UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D.C. 20460 

MEMORANDUM 

Date: March 27, 20 14 

OFFICE OF CHEMICAL SAFETY 

& POLLUTION PREVENTION 

SUBJECT: Thiram Tolerances. Conversion to Carbon Disulfide Equivalents to Harmonize 

with CODEX Expression of MRLs. 

PC Code: 07980 1 

Decision No.: 343502 

Petition No.: N/ A 

Risk Assessment Type: NA 

TXRNo.: NA 

MRID No.: N/ A 

DP Barcode: D418504 

Registration No.: N/ A 

Regulatory Action: Tolerance Change 

Case No.: 0122 

CAS No: 137-26-3 

40 CFR: § 180.132 

From: Susan V. Hummel, Senior Chemist ~ --------/ <ZA...--

Risk Assessment Branch IV '-~ _.,.,- b 

Through: 

To: 

Health Effects Division (7509P) ~ 

Thurston G. Morton, Senior Chemist ;J._j/1 Risk Assessment Branch IV 

Health Effects Division (7509P) 

Wilhelmina Livingston, CRM, and Joseph Nevola 

Pesticide Reevaluation Division (7508P) 

Tolerances for the dimethyl dithiocarbamates (thiram, ziram and ferbam) and the ethylenebisdithiocarbamates (EBDCs) are being converted to being expressed as carbon disulfide 

equivalents, since it is difficult to distinguish among the various pesticides by analytical methods 

alone. 

The tolerance expression should read: 

Tolerances are established for residues of the fungicide thiram (tetramethyl thiuram disulfide), 

including its metabolites and degradates, in or on the commodities in the table below. 

Compliance with the tolerance levels specified below is to be determined by measuring only 

those thiram residues convertible to carbon disulfide, expressed as carbon disulfide, in or on the 

commodity. 

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International Harmonization. The Codex Alimentarius has established maximum residue limits 

(MRL), for "total dithiocarbamates, determined and expressed as mg carbon disulfide per kg" in 

strawberry of 5 mglkg. HED has recommended that all tolerances for dithiocarbamates, 

including thiram be converted to be expressed as carbon disulfide, so that the tolerance 

expression will be compatible with CODEX, however the tolerance level will not be compatible 

for strawberry, since there are differences in Good Agricultural Practices (GAP). A copy of the 

International Residue Limit Status (IRLS) sheet is attached to this memorandum. 

Table 7. Tolerance Summary for Thiram. 

Current Tolerance Recommended Comments; 

Commodity 

(ppm Thiram) Tolerance (ppm {Correct Commodity Definition] 

CSz) 

Apple 7.0 5 The conversion factor is 0.63x 

Banana' 0.80 2.0 Recommended tolerance is being raised 

from 0.50 ppm to 2.0 ppm CS2 to 

harmonize with CODEX. 

Peach 7.0 Recommended tolerance is being raised 

7.0 from 5.0 ppm to 7.0 ppm CS2 to 

harmonize with CODEX. 

Strawberry 20 13 The conversion factor is 0.63x 

No U.S. reg1strat10ns as of March 13, 2014. 

Enforcement Analytical Method. An Enforcement Analytical Method is available to enforce the 

proposed tolerances. The Pesticide Analytical Manual (PAM) Vol. II lists Method I, II, III, IV, 

and A for the determination of dithiocarbamate residues inion plant commodities. These 

methods are based on the decomposition of dithiocarbamates with release of CS2. Using these 

methods, the CS2 is swept through a trap to remove any H2S and into a reaction tube containing a 

solution of copper acetate and an amine. A colored copper dithiocarbamate complex is formed 

and its absorbance read as a measure of the original dithiocarbamate. The stated limit of 

detection (LOD) for Method I is 0.5-4.0 ppm. More recent submissions have included alternate 

detection methods, headspace GC with Mass Spectrometry detection. 

Thiram may be detectable using PAM I multiresidue methods without Florisil cleanup, but is not 

detected when Florisil cleanup is used. 

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Appendix I. International Residue Status 

Thiram (PC Code 079801 ; Date ofRequest 3/12/14) 

Summary of US and fntemational Tolerances and Maximum Residue Limits 

Residue Definition: 

us Canada Mexico2 Codex

3 

40 CFR 180.1 32 bis( dimethy lthio Plant: total 

carbamoyl)disul dithiocarbamates, 

Plants: thiram (tetramethy l thiuram ph ide detennined as CS2, 

disulfide) evolved during acid 

digestion and expressed 

as mg CS2/kg. 

Commodity1 Tolerance (ppm) /Maximum Residue Limit (mg/ kg) 

us Canada M exico:z Cod ex

3 

Apple 7.0 5 5 

Banana 0.80 -- 2 

Peach 7.0 5 7 

Strawberry 20 7 54 

Completed: S.Hummel; 03/ 13/ 14 

I There are no U. S. regtstrattOns as of 3/1311 4 

2 Mexico adopts US tolerances and/or Codex MRLs for its export purposes. 3 * = absent at the limit of quantitation; Po = postharvest treatment, such as treatment of stored grains. PoP = 

processed postharvest treated commodity, such as processing of treated stored wheat. (fat) = to be measured on the 

fat portion of the sample. MRLs indicated as proposed have not been finali zed by the CCPR and the CAC. 4 MRL estimate based on the use of thiram 

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