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 (Smith 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 measures that are within, as well as outside of, the 

control of growers/applicators. While it is difficult to assign quantitative 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 predicted reductions in emissions are not overstated. 

This memo analyzes the following factors and techniques to determine if new available data 

requires revisions of the buffer zone credits presented 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 treated 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 studies which have been submitted by a variety of stakeholders, 

including: 

• The Methyl Bromide Industry Panel (MBIP) 

o EPA MRID 48006001: Monitoring of Methyl Bromide and Chloropicrin Field 

Emissions From Shank Applications at Shallow and Deep Injection Depths

o EPA MRID 48107601: Monitoring of Methyl Bromide and Chloropicrin Field 

Emissions From Shank Applications (Bedded and Broadcast) and a Methyl 

Bromide Hot-Gas Application Under 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 Salinas, California in September 2007
Page 3 of 78 

• The Metam Sodium Alliance (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 Bromide Alternatives (USDA ARS Areawide) 

o EPA MRID 47820001: Monitoring Chloropicrin, Dimethyldisulfide, 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 Injections 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 Cultural Practice Applicable to Michigan

• The Washington State Potato Commission (WA Potato Growers) 

o 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 

• Washington State University (WSU) 

o EPA MRID 47770001: Estimating Methyl Isothiocyanate Emission Rates 

Following Soil Incorporated Shank and Modified 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 collected from the various studies submitted is 

summarized by individual chemical in Appendix 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 (Dawson; 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 analyses examining mass transfer coefficients of a 

number of agricultural tarps for various fumigants. One of these analyses was performed by the 

United States Department of Agriculture, Agricultural 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 (ACB) 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 this 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 larger 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 treated fields is also provided. 

The recommendations for buffer credits or criteria 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 baseline values and were actually completed under 

conditions which would otherwise elicit a buffer credit. Each of these conditions adds to the 

complexity of developing buffer credit recommendations. 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 submitted field study data was performed using the soil 

moisture GAPs (see Tables X-X for specific soil moisture 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 studies 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 required part of the GAPs that have been developed. 

Where data is available and appropriate, buffer zones 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 increased fumigant emissions with all other factors 

being equal. However, the soil temperature in a field is not a factor that growers can manipulate. 

If conditions warrant for a particular field where 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 associated 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 90o

F for all application 

methods except for drip irrigation 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 recommended for methyl bromide based on its 

extremely high vapor pressure. The soil temperature credit/GAP decisions for methyl 

bromide may be revisited if the MBIP studies discussed above provide more information 

around the effect of soil temperature on methyl bromide emissions. No new information 

has been provided to the Agency at this time 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 measured at a soil depth of 3 inches. All of 

the emissions studies, including those recently submitted, currently used to develop 

buffer distances for chloropicrin occurred at reasonable temperatures, with the average 

soil temperature around 70°F. No new information 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% emission credit was provided for metam 

sodium/potassium to reduce the buffers for applications 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 suggest 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 because the metam sodium/potassium buffer 

tables were based on studies where the average 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 temperatures (and assumed high soil temperatures) 

have now been replaced with studies that were 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 measured at a soil depth of 3 inches. All of 
Page 6 of 78 

the emissions studies currently used to develop buffer distances for dazomet occurred at 

reasonable temperatures, with the average soil temperature ranging from 55-65°F (soil 

temperature was not measured). No new information 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 growers 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 regulatory requirements. Based on all 

of the available data, the Agency recommends the following credits for organic matter: 

• Methyl bromide and Dazomet/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%. No new information has been provided to the 

Agency at this time to suggest this credit scheme should be changed. 

• Chloropicrin and Metam Sodium/Metam Potassium - 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 would 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-A3 in Appendix A for specific organic content 

percentages for individual studies). 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 factor that growers can manipulate. If conditions 

warrant for a particular field where the soil has high clay content it would be reasonable to 

account for that in the associated regulatory requirements since buffers are based on research 

with more typical soil types. Almost all of the recently and previously submitted field study data 

was performed on fields with sand, loam, or sandy loam based soils (see Tables A1-A3 in 

Appendix A for specific soil types for individual studies). In the 2009 credits memo, a 10% 
Page 7 of 78 

credit was given for soils with a clay content >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 information has been provided to the Agency at this 

time to suggest this credit scheme should be changed 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 some fumigants due to physical/chemical properties 

dictate the impact of this condition of application. No credit structure has been instituted for 

injection depth rather, where available, distinct studies were used to establish baseline buffer 

table recommendations for individual fumigants as follows: 

• Methyl Bromide: In the 2009 amended methyl bromide RED, available flux data allowed 

for having different buffer tables for shallow and deep injection levels. Since that time, 

the MBIP produced a methyl bromide/chloropicrin emission study that examined 

differences in methyl bromide emissions from shallow and deep injection applications 

(12” vs. 18”). This study further supported the need for separate 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 amended chloropicrin RED, available flux data allowed for 

having different buffer tables for shallow and deep injection levels. Since that time, the 

MBIP produced a methyl bromide/chloropicrin emission study that examined differences 

in chloropicrin emissions from shallow and deep injection applications (12” vs. 18”). 

This study further supported the need for separate buffer tables for shallow and deep 

injection applications for chloropicrin. However, since 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 irrigation study discussed 

in the 2009 credits memo, the Agency has recently 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 significant 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 applications at this time. The Agency is willing 

to discuss any data that could be produced to better characterize the effect of injection 

depth on metam sodium/metam potassium applications. 

• Dazomet - MITC: There are currently no data that specifically focuses on the impact of 

incorporation depth for dazomet on MITC emissions. 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 applications has not been given at this time. 

Water Seals: Available field scale and laboratory-based data typically show that applying a 

water seal after application of certain fumigants results in decreased 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 received 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 credit for water seals for methyl bromide. No 

new information has been provided to the Agency 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 limited field scale data (tarped, drip irrigation 

fields) produced by Hussein Ajwa and the 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 same way for untarped 

broadcast or untarped bedded chloropicrin applications; the Agency is not providing a 

larger water seal credit for chloropicrin at this time. The Agency is willing to discuss any 

data that could be produced to better characterize 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 water seals are a typical emission control for 

many types of applications of metam sodium (i.e., sprinkler irrigation, broadcast shank 

injection, and drench applications). The Agency’s metam sodium assessment relies on a 

number of emission studies that utilize a number 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 metam sodium broadcast 

untarped shank injection applications. These studies clearly show that water seals can 

significantly reduce MITC emissions during this type of application. However, given 

that waters seals are already required to be used with other metam sodium application 

methods, the Agency does not believe providing 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 applications 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 water 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 label required water seal regime. As a result, 

the Agency is not currently recommending specific credits for water seals because all of 

the flux data utilized in the dazomet PERFUM modeling already incorporated these 

techniques.

Reactive Boundary Layers: Available field scale and laboratory-based data typically shows 

that the use of potassium thiosulfate (KTS) after a fumigant application results in decreased 

fumigant emissions with all other factors being equal. However, use of these reactive boundary 

layers is restricted to the halogenated fumigants only (e.g., methyl bromide, chloropicrin, methyl 

iodide, and 1,3-dichloropropene). KTS is not suitable for reducing MITC emissions resulting 

from metam sodium,metam potassium, or dazomet 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. Since that time, the Agency has received some new 

field scale emissions data and based on all of the data available, the Agency recommends the 

following regarding use of KTS: 

• Methyl Bromide and Chloropicrin: In the 2009 credits memo (Smith and Dawson; 

D362369; 05/14/09), the Agency provided a 15% credit for use of KTS as long as it was 

applied with 1⁄4 to 1⁄2 inch of water for all methyl bromide and chloropicrin applications. 

