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Soil Fumigants

Tarp Testing Guidance

On this page you will find:

Interim Guidance on How to Test Tarps and Submit Data to EPA

We are working to develop an American Society for Testing and Materials (ASTM) standard for tarp testing. Until the ASTM standard is approved, EPA provides this interim guidance for those interested in testing soil fumigant tarps so the tarps may be added, as appropriate, to either the agency’s tarp credit Web page and/or the dimethyl disulfide (DMDS) tarp Web page. We highly recommend that the testing procedures be followed as closely as possible. Since the reactivity, stability, and other chemical properties are different for each fumigant, the permeability of each fumigant through a film will be different. To assess comparability with existing permeability data, we also recommend conducting individual tart permeability tests for more than one fumigant.

Tarp Testing Protocol
In conjunction with the United States Department of Agriculture, Agricultural Research   Service (USDA ARS), EPA has developed the following protocol for testing tarps.

Information to Submit to EPA

A) Description of tarp tested: 
  • Tarp manufacturer
  • Tarp name/designation
  • Tarp material
  • Tarp thickness
  • Other relevant descriptors or technical specifications
B) Test substances: 
  • Test fumigants (% purity)
  • Other additives or solvents mixed with test substances
C) Equipment: 
  • Description of test cells, including details of any modifications
  • Analytical instrument(s) used, including instrumental parameters (e.g., manufacturer(s), column, detector, etc.)
D) Test conditions: 
  • Test cell temperature
  • Test cell humidity (if other than ambient)
  • Testing protocol, including fumigant volumes/concentrations, sample collection schedule (number of samples, sample collection intervals, test duration), number of replicates
E) Test notes: 
  • Description of deviations and modifications from the written procedure
F) Test results: 
  • Calculated mass transfer coefficients from individual tests, including graphs.
    • Averages and standard deviation of all replicates should be tabulated.
  • Compound concentrations or corresponding peak response at each sampling interval, supported by chromatograms.
  • Percent recovery of each compound at each sampling time (sum of source and collection chambers relative to the total amount applied).
  • Analytical instrument calibration data.

How to Submit Tarp Data to EPA
Please submit the following by e-mail to Dana Friedman at friedman.dana@epa.gov.

  • A cover letter that indicates the tarp(s) and fumigant(s) tested.
  • A PDF file containing the information described under Information to Submit to EPA.
    • If the file is too large to email, please send by mail to:
Attn: Dana Friedman
U.S. Environmental Protection Agency
Office of Chemical Safety and Pollution Prevention
Office of Pesticide Programs, Pesticide Reevaluation Division
1200 Pennsylvania Ave., NW
Mail Code 7508P
Washington D.C. 20460
 
AND
 
Attn: Thuy Nguyen
Environmental Science Center
701 Mapes Road
Fort George G. Meade, Maryland 20755-5350

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Background on EPA Tarp Testing

EPA has completed a soil fumigant tarp permeability testing project and is working on developing an ASTM International standard for future tarp testing. The test method titled Film Permeability Determination Using Static Permeability Cells is currently undergoing an ASTM collaborative study. Once approved, the performance standard will eliminate the need for EPA to list individual tarps on the agency’s fumigant tarp web pages.

The development of the standard will provide a commonly accepted testing method and create a set of approved tarp testing criteria that will allow individuals to uniformly test tarps to determine the mass transfer coefficients (MTCs).

  • Instead of referring to the EPA tarp credit web page, soil fumigant labels will list ranges of MTCs and the associated buffer zone reduction credits.
  • The DMDS labels will also list the minimum MTCs for tarps required to be used with the products.

The agency anticipates that the standard will increase the number of tarps that are eligible for either buffer zone reduction credits or for use with products containing DMDS, thereby providing users with more options. We expect that the performance standard will be available in 2014.

During EPA’s reregistration of the soil fumigants, the use of tarps (i.e., high barrier films) was identified as one agricultural practice that can reduce fumigant emissions. The agency began testing commonly used agricultural tarps to determine how effectively each tarp could reduce fumigant emissions. The agency’s laboratory tarp testing method, discussed above, was adapted from a method previously developed by Sharon Papiernik and Scott Yates of USDA ARS (Papiernik et al., 2001, 2002). For more information, please see:

Current labels for the soil fumigants chloropicrin, methyl bromide/chloropicrin, chloropicrin/1,3-dichloropropene, and metam sodium or metam potassium contain a link to our Tarps web page. This page lists tarps that qualify for buffer zone reduction credits based on testing using EPA’s method. In addition, tarps are required for use with products that contain dimethyl disulfide (DMDS). The agency’s DMDS tarps web page lists the tarps that are approved for use with these products.