Tracy Heinzman

202.719.7106

theinzman@wileyrein.com

1776 K STREET NW 

WASHINGTON, DC 20006 

PHONE 202.719.7000 

FAX 202.719.7049 

7925 JONES BRANCH DRIVE 

McLEAN, VA 22102 

PHONE 703.905.2800 

FAX 703.905.2820 

www.wileyrein.com 

August 6, 2010 

Via Electronic Mail 

and US Mail 

Mr. Jeffrey L. Dawson 

U.S. EPA - Office of Pesticide Programs 

One Potomac Yard 

2777 Crystal Drive 

Arlington, Virginia 22202 

Re: Follow-up on Conference Call Discussing Field Flux Studies 

Dear Jeff: 

 This letter follows up on the July 6, 2010 conference we had with OPP staff 

regarding the Field Flux Studies submitted by the Methyl Bromide Industry Panel 

(MBIP). During the call EPA requested additional information from the MBIP in 

three areas: (1) the applicability of the California flux study data to other geographic 

regions; (2) the uptake of specialized tarps in Florida; and (3) an update on VIF/TIF 

for broadcast applications of methyl bromide. The requested information on these 

topic is provided below. 

 1. California Flux Data Representative of Other Regions: 

 The California flux study (Wasco, June 2009 MRID # 48006001) 

encompassed three fields addressing three variations of the shallow broadcast 

application method. Pursuant to our March 2009 flux study proposal, the MBIP 

also conducted a study in Florida in January 2010 (MRID # 48107601). The 

Florida study was designed to include the shallow broadcast method and was 

intended to serve as confirmatory data in support of the California study. It was 

also intended to show that emission rates from Florida conditions would be lower 

than the California study. 

 As you know, due to bad weather and equipment-related problems, the 

shallow broadcast portion of the Florida study was disqualified by the study director 

(Dr. H. Ajwa). Nonetheless, it would be scientifically appropriate and conservative 

to use the California data to calculate buffer zones for broadcast fumigation in 

Florida and other regions of the US. 
Mr. Jeffrey Dawson 

August 6, 2010 

Page 2 

 As we explained on the conference call, the conditions under which the 

California study were conducted represent the worst-case for conditions that may be 

encountered in all regions. Specifically, the California study was conducted in the 

southern area of the San Joaquin Valley, during late-spring/early summer (relatively 

high ambient temperatures), on a light soil (sandy loam), and with the target soil 

moisture (~70% of field capacity) achieved. By comparison, the Florida study was 

conducted in the winter and the data that would have been generated for the 

broadcast application method would have been from light soil with moisture level 

that exceeded 100%. 

 Flux data now available indicate that emission rates are directly impacted by 

higher soil moisture. Florida fields consistently have moisture capacities 

approaching or exceeding 100% due to their sandier soils. Because the California 

study involved soils with significantly less soil moisture, the emission levels 

generated in the California study for the broadcast method are much higher than the 

levels that likely would have been documented in the Florida study if the broadcast 

portion had not been disqualified. 

 The chloropicrin flux studies listed in Table 1 show that fumigant emissions 

under Florida’s more moist conditions are, at most, equal to, and typically less than 

emissions from California. The same would be true for methyl bromide. For the 

shallow broadcast tarp application method, the peak chloropicrin emission rate was 

higher in California (2008) than in Florida (1995 and 2009) and Washington (1996); 

where polyethylene tarp was used in all studies. For the tarped bedded shank 

application method, the peak chloropicrin emission rate was higher in California 

(2008; polyethylene tarp) than in Florida (2009 and 2010; metalized, VIF or TIF 

tarps) and Georgia (2009; polyethylene tarp). For both application methods, the 

chloropicrin emissions were highest in California. 

 This same trend would hold true for shallow broadcast applications of 

methyl bromide, as shown by the much lower methyl bromide emissions we 

recently obtained in Florida for the other application methods compared to the 

historical flux data (1990s) derived from the older California studies that EPA used 

to support the buffer zone calculations underlying the RED. 
Mr. Jeffrey Dawson 

August 6, 2010 

Page 3 

Table 1. Comparison of Chloropicrin Peak Emissions by Application 

Method Across Different States. 