This credit was based on two field scale studies (both 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 applied with water over the top of a bedded, drip 

irrigation field via solid set sprinklers 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 bromide (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 approximately 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 MITC generator application results in decreased 

MITC emissions. The Agency is aware of one laboratory study (Wang 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 generators, 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 previously existing and the most 

current research that proper field preparation and managing application systems to achieve 

proper compaction during application are critical to an application that is compliant with the 

GAPs established for fumigants. There has been substantive discussions around a means to 

categorize and quantify the proper levels of field preparation and 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 season). Assigning a credit structure for field 

preparation or compaction is inappropriate at this 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 emission 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 Dawson; 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 studies 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 permeability 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 performed a thorough examination of MTCs for a 

number of fumigant/tarp combinations which is provided in Appendix B (Qian and Kamel; 

6/17/10). This analysis including examination of MTCs for methyl bromide, chloropicrin, 

MITC, methyl iodide, 1,3-dichloropropene, sulfuryl fluoride, dimethyl 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 Submitted 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, 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 attempted to define tarp groupings based on MTC values 

for individual fumigants as well as across all 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 Appendix 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 grouping 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 results have been less dramatic (see Figure 1 

below). 
Page 13 of 78 

Figure 1: Impact of Temperature on MTCs Using ACB Data

0.00000

0.05000

0.10000

0.15000

0.20000

0.25000

0.30000

0.35000

0.40000

AEP-one

Berry EVOH Supreme Barrier

Cadillac VIF

Dow Saranex A

FilmTec VIF

Ginegar Embossed VIF

Ginegar Ozgard

Guardian Black VIF

Hyplast/Klerk, clear

Mid South Extrusion VIF

Pliant Blockade, Black

Raven, 1.4 mil, Black

Tarp Type

MTCs (cm/hr)

MeBr (Std)

MITC (Std)

PIC (Std)

MeBr (40 deg)

MITC (40 deg)

PIC (40 deg)

Relative Humidity: USDA’s tests focusing on how relative humidity impacts agricultural 

tarps have shown that a tarp’s permeability typically increases as relative humidity increases 

(Papiernik et al.; 2010). This was especially true of so-called virtually impermeable films 

(VIF) and the magnitude of this increase was very significant in some instances. ACB 

completed some similar tests and have shown 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 vapors. The Agency does not believe that these limitations impact 

the tarp credits scheme discussed below. The MTC 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 scale emissions studies that utilize high barrier tarps as well as the 

new MTC data, the Agency is now providing credits 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 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 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 appropriate for tarps in group 4. 

• All MITC Generators: No buffer credit is being 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 individual 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 described 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 testing agricultural tarps, such as an ASTM (American 

Society for Testing and Materials) 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 credit 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 field scale emission studies, a volatile 

organic compound (VOC) meter was used to take real 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 presented 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 identify an issue with a particular fumigant 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 duration 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 their drawbacks. First and foremost, fumigants with ionization 

potentials higher than the UV lamp are not detected by photoionization. The ionization energy 

of chloropicrin is greater than that of the typical 10.6 eV lamp used in the detectors. This 

presents a significant challenge to using these meters 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 are not agricultural fumigants. Correction factors 

must be used to convert the measured readings to VOCs of agricultural fumigants. 

Unfortunately these are difficult to use when mixtures of fumigants are applied and ambient 

temperatures are variable. As a result, typically 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 current 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 Zone 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 Assessment For Methyl Bromide Soil Uses Based 

On Methyl Bromide Industry Panel (MBIP) 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. Chellemi. 06/22/2010. A Standardized Approach for 

Estimating the Permeability of Plastic Films to Soil Fumigants Under Various Field and 

Environmental Conditions. Journal of Environmental Quality. 

Sarkar, B. 8/27/10. Analysis of Mass Transfer Coefficient Data Contained In Analytical 

Chemistry Branch Laboratory Report Entitely Agricultural Tarp Permeability to Fumigants,

D381403. 

Shelat, S. and Smith, C. 01/06/2011. Metam Sodium: 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. Yates. 2000. Transformation and detoxification of 

halogenated fumigants by ammonium thiosulfate. Environ. Sci. Technol. 34:3717–3721. 

EPA MRID 48006001: Monitoring of Methyl Bromide and Chloropicrin Field Emissions From 

Shank Applications at Shallow 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 Chloropicrin Field Emissions From 

Shank Applications (Bedded and Broadcast) and a Methyl Bromide Hot-Gas Application Under 

Totally Impermeable Film; Authors: Ajwa, H. and Sullivan, D,; Sponsor: Methyl Bromide 

Industry Panel and Hendrix and Dail, Inc. 

EPA MRID 47770001: Estimating Methyl Isothiocyanate Emission Rates Following Soil 

Incorporated Shank and Modified Center Pivot Chemigation Metam Sodium Applications; 

Authors: ;4/10/2009; Washington State University Food and Environmental Quality 

Laboratory, 2710 Univertiy Drive, Richland, WA 99354-1671; Sponsor: Washington State 

University, 2710 Univertiy Drive, Richland, WA 99354-1671. 

EPA MRID 47820001: Monitoring Chloropicrin, Dimethyldisulfide, and Methyl Isothiocyanate 

Emissions from Shank Applications at Three Sites near Tifton, Georgia; 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-Dichloropropene, Chloropicrin, and Methyl 

Isothiocyanate Emissions from Shank Applications at Three Sites Near Duette, Florida; Authors: 

Ajwa, Sullivan, and Chellemi; 6/30/2009; 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 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 & Vegetable 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 Applicable 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, Holdsworth, and Sullivan; 4/30/2010; Sponsor: Washington 

State Potato Commission, 108 Interlake Road, Moses Lake, WA 98837 

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; Author: Sullivan; 5/11/2009; 1900 Elkin Street, Suite 200, Alexandria, VA 22308; 

Sponsor: Amvac Chemical Corporation, 4695 MacArthur Court, Suite 1250, Newport Beach, 

CA 92660-1868, Taminco, Inc., 3350 Riverwood Parkway, Ste 1900, Atlanta, GA 30339, and 

Tessenderlo Kerley, Incorporated, 2255 N. 44th Street, Suite 300, Phoenix, AZ 85008. 
Page 18 of 78 

EPA MRID 47956701: Flux Evaluation of a Metam Potassium Application (KAPAM-HL) 

Applied by the Drench Method (Study SEC- 2008D); Author: Sullivan; 3/2009; 1900 Elkin 

Street, Suite 200, Alexandria, VA 22308; Sponsor: Amvac Chemical Corporation, 4695 

MacArthur Court, Suite 1250, Newport Beach, 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 Determination of Chloropicrin Emissions from Shank, 

Bedded, Non-Tarped Applications; Authors: Rotondaro and Rotondaro; 3/16/2010; Sponsor: The 

Chloropicrin Manufacturers Task Force, c/o Niklor 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 Force, c/o Niklor Chemical Company, Inc, 1667 

Purdy Ave, Mojave, CA 93501 
Appendix A: Summary of Field Study Monitoring 

Conditions 
Page 20 of 78 

Appendix A/Table A1: Methyl Bromide Flux Data Overview 

MRID Location Application Type 

Application 

Rate 

(lbs 

ai/treated 

acre) 

Max 

Period flux 

rate 

(ug/m2-s) 

Max 

Application 

Rate (lbs 

ai/treated 

acre) 

Max 

Adjusted 

Period Flux 

Rate 

(ug/m2-s) 

% Field 

Capacity

Air Temp - 

Average 

Day/Night 

(oC) 

Avg. Soil 

Temp 

(oC) 

% OM 

(6-9") 

Soil Type 

(6-9") 

Start T

Appli

Shallow Untarped 

SE1.1 Monterey CA 

Bed (no tarp - rear 

facing chisel - 12" 

depth) 

186 

NA 

430 

282.6 

NA NA NA NA NA N

SE1.2 Monterey CA 

Bed (no tarp - rear 

facing chisel - 12" 

depth) 

180 430 NA NA NA NA NA N

SE1.3 Monterey CA 

Bed (no tarp - rear 

facing chisel - 12" 

depth) 

