Syngenta Crop Protection. Inc. 

Legal Group 

2 Righter Parkway 

Wilmington, DE t 9803 

Heather C. Winett 

Tel. (302) 476-2112 

Fax (302) 476-201 2 

heather.winett@syngenta.com 

September 25,200 1 

Kathleen Franklin 

U.S. Environmental Protection Agency 

Ariel Rios Building -5 104 

1200 Pennsylvania Avenue, N. W. 

Washington, DC 20460 

Re: Requested De-Listing of Paraqua f DichlorideJi.om SARA Title 111, Section 302; 

Zeneca Ag Products Inc. v. U. 5. EPA 

Dear Ms. Franklin: 

Set forth below is the supplement following up on the inf mation sent August 30, 2001 

to demonstrate that Paraquat dichloride, though classified as restricted use pesticide, would 

not be a danger to the community if it were delisted from the SARA 302 ExtrerneIy Hazardous 

Substance List. Would you kindly insert Attachments 3 and ~nto the tabs sent with the 

of Paraquat Dichloride at its Decomposition Point." 

k 

August package. Also enclosed is a report entitled "An Estimation of the Vapor Pressure 

We hope that your questions and concerns have been addressed, However, if you need any 

additional information or discussion, Syngenta would be pleased to respond further. 

Sincerely, 

Heather C. Winett 

Environmental Counsel 

CC: Nina Rivera, Esq. (EPA) 

Alan Carpien, Esq. @PA) 

Peter Gray, Esq. 

Sueanne Pfifferling 

Richard Reiss 
Question 5: Would the proposed change to Paraquat dichloride's status in EPCRA affect all solids 

in solution? Are many other pesticides solids in solution? 

Answer There appear to be only 18 other chemicals (pesticides and non-pesticides) 

classified by EPA as "solids in solution" on the EPCRA 302 list, and therefore assigned 

dual TPQs. At least three of these chemicals have been discontinued in recent years. See 

Attachment 3. However, paraquat1 can be distinguished, because it has both an 

extraordinarily low vapor pressure and no boiling point, key properties in assessing offsite release concerns. Compounds with very low vapor pressure do not volatize at 

atmospheric temperatures. As temperatures rise (e.g., in a fire), the vapor pressure of a 

chemical increases until it reaches that chemical's boiling point, and the chemical 

becomes a gas. Paraquat, however, does not have a boiling point, but rather decomposes 

at between 320-340'c.~ 

For purposes of comparison, Attachment 3 lists the chemicals (pesticides and nonpesticides) classified as solids in solution on the EPCRA 302 list with vapor pressures 

equal to or less than Paraquat. For each chemical, the table includes the vapor pressure, 

boiling point, TPQ, and uses! Of the 1 5 chemicals still in use, only four others 

[Coumaphos, Phenol, 2,2'-Thiobis(4,6-Dichloro), Strychnine sulfate and Thallous sulfate] 

have a vapor pressure equal to or less than Paraquat's also have no boiling points. 

None of these three compounds is widely used for agricultural purposes and are not 

generally used as liquids; therefore, the lower TPQ for each of those is not relevant. 

Additionally, Strychnine sulfate may no longer be registered for use as a bait in rodent 

control. Thallous sulfate is used as a solid for rodent control; its use as a reagent in 

analytical chemistry as a liquid would be only in very small quantities. Coumaphos, an 

insecticide, is not widely used in the u.s.~ 

For non-pesticides, 1998 usage volumes are reported in EPA's Inventory Update Rule 

(IUR) report if the usage is above 10,000 lbs per year. The IUR does not contain usage 

data for any of the non-pesticides on Attachment 3, including the compounds with no 

boiling points (i.e., phenol,2,2'-thiobis(4,B-dichloro), and thallous sulfate), thus the usage 

must be below 10,000 lbs per year. 

1 Unless otherwise indicated, Syngenta's reference to "Paraquat" always refers to Paraquat dichloride. 

J. I. Macnab, "An Estimation of the Vapor Pressure of Paraquat Dichloride at its Decomposition Point." 

1 5 August 200 1 

3 According to annual Pesticide Use Data from the National Center for Food and Agricultural Policy 1997 National 

Pesticide Use Database, only 71,000 Ibs of cournaphos wm used in the U.S. in 1997, compared with nearly 7 million 

Ibs of Paraquat.