Document 3e6eYdzGkkEQy020n4wDMKrqn

tones WALKER March 28, 2018 201 St . C h a r l e s A v e n u e N e w O r l e a n s , L o u is ia n a 70170-5100 Fax 504-582-8583 www.joneswalker.com Robert E. Holden Direct Dial: 7 7 7 I? 2 7 7 -j Direct Fax: 504-589-8139 bholden@joneswalker.com Jennifer Orme-Zavaleta, Ph D Principal Deputy Assistant Administrator for Science United States Environmental Protection Agency 1200 Pennsylvania Ave NW Washington, D C. 20460 Re: Chloroprene Request for Correction #17002 Follow-up Request for EPA Review of PBPK Workplan Our File: 165671-00 Dear Dr. Orme-Zavaleta: On behalf of Denka Performance Elastomer LLC (DPE), I acknowledge receipt of EPA's denial, dated January 25, 2018, of DPE's Request for Correction (RFC) #17002 concerning the 2010 Toxicological Review of Chloroprene. DPE is very disappointed with the EPA denial, and believes the EPA should reconsider its denial. As outlined in the EPA denial, DPE plans to file a timely Request for Reconsideration. DPE's interest, as it is EPA's, is to seek the application of the best available science to this matter. EPA recognizes that it established the inhalation unit risk (IUR) for chloroprene based on the default assumption that human beings are as sensitive to chloroprene exposure as the most sensitive species in the laboratory. Attachment 1 to the January 25 denial explained, "In accordance with the EPA Guidelines for Carcinogen Risk Assessment (2005), in the absence of data to the contrary, EPA uses the most sensitive species and sex in establishing the cancer risk to humans, which, in the case of chloroprene, is the female mouse." EPA Denial, Attachment 1, at 3. The January 25 denial includes a cover letter and attachments 1 and 2. The attachments provide details about why EPA does not consider any currently available physiologically-based pharmacokinetic (PBPK) models to be sufficiently validated to be used to adjust the mousebased IUR to more accurately indicate potential human response. EPA's denial states that, {N3568898.1} -- -------- J o n e s W alker LLP A labam a A r iz o n a D istrict o f C olum bia F l o r id a G e o r g ia L o u isia n a M ississippi N e w Y o r k T exas Sierra Club v. EPA 18cv3472 NDCA Tier 3/4 ED 002061 00268477-00001 March 28, 2018 Page 2 among other things, it contacted Dr. Harvey Clewell in an effort to obtain computer code for some of the most recent PBPK models for chloroprene. DPE has now retained Dr. Clewell, who recently joined Ramboll Environ, to assist in developing a PBPK model that addresses the validation issues raised in the EPA denial. Attached for your reference is a copy of the "Workplan to Provide a Physiologically-Based Pharmacokinetic (PBPK) Model to Support the Inhalation Unit Risk (IUR) for chloroprene)," dated March _, 2018. Dr. Clewell and Ramboll Environ have designed the workplan to address EPA's stated validation concerns, and to deliver to EPA the computer code that EPA can utilize for its own validation review. Dr. Clewell and Ramboll Environ believe they can complete this task in 4 to 6 months. Although DPE has instructed Dr. Clewell and Ramboll Environ proceed with this work, we would highly value EPA's review and comment on the workplan because it is DPE's intention to provide EPA with a PBPK model that meets EPA's validation and other requirements. Towards this objective, perhaps a meeting with you and your staff to discuss this path forward would be beneficial. It might also be desirable to form a joint industry-EPA working group to help develop this PBPK model on such an accelerated schedule. We will be contacting your office shortly to follow up on this request. Thank you for your attention to this. Yours very truly, Robert E. Holden Attorney for Denka Performance Elastomer LLC REH/kb Ends. cc: Ms. Tina Bahadori, ScD ORD/NCEA Director Dr. Stephen Fine, Ph D., Acting Chief Information Officer Mr. David Gray, EPA Region 6 Director of External Affairs Ms. Vincia Holloman, Director of Enterprise Quality Management Division Ms. Anne Idsal, JD, Region 6 Administrator Mr. John Vandenberg, ORD/NCEA RTP Division Director Ms. Kistina Thayer, ORD/NCEA IRIS Division Director {N3568898.1} Sierra Club v. EPA 18cv3472 NDCA Tier 3/4 ED 002061 00268477-00002