180 430 NA NA NA NA Clay N

Deep Untarped 

SE2.2 Kern Cty CA 

Broadcast (no tarp, 

forward chisel, 20' 

depth) 

396 

NA 

430 

222.4 

NA NA NA NA NA N

S104.2-1 Fresno CA 

Broadcast (no tarp, 

forward chisel, 24' 

depth) 

396 430 NA NA NA NA NA N

S100B1.1 Madera CA 

Broadcast (no tarp, 

forward chisel, 24' 

depth) 

400 430 NA NA NA NA NA N

S110.1 San Joaquin CA Broadcast (no tarp, forward chisel, 24' depth) 450 430 NA NA NA NA NA N

Bedded Tarp Studies 

EH164-11 San Luis Obispo Bed (tarp, rear chisel, 1.5 mil black plastic) 206 

NA 

430 

889.6 

NA NA NA NA NA N

BR787.1B Orange 

Bed (tarp, rear chisel in 

bed shaper, 1.5 mil 

black plastic) 

177 430 17.5% M NA NA NA Loam/silt loam N

BR787.1C Orange 

Bed (tarp, forward 

chisel, 1.5 mil black 

plastic) 

176 430 17.5% M NA NA NA Loam/silt loam N

BR787.2B Santa Barbara 

Bed (tarp, rear chisel in 

bed shaper, 1.5 mil 

black plastic) 

245 430 7% M NA NA NA Loamy sand N

BR787.2C Santa Barbara 

Bed (tarp, forward 

chisel, 1.5 mil black 

plastic) 

174 430 7% M NA NA NA Loamy sand N
Page 21 of 78 

Appendix A/Table A1: Methyl Bromide Flux Data Overview 

MRID Location Application Type 

Application 

Rate 

(lbs 

ai/treated 

acre) 

Max 

Period flux 

rate 

(ug/m2-s) 

Max 

Application 

Rate (lbs 

ai/treated 

acre) 

Max 

Adjusted 

Period Flux 

Rate 

(ug/m2-s) 

% Field 

Capacity

Air Temp - 

Average 

Day/Night 

(oC) 

Avg. Soil 

Temp 

(oC) 

% OM 

(6-9") 

Soil Type 

(6-9") 

Start T

Appli

481076-01 Fort Pierce FL 

Bed (tarp, rear chisel in 

bed shaper, Vapor Safe 

TIF tarped)) 

235 19.8 430 36 138% ~25/12 ~18 1.4 (surface~3.1) Sand 9:45 

48006001 Wasco CA Strip, VaporSafe TIF tarped 202.0 22.01 430 47 72 ~32/12 ~29 0.28 loamy sand 1:18 

Tarped Broadcast Studies 

TC199 Kern Cty CA 

Broadcast ("high 

barrier" tarp, Nobel 

plow) 

396 

NA 

430 

183.7 

NA NA NA NA NA N

EH127-1 Monterey CA Broadcast ("high barrier" tarp, Nobel 

plow) 

235 430 NA NA NA NA Clay loam N

48006001 Wasco CA Broadcast, LDPE tarped 189.1 291 430 662 75 

~32/12 

~29 0.63 loamy sand 8:26 

48006001 Wasco CA Broadcast, VaporSafe TIF tarped 180.3 92.41 430 220 73 ~27 0.86 loamy sand 8:28 48006001 Wasco CA 

Broadcast, VaporSafe 

TIF tarped, KTS under 

tarp 

177.9 55.74 430 135 74 ~28 0.35 loamy sand 10:35 

48006001 Wasco CA Deep 18"Broadcast, VaporSafe TIF tarped 181.0 81.17 430 193 71 ~28 0.042 loamy sand 1:13 

Drip Hot Gas Studies 

EH150-1 Riverside CA Drip ("high barrier" tarp, hot gas) 200 

NA 

430 

1481 

NA NA NA NA NA N

EH150-3 Kern CA Drip (1.25 mil clear plastic, hot gas) 200 430 NA NA NA NA Loamy sand NEH150-4 Imperial CA Drip (1.5 mil black plastic, hot gas) 200 430 NA NA NA NA Loamy sand N

481076-01 Fort Pierce FL Hot Gas (Vapor Safe TIF tarped)) 426 150.3 430 152 109% ~25/12 ~21 1.50 Sand 9:50 
Page 22 of 78 

Appendix A/Table A2: Chloropicrin Flux Data Overview

MRID Location Application Type 

Application 

Rate 

(lbs 

ai/treated 

acre) 

Max 1-hr 

flux rate 

(ug/m2-s)

Max 

Application 

Rate (lbs 

ai/treated 

acre) 

Max 

Adjusted 

1-hr flux 

rate 

(ug/m2-s)

% Field 

Capacity 

Soil 

Temp 

(oC) 

% OM Soil Type Start 

App

Bedded Untarped Shank Injection Studies 

44149201 Phoenix, AZ Bedded, untarped 149 114.1 175 134.0 34 (0-6") N/A 0.23 (0-6") Loamy sand 148033801 Elkton, FL Bedded, untarped 258.5 5.9 350 8.0 75 (6-12") 11-23 (6") 1.3 (6-12") Sand 48033801 Elkton, FL Bedded, untarped 281.4 5.6 350 7.0 77 (6-12") 11-23 (6") 1.2 (6-12") Sand 348011601 Coloma, WI Bedded, untarped, water seal (0.1 in) (Field 2) 350 65 350 65 ~50-55 ~7-25 (3") 0.7 Loamy sand 1

Bedded Tarped Shank Injection Studies 

44149201 Phoenix, AZ Bedded, LDPE tarped 377 142.1 350 131.8 35 (0-6") N/A 0.29 (0-6") Sandy loam/Loam 647295203 Bainbridge, GA Bedded, Hytiblock Tarped 77 0.9 350 4.3 N/A N/A 0.45 Sandy clay loam N47295202 Dover, FL Bedded, Metallized Tarped 72 13.6 350 65.6 N/A N/A 1.3 Sand/Loamy sand N47295204 Hart MI Bedded, Blockade Tarped 80 1.0 350 4.2 N/A N/A 0.8 Sand/Loamy sand N

 Wasco 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

47820001 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 clay loam 347820001 Tifton, GA Bedded, LDPE tarped (Field 2) - Bad Soil Prep 151.2 13.3 350 30.8 69 (6-9") ~7-21 (6- 9") 0.6 (0-12") Loamy sand 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 147813801 Duette, FL Bedded, 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 147813801 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 47813801 Duette, FL Bedded, Metallized tarped, without 1,3-D (Field 3) 164.7 9.6 350 20.3 228 (0-6") ~7-24 (6- 9") 1.26 (0-6") NA 448006001 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 48107601 Ft. Pierce, FL Bed (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

Broadcast Untarped Shank Injection Studies 
Page 23 of 78 

Appendix A/Table A2: Chloropicrin Flux Data Overview

MRID Location Application Type 

Application 

Rate 

(lbs 

ai/treated 

acre) 

Max 1-hr 

flux rate 

(ug/m2-s)

Max 

Application 

Rate (lbs 

ai/treated 

acre) 

Max 

Adjusted 

1-hr flux 

rate 

(ug/m2-s)

% Field 

Capacity 

Soil 

Temp 

(oC) 

% OM Soil Type Start 

App

44149201 Phoenix, AZ Broadcast, untarped 171 180 175 184.6 38 (0-6") N/A 0.61 (0-6") Loam 7

 Wasco CA Broadcast, untarped (Field 3) 197 60.5 175 54 72 (6-12") ~20-33 (6") 0.56 (6-12") Sandy loam 1 Wasco CA Deep 18" Broadcast, untarped (Field 4) 321 74.8 350 82 75 (6-12") ~18-34 (6") 0.59 (6-12") Sandy loam 1

