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Njo, Heather

From: Schaeffer, John

Sent: Friday, January 24, 2014 11:12 AM

To: Lickfeldt, Darin (DW)

Cc: Mattheisen, Mike; Lewis, Paul; Njo, Heather; Juberg, Daland (DR); Racke, Kenneth (D); 

Brooks, David; Lin, Chuantung; Boethling, Bob; Townsend, Mark; Sadowsky, Don

Subject: RE: HPV TSCA Testing Complications for DEPCT (CAS 2524-04-1)

Attachments: 2524-04-1_HPV2_Response to Dow AgroSciences Comments dated 01142014FINAL.docx

Darin, 

I have attached EPA’s review of Dow AgroScience’s comments that were provided in your email below. The comments 

in the attachment provide additional details, especially concerning the conduct of the aquatic and mammalian toxicity 

tests required under the test rule for DEPCT. 

I have also inserted in the body of Dow AgroScience’s comments, some additional comments that I received from our 

reviewers (red text). 

Please look these over. If necessary, please feel free to provide additional comments from Dow AgroSciences or request 

additional clarification from EPA. 

Also, understanding the difficulties inherent in testing this chemical, if Dow AgroSciences needs to request additional 

time to provide study plans and submit final reports, do not hesitate to request an extension. 

Best regards, 

John 

John Schaeffer 

Senior Biologist 

USEPA/OPPT/CCD/CITB 

1201 Constitution Ave, NW 

Washington, DC 20460 

Mail Code: 7405M 

Phone: 202-564-8173

From: Lickfeldt, Darin (DW) [mailto:DWLickfeldt@dow.com] 

Sent: Tuesday, January 14, 2014 9:33 AM 

To: Schaeffer, John 

Cc: Mattheisen, Mike; Lewis, Paul; Njo, Heather; Juberg, Daland (DR); Racke, Kenneth (D); Lickfeldt, Darin (DW) 

Subject: HPV TSCA Testing Complications for DEPCT (CAS 2524-04-1) 

John: 

Dow AgroSciences agreed in our Letter of Intent dated 18 October, 2013 to conduct the battery of tests on 

DEPCT (CAS No. 2524-04-1; O,O-diethyl chlorothiophosphate or O,O-diethyl phosphorochloridothioate) as 

published in the Federal Register on 7 January 2011 (V. 76, No. 5, pg 1067). We thank you once again for the 

recent granting of our extension request for submission of the study plan (now due 28 February 2014) and the 

final study reports (now due 31 December 2014). 

In our initial protocol development over the last two months, we have discovered how unstable DEPCT is under 

the requested testing conditions and we will have extreme challenges completing some of the studies as
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requested. We respectfully ask USEPA to reconsider whether all of this testing is needed upon consideration of 

the chemical instability of the DEPCT molecule in aqueous and nonaqueous media. 

DEPCT is highly reactive (hydrolyzes) in water, and the determination of a true water solubility limit is not 

likely possible (or meaningful). Phosphorylchloridate esters such as DEPCT have reactivity similar to that of 

carboxylic acid chlorides. The reactivity will have a significant influence on how testing is done - if it can be 

done at all. The substance will react with water, proteins, alcohols, etc. (any nucleophilic substance), thus 

making it unstable and difficult to verify exposure concentrations in ecological and mammalian toxicity tests. 

[EPA agrees with this statement as concerns testing for the water solubility endpoint. However, EPA notes that 

the results from the hydrolysis study that is cited by Dow AgroSciences (from the REACH registration, 

available on the ECHA website) does not appear to provide enough details to determine if the data are reliable. 

For the hydrolysis endpoint, EPA needs the complete study, not just details or a summary of the study.

Furthermore, if this study is unreliable -- as it appears, EPA recommends that Dow AgroSciences repeat the 

hydrolysis test to determine a reliable and accurate hydrolysis half-life for this chemical. EPA also recommends 

that all products of hydrolysis be quantified.] 

We recently found that a REACH registration has been submitted as an “intermediate use only” substance in 

EU. 

http://apps.echa.europa.eu/registered/data/dossiers/DISS-9ea6e71a-f3c6-6f79-e044-

00144f67d031/AGGR-bbbf528e-5536-47d6-ae3e-1fbe63232a4a_DISS-9ea6e71a-f3c6-6f79-e044-

00144f67d031.html#AGGR-bbbf528e-5536-47d6-ae3e-1fbe63232a4a

The EU submission also mentions reports that indicate the following: 

Hydrolysis half-life is 14 min. at room temp in distilled water 

Water solubility testing was waived, as testing is technically infeasible 

Octanol-water partition was waived, as testing is technically infeasible. 

We do have a calculated (QSAR) value of log Pow = 2.37 

[EPA notes that for the Boiling Point (BP) & Vapor Pressure (VP) endpoints, the cited EU's submission has 

provided the measured values (at the reduced pressures) for BP and VP, the sponsor could also cite these values 

to fulfill the HPV 2 Test Rule requirement for these two endpoints.] 

There is also an OECD 301F test of ready biodegradability, showing 9% BOD after 28 days. I suspect 

this test result is impacted by toxicity/inhibition of the inoculum by the test substance. As far as we can 

tell, this study is not publically available. 

