(tg4)Height

99.9 99 98 95 90 80 70 50 30 20 10 5 2 1 0.1 3.0000

1.5000

0.7500

0.3750

0.1875

0.0938

0.0469

0.0234

0.0117

0.0059

0.0029

0.0015

0.0007

0.0004

0.0002

0.0001**MTC**

**Percentiles Lognormal Probability Plot** 

**EPA IOM Global Cluster 1**  **Global Cluster 2 G**  **lobal Cluster 3 G**  **lobal Cluster 4**

Cluster 1

IOM

Cluster 2 IOM

Cluster 3

IOM

Cluster 4 IOMPage 64 of 78 Table A2-4: Classification of tarps for cis-1,3-D Fumigant: cis-1,3-D Tarps Ranked By MTC Score Tarp MTC (cm hr-1) Cluster Cluster Mean

Canslit HDPE 6.3171 1 4.4222

Pliant, Regular Black 5.6506 1

AEP Sun Tarp High Barrier 4.2344 1

Canslit LDPE 3.2106 1

Cadillac HDPE 2.6985 1

Pliant Metalized 0.3469 2 0.1969

Canslit Metalized Black 0.1286 2

Canslit Metalized White 0.1153 2

Guardian Black VIF 0.0235 3 0.0067

Cadillac VIF 0.0109 3

Ginegar Embossed VIF 0.0033 3

Pliant Blockade, White 0.0025 3

Mid South Extrusion VIF 0.0024 3

Pliant Blockade, Black 0.0022 3

TarpTec VIF 0.0019 3

Dow Saranex A 0.0008 4 0.0002

Ginegar Ozgard 0.0005 4

Dow Saranex B 0.0003 4

Berry EVOH Supreme Barrier 0.0002 4

Raven, 1.4 mil, Black 0.0002 4

AEP-one 0.0002 4

Berry EVOH High Barrier w/Improved toughness 0.0001 4

Berry EVOH High Barrier 0.0001 4

Raven, 1.0 mil, Clear 0.0000 4

Hyplast/Klerk, clear 0.0000 4Page 65 of 78Cadillac HDPECanslit LDPEAEP Sun Film High BarrierCanslit HDPEPliant, Regular BlackPliant MetalizedCanslit Metalized BlackCanslit Metalized WhiteBerry EVOH High BarrierBerry EVOH High Barrier w/Improved toughnessHyplast/Klerk, clearRaven, 1.0 mil, ClearDow Saranex BRaven, 1.4 mil, BlackAEP-oneBerry EVOH Supreme BarrierDow Saranex AGinegar OzgardGinegar Embossed VIFFilmTec VIFPliant Blockade, BlackMid South Extrusion VIFPliant Blockade, WhiteCadillac VIFGuardian Black VIF0 2 4 6 8 12 Cluster Dendrogram

hclust ( *

, "com p lete" ) dist(tg5)Height

99.9 99 98 95 90 80 70 50 30 20 10 5 2 1 0.1 1.0000

0.5000

0.2500

0.1250

0.0625

0.0313

0.0156

0.0078

0.0039

0.0020

0.0010

0.0005

0.0002

0.0001

0.0001**MTC**

**Percentiles Lognormal Probability Plot** 

**EPA cis-1,3-D Global Cluster 1**  **G lobal Cluster 2**  **G lobal Cluster 3**  **G lobal Cluster 4** 

Cluster 1 Cis

‐ 1,3

‐ D

Cluster 2 Cis

‐ 1,3

‐ D

Cluster 3 Cis

‐ 1,3

‐ D

Cluster 4 Cis

‐ 1,3

‐ DPage 66 of 78 Table A2-5 : Classification of tarps for DMDS Fumigant: DMDS Tarps Ranked By MTC Score Tarp MTC (cm hr-1) Cluster Cluster Mean