 Broadcast Tarped Shank Injection Studies 

44149201 Phoenix, AZ Broadcast, LDPE tarped 332 211 350 222.4 32 (0-6") N/A 0.38 (0-6") Loam 744149201 Yakima, WA Broadcast, LDPE tarped 343 70 350 71.4 71 (0-6") N/A 1.59 (0-6") Loam 744149201 Bradenton, FL Broadcast, LDPE tarped 346 58 350 58.7 95 (0-6") N/A 1.88 (0-6") Sand 7

 Wasco CA Broadcast, LDPE tarped (Field 1) 358 75.1 350 73 69 (6-12") ~21-35 (6") 0.52 (6-12") Sandy loam 7

48006001 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 N48006001 Wasco CA Broadcast, VaporSafe TIF tarped (Field 2) 180.3 25.8 350 50 77 (6-9") ~24-35 (6-9") 0.86 (6-9") loamy sand N48006001 Wasco CA Broadcast, VaporSafe TIF tarped, KTS under tarp (Field 3) 177.9 31 350 61 77 (6-9") ~25-33 (6-9") 0.35 (6-9") loamy sand 48006001 Wasco CA Deep 18"Broadcast, VaporSafe TIF tarped (Field 5) 181.0 6.3 350 12 77 (6-9") ~24-35 (6-9") 0.42 (6-9") loamy sand 47813901 Ft. Pierce, FL Broadcast (Low Disturbance Rig), HDPE tarped 233.8 46.8 350 70.1 155 (6-12") ~21-28 (6-9") 2.3 (0-6") Sand 47813901 Ft. Pierce, FL Broadcast (Backswept Shanks), HDPE tarped 222.8 46.5 350 73.0 99 (6-12") ~22-29 (6-9") 1.8 (0-6") Sand 

Drip Irrigation Studies 

45112901 CA Drip irrigation, bedded, VIF tarped 88 15 300 51.1 NA NA NA NA N45112902 GA Drip irrigation, bedded, poly tarped 90 7 300 23.3 NA NA NA NA N47456001 Yuma, AZ Buried (10") drip irrigation, bedded, poly tarped 403 2.85 300 2 100 ~30-34 NA Silt loam N47456001 Yuma, AZ Buried (10") drip irrigation, bedded, untarped 403 16 300 12 100 ~30-35 NA Silt loam N45112901 Salinas, CA Drip irrigation, bedded, poly tarped 300 70 300 70 37 NA 1.36 

Sandy 

loam/Loamy 

sand 

 

47679301 Yuma, AZ Buried (6") drip irrigation, bedded, untarped 298 47 300 47 100 1.3 Silt loam 48087401 Salinas, CA Drip irrigation, bedded, LDPE tarped 345 300 N/A ~16-27 (6-12") 0.7 Sandy loam 
Page 24 of 78 

Appendix A/Table A2: Chloropicrin Flux Data Overview

MRID Location Application Type 

Application 

Rate 

(lbs 

ai/treated 

acre) 

Max 1-hr 

flux rate 

(ug/m2-s)

Max 

Application 

Rate (lbs 

ai/treated 

acre) 

Max 

Adjusted 

1-hr flux 

rate 

(ug/m2-s)

% Field 

Capacity 

Soil 

Temp 

(oC) 

% OM Soil Type Start 

App

48087401 Salinas, CA Drip irrigation, bedded, TIF tarped 345 300 N/A ~16-27 (6-12") 0.7 Sandy loam 48087401 Salinas, CA Drip irrigation, bedded, LDPE tarped, water seal (0.33") with KTS 345 300 N/A ~16-27 (6-12") 0.7 Sandy loam 48087401 Salinas, CA Drip irrigation, bedded, LDPE tarped, water seal (0.33") 345 300 N/A ~16-27 (6-12") 0.7 Sandy loam 
Page 25 of 78 

Appendix A/Table A3: Metam Sodium/Metam Potassium Flux Data Overview

MRID Location Application Type 

Application Rate

(lbs ai/treated 

acre) 

Max 1-hr 

flux rate 

(ug/m2-s) 

Max Application 

Rate (lbs 

ai/treated acre) 

Max Adjusted 

1-hr flux rate 

(ug/m2-s) 

% Field 

Capacity

Soil 

Temp 

(oC) 

% OM Soil Type

Sta

Ap

Sprinkler Irrigation Studies 

45703701 Bakersfield, CA 

Solid set sprinkler, standard water seal 

(2 water seals for a 1" total-0.5" after 

app and 24 hours after app) 

320 358.1 320 358.1 NA NA NA NA 

CSREES 

#74 Bakersfield, CA 

Solid set sprinkler, Intermittent water 

seal (6 water seals for a 1.5" total0.25" after app, 4, 11, 24, 30, and 35 

hours after app) 

320 54.8 320 54.8 NA ~25 NA Sandy loam 

45703702 San Joaquin, CA 

Solid set sprinkler, Intermittent water 

seal (5 water seals for a 1.5" total-0.5" 

after app; 0.25" at 8, 24, 30, and 48 

hours after app) 

320 48.0 320 48.0 ~60-80 NA NA NA 

46969601 Mettler, CA 

Solid 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 0.5-0.8 Loamy Sand 

Broadcast Shank Injection Studies 

45703701 Bakersfield, CA Broadcast, standard water seal (0.5" after app) 320 118.3 320 118.3 NA NA NA NA 

CSREES 

#74 Bakersfield, CA 

Broadcast, Intermittent water seal (6 

water seals for a 1.5" total-0.25" after 

app, 6, 11, 24, 30, and 35 hours after 

app) 

320 52.4 320 52.4 NA ~25 NA Sandy loam 

45703704 Lost Hills, CA 

Broadcast, Intermittent water seal (5 

water seals for a 1.5" total-0.5" after app; 0.25" at 8, 12, 30, and 34 hours 

after app) 

320 36.3 320 36.3 NA ~27 NA Clay Loam 

46379201 Mt. Vernon, WA Broadcast "Roozen Rig" 320 159 320 159.1 NA NA NA NA 47770001 Pasco, WA Broadcast 219 12 320 18.2 NA 7 to 16 NA NA 48011601 Coloma, WI 

Broadcast (Dual Injection at 5.5 and 

9.5"), water seal (0.1" of rain after 

app) 

287 9.8 320 10.9 ~75-80 ~13 to 16 0.7 Loamy Sand 

48011601 Coloma, WI 

Broadcast (Dual Injection at 5.5 and 

9.5"), water seal (0.1" of rain after 

app) 

270 10.7 320 12.7 ~75-80 ~13 to 16 1.3 Loamy Sand 

48005901 Howard City, Broadcast (Injection at 12") 318 2.8 320 2.8 ~60-80 ~7 to 12 1.1-1.6 Loamy 
Page 26 of 78 

Appendix A/Table A3: Metam Sodium/Metam Potassium Flux Data Overview

MRID Location Application Type 

Application Rate

(lbs ai/treated 

acre) 

Max 1-hr 

flux rate 

(ug/m2-s) 

Max Application 

Rate (lbs 

ai/treated acre) 

Max Adjusted 

1-hr flux rate 

(ug/m2-s) 

% Field 

Capacity

Soil 

Temp 

(oC) 

% OM Soil Type

Sta

Ap

MI Sand/Sand

48005901 Howard City, MI Broadcast (Injection at 12"), water seal (0.33" after app) 321 0.3 320 0.2 ~60-80 ~7 to 12 0.5-1.3 Sand 47956901 Bakersfield, CA Broadcast (daytime), double water seal (0.4" after app, 0.4" at sunset) 317 4.4 320 4.4 ~72 ~27 NA NA 47956901 Bakersfield, CA Broadcast (nightime), double water seal (0.4" after app, 0.4" at sunset) 320 34.3 320 34.3 ~54 ~27 NA NA 

 Pasco, WA Broadcast (Injection at 9") 317 7.1 320 7.1 72.4 ~8 1.6-1.9 NA  Pasco, WA Broadcast (Injection at 9"), water seal (0.25" after app) 368 1.7 320 1.5 70.9 ~8 1.1-1.4 NA 

