~ Dow AgroSciences 

Dow AgroSciences LLC 

9330 Zionsville Road Indianapolis, IN 46268 USA 

Bldg 308/2E 

January 31, 2014 

OPPT Document Control Office (DCO) 

EPA East Building Room E6428 (202-564-8930) 

U.S. Environmental Protection Agency 

120 I Constitution Ave., NW 

Washington. D.C. 20004 

Attention: 40 CPR 799.5087; Docket lD Number EPA-H(H)PPT-2007-0531 

CBIC Control Number 

358162 

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Subject: Extension Request for testing ofPhosphorochlorideothioic Acid, 0.0-diethyl Ester (CAS 2524-04-1 or 

DEPCT) 

To Whom It May Concern: 

Dow AgroSciences appreciates the recent granting of an extension request for the HPV TSCA testing for CAS 2524-

04-1 (DEPCT). Our study plan is currently due 28 February 2014 with the final reports for the studies due 31 

December 2014. Our laboratories are not experienced with analytical and toxicological testing of this raw material, 

which we purchase from other suppliers, and when we initiated preliminary testing recently we quickly learned that 

this molecule is highly unstable and quickly degrades in most commonly used exposure media, including water and 

animal feed. We had not anticipated the method development experimentation (preliminary testing) that will be 

required in order to conduct the HPV TSCA testing as required by EPA. 

Therefore, we propose a slight modification to the testing and submission timeline for CAS 2524-04-1 from the 

dates stated above. We could still submit a study plan describing all of the preliminary testing such as hydrolysis 

study in water, degradation in exposure media, and analytical method development by Feb 28,2014. We would then 

report the results of these preliminary studies by August 29, 2014 and include stability and tox data obtained from 

other sources. Dow would then submit a second study plan with protocols specific for the testing described in the 

Federal Register notice for HPV molecules (Vol76, No 5, 7 January 2011, pg 1067), with testing modified based on 

the preliminary stability and degradation testing. This second study plan would be submitted by September 30, 

2014. We would then complete all subsequent physical chem, tox and fate studies, and submit reports by June 30, 

2015. In order to stay on such a timeline, we will need relatively quick (4-6 weeks) study plan reviews from EPA 

after the submissions of study plans, because we don't want to initiate studies until the study plans have been 

approved by EPA. 

®TM Trademark of The Dow Chemical Company ("Dow") or an affiliated company of Dow 
' Attention: 40 CFR 799.5087; Docket lD Number EPA-H(H)PPT-2007-0531 

Subject: Extension Request for testing of Phosphoroch1orideothioic Acid, 0.0-diethyl Ester (CAS 2524-04-1 or DEPCT 

January 31, 2014 

Page2 

Dow AgroSciences is committed to complying with the HPV TSCA testing requirements, but need the flexibility 

accomplished with more time to conduct the preliminary testing required to conduct quality studies. As described in 

prior communications regarding CAS 2524-04-1, the risk to human health and the environment is minimal for this 

raw material used in the production of chlorpyrifos, so hopefully this short extension can be accommodated in order 

to conduct the required studies in a thorough and high quality manner. If you have questions, please contact me at 

317-337-3774 or dwlickfeldt@dow.corn. 

Respectfully, 

Darin Lickfeldt, Ph.D. 

US Regulatory Manager 

Regulatory Science & Government Affairs 

Dow AgroSciences LLC 

9330 Zionsville Rd. 

Indianapolis. IN 46268 

Office: 317-337-3774 

Fax: 317-337-4649 

dwlickfeldt@dow.com