Canslit HDPE 5.6798 1 4.0298

Pliant, Regular Black 5.2480 1

AEP Sun Tarp High Barrier 3.8840 1

Canslit LDPE 2.9652 1

Cadillac HDPE 2.3719 1

Pliant Metalized 0.2771 2 0.1636

Canslit Metalized Black 0.1107 2

Canslit Metalized White 0.1031 2

Guardian Black VIF 0.0120 3 0.0036

Cadillac VIF 0.0060 3

Mid South Extrusion VIF 0.0021 3

Ginegar Embossed VIF 0.0017 3

Pliant Blockade, Black 0.0013 3

Pliant Blockade, White 0.0010 3

TarpTec VIF 0.0009 3

Dow Saranex A 0.0004 4 0.0002

Ginegar Ozgard 0.0003 4

Berry EVOH Supreme Barrier 0.0002 4

AEP-one 0.0002 4

Dow Saranex B 0.0002 4

Raven, 1.4 mil, Black 0.0002 4

Berry EVOH High Barrier w/Improved toughness 0.0001 4

Hyplast/Klerk, clear 0.0000 4

Berry EVOH High Barrier 0.0000 4

Raven, 1.0 mil, Clear 0.0000 4Page 67 of 78Cadillac HDPECanslit LDPEAEP Sun Film High BarrierCanslit HDPEPliant, Regular BlackPliant MetalizedCanslit Metalized BlackCanslit Metalized WhiteRaven, 1.0 mil, ClearBerry EVOH High BarrierHyplast/Klerk, clearDow Saranex AGinegar OzgardBerry EVOH High Barrier w/Improved toughnessRaven, 1.4 mil, BlackDow Saranex BAEP-oneBerry EVOH Supreme BarrierCadillac VIFGuardian Black VIFGinegar Embossed VIFMid South Extrusion VIFPliant Blockade, BlackFilmTec VIFPliant Blockade, White0 2 4 6 8 12 Cluster Dendrogram

hclust ( *

, "com p lete" ) dist(tg6)Height

99.9 99 98 95 90 80 70 50 30 20 10 5 2 1 0.1 6.0000

3.0000

1.5000

0.7500

0.3750

0.1875

0.0938

0.0469

0.0234

0.0117

0.0059

0.0029

0.0015

0.0007

0.0004

0.0002**MTC**

**Percentiles Lognormal Probability Plot** 

**EPA DMDS Global Cluster 1**  **Global Cluster 2 G**  **lobal Cluster 3 G**  **lobal Cluster 4**

Cluster 1 DMDS

Cluster 2 DMDS

Cluster 3 DMDS

Cluster 4 DMDSPage 68 of 78 Table A2-6 : Classification of tarps for MITC Fumigant: MITC Tarps Ranked By MTC Score Tarp MTC (cm hr-1) Cluster Cluster Mean

Canslit HDPE 13.4456 1

9.8645 Pliant, Regular Black 11.7678 1

AEP Sun Tarp High Barrier 8.5298 1

Canslit LDPE 8.1979 1

Cadillac HDPE 7.3816 1

Pliant Metalized 1.1435 2

0.2726 Canslit Metalized Black 0.3596 2

Canslit Metalized White 0.3030 2

Guardian Black VIF 0.2928 2

Cadillac VIF 0.1093 2

Pliant Blockade, White 0.0823 2

Ginegar Embossed VIF 0.0592 2

Pliant Blockade, Black 0.0527 2

TarpTec VIF 0.0512 2

Ginegar Ozgard 0.0180 3

0.0089 Hyplast/Klerk, clear 0.0097 3

Mid South Extrusion VIF 0.0097 3

Dow Saranex A 0.0051 3

Dow Saranex B 0.0021 3Page 69 of 78 Raven, 1.4 mil, Black 0.0008 4

0.0003 Berry EVOH High Barrier w/Improved toughness 0.0004 4

AEP-one 0.0003 4

Berry EVOH High Barrier 0.0002 4

Berry EVOH Supreme Barrier 0.0002 4

Raven, 1.0 mil, Clear 0.0000 4Ginegar OzgardHyplast/Klerk, clearMid South Extrusion VIFDow Saranex ADow Saranex BRaven, 1.0 mil, ClearRaven, 1.4 mil, BlackBerry EVOH High BarrierBerry EVOH Supreme BarrierAEP-oneBerry EVOH High Barrier w/Improved toughnessCanslit HDPEPliant, Regular BlackCadillac HDPEAEP Sun Film High BarrierCanslit LDPEGinegar Embossed VIFFilmTec VIFPliant Blockade, BlackCadillac VIFPliant Blockade, WhitePliant MetalizedCanslit Metalized BlackCanslit Metalized WhiteGuardian Black VIF0 4 8 12 Cluster Dendrogram

hclust ( *

, "com p lete" ) dist(tg7)HeightPage 70 of 78 99.9 99 98 95 90 80 70 50 30 20 10 5 2 1 0.1 14.0000