 Bedded Shank Injection Studies 

47131601 Helms, CA Bedded, untarped 294 18.77 320 20.4 NA ~13 8 Sandy loam 

CSREES 

#74 Citra, FL Bedded, LDPE tarped 320 174.95 320 175.0 NA ~18 NA Sand 

47820001 Tifton, GA Bedded, Blockade Tarped (Field 1) 299.5 16.5 320 17.6 70 ~10 to 21 0.7 Sandy loam 47820001 Tifton, GA Bedded, LDPE tarped (Field 2) - Bad Soil Prep 306.3 55.2 320 57.7 65 ~10 to 21 0.6 Sandy clay loam 47820001 Tifton, GA Bedded, LDPE tarped (Field 3) 295.2 32.9 320 35.7 74 ~10 to 21 0.6 Loamy sand 47813901 Duette, FL Bedded, Metallized tarped (Field 1) 313.6 2.2 320 2.3 142 ~10 to 21 0.94 NA 47813901 Duette, FL Bedded, Guardian VIF tarped (Field 2) 302.6 10.4 320 11.0 189 ~10 to 21 1.38 NA 47813901 Duette, FL Bedded, Metallized tarped (Field 3) 308.4 15.1 320 15.7 171 ~10 to 21 1.26 NA 

Drench Studies 

47956701 Modesto, CA Drench, triple water seal (0.2" after app, 0.2" at sunset of Day 1 and 2) 164.7 128.3 320 267.8 ~67 ~24 to 27 ~1.3 Sandy loam 

 Drip Irrigation Studies 

CSREES 

#74 Citra, FL Bedded, LDPE tarped 383 46.94 320 39.3 NA ~18 NA Sand 

45703708 Irvine, CA Bedded, LDPE tarped 320 15 320 14.9 NA NA NA NA 
Page 27 of 78 

Appendix A/Table A3: Metam Sodium/Metam Potassium Flux Data Overview

MRID Location Application Type 

Application Rate

(lbs ai/treated 

acre) 

Max 1-hr 

flux rate 

(ug/m2-s) 

Max Application 

Rate (lbs 

ai/treated acre) 

Max Adjusted 

1-hr flux rate 

(ug/m2-s) 

% Field 

Capacity

Soil 

Temp 

(oC) 

% OM Soil Type

Sta

Ap

45703708 Irvine, CA Bedded, untarped (drip lines on soil surface) 320 9 320 9.4 NA NA NA NA 

 Center Pivot Irrigation Studies 

47770001 Pasco, WA Center Pviot Irrigation-Drizzle Boom 300 172.1 320 183.8 NA 7 to 16 NA NA 

Flood Irrigation Studies 

47314301 Brawley, CA Flood Irrigation 318 68.34 320 68.8 NA NA NA NA 

Rotary Tiller and Spray Blade 

47572201 Smith River, CA Broadcast Spray/Rototill/Roller 320 49 320 49.4 ~30-35 ~19 to 21 ~4 Clay loam/Clay 
Page 28 of 78 

Appendix B: Agricultural Tarp 

Permeability to Fumigants, 

Qian and Kamel 2010 
Page 29 of 78 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460 

Analytical Chemistry Branch 

701 Mapes Road 

Fort Meade, Maryland 20755-5350 

June 17, 2010 

MEMORANDUM

SUBJECT: Agricultural Tarp 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 

 Special Review and Reregistration Division (7508P) 

Introduction

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

Health Effects Division and Pesticide Re-evaluation Division to evaluate existing testing 

methodology and then conduct tests on commonly-used agricultural films to determine their 

permeability to various fumigants. The objective 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 determine the risk associated with fumigant use and 

guide product label directions for safety buffer zones. 

 During the initial project planning it was agreed that the permeability of a film would be 

best expressed as the “mass transfer 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 agricultural films tested during this study were 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 the U.S. Department of Agriculture (USDA), 

Agricultural Research Service (ARS), at Riverside, CA (Papiernik et al., 2001, 2002). The 

testing apparatus consists of an airtight cylinder constructed from two stainless steel caps 

(chambers) separated by the test film. Test compounds are introduced into the chamber on one 

side of the film (source chamber) and the concentrations of the test compounds from both sides 

of the film (source and receiving chambers) are monitored over time by analyzing the vapor in 

each chamber. The rate of change in the concentrations 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 25o

C. 

In general, triplicate tests of each film were conducted for each fumigant at ambient humidity. 

Several films were selected randomly and the tests 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 conducted 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 test system. Although it has been reported 

previously that no effect was observed for some fumigants, the potential interactions 

among fumigants may affect film permeability. 

2. Tests to evaluate whether different concentration 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. Theoretically, the MTC is independent of the 

fumigant concentration. The calculated MTCs at these different fumigant concentrations 

were compared to assess the impact of fumigant concentration. 

3. Tests to evaluate other factors which could affect film permeability, including humidity 

and temperature. Experiments were conducted to verify the effect of humidity (moisture 

content inside the testing cells) and temperature 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 25o

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 

(25o

C). 

5. Several films were tested after they had been used in the field for soil fumigation. The 

used films were provided by Dan Chellemi 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 films 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 submitted 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, Embossed black Guardian Agroplastics Olefinas 

USA 

Mid South VIF 1.25 mil, embossed black Mid South Extrusion 
Page 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 individually tested fumigants 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 individually tested fumigants for one high density 

polyethylene (HDPE) film. The variation in the obtained MTC values is within the expected 

analytical uncertainty of the method. 

Table 3. Comparison of calculated MTCs obtained 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 fumigant 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 would 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 gradient. Our laboratory 

test results indicate that the MTC is independent of the initial fumigant 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 condensation often occurs under the film. Humidity 

is therefore one factor that might impact the permeability of films. Because 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 25oC was considered to be “low 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 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 relative humidity inside the 

permeability cell does not impact the film permeability. The variation in the calculated MTC is 

within the range of expected testing uncertainty. 

 

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

 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 from the same films tested at both ACB and 

Scott Yates’ lab at ARS, USDA suggests that the 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 the 
Page 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 folding marks and stretched segments) the obtained 

MTCs can vary significantly. The variations in the measured MTCs 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 stretched to some degree during application 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 fresh 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. ACB 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 ACB 

MTC

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 ACB 

MTC

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 ACB 

MTC

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 ACB 

MTC
Page 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 (different samples) was tested 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

MeBr

Propylene Oxide

IOM

1,3 D-cis

DMDS

MITC

Chloropicrin

1,3-D trans

Fumigants

MTC (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

MeBr

Propylene Oxide

IOM

1,3 D-cis

DMDS

MITC

Chloropicrin

1,3-D trans

Fumigants

MTC (cm/hr)

Guardian VIF

0.00

0.10

0.20

0.30

0.40

0.50

0.60

MeBr

Propylene Oxide

IOM

1,3 D-cis

DMDS

MITC

Chloropicrin

1,3-D trans

Fumigants

MTC (cm/hr)

Pliant Blockade

0.00

0.01

0.01

0.02

0.02

0.03

0.03

0.04

0.04

MeBr

Propylene Oxide

IOM

1,3 D-cis

DMDS

MITC

Chloropicrin

1,3-D trans

Fumigants

MTC (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 calculation 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 implemented 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 range 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 the tests were repeated. The obtained MTCs 

are consistent with the initial tests. All the results are included. All the films were tested in 

triplicate, except for one film (Pliant Blockade, Black). It was discovered after the test that one 

of the triplicate samples had a small hole in the film. Consequently only duplicate test results are 

available for this film (Pliant Blockade, Black). 

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

manufacturers are listed in Attachment 3 and 4. Attachment 3 lists the individual MTC values of 

the triplicate tests for all the films. Attachment 4 lists the average calculated MTC and the 

standard error of the replicate tests for each fumigant and each film. All the values are reported 

to four decimal points. 