Application 

Method 

MRID # 

(Year of 

Study) 

Location 

of Study 

Soil Sealing Test 

Substance 

Peak 

Chloropicrin 

Emission 

(μg/m2/sec)1

47576901 

(2008) 

California Polyethylene tarp Chloropicrin 37 

44149201 

(1995) 

Florida Polyethylene tarp Chloropicrin 29 

44149201 

(1996) 

Washington Polyethylene tarp Chloropicrin 12 

48085701 

(2009) 

Florida Polyethylene tarp; 

standard rig 

Pic-Clor 60 36.6 

Shallow 

Broadcast 

Tarp 

 Polyethylene tarp; 

Chellemi lowdisturbance rig 

Pic-Clor 60 36.8 

47576901 

(2008) 

California Polyethylene tarp; 

strip2

Chloropicrin 40 

47813901 

(2009) 

Florida Metalized tarp Chloropicrin 7.7 

47813901 

(2009) 

Florida VIF Chloropicrin 2.0 

47813901 

(2009) 

Florida Metalized tarp Chloropicrin 1.2 

4782001 

(2009) 

Georgia VIF Paladin 

79/214

1.8 

4782001 

(2009) 

Georgia Polyethylene tarp 

with rototill 

Paladin 

79/214

13.3 

4782001 

(2009) 

Georgia Polyethylene tarp 

without rototill 

Paladin 

79/214

15.0 

Tarped 

Bedded 

Shank 

48107601 

(2010) 

Florida TIF Tri-Con 

50/505

10.5 

1

 Peak emission rate normalized to 175 lbs/acre for comparison purposes. 

2

 Pic-Clor 60 is contains approximately 60% chloropicrin and 40% 1,3-

Dichloropropene. 

3

 Shallow strip (flat fume) is functionally equivalent to bedded shank. 

4

 Paladin 79/21 contains approximately 79% DMDS and 21% chloropicrin. 
Mr. Jeffrey Dawson 

August 6, 2010 

Page 4 

4

 Tri-Con 50/50 contains approximately 50% methyl bromide and 50% 

chloropicrin. 

 2. The Use of Non-Polyethylene Row Mulch in Florida 

 You also asked us for information on the use of films in row mulch 

agriculture in Florida. Based on available information, we understand that almost 

all growers in Florida (98%) have switched away from polyethylene films to 

VIF/TIF or metalized films as their choice for methyl bromide applications in row 

mulch use patterns. Of the 98%, approximately 70% of this uptake has been in the 

form of VIF, and 30% has been in the form of metalized film. (In some specific 

instances, the VIFs are also metalized.) This particular row mulch use pattern is 

applicable to methyl bromide bedded shank applications only; where tarp 

preferences are becoming tailored to specific products. For example, Pic-Clor 60 

applied via tarped bedded shank has a use pattern that is 70% polyethylene film, 

20% VIF, and 10% metalized film. 

 3. Additional Information on Commercial Use of Broadcast TIF/VIF. 

During our call, you also asked for additional information on the use of 

TIF/VIF in broadcast applications. 

• Application Experience: Deployment trials, large demonstrations, 

and commercial use of broadcast (13-foot wide) VaporSafeTM (or 

any other low-permeability film) indicate that normal “maximum 

acres-per-day” applications can be maintained; where a typical rig 

can lay about 17-25 broadcast acres per day, depending on the field 

layout. 

• Gluing: Seam failure has been one of the traditional primary 

problems with these low-permeability films. Several groups have 

been working on resolving the gluing issue for years, and various 

materials and/or methods have been developed and continue to be 

refined. Commercial viability has been achieved for some methods 

already, and more gluing methods/options will likely be identified in 

time to meet the field-implementation of the 2011 RED labels. 
Mr. Jeffrey Dawson 

August 6, 2010 

Page 5 

• Commercial Example -- USDA-APHIS Pale Cyst Nematode 

Quarantine in Idaho: 13-foot VaporSafeTM (TIF) was used on 49 

acres in Idaho in May 2010. All acres were treated with 400 lbs/acre 

of MB 98/2. In this particular case, Trident Ag Products and TriCal, 

Inc. used the “band-aid” gluing system developed by TriCal, Inc. to 

seam the broadcast film panels (See Photo 1 and Photo 2 below). 

The band-aid system uses standard, solvent-based glue to adhere the 

panels of VaporSafeTM (or any other low-permeability film) together, 

while simultaneously applying a smaller roll (14-20” wide) of 

polyethylene film over the top of the seam. Because the solvent in 

the glue can readily volatilize through polyethylene film, this upper 

seam-covering layer of polyethylene film anchors the two 

VaporSafeTM seams together quickly; thereby providing more time 

for the glue between the VaporSafeTM panels to cure. 

Photo 1 Photo 2 
Mr. Jeffrey Dawson 

August 6, 2010 

Page 6 

 We trust that the foregoing addresses the Agency’s information requests. If 

you need additional information, please do not hesitate to contact me at the number 

or e-mail address listed above. 

Sincerely, 

/s/ 

Tracy Heinzman 

Counsel to MBIP, LLC 

cc: Steve Weiss, OPP/PRD 

 Sue Bartow, OPP/PRD 

 MBIP Members