7.0000

3.5000

1.7500

0.8750

0.4375

0.2188

0.1094

0.0547

0.0273

0.0137

0.0068

0.0034

0.0017

0.0009

0.0004**MTC**

**Percentiles Lognormal Probability Plot** 

**Global Cluster 1 Global Cluster 2**  **G lobal Cluster 3**  **G lobal Cluster 4** 

Cluster 1 MITC

Cluster 2 MITC

Cluster 3 MITC

Cluster 4 MITC EPA MITCPage 71 of 78 Table A2-7 : Classification of tarps for Chloropicrin Fumigant: Chloropicrin Tarps Ranked By MTC Score

Tarp MTC (cm hr-1) Cluster Cluster Mean

Pliant, Regular Black 2.2710 1

1.5980 Canslit HDPE 2.2558 1

AEP Sun Tarp High Barrier 1.5404 1

Canslit LDPE 1.2124 1

Cadillac HDPE 0.7104 1

Pliant Metalized 0.0828 2 0.0511 Canslit Metalized Black 0.0362 2

Canslit Metalized White 0.0342 2

Guardian Black VIF 0.0016 3

0.0010 Cadillac VIF 0.0011 3

Pliant Blockade, Black 0.0010 3

Dow Saranex A 0.0007 3

Ginegar Embossed VIF 0.0005 3

Raven, 1.4 mil, Black 0.0002 4

0.0001 AEP-one 0.0002 4

Berry EVOH Supreme Barrier 0.0002 4

Dow Saranex B 0.0002 4

Ginegar Ozgard 0.0001 4

Pliant Blockade, White 0.0001 4

TarpTec VIF 0.0001 4

Berry EVOH High Barrier 0.0001 4

Berry EVOH High Barrier w/Improved toughness 0.0000 4

Raven, 1.0 mil, Clear 0.0000 4

Mid South Extrusion VIF 0.0000 4

Hyplast/Klerk, clear 0.0000 4Page 72 of 78Dow Saranex AGinegar Embossed VIFGuardian Black VIFCadillac VIFPliant Blockade, BlackRaven, 1.0 mil, ClearMid South Extrusion VIFBerry EVOH High Barrier w/Improved toughnessHyplast/Klerk, clearRaven, 1.4 mil, BlackDow Saranex BAEP-oneBerry EVOH Supreme BarrierPliant Blockade, WhiteGinegar OzgardBerry EVOH High BarrierFilmTec VIFPliant MetalizedCanslit Metalized BlackCanslit Metalized WhiteCadillac HDPECanslit HDPEPliant, Regular BlackAEP Sun Film High BarrierCanslit LDPE02468 Cluster Dendrogram

hclust ( *

, "com p lete" ) dist(tg8)Height

99.9 99 98 95 90 80 70 50 30 20 10 5 2 1 0.1 3.0000

1.5000

0.7500

0.3750

0.1875

0.0938

0.0469

0.0234

0.0117

0.0059

0.0029

0.0015

0.0007

0.0004

0.0002

0.0001**MTC**

**Percentiles Lognormal Probability Plot** 

**EPA Chloropicrin Global Cluster 1**  **G lobal Cluster 2**  **G lobal Cluster 3**  **G lobal Cluster 4** 

Cluster 1 Chrolopicrin

Cluster 2 Chrolopicrin

Cluster 3 Chrolopicrin

Cluster 4 ChloropicrinPage 73 of 78 Table A2-8: Classification of tarps for trans-1,3-D Fumigant: trans-1, 3-D Tarps Ranked By MTC Score Tarp MTC (cm hr-1) Cluster Cluster