Most of the films that have been tested were labeled as “virtually impermeable film 

(VIF)” and “totally impermeable film (TIF)”. The 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 permeability cells, or the detectable amount was so low that the 

MTC could not be confidently calculated. The calculated MTCs in these 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 determining 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, with MITC being the compound that permeates 

through all the films much faster than the other fumigants. DMDS and 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 fluoride is the slowest compound to permeate 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

Sulfuryl Fluoride

MeBr

PPO

IOM

1,3 D-cis

DMDS

MITC

Chloropicrin

1,3-D trans

Fumigant

MTC (cm/hr)

MTC of Different Tarps

0.000

0.020

0.040

0.060

0.080

0.100

0.120

Sulfuryl Fluoride

MeBr

PPO

IOM

1,3 D-cis

DMDS

MITC

Chloropicrin

1,3-D trans

Fumigant

MTC (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, ACB 
Page 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 2010 
Page 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 Chemistry 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 Analysis Division (7503P) 

John Leahy 

Pesticide Reevaluation Division (7508P) 

Chemistry and Exposure Branch (CEB) was requested to evaluate data contained in the 

Biological and Economic Analysis Division (BEAD) 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 and the impact of varied temperature, relative 

humidity, and challenge concentrations was also evaluated to a limited degree for a small 

number of film/fumigant combinations. A statistical analysis was completed to ascertain if 

clusters could be identified with respect to MTC measurements. Such information could be 
Page 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 the statistical methods which were used; Section 3 presents the 

results of global clustering using range plot and multidimensional clustering; Section 4 discusses 

the results; and Section 5 summarizes conclusions. 

1 INTRODUCTION 

Mass transfer coefficients (MTCs) are widely recognized in the literature as an appropriate 

means for describing the permeability of agricultural films to fumigants. As indicated above, the 

BEAD ACB generated a series of MTCs which serve 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 Branch, 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 Permeability 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 issues 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 individual rankings based on fumigant-specific 

permeabilities? 

2) In what ways do factors such as temperature, humidity, fumigant concentration affect 

the MTC value of a tarp and do these conditions affect estimated MTC values 

consistently? 

3) Is the measurement process adequate and reliable as defined by the similarity among 

replicate MTC measurements in the available 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 analysis, data were obtained from ACB in MS Excel format and imported 

into Stata and R for analysis. Stata and R are statistical software packages available to CEB. 

CEB determined that a “Cluster Analysis” approach would be an appropriate primary statistical 

technique to address the issues associated with the interpretation of these data and generating 

overall conclusions with respect to appropriate grouping or classification 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 characterize 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 describe univariate and multivariate exploratory 

statistical methods which attempt to discern 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 other clusters. Clustering is one 

of the most important unsupervised learning processes that organize objects into groups 

whose members are similar in some way. Clusters, like classes, should partition the data: 

every object in the given set of objects should belong to one, and only one, cluster. 

Nearly all clustering approaches use a concept of distance and operate not on the 

observed raw data per se but rather on an observed inter-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 partitions in which each partition is nested 

into the next (subsequent) partition in the sequence. Hierarchical clustering has been a 

standard component of the statistician’s toolbox since the 1960s and has recently become 

a common method for pattern recognition, machine learning, data mining, and 

bioinformatics. It is one of several general types of cluster analysis methods and, like 

many, uses the concept of “distance” for determining the similarity and dissimilarity 

between observations and uses this “distance” to group or classify those observations. 

Advantages of hierarchical clustering techniques are that 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 granularity. The detailed algorithm is provided in 

Appendix 1. 

There are two typical approaches used in hierarchical 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 substantively 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 divisive), the standard 

output of hierarchical clustering is a dendrogram. A dendrogram 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 shape of a dendrogram gives information on the 

number of clusters. Thus, cutting a dendrogram horizontally at a specific height 

constructs clusters in which similar tarps are grouped.

RANGE PLOT: A range plot is a plot which illustrates a given 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 visualize the grouping and highlight exceptions or special cases, a 

log-normal probability plot technique has also been used for an exploratory qualitative 

cluster analysis of the films based on a single fumigant.3 A log-normal probability plot 

provides a powerful technique for determining 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 over the whole distribution, and can detect any 

systematic departures from a fit. More importantly 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 magnitude 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 classification or grouping can be 

developed which accounts for fumigant-specific disparities among films. 

Together, the above three techniques – range plots, hierarchical clustering techniques with their 

resulting dendrograms, and log-normal probability 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 tarps 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, the plot does create a visual 

ranking which can be complemented by other, more quantitative (and somewhat more objective) 

methods such as hierarchical 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 value4

 and the arrows extend from the 5th to the 95th

percentile MTC values for any given tarp. For example log10(MTC) of Pliant Regular Black 

ranges roughly from -1.8 to 1.1. 

To complement the above range plot and provide 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 clustering6

, 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 log (MTC) of a given film sampled under different 

fumigants. For any given tarp: Range = 95th percentile logMTC value – 5th percentile value; midpoint = 50th

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) (Pihur et al., 2009) available in R package 

RankAggreg to find aggregate ranking of tarps. Figure 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 considered as a whole – into four clusters as 

outlined by the red borders. Each red rectangular box indicates a separate cluster, or “grouping”, 

as determined by the mathematical distance algorithm which was used (described above). As 

can be seen the algorithm determined that there 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

AEP Sun Film High Barrier

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 Tarp
Pliant Metalized

Canslit Metalized Black

Canslit Metalized White

Canslit HDPE

Pliant, Regular Black

Cadillac HDPE

AEP Sun Film High Barrier

Canslit LDPE

Cadillac VIF

Guardian Black VIF

Mid South Extrusion VIF

FilmTec VIF

Pliant Blockade, White

Ginegar Embossed VIF

Pliant Blockade, Black

Hyplast/Klerk, clear

Dow Saranex A

Ginegar Ozgard

Berry EVOH Supreme Barrier

Dow Saranex B

Raven, 1.4 mil, Black

Raven, 1.0 mil, Clear

AEP-one

Berry EVOH High Barrier

Berry EVOH High Barrier w/Improved toughness

0 10 20 30

Cluster Dendrogram

hclust (*, "complete")

dist(tg)

Height

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

Note that the dendrogram does not show the aggregate ranking (ordering) of the tarps. 

Aggregate ranking based on nine fumigants 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 into broad classes or categories with respect to 

MTC values. Both the Range plot shown in Figure 1 and the hierarchical clustering dendogram 

shown as Figure 2 are in basic agreement with respect 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 permeability” groupings, as detailed in Table 2. 

Table 2. Overall (Global) Tarp Groupings Based on Range Plot and 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 and 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 polyethylene tarps are all ranked in Group 1 (highest 

permeability). Metalized tarps appear to form their 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 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. 

 

4 DISCUSSION 

The above results and rankings reflect a global multidimensional score for each of the tarps. In 

reality, these represent for each tarp an average or ‘composite’ permeability score across the 9 

fumigants tested; as such, it is possible that certain tarps are outliers with respect to any given 

specific fumigant and the above multidimensional methodology will not necessarily reflect or 

otherwise incorporate these aberrant permeability values as part of its clustering scheme. The 

well-recognized limitations of the multi-dimensional cluster analysis done above include: 

1. It is difficult to determine ranking of tarps within a cluster. Sophisticated Rank 

aggregation techniques are required for combining individual ordered lists for each 

fumigant into a single list reflective of the overall preference. 

2. The MTC value of the tarps of a cluster is a vector of nine components instead of a 

single scalar which can be difficult to understand and communicate. 

3. A tarp can potentially have widely disparate permeability to different fumigants 

(Papiernik et al. 2010) and/or a specific tarp/fumigant combination can be an 

‘outlier’ with an MTC value that differs dramatically 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 fumigant separately, and evaluate the degree 

to which the overall or global ranking comports with the fumigant-by-fumigant 

rankings for each tarp. 