[EPA notes that there exists a negative result in a 301F test which the sponsor suggests could reflect toxicity (to 

the microbes). If true, ready testing at a lower starting concentration (usually, 301D is used in this case) could 

be helpful. EPA suggests doing a ready biodegradation test, but with 301D.]

Due to chemical instability of DEPCT, especially in, but not limited to aqueous media, we will not be able to 

follow the required testing guidelines for the following studies: 

Water Solubility 

Kow 

Biodegradation 

Fish tox 

Daphnia tox 

Algae tox 

[EPA is in general agreement with the sponsor's argument on the reactivity of DEPCT in aqueous conditions. 

However, the sponsor indicated that DEPCT is highly reactive (hydrolyzes) in water and the cited EU's 
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submission for DEPCT has indicated a hydrolysis half-life of 14 min. at room temp in distilled water. Results 

from a (reliable) hydrolysis test could be cited for the Water Solubility endpoint, instead to fulfill the HPV 2 test 

rule requirement for this endpoint. Therefore, the testing on Water Solubility and Log Kow endpoints are not 

necessary. In addition, the EU's submission data also included a calculated (QSAR) value of 2.37 for Log Kow 

and the sponsor could cite this calculated value for Log Kow endpoint to fulfill the HPV 2 Test Rule 

requirement for this endpoint.] 

There are also challenges with conducting the mammalian tox studies due to instability but maybe there are 

other options for testing media? 

[EPA’s review is attached. EPA maintains that aquatic and mammalian toxicity testing should be conducted 

and provides recommendations for conducting this testing in the attached document] 

The melting point, boiling point, and vapor pressure ought to be determined as requested since we don’t think 

stability will be an issue for those tests. 

. [EPA agrees that a Melting (or Freezing) point determination ought to be determined, however, as noted 

above, for the Boiling Point (BP) & Vapor Pressure (VP) endpoints, the cited EU's submission has provided the 

measured values (at the reduced pressures) for BP and VP, EPA finds that the sponsor could cite these values to 

fulfill the HPV 2 Test Rule requirement for these two endpoints.] 

The FR notice of 7 January 2011, mentions that modifications to testing guidelines will be considered by EPA 

and in some instances testing was even waived when it was deemed irrelevant for given molecules (Section 7, 

page 1080). The FR Notice also states that EPA found a “low potential for adverse economic impact for the 

majority of the chemical substances” (p 1081), but a battery of 13 studies with a highly unstable molecule such 

as DEPCT will likely require extensive stability testing even before valid protocols could be written.

Degradation studies and probe work will be infeasible by February 28 for such a quickly degrading molecule. 

After stability testing in various media, the testing conditions may then be unrealistic for any potential route of 

exposure (i.e. ecotox and mammalian testing in nonaqueous media? 30-day tox testing when the half-life is 14 

minutes? etc...). 

We look forward to EPA dialogue regarding the concerns expressed for testing of DEPCT as described above. 

Respectfully, 

Darin Lickfeldt, Ph.D. 

Dow AgroSciences LLC 

9330 Zionsville Rd. 

Indianapolis, IN 46268 

Office: 317-337-3774 

dwlickfeldt@dow.com 

From: Schaeffer, John [mailto:Schaeffer.John@epa.gov] 

Sent: Thursday, January 09, 2014 12:18 PM 

To: Juberg, Daland (DR) 

Cc: Lickfeldt, Darin (DW); Mattheisen, Mike; Lewis, Paul; Njo, Heather 

Subject: RE: Call 

Daland, 
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In regards to your request, the response I got was a request that you write up your testing concerns and send them to 

us (an email or an attachment in an email is fine) -- that a call at this stage would [only]result in the same request. I also 

got a promise that your written concerns would be processed quickly. 

Best regards, 

John

John Schaeffer 

Senior Biologist 

USEPA/OPPT/CCD/CITB 

1201 Constitution Ave, NW 

Washington, DC 20460 

Mail Code: 7405M 

Phone: 202-564-8173

From: Juberg, Daland (DR) [mailto:DRJuberg@dow.com] 

Sent: Wednesday, January 08, 2014 3:59 PM 

To: Schaeffer, John 

Cc: Lickfeldt, Darin (DW) 

Subject: Call 

Hi John – Would it be possible to have a call with the Agency related to some technical questions/concerns we 

have on the DEPCT testing owing to some significant challenges we’ll have in conducting some of the studies 

owing to the rapid aqueous degradation (hydrolysis) that is associated with the material? Even prior to 

submitting a study plan, it would be very helpful to gain the insight (or at least have us present our concerns and 

then let you react to them subsequently) of the Agency, notably including a chemist, ecotoxicologist, and 

mammalian toxicologist. 

I can set up the call if you are willing and can include from your end a couple of the suggested technical 

scientists noted above. I am looking to get this in the week of January 20. 

Many thanks, 

Daland 

Daland R. Juberg, Ph.D., Fellow, ATS

N.A. Leader, Human Health Assessment 

Regulatory Sciences & Government Affairs 

Dow AgroSciences LLC 

9330 Zionsville Road 

Indianapolis, IN 46268 

317-337-3787 

317-919-3157 (mobile) 

drjuberg@dow.com