mean Canslit HDPE 7.9845 1

5.8703 Pliant, Regular Black 7.3937 1

AEP Sun Tarp High Barrier 5.6792 1

Canslit LDPE 4.4027 1

Cadillac HDPE 3.8916 1

Pliant Metalized 0.6251 2

0.2157 Canslit Metalized Black 0.1982 2

Canslit Metalized White 0.1796 2

Guardian Black VIF 0.0523 2

Cadillac VIF 0.0232 2

Ginegar Embossed VIF 0.0074 3

0.0046 Pliant Blockade, White 0.0067 3

TarpTec VIF 0.0052 3

Pliant Blockade, Black 0.0050 3

Mid South Extrusion VIF 0.0047 3

Ginegar Ozgard 0.0019 3

Dow Saranex A 0.0011 3

Dow Saranex B 0.0005 4

0.0002 Berry EVOH Supreme Barrier 0.0003 4

Raven, 1.4 mil, Black 0.0003 4

AEP-one 0.0003 4

Hyplast/Klerk, clear 0.0002 4

Berry EVOH High Barrier w/Improved toughness 0.0002 4

Berry EVOH High Barrier 0.0001 4

Raven, 1.0 mil, Clear 0.0000 4Page 74 of 78Berry EVOH High BarrierRaven, 1.0 mil, ClearDow Saranex BRaven, 1.4 mil, BlackAEP-oneBerry EVOH Supreme BarrierBerry EVOH High Barrier w/Improved toughnessHyplast/Klerk, clearGinegar Embossed VIFPliant Blockade, WhiteMid South Extrusion VIFFilmTec VIFPliant Blockade, BlackDow Saranex AGinegar OzgardCadillac HDPECanslit LDPEAEP Sun Film High BarrierCanslit HDPEPliant, Regular BlackCadillac VIFGuardian Black VIFPliant MetalizedCanslit Metalized BlackCanslit Metalized White0 2 4 6 8 12 Cluster Dendrogram

hclust ( *

, "com p lete" ) dist(tg9)HeightPage 75 of 78 99.9 99 98 95 90 80 70 50 30 20 10 5 2 1 0.1 8.0000

4.0000

2.0000

1.0000

0.5000

0.2500

0.1250

0.0625

0.0313

0.0156

0.0078

0.0039

0.0020

0.0010

0.0005

0.0002**MTC**

**Percentiles Lognormal Probability Plot** 

**EPA Trans-1,3-D Global Cluster 1**  **G lobal Cluster 2**  **G lobal Cluster 3**  **G lobal Cluster 4** 

Cluster 1 trans

‐ 1,3

‐ D

Cluster 2 trans

‐ 1,3

‐ D

Cluster 4 trans

‐ 1,3

‐ D Cluster 3 trans

‐ 1,3

‐ DPage 76 of 78 Table A2-9: Classification of tarps for SF Fumigant: SF Tarps Ranked By MTC Score Tarp MTC (cm hr-1) Cluster Cluster Mean

Canslit HDPE 0.0691 1 0.0221

Pliant, Regular Black 0.0157 1

AEP Sun Tarp High Barrier 0.0107 1

Canslit LDPE 0.0089 1

Cadillac HDPE 0.0060 1

Cadillac VIF 0.0020 2 0.0008

Ginegar Embossed VIF 0.0007 2

Pliant Metalized 0.0006 2

Canslit Metalized Black 0.0003 2

Canslit Metalized White 0.0002 2

Pliant Blockade, Black 0.0001 3 0.0000

Dow Saranex A 0.0000 3

Berry EVOH High Barrier w/Improved toughness 0.0000 3

AEP-one 0.0000 3

Berry EVOH Supreme Barrier 0.0000 3

Dow Saranex B 0.0000 3

Guardian Black VIF 0.0000 3

Ginegar Ozgard 0.0000 3

TarpTec VIF 0.0000 3

Raven, 1.4 mil, Black 0.0000 3

Mid South Extrusion VIF 0.0000 3

Raven, 1.0 mil, Clear 0.0000 3

Berry EVOH High Barrier 0.0000 3

Hyplast/Klerk, clear 0.0000 3

Pliant Blockade, White 0.0000 3Page 77 of 78Page 78 of 78 99.9 99 98 95 90 80 70 50 30 20 10 5 2 1 0.1 1.0000

0.5000

0.2500

0.1250

0.0625

0.0313

0.0156

0.0078

0.0039

0.0020

0.0010

0.0005

0.0002

0.0001

0.0001**MTC**

**Percentiles Lognormal Probability Plot** 

**Global Cluster 1 Global Cluster 2**  **G lobal Cluster 3**  **G lobal Cluster 4** 

Cluster 1 SF

Cluster 2

SF

Cluster 3 SF EPA SF