In order to address the above issues, CEB conducted a similar hierarchical cluster analysis 

(univariate HCA) on each fumigant separately (i.e., one fumigant at a time) in order to highlight 
Page 48 of 78 

any differences from the results of the composite analysis (or “irregularities”) that a specific 

tarp/fumigant combination may display. As an example, an analysis of MeBr is presented below 

in Figure 3 which illustrates the dendrogram-determined “groupings” that results when only 

MeBr is considered. Cadillac HDPE Canslit LDPE AEP Sun Film High Barrier Canslit HDPE

Pliant, Regular Black

Raven, 1.0 mil, Clear

Berry EVOH High Barrier

Berry EVOH High Barrier w/Improved toughness

Dow Saranex B

AEP-one

Raven, 1.4 mil, Black

Pliant Metalized

Guardian Black VIF

Canslit Metalized Black

Canslit Metalized White

Cadillac VIF

Pliant Blockade, Black

Ginegar Embossed VIF

Pliant Blockade, White

Dow Saranex A

Berry EVOH Supreme Barrier

Hyplast/Klerk, clear

FilmTec VIF

Ginegar Ozgard

Mid South Extrusion VIF

0 2 4 6 8 10

Cluster Dendrogram

hclust (*, "complete")

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 individual 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 Methodology” 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 clusters by looking for and defining 

natural “breaks” (i.e., distinct separations) of the points. Log-normal probability plots permit 

analyst to determine if fumigant–specific exceptions or outliers exist, and allow the magnitude 

and nature of the exceptions to be more easily seen and evaluated. In this way, a more refined 

classification or grouping can be developed which accounts for fumigant-specific disparities or 

exceptions among films. A comparison between the global cluster rankings (indicated by the 

colored symbols) and the MeBr-specific 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 five tarps that are grouped in MeBr Cluster 1 

(for highest permeability) and symbolized by red squares 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 these7

 are classified as Global Cluster 4. This means that 

while these tarps are globally classified as “very low permeability – Group 4”, they would have a 

somewhat different grouping -- “low permeability – 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 

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

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 Global Cluster 2 Global Cluster 3 Global Cluster 4

Cluster 1

MeBr

Cluster  2

MeBr

Cluster 3

MeBr

Cluster 4  MeBr
Page 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 101

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 the one presented above for MeBr are found in 

Appendix 2 of this document. Specifically, the fumigant-specific MTCs associated with each of 

the nine fumigants are investigated and the results -- including 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 Fumigant-specific Statistical Analysesa

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 Classification of tarps for DMDS 

Table A2-6 Classification 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 followed in the Appendix by the fumigant-specific 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 groupings – with their fumigant-specific exceptions 

as determined by the fumigant-specific analyses presented in Appendix 2 -- are listed in Table 5. 

Specific Questions: 

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

Question 1: Is a tarp consistent among fumigants in terms of its permeability? In other words, 

are the relative rankings based on aggregate permeabilities to nine fumigants reasonably 

concordant with the individual rankings based on fumigant-specific permeabilities? 

Answer: 

Tarps do appear to be fairly consistent in terms 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 cluster-3 according to the global clustering 

method but it is grouped in cluster-4 for IOM and chloropicrin using fumigant specific 

clustering. 

• Dow Saranex A is grouped in cluster-4 according to the global clustering method but it is 

grouped in cluster-3 for MITC, chloropicrin, trans-1,3-D and SF using fumigant specific 

clustering. 

All the tarps which are grouped in cluster-4 by global clustering are grouped in cluster-3 for SF 

using a fumigant specific clustering scheme. SF has only three clusters instead of four because 

distances between the tarps within cluster 3 are very small which implies the tarps are very 

similar in terms of MTC score (see Table 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 

Canslit Metalized Black No exceptions 

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: Cluster 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 tarps 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 migrate through all the tarps at a slower rate than MITC but at 

a relatively faster rate than other tested fumigants. SF is the slowest compound to permeate all 

the tested tarps. In addition—and importantly -- SF is the least consistent in terms of cross-tarp 

rankings (as evidenced by the crossed lines): specifically, there are a number of tarps which are 

ranked highly (i.e., low permeability) for other fumigants, 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 for other fumigants (and vice 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 different 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 temperature, and this has been demonstrated in the 

literature for polyethylene tarps but less information 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 increasing 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 and 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 clustering as well as the ranking of 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 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 tarp. 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 25o

 C was considered to be “low 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 considered 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 results of these tests that the relative humidity 

does not impact the MTC score. However, CEB notes that the above lab experiment was 

conducted using only one tarp, and believes the ACB conclusion cannot be extended beyond the 

single tarp tested or generalized to other 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 relative humidity on permeability. Relative humidity 

had a large impact on the permeability of a VIF tarp (FM4) to five fumigants (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 humidity 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 extended 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 properties of the tarp and the chemicals, the 

MTC is theoretically independent of the concentration gradient. Qian and Kamel 2010 

concluded that the MTC is independent of initial concentration (see Table-4 of the ACB memo). 

However, as this experiment was conducted using only one tarp the results cannot be generalized 

to the classification scheme to other concentrations based on the data presented. 

Question 3: Is the measurement process adequate and reliable (e.g., similarity among MTC 

measurements in replicates)? Are there similarities in MTC measurements 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 the 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 concluded 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: Cadillac 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 (25oC) and relative humidity (30 to 40%). Because the 

tarps and fumigants used in ACB’s tests represent 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 could be categorized based on their MTC. 

CEB analyzed the MTC testing data collected by ACB using two statistical 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 fumigants. First, a qualitative-oriented approach 

called the Range Midpoint Method was used to visually compare the 25 tarps by rank-ordering 

their median MTC value and then examining each tarps’ 90th percentile range. Second, a 

quantitative-oriented multivariate hierarchical clustering analysis was performed, which is a 

standard statistical method for evaluating 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 jointly evaluated to group tarps on a global basis using a “weight-ofthe-evidence” approach. In addition to multivariate analysis, univariate hierarchical clustering 

method was used to classify the tarps based on MTC score for a single fumigant. To confirm 

and further visualize the grouping 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 that 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 particular, four categories of tarps were identified using 

MTC scores of tarps from nine fumigants jointly (composite groupings). Moreover, it was also 

observed that polyethylene tarps tended to cluster in Group 1 (highest permeability), metalized 

tarps tended to cluster in Group 2 (moderate permeability), 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 alternative layer of other material 

included typically between layers of polyethylene 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 fumigants in general agree with the groupings of 

tarps based on a single fumigant with some exceptions. 

In addition to cluster analysis, CEB also reviewed the ACB memo (6/17/2010) to determine 

consistency between ACB lab and USDA lab with respect to MTC scores of different tarps. 
Page 56 of 78 

ACB memo compared the MTC values obtained from the same tarps tested at both ACB and 

USDA. Based on the comparison, the ACB memo concluded 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 Branch, 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 permeability of high density polyethylene tarp to 

fumigant vapors. Papiernik, S. K., and S. R. Yates. 2002. Environ. Sci. Technol. 36:1833-

1838. 

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

BMC Bioinformatics .10:62 
Page 57 of 78 

APPENDIX 1 

Hierarchical cluster Algorithms8 : 

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 = (x1-y1)

2

 +..........+(xn-yn)

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.pdf
Page 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 4 
Page 59 of 78 

Cadillac HDPE

Canslit LDPE

AEP Sun Film High Barrier

Canslit HDPE

Pliant, Regular Black

Raven, 1.0 mil, Clear

Berry EVOH High Barrier

Berry EVOH High Barrier w/Improved toughness

Dow Saranex B

AEP-one

Raven, 1.4 mil, Black

Pliant Metalized

Guardian Black VIF

Canslit Metalized Black

Canslit Metalized White

Cadillac VIF

Pliant Blockade, Black

Ginegar Embossed VIF

Pliant Blockade, White

Dow Saranex A

Berry EVOH Supreme Barrier

Hyplast/Klerk, clear

FilmTec VIF

Ginegar Ozgard

Mid South Extrusion VIF

0 2 4 6 8 10

Cluster Dendrogram

hclust (*, "complete")

dist(tg2)

Height

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

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 Global Cluster 2 Global Cluster 3 Global Cluster 4

Cluster1  

MeBr

Cluster  2

MeBr

Cluster3

MeBr

Cluster4  MeBr
Page 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 4 
Page 61 of 78 

Ginegar Embossed VIF

Mid South Extrusion VIF

FilmTec VIF

Pliant Blockade, Black

Pliant Blockade, White

Raven, 1.0 mil, Clear

AEP-one

Berry EVOH High Barrier

Raven, 1.4 mil, Black

Berry EVOH High Barrier w/Improved toughness

Dow Saranex B

Ginegar Ozgard

Dow Saranex A

Berry EVOH Supreme Barrier

Hyplast/Klerk, clear

Canslit HDPE

Pliant, Regular Black

Cadillac HDPE

AEP Sun Film High Barrier

Canslit LDPE

Pliant Metalized

Cadillac VIF

Guardian Black VIF

Canslit Metalized Black

Canslit Metalized White

0 2 4 6 8 10

Cluster Dendrogram

hclust (*, "complete")

dist(tg3)

Height

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

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 Global Cluster 3 Global Cluster 4

Cluster1  

PPO

Cluster  2 PPO

Cluster3

PPO

Cluster4  PPO
Page 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 4 
Page 63 of 78 

Cadillac HDPE

Canslit LDPE

AEP Sun Film High Barrier

Canslit HDPE

Pliant, Regular Black

Raven, 1.0 mil, Clear

AEP-one

Berry EVOH High Barrier

Raven, 1.4 mil, Black

Hyplast/Klerk, clear

Berry EVOH High Barrier w/Improved toughness

Berry EVOH Supreme Barrier

Ginegar Ozgard

Mid South Extrusion VIF

Dow Saranex ADow Saranex B

Pliant Metalized

Canslit Metalized Black

Canslit Metalized White

Cadillac VIF

Guardian Black VIF

Ginegar Embossed VIF

Pliant Blockade, White

FilmTec VIF

Pliant Blockade, Black

02468

Cluster Dendrogram

hclust (*, "complete")

dist(tg4)

Height

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

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 Global Cluster 3 Global Cluster 4

Cluster1  

IOM

Cluster  2 IOM

Cluster3

IOM

Cluster4  IOM
Page 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 4 

 
Page 65 of 78 

Cadillac HDPE

Canslit LDPE

AEP Sun Film High Barrier

Canslit HDPE

Pliant, Regular Black

Pliant Metalized

Canslit Metalized Black

Canslit Metalized White

Berry EVOH High Barrier

Berry EVOH High Barrier w/Improved toughness

Hyplast/Klerk, clear

Raven, 1.0 mil, Clear

Dow Saranex B

Raven, 1.4 mil, Black

AEP-one

Berry EVOH Supreme Barrier

Dow Saranex A

Ginegar Ozgard

Ginegar Embossed VIF

FilmTec VIF

Pliant Blockade, Black

Mid South Extrusion VIF

Pliant Blockade, White

Cadillac VIF

Guardian Black VIF

0 2 4 6 8 12

Cluster Dendrogram

hclust (*, "complete")

dist(tg5)

Height

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

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 Global Cluster 2 Global Cluster 3 Global Cluster 4

Cluster1   Cis‐1,3‐D

Cluster  2 Cis‐1,3‐D

Cluster3 Cis‐1,3‐D

Cluster4  Cis‐1,3‐D
Page 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 4 
Page 67 of 78 

Cadillac HDPE

Canslit LDPE

AEP Sun Film High Barrier

Canslit HDPE

Pliant, Regular Black

Pliant Metalized

Canslit Metalized Black

Canslit Metalized White

Raven, 1.0 mil, Clear

Berry EVOH High Barrier

Hyplast/Klerk, clear

Dow Saranex A

Ginegar Ozgard

Berry EVOH High Barrier w/Improved toughness

Raven, 1.4 mil, Black

Dow Saranex B

AEP-one

Berry EVOH Supreme Barrier

Cadillac VIF

Guardian Black VIF

Ginegar Embossed VIF

Mid South Extrusion VIF

Pliant Blockade, Black

FilmTec VIF

Pliant Blockade, White

0 2 4 6 8 12

Cluster Dendrogram

hclust (*, "complete")

dist(tg6)

Height

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

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 Global Cluster 3 Global Cluster 4

Cluster1   DMDS

Cluster  2 DMDS

Cluster3 DMDS

Cluster4  DMDS
Page 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 3 
Page 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 4 Ginegar Ozgard Hyplast/Klerk, clear Mid South Extrusion VIF Dow Saranex A Dow Saranex B Raven, 1.0 mil, Clear Raven, 1.4 mil, Black Berry EVOH High Barrier Berry EVOH Supreme Barrier AEP-one Berry EVOH High Barrier w/Improved toughness Canslit HDPE Pliant, Regular Black Cadillac HDPE AEP Sun Film High Barrier Canslit LDPE Ginegar Embossed VIF

FilmTec VIF

Pliant Blockade, Black

Cadillac VIF

Pliant Blockade, White

Pliant Metalized

Canslit Metalized Black

Canslit Metalized White

Guardian Black VIF

0 4 8 12

Cluster Dendrogram

hclust (*, "complete")

dist(tg7)

Height
Page 70 of 78 

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

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 Global Cluster 3 Global Cluster 4

Cluster 1   MITC

Cluster  2 MITC

Cluster3 MITC

Cluster4  MITC

EPA          MITC
Page 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 4 
Page 72 of 78 

Dow Saranex A

Ginegar Embossed VIF

Guardian Black VIF

Cadillac VIF

Pliant Blockade, Black

Raven, 1.0 mil, Clear

Mid South Extrusion VIF

Berry EVOH High Barrier w/Improved toughness

Hyplast/Klerk, clear

Raven, 1.4 mil, Black

Dow Saranex B

AEP-one

Berry EVOH Supreme Barrier

Pliant Blockade, White

Ginegar Ozgard

Berry EVOH High Barrier

FilmTec VIF

Pliant Metalized

Canslit Metalized Black

Canslit Metalized White

Cadillac HDPE

Canslit HDPE

Pliant, Regular Black

AEP Sun Film High Barrier

Canslit LDPE

02468

Cluster Dendrogram

hclust (*, "complete")

dist(tg8)

Height

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

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 Global Cluster 2 Global Cluster 3 Global Cluster 4

Cluster1       Chrolopicrin

Cluster  2 Chrolopicrin

Cluster3 Chrolopicrin

Cluster4  Chloropicrin
Page 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 4 
Page 74 of 78 

Berry EVOH High Barrier

Raven, 1.0 mil, Clear

Dow Saranex B

Raven, 1.4 mil, Black

AEP-one

Berry EVOH Supreme Barrier

Berry EVOH High Barrier w/Improved toughness

Hyplast/Klerk, clear

Ginegar Embossed VIF

Pliant Blockade, White

Mid South Extrusion VIF

FilmTec VIF

Pliant Blockade, Black

Dow Saranex A

Ginegar Ozgard

Cadillac HDPE

Canslit LDPE

AEP Sun Film High Barrier

Canslit HDPE

Pliant, Regular Black

Cadillac VIF

Guardian Black VIF

Pliant Metalized

Canslit Metalized Black

Canslit Metalized White

0 2 4 6 8 12

Cluster Dendrogram

hclust (*, "complete")

dist(tg9)

Height
Page 75 of 78 

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

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 Global Cluster 2 Global Cluster 3 Global Cluster 4

Cluster1   trans‐

1,3‐D

Cluster  2 trans‐1,3‐D

Cluster4  trans‐1,3‐D

Cluster3  trans‐

1,3‐D
Page 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 3 
Page 77 of 78 
Page 78 of 78 

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

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 Global Cluster 3 Global Cluster 4

Cluster  1  SF

Cluster 2

SF

Cluster  3   SF

EPA    SF